Hello, just to reawaken this, I spent 4 hours today really trying to make the inside of my scope dark in the daytime. My observing location is quite light bright With an f4 8 inch Newt Astrograph my darks taken no the scope have some reflected light gradients and spikes and my 240s subs mostly have weird spectral rings and gradients that just cannot come from sky conditions.
OK, the cover doesn't totally block the light, but I'm not so worried about that, as I want light frames to be all light from the sky and I can do darks with that covered in material while parked or on the bench.
But on the bench in the daytime, with the front covered, it's like a theme park in there, when the fireworks are going on!
So I started tracing the issues at the mirror end, adding self adhesive velcro strip between the mirror frame and the mirror holder frame (a 1.5cm wide strip does the trick). But the areas around the adjustment bolts let in light so they needed more velcro. gaffer tape, nothing would stop the little holes, and I wasn't willing to disassemble my nicely collimated F4! I also used a smartphone camera light to shine at the mirror.
Then I remembered the black bag that a motorbike helmet came in, and I found with it a smaller bag for the visor. Putting both on the end, with them already elasticated and black, bingo! 240 second dark frame. no light.....from that end...l
I moved the covers from around the camera and focuser......and Oh No - more light! I read up on focussers and how not to worry about the small amount of light they let in through the gap to allow the tube to go up and down. But, the dark shots (now that he mirror end was sorted) showed me the culprit for the weird circular refractions...yep focuser leakage onto the secondary and onto the primary and back to the camera.....What to do?....Baffles Baffles...hmmm....oh flock it!? a special adhesive skirt around the focuser tube that could ride up and down with the focus?
Er - queue brainwave!!!. I found an old black sock, cut the foot part off, and yippee, the leg part of the sock covers the base of the focuser right up to the camera ring. And this sock still had good elastic to hold it securely. And another test....very very small amounts of light....but most acceptable for a budget solution!
I really could see the gradients and rainbow patterns on my lights, and even after applying flats, darks etc....so I would suggest the loss of a sock and an old black bag, a good investment! Astronomy is sooo romantic.