Partial solar eclipse on January 4th

The eclipse season continues, as the Moon's nodes--the intersection line of the Moon's orbital plane and the Earth's orbital plane--continue to point in the direction of the Sun and anti-Sun. After the winter solstice lunar eclipse Europe, Northern Africa, and the Middle East will get a partial solar eclipse on January 4th. The maximum eclipse reaches nearly 86% in Scandinavia, although I wouldn't really trust a low-altitude solar eclipse at the Arctic Circle this time of year to be likely visible.

Since we know the Moon's orbital plane right now, we can extrapolate to the appearance of the Moon in upcoming months and phases. We know that the first and third quarter Moons will be either higher or lower away from the ecliptic, since at new the moon was obviously at the ecliptic (to produce the eclipse). So we need one other piece of information to give us the appearance of the Moon in the sky: is the node ascending or descending? Recall the Moon passing Jupiter about two weeks ago.
Was it above or below Jupiter in the sky?

Sadly, I had to check via a planetarium program because I couldn't remember. It passed above Jupiter. So the node is ascending, and the First Quarter Moon in January will be higher than usual in the sky and the Third Quarter Moon lower (but keep in mind only in deviation from the ecliptic, not in absolute elevation in the sky). In three months (aka March-April) the full Moon will be lower in the sky than usual and rise and set further south than normal.



http://eclipse.gsfc.nasa.gov/OH/OH2011.html

near infrared lights

When I need good near-infrared lighting, I turn to the broadband sources called the Sun and incandescents. They are the closest thing to a blackbody we see on a regular basis.



I presumed on this post that I was seeing an intense sodium line from high-pressure sodium lighting while taking daytime near-IR images. What I didn't realize while speculating at that point was that every high-intensity discharge light has a very hot envelope--for high-pressure sodium, a bulb of aluminum oxide (all jokes about transparent aluminum aside, of course). For metal halide and mercury vapor it's usually fused quartz, but sometimes it's the above alumina or sapphire. The tough requirements of dealing with a circa 3500K corrosive plasma dictate the choice of material. Have you ever seen a cycling HPS streetlight? As soon as the arc extinguishes you can see the pure blackbody glow of the very hot bulb window which is at or just below 1200K. That's what I'm detecting in the infrared shots--any HID light that is on is a great IR source. See this shot of the Chicago Theological Union / Oriental Institute or this one on the central quad of the University of Chicago -- the metal halide lights are on in the early evening with sunlight still streaming in. (Don't get me started on energy decisions here). Or here.


Or this HPS streetlight here at Hull Gate.

Compare that with fluorescents: they on the other hand are very poor in near-IR light, as expected from an efficiency standpoint--visible light is what you want in an efficient system. (The HID lights are highly efficient despite emitting copious near-IR light because the arc is incredibly bright and efficient in the visible. But you can't get such efficiencies in a low wattage bulb).
You can see fluorescents glowing a bit in this test focus shot of the first floor of the Reg:


Around the edges of the room are fluorescents, dimly adding some near-IR that is red or very near red. Notice that the ends of the fluorescent tubes are purple: this is further into the IR, and what you're seeing is the thermal glow of the little filaments that heat up and emit electrons. When I need near-IR indoors, I use old-fashioned tungsten: a single 60W incandescent bulb will outlight a room of fluorescents.

New major exoplanet announcement from Corot?

The Corot satellite is a French astroseismology/transit/photometry project.
Steinn Sigurðsson over at Dynamics of Cats is pushing rumors of an announcement regarding a whole new bundle of exoplanet discoveries soon, possibly today.

For a sample of Corot data, see this 120-day graph of a star:

Image from CNES
showing various stellar oscillations as well as a periodic transit of something across the face of the star.

More rumors here too, for today.

Stellar Oscillations
Convection cells at the surface of a star create a large acoustic noise. The noise has multiple ways of traveling through the stellar interior, and can interfere constructively on the surface as the star 'rings'. It can also be used to probe the interior of the star just like earthquakes on Earth showed us the existence of the solid inner core and the liquid outer core. And it can be used to see the farside of the Sun! The ringing can have many, many modes--over a thousand. See the cute animated gif of a l=2, m=2 oscillation of a star here.


Transmission of acoustic waves through a stellar interior

Phil Plait talks about the Moon's orbital plane

Phil Plait looks at the low southern moon here that I mentioned last month

Fall equinox

It's the autumnal equinox today, the day when the Sun appears to cross over into the southern sky. The stirrings of winter are beginning--little reminders of the fragile nature of our comfort zone on this planet. This last week in the evening twilight the first-quarter moon barely peeked above the trees and buildings to the south, showing roughly where the Sun would be in three months time. It seemed a little low for the winter noon, though, so I checked and indeed the Moon is at its greatest distance from the ecliptic, some 5 degrees south. I have some discussion of the tilt at this previous post. And, to confirm it, there was a lunar eclipse in late August, meaning the nodes (the points where the Moon's orbit meet the ecliptic) of the Moon's orbit were aligned in the Earth-Sun line, which meant my first-quarter moon should have been above or below the ecliptic.

And it now occurs to me the root of eclipse and ecliptic are the same, a point I never realized. This will require another post.

The sunspot belts of Sir John Herschel

"On the conservation of solar energy : a collection of papers and discussions" by C. William Siemens. 1883, p.5.

Questions concerning the energy output of the Sun and how exactly it was doing so without shrinking or dimming.

Personal update

I haven't been posting lately. suffering from a bizarrely strong summer cold, plus work stuff ( I can finally say, after a long legal silence, that my workplace is going with Aquabrowser as the next generation library catalog, which I am administering the boxes it runs on).

An interesting tidbit showed up this week in the blog logs: Google has re-indexed its images again, bringing my violet image of the solar spectrum back to its rankings. Previous to March, it was the first hit for the term "blue-violet". For whatever reason (I believe some stupid google war site misappropriated the image), it disappeared then, dropping monthly hits to my blog by 3,000. The image is now #4; although the hit goes through the same stupid site. The direct link for the blue-violet image is this.

The Sun as a 2.4 GHz source, redux.

I previously wrote an entry about how you can see the Sun interfering with the weather radar at sunrise and sunset, seen here. The weather radar uses radio waves at about 3 GHz. Seen linked at Hackaday is a 2.4GHZ field strength meter using a microwave diode, a few capacitors and a simple "quad" antenna and measured using a digital multimeter. They report that the Sun generates a reading on their device!

The sun as a microwave source

The Sun is a convenient source of radio waves. You can see this yourself by watching weather radar around sunrise or sunset. Radar works by emitting a very short pulse of microwave radiation. Then it listens for the weak returns for a short time (since a radar beam is line of sight, there is no point is listening for returns past 200 miles or so because of the curvature of the earth, or roughly 1 millisecond). The time it takes to hear the return gives you the "range" or distance to the object that reflected the beam. When the sun is low on the horizon, the radar receiver picks up the radiation as if it were a continuous return, and it's visible on all of the weather radars.

The image is of the radar from St. Louis last night at 8:28 PM CDT. You can see how the weather radar interprets a continuous return as if there were stronger reflectors further out, and how far north the sun is at this time of year near the summer solstice.

Blue violet solar spectrum

I read somewhere most of the lines in the blue and violet were due to the gazillion transitions that iron's electrons have.


Click on the above image for a larger version.

Interestingly, in the camera there is more spectral detail in the red channel than the blue. (This is probably related to the fact that most dye filters will transmit light not only of the design wavelength but also double the wavelength--so a blue filter with a peak wavelength of 450nm will also transmit around 900nm.) Edit: While this effect occurs, it wouldn't appear in this instance. It should appear in the near infrared spectrum. After looking at the histogram it is clear the blue channel is totally saturated (aka overexposed). I bet the camera chooses the exposure mostly on what the green channel is seeing.

This is another project: I have the entire solar spectrum from slightly UV-ward of the calcium H & K lines at 400nm to somewhere near 750-800nm in the near-infrared imaged through my spectrograph and the Ryerson telescope. I want to combine the images into a long continuous image. My own solar spectrum.

Also see

The Solar Spectrum -- Magnesium Triplet

Terrestrial Oxygen Red

The Sodium Doublet

Terrestrial oxygen

Terrestrial oxygen as seen in the sun's spectrum, originally taken March 17, 2003.



It's terrestrial only in the sense of being non-astronomical; to all but astronomers it would be called "atmospheric".