The Table of Contents is at the end
The DIS was built at Princeton by Jim Gunn, Michael Carr, Brian Elms, Ricardo Lucinio, Robert Lupton, and George Pauls. It is a medium dispersion double spectrograph, which can either be used in a direct imaging mode, or as a spectrograph. Among the objects observed on its first night on the telescope was 3C273.
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The optical path consists of a slit-mask assembly, a shutter, a dichroic (with a transition wavelength of 5350 angstroms), and two independent collimators and cameras for the blue and red sides. The gratings and mirrors are mounted on a grating turret holding two mirrors (red and blue) and two sets of two gratings. The detectors are a thinned, uv-coated SITe (formerly Tektronics) 512x512 CCD with 27 micro pixels on the blue side, and a thinned 800x800 TI chip with 15 micron pixels on the red side. The gain on the blue side is 0.96 electrons/DN; on the red side it is 1.47 electrons/DN; and the readnoise is about 9.5 electrons. The electronics on the blue side misbehave for very over-full wells; the signal is set to 0, and the pixels to the side of the offending pixels are also set to 0. The way that the CCDs are mounted results in the dispersion in the two chips running in opposite directions.
The collimator focal lengths on the blue and red side are both 963mm; the camera focal lengths are 140.3mm and 141.7mm on the blue and red sides respectively; the resulting reduction is 6.865 in the blue and 6.798 in the red (the measured values are within 1/2% of this value, and vary slightly with collimator focus). The measured scales are 1.086 arcsec/pixel in the blue and 0.610 arcsec/pixel in the red. The beam diameter is 100mm, and the angle between the collimator and camera optical axes is 35 degrees. There are commands to centre given wavelength on the chips.
Because the dichroic is not in a parallel beam there is a ghost image on the blue side, produced by light reflecting off the back surface of the dichroic. It's displaced by about 20 pixels to the red. When the slit is illuminated with an He arc the amplitude is about 10%; inserting the g filter totally removes the ghost. We are considering coating the back of the dichroic to reduce this effect. When using the gratings, this ghost is of course dispersed off the chip. There are also ghosts when you are taking spectra; they will also be improved by AR coating.
When being used as a spectrograph, the entrance aperture can be either a long slit or a slit mask; the total slit length is 6', and slits of width 1.5 and 1 arcsec are installed in slit mask wheels A and B in positions A1 and B1 respectively. In imaging mode the ends of the slit are at approximately (125,250.7) and (492,251.4) in the blue chip, and (120,433.8) and (775,434.2) in the red. At the time of writing, the FWHM at the centre of the slit are about 1.4 and 1.8 pixels.
Two sets of gratings are currently installed: a 150/300 lines/mm pair, and an 830.8/1200 lines/mm pair; the blaze angles are ??. All gratings are run in first order. The low-resolution pair have dispersions of 6.2 A/pix and 7.0 A/pix for the blue and red sides; the high resolution gratings' dispersions are thus approximately 1.1 A/pix and 1.7 A/pix to within a cosine. When used for imaging, the field of view is 4'x6'.
The shutter is a rotating half-circle; this means that there is no aperture correction, even for the shortest exposures.
The slit mask assembly contains five masks; of these the first usually contains a long slit, and the second is clear. The other three are available for user-created slit masks. There are two slit wheels, which can be easily changed by on-site personnel during the night. All other operations can be controlled by the remote observer.
The CCDs are cooled by liquid nitrogen. The cameras are automatically filled from a storage dewar when empty; provided that the storage dewar is pressurised and not empty, the cameras will remain cold. The red side runs at approximately -125 Celsius; the blue side at about -100 Celsius.
There are two optical systems that must be focused in a spectrograph, the collimators and the telescope. We do not expect users to have to focus the collimators (and it can't be done remotely in any case). The telescope is focused in the usual way. Because it is not yet possible to take multiple exposures, you will have to read out the DIS after each movement of the secondary.
There are a total of nine mechanisms that can be commanded remotely: the four grating angles (see section Selecting Mirrors or Gratings, and Grating Tilts); the position of the grating turret (see section Selecting Mirrors or Gratings, and Grating Tilts) and the detent (which we hereinafter ignore); the filter wheel (see section Selecting a Filter); the slit-mask wheel (see section Selecting a Slit Mask); and the shutter (See section Taking an Exposure; see section Homing the Shutter).
The computer systems used to run the DIS are typically baroque. The observer sends commands to a programme called the MC which is responsible for book-keeping and routing commands; in fact, there may well be another layer above the MC -- for example, I use mirella(1) to send commands to the MC, and others may use Bob Loewenstein's mac interface. The MC then passes the commands on to an instrument control computer (icc); in the case of the DIS this involves two more processes. The DIS icc is a PC, and it sends commands over an RS232 line to a TDS microcomputer that is physically on board the instrument.
All commands should be preceded by `dis',
and all commands can be asked for help (e.g. dis grating help).
You should not attempt to send
a second command to the DIS before a first has completed. The
sole exception is expose, when it is safe to send commands after the
shutter has been opened (the integrating for n seconds message).
Commands return a completion code (of :) to
the MC when they have finished.
If the instrument is power-cycled, all responses that it returns will
include the remark, "spectrograph micros are not initialiased!".
If you see this, you should use the init
(see section Initialising the PC and Onboard-Micro) to initialise things. This will also reset the nitrogen
filltimes, a detail that will concern few observers.
Please note that, as of the time of writing, these commands had been used for nearly a week of `remote' observing. They are not well tested, and some of the MC-related parts still need work.
The available command are:
camera [red|blue] prep
Prep the chips (i.e. read them to get rid of old and unwanted charge). If you don't specify a colour (or specify both) both chips are prepped. The chips are automatically prepped before each exposure.
camera skiplines=n
Read out n lines and throw the data away. This is most often used
for focussing.
camera status
Print some status information for the cameras.
camera wipe[=on|off]
Continuously read the chips until told to stop with camera wipe=off.
This command should always be used while the chips are cooling, as it gets trapped charge out of the oxide layer.
The expose commands are used to take data and transfer it to the Unix host, currently tycho. At present the files have minimal headers and appear by default in the directory `/export/home/dis/data'. The file format can be either Mirella (the default) or FITS (see section Specifying the File Format).
Header keywords are described below, See section Keywords in DIS Disk Files..
As explained above (see section Specify the Output File), the DIS usually puts files in a
well-known place on the unix host, expecting the MC to massage them
suitably (e.g. adding RA and dec to the headers) and safely archiving
them somewhere. Until this is done, we have added a temporary command
file and an option to the expose command to choose
file names.
If you don't use these facilities, mirella format files are called `dispic_b.hdr', `dispic_b.img', `dispic_r.hdr', and `dispic_r.img' for the blue and red images respectively. These files are very close to IRAF 2-file formats (.img files are identical to .hhd; .hdr and .hhh are the same to within whitespace); nonetheless without some massage IRAF cannot handle these files, and you should proceed to the next paragraph.
FITS files are called `dispic_b.fts' and `dispic_r.fts' for the blue and red images respectively.
These files are overwritten everytime that you take an exposure! You are responsible for saving them. If you are using the mirella interface there are words to do this for you -- ask RHL for details.
expose abort
Abort an exposure, either in progress or already stopped (with
expose pause).
expose help
Provide a summary of expose options.
expose pause
Pause an exposure, i.e. close the shutter but don't read the chips. You
can resume the exposure later; abort it, or read the
data.
expose read [bin] [red[=0|1]|blue[=0|1]] [old]
Read an exposure; either one that you paused or one that is in
progress that you'd like to halt prematurely. If you want to abandon
an exposure entirely, use expose abort.
You can specify which chip to read and the desired binning; if you don't
specify anything the values used to start the exposure will be used.
The arguments are discussed in more detail under dis expose time=n
You can also read an exposure that has already finished (or even
one that has been aborted, but about which you've had a change of
heart). This is slightly dangerous, as if a chip has already been read
reading it again will replace your data with a bias frame. In
consequence, you must explicitly specify the old flag if you want
to read chips after an exposure has been completed; in addition the
way that colour flags is interpreted is a little different. If you omit
a colour specification neither chip will be read -- the chips
specified in the original expose command are ignored. The same
goes for binning; if you want the data binned you must explicitly say so.
expose resume [bin] [red[=0|1]|blue[=0|1]] [time=t]
Restart a paused exposure.
You can specify which chip to read and
the desired binning; if you don't specify anything the values used to
start the exposure will be used.
The arguments are discussed in more detail under dis expose time=n
If the time specified is different from the original exposure time the integration time will be adjusted (although the total time may differ from that requested by up to half a second); if it is shorter than the time already elapsed the chip will be read immediately.
expose status
Report on exposures in progress or recently completed.
expose [bin] [dark] [file=name] [red[=0|1]|blue[=0|1]] bias|time=t|snap
Actually start an exposure. The time is in seconds and must be provided. If
you specify 0, a snapshot will be taken (snap is an alias).
This is the shortest exposure
possible, and opens the shutter for 0.6s. If you specify bias instead of
time a bias frame will be taken; if you specify dark (as well as a time)
a dark frame will be taken.
Optional arguments are:
bin[=0|1]
Bin the data 2x2.
dark
file=name
file command (see section Specify the Output File);
this flag overrides any filename specifications made there (but it
obeys any dir=name settings).
red[=0|1]|blue[=0|1]
Only read the red or blue chip. If you don't specify a colour, both are read. If you don't specify a value it defaults to 1, meaning that that colour should be read.
It is not the job of an instrument control computer to decide where to
put datafiles on the unix host; it is the job of the MC -- which should
know almost nothing about the instrument. At present at APO the MC is
structured to make this difficult, and therefore as an interim measure the
I have added the commands in this section. There is also an interim flag,
file that expose (see section Taking an Exposure) understands.
You can specify a filename, e.g. `ngc6205', or request the DIS
to generate names for you; in this case you can specify the base part
(e.g. `bias') and the starting record number (e.g. 100), in which
case files will be named `bias00100', `bias00101', `bias00102',
and so forth. The red and blue sides are distinguished by having a
`_r' or `_b' appended, so if you are using FITS format
(as specified using the format command (see section Specifying the File Format)), the next
red file would actually be called `bias00103_r.fts'.
No attempt is made to ensure that the file doesn't already exist on the unix disk! Caveat scrivor.
file auto[=on|off]
off, this is
(of course) disabled.
file dir=name
name on tycho. If
name doesn't start with a / it is interpreted relative
to `~dis'. The directory must be writeable by the dis account.
file file=name
name. If auto is turned off, this is
equiavalent to specifying file=name to expose, but if
you are using the automatic generation of filenames, it is used as the
base part of the filename.
file recnum=####
###.
file status
Both the keywords filter and filters are accepted.
filter 1
filter clear
Put in the clear filters. Actually there are no filters at all in this position.
filter 2
filter gr
Put in the real filters; Gunn-Thuan g and r on the blue and red sides respectively.
filter home
Home the filter wheel (to the empty position).
filter status
Inquire the status of the filter wheel.
The DIS can currently write files on the unix host in either Mirella or FITS formats. The Mirella format is very similar to IRAF, but apparently not quite identical. At some point, quite soon now, the files will be written using standard APO procedures.
format fits
format mirella
format status
Commands to select gratings or mirrors, and manipulate the grating tilts.
gratings or turret is acceptable as an alias for grating.
It takes about 50 seconds to switch between the high resolution and the low resolution gratings; about 30 seconds to go from grating set 1 to the mirrors; and about a 100 seconds to change from grating set 2 to the mirrors. When you tilt the gratings they are first homed, to avoid problems with missed steps, and it takes about 30 seconds to go from step 2100 to step 2101 (a wavelength of about 1.2 microns for the high resolution red grating; about 6.8 microns on the low resolution side). Times for more moderate tilts are somewhat shorter.
grating 1
Select grating set 1, currently the low-resolution (150/300 lines/mm)pair.
grating 2
Select grating set 2, currently the high-resolution (830.8/1200 lines/mm) pair.
grating change1
Move the turret to the correct position to change grating set 1.
grating change2
Move the turret to the correct position to change grating set 1.
grating home
Home the grating turret after a crash or other problem, and home
all the gratings. Use ghome to home an individual grating.
grating col=[r|red|b|blue] n=[1|2] [lambda=l|step=n]
Set a given grating to a given position. You can either specify a
step or a wavelength (in angstroms) to set at the centre of the chip.
The n refers to the
grating pairs. Most users will not want to use the step form,
as it requires a familiarity with the stepping motors used to tilt the
gratings.
grating col=[r|red|b|blue] n=[1|2] ghome=1
Home a specified grating.
grating ok
Tell the DIS that the gratings that it thinks are in the turret are indeed the ones loaded. You need to issue this command after the grating turret door has been opened. If you changed any gratings it is your responsibility to update the DIS's idea of grating parameters; as there are currently only two sets of gratings available, there is no way for naive users to do this.
grating status
What is the status of the gratings and turret?
help
help as an
option, e.g. dis gratings help.
home
init (see section Initialising the PC and Onboard-Micro)
the DIS first.
You will have to home the instrument after powering up
the micro, and after the TDS micro on the instrument has crashed. You
can restore the instrument to the state it had before the crash with the
tds command (see section Recovering from TDS Problems/Reboots).
init
Control or inspect the liquid nitrogen system. The dewars run at liquid nitrogen temperatures (78K), the blue camera runs at about -100C, and the red camera at about -125C.
ln2 cool=t
t minutes before the desired temperature is reached or it gives up.
Don't give it too long a time -- if the supply dewar is empty you'll
have lost control of the instrument until the time finally elapses (or until
someone at APO hits ^C on the PC running the instrument). We start the
CCDs wiping for you.
ln2 off
Turn nitrogen filling off. The chips will eventually warm up.
ln2 on
Turn the nitrogen system back on.
ln2 status
What is the status of the LN2, and the temperature of the chips?
ln2 top
Force a nitrogen fill (top up the dewars).
Control the slit mask assembly.
mask 1
mask slit
Select mask 1, which should be a long slit.
mask 2
mask clear
mask 3
Select mask 3.
mask 4
Select mask 4.
mask 5
Select mask 5.
mask home
Home the slit mask wheel.
mask status
Where is the mask wheel?
mirrors
There is an optional argument:
[home]
Send the grating turret home.
ping
The casual user can probably safely ignore this command.
set-special-mid
Mirella users can use the word init-dis to initialise the DIS and
set the special MID with one simple, easily typed, word.
shutter home
Home the shutter.
shutter status
What is the shutter status?
status devices
Report the status of all the mechanical parts of the spectrograph.
status version
Report the version of the code on the TDS micro.
This command is not currently available. It shouldn't be needed.
sync
The DIS remembers the status of the instrument micro, the TDS. You can use this command to inquire what it thinks its status should be, or reset it to that status. We expect this to be used as
dis status dis init dis home dis tds status dis tds restoreThe first command (
status) reports that the micro is not initialised;
the second (init) initialises it;
the third (home) homes it (as it has no idea where its mechanisms are);
the fourth (tds status) reads the saved status information, and
gives you a chance to see if it makes any sense;
and the final (tds restore) sends commands to the instrument to
restore the desired values.
As a zeroth step, logon to some machine that can communicate with the
MC; for example if you are at APO logon to tycho and start the MC command
line interface. If you are indeed using the raw MC interface (as opposed
to, for example, the mirella interface) you may well want to start a
dis window -- open a window (an xterm or shelltool) and type
~apotop/bin/dis-window &.
First check that you can communicate with the instrument:
dis pingYou should get a number of replies, ending with
COMPUTO ERGO SUM !If you don't, some part of the chain of command to the instrument is broken.
Next, you'll have to initialise things. Try the command
dis initIf you get complaints about needing to home the mechanisms do that:
dis home
Everything should be ready to go. See where things are:
dis statusand what the camera temperatures are:
dis ln2 statusIf it all looks reasonable, you can start observing.
You shouldn't have to focus the instrument, which is fortunate as doing so is impossible for the remote user. To focus the telescope you can either take a number of exposures, reading the chip between each; or close the shutter as you move the focus and telescope, finally reading the chips; or close the shutter and clock some charge as you move the focus.
To take four exposures without reading the chip, but moving the image by 15 lines in the blue and 22 lines in the red between exposures, say
dis mirrors dis mask clear (set initial focus position) dis expose red=0 blue=0 time=10 dis camera blue skiplines=15 dis camera red skiplines=22 (change the focus) dis expose red=0 blue=0 old time=10 dis camera blue skiplines=15 dis camera red skiplines=22 (change the focus) dis expose red=0 blue=0 old time=10 dis camera blue skiplines=30 dis camera red skiplines=44 (change the focus, note that we skipped double before the last exposure) dis expose old time=10The
old keyword tells the DIS not to erase the previous (unread)
image; the red=0 blue=0 tells the DIS not to read the chip.
As
an alternative, the final dis expose old time=10 could be written as
dis expose red=0 blue=0 old time=10 like the other exposures, followed
by dis old bias which has the effect of reading the chips; the
initial exposure could be replaced by dis red=0 blue=0 bias to
initialise
the exposure, followed by dis expose red=0 blue=0 old time=10. If you
follow both these pieces of advice all of the `real' expose commands are
identical, which means that you can put them in a loop ....
You'll need to find where the slit is; if you aren't using custom multi-slits,
you'll want to use the slit in mask position 1; you can refer to this
as either dis mask 1 or, as here, by name:
dis mirrors dis mask slit dis expose time=30(assuming that you can see it against the sky in 30s).
Next acquire a target (I'll assume that a 10s exposure is enough); to save time let's only read the red chip:
dis mask clear dis expose time=10That'll put the data from both cameras on the unix host in mirella format, in the files `/export/home/dis/data/dispic_b' and `/export/home/dis/data/dispic_r'; for details See section Taking an Exposure. If you'd rather use FITS files, say
dis format fitsbefore the
expose command.
The use of standard names for the datafiles is all very well for scratch
exposures, in fact
it's rather convenient, but for real data you obviously want some way to
give your precious frames distinct names. We'll see how to do this in
the next-but-one paragraph.
Next, slew the telescope to put the image where the slit is, put the slit back in and see if the target falls on it:
dis mask slit dis expose red=1 time=30If it's there, put in the gratings; I'll assume that you want the low-resolution set, with the blue set to have 4400A at the centre of the chip, and 7700A in the red (both reasonable numbers):
dis gratings 1 dis gratings col=blue n=1 lambda=4400 dis gratings col=red n=1 lambda=7700 dis expose time=100 file=my_first_spectrumAnd you should have your first DIS spectra.
Note that we explicitly specified that the data be saved as `my_first_spectrum' -- this means as files like `my_first_spectrum_b.fts'. You can't simply repeat the command using some history mechanism as your second spectrum would overwrite your first, so you have to remember to specify unique file names. Another way to proceed is to ask the DIS to think of names for you. For example, to use a set of filenames of the form `R00000', `R00001', and so forth you'd say
dis file file=R recnum=1 autoand not specify
file to the expose command.
When you come to take arcs, arrange for someone on the mountain to attach an arc to the front of the telescope and turn it on. We've had success with an Hg/Ar arc and 100s exposures with the low resolution gratings. Incandescent flats are acquired in a similar way. As I type this (within an hour of the 1st of October 1994) Jim is drilling holes in pieces of aluminium trying to make arcs and flats remotely operable.
Currently (1st October 1994) we can nearly, but not quite, control the arc and flat field lamps mounted on the secondary from the telescope.
Eventually we expect to provide detailed plots and line lists, but for now all that we have is one low resolution spectrum of an Ar-Hg lamp. Click here to see the graph
The DIS has been used from Robert Lupton's mirella interface to the telescope. Your mileage may vary (including changing sign) if used in other ways.
You should be able to send the DIS commands from the MC by prefixing your
command strings with dis; if you are talking to the MC perl directly,
response strings will come back via the mc-window as usual. If you are using
RHL's mirella interface, responses to commands are sent back from the MC on
the same MID as they were sent on.
In addition, all DIS messages are sent to a special distributed class called
dis, which you can subscribe to like any other class.
Messages that correspond to no known MID, such as device timeouts, are
also sent to class dis, prefixed by the string Orphan text:.
Alternatively, you can use the DIS command set-special-mid
(see section Set a Special MID for `Orphaned' Messages).
The state of the instrument is given in the header; keywords are:
CCDNUM
EXPOSURE
FILTER1
FILTER0 (empty) or FILTER1 (Gunn-Thuan g/r).
FILTER2
EMPTY (there is only one filter wheel).
GLAMBDA1
GLAMBDA2
GLAMBDA3
GLAMBDA4
GSTEPn.
GRATING1
GRATING2
GRATING3
GRATING4
lines:blaze
where lines is the number of lines/mm for the grating, and blaze
is the wavelength (in Angstroms) of the blaze.
N.B as of early June, the blaze wavelengths were not known.
GSTEP1
GSTEP2
GSTEP3
GSTEP4
MASK
TIME
TURRET
MIRRORS.
A multitude of things can go wrong with the instrument, so your problem is probably not discussed here. Still, it might be. If you think that it might help you can try calling RHL at work (609-258-3811) or at home (609-466-2431); JEG's numbers are 609-258-3802 and 609-924-1304 respectively. You had better think hard before calling us at home, and please remember that there is a two hour time difference from APO.
ping the instrument.
kills and restarts.
MC is alive message
mc status thinks that the dis_s isn't
running, start it (starticc dis) and try again. If that doesn't
help, kill all the processes that are connected with the client and then
try starting it; you can do this with the unix command
/home/apotop/start-dis -r (if you want to issue the command from
the mc you'll need to preface it with a !). From the mirella interface
you can restart things with the command restart-dis-icc. This
litany may not work if the MC or Hub is playing up; in this case intersperse
start-dis -r commands with the usual MC black magic. You will need
to set the special MID used for orphaned messages (see section Set a Special MID for `Orphaned' Messages).
MC and Client is alive messages
host; if that works (i.e.
there are no complaints) then Mirella is up and in a suitable state. If
it doesn't, the simplest thing to do is to reboot the machine -- press
the three keys ALT-CTRL-DEL all at once (DEL is the keypad
.). If that doesn't do anything, press the white button on the front
panel. Does host work now? If not, proceed to check the cabling.
MC, Client, and Mirella is alive messages
ndis 2400 setbaudto fix it. You may have to repeat this command a few times, and wait for various errors to timeout on the PC. Eventually you should get a message
I trying 9600 baud...followed by no error messages (if you use
setbaud a second time the
success message will be I trying 2400 baud...).
Try power-cycling the logic box on the DIS (that's the one with the smaller power switch).
dis camera prepand go and look at the DIS PC. The left hand column of numbers is a counter; the rest reflect the data coming from the chips. You can examine just one chip with
dis camera blue prepor
dis camera red prep
If the data is all zeros, the problem is probably either in the PC or the onboard micro, or in the cabling. Try power-cycling the PC (push the reset button on the front panel). If this doesn't help, power-cycle the logic box on the instrument (the one with the smaller power switch). Then check the coax cables. Then talk to Jim Gunn.
pre-ping ? to a dis ping command.
This is caused by mirella on the PC getting stuck in an inappropriate
vocabulary. Usually repeating the command will fix it (in fact repeating
any command -- I usually use dis ping).
Are you sure that you should be reading this?
Usually commands sent to the PC are mangled into a suitable form; You can
disable this with the DIS command set-passthrough, and re-enable
it with set-nopassthrough. So you can set the serial port timeout
to 5 seconds on the PC with the commands
dis set-passthrough dis 5000 serialtimeout ! dis set-nopassthrough
If you use mirella, this is done for you by the command ndis:
ndis 5000 serialtimeout !
It is possible to use this facility to cut yourself off from the instrument, for example
ndis byekills mirella on the PC, and it is mirella that listens to you.
The PC can send commands to the TDS, so once you know how to send un-mangled commands to the PC you are almost there (see section Sending Commands Directly to the DIS PC). The litany on the PC is:
" command" >micro ctso from mirella you could say
ndis " DOORRESET" >micro ctto reset the door latch interlock. Many of the most popular commands can be more simply executed by first loading the forth file `3_5micro.m' on the PC (
ndis reload 3_5micro), and then issuing the commands
as if you were talking directly to the micro, for example
ndis 1 ?Pto enquire the position of grating one's stepping motor.
It is possible to reboot either of the computers remotely, but it may not be a good idea. If you insist, the PC can be rebooted with
ndis % c:/bin/rebootb c(omitting the final
c gives a warm boot), and the TDS with
ndis " COLD" >micro ctThis last command in particular seems to sometimes leave the remote observer unable to talk to the instrument, so please be careful.
There are times when you might want to change the code that runs on the PC, for example to temporarily change the number of lines/mm for a grating.
The PC is programmed in forth (well, actually it is running mirella but you won't be changing any C), so any changes that you have to make will involve typing (trivial) forth commands; for example the command
30000 serialtimeout !stores
30000 into the integer variable serialtimeout.
You can print the current value with
serialtimeout ?Using the mirella interface to the MC this would be achieved by saying
ndis serialtimeout ? (see section Sending Commands Directly to the DIS PC).
Variables that you might be interested in are:
Grating Lines/mm
lines/mm with the values for the four
standard gratings. To set the value for the 2nd grating to 1234.5 say
1234.5 4 lines/mm f!; print it with 4 lines/mm f?. Note that
the number must contain a decimal point, and that you use f!
and f? rather than ! and ?.
Grating Zero Points
zero_order. These are the values in steps for the stepping motors
that control grating tilt that put the zero-order image of the slit into
the centre of the chip. They are used when you specify a wavelength to the
grating command. The value for the third grating could be set to
100 with the command 100 3 zero_point !, and inspected with
3 zero_point?.
Serial Timeout
serialtimeout milliseconds. The default is 30000ms, if you wanted
to set it to a minute you'd send the command
60000 serialtimeout !; to print the current value
Unix Host
unixhost, and the directory (relative to the home directory of
the dis user account) by unixdatadir. You could set the
host with " kepler" unixhost cs!, and print the current value
with unixhost ct; how to set unixdatadir should be
obvious. If you fiddle with these value you will have to ensure that the
.rhosts files are set up correctly to allow the user dis on the
machine dis to transfer files.
Verbosity
verbose is 1 some extra chatter is
produced (e.g. a message that commands have been received).
The DIS passes information to the MC in the form of messages prefixed by
diskeys=. These are intended to allow the MC to maintain a mirror
of the DIS's current state; currently they are merely passed out on a
subscription called dis, along with all other DIS output. You can
view them in a unix window with the command
dis-window | sed -ne "s/.*ys='\(.*\)'*/\1/p"
A given diskeys string may contain a number of white-space separated
keywords; if values are provided and contain whitespace they are quoted
with ".
The following list is complete at the time of writing (30th September 1994):
directory=name
expose:abort=true
expose:dark
expose:finished=true
expose:none=true
expose:paused=true
expose:resumed
file:auto=off
file:auto=on
file=name
name.
filter=name
name (one of Empty, Gunn-Thuan gr,
and Unknown).
format=type
type (one of Mirella or FITS).
grating:Name:lambda=####
####A.
Name is
The name of a grating, e.g. GR1 for the red grating in set 1.
grating:Name:step=####
####.
Name is
The name of a grating, e.g. GB2 for the blue grating in set 2.
ln2:blueCam=###C
ln2:blueFill=true
ln2:blueLn2=###K
ln2:elapsedTime=time
ln2=off
ln2=on
ln2:redCam=###C
ln2:redFill=true
ln2:redLn2=###K
ln2:topping=true
mask=#
mask=invalid
receptive=false
receptive=true
shutter:fault=true
shutter=closed
shutter=open
status=powercycled
status=uninitialised
tds:date=str
str.
tds:filter=#
# was in use.
tds:grating1=#
#.
tds:grating2=#
#.
tds:grating3=#
#.
tds:grating4=#
#.
tds:mask=#
# was in use.
tds:turret=#
#.
time:elapsed=###
time:remaining=###
time:specified=###
turret:door=open
turret:door=wasopen
turret=name
name; possibilities are
grating1, grating2, mirrors, change1,
change2, and unknown.
version=str
||.
wipe=off
wipe=on
dis distributed window gets truncated by the MC.
format command to support writing FITS files.
dis.
For details, See section Interactions with the MC.
Look at the claimed position of the gratings to see if the TDS micro has been power-cycled.
Added the tds command to restore the spectrograph to a saved state.
gunnspec to dis.
You can now read the other chip after expose red=1 ....
pause/read/resume seem to work. You can specify a new time, binning
mode, or selection of chips to read.
You can clock the chips some number of lines, (camera skiplines)
permitting focus frames. An example is in the cookbook.
You can take bias and dark frames.
The selection of grating tilt by central wavelength now works correctly.
The camera cont has been replaced by camera wipe, which
can be turned off.
Added aliases for time=0 (snap),
mask 1 (mask slit), and mask 2 (mask clear).
Wrote lots of Cunning forth for mirella users (e.g. to take a set of spectra with the high resolution gratings that cover the entire spectral range of the instrument).
Installed the filters (only the g, but the r as added a day or two later).
Added the file command to specify where the datafiles should be
put. This is a temporary measure.
Added a file=name command to expose. Also temporary.
Made the DIS report its status on the dis subscription stream,
preceeded by `diskeys='.
This is intended to make life easier for Bob Loewenstein.
The gratings are now always homed before being tilted.
More Cunning forth, of course.
Fixed floating point stack overflow bug
An expose abort command now returns an error completion for the
original expose command.
Reset the grating zero points to requested wavelengths should once more be correct.