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What to expect from 180 Maksutov Visual

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#1 HotRod217

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Posted 26 January 2021 - 01:35 PM

Hello everyone, 

 

what can I expect when using a 180/2700 f/15 Maksutov Cassegrain Telescope for deep sky visual observing? I found this video showing a live view from a 10 inch reflector: https://www.youtube....ist=LL&index=21

I know that the field of view with the Cassegrain is much narrower, but would I be able to see anything at all? 


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#2 bignerdguy

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Posted 26 January 2021 - 01:55 PM

Unfortunately that video is rather misleading.  That isn't what you would see with your eye, that is what the camera saw when using a higher ISO setting.  Visually you would not see many of those DSO's because they are too faint.  Things like most nebulas and galaxies are so faint it takes long exposure photography and a larger telescope to bring out the details.  Visually what you will see with some of the brighter nebulas is a fuzzy cloud that looks grey and after learning how to look at it you might start to see some minor color (like red or green).  Star clusters will probably be the easiest to see since they are usually brighter than most fainter DSO's though depending on the size and brightness of the cluster may either resolve individual stars or look like a clump of fuzz.  Your scope will pull planets and brighter objects up well enough but for the really faint objects (like the crab nebula for example) you need a really large scope and a long exposure to see anything at all. Of course if you have a REALLY large telescope (like 18" or above) then you might be able to see some of  the fainter DSO's in a low light pollution environment.

 

Either way what you see with your eye, which isn't as light sensitive as a camera, will not be what you see in online images since the cameras used will always be more sensitive and most images will be long exposures anyway.  Still there is a lot you can see anyway, Orion's nebula for example is a popular target as it is very bright.  Comets and planets are also popular as are many star clusters. Most galaxies wont be visible though you might be able to see the core of andromeda, it wont look like much but it might be doable, idk.  You do need a very dark location though to make out some of the fainter objects, looking at them from a city with bad light pollution wont work for fainter objects, even with light pollution or narrow band filters, depending on how bad the pollution is in your area...


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#3 Voyageur

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Posted 26 January 2021 - 02:07 PM

For each of the objects, the video first shows a couple of seconds of a video capture they have labeled “live view,” which gives a reasonable idea of what to expect under dark skies at the eyepiece with a scope of small or moderate aperture. It’s just a rough approximation. I have seen, for example, M13 and M31 look better in an 8” scope under good viewing conditions than the live views shown in the video for those first few seconds. 

 

For each object, after the so-called “live view,” the video then shows an image acquired over time. You won’t see views like that at the eyepiece of your scope. 
 

The title of the video is incomplete.The description below it is more accurate, but overall, the video creates a misleading impression. If you want views like that, you should investigate EAA. You need a camera, a computer, and video capture software to see views like that, onscreen.


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#4 SeattleScott

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Posted 26 January 2021 - 02:08 PM

7” aperture is a moderate size scope. You could track down quite a few faint fuzzies at a dark sky site but in town you would be limited to star clusters and brighter DSO.

Generally speaking the view will not necessarily be any narrower than a reflector. The AFOV of the eyepiece determines how wide the view is, generally. At low power a reflector will be able to go much wider. But at 100x magnification either scope can go about as wide. The difference is 30-50x is easily attainable with the reflector while the Mak might start out around 75x.

Scott

#5 ngc7319_20

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Posted 26 January 2021 - 02:13 PM

Yes, if you have dark skies, your views will be like the live or instantaneous images in that video.  But nothing like the summed or final images.  The eye is pretty good at live images, but does not have any ability to integrate for many seconds or stack the images.

 

What you have is basically a 7" scope, and you can see lots with that.  But not the details in photographs where they sum minutes of data.


Edited by ngc7319_20, 26 January 2021 - 02:14 PM.

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#6 sevenofnine

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Posted 26 January 2021 - 02:15 PM

Maks sometimes get a bad rap but then everyone seems to have one. Go figure lol.gif  My smaller 5 inch Mak does fine on many of the brighter DSO's. Finding them with a narrow FOV is the trick. Mine rides on a Sky Watcher go-to mount so that problem goes away. The Orion Nebula is up right now so you can get a good idea of your scopes capabilities. Look for the 4 little stars in a tiny cup shape. That's the Trapezium. Pretty cool, no? Other DSO's are not so easy to find. I've found that upgrading your widest eyepiece helps. Good luck and happy hunting waytogo.gif


Edited by sevenofnine, 26 January 2021 - 02:16 PM.


#7 MisterDan

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Posted 26 January 2021 - 02:18 PM

I consider several of the live images/sequences shown in the linked video to be "fairly" representative of visual impressions of nebular extent with dark-adapted eyes and ~medium-ish apertures under decent sky conditions (i.e. not polluted, but not Bortle 1, either). The "noise," of course, would not be there.

 

The M81/M82 live view is not dissimilar to dark-sky views I've had through in my 75mm refractor via averted vision.

 

The Ring Nebula live view shows perhaps a bit more overall contrast than I would expect from my refractor, but a good view through a six-to-seven-inch Mak may yield a similar view.

 

The live M13 view appears to be "fair" for an 8-inch aperture, but my small refractor (and dark-adapted eyes) could never yield that level of core resolution and contrast.

 

One note: his "first" Ring Nebula sequence was actually the Dumbbell (M27).  The 2nd (later) Ring was, indeed, the Ring (M57).

 

The live view of the Crab nebula is/was, I think, fairly comparable to views I've had through my small refractor (again, under dark skies).

 

Best wishes.

Dan


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#8 aeajr

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Posted 27 January 2021 - 03:16 PM

Hello everyone, 

 

what can I expect when using a 180/2700 f/15 Maksutov Cassegrain Telescope for deep sky visual observing? I found this video showing a live view from a 10 inch reflector: https://www.youtube....ist=LL&index=21

I know that the field of view with the Cassegrain is much narrower, but would I be able to see anything at all? 

You will be able to see lots and lots of DSOs. 

 

One of the scopes that I use is a 14" F10 SCT with a 3550 FL and it shows beautiful deep sky objects, planets and the moon. I also have a 127 mm F15 Mak with 1900 mm FL which also does a nice job on deep sky objects, planets and the moon.  In fact it does a really nice job on double stars.

 

Telescopes gather light.  They don't care about the source.   You have about a 7 " scope so yours gathers as much light as any other 7" scope.  

 

So where is the limitation of your scope?  

 

Low power wide field views are where that scope doesn't fit.  But that leaves a HUGE list of targets for you.  And, once you get past about 100X they are all about the same in terms of field of view which is determined by the eyepiece you use.

 

Assuming you have a 2" diagonal and a 38 mm 70 degree eyepiece, the widest field of view you can achieve is a bit less than 1 degree.  My 5" Mak, with a 1.25" focuser, achieves about a .85 degree FOV.

 

With a 1 degree field of view you can view at least 80% of the deep sky objects in the sky in their entirety, in one field of view.  And the ones that are larger than 1 degree can be viewed in pieces.

 

That leaves you enough nebula, globular clusters, double stars, open clusters and galaxies to keep you busy for the rest of your life. We are talking thousands of targets for you to chase. 

 

Now, what about the rest of the targets?   Well, that is why many of us have two or more scopes.  So a nice short focal length scope would make a great companion to your Mak.   

 

For example, I have a 102 mm F7 ED refractor on order to add to the fleet.   With that same 38 mm 70 degree eyepiece I will get about a 3.6 degree field of view. That is wide enough to view the entire Andromeda Galaxy in one field of view.  I can view the Pleiades with lots of room to spare.   

 

I have a 305 mm Newtonian too.  With that same eyepiece I get about a 1.7 degree field of view.  I would guess that more than 90% of all deep sky objects will fit in that field of view. 

 

So, I pick the scope that best matches what I plan to observe. But if the Mak is the only scope you have, well, you still have a lifetime of things to observe.   

 

Have no fear!  The universe is there to be discovered by you and your Mak!  Go get 'em!  wink.gif


Edited by aeajr, 27 January 2021 - 03:37 PM.

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