0.8m Telescope Prime Focus Camera
Operating Instructions
Prepared by Tom Barnes
Last updated 10/13/2005

Web version updated 03 Nov 2005 MF

Basic facts Flat fields
Request for Service Image display Shutter correction
Telescope & dome operation Test operation End of night
Tips for PFC observing Observing Sending tar files home
Starting the night Pointing alignment Writing FITS tapes
Bringing up IRAF & ICE Focus process Writing tar tapes
Transformation & extinction SUN stuff
LN2 facts Performance PFC Stuff
Bias & dark Guider operation

Basic Facts

Request for Services

0.8m Telescope dome and telescope operation

http://nexus.as.utexas.edu/obs_sup/man/manuals/30man.html

Tips for PFC observing

http://banzai.as.utexas.edu/sco/how/het/pfc/

Note: Do NOT use the Notes from Phillip MacQueen on this page. It is seriously out of date. Use this updated version instead:

http://nexus.as.utexas.edu/obs_sup/man/manuals/pfc/ice_pfc.html.

Starting the night


Bringing up IRAF and ICE

It is important to run IRAF and ICE from different windows and different directories. Default directories are created when your computer account is created, but you may make your own if you wish. If you are starting IRAF for the first time or re-making IRAF, go here.

cl> vi login.cl

un-comment the line

cl> mkdir /data1/titan/username (to create data directory)

Every time one starts the system,

Open another luna window using a left mouse click on ‘local’


Telescope interface


ic> epar telpars


Detector interface


Every time the CCD is powered down, the following sequence of commands must be executed from within ICE after the CCD is powered up: bye, flpr, flpr, icex. Then recover filter location, focus and activate the autofocus using “instrfo=h” and the instrument command.


ic> lpar detpars


A subframe readout as shown below can be used to shorten the readout time. Note that the readout time for subframes depends only on the number of rows read.


For binning, 4 x 4 co-addition is specified by setting:


PFC (Instrument) interface

Check visually which filter is centered in the light path by

starting a long integration and looking into the PFC to see the filter color

or

2)gently opening the iris and looking into the instrument.


R is bright orange, V is bright green, the others are not as obvious


ic> epar instrpars (to set up the instrument task)

ic> instrument (to execute the choices selected in the "epar instrpars" step)

ic> lpar instrpars


Observing interface (obspars):

Parameters that are set manually are 'rootname' and 'sequence' (for specifying the filename), `pixtype', 'observers', and 'commands'. The string shown below for 'commands' causes the image to be displayed at the end of a readout on a display tool (ximtool or SAOimage). The display tool must be running at the end of the readout.

ic> epar obspars (to set up the observing task)


ic> lpar obspars


Image display

See here for the DS9 user manual.

Open a display window for the spectrum readout.


The default display ortientation has NORTH at the bottom, EAST at the right.


The IRAF task ‘imexamine’ will create a plot window and display the plot

Place the cursor on the image and type

Quit imexamine before another image is displayed to avoid problems with the task.


Images will display better if the ‘display’ task parameters are modified as


The ICE manual explains ximtool and imexamine well.


Test operation

In the ICE window,


Answer the prompts with parameters or <cr>. It is useful to do an "object" exposure in the test so that a non-zero signal is returned for the test.


Observing

To recover focus at the start of a new night,


Do a "p l" in the titan window to update the airmass parameter.



Move the field slightly on the CCD between sets of exposures on the same field in the same filter to eliminate chip defects when the images are added together.

In standard star frames, it is sometimes possible to change to a sub-field of size 512 X 512 using "detpars" to improve read-out times.

If the integration times are short (so no guiding is needed at all), it is possible to set up a script to take a set of BVRI frames automatically.


Pointing alignment

Change the detector parameter file to restrict the number of rows in the readout to speed the process

ic> epar detpars

Take a ‘test’ image of a moderately bright star.

Move the telescope to shift the bright star on frame until a test exposure shows it to be near coordinates (1024,200).

Adjust the telescope readouts to agree with the star coordinates.


Focus process

A good focus is 1.5 pixels (2.0 arcsec); an acceptable focus is <2.0 pix (<2.7 arcsec).

Choose a field away from the Galactic Plane to avoid crowding.

Change the detector parameter file to restrict the number of rows in the readout to speed the process

ic> epar detpars


ic> epar instrpars


ic> instrument to execute the change


ic> test

ic> epar instrpars

ic> instrument to execute the change

ic> epar instrpars

ic> instrument to execute the change

ic> test to verify the focus


When happy with the focus, set the full frame readout

ic> epar detpars


When logging out of ICE, focus is not lost as the focus information is saved. To recover focus on a restart, run instrument with “instrfocus = l" to recover T of last focus.

Repeat with “instrfocus = h" to reactivate autofocus mode.


Transformation and extinction

Landolt, A. 1992 AJ, 104, 340 gives UBVRI standards in the 11.5 – 16.0 mag range in the Selected Areas.

Typical exposure times for these fields are


LN2 facts

Hold time for the dewar is 8-10 hours, as long as the vacuum jacket has not been contaminated - which can happen. If the vacuum jacket is contaminated, the hold time is reduced drastically. So, monitor the CCD temperature regularly by reading it on the display on the telescope tailpiece. The observing temperature is in the window –99 to –103 C. If it rises above –95 C, put in more LN2. On the xreport ask for LN2 refills in the morning and afternoon if desired. Note that Observing Support may not be able to manage requests for fills at times other than first thing in the morning, especially on weekends or holidays, as the person on report duty is only required to hang around until 10am.


Bias and Dark


Flat field measurements

Twilight flats:

Because of instrument light leaks (no baffle, no shroud), very large field (sky gradient) and 3 minute read-time, twilight flats are useless.

It is possible to create sky flats by adding together many different stellar frames using median techniques. This cannot be done if the moon is up because of the scattered light.


Dome flat set up:


Turn off all dome lights.


In the ICE window,

ic> observe

Shutter correction

Corrections for variation in the exposure time due to the shutter iris closure are necessary for all exposures shorter than a few seconds and good to do for all short exposures for better photometric accuracy.

Set up telescope, dome, door sign, etc., as for a flat exposure

A set of two ‘10 sec exposures plus ten 1 sec exposures’ takes about 37 minutes to do.

<Get instructions from Phillip MacQueen for the process.>


End of night

At the computer:

In the control room:

In the dome:


Sending tar.Z files to your home computer

It is quick and efficient to send tar.Z files over the Internet to your home computer. However, the process does take some preparation. Within an IRAF window on titan,

cl> cd /data1/titan/username/<data directory>

cl> files *.imh > imhlist (to create a file listing all the .imh files in the current directory)

cl> !sed s/imh/fits/g imhlist > fitslist (to change the .imh to .fits on each file name

and store the new list in file fitslist.

cl> unlearn wfits (to get rid of the "yes" or "no" in the "newtape" parameter

cl> epar wfits

"iraf_file = @imhlist"

"fits_file=@fitslist"

"newtape= (blank)"

cl> wfits (to create a fits file for every IRAF file and retain the same name)

cl> cd /data1/titan/username

cl> !/opt/local/gnu/bin/tar cvf /data1/titan/username/nite1/nite1.tar nite1/ *.fits

(to create a file nite1.tar containing the *.fits files inside the directory nite1)

cl> cd nite1

cl> !compress nite1.tar (to create a compressed file 'nite1.tar.Z' of the tar file)

cl> !scp nite1.tar.Z username@astro:/usrename/dirname/<name>

(to transfer the file to directory /username/dirname/<name>

username@astro's password: <password>.

nite1.tar.Z (line showing progress of the transfer)

It takes about 4.5 minutes to transfer 42 Mbytes, but this depends on the internet traffic.

At home, the data may be uncompressed and extracted,

astro> uncompress nite1.tar.Z (to decompress the file)

astro> tar xvf nite1.tar (to extract the *.fits files from the tar file)

The above format for creating the .tar file will lead to the extraction creating a directory /nite1 into which the *.fits files are put.

Writing FITS files to Exabyte tape

Data may be written on exabyte tapes (2292 Mbyte) in FITS format, ~130 full-sized frames fill a tape. However, it is extremely time consuming to put that many files on a tape. It is better to write tar files to tape (see below).


To start the tape dump, in the IRAF window,

cl> cd /data1/titan/username/nite1 (to go to data sub-directory)

cl> dir (to verify location and presence of .imh, .pix files)


Load the Exabyte tape in the drive

cl.> allocate mtaf (to assign drive to titan)

cl > dataio (to launch data I/O package)

da > epar wfits (to verify parameters in write package)

change only the first three parameters as appropriate

"iraf_fil= a*.imh" or @filename (if filename contains the list of files to be copied)

"fits_fil= mtt" (to send the files to tape)

"newtape= yes" or "no"

control-d to escape editor or :go to launch wfits directly

da > wfits (to launch wfits if :go had not been used, do a return for each query)

da > deallocate mtaf (to rewind tape after finished)

Eject the tape

Writing tar files to Exabyte tape

It is vastly faster to write tar files to Exabyte than to write FITS files directly. Note that the name of the 0.8m tape drive is rst4. From within a titan window


% tar cvf /dev/rst4 fits* to write the FITS files in the current directory to a tar file on tape.


% mt -f /dev/rst4 rewind to rewind the tape

% mt -f /dev/rst4 status to check on what the tape is doing

% mt -f /dev/rst4 fsf N to skip N files

% tar vf /dev/rst4 > tapelist.txt to list the tape into a file tapelist.txt

% type tapelist.txt to list on the screen the contents of tapelist.txt


At home, the tape may be read using

% tar xvf /dev/rstN where rstN is the local /dev


SUN stuff

Different menus are generated by each of the 3 Sun mouse buttons when clicked on an open area of the desktop.


Mouse control:

To cut and paste, select text with the left mouse button and paste it at the cursor location with the right one.

Middle mouse button grabs and moves things.

Use the up/down arrows to move to earlier typed lines.

Mouse control:

To cut and paste, select text with the left mouse button and paste it at the cursor location with the right one.


Virtual window:

In the lower right of the screen there is a space showing miniatures of all the open windows, some of which may be positioned off the actual screen. (If you started with twm rather than tvtwm, this will not be available.)

The white, dashed box shows the location of the visible screen in this larger window area.

The white box may be moved about with the middle mouse button to bring open windows onto the visible screen.

Individual windows may similarly be moved about by manipulating their replicas.


Editing control:

To move to previous commands in a SUN window, type "e" for edit mode, <cr>, and then use the up/down arrows to find the desired command. Use the left/right arrows to position the cursor to edit the command. Then a <cr> executes the command.


Performance PFC stuff

There are finder charts for the Landolt fields and an ICE manual in the control room. There is an up-to-date ICE Manual here.

Good exposure times for the Landolt UBVRI standards


A 75 sec exposure in R gave total counts of 65778 ADU on a V = 13.73 mag star.

Sky count was 245 ADU/pixel without moon.


Guider operation

See here for more information on the guider.

- 13 - October 24, 2005