Flats not working

[Joeistotalycool]

Hello, I was wondering why flats were not working correctly - They worked in the past but now they overly correct.

I use a 1200D DSLR and I am shooting h-alpha. Stacking in DSS

I have also included a RAW flat frame

Single__0012__12C_0s5s_NGC2264_2018-10-22_ISO800.CR2

[ollypenrice]

I've had this issue and never understood where it came from. However, things to check:

- Are you using exactly the same capture mode (nothing to do with camera settings like exposure or ISO) in whatever capture programme you are using? Some have a fast download option, for instance. You need to use the same mode for flats as lights.

- Have you taken darks for flats (sometimes known as dark flats?) These would be darks taken at exactly the same exposure and ISO as your flats. Over correction often arises from a failure to do so. (In my case, though, they made no difference, I have to say. My own problem lay elsewhere but yours might not.)

- Inadequate flushing between flats exposures can cause this. It might be worth building in something like a 30 second delay between flats at least to see if this helps.

In one setup I used this was an infernal and intractable problem which I cured once and thought I'd solved. Then it came back and the same cure no longer worked. Very odd....

Olly

[Joeistotalycool]

2 minutes ago, ollypenrice said:

I've had this issue and never understood where it came from. However, things to check:

- Are you using exactly the same capture mode (nothing to do with camera settings like exposure or ISO) in whatever capture programme you are using? Some have a fast download option, for instance. You need to use the same mode for flats as lights.

- Have you taken darks for flats (sometimes known as dark flats?) These would be darks taken at exactly the same exposure and ISO as your flats. Over correction often arises from a failure to do so. (In my case, though, they made no difference, I have to say. My own problem lay elsewhere but yours might not.)

- Inadequate flushing between flats exposures can cause this. It might be worth building in something like a 30 second delay between flats at least to see if this helps.

In one setup I used this was an infernal and intractable problem which I cured once and thought I'd solved. Then it came back and the same cure no longer worked. Very odd....

Olly

Thanks for the tips, I will test them some other time (When its clear out  )

Not being able to diagnose a problem is about one of the most frustrating things you can have in the hobby lol  (Well, apart from equipment straight up breaking of course )