Re: Musings on the NGC

Jeff Goldstein

Ted, this is an amazing historical compilation.  I feel humble with my feeble equipment and light polluted conditions, here.

Thank you for the fine reading and perusal!

Jeff G.


From: <> On Behalf Of Ted Forte
Sent: Wednesday, May 20, 2020 9:23 PM
Subject: [BackBayAstro] Musings on the NGC


I see that Tidewater is immersed in clouds, just in time for new moon. So I offer here, for your cloudy night reading pleasure, some (possibly) interesting, (probably) mundane, and (undeniably) useless facts about the NGC gleamed (mostly) from the work of Dr. Wolfgang Steincke:

  1. John Louis Emil Dreyer (1852-1926) published the New General Catalog in 1888
  2. There are 7,840 entries in the New General Catalog.  263 entries are duplicated, 88 are unverified (nonexistent?), 407 are stars or asterisms and 30 are parts of other cataloged objects.  That results in 7,052 independent non-stellar objects.
  3. Of the 7,840 entries, 7,817 were discovered visually, 22 were discovered visually but with the aid of a spectroscope (15 by Pickering and 7 by Copeland) and one was discovered through photography (NGC 1432 Merope Nebula discovered by brothers Paul and Prosper Henry)
  4. The objects were found by 100 observers mostly between 1800 and 1887.  26 of the observers were before William Herschel. The nine most prolific discoverers were William Herschel, 1738-1822 (2,415 objects), John Herschel 1792-1831 (1,691 objects), Albert Marth 1828-1897 (582 objects), Lewis Swift 1829-1913 (467 objects), Edouard Stephan 1837-1923 (420 objects), Heinrich d’ Arrest 1822-1875 (319 objects), Francis Leavenworth 1858-1928 (251 objects). James Dunlop 1793-1848 (225 objects) and Ernst Wilhelm Temple 1828-1889 (149 objects). 
  5. Dreyer credited the Herschels with a total of 4,318 discoveries of which 4,116 are independent objects. 3,942 are non-stellar; Caroline Herschel is responsible for 10, John Herschel is responsible for 1,569 and William Herschel for 2,363. The remaining independent objects in the NGC were discovered by other observers.  There was a lull in discovery of deep sky objects after 1838 when John Hershel concluded his final survey – astronomers assuming there was nothing left to discover!
  6. 5,880 NGC objects are considered to be “Northern”.  The dividing line is declination -32o48’ which is the declination of William Herschel’s most southernly object (NGC 3621)
  7. 1,184 are “Southern” objects (13 discoverers – but mostly John Herschel and James Dunlop)
  8. 71 different telescopes were used to discover the non-stellar objects: 60 refractors (85%) and 11 reflectors (15%).  The smallest refractor was a 3” but most were in the 6”-7” range.  The largest, however, was the 27” Grubb in Vienna with which only one NGC object was discovered: Palisa’s Galaxy NGC 927.  The smallest reflector was Caroline Herschel’s 4.2inch and the largest was the 72” at Birr Castle.  The earliest telescopic discovery with a refractor was NGC 224 (M31) (Simon Marius in 1612) and the first with a reflector was NGC 7009 (William Herschel in 1782).  There is, however, evidence to suggest that W. Herschel observed and described NGC 6535 while examining Flamsteed stars on 24 August 1780 with the same 6.2” reflector he used to discover Uranus, and if that is the case, then that is both the first discovery with a reflector and Herschel’s first nebula discovery. (John Russell Hind gets the credit for 6535 which he independently discovered 72 years later!) 
  9. The NGC contains 6,028 galaxies (79.5% of the total), 683 Open Clusters, 147 galactic nebulae, 114 globular clusters and 93 planetary nebulae. There are four supernova remnants. 
  10. The brightest object in the NGC is NGC 292 the SMC in Tuc at a visual magnitude of 2.2. The faintest object is NGC 4042, a 16.4 magnitude galaxy in Coma. The most distant object at 832 million light years is NGC 5535, a magnitude 15.0 galaxy in Bootes (distance from NED). The most northern and most southern entries in the catalogues are both galaxies: NGC 3172 in Ursa Minor ("Polarisima borealis") and NGC 2573 in Octans ("Polarissima australis").
  11. Even before the NGC went to press an additional 206 objects had already been discovered.  These became part of the first index catalog to the NGC that was published in 1895 and contained 1529 objects.  The IC2 published in 1908 contained another 3,857 objects.  Most of the IC was discovered photographically but bright objects were still being discovered visually after 1888.
  12. Wolfgang Steinicke’s corrected NGC contains 8,413 entries, adding 573 objects to the “Historic NGC”.  (These have alpha or numeric appendages to the basic NGC numbers).  Of this expanded list, 7,520 are unique non stellar objects.  Another 31 are parts of other NGC objects and are not included in that number.

The special thing about the NGC (to me) is that the objects were discovered visually by amateurs, therefore, it constitutes the ultimate visual observing list. My current observing project  is to observe the 6,600 or so, real, non-stellar, NGC’s that get 15 degrees above my horizon with my 30-inch Dob. I’ve logged just over 5,000 of them so far.

2,484 of the NGC’s I’ve logged so far were independently discovered by Sir William Herschel (his primacy is recognized for 2,363 of them).  The Herschels were the first to attempt a systematic survey of the sky but they missed a bit.  WH’s innovative sweep method ended up covering about 66% of the sky available at his location.  During his observing career, he discovered about 66% of the deep sky objects that were theoretically detectable with his scope. That near 100% correlation speaks to an efficiency that is unmatched by any other visual observer in history!  If he didn’t record it, it was because it just didn’t fall into his field of view.

Retracing his steps has instilled in me a boundless admiration for his remarkable observing skills.  Here I am with a larger telescope, with a far more reflective mirror and armed with the foreknowledge of the object’s existence and exact position and even then, some of the objects he discovered are barely detectable faint nothings that I would certainly have missed if I didn’t know they were there.  He spent every clear hour of darkness at the eyepiece and spent his days making mirrors – more mirrors than any other single human being in history – and they were the highest quality of his day. I wonder if he ever slept?

From my perspective, the most fascinating part of our hobby is participating in the history of visual observing.  Driven as I am to explore the far reaches of our universe, to see deep sky objects with my own eyes, I am drawn to those remarkable observers of the past.

Perhaps the next time you look through your telescope at a celestial object, you might stop and consider, that for that moment in time, you are the last in a string of observers that stretch back centuries in some cases. The fainter and more obscure the object is, the fewer people there are in that string.  In a manner of speaking, you are sharing a visceral experience with everyone, living or dead, that has viewed that object.  There is however, an exclusiveness to the thing.  It is ONLY those (sometimes rather few) observers that share that experience. It’s rather a privilege, don’t you think? 

Ted Forte

BBAA west

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