Comet 46P/Wirtanen, Rocket Launches, and Fog

December 9, 2018 / Add comment

I went out to the Mormon Lake Overlook early last evening (12/08/2018) to photograph a couple of different events. First was the launch of the ULA Delta IV-Heavy NROL-71 mission from Vandenburg Air Force Base. After that, I planned on pointing the camera up towards Comet 46P/Wirtanen.

Only part of my plans worked out. The launch was scrubbed at T-7 seconds but I didn’t know about that until much later. I just kept shooting a series of 15-seconds exposures pointed towards the western horizon and hoping that I would capture it. No launch—and there was nothing to capture.

But, wait, not so fast! It turns out there was a shallow layer of fog in the Mormon Lake basin and the series of 15-second exposures over a period of about 10 minutes resulted in a nice time-lapse movie of the fog. Unfortunately, the camera was pointed at mostly sky with very little of the ground but I’m happy with the lucky result.

Time lapse showing undulations on the top of the fog layer.Next, I shot a series of 60-second exposures of the comet. Although the skies were cloudless, there was a lot of moisture in the air. See the discussion above about fog! The presence of this moisture and very thin fog above resulted in very colorful stars. A nice effect.

For the third act, I pointed the camera back down and over the lake basin towards Flagstaff. The fog was dissipating at this time but still shows up well. What also shows up is the large amount of light pollution in Flagstaff. Flagstaff is the worlds First International Dark Sky City but it takes a lot of work to keep the skies dark. I fear we may be losing the battle.

Bright Objects in the Morning Sky—December 2018

December 6, 2018 / Add comment

The other morning promised an interesting alignment of the planets Venus and Mercury, the waning crescent Moon (3.4% illuminated), and the bright star Spica (Alpha Vir, the brightest star in the constellation Virgo) in the morning sky. All that was required was clear skies.

Morning twilight with Mercury, Venus, Spica, and the Moon (0629 MST 05 December 2018).

Various weather models showed essentially the same forecast. There would be a band of high clouds to our northwest and another band to our southeast. Overhead it would be clear.

And the forecasts turned out correct. Below is a satellite image taken at ~1330 UTC (0630 MST) showing a nice clear gap in the clouds.

IR satellite image at 1332 UTC (0632 MST) showing the gap in the clouds across northern Arizona.

Model forecast for cloud cover. White/gray is cloud; black is clear.

I drove to the overlook on Mars Hill, home of Lowell Observatory, in Flagstaff. It has very good views towards the east and is a location I have used many times over the years for astrophotography.

Comet 46P/Wirtanen Approaches

November 29, 2018 / Add comment

The much-anticipated Comet 46P/Wirtanen is nearing its closest approach (approximately 30 lunar distances) to Earth. From the SpaceWeather.com site (cited 11/28/2018):

Small but hyperactive Comet 46P/Wirtanen is approaching Earth and could soon become visible to the naked eye. On Dec. 16th, the kilometer-wide ball of dirty ice will be less than 11.5 million km away–making it one of the 10 closest-approaching comets of the Space Age.

Earlier this week I made my first attempt at photographing the comet. I had patiently waited until the Moon was several days past full so that I could capture images of the comet without the interference of moonlight. I wasn’t successful because the moon was already rising by the time I was completely set up. Even with the bright sky in the presence of an 85% illuminated moon, I was able to get acceptable images.

Not only was this my first effort to photograph the comet, it was my first effort to even find it in the sky. Having a pair of binoculars helps.

I used a Nikon 85mm f/1.8 lens because it has a moderate field of view (24°x16°) and is a “bright” lens. It can [usually] successfully autofocus at night using bright stars, planets, or best, the moon. And, as I mentioned above, the moon was already above the horizon.

Comet 46P/Wirtanen (85mm, f/2.8, ISO 400, 15x60s)

Later, I switched the lens and used my ancient manual focus Nikon 80–200mm zoom lens. This lens is almost 40 years old—and from the images it appears that it needs some servicing. Many of the stars have a “bulge” in the upper left. Maybe I’ll send it to Nikon servicing—if they still work on this old lens.

Comet 46P/Wirtanen (200mm, f/4.0, ISO 800, 6x60s)

We are now entering an extended period of unsettled weather across the southwest U.S. and there may not be another chance to capture images of the comet for some time. I hope the weather is clear on the night of December 15 when the comet passes very close to the constellation Pleiades. That should make for an interesting sight!

Comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) in the Morning Sky

November 24, 2018 / Add comment

Venus and Spica in the morning twilight.

There’s a new comet in the morning sky. The comet was discovered in early November by three amateur astronomers—one in Arizona and two in Japan. Nowadays, most comets and asteroids are discovered by robotic Near-Earth-Object (NEO) search programs. The discovery of a comet by amateur astronomers is becoming a rare event.

So, with that bit of information, I set out to capture some images of the comet. As an 8th magnitude object it would not be easy using a short telephoto (i.e., 85mm focal length). My first attempt was marred by clouds but after viewing the images later I was finally able to find the small and not very bright comet.

A few days later I tried again. And, once again, high clouds moved across the sky. Finally, just before twilight, the clouds moved out of the way and I was able to get about 25 minutes of images.

Because the comet is so dim, individual images are not very revealing. In this case, better results are obtained by creating a short animation over the 25 minutes showing the motion of the comet relative to the stars.

As the eastern sky brightened the planet Venus and nearby star Spica stood out (image at top of post). A very nice end to a morning of shooting photographs in the cold.