| All our program data is taken in
the account v_tbogle. The data is in /mrt_data/tbogle,
the observer account is /vis/tbogle. Typically we log into mrt-ux1, which is a powerful HP workstation to which the data are automatically copied from the VAX. Sometimes this transfer program does not work (rarely these days) then some subscan files may be missing. They may still be on the VAX, so ask the operator to check and copy them over. The nmb data to read in NIC is in /mrt_data/tbogle/nmb. We now also have a powerful PC, mrt-lx2,
to which you may also log in.
Start observingTo start observing, at the observing console push the OBS icon, log in as v_tbogle, type OBS, answer the questions (observer: your initials, operator: MR (Manolo) or ME (Mariano) etc and initialize with@wstart
Do not forget these inizialisations, else nothing will run! Make sure that the display shows Frontends:
MBOL2 250. GHz BolGain
1 Wobbler 40 0.52 Chan 40 IF 1
where the wobbler throw may be between
32 and 60.
PointingWhen you start after a longer break, pick a strong source such as a planet or secondary calibrator, and try point and focus there first, before you go to a fainter pointing source.To load a source, you do not need to type in the whol name, just enough for that the string is found properly in the source catalog. E.g. you can type 0221+ for the source 0221+067. However, you may not type 0336- for 0336-019, since - at the end of a line is for continuation. It will also not suffice to just type 0336, since there is a large chance that it will find that string in another source. If your target is far from a pointing source (e.g. > 5 deg) then watch out for gradients in the pointing!! Better pick two pointing sources on opposite sides of the target and then interpolate the pointing corrections. Especially for faint (<4 mJy) source a reliable pointing is absolutely necessay for a good observation! There is a pointing source catalog linked to these pages, and a hardcopy of it should be on the observer desk. When you observed a pointing source, please write down the peak counts into these printed version, if there is none yet, or if it is larger than the values (hand)written down. This gives you an idea later what to expect from a particular pointing source, and you can judge -depending on weather- if it is strong enough. This can save you a lot of time spent otherwise pointing at sources too faint. In order to get a better pointing reduction, you can open a small mrt-ux1 winndow on the observer console, login as v_tbogle and cd nic
or @ppp [scan number] where [scan number] is the scan number of the pointing scan you just did. the procedure pp.nic will reduce this pointing applying skynois reduction, which will typically improve the S/N by a factor 2 or more. Thereby you get a much more accurate pointing correction on faint sources. @pp may take 30sec or so to run. For strong sources, you can run @ppp, which does not do a skynois reduction, and should yeid result almost identical to those displayed by obs. Another advantage of @pp and @ppp is that it give you two strings with the pointing corrections and the fit parameter: 10.4 10.2 4965
4494
You can grep the
first string an paste it into the log. The peak values (in this case 5000)
you can enter in the pointing source list if necessary.
Watch the Weather StationWatch out that the weather station is working! Often the hydrometer freezes and the reading is fixed at 105% or such. If you suspect it is, then take the portable hydrometer outside the door and wave it around for a few minutes. You may check if it works inside by comparing it to the one hanging in the control room. If you get a vastly different reading for the outside humidity from the one on the ret display, then turn off the automatic environment reading in obs by typingset ambient 273 702 18 where the first number is the temperature in K, the second is the pressure, the third is humidity. Now you need to monitor all three parameters and update them. To switch back to automatic, type set ambient auto If you don't have the right humidity, your
pointing will suffer. The atmospheric refraction is computed by the pointing
model using the humidity. It is rather important. The other two parameters
are not to my knowledge.
The OBS ConsoleHere is how your obs window might look like when you have set up the numerous windows:
On the upper left: MonScan, which you can start with the left mouse by clicking "MRT Monitoring". It will start a number of windows, all of which this one you may iconify again. On the upper right is the Netscape Composer window with the obs log. Below that onthe right is nic running on mrt-ux1, in /vis/tbogle/nic, using the procedures @pp and @ppp to look at pointings. Read above. On the lower left is the obs command window. I found this to be a rather useful arrangement of the limited space in this window. On the other windows that you acces (see bottom right) I run xepehm in one, and netscape in another. Open the observing logOn the OBS console open a remote window to mrt-ux1 and log in as v_tbogle. Then "cd html" "netscape index.html" A netscape browser will appear with the cover page of the coordiated programs. Look at the bottom where the links to the observing logs are. There is a link to a template, which you click on. Then open this page in the netscape composer by selecting "File > Edit Page". Save it as logDATE.html, where DATE is mmdd, e.g. 1224 for Christmas night. It is not difficult to edit with the composer. Open a new log every day.You can make a link to the new log by editing the index page, or leve it to me (F.B.) to do so. Look at the old log for the format convention in filling in this sheet. Save the log often (ALT-s), because if the session crashes for any reason you lose the log. There is no automatic backup. Once in a while, I will copy the new html files to the "public" web space. Program descriptionsThere is a binder with basic info on all the programs. That also exists on the program's web pages which you can look at locally from mrt-ux1. Not all the program web pages are on the public page. Please update these pages by filling in the observations of the objects.CatalogsThe catalog files are on the VAX in our account.program catalogs: LBG BEMMEL
DEC99 HEITH LBG LOCKMAN
pointing catalogs: ALOK IBOL IRAM SECOND_CALIB Currently there is a printout with pointing
source fluxes next to the OBS console.
It is easy normally to point on a source with >500 mJy. It is more difficult, but not impossible to point at sources down to 100 mJy. You may need to douuble the subscan number to 8: point /sub 8 To look for pointing sources, you can also
use the xephem tool that is running in another window on the OBS console.
There you have to load the following catalogs: ibol,
bolo, alok100 (sources between 100-500mJy), alok500
(>500
mJy), second-calib, plus your source catalog.
On-off observationsOur standard mode is to spend 20 minutes on a source, then point again, and move on to the next source. For faint sources we now prefer to use a small wobbler throw, such as 34".For pointings however, use a larger throw such as 43". We use 16 subscans in /nosym mode: source mysource /cat
mycat
for i 1 to 4
Each 16 subscan scan takes 4 minutes.
Check the focus especially after sunset and sunrise, since that's where it changes most. Otherwise it is usually only necessary every 2 hours. Do not observe a source for much more than 20 minutes at a time- rather go back the next day for another 20min. This is better to check for consistency. To start an onof mor quickly, you can use the procedure onf.pro in that you simply type @onf 16 which will start an asymmetric onof with
16 subscans.
MappingStandard maps should take 1 hour, then you need to check pointing again. that puts a limit to the map size. For deep fiedl mapping we used to take maps of size 240 x 200" with 4" spacing an 4"/sec speed. To start such a map:source a851-0-0 /cat
a851
This map has 200/4+1=51 subscans of 60 sec each, and thus takes about 55min including overhead. This map is scanned from low to high elevation. If you want to start at high elevation, then use map 240 4 200 -4 /time 60 Since we map in azimuth-elevation, in equitorial
coordinates the map diverges in one direction, depending on +4 or -4. If
you mosaic with many coverages, try to have the different overlapping maps
as orthogonal as possible, by observing at different times, or at +4 and
-4 steps.
Maps with subscan spacing of 4" are fully sampled for each channel. If you want full sampling only for the whole array you may set the spacing to 23", which is the spacing of the rows in the array. Thereby you can scan a larger area in an hour. A map with map 600 4 460 23 /time 150 will make 21 subscans of 150sec and take about an hour. You could also scan at 6"/sec, but i dont recommend that for deep imaging - though we have not really investigated the effect. For mosaicing a large field, create separate target positions in you catalog, such as here in A851.CAT: INDIVIDUAL: SNAM
SLAM SBET
SNAME=A851-0-0
; SLAM= 09 43 00 ; SBET= 47 00 00
;
Master listsThese you find in /vis/tbogle/master. e.g. r20001130.LIST which contains a list of scan names relative to /mrt_data/tbogle from Nov 30. You can read these lists in mopsi and select out objects or times:in-dir "/mrt_data/tbogle"
which will write a list containing all
observations of 3C79 from nov 30 to dec 5. Note that the list r20001130
contains observations from nov 30 to dec 2, so not every day hs its own
data subdirectory, because for a new one to start one needs to get out
of OBS.
Experimental SkydipOpacity corrections derived from skydips are a major source of flux uncertainty, since they use very simple atmosphere models and they typically do not acknowledge the actual flux arising from the receiver cabin, telescope, spillover etc.One attempt to get a better or alternative estimate of the opacity is to do a skydip in total power mode: continuum br tot
The reading we currently get from this differs from the normal bolotip. We dont know why yet. In the future this will however be the standard skydip. Albrecht Sievers is working on it. We are about to install a window which plots the current zenith opacity derived from the total power channel signal, calibrated during total power skydips. This should be a big help in deciding when to do the next skydip. In the mean time, try to do a skydip every two hours, or if the weather seems unstable, more often. Watch out: if you are at azimuth > 400 deg, and you type bolotip, then the telescope will try turn around by 360 degrees, which takes a lot of time. To avoid this, type bolotip 399 and it will do the skydip at az=399.
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