TELESCOPE OPERATIONS MANUAL
By Heidi Schweiker
Edited By Hillary Mathis
TABLE OF CONTENTS
PDF version of the February 2011 manual (2.5Mb)
Location of the 0.9m Telescope
Filling the Dewar
The Dome Cameras
The Exhaust Fan
The Wind Screen
The Dry Air System
Dome Vent Operation
The ACE TCS
Overview of the TCS
Starting Up the TCS
Telescope Park Positions
Importing Coordinate Catalogs
Aquiring an Object
Small Telescope Motions
Moving the Dome
Checking the Weather
Data Acquisition Computers
Checking and Zeroing Pointing
Changing Filters with S2KB
Guiding with Mosaic
Guiding with S2KB
Automated CCD Log
WIYN 0.9m/S2KB FAQs
The MOSAIC Manual
End of Run Checklist
Lightning Shutdown Procedures
Extended Horizon Map
Additional S2KB Information
The KPFILT script
More on the Mosaic Guider
A Unix Cheatsheet
An IRAF Cheatsheet
An SFTP Cheatsheet
An EMACS CheatSheet
An Vi CheatSheet
A Guide to Taking Sky Flats
Dewar Filling Tips and Tricks
Taking a Seeing Measurement
0.9m User's Manual
ICE Observing Manual
Direct Imaging Manual
The MOSAIC Manual
Conditions for observing
At the start of every night the Observing Assistant at the 4 meter telescope
should send out a weather status report. This will show up in any xterm window
on the VNC viewer window to Taupe as "Domes are
open" or "Domes are closed due to...", etc.
This statement is only a guideline - you are ultimately responsible
for the decision to open or close due to weather. You can check
the weather status at any time by typing "weather" in any xterm window on
Taupe or Emerald or can be found on the web at
Note that this is not always updated.
There are several criteria that have to be met before the dome may be
opened. These criteria have been set with the safety of the equipment and
the telescope in mind and are not flexible.
- The humidity may not exceed 90%.
- Wind speeds may not exceed 45 mph (20.25 m/s).
- Dome surfaces must be dry and free of ice.
- Skies must be free of threatening clouds and rain.
- Air must be free of blowing dust, snow, fog or dripping water.
- The outside temperature must be above -10C.
As an added protection measure, whenever the sky is too overcast to observe
through, the mirror cover, and preferably the dome, shall be closed.
There are a couple ways to check the humidity and wind speed:
- From the background menu on the VNC Taupe GWC select "WIYN Weather
Info". Then click on Weather data. This GUI displays Outside Temperature,
Relative Humidity, Wind Speed (in meters/sec), and Wind Direction. These
readings are taken from the WIYN 3.5m Telescope control system. That means
that if the WIYN TCS is down you will not receive current readings.
- The wind speed from the 2 meter and 4 meter telescopes is logged and
broadcast on the intranet here.
- The humidity from the 2 meter, 4 meter, and WIYN are logged and broadcast
on the intranet here.
- There is a digital hygrometer mounted on the wall in the dome. It is located
on the wall at the top of the stairway.
- Kitt Peak site informtiton is here.
- The Kitt Peak all sky camera (internal access only) is here.
- Kitt Peak all sky camera (external access) is here.
DATA ACQUISITION COMPUTERS
Data acquisition is done on the computer Emerald via the program
VNC Viewer for S2KB and via ssh for Mosaic. VNC stands for Virtual Network
Computing, a software program that allows one to view and manipulate
windows on another computer. We use VNC to remotely view the the ICE acquisition
computer, Taupe (used with S2KB). For more information on VNC see
Emerald has 2 monitors. The computer Emerald is a fast Linux box with a 3.4 GHz
(Pentium 4) CPU and 4 Gbytes of memory.
To begin your observing session with S2KB you should follow these steps.
- Log on to Emerald
as user 36inch.
- Select VNC Viewer Taupe icon from the desktop. This will
open the VNC client in emerald, in which the window from Taupe will be displayed.
Within this Taupe VNC ICE window you will need (i) a Data Acquisition window, (ii) a Data Reduction
window, and (iii) an Ximtool-alt. If they are not already up and running, you can bring up
these windows from the background menu (right-click) within the Taupe VNC ICE window.
Commands for acquiring data will be executed in this Data Acquisition window within the
Taupe VNC ICE window.
- Select VNC GWC Taupe icon from the desktop. This will open the VNC client
in emerald, in which the router (socket server information) is displayed. There should
be an xterm window within this Taupe VNC GWC window in which numbers are continuously
scrolling by. If not, see the TCS/Instrument Communications section for how to restart this.
To begin your observing
session with Mosaic you should follow these steps.
- Log on to Emerald
as user 36inch.
- Select Mosaic1 Menu icon from the desktop. This will open a menu where you can start the Mosaic software, stop the Mosaic software, open an autolog, start the guider and the guider gui.
- Click on Start Mosaic. Please refer to the Mosaic Manual for a description of the windows that appear when starting Mosaic, as well as instrucitons on how to run Mosaic.
- Select VNC GWC Taupe icon from the desktop. This will open the VNC client
in which the router (socket server information) is displayed. There should
be an xterm window within this Taupe VNC GWC window in which numbers are continuously
scrolling by. If not, see the TCS/Instrument
Communications section for how to restart this.
The system is now ready for you to start observing.
HOW TO CHECK AND ZERO TELESCOPE POINTING
How to Check Telescope Pointing
It's best to check your pointing with a bright star at zenith. The first
thing to do is load the Bright Star Catalog into the TCS. To do this right
click anywhere within the TCS and select the first option "Open Existing Database".
This should take you to the file containing all of the coordinate catalogs.
The path is
ACE Control System (D:) => ACE => CurrentRelease
The bright star catalog is labeled ACE_BSC5.cat. Select this and click "Open".
The catalog will open up into the center of the TCS.
Now find a star near zenith. You can sort the catalog by clicking on
the title of any column. Clicking that same column title a second time will
sort the catalog in descending order. Scroll down until you find the stars
around the current Sidereal Time (this can be found on the right side of
the TCS screen, labeled S.T. in purple). Select one that is close to the sidereal time
and near a Declination of +32. A 5th magnitude star works best. Once you've
selected a star double-click anywhere on that line in the catalog to send
the coordinates to the appropriate RA boxes. Confirm the coordinates in the
boxes are reasonable and click the "Go To" button.
The best way to discern your pointing with either S2KB or Mosaic is to take a very short
image (~2 second exposure). Once the image has read out you can fine-tune
the pointing if the star doesn't land exactly where you would like it. You
can find how far you need to move the telescope from the image. (The pixel
scale is 0.6 arcsec/pixel for S2KB and .43 arcsec/pixel for Mosaic).Be aware that if the
pointing is centered exactly the star may fall in the gap between the chips with Mosaic.
If this has happened, you can offset the telescope by 60 arcsec in two directions
(ie N and W or S and E) and if the star was centered it will now fall on one of the chips.
How to Zero the Telescope Pointing
If telescope pointing needs to be rezeroed please contact the Site Manager.
There are two filter wheels in the Filter Shutter Assembly associated
with S2KB. Each wheel contains 8 slots, giving the capability to house up
to 14 filters at any one time. The filter wheels are stacked, meaning both
filter wheels are in the light path at all times. For this reason it's important
to make sure that at least one of the filter wheels is in an "empty" position
when taking data.
To change filters you need to bring up the Filter Wheel GUI (displayed
Move the desired filter into the light path by selecting the radio button
to the left of it's name. Do this for both wheels. After selecting a filter
in one wheel you should see all the names in that wheel turn gray while the
filter wheel moves. Once it has reached the desired position the names will
reappear as usual. If the filter names do not reappear black you may need
to reinitialize that wheel. To do this, click on the appropriate INIT Wheel
# button within the Filter Wheel GUI.
- From the Instruments menu, select Filter Wheel.
Currently, filters are listed in the headers with numbers as opposed to
names. To convert these numbers to their corresponding names you can edit
and run the kpfilt script on a specific image (or list of images). The script
and instructions for it's use can be found here.
Beware of changing filters while slewing. This can result in filter wheel lockups.
Send the telescope and dome to the flat field position by selecting the
Dome Flat Park position from the Telescope pulldown menu
on the TCS. A box will appear with HA, Dec and Dome azimuth. The correct
positions should be HA 3:28, Dec 13:00, Dome az 74. Press "Park" to move
the telescope and the dome to the correct positions. It's a good idea to
go upstairs and sight along the telescope tube to check the telescope/dome
alignment. You may need to bump the dome left or right via the control panel.
The Flat Field lamp control is in the computer room. It is located in
the middle of the first electronics rack as you enter the computer room.
Control for the High lamps is on the left, and control for the Low lamps
is on the right. Each has a toggle switch to turn power on/off and a rheostat
to change the voltage to the lamps. To turn on a bank of lights turn the
voltage to 0 by turning the rheostat counter-clockwise. Turn the power on
with the toggle switch and then turn the voltage to the desired setting.
When turning off the lamps be sure to turn the voltage all the way down before
turning the power off. Ramping of the lights like this will help preserve
the lifetime of the lamps.
Suggested lamp settings and exposure times for each instrument are listed
Suggested exposure times and lamp settings for MOSAIC
are listed below. These exposures should produce images having 5,000-10,000
ADU per pixel to stay within the linear regime (note that each ADU represents
~3 electrons, so there is plenty of signal with these recommendations. To
minimize thinking at the telescope, we tried to use the maximum voltage settings
when possible (i.e. 100%).
|[OIII] +29 #2
Due to the mechanics of the secondary system there is some inherent focus
drift (~50 units). To try to eliminate this drift there is a routine that
keeps the telescope at the last commanded focus position. If you would like
to use this routine, simply check the box beside "Servo" in the Focus GUI.
Each time you change the focus the system will automatically keep the focus
at this new position. It is highly recommended to keep this box checked.
WARNING: Only click buttons in Focus GUI once and wait until action has taken place!
WARNING: Do not perform other tasks in TCS while changing focus!
The best way to focus the telescope is to run a focus sequence "manually".
You will be running a focus sequence from a Mosaic
setting the focus on the TCS manually at each step.
See the Mosaic Manual for instructions on how to set up a focus script. Start a focus sequence and you will be prompted to set the focus each
you are trying to find focus at the beginning of the night it's best to set
the number of exposures taken in the focus sequence to 7 (set at the default for the focus script). If temperature
from night to night has remained constant you can use the previous night's
ending focus as your middle focus value. A typical step sizes to use are
100 units (set as the default for the focus script). The smallest focus increment detectable is ~25 units. Once you start the script for the focus sequence you will
be prompted to manually set the focus for each exposure in the sequence.
To do this you need to bring up the Focus Inspector Gui on the TCS. You can
bring this us from the Telescope menu on the main toolbar: Select Telescope
You can enter a desired focus into the box beside "Go To Focus" and then
hit the "Go To Focus" button. Or you can use the JOG+ or JOG- buttons to
jog the focus a specified amount. The current focus is displayed on the toolbar
of the Focus GUI, on the main TCS screen near the middle left and at the
bottom of the ACE SoftPad.
The range of focus is from 0 to 60000. One step is approximately 0.5 microns.
You always want to increment the focus to larger numbers to remove backlash.
Nominal focus for both Mosaic and S2KB is around 32000.
Once your focus exposure has read out you can use the mscfocus
routine to determine the best focus.
When using S2KB it's best to run a focus sequence manually where ICE prompts
you to enter the desired focus in the TCS. In the Data Acquisition window
type observe and then focus. You will then be prompted
for exposure time, starting focus number, etc. If you have a good idea of
where focus should be, a good step size to use is 50 units. Otherwise use
a step size of 100 units. It is a good idea to do 7 steps in your focus sequence. The smallest step size you will be able to detect
is 25 units. You should always move the focus in the positive direction,
(ie your focus sequence steps should be +50 units).
Below is a typical focus sequence as seen in the Data Acquisition window.
When the image has read out you can use the kpnofocus routine
to determine the best focus. See the IRAF help page on
kpnofocus for more information. In your Data Reduction window type kpnofocus.
Once you have determined the best focus type it into the Focus Inspector
GUI (see above).
When changing the focus make sure to watch the focus values so (a) it reaches the desired focus value and (b) you will notice if the focus value starts to run away. A runaway can result in hitting the focus limit and restoring the system may result in the focus being significantly off from the previous value.
GUIDING WITH MOSAIC - THE LINUX GUIDER
Mosaic has two fixed guide cameras - one North of the science field and
one South of the science field. Guiding is accomplished by selecting a star
from one of these fields. Both guide cameras are at fixed positions relative
to the science field (~2400 arcseconds North/South). Suitable guide stars
are almost always available without moving the telescope from the desired
position. The field of view of each camera is approximately 5 arcminutes
on a side. It is possible to guide on stars as faint as V~17 near new moon.
Mosaic's guide cameras are intensified fiber-optically coupled CCD cameras
(ICCD's), and can be damaged if exposed to bright light, so it is important
to protect these cameras from bright stars. The camera controls (shown below)
reside on the shelf above the TCS computer, Olive, and are labeled "North"
and "South". The video switcher above the controls allows you to switch between
cameras. The buttons needed to select the North and South cameras are labeled.
Video signal is routed from the cameras, through the controls and
to the guider computer, Moss. Select the desired camera
from the video switcher and adjust the camera from the ICCD Control Panel:
- Turn the high-voltage potentiometer completely counterclockwise (10
- Toggle the power switch on (on Moss's monitor, pixel defects will appear).
- Nuetral density switch should be up (on)
- Push the momentary button to enable high voltage (red button).
- Slowly turn the high voltage potentiometer clockwise to see if there
are any bright stars in the field. If you don't see any stars, turn the potentiameter
counter-clockwise, toggle the neutral density switch off (down) and slowly
turn the high voltage potentiometer clockwise again, monitoring the video
monitor until guider stars appear.
When switching between the two TVs, be sure to turn the high voltage potentiometer
fully counterclockwise and turn off high voltage on the TV no longer in use.
The computer Moss is the guider control computer. Moss is a dual-boot
machine with Windows2000 and Lunix RedHat. When the S2KB camera is in use Moss
is booted into Windows and the MaximDL software is used to control the guider.
When Mosaic is in use Moss is booted into Linux.
By default Moss should boot into Linux. However, if it stops booting and
you see lilo: in the upper left hand corner of the screen, type linux. This
will boot Moss into Linux and you will eventually get the login prompt.
The login and password are on the white board, but you do not need to login to Moss in order for the software to work.
At this point you'll need to restart
the guider software from Emerald. Select "Restart Guider" from the Mosaic Menu.
This should bring up an xterm window. Eventually this should bring up the
video screen on Moss and then the Guider GUI on Emerald. You may see the
message "waiting...." repeated many times in this xterm window on Emerald.
If so, be patient as it may take a minute or so for the video screen to appear.
The Guider Gui on Emerald should appear immediately after the video screen
on Moss appears. If not then select
"Restart Guider GUI" from the Mosaic Menu. This should bring
up the Guider GUI.
When the guider is running, Moss will
show a video picture with two white boxes. The smaller box is the cursor,
and the larger box is the guide box. There will also be one or more status
lines at the top of the screen containing useful information.
The guider video screen on Moss.
The Guider GUI on Emerald.
For more on the Guider Control GUI, see the section "More on the Linux
Guider" in the appendix.
You will need to make sure the video screen is running on Moss and the
Guider Gui is running on Emerald. If not, follow the instructions above under
"Guider Software" to start them.
Video signal is routed through the ICCD controller (the gray box above
Olive). Make sure the gain on the controller is turned all the way down.
Turn on the controller power (left-most toggle switch). Push the red INTEN
button on. Make sure the ND filter is on (middle toggle switch). Slowly
turn up the gain to ensure there are no bright stars in the field. If you
see no stars, turn the gain back down (counter- clockwise), remove the ND
filter (toggle switch down) and slowly turn the gain up again, watching for
guide stars on the video screen.
There are 2 fixed cameras to choose from - North and South. You can switch
between them with the Monitor Input Selector that's just above the ICCD controller.
There are 2 ways to select guide stars.
- On the Guider GUI on Emerald, under Guider select "Warp to Star". This
should move the large box to the brightest star in the field.
- You can also move the cursor on Moss over a star and then left-click
to move the guide box over the star.
Now select Guider => Guider On from the Guider GUI on Emerald.
You're not guiding yet. You must also turn on the guider on the TCS. On Olive, under the
Instrument dropdown, there is an option for Autoguider. This brings up the guider GUI seen
to the right.
In the Control Status box on this GUI you'll see OFF, ON, N, S. Disregard
the N, S buttons as these are only used with S2KB and not with Mosaic. Click
the On button. Near the bottom of the TCS autoguider GUI you should see numbers
changing in the boxes below "Corrections". If you do not see these numbers
changing, you are not guiding. See the troubleshooting section
You will need to turn guiding off in both places (on Olive and Emerald)
before moving the telescope. On Olive, click the radio button beside "Off".
On Emerald, select Guider => Guider Off from the Guider GUI. Order counts,
be sure to turn the guider off via Olive first.
The orientation on the guider video window: North is down and East is
to the left.
Hints and Troubleshooting
- If the star drifts from the box change the leak average to 3.
- If the background is high and/or the guide star is faint, consider removing
- If the box doesn't move on "Warp to Star", a) try it again, b) check
it's not too near the edge. If the brightest star is too close to the edge,
you need to select a different star by (left button) double-clicking on another
- The "Leaky AV" option averages incoming video frames before analysis.
New frames 'leak' in at the same rate as old frames 'leak' out. Use this option
to reduce the noise and guide on fainter stars. Note that this does not enable
you to see below the camera's abilities and may be of no use with bright
backgrounds, such as on moonlit nights.
- If the Guider GUI never appears on Emerald, select "Restart Guider
GUI" from the background menu on Emerald. You may need to wait a minute or
so as the "waiting..." message appears. If the Guider GUI does not appear
immediately following the close of this window, bring up an xterm window
on Emerald and type "xhost moss" (no quotes) and try again.
- If the video screen on Moss freezes:
- Turn off the guider on the TCS (on Olive) and on the Guider GUI on Emerald.
- From the background menu on Emerald select "Restart Guider". Eventually
this should refresh the video screen on Moss and restart the Guider GUI.
Note you may need to wait a minute or so as the "waiting..." message appears
- If the Guider GUI refreshes but the video screen on Moss never
refreshes and is still frozen you will need to do a hard reboot of Moss.
Go into the computer room and locate the CPU for Moss (at the bottom of the
second rack as you enter the computer room - it has a blue plate on the front).
Pull down the blue face plate for Moss. Hit the red
Reset button and wait for the computer to reboot. Moss is a dual-boot machine
and should automatically boot into Linux (you may need to type 'linux' at
the 'lilo:' prompt). Login and password are on the white board. After logging
in you will need to restart the guider software to get the video screen to
appear. On Emerald, select "Restart Guider" from the background menu. This
should initiate the guider video screen and refresh the Guider GUI.
GUIDING WITH S2KB - the MaximDL software
The computer Moss is the guider control computer. Moss is a dual-boot
machine with Windows2000 and Linux RedHat. When the S2KB camera is in use Moss
is booted into Windows and the MaximDL software is used to control the guider.
Linux is used with Mosaic. Linux is the default boot. After a hard reboot of Moss, in order to use the MaximDL software for guiding with S2KB, you must type windows2000 at the lilo prompt.
Both North and South guide cameras are fully functional,
increasing the likelihood of finding suitable guide stars. See the section
below on switching between cameras.
Field of view = 3.3 arcmin x 2.2 arcmin
- The North guide camera is 0 arcsec West and 2610 arcsec North of the
main CCD field.
- The South guide camera is 25 arcsec West and 2410 arcsec South of the
main CCD field.
To launch the MaximDL software click on the icon on the desktop.
When the program is launched you will get a window like this.
After launching the program select View => CCD Control Window.
| Click on the Setup tab in the CCD control window.
Make sure the box below Main Camera reads "SBIG Universal" and the
box below Autoguider reads "Same as main camera". You can change what's displayed
in these areas by clicking the Setup buttons beside each area.
On the same Setup menu now select Connect and wait for the mouse
to return to an arrow. Then select Cooler On.
Select the Guide tab again. Choose an integration time of 3 sec or more, and select the Expose radio button. Click Start to start exposing.
A star field should soon appear. The program will pick a suitable guide
star and place its coordinates into the Guide Star X and Y boxes. You can
select a star manually by entering different coordinates into these boxes,
or by clicking on the star of your choice.
If you get a message that there are no guide stars available, you will
need to try taking a longer exposure or shifting the field slightly. You
can change the length of the exposure by using the up and down arrows below
Exposure on the Guide Menu. Recommended exposure times are between 3 and
5 seconds. To shift the field you will need to jog the telescope slightly
via the ACE SoftPad on the TCS.
After the guide star has been chosen, you must set the exposure time to at least 3 sec before you start guiding. Click on Track and then click Start.
You are not guiding yet. You need to then turn guiding on via the TCS Autoguider GUI.
Bring up the Autoguider GUI from the main toolbar: Select Instruments
=> Autoguider. Select the N or S for the guide camera you are using. Click On. When the guider is on you should see numbers
changing in the boxes below Corrections. Make sure these numbers are changing
and that your star is not wandering before starting your exposure.
The guide camera focus is controlled via the TCS Autoguider GUI displayed
above. The focus range is between 0 and 30000, with typical focus values
around 0 for the North camera and 20000 for the South camera, but be aware that these values can change. The current focus is indicated in the yellow box beside
Encoder. To change the focus, enter a desired focus value into the box beneath
the current focus setting and click on GO TO.
The easiest way to focus the guider is to turn guiding on with the MaximDL software (but not the TCS) and change the focus values in the Autoguider GUI until you reach a desired focus.
Note: You will need to change the guider focus when changing filters.
| You can also setup the MaximDL software to take continuous exposures
of a single star while you change the guider focus on the TCS.
- Stop guiding.
- Click on the Focus tab
- Make sure there is no check mark to the left of Continuous. If
there is, click on that box to deselect it.
- Click the Reset button.
- Click Start Focus. This will take a single exposure of the entire
- When the image has fully downloaded you will need to select one
of the stars to focus. Drag a box around a star. You should see the numbers
in the boxes within the Subframe area changing to the coordinates of the
- Now click on the box beside Continuous to select it. This lets
you take continuous exposures of the guide field.
- You may want to change the exposure time or the time delay between
exposures. To adjust these use the arrow keys beneath Seconds and Delay (s).
- Click Start Focus and change the focus when the status bar reads
"Downloading image" until you get a reasonable looking focus.
| You can do a rough analysis of your guide star a few different ways:
Once you've found a good focus value, click Stop on the Focus Menu and start
- Click on the Inspect tab of the CCD control window to give a surface
plot of the star as well as FWHM and Half Flux diameter.
- From the main toolbar in MaximDL select View => Information
Switching guide cameras
When changing between guide cameras you need to disconnect the communications to the camera currently in use and reconnect to the other.
- Click on the Setup tab in the CCD Control Window
- Click on Cooler Off
- Click on Disconnect
- In the same window (Setup tab) click the Setup button just below "Main CCD Camera". This brings up the "Setup SBIG Universal" window below.
- You have several choices of cameras. The two that are used for guiding are the two on the bottom of the list, ST-402 and ST-402 (yes they both have the same name). Which camera is the north one and which is the south one is listed on the whiteboard. Choose your desired camera and click the ok button.
- Under the Settings tab there is a choice on the right for Options. Click on the arrow.
- In the menu you should see, among other options, one for FLIP HORIZONTAL and one for FLIP VERTICAL. The north camera is always flip horizontal and the south camera is always flip vertical. Select the proper flip for the camera you have selected. MAKE SURE YOU ONLY HAVE ONE OPTION SELECTED AT A TIME. THEY DO NOT UNCHECK THEMSELVES. YOU MUST DO IT YOURSELF.
- Back in the Setup tab window, click on Connect
- Click on Cooler On
- You will also need to change cameras on the TCS Guider GUI (select
N or S)
GUIDESTAR SEARCH WITH S2KB
This feature is currently unavailable, but will return in the near future.
THE AUTOMATED CCD LOG
The autolog runs on Emerald, and pulls information from your image headers
to create the log. In order for autolog to run, you must have the TCS/Instrument communications up and running.
To start the S2KB autolog program, on Emerald:
- Select S2KB Autolog on the desktop.
- In the "image directory" box, you will need to type in the full
path to your working directory of your Data Acquisition window (e.g. /data1/36inch/night1).
- Select which instrument you are using.
- Click on Start Logging. Images will only be written to the log
after selecting Start Logging.
The images (.fits) are written to the log after the exposure
has readout. An example log is show below. Every time a page is completed,
the log page is written to a postscript file and saved. At the end of the night you will need to quit the autolog program to get your last (unfinished) page to write to a file. These files are stored
in the same directory as your images and are called autolog_page1.ps, etc.
Each page is then printed when it is full. One nice feature of this log is
that you can type virtually anywhere within the log - you can edit any field
or add comments wherever you like.
Note: Image root names that contain a period will not show up
correctly in the log (e.g. n001.0002.fits). To avoid this, make sure your
image root names do not contain periods.
To start the Mosaic autolog on Emerald:
- Select Autolog on the Mosaic Menu GUI
- Follow the same instructions for S2KB set up
For printable paper sheets go here.
S2KB CCD INFORMATION
CCD NAME : S2KB
CCD SN : 1383BR03-01
PIXEL SIZE : 21x21 microns
PIXEL SCALE : 0.60 arcsec/pixel
CHIP SIZE : 2048 x 2048
DIGITAL LIMITATION : 65,534
BIAS LEVEL : ~750 (gain=#3)
MICROCODE : "Harcon1009"
PREFLASH, e- : none
NOISE, e-/RMS :? ? 20 14-15 9-10
GAIN, e-/ADU : 9.8 6.5 3.9 2.5 1.3
GAIN, DETPARS#: 1 2 3 4 5
COLUMN SPILLOVER, e- : ~240,000
INTERNAL RADIATION EVENT RATE, EVENTS/HR : ~2700
CONTROL TEMP. deg C (thermocouple) : ~-107
COMPUTER TEMP. deg C (ccdinfo) : ~-109
DARK CURRENT, e-/hr/pix : ~5-10
DEAD COLUMNS : HOT COLUMNS : [1571:1571,1134:2048] bias
LOW COLUMNS : [1103:1103,744:2048] flat field
efficiency of S2KB is given in this figure. The abscissa is wavelength
in nanometers and the ordinate is dQE (%).
Here are examples
of the original calibration frames for S2KB. Click on the link to display
the (BIG) image.
S2KB has developed an enhanced bias level in one corner amounting to a
peak of ~1500 ADU above an overall level of ~965 ADU. Here is a bias exposure
which shows this effect. The enhancement is limited to the region X <
~240 pix and Y> ~1800 pix.
You can estimate
exposure times for S2KB using the CCDTIME package in IRAF v2.11.3 which
should still have the necessary information in its ccdtime$kpno.dat database
file. If it does not, here is the kpno.dat file.
WIYN 0.9m / S2KB Frequently Asked Questions
- Q. What do I need to know about taking bias frames?
A. While the overscan (or DC offset) region records
the absolute value of the bias level as each observation is taken, zero exposure
images (i.e. bias frames) are used to correct for two-dimensional structure
in the bias level. These are typically taken in the afternoon before the
dome flats. Be sure the inside of the dome is dark. You will probably want
to obtain 9 bias frames, which will later be combined with the zerocombine
task in IRAF. It is advisable to intersperse a few bias frames throughout
the night as you obtain your program observations in order to track any temporal
variations in the bias structure.
- Q. What do I need to know about taking dome flats?
A. Dome flats are used to correct for pixel-to-pixel
sensitivity variations in the CCD. They are usually taken in the late afternoon
1 to 2 hours before you open the dome slit to begin your evening of observing.
If it is not possible to obtain the dome flats in the late afternoon, they
can also be procured in the morning after your night of observing is done.
Making sure the lights in the dome are off, position the dome at an azimuth
of 73 +/- 1 degrees and point the telescope at HA = +3:28 and Dec = +13d (this
is usually done using the 'flat-field park position' selection in the TCS
GUI). Go to the computer room and turn on the flat-field illumination lamps
(high intensity for the U filter or narrow band filters, low intensity for
BVRI and other broad band filters); then, ramp up the rheostats to achieve
the proper level of intensity (usually 100%). You will need to expose the
CCD to achieve a mean level equal to about half the saturation of the A-D
converter - ~30,000 ADU - making sure that the CCD itself has not become
nonlinear, which occurs at ~210,000 electrons (the limit of the A-D converter
for a gain of 3e/ADU). Recommended exposure times for the UBVRI filters are
given in the manual. You will probably want to obtain ~5 dome flats in each
filter, which will later be combined with the flatcombine task in IRAF.
- Q. How many dark current exposures should I take?
A. The dark current on the S2KB CCD is low (5-10
e/hour/pixel), which means that there is no need to obtain dark current exposures.
- Q. What's that bright corner on the CCD?
A. It is unfortunate but true that the upper left
corner of the CCD is plagued by higher than average background counts - even
in a bias frame. This results from a faulty LED that is illuminating one
corner of the chip. The good news is that the standard technique of bias
(image) subtraction does an excellent job of removing this gradient - to
better than 1%.
- Q. What are the most useful IRAF commands to know for observing?
- ccdinfo - outputs basic information about the CCD including the available
- detpars - set the gain value, region of the chip to readout, etc.
- display - displays an image in the ximtool window
- flpr - stands for 'flush process.' It is recommended that flpr
be issued anytime cntr-c is used to interrupt a process.
- imexamine - allows the user to use certain keystrokes to operate
on the currently displayed image in the ximtool window. Useful keystrokes
include r (plots a radial profile and outputs profile diagnostics), a (only
gives the profile diagnostics), a (plots a contour plot), and s (plots a
- imhistogram - plots a histogram of the pixel intensity values.
Note that the ordinate is a logarithmic scale. This is useful for checking
the distribution of pixel values looking for a stuck bit, which would manifest
itself as a sequence of intensities with no pixels.
- implot - plots pixel intensities along rows and columns.
- observe - the primary observing command, which initiates and otherwise
controls CCD exposures.
- obspars - set the run information, nightly file prefix, update
the current image index number, etc.
- rfits - read a fits file or convert a FITS image to an imh/pixel
- test - takes one exposure and saves it to test.imh without incrementing
the image index.
- unlearn - resets IRAF parameter sets to their default values.
Use this with caution because it may restore parameters to undesirable values.
- wfits - write a FITS file or convert an imh/pixel image to a FITS
- Q. Do I need twilight sky flats?
A. Twilight sky flats are taken just after sunset
before the sky is completely dark. The idea in taking these is to correct
for any illumination differences between the dome flat white spot and the
actual sky. Since time is limited, one usually tries to acquire at least
3 twilight sky flats in each filter to be used for the program. You should
aim to expose each flat to a mean level equal to about half the saturation
of the A-D converter - ~30,000 ADU - making sure that the CCD itself has
not become nonlinear. If enough twilight sky flats are obtained in each filter
(i.e. > 4) on each night with the appropriate mean intensity levels and
no stars, then they can be used to flatten the program images in place of
the dome flats. However, if less than ~3 twilight sky flats have been obtained
on a given night, it is better to use them as an illumination correction
(if one is needed) after the dome flats have been applied to correct for
pixel-to-pixel sensitivity variations.
- Q. Do I need dark sky flats?
A. Generally speaking, the answer to this question
is 'no.' However, if you feel particularly uncertain about the quality of
the dome and twilight flats you have obtained, you are encouraged to also
take dark sky flats. The direct imaging manual lists the locations of 'blank'
sky fields on page 16 to be used for this purpose.
- Q. Is there a significant shutter correction?
A. The S2KB shutter moves linearly across the field
of view. As a result, any shutter correction will be an additive offset that
is applied to the requested exposure time. On two separate occasions, this
correction was measured to be +0.016 +/- 0.002 sec. Thus, a requested exposure
time of 1 second will actually be 1.016 seconds. This means that requested
exposure times of 2 seconds and longer will incur errors of less than 1%.
- Q. What gain setting should I use?
A. The CCD has a full well capacity of ~210,000 electrons
which means that at a gain of 2.5 e/ADU (index = 4), the A to D converter uses
the full dynamic range of the CCD up to 65,536 DN. Gain values as high as
9.8 e/ADU are available. The read-out noise of S2KB varies with gain value. Please see S2KB info above for read noise values with each gain setting.
- Q. What trim section should I use?
A. The recommended trim ([1:2048,1:2048]) and overscan
sections ([2049:2080,1:2048]) are given in the image headers. Feel free to
check these by plotting intensity vs column number to be sure that the trim
and overscan regions are appropriate.
- Q. When should I call the Site Manager?
A. The problem you have encountered is not covered
in the manual, the troubleshooting guide,
or this FAQ. Telephone numbers are on the whiteboard.
Last updated September 5, 2008