Quote:
Originally Posted by BigJ
I have been doing a lot of reading, and seem to have come to the conclusion that for general planetary, lunar and DSO work, an 8" Dob is ideal, especially considering the price.
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I have been doing a little reading around on this subject too and have come to the conclusion that it pays to really figure out what you want to do with your scope before you purchase. Here is an informative article on some of not so obvious aspects of scope size and mount type, I have posted a few extracts below.
http://www.ayton.id.au/gary/Science/...old%20contrast:
planetary observation:
"
seeing" conditions impose the greatest limitation on a telescope's usable magnification & resolution, and at times of average seeing conditions which is most of the time, the resolution of planets will be as good in a 5" as a 16", it is only on those handful of rare nights of excellent seeing that a 16" can be used to its fullest.
in addition, the lack of a guided telescope such as by an equatorial mount with motor drive, limits useful magnification to 200-250x as you will otherwise need to be continuously moving the telescope by hand creating vibrations. This applies to Dobsonian mounts in particular...
telescope threshold contrast:
unlike light-gathering power, telescopes of increasing aperture quickly approach a limit to its threshold contrast - the ability to display an object of given brightness on a given background sky brightness...
deep sky:
the ideal magnification for general viewing of faint objects is 10-15 x telescope aperture in inches (5x aperture in cm)
objects become too dispersed if magnification is higher, sky brightness intrudes if magnification is lower. However, many say that for a 10" SCT, 50-60x magnification is most useful with occasional use of 100x ...