[Aavso-photometry] Re: [cvnet-discussion] VV is one lonely Pup!

[Arne Henden]

Expanding on Aaron's reply to Berto...

Berto Monard wrote:
> Recent 'unfiltered' observations show VV pup evolving around 17.5CR. I
> wonder if, at this faint level, any precise timeseries photometry via
> filtered observations can be done by the usual amateur instrumentation.
> 
Depends on the size of the telescope, the desired signal/noise, the
bandpass and the required time resolution.  It may be true that only
the larger amateur telescopes will do good time resolution, but you
don't know for sure until you try.  We already consider this; the
announcement suggested red filters for the smaller telescopes and
B/V for the larger ones.
> 
> But if VV Pup is a polar, it will give a reasonably good signal over
> the unfiltered CCD band while measurements in the different bands will
> likely show a similar light curve. 
> 
Polars look quite different depending on the wavelength.  This is
why Steve is requesting filtered observations.

> At decl -19, VV Pup is very much equatorial, which means that longer
> exposures (more than 30 sec) will produce significant star trailing on
> most of the images with the commercal type telescopes. This will firmly
> reduce the magnitude reach in filtered photometry.
> 
I don't follow this.  Dec = -19 is not equatorial by my definition.  The
30sec comment doesn't make sense; many telescopes will go longer
unguided, and if you are autoguiding, you can certainly do very long
exposures.  So Brad, you are not the only person confused by this
statement!

> If someone were (in addition to unfiltered runs, produced by others
> perhaps) to make (by means of stackings) 'deep' snapshot observations in
> the different filters, the overall information can still be had. From
> past experience I am not a strong believer in the quality of timeseries
> derived from stacked images...
> 
"Deep snapshots" is essentially what we are asking for; the difference
in your description, I think, is that you are planning a single snapshot
per filter per night and we want as many such exposures as you can take
for each night (that is, a coarse time series).  Please do not observe
unfiltered for Steve's project.

Tim, the f-scale chart is an image from the DSS, with the variable pretty
easily visible.  We have a hundred high-resolution images taken with the
1.55m telescope of this field, since it was on our parallax program.
However, there is a blowup with the variable marked in the
Downes Living Edition catalog that will be useful for identification:
http://icarus.stsci.edu/~downes/cvcat/

Arne