Which Telescope Should I Buy for Astrophotography and Viewing?

[Saladsamurai]

I think I have it collimated; however, I have one question: should the focuser be all the way in or out while collimating. When I look through the sight tube (the dust cap with the hole in it) I can get the "dot" center inside og the the center mark in the primary mirror; however, if I move the focuser all the way out, it becomes slightly ou of line again. This leads me to believe that the focuser itself may need collimation.

Any ideas?

Casey

 

[chemisttree]

I think you are noticing "image shift" in your focuser. This is usually caused by some play in the focuser tube. Read a review about your telescope here where the problem is identified and a partial solution offered.

I also adjusted the focuser itself to remove most of the slop. During first light I realized how much of a problem the focuser was. The image shift at high magnifications was awful. To eliminate as much of this slop as I could, I used a small Allen screw to adjust the tension on the two small Allen screws atop the focuser. Using small adjustments and setting the screws' tension to about the same level, I was able to eliminate a great deal of the image shift. Images still shift at high magnifications, but not nearly as bad as before I made the adjustment.

http://www.cloudynights.com/item.php?item_id=882

If you are really seeing the collimation change as a function of the focuser position, you should place a low power eyepiece in the focuser and focus on a very distant image (daytime). That is the position the tube will be in most of the time. Adjust your collimation using this focuser tube position. Note that the actual collimation (primary and secondary position) will not change as a function of focusser position. After that, I would implement the suggestion that I quoted above.

Good luck.