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Celestron CG5 is on sale?

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#1 cruling

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Posted 13 March 2013 - 03:20 PM

Hi everyone

I just see that celestron CG5 is on sale for $549 at OPT and hight point scientific, is this a good deal?

I was looking for one of these for imaging these days, and I happen to have some discount code from high point, so I put my order.

how good is the tracking of this mount without guiding? with my old alt-az GOTO mount, the best I can do is 3s, I have to take a lot of shots on one object, 500 normally, kinda worry about the shutter on my new camera.
if I can do a better job on polar alignment, say by drifting polar align, will I be able to get 60s unguided?

Thanks,
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#2 kbev

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Posted 13 March 2013 - 04:10 PM

With good polar alignment you should be able to easily get 60s unguided images, 120s is possible but you may throw a few out due to periodic errors in the drive that even the best polar alignment can't overcome. $549 for a new CG5 is not bad, just keep in mind that I believe this mount has been discontinued with the introduction of the AVX model but the CG5 can still do a very good job for you.

#3 mclewis1

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Posted 13 March 2013 - 05:13 PM

The issue of how long you can go unguided is dependent on the focal length of your imaging setup.
Short focal length setups (smaller refractors, or larger scopes with focal reducers) are much easier on the mount. Your not going to be happy trying 2-3 minute subs with something like a C8 at it's native focal length (over 2000mm).

Used under the right conditions (with an appropriate scope/camera) and with realistic expectations the CG-5 is a great deal on sale right now.

#4 cruling

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Posted 13 March 2013 - 07:19 PM

I heard about the periodic errors, but what is it exactly?

I do imaging with a 80EDF with 500mm FL, not a long FL I guess.

#5 Ranger Tim

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Posted 14 March 2013 - 03:07 PM

Periodic error is the error or "jump" that the mount displays when the worm engages another tooth on the gear, or could be some other type of frequent, chronic, repeated and/or undesired movement. It is generally not an error that is random in nature and can be guided out by periodic error correction or "PEC." PEC must be recorded and engaged by the mount's operator and must be available for your respective model. I don't know if it is currently available for the CG-5 software. It is also possible to guide out most PE with an autoguider set-up.

Your 500mm focal length will yield acceptable tracking for AP for at least a couple of minutes, provided you spend the time to accurately and critically polar/drift align your equipment. Of course the term "acceptable" is subjective... At this price point there are few other options that are the CG-5's equal.

#6 cruling

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Posted 14 March 2013 - 10:13 PM

Thank you Tim, for the detailed explanation.
I just got my CG5 today, the tripod is impressive, feels very sturdy, and yet the whole mount is not too heavy. will try it outside when the sky is clear.

but I have a little problem with the counter weight, it's too heavy to balance my little 80EDF, I will need a lighter one, maybe 5lb, any advice?

#7 t.r.

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Posted 15 March 2013 - 07:41 AM

You can use the smaller (8# & 4#) counter weights that come with the Vixen Super Polaris mounts on the CG5 shaft. Check ScopeStuff...they may have some or check used on Amart.

#8 jbalsam

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Posted 15 March 2013 - 12:16 PM

Cruling:
The best investment I've made so far in AP has been my guidescope. I picked up an 80mm f/5 refractor with a QHY5 camera for $300. That instantly let me go from 2 minute subs to 15 minute subs. The only other cost for me was the rings to mount the scope (I think I got those for around $40).

Guiding can also eliminate the problem of periodic error as long as the errors are not extreme. I think that getting a guidescope will *greatly* enhance anyone's enjoyment of the hobby as it lets you reach deeper and fainter targets. So, once your wallet recovers from buying the new mount, I'd say watch the classified ads on here for a guider =)

#9 Ranger Tim

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Posted 15 March 2013 - 04:12 PM

I sometimes use weights from weight lifting sets. I make a wooden disc with the proper hole size and then velcro the weight to the wooden disc so that it wont move. Budget astronomers can sometimes make do by inventing solutions...

#10 cruling

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Posted 15 March 2013 - 07:31 PM

Hi jbalsam, I have the plan of getting the guider too, I have another C6 SGT, so i would like to use my 80mm ed as guide scope, and imaging on C6 with a 0.63 FR, but that's a later plan, for now, I will first get familiar with the mount and practice on the skill of polar alignment.

and Tim, good idea on using weight lifting sets, really worth trying, i can make of the these myself.






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