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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.

 

M42rebelxtArtifacts.thumb.png.9112e325d47e3bb4a1e9319c351f9271.pngHorseheadmultitools.thumb.png.e4426b9d8a11157cfdd01fe62ce85d2a.pngIMG_4897.thumb.png.2001b07d9404f0b058e9a4fca1f73eb6.png

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I think you need to take a few flats to confirm....certainly looks like dust in the camera.

I find with my solar imaging it's good to test the camera separate from the usual filters etc. 

Just set up a scope, cover the objective with a clear plastic bag and fit a Barlow/ PM etc to get as high an f ratio as possible (higher f ratios shows more dust/ motes especially on the sensor surface)

I get good (well bad - if you know what I mean!) results at around f19 on my ED80 - seems to show up the smallest dust mote!!!

I clean the sensor and the cover plate with IPA and KimiWipes.

Well worth doing, then at least you know the camera is 100% clean - any subsequent "dust bunnies" must originate in the front filters etc etc.

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