Re: Newbie: observation request?

[Tom Droege <tdroege@veriomail.com>]

Aaron and all,

Last night I operated MIKE for test.  I had fixed a few things so I just 
got out the protractor and set it for +38 Decl, set the exposure for 60 
seconds, and just ran in scan mode.  That is I take an image, move back to 
the stop, take another image etc..  I ran till 2 AM or so in this mode.   I 
got 127 image pairs.

Aaron's star RR CrB appears on 9 of these images.  I was running in the 
mode where every 8th image is a dark or I would have gotten 11.  They look 
pretty good.  The I images are clean.  The V images have a few ice crystals 
but I think they will miss the star as it marches across the image 
sets.  The star is almost saturated on the I images.  It is well below 
saturation in the V images.  I will try to get a shorter exposure tonight.

Something is wrong with the gain setting in MIKE.  Saturated stars only get 
to -3000 counts.  So a saturated star is only 22000 counts above the 
pedestal.  Looks like a factor of two somewhere.  This should not affect 
the usability of these images, just a tiny decrease in signal to noise.  I 
will have to find where the red resistor stripe is installed in place of 
the brown.  Those colors look very much alike to these old eyes.

I will try to run in the same mode tonight.   I will try 50 second exposure 
to get another image or two, and to reduce the saturation in I.

OK Aaron, don't expect this kind of service for every request.  You just 
caught me testing in a mode where it was easy to try for your star.

Now you will have a problem.  Start looking at Michael Richmond's 
pipeline.  You will need it to get from these images to good 
measurements.  Of course you could just take the images and count pixel 
values.  It is easy to find the star.  But we have done a lot of work on 
how to get good measurements from these images, so you might as well make 
use of the tass work.  It is an entirely different approach from the 
AAVSO.  Based on what others have done with similar images, this star 
should be measurable to the 0.01 to 0.02 mag level.

I will try to take data on this star for the next few nights.  Looks like a 
clear patch coming over.  We shall see.

Aaron, expect a CD Rom or two with data.  But not for a week or so.  Note 
that as a bonus, you get measurements on thousands of other stars.  Some 
might be just as interesting as RR CrB.  But no one has yet looked at 
them.  According to Bohden Paczynski (PASP 112:1281-1283 "Monitoring All 
Sky for Variability") 96% of variable stars in this magnitude range are yet 
to be discovered.  He also says a few percent of stars are variable.  There 
should be about 2000 stars in each frame.  So there should be 50 or so 
undiscovered variable stars in each frame that I send you for RR CrB.  Go 
get 'em Aaron.

Tom Droege

At 08:22 PM 6/8/01 -0400, you wrote:

>  Hi, I'm new to TASS and trying to get up to speed. I've spent much time
>at the web site over the past few weeks and have read the last 4 months in
>the archive of this group. I hope I'm not bothering anyone with this
>request.
>  I'm looking for observations of RR CrB, a red semiregular with some very
>short pulsation periods. The main period is around 60 days, but Hipparcos
>detected 2 shorter periods. One is 4 days with a .13mag amplitude and the
>other is 8 days with .08mag amplitude. A call was issued by some
>astronomers a year or two ago for photometry on one of these objects to
>try and determine the cause of this microvariability (it is believed these
>short periods are overtones).
>  I cannot perform observations of this object because of limitations in my
>field of view where I live. I tried phasing together 14 days of
>observations spread out but that isn't enough. What I really need is 4-5
>days of continuous coverage. I don't believe the new data set covers this
>object, but maybe someone with a working TASS camera and some spare time
>(hah) could help out?
>  The object is around mag 8 located at 15h 41m 26.1s and +38:33:28. I can
>provide much more info to anyone interested, including a paper I wrote on
>this object for a class. I would like to publish the results of this data
>in a professional journal and have lined up a couple of professionals to
>advise me on the analysis and math. Anyone who can help will, of course,
>be listed as a co-author.
>  Thanks and I hope this wasn't off topic for the list.
>
>Aaron