Notes for Observers


Note that the reflective coating on the continuum filter does NOT cover the entire surface.  Care must be taken to ensure that when fitting this filter, the filter sits square and centred in the holder.  If not, light can leak past the edge of the filter.  This can be seen as a very bright streak on the edge of the CCD, e.g. when doing flats.  This can be checked during the day by doing a `dome-flat', with the mirror covers open and the dome lights on.  If there is a problem it will be immediately evident.  Note that this procedure is purely to check the filters; twilight sky flats are much preferred.


The filters to be used are the Harris R filter (number 39 on the ING filter database); the 115 Angstrom FWHM filter centred on 6471 Angstroms, purchased for this project by PAJ (not on the ING database) for continuum observations; and the following H alpha narrow-band filters:  6570/55 Angstroms (number 61, recession velocities 0-950km/s), 6594/44 Angstroms (number 63, recession velocities 950-2100 km/s), and 6626/44 Angstroms (number 65, recession velocities 2100-3000 km/s).


The exposures to be taken are as follows:

The exposures are to be read out in QUICK mode.


If the Major axis of the galaxy is less than 3 arcmin the CCD should be windowed (1000x1000 sub-array), providing there are enough stars remaining in the sub-array to align images.

It is possible to keep the bias strip, even with a sub-array.  Set up two windows, e.g. like this:

window 1 1000 1000 500 500
window 2 70 1000 2070 500

The trick is to use the same ystart (500) and ysize (1000 in the
example), the bias strip is then e.g. 2070-2140. You end up with a nice
fits file which has the bias strip glued to the right.

If windowing make a note of the startx and starty values of the window for flat-fielding.


Because of the narrow-band filters, it is important to use spectrophotometric standards.  A list of these is kept in the JKT control room in a red file labelled FLUX STANDARDS.