DIY solar filter for my 200P

[spaceboy]

Hi All

I have been wanting to make a full size solar filter for my scope for some time and with the sun finally showing its face I decided to get on with making one. I had purchased a second dust cover for my 200p some time ago off buy & sell with the intension of making an off axis stopper for observing the moon but soon found that I would not be able to make much of an improvement over the 2" stopper that's already in the cover. As the dust cover was now surplus to requirement I decided I would make a solar filter out of this. A hacksaw, file, emery cloth, wire wool and elbow grease had me a 6" aperture chopped out of the dust cover. Although this is 2" short of the 200p's primary I soon found I wouldn't have got much more out of the Baader solar film anyway. With some super strong weatherproof sticky back foam the film was set in place. As an additional precaution I also taped over the back edges with strips of duck tape both for added adhesion and to cover any gaps that might allow sunlight through. As you can imagine the filter is used with caution being such a large sheet of film for tiny pinholes to hide in. It is also checked regularly while on the scope but so far so good. It obviously fits as dust covers do if not a little snugger thanks to the extra duck tape on the inside which is not a bad thing. I am still trying to figure out my DFK but the below image is my first attempt. There were a few clouds around yesterday and only managed a single AVI with a stack of 40 out of 2900+ but I feel it's already a drastic improvement over my previous attempts at solar imaging. For visual I have to admit I was always dubious about requiring large apertures for solar observing given how bright the sun is anyway but I was surprised to see what an improvement it dose make. It's not that I can't see details with my 60mm refractor solar setup it's just that it's so much more obvious with the now f/6.6 150mm. The total cost was £15 for the Baader film (now £20 at most vendors) and if memory serves me I paid £8 for the dust cover. I have a slither of film left which I plan to use on the 2" stopper of my 150PDS so for a total of £23 I think it's was a worth while project and one I would recommend to other members. I believe there is a 200p dust cover in astroboot at the moment if anyone did fancy giving this a go.

[Moonshane]

good job matey! I agree a full aperture filter makes sense if you can. I put some holes in my filter surround and added some elasticated cord on two sides. this allows me to loop them around the focuser and dob knob as an added safety. possibly overkill but worthwhile in my opinion.

[Gina]

Nice neat job Makes my cardboard one (as per Baader instructions) look decidedly "Blue Peter"

[spaceboy]

Thanks for the positive feedback

Funny you say that Gina. At least you have been able to make one. I had originally planned to make a filter as per Baaders instructions but fell at the first hurdle as I wasn't sure how you go about fixing the actual cell part to the tube part with out risking it falling off or leaving gaps?? Then there was how do you secure them sturdy enough that you don't have to worry about them falling of in the slightest breeze. I have heard some horror stories of home made filters blowing off.

Using the dust cap it's all one piece so all I needed to do was cut out a circle leaving enough room for the film to adhere to. Not that I have had any problems and I can't say I have ever had a dust cap fall off I figured if there was a problem it would be easy to get the dust cap to get a secure fit by tightening the spider vane nuts slightly and in doing so tightening the aperture and so the fit of the dust cap. I assume this would requires a collimation check but once done as long as it's not overly tight I assume it wouldn't cause collimation issues in the future. Failing that a little bit of flock in the dust cap just to tighten the fit.

[Gina]

My cylindrical part of the filter is a really tight fit on the dew shield. I made it by wrapping thin cardboard round the dew shield and gluing it as I went. It consists of several layers. I attached that to the flat part (consisting of two thick rings of cardboard with the filter film sandwiched between. I attached the cylinder with hot melt glue all round the outside. I don't do visual - all my astronomy is imaging or live view from the cameras.

[spaceboy]

Thank you for the info Gina

[Andy Dodson]

Nice job Spaceboy. I've made several 'Blue Peter' Baader film cells for refractors but when it came to making one for my dob I resorted to buying the Orion cell (aly) and replacing the original material with Baader Astrosolar ND5. The aly cell is a really good tight fit and also has radial nylon thumbscrews.

andy