Occultation by Venus on April 26/27 was too difficult - New 2007 May 4, 0h UT

Message to Brad Timerson in Newark, NY (where the altitude was lower)

Brad,

     Thanks for your account.  It was similar for Jose Guzman and 
me.  Earlier we decided to cancel since the national weather service 
forecaster was less optimistic about chances in WV than Astro Meteo.  
But about 6:30 pm, I noticed that the situation was improving behind 
the front apparently faster than Astro Meteo was predicting, so we 
made a last-minute dash to Morgantown, WV, driving through rain much 
of the way.  The sky did break up into partly cloudy conditions as 
we approached Morgantown about 10 miles east of there, so we found a 
church parking lot on a ridge near I-68 exit #1 and set up to see ZC 
753 = HIP 23550 appear to approach the bright planet.  I found that 
2 layers of Mylar were needed to dim Venus' bright disk, but even 
so, the glare from the planet was too much and I think we lost the 
star a little earlier than you. The wind picked up after we set up, 
and that didn't help, either, making it impossible during the last 
several minutes to keep the star and Venus continuously on opposite 
sides of the edge of the Mylar cover that I put over half of the 
PC164C CCD chip.  I used a 20cm SCT without any focal reduction, to 
increase the scale.  The "defect of illumination", the distance 
between the star at the time of disappearance and the terminator of 
Venus' sunlit disk, was only a few arc seconds in this case, just 
not enough with such a bright object; I think a larger crescent 
Venus is needed to effectively observe such events (Venus' disk was 
70% sunlit and 16" in diameter).  We were fortunate with the 
clearing because Venus, at about 8 deg. altitude, disappeared in 
clouds during the 2:50 UT minute, about the time of the occultation, 
and it became overcast soon after that. So at least we saw enough to 
appreciate the difficulties of such observations, useful information 
for future Venus occultations.  There's another similar event on 
Sat. evening May 19 when conditions are slightly better with Venus' 
19" disk 60% sunlit, but the star, SAO 78893, is only mag. 8.9 so I 
don't give much hope for it. 

David

At 09:22 AM 4/27/2007, you wrote:

>I was not able to see the star after 2:47 UT, just too close to Venus 
>(tried powers ranging from 47-475x in my ETX-125). Still a great event 
>to me, watching the approach!

David Dunham, e-mail dunham@starpower.net and (office, connected to 
my Blackberry) david.dunham@jhuapl.edu, cell phone 301-526-5590.