Who owns the largest (in aperture), guided amateur telescope in the
continental US, and how big is this aperture?  Must be a guided scope:
unguided Dobsonians don't count.  Must be amateur, not University or
government.  I have found up to 42 inches on my own: must be larger
than that.

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Request for Question Clarification by pafalafa-ga on 21 Jan 2005 19:45 PST

Here's a 48-incher that seems a good candidate.  I presume it's
guided, but that isn't explicitly stated in this article:

http://www.fullerton.edu/titanmagazine/S2004/searchers/print.html


What do you think...?

pafalafa-ga

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Clarification of Question by tommy81-ga on 22 Jan 2005 21:58 PST

This looks like a winner, assuming it's guided, which presumably it
is: otherwise, research would be impossible.

Please accept our $200 bounty with gratitude.

If anyone else can find a significantly larger amateur scope, I will
provide an additional $200 to him (or her).

Two questions:

1.  Can you provide contact information?

2.  Just curious, but I have spent a lot of time searching for large
amateur scopes.  If you don't mind, how did you find this one?

Many thanks,

Tom-

tommy81@comcast.net

Hello Tom,


Thank you so much for accepting the information I offered as an answer
to your question.  I agree...the telescope must almost certainly be
guided in order to be of use.

You asked about my search strategy.  I tried a number of combinations
of obvious search terms, with no real success, but finally tried an
exact-phrase Google search using quotation marks:


[ "largest amateur telescope" ]


and...bingo!...came up with the article on Hoffert and Dingle as the
very first search result.


As for contact information, that's a bit trickier.  I did not search
California telephone directories for the names of any of the
individuals mentioned in the article, as Google Answer policies
prohibit providing personal information on private individuals.  You
may want to conduct such a search yourself, however, to see what turns
up.


I did find address information for the Tierra Astronomical Institute,
the organization set up to raise funds for the telescope.


A search on the State of California's database of charitable
institutions turned up the following:



http://justice.hdcdojnet.state.ca.us/charitysr/default.asp


TIERRA ASTRONOMICAL INSTITUTE
5639 JACKSON DRIVE #110
LA MESA, CA  92041



while a similar search at the Corporations database turned up a different address:


http://kepler.ss.ca.gov/

TIERRA ASTRONOMICAL INSTITUTE 
2364 SO ANNADE 
ROWLAND HEIGHTS, CA 91748  



Unfortunatley, neither database provides telephone numbers.  

It's not unusual for an organization to have more than one address, so
you might try contacting them at both of the above addresses just to
maximize your chances.



==========


In case you haven't seen this, you might want to also check out the
folks vying to create a 70-inch amateur telescope:


http://group70.org/


Sounds like they have a mirror, but not a functioning telescope yet.



I trust this information fully meets your needs.  But before rating
this answer, please let me know if there's anything else I can do for
you to refine or enhnace this information.  Just post a Request for
Clarification, and I'm at your service.

All the best,

pafalafa-ga

Excellent job with good follow-up.

Hi Tommy,

Is the aperture the receiving bit at the end of a 'scope? If so, the
largest I have used is about 12" in diameter. The 'scope body however
was near 7' long. While you're at it, what is the difference between a
reflector and a refractor?

Phil

I don't know the answer, but I've a couple of questions - can we
assume you're only interested in optical 'scopes?  Do they have to be
for visual / photographic use; I've heard of some big 'scopes being
made with thin mirrors, but they were only suitable for photometric
work.  How about dobs on equatorial platforms?

Ian G.

Is the aperture the receiving bit at the end of a 'scope?

Yes.  Aperture is the diameter of the main photon harvesting element. 
12" is relatively small.  40" is relatively large.  The length of the
"tube" is more-or-less irrelavent.  Cass's are short, Newtonians are
long.  The Cass essentially "folds" the light into a shorter tube for
a given aperture.

While you're at it, what is the difference between a
reflector and a refractor?

Reflectors use a mirror as the primary light focusing element, while
refractors  use a lens.  All large telescopes use mirrors, not lenses.
 This does not mean that reflectors don't use secondary lenses.  By
the same token, refractors may incorporate secondary mirrors.

can we assume you're only interested in optical 'scopes?

Yes.

Do they have to be
for visual / photographic use; I've heard of some big 'scopes being
made with thin mirrors, but they were only suitable for photometric
work.

Good question.  We are essentially interested in photometrics of very
faint objects.  Detailed image formation is not essential for our
purpose.

How about dobs on equatorial platforms?

OK, as long as they can track a very faint object (m > 12-14).

Tom-

Tom,

Thank you for sharing the knowledge. Especially so, that it's your
question. Very considerate and patient of you. Having read your
explanation I will happily appear more knowledgeable tonight when I
share a steak and a beer with a friend learned in astronomy.

Good luck with your hunt for the 'scope. It appears to be more
allusive than the stars.

Phil

>OK, as long as they can track a very faint object (m > 12-14)

Are the objects extended? Mag 12-14 isn't that faint.  And while I
think about it, what rate(s) do you need to track at?

Ian G.

Are the objects extended? Mag 12-14 isn't that faint.

No, they are not extended.  The targets are quasars, which are
essentially star-like points.  The (apparently) brightest quasar is
3C273, at about mag 12.5.

And while I
think about it, what rate(s) do you need to track at?

I'm not sure I understand this question.  The object needs to stay
centered in the scope (i.e., keep up with the Earth's rotation) for
about an hour at a time.

The normal tracking rate would be sidereal - which you'll need for
quasars.  If you were tracking comets or minor planets you might need
to define the rate. And as for satellites....

However, I've just seen a couple of posts on the ATM list from Tom
Miller.  Assuming you're one and the same it looks like you're already
in touch with the right people.  Good luck!

Ian G.