Observing the Moon & Planets - the good juice, and cheats...

[mental4astro]

New comers to astronomy – WARNING!

Maxing out the magnification of your telescope is not the way to use it. And, most likely than not, you will also be exceeding the optical limits of your scope by maxing it out with the eyepieces and barlow lenses supplied with cheap telescopes.

Here’s the really bad news: your 60mm refractor IS NOT capable of 525X magnification! despite the box your scope came in having plastered on it 525 power telescope! Yes, there is a little telescope that is currently marketed by a high profile telescope company with this misleading claim on the box. Truth is, the most this little scope can ACTUALLY punch out is just 120X before the image craps itself!

Sorry for the rather dire start to this piece. It’s just that there are many misconceptions that new comers to astronomy have, and the worst one of the lot is that one of the outrageous claims of 402X, 450X and even 525X magnification from really small telescopes, accompanied by photos of Jupiter and Saturn taken by the Voyager spacecraft, deliberately misleading the ignorant beginner that this is how they will see the planets with THAT telescope.

In this article, I will describe just a few basic aspects of what a telescope is ACTUALLY capable of providing, how to maximize its efficiency regarding its optical limits, the Great Equalizer and severe task-master that is the atmosphere, and then a few tips on how to rip the most detail out of the Moon & planets. Believe it or not, there are even some cheats that can be done that cost nothing in order to improve the quality of your viewing when the atmosphere is not playing nice.

One thing I will try my utmost to do is keep the astro-techno-jargon to a minimum, and what I do use explain it as I go as some of this astro-techno-jargon is very useful shorthand and important to know. Not understand some of these aspects, and you won't know why your telescope "is not working", when in reality there may be several things working against you, some of which you have absolutely no control over.

The whole article will evolve over a few posts as I develop them, and in a way form separate "chapters", much like my earlier article on nebulae. And of course, any questions as we go are MOST WELCOME. I mean this most sincerely as I can overlook some items, and your questions will also help me develop this article. Don't be shy as the only dumb question is the one that is not asked, and we all start from knowing nothing.

Alex.

[mental4astro]

The Golden Rule.

There is actually an optical limit to the maximum practical magnification ANY telescope can provide before the image begins to degrade. And this is entirely related to the aperture of the telescope. This maximum limit is known as The Golden Rule

The Golden Rule is: 50X per inch of aperture

So, that 60mm (2.3”) telescope that Tasco boasts as punching out 525x, is actually limited to 120X. A 200mm (8”) telescope maxes out at 400X. And so on.

Exceed this optical limit, and the image goes to crap as the optics because the resolution limit of a telescope is a function of the aperture size. Of course, with the right combination of eyepiece and barlow you can push any telescope to outrageous “magnification”, but the image will not be useable AT ALL. It will be dim and a fuzzy mess. THIS is what Tasco is not telling you, and you are suckered into buying that scope because of that bullcrap implication that’s accompanied by those photos taken by spaceprobes…
I have a lovely 200mm (8”) telescope that I use just about exclusively to sketch the Moon and planets with. If I listened to what Tasco claims I should be able to do with its 60mm telescope, I should be able to rip 1750X out of the 8" scope! My 8” scope is 11X larger in area than that 60mm, I limit my max magnification to 400X, yet that Tasco can do 525X!?!? Someone is telling a porky here…

This is all I will say about maxing out your telescope. Eyepiece selection is another topic altogether, and not relevant to this article. Of course eyepiece quality is important, so all I will say about eyepieces is that BIG$$$ is not everything with eyepieces either. There are some very good eyepieces that are actually very modest in price. Like I said, this is another topic altogether. For now, learn to use the eyepieces that came with your telescope, obey the practical optical limits of your scope, and you will come to see that those very same eyepieces can actually do a commendable job! :)

Alex.

[mental4astro]

The Atmosphere – the Great Equalizer & task-master

While you can get higher magnification with a larger telescope, how high you can actually take it ALL DEPENDS on the atmosphere on any given day! This is called “SEEING”.

Seeing means how thermally stable the atmosphere is. If the atmosphere is thermally active, the image through the telescope will shimmer and look like it’s boiling. It will look very much like it does looking across a hot road and you see the image in the distance just above the road surface shimmer and roll about – essentially it is a mirage. So in “poor seeing”, the image will begin to shimmer and boil as low as 100X (sometimes even lower). In “average seeing”, the max useable magnification will be around 250X. In “very good seeing” it is possible to go to 400X. BUT this is also limited to your aperture!

Here’s the kicker…
Sometimes, a smaller aperture is better to use than a large aperture!

The larger the aperture, while being able to provide higher magnification and having greater resolution, it is also much more sensitive to the prevailing seeing conditions of the night. So while I may prefer to use an 8” scope with the Moon and planets, sometimes a modest 80mm telescope is the better option. While I will only be able to max out the 80mm scope with 160X, my 8” scope at 160X in poor seeing might produce a totally boiled out image, but that 80mm scope at 160X will be just fine!

CHEAT!
Not everyone is in a position to have two or more telescopes. If you have just the one telescope, and seeing conditions are not great on a given night, there is one thing you can do to help sway things a bit more in your favour - crop the aperture of your scope.

Say your scope is 8" in aperture. As a smaller scope is less susceptible to the ravages of poor seeing, you can make a mask that has an opening of say 6" and put this over the front of your scope.

TRADE-OFF
Of course, with any cheat there is cost involved. By making the aperture smaller, you make the image a bit dimmer, and you reduce the resolving power of the neat aperture of the scope. But sometimes this cheat can mean the difference between a productive night and a night of frustration.

Alex.

[mental4astro]

Observing tips with the Moon and planets.

The Moon
The Moon is our closest neighbour in the sky. It is often the very first thing most people ever look at when they first look through a telescope. But this initial fascination all too often and all too quickly turns into loathing and disdain as its brilliance overwhelms the dimmer deep sky objects. Yet the Moon can provide a lifetime of observing joy, and every phase providing a unique treasure trove of details and features, can teach us a lot about our own Earth and even teach us about our own human history with the names its features carry.

Viewing the Moon is actually very easy. There are very few technical tips that make viewing easier, and sometimes less painful due to its brilliance. What is KEY to viewing the Moon however is understanding what can be seen on the Moon. Understand this, and the Moon will never be a dull and repetitive place.

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Telescope tips:

The EASIEST tip to follow about viewing the Moon is:
• You don’t need to turn all the lights off!
There is NOTHING subtle about the Moon. Your eyes WILL NOT be dark adapted. So there is not only no need to view the Moon in the dark, it can actually be dangerous to do so as your stunned eyes will not be able to see hazards when you walk around in the dark. Keep all the lights on that you want!

• The lower the magnification, the more painful the image to your eyes. To help control this as sometimes low power viewing is most pleasing, you can mask down the scope’s aperture or use a filter in the eyepiece.
There are many different types of filters available to deal with the Moon’s brilliance. Some are a green tinted filter (horrid thing), others are called Neutral Density filters which are essentially grey tinted filters that come in different grades of transmission. The difficulty with these is which filter do you buy??? Different phases have different brilliance impact, so to recommend any one Neutral Density filter I never do. The filter I do recommend is a Variable Polarized filter set – these two polarized filters are used together to regulate the amount of light that is transmitted, and so you can control the Moon’s brilliance to whatever amount you want regardless of the phase.

• High magnification doesn’t require a filter.
With my own lunar sketching, I use a large 8” telescope, which in turn collects A LOT of light, but I don’t use a filter. As the features being viewed will be along the Terminator, the brilliance of the Moon is more tempered, so a filter is not necessary. On those areas where the shadows are nonexistent on the Moon, yes its brilliance can be painful, but these are not areas where most details are visible.

If you are examining those areas where and when there are no shadows, then a filter is necessary. Examining these shadow-less areas is a niche aspect of lunar observing. Some features, most often volcanic in origin, can be impossible to view if there are strong shadows about, and the best time to view these unique features is when there are no shadows visible and you rely upon subtle variations in shading to identify these areas. A neutral density or variable polarizing filter set can be very handy here.

• Adapt the magnification you are using to best suit the prevailing seeing conditions!
When seeing is poor, the lunar surface can appear to shimmer, ripple like a flag in the breeze, and even boil. When this is happening, the best thing to do is turn down the magnification. As the night wears on, seeing conditions may improve (often happens), or even go pear shaped (sucks when this happens!), so you need to be aware that being adaptable to the conditions will mean a productive time or just maddening frustration.

What to see on the Moon?
Oh, yeah! Now this is what REALLY excites me about the Moon! Because there is no atmosphere, no water, no weather on the Moon, its surface is an open storybook of its entire violent and terrifying history. Like I mentioned earlier, there is NOTHING subtle about the Moon. And the processes that formed and keep forming its surface are nothing gentile and cute, but conjured up from the very depths of Hell itself!

And as I did with the Nebulae article, I will let heavy lifting of describing what can be seen by another brilliant page: Observing the Moon along the terminator (http://www.packerlighting.com/Lunar_Articles/Moon%20Article%203of6.html).

Many of us are aware that the dark Seas and Oceans on the Moon’s surface is lava. But how many of us then consider that if there is lava, then there has to be volcanoes too! And if there were volcanoes, then it also stands to reason that there will also be the many different features associated with volcanic activity: lava rivers, collapsed lava tube, lava fields and folds, and flooding of craters. And a volcanically active body will also give rise to other planet forming forces such as tectonic forces creating different faults (sheer and rift), mountains, fractures. Of course, today none of these forces are active on our Moon. But as there is no erosion taking place on the Moon, its entire history is on display, and with a little understanding you will be able to identify a 4 billion year story all within one small area of the Moon, just by identifying the features visible, the forces that formed them, and hence the timing of the Moon’s age as to when these different features formed.

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Which is the best phase to view the Moon? EVERY PHASE is the best time to view the Moon!!!!

A very common misconception about the Moon is that “there is nothing to see during the full Moon”. And those people who profess this myth have never taken a close look at where the REAL TREASURE of the Full Moon lies – along its limb!

Here we don’t see craters or mountains from above. Instead all the lunar features are seen in profile, just like looking across a landscape here on our home planet. And the features, shadows and landscape all give us a totally different perspective of the lunar surface.

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~x.X.x~

I hope this chapter has given you some helpful tips on how to deal with the Moon, the many different features visible, some appreciation for the history it shows us every month and even some insight to the forces that formed the Moon are still active here on our Earth today!

Alex.

[Rkonrad]

100% Alex many people boast that they can get 200x and more with 60mm Unitron ?
I have an old Tasco 10TE-5 and have manages the magical 50x per inch (150x) for this scope on numerous occasions , thats why I still have it.,that scope however is only good for splitting stars , planets etc.
The highers magnification with my limited scopes was 250x thats with very clear sky and high altitude of 1650m Above sea level
The Moon is different and can have much higher magnification doe to its brightness

[mental4astro]

Thanks Richard for the confirmation! :)

It's also always nice to get some feedback on what one writes.

CHEAT!

There is one thing that both lunar and planetary observing require, and that is patience.

There is no shortcut to this. And the reason is the environment that our eyes are looking into – a high contrast situation of a very bright Moon or planet against a jet black background, and surface details that are actually of low contrast set atop of the bright Moon or planet.

If you rush, being impatient to see details, you will miss those fine details that our telescopes are actually very capable of providing.

Patience creates experience, and that experience will have you slow down so that you can get your eye “in” on the difficult conditions our eyes are being required to look into.

With the Moon, there are so many fine details that will only reveal themselves with patience. Lacework-like fine riles, clusters of tiny craterlets that pepper the floor of a flooded crater, identifying domes/volcanoes from the surrounding features, the fine and subtle shading & lines along the terraced walls of massive craters that reveal that these are the result of landslides – these are all the sorts of features that require a patient eye.

CHALLENGE!
There are three very small craters that I will use as one of two challenges I will make in this article. These three craters are Armstrong, Collins & Aldrin. They form a straight line in their orientation in Mare Tranquilitatus. Armstrong is the largest of the trio at 5km in diameter, Aldrin the smallest at about 2.5km in diameter. These sizes might sound BIG, but from here on Earth, they are getting to be the smallest craters we can see. If your scope is less than 5” in aperture, you will not see these as they are too small for scopes smaller than 5” to resolve.

Patience is the key to spotting this trio when the lunar phase is favourable (between 5 days old and 7 days old being optimal. Good seeing conditions are also necessary – Remember, these craters ARE VERY BLOOMING SMALL! You will need good seeing conditions.

Rush, and you will not see them. Give your eye the chance to adapt to the difficult brilliance of Mare Tranquilitatus. These three craters have no prominent landmarks close by to assist with spotting them. The available landmarks are far away and the entire exercise will test your patience. But they are visible.

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Oh, and you will not be able to see the Apollo 11 landing site. Not even the Hubble Space Telescope is capable of seeing the site - and they tried! The Apollo 11 landing site, and that of the other 5 landing locations were only visible just a few years ago by the Lunar Reconnaissance Orbiter.

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NASA photograph.

Alex.

[mental4astro]

Observing the Planets

TIP:
The planets will ALWAYS appear small in a telescope. You will never see any of the planets appear like the size of a dinner plate. The pretty photos that typically come on the box of a telescope are very misleading.

However, despite their small size, a surprising amount of detail can be seen. With your main tool being patience…

I am REALLY hammering this patience thing in these last two posts for a reason. Astronomy is NOT a “smash’n’grab” thing. It requires being calm, concentration, and a keen eye, and it doesn’t matter if it’s with the Moon, Saturn, the Orion Nebula, or the impossibly faint globular cluster Mayall 11 that belongs to the Andromeda Galaxy!

Be patient, and amazing wealth of exquisite details will become visible to you, such as the polar caps on Mars (Yes! Snow on another planet!!!), or like one of my greatest ever thrills, seeing clouds on Mars!!! :)

FILTERS help with the planets.

While not essential, colour filters can help a great deal with seeing details on the planets. What features and which filters is the subject of this part.

The way I will mention what features are visible will be contained in the following link to astronomical filters. Half way down the following link, you will find a list of the planets, what features are visible, and the best filters to see those features with:
https://www.myastroshop.com.au/guides/filters.asp

CAUTION!

If you do think about getting yourself some colour filters, GET NO MORE THAN THREE OR FOUR.

STUDY that filter guide very carefully, and then compile a list of no more than 4 filters. The reality is YOU WILL NOT USE THESE FILTERS VERY MUCH. So having just a clutch of them is all you will really need.

DO NOT BUY READY MADE FILTER SETS!!!! These are made up of colours that are way too deep and intense, and these filter sets are designed to appeal to novice eyes because of their strong colours. Truth is that these strong colours are not the best options for the planets. Instead, the better/more practical filters are more subtle in hue intensity.

Me, I only have four colour filters, and I use three of these the most, and not very often at that. Only sometimes do I ever bother using filters with the planets. A couple of these really I don’t use all that much, and sometimes I think about getting one or two others to replace them, but I’ve never acted on this as I doubt I would use these filters very much at all too. <sigh>…

Uranus and Neptune.

I will only expressly discuss these two planets because they are particularly challenging in that they really have no discernible disk to make out at all. Instead, the best way to identify these two is by their colour. Uranus has a very distinct bluish-green colour to it, and Neptune is an intense blue that is much too rich to be a star. Because there is no discernible disk with these two planets, don’t worry about using filters with them.

Uranus is actually visible to the naked eye! What you require is a very dark location, good transparency, and an accurate, up to date chart such as one of the astro apps. I’ve been able to see Uranus from up in the Blue Mountains just west of Sydney on many occasions, and I was also able to see fainter stars around Uranus to so I was not confusing things. And of course a quick look through a scope confirmed this too.

Uranus is also VERY EASY to spot with binoculars from under urban skies! At magnitude 6, it is not a challenge for a 7X50 pair of binos. Again I’ve managed this from my home in Sydney.


TIP
You will see more detail on the Moon and planets with a larger telescope due to a larger scope having a greater resolving capacity. But even so, a surprising amount of detail can be seen with smaller apertures. A wee 2” refractor will show the two main equatorial belt of Jupiter and reveal the four Galilean Moons. A good 80mm scope will reveal the Cassini Division in Saturn’s rings. A 14” scope will allow you to spy out the main five moons of Uranus and Neptune’s largest moon Triton.

CHALLENGE
This challenge will be a real test of the quality of your scope. You will also require a scope larger than 6” in aperture for this, and good seeing conditions too.
Saturn’s rings are made up of thousands of individual rings and even gaps. The Cassini Division is the largest of these (roughly 4000km wide). There is another ring division that is visible, the Encke Division. It is much smaller in size (roughly 400km), and to be able to resolve it in any scope over 6” in size is a testament to having a blooming brilliant set of optics in your scope! The Encke Division is a real test of optical quality.

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If you would like me to prepare other challenges, such as challenges for smaller scopes, deep sky objects, Moon, planets, whatever, let me know. I’d be only too happy to devise a few! :)

Alex.

[Outcast]

Another awesome thread Alex,

I am learning so much from this & your nebula thread.

Looking forward to taking up your challenges.

Cheers

Carlton

[Madanie7]

Another ripper piece Alex.
Thankyou

[mental4astro]

Thanks Carlton and Brendon :)

RESOLUTION - What da??? :question: :question:

I've been involved in astro for more than 35 years. Yet I've only recently come to understand one of its most oft mentioned but most poorly understood aspects - Resolution - and how there are two very different aspects to this with our scopes.

WARNING: Physics talk below! :lol::lol:

When we read the specs table of our scope, frequently we will read a spec called "resolving power". In short it is the "smallest" size detail our scopes are supposed to be able to make out.

HOWEVER! This value is somewhat misleading! Our scope are actually capable of resolving much smaller details, close to 10X smaller than the quoted value!

There's two parts to this resolution thing. Let's start with the quoted figure and what it means. I promise to keep it simple.

Here's the thing with stars and our scopes. We may think that the stars we see through our scope are just pinpoints of light. They are actually a tiny, tiny disk (airy disk) with a series of faint rings (diffraction rings) that get fainter out from centre.

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You can actually see this Airy Disk and at least the first diffraction ring when you use high power on a very bright star and under good seeing conditions. So none of this is techno-mambo-jumbo! :lol: It's real and easy to see for yourself.*

So, being a tiny disk, the quoted "resolution" comes to be the smallest distance the a given aperture can provide a distinct separation - NOT a total separation.

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If you would like to follow this up with the maths that's involved with this, you can follow this excellent link that deals entirely with telescope optics:

Telescope Resolution (https://www.telescope-optics.net/telescope_resolution.htm)

NOW, this resolution value is ONLY for two Airy disks.

When it comes to expended objects such as the Moon and planets, things are very different!

Because you are not dealing with point sources of light, the entire situation is different. The apparent diffraction patterns are totally disrupted. This in turn means that the actual resolving capacity of the optics is now greater than that provided by two airy disks.

The evidence for this is seen in those amazing photos of Saturn's Encke Division. It's angular size is 0.05 arcsec. This is more than 1/10th of the quoted resolving power of an 8" scope! Yet there are photographs of Saturn showing the Encke Division taken by 6" telescopes. I have also seen the Encke Division in a 7" and 8" scopes. I have also been able to resolve markings on the Moon that are smaller than 250m, and using simple trigonometry maths, these features come in at 0.15 arcsec.

So, this is why I am putting up these two particular challenges. These will show you finer detail than the quoted "resolving power" of your telescope.

~x.X.x~

Knowing this now, how does this affect you and your telescope?

Easy.

The "quoted" resolution of your scope you now need to think of only in terms of two stars. This resolution value will only affect the smallest separation that can be resolved say for double stars. When it comes to the Moon and planets, the resolving capability of your scope will be better than 1/10th of this

If you do not know the resolving power of your scope, the following telescope resolution calculator will give you this. All you need to do is input your aperture:

Telescope resolution calculator (https://astronomy.tools/calculators/telescope_capabilities)

This link has two values, the Dawes Limit and the Rayleigh Limit. The Dawes Limit is the smaller of the two, and you will be able to resolve finer details than 1/10th of this with the Moon and planets

Alex.

* One thing needs to be kept in the back of your mind when it comes to the Airy Disk. This disk is not the actual disk of any single star. All stars are actually impossible to resolve into there actual disk. Instead this a phenomenon to do with point sources of light meaning that ALL point sources of light will show an Airy Disk. So it does not matter if you look at Alpha Centauri (4.3 light years away) or the quasar 3C 273 in Virgo (which is 2.4 Giga light years from us, and visible in amateur scopes as it shines at magnitude 13!), both will show an Airy Disk.

[Outcast]

Alex,

Would it be possible to put together a beginner's guide to compiling observation reports.

I read the ones posted but, have no idea about how to accurately compile one.

Thankyou in advance

Carlton

[mental4astro]

Carlton,

Writing formal reports is not something I normally do. However, I've asked a mate who does have a lot of experience in this if he could offer some insight into preparing astro reports. Les has also written many articles for various astro magazines. Les is The Man for this!

Alex.

[Outcast]

Thanks Alex,

I'm just curious at this point & want to try & understand the reports that are in the visual observations sub-thread.

Then maybe have a go... see if it might become my thing..

Cheers

Carlton

[N1]

http://www.iceinspace.com.au/forum/showthread.php?t=12753

[mental4astro]

Brilliant, Mirko! :thumbsup: :D

[morls]

Brilliant thread Alex, thank you! :2thumbs:

I'm wondering if you could do a follow-up on your last post dealing with resolution, and explain how to do basic star testing of optics? I'm doing this a lot with my new scope, but I'm not sure what all the different rings represent, and whether they can be used to determine 'x-number of waves de-focus...

It could well be explained elsewhere, but you have a great way of presenting the information clearly...

Cheers

Stephen

[Wavytone]

Hi Stephen, Part I - your scope.

You will need a pretty steady mount for this, and one that tracks. On an unguided mount this is very difficult.

1. Choose a bright star near the zenith mag. 1-3 are ideal - altitude at least 70 degrees above the horizon.

2. Align scope on the star.

3. Make sure the optics are collimated to the absolute best you can, this is a subject in itself.

4. Precisely centre the star in the scope, and increase magnification to at least 2X per mm of aperture (changing eyepieces as needed) and centre it if need be.

5. Accurately focus. You should be able to clearly see the Airy disk and a couple of rings around the star at best focus.

Defocus one way (let’s assume inwards) by a small amount until the central Airy disk is gone and you have 2-3 concentric tiny rings. In the centre of these you will still see a tiny dot of light - the Poisson spot - which is caused by diffraction around the central obstruction in a Newtonian or catadioptric scope.

6. Compare with the images at

https://www.telescope-optics.net/aberrations_point.htm

And

https://www.telescope-optics.net/diffraction_pattern_and_aberrations .htm

7. Refocus and then defocus the other way, and repeat.

Note that the Poisson spot is useful it shows where the exact optical axis is.

Lastly at step 5 there are situations where you may nit be able to clearly see the Airy disk and one or two rings:
- poor seeing,
- thermal issues within the telescope causing air currents,
- poor optics.

I have seen scopes that optically will not show the Airt disk - at high power they give a blurry mess. Sometimes the optics are pinched or strained because someone has over tightened something, or a mirror is badly supported. But some are just plain bad.

[mental4astro]

Thanks Nick. You were able to better explain this than myself, :thumbsup:

Nick explained a formal method of star testing. There's a couple of empirical ways of testing.

The basis of this is one thing that Nick told me: "When all the photons go where they should go, then seeing conditions have less of a deleterious effect".

So when comparing two scopes, and seeing is less than perfect, these conditions are great for comparing the relative optical quality of the two scopes. The instrument with the better optics will be less affected by the poor seeing than the poorer set.

Stands to reason as with the poorer optics, photons are less well controlled, so the image will be more easily disrupted.

Another informal way of star testing can be done with splitting double stars. If you look at the second picture in post No. 10, you will see that splitting double stars does not require a full separation.

One last empirical test is done by pushing the optics to its limits with attempting to resolve the finest details possible. This is the reason behind the two challenges. The Encke Division has an angular size that is much smaller than the "theoretical" limit of many scopes 7" and larger. There are many 8" scopes that cannot resolve the Encke Division. The lunar crater resolution is more tricky as it requires the individual to compare the scope's image with images from a very detailed atlas, such as Virtual Moon Atlas. An atlas such as by Antonin Rukl is not detailed enough for this purpose.

[Wavytone]

Hi Stephen,

Part II - the Rayleigh & Dawes criteria vs what you can actually see, and optical quality.

The Rayleigh & Dawes criteria concern the closest pair of stars - of equal brightness - that can be discerned visually as not a single star, assuming ostensibly perfect optics. It turns out - with the help of optical theory - that this depends solely on the aperture of the telescope, and the wavelength of the light. See https://www.telescope-optics.net/telescope_resolution.htm In essence, the two central Airy disks overlap and resemble a dog-biscuit, just enough that an observer can say with confidence it is not a circular disk (ie single star). Note there is NO black gap visible between the stars.

Conversely, armed with a list of close bright double stars of similar magnitudes - and there are several - you can test the quality of the optics of your scope in the harsh real world if you are blessed with a night of excellent seeing. I guarantee you will find it very very difficult to split double stars at double the Rayleigh limit for your scope, never mind close to the Rayleigh limit. This also says something about the quality of the refractors available in the 19th century - some of them clearly did have exquisite optics despite the simple eyepieces of that era.

Note however that these resolution limits only apply in the context of two close bright stars of equal magnitude. In other contexts the limits to what you can see will differ - particularly double stars of unequal magnitude - a dimmer star is much harder to see and the minimum separation that can be clearly resolved will be greater than the Dawes limit.

Similarly the moment the subjects cease to be point objects (stars) the Dawes/Rayleigh criteria do not apply - eg observing Jupiter and its moons, or Saturn/Mars/Venus/Neptune/Uranus which can all be resolved in amateur scopes.

With excellent optics it is also possible to see features smaller than the Dawes limit, such as a dark linear feature against a bright background, for example a slender shadow on the moon cast by a crater rim or rille, or Cassini's division and Encke's division in the rings of Saturn.

Optical theory suggests - using somewhat simplistic maths - that a scope producing a wavefront error not exceeding quarter of the wavelength of light will resolve stars at the Rayleigh limit. For a reflector this means the surfaces of mirrors must conform to the required shape with 1/eighth of the wavelength as a defect in a mirror produces a wavefront defect twice as high.

A few telescope manufacturers will guarantee their products meet a specific criterion in terms of wavefront error - many do not.

[morls]

Thanks Nick and Alex,
Thanks for the info. There's a lot here to get my head around and I'm sure I'll have more questions, so rather than clutter this great article of Alex's I think I'll start a separate thread for learning about star testing and collimating my scope.
http://www.iceinspace.com.au/forum/showthread.php?p=1399240#post139924 0


Looking forward to getting into the observation challenges put out in this thread...

[mental4astro]

Stephen, to finish answering your question about a numerical value that quantifies the ultimate quality of your optics, this can be approximated by visual techniques, but it is only possible following a lot of experience and knowing how to conduct bench tests, the various tests required and how to interpret the information these tests provide.

An example of this is the testing carried out by a Russian optical lab. They have the necessary equipment to thoroughly investigate a set of optics that access the different values and provide the ultimate quality value that is provided in a series of values, such as Strehl, RMS, P-V, and a few others. These all tell slightly different things about the optics, though not contradictory. Of these different values, the Strehl rating is the one that's most significant as it is the overall quality rating, as a ratio where 1.0 is "perfection", exceptional quality would be something like 0.974, mediocre quality is 0.767.

I'll chase up a link to this Russian lab.

Alex.

[Wavytone]

http://fidgor.ru/Observers/test.html

Back up your PC and make sure it has malware defences BEFORE you try that link as it is known to dish up some real nasty stuff.

[JeniSkunk]

What about the really small table top reflectors, like the 76mm reflector (Orion FunScope 76mm, Celestron FirstScope, Sky-Watcher Heritage 3 inch, Saxon Mini Dobsonian, ect) ?
Such supermarket/department store priced 76mm reflectors have even been sold by Aldi.

[Saturnine]

Wavy, why provide a link that has known malware issues !!!

This thread is something that I'm sure that would be useful to a lot of amateurs, old and new, about how telescopes perform and what we are actually seeing through them and how to interpret what we are seeing. When it comes to fine lunar features it is obvious that they exceed the supposed resolution of the telescope in use, in good seeing of course.
Have had a few memorable nights where I've pushed the old Jaegers 4" f9 to 75X per/ inch on the planets and moon and double stars. My NG 5" triplet does perform better than the old achro by are fair margin even taking the extra aperture into account.

Alex and yourself have provided a great resource with your knowledge and insights, thank you.

[mental4astro]

Jenifur,

Now we head into the Dark Side of astro - the cheap.

What Nick and I have been discussing so far has been in relation to GOOD astro gear. To be able to push a scope to its theoretical limits, it needs to be a quality instrument. Sadly, the majority of what newcomers to astro buy is not good.

Before I go into tearing shreds off any item, I need to make something very clear, and something that is VERY CLOSE TO BOTH NICK AND MINE HEARTS:

"The best telescope is the one that gets used. If all you can afford is an inexpensive item, and you use it all the time, then it is just as good as the finest, most exquisite instruments humans have ever devised! And Damned be anyone who dismisses this."

So, knowing that cheap supermarket scopes are poor, we can discuss the Good, the Bad and the Ugly.

To make a scope cheap, then cheap and crude manufacturing techniques need to be used. And in turn, cheap scopes appeal to those people who unfortunately on a whole don't understand what they are buying. There's no right or wrong here, just a merge of two different forces - ignorance and market.

The requirements needed of an astronomical telescope are very stringent, and to produce such a high standard of instrument needs high quality materials and highly controlled manufacturing processes. And this costs money. Don't make the mistake of blaming China for cheap and nasty stuff. The Chinese are also very capable of making outrageously fine equipment, and today can rival and even surpass many traditional manufacturing powerhouses! Don't forget, some high profile Japanese and American brands have their entire product line now manufactured in China, and no one blinks an eye.

Those supermarket telescopes are not made using the optimal processes for a good astro telescope. They can't. These cheap scopes are entirely made to a price, and quality is only skin deep. Those 76mm reflectors are made with a poor quality spherical mirror, not a parabolic one. The eyepieces use plastic lenses, or uncoated glass lenses. This means that they are very poor at high magnification. These cheap scopes are best for low power wide field viewing, and they can deliver a very nice low power image. But they do not deliver a good high power image at all. They can't, and many people end up very disappointed with astronomy within 5 minutes and take it no further. And it's not just the figure of the primary mirror, but the cell it sits in, the focuser, the secondary mirror and its holder and the stalk that holds it. These can be altered to an extent to improve the little scopes performance, but these mods should not be something that the end consumer should be responsible for. These scopes are made to a price after all.

I have owned 3 of the Celestron FirstScope table top reflectors. All have been terrible at high power. I suspected this when I purchased my first, but I bought it as a had a particular use in mind with it, as big aperture finder scope, which meant I was exploiting its greatest strength - low power. And these scopes proved to be great for this. I had one mounted on my 17.5" dob! :)

234806

Would I recommend these cheap little scopes to anyone? It depends. These would not be my first or second suggestion, but for better or worse they do fill a niche. As a first telescope, they may work out to be a wonderful introduction to astronomy for a little kids - my own children when little enjoyed this little FirstScope. For older, more discerning kids and for adults, not a chance.

[JeniSkunk]

Thank you very much for the reply, Alex.
:)

In my case, getting the 130P reflector, price was important, but the physical size of the telescope mattered more due to where it would be set up.
Block of flats with small patio, and not much front to back depth. You can get an idea of how shallow a depth, from my avatar pic.
There's no way I could use a refractor here.

[mental4astro]

Jen (I hope you don't mind me calling you Jen), I have only heard good things about that scope of yours. It is a clever design! Despite its price, you thought about it more than a lot of people to make sure you got something that suited your situation. That's blooming brilliant! :D

Don't get me wrong, some inexpensive scopes are real gems. Your's is one of those gems. You didn't buy that scope at Aldi. There's a few things you can do improve your experience with this little scope too. I'd be happy to PM you about some of these as this goes beyond the scope of this thread. Drop me a PM if you like :)

Alex.

[JeniSkunk]

For buying a scope, the display of scopes in the window of my local Australian Geographic, caught my attention back in March. I had cash to spare and I could have all too easily bought a scope right there and then. Thankfully, I didn't.
At home, I started looking up info on beginner scopes, thinking about where I'd be using the scope, it's portability, storage size, the stuff that really matters when you're wanting to use a scope, and you live in a block of flats which only has stairs. I was thorough in doing the homework before heading to my nearest specialist astronomy shop here in Brisbane, Astro Anarchy, to 'kick tyres'. I wasn't going to spend a cent till I could actually see the scope, to be certain if it'd fit. I was lucky when I bought mine, as at the time it was on sale for about 40% off its usual RRP, so not expensive to start with and then sale price to make things even better.
In terms of what I've bought since getting the scope, that I use pretty well every viewing session, it's listed in my sig.
And that brings things right back to topic, on a point you raised. Eyepieces.
The stock ones with my scope would basically be a good way to dissuade anyone from astronomy. The 25mm has a nice wide field of view, but not enough magnification. The 10mm has better magnification, and bad chromatic aberration.
That meant getting better eyepieces was a must.

[JeniSkunk]

Should this very useful Beginners thread be stickied?

[mental4astro]

Jen, changing the stickies situation is one of the many things on the Administrator's list of "things to do"...

Ok, I've been asked to supply a few more challenges, so here goes

CHALLENGE NO. 3

Martian Clouds!
With the Martian global dust storm finally showing signs of breaking, it gives us an opportunity to chase down not just the polar caps (YES! Snow on another planet! And you can see it from here on Earth) which is easy, but the real teaser that is Martian clouds!

Steady seeing is a must. And another thing that helps is an #80A colour filter, or a #8 filter as it helps to tone down the glare of the red surface and allows the white clouds to show up more easily. But be patient! These clouds are not as dense as our Terrestrial ones. They are also best seen close to the limb of the disk (outer edge) as this is where they will be most dense in line-of-sight.

NOTE ABOUT COLOUR FILTERS:

Using colour filters with the planets will not necessarily make those features you seek stand out more obviously or how you expect them! Many features are very difficult to spot, and may appear in a way opposite to how you might expect. So be patient, understand what you are trying to see and give yourself time to interpret the image you are seeing.

Alex.

[JeniSkunk]

Thanks Alex, I didn't know of the state of play for the to-do list.

Right now, Brisbane is stuck with ugly stormy weather. Getting a long enough break to see anything is a challenge.

This challenge is something I've wanted to be able to observe since getting my scope.

[mental4astro]

CHALLENGE NO. 4

A cluster of volcanoes!

From just finding out that there are volcanoes on the Moon, this challenge is to spot one of the easiest clusters of lunar volcanoes, the Hortensius Omega cluster, also known as the Hortensius Domes.

234914
NASA photo

This is not so much of a "can you see this feature" sort of challenge, but one of teaching yourself how to distinguish run-of-the-mill-mountains vs shield volcanoes on the lunar surface. But note the individual domes are small, the largest about 12km in diameter, so it will be a challenge for scopes under 3" in aperture.

Unless you knew what to look for, if you happened to come across this cluster of volcanoes you would just dismiss them as just a cluster of mountains. Instead, there's a couple of distinguishing features that go to help identify these as shield volcanoes.

Because these are not particularly high features, timing of the lunar phase is important, two days after first quarter or a day or two after last quarter.

What is most remarkable about this region is that there are literally dozens of volcanic domes that dot the entire area. The above NASA photo shows how wide spread they are. Making it easier to identify this area is it lies due west of Copernicus.

Happy hunting!

Alex.

[morls]

Great stuff, thanks Alex.

I've found some great moon maps, published by the US Geological Survey:

https://pubs.er.usgs.gov/publication/sim3316

Stephen

[PSALM19.1]

You've excelled again, Alex! Such helpful info...

Just out of interest, Mars and Neptune will be within one degree of each other on December 7...will make Neptune easy to find 😁 Alex, do you have any observing tips for finding Neptune - it is still a real challenge 🤔

[mental4astro]

Thanks Stephen and Shaun :)

Stephen, great link mate!

Shaun, Neptune and Uranus are not difficult to spot. Both can be easily found using binos, even under urban skies. From a dark site, Uranus is also visible to the naked eye, but it does also require a transparent sky. I've seen Uranus many times where I go in the Blue Mountains west of Sydney, and there were also fainter stars visible than Uranus.

What distinguishes both Neptune and Uranus is their distinct intense colour. Neptune an intense blue, Uranus a bluish-green. Don't bother too much to resolve a disk with either as both are really small, and no surface features can be made out either. You could use their disk to help distinguish them from surrounding stars, but you will require very, very good seeing conditions so that you don't have bloated stars to contend with.

Actually, thanks to you Shaun, I nearly forgot that I have another challenge, this time not just involving ALL the planets, but EVERY major body in the solar system that orbits the Sun. I'll make my next post about this. There's only a few days left this year from today's date (20th of October), and then two more opportunities to see the same next year, and then that's it for several hundred years: The Massey Alignment! Read all about it in the next post! :D

[mental4astro]

Challenge No. 5

The Massey Alignment

Firstly, I am not so arrogant as to name something after myself! Instead, this name was given to this most unique apparition by some of my friends, so why not go with the flow :D

For the next few days from the writing of this post, and on two more occasions next year, it will be possible to view ALL the planets, plus the Moon and Pluto all in the sky at the one time!

This is not a linear alignment as the planets will be spread out across 180° east to west. Linear alignments also won't show all the planets in the sky at the one time - Venus and Mercury will be between the Earth and Sun.

I chanced upon this whole of planetary alignment by chance a few months ago while researching possible dates for outreach. This apparition is only visible for about half an hour to 45 min as Venus and Mercury disappear below the western horizon these next few days, and Uranus is just rising in the east at the same time. No one had noticed this alignment of every major body in the sky all at the one time, not individuals or professional astronomers. Me! :)

There will be three opportunities all up that this apparition will happen. This October just after sunset, in late April next year (2019) just before sunrise, and end of October/start of November next year (2019) again just after sunset. This apparition is only visible for a couple of weeks during these dates. And then that's it for several hundred years!

I started a thread here in IIS about this:

http://www.iceinspace.com.au/forum/showthread.php?t=167278

I've also made a post entry on my blog about this event too:

http://alexanderastrosketching.blogspot.co m/2018/06/unique-planetary-alignment-coming-up-in.html

Oh, and a mate of mine started a thread about the current Massey Alignment here in IIS. I managed to complete the Massey Alignment last night! :D :D Crazy really as last night was the first clear night in Sydney for the last two weeks and the only clear night forcast for the next week too:

http://www.iceinspace.com.au/forum/showthread.php?t=170866

Below are two Sky Safari screen shots of this October's apparition, looking West and looking East at 7:57 pm.

So, if you miss this October's apparition, you'll have two more next year. Then that's it for a very, VERY long time.

[PSALM19.1]

:eyepop: wow, that's awesome! Pity I won't be able to see Pluto with my 8" Dob 😏 Or for that matter, see through the clouds here in Shellharbour...better wait until next year 😊 Maybe you could patent the Massey Alignment 😜

[JeniSkunk]

I'd hoped we'd have good clear skies this evening in Brisbane, like BOM predicted.
This eveing, after being driven back upstairs from the back yard by the mozzies, I remembered Challenge number 4. Figured I'd have a go at seeing if I could see it.
Set up the scope on the patio, then checked what I was looking for, and returned to the scope, and in those scant 5 to 10 minutes of looking up what I needed, clouds had rolled in and there was no chance of seeing the Moon.
Damnably frustrating.

edit: fix typo

[mental4astro]

Challenge No. 6

Naked eye observation of Uranus!

I mentioned earlier that Uranus can be seen naked eye. I've seen it on many occasions myself.

So, the challenge is to do it yourself!

Reckon it's easy? Here's what you need:

* Mk 1 pair of eyeballs - no telescope or binos - eyeglasses permitted... :P
* Dark site - Uranus shines at around magnitude 5.8, so forget seeing it from Sydney's CBD...
* Good transparency - this is the deal maker/breaker! You may be under the darkest of skies, with no light pollution anywhere other than that created by the stars themselves. But unless the sky is VERY TRANSPARENT, you won't stand a chance. Transparency is how clear and clean the atmosphere is. Any hint of mist or fog (heavy dew is a tell-tale sign of dodgy transparency), smoke, dust, or any other type of haze inducing muck, then the sky will lack transparency, and the faintest stars that are actually visible will not be. Being able to see Uranus naked eye is a good indicator of good transparency.

TIP: If you manage a night and site that ticks all of the three conditions above, you will also be able to see star fainter than Uranus, even pushing magnitude 7.

With Uranus being visible naked eye, it means 7 out of our Solar System's planets are visible naked eye.

There are many good apps that will show the current location of all the planets, some of which are also free.

Have a shot! :D

Alex.

[JeniSkunk]

Doubt I'll get a chance to try to do this one.
With the space needed for my wheelie walker (Post a photo of yourself thread), and the kitchen chair I use as a stand for my telescope, being able to get a lift out to any dark site seems quite unlikely, so I'll have to endure the grey haze of bad light pollution, and pass up on dark site challenges.

[mental4astro]

Jen, i sympathize with your situation. I certainly understand mobility difficulties. I'll come up with some more urban-doable challenges. There are many people, young and old, who have mobility difficulties - video astronomy is a great way that helps many people participate in astronomy, and at minimal cost :)

That's given me an idea for this last Challenge...

Challenge No. 6.1... :lol:


Uranus & Neptune using binos or small aperture under urban skies.

Following on from Jen's post, I don't see why I cannot modify my challenges. Both Uranus and Neptune can be tricky to pin under urban skies, so have a crack with your binos, small scope or evdn just your finderscope!

Alex.

[mental4astro]

Challenge No. 6.2

Mars & Neptune conjunction this early December!

Ok, are you still struggling to find Neptune?

Well, here's your chance to nail it for certain!

Next week between the 6th and the 8th of December, Mars will come within 1° of Neptune. In fact, on the 7th it will be within 4 minutes of arc! In other words, both planets will be in the one field of view, with as much magnification as you can muster on the 7th!

Below are a few Sky Safari screenshots of the conjunction for the 6th, 7th and 8th of December, along with a screenshot of the location Mars can be seen in the sky - not hard really as it will be the brightest "star" in the western sky in the early evening.

NOTE TO SCREENSHOTS BELOW: Be aware that the three zoomed-in screenshots are all of slightly different scale! While the spacing may look similar between each, note that each screenshot lists the angular separation between Mars and Neptune for all three nights. And in the top right of the screen shot the field of view of each shot is also noted.

Happy hunting,

Alex.

[morls]

Thanks Alex, this is great. :thumbsup:

[ausastronomer]

Congratulations Alex,

Don't be surprised if your friends soon name a space mission, or spacecraft after you and in 200 or 300 years time you will be remembered along with the greats like Galileo, Cassini, Huygens, Hubble etc !

Cheers
John B

[Wavytone]

Found Neptune a pretty easy target last night - start at Mars and offset from there. Small blue-green disk at 200X in poor seeing.

The conjunctions of Neptune are also interesting historically in another respect because when it was discovered it was 1 degree from Saturn.

Some of the C18-C19 scopes clearly had exquisite optics based on the double star observations, I’m a little surprised this 8th mag interloper wasn’t noticed in earlier conjunctions.

[mental4astro]

We see more than 50% of the lunar surface from Earth!

Actually, we get to see closer to 60% of the lunar surface because of the Moon's wobble.

This wobble is called libration. The little manic gif below shows this pattern of libration over the course of a lunar cycle. Part of this also sees the Moon get closer (perigee) or further away from us (apogee) in its orbit around the Earth. When the full Moon coincides with its perigee, we get the so-called Super Moon.

241968

For features along the limb of the Moon, libration can make these features more prominent or even disappear behind the Moon.

I have a couple of sketches I've done show a large crater along the limb, Drygalski, one with a favourable libration apparition, and the other during a poor libration.

241969 , 241970

There are many significant features that are totally dependent on a favourable libration in order to be seen. If you've ever attempted to track down a particular feature along the limb, and were frustrated in not being able to see it, very likely it was due to that feature having a poor libration apparition. Or a feature you saw once along the limb, pretty much disappearing next time you tried to spot it.

Alex.

[JeniSkunk]

I think you need to increase the time between frames of that animated .GIF of the moon.
The frames are cycling too fast to be able to make out details.

[mental4astro]

Thanks for the suggestion, Jenifur.

This is a gif I found that was small enough in file size for the IIS picture editor to allow posting. Every other libration gif was too large. If you can find a better libration gif, or know how to manipulate a gif graphic, let me know and I will gladly replace the manic one I posted :)

Alex.

[Wavytone]

Challenge 6 - yes Uranus is naked eye in good condition.
Challenge 6.1 - last year my 70mm APO easily showed Uranus nicely as a tiny blue green disk but Neptune is quite a bit harder as it was not resolved.

[JeniSkunk]

I had a look at the .GIF in one graphics program I use, NeoPaint.
The .GIF was using 20ms between frames.
I edited the .GIF for 50ms and 75ms, and attached them to this post.

[mental4astro]

Challenge No. 7


Concentric or Bullseye craters.

Time to get funky with the Moon!

I have to say I've only come across concentric craters in the last four weeks! All by chance after a sketch I did last month of Palus Epidemiarum, the Marsh of Epidemics. While working on the inner most part of the flat lava field, there was one really small crater that seemed to "wink". While all other features were quite static when seeing was stable, this little crater seemed to shimmer sooner and for longer when a band of thermal interference wafted across the field of view that makes the image blur just a little.

When I concentrated on that little crater, I got a heck of a surprise, it was a concentric crater! My first ever! :D

Yes, sure I had heard about concentric, or bullseye, craters, thinking that these were just coincidental double impacts in the same spot that created these. I also thought that the likelihood of finding these would be bugger all to none because of the probability of this happening is just soooo remote that these would also have to be very, very small craters to cope with the impact forces. So I didn't pursue these any further than a fleeting thought.

But then the crater Marth made an unexpected appearance, and set me on a new path of discovery with the Moon :D

Lunar 4 orbiter image of Marth. NASA photo.
243811


Lunar Reconnaissance Orbiter image of Hesiodus A. NASA photo.
243823

Both of the above concentric craters are targets in this Challenge.

Concentric craters are rare. However, their origin is not from double impacts as one would initially think as I did. Instead these are a combined result of first an impact followed then by subsequent magma intrusion caused uplift in the floor of the crater, but not enough to have lava flow into the crater, instead just enough to cause an upheaval within the crater floor.

A few things all concentric craters share is they are all smaller than 20km in diameter, most between 8km and 9km in diameter, and all are very old features. About 80% of concentric craters also occur around the edge of the Seas, with the balance deep inside the Seas and within the mountainous features.

Because of their relatively small size, concentric craters are not a commonly known feature and very rarely made a specific feature to chase down. Despite their small size, there are a few that are large enough for most amateur size scopes to resolve. And that they are rare makes them a worthy and challenging feature to chase down. And with the current new lunation phase of the Moon coming in, it is a timely Challenge to prepare for.

Below is a list of the larger concentric craters to look for. The list progresses from East to West. A good lunar atlas such as “Virtual Moon Atlas” (https://virtual-moon-atlas.en.uptodown.com/windows) will show all of the concentric craters below. One tip to find them is to have the terminator one, two or three days past the target's location to take advantage of the shallow angle of the Sun to produce the longest shadows. The two smaller ones listed, Marth and Gambart J, will really test the quality of your optics to be able to resolve the very fine details/shadows.

Name & Diameter
Firmicus C, 15km
Apollonius N, 10.8km
Colombo B, 16km
Crozier H, 11km
Leakey, 13km
Pontanus E, 13.7km
Fontenelle D, 16.8km
Hesiodus A, 15km
Gambart J, 7.7km
Marth, 7km
Damoiseau D, 17km
Cavalerius E, 10.1km

Concentric craters are unique, small and very niche features. Just perfect for a lunar challenge!

Happy hunting,

Alex.

[mental4astro]

I'm looking at Pontamus E right now (Sunday May 12, 9:14pm). Very easy to make out its concentric structure at 364X in my 7" Intes Mak. I struggled make out the concentric structure at under 110X.

What is very interesting is Pontamus E is much shallower than the craters around it, including those smaller in diameter - evidence of the volcanic material that had pushed up from underneath, lifting the floor of the crater. Fascinating stuff! :)

The shallow nature of these craters then stands to reason why I struggled make out the concentric structure of Pontamus E below 110X. Most likely tomorrow night the shadows may be already too short to make out the concentric structure. One, two and no more than three days out from the terminator is optimal to view these.

No sketch tonight though <sigh> - way too dewy here at home as this will stuff the paper. Seeing was pretty good too, but no cigar tonight.

Alex.

[JeniSkunk]

Here in Brisbane, we got clouds last night, after a beautifully clear Saturday night.
Tonight looks like being more clouds and rain. :(

[mental4astro]

If tonight (Tuesday May 14) becomes clear, Hesiodus A is target No. 1! Terminator is clear of it, but not too far to make spotting Hesiodus A easy.

Gambart J is also visible, and a similar distance from the Terminator as Hesiodus A. Contrast in the size between these two is the main thing, with Hesiodus A being 15km in diameter, and Gambart J being 7km.

Fontenelle D is right on the Terminator, so should be an interesting proposition too.

If you are looking for a very good lunar atlas app, LunarMap HD (https://play.google.com/store/apps/details?id=mobi.omegacentauri.Lunar Map.HD&hl=en_AU) is excellent. It shows and lists all of the concentric listed below too.

Alex.

[JeniSkunk]

Just had a look at Clear Outside for my part of Brisbane. No joy for getting a clear night tonight.
I was told about Clear Outside by Pete from Astro Anarchy. He runs it on his iPhone, and I found it on the Google Play Store for Android (https://play.google.com/store/apps/details?id=com.firstlightoptics.cle aroutside). I regularly use it to get an idea of if it will be worthwhile even thinking about setting up my scope for an evening.

edit: fix typo

[mental4astro]

Had a squizz at the Moon last night, with one of my main aims being to nab the three concentric craters Hesiodus A, Gambart J and Fontenelle D.

Hesiodus A is surprisingly easy to see and make out its bullseye structure. I have done so many sketches around that area, but Hesiodus A has always escaped my attention, yet it is so blooming easy to make out its concentric structure... :doh: Easy to make out at 100X.

Gambart J is not 7km in diameter as listed. If Hesiodus A is 15km, then Gambart J should still be easy pickings at higher magnification. But it's a real challenge. Seeing conditions were not too good last night, and other than seeing a small crater, I wasn't able to pull out its concenctric nature. Seeing conditions need to be much better for this little sucker. When I saw Marth a few weeks ago, yes seeing was much, much better that night.

Fontenelle D is a tricky sucker too. It is easy to see this crater, but it is much more foreshortened due to its closer proximity to the lunar limb. It also needs the terminator to be further away from it than it was last night as the crater's interior was totally in shadow. If I could have another shot at it tonight I'm sure the crater floor would be better illuminated, though the foreshortening would mean a bit more concentration to make out its internal structure.

Alex.

[mental4astro]

I was mistaken about Gambart J - it is the diameter quoted. I had another look for it last night. Seeing was better and I was able to make it out. It is though very shallow, much shallower than the two very small craters beside it to the point that Gambart J the previous night had next to no shadow that was perceptible compared with those two tiny craters. Last night what I saw was the brighter edge of its rim which was easy enough to identify under the better seeing conditions, but no shadows to be able to see its concentric structure.

Fonetenell A's concentric structure may need until tonight to spot due to its position close the the lunar limb and the Sun needing to be higher up.

Next is Marth, hopefully tonight.

Alex.

[sil]

Sorry to be so long in reading this great thread. Just wanted to add my pov on the FirstScope. I could not recommend this to anyone. It does resolve surprisingly well with a better eyepiece, I used Baader Hyperions. However the point of a first telescope should not be to teach " this product will not live up to any expectations out of the box despite the claims written on it. You need to spend more money for reasons we wont tell you right now to be happy and comfortable using this telescope". A first telescope should make people go wow and this package cant. Like most telescope packages bundled with everything you need the extra bits you need are always lowest quality to keep the bundle cost low, so mounts tend to be flimsy and eyepieces which do the heavy lifting with the photons give a view thats uncomfortable to get your eye in and full of all sorts of distortions further ruining expectations.

I have many times recommended and bought for friends The Orion 100mm Tabletop Dob that I bought. Its similar to the firstscope, a little bigger, red aluminium tube. But key with this scope is that the two eyepieces (10 & 25mm) it comes with are good quality, far above all other "supplied" eyeipeces I've had. Views out of the box really are crisp and comfortable which makes for an instant happy experience. Sure its only a little larger than the FirstScope and was when I got mine over twice the price, my experience was easily ten times better and I still use it regularly. I think it may be a true unicorn: a package that outperforms its price by miles nothing more to buy or replace to "get it working". Its the sort of scope that helps grab someone and keep them in the hobby. Yes you can spend a bit more and get something bigger and more capable but I bet thats only if you buy better eyepieces and for newbies they expect, and deserve, a good viewing experience out of the box. A bad experience they blame the OTA since they dont yet know a better eyepiece would help matters. Especially at the low end entry scopes a new eyepiece could easily cost more than the scope did. Children using my little orion have no trouble with kidneying blackout in the eyepieces and love to be able to point it all around the sky looking for things. Its also my first scope to show me Neptune about 6 years ago, star hopping with paper and digital charts I easily found the blue dot. Wasn't a disk, just a dot, definitely blue and definitely not sharp as the surrounding stars. Right where my digital map said it would be . It was a memorable find for me and still is on this little entry level scope. Saturn and Jupiter look beautiful in it too. So that's my recommendation for first timers or if you want to get someone into the hobby, even though it doesnt look impressive like the garbage that sometimes show up in aldi etc its simple and it really works well. No need to buy anything else. It also has a threaded socket under the mount to allow it to be attached to a regular camera tripod if you want. My First scope I converted to a white light solar telescope for sharing views with others, It won't focus with cam attached though (more modding required).

[JeniSkunk]

Sil, what you describe with the cheap and nasty 76mm Newts, is more of the same complaints I read about them 12 months ago, when I was looking at buying my first telescope.
It's why I decided on the 130mm SkyWatcher. Because the shop I was buying from didn't carry Orion, no way to consider the 100mm. The 130mm I have is a really good balance between size and capability for a first scope.

[mental4astro]

Challenge No. 8

White ovals on Jupiter.

While Jupiter is still a good target in the sky, it is a good time to try to spot an illusive feature. We are familiar with the Great Red Spot, there's another storm feature that is not so well known, or even expected, White Ovals.

These are also storm systems on Jupiter, however they are not long lived systems. There may also be none visible at any given time, or maybe one, or sometimes several.

White ovals can appear in the the Equatorial Belts (sometimes even right beside the GRS) and are frequently seen in the subtle belt system immediately out from the Eq Belts towards the poles.

However, these White Ovals are illusive and can be difficult features to spot. Good seeing conditions certainly are important for a stable image, but these will also test the contrast capacity of your gear, particularly those White Ovals on either side of the Eq Belts. An 80A Blue filter can help, as can a 30 Magenta filter. Patience is the key here.

This is a small sketch I did of Jupiter showing a White Oval sitting in the North Eq Belt, along with the GRS and a shadow transit of Europa from May last year. I used my 8" f/4 dob.

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The NASA pic below shows these White Ovals and gives a good idea on where they can appear on Jupiter. You will also notice a second but smaller and more subtle Red Spot.

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"Trick of the camera". Please note that photos of Jupiter are not an accurate representation of how it appears through the eyepiece. Photos are processed to help bring out colours and features that in the eyepiece are actually very subdued. Do not expect to see Jupiter the same way as the above NASA photo does. The features are there, but they really do require a patient eye to see them. Rush, and you will miss them. THIS is what makes the Challenge! THIS Challenge is one what will really test you.

Happy hunting,

Alex.

[mental4astro]

If you have attempted any of the Challenges I have posted, please relay your experiences here. This is significant in so many ways!

If you have struggled there may be various reasons that could actually be very easily addressed and remedied, but only if you say something. It could be an experience thing. It could be a scope thing. It could be atmospheric and nothing to do with the scope or your experience, but frustration may get the better of you, and you just don't recognize the tell-tale signs. These Challenges are not designed to be Mission Impossible, but to offer different lunar and planetary features to look for, some of which will yes be difficult, but not all of them, and not most of them!

If you have succeeded with any of them, sharing your experiences here will encourage others to do the same, and show me that I am providing a good source of info.

Your experiences are unique to you, your scope and your level of experience, all of which are different to mine. By sharing your experiences you not only inform others with similar points of experiences as you, AND you also help me see things in other ways that I would not have thought of before. For despite what experience I may have, I might have forgotten some of those little details that can help others even more.

You might have some questions but you may feel that your questions could be seen as silly. The ONLY dumb question is the one that is not said! I DON'T know it all, and other people will certainly be able to fill voids I cannot :)

Don't be shy, and don't feel intimidated by what I say or my sketches. I too started from ZERO and my sketches are just my niche and nothing I make any judgements on others. I use my sketches to show people what they can REALLY SEE through a telescope! as photos can be deceptive at times.

And ultimately, without feedback I end up seeing no point in continuing to offer help.

Alex.