Greene
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greene clear sky chart from 2005-11-06 to 2024-02-15.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	18% 7% 3 5% 5% 3 4 4 5% 7% 39%	77778
	Night	18% 8% 3 5% 5% 3 4 4 5% 6% 38%	81284
Transparency	Day	45% 6% 12% 22% 14% 2	77483
	Night	46% 6% 12% 22% 13% 2	81114
Seeing	Day	23% 17% 31% 19% 8% 2	13918
	Night	22% 13% 31% 25% 8% 1	23045

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 7% 3 5% 5% 3 4 4 6% 7% 41%	2517
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 4 5% 7% 40%	2520
	21st to end	Day	16% 12% 3 6% 4 2 4 5% 5% 5% 37%	2772
February	1st to 10th	Day	16% 9% 3 5% 5% 4 4 4 5% 6% 37%	1667
	11th to 20th	Day	13% 9% 3 6% 7% 4 5% 5% 4 5% 39%	1788
	21st to end	Day	16% 10% 4 6% 5% 2 6% 5% 7% 6% 34%	1480
March	1st to 10th	Day	16% 9% 3 6% 5% 4 4 5% 6% 7% 37%	1797
	11th to 20th	Day	16% 7% 3 6% 5% 3 4 5% 4 5% 41%	1938
	21st to end	Day	17% 8% 3 5% 6% 3 4 3 5% 5% 41%	2232
April	1st to 10th	Day	21% 9% 3 6% 4 3 4 3 4 6% 36%	2160
	11th to 20th	Day	18% 6% 2 5% 6% 3 5% 5% 5% 7% 39%	2226
	21st to end	Day	24% 7% 3 6% 6% 3 4 5% 4 5% 32%	2340
May	1st to 10th	Day	25% 7% 3 5% 5% 3 4 5% 4 7% 32%	2340
	11th to 20th	Day	20% 6% 3 6% 5% 3 4 5% 4 7% 38%	2343
	21st to end	Day	17% 6% 3 6% 6% 3 4 5% 6% 7% 38%	2725
June	1st to 10th	Day	23% 7% 3 5% 5% 3 5% 6% 6% 8% 29%	2520
	11th to 20th	Day	18% 5% 3 6% 5% 3 4 5% 5% 7% 39%	2520
	21st to end	Day	23% 7% 3 4 5% 4 6% 5% 5% 6% 31%	2520
July	1st to 10th	Day	16% 5% 3 6% 4 3 5% 5% 6% 8% 38%	2520
	11th to 20th	Day	14% 6% 3 5% 6% 4 6% 6% 7% 8% 35%	2520
	21st to end	Day	14% 5% 2 6% 5% 4 6% 5% 6% 10% 37%	2744
August	1st to 10th	Day	14% 5% 2 5% 5% 3 5% 5% 7% 9% 40%	2352
	11th to 20th	Day	15% 6% 2 5% 6% 4 5% 5% 6% 8% 38%	2304
	21st to end	Day	12% 4 2 5% 5% 3 4 5% 6% 7% 46%	2473
September	1st to 10th	Day	13% 4 2 5% 4 3 4 4 5% 8% 48%	2120
	11th to 20th	Day	13% 5% 1 4 4 3 3 3 4 5% 55%	1980
	21st to end	Day	16% 4 2 4 4 2 4 4 5% 8% 46%	1980
October	1st to 10th	Day	19% 7% 2 6% 5% 3 4 4 4 7% 40%	1980
	11th to 20th	Day	18% 7% 3 5% 5% 2 4 4 4 7% 41%	1730
	21st to end	Day	24% 8% 2 5% 4 2 5% 3 4 6% 37%	1782
November	1st to 10th	Day	18% 6% 2 4 3 2 3 4 5% 6% 46%	1671
	11th to 20th	Day	21% 5% 2 3 4 2 5% 4 6% 6% 43%	1710
	21st to end	Day	23% 7% 2 4 3 2 3 2 5% 6% 43%	1687
December	1st to 10th	Day	22% 10% 4 5% 5% 2 3 4 5% 5% 36%	1345
	11th to 20th	Day	22% 9% 2 4 4 3 3 3 4 4 41%	1703
	21st to end	Day	26% 11% 2 5% 5% 3 4 4 5% 6% 31%	2772
January	1st to 10th	Night	16% 10% 3 5% 4 2 4 4 5% 6% 41%	4429
	11th to 20th	Night	14% 9% 3 8% 6% 3 5% 5% 5% 7% 35%	4440
	21st to end	Night	19% 11% 4 7% 5% 3 5% 4 4 5% 32%	4884
February	1st to 10th	Night	16% 8% 4 6% 6% 4 5% 5% 5% 6% 35%	2510
	11th to 20th	Night	13% 9% 4 5% 6% 3 5% 4 4 5% 40%	2153
	21st to end	Night	15% 9% 2 6% 5% 3 5% 4 4 7% 39%	1776
March	1st to 10th	Night	15% 12% 3 5% 5% 3 5% 5% 5% 5% 38%	2150
	11th to 20th	Night	17% 8% 4 6% 5% 3 5% 5% 4 7% 37%	2020
	21st to end	Night	19% 7% 3 6% 4 3 4 4 5% 5% 41%	2120
April	1st to 10th	Night	21% 10% 3 4 5% 3 4 4 4 6% 35%	1800
	11th to 20th	Night	19% 6% 3 5% 6% 3 5% 5% 4 7% 38%	1683
	21st to end	Night	25% 7% 2 5% 4 3 5% 5% 5% 5% 34%	1620
May	1st to 10th	Night	20% 10% 3 4 5% 4 5% 5% 5% 7% 32%	1620
	11th to 20th	Night	21% 7% 3 5% 6% 3 5% 5% 6% 8% 32%	1565
	21st to end	Night	19% 9% 4 6% 6% 3 4 5% 5% 6% 34%	1550
June	1st to 10th	Night	23% 7% 3 7% 4 4 5% 4 4 8% 32%	1440
	11th to 20th	Night	19% 6% 2 5% 4 2 5% 4 6% 8% 40%	1440
	21st to end	Night	23% 8% 3 4 4 3 4 6% 6% 7% 33%	1440
July	1st to 10th	Night	16% 5% 3 4 6% 4 5% 5% 6% 7% 38%	1440
	11th to 20th	Night	16% 6% 2 5% 5% 3 4 5% 5% 8% 40%	1440
	21st to end	Night	16% 4 2 4 5% 3 6% 5% 7% 8% 41%	1574
August	1st to 10th	Night	12% 5% 2 5% 5% 4 5% 6% 5% 8% 42%	1567
	11th to 20th	Night	14% 6% 2 6% 6% 4 4 5% 6% 9% 37%	1596
	21st to end	Night	15% 4 2 5% 4 2 3 4 5% 8% 47%	1880
September	1st to 10th	Night	14% 6% 1 3 4 3 3 4 5% 7% 49%	1840
	11th to 20th	Night	16% 5% 2 3 4 2 3 4 4 7% 50%	1980
	21st to end	Night	16% 5% 2 4 4 3 3 3 6% 6% 48%	1980
October	1st to 10th	Night	19% 7% 2 5% 4 3 4 4 5% 6% 40%	1980
	11th to 20th	Night	18% 6% 2 5% 4 3 4 5% 6% 6% 41%	2227
	21st to end	Night	26% 6% 2 5% 4 3 3 4 4 6% 36%	2574
November	1st to 10th	Night	18% 6% 2 4 5% 3 4 4 4 6% 44%	2407
	11th to 20th	Night	19% 6% 3 3 4 3 4 4 4 5% 44%	2470
	21st to end	Night	17% 6% 3 5% 5% 3 4 3 5% 6% 42%	2487
December	1st to 10th	Night	22% 9% 3 6% 5% 3 4 4 4 6% 33%	2831
	11th to 20th	Night	24% 8% 2 4 5% 3 3 4 4 5% 39%	3487
	21st to end	Night	25% 9% 3 5% 5% 3 4 4 4 5% 34%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	42% 5% 14% 27% 11% 1	2518
	11th to 20th	Day	43% 6% 14% 24% 11% 2	2520
	21st to end	Day	48% 6% 12% 20% 13% 1	2772
February	1st to 10th	Day	47% 4 12% 20% 14% 3	1667
	11th to 20th	Day	48% 6% 10% 19% 13% 3	1797
	21st to end	Day	49% 6% 9% 18% 13% 4	1480
March	1st to 10th	Day	47% 4 12% 18% 15% 4	1800
	11th to 20th	Day	44% 5% 9% 21% 16% 5%	1938
	21st to end	Day	46% 5% 8% 18% 18% 6%	2232
April	1st to 10th	Day	51% 4 9% 17% 15% 4	2160
	11th to 20th	Day	44% 6% 10% 22% 15% 3	2226
	21st to end	Day	53% 6% 8% 16% 13% 4	2340
May	1st to 10th	Day	51% 6% 8% 20% 14% 2	2340
	11th to 20th	Day	46% 6% 8% 20% 17% 3	2347
	21st to end	Day	44% 7% 14% 20% 12% 2	2725
June	1st to 10th	Day	52% 7% 12% 20% 10%	2520
	11th to 20th	Day	44% 7% 10% 20% 16% 3	2520
	21st to end	Day	53% 7% 11% 19% 9% 1	2520
July	1st to 10th	Day	41% 7% 14% 23% 14% 1	2450
	11th to 20th	Day	43% 7% 14% 25% 10% 1	2445
	21st to end	Day	41% 8% 16% 23% 12% 1	2591
August	1st to 10th	Day	38% 9% 16% 26% 10%	2338
	11th to 20th	Day	43% 7% 15% 25% 11% 1	2304
	21st to end	Day	35% 8% 13% 24% 19% 1	2473
September	1st to 10th	Day	34% 7% 14% 27% 17% 1	2120
	11th to 20th	Day	32% 4 10% 29% 22% 3	1980
	21st to end	Day	36% 5% 12% 28% 17% 1	1980
October	1st to 10th	Day	45% 5% 11% 23% 15% 2	1980
	11th to 20th	Day	43% 5% 12% 27% 11% 1	1730
	21st to end	Day	49% 5% 10% 20% 14% 2	1782
November	1st to 10th	Day	39% 5% 13% 24% 16% 3	1671
	11th to 20th	Day	41% 6% 11% 21% 18% 3	1710
	21st to end	Day	43% 4 18% 22% 12% 1	1687
December	1st to 10th	Day	51% 4 11% 21% 12% 2	1345
	11th to 20th	Day	47% 5% 9% 20% 15% 4	1703
	21st to end	Day	56% 5% 11% 17% 9% 3	2772
January	1st to 10th	Night	43% 5% 13% 27% 10% 2	4429
	11th to 20th	Night	47% 7% 13% 19% 12% 2	4440
	21st to end	Night	52% 6% 9% 20% 12% 1	4884
February	1st to 10th	Night	49% 6% 12% 18% 12% 3	2510
	11th to 20th	Night	46% 5% 10% 21% 16% 2	2155
	21st to end	Night	46% 4 10% 21% 15% 4	1776
March	1st to 10th	Night	48% 6% 8% 21% 15% 3	2160
	11th to 20th	Night	47% 5% 11% 18% 14% 4	2021
	21st to end	Night	44% 5% 9% 19% 19% 5%	2120
April	1st to 10th	Night	51% 4 9% 18% 15% 4	1800
	11th to 20th	Night	44% 6% 10% 22% 17% 1	1683
	21st to end	Night	50% 5% 11% 18% 11% 4	1620
May	1st to 10th	Night	51% 5% 10% 19% 14% 2	1620
	11th to 20th	Night	48% 8% 10% 19% 12% 4	1566
	21st to end	Night	50% 6% 12% 18% 12% 1	1551
June	1st to 10th	Night	51% 6% 10% 22% 9% 1	1440
	11th to 20th	Night	42% 6% 14% 21% 14% 2	1440
	21st to end	Night	49% 7% 15% 18% 9% 1	1440
July	1st to 10th	Night	42% 8% 16% 21% 13% 1	1400
	11th to 20th	Night	41% 6% 17% 25% 11%	1392
	21st to end	Night	39% 8% 17% 25% 10% 1	1486
August	1st to 10th	Night	38% 8% 16% 27% 10%	1557
	11th to 20th	Night	42% 8% 16% 22% 13%	1596
	21st to end	Night	36% 6% 13% 28% 17% 1	1880
September	1st to 10th	Night	35% 6% 13% 31% 15%	1840
	11th to 20th	Night	35% 4 12% 29% 18% 2	1980
	21st to end	Night	36% 6% 11% 30% 14% 2	1980
October	1st to 10th	Night	44% 5% 12% 23% 14% 1	1980
	11th to 20th	Night	42% 6% 14% 26% 12% 1	2227
	21st to end	Night	50% 4 12% 19% 13% 2	2574
November	1st to 10th	Night	42% 5% 11% 25% 15% 2	2407
	11th to 20th	Night	43% 4 11% 23% 16% 3	2470
	21st to end	Night	43% 5% 14% 22% 14% 2	2487
December	1st to 10th	Night	52% 5% 10% 21% 11% 1	2831
	11th to 20th	Night	47% 5% 10% 19% 17% 1	3488
	21st to end	Night	53% 5% 11% 19% 11% 1	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	30% 21% 30% 15% 4	180
	11th to 20th	Day	27% 24% 30% 14% 3 2	180
	21st to end	Day	20% 24% 32% 20% 4	198
February	1st to 10th	Day	27% 19% 33% 18% 3	327
	11th to 20th	Day	23% 26% 35% 13% 2	432
	21st to end	Day	26% 20% 34% 17% 3	346
March	1st to 10th	Day	27% 22% 33% 14% 4	420
	11th to 20th	Day	22% 28% 32% 15% 3	420
	21st to end	Day	26% 22% 32% 12% 6% 2	462
April	1st to 10th	Day	31% 23% 26% 14% 4 1	420
	11th to 20th	Day	27% 22% 30% 13% 6% 2	412
	21st to end	Day	31% 20% 26% 15% 5% 2	420
May	1st to 10th	Day	32% 21% 25% 19% 3 1	423
	11th to 20th	Day	20% 21% 35% 15% 7% 2	447
	21st to end	Day	21% 15% 35% 21% 6%	485
June	1st to 10th	Day	20% 19% 32% 18% 8% 2	450
	11th to 20th	Day	19% 17% 32% 21% 9% 2	450
	21st to end	Day	24% 13% 32% 21% 8% 2	450
July	1st to 10th	Day	20% 8% 36% 25% 9% 2	445
	11th to 20th	Day	14% 8% 36% 26% 12% 4	444
	21st to end	Day	15% 8% 37% 27% 11% 3	488
August	1st to 10th	Day	13% 10% 28% 31% 15% 2	446
	11th to 20th	Day	18% 9% 25% 28% 14% 6%	439
	21st to end	Day	13% 12% 29% 28% 12% 5%	495
September	1st to 10th	Day	17% 8% 30% 23% 17% 4	450
	11th to 20th	Day	17% 14% 29% 18% 13% 8%	450
	21st to end	Day	16% 14% 31% 22% 11% 6%	450
October	1st to 10th	Day	23% 15% 25% 21% 12% 4	450
	11th to 20th	Day	22% 15% 31% 19% 10% 2	365
	21st to end	Day	33% 17% 25% 17% 8%	396
November	1st to 10th	Day	24% 16% 29% 20% 9% 2	365
	11th to 20th	Day	30% 16% 28% 20% 5% 1	370
	21st to end	Day	30% 17% 27% 18% 7% 1	370
December	1st to 10th	Day	28% 16% 34% 13% 8%	195
	11th to 20th	Day	32% 22% 36% 8% 3	180
	21st to end	Day	32% 20% 26% 17% 4 1	198
January	1st to 10th	Night	23% 18% 35% 21% 3	760
	11th to 20th	Night	26% 19% 32% 19% 4	760
	21st to end	Night	19% 19% 39% 20% 3	836
February	1st to 10th	Night	22% 17% 34% 23% 4	760
	11th to 20th	Night	22% 18% 39% 18% 3	722
	21st to end	Night	23% 16% 34% 22% 4	592
March	1st to 10th	Night	23% 18% 38% 19% 2	720
	11th to 20th	Night	22% 18% 34% 20% 6%	720
	21st to end	Night	23% 18% 33% 22% 4 1	792
April	1st to 10th	Night	28% 17% 32% 19% 4	720
	11th to 20th	Night	21% 16% 35% 23% 5%	619
	21st to end	Night	29% 14% 31% 22% 5%	540
May	1st to 10th	Night	25% 11% 32% 24% 7% 1	540
	11th to 20th	Night	24% 13% 32% 26% 5%	504
	21st to end	Night	24% 7% 26% 35% 7%	389
June	1st to 10th	Night	27% 8% 29% 28% 9%	360
	11th to 20th	Night	20% 6% 27% 35% 13%	360
	21st to end	Night	26% 4 25% 35% 10%	360
July	1st to 10th	Night	19% 3 25% 39% 14%	350
	11th to 20th	Night	18% 3 26% 35% 18%	348
	21st to end	Night	15% 3 24% 41% 16% 1	394
August	1st to 10th	Night	15% 3 25% 41% 15% 1	493
	11th to 20th	Night	15% 5% 27% 35% 16% 1	532
	21st to end	Night	14% 7% 25% 35% 16% 2	692
September	1st to 10th	Night	15% 4 33% 33% 15% 1	720
	11th to 20th	Night	19% 8% 27% 27% 17% 3	720
	21st to end	Night	19% 8% 29% 27% 15% 1	720
October	1st to 10th	Night	22% 10% 24% 29% 13% 1	720
	11th to 20th	Night	21% 11% 30% 26% 10% 1	720
	21st to end	Night	29% 14% 30% 22% 5%	792
November	1st to 10th	Night	21% 12% 33% 24% 8% 1	740
	11th to 20th	Night	24% 14% 31% 23% 7% 1	760
	21st to end	Night	23% 19% 30% 22% 5%	769
December	1st to 10th	Night	26% 15% 35% 18% 5%	850
	11th to 20th	Night	26% 18% 32% 20% 3	835
	21st to end	Night	28% 16% 33% 20% 3	836

Page generated at 2024-02-12 06:35:35. Version ac07

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