|
First of all folks, thanks for listening and your comments.
I found out last night that my focuser must shift alignment depending on how far in or out it is. The way I proved this was, by colimating with the tube all the way in, and then winding it all the way out with the tool still in place. Well the colimation was way off when I wound the focuser out. When wound back in it realigned itself nicely, (atleast thats something, it doesnt wobble it just changes alignment). So as a test I recolimated with the tube all the way out, and likewise when wound back in the colimation moved out of alignment. OK i tested my ep's and found that they all came to focus more or less with the focuser about half out position. When barlowed slightly further out but nowhere near all the way out. With this information, I decided to put the focuser in the middle position and recolimate. When wound in and out, slight missalignment occured, but my ep's will never focus in these positions so hopefully this won't be a problem.
I took the scope outside and tested it against a star again. I have no idea what I'm doing with this star test thing, and I cannot get the rings that I have seen pictures of to appear at all. All I get is a dark disc surrounded by one white ring. So I decided to use the views as an indication of whether things were ok. That being said I could focus very crisply, and the views went back to the way they were before I moved the centre spot. Comet tails at the edge of the field, but a conciderably larger FOV without this effect. I decided to have a look at the left hand pointer (a double that I like). Normally I have to use my 10MM ep 50X to split this double, but to my surprise tonight I could very clearly split them with the 20MM ep 25X. Not sure whether perhaps, the seeing was acceptional or if it is a direct result from now being colimated better than before I moved the spot, I suppose time will tell. I also looked at the moon, extensively with my 4MM ep with 2X barlow = 250X, something I have never been able to do. Usually even the 4MM without barlow gives slightly fuzzy views. Last night they were crisp and very clear. Once again, could have been the seeing.
Astro_nut, I will check to see if my focuser has these adjustments tonight, I'm not sure it does. My ep's are in good order, just not good quality. Will be upgrading to a 12" after Chrissy, so will have slightly better ep's at that stage. It would appear that "Drift" as you call it is the culpret.
Satchmo, How do I fix SA? and what causes it?
Space Dog, it would appear that you were correct, at certain focuser positions.
Thanks again for your help people.
Ok things seem to be back to a level where I am happy to use my scope again. If anyone has any ideas about how to fix this problem, or even what causes it, I would be only too pleased to hear from you.
|