Hi everyone, long time lurker here.
I recently managed to get my hands on a pretty good condition JSO Space 10.
For those of you that don't know it is an old 100mm f/10 SCT from the mid 80s by a company that no longer exists (Japan Special Optics). Mine seems to have been purchased in 86' right around the time when comet Halley was swinging last!
I cleaned off some mold from the corrector plate and mirror (it was a small amount), afterwards I decided to conduct and indoor star test and collimate (really lousy weather these days...).
After successful collimation I decided to check that optics quality (indoor star test). The results were intriguing to say the least:
1. Perfect in focus image shows a bright center with 4 or 5 disks surrounding the center spot (spherical aberration??).
2. Being slightly, very slightly, out of focus both in and out appear to show these spikes surrounding the bright spot (astigmatism?).
3. When in and out of focus the spot is no longer a circle and it is slightly elongated along one axis, the elongation is orthogonal between the in and out of focus images.
4. The in and out of focus are not exactly identical (even when not counting the elongation).
It is the third result that makes me ask, is the corrector plate not properly aligned on the telescope?
I searched through CN for people with similar questions and it appears that if the corrector plate where to be misaligned it would present itself as astigmatism.
I then carefully opened the scope and unfortunately there are no alignment marks on the telescope at all... So I closed it back up.
So if I want to align an SCT corrector plate with no markings is there anything I can do?
Also, I must admit I am a novice at optics quality assessment, so these are the only major issues I noticed (thanks to Suiter's star testing book). I am not even sure what a perfect SCT's star test looks like...
The reason I would like to get it as close to perfect alignment as I can is because I'd like to use this telescope for planetary imaging, and having the best resolution and contrast requires a perfect alignment of the optics. It's such a light scope I might even get away with using it on my Sky Adventurer mount!
If any of you want more pictures let me know! This telescope is beautiful! But I don't just want a pretty scope, I want a scope that blows me away with its optics too!