Hey! Is it possible to do the unguided dithering while recording a SER?
My use case is lucky imaging of planetary nebulae where I would prefer recording a bunch SER files instead of thousands of standalone images I'd get due to very short exposures.
There's no way to enable dithering for a simple recording, so I've tried setting it up in sequence editor but when running such a sequence I get an error that dithering (both each N frames or each N seconds) is not available when camera is not in still mode. I assume still mode is not what I want because it would record to a standalone image files.
you will need to use the advanced sequence editor if you want to achieve that - normally, SharpCap will try to arrange for dither operations to happen between captured frames, so that the captured images are not affected by mount movements. This either means the camera must run in still mode, or SharpCap needs to take steps to reduce exposure and discard affected frames (as during live stacking with dithering). This means that none of the 'easy to use' functionality will support what you are trying to achieve.
However, it's certainly possible to build a sequence to do this - the file attached below shows a simple example. Note that nothing stops the dithering from happening during a captured frame - in fact it could well occur across two frames in some cases, meaning that one to two frames will need to be discarded from the captured data per dither.
Thanks for the answer and the sample setup!
Now, I wonder if recording as a SER is not how people usually do it - I was under impression that reading out frames in video mode is faster than in still mode, so in case of very short exposures (up to 1s, for example) it should save quite a lot of time. Am I wrong?
yes, at an exposure of 1s, you are likely to see a reduction in throughput if you move into still mode rather than live mode - you might get 1 frame saved every 2 or 2.5s or so (a lot depends on how fast the camera can transfer the image data to the PC, so will depend on resolution, USB2 or 3, etc). At that sort of speed the choice of SER is probably not a key factor - saving to PNG or even FITS will probably not have much effect unless your PC is very slow. If you increase the exposure to 5 to 10s then the slowdown by moving from still mode into live mode becomes much less significant.
I guess this all leads to the question of why capture frames of (presumably) deep sky objects with exposures of 1s? That seems very short, unless you happen to have truly horrible light pollution or are using a very fast optical system like a RASA or SCT + Fastar.
I'm doing lucky imaging on planetary nebulae, hence the very short exposures of 0.5-2s (works alright with f/4 300mm newtonian). Also, I image at lat 55, so the nights here are also pretty bright these days but probably I'd do short exposures even during astronomical darkness as it would still help to squeeze more details.
Thanks for confirming regarding overhead of short exposures. For now I'm imaging using NINA which seems to be using native driver for ASI cameras, so there's not much overhead for 1s subs (whilst it was terrible, around 2-3s extra per sub, with SGP). In case I need even shorter exposures, I'll likely move to Sharpcap since dithering is possible and will just record SER and split it into multiple subs later in the process.
