[vsnet-chat 3046] Re: Reszelski's observation

[GeneHanson@aol.com]

Taichi: << What a quick and deep observation!  Reszelski observed
12 CVs within 0.005 d = 7 min! >>

Lasse: << But an experienced observer using a dobsonian scope can
easily observe 12 CV with 7 minutes.  That's no problem if you
know the star fields from thousands of previous observations.
Of course it helps if the stars are in the same part of the sky.
>>  << I guess observers like Gary Poyner and Gene Hanson often
make observations that fast. >>

Though I agree it's possible and has been done, there are some
caveats and Lasse sites some of them.  If the CV's are bright
(that is, easily visible), a theoretical limit probably lies in
the one estimate every 30 second range which would be 14 in 7
minutes.  But if you're talking about very faint CV's or (as is
usually the case) plus those beyond the limit of your scope, it's
always going to take longer.

With faint CV's, my average always gets close to one per 75
seconds.  But that varies widely.  The closer the better and some CV's
are extremely close (RZ/WZ Sge, V630/V632 Cyg, T/RZ Leo) so 30 to
40 seconds is not too difficult.  But if the variable is
relatively low in the sky (where the seeing is bound to be
terrible) or the variable is very high (needing the step stool
and contending with the so-called "dobsonian hole") that average
can easily be 80-100 seconds.  With my recent back trouble, I've
avoided variables high in the sky because I discovered the
twisting and turning to be a heavy contributor to my ailment. 
Now I wait at least an hour so for those stars to drift to a more
comfortable position.  This has really helped my average, but I
no longer do just one session to cover the entire sky.  

Another real time waster is strong moonlight.  You can get
surprisingly faint even under these conditions by spending time
in the field essentially readapting your eye.  That will often
bring the average to 120 seconds per CV if even that fast.     

But on average on the moonless nights, it's often close to the 60
seconds per CV because of the mix of relatively brighter CV's. I
have been up to 70-75 estimates in one hour.  However, I must state
it only happens when I'm in a big hurry, as in trying to finish before
the weather turns cloudy.  Time is always a premium but 70-75 is
simply too fast (I call it a fire drill) to be fun because it's almost
exhausting.  I find an average of 50 to 55 per hour is a lot more
comfortable and therefore fun.

Lasse: <<  I did the same when I observed visually using my 13.1
inch dobsonian. >>

Gary: << Lasse I know was a fast -AND accurate observer.  Pity we
lost him to CCD really. >>

Was anyone faster than Lasse?  However, at the rate Maciej
Reszelski's is going, he'll do the work of me and Gary combined.
:)

I really should comment on Gary's mention of CCD- a topic we've
discussed in private.  It is inevitable that many visual
observers will move to CCD, especially those who have the
technical and financial resources.  I think it would great if
most of the new variable star CCD observers came from the ranks
of amateurs who bought this equipment merely to take pictures. 
In the short run, however, it seems that the ones most likely to
make the investment are those who already have the love of these
special objects.  This means the loss of many of our visual
observers, a number which is way too small in my opinion.  

I myself have struggled with this decision.  As a visual
observer, I'm one of the most productive.  As a CCD observer, who
knows?  It is a foregone conclusion that I'll someday do CCD
work.  I have the financial resource to do so and I am a computer
professional so the technical obstacle isn't there.  In the short
term I simply don't have enough time.

I sincerely hope that there is a place for visual observers for
many decades to come.  There is no doubt in my mind that the
usefulness will continue to narrow, but I hope what is left is
that much more valuable.  If so, it will continue to provide an
inexpensive path to variable star observing.  Visual, PEP, CCD,
... we need all the observers we can get!        

Clear skies,

Gene

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