Wow... real astronomy. And all I thought we did was gossip on this list.
Thanks Albert for this most interesting piece of research.
Michelle
Custom Telescopes by Plettstone
http://www.plettstone.com/telescopes
> -----Original Message-----
> From: sf-bay-tac-bounces@No-Spam [mailto:sf-bay-tac-bounces@No-Spam]On
> Behalf Of Albert Highe
> Sent: Thursday, September 04, 2003 7:15 PM
> To: TAC
> Subject: [TAC] 130 year old puzzle solved: Location of NGC 6138
>
>
> There are a few reasons I'd like to inform TAC of a group effort to locate
> NGC 6138.
>
> 1) We are among the first to know the answer to this 130 year old puzzle.
> 2) The story provides some insight into what the NGC/IC Project Team does.
> 3) I learned some new information that might be helpful to others.
>
> Bob Czerwinski and I recently have been hunting down objects in the galaxy
> cluster Abell 2197. On TAC, Bob had mentioned his difficulty finding NGC
> 6138. "The Sky" says it doesn't exist, as well as gives a
> location for it 2'
> from where the sources below say it is. Uranometria and the NASA/IPAC
> Extragalactic Database (NED) place NGC 6138 at RA 16h 24m 54.1s, DEC +41d
> 03m 03s. The Digitized Sky Survey also shows a galaxy at that
> location. Sure
> enough, I was able to see it. For me, that would have been the end of the
> story.
>
> However, thinking that NGC 6138 was one of those NGC objects incorrectly
> identified, Bob consulted the NGC/IC Project page. Bob posted on TAC that
> the NGC/IC Project identified NGC 6138 as NGC 6263. This puzzled
> me, since I
> had seen a galaxy at the "correct" location. In addition, NGC
> 6263 is nearly
> 15 degrees away!
>
> So, I consulted the ultimate source - Steve Gottlieb. Steve is an amazing
> resource who seems to have endless knowledge about amateur astronomy. He
> impressed me by taking the time to immediately respond with the following
> detailed information.
>
> "Stephan's discovery was "announced" in his list II, which was
> published in
> Monthly Notices of the Royal Society (November 1871). He gave a position
> for 1870 as 16h 18m 28.76s +41d 14' 18.5" which precesses to 16h 22m 50.9s
> +40d 56' 04" (2000). This position was micrometrically computed using an
> offset star which was identified in the Monthly Notices paper as
> "2,821 Arg.
> Z +41d". The actual micrometric offset is not given in the paper but the
> position of the star is listed at 16h 17m 7.32s +41d 10m 39.7s
> (1870) or 16h
> 21m 30.1s +40d 52' 11" (2000) with a magnitude of 9.2. If you
> subtract the
> RA and Dec positions for the offset star and NGC 6138 we can
> infer Javelle's
> offsets as 1 minute 21 seconds in RA and a bit under 4' in
> declination. Fair
> enough. But if you look up the position of 16h 21m 30.1s +40d 52' 11"
> (2000) on sky charting software, there is no 9th magnitude star
> there! So,
> clearly Javelle gave the wrong position for his offset star but I
> don't know
> where the star he mentioned is located -- and even then it's possible he
> misidentified the offset star. Corwin claims the modern designation for
> this star is BD +41 deg 2821. If you can track down the 2000 coordinates
> for this star, we could go from there."
>
> Well, I did as Steve suggested and found BD +41 2821 in the Bonner
> Durchmusterung catalog.
> BD +41 2821
> RA 17 16 38.5, DEC +41 11.6 (1855), mag 9.2
>
> Stephan reported his discovery was near 2821 Arg. Z +41d.
> RA 16 17 7.31, DEC +41 10 39.7 (1870)
> It appears that the 16 and 17 for RA degrees and minutes were
> transposed in
> Stephan's report. Fortunately, he named the star so it was
> possible to look
> up the correct coordinates for it.
>
> The 1855 coordinates for BD +41 2821 translate to:
> RA 17 21 17.7, DEC +41 03.0 (2000).
>
> There is a star very near these coordinates at RA 17 21 18.5, DEC +41 02
> 13.9. "The Sky" says it is a mag 10. The Guide Star Catalogue says it is a
> 9.88. It looks like a match to Stephan's reference star.
>
> That puts NGC 6363 (not NGC 6263) at exactly the right offset. Stephan
> apparently made a mistake and transposed the numbers for RA degrees and
> minutes for his reference star. He actually discovered NGC 6363 and
> calculated its position using the transposed numbers. That is why
> no object
> appears at his coordinates. So, the galaxy cited as NGC 6138 in
> Uranometria
> and NED is mislabeled. It should have one of its other
> designations, such as
> MCG+7-34-20.
>
> Apparently someone has figured this out before, but incorrectly wrote down
> NGC 6263 instead of NGC 6363. Steve confirmed that this is true. The
> correction will eventually make its way into the appropriate professional
> and amateur databases.
>
> This was a nice exercise since I learned quite a lot from it.
> Here are some
> of the lessons learned.
> 1) TAC is a great tool for sharing observations. Bob's posts of his
> observations set the ball rolling.
>
> 2) Steve is a wonderful resource. If he hadn't already done the background
> research, hadn't the info at his fingertips, or hadn't been so responsive,
> the ball would have stopped. He also directed me where to look.
>
> 3) The information readily available through the Internet
> continues to amaze
> me. Steve probably gave me more credit than I deserved. I know very little
> about star designations and had no idea what BD +41 deg 2821 meant. But a
> search of "stellar databases" quickly gave me a review of various systems
> for naming stars. I learned that BD stands for "Bonner Durchmusterung."
>
> 4) From my research on galaxy clusters, I was aware of various catalogues
> and a variety of search methods for finding galaxies. I was very surprised
> to learn that the Bonner Durchmusterung catalog
> (http://vizier.u-strasbg.fr/viz-bin/Cat?I/122) of stars, first
> assembled in
> 1859-62, is available and searchable on-line. The updates in years 1903,
> 1951, and 1968 are also included. It was straightforward to search the
> database using VizieR
(http://vizier.u-strasbg.fr/viz-bin/VizieR-3). VizieR
can also be used to translate the older stated coordinates into modern Epoch
2000 coordinates.
As amateurs, we use the published databases extensively to select and/or
identify objects. Many errors still exist among objects readily observable
by us. We shouldn't hesitate to question the accuracy of what we read when
we discover discrepancies between our observations and the published data.
Doing so may allow us to make a small, yet satisfying contribution to
astronomy.
Albert