Introduction

Publishing observations of double stars is a natural consequence when an observer feels confident enough in the quality of his or her measures that they feel it is time to share them with the rest of the astronomical community. A lot of effort has gone into this work so it is only fair that the observer should gain credit for it. There is no fixed formula which can be applied to decide whether measures are of publishable quality or not. But recent lists of bright, close (0.5 to 2") pairs (Mason et al.1) are available, so some comparison can be made to check on how good the agreement is. Other factors to consider include whether a particular pair has been observed many times or virtually ignored since discovery. A really accurate measure of a bright, relatively fixed, over-observed pair will not be as useful as a less accurate measure of a pair which has been ignored for 100 years or more, especially if it turns out that the latter has significant motion.

Measures can be published in several formats and in both professional and amateur journals but one thing cannot be over-emphasized. It is absolutely vital that the same measures are never published more than once since it can cause great confusion to the astronomers who collate all measures of visual binary data for the Observations Catalogue at the USNO in Washington. An example showing the publication of double star observations by the Webb Society can be seen in Figure 25.1. These data are the raw measurements and

(j09

Star

RA

Dec

Mags

PA

Sep

Epocli

N

Obs

S2434A-BC

1902.7

-0043

8.4, 8.8

92.S

26.40

2000.44

3

RA

Ï2455AB

1906.9

+2210

7.2, 9.4

28.7

8.42

2000.64

4

RA

/3248AB

1917.7

+2302

5.5, 9.0

131.3

1.74

2000.68

4

RA

£2497

1920.0

+0535

7.6, 8.5

356.3

30.3

2000.62

4

•IC

Ï2498AB

1920.2

+0403

8.4, 9.0

65.5

12.15

2000.68

4

JC

H84

1939.4

+ 1634

6.4, 9.5

.300.7

28.43

2000.68

3

RA

525S5AB-C

1949.0

+ 1909

5.0, 9.0

310.0

8.05

2000.68

4

RA

£2596

1954.0

+1518

7.0, 8.3

299.2

2.00

2000.10

4

IIA

S2607AB-C

1957.9

+4216

6.1, 8.9

2S9.9

3.1

2000.63

4

JC

S730AB

2000.1

+1737

7.0, 8.4

14.0

112.45

2000.69

3

RA

S730AC

2000.1

+1737

7.2, 9.5

337.1

78.12

2000.72

3

RA

H100AB

2000.2

+1730

9.5,10.3

256.1

24.11

2000.78

4

JC

H100AC

2000.2

+1730

9.5, 5.6

295.7

113.7

2000.81

4

JC

S2615

2002.9

+0824

7.9,10.8

304.3

9.15

2000.64

4

JC

52653

2013.7

+2414

6.6, 9.5

275.4

2.7

2000.68

4

JC

Figure 25.1. An example of double star measures published in the Webb Society Double Star Section Circulars.

other tables contain notes on systems of interest and residuals from known orbits where applicable.

The paper should contain details of the micrometer type, the instrumental constant and the magnification employed.

The format of any list should contain the following information:

Identifier Currently the standard is the WDS

format (see Chapter 24). This also includes the J2000 position.

Catalogue An alternative identification, not always necessary but it can be useful when using star atlases and catalogues such as Burnham, Webb's Celestial Objects and the Sky Catalogue 2000.0.

Mean position This should be the mean value from angle the individual nightly values. Usually quoted to one decimal place for visual work but CCD astrometry may justify more. Avoid using angles greater than 360.0.

Number of PA The number of independent nights measures from which the mean is formed. This will usually be the same as the number of nights used for the mean separation.

Mean separation In arcseconds, usually quoted to two decimal places - if the observer con-

Number of separation measures

Mean epoch

Observer

Orbit residuals siders this to be a fair reflection of the scatter in the individual measures.

As for position angle. It may be for a highly inclined binary where the change is nearly all in separation that more measures in separation would be a sensible approach. Usually quoted to two decimal places in visual work.

This is much easier to work out if each individual night is converted to a decimal of a year in the observing log. A day is 0.0027 of a year so midnight on 2001 Jan 10, for example, is 2001.027. It is quite sufficient to use the midnight value for that night and in fact mean epochs can be quoted to two decimal places for most small telescope observations. Chapter 22 contains a short algorithm to calculate decimal date from calendar date - use program JD&Epoch from the CD-ROM.

This will usually be given at the head of the paper for a single author. Usually a two-letter code is inserted at the end of each line in the data table if the list contains the measures of more than one observer. Those whose measures are included in the WDS Observations Catalogue are given a three-letter identifier by the compilers.

The differences (observed - computed) for both position angle and separation from the orbit for every epoch of observation. Include the author of the orbit and its date of publication. Include other orbits if there is little to choose between them. The CD-ROM contains the latest version of the orbital elements catalogue published by the USNO.

The following data can be given depending on taste:

(i) Difference in magnitude: usually estimated visually to 0.1 magnitude.

(ii) Standard error of position angle and separation. calculated from the individual measures that make up the means.

(iii) A note of whether the eyes were vertical to the wires (:) or parallel to the wires (..) when the observations were made.

(iv) The quality of the night - transparency and seeing, for instance.

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