Category: double

A Smoky Cascade

IC 1318(c)

IC 1318(c)
Sketch and Details by Eric Graff

Object Name: IC 1318(c) (West Extension)
Also Known As: LBN 236, LBN 240, LBN 241, DWB 52, GAL 077.7+03.4
Object Type: Emission Nebula
Constellation: Cygnus
Right Ascension (2000.0): 20h 17.1m
Declination (2000.0): +40° 50′
Magnitude: —
Size: 40′ x 25′

Date/Time: 27 July 2008 • 05:45 to 07:00 UT
Location: Oakzanita Springs, San Diego Co., California, USA
Telescope: Parks Astrolight EQ6 • 6″ f/6 Newtonian Reflector
Eyepiece/Magnification: Parks 20mm Gold Series Plössl • 45x • 70′ FoV
Filters: Lumicon OIII
Conditions: Clear, Calm, 64°F
Seeing: Pickering 6-7
Transparency: NELM 6.4; TLM 14.2

This cascade of stars shrouded in smoky wisps of nebulosity caught my attention as I made the star hop from Gamma Cygni to IC 1318(b). The cascade ends at the sparse open cluster Collinder 419, whose brightest star is a close pair known as Struve 2666 (6.0, 8.2; 2.6″; 245°). Just northeast of this cluster the narrow stream of nebulosity blossoms into a hazy morass of delicate nebulosity – this is IC 1318(c). Fifth magnitude HD 193092 blazes with a reddish-orange light to the south.

Sketch Info: Nebulosity sketched with graphite applied with artist chamois and blending stump on 24# paper in 7½” circle. Stars with pencil and ink, cleaned up digitally (and colorized) in Microsoft Picture It!

A Double and a Trifid

M20

M20 (The Trifid Nebula)
Sketch by Eiji Kato

M20, The Trifid Nebula, is a famous and beautiful target for astro-photographers. The red emission nebula contains a young star cluster at its center, and is surrounded by a blue reflection nebula that is most noticeable at the northern end. It’s distance is not well agreed upon, and is listed anywhere from 2,200 light years (Mallas/Kreimer) to 9000 light years (Jeff Hester).

The dark nebula that crosses the Trifid was cataloged by Barnard and listed as B 85. The object was originally cataloged by Charles Messier in 1764, when he described it as a cluster of stars. William Herschel assigned catalog numbers to 4 different parts of the nebula (H IV.41, H V.10, H V.11, and H V.12).

Graffias of Scorpius

Beta Scorpii

Beta Scorpii (Graffias)
Sketch by Michael Vlasov

This pair of hot B-class stars lies about 530 light years away. Their separation of 14 arc seconds places them at least 2200 astronomical units from each other. Beta-1 has another companion hugging it much closer at .5 arc seconds. Both Beta-1 and Beta-2 are also thought to be spectroscopic binaries, bringing the total number of stars in the system to 5.

Source: Wikipedia.

Porrima’s Clockwise Progression

Gamma Virginis

Gamma Virginis
Sketch and Details by Jeremy Perez
Move mouse over sketch to compare change in position from January 2007 to April 2008.
Click the image for a larger version.

About 38 light years away in the constellation Virgo, this pair of twin stars orbit one another once every 169 years. When I last observed them in January 2007, they appeared as a single, elongated, pill-shaped star. On April 10, 2008, the diffraction discs were now clearly separated into two distinct stars with no overlap. Position angle had also proceeded about twenty degrees clockwise since my last look.

During my January 2007 observation, I estimated a position angle of 60 degrees. However, the data in Brian Workman’s Double Star calculator indicated they should have been 49 degrees. I thought this was strange at the time, since I would probably have guessed 45 degrees if that were the case. Recently, I had a look at some more refined data provided by Brian Skiff. Plugging that into the calculator led to January 2007 value of 58 degrees–much closer to my estimate at the time.

For the April 10, 2008 observation, I was able to put the astrometric eyepiece to use on the pair, and arrived at a position angle of 36 degrees. Skiff’s data points to a value of 37.9 degrees. Based on diffraction discs that are not quite touching, I estimated a separation of .92 arc seconds. Skiff’s data comes out to .993 arc seconds.

I was excited to see such a pronounced difference since last year. What a privilege to watch the slow dance of this stellar couple.

Subject Gamma Virginis (Porrima / STF 1670)
Classification Double Star
Position (J2000) Virgo [RA: 12:41:39.9 / Dec: -01:26:58]*
Position Angle* 36° [My measurement 2008.27]
37.9° [Skiff Data interpolated 2008.27]
Separation* 0.92″ [My measurement 2008.27]
0.993″ [Skiff Data interpolated 2008.27]
Magnitudes* 3.6; 3.7
Spectral Types* –
Date/Time APR 10, 2008 – 10:30 PM MST (APR 11, 2008 – 05:30 UT)
Observing Loc. Flagstaff, AZ – Home
Instrument Orion SVP 6LT Reflector (150 mm dia./1200 mm F/L)
Eyepieces/Mag. 12 mm Meade Astrometric Eyepiece+ 2X Barlow (200X)
Conditions Clear, calm, first quarter moon
Seeing 6/10 Pickering
Transparency NELM Mag ~5.0
*References The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); Brian Workman’s Double Star Calculator (Using orbital elements supplied by Brian Skiff)

Ripples Around Castor

Castor

Castor (Alpha Geminorum / Struve 1110)
Sketch and Commentary by Jeremy Perez

The fussy seeing provided a beautiful view of this brilliant double. The diffraction patterns shimmered and danced, adding a bit of challenge to viewing the pair, but also providing a mesmerizing, speckled light show. The primary of Castor appeared bright white while its companion hinted at a subtle blue.

Measuring this duo using the Dobsonian scope was very challenging. I was attempting the PA measurement without my external dial, and although it was very tough to get the primary to drift through the exact center of the eyepiece, the measurement worked out fairly well–differing from Workman’s calculated 2008.2 value by only .8 degrees. The separation estimate was worse though, since I couldn’t track and allow the stars to hover over the scale. (My estimate of 6.9 arc seconds was a bit over compared to the calculated value of 4.5 arc seconds).

Subject Alpha Geminorum (Castor / STF 1110)
Classification Multiple Star
Position (J2000) Gemini [RA: 07:34:35.7 / Dec: +31:53:16]*
Position Angle* 59° [2008.2 my measurement]
58.2° [2008.2 Brian Workman’s DS Calculator]
Separation* 6.9″ [2008.2 my measurement]
4.5″ [2008.2 Brian Workman’s DS Calculator]
Magnitudes* 2.0 / 2.9
Spectral Types* A1V / A2Vm
Date/Time MAR 19, 2008 – 10:45 PM MST (MAR 20, 2008 – 05:45 UT)
Observing Loc. Phoenix, AZ
Instrument Orion XT8 (203 mm dia./1200 mm F/L)
Eyepieces/Mag. 10 mm Sirius Plössl + 2X Barlow (240X)
12 mm Meade Astrometric EP + 2X Barlow (200X)
Conditions Mostly Clear, Gibbous Moon
Seeing 3-4/10 Pickering
Transparency NELM Mag ~4.0
*References The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); Starry Night Pro Plus 5.8

Head of the Twin

Castor

Alpha Geminorum or Castor
By Wade V. Corbei

Geeze…I so enjoy the oncoming winter and the splendid objects and constellations that it offers. Below is a sketch of Castor, the double star that makes up one of the “heads” of Gemini, The Twins. In Arabic Castor is called Al-Ras al-Taum al-Muqadim, meaning “The Head of the Foremost Twin”.

Both stars seemed close to the same size and magnitude, being 2.8 and 2.0 respectively, with just a hint of a blue fringe around both. A close double that is easily split with higher magnifications.

Wade V. Corbei

Double Delight

Epsilon Perseus

Epsilon Perseus
By Wade V. Corbei

Epsilon Perseus

Here is a simple Double Star (and another I never knew about until dilly-dallying with the COL). I don’t know if this is normal for the primary star, but on the night I observed this double, there was a large halo surrounding the star in addition to the diffraction spikes.

I have noticed that there are times when some stars have a halo or diffraction spikes (although I think this is the only time I have seen both at the same time, I’ll have to check my notes); and other times they have none.

Is this a result of weather/atmospheric conditions by chance. It seems as if I notice these oddities when it is getting damp or dewey.

Colorful Witness to Tombaugh’s Discovery

Delta Geminorum

Delta Geminorum

By Wade V. Corbei

This is an interesting double star (in all actuallity a Binary star) found in the constellation Gemini (as noted by the name). The Primary star is much larger than the companion star, and appears as a yellowish-white, while the companion appears as a nice contasting purple. Delta Geminorum also holds a historic significance as well, as in 1930 Clyde Tombaugh discovered the planet Pluto 1/2° east of this star.

A unique star with an equally interesting history.