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Hi! I've recently acquired a new Astromodified Canon rebel XT and I've tried to take pictures of nebulas using it but I've noticed that there are these weird black artifacts that keep appearing in my images. Would like to know if anyone has experienced this before? Or are these dirt/dust specs on the camera, filter, and telescope glass? I've attached some of my edited and raw pictures for your reference. The black artifacts can already be seen in the raw image of the horsehead nebula and after stacking I think it got amplified. Anyway, advance thanks and I hope everyone's doing well.
To celebrate the 25th anniversary of Sir Patrick's DSO catalogue, I've added the available Caldwells to my basic Marathon search sequence.
Those interested may be pleasantly surprised by how many of the additional treasures are only a short hop from a given (or en route to the next) Messier.
The sequence for 40°N can be found at the SEDS Messier Marathon homepage or at my blog.
So, although I had some issues with my auto guiding (which I found out afterwards) I did manage to get 9x180s exposures and 5 darks of Andromeda and give both stacking (using DSS) and processing (using GIMP).
My first attempted DSO....
I am pretty sure that people could get far more information out of the TIFF file from the stack.
Hopefully I will get another clear night soon. I am in a heavily light polluted area so I do have a clip in filter on my DSLR which I think took a lot away.
More practise needed!
I am thinking on grinding my own lightweight mirror (first f4 16", later f4 24"). The lightest and cheapest option is to get a thin blank and slump it in a decent kiln.
Anyone has longer term experiene with slumped mirrors? Overall doesn't seem to be more work than a normal (not pregenerated) blank.
Do I have to grind the backside as in case of normal flat back mirrors to avoid astigmatism? How do people support a convex back while grinding? Does it make sense to grind a hole in the middle for additional support? I am remotely considering a convertible Newtonian/Cassegrain system anyway...