Re: DS24 problems

[Tom Droege <tdroege2@earthlink.net>]

This is a problem caused by a deteriorating RA drive.  I have since fixed 
it.   I believe I mentioned this in a post here.  OK, I just looked, and I 
mentioned "cork screw" shaped stars in the 12 Jan 2003 23:16:05 
post.  Looks like I failed to mention the rebuild of the RA drive.  I 
started seeing problems on 9 Dec 2002 when the log book shows that I 
tightened the screws on the drive.  We appear to have rebuilt it on 11 Jan 
2003.  Sigh!  Some things just don't make it to posts or to the log book.

Look folks, this is real data.  Real data is never perfect.  Well, if you 
wait for perfect data then you never take any.  So you have to have built 
in ways to detect problems.  You also have to look at the data 
constantly.  This is why I asked Rob to write the monitor program that I 
constantly watch.

One reason for sending out all the data that I do is so that some of you 
will notice problems with the data and complain for me to fix it with some 
indication of priority.  I do look a lot at the data and am aware of most 
problems.  But I may miss something serious due to lack of experience.

I do remember that I posted a comment about how I thought Andrew would have 
a problem with the data because the images looked like little cork screws 
and I did not see how one fits a psf to a cork screw.

The good news is that I am taking data with pretty round stars now.  There 
is a slight north pointing error so the images are stretched N-S, and an 
even smaller RA drive error, which gives a very small E-W elongation.  So 
the images have a very slight tilt.

This is not just astronomy.  I have a lot of experience taking bad data at 
Fermilab.  This is why you design experiments (at least in High Energy 
Physics) with a lot of redundancy.  You hope that enough of your design 
works well enough that you can figure out a result.

Somehow you have to be able to rate data as to quality as is goes through 
the system.  More on this later.

My goal is to take a lot of variable star data.   I seem to be choosing 
quantity over quality.  This is partly due to my location.  I cannot take 
high quality data here.  So I am opting to take data that allows discovery 
and classification of variable stars.  Later someone else at a good 
location can take the definitive measurements.  One does what it possible 
at one's location.

Having said this, I think I have switched over from engineering development 
to production of data.

Tom Droege

At 08:27 PM 1/17/03 +0000, you wrote:
>HIRA2604776.FITS always gave my program problems:
>on looking at the image, it turned out that all
>the stars were close doubles. I foolishly decided
>that this was an isolated problem and carried on
>without looking closely at all the other images. Not
>even the V of the pair. Very stupid of me.
>
>I have finally got round to taking a closer look
>at a few. Oops: the problem affects both V & I.
>
>The ones I have looked at:
>719, 721, 2, 4, 5 All OK
>774 OK
>776 unequal closish doubles on both V and I
>777 OK
>935 OK
>937 more or less equal doubles, slightly further apart
>938 OK
>939 doubles, further apart again
>941 OK
>
>Except for I776, where the matching routine gets confused,
>there are no blatant signs of trouble in my statistics.
>Ouch!
>
>So: please don't kick the mount in future.
>
>PS you always seem to kick it in the same place but, as
>noted, you kick it harder as the night goes on.
>
>Andrew Bennett, Avondale Vineyard