Sped up dithering routine when using very long guide exposure times

Hello,

my situation soon to come:

  1. Mount with Encoder running long sub exposure times on the main camera
  2. guide camera “helping” (dec drift/flexure/refraction) by running on very long guide time like e.g. 20s-30s

By using PHD2 with such long guiding rates brings up the issue, that when dithering (I assume I would still have to use dithering via the guider, not the “direct mount” option) I would have to wait for a pretty long time (several guide cycles).
The “unguided” dither option via random pulse duration and paused/resumed guider would seem to be the way to go in this constellation, but I dont know of such an option in SGP.

So is there a way to speed this up or am I creating problems that dont exist? :slight_smile:

thanks and cs,
Wolfgang

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I am not sure I understand. What do you mean that the guide camera is “helping”? I am not familiar with the guider setup.

No problem.
Basically, it is a unguided system, which is portable and I would like to counter residual tracking errors (by minimal PA error or flexure) with my guider at hand, which would just slightly bump DEC every 20-30s or so - if needed of course.
I was told by my local astro shop, that this is very common among fellows which are using a portable mount with encoder(s).

But I came to the conclusion, that in such a case, the dithering routine (which is using the same guide exposure durations as the regular guide routine) would mount up quite some time until PHD2 would consider the star settled again. (several times the guide exposure of 20-30s)

So I came up with the least complicated solution, which seems to be:
pause PHD -> dither via random guide pulse (as when running fully unguided dithering) -> resume PHD (and autoselect star if necessary)

I hope, I could make my point. :slight_smile:

Yes, thx. I understand now. There is nothing at the moment to compensate for this. We’ll need to give this one some thought… the challenge is to add this functionality without forcing all users to see it (since only a very small percentage of ppl would use it. Maybe? At least nobody has ever asked for it until now).

Okay, thank you very much for considering.
I dont know, how many folks are using this constellation and are either doing a workaround I can not imagine or they even dont dither at all (which seems pretty adverse to me).

I will ask my local shopkeeper again about this very topic, still a future feature within SGP would be fantastic (to me at least :wink: )

I’m interested in any solution on this. I have a 10Micron Mount and would prefer to use guiding for long exposures but have not done so for the reasons indicated above. With guiding camera set on 15-30s and dithering, guide settling may take a very long time.

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I’d use this. I have a CEM60 EC and it almost runs unguided, with just the odd RA correction and very low DEC drift. I’ve compromised with 4s guide exposures, any more and settling takes an age.

Does PHD expose the guide exposure timing to SGP? This would be great and SGP could ask PHD to settle at 1 or 2s and then go back to the normal guide exposure time.

@Starflyer:
Your suggested solution via decreased guide exposure intervals would impose the risk of losing the guide star.
Also I am afraid, that PHD2 wont let external programs mess with its settings on the fly.

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My mount is an ME permanent mount running ProTrack and a large model so can do 15 minutes unguided with an FSQ (less with longer FL, of course)

What I suggested a year or more ago on the PhD forum is that for well tracked mounts, instead of long guide exposures (which, among other things, would saturate the guide star) to average seeing, what would be best is to create set of two centroids made from regular (2-5 sec) guide exposures for however long the user selects. One of the centroids would be created from exposures early in the correction interval and one from those late in the correction interval. Drift would then be calculated and corrected at the end of the correction interval. The actual correction interval (time between corrections) could be as much as 10-15 minutes (or even more, depending on the mount).

During the dither, the short exposures could be used in standard fashion to do the dither and therefore would be quick.

At the time I made the suggestion, it seemed this was in the works but I have not heard anything about it since.

This is not to be confused with the “Z filter” option, BTW…