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Hatan
2006-Mar-16, 12:35 PM
I was looking for scope price and found out that the Dobsonian are MUCH less expensive than schmidt.

Considering 2 10 inch scopes, one dob one schmidt. Both officially gather same light and have the same practical visual power. If I look at the dob price (meade standard dob): 650$. meade standard schmidt: 2500$-3500$.

Ok, the smchmidt might be easier to transport and can do astrophotography while dob might be quite hard... but what exactly creates this big gap between both scope?

Let say I look through both of them a planet or deep-sky object, what will be the difference in viewing? will the difference worth the 4-6x price? or might is it better to get a 45 inch dob for the price of the 10 inch schmidt :)

Thanks

mickal555
2006-Mar-16, 12:59 PM
The price difference is all in the mount- and the smhidt has a correcter plate also... which is a big thin, lens....

What to buy depends on what you want to do with it...

Could you really transport a 45" dob? :lol:

A 45" will produce spatacular views... the largest I've looked through is a 30"

Dave Mitsky
2006-Mar-16, 01:09 PM
The Newtonian Dobsonian has a very simple, inexpensive mount, does not have a drive or GoTo capability, and has no Schmidt corrector plate. It will actually have a bit more light throughput than the Schmidt-Cassegrain since the central obstruction (secondary mirror and spider) is smaller and there is no need for a corrector plate and yet another set of light losing optics, namely a diagonal. Furthermore, the SCT will produce somewhat less contrast due to its larger central obstruction.

The Schmidt-Cassegrain is a good general purpose telescope, is fairly portable, and is well-suited for astrophotography/imaging but, because of its design and the compromises made in its construction, is not the best type of telescope optically.

To the best of my knowledge, the largest commercially produced Dobsonians currently available are the 30-inch Obsession that costs $14,995 without options and the 32-inch Webster that runs $19,999.

http://www.globaldialog.com/~obsessiontscp/30page.html

http://www.webstertelescopes.com/scopes_currently_in_stock.htm

A ServoCAT GoTo drive with an Argo Navis DSC is going to add another 3 grand to the total.

The largest privately owned amateur telescope that I'm certain of is Tom Clark's 42-inch at Chiefland, Florida. I've heard that someone has a 48-incher.

Dave Mitsky

Dave Mitsky
2006-Mar-16, 04:04 PM
Hatan,

For an eye-opening exercise in telescope prices, look up how much a 10-inch Thomas Back apochromatic refractor costs sometime or, shudder, an 8-inch Takahashi apochromat. ;)

Hey, I'll make it easy for you, and remember these prices are for the optical tube assemblies only:

http://www.tmboptical.com/itemsRecord.asp?item_id=17&cat_id=4&

http://www.takahashiamerica.com/catalog/product_info.php?products_id=37&osCsid=71a438ccfc53a95390d9a08be0b4a130

Dave Mitsky

redshifter
2006-Mar-16, 06:50 PM
I'll get out my checkbook... :)

Kaptain K
2006-Mar-16, 07:00 PM
If you've got that kind of money to throw around, get me one too! ;)

aurora
2006-Mar-16, 09:11 PM
The largest privately owned amateur telescope that I'm certain of is Tom Clark's 42-inch at Chiefland, Florida. I've heard that someone has a 48-incher.



If I recall correctly, Tom Swayze
http://www.europa.com/~swayze/
also has or had a 40 inch scope.

I believe the largest scope I have seen at a star party is also a 42 inch.

There probably are larger ones somewhere, but the really serious amateurs now seem to be putting more time and money into digital imaging systems and less into really huge scopes.

skywatch
2006-Mar-17, 03:17 AM
any body correct me if i'm wrong but isn't a schmidt cassigrain a short tube with a lens on the front a primary mirror in the rear a secondary to reflect it out through the center of of the primary mirror. dobson is a type mount. for photos you will need an equitorial mount. personaly i would get a newtonian more light gathering fot the buck

Hatan
2006-Mar-17, 12:44 PM
thanks for the answers. Actually the 40 inch was more a joke, but idea whas there: why would I choose a 10 inch schmidt instead of a (let say) 18 inch dob for the same price. I'm just trying to figure out the reason why they are so expensive and the reason I would choose it instead of a bigger simplest one.

And no I don't have the money to buy that 200k scope, not even this 15k one :) but 2k would be in the budget when I want to invest in it (other priorities for now).

Thanks again

aurora
2006-Mar-17, 03:30 PM
any body correct me if i'm wrong but isn't a schmidt cassigrain a short tube with a lens on the front a primary mirror in the rear a secondary to reflect it out through the center of of the primary mirror. dobson is a type mount. for photos you will need an equitorial mount. personaly i would get a newtonian more light gathering fot the buck

A SCT does have a corrector plate, a secondary mirror, and a primary mirror that has a hole in the center. It has a relatively short tube length because the light is folded back and forth inside the scope.

A Dobsonian is a type of mount, you are correct, but they are almost always holding a Newtonian scope.

JohnW
2006-Mar-17, 04:55 PM
thanks for the answers. Actually the 40 inch was more a joke, but idea whas there: why would I choose a 10 inch schmidt instead of a (let say) 18 inch dob for the same price. I'm just trying to figure out the reason why they are so expensive and the reason I would choose it instead of a bigger simplest one.
Because there's more than just aperture to consider. SCTs are more compact, more suitable for photography, and usually come with a lot of electronic bells and whistles which Dobs don't have. There is no one "best" scope for everyone. It depends what you want the scope to do.

Dave Mitsky
2006-Mar-17, 07:24 PM
If I recall correctly, Tom Swayze
http://www.europa.com/~swayze/
also has or had a 40 inch scope.

I believe the largest scope I have seen at a star party is also a 42 inch.

There probably are larger ones somewhere, but the really serious amateurs now seem to be putting more time and money into digital imaging systems and less into really huge scopes.

The largest Dobs that I have heard of that travel the star party circuit are 40 and 41 inches in aperture. I've done some observing with Tom Clark's original 36-inch Tectron Yard Scope at the WSP and a couple of other star parties and a 36-in Obsession that was at Stellafane a few years ago. Hanging from those tall ladders in the middle of the night is a lot of fun. ;)

The Hercules Dob has a 41.2-inch mirror - http://www.runway.net/pilots/dan/fortyone-page1.html

Dave Mitsky

Dave Mitsky
2006-Mar-17, 07:34 PM
thanks for the answers. Actually the 40 inch was more a joke, but idea whas there: why would I choose a 10 inch schmidt instead of a (let say) 18 inch dob for the same price. I'm just trying to figure out the reason why they are so expensive and the reason I would choose it instead of a bigger simplest one.

And no I don't have the money to buy that 200k scope, not even this 15k one :) but 2k would be in the budget when I want to invest in it (other priorities for now).

Thanks again

Well, your questions have been answered. You won't be able to get a new 18-inch truss-tube Dob for a total (including shipping) of $2K but you might find a good 12.5-inch for that kind of money or a bit more. My tastes run towards larger apertures but an 18-inch would be the limit for what I'd be willing to haul around.

Dave Mitsky

Dave Mitsky
2006-Mar-17, 07:49 PM
I just found some photos (rather poor ones, unfortunately, since it's inside an observatory) of Tom Clark's 42-inch telescope, which is affectionately known as the Beast.

http://www.palmbeachastro.org/parties/cav0404.htm

Dave Mitsky

mickal555
2006-Mar-24, 03:46 AM
Hmmm

The largest 'scope I've looked through was a 30"

It was a goto dob.... The ladder was huge!