27 March 2012

The president of AAA has been divesting himself of his astronomy book collection and Peter picked up one of the books, Star-Hopping: Your Visa to Viewing the Universe by Robert Garfinkle (ISBN 0-521-41590-X) for me.  I have started reading the introductory chapters and found mention af appendices so I immediately skipped to the back of the book to check them out.  I have reformatted the data from two of them dealing with stars here since they are objects that I routinely observe.

When we observe double stars we often refer to them as being wide or close or even very close.  For me these have always been relative terms and would therefore change with the magnification I was using.  What appeared a close double at 25X could become a wide double when viewed at 75X (now that I have telescopes and can change my magnification).  But now I see that these terms have actual numbers behind them and that there are Open and Standard categories of doubles that I have never used or, in the case of Standard, even heard of.  I have color coded it with information about the resolving powers (Dawes Limit) of my scopes to make the table relevant for me.  Now I have to become proficient at estimating distances in the eyepiece.  I have heretofore use descriptive terms like the size of a pea, the width of a paper match, or whatever else seems appropriate at the time.

Double Star Separation
Open	>30.0"
Wide	10.1" - 30.0"
Standard	5.1" - 10.0"
Close	2.1" - 5.0"
Very Close	0.5" - 2.0"
Naked-Eye
Both scopes
Dobsonian only
Not Possible
6" Dobsonian 0.76"	70mm Mini Mak 1.65"

When Peter and I observe open clusters we often describe their appearance to us to each other while at the eyepiece.  We speak of levels of star brightness - I can often discriminate two levels of brightness and a "crunchy" under level behind them.  We also speak of the clusters being "rich" or "poor," but again these have been relative terms for me.  In the Double Cluster, NGC ___ appears to me to be a ring of bright stars with a basically empty center which I term sparse while NGC ___ appears as a filled in circle which I have called rich.  But somewhere I read a description of this feature that described both clusters as being rich.  Now I have numbers that will allow me to more accurately describe what I am seeing.  This ability will obviously be tempered by my eyesight which isn't great ar seeing faint things.

                    

Trumpler Classification of Open Clusters
Concentration	Magnitude	Richness
I Detached from surrounding central concentration      II Detached with little central concentration      III Detached with no central concentration      IV Not well detached	1 Small range from brightest to faintest member      2 Moderate brightness range      3 Large range	p Poor: <50 stars      m Medium: 50-100 stars      r Rich: >100 stars
Example: NGC 1891 (Cr 73)	III2p	Detached, no central concentration Moderate brightness range; fewer than 50 stars

14 December 2011

It has been so long since I have actually written a blog post that it is a real reach to pull out all of the HTML to get this one done.

Peter and I were discussing the possibility of mounting a dark sky expedition between Christmas and New Years.  

First we need to decide where to go.  That is a tradeoff between how dark the sky is and the drive time to get to it.

I have previously compiled and posted a list of the darker dark sky public observing sights as listed in Clear Sky Clock but can't find it now that I need it.    I only remembered two areas of the NE that have Bortle 1/2 skies: an area in northwestern Maine and the area of West Virginia between Spruce Knob and Green Bank.  Both of these areas have some detractors.  West Virginia is 7-9 hours away, not counting breaks, and, as I remember it, the Maine site is a similar distance, is hard to get too because it is in the middle of nowhere (maybe that is why it is dark) and doesn't look like there are a lot of resources (lodging, sustenance, cell phone coverage, WI-Fi).
[I just found the Dark Sky Finder that has a copy of the Bortle map that will make it easier to do this search in the future.  I don't know what they are using for their data source but a quick look indicated some good data categories an the tabular data associated with each push pin.  And I suspect there are different sites there than on other sites.]

So I "Googled" "dark sky sites" and came up with ObservingSites.com.  Peter and I discussed some possible candidates.  He is partial to sites in western PA where the conditions are Bortle 3-3+, while I am partial to the WV sites which are Bortle 1/2-2+.

Anyway in looking at this we found a county park near Grantsville, WV, in Bortle 1/2 country, that is supposed to have impressive skies and an old barn you can stay in for cheap.  Peter will consider WV -- the difference in drive time is not that great when you consider the total drive time, and the price is right if it is available in the winter -- but is keeping his options open for PA.  While I figure if we are going to a dark sky site we should shoot for the darkest one possible I recognize that a dark sky site is wasted on me since after the sky fills up with more than our six Central Park stars I am lost and can't even find bright things like the Big W or the Big Dipper.  I am thinking mostly I will be appreciating how much we are missing in The City and trying to identify the familiar constellations.

And now I am remembering the cabin in the mountains on the margin of a Bortle 1/2-3 area where I spent weekends one semester in college.  It looks like the cabin is still there (if I am remembering the geography from 30 years ago and am correctly translating it onto Google Earth and Maps), but I don't know if my classmate's brother still owns it and would let us use it.  It is on the side of a hill so would have an obstructed western horizon and there is another hill across the valley to the west.  The area is within the Manongahela National Forest and is very rural (when I was in college you could get fresh deer meet and moonshine  there all year round).  And we could always use it as a base to access other areas like Spruce Knob and Green Bank, and for side trips to tourist attractions.

To aide and abet our selection process I looked at the historical weather information in Clear Sky Clock.  In the table beneath the chart there is sometimes a link to this data in the rightmost cell of the bottom table row.  If you look at the listing of sites within a state the locations that have this data are indicated by a red star in the first column.  There aren't many of them and, as in this case, they are probably not the site you want, but at least they give an indication of conditions this time of year around the state.  WV and PA are not looking great.

Then I remembered dry day.com, a site that predicts the likelihood of a given day being dry 18 months in advance and locks in their forecast.  They claim an 85% accuracy rate.  I have used the site numerous times but have no idea how their predictions stack up against ground truth in NYC.  So I decided to find out.  I have looked up the forecast going forward and am going to compare it with the Central Park observed conditions for the remainder of the month.  I will be looking at "average" cloud cover, humidity and precipitation recorded each calendar day

dryday.com graphic

dryday.com graphic

Date	dry day.com		Central Park	LGA
	Condition	Risk of Precipitation	Reported Conditions	Observed Conditions
15	Risky	48%	Day: O Night: MC Precip: T RH: 68%	Day: O Night: MC Precip: T RH: 66%
16	Transition	42%	Day: O Night: MC Precip: 0.00" RH: 48%	Day: MC Night: MC Precip: 0.00" RH: 48%
17	Transition	48%	Day: O Night: O Precip: 0.11" RH: 89%	Day: MC Night: MC Precip: 0.00" RH: 54%
18	Risky	58%	Day: C Night: C Precip: RH: 0.00"	Day: PC Night: PC Precip: 0.00" RH: 46%
19	Risky	50%	Day: MC Night: O Precip: 0.00" RH: 54%	Day: MC Night: O Precip: 0.00" RH: 53%
20	Transition	42%	Day: MC Night: O Precip: 0.01" RH: 64%	Day: O Night: O Precip: 0.01" RH: 62%
21	Dry	25%	Day: O Night: O Precip: 0.11" RH: 89%	Day: O Night: O Precip: 0.08" RH: 83%
22	Dry	40%	Day: PC Night: MC Precip: 0.06" RH: 60%	Day: MC Night: O Precip: 0.05" RH: 59%
23	Dry	11%	Day: O Night: C Precip: 0.75" RH: 77%	Day: MC Night: PC Precip: 0.76" RH: 72%
24	Dry	10%	Day: PC Night: C Precip: 0.00" RH: 4%	Day: PC Night: PC Precip: 0.00" RH: 52%
25	Transition	42%	Day: MC Night: PC Precip: 0.00" RH: 57%	Day: MC Night: O Precip: 0.00" RH: 55%
26	Risky	49%	Day: PC Night: C Precip: 0.00" RH: 56%	Day: PC Night: PC Precip: T RH: 52%
27	Transition	40%	Day: MC Night: O Precip: 1.02" RH: 79%	Day: O Night: O Precip: 1.17" RH: 73%
28	Dry	18%	Day: O Night: MC Precip: 0.00" RH: 59%	Day: MC Night: PC Precip: 0.00" RH: 57%
29	Transition	43%	Day: PC Night: Precip: 0.00" RH: 46%	Day: MC Night: O Precip: 0.00" RH: 43%
30	Risky	52%	Day: C Night: PC Precip: 0.00" RH: 65%	Day: MC Night: MC Precip: 0.00" RH: 61%
31	Risky	70%	Day:MC Night: C Precip: 0.01" RH: 73%	Day: MC Night: PC Precip: 0.01" RH: 73%
Legend C = Clear PC = Partly Cloudy MC = Mostly Cloudy O = Overcast

I am comparing the dryday.com assessment against the automated observations from Central Park which may not be fair. I have long felt that the instruments at the Central Park weather station are optimists. When I was out this afternoon it was overcast but Central Park reported it as clear and tonight the GOES images show clouds blanketing the area while it is supposed to be clear at Central Park. So maybe I should add another column and also compare the La Guardia Airport observations. At least there are people there who might be looking out a window and notice clouds. Then I will be able to validate the two weather stations against each other and the dryday.com forecast against them.

Converting hourly observations of the current weather to Day and Night generalizations wasn't easy. I ended up loosely defining Day as 0751 to 1751 and Night as 1851 to 2351 and kinda averaging out what was reported over the period. It was hardest when the observations ranged between Clear and Overcast. I probably should have converted the text into octas and averaged them but even that would have had a lot of slop in it since a cloud cover description can span several octas and some of them overlap in their octa values.

I looked at what condition they assigned each day relative to their predicted Risk of Precipitation.

Risk of Precipitation	Dry	Transition	Risky
90%-100%
80%-99%
70%-79%	1
60%-69%
50%-59%			3
40%-49%	1	6	3
30%-39%
20%-29%	1
10%-19%	3
0%-9%

I looked at Risk of Rain compared about actual rainfall.

Risk of Precipitation	Rain	No Rain
90%-100%
80%-89%
70%-79%	1
60%-69%
50%-59%		3
40%-49%	6	3
30%-39%
20%-29%	1
10%-19%	1	2
0%-9%

As you would expect, when they predicted a low Risk of Precipitation they also predicted that it would probably be Dry. When the Risk of Precipitation rose they said it would be a time of Transition. And when the Risk of Precipitation was very high they said it would be a Risky time to schedule outdoor activities. There appears to be about a 10% overlap between Dry and Transition and is aseumedly a similar overlap between Transition and Risky. When compared with the Risk of Precipitation vs Condition chart above I come to the conclusion that it rained about 50% of the time when they said there was a high probablility that it would and that it rained about 50% of the time when they said there was a low probablilty that it would.

Lastly I compaired when it would rain against the risk condition they assigned each day.

	Rain	No Rain
Dry	3	2
Transition	3	3
Risky	3	3

Again it looks like it didn't tain about 50% of the time when they said it would probably be dry and rained the other 50% of the time. And during the time when they said it would probably rain it rained about 50% of the time and was dry the other 50% of the time.

Based on this short assessment I don't see this forecast being much good for astronomy or for anything else other than possibly as a CYA if you have to schedule an weather dependant event well in advance. You might as well flip a coin.

Looking at the reported conditions for Central Park and LaGuardia Airport I only found one instance where their cloud cover data was more than one "unit" in difference (25Dec11: Partly Cloudy vs Overcast) so my feeling that Central Park is overly optimistic remains a feeling. I have built a mirror to take cloud cover measurements . I tried it out at Bryant Park when I was doing solar observations on 26Dec11 and found that the clouds moved so quickly that it was hard to get an accurate count. Maybe I will have better luck taking pictures of the mirror and counting the clouds that way. My plan is to count the clouds at 51 minutes past the hour at Belvedere Castle and compare my assessment with the report of the Central Park automated weather station submitted at the same time.

7 January 2011

Filters

I have seen several listings of filters and what they are good for and the ones I have seen so far have always been arranged by filter color which seems bass ackwards to me. It is like the people who write these lists are saying

“Gee, I have this red filter. What can I look at with it?”

I approach filters from the other side of the coin saying

“I am not seeing as much detail in Jupiter as the space telescope pictures tell me is there. Do I have a filter that will alter the view to let me see more?”

So I have been collecting filter data and have organized it by object so it is easier for me to use.

Sources: Celestron; Astronomy Hacks

Sun
Wratten	Color	Use
#21	Orange	With a Mylar filter, adding the orange filter will return the Sun to its “true” color

Moon
Wratten	Color	Use
#8	Light Yellow	Improves contrast Better appearance of features
#12	Yellow	Improves contrast Better appearance of features
#15	Deep Yellow	Enhances features
#21	Orange	Greatly enhances features
#25	Red	Improves features
#47	Violet	Improves detail
#56	Light Green	Enhances features
#58	Green	Enhances features
#82A	Pale Blue	Brings out low contrast features
#80A	Blue	Enhances detail
Moon	Neutral Density	Reduces brightness making it more comfortable to view the Moon Improves contrast Brings out detail Clear aperture is 21mm, ~84% of normal; 18% transmission

Mercury
Wratten	Color	Use
#21	Orange	Reduces brightness of sky during daytime/twilight Brigs out surface features
#25	Red	Improves observation in twilight when the planet is near the horizon During daylingt, reduces brightness of sky Brings out surface eatures
#29	Deep Red	Improves sky contrast during daytime and twilight Brings out surface features
#47	Violet	Observing clouds Improves contrast Brings out features
#80A	Blue	Improves dusky surface markings at twilight when the planet is near the horizon

Venus
Wratten	Color	Use
#11	Yellow-Green	Observing clouds
#15	Deep Yellow	Reveal low-contrast surface features Observe Clouds Observe ice caps
#21	Orange	Reduces sky brightness during daytime observing
#25	Red	Reduces brightness of daytime sky Terminator deformations
#29	Deep Red	Inproves daytime and twilight sky contrast Observe clouds Increases Contrast Brings out surface detail
#47	Violet	Observe clouds Improve contrast Brings out detail Favorite Venus filter for many observers
#56	Light Green	Observing clouds Reduces daytime sky brightness
#58	Green	Observing clouds Reduces daytime sky brightness
#80A	Blue	Increases contrast of dark shadings in upper clouds
#38A	Deep Blue	Observe clouds

Mars
Wratten	Color	Use
#8	Light Yellow	Observe maria
#11	Yellow-Green	Observe maria Observe ice caps
#12	Yellow	Observe maria
#15	Deep Yellow	Reduce light from blue and green areas which darkens the maria, oases and canal markings, while lightening the orange-hued desert regions Sharpens boundaries of yellow dust clouds Increases contrast
#21	Orange	Reduce light from blue and green areas which darkens the maria, oases and canal markings, while lightening the orange-hued desert regions Sharpens boundaries of yellow dust clouds
#25	Red	Observe polar ice caps Observe surface features sharpens boundaries of yellow dust clouds
#29	Deep Red	Observe Maria Observe ice caps Observe surface detail
#47	Violet	Observe ice caps
#56	Light Green	Observe dust storms observe ice caps Observe dust storms
#58	Green	Excellent to increase contrast of polar ice caps, low clouds and yellowish dust storms
#82A	Pale Blue	Brings out low-contrast features Improves detail
#80A	Blue	Observe dust storms
#38A	Deep Blue	Observe dust storms

Jupiter
Wratten	Color	Use
#8	Light Yellow	Observe belts
#11	Yellow-Green	Observe clouds Improves feature contrast
#12	Yellow	Observe belts
#15	Deep Yellow	Penetrate and darken atmospheric currents containing low-hue blue tones Enhance orange and red features of the belts and zones Useful for polar cap studies Increases contrast
#21	Orange	Improves appearance of detail revealed in structure of belts Enhances festoons Enhances polar regions
#25	Red	Used to study bluer clouds Observe belts Observe transits
#29	Deep Red	Observe clouds Observe belts Observe transits
#56	Light Green	Observe Clouds Increase low-contrast detail
#58	Green	Observe clouds Reduces sky brightness during daytime
#82A	Pale Blue	Observe low-contrast features Increase observed detail
#80A	Blue	Enhance boundaries between the reddish belts and adjacent bright zones Observe Great Red Spot
#38A	Deep Blue	Observe belts Observe Great Red Spot

Saturn
Wratten	Color	Use
#8	Light Yellow	Observe belts
#11	Yellow-Green	Observe the Cassini Division
#12	Yellow	Observe belts
#15	Deep Yellow	Increases contrast
#21	Orange	Improves band structure Highlights blue polar regions
#25	Red	Observe bluer clouds
#29	Deep Red	Observe clouds
#47	Violet	Observe ring structure
#56	Light Green	Observe clouds Observe surface detail
#58	Green	Observe clouds Observe belts Observe polar regions
#82A	Pale Blue	Observe low-contrast features Increases observed detail Observe cloud belts
#80A	Blue	Penetrate and darken atmospheric currents containing low-hue blue tones Enhance orange and red features of belts and zones
#38A	Deep Blue	Observe rings Observe belts Observe clouds

Uranus
Wratten	Color	Use
#8	Light Yellow	Increases observed detail
#11	Yellow-Green	Increases contrast Increases observed detail
#12	Yellow	Increases observed detail
#15	Deep Yellow	Improve detail in larger telescopes (>10”)

Neptune
Wratten	Color	Use
#8	Light Yellow	Increase observed detail
#11	Yellow-Green	Increase contrast Increase observed detail
#12	Yellow	Increase observed detail
#15	Deep Yellow	Improve detail in larger telescopes (>10”)

Comets
Wratten	Color	Use
#8	Light Yellow	Increases observed detail
#15	Deep Yellow	Enhances tail definition
#21	Orange	Enhances definition in dust trails and heads in larger telescopes (>10”)
#58	Green	Useful for observing brighter comets
#82A	Pale Blue	Observe comet tails
#80A	Blue	Best definition in gast tails
#38A	Deep Blue	Bright comet tails

Galaxies
Wratten	Color	Use
#82A	Pale Blue	Observe detail in bright galaxies

6 April 2010

Forecasting Weather based on Wind and Barometer

Wind Blowing From	Barometer Reading Barometer Trennd	Probable Weather
SW to NW	30.10 to 30.20 Steady	fair then temperature change lasting 1-2 days
SW to NW	30.10 to 30.20 Rising Rapidly	fair then rain within 2 days
SW to NW	=> 30.20 Falling Rapidly	slowly rising temperature fair for 2 days
S to SE	30.10 to 30.20 Falling Slowly	rain within 24 hours
S to SE	30.10 to 30.20 Falling Rapidly	increasing wind strength rain within 12-24 hours
SE to NE	30.10 to 30.20 Falling Slowly	rain in 12-18 hours
SE to NE	30.10 to 30.20 Falling Rapidly	increasing wind strength rain within 12 hours
E to NE	30.10 to 30.20 Falling Slowly	Summer: no rain likely for several days Winter: rain within 24 hours
E to NE	=> 30.10 Falling Rapidly	Summer: rain likely within 12-24 hours Winter: rain or snow, increasing winds
SE to NE	<= 30.00 Falling Slowly	rain to continue 1-2 days
SE to NE	<= 30.00 Falling Rapidly	rain & high wind followed by clearing within 36 hours and by colder temperatures in winter
S to SE	<= 30.00 Rising Slowly	clearing within a few hours and fair for several days
S to E	<= 29.80 Falling Rapidly	severe storm soon followed by clearing within 24 hours and by colder temperatures in winter
E to N	<= 29.80 Falling Rapidly	severe NE gale and haavy precipitation Winter: heavy snow followed by cold wave
changing to W	<= 29.08 Rising Rapidly	clearing and colder

---

Wowbagger gazed for a moment at the fantastic jewelry of the night; the billions of the tiny diamond worlds that dusted the infinite darkness with light. Douglas Adams Life, The Universe and Everything

15 March 2010

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Barometric Pressure METAR Code

I have been reporting barometric pressure for some time now and as well as the actual inches of mercury have been including is statement as to the pressure trend (rising, steady, falling). So far this trend statement has been subjective based on what the pressure has been the past couple of hours before the observation. Tonight I investigated METARs -- routine meteorological observations reported at the end of each hour (51 minutes after the hour) -- and found that there are actually standards for making this assessment and the gradations are much finer than what I have heretofore reported. So wherever possible I will report by the following scale.

Rising higher than 3 hours ago	0	increasing then decreasing
	1	increasing then steady or increasing then increasing more slowly
	2	increasing steadily or unsteadily
	3	decreasing or steady, then increasing or increasing then increasing more rapidly
Steady same as three hour ago	0	increasing then decreasing
	4	steady
	5	decreasing then increasing
Falling lower than 3 hours ago	5	decreasing then increasing
	6	decreasing then steady or decreasing then decreasing more slowly
	7	decreasing steadily or unsteadily
	8	steady or increasing then decreasing or decreasing then decreasing more rapidly

---

With all of the shaking that has been and is still going on in Chile and its movement to the east I was wondering how it might be affecting all of the big new telescopes down there.

I looked up their locations and plotted them in Google Earth along with the locations of the earthquakes greater than Richter magnitude 4.5 (automatically plotted based on a KMZ file from USGS.

Google Earth graphic

Based on the strength of the initial and strongest temblor and the descriptions of the Richter scale (below) it doesn't seem like any of the scopes should have been effected by the shaking but if any of them use polar alignment, which is doubtful in this day and age, they would probably need to be realigned or otherwise adjusted. There was also an elevation change across the continent so that probably needed checking out and possibly compensating for as well.

Richter Magnitude Scale for Earthquake Severity

The Richter Scale is a measure of the energy released beneath the Earth's surface at the epicenter of the earthquake.

Richter Magnitude	Descriptor	Probable Effects	Frequency
<2.0	Micro	microearthquakes not felt	~8,000/day
2.0 - 2.9	Minor	generally not felt but recorded	~1,000/day
3.0 - 3.9		often felt but rarely cause< damage	~49,000/year
4.0 - 4.9	Light	Noticeable shaking of indoor items, rattling noises Significant damage unlikely	6,200/year
5.0 - 5.9	Moderate	Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings	800/year
6.0 - 6.9	Strong	Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas	120/year
7.0 - 7.9	Major	Can cause serious damage over larger areas	18/year
8.0 - 8.9	Great	Can cause serious damage in areas several hundred miles across	1/year
9.0 - 9.9		Devastating in areas several thousand miles across	1/20 years
10.0+	Epic	Never recorded	extremely rare none recorded
based on Wikipedia

Modified Mercalli Intensity Scale

The Modified Mercalli Intensity scale measures the impact of the earthquake at the surface of the Earth.

Category	Description	Corresponding Richter
I. Instrumental	Not felt by many people unless in favourable conditions.	1.0 - 3.0
II. Feeble	Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing.	3.0 - 3.9
III. Slight	Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated.
IV. Moderate	Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rock noticeably. Dishes and windows rattle alarmingly.	4.0 - 4.9
V. Rather Strong	Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house.
VI. Strong	Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.	5.0 - 5.9
VII. Very Strong	Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars.		6.0 - 6.9
VIII. Destructive	Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved.	7.0+
IX. Ruinous	General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.		6.0 - 6.9
X. Disastroud	Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent.
XI. Very Disasterous	Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.
XII. Catastrophic	Total damage - Everything is destroyed. Total destruction. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock move position.
after Wikipedia

Gerassimos Papadopoulos and Fumihiko Imamura Tsunami Intensity Scale

Category	Wave Height	(a) effects on humans (b)effect on objects including boats (c) damage to buildings
I. Not Felt	0
II. Scarcely Felt	0	(a) Felt by few people onboard small vessels. Not observed on the coast. (b) No effect. (c) No damage.
III. Weak	0	(a) Felt by most people onboard small vessels. Observed by a few people on the coast. (b) No effect. (c) No damage.
IV. Largely Observed	0	(a) Felt by all onboard small vessels and by few people onboard large vessels. Observed by most people on the coast. (b)Few small vessels move slightly onshore. (c) No damage.
V. Strong	1 m	Felt by all onboard large vessels and observed by all on the coast. Few people are frightened and run to higher ground. (b) Many small vessels move strongly onshore, few of them crash into each other or overturn. Traces of sand layer are left behind on ground with favorable circumstances. Limited flooding of cultivated land. (c) Limited flooding of outdoor facilities (such as gardens) of near-shore structures.
VI. Slightly Damaging	2 m	Many people are frightened and run to higher ground. (b) Most small vessels move violently onshore, crash strongly into each other, or overturn. (c) Damage and flooding in a few wooden structures. Most masonry buildings withstand.
VII. Damaging	4 m	(a) Many people are frightened and try to run to higher ground. (b) Many small vessels damaged. Few large vessels oscillate violently. Objects of variable size and stability overturn and drift. Sand layer and accumulations of pebbles are left behind. Few aquaculture rafts washed away. (c) Many wooden structures damaged, few are demolished or washed away. Damage of grade 1 and flooding in a few masonry buildings.
VIII. Heavily Damaging	4 m	(a) All people escape to higher ground, a few are washed away. (b) Most of the small vessels are damaged, many are washed away. Few large vessels are moved ashore or crash into each other. Big objects are drifted away. Erosion and littering of the beach. Extensive flooding. Slight damage in tsunami-control forests and stop drifts. Many aquaculture rafts washed away, few partially damaged. (c) Most wooden structures are washed away or demolished. Damage of grade 2 in a few masonry buildings. Most reinforced-concrete buildings sustain damage, in a few damage of grade 1 and flooding is observed.
IX. Destructive	8 m	(a) Many people are washed away. (b) Most small vessels are destroyed or washed away. Many large vessels are moved violently ashore, few are destroyed. Extensive erosion and littering of the beach. Local ground subsidence. Partial destruction in tsunami-control forests and stop drifts. Most aquaculture rafts washed away, many partially damaged. (c) Damage of grade 3 in many masonry buildings, few reinforced-concrete buildings suffer from damage grade 2.
X. Very Destructive	8 m [12 m ??]	(a) General panic. Most people are washed away. (b) Most large vessels are moved violently ashore, many are destroyed or collide with buildings. Small boulders from the sea bottom are moved inland. Cars overturned and drifted. Oil spills, fires start. Extensive ground subsidence. (c) Damage of grade 4 in many masonry buildings, few reinforced-concrete buildings suffer from damage grade 3. Artificial embankments collapse, port breakwaters damaged.
XI. Devastating	16 m	(a) (b) Lifelines interrupted. Extensive fires. Water backwash drifts cars and other objects into the sea. Big boulders from sea bottom are moved inland.(c) Damage of grade 5 in many masonry buildings. Few reinforced-concrete buildings suffer from damage grade 4, many suffer from damage grade 3.
XII. Completely Devasating	32 m	(a) (b) (c) Practically all masonry buildings demolished. Most reinforced-concrete buildings suffer from at least damage grade 3.
based on About.com: Geology

19 January 2010

In The Observing Sky Atlas E. Karkoschka has a table on sky brightness that is supposed to help you figure out which faint fuzzies you can see on a given night. The table equates the brightness of a NYC sky to that of a mountaintop under a Full Moon. I wondered what it would be like in NYC under a full moon so extended the chart to include projections for large cities under other than New Moon conditions.

Illumination Mountains or New Moon Field or Crescent (25%) Moon Suburb or First/Last Quarter (50%) Moon Small City or Gibbous (75%) Moon Large City or Full Moon Large City and New Moon Large City and Crescent (25%) Moon Large City and First/Last Quarter (50%) Moon Large City and Gibbous (75%) Moon Large City and Full Moon	Sky Brightness 14/square’ 13 12 11 (10) (10) (9) (8) (7) (6)
after E. Karkoschka numbers in ( ) are extrapolations

17 January 2010

Resolution

The resolution of the naked eye is 5 arcminutes or 300 arcseconds.

The resolution of optics is 300/power of the optic.

Assumedly if you eyesight is not great, like mine, you need to substitute your personal resolution in arcseconds for the 300 in the above formula.

Resolving Power and Resolution of Optical Systems

Optics	power	Aperture	Limiting mag.	FoV	Lunar Size	Resol- ution	Visibi- lity
naked-eye	1x	6 mm	6	120°	30’	300”	6
opera glasses	3x	20mm	8	at°	10’	100”	5
finder scope	6x	30,,	9	7°	5’	50”	4
binocular	12x	50mm	10	4°	2.5’	25”	3
guide scope	60x	75mm	11	50’	30”	5”	2
telescope	35x 350x	150mm	13	80’ 8’	50” 5”	8” 0.8”	1
Takahashi 102	31.8x 97.7x 118.4x	102mm		:° 82° 82°		9.4” 3” 2.5”
TelePort 10	31.8x 74.7x 181.4x	254mm		70° 82° 82°		9.4” 3.0” 1.7”
Galileoscope	17x 25x 50x	50mm		1.5° 0.75°		17.6” 12” 6”