[vsnet-chat 3356] Re: [vsnet-campaign-nova 29] RE: V382 Vel recent data

["Mati Morel" <morel@ozemail.com.au>]

Thanks, Sebastian, for your thorough discussion on comparison stars for V382
Vel. I endeavour to produce a standard chart for each new nova discovery,  a
la AAVSO, and it is mailed or faxed to members of the VSS, RASNZ, in New
Zealand and Australia. A sequence of V mags is included. This ensures a high
degree of standardization among our members. Our sequence may have errors,
but at least we are in error by the same amount !!  As we have seen,
observers in other parts of the world will select their own comparison
stars, which may be mv, Tycho-1 or Tycho-2, GSC, etc in place of true V.
The age-old problem of  mixing different sequences has been alleviated for
VSS RASNZ members,at least for far southern novae, by _rapidly_ issuing
standard charts and sequences. At least, I assume things are better now than
they were 15-20 years ago when things were a bit "mickey mouse", with
different sequences and comparison stars being used for a number of novae.

Cheers,
Mati

Morel Astrographics
c/o M. Morel, 6 Blakewell Rd, Thornton NSW 2322 AUSTRALIA
*Specialized Charts** Variable Star Studies** Stellar Data**
151o38'33" E, 32o46'47"S.               morel@ozemail.com.au
----- Original Message -----
From: Sebastián Otero <varsao@fullzero.com.ar>
To: Mati Morel <morel@ozemail.com.au>;
<vsnet-campaign-nova@kusastro.kyoto-u.ac.jp>
Cc: <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Wednesday, July 05, 2000 4:41 AM
Subject: [vsnet-campaign-nova 29] RE: V382 Vel recent data


> Dear Mati and VSNET folks:
>                                                   The nova is slowly
fading.
> I think problematic comparison stars are in use. The star is obviously
> whiter than before so it's not useful to use red stars for comparison. The
> two stars Mati mentions are brighter than the variable, but the red colour
> of  GSC 8210-00801 makes it look fainter if seen with peripheral or
> parafoveal vision ( as most cases with faint stars.)
>                                                   Furthermore, Tycho
> comparisons proved to have a greater error than Tycho 2, evident through
the
> eyepiece. AAVSO charts use Tycho magnitudes and the sequence ends in 10.8.
> It is probably making observers using this chart to put a lower limit for
> V382 Vel when the star is really fainter than that.
>                                                 GSC 8210-01423 (10.00V,
0.45
> Tycho2) is too bright and GSC 8210-00801 (10.54V, 1.49 Tycho2) is too red
so
> they should be avoided for comparison at this stage.
>                                                 It's better to look for
> whiter and fainter stars now and avoid Tycho stars that faint.
> An appropriate Tycho 2 sequence would be:
>
> GSC 8614-00500    10.64,  0.44  ( 107 AAVSO/Tycho)
> GSC 8210-01225    10.82,  0.42
> GSC 8210-00897    11.00,  0.25
> GSC 8614-00300    11.05,  0.02
> GSC 8210-00423    11.41,  0.73
>
> 105 (GSC 8210-00023) and 108 (GSC 8614-00338) Tycho/AAVSO stars are orange
> and brighter than the variable so they also should be avoided.
>
> GSC 8210-00897 , the most suitable star at the moment is 0.23 magnitudes
> brighter in Tycho than in Tycho 2. I suggest again avoidig the use of
Tycho
> magnitudes.
> Mati's guess was OK: these were the two stars being used (at least by me)
>
> I agree that we should try to get an agreement about which sequence to
use.
>
> Best regards'
> Sebastián Otero.
>

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