---------------------	README-date: 16.08.04  ---------------------

Star Clusters  -  Targets:
NGC 1808	2 clusters	RA ~ 05 h
NGC 253		2 pointings	RA ~ 01 h 


The goal of the observations of these star clusters is to determine their
ages from equivalent widths of either hydrogen recombination lines or
stellar absorption features. Therefore the H+K grating should be used.
The clusters are expected to be young, around 8 Myrs old, therefore it
is not a priori clear whether to expect line emission, absorption, or both.
The targeted clusters in both galaxies should be just bright enough to
use the AO. However, in order to detect larger scale features (for example
expanding shells, which would be visible in Brg), which bears the
additional benefit that some more targets may be included in the field,
each pointing should be executed once in seeing mode and once in AO mode.
10 min on source for the seeing (0.25"/pix) mode gives enough SNR to 
measure the equivalent width also on the fainter He line, for example.
20 min on source for the 0.025"/pix+AO should allow us to detect structure
like Brg-shells, dust structures, winds, whatever. If it's just a plain
point source, stop there. If the features can be clearly seen, stop, too,
if we underestimated the required time, and you can just make out something
interesting, but the SNR is too low - please add some exposure time.
All targets should be observed in ON/OFF mode, so please go clearly off
to sky, 30"-1' for example. 



------------
| NGC 1808 |
------------

*****************************
Observation setup:
*****************************

Pixel scale 0.25":
==================
DIT	NDIT	SEQUENCE	Number of Exp	Total time ON	Total exp time
120	1	ON-OFF-OFF-ON	5 On, 5 Sky	600s		1200s


Pixel scale 0.025":
===================
DIT	NDIT	SEQUENCE	Number of Exp	Total time ON	Total exp time
240	1	ON-OFF-OFF-ON	5 On, 5 Sky	1200s		2400s



*****************************
Target properties:
*****************************

Name		mK	RA			Dec

N1808-12	13.6	05:05:58.46 (1950!!!)	-37:34:41.6 (1950!!!)
N1808-20	13.4	05:06:58.72 (1950!!!)	-37:34:38.3 (1950!!!)


Notes:

Because total exposure time is so short, we think
it should be best to go for 120/240s DITs, in order to be able to jitter around
a little. If you think this is unnecessary (few bad pixels), feel free to
increase DIT and to decrease the number of positions. 



-----------
| NGC 253 |
-----------

*****************************
Observation setup:
*****************************

Pixel scale 0.25":
==================
DIT	NDIT	SEQUENCE	Number of Exp	Total time ON	Total exp time
15	4	ON-OFF-OFF-ON	4 On, 4 Sky	240s		480s


Pixel scale 0.025":
===================
DIT	NDIT	SEQUENCE	Number of Exp	Total time ON	Total exp time
15	10	ON-OFF-OFF-ON	6 On, 6 Sky	900s		1800s


*****************************
Target properties:
*****************************

NGC 253-Tar 1	10.1	00:45:05.59 (1950!!!)	-25:33:40.57 (1950!!!)
NGC 253-Tar 2	10.5	00:45:05.81 (1950!!!)	-25:33:38.43 (1950!!!)


Notes:

We set these small DITs to avoid saturation/non-linearity. Despite these clusters
being much brighter (note that Target 1 looks like the nucleus, but isn't), our anticipated
integration times are not much shorter than for 1808, because the quoted magnitudes are
not background-subtracted, and the background is quite noticeable here.



Please, send questions to smengel@eso.org, and to ltacconi@eso.org (who is the primary
contact person, but currently on vacation. He nevertheless reads his mail often 
and will be back Aug 21st).

Cheers,
Sabine