Re: [ATM] 40" mirror

["matt" <mariusrf@bellsouth.net>]

-----Original Message-----
From: Ken Lowther <hermit@outofoptions.org>
To: atm@atmlist.net <atm@atmlist.net>
Date: Thursday, December 23, 2004 8:17 PM
Subject: Re: [ATM] 40" mirror


>Quoting matt <mariusrf@bellsouth.net>:
>
>> Jerry,
>>
>> You are right in one aspect, you won't be able to lift the scope.
>> However, reducing primary weight matters a lot . For the extra 100 lbs in
>> the primary, you will need a stronger and heavier cell, then a stronger
>> scope structure, starting with mirror box. Then a heavier scope front to
>> balance the heavier mirror , cell and mirror box.
>
>Doesn't he just shift the side bearings back to accomplish this last point?
I
>believe he said it would be a dob.
>
>
>Hermit, holed up in Youngstown, Ohio


even so, an extra 100 lbs of mirror, requires some extra tens of lbs for the
cell, plus some extra tens of lbs for the mirror box , side bearings etc .
All these extra materials cost extra money, time, versus the lighter weight
design. They also store more heat. It takes them longer to cool , and the
end result is less desirable than a thinner or lighter mirror . Maybe even
sell the blank and with the funds from the sale and the money that would
otherwise go into the heavier cell+mirror box, buy a cellular blank .
There's a huge difference between a scope that has perpetual dome+instrument
seeing problems and one that tracks ambient well . Even if the dome is by
chance at thermal balance in the evening, the larger the thermal mass, the
worse it will track overnight .

best regards,
matt tudor

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