Quote:
Originally Posted by bluesilver
Thanks for the replies.
Yes the Dobsonian is a great telescope,
Just was looking for something would deliver more sharper / detailed views i guess you could say.
I would be looking for a new mount also as i might possibly dabble into a little atrophotograghy of the planets, but for now mainly what i go with the best visual scope.
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A Newtonian with a first class primary and secondary mirror is one of the best telescopes available for planetary viewing especially when on a driven platform to allow long term study of planetary detail.
If you feel the image in your current mirror breaks down at higher powers even under excellent seeing then consider having the primary refigured. A first class mirror gives the following when seeing allows:
1. Allows higher magnification giving a larger image scale to see more detail.
2. At higher powers the image is less bright meaning no need for polarising filters. Such filters do in fact compromise resolution meaning fine detail will be lost. (I have a Meade model and it eats small craters on the Moon; they simply vanish as I dim the image by polarising).
3. The high degree of polish and surface accuracy of a first class mirror will improve contrast of fine low contrast planetary details.
4. No need for an aperture mask which really only throttles your telescope in terms of resolution. Why do that if seeing permits full aperture viewing even for only the briefest of glimpses. Note if using an aperture mask you want an off axis one to provide an unobstructed view. For a 12” Mirror you will be limited to approx. 4.5” aperture mask, likely a little less. (Pri-sec /2). You need to fit the smaller aperture between your spider vanes. An 8” aperture must would not be possible with a 12” telescope without obstruction and if on axis would effectively give less contrast due to the effects of a greater secondary obstruction ratio.
Having tracking when planetary viewing offers one of the greatest benefits. Not having to constantly nudge the telescope means you can concentrate on the image itself enabling you pick out the finer detail more easily. Yes wide AFOV eyepieces can and do help with untracked telescopes provided they are highly corrected to give a sharper image to as close to the edge as possible in your telescope.
If you feel your mirror is up to the task then it’s likely seeing (local and atmospheric) that is limiting what you can see. (Assuming your telescope is well collimated too). Observe as many times as you can and you will know when you get excellent seeing as the image will suddenly show detail that simply wasn’t seen before. Enjoy!