Since I picked up this wonderful hobby that is 15 years after a stop of astrophotography, full in the digital age, I found myself in a new world, the guide of the pictures that was done manually with the Illuminated Reticle eyepiece has evolved in the Guide Camera for your personal computer or stand-alone, Foucault knife has been replaced by the Bahtinov mask and between those novelty I discovered “Flatfield machine” …
The principle of flat-machine is nothing but a white Panel illuminated as possible and allows you to highlight in photography all impurities, dust specks, small fibers that a dirty sensor is to be removed from hosting by stacking (the total of images) and you get a field without “fall light” at the edges and without those hateful impurities present on the sensor that penalize the final image.
Unfortunately, despite the rather trivial principle and electrical components very poor, these things depending on your invoice and high priced tool diameter in relation to the material and what they do, it is called 100 and more dollars for the 8-inch pipe for flatfield (the classic Celestron 8 “) but the cost can go up depending on the invoice and if you are amateurs like myself, but especially messy transhumant is easier, especially if they fail to save like me you bought to lowest quality.
After yet another break of the flatfield, and yet another patch, one evening we were unable to revive him, but fortuitously Macgyver, I found a simple and cheap way to make good flat with what I had on hand:)
It’s just a blank sheet of paper, without impurities, or better yet a white Plexiglas Panel (in my case I recycled the replacement Panel of my flatfield without electrical connections glued) and a smartphone with FLASHLIGHT that activates the flash continuously.
Simply place the white Panel to the tube, like the flatfield, will light the torch smartphone, point it at the Panel and move it away about 1/2 a foot. To find the correct distance is sufficient to check when the Panel lighting is uniform to the eye, it will look like empirical solution, but it works! 🙂
On the net I found an article that talked about using the display of a Notebook after you open a picture completely blank, but if you don’t have a nice screen on laptop it will have uneven lighting zones.
Finally, it is possible to build with your own hands, the principle is simple, and I refer you to this excellent tutorial by Lorenzo Comolli: http://www.astrosurf.com/comolli/flatfield.htm