Category: Astronomy

A look at Comet 21P/Giacobini-Zinner

Comet 21P/Giacobini-Zinner is a periodic comet with an orbital period of 6.6 years. It made its closest approach to Earth on September 10–11 when it was ~58 million kilometers distant. At that time it brightened to around magnitude 7–which is still too dim to be an unaided eye object. Binoculars, telescopes, or long-exposure photography are still necessary.

My first attempt to capture images was on September 15 when the comet passed in front of M35. Oddly enough, I was unable to clearly see the comet because of the large number of stars in the star cluster.

First attempt at Comet 21P/Giacobini-Zinner.
First attempt at Comet 21P/Giacobini-Zinner.

My second attempt was a few days later (September 18) after it had moved away from M35. This was a better setup. But my imaging wasn’t great. Perhaps the sky wasn’t as clear as I thought it was or my technique isn’t as good as I think it is. Either way, the results aren’t as sharp and clear as I hoped.

Comet 21P/Giacobini-Zinner.
Comet 21P/Giacobini-Zinner.

Still, it was fun—especially the second attempt. After setting up the tripod, aligning the equatorial mount, and getting [almost] sharp focus I let the camera run for over an hour taking 120 second exposures (followed by 120 seconds of Long Exposure Noise Reduction, LENR).

I was surprised (but should not have been) at how much movement there was in the position of the comet in just a bit over an hour. The video covers the time period from 0320 to 0431 MST.

 

I also used Deep Sky Stacker (DSS) to stack the individual images in which the software keeps the comet sharp while the stars have trails. Because of the 2-minute gaps between images, there are also gaps in the star trails.

Comet 21P/Giacobini-Zinner.
Comet 21P/Giacobini-Zinner.

During the 1-hour period in which the camera was on “autopilot” I was able to lie back and stare up at the sky. I saw about two dozen meteors during that period and many of them seemed to have origins near the constellation Orion. The Orionid meteor shower doesn’t peak for another several weeks (active from September 23rd to November 27th with a peak on October 21–22) but it’s possible these were early arrivals of that meteor shower.

Milky Way and Sunset Crater National Monument

The weather has been fairly typical for late June and early July: warm temperatures, breezy afternoon winds, and mostly clear and sometimes absolutely clear skies.

That will change dramatically over the next few days as the North American Monsoon ramps up across Arizona and the desert southwest. As subtropical moisture begins to move northward we will see a significant increase in cloudiness and thunderstorms. Clear night skies will quickly become a distant memory.

With that in mind, I took advantage of clear skies and did some Milky Way photographs. I decided to try Sunset Crater Volcano National Monument so that I could get some of the volcanic hills and ridges in the image.

The Milky Way arches across the sky at Sunset Crater Volcano National Monument.
The Milky Way arches across the sky at Sunset Crater Volcano National Monument.

Near the horizon is Mars which is becoming very bright in the evening sky—and will reach its peak brightness later in July. The planet Saturn is also visible within the starry mass of the Milky Way.

Moonrise and Cathedral Rock — June 2018

Another month and another moon rise behind Cathedral Rock. This was an easy setup with the location in Crescent Moon Picnic Area in Sedona. The day before the full moon resulted in this image taken from the meadows near the entrance to Crescent Moon. There were about a half-dozen “moon chasers” there to photograph the moon rise—and there were many others who just happened to be in the right place at the right time to enjoy the event.

Moonrise behind Cathedral Rock.
Moonrise behind Cathedral Rock.

The previous night (i.e., two nights before the full moon) presented another chance to capture the rising moon with Oak Creek in the foreground. This one was harder because a better position was more to the right (i.e., south) but there was nowhere to go because of trees and heavy brush. Still, I’m happy with the result.

Moon rise behind Cathedral Rock with Oak Creek.
Moon rise behind Cathedral Rock with Oak Creek.

Both nights I was testing a recently purchased lens (Nikon AF-P 70-300mm). So far, the results have been pretty good.

Venus and Mercury in Evening Twilight

Earlier this year in March the planets Venus and Mercury were close to each other in the evening sky. The crescent Moon also joined the two planets one evening (18 March 2018) resulting in a photogenic scene in the western twilight sky.

Mercury faded from view shortly thereafter and shifted into the morning sky. However, Mercury recently reached superior conjunction (06 June 2018) passing from the morning back into the evening sky. So, once again, Venus and Mercury share the western twilight sky. Mercury will continue to climb higher in the sky through mid July when the two planets will be at their closest approach.

Venus and Mercury in evening twilight.
Venus and Mercury in evening twilight.

A very nice animation of the positions of Venus and Mercury, as well as Jupiter and Saturn, can be seen the Shadow and Substance website video.

Exceptionally clear skies resulted in these images of Venus high in the western sky with Mercury much lower and a bit more difficult to see in the bright evening twilight. Mercury should become easier to see over the next few weeks.

Bright Objects in the Night Sky — May 2018

The past two weeks have offered several opportunities for photographing the moon in the evening sky. Beginning on May 16, we had a crescent Moon with just 3.7% of the disk illuminated by the sun. During the months of May, June, and July, the thin crescent Moon lines up with the long axis of Upper Lake Mary. This results in nice reflections of the Moon on the waters of the lake—but only if there is little or no wind. The first two images were taken in the early evening with some reflections over portions of the lake. The image also shows the unlit part of the crescent Moon illuminated with Earthshine, also known as Da Vinci Glow. Yes, that Leonardo Da Vinci. Quite an amazing bit of scientific deduction on his part.

A thin crescent Moon above Lake Mary.
A thin crescent Moon above Lake Mary.
Crescent Moon with reflections on Lake Mary.
Crescent Moon with reflections on Lake Mary.

The following evening the Moon was located near the planet Venus. Capturing both of these objects and getting reflections in the water was a bit more difficult as they were higher in the sky.

Moon and Venus above Lake Mary.
Moon and Venus above Lake Mary.

Next up was the day-before-the-full-Moon in Sedona. Using The Photographers Ephemeris it’s not very difficult to determine at what time and in which location to find the Moon rising between the spires of Cathedral Rock. I’ve done this shot before but never get tired of traveling to Sedona to see it happen again. Not surprisingly, I often run into other photographers and friends with the same idea so it becomes a bit of a social gathering as well.

Moonrise above Cathedral Rock in Sedona, Arizona.
Moonrise above Cathedral Rock in Sedona, Arizona.
Moonrise above Cathedral Rock in Sedona, Arizona.
Moonrise above Cathedral Rock in Sedona, Arizona.
A couple watches the Moon rise from Cathedral Rock.
A couple watches the Moon rise from Cathedral Rock.

The first image shows the Moon having just risen into the left gap. The second image is a crop and closeup of the Moon. The third was taken several minutes later after adjusting my position a bit to capture the Moon in the middle gap. A couple can be seen in silhouette gazing at the rising Moon.

The International Space Station cross the sky.
The International Space Station cross the sky.
The ISS and OA-9 Cygnus move across the sky.
The ISS and OA-9 Cygnus move across the sky.

Finally, there was a transit of the International Space Station (ISS) and the resupply ship OA-9 Cygnus—both moving near the North Star. The transit is a 5-minute sequence of images while the star trails is a 30-minute sequence. The second image shows the bright ISS with the faint OA-9 Cygnus following behind. A day later, the OA-9 docked with the ISS.