Re: Focus steps on CD7

[Tom Droege <droege@wwa.com>]

Andrew,

OK, I can do both.  Take a large step run.  Measure it once.  And put in a
stop.  

All should give useful information.

All I need is a clear night and a computer that has not yet died because it
is going click, click.

Tom Droege

At 03:51 PM 2/10/00 GMT, you wrote:
>On Tue, 08 Feb 2000 20:08:40 -0600, you wrote:
>
>>Andrew,
>>
>>Well, I do have a bunch of different ones for the RA drive and the other
>>places where I turn a shaft, but for linear motion, I use all the seme
>>devices.  These have an internally threaded armature.  The lead screw goes
>>through the motor.  All have the same thread, and the drive is full
>>stepping.  So they move 0.001" per step, no more, no less.
>
>On further thought, the results can be just about
>squared with the assumption that the entire coma
>comes from the outer reaches of the lens and the
>bright core is light that goes down the middle with
>a higher effective f number/lower aperture. It's still 
>a bit tight; 2/3 of the light is in the core so there's 
>a lot of middle and not much by way of outer reaches!
>
>The thing to try next dark night might be that
>cardboard stop that you were talking about rather
>than wasting time with calipers! The 1/3 coma
>suggests only covering 1/3 of the aperture.
>
>Andrew Bennett, Avondale Vineyard, Nova Scotia, Canada.
>