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Hi guys, I’m making a topic again for flat frames. i am using a dslr (canon 6d) and i’ve been experimenting with flat frames because i was never able to get them to work. I’ve tried everything that i was reading online and all recommendations from other astrophotographers. I’m using a white panel with a tshirt, i tried the histogram from all the way to the left to all the way to the right, i’ve tried exposure times from just below a second to 1, 2, 3 up to 10s. I tried using flat darks, bias, tried not using any of those and it makes no difference. I even measure the adu for my camera! Nothing worked! 😩 what am i doing wrong? Any ideas?? |
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| The usual culprit to this predicament is that you have a light leak of some sorts. which is normally quite difficult to give advice for because we aren't simply there with you. Given that you use a Newtonian the risk there is rather significant. |
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andrea tasselli: If i’m not mistaken the light leak will introduce uneven illumination in certain areas of the image therefore inaccurate corrections. Am I correct? In my case it either overcorrects or does nothing at all. The closests i got to correcting the image was when i used a histogram matching the light frames and even then it was not good enough. |
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| Can you post an example image of what your calibrated subs look like when the flats dont work? Simple stretched JPEG will work for that use. |
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If i’m not mistaken the light leak will introduce uneven illumination in certain areas of the image therefore inaccurate corrections. Am I correct? In my case it either overcorrects or does nothing at all. The closests i got to correcting the image was when i used a histogram matching the light frames and even then it was not good enough. Indeed you are, a light "leak" can take many different shapes, Overcorrection is a typical example of the effect a light leak has on the flat normalization operation. |
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| An autostretched image of the flat would be helpful as well. I find using NINA flat wizard to be most helpful in getting the correct exposures for my flats. |
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Jeffery Richards: i’m using an asi air is there an equivalent to NINA? |
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| Ahhh, then NINA won't work for you. But providing an autostretched flat would still be useful so we could see what it looks like. Also a light processed with and without your flat as well. |
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You're flats should have a reading between 25000-30000 adu. Just adjust the exposure time to achieve that. Mike |
