Large Format Camera (LFC) Cookbook

View the original cookbook.

The Large Format Camera (LFC) is a mosaic of 6 ccds located at the prime focus of the Palomar 200-inch Telescope. The ccds are SITe SI-002 chips with 15 micron diameter pixels. Each chip is 2048 pixels across by 4096 pixels tall.

At the prime focus (f/3.33), the pixels correspond to ~ 0.18″/pixel (0.175″/pixel at the field center; 0.185″/pixel at the field edge). The total field of view is 24′ x 24′. The field is unvignetted from the center of the mosaic out to a 22′ diameter circle. Beyond that a circular vignetting pattern increases uniformally (due to the Wynne Corrector) to a maximum of 10% at the outer edge (25.3′ diameter circle). There are 15 arcsecond gaps between each of the 6 chips.


1. Pre-Arrival

If you choose to write all 6 CCDs to disk for each exposure, then you will typically end up with about 6-8 Gb of data per night in the summer and perhaps as much as 10-12 Gb in the winter, maybe even more if you're doing something truly exotic. As of May 2006, Palomar provides a fast DVD burner in each of two dual-processor PCs that are cross mounted to the LFC control computer oasis. Support staff will show you how these work. You will need to bring blank DVD-R disks, Palomar does not supply blank disks or tapes.

You can transfer data off the mountain using secure FTP if you prefer, but please note that internet connectivity to our remote mountain site is not always as stable as we would like it to be. Plan accordingly. Palomar continues to support an exabyte tape drive mounted to oasis, and we would enjoy experimenting to see if it still works.

Note that when your last night is over, we like to have the data room and instrument ready for the next observer by noon the following day. Please try to get your data backed up before this time. If this is not possible, please let somebody know and we will do our best to accomodate you. Also please note that we do not archive data at Palomar. At best, we delete "old" data first when making room for our new observers. We strongly urge you to backup your data promptly, and let us know if you have any troubles or any special needs.

2. Workstation Setup

The Palomar daycrew will set up a workstation in the data room to run LFC. Currently that workstation is planetx. If you want or need to set up this workstation yourself, follow these directions:

Log into the Palomar workstation planetx as user, the password is provided.

  1. Click on the start_lfcguide icon or type start_lfcguide in a terminal window. This brings up a VNC client window connection to oasis. After a few seconds, an outline of the LFC guider program window will appear. Click somewhere in the VNC window to anchor the guider. Even if you are not going to use the guider, it needs to be running in order to establish TCS connection.
  2. Click on the monitor_lfcguide icon or type monitor_lfcguide in a terminal window. This program is a temporary solution to a VNC bug that causes the VNC client to disappear. As long as the monitor program is running, you don't have to worry about anything. That's right, nothing at all.
  3. Open a terminal window and type ssh lfc@oasis, the password is provided (oasis is the computer that runs LFC; it is located in the computer room downstairs).

You are ready to start the LFC program. Make sure you are in one the of 4 proper data disks:

/scr1/lfc/ /scr3/lfc/ /data1/ /data2/
Do NOT use /scr6/ (reserved for the home directory and system files)

Do a df -k to determine which of the disks are free for use. Note that you have write permission in any of the /scr#/lfc directories, but you do NOT have write permission one level higher in any of the /scr# directories. Delete old data if necessary, and then create a new subdirectory for your data.

3. Start-Up Sequence

Now enter the following commands in this order to start the LFC program (the order is crucial):

  1. oasis% mcdcom  —  This starts the LFC program. Once started, mcdcom will start writing data into the current directory. Mcdcom recognizes the Unix commands ls and cd, and will write to any new directory that you point to. You can issue any other Unix command with the standard ! escape.
  2. ccd.001> mosaic <mode>  —  This downloads the appropriate code to the DSP controller and configures mcdcom. The mode sets the clocking parameters. Currently, there are 5 modes:
    • mosaic lfc2  —  This will setup Mcdcom to readout the entire mosaic, binned 1 × 1.
    • mosaic lfc2bin  —  This will setup Mcdcom to readout the entire mosaic, binned 2 × 2.
    • mosaic lfcfour  —  This will setup Mcdcom to readout the central four chips, binned 1 × 1.
    • mosaic lfczero  —  This will setup Mcdcom to readout only chip 0, binned 1 × 1.
    • mosaic lfczerobin  —  This will setup Mcdcom to readout only chip 0, binned 2 × 2.
    • mosaic lfcfind  —  This will setup Mcdcom to readout only chip 0, binned 2 × 2; useful for a quick find exposure.
    • The Binning Value and Raster Value parameters can be changed should the above options not meet your needs (the chip numbers readout cannot be changed). Seek assistance if you want to do this. For more information, see the mosaic command.

  3. ccd.001> shutter startup  —  This initializes the shutter.
  4. ccd.001> shutter home  —  This sends the shutter to the home position.
  5. ccd.001> filter home  —  This homes the filter wheel; make sure estoff = 0!
  6. ccd.001> utility stat  —  This displays and tests the current status of the utility board.
  7. If shutter, filter, or utility commands report an error, quit mcdcom and retry this sequence. If you get the error again, try a cold boot or seek help.

  8. ccd.001> fp <prefix>  —  This sets the file prefix value. The default is ccd. (note that you need to specify the dot (".") if you want one to separate the prefix and the frame number).
  9. Example fp lfc.

  10. lfc.001> fn <#>  —  This sets the frame number. The default is 1.
  11. lfc.001> fs <#>  —  This sets the frame suffix. The iraf command now appends .fits when it is toggled ON, and it removes the .fits when it is toggled OFF.
  12. Example fn 101

    Example fs .fits

  13. lfc.101.fits>  —  You should now be ready to take data. Note that charge accumulates on the chips during the startup procedure. The only way to fully remove this charge is to readout the chips with either rm or a 0 second bias exposure. Exposures are written in the format prefix###.chip, so the first exposure from this example would produce six 17 Megabyte FITS files:
  14. lfc.101.0 lfc.101.1 lfc.101.2 lfc.101.3 lfc.101.4 lfc.101.5
  15. lfc.102>  —  You should now be more than ready to fill up some disks. Note that your prompt has changed to the next exposure's filename.

4. Logsheets

View logsheet.

Logsheets can be printed from planetx using:

planetx:/home/user> lpr logsheet5.ps  —  Prints 5 logsheets

As of May 2006, there is an icon on planetx's right hand monitor called Print 5 LFC Logsheets. I'm not sure why, but some people like to delete icons.

5. Camera Characteristics

5.a. CCDs

The ccds collect light at slightly different rates (gain). We've plotted the linearity curves together to create a tool to help you guage this rate difference. This can be useful if you want to keep the raw, unbiased chip4 below 21000 DN while displaying other chips.

Unbinned raw signal rates (jpg, postscript)

Binned (2×2) raw signal rates (jpg, postscript)

There are five LFC mosaic configurations (modes) that you can use. The lfc2 mode, using all 6 chips, is the default mode setup by the daycrew before you arrive. If you want to change this mode or build a custom mode, see the Mosaic section of the Commands manual.

The binned modes (2×2; ~ 0.36″/pixel) have been tested on sky, and they appear to work very well. In fact, the wavy patterns in the bias frames disappear in binned mode. The readout is faster (56 seconds instead of 115 seconds) and the image file sizes are smaller (4.3 Mb instead of 17 Mb). The seeing at Palomar is typically ~ 1.0″ to 1.5″ FWHM, sometimes as good as 0.8″ to 0.9″. In the binned mode, this would correspond to ~ 2 pixels per seeing disk in the very best conditions and ~ 3 – 4 pixels per seeing disk in the average Palomar conditions.

Orientation
North-South

N-S orientation.

East-West

E-W orientation.

Note: When the LFC is installed in the East-West orientation, the Position Angle of the guider must be manually addressed:

  • At the top of the guider GUI, click the Menu button.
  • Click Black Belt Status. A pop-up window appears (you must anchor it in the VNC window). In the Position Angle field, enter -90.
  • Click the Set button, then click the Dismiss button.

5.b. Dewar

The LFC dewar is large enough to hold LN2 for over 24 hours. The daycrew typically fills the dewar once during the day.

Dry nitrogen is continuously blown across the LFC dewar window at 5 PSI. If the weather is very humid you may want to ask the daycrew for more (~10 PSI). If condensation starts to form on the entrance window, you will see dark blobs grow near the center of the LFC field (upper left of chip 0, upper right of chip2...).

5.c. Filters

LFC Filter Specs
Custom LFC Filters

5.d. Shutter

The shutter is comprised of two large rectangular blades. While one moves away from the field to start an exposure, the other moves over the field in the same direction to end an exposure, thus providing uniform illumination. The shutter will NOT go faster than 0.6 seconds. You will receive all sorts of trouble if you try to go faster than 0.6 seconds. The shutter is very stable at and above 0.6 seconds. The linearity curves show that the chips are very linear all the way down to 0.6 seconds.

There is no light leak around the shutter, you can take bias frames during the day if you want.

6. Calibration Images

6.a. Bias Frames

Bias.



Flat.



Ghost.

When you are ready to take your first exposure, take a bias frame to clear all of the charge off of the chips. Charge will accumulate on the mosaic during the start-up procedure. The clear command will not remove this charge, no matter how many times you try to use it (caveat: I haven't tried more than 100 clear commands in a row. Feel free....).

lfc.102> bias 0 bias  —  This tells Mcdcom to prepare to take a bias exposure for 0 seconds and name it bias.

lfc.102> go  —  This starts the exposure.

This first exposure will likely show residual charge on the chips, you can throw them away if you want. The next exposures will be fine. To take 5 bias frames in a row, type:

lfc.103> go 5

Your bias frame should look like the one on the right.

6.b. Dark Frames

As with most modern CCDs, there is no appreciable dark current in these chips. You can prove this for yourself with:

lfc.103> dark 600 dark  —  This tells Mcdcom to prepare to take a dark exposure for 600 seconds and name it dark.

lfc.103> go  —  This starts the exposure.

You'll find some hot pixels, some hot columns, and nothing to be alarmed about.

6.c. Dome Flats

Once the dome is dark (~ 4:00 pm), have someone open the mirror cover and make sure all of the dome lights are off. All domeflats are done with the telescope pointed up at the white part of the dome slits (no need to move the telescope). If you want to take u' domeflats, you will need to use the highlamp.

See the Filters section for exposure times.

lfc.108> tel lowlamp  —  Turn on the lowlamp

lfc.108> flat 5 domeflat-z  —  This tells Mcdcom to prepare to take a flat exposure for 5 seconds and name it domeflat-z.

lfc.108> go  —  This starts the exposure.

To take 4 domeflats in a row, type:

lfc.109> go 4

Your domeflat should look like the on on the right.

6.d. Sky Flats

Since the LFC has a light tight shutter (unlike COSMIC), you can take good skyflats. Note the LFC command istat gives you a quick one-line text output of the mean value of chip 0. This can be useful to check your sky level without having to take the time to display an image.

6.e. Defects / Features

The left sides of the ccds (column 1 to about column 75) are ~ 30 to 100 counts "hotter" than the rest of the chip. This is in the bias, and subtracts out nicely.

The field of view is unvignetted from the center of the mosaic to a circle about 22′ out from the center. From this circle and continuing out to the field edge (22′ to ~ 25′) the field is up to 10% vignetted by the Wynne corrector lens. You will see the vignetting pattern at the outer edge of each chip, especially chips 4 and 5.

Look out for condensation "blobs" that might appear near the center of the mosaic field when the humidity gets very high.

If this happens to you, have somebody check that the dry nitrogen is flowing over the dewar window. If it is, the dry nitrogen flow should be turned up.

Each chip has a few bad columns and a few small dead spots. Chip 4 has two bad columns down the center of the chip. Chip3 has small, in-focus "marks" (dare I say, "spooges") all over the ccd (need light to see them and you have to look close). These are defects on the surface of the ccd, and they will flatten out.

The 6 ccds are wired together in pairs to one of three controller boards. As a result, if something saturates (star, background) on one chip you will see a "ghost" of the saturation on the chip that shares the board. The ghost is usually tens of counts, which you can remove later through filter processing. In the image on the right, the core of a bright star saturated on chip 0 during a long exposure, which led to "bloom" trails. The pixels that actually saturated show up in the same location on chip 1, seen here.

7. Displaying Your Images

You can use Ximtool as a stand-alone to display your images. If you want to use iraf you need to append a .fits to each image filename to keep iraf happy. And note that the images that LFC writes are unsigned integers; iraf wants to display signed integers by default.

You can use the IRAF toggle to scale the output image data to iraf friendly signed integer values. Here's the original ccdcom explanation (this was verified to work on LFC images in February 2005):

lfc.113> iraf

IRAF (among others) is finicky about dealing with 16-bit FITS
images, but the dynamic range and A/D converters for our CCDs are such
that we want to save all 16 bits.  The "iraf" option causes 
ccdcom to scale all FITS images to pack 16-bits of unsigned data
(so-called "ushort") into standard FITS signed 16-bit integers
("short" or BITPIX=16 FITS format). 

Specifically, this the FITS header parameter BZERO is set to 32768, and
the image is written as a FITS-standard 16-bit integer data file.  IRAF
et al. use the value of BZERO in the FITS header to restore the pixel
values to those provided by the camera.

By contrast, the old "not IRAF" format images stored pixel data as
unsigned 16-bit integers, resulting in a non-standard FITS format image
(a "ushort" image in IRAF parlance) that most FITS readers cannot read
without special handling.

To start an iraf session from planetx, click on the icon called LFC iraf or type start_LFC_iraf in a terminal window. The path out of planetx to oasis is /lfc.

8. Pointing

You should check the pointing at the start of your first night, especially if a previous observer used a different instrument. Have the telescope operator point to a 5th or 6th magnitude star and take a 1 second exposure:

lfc.113> obj 1 point  —  This tells Mcdcom to prepare to take an exposure for 1 second and name it point.

lfc.113> go  —  This starts the exposure.

The star should be somewhere near the center of the field, so display chip 0 first and look at the top left of the chip. A 5th magnitude star is bright enough that you should see the reflection somewhere on chip 0, if it isn't totally there already. If the pointing is good, the star might be behind the 15 arcsecond gaps at the center. Change the low-high display values to see the core of the star, and then move the telescope as appropriate to set the pointing wherever you want. You may need to display another chip in order to see the star.

Take another exposure to verify that you put the star in the right spot. When you are happy, have the night assistant "X" the pointing, which sets the telescope's pointing model to its current position. The pointing should now be good for the rest of your run.

9. Focus

During the winter season, you will likely find focus values from 31.00 to 34.00 millimeters. In summer, you may find focus values from 28.00 to 31.00 millimeters. The Sloan r', i', and z' filters are parfocal. The Sloan g' and u' filters are 1.5 to 1.7 millimeters higher.

Note that due to the curvature of the field at the 6 ccds in the focal plane, the best place to inspect focus stars is about 1/3 out from the center of the mosaic. This will provide the best focus distribution over the entire field. Note the following LFC array focus maps:

LFC array focus maps.

Run the focus_fine and focus_coarse scripts to focus the telescope. View this help file for instructions on how to use the focus scripts.

10. Image / Seeing Analysis

You can measure the seeing and do some simple statistics with the iraf command imexamine. Put the cursor over a star and hit the r key. A radial plot should appear with three numbers in the lower right corner of the window. The middle number is a good approximation of the profile fit in pixels. In unbinned mode, a pixel is 0.18″. In binned mode, a pixel is 0.36″.

The primary mirror is astigmatic. Use this to your advantage. With the cursor over a star, hit the e key and look at the contour plot. When the telescope focus is a little too low, you will see that stars are elongated either left to right, or up and down. When the telescope focus is a little too high, the axis flips. When the telescope focus is just right, the star will be round. As you inspect stars in your science field later in the night, you can use this information to bump focus a little as stars start to elongate one way or the other.

If the seeing is bad, say greater than 2.0″, all bets are off; everything is round.

11. Science Exposures

Here are some examples of what you might do when taking normal exposures:

lfc.115> object 300 target1_zprime  —  This sets up mcdcom to take a 300 second exposure and name the FITS header target1_zprime.

lfc.115> go  —  This starts the exposure.

lfc.116> telescope offset 15 15  —  This moves (dithers) the telescope 15″ EAST and 15″ NORTH.

lfc.116> et 500  —  This increases the exposure time to 500 seconds while keeping you in object mode and leaving the name as target1_zprime.

lfc.116> go

lfc.117> telescope goffset -15 -30  —  This moves the telescope AND the guider box (guided offset, note the g) 15″ WEST and 30″ SOUTH.

lfc.117> telescope focbump 1.5  —  This increases the telescope focus by 1.5 millimeters.

lfc.117> filter move 1  —  This moves the filter wheel to position number 1.

lfc.117> object 600 target1_gprime  —  This sets the exposure time to 600 seconds and names it target1_gprime.

lfc.117> go

To see the full list of mcdcom commands, see the LFC Commands page.

12. Guiding

Guider GUI.

Most of the guider information can be learned from the guider's HELP window invoked by the Help menu option on the GUI (view this help file).

To start the guider, click the icon labeled start_lfcguide located on the planetx desktop.

The LFC guider is a SITe 512 x 512 ccd with 0.54″ pixels, corresponding to a field size of 138″ x 138″. This ccd is located in the southeast corner of the mosaic next to LFC chips 3 and 5 at the outer edge of the field. Since it is in the cooled focal plane (which means that it is behind your filter AND the shutter), the guider is very sensitive to faint stars. Two important points:

  1. When you are in good focus, the guider should be in focus too (although the image quality is not as nice at the outer edge of the LFC field).
  2. The shutter needs to be OPEN in order for the guider ccd to see anything.
  3. A typical exposure and guiding sequence:

    • Start your science exposure.
    • Make sure the Exposure slider is set to a reasonable value, like 10 seconds. This slider controls the integration time that the guider ccd uses before displaying the first image (when set to 0.0 seconds, the guider reads out as fast as it can which is 0.7 seconds).
    • Once the guider displays its first image, look for a guide star. Change the display gray scale if necessary by holding the right button down and moving the mouse around in the guide display field. If you don't see anything, increase the guider exposure time.
    • Grab and move both the sky box and the signal box over a star (don't need to be centered).
    • Press Start. If the guide box detects the star it will turn yellow which means the next frame will start guiding. A green box means it is guiding happily.
    • The good news is the telescope tracks like a champ for up to 300 seconds. If you're not happy with this method, you can use the find command to open the shutter and send the guider images to the GUI. This way you can locate a guide star, quit the find routine with ^C, and then start your exposure. Note that find opens the shutter exposing the science chips to the sky too. Nobody ever uses this method. But feel free...

The guider crashes and dumps core every once in a while. This may be a feature to keep you awake. Also note that the guider isn't happy when you move the guide box too near to the edge of the field (either manually or with a guided offset). Crazy things will start to happen in this case, so quit the guider and simply restart it.

The strip charts are nice tools to help you gauge seeing and sky transparency.

The display scales automatically by default. If you don't like this, uncheck the Auto Scale button. The background level is determined from the sky box, so if a bright star is in the field, you may not like the autoscale.

13. Dithering / Telescope Commands

The guider provides communication between the LFC and the telescope. The guider must be running for the following telescope commands to work:

lfc.118> telescope focbump <dfocus>  —  Move the current telescope focus by the amount dfocus in millimeters. Positive value moves focus out, negative value moves focus in.

lfc.118> telescope focgo <focusmm>  —  Move the current telescope focus to the absolute position focusmm in millimeters.

lfc.118> telescope goffset <dra" ddec">  —  Move (dither) the telescope AND the guider box in arcseconds for both right ascension and declination. Positive values move the telescope and guider box east and north respectively. Negative values move the telescope and guider box west and south respectively. Note that your guide field is about two arcminutes across. Take care to keep your guide star within the guider field.

lfc.118> telescope offset <dra" ddec">  —  Move (dither) the telescope in arcseconds for both right ascension and declination. Positive values move the telescope east and north respectively. Negative values move the telescope west and south respectively. Note that you are NOT moving the guide box with this command.

lfc.118> telescope highlamp  —  Turn on the highlamp.

lfc.118> telescope lowlamp  —  Turn on the lowlamp.

lfc.118> telescope arclamp  —  Turn on the arclamp.

lfc.118> telescope lampsoff  —  Turn off the lamps.

For a full list of telescope commands, see the Telescope Commands section.

14. Scripts

There are several scripts available in the oasis /scr6/home/lfc/scripts directory that you can copy to your data directory to use (and edit, once copied). Look at the scripts. You will notice how easy it is to write your own, perhaps to setup an observing dither pattern, etc.

To run a script, type source <script>.

  • dither5, dither9  —  These scripts will run a series of exposures (5 steps or 9 steps) using a boxed dither pattern starting with a guide star located at the center of the guide field. The best way to implement one of these dither scripts is to take a normal, guided science exposure using a guide star anywhere in the guider field. When the exposure is done, move the telescope to put the guide star in the center of the guider field and then run the script.
  • After starting a normal exposure, say you select a guide star that is 20″ east and 30″ south from the center of the guider field. The guider field of view is about 90 arcseconds across. When this exposure is complete:

    lfc.118> tel goffset 20 -30

    lfc.118> source dither9

  • doflats  —  Without editing, this script assumes that you are in reasonably good focus. It takes 5 filter position 1 dome flats, followed by 5 filter position 2, 5 filter position 3, and 5 filter position 4 dome flats. After copying to your working directory, edit the script to suit your needs (your position # filter name will likely be different).
  • lfc.118> source doflats

  • focus_fine  —  Without editing, this script takes a 5 second exposure, increments the telescope by 0.1 millimeters, and moves the telescope. After the first exposure, the telescope is moved 15 arcseconds north. Six more exposures are taken, followed by 7 arcsecond north telescope moves. If you would like to change the exposure time you may do so by editing the first line of the focus scripts, focus (N) focus_fine. Rm is used at the end of the script to readout the mosaic. Obj 5 is the last line, intended to get you back into normal exposure mode lest you forget that you are in the no-read focus mode. After copying to your working directory, edit this script to suit your needs.

    The two best variations of focusplate are focus_coarse and focus_fine. We have also added a .5 mm increment focus script for the first night of a run focus_first.

    Note the ! sleep # lines. Make sure you wait long enough before executing the next command, especially if you increase the size of telescope moves or focus changes.

    lfc.118> source focusplate

  • standard4  —  Without editing, this script takes two dithered exposures of a standard star or field in each of the four central chips. You should be near the center of the mosaic when you start the script; the telescope will move 120 arcseconds north and 120 arcseconds east to start; then return each time before moving off to the next ccd. After copying to your working directory, edit this script to suit your needs. There should be a standard6 script that incorporates all 6 chips now too.

    Note the ! sleep # lines. Make sure you wait long enough before executing the next command, especially if you increase the size of telescope moves or focus changes.

    lfc.118> source standard4

  • tarem, todat-lfc  —  These scripts work together to create a single tar file for each image frameset. Look at todat-lfc for more information.

15. Trouble Shooter

The most common problem with the LFC is a "hung" utility board. The utility board controls the shutter and the filter wheel. When it hangs, you won't be able to move the filter wheel or take an exposure. Usually, a scary Timed-out error message appears several times in the mcdcom window if you try to do something when the board has hung. At other times, the failure may be subtle. If you suspect trouble, look at the output from the utility stat command. At the left of the output, you should see a list of voltages (+40, +15, -15, +5) followed by the actual voltage value. If these actual values are zero (or some outrageous number), then the utility board is likely hosed. If you think the utility board has gone bad, do a cold boot.

The utility board hangs about once or twice every 2 – 3 nights.

Sometimes, the filter wheel will fail to converge to the proper position after a move request, and a warning "filter wheel didn't make it into fine lock" will result. If this happens, just issue the filter move # command again until the filter wheel has seated properly. Pay attention to the estoff= value. This value should be 0 before you take an exposure.

For a full list of LFC troubleshooting errors, go to Rob Simcoe's LFC Troubleshooter Web Page.

16. Data Backup

The tape drives are located next to oasis in the computer room on the mezzanine floor (next to the E-lab). Your taping options are:

  • Eliant 8500 type 8mm Helical Scan tape drive (device number 0)
  • tar cvf /dev/rmt/0cbn lfc.*

    We can typically get 7 Gb on a 112M Exabyte tape (5Gb native : 10Gb compressed) using compressed mode, so that's about a 1:1.4 compression of LFC images. A 160M tape (7Gb native : 14Gb compressed) should hold about 10 Gb.

  • Sony 4mm DAT DDS3 tape drive (device number 2)
  • tar cvf /dev/rmt/2cbn lfc.*

    A 125M tape will hold 12Gb native and 24Gb compressed, but we haven't tested this.

  • There are two fast PCs in the data room (planetx and vulcan) with DVD burners. See the mountain staff for help.

17. End of the Night

Nothing special needs to be done at the end of the night. The dewar should still have plenty of Ln2, and the daycrew will fill it in the afternoon.

When your last night is over, please try to have your taping done before the next observer arrives in the afternoon. With the limited disk space on oasis, your data can't be guaranteed to remain on disk after you leave. Contact the mountain staff and the next observer if you need to make special arrangements.

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LFC Cookbook / v 2.0
Last updated: 13 June 2015 ACM