|
Mark
Well done on doing some research and trying to learn a bit before pulling the trigger. Scopes can be a very confusing item for newcomers and it is very easy to end up buying something unsatisfying. I usually recommend buying a dob as a first beginners scope, especially if your interests are primarily visual. If you find the imaging bug hits, you will still have a great visual scope for those night when just a bit of visual work is all you want and you cannot be bothered polar aligning, getting laptops working etc.
I will attempt to answer your specific queries.
1) Polar aligning. Inexpensive EQ mounts are really only worth roughly polar aligning. I played around with an EQ2 wobbletronic mount for quite a while and found it worked OK for solar imaging at a very short focal length. For deeps sky it was fine for visual but could only mount a small scope. I usually just used a compass to align it so was probably no closer than 1 or 2 degrees. If wanting to do accurate polar aligning a HEQ5 is probably the minimum.
2) Once polar aligned simply moving the scope through the RA axis will keep the object in the field of view. How long it stays there is dependant up how good the mount is, how accurately you polar align and the focal length ( and hence the size of the field of view) of your scope. Short FL scopes have a much wider field, that is why a basic PA for me worked fine on a 400mm solar scope.
3) Rotating the tube. This occurs with newtonians as the focuser can end up in some odd positions. Rotating the tube risks unbalancing the scope. It is one reason why I recommend dobs as it not necessary with them
4) the pic of the moon through a 10" is maybe a little optimistic. It is at high power I think so you would usually get seeing issues with a bright target like that meaning the atmosphere would be making the image blur and move about a bit.
5) When comparing a 10" dob to a refractor it would be on deep sky objects that you would really see the difference. There are great refractors out there but my opinion, and that of many is that on galaxies, clusters, nebula etc, a decent size aperture dob will win everytime. More detail and brighter images at the eyepiece.
6) Cooling. People often get worried about cooling. Ideally yes a dob needs to have its mirror cooled and dragging a dob out of a warm house into a cld backyard will result in mushy images. But take it out at sunset and by the time it gets dark, it will have cooled enough.
7) 10" vs 8" dob. Probably no significant difference with cooling. Main issue with these is that the 10" is a bit bigger and heavier. But it will enable you to see more. That said the difference in views would not be enough to justify getting the 10" if you are worried about handling it. Of course any adult will easily handle either scope and a 7yo will probably struggle with either.
Hope this helps, PM me if you would like anything clarified.
Malcolm
|