[vsnet-chat 3360] Re: V382 Vel comparison stars

["William S G Walker" <astroman@voyager.co.nz>]

Hi Arne and all,

Interesting to hear about TASS. It would be good to see an R image,
perhaps, but V and I are a great improvement on nothing! On to V382.

It seems the problem in this area is between magnitudes 10 and 11 which is
a difficult area for CCDs in that you're back to ordinary sequential
photometry over a wide field. I don't really want to get involved in that.
But if the weather ever clears I'll get a few BVR frames to help resolve
the present problem. 

I must admit that Bruce's recent quietness led me to believe that the
problem wasn't so great any more and that the photographic sequences were
proving adequate. Apparently that is not so. I tried my hand at the 12-15
range earlier but without many results. You can either do sequences or CV
monitoring, but in practice not both. I've been talking to the people in
Auckland about getting images of other fields but that's probably two to
four months away.

I found that vignetting with the filters and the need to refocus
(unfiltered and BVRI don't share the same focal plane) was a constant
annoyance, as was the need to locate a series of new fields. Also, the cold
emanating from the CCD area seemed to cause dewing on the filters. I now
have a heater for these. But the next good night without a moon I'll try to
catch up on some of the ones I promised earlier. There are not as many sets
of BVRI filters in use as you might think amongst southern amateurs and not
all owners have much background in filtered photometry. Without this
background all you're doing is producing another set of poor comparisons.

Also there is probably some reluctance to get involved in an area where
another group is reputedly active. Most of the amateur photometrists have,
in the past, produced UBV sequences down to V = 14 or more in southern VS
fields. But many haven't seen the light of day - or night - yet. So most of
us have given up sequences. I would like to see good charts for all
southern CVs, or suspected CVs, and emailed Bruce about this earlier this
year. It's a waste of time making sequences if they're not adopted by
everyone. I'm submitting the proposal about the CV sequences to a group
with an automatic 35cm telescope next month - whether they'll wish to
produce charts as well is not clear. But with the much easier way to
describe faint stars now it will be easy to publish results at intervals. 

Regards,
Stan  

----------
> From: aah@nofs.navy.mil
> To: vsnet-chat@kusastro.kyoto-u.ac.jp
> Subject: [vsnet-chat 3355] Re: V382 Vel comparison stars
> Date: Tuesday, July 04, 2000 9:50 PM
> 
> Bruce Sumner asked when some group was going to do real
> two color photometry of the sky.  This must have been
> a leading question, as I think Bruce knows that I am
> involved in The Amateur Sky Survey (TASS).  That survey
> (using Droege's Mark IV cameras) is scheduled to begin
> in September, covering initially the northern sky from
> -30 to the pole in Johnson-Cousins V&I down to V=16.
> There are several cameras in queue to head south and
> complete the entire sky.  So, within a year or two, there
> should be both UCAC covering the entire sky for astrometry
> and TASS covering about the same stars with photometry.
>   In the meantime, what are observers in the southern
> hemisphere that have CCD systems doing with their equipment?
> I know a few have photometric filters, but they don't seem
> to be jumping at the opportunity to clear up some important
> questions.
> Arne

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