Alpha Herculis (Rasalgethi / Struve 2140)

Sketch of Alpha Herculis (Rasalgethi/Struve 2140/STF 2140)

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.

SubjectAlpha Herculis (Rasalgethi / STF 2140 / ADS 10418)
ClassificationDouble Star
Position (J2000)*Hercules [RA: 17 14 38.9 / Dec: +14 23 25.2]
Position Angle111° [My Measurement 2009.3]
105° [WDS 2007]*
Separation6" [My Measurement 2009.3]
4.8" [WDS 2007]*
Magnitudes*A: 3.5; B: 5.4
Spectral Types*A: M5Iab; B: F2V
Date/TimeAPR 5, 2009 - 3:45 AM (APR 5, 2008 - 10:45 UT)
Observing Loc.Flagstaff, AZ - Home
InstrumentOrion SkyQuest XT8 Dobsonian (203 mm dia./1200 mm F/L)
Eyepieces/Mag.Pentax XW10 + 2X Barlow (240X)
Meade Astrometric EP + 2X Barlow (200X)
ConditionsClear, light breeze
Seeing7/10 Pickering
TransparencyMag 5.5 NELM
*ReferencesThe Washington Visual Double Star Catalog (Mason+ 2001-2009); Catalogue of Stellar Spectral Classifications (Skiff, 2009); SIMBAD



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,

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This page contains a single entry by Jeremy Perez published on December 8, 2009 10:31 PM.

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