Ic434: Horsehead Nebula

I imaged this famous object about the same time than the double cluster. The following night I tried to take the color data but there was a thin layer of high clouds that really ruined my session.

After calibrating these Ha-images I thought my flats were poor because there were huge dark spot on one corner. So  I made one only flat-calibrated combined image and then deleted the flats. Now I took a better look to the combined image and noticed that the background is actually very flat, except that one spot of course. Again something to learn for me...

But... This was actually a training session because I also change my guiding system to work with OAG (off-axis guider). I had quite bad flexure earlier which reduced sub exposures to 5 minutes and I couldn't get rid of it, so this was maybe the easiest way to solve that.  I also took the pictures without focal reducer, so the stars in the corners are not round.

Here is 9 of 20 minutes sub exposures calibrated with flats only, combined with CCDStack and processed.