PHD2 multi star support ...

[GazAstro]

Looks interesting, multi star support in new snapshot build.

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

[Dmack1]

Posted by: @GazAstro

Looks interesting, multi star support in new snapshot build.

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

I have enough trouble with one star, why would I want to use multiples ? 

[AstronomyUkraine]

Here is the information on multi-star guiding in PHD2. It looks like it could be of some benefit, or not, and that is the words of the developers.

Multi-Star Guiding

Some guiding configurations can benefit from guiding on multiple stars rather than just one.  This results in using a weighted average centroid position of multiple stars rather than just the centroid of a single star.  Multi-star guiding is enabled using a check-box on the Guiding Tab of the Advanced Settings dialog.  When this option is enabled, the Auto-select function will identify up to 12 stars in the field of view that have adequate SNR.  No more than 9 of these will be used at any one time, but the remainder will be used to replace secondary stars that are lost or rejected for some reason.  The "primary" star is the single best candidate, the same one that will be selected if multi-star guiding is disabled.  As guiding proceeds, some of the secondary stars may be rejected because they are too dim or have drifted outside the field of view.  This is of no concern, the multi-star guiding algorithm handles the secondary list automatically.  When multi-star guiding is active, the PHD2 image display will show the usual rectangle around the primary star and circles around the secondary stars.  All other UI features associated with a guide star - brightness properties, SNR, FWHM, etc - relate to the primary star, not the entire list.  Multi-star guiding can be enabled or disabled while guiding is active.  However, enabling the feature will force another 'auto-select' procedure. The multi-star algorithm uses the secondary stars to refine the centroid position and reduce its volatilty, so there is essentially no way for it to degrade guiding performance.  Whether it produces a material benefit to your overall guiding will depend on many factors including image scale, star and background sky brightness, star size, focus, and camera noise.  Because of the way the algorithm is implemented, your best option will be to try it and decide for yourself.

[TerryMcK]

PHD2 and EKOS are now both offering multi-star guiding. My experience of the EKOS implementation it is very good so I will also try PHD2 multi-star when it becomes available within Linux as a full release rather than beta or release candidate.

[Gina]

I use standard Ekos guiding and find it fine and more than adequate.  So...  "If it ain't broke, don't fix it!" ? 

[Skipper Billy]

Used the multistar tonight for the first time - it was a good test for it as the seeing is shocking and it coped remarkably well.

 

[TerryMcK]

What sort of guiding rms were you getting David? I noticed when I arrived home last night it was clear but seeing was appalling.

[TerryMcK]

It has now been built for the Astroberry build on the Raspberry PI. It adds an extra box in Guide>Advanced Settings>Guiding Tab

I've not had chance to try it out yet but just upgraded my PI4 to the latest Astroberry build which includes PHD2 latest (2.6.9 dev2) and Kstars 3.5.0 2020-12-06T18:17:19Z

[ApophisAstros]

Posted by: @skipper-billy

Used the multistar tonight for the first time - it was a good test for it as the seeing is shocking and it coped remarkably well.

 

About the same RMS as my last session on 1 guide star in the distant past..but will give it a go if i ever get imaging again.

Roger

[Skipper Billy]

Posted by: @TerryMcK

What sort of guiding rms were you getting David? I noticed when I arrived home last night it was clear but seeing was appalling.

It was hovering around 0.4" Total RMS using multistar and around 0.5" on single star but the seeing was shocking. I wouldn't have bothered imaging normally but I only wanted RGB stars for another image and the high cloud effectively softened the stars and saved me running Convolution !!!

[TerryMcK]

@skipper-billy
interesting. It sounds worthwhile selecting multistar when seeing conditions are not too good.

[Jkulin]

I have used the Multistar guiding in PHD2, but it did find that it wasn't automatic, you had to enable it each time?

My guiding was no better or worse, I was averaging between 0.17-0.29rms @ 2007mm FL, however I do believe that it will cope far better when cloud comes across, as even though it happened on a number of times it maintained the guiding allowing me to finish my sub, especially when you only have 30 secs of a 20 min sub left to capture.

[TerryMcK]

I have enabled it for PHD2 within the Linux release that is installed on AstroBerry. It seems to stay enabled between sessions ok.

[Dmack1]

Just coming back to this one to say that I have started using multi-star guiding and also started using the Predictive PEC algorithm instead of the standard hysteresis (what does that even mean ???? 😁)

 

Between the two I seem to have improved my guiding by 30- 50% in terms of total RMS (in ") - (NEQ6 mount) which is pretty good. So its definitely worth trying out these things - personally I'm always reluctant to change ANYTHING because I get so few clear nights I never want to risk losing time to trouble-shoot changes!

 

@Jkulin it was automatic for me - no need to re-enable on the next night.

Edited March 18, 2021 by Dmack1