Previous: Astronomical codes
Up: Astronomical Overview
Previous Page: Object-type code
Next Page: The Captive Account and Mailserver

Catalogue Maintenance

The archive receives the observations as they are produced by the Data Acquisition System (DAS) of ING telescopes. Unfortunately, the desciption of the data with the FITS headers has not always been completely reliable, due to technical or operational difficulties encountered during an observing session. For instance, a failure of the computer link between the Telescope Control System and the DAS at the time of observation will have resulted in missing position information in the FITS descriptors, hence in the catalogue.

Problems have occurred with the description of a whole range of catalogue items, and a substantial number of observations may have one or more item undefined, or sometimes even uncorrectly defined ( e.g. temporal information, instrument and filters names, etc. ).

The correction of such missing or erroneous information in the catalogue is an on-going effort, and very time consuming. Archive users might, therefore, take this health warning into account (and spare a thought for the archive manager), if they stumble upon missing information when searching through the catalogue.

TO BE COMPLETED

General comments:

• [*] with camera name, indicates usage on several instruments.
• "c" with chip type, refers to a dye-coating to give enhanced UV-response.
• "M" with chip type, refers to a `Metachrome' phosphor coating, for UV response.
• "t" with chip type, refers to a thinned CCD, for enhanced peak/UV response.

• Typical digitised areas exceed the size of the imaging area; e.g. 11241124 for TEK Cameras.

• Read-noise is quoted at the STANDARD readout speed.

• ADU = analogue-digital converter units. The e/ADU figures are believed correct to about 10% . The figure is given for the default (standard) readout speed.

• The maximum available digitised count is always 65535 (). This is a purely electronic limitation. In some cases measurements close to this limit have not been made; these are often indicated by, e.g. , `>55K'. Usually the linearity limit is constrained by the ADC range combined with the electronic gain of the system, rather than by a real limitation of the CCD (which exceeds 100000 electrons in most cases).

• The GEC CCD was originally made by GEC-Hurst Research Centre; however all devices are now made by EEV (Chelmsford, part of GEC group). We have retained the original `GEC' camera names, for camera-heads containing small CCDs (although they are now supplied by EEV; `GEC7' is such an example).

Further notes with individual CCDs:

1

The original RCA chip; began to deteriorate early 1987.

2

This is our last but one remaining RCA CCD.

3

This chip suffered from poor charge transfer; it was replaced in May 1988.

4

This is a high-quality coated-CCD.

5

Originally fitted to IDS Camera. A nominal preflash (pf) was routinely used. Chip electronics were reset in Oct/Nov 1984. From Oct 1986 chip performance was poor.

6

No preflash required; un-coated chip.

7

This coated chip is was destroyed by preamp-OS s/c in April 92.

8

A-grade chip originally fitted to this camera, replaced in March 1986.

9

A 3/4 scale chip; temporary spare in JKT camera.

10

A normal-sized chip; does not require preflash; replaced Jan 1988.

11

For the first month of use the gain was 2.2e/ADU; later 1.1 e/ADU. Developed a threshold fault in May 89.

12

A standard ESO-coated EEV CCD; poor blue response.

13

A standard ESO-coated EEV CCD.

14

Dye-coated EEV CCD, with negligible preflash needed. Destroyed (by GEC3 P-A fault), in May92.

15

Dye-coated EEV CCD; no preflash used. This chip has the normal coated UV/blue response. In July 89 switched to operate with the new WHT Dwingeloo CCD controller. High noise has been seen if FOS-body is not well earthed.

16

A large-format setup-grade CCD for ISIS; operates with the WHT Dwingeloo CCD controller only; replaced in Dec 89.

20

Super-grade, un-coated '88200' CCD. Gain adjusted to reduce e/ADU factor.

21

Metachrome-coated, super-grade device; used on ISIS blue arm.

22

Coated, super-grade chip.

23

Large-format, coated, super-grade chip, used on INT/IDS.

24

The default ISIS-red sensor.

25

This is a grade-1, thinned CCD. Used at first for LDSS, but available for use at any WHT focus. At the observatory, it exhibited higher noise (13e) than during tests at Cambridge (5e); In Oct 92 it was returned to Cambridge, for examination. The problem was traced to a noisy preamp. connection. The head was returned to ING in Nov 92; the preamp-gain was increased (to give minimum noise, for spectroscopic applications).

26

This super-grade sensor is similar to the EEV5 one, and is now the default on the JKT, where it has replaced the GEC head.

27

This is a GEC small-format sensor; it has been thinned and Metachrome-coated. It has lower noise, but is less uniform than the RCA2 head. For use on INT/JKT.

29

Replacement chip for GEC3; used on various instruments.

30

Duplicate of TEK1, with a larger cryostat. 5 readout speeds now introduced. Installed at WHT Prime Focus, but also for use on ISIS and UES.

33

The new Tek head (for INT), which is mechanically similar to TEK2 (larger 2.5l cryostat). Delivered to ING in May 94, with extra readout modes and speeds. Simultaneous binning with window, and a double-window mode.