Quote:
Originally Posted by sharptrack2
Thanks Sil,
Appreciate the advice. I took some time to investigate the difference between Plossl and Nagler eyepiece, so I would have a small understanding of what I would be looking for. You mention specific brands, which I'll now look up, thank you! I'm still a little clouded by the fact that most of you use eyepieces with focal lengths greater than 10mm. My understanding of magnification indicates this it counter intuitive, but then I'm also sensitive to the fact your telescopes are probably 100x better than what I'm currently working with (focal ratios greater than f/5) coupled with barlows of various magnifications. Practical experience will help me get my brain around this.
I managed to get out this evening for a short viewing of Saturn, it was very impromptu and in my back yard. The light pollution was horrible but I did get what I think was reasonable view of the planet with its moon Titan just below and to the right (looking through the scope). The view matched what Stellarium displayed in the Occular view with one major exception, both objects looked prismatic. I could not focus a clear "round" spot of light. This goes back to my original question, which is what could be causing this aberration? I'm now quite open to the possibility it could be the eyepiece but could both the 20mm and the 10mm have the same response? Maybe this should be another thread, I don't want to wear out my welcome in the beginners intro area. Plus I haven't searched for similar posts yet.
Thanks again for the advice... I'm looking forward to attending a star party (hopefully close to my home) and making a nuisance of myself with lots of questions.
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Hi Kevin and welcome.
Firstly Saturn. It was probably low in the west when you saw it. Planet especially are disappointing when viewed low, the turbulence and extra air the light has to travel through pretty much ruins the view. Plus early evening is often the worst seeing with the atmosphere boiling away.
Best way to test your scope is to wait until it nicely dark and then pick a moderately bright star high in the sky. See how that focuses. If you cannot get good focus, there may be an issue. Most likely cause is collimation. If you have not yet done so,here is a basic guide to collimation that I have found useful.
http://www.astro-baby.com/collimatio...on%20guide.htm
Also has some good info on various aberrations that you may see.
Eyepiece focal lengths can be confusing. If you know anything about photography, you are used to longer focal things giving more magnification. But you have to remember that an eyepiece is part of a system along with a fixed focal length telescope. Magnification is arrived at by dividing the scopes focal length by the eyepieces focal length.
So if your scope is say 900mm and you use a 10mm EP then you get 900/10= 90x. Easy!!
Cheers
Malcolm