Perkil8r Posted June 15, 2012 Share Posted June 15, 2012 I've come up with a cunning plan to fit filters to my 350D at prime focus on the standard SW200p focuser. What I need is filters with an outside dia of 48mm or just under. Not the thread size, but the OD of the "holder" for want of a better word. I have various filters here for cameras, but none the right size. Would anybody have a std 46mm camera filter they could measure for me at all please? The idea is to put it in between the T ring adapter and the body of the 350d, there is room, as long as I can find something a nice close fit. I could of course use slightly smaller and pack it somehow, but 48mm is the ID of the back part of the T ring adapter. Looking on the web, if I can find something suitable size wise, I should be able to get coloured filters and allsorts for around £20 a pop, which is a lot cheaper than clip ins. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 15, 2012 Author Share Posted June 15, 2012 Alternatively, have one of these made up, but with a filter thread in the back end? It's the standard adapter off the 200p focuser. The wedge fits in the end of the focuser tube, the T2 thread is on the outer end for connecting the DSLR and internally the 1.25" ep holder scres into it. I could maybe get something made without the internal thread for the ep holder, but instead a filter thread? Link to comment Share on other sites More sharing options...
+Graham Posted June 15, 2012 Share Posted June 15, 2012 That is the kiddie I was on about Mike. Exactly the same on mine. Now if you can tell me the size of the filters you want to screw into it we are away. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 15, 2012 Author Share Posted June 15, 2012 (edited) At least we're on the same page. I'm not sure which filters to go for, maybe somebody has a sugestion? I think 2" eyepiece filters are 48mm thread, although I may be wrong. Having measured inside the part this fits into though, the ID is just under 50mm, so I'm guessing a 2" EP filter might not clear it? I need to have a look to see what are readily available in a good range of colours etc. Assuming std 2" ep filters will be too large, I'm thinking 46mm filters. There are quite a few available at good prices. Edited June 15, 2012 by Perkil8r Link to comment Share on other sites More sharing options...
+Graham Posted June 15, 2012 Share Posted June 15, 2012 I will await to hear what filters you get and the thread size. Then I can knock a couple up as that is a bloody good idea and I need some filters as well. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 15, 2012 Author Share Posted June 15, 2012 (edited) Been thinking about this whilst out tonight. I've been over thinking it, what we should do is simple. Make exactly the same adapter but instead of the inner thread being 36mm, make it to accept 1.25" filters! That way we could use the filters with the DSLR or in eye pieces, or with the webcam etc. Much more versitile, and easier to machine too. Still needs to be a good apature at the inner end though as per the original. That way the filter will sit inside the T Ring adapter, won't interfere with anything and we have a vast array of filters available, rather than a slightly less astro friendly range in 46mm camera filters. What do you think? I reckon you might sell a few of them if you were to make them as I searched google for ideas and the question keeps cropping up with no solution other than very expensive clip filters. Having said that, there are a lot of 46mm filters available including IR cut and IR pass, as well as UV filters, colours etc. Just none specifically for astro work. They are considerably cheaper too, IR Pass for instance at £7 delivered although obviously I expect quality may suffer on some of them. I'm swaying towards 1.25" just for the re-usability factor with EP's and webcams, not just with the DSLR, the only concern I have is that the 1.25" filter in that position might interfere with the image and crop the edges off. Maybe a bit of R&D required on that one on a suck it and see basis? Edited June 15, 2012 by Perkil8r Link to comment Share on other sites More sharing options...
+Graham Posted June 16, 2012 Share Posted June 16, 2012 Thinking about it logically The widest part of the focal beam for want of a better word is at the junction between the T ring and the focus tube so a 1.25 filter should not crop off the image to that greater extent especially if it is down near the sensor. If I get a min tonight I might screw in the 1.25 ep tube and see if it makes any great difference to the image size. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 16, 2012 Author Share Posted June 16, 2012 Having slept on it, I think 1.25" filters is the way forward on this. The array of filters available is the main deciding factor for me. Along with as I say, the fact that the filters can then be used for other things, whereas the 46mm option would mean they were good only for that use. I think I'd like one please Graham, what's the worst that can happen Link to comment Share on other sites More sharing options...
+Graham Posted June 16, 2012 Share Posted June 16, 2012 Sleep I knew I was missing something. lol I will knock one up next week. Link to comment Share on other sites More sharing options...
Perkil8r Posted June 16, 2012 Author Share Posted June 16, 2012 Cool, let me know details I reckon if we can get it to work well enough there could be a market for them you know. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now