Finally took the plunge into 3D printing and a big incentive was to do custom astronomy stuff and one thing very high on my wish list was a light shield for my Comet Catcher.
The Comet Catcher is one of my most used scopes and this is because when I use my night vision eyepiece, I can hand hold it or sit with it in my lap. The portability allows me to walk around the yard or even down the street to get views past obstructions. The issue I encounter though is that because there is zero baffling in the Comet Catcher, and because a lot of neighbors have porch light, I am constantly getting light flooding into the field of view. Using an image intensifier makes this many times worse because even the smallest leak pretty much gets picked up and amplified 80,000 times.
The answer then would be to have a light shield that would project enough to deal with most of the lights, but not long enough to make the scope cumbersome.
Design goals were to allow for a slip fit over the front of the tube but there was a secondary design objective that would be that when in the stored position, it would have enough extension to act as a support when standing the Comet Catcher on end. The Comet Catcher has a weirdly rounded back casting so it cannot be stood on its base. Having the light shield extend down 25mm when the shield was in the storage position would fix this.
This though adds a problem. There are three screw heads around the tube at either end to hold the corrector cell and the mirror cell. There are curved channels designed into the ID of the tube that run all but 25mm of the tube length, where the tube thickens to 10mm to support the base when in the stored position. In order to self store, I could not use an internal stop in the scope to keep the light shield from sagging. I attempted to address this by making the shield long enough so that it extended past the focuser, so I designed this into the shield. Even with this though, there is still a bit of sag and the solution will be to simply print a small radius block that will act as a limit and attach this to the tube at the correct point so that the shield butts up against it when it is installed.
Material is PETG. This was very hard for me to print. Even after trying to optimize my slicer for stringing, I could not make it go away, so the print had a lot of strings and in a couple of cases, these formed little lumps in the finished print, but these were dressed out with a fine file.
It fits pretty well but I still need to dress some irregularities on the inside.
Still needs some sanding and I will try to polish the outside but flat black paint the inside.
If anyone that has a Comet Catcher wants the .stl, just PM me your email.
Shield in storage position showing extension that allows scope to sit on base:
Shot showing the design to clear focuser and allow some extension for alignment (again, may need a small butt stop on the OTA opposite the focuser side):
Last, shield in place. It does sag a tiny bit, but not enough to tip into the light path.. Again, I will print up a little radius block to attach to the tube so that it registers even all around:
Still learning, but this was a very big print and while the finish was a bit rough, but I think I can clean it up nicely.
Looking forward to making a lot of useful Astronomy stuff!
Edited by Eddgie, 06 January 2019 - 01:10 PM.