The Venus / Mars/ Moon Triple Conjunction, and the Occultation by Hispania

Feb 20, 2015

This conjunction is arguably the most photogenic of 2015, as the trio spanned less than 2 degrees and were in true conjunction perfectly placed for the West coast. Skies were clear, and I changed plans at the last minute to take the opportunity to photograph this beautiful show. Late in the afternoon, Ted Swift emailed me details of an asteroid occultation which was not on the Preston or Breit lists, and yet which looked do-able(?) for the 12" scope using the star trail method, at 7:35pm. So my plan was to photograph the conjunction from outside the dome, and then quickly go in and ramp up the 12".


Taken with the Nikon D7000, with 18-200mm zoom at intermediate focal length.

Exposure 4 seconds at 200mm, manually focused seemed better than the automatic focus. ISO 1000

Exposure 2 seconds at 200mm, ISO 1000, with some photoshop'ing


I got these shots off as quickly as possible, since the asteroid occultation was less than an hour away now. From past experience, I know that a 50 second trailing exposure is about the longest that's sure to stay completely on-chip. The predicted occultation was 8 sec maximum, at 7:35:31 PST, so I decided I'd prepare for starting the trail exactly at 7:35:00.0 for 50 seconds. The path nominally passed north slightly, with the southern limit pretty much across Derek Breit in Morgan Hill, and the northern limit across Ted Swift in Davis, who also got observations.

This shot was taken about 15 minutes after the event, as Hispania was separating from the target star. Hispania is the brighter of this tight pair, on top. Here's the full resolution .tif file

The star trail image. There's a suggestion of a ~2 sec long fade at the spot shown. However, there are similar fades or blurring on the 3 brighter stars further to the right at this same time. So most likely it's a period of poorer seeing. The full resolution .tif image



After the occultation, I had to mount the newly arrived 1.25" eyepiece extender on the end of the Orion 80mm ShortTube finderscope so that the PC165DNR video camera could come to focus. Then twist to get the orientation right, and focus it. Happily I got all that accomplished and was gratified to see that I could reach 12.3 magnitude (barely) at 1.5 air mass altitudes, with 8x integration mode.

I also did some other tasks while there; replaced the rusted steel adjustment screws with nylon screws on the Orion Short Tube, re-centered the image to coincide on the TV screen as the same place as the wide field video camera and CCD camera. Have not yet tried hooking the video occultation rig to the PC165DNR video output. Also, I note the pointing is off by several degrees when flipping over the meridian. Likely due to a snag on the wires recently on a certain pointing. I also tried tightening up the wire harnessing to avoid any more snags. I also did a series of 5 minute exposures of Comet Lovejoy while trying to load and learn scantracker.exe

A stack of five 5-minute images on the 12" f/6.3 big scope, with SBIG ST2000xcm CCD camera.