Port Allegany
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Allegany clear sky chart from 2005-11-06 to 2024-01-17.

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	16% 12% 5% 8% 6% 3 5% 5% 5% 6% 29%	74704
	Night	16% 12% 5% 8% 6% 3 5% 4 5% 6% 29%	75112
Transparency	Day	55% 7% 11% 17% 9% 1	74420
	Night	55% 7% 12% 17% 9% 1	74930
Seeing	Day	26% 18% 28% 17% 8% 3	13530
	Night	24% 17% 28% 21% 9% 1	23082

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	14% 16% 10% 13% 9% 4 4 4 4 5% 18%	1517
	11th to 20th	Day	14% 18% 8% 14% 9% 4 5% 4 3 5% 17%	1646
	21st to end	Day	12% 18% 10% 14% 10% 4 4 4 4 5% 15%	1782
February	1st to 10th	Day	16% 17% 9% 11% 10% 4 5% 4 3 4 17%	1620
	11th to 20th	Day	13% 15% 9% 13% 8% 4 5% 4 4 6% 20%	1573
	21st to end	Day	19% 14% 5% 11% 8% 2 4 3 3 5% 25%	1426
March	1st to 10th	Day	15% 14% 7% 9% 7% 3 4 3 4 6% 28%	1972
	11th to 20th	Day	14% 15% 7% 9% 7% 3 4 4 4 5% 27%	1980
	21st to end	Day	19% 13% 5% 8% 6% 3 4 4 5% 4 28%	2179
April	1st to 10th	Day	15% 15% 6% 8% 5% 3 4 4 5% 6% 30%	2160
	11th to 20th	Day	19% 13% 3 5% 5% 3 5% 5% 6% 5% 31%	2134
	21st to end	Day	22% 10% 3 7% 5% 3 4 4 4 5% 32%	2286
May	1st to 10th	Day	20% 11% 3 8% 7% 3 4 5% 5% 6% 28%	2340
	11th to 20th	Day	22% 9% 3 6% 7% 3 5% 5% 4 7% 30%	2456
	21st to end	Day	14% 6% 3 6% 6% 3 6% 5% 6% 8% 38%	2725
June	1st to 10th	Day	17% 8% 2 6% 6% 3 6% 4 5% 7% 34%	2520
	11th to 20th	Day	15% 8% 3 7% 6% 3 6% 5% 6% 9% 32%	2520
	21st to end	Day	15% 6% 3 6% 6% 3 6% 6% 6% 7% 36%	2520
July	1st to 10th	Day	10% 6% 4 5% 7% 5% 6% 6% 6% 8% 37%	2520
	11th to 20th	Day	12% 7% 3 6% 5% 4 7% 6% 8% 9% 34%	2520
	21st to end	Day	13% 7% 3 7% 7% 4 6% 5% 6% 8% 34%	2553
August	1st to 10th	Day	11% 6% 3 7% 7% 5% 5% 6% 7% 10% 33%	2327
	11th to 20th	Day	13% 8% 3 7% 7% 5% 6% 6% 7% 9% 28%	2303
	21st to end	Day	14% 7% 3 7% 6% 4 6% 6% 6% 8% 31%	2394
September	1st to 10th	Day	19% 8% 3 5% 4 3 4 4 5% 7% 37%	2160
	11th to 20th	Day	15% 6% 3 7% 5% 4 4 5% 5% 7% 41%	2123
	21st to end	Day	19% 8% 3 6% 6% 4 5% 5% 4 7% 33%	1900
October	1st to 10th	Day	20% 9% 3 6% 6% 3 4 5% 5% 7% 33%	1800
	11th to 20th	Day	22% 9% 4 7% 6% 4 4 4 4 7% 30%	1800
	21st to end	Day	24% 16% 3 7% 6% 3 4 5% 4 5% 24%	1980
November	1st to 10th	Day	13% 14% 3 7% 5% 3 5% 5% 5% 7% 34%	1730
	11th to 20th	Day	17% 18% 5% 8% 5% 3 4 5% 5% 6% 25%	1520
	21st to end	Day	19% 19% 6% 8% 8% 3 3 4 5% 6% 20%	1520
December	1st to 10th	Day	17% 22% 9% 13% 7% 4 4 4 4 5% 13%	1520
	11th to 20th	Day	16% 19% 8% 13% 6% 3 4 4 4 6% 18%	1906
	21st to end	Day	21% 24% 9% 9% 6% 3 3 3 3 4 14%	2772
January	1st to 10th	Night	15% 17% 8% 13% 7% 4 5% 5% 4 6% 15%	2649
	11th to 20th	Night	16% 17% 8% 12% 9% 3 5% 5% 4 5% 17%	2454
	21st to end	Night	12% 17% 9% 13% 10% 5% 5% 5% 4 5% 15%	2574
February	1st to 10th	Night	15% 17% 7% 10% 10% 4 5% 4 4 5% 18%	2340
	11th to 20th	Night	14% 13% 8% 13% 9% 5% 7% 4 4 6% 19%	2273
	21st to end	Night	16% 14% 6% 13% 8% 4 4 4 4 4 22%	1828
March	1st to 10th	Night	14% 12% 7% 12% 8% 3 5% 4 5% 5% 25%	1972
	11th to 20th	Night	16% 13% 6% 10% 6% 2 4 4 4 6% 28%	1979
	21st to end	Night	14% 15% 5% 8% 7% 3 4 4 5% 5% 30%	2176
April	1st to 10th	Night	17% 13% 5% 8% 5% 3 5% 5% 4 6% 28%	1800
	11th to 20th	Night	18% 14% 3 6% 4 2 4 4 5% 6% 36%	1775
	21st to end	Night	16% 11% 3 6% 5% 3 4 5% 5% 7% 34%	1689
May	1st to 10th	Night	18% 10% 4 7% 5% 4 5% 4 4 6% 33%	1620
	11th to 20th	Night	15% 9% 3 6% 6% 4 4 4 5% 6% 36%	1433
	21st to end	Night	13% 6% 3 5% 5% 4 5% 4 5% 8% 42%	1550
June	1st to 10th	Night	14% 7% 3 6% 5% 3 4 6% 7% 9% 37%	1440
	11th to 20th	Night	12% 7% 3 6% 5% 3 5% 6% 7% 8% 39%	1440
	21st to end	Night	13% 6% 3 5% 4 3 4 5% 6% 7% 43%	1440
July	1st to 10th	Night	10% 6% 2 6% 6% 4 4 5% 5% 7% 44%	1440
	11th to 20th	Night	10% 4 2 5% 5% 3 5% 4 6% 7% 49%	1440
	21st to end	Night	12% 5% 3 5% 5% 3 5% 6% 7% 10% 39%	1761
August	1st to 10th	Night	9% 6% 2 7% 5% 4 5% 5% 7% 9% 42%	1611
	11th to 20th	Night	14% 6% 3 6% 5% 3 4 6% 6% 9% 38%	1598
	21st to end	Night	12% 6% 3 5% 5% 3 5% 5% 6% 9% 41%	1944
September	1st to 10th	Night	15% 6% 3 6% 5% 2 4 4 5% 7% 43%	1800
	11th to 20th	Night	14% 7% 2 4 4 2 4 4 5% 7% 47%	1834
	21st to end	Night	18% 7% 3 6% 6% 3 5% 4 5% 6% 37%	2060
October	1st to 10th	Night	17% 9% 2 5% 6% 3 4 4 4 6% 39%	2160
	11th to 20th	Night	20% 12% 3 5% 6% 3 3 4 5% 8% 31%	2160
	21st to end	Night	26% 14% 3 7% 6% 2 4 3 5% 5% 26%	2376
November	1st to 10th	Night	12% 13% 3 6% 4 3 4 5% 5% 5% 38%	2344
	11th to 20th	Night	17% 17% 5% 8% 5% 4 5% 5% 4 6% 26%	2660
	21st to end	Night	16% 18% 7% 9% 6% 3 5% 5% 5% 6% 21%	2660
December	1st to 10th	Night	19% 18% 9% 11% 7% 4 5% 4 3 5% 14%	2660
	11th to 20th	Night	18% 16% 7% 14% 7% 3 5% 4 4 5% 18%	3288
	21st to end	Night	22% 18% 10% 10% 8% 3 4 4 4 4 12%	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	68% 5% 9% 13% 5%	1518
	11th to 20th	Day	71% 5% 10% 8% 6%	1646
	21st to end	Day	72% 4 8% 9% 5% 1	1782
February	1st to 10th	Day	72% 5% 9% 9% 4	1620
	11th to 20th	Day	66% 5% 7% 15% 6%	1582
	21st to end	Day	62% 4 9% 16% 6% 2	1426
March	1st to 10th	Day	58% 6% 10% 18% 8% 1	1975
	11th to 20th	Day	59% 5% 9% 16% 8% 3	1980
	21st to end	Day	58% 4 7% 17% 11% 2	2179
April	1st to 10th	Day	55% 5% 10% 17% 11% 1	2160
	11th to 20th	Day	52% 7% 10% 17% 13% 1	2134
	21st to end	Day	54% 6% 8% 18% 12% 2	2286
May	1st to 10th	Day	57% 6% 9% 16% 9% 2	2340
	11th to 20th	Day	53% 7% 10% 17% 11% 1	2460
	21st to end	Day	44% 8% 15% 20% 11% 1	2725
June	1st to 10th	Day	48% 7% 12% 19% 13% 1	2520
	11th to 20th	Day	47% 9% 14% 19% 11% 1	2520
	21st to end	Day	45% 8% 14% 23% 11%	2520
July	1st to 10th	Day	44% 10% 11% 22% 13% 1	2450
	11th to 20th	Day	43% 9% 15% 20% 12%	2445
	21st to end	Day	44% 10% 13% 21% 11% 1	2410
August	1st to 10th	Day	43% 10% 14% 23% 9%	2314
	11th to 20th	Day	48% 10% 15% 18% 8%	2303
	21st to end	Day	47% 8% 12% 20% 11% 2	2394
September	1st to 10th	Day	46% 7% 11% 20% 14% 1	2160
	11th to 20th	Day	42% 7% 10% 23% 16% 2	2123
	21st to end	Day	51% 6% 10% 19% 13% 1	1900
October	1st to 10th	Day	50% 7% 12% 17% 12% 2	1800
	11th to 20th	Day	54% 6% 12% 19% 8%	1800
	21st to end	Day	62% 6% 10% 13% 8% 2	1980
November	1st to 10th	Day	48% 7% 12% 17% 13% 3	1730
	11th to 20th	Day	60% 5% 12% 16% 6% 2	1520
	21st to end	Day	66% 6% 9% 13% 5% 1	1520
December	1st to 10th	Day	75% 4 9% 8% 4	1520
	11th to 20th	Day	68% 6% 10% 12% 4	1906
	21st to end	Day	74% 7% 9% 9% 1	2772
January	1st to 10th	Night	69% 6% 9% 11% 5% 1	2649
	11th to 20th	Night	69% 6% 11% 9% 3 1	2454
	21st to end	Night	70% 5% 9% 10% 6% 1	2574
February	1st to 10th	Night	67% 5% 10% 11% 6%	2340
	11th to 20th	Night	66% 6% 9% 13% 6% 1	2275
	21st to end	Night	65% 5% 9% 12% 8% 1	1828
March	1st to 10th	Night	59% 6% 10% 18% 6% 1	1982
	11th to 20th	Night	58% 4 11% 17% 8% 1	1980
	21st to end	Night	56% 5% 9% 15% 13% 3	2176
April	1st to 10th	Night	56% 6% 10% 16% 11%	1800
	11th to 20th	Night	49% 7% 11% 19% 12% 2	1775
	21st to end	Night	49% 7% 11% 19% 12% 2	1689
May	1st to 10th	Night	53% 6% 10% 19% 10% 2	1620
	11th to 20th	Night	48% 9% 10% 19% 13% 1	1434
	21st to end	Night	40% 9% 13% 23% 12% 3	1551
June	1st to 10th	Night	41% 8% 14% 22% 13% 1	1440
	11th to 20th	Night	39% 11% 14% 22% 13% 2	1440
	21st to end	Night	38% 9% 13% 27% 13% 1	1440
July	1st to 10th	Night	38% 8% 12% 23% 17% 1	1400
	11th to 20th	Night	33% 7% 16% 24% 18% 1	1392
	21st to end	Night	37% 10% 15% 20% 17% 1	1663
August	1st to 10th	Night	35% 10% 16% 28% 10% 1	1600
	11th to 20th	Night	40% 9% 14% 26% 10%	1598
	21st to end	Night	38% 9% 15% 24% 13% 2	1944
September	1st to 10th	Night	40% 7% 13% 24% 13% 3	1800
	11th to 20th	Night	36% 7% 14% 24% 17% 2	1834
	21st to end	Night	47% 7% 13% 20% 13% 1	2060
October	1st to 10th	Night	45% 7% 13% 20% 14% 1	2160
	11th to 20th	Night	51% 7% 14% 17% 10% 1	2160
	21st to end	Night	59% 5% 12% 15% 8% 1	2376
November	1st to 10th	Night	45% 7% 13% 19% 13% 2	2344
	11th to 20th	Night	59% 6% 11% 15% 7% 2	2660
	21st to end	Night	62% 7% 11% 15% 4 1	2660
December	1st to 10th	Night	73% 6% 8% 9% 3	2660
	11th to 20th	Night	69% 6% 10% 13% 2	3288
	21st to end	Night	73% 7% 10% 9% 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	33% 28% 24% 9% 4 1	180
	11th to 20th	Day	37% 31% 27% 4 2	245
	21st to end	Day	32% 29% 31% 7% 1	264
February	1st to 10th	Day	38% 34% 25% 4	240
	11th to 20th	Day	39% 30% 28% 3	240
	21st to end	Day	43% 27% 23% 7%	292
March	1st to 10th	Day	35% 27% 25% 10% 3	420
	11th to 20th	Day	30% 25% 30% 11% 3 2	420
	21st to end	Day	35% 24% 25% 12% 3 1	462
April	1st to 10th	Day	32% 24% 25% 15% 3 1	420
	11th to 20th	Day	29% 23% 25% 13% 7% 2	412
	21st to end	Day	30% 19% 34% 11% 6%	420
May	1st to 10th	Day	31% 22% 24% 14% 7% 2	423
	11th to 20th	Day	27% 18% 29% 16% 8% 2	447
	21st to end	Day	19% 15% 28% 20% 12% 5%	485
June	1st to 10th	Day	20% 15% 33% 22% 8% 2	450
	11th to 20th	Day	19% 16% 26% 24% 13% 2	450
	21st to end	Day	17% 16% 34% 24% 8% 2	450
July	1st to 10th	Day	14% 9% 28% 26% 17% 6%	445
	11th to 20th	Day	12% 12% 28% 27% 15% 5%	444
	21st to end	Day	14% 11% 32% 27% 11% 4	488
August	1st to 10th	Day	12% 9% 27% 28% 17% 7%	446
	11th to 20th	Day	17% 8% 28% 26% 13% 8%	439
	21st to end	Day	16% 12% 29% 24% 12% 8%	495
September	1st to 10th	Day	21% 14% 23% 22% 14% 8%	450
	11th to 20th	Day	16% 8% 26% 22% 19% 8%	450
	21st to end	Day	25% 16% 24% 18% 13% 4	450
October	1st to 10th	Day	23% 14% 26% 18% 16% 4	450
	11th to 20th	Day	29% 21% 28% 15% 7% 1	450
	21st to end	Day	36% 20% 26% 15% 3	495
November	1st to 10th	Day	26% 18% 29% 16% 9% 2	390
	11th to 20th	Day	38% 22% 26% 12% 2 1	180
	21st to end	Day	39% 22% 31% 7% 1	180
December	1st to 10th	Day	39% 31% 20% 6% 2 2	180
	11th to 20th	Day	42% 22% 28% 6% 2	180
	21st to end	Day	38% 27% 29% 4 2	198
January	1st to 10th	Night	29% 27% 31% 10% 3	760
	11th to 20th	Night	30% 24% 30% 14% 2	748
	21st to end	Night	27% 27% 31% 14% 1	792
February	1st to 10th	Night	33% 24% 30% 13% 1	720
	11th to 20th	Night	29% 31% 30% 9% 1	703
	21st to end	Night	32% 27% 28% 11% 2	592
March	1st to 10th	Night	26% 26% 32% 14% 2	720
	11th to 20th	Night	31% 23% 25% 17% 4	720
	21st to end	Night	24% 22% 32% 16% 5% 1	792
April	1st to 10th	Night	26% 23% 30% 17% 3	720
	11th to 20th	Night	30% 15% 28% 19% 7% 1	711
	21st to end	Night	23% 13% 34% 25% 5%	609
May	1st to 10th	Night	24% 13% 24% 29% 10% 1	540
	11th to 20th	Night	17% 12% 31% 33% 7%	372
	21st to end	Night	16% 7% 27% 30% 19% 1	389
June	1st to 10th	Night	13% 9% 31% 34% 13% 1	360
	11th to 20th	Night	16% 9% 23% 40% 12%	360
	21st to end	Night	10% 8% 33% 35% 13% 1	360
July	1st to 10th	Night	13% 3 25% 38% 18% 2	350
	11th to 20th	Night	10% 3 24% 40% 22% 1	348
	21st to end	Night	14% 3 23% 39% 19% 2	581
August	1st to 10th	Night	12% 3 21% 40% 23% 1	537
	11th to 20th	Night	16% 5% 18% 32% 26% 3	534
	21st to end	Night	13% 7% 20% 34% 23% 3	756
September	1st to 10th	Night	18% 8% 24% 29% 19% 3	720
	11th to 20th	Night	17% 6% 22% 27% 25% 4	720
	21st to end	Night	20% 12% 23% 24% 19% 3	720
October	1st to 10th	Night	21% 11% 26% 23% 16% 2	720
	11th to 20th	Night	27% 16% 30% 21% 6% 1	720
	21st to end	Night	35% 14% 30% 17% 3	792
November	1st to 10th	Night	20% 17% 32% 24% 6%	740
	11th to 20th	Night	30% 19% 28% 16% 6% 1	760
	21st to end	Night	29% 21% 30% 15% 4 1	760
December	1st to 10th	Night	33% 26% 26% 11% 4	760
	11th to 20th	Night	30% 25% 28% 14% 3	760
	21st to end	Night	32% 24% 30% 12% 1	836

Page generated at 2024-01-14 09:54:59. Version ac07

Copyright 2024 Attilla Danko