[vsnet-j 1554] V4739 Sgr (Nova Sgr 2001-2) discovery story by A. Pereira

[Taichi Kato <tkato>]

V4739 Sgr (Nova Sgr 2001-2) discovery story by A. Pereira

-- 
Nova Sgr 2001 #2 Discovery Story:

I had just started another searching session at 2043 UT.  The Moon was 
starting to interfere but I still could see my memorized patterns well. 
I started scanning near M7 as usual, and 3 minutes later immediately 
saw the very bright 7.6 mag object within my 8th mag star patterns.  
It completely disturbed my binocular constellations.  I waited a minute 
or so and saw it was no satellite.  It was white-yellowish in contrast 
to V1494 Aql that was orange to my eyes at discovery.  
 
I quickly estimated the mag, and rushed into the house with a sketch of 
its position.  As usual I had the computer turned on with GSC7 in red 
star mode to save dark adaptation.  I quickly got the position with the 
mouse and I did careful checks (asteroids, variables, etc).  I typed 
the data into the e-mail template I always have ready to go.  Then I 
went out to see the object one last time before sending the mail.  
Back in the house again, 12 minutes after first seeing the object I 
had the mail out to CBAT.

Then I went on observing my other Milky Way fields, while keeping an 
eye on the nova and e-mailing CBAT with follow-up magnitude estimates.  
After the object set, I started looking for the time when it would be 
night-time in several places around the world, as confirmation took 
quite a while.  It was an even more painful wait than with V1494 Aql.  
I nervously walked a lot back and forth in the house.  

Between my discoveries in Aql and Sgr, 149h 20m of search time elapsed.  
The grand total since I started binocular patrol on a significant enough 
scale (back in June 1991), is 614h 01m.  At the current pace I typically 
search ~3h each clear night regardless of the Moon, broken cloud, thin 
cirrus, low altitude or twilight.  As long as conditions allow me to see 
my memorized patterns, I search.  Before 1996, there were frequent gaps 
when for a few months (mainly due to social and logistical reasons) I 
did not search.  By 1998 I was searching some 1.5h each night whether 
permitting.  Then in late 2000, again came a 7 month gap, but afterwards 
the pace has step-like increased to 3 hr/night.

I use 9x34 and 14x100B's.  My search area is ~3000 square degrees, with 
several thousand stars memorized, and includes parts of the following 
constellations: Sgr, Sco, Oph, Sct, Ser, Aql, Her, Lyr, Sge, Vul, Cyg, 
Cep, UMi, Lac, Cas, And, Aur, Gem, Tau, Ori, Pup, and Pyx.  Generally I 
search down to mag 7.5-8.0, but in Sgr/Sco/Oph//Sct/Aql, I try to go deep 
to mag 8.5 using 14x100B's (occasionally a rich-field 15-cm f/4 L @ 26x).

Miras and asteroids are usually picked up when in the mag 8.3-8.7 range, 
but the location of the object within memorized patterns is important.  
Pallas easily caught up in Pup at mag 8.5, later when at mag 7.5, there 
were occasions when its position "disguised" it a bit.  More recently, I 
overlooked V2275 Cyg at mag 7.0.  According to my notebook, I swept the 
nova's field with 9x34B's in the course of two sessions on Aug. 18.93-
-18.95 UT and 19.08-19.11 UT.  I suspect that I mistook the 7th mag nova 
for a nearby 8th mag star (in turn disregarded as a faint non-memorized 
star). 

Optimizing the design of one's asterism patterns is not easy, because of 
different field orientations and variable seeing limit.  Collins [JAAVSO 
vol 23, 1, p. 64, 1994] swept right around N Her 91 at 5th mag!  I think 
that the observer has a natural tendency to move from asterism to 
asterism, and the gaps may not get properly checked, and a bright nova be 
missed there.  I always try to have this present and make an effort to go 
check those gaps.  Often I sweep the same area with both binoculars plus 
the naked eye (to mag 4.5-5.0) during a single night.

I've always been prepared to be beaten by weather or other friend observers, 
but after passing right over a 7th mag nova twice, I tried to understand 
what went wrong, and think of improvements in search method.  I was feeling 
a bit frustrated because the next chance was likely to be years away.  Now 
less than two weeks later, I certainly feel rewarded by having persisted.  
Visual patrol may have its flaws, but has the advantage of an extremely 
prompt alert, and I am very happy that my swift reports on two occasions, 
provided the opportunity for very early stage observations. 

Alfredo Pereira
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