200mm aperture, 3.8 Photo version White light filter for C9.25.

[Pete Presland]

I have been wanting to try my C9.25 SCT for white imaging for ages.  I started by making a Prototype out of very thick Cardboard and masking tape in April, which delivered some superb granulation, as well as fine details in the spots 

While this result was very pleasing the masking tape did not feel very secure or look very long term. 

So a MK2 version was required. Fortunately, i was asked at work what i was doing, while i was painstakingly cutting out 2 thick cardboard discs. After explaining i was lucky enough to have a couple of CNC cut rings, perfectly round and exactly 200mm in aperture. I drilled six 6mm diameter holes for the nylon fixing bolts that i planned to use to hold the filter in place on the scope.

The two rings were then sprayed with several coats white satin paint. The Baader film was then fixed in position with masking tape, then both discs glued together with PVA glue. The nylon screws were then fitted in position.  All seemed pretty secure when i tried it on the scope, but i could not leave it at that. I decided to put some shrink tubing on each nylon thread to give the filter more "grip" when in position on the scope.  Unfortunately "DISASTER"  not only did the film look really stretched due to the heat gun used to shrink the tubing, but i could see damage to the surface of it.  Gutted!!! £28 down the drain and all that work. So i ordered another piece of Baader film, talked nicely to my colleague and.......

Enter the MK3 version which i have posted the pictures of in this thread.  A couple of differences from the lessons learned though.

1st Was not gluing the two halves together will enable me to replace the film if damaged, seems like a sensible idea 🙂 

2nd  Added large steel washers to the nylon fixing screws, little bit more weight feels a bit more secure.

3rd I used Air stone tubing, warmed by rubbing between my hands to help fitting, these give some purchase when fitted to the scope.

Another thing to remember is the A4 sheets that are sold. They are not A4 in size, they are close but not quite, 208mm X 293mm the 2nd film measured.  Not a big difference, but A4 should be 210mm X 297mm. Which did not leave much fiving room across the 200mm aperture of the filter.

[Pete Presland]

Forgot to mention i also i made another solar finder from an old red dot finder scope 🙂 

[Victor Boesen]

Excellent Pete, looking forward to your results!!

[Pete Presland]

1 minute ago, Victor Boesen said:

Excellent Pete, looking forward to your results!!

Posting in a couple of minutes 🙂 

[neil phillips]

Looks great way better than my effort. Nice job