whzzz28
03-10-2012, 06:08 PM
Finally got a chance to play with my VC200L the other night.
From what i was hearing, and reading, the scope comes pre-collimated by Vixen, so it should be pretty good to go straight out of the box.
Well it wasn't.
Threw it up and did a quick polar alignment and then tried to focus.
I was getting what looked like double stars - both of which were elongated; at 0.5s exposures.
Im guessing it was a collimation issue so i threw my laser collimator in to see if the secondary was aligned. It wasn't. The laser beam came back off-center.
I followed Vixen's instructions on collimating the scope - had to peel the Vixen sticker off the secondary to adjust it, but finally got the laser centered. Then i did a star test. Out of focus i checked to make sure it was centered. It probably isnt perfect but it should of been pretty close.
So i threw the camera back on and slewed to two random galaxies to try (M77 and NGC1097 - both are bright). Did 10min shots in lum of each galaxy and the results are terrible. Focus wasn't perfect but should have been pretty good (according to the FWHM i was getting).
See attached.
For 10min subs, there sure is a lack of data. These are stretched very far.
The 'drift' i thought was poor polar alignment, so i went back and checked, but the mount was aligned pretty well and these eggs appear even after only a 1-5sec exposure.
There are two things i can think of that are causing this:
Collimation. Maybe i made things worse? the central obstruction on an out of focus star test is pretty close to the center (checked slightly off-axis).
Improper back focus. I was doing these tests without the reducer, so native @ f/9.
I was not entirely sure at the time of what back focus was required and after reading what others were using, decided to use a 50mm extension tube. After some more reading today i found that the back focus is ~143mm without reducer. So my QHY9 + 50mm was only getting me 100mm or so.
Ive never seen the affects of an improperly placed FF to sensor before so i don't know what it should look like.
Alarmingly i read just before that the secondary is fixed and you only adjust the primary. That might explain the fact that the screws for collimation of the secondary were behind a sticker and were alan screws.
But i think they were wrong and meant that the primary is fixed (as i have also read...).
Thoughts?
Thanks.
From what i was hearing, and reading, the scope comes pre-collimated by Vixen, so it should be pretty good to go straight out of the box.
Well it wasn't.
Threw it up and did a quick polar alignment and then tried to focus.
I was getting what looked like double stars - both of which were elongated; at 0.5s exposures.
Im guessing it was a collimation issue so i threw my laser collimator in to see if the secondary was aligned. It wasn't. The laser beam came back off-center.
I followed Vixen's instructions on collimating the scope - had to peel the Vixen sticker off the secondary to adjust it, but finally got the laser centered. Then i did a star test. Out of focus i checked to make sure it was centered. It probably isnt perfect but it should of been pretty close.
So i threw the camera back on and slewed to two random galaxies to try (M77 and NGC1097 - both are bright). Did 10min shots in lum of each galaxy and the results are terrible. Focus wasn't perfect but should have been pretty good (according to the FWHM i was getting).
See attached.
For 10min subs, there sure is a lack of data. These are stretched very far.
The 'drift' i thought was poor polar alignment, so i went back and checked, but the mount was aligned pretty well and these eggs appear even after only a 1-5sec exposure.
There are two things i can think of that are causing this:
Collimation. Maybe i made things worse? the central obstruction on an out of focus star test is pretty close to the center (checked slightly off-axis).
Improper back focus. I was doing these tests without the reducer, so native @ f/9.
I was not entirely sure at the time of what back focus was required and after reading what others were using, decided to use a 50mm extension tube. After some more reading today i found that the back focus is ~143mm without reducer. So my QHY9 + 50mm was only getting me 100mm or so.
Ive never seen the affects of an improperly placed FF to sensor before so i don't know what it should look like.
Alarmingly i read just before that the secondary is fixed and you only adjust the primary. That might explain the fact that the screws for collimation of the secondary were behind a sticker and were alan screws.
But i think they were wrong and meant that the primary is fixed (as i have also read...).
Thoughts?
Thanks.