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  #41  
Old 06-11-2018, 03:30 PM
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mental4astro (Alexander)
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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...


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.
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  #42  
Old 29-11-2018, 04:06 PM
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mental4astro (Alexander)
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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.
Attached Thumbnails
Click for full-size image (Mars & Neptune conjunction (4).jpg)
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Click for full-size image (Mars & Neptune conjunction (3).jpg)
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Last edited by mental4astro; 29-11-2018 at 06:15 PM.
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  #43  
Old 29-11-2018, 06:47 PM
morls (Stephen)
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Thanks Alex, this is great.
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  #44  
Old 02-12-2018, 12:54 PM
ausastronomer (John Bambury)
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Quote:
Originally Posted by mental4astro View Post
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

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!
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
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  #45  
Old 02-12-2018, 04:30 PM
Wavytone (Nick)
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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.
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  #46  
Old 25-03-2019, 04:17 PM
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mental4astro (Alexander)
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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.

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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.

Click image for larger version

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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.
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  #47  
Old 25-03-2019, 11:00 PM
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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.
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  #48  
Old 26-03-2019, 08:34 AM
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mental4astro (Alexander)
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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.
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  #49  
Old 26-03-2019, 08:52 AM
Wavytone (Nick)
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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.
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  #50  
Old 26-03-2019, 10:34 AM
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Quote:
Originally Posted by mental4astro View Post
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
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.
Attached Images
  
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  #51  
Old 10-05-2019, 08:23 PM
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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!

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

Lunar 4 orbiter image of Marth. NASA photo.
Click image for larger version

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

Last edited by mental4astro; 11-05-2019 at 08:16 AM.
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  #52  
Old 12-05-2019, 09:17 PM
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mental4astro (Alexander)
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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.

Last edited by mental4astro; 13-05-2019 at 11:06 AM.
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  #53  
Old 13-05-2019, 09:58 AM
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Here in Brisbane, we got clouds last night, after a beautifully clear Saturday night.
Tonight looks like being more clouds and rain.
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  #54  
Old 14-05-2019, 11:22 AM
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mental4astro (Alexander)
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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 is excellent. It shows and lists all of the concentric listed below too.

Alex.
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  #55  
Old 14-05-2019, 11:46 AM
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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. 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

Last edited by JeniSkunk; 14-05-2019 at 11:47 AM. Reason: fix typo
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  #56  
Old 15-05-2019, 09:02 AM
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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... 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.
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  #57  
Old 16-05-2019, 12:54 PM
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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.
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  #58  
Old 20-05-2019, 12:07 PM
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I have owned 3 of the Celestron FirstScope table top reflectors. All have been terrible at high power....Would I recommend these cheap little scopes to anyone? It depends.
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).
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  #59  
Old 20-05-2019, 12:25 PM
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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.
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