Sketch of Xi Scorpii (Struve 1998) and Struve 1999
Click image to view larger version.
Observation Notes:
There are a number of double-doubles scattered across the sky. Although Epsilon Lyrae may be the best known, there’s really some great competition out there. Xi Scorpii/Struve 1998 and its southern counterpart, Struve 1999, are a brilliant and beautiful sight in the northern reaches of the scorpion. These two yellow/orange pairs are separated from each other by under 5 arc minutes.
Struve 1998 appeared as a bright yellow primary with an orange secondary 8 arc seconds to the northeast. The primary of Struve 1998 is itself another close double, separated by 0.9 arc seconds. I just made out its pill-shaped elongation and roughly measured a PA of 1 degree. It’s actual position is 10 degrees further clockwise at PA 351 degrees. Struve 1999 was a fainter pair and the color more subtle, but still a yellow primary with an orange secondary 11 arc seconds to the east.
This is definitely another sight not to be missed by the double star enthusiast. Be sure to catch it next summer!
| Subject | Xi Scorpii/STF 1998 and STF 1999 (ADS 9909 and ADS 9910) |
| Classification | Multiple Star |
| Position (J2000)* | STF 1998: Scorpius [RA: 16 04 22.3 / Dec: -11 22 20] STF 1999: Scorpius [RA: 16 04 25.9 / Dec: -11 26 57.8]* |
| Position Angle | STF 1998 AB: 1° [My Measurement 2009.3] 351° [WDS 2008]* AC: 47° [My Measurement 2009.3] AC: 41° [WDS 2005] STF 1999 |
| Separation | STF 1998 AB: 0.7″ [My Measurement 2009.3] 0.9″ [WDS 2008]* AC: 8″ [My Measurement 2009.3] AC: 7.9″ [WDS 2005] STF 1999 |
| Magnitudes* | STF 1998 – A: 4.9; B: 5.2; C: 7.3 STF 1999 – A: 7.5; B: 8.1; C: 11.0; D: 4.4 |
| Spectral Types* | STF 1998 – A: F5IV; B: G1V; C: F7IV STF 1999 – A: G8V+; B: K1V(k) |
| Date/Time | APR 5, 2009 – 2:15 AM (APR 5, 2008 – 09:15 UT) |
| Observing Loc. | Flagstaff, AZ – Home |
| Instrument | Orion SkyQuest XT8 Dobsonian (203 mm dia./1200 mm F/L) |
| Eyepieces/Mag. | Pentax XW10 + 2X Barlow (240X) Meade Astrometric EP + 2X Barlow (200X) |
| Conditions | Clear, light breeze |
| Seeing | 5/10 Pickering |
| Transparency | Mag 5.2 NELM |
| *References | The Washington Visual Double Star Catalog (Mason+ 2001-2009); Catalogue of Stellar Spectral Classifications (Skiff, 2009); SIMBAD |
Jeremey,
Thank you for this run of excellent double star sketches (from back in April?); Xi Sco is particularly inspiring and the split-view close-up is a nice touch.
Looking forward to seeing what you post here next…
Eric
My pleasure, Eric 🙂
I’m wondering if I’ll be sorry later that I did the half-cut lunch sandwich approach on the detail inset. I considered doing two whole boxes–one for each double–but these images are huge as it is.
I’ve got 2 more double stars to post from the way back machine. Then I can start posting a batch of 11 I just completed a couple weeks ago from Leo & surroundings–including another spectacular double-double.