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Decision for planetary/lunar telescope.

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 I am looking for a good but small,maneageable scope for visual observation of lunar,and planets. ,also Messier brilliant,luminous...and I like know your advice on this theme.

I have some canditates, a refractor ED70/80 with I think a good Barlow lens 2X or 3X factor, or a Maksutov-Cass. 127mm f/1500 ..

In other hand, for this telescopes , is best a star diagonal mirror or a prism diagonal ?

In your opinion which can be the best for this kind observation ?

Thanks in advance for yours opinions and advices.



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In my opinion there is no substitute for aperture, visually. The ED 70/80 will be very nice on larger deep sky objects (I have an 80mm F/6 triplet in that role), but will be limited on planets. A Mak-Cass of 127mm will outperform an ED 80 on planets quite easily, and also be better on almost all DSOs. Several Mak-Cass scopes come with a star diagonal, so I wouldn't worry about getting a better one initially. An ED 70/80 would require a 2" diagonal, and most of those have a mirror rather than prism

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I agree with Michael.

I have the same Mak in your list (a Celestron SLT 127), and I'm very satisfied with it.

You won't need a barlow, and if you buy a camera with small pixels (like mine) not even for imaging.

Of course, it's a slow focal ratio scope, so for deep sky object won't be extremely satisfying (though certainly not that bad either, with a couple of good eyepieces).


Edited by GuLinux
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Hi pluton. Of the 'scopes you mention go for the Maksutov-Cass. 127mm. Is it the SkyWatcher branded model? - if "Yes!" they do have a good following here on SGL.

In my opinion catodioptrics are lunar/planet killers. The only downsides are...

  1. a dew shield is a must have.
  2. cooltime of 30+ minutes prior to use.
  3. a narrow field of view.
Edited by Philip R
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BTW, the speed of the optics is irrelevant for visual use on DSOs: an F/5 Newtonian with a 10mm EP gives the same 2mm exit pupil as an F/12 Mak-Cass with a 24mm. In fact, the smaller central obstruction of the Mak-Cass will mean a bit more light than the F/5 Newt of the same aperture. The main advantage of a fast scope on DSOs is that it allow a wider maximum FOV for a given EP barrel diameter. Most DSOs fit easily within the FOV of my Celestron C8, for the few that don't, I use either binoculars or the 80mm F/6.

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If all you want to use it for is viewing and you want to use a refractor me personally will not go smaller than a 80mm with good EP's and a good 2x barlow . If you can go bigger up to a 5" or a 6" refractor that would be great too . Celestron has  a  6" refractor that all I have heard is how great the views are but it's a Chromatic so CA will be evident . Basically tho any refractor 80mm or bigger I recommend or a 8" or bigger dob . A 6" will work but a 8" will give more light and a bigger object . Out of all scopes tho a refractor will give you the best clearest image for viewing and small ones are easily transported . Anything else maybe a little more harder but can easily be transported also .

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Personally my minimum aperture for satisfying observations is 100mm but 120mm is better still. Given the choices stated  I'd go for the 127mm Maksutov but I'd suggest a 6" f8 newtonian or dobsonian if you don't have a suitable mount already.

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Owning and having used a 80mm refractor, 8" SCT and a 14" Dobsonian, comparing the three the easiest to use/setup with most visible objects considering the aperture is the 8" SCT. On a dark night the 8" SCT shows an amazing amount of DSO as well as moon and planetary detail, setup and collimation is very easy and quick.

The 80mm refractor doesn't show anywhere near as much detail as the 8" on both DSO or planets and the moon and I really only use it for wide field astrophotography. 

The 14" Dobsonian definitely shows more detail on Jupiter (fine structure easily visible in the cloud belts) and shows DSOs brighter with much more details, but the collimation, setup time and sheer size of it make it a lot lot less portable.

Taking all of the factors into consideration, I recommend to get a 8" SCT and you'll never look back.... by far the best bang for the buck/aperture/size.


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