Re: Is this real?

[Tom Droege <tdroege2@earthlink.net>]

Yep, it looks like it is an ice crystal.  It is not very easy to look 
things up.  The time on the output data is a day diferent from the day 
written into the disk file label.  Which is correct?  I ended up also 
looking at the day before and the day after.  

Very strange though.  I found that the likely evening of the funny point 
had both clouds and an ice crystal in about the right spot.  But I did 
not have the data images saved for this position.  This is odd because I 
save the images by hand.  There is low probibility that I would fail to 
save both the V and the I images.  I save every fits file that has a 
.ast file associated with it.  Since I did not save the files, there 
should not have been an output data point at all.

It is also strange that the "ice crystal" produced an output 
measurement.  It is white spot about 100 pixels in diameter. I think 
these are caused by a round drop of water freezing.   I would think that 
the program would reject such things.  Since I don't have the image 
saved (why, I don't know, it should have been saved) I cannot 
investigate this.    

Looking up images is a painful process.  I think I will not do it very 
often unless there is a Nobel prize involved.  Since this June, I have 
been writing the JD from the source data on the CDs.  It now appears 
that I have to add 1 to the day from the measurement data time to get 
the day number of the original data.  Some of you may be experts in 
getting this sort of thing straight.  I am not.

At this point, there are 600 CDs sitting on my desk, 1000+ on the shelf, 
and another 1000 or so of early data spread around the lab.  If we need 
to look up images often, then this is going to be monumental task in 
library science.  With just the 3 TOMs I will generate about 2000 CDs a 
year.  It is thus a 5000 Gbyte problem.  I think too much to keep on 
disk for this project.  

I think I prefer to have an appropriate approach to the data.  Sorry, it 
would be nice to consider a single point significant.  But it is not. 
 The data will contain noise. My goal is to keep it to a minimum  It is 
just not possible to look at every data point or at every image.  I do 
look at a lot of images, possibly 3%.  (last night I collected 520 
images with one sick telescope) It is not possible for me to keep all 
the telescopes running perfectly. There are many things that can happen 
to make the data funny.   It is unlikely that we will be able to keep 
funny data points out of the data base.  So any use of this data will 
have to consider noise a fact of life.  I don't know how other project 
handle this.  I would be interested in hearing.

Tom Droege

Stupendous Man wrote:

>  This looks very suspicious.  My first reaction is to say,
>"something really went wrong on that image."  Something might
>be an airplane going overhead.  Hmmm.
>
>  This is a case where I would go straight back to the images in
>question and just look at them.
>
>  Another possibility: pick another star or two within 1 arcmin
>of this one, and look at its measurements compared to its
>mean values.
>
>                              Michael
>
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>  
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