[AZ-Observing] Re: IC 1296
- From: "Jack Jones" <Telescoper@xxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Mon, 28 Aug 2006 20:25:52 -0700
Hi Brian,
No, a lot of DSC databasers don't even bother to tell us what their sources
are, much less what the passband was. They pay for the database and that's
about as far as they go, and they consider it absolute and why are we asking.
It's really all they can do. I'm sure if you took them to task on their "15.1
mag ", they would say well that's +/- 0.5! Megastar usually gives (p) since it
has to draw from huge databases. (I don't blame Emil, what else could he do
with all that.) Anyway I'm glad you pretty much agree on the mag and SB, even
after it's put thru the grinder. Now I know what a 'real' 15th mag GX looks
like!
Of course as an amateur, I'm interested in 'v' mostly and at the zenith
preferably. I don't care if I see another (p) magnitude, it's pretty much
archaic nowadays isn't it? 'Blue' film probs are gone. I like how how the NSOG
(Kepple & Sanner) handled mags by making them all 'v' (they asked and got a
lot of help from the amateur community). But I guess if everybody published
their own there would be chaos wouldn't there, and then I'd wish for the "raw"
(p) data back.
Jack
----- Original Message -----
From: "Brian Skiff" <bas@xxxxxxxxxx>
To: <az-observing@xxxxxxxxxxxxx>
Sent: Sunday, August 27, 2006 9:30 PM
Subject: [AZ-Observing] Re: IC 1296
> The total magnitude of IC 1296 is not well in hand. The photo-blue
> value of 14.8 evidently quoted by Megastar is the Zwicky 'mz' magnitude
> corrected for global systematic errors. Don't know how anyone gets
> 15.1 from published data in the visible, though Jack doesn't specify
> what passband it is supposed to be for. The NED database, where one
> shuld always look first for source data on galaxies, shows 2MASS
> near-infrared photometry including total J magnitude of 13.0.
> The J passband is out at 1.2 microns. Folks on the 'amastro' list
> found that an empirical offset of "about 2" is in the ballpark for
> the V-J color of typical galaxies. Thus one could estimate V=15.0
> (maybe +/- 0.5) for IC 1296. Given the likely reddening in this part
> of the sky together with the usual B-V color of a late-type galaxy
> like this one, the B magnitude is something like 16.0. Thus the
> corrected blue magnitude of 14.8 is too bright (implies V of ~13.8),
> but figures around 15th for visual are about right. The standard
> dimensions also imply mean surface brightness around 15.0, so this
> is not an easy object. I've seen it in a 16-inch from Anderson Mesa,'
> but it was pretty marginal.
>
> \Brian
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