I've been curious.

[Manok101]

I've often wondered at the difference between say, my local observatories 26" refractor, and a 26" dob, I know a dob would collect more light, but would there be much noticeable difference between the two? Not that I would be able to afford either.

[JimStan]

A lot would depend on the focal lengths of each scope. I am assuming that the observatory's refractor would be a very long scope, as most of an observatory's work is done on rather small, faint and remote objects.

A 26 inch Dob would be a rather "fast" scope, because one would usually require a ladder to access the eyepiece which would be at the front of the scope, and even a fast scope would have that eyepiece rather up in the air, unless the object of choice was fairly close to the horizon. ( in which case, seeing effects would be terrible ! )

The Focal Length of a scope would determine how much magnification one would get with a certain eyepiece, or by directly focusing the image from the main mirror to a camera. The Dob would probably have a smaller image scale than the observatory scope. It would most likely be used with an eyepiece for visual work, whereas the observatory scope would most likely be attached to various instruments for using the data which it gathers.

Many, many differences between the two scopes.

Jim S.

[umadog]

They both collect the same quantity of light. Well, the Dob will collect a little less due to the central obstruction, but that's not really significant. If the central obstruction on the Dob is below 20% then this will not affect the contrast, so in this respect the scopes will be the same. However, tube currents are easier to manage in a refractor so it's more likely to produce sharp images. That's not to say this isn't possible in a Newtonian, just that's harder to achieve. It's also easier to baffle a refractor, and fans of the design argue that this produces a higher contrast image.

Don't forget that a lot depends on the optical quality. A large optic which isn't of good quality will produce mushy images. It's harder to make large optics well.

[che guevara]

I've often wondered at the difference between say, my local observatories 26" refractor, and a 26" dob, I know a dob would collect more light, but would there be much noticeable difference between the two? Not that I would be able to afford either.

Slightly less surely ?

[ronin]

They are both 26".

The reflector should get a little less.

A DOBSONIAN is the wooden mount that the newtonian scope sits on/in. A dobsonian is not a scope, you would therefore see nothing through a dobsonian. It is a mount like an equitorial mount. It is actually an Alt/Az mount.

[pastiche]

A dobsonian is not a scope, you would therefore see nothing through a dobsonian. It is a mount like an equitorial mount. It is actually an Alt/Az mount.

I never knew that! You learn something new every day.

[brantuk]

Yup - the dobsonian mount is just a rocker box on a turntable. You usually mount a Newtonian reflector telescope on them, but the whole thing gets referred to as a "Dob".

But at 26" I'd go for the refractor over the reflector - but I'd need to upgrade the car to an articulated lorry first lol

[661-pete]

Did you say 26"? That's some refractor!

In fact, I'm curious, in turn, trying to figure out which one you mean. There are not many refractors of that size around the world, and the nearest to you that Wiki has on its list is at McCormick observatory, Charlottesville VA, a good 400 miles from your locality, so I assume you don't mean that one!

Or did you mean "reflector" perhaps?

[Manok101]

Roper Mountain Observatory. It currently has the former Lowell Observatory one. Or did it may not anymore. I may also be slightly off on the size.

[661-pete]

Ah yes: this must be the one.

Roper Mountain Science Center

It is listed in Wikipedia, I just didn't notice the entry. If you have access to it, no contest, go for the refractor! You are one lucky guy, not many people get the chance to use a refractor as big as that one, the difference in the amount of contrast and fine detail you'll be able to see, compared to a Dob, will be immense.

Of course, if you do decide to save up for a big Dobsonian, at least you'll have the advantage of having a telescope you can call your own, that you can use any time (weather permitting) and take wherever you like. And you'd certainly not need quite so big a car to carry around a 20" Dob, compared to a 23" refractor!

[Manok101]

I remember looking at saturn when i was a kid through this thing. The view was amazing.