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Specifying Telescope Details in the Observational Header

It is important that information supplied by observers in the observational headers accompanying each batch of observations be checked for validity before the information is published in the MPCs or the MPECs. Unverified material should not be permitted into either journal. Due to the volume of incoming observational material, it is impractical to inspect manually all incoming batches for compliance of header material with the requirements listed on these pages. Such verification must be handled entirely automatically. To this end, it is necessary for observers to follow broad guidelines when supplying information with all the keywords in the observational header. Historically, the most problems have come from the descriptions of the telescopes (specified using the TEL keyword).

This document describes how to format the information contained on the TEL line so that the automatic processing code can make sense of it.

1: The TEL Line

A valid TEL line consists of an ASCII line containing TEL in columns 1-4, followed by one or more telescope descriptors. A telescope descriptor describes a single instrument, in a format consistent with the descriptions below. If more than one telescope descriptor is given on the same TEL line, the descriptors must be separated by commas followed by a space.

TEL <descriptor>[, <descriptor>]...

where items enclosed in square brackets are optional, ... indicates possible multiple repeats of the preceding item, and characters not surrounded by <> are string literals.

In the descriptions below <real> indicates a positive real number, either integer or non-decimal: if the value is less than 1, a leading zero must be given. Examples of valid values are "1", "3.44" and "0.76". Also, <int> indicates a positive integer, and | indicates a logical OR.

2: The Notification Process

As of 2004 August 2, the automated acknowledgement message includes information on the success or otherwise of the processing code's understanding of the TEL lines included in each submission.

This notification includes a list of each TEL line found in your message, followed by the value extracted by the processing code. Then follows one of three summary messages, informing you that:

  • Your TEL lines are completely compliant with this document.
  • Your TEL lines are not completely compliant with this document, but the processing code thinks it has corrected them.
  • The processing code couldn't understand your TEL lines.

If you get the second or third summary message, you are pointed to the observational header documentation, in the hope that future TEL lines will be specified correctly.

3: The Correction Process

The processing code has the ability to fix malformed descriptors. It is not possible to fix all malformed descriptors in an entirely automatic fashion (and some are so malformed, it is even difficult to do the fix manually!), but the processing code applies a series of rules to each malformed descriptor it finds, trying to make the descriptor valid.

The complete rules by which the processing code attempts to fix incoming headers will not be documented. Suffice to say, the code will cope with many types of malformed descriptors. However, the notification procedure now informs observers when their TEL lines require fixing, so observers should make their TEL lines valid on future batches.

If you get back a message saying that the processing code could not understand or changed what you believe to be a valid TEL line, please report this immediately. Be sure to include the observational header (please do not include the observations).

4: The Simple Description

For most observers, the simple description of telescope descriptors given below (it is also described elsewhere) will be sufficient:

<descriptor> = <aperture> [<f/ratio> ]<instype>[ + CCD][ +[ <f/ratio>] focal reducer]

where:

  • <aperture> is the aperture of the instrument in meters: <aperture> = <real>-m. E.g., "0.50-m" or "1.0-m". If the aperture is given to more than two decimal places, the value will be rounded to two decimal places.
  • <f/ratio> is the focal ratio of the instrument or the focal reducer: <f/ratio> = f/<real>. E.g., f/6.7 or f/3. If the focal ratio is given to more than two decimal places, the value will be rounded to two decimal places.
  • <instype> is the type of the instrument. Types have to match one of the types listed below.

Simple Examples

The following examples of TEL lines have been verified as correct by the code that vets incoming observation batches:

TEL 0.30-m Schmidt-Cassegrain + CCD
TEL 0.6-m f/6 reflector + CCD
TEL 0.28-m f/4.3 reflector + CCD
TEL 0.41-m f/10 Schmidt-Cassegrain + CCD + f/6.3 focal reducer
TEL 0.15-m f/12 refractor

5: The Full Description

The full description of telescope descriptors is as follows:

<descriptor> = <aperture>[/<aperture>] [<f/ratio> ]<instype>[ +[ <CCDsize>][x<CCDsize>] CCD][ +[ <f/ratio>] focal reducer][ + <extra>]

where the items are as defined in the Simple Description, with the addition of the following:

  • <CCDsize> is the size in pixels along one dimension of the CCD. <CCDsize> = <int>|<int>K. Examples of valid values are "2048" and "8K". For a square CCD it is anticipated that only one value be given: e.g., "1024". For rectangular CCDs, the sizes in both dimensions should be given: e.g., "8Kx1K".
  • <extra> is an "extra", taken from the list of allowable extras listed below.

Detailed Examples

The following examples of TEL lines have been verified as correct by the code that vets incoming observation batches:

TEL 2.2-m University of Hawaii reflector + 8K CCD
TEL 0.5-m/0.8-m Schmidt + CCD
TEL 3.58-m New Technology Telescope + EMMI-RILD system

6: Defined Types of Instrument

The list of defined instrument types is as follows:

Ritchey-Chretien         Schmidt-Cassegrain       Schmidt
Newtonian reflector      Cassegrain reflector     Cassegrain
hyperbolic astrograph    double astrograph        visual astrograph
astrograph               reflector                refractor
Deltagraph               Hypergraph               Maksutov-Newtonian
Maksutov-Cassegrain      Maksutov                 Schmidt-Newtonian
Coude                    Corrected Dall-Kirkham   Riccardi-Honders

Requests to allow further instrument types will be entertained.

In addition, there are a number of named professional instruments that are permitted:

University of Hawaii reflector          Spacewatch telescope
KLENOT Telescope                        Canada-France-Hawaii Telescope
New Technology Telescope                Danish Telescope
Nordic Optical Telescope                Keck IV
Keck III                                Keck II
Keck I                                  LONEOS Schmidt
Uppsala Schmidt                         Oschin Schmidt
Isaac Newton Telescope                  Hale reflector
Jacobus Kapteyn Telescope               Perkins reflector
GEODSS telescope                        Plaskett telescope
Subaru Telescope                        SoTIE reflector
SALT                                    MMT
Calar Alto reflector                    CTIO reflector
WIYN reflector                          Gemini North
Gemini South                            VLT UT1
VLT UT2                                 Lowell Observatory Discovery Channel telescope
Discovery Channel Telescope             Magellan-Baade telescope
Magellan-Clay telescope

A number of common abbreviations of the above-listed named telescopes are also allowed. These are expanded to the full name by the processing code:

UoH  -> University of Hawaii
CFHT -> Canada-France-Hawaii Telescope
NTT  -> New Technology Telescope
NOT  -> Nordic Optical Telescope
INT  -> Isaac Newton Telescope

Requests to allow further named professional instruments will be entertained.

7: Defined Extras

The list of extras is as follows:

prime-focus corrector    90prime camera           EMMI-RILD system
WFI system               MegaCam

Requests to allow further extras will be entertained.