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Hi Drew, congratulations on your restraint! In response to your questions:
1. The mount is the only difference – the Dobsonian is just the style of mount, the tube itself is still a Newtonian, and should be more or less the same regardless of the mounting system. The dob is possibly a touch more cumbersome to transport, but if you’re only interested in visual, I can’t see the point in lashing out big dollars for a tripod/mount sizable enough to support a decent sized Newtonian. Dobs, particularly non-goto dobs, are as easy as pie to use – just plonk it down, collimate it, and away you go. The larger the dob, the more time you should allow for the mirror to cool before expecting optimum performance, but that’s another issue.
2. Telescopically-essential to me would be a few decent eyepieces and a nebula/narrowband filter of some description, and maybe a polarizing filter if you plan on looking at the moon. I won’t go into eyepieces here, as every member will have their own opinion as to what constitutes “essential”, and there are a couple of reasonably current threads on good eyepieces for those just starting out. Viewing-session essential for me would be a decent table to lay your stuff on, a comfy chair, red torch/headlight, collimating laser/eyepiece, and some type of planetary software on your phone/tablet to get you familiar with the sky.
3. I would recommend goto if the budget allows, although learning your way around the sky as well as learning how to align/use a telescope can be a steep learning curve. For me, once you’ve used goto, it’s hard to go back to manually slewing around, although manually finding objects does tend to teach you the general layout of the sky much better. Each to their own - I love my goto.
4. The focal length of a scope will determine the magnification achieved by a particular eyepiece. The formula for this is:
Telescope Focal Length / Eyepiece Focal Length = Magnification.
So a 1200mm FL scope with a 20mm FL eyepiece will give you 60x magnification. An 1800mm FL scope with the same 20mm eyepiece will provide 90x magnification.
Aperture has nothing to do with magnification, it’s just the width of your mirror (in a reflector) or objective lens (in a refractor). The larger the aperture, the more light you’ll gather, and the brighter/clearer things will look, which is particularly relevant if you’re hunting nebulae and faint galaxies. A lot of beginners drift towards an 8" dob as it combines good light gathering with reasonably use and transport.
If you plan on getting into photography, then basically disregard 95% of what I just wrote.
Good luck!
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