Fredonia Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fredonia Observatory clear sky chart from 2005-11-06 to 2024-01-22.

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% 12% 5% 7% 6% 3 4 4 5% 7% 30%	74726
	Night	18% 14% 5% 8% 6% 3 4 4 4 6% 27%	75202
Transparency	Day	56% 4 11% 19% 9% 1	74443
	Night	61% 3 10% 17% 8% 1	75019
Seeing	Day	27% 16% 29% 18% 8% 2	13442
	Night	27% 16% 27% 20% 9% 1	23053

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% 21% 10% 15% 10% 3 4 4 3 4 9%	1529
	11th to 20th	Day	16% 23% 11% 16% 9% 3 4 3 3 3 10%	1710
	21st to end	Day	13% 20% 9% 18% 10% 5% 5% 5% 3 3 9%	1791
February	1st to 10th	Day	17% 20% 9% 15% 10% 4 4 4 3 3 12%	1620
	11th to 20th	Day	14% 18% 11% 16% 9% 3 4 3 3 3 15%	1573
	21st to end	Day	19% 16% 6% 11% 8% 3 5% 4 3 5% 19%	1417
March	1st to 10th	Day	18% 15% 6% 10% 6% 2 4 4 4 5% 25%	1977
	11th to 20th	Day	15% 15% 8% 7% 5% 3 4 4 4 6% 28%	1980
	21st to end	Day	21% 13% 3 9% 6% 3 4 4 4 5% 28%	2178
April	1st to 10th	Day	17% 14% 5% 6% 5% 3 5% 3 4 6% 31%	2121
	11th to 20th	Day	19% 11% 3 5% 4 3 4 4 5% 7% 35%	2164
	21st to end	Day	21% 11% 3 6% 5% 3 4 4 4 5% 34%	2340
May	1st to 10th	Day	20% 9% 3 5% 5% 3 5% 4 6% 7% 34%	2340
	11th to 20th	Day	19% 7% 2 5% 5% 3 5% 4 5% 7% 36%	2412
	21st to end	Day	13% 5% 2 5% 4 3 5% 5% 6% 9% 43%	2725
June	1st to 10th	Day	17% 5% 2 6% 5% 3 5% 4 5% 7% 40%	2520
	11th to 20th	Day	15% 5% 2 5% 5% 2 5% 5% 7% 9% 39%	2520
	21st to end	Day	15% 4 2 4 5% 4 4 5% 5% 10% 43%	2520
July	1st to 10th	Day	11% 3 2 4 5% 2 5% 4 6% 9% 49%	2520
	11th to 20th	Day	14% 6% 3 5% 5% 3 5% 6% 6% 10% 40%	2478
	21st to end	Day	12% 5% 2 5% 7% 4 6% 6% 5% 8% 40%	2547
August	1st to 10th	Day	11% 5% 2 5% 4 3 5% 5% 6% 8% 45%	2327
	11th to 20th	Day	14% 5% 2 5% 5% 3 6% 5% 6% 10% 39%	2303
	21st to end	Day	15% 5% 2 4 4 3 5% 4 6% 9% 42%	2453
September	1st to 10th	Day	17% 6% 3 5% 5% 3 5% 5% 5% 8% 38%	2160
	11th to 20th	Day	16% 4 2 4 6% 3 5% 5% 6% 8% 42%	2053
	21st to end	Day	19% 7% 3 7% 5% 4 6% 4 5% 7% 33%	1942
October	1st to 10th	Day	24% 8% 3 5% 5% 3 4 4 5% 7% 32%	1800
	11th to 20th	Day	26% 10% 3 7% 6% 2 4 5% 4 6% 27%	1800
	21st to end	Day	31% 14% 4 6% 6% 3 4 5% 3 4 19%	1980
November	1st to 10th	Day	18% 17% 4 6% 5% 3 4 5% 5% 6% 27%	1688
	11th to 20th	Day	19% 25% 5% 7% 4 3 3 4 4 6% 20%	1520
	21st to end	Day	22% 25% 8% 7% 5% 2 3 4 5% 5% 15%	1520
December	1st to 10th	Day	22% 29% 12% 9% 4 2 3 3 3 3 11%	1520
	11th to 20th	Day	19% 22% 10% 13% 5% 2 3 4 4 4 13%	1906
	21st to end	Day	25% 26% 9% 10% 5% 2 3 2 3 3 11%	2772
January	1st to 10th	Night	18% 25% 8% 14% 9% 4 4 3 3 3 9%	2635
	11th to 20th	Night	18% 23% 9% 13% 9% 3 4 3 3 3 12%	2470
	21st to end	Night	13% 22% 9% 16% 12% 4 4 3 3 3 11%	2599
February	1st to 10th	Night	19% 19% 8% 15% 9% 3 3 3 3 3 14%	2340
	11th to 20th	Night	16% 16% 8% 14% 9% 4 5% 4 4 4 15%	2273
	21st to end	Night	18% 17% 7% 13% 7% 4 4 4 3 5% 18%	1836
March	1st to 10th	Night	16% 16% 8% 8% 7% 4 5% 4 4 4 24%	1970
	11th to 20th	Night	20% 12% 6% 8% 5% 2 4 3 4 6% 29%	1979
	21st to end	Night	18% 15% 4 9% 6% 3 4 4 4 4 29%	2178
April	1st to 10th	Night	19% 14% 6% 6% 5% 3 3 4 4 6% 29%	1838
	11th to 20th	Night	20% 10% 3 6% 5% 3 4 4 5% 6% 34%	1759
	21st to end	Night	19% 10% 3 5% 6% 3 4 5% 5% 7% 33%	1620
May	1st to 10th	Night	20% 8% 3 7% 5% 3 5% 5% 5% 6% 33%	1620
	11th to 20th	Night	15% 7% 3 6% 5% 4 5% 4 6% 7% 38%	1479
	21st to end	Night	13% 5% 2 5% 4 3 4 4 5% 10% 45%	1550
June	1st to 10th	Night	14% 5% 2 6% 7% 3 6% 5% 6% 9% 37%	1440
	11th to 20th	Night	14% 6% 2 5% 6% 4 5% 5% 6% 8% 40%	1440
	21st to end	Night	15% 6% 3 5% 5% 3 6% 4 6% 7% 41%	1440
July	1st to 10th	Night	9% 5% 2 6% 4 2 4 4 5% 9% 48%	1440
	11th to 20th	Night	13% 4 2 5% 5% 4 5% 6% 5% 9% 43%	1479
	21st to end	Night	12% 5% 2 5% 6% 3 5% 5% 7% 8% 43%	1771
August	1st to 10th	Night	11% 5% 2 4 5% 2 5% 5% 6% 9% 45%	1611
	11th to 20th	Night	12% 7% 2 5% 5% 3 4 6% 7% 9% 40%	1598
	21st to end	Night	14% 6% 2 5% 5% 2 5% 5% 5% 10% 41%	1885
September	1st to 10th	Night	18% 7% 2 5% 5% 3 3 5% 5% 6% 42%	1800
	11th to 20th	Night	17% 5% 2 4 4 2 3 4 5% 6% 49%	1903
	21st to end	Night	21% 7% 2 7% 5% 3 4 6% 6% 7% 34%	2017
October	1st to 10th	Night	19% 7% 3 6% 5% 3 5% 5% 5% 7% 36%	2160
	11th to 20th	Night	25% 10% 4 6% 6% 4 3 5% 4 7% 26%	2160
	21st to end	Night	35% 11% 3 5% 5% 2 4 3 4 5% 22%	2376
November	1st to 10th	Night	20% 16% 4 6% 5% 2 3 4 4 5% 31%	2384
	11th to 20th	Night	19% 22% 5% 6% 5% 4 4 4 4 5% 22%	2660
	21st to end	Night	21% 24% 7% 7% 5% 3 4 3 3 5% 18%	2660
December	1st to 10th	Night	23% 29% 11% 9% 5% 2 3 3 3 3 10%	2660
	11th to 20th	Night	20% 23% 12% 12% 6% 2 3 3 3 4 12%	3288
	21st to end	Night	25% 25% 8% 10% 6% 3 4 3 3 4 9%	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	80% 3 6% 9% 2	1530
	11th to 20th	Day	81% 2 8% 6% 3	1710
	21st to end	Day	82% 2 6% 7% 3	1791
February	1st to 10th	Day	81% 3 7% 6% 2	1620
	11th to 20th	Day	76% 3 6% 11% 5%	1582
	21st to end	Day	70% 3 7% 13% 5% 2	1417
March	1st to 10th	Day	64% 3 10% 16% 6%	1980
	11th to 20th	Day	60% 3 9% 18% 8% 2	1980
	21st to end	Day	61% 3 5% 19% 11% 2	2178
April	1st to 10th	Day	57% 2 10% 19% 11%	2121
	11th to 20th	Day	51% 3 9% 23% 12% 2	2164
	21st to end	Day	55% 3 10% 19% 13% 2	2340
May	1st to 10th	Day	52% 3 10% 23% 10% 2	2340
	11th to 20th	Day	49% 5% 10% 22% 13% 2	2416
	21st to end	Day	39% 6% 17% 24% 13% 2	2725
June	1st to 10th	Day	44% 4 13% 24% 14% 1	2520
	11th to 20th	Day	42% 5% 15% 25% 13%	2520
	21st to end	Day	40% 5% 13% 27% 14% 1	2520
July	1st to 10th	Day	34% 4 14% 30% 16% 2	2450
	11th to 20th	Day	40% 5% 14% 27% 13%	2403
	21st to end	Day	43% 6% 13% 23% 13% 1	2405
August	1st to 10th	Day	38% 5% 15% 31% 11% 1	2314
	11th to 20th	Day	43% 5% 16% 28% 8% 1	2303
	21st to end	Day	41% 4 14% 27% 13% 1	2453
September	1st to 10th	Day	45% 4 13% 26% 11% 1	2160
	11th to 20th	Day	41% 4 12% 28% 14% 1	2053
	21st to end	Day	51% 4 11% 24% 10% 1	1942
October	1st to 10th	Day	54% 3 12% 18% 12% 1	1800
	11th to 20th	Day	60% 4 13% 16% 7% 1	1800
	21st to end	Day	69% 3 9% 11% 7% 1	1980
November	1st to 10th	Day	60% 3 9% 17% 9% 2	1688
	11th to 20th	Day	66% 3 9% 13% 6% 2	1520
	21st to end	Day	73% 2 9% 11% 4 1	1520
December	1st to 10th	Day	81% 1 7% 9% 2	1520
	11th to 20th	Day	78% 2 11% 7% 2	1906
	21st to end	Day	82% 1 10% 6% 1	2772
January	1st to 10th	Night	83% 2 6% 6% 3	2635
	11th to 20th	Night	79% 2 9% 7% 3	2470
	21st to end	Night	81% 2 7% 7% 3 1	2599
February	1st to 10th	Night	78% 2 9% 8% 3	2340
	11th to 20th	Night	74% 3 7% 11% 5%	2275
	21st to end	Night	71% 2 8% 12% 7% 1	1836
March	1st to 10th	Night	64% 4 8% 17% 6% 1	1980
	11th to 20th	Night	60% 2 9% 19% 9% 1	1980
	21st to end	Night	60% 3 6% 15% 14% 2	2178
April	1st to 10th	Night	58% 3 10% 18% 10% 1	1838
	11th to 20th	Night	52% 3 10% 19% 13% 2	1759
	21st to end	Night	52% 4 9% 19% 12% 3	1620
May	1st to 10th	Night	53% 3 9% 22% 12% 3	1620
	11th to 20th	Night	47% 5% 11% 23% 12% 3	1480
	21st to end	Night	37% 5% 14% 27% 15% 2	1551
June	1st to 10th	Night	43% 5% 11% 25% 14% 2	1440
	11th to 20th	Night	42% 4 12% 24% 16% 2	1440
	21st to end	Night	43% 5% 13% 26% 13% 1	1440
July	1st to 10th	Night	36% 4 12% 27% 17% 4	1400
	11th to 20th	Night	37% 5% 13% 29% 15% 2	1431
	21st to end	Night	38% 5% 15% 26% 14% 2	1672
August	1st to 10th	Night	36% 4 14% 34% 11% 2	1600
	11th to 20th	Night	40% 5% 16% 29% 10%	1598
	21st to end	Night	40% 4 15% 27% 12% 2	1885
September	1st to 10th	Night	44% 4 12% 26% 12% 2	1800
	11th to 20th	Night	38% 3 12% 28% 17% 1	1903
	21st to end	Night	50% 4 11% 23% 12% 1	2017
October	1st to 10th	Night	48% 4 10% 21% 15% 1	2160
	11th to 20th	Night	59% 3 12% 17% 9% 1	2160
	21st to end	Night	65% 3 10% 14% 7% 2	2376
November	1st to 10th	Night	57% 3 9% 20% 9% 3	2384
	11th to 20th	Night	65% 3 10% 14% 6% 3	2660
	21st to end	Night	72% 2 11% 12% 3	2660
December	1st to 10th	Night	83% 2 7% 7% 2	2660
	11th to 20th	Night	79% 2 10% 7% 1	3288
	21st to end	Night	82% 2 9% 6% 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% 32% 28% 6% 3 1	186
	11th to 20th	Day	39% 32% 20% 6% 2 1	270
	21st to end	Day	25% 37% 28% 7% 2	267
February	1st to 10th	Day	33% 33% 29% 4	240
	11th to 20th	Day	32% 38% 27% 4	240
	21st to end	Day	40% 25% 30% 5%	236
March	1st to 10th	Day	32% 25% 29% 10% 4	420
	11th to 20th	Day	30% 22% 35% 10% 2 1	420
	21st to end	Day	37% 20% 27% 11% 5%	462
April	1st to 10th	Day	29% 23% 30% 13% 4	420
	11th to 20th	Day	33% 20% 25% 13% 7% 2	412
	21st to end	Day	30% 19% 32% 14% 3 1	420
May	1st to 10th	Day	34% 15% 30% 15% 6% 1	423
	11th to 20th	Day	26% 14% 30% 22% 6% 1	447
	21st to end	Day	17% 9% 36% 23% 10% 5%	485
June	1st to 10th	Day	19% 15% 36% 21% 8% 1	450
	11th to 20th	Day	22% 12% 30% 24% 10% 3	450
	21st to end	Day	19% 11% 34% 26% 9% 1	450
July	1st to 10th	Day	15% 6% 27% 30% 17% 5%	445
	11th to 20th	Day	19% 7% 30% 28% 12% 5%	444
	21st to end	Day	15% 7% 38% 25% 13% 3	488
August	1st to 10th	Day	13% 5% 28% 33% 14% 7%	446
	11th to 20th	Day	19% 4 28% 27% 17% 6%	439
	21st to end	Day	18% 7% 30% 26% 12% 5%	495
September	1st to 10th	Day	21% 9% 26% 24% 14% 6%	450
	11th to 20th	Day	16% 6% 25% 29% 16% 7%	450
	21st to end	Day	23% 16% 24% 22% 11% 4	450
October	1st to 10th	Day	29% 10% 25% 21% 12% 3	450
	11th to 20th	Day	33% 17% 30% 14% 5% 1	450
	21st to end	Day	42% 17% 25% 13% 2	495
November	1st to 10th	Day	30% 22% 30% 13% 4 2	324
	11th to 20th	Day	44% 16% 28% 9% 3	180
	21st to end	Day	41% 24% 28% 5% 2	180
December	1st to 10th	Day	43% 22% 26% 7% 2	180
	11th to 20th	Day	36% 30% 26% 9%	180
	21st to end	Day	37% 30% 28% 4 1	198
January	1st to 10th	Night	34% 26% 26% 9% 3	760
	11th to 20th	Night	33% 28% 26% 12% 1	760
	21st to end	Night	24% 29% 31% 14% 3	800
February	1st to 10th	Night	32% 28% 26% 13% 1	720
	11th to 20th	Night	27% 29% 30% 11% 3	703
	21st to end	Night	31% 27% 28% 13% 2	592
March	1st to 10th	Night	28% 22% 30% 16% 4	720
	11th to 20th	Night	28% 23% 29% 16% 4 1	720
	21st to end	Night	28% 15% 32% 18% 7% 1	792
April	1st to 10th	Night	28% 19% 29% 19% 5%	720
	11th to 20th	Night	28% 15% 30% 20% 6% 1	695
	21st to end	Night	26% 11% 32% 23% 6% 1	540
May	1st to 10th	Night	27% 7% 27% 28% 10% 1	540
	11th to 20th	Night	19% 7% 32% 33% 9%	418
	21st to end	Night	15% 9% 29% 31% 15% 2	389
June	1st to 10th	Night	15% 7% 35% 29% 13% 1	360
	11th to 20th	Night	20% 8% 24% 36% 12% 1	360
	21st to end	Night	17% 6% 31% 32% 13% 1	360
July	1st to 10th	Night	12% 3 25% 39% 19% 3	350
	11th to 20th	Night	14% 4 27% 33% 19% 3	387
	21st to end	Night	13% 4 26% 38% 19% 1	591
August	1st to 10th	Night	13% 3 23% 36% 22% 3	537
	11th to 20th	Night	14% 4 20% 34% 25% 3	534
	21st to end	Night	17% 4 24% 30% 22% 4	697
September	1st to 10th	Night	20% 7% 20% 29% 19% 4	720
	11th to 20th	Night	20% 4 21% 29% 22% 4	720
	21st to end	Night	25% 10% 20% 26% 14% 4	720
October	1st to 10th	Night	24% 10% 27% 23% 14% 2	720
	11th to 20th	Night	34% 15% 28% 18% 5% 1	720
	21st to end	Night	42% 16% 25% 15% 2	792
November	1st to 10th	Night	32% 15% 25% 21% 6%	740
	11th to 20th	Night	36% 20% 27% 11% 5% 1	760
	21st to end	Night	36% 23% 26% 10% 4	760
December	1st to 10th	Night	41% 24% 23% 9% 3	760
	11th to 20th	Night	33% 30% 23% 12% 2	760
	21st to end	Night	35% 27% 28% 10% 1	836

Page generated at 2024-01-19 09:28:31. Version ac07

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