Archive for April 2nd, 2017

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Observing report: Saturday night stargazing on Mount Baldy

April 2, 2017

Waxing crescent moon, afocal shot by Eric Scott with Samsung Galaxy S6, shooting through Orion XT10 reflecting telescope.

London and I went up Mount Baldy last night with our friends Thierra Nalley and Eric Scott. Marco Irigoyen and Leandra Estrada joined us up on the mountain. We went up to look for comet 41P, but that didn’t pan out.

Since we went ostensibly to look for the comet, I brought the XT10 for firepower, and lots of binoculars. We got set up at Cow Canyon Saddle at about 8:30. Our first target was Orion, before it could sink into the light dome over LA. Second targets were the Pleiades and the Double Cluster. The Double Cluster in particular looked magnificent. I’ve been on a small-scope kick for a while so the XT10 hasn’t been out much, and I tend to forget what a potent instrument it is, especially under dark or semi-dark skies.

The skies on Mount Baldy last night were definitely semi-dark. Even three days shy of first quarter, the waxing crescent moon was bright enough to throw shadows and rather seriously degrade the darkness of the sky.

I tried for the comet but just couldn’t see it. I had the chart, knew where to look, and swept the area repeatedly with binoculars of all sizes and with the XT10, and I got bupkiss. This was after catching the comet easily in 7×50 binos every time I looked for it in Texas last weekend – but I wasn’t fighting any moon then. I think the comet is so big and diffuse that the surface brightness is low, and therefore it is easily swamped by moonlight. It certainly was not evident last night.

While we were in the neighborhood of the Big Dipper, we had a look at Mizar and Alcor, the famous double star in the dipper’s handle. Then for comparison we checked on Sigma Orionis, and then Marco wanted a look at Jupiter. After Jupiter we went on an extended tour of the deep sky, in which we observed:

  • M81, M82 (interacting galaxy pair)
  • M97, M108 (planetary nebula and galaxy in same field)
  • M3 (globular star cluster)
  • M37 (open star cluster)
  • M35 (open star cluster)
  • M104 (Sombrero galaxy)

In addition, we also saw three more open star clusters with our naked eyes and/or binoculars: the Hyades, M44, and the Coma Berenices star cluster.

We finished up on the moon, and then Jupiter again. We spent quite a bit of time getting pictures of both with Thierra’s and Eric’s phones. By coincidence, they both have the Samsung Galaxy S6, which has a very full-featured slate of camera options. Leandra is a pretty talented photographer and she was able to coach us on what settings to use. I think the results are pretty astounding, for handheld shots using phones. Here are the two best images of Jupiter, captured by me using Thierra’s phone and Leandra’s advice:

Here’s a composite of Jupiter and the Galilean moons – the planet was overexposed in the original to get the moons to show up, so I replaced it with the better of the two shots above.

And here’s a comparison screenshot from Sky Safari Pro 5 identifying the moons – from left to right in the above image they are Callisto, Europa, Io, and Ganymede.

As usual, the view at the eyepiece was about an order of magnitude more detailed than what the photos captured. One thing that I had never seen before with one of my own scopes was a band of ruffled white clouds within the north and south equatorial belts (the prominent orange-brown stripes on either side of the equator). The barest hint of this survives in the photos. It was a pretty mesmerizing view. For eyepieces we used a 32mm Plossl (37.5x), 28mm RKE (43x), 24mm ES68 (50x), 14mm ES82 (86x), 8.8mm ES82 (136x), and 5mm Meade MWA (240x). The most used were the 28mm RKE, 14mm ES82, and 5mm MWA. If you’re wondering why we used both a 32mm Plossl and a 24mm ES68 – since they give the same true field of view – we used the Plossl during the afocal photography because it gives a wider exit pupil, which is easier to keep the camera’s aperture centered inside.

Even though we missed the comet, I was pretty happy with what we did see – at least one of every major class of deep-sky object, including all of the stages of the life cycle of stars. In the disk of the Milky Way, new stars are born from vast nebulae of gas and dust, like Orion. In time, heat and light from the newborn stars push away the remnants of their birth clouds, leaving behind only the stars themselves, as open star clusters (‘open’ as opposed to globular). Over time, the stars in open clusters drift apart to become ‘field stars’ like the Sun, no longer gravitationally bound to their siblings. When the run out of fuel, stars blow themselves apart in supernovae if they are 8 times the mass of the Sun or larger, whereas smaller stars blow off their outer layers of gas to form planetary nebulae like M97. Whether stars die suddenly in supernovae or slowly as planetary nebulae, the matter blown out by dying stars enriches the galactic gas and dust clouds, and in time it will be incorporated into new generations of stars and planets. We are products of this process – all of the elements in our bodies other than hydrogen were born by fusion in the hearts of stars, and seeded into the galaxy’s spiral arms when those stars died.

Farther out, globular clusters like M3 orbit the core of the galaxy on long elliptical orbits that are not flat, but come looping in from all directions. The stars in globular clusters are typically very old, 12 billion years or more. We know very little about how and why globular clusters formed, and how they came to have such weird orbits. Probably they are some kind of developmental leftover from the formation of the earliest galaxies in the first billion years after the Big Bang – astrophysical fossils, if only we knew how to interpret them.

All of these processes are going on in other galaxies as well, especially spiral galaxies like M81, M104, and M108.

To put all of that into context, here are all of the objects we observed again, this time ranked from closest to farthest:

In our solar system:

  • moon – 240,000 miles or 1.3 light seconds
  • Jupiter – 370 million miles or 33 light minutes (currently – Jupiter is about 5 AU out from the sun, but right now we’re on the same side of the sun so it’s only 4 AU from us)

In our spiral arm of the Milky Way galaxy (the Orion spur):

  • Mizar and Alcor (double star) – 83 light years
  • Hyades (open star cluster) – 151 light years
  • Coma Berenices cluster (open star cluster) – 280 light years
  • M45 (Pleiades; open star cluster) – 440 light years
  • M44 (Beehive; open star cluster) – 577 light years
  • Sigma Orionis (multiple star) – 1255 light years
  • M42, M43 (Orion nebula; star-forming region) – 1344 light years
  • M97 (planetary nebula in same field as M108) – 2030 light years
  • M35 (open star cluster) – 2800 light years

In the next spiral arm out from the galactic center (Perseus arm):

  • M37 (open star cluster) – 4500 light years
  • NGC 869/884 (Double Cluster; open star clusters) – 7500 light years

In the galactic halo of the Milky Way:

  • M3 (globular star cluster) – 34,000 light years

External galaxies:

  • M81, M82 (interacting galaxy pair) – 11 million light years
  • M104 (Sombrero galaxy) – 31 million light years
  • M108 (galaxy in same field as M97) – 46 million light years

That is very satisfying to me, to take in such a menagerie of celestial objects, at so many scales and distances, in the space of a couple of hours armed only with a comparatively inexpensive telescope and an idea of what’s out there to be seen. I can’t wait for next time.

Saturday night astro crew. Left to right: Marco Irigoyen, Leandra Estrada, London Wedel, Matt Wedel, Thierra Nalley, Eric Scott. Photo courtesy of Eric Scott.

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