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Equipment Discussions >> Mounts

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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: Jared]
      #5284397 - 06/22/12 08:06 PM

And it's a good advice!Indeed i use that method and it works just fine

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bunyon
Post Laureate
*****

Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: Mike X.]
      #5284911 - 06/23/12 08:48 AM

I, too, had the dec problem with the CG5. My solution is to simply nail polar alignment so that I only guide in RA. Essentially I turn the guider into a periodic error corrector. Using that, I can do 6 minute subs at 400mm with no problem and 2-3 minute subs at 1200mm. All depends on how good my polar alignment is. I grew up using a GEM so am fairly good at polar alignment.

It isn't an ideal solution but it is much cheaper than a more expensive mount.


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nomosnow
sage


Reged: 03/21/11

Loc: Fort Saskatchewan,Ab ,Canada
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: bunyon]
      #5285115 - 06/23/12 11:27 AM

The Dec backlash was not the only dec guiding problem I was having with the CG-5 the other problem was stiction. When guiding in one direction on Dec a number of pulses would be sent to the mount with no movement until.. BAM!! a great big over correction would occur. I know that dec balance is a problem (on my system) as it is variable depending on the scopes position.
For the price though it is still an excellent mount and I still use it for solar system imaging and general viewing .

Edited by nomosnow (06/23/12 11:28 AM)


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rmollise
Postmaster
*****

Reged: 07/06/07

Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: nomosnow]
      #5285224 - 06/23/12 12:35 PM

Never had any problem with stiction on RA. The modern mounts have ball bearings on that axis. I am guiding through the autoguide port, however, so you might want to check things out software wise if you are guiding through the port on the HC.

As for dec backlash, if it's a problem for guiding, it's fairly easy to work around. Don't do a dead-on drift polar alignment. With polar alignment just a little off, declination corrections will be biased in one direction and backlash will not be a problem _at all_.


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ic1313
journeyman


Reged: 05/06/10

Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: Jared]
      #5431223 - 09/20/12 03:57 PM

cg5-gt is not a perfect mount but precision of guiding is a matter of good polar alignment
If you do a proper balance as already mentioned you can do long exposures

I managed to do 100s without guiding and 300s with guiding on actual polar alignment. this is proportion of time 1/3 that I managed.
Also to mention this was made on 1200mm C8 with f6.3 reducer


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: ic1313]
      #5431533 - 09/20/12 07:24 PM

I don't normally post pictures but I can post this test image!

15min guided CG5GT-AS (DSP Hypertuned) ADM side by side, ADM Max Guider
31 lb's

Celestron Onyx 80edf f/6.25 Stellarvue Field Flattener
Mallincam Extreme EXView Had Class 0
Baader 2" Narrowband OIII

Lunt 60mm Cak Scope. Guider (Cak BF taken off of course :P)
Lodestar

Raw and Unprocessed Veil Nebula OIII Test Shot @ 15min. White Red Zone of Los Angeles.

APC Setting 0 and 1



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Mkofski
Pooh-Bah
*****

Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: wolfman_4_ever]
      #5431575 - 09/20/12 07:59 PM

Dave,

I'm just getting int AP and am no expert but I'd be delighted with that shot as a final not just a test! That was shot with a Mallincam?


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: Mkofski]
      #5431967 - 09/21/12 12:01 AM

Hi Mike.

Just a mallincam, flatner and filter.. guided..

Just showing the OP the possibilities with the CG5. That was his topic after all.

Here is another test shot..

This is a 25min test shot.. just to compare from 15 to 25.. All the same parameters.. CG5 500mm vocal length f/6.25 Onyx 80



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A. Viegas
scholastic sledgehammer
*****

Reged: 03/05/12

Loc: New York City/ CT
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: wolfman_4_ever]
      #5437006 - 09/23/12 09:22 PM

Dave,

Great shots with your MCX! Amp glow is very pronounced but the detail with you Oiii filter is amazing. You said AGC 1 or were those in CCD mode?

al


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: A. Viegas]
      #5438407 - 09/24/12 04:29 PM

Thanks Al.

This was just a screen capture of what was displayed. I could of taken darks and flats to get rid of the amp glow.. But that's not what the Mallincam is designed for.. It does show what it is capable of the Mallincam.

My APC was 0 and 1, my AGC was 0. I was not in CCD mode. CCD mode would of also turned off APC..


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ic1313
journeyman


Reged: 05/06/10

Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: wolfman_4_ever]
      #5555790 - 12/05/12 02:39 PM

For newbie it may be the problem, but if you do excellent polar alignment you can do 100sec without guiding
With actual alignment and 100sec subs and pinpoint stars you can do 300 sec exposures easily with guiding(OAG on C8, f6.3, f-1200mm)
Dec backlash may be the problem but good balance of the telescope is important.
Put the new lubricant in the gears of the mount and you will have smooth action(myself)

my max exposure is 400 sec (not the best one) but sometimes I could do even 500sec when I did proper polar alignment.
guide star is problem on f 1200mm as it is on my setup(C8)

Edited by ic1313 (12/05/12 02:42 PM)


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Mkofski
Pooh-Bah
*****

Reged: 07/19/11

Loc: Greenfield, Indiana, USA
Re: Longest Exposures Auto Guiding a CG-5 GT? new [Re: Patrick]
      #5556272 - 12/05/12 07:33 PM

Patrick,

I love your shot of Andromeda! It's good to see results like that from a CG5 and DSLR. There is hope!


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