Sketch of Alpha Herculis (Rasalgethi/Struve 2140)
Click image to view larger version.
Observation Notes:
Rasalgethi is a fantastic, colorful double. The bright primary shone a yellowish orange with--get ready for it--a sage green secondary. The diffraction pattern was captivating in better than normal seeing.
| Subject | Alpha Herculis (Rasalgethi / STF 2140 / ADS 10418) |
| Classification | Double Star |
| Position (J2000)* | Hercules [RA: 17 14 38.9 / Dec: +14 23 25.2] |
| Position Angle | 111° [My Measurement 2009.3] 105° [WDS 2007]* |
| Separation | 6" [My Measurement 2009.3] 4.8" [WDS 2007]* |
| Magnitudes* | A: 3.5; B: 5.4 |
| Spectral Types* | A: M5Iab; B: F2V |
| Date/Time | APR 5, 2009 - 3:45 AM (APR 5, 2008 - 10:45 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 | 7/10 Pickering |
| Transparency | Mag 5.5 NELM |
| *References | The Washington Visual Double Star Catalog (Mason+ 2001-2009); Catalogue of Stellar Spectral Classifications (Skiff, 2009); SIMBAD |
Spectacular!
Wonderful job in drawing the diffractionrings.
Have you drawn those digitally or by hand?
Hi Harro, thank you. When I'm at the eyepiece, I first make a rough sketch of what the diffraction rings look like. You can see a basic example here: Double Star Log Sheet. For doubles that are separated by just a few arc seconds, I try to estimate how many diffraction ring radii separate them and note that on the rough sketch. That sample I linked to is an earlier set of drawings. Since then, I've tried to make a greater effort to portray the general nature of the flickering patterns in the rough drawing--showing the rings, arcs, speckles and diffraction spikes that the stars, scope and the atmosphere are portraying for me.
After scanning the drawing, I use Photoshop to re-create what I roughly sketched using different paint brushes, layers, masks, and filters. I've experimented with a lot of different methods to try and display a snapshot of what I saw. It has gotten to be a little complex, so it takes a while to get each sketch processed and posted. I've still got a decent backlog of sketches I need to finish up.
Thanks for asking the question,
Jeremy