Date: Wed, 24 Aug 2016 20:48:50 -0000 (UTC)
Subject: Re: [sloan-25mlog 3057] Re: 2.5m obslog 20160823 (SJD 57624)
From: "Dmitry Bizyaev"
>> We planned to take focus sweep data for R2, but could not focus R2. We
>> sent
>> several hours in taking arc exposures at every 300 degrees or so from an
>> thread
>> end of R2 focus ring to the other end. We didn't see changes in arc
>> images.
>> Compared with out-focus images on r1, we believe that R2 is out of focus
>> by more
>> than 300 degrees. Looks like that, for some reason, moving R2 focus ring
>> doesn't
>> move R2 camera itself; or the real R2 focus is more than 500 degree away
>> from
>> the movable range of its focus ring. See log for more details. Please
>> check.
>
> From the Hartmanns taken on Cart 4 earlier last night, i can see the
> centers of the
> Hartmann half-circles moved by about 12 pixels in the Y-direction between
> left and
> right hartmanns. IF the coefficients of the red focus ring is identical to
> the blue focus ring,
> then this translates to about 250 deg of focus ring rotation, or 54.7
> microns in the CCD
> position, roughly (assuming each 360 deg turn is 1/32 inch).
Hi Renbin,
this is not directly connected to your question, but
just in a case, the rotation-to-focus length translation
for the red ring is different. When I moved it, the red r2
move translated as +10 degrees = +1000 piston steps
(compared to +10 deg = -3170 steps for the blue.)
Cheers,
Dmitry
> best,
> -renbin
>
> --
>
> Renbin Yan
>
> Assistant Professor
> Department of Physics and Astronomy
> 177 Chemistry-Physics Building
> University of Kentucky
> Lexington, KY, 40506-0055
> (1) 859-257-0795
>
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