I started my (daughter's) astronomy journey with a Celestron Powerseeker 127eq. It came with a 20mm EP, 4mm EP and a 3x barlow.
I have great success with 20mm EP: I can see clear images, focus is easy, etc.
Less so with the Barlow: I can't seem to focus it properly - the image is softened regardless of what I do. Note that this is 150x magnification, which should be perfectly in order for this scope, I understand. So far I have not invested significant effort into making it work.
Finally, my greatest issue and the subject of this post is the 4mm lens:
I'd like to use it to observe Jupiter and Saturn (goal is to see Cassini's division) as they are nicely visible in the early night sky right now. I realise that the 250x magnification this EP offers is on the optimistic side of the spectrum, and I concur: the planets are so low on horizon that I can't really expect a sharp image, especially with all the light pollution where I'm observing from.
But, even that is not the issue. The issue I have with the eyepiece is, that with the best focus I can get with the EP, the observed object is smudged: it looks about like a comet. Half of it is in focus, but the other half looks like another planet just hit it. With debris and all
Anyway, I tried rotating the EP in the mount and the "comet" thingy doesn't rotate with it.
So I'm assuming this is about primary mirror / 45° mirror alignment. Sorry about my terms, I'm really green here.
I don't really care if my analysis is correct, so: is there a way I could fix this issue?