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CG-5GT or CGEM for unguided photography?

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#1 Jim Romanski

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Posted 23 March 2009 - 04:17 PM

Similar to the another post. I'm looking at these two mounts for doing unguided short exposure photos with my NP101 and Canon XSi.

I see that the CGEM has a special polar alignment function and permenant PEC. I have to imagine that those features would be helpful for unguided photos.

I'm thinking of selling my CG-5 non-GOTO and getting a CG-5GT since they can be had for not much money. But maybe I should wait and save up for a CGEM?

For now I don't want to use a laptop at the telescope. I might in the future but I'd like to stay simple for now.

So what do yo think, is there a big difference between these two mounts for what I want to do or should I save my money?

#2 waassaabee


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Posted 23 March 2009 - 05:17 PM

The CG5-ASGT's hand controllers can be updated to the same version as the CGEM giving you the All Star alignment. But the CGEM (from my understanding) is a step up from from the CG5 in more ways. Tighter tolerances, larger bearings and shafts, heavier payload to name a few. But if you are looking to keep it simple, an ASGT might be the way to go. But if I had an NP101 and was planning on imaging, I'd put it on something a bit more substantial. The CGEM will also sport the guidescope when you are ready, and the big triplet you know you want.... :cool:

#3 Al Canarelli

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Posted 23 March 2009 - 08:22 PM

I had the same feelings about 18 months ago that you have today. I didn't want to complicate my imaging sessions with a computer, but there is no other way, under the circumstances. Believe me, you will not be satisfied with the results of short, unguided exposures. It's much easier to buy an inexpensive 80mm Orion shorty, attach it to your main scope with a first generation Meade DSI and let PHD Guiding do the rest. For this task, the CG5 goto is perfect.

#4 Jim Romanski

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Posted 24 March 2009 - 06:00 AM

I don't rule out using a computer. But I've been a visual astronomer for many years and I'm just dabbling in astrophotography. For now and probably for a while I'd like to see how much I can get out of unguided photography.

I think guiding and imaging with a PC for me is still a few years out.

I'm encouraged to read that I can upgrade the CG-5GT to use the same polar alignment routine as the CGEM.

#5 waassaabee


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Posted 24 March 2009 - 06:36 AM

I think the hand control has to be a version 4.xx to be upgradeable.

#6 jason_milani



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Posted 24 March 2009 - 07:31 AM

If you can get a fairly accurate polar alignment you can get 30 second to 2 minute subs at that focal length without guiding without much problem. Unless you're getting into narrowband imaging that's all you'll be able to use anyway in a semi light polluted area. Where i'm at, i use a broadband filter and i can't use anything longer than a few minutes without the image being washed out.

#7 Patrick


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Posted 25 March 2009 - 02:41 PM

Hi Jim,

With unguided AP, short focal lengths are your friend. I was able to get some decent images of the Andromeda Galaxy with 1 minute exposures at 320mm focal length (with the CG-5GT unguided). See HERE. I attempted to go longer but got too many bad frames.

If you add a TV 0.8 focal reducer, I think your focal length will be around 430mm, so I'd give it a try to see how long you can go with your current mount. If you stay unguided,the CGEM's PEC is a good feature to have and may well keep you in the 'okay' range for your scope and let you expose a little longer. I believe the CGEM has permenant PEC which is also a plus because you won't have to retrain the drive each time you setup.

The tradeoff is that the CGEM is more expensive and weighs a lot more than the CG-5GT.

Let us know what you decide!


#8 hwman



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Posted 25 March 2009 - 04:50 PM

I really like that shot Patrick. It's really crisp and the wide FOV frames it nicely.

#9 Jim Romanski

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Posted 26 March 2009 - 10:51 AM

Let us know what you decide!

Well I'm leaning towards the CG-5GT for now.

The latest TV eyepiece sale is calling out to my budget so maybe I won't spring for as expensive a mount upgrade.

I have the non-GOTO version of this mount so I could live with that but... I don't really need GOTO but there are many other reasons for having the better electronics. Not to mention the new Solitaire Autoguider from Orion that can autoquide without a PC.

OPT has the CG-5GT for $590 + $57 shipping. I figure I can sell my non-GOTO unit for $350 so it's not that pricey of an upgrade for me. Although I might just wait till NEAF.

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