Re: Two new Show-and-Tells

[Tom Droege <tdroege@veriomail.com>]

Sorry, Mark does have a sign on the angular drift.  Sometimes my eyes do 
not see little things like signs.  Still, the angular data does not make 
complete sense since it does not plot as a straight line piece of a some 
sort of angular function.  This means that the Mark IV probably bends as 
one moves it.  You can probably not move it from A to D to A and get the 
same result again at A.  This is no doubt why Arne complains that the Mark 
IV is not stiff enough.  There are things that could be done, but they are 
probably not worth doing.

Tom Droege

At 03:40 PM 12/8/01 -0600, you wrote:
>Michael and Mark,
>
>Thank you for the show and tell notes.  It is great to see the 
>progress.  Just in time to be buried in the snow.  I hope you can keep the 
>snow plows away.
>
>I am glad that you have a student involved.  Nothing like learning how 
>science is really done.  I would suggest that the sign of the angular 
>drift is needed in the table, otherwise it does not make sense.  One might 
>also measure the shift in the tape marks and convert to degrees/radians to 
>relate to the drift.  Then one could show angular change vs pixel drift in 
>the table.  Then Mark might be able to derive a formula.
>
>A question for Mark.  The CCD is mounted in the camera head on a printed 
>circuit board.  This board is mounted to the cooling back on three 
>screws.  The cooling back is mounted to the Mark IV frame on trombone 
>slides.  There can be errors everywhere, so the CCD pixels may not be 
>pointing NS - EW even though the Mark IV is.  How does this affect the 
>alignment process?  Suppose we mounted the camera at 45 degrees to the 
>present position.  How would you then do this alignment?  (Note, I worried 
>about this in the design.  It would appear that the scheme does pretty 
>well.  It relies on screw clearances, printed circuit boards, and 
>machining of the trombone bearing holes and cooling back to work.  I 
>estimate that these errors might total to a maximum of 20 minutes of arc.)
>
>In the dome I have a piece of steel ruler nailed under the frame that 
>holds the Mark IVs.  I can adjust the frame position to about 1/16"  This 
>should be 8 minutes of arc with the 25" (with the angles) lever arm.  I 
>cannot do so well with TOM1 since the slide out rails wiggle a 
>little.  The last time I checked, I was drifting 24 pixels per hour 
>NS.  The drift EW was measured as 0.  This with a 2.3 hour run looking at 
>image shift.
>
>Tom Droege
>
>At 03:11 PM 12/8/01 -0500, you wrote:
>
>>   One of my students at RIT, Mark Teseny, is helping me
>>set up the Mark IV here.  We've put together some pictures
>>showing our enclosure, and how we aligned the camera.
>>Check out
>>
>>
>>         http://a188-l009.rit.edu/tass/showtell/st0008.html
>>         http://a188-l009.rit.edu/tass/showtell/st0007.html
>>
>>                                        Michael Richmond
>