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Home > Astronomy > Telescope Operator Notes > Working with PNS


Designed and built by the Anglo-Australian Observatory, Kapteyn Institute, the Netherlands, Mt Stromlo and Siding Springs Observatory, Australia and ESO, Garching, the Planetary Nebula Spectrograph was commissioned at the WHT in July 2001 and is a slitless spectrograph used with three detectors simultaneously: PNSL, PNSR and PNSHA. More info can be found on the AAO PNS page or the Dutch PNS page.

All 3 of the detectors for PNS are now filled with the automatic LN2 filling system at Cass. In April 2012, the detector Marconi2 (used for PNSHA) was beginning to warm up before the end of every night, depsite the filling completing successfully each time. If all the cryostats are filled as late as possible before starting to observe, it should last until well into morning twilight, but this could be a problem on longer nights.

  • Zeroset as usual
  • USER> FOCUS 97.90-98.0 (April 2012)

Set instrument to OWN. PNS is an instrument with large field of view, therefore choose a guide star with autoradial larger than 20000 as otherwise the guide probe is vignetting part of the field. In fact, the exact autoradial which will cause vignetting is unknown, therefore the safest thing to do is to choose a guide star with the largest possible AGR, which still gives suitable S/N.

Use direct viewer (AGCOMP), to be removed for observing (AGMIRROR OUT).

Observing System:


Telescope focus:
Focus is determined by the observer, using measurements of a standard star, changing the focus and offsetting the telescope between each exposure, with readout only at the end, not after each focus change. For focussing, sky PA is usually set to 45 or 225 degrees.

Determine rotator center:
Use direct viewer (AGCOMP) to view the image. Measure x,y of a star at sky PA 0 and sky PA 180 (or any angles 180 degrees apart) and calculate the centre point.

Calibrate procedure:
CAL FAINT: acquire stars on the rotator center and at fixed mount PA (any PA is OK). When each star is centred, hit HANDSET to move to the next one.

Determine aperture offset:
No need for defining any offsets, instrument found always well aligned.


Sky Flats:
These can be started soon after sunset. Go to a suitable blank sky field at any sky PA and offset the telescope between exposures (the observer can do this themselves).

Combining data taken at different PAs is VERY complicated, even if the PAs differ by 180 (but observers should know this!). So if data are to be combined always use the same PA as last time. To set the dispersion direction along the minor axis, set sky PA = PA(min) + 90 = PA(maj).

  • GOCAT to the target and the observer will take an acquisition image with PNS and say if they need any offsets. These will probably be in RA_DEC mode using the handset. Make any offsets required and then start guiding. Small offsets may also be done between exposures, so stop the guiding before offsetting if the offset is in RA_DEC.
  • If required (usually it's not), the object can be acquired using AGCOMP, and blind offsets can be done from a nearby reference star as usual if necessary, centering up the target on the rotator center. This might be needed for extremely extended objects.
  • To acquire objects onto the same pixel as previously, note sky PA, prag AGR and AGT positions and x,y guiding coordinates. Set the sky PA, send the probe to the required position and then do "auto on x y" on the TCS. This may be useful due to the field distortion.
  • For observing, move the AG mirror out to AGMIRROR OUT. Note that from this point onwards you will no longer be able to see the object on the TV.
Standards can be observed at any PA since there is no slit in PNS. However, if the standard is used for focussing, use PA 45 or 225.

Use the normal CuAr+CuNe lamps. You shouldn't need to stop guiding during arcs, but if the lamps are interferring with the guiding, stop the guiding first and start it again afterwards.

Field Orientation:
For sky PA 0: with PNSL, North is left and East is up; for PNSR North is right and East is down.
For sky PA 180: with PNSL North is down and East is left; for PNSR North is up and East is right.

Data Handling

On DVD as usual.

Incomplete headers are a known problem, see fault reports 14433 and 15360. When ICL is configured before a PNS run, both the spare channels SPARE1 and SPARE2 should be selected. This can be done by selecting option 15 on the configuration menu presented when you select manual configuration when starting ICL. As well as the SPARE1 and SPARE2 channels, the CAGB should be selected also (example for selection used 10/10/2002 successfully: 4,17,18).

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Last modified: 19 April 2012