From: "Wolfgang Renz" <w_renz
To: "Chris Sauer" <chris
References: <200604071053.k37Aruk0030573
Date: Sun, 9 Apr 2006 10:45:28 +0200
Date: Sun, 9 Apr 2006 10:45:28 +0200
Organization: privat
	login:3dee00f7b36e90fde3f9fae8583d3574
	k398jYvG018751

Hello Chris

I had a look at the FITS file.

There are some hot pixel that weren't removed by bias/dark
processing !
When I looked at the FITS header I noticed that you did the
Thats probably the cause for the remaining hot pixel.
What software did you use for the bias/dark/flat processing ?

It might be easier and will be more accurate without bias and
scaled dark frames (using bias frames introduces additional
noise) using darks that match the light/flat frames.
Remember that the bias and dark frames will change with time.
So if you notice remaining dark or hot pixel in your light/flat
frames after bias/dark processing, its time to check them and
often (if the temperatures etc. are OK) also to take new ones.

The diameters of the stars seem to be a bit large (~ 22 pixel
close to the background level and ~ 7 pixel FWHM for the
FL, FoV ~ 21.8' x 14.7', 1x1 Resolution ~ 0.6 arcsec/pixel).
Is your seeing so bad ?
Or did you defocus a bit on purpose to spill the light over more
pixel to increaed the photometric accuracy ?

Clear skies
  Wolfgang

Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



    300.



From: "Chris Sauer" <chris
Sent: Friday, April 07, 2006 12:53 PM


> Hi,
> 
> The skies cleared and I was able to get 30 minutes of data on RS
> Leonis last evening.  First off, I was amazed at how much the V filter
> attenuates the light.  In 1 X 1 binning, I needed three minute subs to
> get decent ADU counts on RS Leo itself.
> 
> So my question now is what to do with the data?  I've calibrated the
> sub frames separately via dark subtraction/flat division and I'm left
> wondering what to do next.
> 
> Do I combine all 10 images into one averaged final and perform the
> photometry or do I approach each image separately?
> 
> Also, what's the best way to perform the photometry?
> 
> I've placed one of my calibrated images on my website in case
> someone would like to check my work.  North is up.
> 
> Thanks for your help,
> Chris
> 
> 
> 
> Sent: Thursday, March 30, 2006 5:39 AM
> 
> Hi,
> 
> As most of you already know, this winter has been horrific for astronomical
> imaging here in the northeast.  As a result, I'm only now getting to the
> stage where I need to ask these questions despite having completed an
> observatory back around Thanksgiving.
> 
> Just this past week, I finally got a chance to finalize bringing the
> observatory into an online mode.  My primary scope is mounted and working
> well, polar alignment has been refined so that 2 minute unguided images are
> showing no noticeable drift and the mechanism I devised for flats seems to
> be working well.  In other words, I think I'm ready to begin my first "real"
> imaging session of a variable star.
> 
> I'm looking for suggestions on a good first target in the eastern part of
> the sky (west is light polluted) between the hours of 19:00 & 00:00 EST.
> Additionally, I could use a little tutelage on exactly what to do with the
> data once my images are calibrated with darks/flats.
> 
> Are there any takers out there willing to assist a fledgling variable star
> observer in coming up to speed?
> 
> Thank you,
> 
> Chris

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