Large 20"+ Dobs with Ultra Thin Mirrors? Carbon Fiber Composite Structures?

A question for the large dob owners in this group, what is the most extreme
amateur large mirror to date ? I found some web references to a 41" dob .
Are there any real thin mirrors in use, let's say 30" diameter and 1" or
less thickness? Any Zerodur, Sitall, BVC, quartz ? Any composite structures
, carbon trusses is obvious but what about carbon/epoxy plus foam core or
honeycomb for the mirror cell, dob base, bearings, spider , even focuser?
Just curious to what's state of the art now for dob scopes.
As a comparison, I own a sailboat (a catamaran) and all wood is gone .
Composites everywhere , and this is a relatively low tech industry vs.
aerospace. How far along is telescope making? From weight to focus
dependency with temperature and to maintenance and transport there are a
number of arguments in favor of composites.

thanks,
matt

Hi Matt,

You might enjoy checking the links at
http://members.efn.org/~mbartels/tm/tm.html

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
Lunar Picture of the Day http://www.lpod.org/
************************************

"matt" wrote in message
.. .
A question for the large dob owners in this group, what is the most
extreme
amateur large mirror to date ? I found some web references to a 41" dob .
Are there any real thin mirrors in use, let's say 30" diameter and 1" or
less thickness? Any Zerodur, Sitall, BVC, quartz ? Any composite
structures
, carbon trusses is obvious but what about carbon/epoxy plus foam core or
honeycomb for the mirror cell, dob base, bearings, spider , even focuser?
Just curious to what's state of the art now for dob scopes.
As a comparison, I own a sailboat (a catamaran) and all wood is gone .
Composites everywhere , and this is a relatively low tech industry vs.
aerospace. How far along is telescope making? From weight to focus
dependency with temperature and to maintenance and transport there are a
number of arguments in favor of composites.

thanks,
matt

Telescope industry got away from the heavy cast iron, steel and brass
constructions materials, in the last 20 years.
Aluminum, plastic and wood(bigDOB's) has been used since and now carbon
fiber is appearing in the market, for more expensive scopes.
Since telescopes price is set buy aperture size and not buy weight, it's
hard to change. Vs. aerospace industry, where price is measured by weight.
For example: to lift a satellite into orbit, cost $10 thousand/LB.
As people use and demand larger and larger telescopes, weight will be
dominating, since one has to carry it and lift it. Most of us don't have
the luxury to have a observatorium in the back yard. I see many for sale
adds, stating:"I'm selling this telescope, because it's too heavy and I have
a bad back, can't lift it any more etc..."
There are many good light-weight telescope designs out there from
individual armatures, but the industry is slow to change, putt at in
production for the masses, they looking for quantity. Course of nature, they
will change.

JS


"matt" wrote in message
.. .
A question for the large dob owners in this group, what is the most
extreme
amateur large mirror to date ? I found some web references to a 41" dob .
Are there any real thin mirrors in use, let's say 30" diameter and 1" or

Have a look on the Johnsonian goto structure at www.johnsonian.com or on the
materials used in scopes from http://www.infinityscopes.com

David

matt wrote:

...Any composite structures
, carbon trusses is obvious but what about carbon/epoxy plus foam core or
honeycomb for the mirror cell, dob base, bearings, spider , even focuser?

Have a look on the Johnsonian goto structure at www.johnsonian.com or on the
materials used in scopes from http://www.infinityscopes.com

David

matt wrote:

...Any composite structures
, carbon trusses is obvious but what about carbon/epoxy plus foam core or
honeycomb for the mirror cell, dob base, bearings, spider , even focuser?

On Sat, 27 Mar 2004 23:07:13 GMT, "Szaki" wrote:

Telescope industry got away from the heavy cast iron, steel and brass
constructions materials, in the last 20 years.
Aluminum, plastic and wood(bigDOB's) has been used since and now carbon
fiber is appearing in the market, for more expensive scopes.
Since telescopes price is set buy aperture size and not buy weight, it's
hard to change. Vs. aerospace industry, where price is measured by weight.
For example: to lift a satellite into orbit, cost $10 thousand/LB.
As people use and demand larger and larger telescopes, weight will be
dominating, since one has to carry it and lift it. Most of us don't have
the luxury to have a observatorium in the back yard. I see many for sale
adds, stating:"I'm selling this telescope, because it's too heavy and I have
a bad back, can't lift it any more etc..."
There are many good light-weight telescope designs out there from
individual armatures, but the industry is slow to change, putt at in
production for the masses, they looking for quantity. Course of nature, they
will change.

JS

There is a company making truss tube dobs for about
the same price that Orion sells theirs for. $299 for their
6" F8, which also only weighs 23 lbs. I don't believe
this includes a finder, but it looks like a good deal.

Here is the url if anyone is interested:

http://blastoff8.tripod.com/northstarsystems/id2.html

Jerome Bigge
Member, Muskegon Astronomical Society
Author of the "Warlady" & "Wartime" series.
Download at "http://members.tripod.com/~jbigge"

On Sat, 27 Mar 2004 23:07:13 GMT, "Szaki" wrote:

Telescope industry got away from the heavy cast iron, steel and brass
constructions materials, in the last 20 years.
Aluminum, plastic and wood(bigDOB's) has been used since and now carbon
fiber is appearing in the market, for more expensive scopes.
Since telescopes price is set buy aperture size and not buy weight, it's
hard to change. Vs. aerospace industry, where price is measured by weight.
For example: to lift a satellite into orbit, cost $10 thousand/LB.
As people use and demand larger and larger telescopes, weight will be
dominating, since one has to carry it and lift it. Most of us don't have
the luxury to have a observatorium in the back yard. I see many for sale
adds, stating:"I'm selling this telescope, because it's too heavy and I have
a bad back, can't lift it any more etc..."
There are many good light-weight telescope designs out there from
individual armatures, but the industry is slow to change, putt at in
production for the masses, they looking for quantity. Course of nature, they
will change.

JS

There is a company making truss tube dobs for about
the same price that Orion sells theirs for. $299 for their
6" F8, which also only weighs 23 lbs. I don't believe
this includes a finder, but it looks like a good deal.

Here is the url if anyone is interested:

http://blastoff8.tripod.com/northstarsystems/id2.html

Jerome Bigge
Member, Muskegon Astronomical Society
Author of the "Warlady" & "Wartime" series.
Download at "http://members.tripod.com/~jbigge"