Astrometric eyepiece observations of Carina Double Stars
Magda Streicher
Introduction
I have been using a 12mm Meade MA astrometric eyepiece with my 12 and 16-inch telescopes based in Limpopo Province in South Africa. A picture of the 16-inch appears in the Webb DSO (1). The Meade has an LED illuminator, a linear scale, a semicircular position angle scale as well as a full circular scale and double cross-line concentric circles (see Argyle(2) for a diagram). I have been using this eyepiece to measure southern double stars but first I determined the size of each division of the linear scale by taking a number of star transits. I timed twelve transits of a star at declination -60 with the drive turned off, each of which covered 50 divisions of the scale. The average time for one transit was 38.55 seconds which translates to 5”.8 per scale division and it was this figure which I used in the following observations.
Observations
HJ 3884 – CARINA – G8III – year 1918
RA: 06h37m.6 – DEC: -55o21’
Magnitude of stars: 6.9 and 10.8
Separation: 25.6” – Position Angle: 282
Tel: 12-inch – 76x – 218x – Date: 3 February 2003 – V: 5.8
Bathed in a light terracotta hue, the primary is accompanied by a grey companion. Known as a red star by John Herschel.
Tel: 16 inch 127x – 290x – Date: 28 February 2013 – V: 5
A lovely deep-terracotta primary and white-yellow companion. Metric eyepiece shows the stars separated by slightly less than 5 divisions giving an estimated separation of about 27”. The magnitude and position angle in the catalogue seem correct. Measure again field star it is more or less in a 279 PA.
I 480 – CARINA – B6/7V – year 1921
RA: 06h42m.9 – DEC: -55o07’
Magnitude of stars: 7.9 and 11
Separation: 5”.6 – Position Angle: 1
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
Only a dirty-white primary could be seen, the companion not visible. I noted that the star field towards the east is exceptionally beautiful with stars in strings and some visible doubles.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
The primary shines with an off-white colour, and I could see the companion in approximate position angle PA 358. I also pick up a faint star about magnitude 13.5 in a position angle of perhaps 207 and a separation of about 55”. Metric eyepiece measures of AB show they are separated by one division indicating a separation of 5.8” according to my telescope measurements.
I 483 – CARINA – K3III – year 1912
RA: 07h03m.3 – DEC: -57o30’
Magnitude of stars: 8.2 and 11.3
Separation: 11”.1 – Position Angle: 34
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
The primary displays a dark yellow, the companion could not be seen. A few visual doubles can be seen in the south-east in the field of view.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
No change, the indicated data seems to be correct. Metric eyepiece show just short of 2 divisions indicated 11”.5 between the two stars. The primary still in a dark yellow, companion shines with a white colour.
DUN 39 – CARINA – B9IV – year 1952
RA: 07h03m.3 – DEC: -59o11’
Magnitude of stars: 5.8 and 6.9
Separation 2”.5 – 1”.7 – Position Angle: 76 – 82
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
Lovely blue primary, the companion undetectable. A lovely string of 6 stars are lined up north-south 22’ towards the north-west.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
The combine double star had a definite oblong impression in around the same PA, indicate that the star is on the brink of been split. The separation must be less than 2”.5. The reason is that I split a 2” quite easy but this two seems to a real oblong impression. I should say around 1”.5 although the position angle is also debatable, found to be more PA 358 to 0? As measure with cross hair against field stars, just estimate. The other companion star was split easily in a position angle of 82.
COO 47 – CARINA – M1III – year 1923
RA: 07h05m.4 – DEC: -52o37’
Magnitude of stars: 7.9 and 10.7
Separation: 22” – Position Angle: 89
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
This double forms part of a string of stars situated from north-east to south-west. The primary appears as dark yellow bordering to orange with the companion a buttery yellow.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
The primary still shines in a dark yellow bordering to orange. The companion white/yellow in colour and seems correct position angle 90 as measure against stars in the field. Metric eyepiece show 3 full divisions indicate a separation of about 19”.
RMK 5 – CARINA – G9III + G9III – year 1954
RA: 07h10m.4 – DEC: -55o35’
Magnitude of stars: 7.7 and 7.9
Separation: 7” – Position Angle: 225
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
Two lovely yellow stars, though the primary has a shade of creamy-yellow, whereas the companion to the south-west appears a slightly yellow-white.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
Both the stars equal in a buttery yellow colour and magnitude. Metric eyepiece show a tad larger than 1 division which is more or less 6”.5 in separation. Measure against the field stars the position angle could be slightly less, around 220 perhaps.
HDO 304 – CARINA – A1/2V
RA: 07h12m.8 – DEC: -57o29’
Magnitude of stars: 6.8 and 10
Separation: 15” – Position Angle: 350
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
The primary appears as pure white, whilst the companion to the north seems a dirty white.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
A pure white primary and a grey-white companion. Metric eyepiece show close to 3 full divisions which indicate a separation around 17”. The position angle seems correct as indicated. Pick up a faint star around magnitude 14 in the PA 40 and about 50” away from the primary, could it be a companion?
HJ 3952 – CARINA – K1III – year 1917
RA: 07h16m.2s – DEC: -54o03’
Magnitude of stars: 7.2 and 11.9
Separation: 16”.2 – Position Angle: 227
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
Only one slightly dirty yellow star. Could not detect the faint companion.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
Primary displays a cream yellow with a light yellow-grey companion only glimpse the companion with averted vision at the indicated position. The companion could also be fainter than the indicated 11.9 magnitude, I would suspect around 12.5 in magnitude. The position angle could be gain up to 275 if measure against the stars in the field. Must check!
I 485 – CARINA – F5V – year 1926
RA: 07h19m.0 – DEC: -52o32’
Magnitude of stars: 8 and 10.8
Separation: 3”.1 – Position Angle: 356
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
The primary displays a dull yellow. The faint companion is lost in the primary’s glare, and as such could not be detected.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
The primary shines with a more subtle yellow with the companion a dull white-blue colour seen with ease. The position angle and separation seems to be correct.
DUN 87 – CARINA – M2IIIe – year 1919
RA: 10h30m.7 – DEC: -61o21’
Magnitude of stars: 6.6 and 7.6
Separation: 82”.6 – Position Angle: 331
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
Good contrast in colour with a deep-orange and white companion.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
In contrast just a beautiful pair. Primary appears yellow to orange, with a subtle white colour companion. Metric eyepiece show just short of 14 divisions which gave me an estimated separation of 80”.
I detect a very faint star around 14-magnitude at PA 290 less than 20” from the primary. Any unknown companions perhaps?
R 151 – CARINA – A0V – year 1913
RA: 10h31m.1 – DEC: -68o54’
Magnitude of stars: 7.6 and 9.
Separation: 3”.4 – Position Angle: 192
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
Although rather close, it can be split fairly easy. The primary appears as subtle cream with a light orange companion. Could the separation more than as indicated?
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
The primary appears in a cream colour with a yellow companion. The pair seems to be in the right position angle, magnitude and separation.
COO 107 – CARINA – G8/K0III – year 1934
RA: 10h35m.1 – DEC: -57o41’
Magnitude of stars: 7.0 and 9.9
Separation: 5” – Position Angle: 239
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
A light orange primary accompanied by an off-white secondary.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
Apart from the primary which is light orange with an off-white companion, there seems to be another member closer to the primary in more or less the same position angle perhaps less than 20” distant.
DUN 97 – CARINA – 1950 – B3III
RA: 10h43m.2 – DEC: -61o10’
Magnitude of stars: 6.6 and 7.9
Separation: 12”.4 – Position Angle: 174
Tel: 12-inch – 76x – 218x – 3 February 2003 – V: 5.8
Lovely grouping which displaying both the primary and companion as white in colour. Very busy star-field.
Tel: 16-inch – 127x – 290x – 28 February 2013 – V: 5
The pair seems to be as indicated although I should say the primary show a hint of a yellow hue to its colour. The magnitude, separation and position angle seems unchanged, but a busy star-field.
R 164 – CARINA – 1873 – B8IV
RA: 10h 59m.2 – Dec –61o19’
Brightness of stars: 6.5 and 10
Separation: 3”.7 – 4” – Position Angle: 83 – 78
Tel: 12-inch – 76x – 218x – 346x – 3 February 2003 – V: 5.8
The primary appears white, whilst the rather faint close secondary a very blue.
Tel: 16-inch – 127x – 290x – 462x – 28 February 2013 – V: 5
Primary still in a dull white colour with the companion in a real lovely blue although faint. The position angle could be slightly less.