Quote:
Originally Posted by astronobob
Hi Bill,
So - I assume your focus train is fully & totally extended with absolutely no more room to extend, not even a few mm ?
Just for any other 'onlookers' Can you post a 'close-up' pic of your Focus train, maybe a hack with the actual focuser that may give a few more mm?
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That sounds like a good idea. I don't have a photo of the whole train from the OTA to the DSLR - I'm at work at the moment, but I'll get one up when I get the chance. But it's not the focuser, the "fully extended" problem that I have is that I'm really pushing for space between the flattener and the DSLR. This one I do have a photo of:
https://www.flickr.com/photos/skogpingvin/35614038593/
The DSLR is on the left, then there's the t-ring attached, then the stepdown (with the M42 to the left and the M48 to the right) then the flattener. This part of the train is all fixed together with threads - obviously the focuser is on the right of the flattener. Even with this setup, I'm getting streaky stars in the corners, so I need to get the DSLR closer to the flattener. (Believe me I've taken heaps of test shots - lengthening the train makes it way worse. I think I need to compress the flattener-sensor distance by about 0.5 or 1.0 mm).
I've designed an adapter that will allow me a couple of extra millimeters and a good mate with a lathe is going to make the part up in the next couple of weeks. There's just no way I can get MORE equipment in there and get a decent photo.
The question therefore is where can I sneak a filter in - I'm thinking it might be possible up in the part of the train where the focuser actually adjusts the length - but can you get a screw-in Ha filter in an M68 (and not have to sell a kidney to afford it)?
Bill