Cassiopeia Observatory

Occultation of Venus

Posted: 13 August 2012

Our monsoon weather pattern returned during my last session in the observatory and cloudy skies continued through the Perseid Meteor Shower maximum the night of 11-12 August, and continued the next night. So, I missed the best opportunities to see Perseid meteors.

Monday, 13 August, dawned with partly cloudy skies. I was able to capture this photo of Venus and the crescent moon almost 7 hours before the start of the occultation of Venus. The photo was taken at 0642 MST using a Nikon D7000 DSLR, f/8, 1/1600sec, ISO 500, 300mm lens, and has been cropped. Sunrise was 0546 MST and the occultation was to begin at 1346 MST.

I opened the observatory at 1258 MST, 117°F. I added the dewshield to the 8" LX200-ACF to act as a "sunshield". There were some clouds in the sky but I hoped for the best. At 1313 MST, did a GOTO Venus. The faint crescent moon and the half-illuminated Venus were both in the 26mm (77X) eyepiece field-of-view. Seeing was lousy and focusing was very difficult.

I took this photo of Venus and the moon at 1312 MST, f/8, 1/1600sec, 300mm lens, ISO 500, to show how much closer the moon was now to Venus:

I then mounted the D7000 DSLR at prime focus + visual back + 2X Barlow Lens on the 8" telescope. There was not a lot of contrast between the moon and the bright sky but this 1/320sec, ISO 1000, exposure does show the moon and Venus at 1324 MST:

At 1330 MST, clouds were approaching the moon. These views, taken with an iPhone 4, show overhead (top) and to the east (bottom):

These photos with the D7000 and 8" telescope were taken at 1333 MST (top) and 1340 MST (bottom):

This iPhone photo shows the sky by the moon at 1340 MST, just 6 minutes before the occultation was to begin:

Things were looking fairly good for the start of the occultation. I did a HD video recording, 1/320sec, ISO 1600. Click the image below to view the video. The audio in the background was what was playing on my Apple iPod in the SkyShed POD. The video is real-time and runs 1m15s.

(If you are using Firefox and can not view the video above, click here to see the HD full video, 182 MB.)

So, I got lucky and captured the ingress. But one minute later I started hearing large raindrops hitting the observatory! It was a good thing I had attached the dewshield to the telescope as it was now acting as a "rain shield"! I quickly closed the observatory dome. Rain and even thunder continued for several minutes. At 1355 MST, it was really pouring. Fortunately, it was just a brief rainshower.

At 1355 MST, I removed the Barlow Lens for imaging egress, if the clouds went away. At 1413 MST, the rain ended as the storm moved off to the northwest. I went outside and wiped the water off of the dome. I then re-opened the dome. The moon was visible in a small clear area. I took this iPhone photo at 1423 MST; the moon is near the center of the frame, in the small blue sky area:

Unfortunately, the clouds covered the moon at 1440 MST (12 minutes before egress). At 1448 MST, the moon became visible briefly in a hazy sky, but disappeared again within a minute. It stayed hidden by clouds until after egress was over. At 1458 MST (6 minutes after egress), I took this photo at prime focus of the 8" LX200-ACF, 1/400sec, ISO 100:

As I was uploading this report to my web server, another monsoon thunderstorm came through about an hour before sunset. There was some rain and frequent lightning. A nice double rainbow appeared. I took this panoramic photo with my iPhone 4 and Photosynth. When I viewed it, I was surprised that I also captured a lightning bolt! Neato!!!

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