Ryerson office background radiation

Steven conveniently graphed the data from my geiger counter, covering a week in the Ryerson Astronomical Society office. http://gateway.spc.uchicago.edu/~stevenl/cosmic/

Another airline plot

This was a trip to Las Vegas. Maximum altitude was at 39,000ft, and the flightpath was a relatively northern one across Nebraska and Colorado, then turned south in Utah. We flew for a while in southern Utah at a lower altitude while getting into the inbound approach, and you can see that on the graph.

http://www.lib.uchicago.edu/~dean/blog/mdwtolas.jpg

more near-IR tests

I added a third layer of color negative to the filter, and this makes the sandwich completely opaque to the naked eye. The sun is barely visible (but not at all safe to look at) through it. I can get a reasonable if slightly underexposed image of open shaded areas with an exposure of 4 seconds at f/5.6 at ASA 400. With the third layer there is no difference between the red and blue filters, so I believe whatever I am getting is residual IR leakage.

http://www.lib.uchicago.edu/~dean/blog/reynoldsclub-ir.jpg


That isn't snow, it's grass.

A clue to what wavelengths we are seeing is the fact that the streetlight happened to be on, and we can see it, and HPS lights emit a very intense 819.3nm and 819.5nm doublet.

near-IR world

http://www.lib.uchicago.edu/~dean/blog/ir1.jpg
http://www.lib.uchicago.edu/~dean/blog/ir2.jpg
http://www.lib.uchicago.edu/~dean/blog/ir-normal.jpg
These were shot with a near-IR filter over my camera
(a near infrared filter being two pieces of fully exposed color negative film).

If you swap the RGB colors around, you can eventually get something almost, but not quite entirely unlike, normal. http://www.lib.uchicago.edu/~dean/ir2-rgb-bgr.jpg

Some more (post-processing):
http://www.lib.uchicago.edu/~dean/blog/ir1-auto.jpg



http://www.lib.uchicago.edu/~dean/blog/ir2-colorswap.jpg

From looking at the RGB histograms out of the camera, it appears that the red and blue filters let the most near-IR through. Traditionally this is the case. The red lets very near-IR through, and the blue lets in IR at double the blue wavelength (a 450nm blue filter will let in 900nm IR, e.g.). The blue channel shows the most chlorophyll fluorescence too.

Lunar maria colors

A nice image of exaggerated maria colors on the Moon: http://www.rc-astro.com/img/moon_colors_2005-04-18_web.jpg.

Visually, you can see this, especially between Mare Serenitatis and Mare Tranquilatis (wow I can't believe I spelled that right the first time). They are the two prominent, quasi-circular touching maria on the left side. The color difference for maria basalts is the difference in composition of TiO2.

Tranquilatis, the bluer one, is very rich in TiO2.

Giguere, Thomas A.; Taylor, G. Jeffrey; Hawke, B. Ray; Lucey, Paul G.
The titanium contents of lunar mare basalts
Meteoritics & Planetary Science, vol. 35, no. 1, pp. 193-200 (2000).

Another down

Another down. However, this rejection letter was very nice, as opposed to Arizona's. Mahalo, Hawaii.

I've been on vacation

I've been away. I didn't do much. I note that I heard many more stations in Nevada with an Icom R-71a in the 15 MHz and 17MHz broadcast bands than in Chicago. It probably proves that the old tube Hallicrafters S-40A needs work on stage 4, 15-40MHz. I heard Radio Netherlands on multiple frequencies, and it was neat to note one of the stations was 1/4 second behind the others. Steven and I have decided that proves it has 1 satellite hop extra to that relay station than the others. (Geosynchronous orbit is 23,000miles, roughly 1/8 light-second away). I bet stringing a simple wire out to the west edge of the roof (past the skylight) would give us a great signal and some immunity to the elevator noise. The current antennas, save for the magnetic one, aren't shielded and pick up noise (and signals too) from the coax braids, since they aren't correctly balanced.

"Your academic record is ... substantially below"

3 down.

Bad Astronomy Bulletin Board :: View topic - Evidence of current life on Mars

Bad Astronomy Bulletin Board :: View topic - Evidence of current life on Mars

A followup to a previous post.

VLF radio part 1

A long time ago I dabbled in Very Low Frequency radio. These are radio waves with frequencies under 20kHz. They have obscenely huge wavelengths and as a result can penetrate into "conductors" a significant distance before being absorbed/reflected. The Navy used to use VLF for communicating with submerged submarines at 76Hz and 58Hz. There is a navigational system located down near 100kHz called LORAN-C, and the WWVB signal at 60kHz. Lightning is the dominant natural signal in this wavelength band. But, nearly everything creates electrical noise down there. For instance, let's talk about switching power supplies.

Nowadays nearly everything is powered via a switching power supply, as opposed to a linear supply. What's the difference? A linear supply uses transformers to convert the AC running at 120 volts and 60Hz into a lower, often 13.8 Volts 60Hz AC. This is then rectified into pulsing DC via a set of diodes and smoothed out with capacitors. It's wasteful--a percentage of the power is lost via heating in the transformers. They have to be very large to keep the 60Hz oscillating magnetic field inside the transformer.

Switching power supplies first convert the AC into a high voltage DC (around 200-300V). Then, the DC is switched quickly on and off at a high frequency, often 50kHz or higher. This is then put into a much much smaller transformer since high frequency transformers can be much much smaller and still be efficient as a big transformer running at a lower frequency. On the other side, power requirements are measured and there is feedback to provide a pulse-width-modulated approach to supply the power needed.
http://mrtmag.com/mag/radio_switching_vs_linear/
gives a good overview.

Anyways, they are noisy. The world is a very noisy place in the VLF band.

Long ago, my friend John Crocker ran a 1000ft wire down the length of the Midway, stuck a ground rod into the earth, and placed a pair of high-impedance headphones in between. The VLF radio waves are directly converted into audio frequencies.

Read VLF Radio Part 2: Sferics

Pentax Takumar lens

I bought a 55mm f/1.8 Pentax screw mount lens off of Ebay last week to use as a wide-field imager in front of the Starlight Express SXV-H9 CCD camera. The total cost was $11. What I didn't expect was that the rear element of this lens was made with a thorium-rich glass. The radiation might preclude use of this lens. I get counts of 6000 microrem/hr with the counter at the surface of the element. I did some counting last night:

With the detector 2 cm away and 10 samples of 10 seconds each:
Bare: 2743
Single sheet of paper: 2466
Aluminum (1/16 inch thick): 577
Aluminum and paper: 563
With geiger counter reversed: 80
With geiger counter reversed and Al: 60
From side of geiger counter: 96
From side with Al: 87
Background count was 12.

Then, I did some distance counting.
Distance Count rate
2cm 2721
4cm 1145
6cm 647
8cm 391
10cm 282
12cm 203
14cm 165
16cm 130
18cm 98
20cm 87
22cm 80
24cm 57
26cm 59
28cm 47
30cm 38
32cm 42
...
40cm 26

I also measured the rates with the 1/16 inch thick Aluminum sheet in the way--this way, I was hoping for only the photonic component of the radiation, so no air absorption.
6cm 156
8cm 88
10cm 64
12cm 48
16cm 30
20cm 18

Graphs are needed, I know. I just wanted to post something. Everyone else is busy with end of quarter work.

Insert witty yet biting title here

2 down, 4 left.

The size of modern mirrors

http://www.pbase.com/polakis/image/40260687

Don't miss the next photo showing her thermal signature on the glass.

Cosmochemistry laughs

It's amusing when while searching for a nice graph of the "Standard Abundance Distribution" that you end up on a website of a professor who studies such things, and the book lying open in your lap with the nice graph you only wish you could scan into a computer is by the same person.

Horsehead Nebula

Composed of 143 images of 30 seconds each.