Would I notice a rock slide if it were right in front of me?

I once emailed a link to one of my climate illustrations and told the recipient, "make sure you read the caveats tab." She replied, "everyone should have a caveats tab."

And so I continue to look for opportunities to test what I know, as well as what I remember.

Two years ago I started exploring a hiking route that involves some rock climbing and a lot of scrambling. Think if it a course of constant deep knee bends and limbo manuvers. After about a half year of exploring this route I noticed a rock slide:

This hike is in a canyon with a lot of loose rock and rapidly eroding slopes. Therefore, I stay away from these hazards. But still, I always look at where I walk and observe my surroundings, and I should have been looking out for something so obvious a hillside of newly exposed rock and dirt. Or would I notice such a thing?

Did I witness a significant erosion event in the short time I'd been exploring this canyon? Or did I fail to notice something that occurs on a longer scale? -- and therefore, need to examine my observation skills for overconfidence.

This rockslide also knocked over a cotton wood tree. Here is a photo of it sideways on the ground with a new shoot growing upright.

The photo above shows dead limbs (angled downward) and a new limb (angled at 2:00 ) which is actually vertical, though this isn't obvious in the photo. In fact, the tree had about a half dozens of these newly started vertically growing limbs. The presence of new vertically growing limbs when the rest of the tree is horizontal offered a proxy measurement of the date at which this tree was suddenly knocked over.

I selected one of the thickest limbs (the one in the photo above) and cut off a sample of the limb near the base. Below, I've counted and labeled the growth rings. I count three more than the time I've been visiting this rock slide.

So, I add this to my metaphorical caveats tab. I can miss the obvious. Do others?

jg

Comet Hunt for October

Comet ISON is in the morning sky, but I haven't seen it. I took some photos of the region this week. In the photo below, ISON is supposed to be a coupled degrees distant from Mars and Regulus (the two bright stars in the picture):

I scrutinized the picture, but can find no sign of a comet, suggesting that viewing the comet needs a telescope, which can improve the contrast between it and the glow of my light polluted sky. Perhaps a longer exposure under a darker sky would reveal the comet. My photos were taken on the morning of Oct 16. By now, the full moon interferes, so the next prime opportunity to search will be in about 9 days.

Meanwhile, the morning sky enabled my first photo of the southern star Canopus, which is the second brightest star in the sky. Here is Canis Major, with canopus on the horizon (just right of the tree).



This  is the same area, but a little longer exposure. The stars and star clusters in Canis Major are easier to see, but Canopus is not as bright because it hadn't yet cleared the tree:

Sirius is the brightest star in the night sky, and the brightest in Canis Major. Canopus is the second brightest star in the night sky. It is rare for northern hemisphere observers to see both. 

jg

What's Up, Orange County Astronomers, 11 Oct 2013

I'm doing the October What's Up presentation for the Orange County Astronomers (http://www.ocastronomers.org/e-zine/monthly_meetings/details/MM201310.asp), which is tonight at 7:30. Here are a few highlights that I'll be sharing

 

The Delphinius Nova fades, as shown in this comparison of photos from Aug 15 with Oct. 5. The first overlays the nova taken on 18 Aug with the same star field photographed a year ago.



 

The second photo shows that the nova has faded to a dim star.

I got a fresh image Andromeda rising in the east last weekend. Here I've diagramed how to find M31 and M33. M31 is visible from a moderately light polluted sky. M33 needs pure darkness, but can be seen with binoculars.

The full moon stomps on the next two significant meteor showers, so I'm sharing a consolation prize, a time when the moon helped the photo.

The above includes the full moon, anticrepuscular rays, and the Earth's shadow. The rays (shadows on the left, are from the sun and converge on the anti-solar point just below the moon. The blue horizon is the earth's shadow. Both of these are corroborated by the presence of a full moon, which you see as full only when the moon directly opposite the sun.

 

jg