23 December 2006

I worked on a variation on the jam-jar magnetometer developed be the BAA. The main change I made was substituting a plastic pistachio jar for the glass jam jar they used. I happened to have a pistachio jar while I do not have a jam jar, let alone a big one. I don't think either material will be better than the other since we are not talking about scientific grade glass or plastic that has a uniform thickness.

I got a pair of bar magnets from a local art supply store. It is the only place I could find anything other than refrigerator magnets. They weren't as long as I had hoped but I butted them together and they fit nicely in the Pistachio jar.

I had excess #8 bare copper wire from my satellite Yagi antenna project so used it to build a cradle for the magnet. It is shaped to try and get the center of the yoke above the center of mass of the magnet so that the later hangs vertically and will reflect light horizontally.

I had a small mirror that I planned to use with it but can't find it now that I am building so have covered the center of the magnet with silver metallic tape. I don't think it has a smooth enough surface to reflect a good beam of light, but it is fine until I find out where this thing will live and complete my light source.

Right now it is set up atop an old fish tank in the living room. It has been there for over an hour and the magnet is still swinging through about 5° of arc. The magnet should align itself with the earth's magnetic north pole but mine points roughly to the NW. The articles I read on building this thing (Sky at Night, Nov06?; and Sky &.amp; Telescope, Oct89) say to locate it away from magnetic influences but that is hard when your building is built around steel beams. A bigger concern is ferrous metals that change location during the observing period. I can control that in my apartment, but not in the apartments around me. I am hoping that the Earth’s magnetic field will be sufficient to overcome their influence.

I haven't finished my light source yet. A while back Kin told me about a rechargeable flashlight available in one of the 99-cent stores in Chinatown which I bought. I found that it was not rechargeable as advertised, but ran off of two button cell batteries, I have cannibalized that light for use on this project. I made a slit out of metal tape in front of the LED. (They used razor blades to make a 1mm slit in front of a normal incandescent bulb of an unmentioned type. The Sky at Night article mentions using a laser which I might investigate if I can find a cheap one that I can scavenge.), and added a switch on a long wire so I can hopefully turn it on without shaking it. Initially I had planned to glue the lamp to the side of my pistachio jar but on reading the construction instructions in S&T I see that they have their light source about 9" from the mirror so am going to have to figure something else out once I decide where I can set it up long term.

Now I need to figure out where the magnets are going to point so I can figure out where I can put it to get the scale far enough away to give it some sensitivity.

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Observing Location	McGraw Ave @ Virginia Ave, Bronx, NY
Observational Period	1830-1845 EST
Atmospheric Conditions	Cloud Cover Scattered Clouds Temperature low 50s F Wind Moderate Breese Humidity low Feels Like Cool There were alternating stripes of cloud and clear air. Transparency Fair Seeing II
Instruments	Canon 15x50 IS binocular (habd-held) - Charlie
Observing Party	Charlie Ridgway

Target Old Moon in the Young Moon's Arms Constellation Cap Category Lunar Time yyyymmdd.hhmm 20061223.1830 EST Comments Lunation 1039 Phase Waxing Crescent Age 3d9h28m Elongation 42.87°E % Illuminated 13.4% Magnitude -7.9 Altitude 11.70° The Moon was out in the middle of Capricornus almost directly beneath Neptune. The earthshine is dim but noticeable.

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Target Neptune Constellation Cap Category Planet Time yyyymmdd.hhmm 20061223.1840 EST Comments I think I saw a flash of the planet in a moment of better seeing. At various times I identified everything around it including one slightly fainter star.

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Observing Location	MetOval
Observational Period	1938-2200 EST
Atmospheric Conditions	Cloud Cover Scattered Clouds becoming Clear Temperature 40s F Wind Gentle Breeze Humidity Low Feels Like Cool At the start of the session there were clouds obscuring all but the brightest stars to the naked eye everywhere but in the SE. It cleared some but the floodlights make it hard to tell just what the conditions really are. The wind had slackened a bit and the temperature was dropping a bit. Transparency Fair Seeing II
Instruments	Canon 15x50 IS binocular (hand held) - Charlie
Observing Party	Charlie Ridgway Parkchester Security

Target Uranus Constellation Aqr Category Planet Time yyyymmdd.hhmm 20061223.1730 EST Comments being three magnitudes brighter than Neptune this should have been an easier planet to find but it wasn't. I was having trouble finding stars to hop to it from. Auriga was the only prominent constellation at the time. I eventually found the Great Square of Pegasus and what I think was β Cet. Late in the evening I think I found Uranus.

Star hopping with the hand held binocular is difficult when you have to continually refer to the atlas to see where you are and where you are going. Every time I take the binocular away from my eye to look at the atlas I loose my place in the sky and have to go back to my landmark and begin the hop again.

Target Orion Constellation Ori Category Constellation Time yyyymmdd.hhmm 20061223.2000 EST Comments Orion was just emerging from behind a block of apartments into the clearest part of the sky. I could see the Trapezium and occasionally ι Ori naked-eye. In the binocular there is some nebulosity around the Trapezium. I have been thinking Mintaka is a double star but it does not appear to be an official one according to the S&T Pocket Atlas, that distinction goes to Alnitak. Alnitak, however, is to close a double (2.") for me to see it. Both Alnitak and Mintaka have nearby stars that are in roughly the same position and the same distance. The star near Alnitak is too faint for me to see it with the binocular.   Alnitak Mintaka Primary Mag 1.74 Mag 2.25 Secondary Separation 2.4" Mag 4.0   Close Star TYC 4771-01207-1 Separation 57" Mag 9.54 PA ~350° TYC 4766-02444-1 Separation 57" Mag 6.84 PA ~340° [24Dec06 - The Audubon Field Guide says that Mintaka is a double star.]

Target the Pleiades, M45 Constellation Tau Category DSO: OCl Time yyyymmdd.hhmm 20061223.2030 EST Comments Initially I counted 4 stars but later in the night, when it was higher overhead, I counted six stars.

Target Praesape, the Beehive Cluster, M44, NGC2632 Constellation Cnc Category DSO: OCl Time yyyymmdd.hhmm 20061223.2140 EST Comments While looking for M44, of which I could only see one star tonight, a fast golden Geminids meteor streaked across the FoV.

Target Saturn Constellation Leo Category Planet Time yyyymmdd.hhmm 20061223.2150 EST Comments I had to move around a bit to find a gap between the buildings that was low enough and not obstructed by trees. It looks like a piece of gold reflecting a bright light.