Do the flat frames ...
 
Share:
Notifications
Clear all

Do the flat frames for bad pixel maps need optics?  

  RSS

(@blairconner)
Molecular Cloud Customer
Joined: 12 months ago
Posts: 3
June 26, 2020 18:23  

Started my 30 day trail for APP recently and so I've been playing around with a bunch of different features. One feature I like in particular is the Bad Pixel Map. Thinking through the process though is there any reason that the camera needs to be attached to its optics? I tried just using a white computer screen and placed my DSLR up against the screen to capture the flats. Seems like the generated bad pixel map is working, but I was just curious if there's something I'm missing as to why taking the flats (for the purpose of a bad pixel map) would need the optics since its just looking for hot and cold pixels.

 

Side question, about how long of an exposure would you recommend for dark frames? Tried 30s and it seems okay but not apposed to making a new make using longer exposures.

 

Thanks!


ReplyQuote
(@solo05)
Brown Dwarf Customer
Joined: 4 years ago
Posts: 6
June 26, 2020 19:10  

Hi Blair

Your darks must be the same iso, time(seconds - minutes), temperature, as the lights.  At least you can do these while packing up your gear for the night.

Flats are to see dust bunnies, vignetting and other imperfections in the complete optical train.  Must be done at same focus as lights right after imaging and before darks especialy on a DSLR as you might move the focus accidentaly when you cover the lens for the darks. 

https://www.astropixelprocessor.com/how-to-create-a-bad-pixel-map-bpm-by-sara-wager/

Regards

teve


ReplyQuote
(@blairconner)
Molecular Cloud Customer
Joined: 12 months ago
Posts: 3
June 26, 2020 19:14  

@solo05 Thanks for the response. Yes for calibrating my lights I'm aware the darks need to have the same settings and for flats to calibrate lights they of course need to be with the same optics, focus, etc.

I'm specifically interested for only generating a Bad Pixel Map, not in calibrating Lights. If you're only trying to find the bad pixels why would the optics matter?


ReplyQuote
(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3410
June 26, 2020 20:37  

It wouldn’t indeed. Unless you have cold pixels, those show up in flats, but modern sensors don’t seem to have those a lot anymore. So purely for the BPM you can use a long dark (longer is noisier and better for that). 


ReplyQuote
Share: