How best to take flats within a sequence

Hi folks,

I’m struggling to work out how best to take flat frames within a sequence of lights.

My filter wheel hasn’t been consistent in returning my filters to exactly the same place with respect to my camera sensor, which has meant that dust and other blemishes have occasionally been incorrectly corrected if I use flats taken at the very end of a multi filter sequence (given I have to rotate back through the filters). The best solution would be to take the flats after completing each set of lights exposures for that filter before moving on to the next filter. I’m finding this difficult and overly cumbersome. I used to be able to pause the sequence, place a lightbox on the scope (without moving or parking the scope) and take the flats, then pause the sequence again, remove the lightbox, and continue. When I do this now the sequence goes into recovery mode and makes taking flats very difficult, and if instead of pausing the sequence I park the scope (no recovery mode ensues) I then can’t continue a sequence after that point (SGP gives me a warning that light frames are scheduled after a park command and won’t initiate the sequence). There must be an easy way to take flats within a sequence surely? A certain combination of settings perhaps that I’m missing? Ideally I’d love it if SGP could recognize that I’m taking a flat frame, pause the sequence (to add a flat box), pause guiding and avoid a recovery operation, take the flats, then recognize the next light sequence, pause the sequence (to remove the flat box), resume guiding on the same guide star (to avoid a new plate solve) and begin the best light event with the next filter. Can I somehow automate this?

Any help appreciated. I’ve tried a number of things without luck. Perhaps it makes a difference where a pause in the sequence is added - at the end of the previous light frame certainly doesn’t work, but perhaps pausing the sequence at the start of the flat frame does? Some of these things I’m yet to test
but with quite a few combinations possible I’m hoping someone has a great solution already.

Any help is greatly appreciated :slight_smile:


P.S. I use a portable setup that gets packed up and down for each session so I need to take flats for every imaging session

The workflow you were using seems reasonable and this should not be happening. Can you help us understand exactly how to recreate this issue? For instance, is “pause” from the Pause button or is it part of a pre / post event? The more detail you can give the easier it will be for us to recreate and stop this from happening. Logs showing this sequence of events can also be very helpful to us. Thx.

I’ll see if I can dig up a log of this although I’m not sure I have it. I had enabled pause in the event settings as a post event action in the light frame before taking the flat. I’d put the light box on and then guiding (I’m using an OAG) reports errors and the sequence goes into recovery mode. My next plan was to put the pause (in event settings) at the start of the flat frame event and see if that changed the behavior (that there is some internal recognition by SGP that this is a flat frame and that a lost guide star - or guiding - is not important and the flat frame sequence can continue without needing to recover). Similarly I thought maybe the next pause could be at the end of the flat frame event (post event), to remove the flat box, so that the sequence can move onto the next light event and resume guiding? I guess if I could have a pause guiding check box for these events it would solve the problem?

ok… this seems like the problem. A loss of guide star when a sequence is not running (is paused) should not be a meaningful event. I’ll see if I can recreate that.

Thanks for looking into it Ken :slight_smile: Just keen to get a workflow going that can keep the filter in exactly the same place for the flats as for the light frames (so flats taken straight after the light frames) and that also allows a sequence to continue on afterwards without the need to re-platesolve and re-autofocus etc. The flat box with the OAG obviously destroys guiding every time I take flats so would be nice not to have a lot of guiding errors arise. If it involves manually stopping guiding in PHD2 that is fine, as I’m manually placing a flatbox on the scope anyway, although I’m not sue what SGP’s response to me stopping guiding mid sequence would be. Also maybe an option to re-platesolve might be a good thing if the scope moves a little when placing the flatbox on the scope. It seems though PHD2 can recenter on the previous guide star too (which has roughly the same effect).

I think we are having a miscommunication here.I have tried everything I can think of to evoke a recovery response from SGPro using a process similar to the one you describe. So… we are doing different things. I created light / flat combos where the last light frame has a pause action attached. When the last light is done, SGPro pauses. At this point, I wreak all sorts of havoc on the guider and, as expected, SGPro ignores all of it. When I am done simulating placement of a flats box over the OAG. I click “Resume Sequence” and SGPro continues on with the flats and never complains about anything.

Really, the fastest way to cut through these types of communication issues is with logs. SGPro 3.1 has a log browser to help you find logs. Recreate the issue, then go to Help -> Open Support Request. Pick “Current Session” and hit OK. I’ll take a look.

Thanks Ken and apologies if this has sent you down a bit of a rabbit hole. I’ll see if I can recreate the issue (won’t be until the new year I think) and send a log if the error persists. Appreciate the support nonetheless especially around this holiday period.

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