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2022-05-29: APP 2.0.0-beta2 has been released !

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Newbie question regarding calibration frames from imaging session

Brown Dwarf Customer
Joined: 1 year ago
Posts: 10
Topic starter  

Hello everyone!  I'm in only my second month of attempting some DSO imaging and have primarily spent that time on capturing exposures of the Orion nebula.  I downloaded the trial version of APP a couple of weeks ago, but totally forgot that I had until I received the email reminder that I only have 14 days left to evaluate yesterday.  I downloaded one night after an imaging session at 2 am in the morning and was fast asleep 5 minutes later, thus the reason I'd forgotten I'd downloaded in the first place.  So, I've been trying to work my way through APP and load some data into it to see the resultant output and evaluate if it's worth justifying the price it would cost.  My wife just lost her job a couple of months ago, so excess spending is limited right now.

Anyway, I'm starting out small, so to speak.  I have a fork mounted mid 80s Powerstar C8 on a wedge, which I realize is not the best for DSO imaging and can frustrate a beginner, such as myself.  So, I'm sticking to imaging with my Sony A57 DSLR and using some of the multitude of Minolta lenses I have, piggybacked on my C8.  While the fork mounted C8 on a wedge with Byers worm drive may not be up to snuff, as far as the most modern of tracking devices, it's a great star tracker for using a DSLR with moderate zoom and I have no trouble getting 30 sec subs with no star trails.

My question is regarding calibration frames and their integration into the stacking process.  Last night, I processed some data from an imaging session a couple of weeks ago.  It consisted of 70 * 17 sec light frames (ISO 1600), 15 * 17 Dark frames (same ISO), 30 flats and 30 bias frames.  I followed a tutorial on Youtube and the resulting image produced by APP was fairly decent.  I took a series of 30 second exposures using the same setup on the same night, as well as 8 second exposures, the idea being to combine those stacked images into a sort of HDR composition.  

After stacking the exposures from the 17 second session, is it necessary to load all of the flats and bias frames back into the imaging stack when I do process the 30 sec and 8 sec lights and darks from the same session or can I just use the master flats and master bias frames created by APP during the stack of the 17 second exposures?  Obviously a newb question so any help in understanding the process is appreciated.  Thanks!

This topic was modified 1 year ago by Jason Bumgarner

Galaxy Admin
Joined: 4 years ago
Posts: 1781

@jasonjeremiah Hi Jason,

A master bias frame can be used up to a year or sometimes more, depending on the quality of the sensor, provided the ISO and temperature were the same. The temperature is hard to manage on a DSLR though. A master dark can be reused as well even if the lights have a different exposure time since you also have a master bias. Flats usually have to be taken after each imaging night, especially if you remove the camera from the lens or telescope. Since you were shooting with multiple exposure times during the same night, the master flat can be reused.


HTH, Wouter