Friday, December 26, 2014

NOW It's A Holiday!

Looking at the calendar, it is almost a week past Winter Solstice, long past the normal times I'd try the Kitt Peak solstice alignment.  The pull off along the Mount Lemmon Highway is normally the spot to be about 3 days before and 3 days after solstice for a good alignment, but it isn't an exact science.  Melinda and I were out of town on the normal dates, and to really make it seem like Christmas, I needed the tradition of chasing the alignment!  I also noticed something else to shoot for...  More on that later.

I helped the alignment a little by biasing my position along the pull off so that I was on the far southern edge of the spot along the busy highway.  The image at left shows the spot along a long bend to the left, paved pullout on the outside edge.  The image at right shows my setup this year - the TEC 140 (1,000 mm focal length), and a very sturdy home-built mount and tripod.  Of course, the smashed-in rear of my van is still there too, status still unknown... 

Even though I was pushing the limits of what I knew about the alignment, I was pretty confident I'd still catch it.  I got there in time to set up, let the telescope and optics cool down, and align the field to Kitt Peak National Observatory before the sun came into the field.  I was using a Thousand Oaks Type II photo filter which leaves the image too bright for visual use, but fine for photographic, especially near the horizon.

Finally the disk came into the field and I fine-tuned focus and exposure.  Sure enough, it is almost like I know what I'm doing as the Sun was just south enough to cover the extremes of the Observatory for just a couple seconds.  Taking a picture every 4 seconds, the one before and after the one shown I would call unacceptable...  There were even some nice sunspots showing a little activity!  With the XSi and TEC going on auto, I took a few hand-held shots with Melinda's T1i and a 300mm lens.  The unfiltered shot at right was a 2000th second exposure showing the 4-meter and peak of the mountain bifurcating the remaining disk of the sun.

It is always fun to tarry in putting gear away and looking to see what else can be seen in the twilight.  There are often some projection effects in the shadow of Kitt Peak, though the very clear sky minimized some of these effects, but still, the shadow of the 4-meter can be seen cast into the sky in the image at left.  At right, a transmitter array located atop  one of the peaks of the Tucson Mountains across the Tucson Valley is seen across a much nearer hilltop of the Catalina Mountains, where I was located.

While on the computer earlier in the day, looking up the sun's position to see if I could catch the alignment, I noticed that Venus, now up in the evening sky, was nearly at the same declination (north-south position) as the sun, so would also set behind Kitt Peak about an hour after sunset.  Actually, it was about a quarter of a degree north of the sun, so to help out the alignment again, I moved a couple hundred yards down the road to the "Thimble Peak Viewpoint" to bias my position a little.  Venus is now easily visible shortly after sunset, and re-setup my gear at the new position.  Sure enough, it moved almost into prime position, eventually setting behind the 4-meter telescope.  The left image shows a partially cropped view of Venus still above the observatory, the assemblage at right shows Venus at 10 second intervals setting behind the very peak of the mountain.  If Venus were more properly exposed, it would likely show more colors due to atmospheric dispersion.  Because it is so overexposed, the colors are re-blended into a mostly-white image.

Unfortunately, it was tough to balance exposure of the twilight-backlit observatory and brilliant Venus.  The planet remains very over-exposed, but needed a half-second exposure to catch the remains of twilight.  In addition, Venus, over 120 million miles away, subtends a very small disk.  It would be nice to try again when showing a skinny crescent.  So the opportunity for a "perfect" shot remains!

1 comment:

Irene Kitzman said...

Great effort and well worth your sleuthing the best spot on the Catalina Highway - Thanks for the great photos! Irene Kitzman