I have often based at the stars and have been fascinated by what is outside our atmosphere. I have decided to buy a telescope so I can enjoy some of the wonders of our universe. I have been researching for a week or 2 and was surprised at the available options, every time I found a telescope I liked, up pops another one and have been going around in circles so I thought i would ask the experts.
One thing I am lacking is i have no reference as to how the images will look like for each type of telescope.
Here are my priorities, ( which have been constantly changing over the past few days) .
Priority 1: portability, I want to be able to take it with me in the car when I go away. ( due to go to south coast, Berry and Tilba Tilba over Easter and want to take one with me) Priority 1a: I am interested in DSO’s but love to look at planets. I am guessing if I get great DSO views the planets will also look great. Priority 2: Auto-tracking plus manual capability but will settle for manual only if i can get some great DSO views within my budget Priority 3: Terrestrial viewing.
Here are the ones I have narrowed it down to ( in my budget - around AU$600):
1/ Skywatcher Heritage 130 Tabletop Dobsonian fl 650mm (collapsible)
2/ Skywatcher Virtuoso Mak90 tracking tabletop Dobsonian fl 1250, I like the upgrade path to a GOTO as well ( there is a 114P version fl500mm but I can’t seem to find one for sale)
3/ Skywatcher 6 inch Dobsonian ( not as portable as the others but the 6 inch aperture would give me clearer images and ability to look deeper into space ( did I get that right?)
No preference to skywatcher willing to look at others, I am also willing to upgrade the viewing lenses if I need to.
I think I got the handle of the aperture size importance, please confirm - the bigger it is the more light it will allow through which means I can look deeper into space also the larger the max magnification.
I still have trouble working out the role of the focal length on the quality of the images, eg the virtuoso Mak90 with fl 1250mm and the 114P with fl 500mm what differences can I expect from them ?
Thanks in advance for any advice that gets me started.
Welcome Mario to IceInSpace
So the highest theoretical magnification is often regarded as being twice the aperture (in mm). So a 125mm (5") scope could produce magnification upto 250 times. (subject to atmospheric conditions etc). Note we rarely get to the theoretical max due to crappy seeing conditions.
The magnification you can get is a function of the focal length and the eyepiece. Eg: a telescope with 650 mm focal length and using a 10mm eyepiece will produce a magnification of (650 / 10) 65 times. A 25mm eyepiece with the same scope will give 26 times.
Planets are relatively small, so you need a high magnification to get a pleasing view (people often suggest around 100-150 magnification).
DSO's are normally much larger so much smaller magnification is usually better viewing. But these are distant and dimmer, so the more light (bigger aperture) the better.
Hope this helps as a starter.
Feel free to ask lots of questions.
Oh, and re priority 4: astronomic scopes are not normally much good for terrestrial viewing due to image inversion and/or reversal (depending on type of scope).
All scopes are compromises; no one type or size will do everything really well.
Refractors[lenses, not mirrors] are great for astrophotography, grab and go,
[in the small to medium size range], and lunar/planetary work. They can, of
course, be used for any type of viewing/imaging, but other types will do a
better job. They are low maintenance, no mirror cleaning[or recoating when
scope gets old], and only a very infrequent collimation check.
Downside, achromatic refractors display more or less chromatic aberration[
false colour around the edges of bright objects] depending on focal length
and quality]. This can be greatly ameliorated, indeed almost completely
overcome, if you throw enough money at it, by buying an apochromatic one.
Reflectors are much more bang for your buck, being far cheaper aperture for aperture than other types of scope, and have the advantage of no
chromatic aberration,[if you ever see any false colour it will normally come from the eyepiece]. A 6"[150mm] scope has 4x the light gathering power of a 3" [75mm]. Square of the aperture in inches, so 3x3=9, 6x6=36. 8x8=64
so an 8" has just over 7x as much as a 3". A reflector is also generally size for size lighter than a refractor. Larger aperture also usually means higher usable magnification depending upon seeing conditions].
Downside, mirrors are exposed, so need occasional cleaning[and eventual
recoating], and collimation[ how frequently depends on whether one is a perfectionist, and whether the scope is moved around much]. Over about 6 " wind becomes more of a factor, and bulk also, if you are in any way
disabled, or perhaps elderly. The final downside is coma, where stars in
the outer part of the field of view are distorted, this being worse the
shorter the focal length of the scope. An f/6 is normally not too bad, but
f/5 or shorter, for imaging especially, a coma corrector is pretty much essential[not that cheap]. Years ago many Newts were f/8 or even "slower", but today most are f/6 or "faster".
Catadioptric scopes such as Maks and Schmitt Cassegrains are probably
the best all rounders, and can be pressed into service for most needs.
SCTs as they are known, have by virtue of their design, great focal length,
so any given eyepiece produces higher magnification than it would in
either of the other two types. This means they are good for small targets
such as planets, planetary nebulae,and separating close double stars. Also good for high mag lunar work. They hold collimation much better than a reflector, and are simpler to collimate. They have a short tube, so wind is
not much of a problem. The eyepiece remains in a convenient position most
of the time. When an eyepiece is in place the tube is sealed, so the mirrors
can remain in pristine condition for a very long time. You can fit a reducer
which will give lower mag and a wider field of view for larger objects.[not
cheap].
Downside, relatively expensive compared to reflector[Newt], can be awkward to use when focuser is between the forks of a fork mount,
particularly when the mount is fitted with a wedge.At f/10 photographically
slow, better when fitted with reducer at f/6.3. Corrector plate prone to
dewing up. For perfectionists; slight loss of contrast due to central
obstruction, which is generally a bit larger than a Newt's one. Some
suffer from image shift when focusing.
Maks. Similar in some obvious visual ways to the SCT, but in fact quite different.
Being more complex to make, size for size Maks are a bit more expensive
than SCTs, and are limited in size on the commercial market. Anything
over 7" being very expensive. They are generally of even longer focal length than the SCT[typically f/12.5-f/15, and so are even slower photographically.
They are noted for high quality often high mag images of planets, small
star clusters, and lunar close ups etc: Downside: narrow field of view, so
not usually an owner's only scope.
raymo
Last edited by raymo; 22-03-2019 at 09:24 PM.
Reason: correction
Welcome to IIS, Mario.
Hope you enjoy the discussions here.
Quote:
I have often based at the stars and have been fascinated by what is outside our atmosphere. I have decided to buy a telescope so I can enjoy some of the wonders of our universe. I have been researching for a week or 2 and was surprised at the available options, every time I found a telescope I liked, up pops another one and have been going around in circles so I thought i would ask the experts.
One thing I am lacking is i have no reference as to how the images will look like for each type of telescope.
What you generally see in astronomical photos are hours long exposures, heavily processed. So any scope you use you won't see that, since the human eve is not sensitive enough to resolve that detail.
It doesn't mean that it's pointless to want to see more detail of what you CAN see though.
Quote:
Here are my priorities, ( which have been constantly changing over the past few days) .
Priority 1: portability, I want to be able to take it with me in the car when I go away. ( due to go to south coast, Berry and Tilba Tilba over Easter and want to take one with me) Priority 1a: I am interested in DSO’s but love to look at planets. I am guessing if I get great DSO views the planets will also look great. Priority 2: Auto-tracking plus manual capability but will settle for manual only if i can get some great DSO views within my budget Priority 3: Terrestrial viewing.
Here are the ones I have narrowed it down to ( in my budget - around AU$600):
1/ Skywatcher Heritage 130 Tabletop Dobsonian fl 650mm (collapsible)
2/ Skywatcher Virtuoso Mak90 tracking tabletop Dobsonian fl 1250, I like the upgrade path to a GOTO as well ( there is a 114P version fl500mm but I can’t seem to find one for sale)
3/ Skywatcher 6 inch Dobsonian ( not as portable as the others but the 6 inch aperture would give me clearer images and ability to look deeper into space ( did I get that right?)
Priority 3 and options 1 or 3 are NOT a viable combination.
A Newtonian reflector turns the viewed image upside down.
Options 1 and 2 as a combination is where things get interesting.
The weight limit for the Virtuoso mount is not exceeded by the 130mm collapsible Newtonian. So you can run the scope from the 130p, on the Virtuoso mount, or just as easily use the Maksutov-Cassegrain on the manual Dobsonian mount of the 130p.
For the record, I own a 130p, and I know how much its scope weighs.
Quote:
No preference to skywatcher willing to look at others, I am also willing to upgrade the viewing lenses if I need to.
Upgrading eyepieces is pretty well a must.
First up, a simple rule of thumb, the bigger the eyepiece value in mm, the lower it's magnification.
However telescopes do have a limit in what they can use. Get a too short eyepiece for your scope (smaller eyepiece value in mm), and it will over-magnify, blurring what you can see.
This becomes very important when you start using Barlows. A Barlow works on the focal length of a telescope.
So for the 650mm focal length of the 130p, a 2x Barlow turns it into effectively 1300mm.
Use a 6.5mm eyepiece in the 130p, and it magnifies to 100x. Use a 6.5mm with a 2x Barlow, and it magnifies to 200x. A 3x Barlow and the 6.5mm would be too much magnification for the 130p to work with.
Downside to higher magnification is, objects move across your field of view, fast, so you have to constantly slightly move the altitude of the scope to keep the object in view.
Second reason for upgrading, the quality of the optical glass used, the lens design, and the field of view.
Better eyepieces have better glass, more effective lens design, and a wider field of view than the stock eyepieces supplied with a telescope.
Third thing to be aware of, eyepiece diameter. The common standards are 1.25inch and 2inch. The three telescopes you list for consideration all use 1.25inch focusers.
Quote:
Thanks in advance for any advice that gets me started.
I'm not going to wade in on the choice of scope; there is some great advice in the post's below & Raymo in particular has put together a great summary of the strengths and weaknesses of each scope type.
I will however, direct your attention to some threads in the beginners talk section posted by Mental4Astro regarding Lunar, planetary & nebula viewing..
These among some other posts Alex(M4A) has posted are an excellent resource for starting out as they explain what you can actually see, why & how to get better at seeing (because it does take practice)...
I was going to link to them in this thread but, I can't actually find them.. however, I have them collated in word format so, if you would like them, send me a PM with your email address & I will happily forward them to you.
Oh, and re priority 4: astronomic scopes are not normally much good for terrestrial viewing due to image inversion and/or reversal (depending on type of scope).
Regards
Allan
You can get a diagonal that allows it and not expensive, I use one for my ED Skywatcher grab and go 72mm
I am new to this so not sure if i have used quotes properly.
Quote:
Originally Posted by JeniSkunk
Options 1 and 2 as a combination is where things get interesting.
The weight limit for the Virtuoso mount is not exceeded by the 130mm collapsible Newtonian. So you can run the scope from the 130p, on the Virtuoso mount,
What will i need to do this, I am guessing a suitable mount connected to the 130P installed at the right spot to allow the 130P to rotate to a vertical position.
Also because of the eypiesce location on the 130P I will have to choose the right height to set up the 130P. I believe i can get a the Virtuoso onto a tripod which would solve this challenge, is that right?
Quote:
Originally Posted by JeniSkunk
or just as easily use the Maksutov-Cassegrain on the manual Dobsonian mount of the 130p.
So I will need another Telescope, a Mak, to load on the 130P mount?
Quote:
Originally Posted by JeniSkunk
Third thing to be aware of, eyepiece diameter. The common standards are 1.25inch and 2inch. The three telescopes you list for consideration all use 1.25inch focusers.
I haven't come across so far, if this is the case is there an adapter that will allow me to use a 2inch eyepieces?
I am new to this so not sure if i have used quotes properly.
You got the quoting system exactly correct.
Quote:
What will i need to do this?
Nothing extra needed, to use the scope from the 130p on the Virtuoso mount, or use the 90mm Mak-Cass on the 130p mount.
Both scopes use a standard Vixen rail.
On the mount, you tighten a mount rail bolt, to hold the Vixen rail on the scope, securely on the mount.
When you look at photos of the 130p, there looks to be a lever to adjust the altitude of the scope. That's actually the mount rail bolt.
When you unpack the 130p, or the Virtuoso, you need to loosen the mount rail bolt, so you can get the scope clear of the packing foam at the rear of the scope. So basically right from the get-go, you get to learn how to use and adjust the scope on the mount.
Quote:
I am guessing a suitable mount connected to the 130P installed at the right spot to allow the 130P to rotate to a vertical position.
On the 130p mount, there is plenty of back clearance to move the altitude of the 130p scope to zenith.
However, on the Virtuoso mount, using the 130p scope, you need to move the scope forwards on the mount, to an unbalanced position, to have the back clearance, to move the scope to zenith.
Quote:
Also because of the eypiesce location on the 130P I will have to choose the right height to set up the 130P.
I just have my 130p set up on an old wooden kitchen chair. You can see that in my avatar pic. As you move a Newtonian scope's altitude up, the eyepiece also moves up. So you use a lower stand to set the scope up on.
With the Virtuoso, you need something a bit higher, like a table, since the eyepiece on it moves lower, as you move the scope's altitude up.
Quote:
I believe i can get a the Virtuoso onto a tripod which would solve this challenge, is that right?
People have modified the 130p mount to put it onto a tripod. But with the motors in the Virtuoso mount, I don't think you could do such a modification.
Quote:
I haven't come across so far, if this is the case is there an adapter that will allow me to use a 2inch eyepieces?
There's is. Outcast mentioned he has one for sale, a couple of posts earlier in this thread.
Apparently I withdrew the ad; can't remember doing that but, anyway, I've reposted it in the Accessories section of the classifieds if anyone is interested.
Adapters from China etc under £8 including postage, what is that $7,
Check out all small items on Ebay, I buy a lot of "bits" from China at MASSES less than other places and you are covered by Ebay/Paypal, I have NEVER had a problem and I am a 2000 item ebay seller and buyer
Nothing extra needed, to use the scope from the 130p on the Virtuoso mount, or use the 90mm Mak-Cass on the 130p mount.
Both scopes use a standard Vixen rail.
On the mount, you tighten a mount rail bolt, to hold the Vixen rail on the scope, securely on the mount.
When you look at photos of the 130p, there looks to be a lever to adjust the altitude of the scope. That's actually the mount rail bolt.
When you unpack the 130p, or the Virtuoso, you need to loosen the mount rail bolt, so you can get the scope clear of the packing foam at the rear of the scope. So basically right from the get-go, you get to learn how to use and adjust the scope on the mount..
I'm warming up to the idea of buying a Heritage Virtuoso Mak 90mm, and a skywatcher 130P.
That way I have a portable system with a tracker, 2 scopes one at f13.8 and another with f5 which will allow me to observe DSO and planets as well as terrestrial objects.
Astro Pete's http://www.astroanarchy.com.au/teles...Dob_Mak90.html, says I can mount the virtuoso on a tripod as well. I think I can do this within my original budget as well.
Anything wrong with my thinking here?
Last edited by PTZONE; 26-03-2019 at 08:03 AM.
Reason: Auto correction
Nothing extra needed, to use the scope from the 130p on the Virtuoso mount, or use the 90mm Mak-Cass on the 130p mount. 6
Both scopes use a standard Vixen rail.
On the mount, you tighten a mount rail bolt, to hold the Vixen rail on the scope, securely on the mount.
When you look at photos of the 130p, there looks to be a lever to adjust the altitude of the scope. That's actually the mount rail bolt.
When you unpack the 130p, or the Virtuoso, you need to loosen the mount rail bolt, so you can get the scope clear of the packing foam at the rear of the scope. So basically right from the get-go, you get to learn how to use and adjust the scope on the mount..
I'm warming up to the idea of buying a Heritage Virtuoso Mak 90mm, and a skywatcher 130P.
That way I have a portable system with a tracker, 2 scopes one at f13.8 and another with f5 which will allow me to observe DSO and planets as well as terrestrial objects.
Astro Petes http://www.astroanarchy.com.au/teles...Dob_Mak90.html I can mount the virtuoso on a tripod as well as upgrade with a GoTo if I want to later I think I can do this within my original budget as well.
I'm warming up to the idea of buying a Heritage Virtuoso Mak 90mm, and a skywatcher 130P.
That way I have a portable system with a tracker, 2 scopes one at f13.8 and another with f5 which will allow me to observe DSO and planets as well as terrestrial objects.
Astro Pete's http://www.astroanarchy.com.au/teles...Dob_Mak90.html, says I can mount the virtuoso on a tripod as well. I think I can do this within my original budget as well.
Anything wrong with my thinking here?
With getting a tripod for the Virtuoso, you just have to make sure it can handle the total weight and remain stable.
The main weights involved:
4.0 Kg Virtuoso mount with batteries
1.4 Kg 90mm Mak-Cass scope
3.6 Kg 130p scope
So using a tripod with the Virtuoso mount, the tripod has to be able to handle weights of at least 8Kg (the total weight of the Virtuoso mount and the 130p scope).
I'm not sure what prices, properly stout camera tripods are, and how badly such a tripod will dent your planned budget.
There's also another weight limit to be aware of. The one for the helical focuser on the 130p, 250g. Too heavy an eyepiece, and the plastic plate the focuser is on, will sag.
The 130p scope isn't much good for cellphone astrophotography because of this.
170g and up decent eyepiece
60g - 70g 2x Barlow
150g - 180g cellphone
285g telescope cellphone holder
So for cellphone astrophotography, you're well over the weight limit for the focuser of the 130p.
You could record short hand held videos through the eyepiece using your phone, then process them as you would a video taken with an astro specific camera. This works well enough for lunar or planetary and will teach you right from the start one of the main elements of AP: data processing
BTW dobs make awesome terrestrial scopes if you can live with the tilted view. I've used my 8" for birding several times and the detail visible was insane.