Is there anyway to make suggestions for upcoming releases

[Anthony Law (DrhexUK)]

I have a couple of suggestions for additions to future PHD2 releases.

1. Plate solving with the guide scope / camera inside phd2.

This would help in two ways, For planetary imaging, users can use the guide scope to sync the main scope to point to planets. and then use guiding for better imaging.

The second use would be during the calibration assistant, directly after a slew if the guide scope was plate solved PHD2 would have an accurate picture of where the mount was pointing make the calibration more accurate. I often manually do this during a calibration with the main imaging camera

2. Is it possible to allow the use of different guide rates and Calibration steps for RA and DEC. This is for use with Hybrid strain wave RA / Worm Gear DEC mounts where having a higher guide rate in DEC allows for shorter backlash compensation,  but a lower guide rate in RA would help guide the strain wave RA.

[Brian Valente]

Hi Anthony

Regarding new features, posting here is a good start. 

My feedback regarding your suggestions

1. plate solving - I think this doesn't belong in a guiding app, and is already widely available in imaging programs. For planetary specifically, Sharpcap has had this for a while. Have you tried it there? The vast majority of guiding is used for deep space objects, so it would be a feature of limited value even if it were implemented in PHD. The majority of planetary imagers (myself included) don't need or use guiding, but maybe others will chime in

2. Different guide rates - do you have any examples that demonstrate what you're describing? This seems like a reasonable request, but for a pretty limited audience. It also adds complexity, and I have seen Bruce rightfully focuses on "keeping it simple". What mounts are out there that have a worm Dec and a strainwave RA? Seems like it's just a couple models from iOptron although I really don't know. 

Brian

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Brian 

Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[Anthony Law (DrhexUK)]

Hi, Thanks for the response.

1, Understood, it was only a thought as I tend to run a plate solve after the calibration assistant slew but before the calibration to make sure the mount is pointing where PHD2 actually thinks it is. I did wonder if plate solving through the guide scope/ camera would make for a more accurate calibration.

2, Yes it is only the iOptron HEM mounts that I believe are currently Hybrid, myself Owning a HEM15 and trying to get a good balance of guiding both the strain wave mount and the worm gear has been, lets say interesting. The mount is capable of guiding at different rates in RA and DEC and having the option in PHD2 would be useful I believe.  

Anthony

[Brian Valente]

>>> . I did wonder if plate solving through the guide scope/ camera would make for a more accurate calibration.

exact position is not important for good calibration, so plate solving here won't make any difference

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[Anthony Law (DrhexUK)]

Hi,

Understood

Anthony

[Bruce Waddington]

Just to close this, PHD2 doesn't require that the mount guide speeds are the same for both RA and Dec, that all gets sorted out during calibration.  The only place that's likely to affect you is with the Calibration Assistant.  Depending on your single setting for the calibration step-size, the RA calibration might take 12 steps and the Dec calibration only 6 - just to pick one example.  You can calculate and set the calibration step-size yourself using the Guiding tab in Advanced Settings - there's an 'Advanced' button there.  So you could choose a calibration step-size that results in a reasonable number of steps for both RA and Dec, maybe based on an average of the two different mount guide speeds.  Once you've done that, you can ignore any recommendations from the Calibration Assistant about changing the calibration step-size.

Good luck,

Bruce

[wes McDonald]

Bruce:

So that’s interesting.  You just told us we can have whatever guide rates we want in each axis (this would be established despite how the Dover might report the guide rates to calibration assistant).  During calibration the movement per pulse in rash axis is measured and used independently for guiding the respective axes.  

Man. That is really helpful for mounts with Dec backlash.  

Is there a limit to the rate enforced by PhD?  Meaning if the Dec moved, for example, at the equivalent of 2x sidereal per pulse interval phd would just employ this information gleaned from calibration?

Wes

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[Anthony Law]

Thanks Bruce, I will try the different guide rates again when I get the opportunity. The last time I tried I had thought it wouldn't allow the calibration until the rates where the same but it may have indeed just been a warning I misinterpreted.

For reference I'm using the none Dev version of PHD2 at the moment.

I will try the Dev version in the near future.

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[Bruce Waddington]

@Wes:  The drivers report separate guide speeds for RA and Dec but of course these are usually the same values.  Unfortunately, it's been common for new drivers to foul this up and report guide speeds that are wrong - for example in the wrong units.  So PHD2 has to sanity check the reported values before trying to use them.  This is critical for the PPEC algorithm which needs to translate between wall-clock elapsed times and imputed gear positions.  The sanity check will accept guide speeds below 1.2x sidereal.  In general, it's a poor idea to use guide speeds above 1x sidereal.  For RA, it's a really bad idea because it makes RA guiding subject to backlash in the RA gear system, something that isn't relevant if the guide speed is 1x sidereal or less.  If we turn the question around, from a purely mechanical point of view, guide speeds of 1x sidereal are the best choice because they help the gear system to push through small amounts of static resistance while minimizing the elapsed time it takes to complete the guide correction.  However, 1x sidereal guide speeds have implications to the mount controller firmware which is a vendor-specific black-box from our point of view.  For example, as the guide speed increases, the duration of the guide commands decreases, meaning there is more pressure on the firmware (or driver) to accurately handle small time durations.  There are probably other issues for the firmware that I'm not aware of, and many mount vendors recommend guide speeds that are less than 1x sidereal.  Our usual advice is to try using guide speeds close to or equal to 1x sidereal but subject to whatever contrary advice is given by the manufacturer.

Hope this clears things up a bit,

Bruce

[wes McDonald]

Bruce:

Thanks.  Yes, very helpful.  We also recommend less than 1x for RA, but DEC reverses anyhow.  Did I see the threshold for PHD is one point 2 (1.2) times sidereal?  Going to play with that.  

Your concern about a system having a minimum effective guide pulse length is indeed a real thing.  

Thanks.

Wes.

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