Observational Lab
with the Bengt Westerlund
Telescope (BWT)

Goals

Take images of bright galaxies in three filters.

Strategy

Try to achieve the best dynamic range by adjusting the exposure time with each filter.

Calibrations

a)    Take calibration frames for the dark current at different exposure times and derive bias level and dark current rate. Keep track of temperature of the CCD.

b)   Take flat fields using the same derotator position as for the targets (see below).
Hint: if the same derotator position is used for all targets and filters than a single set of flat fields can be used for all observations.

Targets

a)    Go to the first object, make sure you are there and note the current ART angle in AutoSled (Angle of the camera mount Relative to the Telescope).

b)   Take images (longer than 5 minute exposures require the use of offset guider) in the first filter.

c)   Move back the derotator to the initial ART value. Take next filter images.

d)   Repeat c) for the last filter.

e)    Go to next object, return the derotator in the initial position and repeat steps b), c) and d).

Questions and topics to include in the report

a)    What was the level of bias and dark current derived and how did you do it?

b)   How did you combine flat field exposures?

c)   What was the signal-to-noise ratio in the combined (master) flat?

d)   How did you determine the dynamic range of the target images?

e)    What was the limiting factor for the length of a single exposure?

f)    How does the optimal exposure time depend on the filter and why?

g)   Present images.

List of targets

The table below contains a list of galaxies that can be observed in the evening during the winter. Columns give name in Messier catalogue, coordinates (2000 epoch), hour (local time) from which observations can be carried out, angular diameter (arcmin) and B magnitude.

 Target a d Time Size in arseconds Bmag M110 00 40 22.00 +41 41 07.0 18 18.62 x 11.48 9.4 M32 00 42 41.87 +40 51 57.2 18 9.12 x 6.61 9.2 M74 01 36 41.84 +15 46 59.6 18 10.47 x 9.55 10.5 M81 09 55 33.17 +69 03 55.1 18 22.38 x 11.48 8.1 M82 09 55 52.19 +69 40 48.8 18 10.47 x 4.36 9.2 M108 11 11 31.29 +55 40 31.0 20 8.13 x 2.75 10.7 M109 11 57 35.90 +53 22 35.0 20 7.08 x 4.57 10.7 M106 12 18 57.54 +47 18 14.3 22 16.98 x 6.46 9.6 M94 12 50 52.63 +41 07 09.3 23 12.58 x 10.96 8.7 M63 13 15 49.28 +42 01 46.5 23 13.18 x 7.94 9.7 M51 13 29 52.37 +47 11 40.8 23 8.32 x 7.08 8.8 M102 15 06 29.48 +55 45 47.2 23 6.46 x 3.16 11.1

Target assignment

 Kjell Rosengren Björn Eckerbom M81 eller M82 Sascha Kulas Andreas Lundin Vibeke Moving Mattia Levi Erik Aronson Tuomas Mattson Izabel Roca Vich Sergio Velasco M109