5ash
12-07-2015, 02:26 PM
I posted a picture of the Tarantula last month using "twilight flats" obtained by taking pictures through the telescope whilst covering the objective with layers of milky white acrylic sheets. Since I need 2 second exposures with my CCD camera and they take 6 seconds to download , there is not sufficient time, to get a reasonable number of similar flats , as the light intensity falls with the setting sun. Anyway I have been using them captured this way with DSLR's and had no problem as the time needed was much less. However it was obvious on my Tarantula picture that all was not well.So I invested in one of "Exfos" (Peter) Light boxes and what a difference! compare the two pics below , the first processed with a twilight flat and the second with a lightbox flat. Most obvious is in the first where there is a darker area to the right hand side with few stars compared to the second picture where it is lighter and more abundant in stars.
philip
philip