Flat-field Frame Box (Astrophotography)

Flat-field frames are an important part of quality astrophotography images. Like "Dark Frames" they help us remove image artifacts caused by distortions in the optical path. Specifically they help with what's known as vignetting, which is the uniform brightness or saturation throughout an entire image. Normally in order to acquire these frames you would have to wait and take a photo of the dawn or dusk sky through your telescope. These are simple instructions on how to make your own flat-field box out of an electroluminescent panel and some cardboard so you can gather your frames at any time.

Electroluminescent panel (You can find these cheap online)

Free cardboard from your local post office

Tape

9v Battery

For my box I used one of the free boxes the post office offers for priority flat rate shipping, but don't tell them I didn't use it for shipping. You can use whatever you have lying around, all you really want is something you can easily hang in front of your telescope. Simply fold your box together but cut the flaps off either the top or bottom.

Secure your panel to the inside of the box with whatever means you have available. I just folded a piece of tape over to make it double sided which holds it perfectly. You can also tape the wires to the boxes side to keep them out of the way if you want.

To take your flat frames its best to wait till its dark outside, but you can use a dark room if you have one your telescope can fit in. Your also going to want to use the same gain or ISO settings that you took your original picture in. The exposure time can vary depending on the camera but will be relatively fast. Your frames should come out like the included photo above. Don't worry about spots caused by particles or imperfections, your main objective is to have a uniform brightness throughout the frame.

You can use your Flat-field frame to calibrate your main image using free software such as Deep Sky Stacker or Registax. With a proper Flat-field frame you should notice significant difference in your image quality.