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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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Ron (Lubbock)
sage


Reged: 08/17/12

Loc: West TX
Re: Guiding Issues new [Re: CounterWeight]
      #5931243 - 06/20/13 12:57 PM

I did read that the OP had stopped and restarted guiding. However, there is no way he could get such declination drift unless his polar alignment was significantly off and the mount was also ignoring corrections in Dec. from Ph.D.
Those two factors point to Dec. cogging.

The reason the sawtooth did not happen on its own is that his max. Dec. was set to 200, which is generally too low to make it jump back to the setpoint on its own. I've witnessed my mount ignoring corrections of 800-1200 in Dec. from Ph.D., if you can believe that. Increase the Max Dec. to 1600, and you'll get some nice sawtoothing without stopping and restarting.

The beta firmware fixes are good enough that I'd suggest upgrading right away, rather than waiting for the public release. Any bugs left in the beta firmware are way insignificant compared to the dec. cogging. I've only managed to "break" the beta firmware by deliberately misaligning the scope by about a degree. It otherwise worked great in 8 or 9 imaging sessions last month. If not for the fix, I would have sold my CGEM already.


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woolbrig
sage


Reged: 02/01/13

Loc: Bethalto, Illinois
Re: Guiding Issues new [Re: Ron (Lubbock)]
      #5932942 - 06/21/13 12:47 PM Attachment (8 downloads)

I made some progress last night with my guiding. I've attached the PHD graph from last night. I'm guessing the first spike is the dec cogging problem. The 2nd one is where I stopped and started guiding again.

The calibration is occurring in about 12 steps.

This weekend I'm going to try to get the HC updated with the beta version of the software. Hopefully that will help some too.

The only thing I couldn't figure out was how to set the guide rate in the HC. I couldn't find it on the menu any where. Can someone point me in the right direction for that?


Edited by woolbrig (06/21/13 12:50 PM)


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woolbrig
sage


Reged: 02/01/13

Loc: Bethalto, Illinois
Re: Guiding Issues new [Re: woolbrig]
      #5932954 - 06/21/13 12:53 PM Attachment (9 downloads)

New PHD Settings:

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fishonkevin
Carpal Tunnel
*****

Reged: 04/29/07

Loc: Michigan
Re: Guiding Issues new [Re: woolbrig]
      #5933072 - 06/21/13 01:58 PM

Guide Rate in HC = Tracking Rate/Speed ??

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Ron (Lubbock)
sage


Reged: 08/17/12

Loc: West TX
Re: Guiding Issues new [Re: fishonkevin]
      #5933175 - 06/21/13 03:23 PM

I think the factory default guide rate is fine. I once looked it up, but don't remember how to get there in the menu. I would guess Menu -> scope setup is the right way to start.

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Madratter
Postmaster


Reged: 01/14/13

Re: Guiding Issues new [Re: Ron (Lubbock)]
      #5933284 - 06/21/13 04:36 PM

Mine was set to .5x although I had the CG-5, not the CGEM.

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Mike7Mak
Pooh-Bah
*****

Reged: 12/07/11

Loc: New York
Re: Guiding Issues new [Re: Madratter]
      #5934957 - 06/22/13 04:38 PM

Quote:

Just make sure your step size is smaller than the # of seconds for your exposure (so if you expose for 4 seconds, you better not go above 4000ms).



Why?

Calibration step and exposure happen sequentially. A 4 second guide pulse and 2 second exposure would just mean 6 seconds between iterations.

Unless I'm missing something. Don't think I've ever needed a cal step above 700ms or so.


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Madratter
Postmaster


Reged: 01/14/13

Re: Guiding Issues new [Re: Mike7Mak]
      #5935117 - 06/22/13 06:26 PM

Quote:

Quote:

Just make sure your step size is smaller than the # of seconds for your exposure (so if you expose for 4 seconds, you better not go above 4000ms).



Why?

Calibration step and exposure happen sequentially. A 4 second guide pulse and 2 second exposure would just mean 6 seconds between iterations.

Unless I'm missing something. Don't think I've ever needed a cal step above 700ms or so.




Well, I just learned something new. There is a reason why I'm in the beginners/intermediate forum.

I use a calibration step of 3000ms but I have my tracking rate at .5x. My guidescope is a 50mm finder with 162mm focal length. So things don't nudge very far.


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