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After staring at and playing with the filter drawer, the extention tube, the multitude of spacers, reducers and the camera in an effort to figure out what bits to order so I could relocate the filter drawer to have it as close as possible to the sensor rather than the "get something working" position with a 20 mm extention tube between the filter drawer and the sensor, it occurred to me if I removed 2.5 mm of a particular external thread then I could cobble together the current bits with a repositioned filter drawer and correct back focus.
So call in the trusty angle grinder and my rock steady hands and cut that sucker off ...mmm...think about this ...what is the worst that can happen?...ruin the filter drawer that you waited months to sort out...have lunch and ponder...well fed and fueled I got to work..ground most of it off and finished it with the smooth file however I could not find my sanding paper so not entirely finished to my high standards.
So testing..night fall saw cloud everywhere but I need to know..there are gaps and with everything the way I want it hole shots will... so.open up and point the scope where it might open up and wait...half second exposures to focus...yes yes yes...I have focus and it seemed better although I could not do adequate tests..but it must improve things particularly at F2.2 you want those filters as close as possible to the sensor for sure.
I think the little doughnut stars I was finding in the bottom left hand corner are gone but this thing is so touchy with focus if it is not spot on you don't see them ..a curious situation where a little off focus produced overall better stars.
I looked into fixing tilt and that involves more than I was thinking so building a jig may be the next to do...
Latter the clouds cleared and for what ever reason I just could not bring my self to do more testing and contented myself by getting some luminance on the Prawn Nebula which I can compare with the ones I took a week ago which is a wishy washy test given moisture levels were different..
.ANYWAYS...A huge step forward and I have put off moving the filter drawer because it looked to be a pain working out the bits .. well of course it was a pain as that was what I was doing before the angle grinder opition occurred...more than an hour just looking and measuring and seeing what you can buy stuff..diagrams photos..an email to a supplier.
Again what a lucky little chap am I..getting it done and getting some sky.
Alex
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