[AZ-Observing] Re: Changes in 17P/Magnitude

Hello Brian,

Here is my latest try:

Annulus set at 20 pixel diameter

Aperture   V Mag
       6         2.206
       8         2.305
     10         2.333
     12         2.345
     14         2.349
     16         2.351
     18         2.353

Annulus set at 18 pixel diameter

Aperture   V Mag
       6         2.461
       8         2.306
     10         2.335
     12         2.347
     14         2.352
     16         2.354

Jeff

At 15:03 -0700 10/25/2007, Brian Skiff wrote:
>      Thanks for the data and profile.  If I'm reading the chart
>correctly, the comet is about 15 pixels diameter (and what is the
>image scale in arcsec/pixel?).  So I would set the sky annulus to
>start at at least 15 pixels _radius_ and go out from there several
>pixels to get enough counts.  Leave the sky annulus fixed, and
>re-do the aperture photometry with steps of maybe 2 pixel increments
>from 2 to 10 or 12 pixels radius.  In the list you sent, you have
>evidently changed the sky annulus with each step in aperture,
>so the results are not interpretable (basically you've include
>some of the comet in the sky reading for the smaller annuli).
>The sky annulus needs to be way outside the comet and _fixed_.
>
>\Brian

-- 
Jeff Hopkins
HPO SOFT
Counting Photons
http://www.hposoft.com/Astro/astro.html
Hopkins Phoenix Observatory
7812 West Clayton Drive
Phoenix, Arizona 85033-2439 U.S.A.
(623)849-5889
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