Turn Off Declination Dependent Guiding

[steve....@gmail.com]

Can this "feature" be turned off?  I'm using a Sitech servo controller on my G11 and it automatically adjusts the guide rate based on declination so that Declination Dependent Guding is not needed, and may be more harmful than helpful.  If it can't be turned off, I would need to recalibrate on changes in Dec.

Steve Barkes

[bw_msgboard]

It can’t currently be disabled – this is the first I’ve heard of anyone trying to put this adjustment down at the firmware level.  Can this “feature” be disabled in the servo controller?  Subject to UI real estate and complexity issues, we could provide a way to disable declination compensation.  In the meantime, these are the options that come to mind:

 

1)       If you’re using the default hysteresis algorithm for RA guiding, you could adjust the aggressiveness parameter yourself by a factor of cos(dec).  That will effectively cancel out the adjustment PHD2 makes (there’s no great precision required here) OR

2)       Guide using the ST-4 and “on camera” options in PHD2 and don’t specify an “Aux Mount” connection.  At that point, PHD2 won’t know where the scope is pointing and won’t make any adjustments at all – including meridian flips.  So when you do a meridian flip, you’d have to manually flip the calibration data (‘Tools/Modify Calibration/Flip…’)  OR

3)       Before you start guiding on the target, use ‘Tools/Modify Calibration/Enter calibration data’ and manually edit the bottom field in that form – the declination field.  Unfortunately, that’s in units of radians so you’d enter your target declination in radians (=declination * 3.14/180) OR

4)       Re-calibrate when you make a significant change in Dec pointing position

 

I realize none of these are terribly attractive but they’re all I can think of right now.  Personally, I’d use option 1 unless I was imaging between about 40 and 60 degrees declination.  Also, PHD2 doesn’t apply any compensation when the pointing dec is above 60 degrees, so you wouldn’t have to do anything in that part of the sky. I’ll add this to our list of new-feature requests.

 

Good luck.

Bruce

 

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[steve....@gmail.com]

Thanks or the reply Bruce.  From the Sitech controller manual:

"One more item if you are using version 1.7 of the controller firmware. There is a feature that changes the Pan and Guide rates for the azimuth/RA as you raise in altitude/declination. This feature is called Equal Area Panning and Guiding. What happens when you near the zenith (or pole on an equatorial mount), the azimuth has to move a much farther distance for an equal area of sky while you are pointed at the horizon (or celestial equator). In version 1.7, the pan speed and the guide speed are automatically increased as you move toward the zenith (or celestial pole). This is a truly cool feature, and when experienced, you won't want to go back to the old way!"

I don't see a way to turn if off there, and wouldn't want to do it because it's a really handy feature for centering on a CCD using the Pan speed.

Looks like your option #1 would be the simplest solution, but I would request that the ability to disable it as a new feature.

Steve

[bw_msgboard]

Ok.  I do have one correction to what I said earlier, I didn’t look closely enough at the code.  PHD2 *does* do declination above Dec=60 degrees; it only skips the compensation if the *original calibration* was done at Dec > 60 degrees.  You can track the new feature request here: https://code.google.com/p/open-phd-guiding/issues/detail?id=435&thanks=435&ts=1432320629

 

Just IMHO, embedding these things at the firmware level is not a good idea unless there are ways to disable them.  For example, I think I saw in the SiTech manual that they also do automatic adjustments for atmospheric refraction, something that is also better done at an application level.  You might want to ask the SiTech people to give you some control over this stuff.  Or at least you can be aware of it, because it could easily bite you down the road…

[steve....@gmail.com]

It's always tough when different applications/features step on each others toes.  I believe my old LX200 did refraction offsets as well.  I suppose if I had the ability to turn it off in either PHD2 or Sitech I would choose disable in PHD2, but someone else would certainly make a case to do it the other way!

Anyway, seems I can do a calibration above 60 degrees and get the effect I want.  Headed to https://sites.google.com/site/cosmiccampgroundinformation/  over the weekend, so I'll give it a try.

Thanks,

Steve

[bw_msgboard]

No, I wouldn’t do a calibration above 60 degrees, that will make your situation worse because the computed RA rate will be too low. If you’re going to let the mount controller do dec-compensation, you need to have PHD2 calibrate near the celestial equator. Just another reason why this isn’t a good approach – the SiTech can’t know where the application has done the guider calibration. <g>

 

Have fun.

Bruce

 

 

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From: bw_msgboard [mailto:bw_m...@earthlink.net]
Sent: Friday, May 22, 2015 2:04 PM
To: 'steve....@gmail.com'; 'open-phd...@googlegroups.com'
Subject: RE: Turn Off Declination Dependent Guiding

 

Ok.  I do have one correction to what I said earlier, I didn’t look closely enough at the code.  PHD2 *does* do declination above Dec=60 degrees; it only skips the compensation if the *original calibration* was done at Dec > 60 degrees.  You can track the new feature request here: https://code.google.com/p/open-phd-guiding/issues/detail?id=435&thanks=435&ts=1432320629

 

Just IMHO, embedding these things at the firmware level is not a good idea unless there are ways to disable them.  For example, I think I saw in the SiTech manual that they also do automatic adjustments for atmospheric refraction, something that is also better done at an application level.  You might want to ask the SiTech people to give you some control over this stuff.  Or at least you can be aware of it, because it could easily bite you down the road…

 

Bruce

 

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From: open-phd...@googlegroups.com [mailto:open-phd...@googlegroups.com] On Behalf Of steve....@gmail.com

Sent: Friday, May 22, 2015 12:19 PM
To: open-phd...@googlegroups.com
Cc: steve....@gmail.com; bw_m...@earthlink.net

[Bruce Waddington]

Hi Steve.  We've implemented a UI control to disable Dec compensation in PHD2.  It's in the dev2 development release if you want to give it a try. 

http://openphdguiding.org/development-snapshots/

Good luck.
Bruce

[ch...@beyondmonochrome.co.uk]

Thanks for putting the disable feature into the latest version.  I typically calibrate at low DEC and don't want to change that for high DEC. In my case, my tracking errors are considerably less than seeing noise and at high DEC, the compensation essentially amplifies the seeing noise and makes my RA guiding to reactive to seeing. As a workaround, I was manually changing my integration  times when I'm at high DEC.

regards

Chris Woodhouse