Best choice for imaging on equatorial mount

[redstamp]

Hi,

Sorry if postng in wrong place - didn't know if was general, equipment or imaging question - but I'll ask anyway...

I have been using my Skywatcher 130p Supatrak for a while and imaging was fun, but nothing serious.  Looked at this and other forums and recommended an equatorial mount, to keep the scope smoothly in the right plane for astro-imaging.

After some more researching, I found the Celestron CG5-GT came highly recommended and eventually found one for a decent price.

So now I wondered about upgrading the OTA itself.  I like the simplicity of a SCT, as I will be travelling to get to a dark sky site and no longer need worry about things falling into my scope, but research suggests staying with a reflector is probably better in terms of focal plane.  Imaging will be of moon and planets, unless I get alot better ;-)

Can anyone suggest a good scope for astro-imaging that will fit nicely on my new mount?  Budget about £400-£700.  The imaging will be through my Nikon D7100 or my MS adapted webcam.

Thanks for help.

[miafey]

If you have already tried Newtonian reflector and you have CG5-GT in mind for mount, why don't you try a small refractor?

The CG5-GT has a payload of 7kg for imaging so you probably won't be able to have anything bigger than a 6inch on that anyway. 

A 80mm ED refractor is a good choice for imaging, portable, well within the payload limit of your mount, and with your webcam and your Nikon you could go both planetary and deepsky (although I've learned Canon is much better than Nikon for astrophotography, so you may wish to get a second-hand astro modified Canon dedicated for AP). 

SW Equinox 80ED is a reasonable one to start with, so I've heard!

[redstamp]

The CG5-GT has a payload of 7kg for imaging so you probably won't be able to have anything bigger than a 6inch on that anyway.

Is that all?  The manufacturer specs say 35lbs - and other forums reckon take this down to 30lbs - which would still be 13kg... Does astrophotography require another 50% reduction in specs to get into the right realm for useful pitures?

Thanks

[redstamp]

After looking around, mclewis1 on this post - http://www.cloudynights.com/topic/456640-celestron-cg5-computerized-honest-weight-capacity/reckoned:

"The published capacity is accurate for visual work ... if you are careful. The tripod under the ASGT mount is a heavy 2" steel tubed model, effectively the same as what is used under the heavier CGEM mount. There are plenty of examples of folks running 30lb setups (C11 etc.) on ASGT mounts. Some have problems with that type of setup, others do not. Large refractors are more likely to be a problem than large SCTs."

Any idea why refractors would be more of a problem?

And in the same post, RLTR 12 reckoned:

"I have CG-5s and run up to 30+ lbs on them without any problems at all. The mount handles the weight and the GoTo and Tracking are perfect. I have also done long exposure AP with the mount loaded to almost full capacity and I have had good success doing so.
I mount my WO FLT132 APO that weighs in at 26.5 lbs mounted amnd I mount my C8 with my Onyx 80 EDF stacked on top with 2 cameras and AP equipment."

[D4N]

An SCT is a reflector, it just has enclosed optics unlike a Newtonian reflector where the OTA is open at the end.

An SCT would certainly be sensible for planetary work as the aperture and focal length naturally tend towards this.

Refractors tend to shine in deep space imaging, a short focal length frac is an easy way into DSO imaging and much easier to learn the ropes on than a long focal length SCT.

With respect to refractors being a problem on a mount I can only assume they mean if you had an SCT and a frac of the same focal length the frac would be much harder on the mount as the extra length would increase the turning moments. Small frac's are incredibly easy on mounts

/Dan

Sent from my iPad using Tapatalk

[Mr Spock]

For planetary imaging an SCT is perfect. A C8 would cost £779 and would sit nicely on the CG5 http://www.firstlightoptics.com/optical-tube-assemblies/celestron-c8-xlt-optical-tube-assembly.html

[miafey]

Is that all?  The manufacturer specs say 35lbs - and other forums reckon take this down to 30lbs - which would still be 13kg... Does astrophotography require another 50% reduction in specs to get into the right realm for useful pitures?

Thanks

For imaging you could only use at most 70% (only if you have a very good mount), preferably 50%, of the payload capacity before tracking gets inaccurate. 

I think I've heard CG5-GT = EQ5 Pro, Advanced VX = HEQ5 Pro, so starting from 6inch, you really want to have at least a HEQ5 for imaging

[miafey]

After looking around, mclewis1 on this post - http://www.cloudynights.com/topic/456640-celestron-cg5-computerized-honest-weight-capacity/reckoned:

"The published capacity is accurate for visual work ... if you are careful. The tripod under the ASGT mount is a heavy 2" steel tubed model, effectively the same as what is used under the heavier CGEM mount. There are plenty of examples of folks running 30lb setups (C11 etc.) on ASGT mounts. Some have problems with that type of setup, others do not. Large refractors are more likely to be a problem than large SCTs."

Any idea why refractors would be more of a problem?

And in the same post, RLTR 12 reckoned:

"I have CG-5s and run up to 30+ lbs on them without any problems at all. The mount handles the weight and the GoTo and Tracking are perfect. I have also done long exposure AP with the mount loaded to almost full capacity and I have had good success doing so.

I mount my WO FLT132 APO that weighs in at 26.5 lbs mounted amnd I mount my C8 with my Onyx 80 EDF stacked on top with 2 cameras and AP equipment."

If you read it on you'll see the comments:

"The weight capacity depends on many factors.....(0 wind was a must)"

To push the capacity to the absolute limit of the mount you will need good weather, solid base, balance the mount very well, and more importantly, a lot of experience. You will need to align and guide very well, and, pray that you won't have any gust during your entire AP session. It's just not worth it. I do think the weather in the UK is more hostile in this regard, compared to many area in the US 

One thing that is true for celestron mounts (CG5 and AVX) though, the tripod is a 2inch heavy duty one so some people like them. That is probably why you could put a lot of weight on it and it stands well against wind. I have seriously considered AVX before but gave it up because the weight of the tripod would mean it is less portable to me (around 8kg). 

For AP, you actually don't need a large refractor. Many people use a 80 or 100mm refractor to get fantastic results. The light you lose in aperture, you make it up by long exposure. You can use you SW130 for planetary, and a small refractor for DSOs. A 80mm weights only 2-3 kg so is extremely portable. 

[redstamp]

So it sounds like I need to choose between a SCT - for planetary and moon astrophotography OR a 6" ED refractor, which I could use for DSOs and longer imaging (when I would also need a guide scope, CCD camera and alot more patience.

I would love to get into DSO astrophotography, but England doesn't strike me as the way to enjoy DSO AP!  Surely we rarely get enough clear and warm enough nights to make this an enjoyable hobby.  I dont mind putting a bit of work into my hobby, but spending hours setting up my rig in some far-flung field, stamping my feet and carrying a 50l thermos full of tomato soup just to keep my body from hypothermia, sounds like a bridge too far.  And if the cloud cover suddenly decends to waste my entire night, I can foresee a quick eBay selling spree after a few months of disappointment - or am I getting the wrong idea?

All views most welcome - as spending enough to buy a small car, just to test my theory doesn't strike me as very sensible without asking the experts!

[miafey]

So it sounds like I need to choose between a SCT - for planetary and moon astrophotography OR a 6" ED refractor, which I could use for DSOs and longer imaging (when I would also need a guide scope, CCD camera and alot more patience.

I would love to get into DSO astrophotography, but England doesn't strike me as the way to enjoy DSO AP!  Surely we rarely get enough clear and warm enough nights to make this an enjoyable hobby.  I dont mind putting a bit of work into my hobby, but spending hours setting up my rig in some far-flung field, stamping my feet and carrying a 50l thermos full of tomato soup just to keep my body from hypothermia, sounds like a bridge too far.  And if the cloud cover suddenly decends to waste my entire night, I can foresee a quick eBay selling spree after a few months of disappointment - or am I getting the wrong idea?

All views most welcome - as spending enough to buy a small car, just to test my theory doesn't strike me as very sensible without asking the experts!

Well I have to guess that you are also in the dreadful south west where people lose faith in the weather very quickly....    Those in the SE or mid-land might see far more clear nights than we do here. 

I am actually very new to this forum as well, and before my first post here (which was two days ago) I had exactly the same vision as you do - surely astronomy is something to enjoy in a warm, clear summer night?? Who would go out in dark, freezing winter night spending hours in the field?? But no....to quote @brantuk's response to my post:

"A lot of newbies picture astronomy as something nice to do on warm summer nights. The reality is that is the worst time due to heat currents and short nights. Astronomy is really a winter hobby and long dark nights can be spent standing in a field in the middle of nowhere, to avoid light, doing it."

So, yes you'll probably need to spend a lot of winter nights in the field if you go down the route of AP. But it'll be fun! I can't imagine myself doing it on my own but I'm joing a local astro club and considering going to star parties, when a lot of like-minded people will be doing the same. I'm sure you'll enjoy it! And the reward is worth every second of it. 

For scope, I think a 6inch ED will be out budget for you. a 3-4 inch one will be a very good starter. And you don't have to use the full package to start with. A lot of people use DSLRs, either unmodded or modded (preferred) for DSOs and you'll still get good results. Check this forum and also the UKastroimaging forum for what people get from very basic setups. And you can sometimes get good pictures without guiding as long as the exposure is not too long. You have a lot of options, there are even kits out there to get your camera cooled. Although serious APers would, perhaps, eventually have a cooled mono CCD + filters and perhaps a permanent setup (for example an observatory) at home, you don't have to start with all these. If you get a 3inch refractor your CG5-GT will be sufficient, and with a DSLR you are all set for AP!

Again I'm very new myself so I might be wrong Listen to those experienced members here they are fantastic.