Tutorial: Flat Frames # 1

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Merlin66
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Tutorial: Flat Frames # 1

Post by Merlin66 » Wed Apr 18, 2012 12:27 pm

Some notes from the forum on flat frames....

Earl:A flat frame is used to remove lens issues like dust spots and Newton rings.

I defocus on the center of the sun until I can only see the dust spots against the background. If I am using a barlow lens I will also see the newton rings. I increase brightness to about the same as the focused images. Then I take an avi that is as long as my images. I usually take a 500 or 1000 frame avi. Every time I change lens combinations or change the length of the avi I take a new flat so I can end up with several flats during post processing. Using the histogram to adjust the flat is the best way to getting good results. If you are not familar with using histogram I have a tutorial on my website - www.hapb.net/Solar/histogram/histogram.html

The dark frames are taken with the telescope lens cover still on. I usually take a couple of these throughout the session. The longer the session the hotter the camera can get so noise changes throughout the session.

Stephen:If anyone is using ASTRO IIDC you may already know, but it has a built in flat frame feature which allows you to create a flat frame in real time and apply it in real time to the recorded image. Just defocus and hit "record flat frame" and them "apply it". The software subtracts the dust and other stuff while recording the .mov file.

Earl:Registax -Open you flat or dark frame just like any other image. Once loaded select either create flat or create dark frame. It will stack the images. Once completed save the image. No wavelets. Then you select load flat or dark frame. Open up your solar image and process as usual. It will automatically process you frames into your final stack. It's pretty easy.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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