Dragscript to take simultaneous sky flats on two scopes

Hi, not sure if anyone else has a similar problem:

I’m using two scopes on one mount with Voyager Array. In my “all-night” drag script I switch profiles of the master between the two configurations and take sky flats in sequence, during dusk and dawn. Unfortunately in some months this means there is not enough time to take 20 flats of each channel on each scope between e. g. sunset and the time flats become longer than about 30s (or the other way around during dawn). So I’ld like to take them simultaneously on both scopes and still automated.
Since you can’t start a flat sequence on the slave directly (which basically would be the solution), I have thought about starting a drag script which does the sequence - would that run asynchronously? I’ld also have to make sure the slave never takes longer for flats than the master.

Any ideas?

Sky flat cannot be done in an Array system at same time for all nodes … you cannot sync the mount that is necessary for a skyflat.

Instead is not necessary to take so many flats for filter like you have reported ( the time is never enough also for one node). Do small number each night and use for master flat more night flat.
Flat is not necessary to do every night, a set of flat can be useful for months.

All the best

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Thanks for the tips Leonardo, I know you can not currently do this - for my use case, just asynchronously shooting with the second camera would work, it doesn’t matter if the mount slews during exposure of a flat.

Personally, I think 20 flats per channel is not overkill, but the minimum. Especially with (blue) sky flats with the chance of high clouds, passing birds and airplanes. I would, if I could, take 100 for proper outlier rejection.

I have two open-tube scopes (an RC and an Epsilon). This has, in the past, lead to not few nights of ruined images: Moving/leaving or new dust spots on the filters made old flats unusable and new ones taken a few days later, too. (Due to time constraints I can not always check on the same day if flats calibration has worked acceptably). So I started to shoot flats on each dawn and dusk, just to be sure.

Furthermore, weather here is capricious. If flats aren‘t taken the same night, weeks may pass before I can open up everything again.

In addition, a rotator will soon (again) be attached to the RC, making it necessary to match flats rotation to the camera angle - which is most easily done if matching flats are shot per night or at least per target.

Lastly, the construction of the RC make the „point it up and shoot with a panel“ rather unpractical because I would have to design/build a custom flat box that attaches to the secondary holder ring - there is no spot to balance a panel.

Thus my question if I can somehow trigger an asynchronous dragscript run on the slave telescope - it would be the easiest way for me to get enough flats every night.
Note that on many nights I don‘t use all filters (e. g. shooting RGB on one, L on the other, or only HORGB) - the reduced filter count leaves enough time to take flats.

I have the same telescopes as you have and have been using them for many years and my experience is just the opposite. Even the rotation of the rotator does not involve having to redo the flats in 99% of cases.

It is not to argue but because you have your experience I that of countless users who instead do like me without problems, I would like this indication to remain in the forum because we often tend to complicate our lives with not completely correct beliefs.

It remains that the flats on the sky in case of arrays cannot be made on more nodes, not because the function is missing but because it would be wrong due to lack of synchronism. Synchronizing in flats would be a disaster and the mount that moves too much is a problem. While you say that the movement of the frame does not give problems, I have exactly feedback on the opposite, what does not bother and is useful is the stop of the tracking during the exposure of the flats.

In any case, even if you did an asynchronous start of a remote dragscript you would have no information about it being finished and therefore the general Dragscript could create serious problems. I should also add a DO IF to understand if the slave nodes are free with no operations in progress.

These last two things can be done and can be useful in general even if dangerous, I think about it.

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Thank you, Leonardo.

I agree that „in general“ I can reuse my flats and do multi-night flats and use those. The problem is that in the cases when it doesn‘t work, the data is irrevocably lost. As said this is not an urgent problem because „usually“ I don‘t need flats for all filters for both scopes.

The proper solution, of course, would be to build an observatory, wall-mount a flat panel and take the flats with the roof/dome closed. I am considering this.