Scope Options for Imaging DSOs

[gnomus]

I have been slowly coming round to the realisation that, as with any form of photography, one needs different "lenses" depending upon the subject being photographed.

I currently have an 8" SCT of a little over 2000 mm focal length and a focal ratio of f/10.  This is fine for many objects.  However, it is unsuitable for some of the larger DSOs and, even for the smaller ones, the long focal length and slow "speed" of the scope is going to make long exposures challenging (I am already finding that out).  I am wondering, therefore, if I should get a second scope.

I have a Celestrom CGEM mount that has the wide (Losmandy) dovetail fitting.  I will be using my Nikon DSLR for imaging.  I have a ZWO ASI120 that should be usable for autoguiding.  I've read "Making Every Photon Count", and I have been following various threads here.  I have played around in Cartes du Ciel comparing the FOV of my camera (in FF and DX mode) and different scopes.

All of this has led me to wonder if the next logical thing to do is to get hold of a shorter focal length (and "faster") refractor, such as a Skywatcher ED 80 Pro: http://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-outfit.html

I appreciate that I would probably need to get the focal reducer to go with that.  

In searching around, however, it seems that there are a near endless combination of alternatives (even without the cost getting too out of hand).

Would any of the following be a better bet than the Skywatcher?  Or - a better discussion would be - what are the relative benefits versus downsides of these compared with the Skywatcher.....

http://www.firstlightoptics.com/equinox/skywatcher-equinox-80-apo-pro-ota.html 

http://www.firstlightoptics.com/user/william_optics_zs71_review.pdf or http://www.firstlightoptics.com/william-optics/william-optics-gt-81-triplet-refractor.html

https://www.altairastro.com/product.php?productid=16496&cat=270&page=1

or the possibly out of budget:

http://www.firstlightoptics.com/vixen/vixen-ed-81s-apo-refractor.html

I would be happy to consider other alternatives.

One issue is that these scopes seem to come with the narrower dovetail brackets and won't, therefore, fit directly to the CGEM.  What adaptor plates are recommended?  Or should I be thinking about something like this:

http://www.firstlightoptics.com/adm-replacement-saddles/adm-dual-saddle-upgrade-for-celestron-cgem-mount.html

If I went for the original choice I don't know whether I could get away with just getting the tube.  I have a diagonal (although it is only 1.25"), I have a Telrad and could get a new mounting plate for that.  So perhaps I could get away with just - http://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html

Any guidance, at this early stage, would be much appreciated.

Thanks in anticipation.

[Tinker1947]

Your first item should be a mount, something like this.....

http://www.iankingimaging.com/show_product.php?id=1256

or this 

http://www.iankingimaging.com/show_product.php?id=1287

[iksose7]

Looks like you have a few to choose from there!

The most obvious answer is to go with what you can afford. I personally would probably go for the William Optics GT81 if its in budget. Its a triplet which usually use better quality glass than doublets, such as the SW ED80, the WO71, and the AA L80ED you linked. A triplet will give you better colour correction and should hopefully have a little better build quality. I dont here much about Vixen scopes so tend to sway away from reading up on them but there price always seems very high so they cant be too bad.

Cant help ya with the saddle as i dont own a CGEM and wouldnt know what would work there!

Callum

[gary1968]

I think your CGEM will be a good imaging mount, despite its lack of compatibility with EQMOD. The skywatcher ed80 is a cracking scope for the money but the focuser let's it down so you might need to factor in a budget for a focuser upgrade......

Edit, the sw esprit is probably a better bet as the focuser is pretty good.

Sent from my Vodafone Smart 4 turbo

[Uplooker]

Your first item should be a mount, something like this.....

http://www.iankingimaging.com/show_product.php?id=1256

or this 

http://www.iankingimaging.com/show_product.php?id=1287

Hi Tinker1947,

I think you are being a bit harsh. The Celestron CGEM mount should certainly suffice, albeit as has already been mentioned, it does not allow the utilisation of EQMod. Others are better placed to recommend a scope from those suggested.

Ian

[gnomus]

Hi Tinker1947,

I think you are being a bit harsh. The Celestron CGEM mount should certainly suffice, albeit as has already been mentioned, it does not allow the utilisation of EQMod. Others are better placed to recommend a scope from those suggested.

Ian

Hi Tinker1947,

I think you are being a bit harsh. The Celestron CGEM mount should certainly suffice, albeit as has already been mentioned, it does not allow the utilisation of EQMod. Others are better placed to recommend a scope from those suggested.

Ian

I assumed he hadn't read all of my thread. That happens sometimes, in all the excitement.

[iksose7]

Hi Tinker1947,

I think you are being a bit harsh. The Celestron CGEM mount should certainly suffice, albeit as has already been mentioned, it does not allow the utilisation of EQMod. Others are better placed to recommend a scope from those suggested.

Ian

I assumed he hadn't read all of my thread. That happens sometimes, in all the excitement.

I thought so too at first also but considering the mounts he linked are Avalon and 10 micron i cant help thinking he was only having a bit of fun not exactly what you would recommend to someone you assume has no mount and is only starting the hobby!

Callum

[Tinker1947]

I thought so too at first also but considering the mounts he linked are Avalon and 10 micron i cant help thinking he was only having a bit of fun not exactly what you would recommend to someone you assume has no mount and is only starting the hobby!

Callum

I took note of the 2000FL, this does require a quality mount.....

[DaveS]

Yes, but reading the whole post he's planning to ditch the SCT for imaging and get the short. fast apo that would be ideal.

[gnomus]

I took note of the 2000FL, this does require a quality mount.....

OK. However, I am looking to drop the focal length quite considerably. That is why I am looking for scopes to use with the existng mount.

[gnomus]

Yes, but reading the whole post he's planning to ditch the SCT for imaging and get the short. fast apo that would be ideal.

Exactly .... but which one?

(And thanks for making my point for me. I must have been replying just as you did.)

[gary1968]

You could get a focal reducer for the sct, thay would take it down to f6.3......

[Thalestris24]

Hi

Yeah, there are just too many 80mm scopes to choose from! I've thought about getting one myself (I have an ST-80 but it would be nice to have an ED/Apo) but can't really afford one yet. I think Explore Scientific Essentials are worth considering e.g. http://www.explorescientific.co.uk/en/Explore-Scientific-ED-APO-80mm-f-6-Alu-essential.html I'm tempted by that one... Don't forget to budget for a matching focal reducer / field flattener. I'm trying to narrow down based on focal length (I don't want a scope that's too short for my personal tastes  ) together with looking at what others have written about particular scopes (here and elsewhere) and particularly trying to pick up on problem areas e.g. unwanted haloes, focuser problems. It's taking me a long time and I frequently pause for a while and put my search to one side in the hope I might win the lottery...

Good luck!

Louise

[MiguelMJr]

Hello Gnomus,

I would suggest an Astro-Tech 65EDQ. It is an astrograph so it is made for imaging and so has the flattener built in. It is APO. It is discontinued, so you should be able to get a good price on a used scope ($600 new) and it is wide field making tracking less of a chore.

[gnomus]

Hello Gnomus,

I would suggest an Astro-Tech 65EDQ. It is an astrograph so it is made for imaging and so has the flattener built in. It is APO. It is discontinued, so you should be able to get a good price on a used scope ($600 new) and it is wide field making tracking less of a chore.

Thank you all for all your suggestions. Please, keep them coming. I was always a little dubious about buying used lenses, since you never knew how much abuse they had suffered at the hands of their previous owner(s). I would have similar concerns about telescopes - they seem to me to be more 'delicate' than camera lenses. Are my concerns misplaced?

[gary1968]

Most amature astronomers really look after their kit, so in the most part your worries are a bit misplaced..... There will be the odd exception to this.

Sent from my Vodafone Smart 4 turbo

[iksose7]

I took note of the 2000FL, this does require a quality mount.....

Maybe so but in my opinion an Avalon or 10 micron may be a bit over kill considering a NEQ6 would do a fine job!  Bang on target if you have bottomless pockets though. Anyway, back on topic.

Do you have a budget for the scope Gnomos? Might make things a bit easier if we know how much we can spend 

Callum

[gnomus]

Maybe so but in my opinion an Avalon or 10 micron may be a bit over kill considering a NEQ6 would do a fine job!  Bang on target if you have bottomless pockets though. Anyway, back on topic.

Do you have a budget for the scope Gnomos? Might make things a bit easier if we know how much we can spend 

Callum

Well ... the Skywatcher ED80 Pro comes to just a shade under £600 (including the reducer). I don't mind adding another £200-£250 onto that number so long as I am getting additional value. (I don't want to pay more only to find that it comes from the same factory and just has a different badge on it, if you know what I mean.)

[ollypenrice]

There are lots of workable small semi-apos. The most boring suggestion is the ancient ED80. Personally I would probably buy exactly that. Doing this for a living means I can be far more indulgent and lash out on the top kit (second hand every time) but, hey. I would also look at the small Skywatcher Newts with coma corrector. Have a look at the DS imaging boards where some really remarkable DS images have come from these inexpensive instruments.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2266922474&k=Sc3kgzc

[gnomus]

There are lots of workable small semi-apos. The most boring suggestion is the ancient ED80. Personally I would probably buy exactly that. Doing this for a living means I can be far more indulgent and lash out on the top kit (second hand every time) but, hey. I would also look at the small Skywatcher Newts with coma corrector. Have a look at the DS imaging boards where some really remarkable DS images have come from these inexpensive instruments.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2266922474&k=Sc3kgzc

Thank you for your thoughts.  Those images are stunning.  Is there a way of telling what equipment was used to obtain each of these images?  (I can see that one day I am going to have to make the pilgrimage to France to sit at the feet of the master.)  

Would you have any particular ED80 in mind, or do you consider them all much of a muchness?  Also, I'm still thinking about how best to attach the scope to my CGEM mount.  Should I: 1) get an adapter for the scope; 2) replace the bracket on the scope with a Losmandy bracket; or 3) change the head on the mount so that it accepts both Losmandy and Vixen.

Finally, should I, at this stage, be thinking about doing away with the idea of using a finderscope for autoguiding?  That is, should I buy one of these http://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-ota.html and one of these http://www.firstlightoptics.com/startravel/skywatcher-startravel-80-ota.html from the get-go?  (I can't wait to see the look on my wife's face when I tell her we need two new telescopes.)

[iksose7]

With your budget , i personally would go for the SW Equinox which has better optics than the regular ED80. But if you can push your budget like you suggested i would really consider getting the triplet WO GT81. 

As for your question about replacing your finderscope for guiding, i wouldnt bother. I guide my AA115EDT which has near to twice the focal lenght of the 80mm scopes, using a 50mm guidescope which is probably around the same as your finderscope, and a starshoot autoguider. I manage 10 minute exposures no problem and i bet i could push it much more if i was brave enough to try! No point in adding the extra weight and money if you dont need to.

Callum

[gnomus]

With your budget , i personally would go for the SW Equinox which has better optics than the regular ED80. But if you can push your budget like you suggested i would really consider getting the triplet WO GT81. 

As for your question about replacing your finderscope for guiding, i wouldnt bother. I guide my AA115EDT which has near to twice the focal lenght of the 80mm scopes, using a 50mm guidescope which is probably around the same as your finderscope, and a starshoot autoguider. I manage 10 minute exposures no problem and i bet i could push it much more if i was brave enough to try! No point in adding the extra weight and money if you dont need to.

Callum

Thanks for all the helpful suggestions.

Callum:  Yes ... I've been looking closely at the WO GT-81. http://www.firstlightoptics.com/william-optics/william-optics-gt-81-triplet-refractor.html I may save up with a view to a purchase in the New Year.  (Does FLO do a New Year sale, I wonder?)

I assume that the 9x50 finderscope that came with my Edge HD 8" would fit in those rings??  However, I wonder if I would be better with a dedicated finderscope for the GT81 - changing the finderscope around from one scope to another could become a little wearing.  Any suggestions as to a suitable finderscope with the WO, bearing in mind that it must be suitable for guiding?

Also, I'm still looking for the best way of getting that narrow foot (image 2 on the FLO webpage) onto my wide CGEM (Losmandy) mount.  Any thoughts on that?

[MiguelMJr]

Have you looked into Stellavue? Their 80mm scopes are not much more money than a WO but I believe that the quality of the optics is far superior.

http://www.stellarvue.com/stellarvue-sv80st-25sv/

http://www.stellarvue.com/stellarvue-80-mm-apochromatic-triplet-with-feather-touch-focuser/

If either one of these scopes are not out of your price range it would be hard to find a better 80mm and not spend a lot more. IMHO

Miguel

[Phillyo]

Just another option for you (Haven't read every post so not sure if it's been mentioned already) but the William Optics Star71 is a superb little scope. Around 348mm focal length, very flat and doesn't require a FF/FR either. I think speed is around F4.9? I have one and it's an awesome little scope with a wonderful wide FoV, and it's made for use with a DSLR too.

Not the cheapest scope out there but when you factor in a FF/FR too (and it just works, with no faffing about with spacing) for me it was money well spent.

Phil

[gnomus]

Thanks again.  There are almost too many options.  I looked seriously at the Williams Optics scopes, but I was put off a little bit by this thread http://stargazerslounge.com/topic/229325-wo-gt81-stars-with-many-peaks-help/

It is clear that you can spend astronomical sums on these refractors.  I'm obviously wanting to get in at the "low end" - I'm not going to spend thousands as a beginner.  That being the case, I wonder if I may be deluding myself by thinking that another couple oif hundred quid is going to make all that much difference at my entry point.  That being the case, I am leaning towards either the seemingly ubiquitous SkyWatcher ED80 or the Equinox.  

I would still appreciate any pointers on attaching a narrow dovetail scope to my wide dovetail mount.  It seems that adapters are insanely expensive. (Or am I just looking in the wrong place?)