[vsnet-chat 5091] Re: eta Carinae

["Stan Walker" <astroman@xtra.co.nz>]

Brian,

We've been measuring this star since 1970 and have tried to keep things
consistent. But due to the change from the Auckland Observatory system which
used a 30" aperture to the Williams system using a 60" aperture there is a
discontinuity about 1990. Obviously Harry's measures take in more of the
nebulosity but the actual V disparity is quite small - probably less than
5%, or 0.05 magnitudes, and probably much less than this. Once you're out
past the Homunculus the nebulosity is quite faint by comparison with the
main object.

As for the sky we always measure between the comparison and check stars. I
can't find their HD or BS numbers offhand but the values are 6.47 and 6.00.
The first is a rather blue foreground star(-0.13, -0.60), the latter is
rather reddened and has been stated to be variable but our 400 measures show
this to be less than 5%. The sky measure in this region is very difficult
and it would probably be fair to say that a measure nearer eta would reveal
a brighter but more variable background. So this is why we quote these
measures as 2-5%. In other situations using this equipment conventional
pep - we expect an SD of 0.007 magnitudes in good conditions.

I'm off to Auckland for my daughter's wedding which is why I can't spare the
time to chase up details of the comparison and check

Regards,
Stan

----- Original Message -----
From: Brian Skiff <bas@lowell.edu>
To: <astroman@xtra.co.nz>
Cc: <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Friday, February 08, 2002 9:00 AM
Subject: Re: [vsnet-chat 5089] eta Carinae


>      It seems as though for eta Carinae it would be especially important
> to indicate the photometer diaphragm size used for such observations
> so that the contribution from the nebulosity could be accounted for.
> And just how _are_ you dealing with "sky" subtraction for such
> measurements?
>
> \Brian

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp