7 October 2006

From Wikepedia:

disaster (from Greek meaning, "bad star")

Merriam-Webster Online says it is from Latin

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I found the following information in the Doing Good RadioScience Observing chapter of RodioScience Observing

Measurement Data Classas

Qulitative Data		Quantitative Data
non-nnumerical or categorical in nature		data that naturally results in a number to represent the factor
presence vs nonpresence good vs bad defective vs nondefective gender race		amount of money length temperature number of defects per unit total number of defective units voltage pressure weight
Nominal Data	Ordinal Data	Interval Data	Ratio Data
Qualitative data with no inherent order or rank	allows ranking, but differences between data points are either nonexistant or meaningless	allows for meaningful comparrison of differences, but not the relative values of two or more factors; made relative to an arbitrarily selected standard zero point	based on some fixed or natural zero point
lists of names labels groupings	first, second, third better vs worse strongly oppose=1, oppose=2, neutral=3, support=4, strongly support=5	calendar dates (relative to the birthdate of Christ) degrees Celsius (relative to freesing and boiling points of water) and degrees Fahrenheit	degrees Kelvin

Measurement Variation and Error

[Variation is] caused by small random errors (normal random variation due to inherent limitations of the measurement system (instrument and its operator) in the measurement process, and by actual variation in the measurement parameter.

There are many different causes of random variation. Some errors are dependent on the particular type of measurement being made (and are a function of the type of instrument being used), while other errors are due to inherent variation in the process being measured. Still others are due to problems in using the instrument or making the measurement; i.e., human error.

Consider an ordinary ruler (such as a yard stick) as an analogy for random error. It is divided into 36 large divisions of 1 inch each, and 288 smaller divisions of 1/8 inch each: or is it? In truth, the distance from 0 to 36 inches is not exactly 39.0000", but rather will be 36 +/- epsilon;", where epsilon; is a small error. In addition, the spaces between small divisions (either 1/4" or 1/8") are not exactly the same size, but vary somewhat from mark to mark. As a result, when you measure the size of an object, there will be some inherent error due to the limitations of the particular ruler selected.

Categories of Measurement

Driect	When you can directly compare what’s being measured with a standard
	Measure a length with a ruler
Indirect	Made when the actual measurement is too hard, too inconvenient or too dangerous
	Blood pressure cuff (too dangerous)
Null	Made by comparing a calibrated source to an unknown measured, then adjusting either one of the other until the difference between them is zero
	Tuning a piano to a pitchfork

Accuracy vs Precision

Accuracy	How far from the mean (peak value in a bell-shaped curve) is from the correct value
	You are at an exact location but your GPS keeps telling you you are at slightly different locations every time you look at it. The eror is the difference between the true location and the averaged location of many GPS readings.
Precision	Determined by the dispersion of the measurements
	The difference between the maximum and minimum readings recorded, measured in standard deviations, σ

Target shooting is a good analogy for precision and accuracy. Good shooting instructors know that it’s better to first work on precision, i.e., getting the cluster smaller (called grouping in shooting). This is analogous to reducing the random variation in a measurement process. Some of the clustering is due to the mechanics of the gun, but most of it happens to be due to the shooter. Once the shooter (or worker) is consistently shooting tight clusters, then it’s time to worry about moving the impact point (i.e., moving the average). How is this done? Not by adjusting the person making the measurement (i.e., shooter), but by adjusting the process (i.e., the gun).

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Information from the Oct06, Vol, 259, No. 4, issue of Scientific American from the feature article How To Blow Up A Star

• Type I supernovae
  • No hydrogen evident in spectra
  • Thermonuclear explosions – Type Ia
    • Carbon and oxygen are fused
  • Collapsed stars that shed outer layers Type Ib and Type Ic
• Type II supernovae
  • Include hydrogen in the spectra

Stars auto regulate themselves so they are unlikely to go supernova

Thermonuclear Supernova

Type Ia, sudden nuclear detonation of an entire star

1. The more massive member of a pair os sunlike stars exhausts its fuel and turns into a white dwarf star.
2. The white dwarf sucks in gas from its companion, eventually reaching a critical mass.
3. A “flame” – a runaway nuclear reaction – ignites into the turbulent core of the dwarf.
4. The flame spreads outward, converting carbon and oxygen to nickel.
5. Within a few seconds, the dwarf has been completely destroyed. Over the following weeks the radioactive nickel decays, causing the debris to glow.

Core-Collapse Supernova

Type Ib and Type Ic, implosion of a star at least eight times as massive as the sun

1. As the massive star nears its end, it takes on an onion-layer structure of chemical elements.
   Iron > Silicon > Oxygen > Carbon > Helium >Hydrogen
2. Iron does not undergo nuclear fusion, so the core becomes unable to generate heat. The gas pressure drops, and overlying material suddenly rushes in.
3. Within a second the core collapses to form a neutron star. Material rebounds off the neutron star, setting up a shockwave.
4. Neutrinos pouring out of the nascent neutron star propel the shock wave outward, unevenly.
5. The shock escapes through the entire star, blowing it apart.

Supernova Rocket Effect

Causes core collapse supernovae to move rapidly through a galaxy

1. The newborn neutron star, at the center of the incipient explosion, is nearly still.
2. The gravity of the lopsided debris pulls the neutron star in a certain direction, and debris falling onto the neutron star provides an additional kick.
3. These forces eject the neutron star. (Because of the overall momentum balance, the neutron star is pulled in the direction from which the infalling debris is coming.)

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I was doing some searching to find the recommended method for estimating cloud cover. I didn't find anything that didn't rely on satellite imagery but did come up with a lesson plan for having children estimate the amount of cloud cover by looking at torn white paper clouds on a blue paper simulated sky. It included the following descriptions of sky cover relative to the percent of cloud present:

10%	25%	50%	90%	100%
Clear	Isolated	Scattered	Broken	Overcast

Asking Google to define Broken Clouds I found the definition came from the Glossary of Meterology of the American Meterology Society. So I looked up all of the terms above to get the "official" definitions for them.

Clear Sky

A sky free of clouds and other obscurations as observed from the point of observation.

Isolated

[not found]

Scattered

A sky coverage of 1/8 through 4/8. In U.S. weather observing procedures, this is reported with the contraction “SCT.”

Broken

Descriptive of a sky cover of from 0.6 to 0.9 (to the nearest tenth). This is applied only when obscuring phenomena aloft are present, that is, not when the sky cover is composed entirely of surface-based obscuring phenomena. In aviation weather observations, a broken sky cover may be explicitly identified as thin (predominantly transparent); otherwise a predominantly opaque status is implicit. An opaque broken sky cover is the minimum requirement for a ceiling, and this is frequently termed broken ceiling.

Overcast

1. Descriptive of a sky cover of 1.0 (95% or more) when at least a portion of this amount is attributable to clouds or obscuring phenomena aloft; that is, when the total sky cover is not due entirely to surface-based obscuring phenomena.
In aviation weather observations, an overcast sky cover is denoted by the symbol “symbol”; it may be explicitly identified as thin (predominantly transparent); otherwise a predominantly opaque status is implicit. An opaque overcast sky cover always constitutes a ceiling. See obscuration. 2. Popularly, the cloud layer that covers most or all of the sky.
It generally suggests a widespread layer of clouds such as that considered typical of a warm front.

That lead me to think about wind related terms and I found a NOAA site with the following table.

Beaufort Number	Description	Speed	Visual Clues and Damage Effects
0	Calm	Calm	Calm wind. Smoke rises vertically with little if any drift.
1	Light Air	1-3 mph	Direction of wind shown by smoke drift, not by wind vanes. Little if any movement with flags. Wind barely moves tree leaves.
2	Light Breeze	4-7 mph	Wind felt on face. Leaves rustle and small twigs move. Ordinary wind vanes move.
3	Gentle Breese	8-12 mph	Leaves and small twigs in constant motion. Wind blows up dry leaves from the ground. Flags are extended out.
4	Moderate Breeze	13-18 mph	Wind moves small branches. Wind raises dust and loose paper from the ground and drives them along.
5	Fresh Breeze	19-24 mph	Large branches and small trees in leaf begin to sway. Crested wavelets form on inland lakes and large rivers.
6	Strong Breeze	25-31 mph	Large brances in continous motion. Whistling sounds heard in overhead or nearby power and telephone lines. Umbrellas used with difficulty.
7	Near Gale	32-38 mph	Whole trees in motion. Inconvenience felt when walking against the wind.
8	Gale	39-46	Wind breaks twigs and small branches. Wind generally impedes walking.
9	Strong Gale	45-54 mph	Structural damage occurs, such as chimney covers, roofing tiles blown off, and television antennas damaged. Ground is littered with many small twigs and broken branches.
10	Whole Gale	66-63 mph	Considerable structural damage occurs, especially on roofs. Small trees may be blown over and uprooted.
11	Storm Force	64-75 mph	Widespread damage occurs. Larger trees blown over and uprooted.
12	Hurricane Force	over 75 mph	Severe and extensive damage. Roofs can be peeled off. Windows broken. Trees uprooted. RVs and small mobile homes overturned. Moving automobiles can be pushed off the roadways.

The Beaufort system was developed not as a weather instrument but so that captains of British naval vessels knew how much sail they should have hoisted at any time. They didn't want captains to drive their ships, and crews, too hard, but didn't want chickens either.

And that lead to a search for information on estimating rainfall rate at the NOAA JetStream Online School of Weather glossary of weather terms.

Rain Intensity	Rate of Fall		Visual Estimation
	6-minute	One Hour
Light	<0.01"	up to 0.10"	From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen.
Moderate	0.01"-0.03"	0.11"-0.30"	Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces.
Heavy	>0.03"	>0.30"	Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to the height of several inches is observed over hard surfaces.

While trying to find the above information I stumbled across this information on estimating ice pellet intensity at JetStream.

Ice Pellet Intensity	Rate of Fall		Visual Estimation
	6-minute	One Hour
Light	<0.01"	Up to 0.10"	Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected.
Moderate	0.01"-0.03"	0.11"-0.30"	Slow accumulation on the ground. Visibility reduced by ice pellets to less than 7 statue miles.
Heavy	>0.03"	>0.30"	Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statue miles.

And then there is this table for estimating hail size, also from JetStream.

Description	Size
pea	0.25"
marble or mothball	0.50"
penny	0.75"
nickle	0.88"
quarter	1.00"
half dollar	1.25"
walnut or ping pong ball	1.5"
golf ball	1.75"
hen egg	2.00"
tennis ball	2.50"
baseball	2.75"
tea cup	3.00"
grapefruit	4.00"
softball	4.05"

Most of this is irrelevant to astronomy, since I don't plan to be out if it is cloudy, raining, hailing, or if the wind is really kicking up.

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Observing Location	TotL There were a lot more police driving around the park tonight than. We have seen in a while. They stopped by about 0042 EDT and talked for a few minutes before driving a little further on and telling people sitting on the benches the park was closing. They then drove past is a couple of timed and drove up in our direction but turned off the pathh before reaching is several times. Earlier we were talking with Hugo Capra about observing the Pleiades Occultation Monday night/Tuesday Morning and I said that I am more inclined to go to CSP when I am planning to observe past curfew because we have never been rousted there. If I could be sure we wouldn't run into the wrong cops on Monday night it would be much more convenient to observe from TotL than going all the way over to CSP.
Observational Period	1945-0230 EDT
Atmospheric Conditions	Cloud Cover Clear to Overcast Temperature 59°-52°F Wind 0-10 mph Humidity Moderate and Increasing Feels Like Chilly and Raw I out a flannel shirt on over my T-shirt and threw my polyester vest and a pair of fingerless gloves in my observing bag for emergency use. I was already wearing a fleece-lined jacket. It wasn't long after I got there that the humidity began to climb and I had to out the vest on. I wasn't too far from putting on the gloves. On the way to the subway my feet felt chilled. The police stopped to talk to is shortly before 0100 EDT and the heat coming off the engine and out of the open window felt good. The subway platforms still haven't cooled off and I was starting to overheat, then I got onto the air conditioned subway and began to shiver. When I arrived there were a few clouds low on the eastern horizon but it was essentially clear. Ad the night wore on the SE through Q sky clouded up like a warm front was moving in from the ocean. Then clouds started moving down from the NE. There were times when it was overcast alternating with periods of clear skies. After about 0100 EDT all the clouds disappeared. Transparency Fair Seeing III Antoniadi Seeing Scale I Perfect seeing, without a quiver II Slight undulations, with periods of calm lasting several seconds III Moderate seeing, with larger air tremors IV Poor seeing , with constant troublesome undulations V Very bad seeing, scarcely allowing a rough sketch to be made
Instruments	Canon 15x50 IS binocular - Charlie The Kite: 6" DIY Newtonian Reflector - Peter Takahashi 22x60 binocular - Peter Celestron 7x50 binocular - Kin
Observing Party	Charlie Ridgway Peter Tagatac Kin Lee Hawaiian George

Target Hercules Galaxy, M31 Constellation Her Category DSO: Gal Time 20061007.2015 EDT Comments With the corner star of the Great Square in the 2:00 corner of the FoV, M13 is about 1/3 into the FoV from the left edge just below center. There are two stars there on a diagonal and M13 is half way between them and a little but to the right. Easiest with averted but occasionally takes direct.

Target Double Cluster Constellation Per Category DSO: OCl Time 20061007.2030 EDT Comments diagonal line of there bright stars running 10:00-4:00 over curving line of dim stars terminating in two bright stars on a line parallel to the diagonal line above A diagonal line of paired bright stars ending in a backwards L. NGC869 is around the lower pair of stars and if the more obvious cluster tonight. I can see stardust around the two bright stars. NGC884 is just to the right of the vertical arm of the L and is easiest seen when it is off axis (averted)

Target Kemble's Cascade & NGC1501 Constellation Cam Category Asterism & DSO: Time 20061007.2050 EDT Comments The stars of the upper cascade were difficult to pick out. The bright stars of the bird's foot were easy but I did not are NGC1501.

Target Milky Way? Constellation Cyg, Cas Per Category Time 20061007.2100 EDT Comments I am seeing a stripe of lighter sky passing through Deneb, Caph, and η Per. I know the Milky Way goes near this area but don't know if that is what I am seeing. If I were facing south I would suspect that it is light from Times Square. But I don't know of anything up in Spanish Harlem that would be throwing up that much unmoving light.

Target Neptune Constellation Cap Category Planet Time 20061007.2115 EDT Comments Not Seen

Target Uranus Constellation Aqr Category Planet Time 20061007.2130 EDT Comments It looked like a pyramid viewed from above, with λ Aqr in the center and Uranus at the bottom.

Target α Cap Constellation Cap Category Double Star Time 20061007.2150 EDT Comments Observed naked-eye. I didn't think Cap was that big, Algenib, δ Cap was in the SE while Arcinds Girdi, α Cap, was in the SW. I could are both α2, Mag 3.58, and α2, Mag 4.30, shining side by side.

Target Ring Nebula, M57 Constellation Lyr Category DSO: Supernova Remnant Time 20061007.2205 EDT Comments Detected From Sheliak go to a dim star at 2:00. From there find a dim equilateral triangle to the left. M57 is just off the left point of the triangle. Peter and I both looked for it in my binocular without success. I am not sure that I looked for it in the telescope, and if I did, if I saw it.

Target Moon Constellation Psc Category Lunar Time 20061007.2231 EDT Comments Lunation 1036 Phase Waning Gibbous Age> 15d14g45m Elongation 166.02°W % Illuminated 98.5% Magnitude -12.5 Altitude 41.66°

There was nice detail on the eastern limb, particularly around Mare Crisium. I set my binocular up with the Moon filters for the comfort of the attenuated light. Peter and I compared impressions of limb features in his scope. We mostly worked the south pole but also spent some time near Mare Crisium.

Target Double-Double, ε Lyar Constellation Lyr Category Double Star Time 20061008.0003 EDT Comments In Peter’s scope the right star split, but not cleanly, over-under. I thorough the other star did the same but Peter thought they were side-by-side.

Target Albiero Constellation Cyg Category Double Star Time 20061008.0013 EDT Comments With the Moon filters on I could fee the two stars but could not tell that they were different colors, After taking the filters off Albireo, β1 Cyg, Mag 3.05, appeared somewhere between cream and butter colored (maybe the natural color of butter) and βt Cyg, Mag 5.12appeared powder blue.

Target The Pleiadea, M45 Constellation Tau Category DSO: OCl Time 20061008.0019 EDT Comments I counted eight stars naked-eye and 38 in the binocular. The background sky looked very black in contrast with the stars, like a 100 Watt light bulb shining thrugh pin pricks in a sheet of black construction paper in a darkened room. Most of the stars look like they are paired with another star, like very wide doubles that all have different planes of rotation.

Target NGC1647 Constellation Tau Category DSO: OCl Time 20061008.0024 EDT Comments I can are one prominent star and another fairly bright star that comes and goes, then a bunch of stardust surrounding them.