Can PHD2 guide on the Moon?

[Michael Owen]

Good morning. I am close to giving up on SharpCap's "Feature Tracking" feature, as it seems unable to consistently calibrate to guide on planets and the Moon. My mount, a CGEM, has a gear box between the DEC motor and worm gear resulting in an unavoidably large backlash that SharpCap apparently cannot be made to deal with, whereas I know that PHD2 can, via guiding in one direction in DEC. I'm pretty confident that PHD2 can be made to guide on a planet, but I am not at all confident that it will be able to guide on the Moon, given its extent. So the question is, can PHD2 guide on the Moon, and are there any special settings required to get it to do so?

Thanks,

Michael Owen

[Brian Valente]

Hi Michael

>>>can PHD2 guide on the Moon

short answer is no, PHD needs star(s) to guide on, it doesn't have feature tracking

However, a few thoughts on Sharpcap:

• the same strategy of one direction guiding should also be usable in sharpcap, it's general guiding principles are pretty much the same
  
  
• have you tried feature tracking via ROI and not via mount? Many planetary imagers (myself included) use ROI tracking which does not interact with the mount at all. You want to use the latest sharpcap 4

Brian

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[Michael Owen]

Brian,

Thanks. I was afraid of that. I still may have a trick up my sleeve if I can get the image of the Moon in the guide camera not blown out; the Moon has many very small, extremely bright features that PHD2 may be tricked into thinking they are stars. I'll have to see if I can work it out.

SharpCap does not support one way guiding. But the real problem is not that; if it could get past calibration it would end up one way guiding automatically, as my polar alignment is offset in order to drift in one direction to avoid having to keep taking up the dec backlash when the direction changes. The real problem is that SharpCap's calibration routine does not seem to be able to consistenly deal with the CGEM's large declination backlash during calibration. It simply does not allow enough time to take up the backlash and declares a failure of calibration. I have been trying to get Robin to address this for a long time, and for whatever reason he seems very reluctant to do so. It's quite frustrating. 

ROI is not suitable for the Moon; I am imaging with the entire sensor.

Mike

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Michael P. Owen, Ph.D.
CFD Applications Specialist
 
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Michael...@gmail.com

[Brian Valente]

>>>ROI is not suitable for the Moon; I am imaging with the entire sensor.

you also mentioned planets which is why I suggested that

>>>The real problem is that SharpCap's calibration routine does not seem to be able to consistenly deal with the CGEM's large declination backlash during calibration.

yeah i can see that would be a problem. Another thought is maybe using the mount's built-in backlash compensation and set it really high to try and get over that hump (assuming it has that feature: i'm pretty sure it does)

Honestly I doubt you'll be able to trick PHD into thinking a moon surface feature is a star. 

Another possibility is doing custom tracking rate via something like orbitals plugin in NINA just to set an accurate rate (it can also set an accurate rate for PHD as well) 

 (there are other solutions that utilize JPL horizons)

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[Michael Owen]

Thanks. I'm pretty sure PHD2 can guide on a planet, though.

The idea of PHD2 guiding on surface features of the Moon is not actually mine; I recall reading a post maybe a year ago on CN from someone who actually got it to work. That's what prompted me to ask the question. I tried searching for the post but came up empty.

I'm not sure that just having a custom tracking rate would be sufficient, given drift and PE, and I've never used NINA, but I will look into it. I wish Robin would just fix SharpCap. I mean, if *I* can eyeball the drift on the screen and the mount is capable of correcting it via the hand controller, which it is, then there is no technical reason that SharpCap shouldn't be able to do it automatically. It's the entire purpose of feature tracking. Anyway, I digress. 

Thanks again,

Mike

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[Leo Shatz]

Yes, it's possible - using my custom version of PHD2 for planetary tracking. I've added 3 different algorithms including detection and tracking full planetary disk, crescent shapes (great for lunar imaging or eclipses), and recently added - surface feature tracking. For more details and download links to please join by FB group:

PHD2 Solar & Lunar Tracking (beta) Forum

Cheers,

Leo