[Lvas] Spring 2009 Supplemental Observers Challeng - The Virgo Diamond

Sun May 10 18:42:03 PDT 2009

MONTHLY OBSERVER’S CHALLENGE
Compiled by:
Roger Ivester, Boiling Springs, North Carolina
&
Fred Rayworth, Las Vegas, Nevada

Supplemental
Spring 2009 – The Virgo Diamond

Introduction
The purpose of this observer’s challenge is to encourage others to take up visual observing.  It is open to everyone that is interested, and if you are able to contribute notes, drawings, or photographs, we will be happy to include them in our monthly summary.  Observing is not only a pleasure, but an art.  With the main focus of amateur astronomy on astrophotography, many times people tend to forget how it was in the old days before cameras, clock drives, and GOTO.  Astronomy depended on what was seen through the eyepiece.  Not only did it satisfy an innate curiosity, but it allowed the first astronomers to discover the beauty that is free for the taking.
Before photography, all observations depended on what the astronomer saw in the eyepiece and how they recorded their observations.  This was done through notes and drawings and that is the tradition we are stressing here today.  By combining our visual observations with our drawings, and sometimes, astrophotos (from those with the equipment and talent to do so), we get a unique understanding of what it is like to look through an eyepiece, and to see what is really there.  The hope is that you will read through these notes and become inspired to take more time at the eyepiece studying each object, and looking for those subtle details that you might never have noticed before.  Each new discovery increases one’s appreciation of the skies above us.  Please join us and learn how to get the most from peering into an eyepiece.
Virgo Diamond
For the visual observer, there is nothing more exciting than seeing the unusual.  When one considers a bunch of deep sky observers wowing over a tiny asterism instead of some faint fuzzy, what is there to get excited about?  The short answer is that not only is the Virgo Diamond a challenging object to find by star hopping, it is also not your run-of-the-mill asterism.  What you will see is a small clump of four (or five) stars that form an almost perfect diamond shape.  It is located in Virgo in an area relatively free of bright stars, or galaxies.  If one elects to find it the old fashioned way with star hopping, it is a real challenge.  The 2000 coordinates are:  RA: 12h 32m.8  Dec: -0° 39’.
The magnitudes of the four main stars range from 10.8 to 13.7. However, seeing the fifth star is especially hard with anything less than a 12” aperture.  It is somewhere at the dimmer end of 13th magnitude, but is close to one of the other stars and is hard to split.
In the December 1, 1991 Monthly Notices of the Royal Astronomical Society, Noah Brosch (Tel Aviv University, Israel) discusses his investigation of a newly discovered asterism in Virgo.  He noted five stars all appearing brighter than 13th magnitude, comprising a diamond shaped area with sides only 42 arc seconds long.  The probability is small that five stars with similar brightness could be so closely aligned by chance, and Brosch suggest that that the stars of the diamond are physically associated.
Roger Ivester’s fascination with this object came from an article in the May 1993 issue of Sky and Telescope, Page 110. Since then, he’s repeatedly observed this unusual and virtually unknown asterism.  It prompted our supplemental observing challenge for spring 2009, and includes notes from a group of amateur’s around the country. The contributors this time are:  Roger Ivester, Fred Rayworth, Tom English, David Blanchette, Dr. James Dire, Dr. Don Olive, and Hap Griffin. This is what they saw:
Observations/Drawings/Photos
Roger Ivester (see roger .jpg): Observer from North Carolina
Roger first observed this faint and small asterism on April 14th 1993 using a 10-inch f/4.5 equatorially mounted telescope. He said it required a minimum of 150x to see four of the components. He has been unable to see all five stars. The diamond presents itself as an almost perfect diamond shape, with the northern and western stars being brighter than the south and eastern stars. On nights of poor seeing it can be difficult to see the two fainter stars with his 10-inch.
Roger would be most interested in finding out how this object is presented in a larger scope. He would also be interested in finding out what is the smallest scope to show all five stars. Since that night in 1993, he has observed this faint asterism on many occasions, always failing to see the fifth star with his 10-inch (see rogersdiamond.jpg).
Fred Rayworth (see fred.jpg): Observer from Nevada
He used a Meade 16” f/4.5 LightBridge. His eyepieces were an Orion Q-70 26mm, an Adorama 12.5mm Ortho, and a Parks 2” Barlow. At 70X, it was just a little clump of stars. By looking close, he saw the diamond shape and all four main stars. The two bottom stars were the bright pair, and the two top ones were the dim pair. Sort of a box tilted to the right side (or a diamond shape). Bottom right star was the brightest of the four, but just barely over the bottom left one. The dim upper pair looked identical in brightness. At 140X, the 5th star jumped out but the four main stars looked about the same. Just above the lower left one and between it and the upper left star of the diamond, he spotted the 5th star. It winked in and out of focus and view, but was definitely there. At 292X, though the Diamond was a bit bigger, the extra magnification didn't do much for it. The 5th star was still there, but winked in and out just as much as at the lower 140X. Overall, 140X gave the best view (see fredsdiamond.jpg).
Tom English: Observer from North Carolina
He drew the first sketch quickly at the observatory, and added the notes, then drew the second sketch after shutting down and walking over to his office. He then took a look at the SDSS image and realized he probably drew the diamond too large. (He tends to do this - like most people, apparently, judging from his student observing form submissions - it's easy to stretch the object in one’s mind as occupying more of the field of view than it really does.) After that, he went home and made the final sketch, which is representative of what they saw. He is still not absolutely certain of the actual size, since he didn't do any specific measurements. However, visually, it's likely closer to the final sketch, or maybe somewhere between the two renditions (see tomsdiamond.jpg).
He looked at it again with the 16-inch observatory scope at the end of a public night session. The observing conditions were great. He saw the four stars right away with a 32mm at 127x, but couldn't see the double (fifth star). The fifth star showed up with the 21mm at (193.5x), and looked great with a 10.5mm at (387x). He said it was really nice object.
Dave Blanchette: Observer from Nevada
David was observing from a site near Jean, Nevada. This night he said was not the best for observing. Despite the clear (non-cloudy) sky, the air was "thick", and the lights of Vegas washed out the entire sky. There was a distinct lack of contrast. The light dome itself was close to 40 degrees, encompassing the Little Dipper. He could just make out the mag. 4.27 star in the bowl, but not the 4.96 mag. star next to it
Both images were using a Meade LX200, 12 inch, f/6.2 focal reducer. davesdiamond.jpg is the Virgo Diamond (60secs, ISO1600) Emacs! davesdiamond2x.jpg is the same image, 2x enlargement. Emacs!
He said the Virgo Diamond was a pretty thing. He used the computer's RA/Dec info to get to the coordinates, and there it was. He didn’t work real hard at seeing it visually, as the sky was just not dark enough. He calculated the companion on the right hand star (invisible in the eyepiece) is about 7 seconds separation and about mag. 14.5. He'd like to get to a dark site with a dark sky and see if he can pull it out visually.
Dr. James Dire (see jamesd.jpg): Observer from North Carolina
He shot the Virgo Diamond last weekend.  The seeing was poor and it was his opinion that he didn’t have a long enough focal length telescope to do it justice (see jamesdiamond.jpg).
Dr. Don Olive (see donolive.jpg): Observer from North Carolina
He sent us a 90sec exposure of the Virgo Diamond on an Epsilon 180 corrected Newtonian with an SBIG ST-2000 camera (see donsdiamond.jpg). f/2.8 Field of view is 80.5x60.4 arc minutes. The scope is at the Tzec Maun Observatory in Western Australia.
Hap Griffin: Observer from South Carolina
Here’s a picture he shot recently (see hapsdiamond.jpg). He’s not completely done with processing it, but this is a start.
References
(Submitted by Tom English) He looked up the Virgo Diamond on the Sloan Digital Sky Survey and Wikisky. An SDSS image is attached (see SDSS.jpg). This is a very neat little group. Go to Wikisky (http://www.wikisky.org/),  zoom out from M31 (the default view), drag the view around until you find Virgo, then zoom in on the appropriate coordinate. If you move your mouse over an object it will give you information. The diamond is clearly seen in these interactive surveys, and the westernmost star is a double, giving 5 stars. Looking for this 5th star is certainly a greater challenge than looking for extra stars in the Trapezium.
The northernmost star is TYC 4948-53-1 (12h33m18.96s, -0d38'32.3", m=10.892)
The westernmost star (the double) is USNOA2 0825-07771246 (12h33m17.88s, -0d38'59.1", m= 12.1)
The southernmost star is USNOA2 0825-07771362 (12h33m19.61s, -0d39'15.7", m=13.7)
The easternmost star is USNOA2 0825-07771459 (12h33m20.79s, -0d38'50.5", m=13.45)
The TYC star was measured by the Hipparcos mission, thus explaining its precise magnitude measurement. Tom looked it up at the Hipparcos web site, and found that its parallax had been measured to be 64.8 milliarcseconds, putting it at around 50 light years from us.
Here's the Simbad page for the star: http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=TYC+4948-5 

(Submitted by Dave Blanchette) davesdiamondskymap.jpg is the Virgo Diamond area, with magnitudes of some stars for reference from Skymap ver 11. Emacs!
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