Monday, September 28, 2015

ECLIPSE!

If you get your news off of the Interwebs (you poor thing!), you certainly would have known about the "Supermoon Eclipse" or "Super Blood Moon", or "Blood Moon Spells Doom", or some combination of the above. While I learned that the last "Supermoon Eclipse" was in 1982, back those days we NEVER called a moon at perigee a Supermoon. In those "olden" days, we also NEVER called a total lunar eclipse a "Blood Moon". I do not know how these terms get into the vernacular, and I hate it, so you will note that outside this paragraph, these terms will NEVER be used again here!

From the western part of the country, where we live (Tucson, AZ), the full moon rose right at sunset, of course, just as it was moving into the shadow of the earth. Since we just passed the autumnal equinox a few days ago, the eclipsed moon would pretty much rise due east. We were invited to a 5-year-old's birthday party late in the afternoon, and I suspected we'd be arriving home right about the start of the eclipse, so I at least thought about what I wanted to do. I actually went out the evening before scouting some locations, looking for a foreground that might say "Tucson". I went wandering around downtown, and found this scene looking east down Congress Street, but it didn't yell "Tucson" enough for me, even with a rising eclipsed moon down the street...



So I gave up on a scenic background, especially with the party taking up a chunk of the afternoon. We just went home afterwards for Melinda to rest after spending time at a Hispanic birthday with Techno band and hyperactive children (actually, I could use some quiet time too!). We got home about 15 minutes before sunset and I started setting up the equatorial mount in the back yard to set up the TEC 140 refractor. Right about sunset, I took an amble around the neighborhood with telephoto zoom to look for the rising moon. In the alley behind our house I ran into the neighbors, who were holding a small party with chairs facing west. I pointed out the moon would be rising behind them, but they were celebrating the sunset first... They joined me in the trek towards the rising moon, soon spotted rising due east as expected, shown at left. We have lots of suspended power and cable lines, so walked a hundred yards to clear some of them, as shown at right. These shots taken with the 70-200 zoom off a monopod, 200mm at left, 140mm at right.

It soon got dark enough that the short exposures to properly record the moon way underexposed the background, so I departed to set up the scope. Plus there was lots of good stuff on TV! There was the Cubs game against the Pirates (CUBS WIN!), there was the CSI finale, and a little later there was the Silent Sunday features on TCM. Fortunately, working in the yard, I could keep track of the game while stepping out frequently to monitor the eclipse. My first mistake was assuming the eclipsed moon would clear the tree from where I had first set up the mount. Wrong! Moving an assembled AP 1200 needed more strength than I had, so needed to disassemble and set up against my western fence. It amazing how fast the thing goes together with an eclipse progressing over your shoulder! The shot at left was taken with the zoom lens again off a tripod for 6 seconds at F4.5, showing the total phase of the moon against the stars of Pisces. The TEC 140 works at F/7, so is just about 1 meter focal length, just about perfect for an eclipsed moon, even at perigee! My first guess at an exposure was 20 seconds, shown at right - a little overexposed, but shows more stars than in the shorter, properly exposed images.

I finally settled on 8 second exposures at ISO 200 that didn't saturate any of the channels. With the scope set to lunar rate to track the moon, I used an intervalometer to take an image every 60 seconds. It finally started routine exposures at 7:42, just a couple minutes before mid-totality when the moon was deepest into the earth's shadow. The image at left shows mid-eclipse at 7:47. I let it go pretty much automatically, occasionally adjusting the north-south position of the moon, as lunar tracking only handles the east-west motion. After the deepest part of the eclipse, the moon slowly got brighter at lower left until it eventually left the full shadow of the earth. The image at right was at 3rd contact, just as the edge of the earth's shadow hit the edge of the moon.

The partial phases don't interest me much, so I took down the gear after 3rd contact and put things away. After work today I finally started messing with all the frames, about 43 all told. The limitation turned out to be the visibility of a single star to center on during the sequence, taking out the declination adjustments, and visible throughout. Using Nebulosity 2 software, I centered on the same star, so that in a time-lapse, shown below, the stars appear fixed and the moon moving through the field, as it should be. Since the earth's shadow moves slowly (about 1 degree per day), the moon's motion of about a half degree per hour dominates and zips through in a couple hours at most. Here is the result, uploaded to Youtube. Be sure to go full screen and HD for best visibility of stars and details...




All in all, a pretty good eclipse! The last few we've had had issues, clouds, or shooting from Mexico w/out a tracking mount. They are about to get a lot rarer - after 3 of them every 6 months, the next total lunar eclipse for North America won't be till January, 2019! Seems like a long time off...

1 comment:

Anonymous said...

the term "blood moon" comes from writings of the antiquities; biblical, and secular. descriptive of observed times when the "moon (turns to) the color of blood" so... not a new concept at all.

as for supermoon, well that is a kind of colloquialism that just oversimplifies the science, to the point that most don't even know what supermoon means. that's my five cents worth...