MegaStar5 Error

I don't know if this has been found by others, but MegaStar v5.0 incorrectly
identifies NGC 90 & NGC 91. MegaStar ID's a 3'.0x0'.9 galaxy at RA: 00h 21m
51.7s, DEC: +22d 24.02m as NGC 91. The NGC/IC project and NED both identify NGC
91 as a star located 2' south of the above position. The object at the above
coordinates is NGC 90, a 13.7 magnitude spiral, 1'.9x0'.8 in size.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
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I don't know if this has been found by others, but MegaStar v5.0 incorrectly
identifies NGC 90 & NGC 91.

Hi Bill:

Hadn't noticed that one. But I do know there are a few errors of this kind in
the program.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

I don't know if this has been found by others, but MegaStar v5.0 incorrectly
identifies NGC 90 & NGC 91.

Hi Bill:

Hadn't noticed that one. But I do know there are a few errors of this kind in
the program.

Hi:

Lest someone get the wrong idea...read that as "surprisingly few." Megastar is
one fine piece of work, and has been one of my favorites for over a decade.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Bill Ferris wrote:

I don't know if this has been found by others, but MegaStar v5.0 incorrectly
identifies NGC 90 & NGC 91. MegaStar ID's a 3'.0x0'.9 galaxy at RA: 00h 21m
51.7s, DEC: +22d 24.02m as NGC 91. The NGC/IC project and NED both identify NGC
91 as a star located 2' south of the above position. The object at the above
coordinates is NGC 90, a 13.7 magnitude spiral, 1'.9x0'.8 in size.

Is it? Here is the issue I've been struggling with: is it really an
error to refer to a galaxy by the designation by which it has been known
for decades? I see the utility of the NGC/IC project in an historical
sense, but what of the confusion of renaming an object that has long
been known by the "erroneous" designation? It seems to me that we
should take some care about this issue!

What about the researcher who tries to look up all the papers on NGC 90
only to find half of them refer to another galaxy? Or what about the
log entry for NGC 91 of a deep sky observer made before the NGC/IC
people suggested renaming some faint star NGC 91?

Here's my perspective: having consistent designations is more important
than restoring the original discovery observation. When it comes to
actually changing a designation of an object we should think twice about it.

What do others here think regarding this issue? Am I the only one who
believes renaming NGC objects is opening a can of worms best kept closed?

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

To reply have a physician remove your spleen

What do others here think regarding this issue? Am I the only one who
believes renaming NGC objects is opening a can of worms best kept closed?


Hi Greg:

Frankly, I don't know what to think. I ran into problems like this when I was
designing the observing club for a recent star party.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

I agree with Greg, it's a subject that should be addressed with care. Perhaps,
I should have added the word, possible, or a "?" to the subject title to
acknowledge the uncertainty of the situation.

I lean toward having the data in a catalog as accurate as possible. If after
publication errors are discovered, it's more helpful than confusing to make
corrections. This is certainly the case with
positional errors. It seems obvious in the case of mistaken classifications
(e.g. planetary nebula vs. galaxy), as well. I apply the same principle to
errors of identification and designation.

From Dr. Corwin's discussion, it appears we can be reasonably confident that
Dreyer misinterpreted Lord Rosse's observations. Rosse saw only two nebulous
objects in the immmediate area and his positions correspond to NGCs 90 and 93.
Also, Schultz measured
accurate position for the three principle objects in the area. And the object
at his position for NGC 91 is a star.

The current situation is one where confusion reigns if we continue to use the
Dreyer IDs, positions and descriptions. The object at NGC 91's position is a
star, not a galaxy as described in Dreyer. Correcting the errors doesn't
immediately elliminate confusion but, at least, we've made that a future
possibility.

There is also the issue of errors introduced by the authors of software
products like MegaStar. It's impossible to create such a product that is
error-free. I accept that and appreciate the hard
work and long hours Greg and others put into these incredibly powerful, useful
tools. If an error is found to have originated within the software, then I
would encourage the author to correct it
in a future release.

I don't know if my initial confusion about MegaStar's presentation of NGCs 90,
91 and 93 resulted from errors in the software, the source catalog, or the
user--moi. I do know that I was confused...until reading Dr. Corwin's lucid
explanation of the situation, and wanted
to make others aware of a possible error in a popular deep-sky charting
application.

Looking forward to reading others' thoughts on this.

Bill in Flagstaff
www.cosmic-voyage.net

Bill Ferris wrote:

I don't know if this has been found by others, but MegaStar v5.0
incorrectly
identifies NGC 90 & NGC 91. MegaStar ID's a 3'.0x0'.9 galaxy at RA: 00h 21m
51.7s, DEC: +22d 24.02m as NGC 91. The NGC/IC project and NED both identify
NGC
91 as a star located 2' south of the above position. The object at the
above
coordinates is NGC 90, a 13.7 magnitude spiral, 1'.9x0'.8 in size.

Is it? Here is the issue I've been struggling with: is it really an
error to refer to a galaxy by the designation by which it has been known
for decades? I see the utility of the NGC/IC project in an historical
sense, but what of the confusion of renaming an object that has long
been known by the "erroneous" designation? It seems to me that we
should take some care about this issue!

What about the researcher who tries to look up all the papers on NGC 90
only to find half of them refer to another galaxy? Or what about the
log entry for NGC 91 of a deep sky observer made before the NGC/IC
people suggested renaming some faint star NGC 91?

Here's my perspective: having consistent designations is more important
than restoring the original discovery observation. When it comes to
actually changing a designation of an object we should think twice about it.

What do others here think regarding this issue? Am I the only one who
believes renaming NGC objects is opening a can of worms best kept closed?

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

Owen Brazell was kind enough to send me an email giving some background on
MegaStar5 creator Emil Bonanno's thought process regarding this challenging
issue. Bonanno chose not to go with the corrected NGC/IC because, though
historically accurate, to do so would ignore long-established ID useages.

Considering this, the NGC 90 and NGC 91 idents in MegaStar should not be
considered errors and I've changed the subject header to reflect this.

Regards,
Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
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