modified, Sept 20, 06)
Here is the
current operation mode for Hecto observing runs.
The PI makes a catalog of objects, which may be ranked in
preference. The catalog must also include guide stars on the
same coordinate system. Guiding is done at the edge of the Hectospec
not on the surface where the object fibers are positioned.
Thus, there are very stringent requirements on guide
stars by the small area of sky available and the limited range of
allowed by the TV cameras.
2mass and GSC II catalogs can be used where an observer catalog
minimal in stars. In that case, the program tmcguidestars
used. This program searches the 2mass catalog for coincidences with the
observer catalog, and computes a coordinate
transformation. 2mass and GSC II stars are selected in the field,
transformed to the observers' catalog coordinate system, and added
to the catalog. Note: the target catalog must have some stars in
common with the 2mass catalogs. You might need to add stars to
insure that, even if you don't intend on observing them. Bad News tmcguidestars is not
for export. It does run on CfA computers, in a command line mode.
External projects should contact instrument scientists if they need
help with guide star selection.
The PI downloads the configuration program from CfA,
and runs the config program for approximate dates of
observation. In this process, guide stars are checked for
suitability using a number of criteria (magnitude range, not a
galaxy, no neighbors, etc).
xfitfibs requires information such as date and length of
observation, number of exposures, ranking of config, and for Chelle
observations, the filter and binning needed, all which will be
used in scheduling.
The output of the program is a number of files which
would now be sent to a CfA computer for human checking, via the
button Submit .
The configuration file is modified a few minutes before the observation
in order to update positions, rotation angles, random sky selections,
and guide stars.
submit your configuration files at least 10 days before the run starts.
Brief Instructions on Running
Here, I describe the
basics of obtaining a fiber assignment file from a catalog. The
xfitfibs program itself contains many pages of help for particular
items, and after going through these steps, one should consult those
pages for detailed help. The observers manual, which
this section is at
(it tends to
be updated later than this page, however).
I. Make a catalog
The catalog should be in starbase
format (Tab delimited) with at least these columns:
but it's probably better to have more:
object rank type
A sample catalog would look like:
object rank type
---------- ---- ----
008-060 1 TARGET
010-062 1 TARGET
Note the row with dashes (also tab delimited). "guide" indicates the
guide stars, located at the end of the file. In this case, the
guide stars have no rank or object name (but the tabs are there).
The starbase suite of programs may be downloaded at
The command check
useful top run on your catalog to see that the format is valid (type
"check < mycatalog"; no message means that the catalog is
valid). The command fldtotable
will convert an ascii table to starbase (see the help pages).
It is nothing
short of essential that the targets and guide stars be on the same
The coordinate transformation program is
but will have difficulty running if
the field is dense in stars because of the web interface time out
II. Run Xfitfibs
II.1 Load catalog and select field centers
- Start up program. this brings up the drawing window and the field
- Load a file with pull down menu. This will draw the objects
1d circle centered on the objects' centroid, and also make 1 target
center in the fld window.
- In the latter window, enter the start time in UT, e.g.:
3 03:00:00 2005
- Enter an exptime in minutes and nexp (e.g., 15 and 3). (Leave pa,
minutes, r0, r1 and r2 alone)
- For each entry in the field table, enter a priority which will be
in the schedule.
- If you need sky offsets, please enter the number and
time in minutes per exposure. Offsets will typically be 5
arcs; successive exposures will be in different locations with the same
- for Chelle observations, select the on-chip binning, either 1x1
or 2x3. Spec projects leave this and the filter blank.
- for Chelle observations, select the filter. Choices are
Ca19, OB21, OB24, OB25, OB26, Na28, RV31, OB32, OB33, OB37, Ca41,
iodine, and dumiodine. OB25 is the Halpha filter. See http://cfa-www.harvard.edu/cfa/oir/MMT/MMTI/hectospec/Filter_Specs_a.pdf
- for Spec observations, select the grating: 270 or 600. Then select the
centralwave(length). For the 270, this is always 6500. For the 600gpm
grating, you have a choice of 4800, 5300, 5800, 6300, 6800, 7300, 7800,
8300. Errors will occur upon submission if you enter invalid
- Click on the box next to the config number (beginning of
should turn red indicating it is being operated on.
- In the drawing window you may now move the circle to where
you want it
by clicking and dragging, or enter new coords by hand. You may add
fields by using the table pull down menu. When you are through
moving things around, you should turn those
- Click on parameters in
the field table window, and set
the # of sky fibers. Once you are
happy with your field centers, we need to...
II.2 select candidate guide stars
Click on Fit Guides tab,
then begin fit.
The number of guide stars will appear at the far right of the fld table
row. A red background means too few stars available. You may have to
move the circle center or change the mag limit on the guide stars (at
the peril of them not being seen at the telescope).
It may also be the case that the rotator angles are red, even though
there are enough guide stars. In this case you can change those
angles by clicking on "toggle guide
annuli", going to the drawing window clicking on the (faint) red
circle at the ends of any of the 3 annuli and dragging the annuli
around until r0,r1 and r3 are green.
Next you need to classify the guide stars to remove double stars,
stars that are too faint, and plain old galaxies. Click on
After a while a message will come back with the results. Some stars may
be rejected. Click on ok to rerun the guide star selection.
You can view the guide stars by bringing up the "Guide" window.
Use view to elect each config
Clicking on show, will
start up ds9 and display all the guide stars in different frames. Nixed
stars may also be seen by using view. If you are left with no
guide stars, you may try to lower the faint mag limit in the parameters
menu, but please advise us that you have done so, and expect some
trouble at the telescope.
II.3 Fit fibers.
Click on fit fibers, if your
objects have a ranking system, then select rank, otherwise don't click on it.
Make depth=7. If you are
for Chelle, click on that as well. Now, begin fit.
Note that all the field centers you have entered in the fld table are
fit at once, such that no target is assigned more than once. If
you create two different output files from the same catalog, by running
xfitfibs at different times with different field centers, then you may
Check to see that you have fit the number of targets you expected,
otherwise, change your sky fiber numbers in parameters. Ranking
of targets may be changed by using the rank window. See the
details in the help page.
Now you ready to submit:
Click on the Send tab.
Pick the current trimester (e.g., 2005a)
Pick the PI number,
Click on send
You may get a warning about changed parameters in the field table,
which I think can be ignored. A number of files are then sent to
CfA, where they are checked again before being sent out to Mt
Hopkins. Note that sending a config file (the one actually used
at the telescope) directly to Mt Hopkins is discouraged, since such a
file would not have the Program number identified, that being added
during the "send" process.
Send will fail if you did not classify the guide stars. Go back and
classify them, and then run Fit fibers again.
Send will fail if you did not enter a valid filter or binning for
Chelle observations, or valid grating and centralwave(length) for Spec.
Correct those, and press Fit fibers again. Now submit
Now you can submit.
Questions should be addressed to
hectospec at cfa.harvard.edu
hectochelle at cfa.harvard.edu