Fulton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fulton clear sky chart from 2005-11-06 to 2024-03-01.

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	13% 8% 3 6% 5% 3 4 4 5% 7% 42%	78564
	Night	13% 8% 4 6% 5% 3 4 4 5% 6% 43%	80885
Transparency	Day	41% 7% 12% 23% 15% 2	78276
	Night	41% 6% 11% 23% 16% 3	80693
Seeing	Day	16% 12% 28% 27% 14% 3	14631
	Night	16% 11% 31% 28% 12% 1	24672

By Month

Percentage Cloud Cover SE (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	12% 12% 4 9% 6% 3 5% 5% 5% 7% 33%	2573
	11th to 20th	Day	13% 11% 4 7% 5% 5% 6% 4 4 5% 35%	2850
	21st to end	Day	18% 14% 7% 8% 5% 2 3 4 4 5% 30%	3135
February	1st to 10th	Day	16% 11% 5% 8% 6% 3 4 4 3 7% 34%	1710
	11th to 20th	Day	14% 9% 4 5% 5% 4 4 5% 4 6% 40%	1735
	21st to end	Day	16% 11% 3 6% 5% 3 4 4 4 5% 39%	1570
March	1st to 10th	Day	14% 9% 5% 6% 5% 3 4 4 3 7% 40%	1929
	11th to 20th	Day	19% 9% 5% 7% 5% 3 4 4 5% 5% 35%	1980
	21st to end	Day	21% 12% 3 8% 5% 3 4 4 5% 7% 28%	2222
April	1st to 10th	Day	12% 8% 2 5% 6% 3 5% 4 5% 7% 44%	2160
	11th to 20th	Day	18% 9% 3 5% 5% 2 3 4 5% 6% 41%	2134
	21st to end	Day	21% 7% 3 6% 5% 3 5% 4 4 8% 34%	2160
May	1st to 10th	Day	18% 7% 3 5% 5% 3 5% 4 6% 8% 36%	2256
	11th to 20th	Day	17% 7% 3 5% 5% 3 5% 5% 5% 7% 39%	2425
	21st to end	Day	12% 7% 3 5% 7% 4 6% 5% 6% 9% 37%	2725
June	1st to 10th	Day	8% 4 2 5% 5% 3 5% 6% 7% 10% 46%	2520
	11th to 20th	Day	9% 4 2 4 5% 3 6% 5% 6% 10% 47%	2520
	21st to end	Day	7% 3 2 4 5% 3 5% 5% 7% 10% 49%	2520
July	1st to 10th	Day	10% 4 2 5% 5% 3 6% 6% 7% 11% 42%	2520
	11th to 20th	Day	5% 4 2 4 5% 3 5% 5% 6% 9% 52%	2460
	21st to end	Day	9% 5% 2 4 4 3 5% 6% 7% 10% 45%	2546
August	1st to 10th	Day	8% 4 2 5% 6% 4 5% 6% 7% 9% 43%	2328
	11th to 20th	Day	9% 4 3 4 6% 4 5% 5% 7% 9% 45%	2208
	21st to end	Day	7% 4 2 5% 5% 3 4 4 5% 9% 52%	2376
September	1st to 10th	Day	11% 5% 2 4 5% 3 4 4 5% 7% 50%	2160
	11th to 20th	Day	10% 5% 2 4 4 3 4 4 5% 8% 53%	2160
	21st to end	Day	7% 4 3 4 4 3 4 5% 5% 7% 54%	1902
October	1st to 10th	Day	11% 5% 2 4 5% 3 4 4 4 5% 53%	1800
	11th to 20th	Day	16% 7% 2 4 4 1 3 3 4 5% 52%	1800
	21st to end	Day	18% 9% 3 5% 4 2 3 3 3 5% 47%	1980
November	1st to 10th	Day	11% 6% 3 3 3 2 3 4 4 7% 54%	1746
	11th to 20th	Day	14% 7% 2 5% 3 2 3 4 5% 7% 47%	1710
	21st to end	Day	16% 10% 3 5% 4 3 4 3 4 5% 44%	1523
December	1st to 10th	Day	12% 11% 4 6% 4 3 3 3 5% 7% 41%	1520
	11th to 20th	Day	13% 9% 5% 7% 5% 2 4 4 5% 5% 41%	1918
	21st to end	Day	19% 16% 5% 10% 5% 3 5% 4 4 5% 24%	2783
January	1st to 10th	Night	11% 10% 9% 10% 6% 3 4 4 4 5% 35%	4364
	11th to 20th	Night	12% 11% 5% 10% 6% 4 7% 6% 4 5% 30%	4120
	21st to end	Night	20% 15% 7% 7% 5% 2 3 3 4 4 30%	4532
February	1st to 10th	Night	15% 10% 4 8% 7% 3 4 5% 5% 5% 34%	2470
	11th to 20th	Night	14% 7% 4 7% 5% 3 4 4 5% 5% 41%	2330
	21st to end	Night	15% 11% 3 6% 5% 2 4 3 5% 4 42%	1884
March	1st to 10th	Night	15% 10% 3 5% 4 3 3 4 4 5% 45%	2054
	11th to 20th	Night	18% 8% 4 6% 5% 3 5% 4 5% 6% 36%	1980
	21st to end	Night	20% 12% 3 7% 6% 4 5% 5% 5% 6% 28%	2134
April	1st to 10th	Night	11% 7% 3 5% 5% 3 3 4 4 6% 48%	1800
	11th to 20th	Night	13% 9% 3 5% 4 2 4 4 4 7% 45%	1775
	21st to end	Night	19% 7% 3 4 4 3 4 5% 4 8% 40%	1800
May	1st to 10th	Night	15% 5% 2 5% 5% 3 4 4 6% 9% 42%	1702
	11th to 20th	Night	16% 7% 2 5% 5% 2 4 5% 4 7% 43%	1466
	21st to end	Night	12% 5% 3 5% 5% 3 4 5% 6% 8% 42%	1551
June	1st to 10th	Night	7% 4 2 3 4 3 4 5% 6% 9% 53%	1440
	11th to 20th	Night	6% 4 3 5% 5% 3 4 6% 6% 11% 49%	1440
	21st to end	Night	5% 3 1 3 3 3 4 5% 7% 10% 57%	1440
July	1st to 10th	Night	8% 4 1 5% 4 3 4 4 5% 10% 51%	1440
	11th to 20th	Night	5% 2 1 3 4 3 4 5% 4 10% 59%	1496
	21st to end	Night	6% 4 2 5% 4 3 5% 5% 6% 10% 50%	1772
August	1st to 10th	Night	6% 3 1 4 4 3 4 6% 7% 9% 52%	1611
	11th to 20th	Night	6% 4 2 4 4 3 4 5% 6% 8% 54%	1693
	21st to end	Night	5% 4 2 3 4 2 4 4 4 9% 58%	1980
September	1st to 10th	Night	12% 4 2 3 3 2 4 3 3 8% 56%	1800
	11th to 20th	Night	9% 4 2 4 4 3 3 4 6% 8% 53%	1800
	21st to end	Night	7% 4 2 3 5% 3 4 3 5% 8% 56%	2037
October	1st to 10th	Night	9% 4 2 4 3 2 4 4 5% 6% 58%	2160
	11th to 20th	Night	15% 5% 2 4 4 2 3 3 4 5% 51%	2160
	21st to end	Night	17% 8% 2 4 4 2 3 3 4 5% 48%	2376
November	1st to 10th	Night	10% 5% 2 4 3 2 4 3 4 5% 56%	2330
	11th to 20th	Night	12% 6% 3 6% 5% 2 3 4 3 6% 49%	2470
	21st to end	Night	16% 9% 3 5% 5% 2 3 4 4 5% 45%	2655
December	1st to 10th	Night	13% 11% 4 6% 4 3 4 4 5% 6% 39%	2660
	11th to 20th	Night	14% 11% 5% 7% 4 3 3 4 5% 6% 40%	3279
	21st to end	Night	19% 19% 7% 8% 6% 3 3 3 3 4 24%	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	50% 7% 10% 22% 10% 1	2574
	11th to 20th	Day	51% 6% 12% 20% 11%	2850
	21st to end	Day	57% 5% 10% 15% 12% 1	3135
February	1st to 10th	Day	52% 5% 11% 21% 11% 1	1710
	11th to 20th	Day	45% 6% 12% 20% 14% 3	1744
	21st to end	Day	47% 4 9% 22% 13% 4	1570
March	1st to 10th	Day	46% 4 10% 23% 14% 3	1929
	11th to 20th	Day	52% 6% 10% 18% 12% 2	1980
	21st to end	Day	57% 6% 10% 17% 9% 1	2222
April	1st to 10th	Day	40% 7% 11% 25% 16% 1	2160
	11th to 20th	Day	45% 5% 10% 24% 13% 3	2134
	21st to end	Day	48% 6% 13% 19% 13% 1	2160
May	1st to 10th	Day	46% 7% 15% 21% 10% 1	2256
	11th to 20th	Day	44% 8% 12% 21% 14% 2	2429
	21st to end	Day	43% 10% 13% 20% 12% 2	2725
June	1st to 10th	Day	31% 10% 16% 28% 15% 1	2520
	11th to 20th	Day	31% 9% 15% 24% 18% 4	2520
	21st to end	Day	29% 10% 17% 25% 16% 4	2520
July	1st to 10th	Day	33% 9% 16% 25% 13% 4	2451
	11th to 20th	Day	27% 9% 15% 28% 18% 3	2385
	21st to end	Day	33% 8% 15% 29% 13% 2	2405
August	1st to 10th	Day	33% 10% 18% 25% 12% 1	2314
	11th to 20th	Day	35% 8% 14% 28% 15% 1	2208
	21st to end	Day	29% 7% 14% 24% 21% 6%	2376
September	1st to 10th	Day	33% 6% 12% 25% 18% 5%	2160
	11th to 20th	Day	31% 6% 10% 27% 23% 4	2160
	21st to end	Day	29% 7% 11% 26% 23% 4	1902
October	1st to 10th	Day	33% 6% 10% 24% 23% 4	1800
	11th to 20th	Day	36% 5% 8% 26% 21% 5%	1800
	21st to end	Day	43% 4 9% 23% 18% 3	1980
November	1st to 10th	Day	31% 5% 13% 24% 22% 5%	1746
	11th to 20th	Day	38% 5% 9% 23% 21% 4	1710
	21st to end	Day	44% 5% 10% 27% 14% 1	1523
December	1st to 10th	Day	43% 5% 13% 27% 12% 1	1520
	11th to 20th	Day	44% 6% 12% 24% 12% 2	1915
	21st to end	Day	61% 7% 9% 14% 8% 1	2783
January	1st to 10th	Night	52% 5% 11% 22% 10% 1	4364
	11th to 20th	Night	55% 6% 10% 19% 9% 1	4120
	21st to end	Night	59% 4 10% 19% 7% 1	4532
February	1st to 10th	Night	52% 6% 10% 18% 13% 2	2470
	11th to 20th	Night	44% 5% 11% 21% 16% 3	2331
	21st to end	Night	46% 4 10% 21% 15% 4	1884
March	1st to 10th	Night	41% 5% 11% 22% 17% 3	2054
	11th to 20th	Night	48% 7% 9% 20% 13% 3	1980
	21st to end	Night	56% 7% 12% 16% 7% 1	2134
April	1st to 10th	Night	37% 5% 11% 25% 18% 3	1800
	11th to 20th	Night	39% 7% 9% 24% 15% 5%	1775
	21st to end	Night	43% 6% 10% 22% 17% 1	1800
May	1st to 10th	Night	38% 9% 16% 21% 15% 1	1702
	11th to 20th	Night	41% 9% 12% 22% 16% 2	1467
	21st to end	Night	37% 9% 15% 20% 16% 3	1552
June	1st to 10th	Night	26% 8% 16% 29% 18% 3	1440
	11th to 20th	Night	28% 8% 11% 27% 23% 3	1440
	21st to end	Night	21% 8% 18% 27% 19% 6%	1440
July	1st to 10th	Night	28% 8% 15% 30% 15% 4	1400
	11th to 20th	Night	21% 7% 16% 30% 23% 3	1448
	21st to end	Night	27% 8% 14% 33% 17% 1	1673
August	1st to 10th	Night	26% 9% 16% 33% 15% 2	1601
	11th to 20th	Night	27% 7% 12% 32% 21% 2	1693
	21st to end	Night	23% 8% 16% 25% 23% 6%	1980
September	1st to 10th	Night	28% 6% 13% 24% 23% 6%	1800
	11th to 20th	Night	28% 7% 12% 24% 24% 5%	1800
	21st to end	Night	28% 5% 9% 26% 27% 4	2037
October	1st to 10th	Night	28% 5% 11% 26% 26% 5%	2160
	11th to 20th	Night	36% 4 7% 28% 19% 6%	2160
	21st to end	Night	41% 4 9% 20% 22% 4	2376
November	1st to 10th	Night	30% 5% 13% 27% 19% 6%	2330
	11th to 20th	Night	37% 4 8% 25% 22% 4	2470
	21st to end	Night	43% 4 11% 24% 16% 2	2655
December	1st to 10th	Night	46% 6% 11% 23% 13% 1	2660
	11th to 20th	Night	46% 4 10% 25% 14% 1	3281
	21st to end	Night	65% 5% 9% 13% 7% 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	26% 19% 37% 16% 3	270
	11th to 20th	Day	34% 20% 34% 11% 1	270
	21st to end	Day	21% 24% 39% 13% 3	297
February	1st to 10th	Day	28% 21% 34% 15% 2	270
	11th to 20th	Day	24% 26% 34% 14% 2	270
	21st to end	Day	31% 22% 34% 12% 1	225
March	1st to 10th	Day	19% 25% 46% 10% 1	240
	11th to 20th	Day	30% 17% 36% 15% 2	240
	21st to end	Day	36% 21% 29% 13% 1	308
April	1st to 10th	Day	18% 16% 39% 20% 6% 1	420
	11th to 20th	Day	27% 16% 32% 19% 6%	412
	21st to end	Day	27% 14% 35% 20% 4 1	420
May	1st to 10th	Day	20% 13% 37% 23% 6% 1	519
	11th to 20th	Day	19% 14% 29% 25% 11% 2	625
	21st to end	Day	14% 11% 31% 25% 14% 5%	679
June	1st to 10th	Day	9% 4 24% 37% 20% 6%	630
	11th to 20th	Day	9% 5% 26% 41% 17% 3	630
	21st to end	Day	7% 9% 30% 36% 15% 3	630
July	1st to 10th	Day	11% 4 15% 31% 31% 9%	621
	11th to 20th	Day	7% 5% 21% 36% 27% 4	618
	21st to end	Day	8% 4 18% 36% 29% 5%	684
August	1st to 10th	Day	9% 3 16% 44% 23% 5%	626
	11th to 20th	Day	9% 2 21% 36% 25% 7%	522
	21st to end	Day	9% 2 16% 32% 32% 10%	495
September	1st to 10th	Day	12% 5% 17% 31% 28% 7%	450
	11th to 20th	Day	8% 3 20% 34% 25% 10%	450
	21st to end	Day	8% 10% 26% 31% 21% 3	326
October	1st to 10th	Day	15% 9% 35% 26% 13% 2	270
	11th to 20th	Day	21% 22% 30% 22% 5%	270
	21st to end	Day	33% 19% 29% 18% 2	297
November	1st to 10th	Day	15% 13% 36% 23% 9% 3	270
	11th to 20th	Day	21% 19% 31% 23% 6% 1	270
	21st to end	Day	27% 16% 29% 25% 3	270
December	1st to 10th	Day	18% 20% 37% 16% 7% 2	270
	11th to 20th	Day	22% 19% 37% 18% 3 1	270
	21st to end	Day	25% 28% 33% 14%	297
January	1st to 10th	Night	17% 18% 40% 19% 5%	950
	11th to 20th	Night	21% 19% 36% 19% 4	950
	21st to end	Night	18% 18% 39% 22% 2	1045
February	1st to 10th	Night	21% 17% 39% 20% 3	950
	11th to 20th	Night	20% 18% 38% 22% 2	856
	21st to end	Night	24% 20% 36% 17% 2	628
March	1st to 10th	Night	22% 15% 41% 20% 3	610
	11th to 20th	Night	23% 14% 35% 24% 4	540
	21st to end	Night	27% 15% 36% 19% 3	594
April	1st to 10th	Night	15% 17% 39% 24% 5%	540
	11th to 20th	Night	18% 16% 34% 25% 7%	533
	21st to end	Night	21% 9% 40% 24% 6%	540
May	1st to 10th	Night	17% 8% 33% 34% 8% 1	540
	11th to 20th	Night	18% 6% 27% 35% 13% 1	531
	21st to end	Night	13% 5% 28% 33% 18% 2	584
June	1st to 10th	Night	8% 4 20% 41% 26% 2	540
	11th to 20th	Night	6% 3 26% 42% 21% 1	540
	21st to end	Night	4 2 29% 46% 16% 2	540
July	1st to 10th	Night	10% 2 12% 37% 33% 5%	525
	11th to 20th	Night	5% 2 18% 40% 33% 2	522
	21st to end	Night	7% 2 16% 41% 32% 2	591
August	1st to 10th	Night	6% 3 13% 45% 32% 2	537
	11th to 20th	Night	8% 1 13% 41% 34% 3	534
	21st to end	Night	7% 1 15% 38% 35% 3	594
September	1st to 10th	Night	13% 3 17% 38% 24% 5%	540
	11th to 20th	Night	11% 2 16% 39% 27% 5%	540
	21st to end	Night	9% 6% 24% 34% 22% 5%	656
October	1st to 10th	Night	10% 7% 27% 31% 21% 3	720
	11th to 20th	Night	18% 12% 36% 26% 8%	720
	21st to end	Night	22% 15% 32% 24% 7%	792
November	1st to 10th	Night	13% 11% 37% 29% 9%	740
	11th to 20th	Night	16% 16% 36% 25% 7%	760
	21st to end	Night	22% 13% 35% 24% 6%	945
December	1st to 10th	Night	21% 15% 36% 23% 5% 1	950
	11th to 20th	Night	24% 12% 34% 26% 3	950
	21st to end	Night	25% 18% 34% 21% 2	1045

Page generated at 2024-02-27 05:30:12. Version ac07

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