Flat Frame Issues

@rockinrod Hi Rodney, APP requires either dark flats (dark frames with the same exposure time as the flats) or bias frames to be available. You can use master dark flats or master bias as well. Do you have those?

@wvreeven

I don't have any Master Flats or Master Bias...Or dark/flats...My Flats are always .4 sec as per the instructions I use.

My Bias also get kicked out as well...I'll have to re-think this to see how to do it...I can build a Master Flat from the Nebulosity Program, but I'm not sure APP will accept that. Will it?

@rockinrod Creating a master in another application will indeed not work.

In order for APP to work well, you will need darks and flats. Apart from that you can choose to either use bias or dark flats. One processed APP will create masters for all of those and the masters for dark, dark flat and/or bias can be reused. It usually is a good idea to take new flats after every imaging session. So if you do not have master dark, dark flat and/or bias then please start with taking the frames and adding them to your processing.

When you say that "your bias got kicked out" what do you mean exactly? Did your raw bias frames get kicked out? Was there an error message involved with that?

@wvreeven

I have a whole set of Flats which I've been using, but these were taken with Nebulosity, or Astro Photography Tools program...

I took these flats this morning from last nights imaging. Using the same Gain 200, but the exposure time was .4 sec...These are the ones getting rejected. You saying these flats need to be the same exposure as my Darks? They are also 300sec exposures at 200 Gain.

I've never used a Dark/Flat with any of these other programs, so i don't have a clue what those are, or how to take them.

Okay, perhaps i found the problem. I was not using any Bias Frames, just Lights, Darks, and Flats. It seems APP like them both, not separate...

When i added Bias I received no error boxes...I'm doing a sample of 5 subs, etc, just to see

Yes, a bias or darkflat (which is almost like a bias) is necessary to be able to correct properly. If other software is using them without correcting for bias, something will go wrong in the background I think (that usually needs close inspection).

@vincent-mod

Got it...I'll do the 48 Lights now and add everything...

Thanks!

Posted by: @rockinrod

@wvreeven

I have a whole set of Flats which I've been using, but these were taken with Nebulosity, or Astro Photography Tools program...

I took these flats this morning from last nights imaging. Using the same Gain 200, but the exposure time was .4 sec...These are the ones getting rejected. You saying these flats need to be the same exposure as my Darks? They are also 300sec exposures at 200 Gain.

I've never used a Dark/Flat with any of these other programs, so i don't have a clue what those are, or how to take them.

Actually, I wrote that the dark flats, if you use them instead of bias, need to be of the same exposure time as the flats. But I see that you solved the issue. Well done!

@wvreeven

I just have yo make sure all the Gains/Iso's are the same....I've never done a Dark/Flat so I have to learn that one. I always used with a Dark or a Flat

It's very straightfoward, a darkflat is exactly like taking a dark, but with the same exposure as your flat. That is all. 🙂

@vincent-mod

Okay, I've never tried that, or had to do it.

Seems to be working now. I just keep the gain the same on both Flats and Bias frames, and it's fine...

Thanks

Yep excellent. A darkflat isn't much different from a bias, it's just that some sensors might have a slightly different noise pattern coming up if you expose just a bit longer, like you do when taking flats. From a more scientific perspective, having the same exposure length for a calibration frame as the data you want to correct is always the best approach as you're sure that should produce the exact same noise pattern (* not the exact same, but approaching a similar pattern, thanks Wouter 🙂 ).

@vincent-mod

Makes sense...!

Thanks again,

Rod