Author: Webmaster

Neil Webster, REDACTED

e-mail:     REDACTED

Introduction

The following measurements were made throughout 2017 using a Meade 12mm astrometric illuminated reticle eyepiece plus 2.5x powermate attached to a Altair Astro 115mm refractor (focal length 805mm, f7). The total magnification was 167.5x with a field of view of 0.3 degrees.

All final separation values were calculated from a calibration determined by the timing/transit method (Simple Techniques of Measurement: E.T.H. Teague, Chapter 12 in Observing and Measuring Visual Double Stars ed. Argyle, pub. Springer). The final calculated value used was:

12^’’.49 +/- 0^’’.04 per division on the reticle measuring scale.

Position Angle measurements were made using the method previously outlined in DSSC 25 which involves using the directional west arrow on the handset to electronically steer the primary to the outer edge of the protractor scale rather than turning off the mount motor for an unaided drift. This has proven to be very reliable and greatly increases the number of measures that can be performed during an evening. As previously stated it relies on as precise polar alignment as possible.

10 separation and 10 position angle measurements (N = 20) were performed on the same evening for each pair and the final results and associated uncertainties calculated.

Extensive use was made of the Astroplanner software. Separations throughout the year were limited to a range from 15 arc-seconds to 100 arc-seconds. The faintest magnitude measured was 8.5. These values were out of necessity given the limiting magnification, the high calibration value and the considerable local light pollution. The red light in the eyepiece, even when used at its minimum intensity, also limits the faintest magnitude that can be reasonably measured.

These parameters were set up in the software for whatever constellation was convenient at the date of measurement. All measurements made on any evening were for doubles in close proximity (usually in order of increasing RA) so time was not wasted slewing between distant pairs. This allowed far more measurements to be made than for previous years.

As most of these systems are comparatively wide the orbits are generally very long (1,000 years+) and very few have accurate orbital calculations. Residuals (from the online version of 6^th USNO Catalogue of Orbits of Visual Binary Stars) have been given for the few systems calculated but none have a better than grade 4 certainty.

Values from the Fourth Catalogue of Interferometric Measurements have provided a more extensive set of residuals but most of these are from 1991 which is 26 years before the author’s measurements. Although many of the systems have not changed in this time some have and, in certain cases, this shows in the larger residuals calculated.

Where residuals are large (greater than 1^o in PA or 1” in separation) relative proper motions have been analysed. Any notable differences between the components’ proper motions that may explain the larger than average residuals are presented in table 4.

Table 5 presents three alternative, more favourable residuals for three systems that have larger than expected residuals.

It should be stressed that these final two tables represent very basic analysis and further professional data and work would be needed to clarify the exact natures and evolving properties of these systems.    

References:

The Cambridge Double Star Atlas, (Mullany J. Tirion W. pub. Cambridge)

Observing and Measuring Visual Double Stars (ed. Argyle R.W. pub. Springer)

Washington Double Star Catalogue (Mason, B.D., Wycoff, G.L. & Hartkopf, W.I.):

http://ad.usno.navy.mil/proj/WDS

Sixth Catalogue of Orbits of Visual Binary Stars (Hartkopf, W.I., Mason, B.D. & Worley, C.E.):

http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6/sixth-catalog-of-orbits-of-visual-binary-stars

Fourth Catalogue of Interferometric Measurements of Binary Stars:

 http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/int4

Astroplanner:

 http://www.astroplanner.net/

Table 1: Measurements

Table 2: Residuals from Known Orbits

(All Residuals: Observed – latest Catalogue measurement)

Table 3: Residuals from Fourth Catalogue of Interferometric Measurements

Table 4: Doubles with significant proper motion differences

(All Proper Motions: WDS 2017)

Table 5: Alternative Residuals

*Fourth Interferometric Catalogue gives a PA of 15.5 degrees?? WDS (2015) gives 197 degrees and NW measured 194 degrees.

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Neil Webster, REDACTED
E-mail : REDACTED

Introduction

The following measurements were made with a Meade 12-mm astrometric illuminated reticule eyepiece attached to a recently purchased Altair Astro 115-mm refractor (focal length 805mm, f7). The optical train also employed a 2.5x Powermate to give a total magnification of 167.5x. Calibration was achieved over two evenings using the timing transit method as outlined in Teague1 Three separate stars were used and the results (reassuringly close) averaged to give a calibration of: 12".49 ± 0".4 per division on the measuring scale.

Method

Earlier attempts with a smaller scope (SIV 80-mm APO) had indicated the necessity of taking multiple readings to achieve a credible result. Unless stated, each system has 10 separation and 10 position angle measurements (N 20) from which a final result and associated uncertainty were calculated. As expected the later results were, overall, found to be closer to \VDS values especially in P.A. Early P.A. values were made by turning the motor off and allowing the primary to drift and cross the, outer protractor scale. The scope was moved manually in R.A. to allow further measurements to be made. However, even with a relatively small system this was not easy and the following method was adopted:

With the motor on, the two stars were positioned parallel to the measurement-axis with the primary positioned to pass through the centre-point. The system was then steered to the outer scale using the R.A. control on the handset. The value that the primary passed through was noted and the appropriate conversion to the correct P.A. value made afterwards.
This has the advantage that repeated measurements can be, easily made and the scope can be easily slewed to the next system afterwards. The PA results were seen to immediately improve using this method. It, of course, relics on precise polar alignment of the mount so movement in declination is at an absolute minimum.

Duc to the small magnification of the, system the limiting useful minimum separation measurement is about 14" . The accuracy of PA for small separations is also harder to achieve especially if the secondary is very faint. The faintest magnitude used for measurement was 10.3 due partly to local light pollution but also due to the obscuring rcd light used to illuminate the measuring eyepiece.

As most of these systems arc comparatively wide the orbits are, generally very long (30,000 years ) and very few have accurate orbital calculations. Residuals (from the online version of 6th USNO Catalogue of Orbits of Visual Binary Stars) have been given for the few systems calculated.

Residuals from the Fourth Catalogue of Interferometric Measurements have provided a more extensive set of residuals.

References

(1) Teague, E. T. H. (2012) in Argyle, R. W. (ed.), Observing and Measuring Visual Double Stars, Springer
(2) The Cambridge Double Star Atlas, (Mullany J. Tirion pub. Cambridge)
(3) Washington Double, Star Catalogue (Mason, B.D., Wy-coff, G.L. Hartkopf, w.l.):
51
(4) http : // ad. usno . navy .mi1/proj/WDS
(5) Sixth Catalogue of Orbits of Visual Binary Stars (Hartkopf, NV.I., Mason, B.D. & Worley,
http : / /www.usno . navy . mil/USNO/astrometry/optical- IR-prod/wds/orb6/sixth- catalog-of-orbits-o (6) Fourth Catalogue of Interferometric Measurements of Binary Stars:
http : //www.usno . navy. mil/USN0/ astrometry/ optical-IR-prod/wds/int4

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Full Report and tables of results

NW Webb 2016 Report

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