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Special Notice #203: Request for monitoring of V842 Cen in support of HST Observations

March 15, 2010: Further to AAVSO Alert Notice 418, the AAVSO requests intensive monitoring of the cataclysmic variable V842 Cen in support of Dr. Paula Szkody's upcoming Hubble Space Telescope observations beginning now (2010 March 15.85; JD 2455271.35) and continuing through 2010 March 19. Observations are requested to show HST ground controllers that the system remains faint and is therefore safe to observe. Telescope operators at the Space Telescope Science Institute (STScI) will make the decision to move forward with HST observations based upon ground-based data from March 16 through the UT morning of Wednesday, March 17 (JD 2455273.0) at the very latest.

The field lacks a good calibration for its current brightness level. As stated in Alert Notice 418, visual observers may use the two stars to the south-southwest of V842 Cen -- one 7 arcseconds distant, the other 20 arcseconds distant -- as comparisons. The NOMAD1 ID, position, and magnitudes for these two objects are:

7": 0323-0709135 , RA 14 35 52.170 , Dec -57 37 43.82 , V=14.88

20": 0323-0709110 , RA 14 35 51.839 , Dec -57 37 57.54 , V=14.76

CCD observers may use the "140" comparison star (AUID 000-BJT-697) as a possible photometric comparison star. Both visual and CCD observers should note in their report both the identity and assumed magnitude of any comparison stars used. If you are uncertain as to the magnitudes, please contact Dr. Matthew Templeton (matthewt@aavso.org) directly, and the details of the observation will be communicated directly to Dr. Paula Szkody.

V842 Cen is located at the following (J2000) coordinates:

RA: 14 35 52.58 , Dec: -57 37 35.1

Charts for V842 Cen may be plotted using AAVSO VSP (http://www.aavso.org/vsp).

V842 Cen is the second of two objects being observed as part of this HST support campaign. For more information on this campaign, please see AAVSO Alert Notice 417.

Please report all observations of V842 Cen to the AAVSO using the name "V842 CEN".

This AAVSO Special Notice was prepared by Matthew Templeton.

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