Comet 168P/Hergenrother

2012/09/10

2012 Sept 10

News came several days ago that this comet was reported to be much brighter than expected, therefore, we decided to spend some time observing this comet. We could confirm that the comet is very bright. MPC observation computed with Astrometrica using both UCAC-3 and CMC-14 star catalogs -- the former for astrometric reduction and the latter for photometric work:

COD C42
OBS M.-T. Hui, X. Gao
MEA M.-T. Hui
TEL 0.36-m f/6.9 Schmidt-Cassegrain + CCD
NET UCAC-3
0168P        KC2012 09 10.77304 00 39 49.47 +02 09 10.6          13.5 N      C42
0168P        KC2012 09 10.77676 00 39 49.21 +02 09 21.3          13.5 N      C42
0168P        KC2012 09 10.78046 00 39 48.95 +02 09 32.5          13.5 N      C42
----- end -----

Photometry result computed with FOCAS II, which processes images based upon the .LOG file of Astrometrica, by means of Multibox method:

COD C42
CATALOG: USNO A2.0 / CMC-14 - BAND: R

                                   10x10  20x20  30x30  40x40  50x50  60x60   SNR   SB   COD
OBJECT        DATE       TIME        +/-    +/-    +/-    +/-    +/-    +/-     N  FWHM  CAT
------------  ---------- --------  -----  -----  -----  -----  -----  -----  ----  ----  ---
168P          10/09/2012 18:38:31  13.52  12.63  12.20  11.93  11.72  11.56  30.5  19.3  C42
168P          10/09/2012 18:38:31*  0.02   0.02   0.02   0.02   0.02   0.02     3   2.6  CMC

FoCAs II - 17/03/2010
www.astrosurf.com/cometas-obs
es.groups.yahoo.com/group/Cometas_Obs

Interpretation of the FOCAS II table headings:

 

Fisrt line:

OBJECT, DATE, TIME: refering to their original meanings respectively

10x10, 20x20 ... 60x60: the aperture sizes of photometry in term of rectangle in arcsec that are used to measure an object's magnitude

SNR: the Signal-to-Noise Ratio for aperture photometry

SB: stars of faintest magnitude on the images used in data reduction with the used star catalog in Astrometrica, rather than the stars of faintest magnitude in the images

COD: MPC Code of the observatory

 

Second line:

+/-: precisions of measurement

N: the number of used images for measurement

FWHM: Full-Width-Half-Maximum of total PSF, relevant to degree of seeing

CAT: the used star catalog in Astrometrica

 

Prior to I exploiting IDL for infinity magnitude fitting, I measured the diameter of the coma, the value of which could be seen in the above image. I did not convert the flux that would have been in corresponding circular apertures from the flux enclosed by square boxes in the same dimension. With several tests, I obtained that $n = 1.12$ best describes magnitudes in different square boxes, thereby $m_\infty = 10.52 \pm 0.04$.

Copyright @ Man-To Hui 2012/09/08

Feel free to e-mail me with any doubts or questions.

Top

Back... -- Zurück...

Home