Archive for April 2012

NGC 2362 – Open Cluster – Canis Major, Often called “The Tau Cluster”

April 18, 2012

LVAS Observer’s Challenge report:

NGC 2362 Open Cluster Canes Major

Open cluster, NGC 2362 is a beautiful and interesting cluster, which can be easily observed with the smallest of telescopes, even with a moderately light polluted sky.   However, like all deep-sky objects, a reasonably dark sky is needed to fully appreciate.       

The bright 4th magnitude star Tau, creates a glare that subdues many of the dimmer members of the cluster.  I could count approximately 20 stars with a greater concentration of faint unresolved stars just west of Tau, creating a light glow.  The cluster has a mostly irregular shape and is comprised primarily of  bluish/white stars.  

The above pencil sketch was made using a 102 mm refractor at 83x, from my moderately light polluted backyard in western North Carolina.  

I used a blank 5 x 8 note card and inverted the colors using my printer.  Roger Ivester

Pictured below is CJ, my dependable observing partner of many years. She is always ready to go outside and keep me company.

April 7, 2012


The Virgo Diamond – Faint Five Star Asterism – A True Observing Challenge

April 6, 2012

A very  transparent sky with excellent seeing is critical for viewing the fifth star.   

On the night of April 12th, 2012, the humidity was near 25% and seeing was exceptional.  I knew this could possibly be my last opportunity to observe the  diamond this year under conditions such as this. This proved to be a good decision, as I was finally able to see the elusive “fifth” star. 

The foothills of North Carolina, can be a difficult location to observe from during the months of May through August.  The humidity and haze can be terrible!   

When I first read about the diamond in Sky and Telescope, May 1993, page 110, it became a bit of an obsession with me.  I could hardly wait to see it for myself.  

The diamond in 1993 was pretty much an unknown asterism for most amateurs and still is today.  In the nineteen years since the article first appeared in Sky & Telescope, there seems to be little interest in the diamond, if any at all.  There is virtually no information concerning the diamond on the internet or anywhere else.  I am hopeful this will change in the future. 

You might ask why I have so much interest in such a unique, faint, small and difficult object that is probably unknown to “maybe” 99% of all amateurs.  I would say these are reasons enough.   

The Virgo Diamond gets its first promotion: 

Being a member of the Las Vegas Astronomical Society, I was able to get quite a few of the members interested.  A special Observers Challenge report covering this object was introduced to the LVAS in the Spring of 2009.      

April 27th 2012:  Expert Finnish amateur; Jaakko Saloranta takes a look at the diamond.

 “To be sure this was just not an asterism, I contacted the Big kahuna Matthias Kronberger for his expert opinion.  He used VIZIER for proper motion data and came to the same conclusion I did using ALADIN (PPMX-data).  So the chance of stars simply aligning like this in the sky might seem remote (4% according to Brosch) but none the less the group is unfortunately, just an asterism despite having similar spectra.”  

“I counted the total magnitude of the Virgo Diamond to be 10.4 using star magnitude data from NOMAD.”   JS

Jaakko has an excellent blog site.  “Breath on a Mirror” please go to the upper right under “Blogroll”  and click on!    Roger

The Virgo Diamond – Faint Five Star Asterism

April 3, 2012

     Have you ever heard of the Virgo Diamond?  No…I’m not talking about the large group of stars, comprised of Cor Caroli, Denobola, Spica, and Arcturus, also called the Virgo Diamond.  I’m talking about a basically unknown and very tiny asterism in Virgo which makes a beautiful diamond shape, comprised of five faint stars.  If conditions are not good this asterism can be difficult, especially the faint companion of the western-most star.   

     When I first read about the Virgo Diamond back in 1993, I became immediately interested, and could hardly wait to see it for myself.   The Virgo Diamond seems to be as unknown today as it was back in 1993.  I know of only a very few amateurs who have observed this most intriguing deep-sky object.

     If you’re interested in learning more about this fascinating object, please continue reading, and you too might want to test your observing skills in an attempt to see all five stars of the “Virgo Diamond.”  

Virgo Diamond: 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.  Five stars all appearing brighter than 13th magnitude, comprise 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 suggests that the stars of the diamond are physically associated.  The diamond is located at:  RA: 12:32.8   Dec: -0.7

Direct Source:  Sky and Telescope Magazine, May 1993, page 110

     My first observation of the Virgo Diamond came on the night of April 14th 1993.  I was using a 10-inch f/4.5 reflector at 190x which presented a faint grouping of four stars.  I was unable to see the fifth star.  The stars range in brightness from 10.9 to 13.7 in magnitude.  Please don’t underestimate this very faint asterism.  If conditions are not good, even the four primary stars can be difficult.  

     Since that night in 1993, I have observed this object many times, however, always seeing only the four primary stars.  However, this changed on the night of April 12th 2012.  The conditions were excellent, and using a 10-inch reflector, I saw the illusive fifth star at a magnification of 266x.  I could not hold the fifth companion star constantly, and averted vision was required.  Exciting to say the least….after all of my attempts over the years to see the fifth star.  

     It should be noted that excellent seeing and high magnification are essential for observing all components of the Virgo Diamond.  

The northern most star is TYC 4948-53-1 (Magnitude 10.9) The brightest and easiest of the diamond.  (RA  12h33m18.96s   Dec.  -00.38m32.3s) 

The western star (the double) is magnitude 12.1

The southern star is magnitude 13.7

The eastern star is magnitude 13.5

Tom English of North Carolina, using a 16-inch SCT described a fabulous view of all five stars using 194x and 387x.

Fred Rayworth of Las Vegas could see the fifth star using a 16-inch Reflector at 130x, but could not hold the faint companion constantly, even from the desert southwest.  

Sue French of New York could see the faint companion using both a 130-mm apochromatic refractor and a 10-inch reflector.  

Jaakko Saloranta of Finland, using an 8-inch reflector, under less than ideal conditions managed to see the elusive fifth star, despite a focuser that kept freezing up under extreme cold conditions.

The following is a pencil sketch from that special night of April 12th 2012, using only a No. 2 pencil on a blank 5 x 8 note card.  The colors were inverted using a scanner. 


The following image by James Dire of Hawaii.  “The image is a 20 second exposure.  Please note the streak below the diamond.  This is a geosynchronous satellite that I watched move from west to east across the field during multiple 20 second exposures.  I know it is a geosynchronous satellite because the Virgo Dimond is a few arch minutes below the celestial equator, the satellite was moving east with respect to the background stars, and the streak is 5 arc minutes long on the 20 second exposure.  Five arc minutes per 20 seconds translates to 360º (one orbit) in 24 hours.  This is my first geosynchronous satellite on an image.”  James Dire

Virgo Diamond 20s

The following image was taken by Don Olive of North Carolina from the Tzec Maun Observatory in Western Australia, using an Epsilon 180 mm corrected Newtonian.  


I’m hopeful that you will attempt the Virgo Diamond, and if you do, I feel certain it will become a favorite springtime object for you also.  Remember, it’s a tiny asterism, with very faint stars, so a good night and high magnification is a must.  

Good luck in your quest to see the Virgo Diamond…and the fifth and most difficult component.  

Roger Ivester