M. Posted July 17, 2015 Share Posted July 17, 2015 (edited) Ok, this is the SCT fitting I recently purchased from FLO. It was a gamble that didn't pay off as the thread pitch is different between the scope and SCT fitting. The thing is that the threads are tight between the diagonal too. Do I have a solution or will I need to get one made? Approx 40mm internal dia. Edited July 17, 2015 by M__ Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 Also, I don't think the vintage C8 was designed to take the extra load of the 2" diagonal and a huge a*s eyepiece, as you can see that the threads are not too genourous here. Link to comment Share on other sites More sharing options...
Doc Posted July 17, 2015 Share Posted July 17, 2015 Having never owned a SCT I was under the impression that the diagonal just slid into the visual back and is tighten via a thumbscrew, it wasn't screwed into the visual back. I'm surprised as I'm sure I've seen them before. Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 Having never owned a SCT I was under the impression that the diagonal just slid into the visual back and is tighten via a thumbscrew, it wasn't screwed into the visual back. I'm surprised as I'm sure I've seen them before. The 1.25" diagonal did just that but as you can see the original SCT fitting is also threaded, the 2" SCT fitting is near enough the same bore size as the scope back and diagonal. I think I may be able to get this SCT fitting reworked at my local fabricators, I'm just concerned about damaging the threads on the back of the scope. Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 I guess it's nothing more than an expensive pipe fitting. Link to comment Share on other sites More sharing options...
Daz Type-R Posted July 17, 2015 Share Posted July 17, 2015 Have a word with Graham on here (Astro-Tec), he specializes in bespoke, one off bits of kit...... Nice chap, always happy to help and quite a few people on here have used his services (me included). http://www.eastmidlandsstargazers.org.uk/topic/5812-hi-folks-its-great-to-be-back/ M. 1 Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 (edited) Well, I've made a discovery! The extension tube screws off and the SCT adaptor fits snug up to the diagonal. I just need to proline threads and I think it will fit. Edited July 17, 2015 by M__ Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 (edited) Failing that, I think a 2" celestron SCT adaptor should work. Edited July 17, 2015 by M__ Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 I've left feedback for the guys at FLO, to be fair they did respond quickly and didn't blame me for being a noob. Link to comment Share on other sites More sharing options...
+Graham Posted July 17, 2015 Share Posted July 17, 2015 The visual back thread on your scope should be a 2 inch by 24 TPI Link to comment Share on other sites More sharing options...
+Graham Posted July 17, 2015 Share Posted July 17, 2015 I guess it's nothing more than an expensive pipe fitting. I can guarantee you it is not an expensive pipe fitting. Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 I like the adaptor but can't get it to screw on! Its looking like I'm going to have to get something made. Link to comment Share on other sites More sharing options...
+Graham Posted July 17, 2015 Share Posted July 17, 2015 You wont. The old C8 has a different sized visual back thread to the newer 11 and 14's Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 You wont.The old C8 has a different sized visual back thread to the newer 11 and 14's Am I likely to struggle getting something off the shelf that will fit then? Link to comment Share on other sites More sharing options...
+Graham Posted July 17, 2015 Share Posted July 17, 2015 You shouldn't have a problem. Most of the Astro shops should hold them just make sure you tell them what you need. Link to comment Share on other sites More sharing options...
+Graham Posted July 17, 2015 Share Posted July 17, 2015 (edited) Martin heres something for you to try. Unscrew that adapter back out of your diagonal and see if the diagonal will screw straight onto the back of your C8. But go gently Edited July 17, 2015 by Graham Link to comment Share on other sites More sharing options...
M. Posted July 17, 2015 Author Share Posted July 17, 2015 Martin heres something for you to try.Unscrew that adapter back out of your diagonal and see if the diagonal will screw straight onto the back of your C8. But go gently Good thinking, but unfortunately the bore is slightly smaller on the diagonal Link to comment Share on other sites More sharing options...
+Graham Posted July 18, 2015 Share Posted July 18, 2015 Thats a shame Link to comment Share on other sites More sharing options...
M. Posted July 18, 2015 Author Share Posted July 18, 2015 Thats a shame I know, I never thought I would get so upset about a telescope not working properly lol Link to comment Share on other sites More sharing options...
M. Posted July 18, 2015 Author Share Posted July 18, 2015 Thats a shame Is it worth me sending you the C8 original 1.25" sct fitting and the william optics 2" sct adapter for you to take a look at? Maybe quote me a price for making a working one for my scope? Link to comment Share on other sites More sharing options...
+Graham Posted July 19, 2015 Share Posted July 19, 2015 Hi Martin Yup please do Link to comment Share on other sites More sharing options...
M. Posted July 19, 2015 Author Share Posted July 19, 2015 Hi Graham, I have your address from your business link, so will get it out to you tomorrow Link to comment Share on other sites More sharing options...
+Bino-viewer Posted July 19, 2015 Share Posted July 19, 2015 Weren't the original 'orange tube' C8s built in the US ? So can you assume the visual back thread has an imperial thread ? Link to comment Share on other sites More sharing options...
M. Posted July 19, 2015 Author Share Posted July 19, 2015 (edited) Weren't the original 'orange tube' C8s built in the US ? So can you assume the visual back thread has an imperial thread ? This was my exact thought when I ordered the modern william optics adaptor, but it seems my original visual back adaptor fits all modern celestron scopes in the shop. I reckon the more modern threads are that better machined and the tolerances are wide on the old SCT fitting, maybe this is why it screws up on newer scopes? Edited July 19, 2015 by M__ Link to comment Share on other sites More sharing options...
M. Posted July 20, 2015 Author Share Posted July 20, 2015 I've just read an interesting article about the C8 and its visual back threads, apparently a few early models used a different thread pitch, but i don't know why and for what advantage this offered Link to comment Share on other sites More sharing options...
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