[vsnet-alert 23919] Re: PNV J17561375-2942546: possible nova (11.5 mag) in Sagittarius

[Josch Hambsch]

Thanks Brian,

In the meantime I have found in Vizier I-band magnitudes for the comp stars
and sent the data to the AAVSO.

Josch

-----Original Message-----
From: Brian Skiff [mailto:bas at lowell.edu] 
Sent: Samstag, 1. Februar 2020 20:46
To: Josch Hambsch
Cc: vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp
Subject: Re: [vsnet-alert 23917] PNV J17561375-2942546: possible nova (11.5
mag) in Sagittarius

Lacking proper Cousins I photometry, you can do pretty well by simply using
Sloan i and z magnitudes:  Ic = (i+z)/2.   In this part of the sky the
Pan-STARRS Sloan data are probably preferable to SkyMapper simply because of
the larger image-scale and psf-fitting (they used aperture-photometry for
the first version of SkyMapper).  The bright limit of Pan-STARRS, however,
is about mag 13.5 in any band.  For brighter stars, use SkyMapper if not too
crowded.  These catalogues are VizieR items II/349 (Pan-STARRS) and II/358
(SkyMapper).  The astrometry in Pan-STARSS, by the way, is at least as good
as UCAC4, so perhaps for most applications you could replace use of UCAC4
altogether.


\Brian


> On Feb 1, 2020, at 3:50 AM, Josch Hambsch <hambsch at telenet.be> wrote:
> 
> I have taken BVI images of this object last night.
> The position is:
> RA 17 56 14.04, DE -29 42 58.2 (J2000.0)
> 
> At JD 2458880.89604 the V magnitude was 11.18 (+/-0.01) mag, B magnitude
was 12.42 (+/-0.03). Airmass was 1.8.
> Still need to find I magnitudes for the comp stars as the ones chosen did
not have I mags in the UCAC4 database.
> Data will be sent to the AAVSO database.