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bonorden
newbie

Reged: 03/25/09
Posts: 3
Beginner Mount Questions
#3175648 - 06/22/09 01:10 AM

I recently purchased a used CG5. It seems to work reasonably well but I tried doing some piggyback photography and the mount seemed to strain when slewing. And the accuracy of the gotos was off some. I rebalanced after putting on the camera but I've come to the conclusion that the mount could benefit from a hypertune. The RA turns fairly easily, but the DEC is a little harder to move. My question is about the weight limit of the CG5. I'm running a C8 with an 11 lb counterweight. I have a 8x50 finderscope, a telrad and my DSLR (4 lbs). I've been told that the CG5's limit is ~30lbs and I should strive to keep the weight to ~15 lbs. I don't see how this can be done unless you don't count the counterweights in the equation.

1) Do you count the counterweights?(I'm assuming you would since weights weigh something). If I remove my DSLR and replace with a CCD for imaging and another for guiding (after replacing my finder for a guidescope), I'll likely be well over 30 lbs.

2) Is it possible to be under the 30 lbs with a C8 with an astrophotography rig I am describing?(I'm assuming yes, but the math doesn't seem to add up).

Thanks,
Jeff

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neptun2
professor emeritus

Reged: 03/04/07
Posts: 580
Loc: Bulgaria
Re: Beginner Mount Questions [Re: bonorden]
#3175747 - 06/22/09 03:50 AM

First the counterweights does not count. The limit is given for the useful load. Giving rating of 30 lbs for cg5 does not sound right to me. It has the same mechanics as EQ5 so it should be rated rather for 20lbs i think. But you should have no problems with c8 and your imaging gear with this mount. Of course at this focal length with this mount and without reducer you will probably need autoguiding for long exposure astrophotography.

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Photo: Sony NEX-5N + 18-15 , Nikon D90 modified, Meade DSI Pro 2 as guider, TS 9mm off-axis guider
Binoculars: Nikon Action 12x50
Telescopes: Skywatcher Evostar 120ED f7.5 APO + TS 2" flattener
Mounts: HEQ5 Pro
Eyepieces: Nagler 11mm type6, Pentax XW 7mm, Televue 2X barlow 1.25"

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Luigi
Postmaster

Reged: 07/03/07
Posts: 5317
Loc: MA
Re: Beginner Mount Questions [Re: neptun2]
#3175842 - 06/22/09 06:54 AM

How old is the CG5? Celestron upgraded the CG5 a few years ago when they started selling it with a C11, which weighs about 30lb. IMO, that's pushing the envelope a bit but at least the C11 is short, which helps. If properly balanced, the weight is no problem for the mount, it's just wobbly when observing. I had a C11 on a G11 for many years and that was a great setup, but when I downsized OTAs I downsized from the G11 to the CG5, which I find works very well with my current ~16 lb OTAs. The CG5 is noisy when slewing at full speed. Don't take the noise as being indicative of a problem.

As for tuning the mount, the only thing that gets done is regreasing and minimizing play and backlash. This usually isn't necessary or beneficial.

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17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha.
Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins

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bonorden
newbie

Reged: 03/25/09
Posts: 3
Re: Beginner Mount Questions [Re: Luigi]
#3175919 - 06/22/09 08:43 AM

Supposedly the mount is only a couple of years old. It looks like the "new" mount style and has an upgradeable hand controller running version 4.12.

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LLEEGE
True Blue

Reged: 03/03/05
Posts: 12767
Loc: Cloud-chester,NY
Re: Beginner Mount Questions [Re: bonorden]
#3176078 - 06/22/09 11:15 AM

I assume you're piggybacking your camera as you don't mention another scope. You should be fine with that setup. You may want to check the worm mesh to make sure it's not too tight.

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A wise man once said........nothing.

A good mount
A few good OTA's
A few good EP's
A decent camera
Crappy skies

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scholastic sledgehammer

Reged: 09/04/04
Posts: 765
Loc: GA
Re: Beginner Mount Questions [Re: LLEEGE]
#3178118 - 06/23/09 12:10 PM

I think 30 lbs for any CG5 is a bit too much. I have an older one and have run it with 24 lbs OK but I would not go higher as it was at its limit there. Hypertuning will help even out the mounts mechanical deviation and ply but will not help with weight at all. I routinely run my CG5 with an olderr, heavier, Celestron C8 and have not had any problems with it handling the weight. Good Luck !!!

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Clear Skies,

Cave Astrola Deluxe 8" f8 (Achilles)
Stellarvue NH-II in Stardust Blue (Cleopatra)
Celestron C9.25 (Maltese Falcon)
Celestron C6R-GT (Criminal Intent)
Oberwerk 15x70
Vixen Polaris Mount

Clear Sky Chart == Macon, GA

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