Hi all,
I've put my binos down and started to use my Celestron Firstscope at 15x & 50x power to have a static view of the night sky recently and while views of the moon and some bigger/brighter open clusters like IC 2602 (Southern Pleiades) at 50x are certainly impressive, I've noticed that this scope struggles to focus at 50x on smaller objects such as NGC 4755 (Jewel Box). Putting aside the fact that the focuser focuses incredibly coarsely, when I do get the stars as focused as best I can, the stars in the Jewel Box still appear slightly fuzzy or smudgy. After a couple nights I thought I'd have a crack at collimating the scope in the hopes of sharpening the view.
I ordered a SVBONY laser collimator and when it arrived I got to work. I did my best to center the laser in the primary and I noticed some quirks about this scope:
1. The primary cannot be adjusted. It seems to be glued into a base plate, and this base plate affixed via screws to the tube itself.
2. The stalk that holds the secondary cannot be adjusted in height, only rotated left or right. The stalk screws into a long nut and it seems like the manufacturer has glued the stalk into the nut, preventing adjustment.
3. The draw tube is loose and has lots of play. With the laser collimator in, focusing in and out wiggles the draw tube slightly and the laser is observed to go in and out of its collimation.
Because I can't adjust the height of the stalk the secondary sits on, the laser sits away from the geometric center of the primary. However after some reading online, apparently spherical mirrors don't have an 'optical center' and collimation is supposedly not as impactful in a spherical mirror as opposed to a parabolic one? I'm not too knowledgeable on mirror shapes and how they reflect rays of incoming light, but is what I've read true? Some diagrams showing light paths reflecting on spherical vs parabolic mirrors do seem to indicate that there isn't a 'true' optical center point on a spherical mirror. I've attached some images of the primary/secondary (with outlines to show mirror shape and laser position) and the laser collimator, this is as best as I could get it. I feel like even 50x is asking too much of this small scope!
If anyone can let me know whether it's worth my time trying to collimate further and sharpen up the view or if my efforts are utterly in vain, it would be greatly appreciated!
