Just wanting to pick some of the more experienced noodles out here, on the weekend i had problems with focusing.
Collmination was correct and has been verified with 3 different methods one with a Astro systems Auto collmination system (Laser for the secondary angle and barlow laser for the primary), cheshire, and my own laser collminator which itself has been collminated to 8 meters with a 5mm circle traced.
Problem.?
- the star pattern looks like a clover leaf (which i think i remember reading is astigmatisim) but where? (I released the primary to collminate only on the collmination thumb screws (not what i normally do i collminate with the locking screws generally) to alliviate any warping of the primary mirror cell. the Secondary mirror is attached by double sided tape, no induced warping of the secondary.). This is the first time i have seen this in the 10".
- Critical focus isn't achived the star comes in and then goes out, this is what the more experienced might be able to decipher. on the way in to focus the star is slightly elongated, coming into a circle (or close enough) once focal point has been reached, but on the other side of focus the elongated star rotates 90 deg then follows the same pattern as coming in.
What has changed?
- i milled a small fraction off the inside of the top collar of the focus tube,
- i milled the standard 2" adaption piece down.(see my post about SW focuser upgrade)
- the focuser has been out and serviced then repalced.
My thoughts
- The focus tube is not Normal to the telescope tube?
- the focuser is skewed to the mounting plate.
The milling that had been done should not of changed anything as it was done in a metal lathe of the prototyping lab for university physics dept.
I havn't had a chance to sit down and have a look yet but im looking for ideas that might help me problem solve this.
I look forward to your thoughts
