best way to take flats

[Astro_mark_c]

Hi,

 

What's the best way to take flat images?  I've read a few different opinions on settings etc.  The flats I've tried doing don't really seem to be removing the vingetting, which becomes really noticeable when stretching my stacked image.

 

Thanks,

Mark

[ollypenrice]

Depends on the camera and the scope. Don't shoot Newtonian flats in the daytime, do it in the dark. It's best in the dark with any scope but Newts often tend to leak light from the bottom. If using a DSLR make sure no light gets in through the viewfinder. If using a CMOS chip shoot darks for flats (AKA flat darks) at the same settings as used for the flats. If using CCD a master bias will do as a dark for flats.  An even light source is needed. EL panels are good, sometimes dimmed with typing paper. For smaller apertures tablet and laptop screens will also work. Aim to get the histogram peak between 1/3 and 1/2 of the way from left to right.

I use CCD so the best DSLR mode will be suggested by someone soon, I'm sure.

Olly

[Astro_mark_c]

1 hour ago, ollypenrice said:

Depends on the camera and the scope. Don't shoot Newtonian flats in the daytime, do it in the dark. It's best in the dark with any scope but Newts often tend to leak light from the bottom. If using a DSLR make sure no light gets in through the viewfinder. If using a CMOS chip shoot darks for flats (AKA flat darks) at the same settings as used for the flats. If using CCD a master bias will do as a dark for flats.  An even light source is needed. EL panels are good, sometimes dimmed with typing paper. For smaller apertures tablet and laptop screens will also work. Aim to get the histogram peak between 1/3 and 1/2 of the way from left to right.

I use CCD so the best DSLR mode will be suggested by someone soon, I'm sure.

Olly

Thanks for the reply, 

 

im using a mirrorless camera and lens so the info about CMOS sensor is very interesting and helpful, thanks!! 

[Astro_mark_c]

1 hour ago, ollypenrice said:

Depends on the camera and the scope. Don't shoot Newtonian flats in the daytime, do it in the dark. It's best in the dark with any scope but Newts often tend to leak light from the bottom. If using a DSLR make sure no light gets in through the viewfinder. If using a CMOS chip shoot darks for flats (AKA flat darks) at the same settings as used for the flats. If using CCD a master bias will do as a dark for flats.  An even light source is needed. EL panels are good, sometimes dimmed with typing paper. For smaller apertures tablet and laptop screens will also work. Aim to get the histogram peak between 1/3 and 1/2 of the way from left to right.

I use CCD so the best DSLR mode will be suggested by someone soon, I'm sure.

Olly

For Flats on one hand I’ve read that it’s the same settings as you took your lights with, but with a bright light source behind a t shirt, paper or using something like a laptop screen.  But I’ve also read that you do the above mentioned but this time using an ISO of between 400-800.  Which one is correct? 

Edited February 25, 2020 by Sidecontrol

[Astro_mark_c]

Heh just realised I’ve been doing flats wrong, doh 🙈😭

[ollypenrice]

1 hour ago, Sidecontrol said:

For Flats on one hand I’ve read that it’s the same settings as you took your lights with, but with a bright light source behind a t shirt, paper or using something like a laptop screen.  But I’ve also read that you do the above mentioned but this time using an ISO of between 400-800.  Which one is correct? 

You can't use all the same settings because your light panel is a hell of a lot brighter than the night sky!

Olly

[Astro_mark_c]

2 hours ago, ollypenrice said:

You can't use all the same settings because your light panel is a hell of a lot brighter than the night sky!

Olly

yeah I get that now, need to put it into Aperture Priority mode.