Re: fun with coadding images on Disk Set 19

[Tom Droege <tdroege@veriomail.com>]

Many thanks to Michael for looking at co-adding.

It was my thought that adding them in fours would be about right.  This 
should get a near factor of two in signal to noise.  At least it did when I 
checked some frames.

The best data is always that which you have not yet looked at.

There are some problems with DS-19.

1) There are only 49 V images on DS192.  At least when I counted them.
2) There are only 44 I images on DS193.

I have no idea of how I did this.  I took 50 (I think).  But the source 
files have been erased.  I have only the copy directories.  Sigh!  Somehow, 
I did not transfer all the files when copying them to the CDs.  Then I 
copied the original CD into a directory on another machine for making the 
copies.  Not a good practice, but it is what I did.

I have made a small improvement in alignment since DS19.  It is now of 
order 3 arc seconds per minute N-S and still <1 arc second per minute 
E-W.  This gives some improvement in star shape.  Since DS-19 I have gone 
to 56 frame sets.  This is about as far as I can go without running into 
the stops.

How good does it need to be?  The present slide out mount will not do much 
better, I think.  The Mark IVs in the dome can probably be aligned more 
accurately, but I have not tried it yet.

Here is something to study:  Look at the drift between frames.  i.e 1-2, 
2-3, ... 48-49.  This in the E-W direction.  This should be constant.  Look 
for variations, particularly at the end of the ranges to check how well the 
RA drive is working.  If anyone wants to do this, I can send a later data 
set which has more frames and goes closer to the limit.

Tom Droege



At 12:14 PM 10/16/01 -0400, you wrote:

>   Check out my quick'n'dirty analysis of coadding frames
>from disk set 19:
>
>        http://a188-l009.rit.edu/tass/markiv/michael/coadd/coadd.html
>
>   People who are working on DS 19 may find the shift in
>position from frame to frame, even in the "follow" frames,
>of some interest ...
>
>                                      Michael Richmond