Theoretically - could you do narrowband imaging during the day?

[nytecam]

I've recorded stars eg point sources to ~mag 3 in daylight via a 30cm goto scope and all the planets Mercury - Saturn in daylight - no filters were used - it's no big deal - once you've found them

[Shibby]

Personally i have no idea how he exposed that many stars in daytime, the most i've managed to image in the day is Venus.

I should think those time-lapses are taken with a full moon rather than daytime!

[jezhughes]

I should think those time-lapses are taken with a full moon rather than daytime!

Scenes like at 1:30 i don't think so. I'd imagine you'd need very large exposures to get that much light in and they wouldn't form a lapse like that if so

[Shibby]

Scenes like at 1:30 i don't think so. I'd imagine you'd need very large exposures to get that much light in and they wouldn't form a lapse like that if so

No longer than the exposures when there isn't a Moon around! Think about how short the exposures would need to be during daytime and how many stars you would pick up with such short exposures...

[FraserClarke]

How far would you get with narrowband imaging... too tired to think about that just now! :-\

Thought about this a bit more...

The really easy way to think about this is remembering that we take narrowband flat fields using few second long exposures of the twilight sky. So pretty obviously the twilight/daytime sky is too bright to let you see astronomical targets. Here's my back-of-the-head calculation on how bright...

Daytime sky is ~4 mag/sq-arcsec. That's over ~300nm (400nm to 700nm), and let's assume it's evenly distributed (OK, it's blue but order-of-magnitude and all that...). Typical good amateur H-alpha filer is 3nm wide (e.g. Astrodon), so has 1% of the total daytime sky background; meaning the sky background in the H-alpha filter is ~9 mag/sq-arcsec.

Surface brightness of M42 (a nice bright H-alpha target) is apparently about 17 mag/sq-arcsec in the core, and if we assume a goodly chunk of that (say 25%) of that is coming out in H-alpha, that gives an H-alpha surface brightness of 18.5 mag/sq/arcsec; i.e. almost 10 magnitudes fainter than the sky.