Why does Autoguiding stop for plate solves & focus frames?


#1

Why can’t we keep autoguiding on when we do Plate Solves and Focus Frames? If autoguiding is turned off, Plate Solves have a higher probability of failing. Also the auto focus sequences are going to be less accurate and maybe close to useless, depending on how good the mount is. Seems to me it should be easier to just keep autoguiding on continuously, except when the mount does a slew.


#2

In the control panel under the autoguide tab, uncheck “Pause guiding during auto focus” and guiding will continue during autofocus.

As far as I know you can’t continue guiding during plate solving. In the short time it takes to do a plate solve, the mount should not move far off target if polar aligned. Also, to have guiding running during plate solving, it would have to pause and resume guiding, possibly multiple times, whenever adjusting position.

Chris


#3

I’ll take a shot at this one …

You can decide not to pause autoguiding during autofocus by simply
clearing the “Pause guiding during auto focus” checkbox in the “Auto
Guide” tab of the “Control Panel”.

For plate solve, I guess it depends on whether that plate solve is part
of a centering option or not. I would think that you would not want to
be autoguiding while trying to center–your autoguiding would tend to
undo any centering corrections, right? If you are plate solving for
sync and autoguiding at the same time, a guide correction could occur
between the solution and the sync, making you sync to the wrong location.

Does that would reasonable?

– Shane

Edited to fix two typos …


#4

If you have an OAG, you’d likely want it disabled though it might be worth trying anyway. The focus changing while guiding might cause a number of issues/corrections that might be invalid … The star might move, be lost, or mirror shift (if applicable) will cause it to jump. This might trash the autofocus frame, likely a lot more than not guiding :). If using a guide scope, might as well keep it enabled!


#5

Thanks for heads up on autoguide checkbox. That will work perfectly for me since I have a separate guide scope.
For plate solve, it seems to me the best solution is to always keep guiding on, both to maintain the current position for the centering operation, and to produce the best quality image so that the plate solve has the best chance of solving.
Obviously, the program needs to stop autoguiding before each correction slew, then resume it after the mount settles, and it can easily to this.
@cmassa: “In the short time it takes to do a plate solve, the mount should not move far off target if polar aligned.” This is true, however to whatever extent it does move off center during the plate solve, autoguiding would eliminate that error. More important it seems to me is if your mount has significant tracking errors when not autoguiding, this will produce fuzzier stars which can cause a plate solve failure.
And why not just do it? There is no downside to doing so. It’s a win-win.


#6

My plate solve only takes a few seconds using PinPoint, less time than a single autoguiding cycle. If my mount was wandering by more than a pixel in that time, plate solve accuracy would be the least of my worries!


#7

It makes no difference whether autoguiding is on or off during the plate solve itself. My fault for not making clear that I am in favor of autoguiding on during the image capture used for the plate solve. The time required for taking the image is what matters. If that is very short, say a few seconds, then you are right on. However, the image exposure time might be much longer. Some posters have mentioned having a fixed filter that requires a very long exposure to get an adequate number of stars on the image. You might also be using a 2x focal extender lens, which would require a 4x exposure time.
Seems to me, although I have not measured it, that my cycle time for autoguiding is quite short. I know I can manually cycle it on and off as fast as I can click the Stop button, Start, Alt-S, Guide.


#8

Really the only case where you need guiding during plate solving is if you’re plate solving through a narrowband filter.

We’ve discussed this before and will likely add an option to do this. It will certainly add additional time to the centering process but if you’re doing 30 second+ frames for plate solving it’s probably not that much of an issue. If you’re running 5 second images for plate solving then the time to start and stop the guider will start to be more significant.

Thanks,
Jared


#9

Just a note here. On the more recent versions of PhD, it will continue to take guide exposures but will not auto-guide unless you have SGP set to do that. This could be mistaken for actual guiding, when it really just continues to expose the guider but not to guide - it will say paused instead.


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