Effects of dusty mirrors on the shape of light halos around bright stars

                                                C.X. 11.09.2000

   Per Rae Stiening's  suggestion, we investigated the effects of dusty mirrors on the shape of light halos around bright stars (< 5 mag). This bears on the question whether the ongoing IPAC attempt of obtaining photometry for bright stars by fitting the light distribution of the halos can be significantly affected by dusty mirrors which occurred time to time through out the 2MASS mission.

     For this purpose, we picked 3 bright stars, with Ks magnitudes ranging from 1.7 to 3.7, that were observed by the 2MASS southern observatory (CTIO) during a period of very dusty mirror (nights 1050 -- 1100, corresponding to 000114 -- 000304)  and then were observed repeatedly after the period. The comparisons between the light profiles obtained during and after the dusty mirror period do not show significant differences (see the plots below).  Given the very small sample, the tentative conclusion from this investigation is that the shape of the light halos around bright stars are not affected significantly by the dirtiness of the optics.
 

Star 1 (J=3.7, H=3.7, Ks=3.7):
 

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Star 2 (J=4.0, H=3.1, Ks=2.9)
 

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Star 3 (J=3.3, H=2.2, Ks=1.7):

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