Aeromoe's Version of Joe Orman's Naked-Eye 100 List

Number 61: Lunar Occultation, Planetary

Page 2: Telescopic Observation

Monday 13 August 2012 and less than an hour to go before the moon overtakes Venus during this daylight occultation. This was my first lunar/planetary occultation of any kind since beginning this list. I cannot count it towards the naked eye objects since I couldn't see Venus with my naked eye leading up to the occultation.

Monsoon season in Arizona often brings overcast skies, humidity, wind, and the potential for moderate to severe thunderstorms. Such was NOT the case on the afternoon of Monday August 13th, 2012 when a daytime occultation of Venus by the moon occured over much of the United States, including Arizona.

I started preparing for the photos on this webpage before dawn. The eastern sky was clear and the moon and Venus made a nice pairing in the sky so I took a few photos before the sky got too bright. I then went about my business for the remainder of my early morning.

I had been anticipating this event for months. I'd run the simulation through Stellarium to see when and where the ingress and egress should occur. With my modest recent success of photographing the 2012 Transit of Venus as well as the Annular Eclipse, I was comfortable trying to photograph this event.

The sky conditions this day were far from pristine. There were monsoon clouds looming low in the western sky, and the sky itself was not really all that was more hazy than not. Despite this, in late morning, I set up the telescope and camera combination for a test run of tracking the moon. During the course of the morning I'd already been testing my ability to locate the thin, waxing, crescent moon. With only 15 percent of its disk illuminated, the moon was a challenging object to locate, given the sky conditions. However, once spotted, it was relatively easy to find in the sky even after looking away for a few moments.

I decided to use my Orion 120ST refractor on my Sky View Pro mount. This combination worked well during the eclipse and transit events a couple months earlier. My scope is not permanently mounted and I didn't bother doing a proper polar alignment. I did a rough alignment with the tripod and then powered up the scope and went through the setup menus while skipping the actual star alignment steps. This would at least give me the ability to slew the scope in right ascension. With my 40mm (15x) eyepiece I first focused on the distant clouds. I then moved back to the area where the moon was and within a few moments I had the moon in the eyepiece. Whew - that was easy. Then I removed the diagonal and eyepiece and inserted the Canon 60D and adapter. With live view, I was able to reacquire the moon and get a reasonable focus. Then I started taking some test exposures. Once I was happy with the exposures I started snapping a photo or two every few minutes until it was time to get serious about the ingress.

Lunch time in Arizona in the month of August is usually a pretty hot proposition...and that day was no exception. As I write this a week later, shows the high in my town for the 13th was 115°, so it was already quite hot while I was waiting for the occultation. I'd take some photos, then step back inside for a little while. Wet hair, lather, rinse, repeat. In the binoculars, Venus shone very brightly in contrast to the waning crescent moon. If it weren't for the hazy sky conditions I might have been able to see Venus without optical aid, but it didn't happen. As I counted down to the ingress, I watched the event on the Canon 60D viewscreen. Clicking away the photos and keeping the moon fairly centered on the viewscreen...right up to the point Venus was nuzzled up against the limb of the moon. Slowly Venus began to disappear behind the moon...and then she was gone.

Below is a table of some photos of the event.
Moon altitude / azimuth data gleaned from

Moon: 19.5° Alt / 77.8° Az

13 Aug 2012, 0350hrs Local
Less than 10 hours to go...
Moon: 38.2° Alt / 89.2° Az

13 Aug 2012, 0523hrs Local
Just over 8 hours to go...

13 Aug 2012
Orion 120ST Scope setup
Moon: 56.0° Alt / 256.2° Az

13 Aug 2012, 1141hrs Local
Just about 2 hours to go...
Moon: 42.8° Alt / 267.1° Az

13 Aug 2012, 1246hrs Local
Just under 1 hour to go...
Moon: 31.4° Alt / 274.4° Az

13 Aug 2012, 1342hrs Local
Just about to disappear...
Moon: 17.0° Alt / 283.0° Az

13 Aug 2012, 1454hrs Local
Venus is back!
Moon: 27.9° Alt / 84.9° Az

14 Aug 2012, 0526hrs Local
About 16 hours later...