Saturday, February 2, 2013

More Robofocus and Lodestar woes

Took out the scope and did the alignment and polar alignment. I wanted to use the lodestar for rough alignment and then the CCD camera for fine alignment. Plus I received the Bahtinov mask for my guidescope and wanted to fine focus the guidescope. But in the autoguide images, all stars we elongated! I never noticed that before. Interestingly, this is not noticeable in PHD! I have no idea if it's the Lodestar or the guidescope. I should put the lodestar into the main tube and check how images look there. But I didn't want to deal with this and rather move on.

First, I wanted to optimize the @focus2 parameters. I set the subframe to 400 - this captured almost all of the defocused star. I then reduced the focus range such that 2 measurement points are inside the v-curve and 3 outside. With that I did 3 focus runs. They resulted in focus position of 17081, 17044 and 17051. The distance here is 37 steps which equates for my focuser to 29 microns. Which is well within the focus range of 85 microns.. But I am surprised that they are so far apart. I would like to play more with these parameters, but that I have to cover/uncover the scope twice for each focus run makes it quite cumbersome.

Next I wanted to try the OIII filter. Took the Ha filter out, screwed the OIII filter in. First thing I realized is that this filter does not dim the stars at all. That should make focusing easier - so I thought. I used my optimized @focus2 parameters ... and didn't achieve any focus :-( Tried 2 more times - same result. I then checked the@focus2 log:

Seems as if the star that I selected was to bright - and as a result, the spike of the v-curve wasn't very high. I should try again with a dimmer star. But it was late and I called it a night...

I really need that filter wheel - or the hyperstar lens with the filter drawer. Then I can just focus with one filter and be done with it. Or maybe I'll get a filter drawer for my current setup...