Dobsonian mount fixings?

[jonathan]

Just a few questions...

Would I be right in assuming that there's a telescope made for a dobsonian mount, and then there's all other telescopes, never the twain shall meet (with an EQ mount)? How exactly is a dobsonian telescope attached to the mount?

Are dobsonian telescopes always newtonian reflectors?

If I have a well supported substantial garden table which is about 3' high and about the same across, what size dobsonian would be usable if just plonked on top of it? I assume they are meant for use on the ground, so it may not be possible to reach the eyepiece if it's stuck right at the top end of the tube, unless it's a particularly small dobsonian (or I'm looking at the horizon, which isn't going to happen from that location).

As my usual observing location appears to have a trailer parked on it at the moment, just exploring other possibilities...

Thanks for answering my silly questions!

[Steep]

Each manufacturer has their own way of fitting the tube to the mount which get fancier as the price goes up. The most basic would simply be two bolts through the base into the sides of the scope, the bolts act as a pivot point and when tightened enough will hold the scope in place. A more expensive type would be a block mounted either side of the tube which slips into a recess in the mount, again with some form of bolt affair to tighten it, these types will most likely also be adjustable for height on the tube to aid balance when using heavy attachments.

[Steep]

As for the table, probably a 6" Dob? but even that might end up with the eyepiece too high when looking at stars nearer the vertical. It depends on how tall you are but you can always use steps.

[jonathan]

Hmm. Maybe just putting it on the ground next to the table would be easier, then I could have a better 10" one, but that cancels out the grab and go easy to carry part of the idea. Also, storage space is currently occupied with other scopes and EQ mounts.

[Steep]

Go with an 8" and a water butt stand

[swamp thing]

Whether a Dobsonian mounted scope can be taken off the Dob mount and put on an EQ is often down to the mirror cell type. Many dobs have simple cells in which gravity holds the mirror in place. These cannot be mounted equatorially without some alterations to the cell. Others can be taken off the Dob mount and mounted equatorially without doing any work at all.

Traditionally a Dob mounted scope is held in with gravity too. The OTA simply rests on the Teflon pads.

Not all dobs are newts. I have seen several Fracs mounted on Dob type mounts. Fracs lend themselves to this type of mounting very well indeed, I'm surprised more frac owners don't build there own Dob type mounts (this could well be my next project).