Alert Notice 628: HST observations scheduled for SDSS J153817.35+512338.0

March 29, 2018: Further to AAVSO Alert Notice 618, Anna Pala (Ph.D. candidate, University of Warwick) informs us that the date and time of the HST observations planned for the faint polar cataclysmic variable SDSS J153817.35+512338.0 have been set for

2018 April 6 17:33:26 - 21:33:19 UT

It is essential to know the brightness of the target just prior to the HST observations in order to protect the satellite equipment. A go/nogo decision will be made 24 hours prior to the observation time based on positive magnitude reports from AAVSO observers.

Nightly V/CV (unfiltered) observations are requested through April 1. From April 2 through April 7, multiple observations per night (not time series) in V/CV are requested, then nightly observations again through April 30.

Ms. Pala thanks the observers who have been monitoring the target - their data are very much appreciated!

SDSS J153817.35+512338.0 has a range of 17.5 - 19.1 CV. In its current low (quiescent) state it is magnitude ~18.6 V.

Coordinates (2000.0):  R.A. 15 38 17.34   Dec.  +51 23 38.0

Charts with a comparison star sequence for SDSS J153817.35+512338.0 may be plotted using the AAVSO Variable Star Plotter (VSP). Be sure to include the space between SDSS and J. It is recommended to select the option to display a DSS chart so that all of the comp star images will show.

Please submit observations to the AAVSO International Database using the name SDSS J153817.35+512338.0. Again, please be sure to put a space between SDSS and J.

This observing campaign is being followed on the AAVSO Campaigns and Observing Reports online forum at

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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