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Walking on the Moon

Telescope for observing and imaging (SCT, RCT, APO?)

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Hi all,

I have been recently doing a lot of researches in order to find a good scope for both observing and imaging planets and deep sky with my DSLR.

I have a budget of 2000$/€ and I was quite interested in the Celestron AVX 8 EdgeHD or the 9.25 standard. I know that the EdgeHD is better for DSOs as it is more accurate and the 9.25 better for planets as bigger aperture. I was thinking getting the AVX 9.25 with a focal reducer f6.3 for improving field of view and correcting field curvature for DSOs, and this scope would still be good for planets. But I am still hesitating?

I did more researches and APOs (refractors) seem to be also a great option, I saw great imaging of DSOs with refractors like ED80 and seem to have better advantages (light weight, easier to setup, better result in bad sky condition like light pollution)? Younger I had a celestron refractor and a reflector and I remember using more often my refractor because it was easier to move, setup and had better result (sharper and more detailed view).

Also, but I don't know much about it, what about RCTs? I just heard that it takes longer exposure for imaging but can be more accurate than SCT?

Newtonian reflectors seem also to be good for DSOs, would one be good for planet as well?

Among all these options, what would be the best to get for both observing and imaging planets and DSOs for a budget of 2000$/€?

Thanks a lot for your help.


Edited by superyoche
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G/day mate as far as celestron sct i own the 925 edge hd it is awsome both of your choices a good but i would look at a heavier mount i run cgem .i think you will find avx bit light by the time you start adding imaging and guiding equipment .

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It sounds like you're floundering around a bit, not sure what you want to image.

For planetary you need a long (-ish) focal length with a high frame-rate camera, taking hundreds of frames and then stacking them, a SC would be a fairly good choice, whereas for DSOs you want a shorter FL (At least to start with) and (Preferably) a cooled CCD camera taking multi minute exposures, though you can get away with a DSLR, and the new breed of cooled CMOS cameras are causing a stir. This is where the short, fast triplet apos rule.

In any case you need to look to the mount. Although you can get away with a tracking Alt-Az for planetary, for DSO you need the best equatorial you can afford, even if it means reigning in your telescope ambitions.

But before you spend any money at all, buy this book, read it twice, think about what you want to do and if you want to go DSO, read it again.


Steve is a moderator on here, posting as Steppenwolf.

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Do read the book.

For DS imaging you need to have a reasonable match between the size of the camera's pixels and the focal length of the scope. This value is measured in arcseconds of sky per pixel. People do image efficiently between about 0.7 arcsecs per pixel and about 3.5. (These are ball park figures.) But  the 0.7 end of things is far, far harder than the 3.5 end of things. That is because the details you are trying to catch are much finer, so the autoguiding of the mount needs to be ultra precise and the seeing (the optical stability of the air) needs to be exceptionally good. If either or both of these factors are not up to scratch then you will simply fail to resolve the details available in theory and you would be far better off with a shorter focal length giving a wider field of view and resolving the same level of real detail.

For me an SCT is not a good choice for DSLR Deep Sky imaging. A DSLR likes a short focal length and a fast focal ratio. A small fast apo is the easiest way to good results, espeicially when starting out, because the setup is tolerant of minor errors and inaccuracies. Long focal lengths are not.

Alas, though, the planetary imager needs a long focal length and large aperture to support it and the visual observer always likes a bit of aperture. One scope does not fit all. Probably the nearest you can get is a Newtonian on a good equatorial mount, autoguided for deep sky. 

A good suggestion which often comes up is a small fast apo for DS imaging and a Dob for visual.


Edited by ollypenrice
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If you want to do imaging as well as observing, the best advice is to buy the best mount you can afford and think of a telescope later.
In m.h.o. The iOptron iEQ45pro is a great mount with good support. A big bang for the bucks. No comparisson with a AVX mount...
On the cloudy nights forum you can find plenty of comments on them.
It could easily carry a moderate sized telescope without any problems and it is quite lightweight. A future 9.25 SCT would be no problem at all.

In the mean time untill can buy a telescope, use your DSLR with the standard lenses and a guidescope with camera to get really familiar with your new mount.

There is no telescope available that can do it all, so you will have to make a choice. There is a way with reducers and/or PowerMates to extend the possibillities of a given telescope, though.

B.t.w.: a RCT is a p.i.t.a. to collimate and has a very small flat imaging circle. I.m.h.o.  not the best choice for a beginner.

Edited by Waldemar
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Thank you all for your replies and advices.

After some long thoughts and researches, I'm gonna go for the Skywatcher 120ED DS Pro with the HEQ5 Pro mount.

Do I need to buy anything else to be able to attach the 120ED to the HEQ5 mount? Basically do I need to buy anything else to start using the telescope?

I'm gonna also buy some accessories for astroimaging and I would require some help on what to take exactly:
- Skywatcher .85x Reducer/Flattener
- T adapter, what to take?
- T mount for Nikon DSLR, any specific one?
- Autoguider, what to take?
- Do I need anything else? Eyepieces?


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