Before being accused of heresy for saying anything bad about the Dob that most of us seem to own - due to the great bang for buck and aperture, I have come across a definite limitation of the Dob, that I cannot remember anybody commenting on
It is this.... The other night, the seeing was appalling, and I thought I would just have a peek at Venus with my Lightbridge 12" to check the collimation. It was shining nice and bright in the West just after sunset. I live in a north of Bris suburb, in a crummy standard residential block - all 26 perches of it. There are trees and hedges around, and although the storm in November cleaned up 3 of my huge trees, to look to the west, I have to look over the chook pen and the neighbour's hedge which is about 2 metres high
Venus was about 45 degrees up from the horizontal.
Here's the problem
Being a Dob, the axis about which it turns (up and down on the trunnions) is very close to the ground and therefore, when I pointed it towards Venus, the 45 degree angle ended up half way up the hedge
No good. So I had to put it away and get out my 120 mm refractor on the tripod. The tripod of course has its axis about 1500 mm above the ground, and when I pointed it to Venus, the light path easily cleared the hedge
So Newbies who live in "restricted" properties, remember that with a Dob (without putting it on a table, where it would be too high to look through), you may not be able to see much from the horizon up to about 45 degrees, if you have hedges, fences etc close by.
This, to my mind, is a big plus for getting a telescope on a tripod mount
Fortunately though Good 'ol Orion is nice and high at the moment, and through the LB 12" it is FANTASTIC