Quote:
Originally Posted by Satchmo
Just to clarify here, the eyepiece focal length sets the magnification for a given amount of aperture. There is essentially no significant difference between say an 8" SCT and an 8" Dob newt used at the same power for DSO observing except perhaps convenience and usability.
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Except that the eyepiece focal length for a shorter native focal length scope will be shorter. To put it more simply, to get 100x magnification with a 2000mm focal length scope (typical 8"SCT), you need a 20mm eyepiece, to get the same with a 1200mm focal length (typical Newt?(f6)) you need a 12mm eyepiece. Now, we all know that typically a 20mm eyepiece will usually have better eye relief and be less prone to "kidney beaning" at similar price range to the 12mm equivalent. So for high power stuff (lunar and planetary) the longer the native focal length of the scope (IMHO) the better. Of course there is the tradeoff between contrast and central obstruction, but this is the beginners forum and the views will be wonderful either way.
The 26mm Plossl that my 8" SCT shipped with was a fine eyepiece, I rarely used much else (I discovered Barlows and powermates), though I have a 13mm Nagler that I also love to use (but it suffers from the kidney bean effect). Now I don't know, but I've also heard that the widefield eyepieces are terrible on short FL Newts because of the coma towards the edge of field, is this also true?
For the beginner, with little knowledge of the night sky either scope is OK, but I feel that the SCT would be better if you can afford one. Of course there's always good ones coming up secondhand on here and fleabay if you're at all patient. Most of us succumb to "aperture fever" at some stage and will sell off the smaller scope relatively cheaply.
Cheers
Stuart