FITS images from a video stream

American Association of Variable Star Observers (AAVSO)
Mon, 05/16/2022 - 18:58

If I am trying to capture photometry for a SuperNova event, one of my fears would be over exposing the images. That would be sad: to be on target for the event but then capturing nothing of value.

What if the DSLR was put into a video mode? Is there experience with video-to-fits? That way you could stack your fits images to any SNR you would like.



American Association of Variable Star Observers (AAVSO)
This would have the benefit…

This would have the benefit of having excellent time-resolution as well.

But would the photometry be that great? The video modes of DSLRs must use heavy compression because at the usual (say) 24 or 25 fps, and (say) full HD resolution, the uncompressed data rate is just too high.

And if the event is, after all, not that bright but is more like 10ish or 12ish mag as it is likely a priori, you would need to stack roughly 1000 frames and more, and wouldn't the read-noise from all those individual frames degrade the SNR very significantly?

Alll in all I would think that  it's better to leave the rather bright events for the all sky cameras, and use the DSLRs for more realistic (likely) magnitude ranges.

Then again, the expected brighness and the sky location of the event are highly correlated: If you choose to point your DSLR  to somewhere outside the band of the Mily Way, (either because the Neutrino detectors told you to look there or because you are just making a random wild guess in the absence of sky localization from SNEWS), any SN in that field will likely be very bright for lack of extinction in that direction. But if you point your DSLR to a field in the Milky Way band (either because the neutrino  detectors told you to do that, or because you are pointing to one or more known Red Supergiants that are all (more or less) at low galactic latitude, or because you are making a wild guess), you should not expect a very bright event because of extinction. So it will depend on where you choose to point, during THAT night.

And there is one other thing to consider: even IF the exposure should saturate, you will still have the timing information of the first optical signal which is in itself very valuable:

This paper has a nice plot of the expected delay between neutrinos and first photons visible for the event depending on the progenitor...the differences are HUGE:

If I understand Figure 2 correctly, it tells us that the "shock breakout" can happen only 100 seconds or less after the neutrino-emitting core collapse for Wolf Rayet stars (they are almost naked cores already anyway) up to several 100k seconds (so days!!!) for Red Supergiants... so conversely the delay time can tell us a lot about the progenitor, even if the progenitor cannot be later identified in historic catalog data. 

Which also leads to the question where to store all that video data if you must prepare to wait for the shock breakout for , perhaps, a day and more.