From: "Jim Miller" 
To: "A. Suykerbuyk" ,
        
Reply-To: "Jim Miller" 


You can overcome some of the "limitations" of a short draw tube
by adding a end of drawtube baffle of proper dimensions. Being lazy I chose
to implement this baffle with a variable iris diaphragm mounted there
instead which is easily adjusted.

jtm

----- Original Message -----
From: "A. Suykerbuyk" 
To: 
Sent: Sunday, February 16, 2003 11:30 AM Subject: Re: ATM truss question



Hi Tom,

Thanks for your interesting information. A added some pictures to my page,
you can see that my scope was designed to fit in a wooden box for storage
and transport. The focuser was mounted on a side of the octagonal secondary
cage and has to fit (together with the mirror cage) in the rocker. Perhaps
a focuser with a longer sliding tube would have been the solution.

Adrie Suijkerbuijk.

-----Oorspronkelijk bericht-----
Van: tkrajci{at}san.osd.mil  Aan: atm{at}shore.net

Datum: zondag 16 februari 2003 11:05 Onderwerp: Re: ATM truss question


>
>> From: "A. Suykerbuyk" 
>>
>> Last summer I built a 16" Dobsonian, using two steel cables (inner
>cables of
>> a bicycle brake) for holding
>> mirror cage and secondary cage together. A picture can be found at
>> http://home.planet.nl/~asuyker/nvws/frames/my_ultralight_dobsonian.htm
>
>Nice scope!
>
>It appears that your focuser and focal plane are in a low profile
>position...fairly close to the secondary mirror.  That forces your baffle
>opposite the secondary mirror to be rather large.
>
>That is not a problem from a weight standpoint, but if you have to deal
>with wind it may be a factor.
>
>See:
>http://overton.tamu.edu/aset/krajci/
>specifically:
>http://overton.tamu.edu/aset/krajci/dobsonian/dobsonian.htm
>for a discussion of not-low-profile focuser position, and the benefits it
>can have for baffle size (low wind profile) and baffle performance (near
>street lights, daylight, etc.)
>
>Tom Krajci
>Tashkent, Uzbekistan
>
>
>
>

--- BBBS/NT v4.00 MP