[ATM] spider rotation

[Jerry]

Loosen the nut (part 4) and slide at parts 2 and 3 at the ends of the hub
tube tilting the rod (tuning fork tine) along a new radial from the common
center of the curve on parts 2 and 3. The center of those curves is at the
center of the mirrors surface.



-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Jan van Gastel
Sent: Wednesday, December 26, 2007 2:18 PM
To: atm at atmlist.net
Subject: Re: [ATM] spider rotation

I can see that the offset point stays centered when rotating the secondary 
and when moving it up and down. I use the same kind of attaching the 
secondary hub to the spider. But I wonder how the tilt of the secondary is 
adjusted, without moving it away from the tube axis. I don't see any 
adjustment screws. But maybe I just don't understand how it works.

The spider vanes are 6 mm thick, which I think is very thick.

Jan
http://home.wanadoo.nl/jhm.vangastel/Astronomy/


----- Original Message ----- 
From: "Jerry" <wa4guu at verizon.net>
To: "'Dale Eason'" <atmpob at yahoo.com>; "'Jerry Hillman'" 
<truckeratm at sbcglobal.net>; <atm at atmlist.net>
Sent: Wednesday, December 26, 2007 20:04
Subject: Re: [ATM] spider rotation


> About a week ago Arjan sent a link to such a design. Jerry must have 
> missed
> it.
>
> Arjan said...
> You mean this one: http://koti.phnet.fi/pulliy/second.html ?
>
> Notice the curves on the top of part #2 and the bottom of part #3. They 
> are
> centered at the center of the mirror's surface. Tilt and rotation is
> possible without changing the location of the center of the mirror 
> surface.
>
> More trouble than I would go through for something that I could do another
> way. I do not like the mirror being on the end of a tuning fork tine. May 
> be
> if the curve of part #2 was the top of the Mirror attach piece and
> adjustment along the main tube axis was by some other method than a
> relatively thin rod I could use this idea. I adjust rotation at the
> attachment to the spider, a tube almost as large as the diagonal minor 
> axis.
> Then tilt and depth in the main tube is done by spider leg attach points 
> to
> the main tube. Very solid that way. Adjustment lasts until the next time 
> the
> diagonal is removed from the tube for recoating.
>
>
>
> -----Original Message-----
> From: Dale Eason
>
> It seems to me that you are worrying about something
> that is not an issue.  That is why you do not find any
> plans for what you think you require.  I know of no
> design that tries to keep the diagonal centered while
> adjusting it.
>
>
> --- Jerry Hillman <truckeratm at sbcglobal.net> wrote:
>
>> Hi All,
>>   Can anyone direct me to a site that has built a
>> spider that is not a variation of the common spider
>> that everyone seems to use. Since the placement of
>> the secondary mirror is so critical, I am looking
>> for a design the uses the surface, center of the
>> mirror as the rotation point, not the tip of a
>> adjusting bolt that on my scope places the rotation
>> point about 3 inches away. Makes for a frustrating
>> time trying to adjust the mirror since centering the
>> mirror moves it out of collimation and collimating
>> it moves it out of center. I have about 1/8" offset
>> but same problem applies. I can provide drawings
>> that illustrate my problem.
>>   Jerry
>> _______________________________________________
>> ATM mailing list http://www.atmlist.net/
>>
>
>
>
>
>
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