Fickle Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fickle Hill Observatory clear sky chart from 2005-11-06 to 2024-04-03.

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	17% 8% 2 5% 4 2 4 4 4 7% 44%	78959
	Night	18% 9% 3 5% 4 3 4 4 4 7% 39%	81209
Transparency	Day	39% 7% 12% 19% 16% 7%	78676
	Night	43% 8% 13% 16% 13% 6%	81014
Seeing	Day	20% 11% 25% 28% 13% 4	14340
	Night	20% 6% 13% 29% 26% 6%	23576

By Month

Percentage Cloud Cover SW (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	31% 15% 3 6% 5% 2 4 4 4 5% 22%	2640
	11th to 20th	Day	36% 10% 3 6% 4 2 4 3 3 4 24%	2860
	21st to end	Day	33% 9% 2 5% 5% 2 4 4 5% 5% 25%	3146
February	1st to 10th	Day	22% 9% 3 5% 5% 3 4 4 5% 7% 34%	1710
	11th to 20th	Day	23% 11% 3 6% 3 3 5% 4 4 7% 32%	1665
	21st to end	Day	25% 14% 3 5% 4 2 3 3 4 5% 32%	1534
March	1st to 10th	Day	25% 15% 4 7% 6% 2 3 3 5% 5% 25%	2090
	11th to 20th	Day	25% 11% 4 5% 5% 2 3 4 4 8% 29%	2090
	21st to end	Day	27% 11% 4 7% 6% 3 4 4 4 6% 25%	2299
April	1st to 10th	Day	23% 13% 3 6% 6% 3 5% 4 5% 6% 25%	2150
	11th to 20th	Day	23% 12% 3 6% 5% 3 4 4 4 7% 32%	2129
	21st to end	Day	17% 10% 3 4 5% 2 4 4 5% 9% 37%	2290
May	1st to 10th	Day	14% 8% 3 5% 3 3 4 4 5% 7% 46%	2340
	11th to 20th	Day	17% 9% 3 5% 5% 3 3 4 5% 9% 38%	2361
	21st to end	Day	17% 8% 4 5% 5% 3 5% 4 5% 9% 35%	2723
June	1st to 10th	Day	15% 9% 3 5% 5% 3 5% 4 5% 8% 39%	2520
	11th to 20th	Day	8% 4 1 4 4 3 4 3 5% 8% 56%	2520
	21st to end	Day	6% 3 1 3 3 2 3 3 3 8% 65%	2520
July	1st to 10th	Day	4 4 1 2 3 2 3 3 4 8% 66%	2520
	11th to 20th	Day	4 3 2 3 2 2 3 3 3 7% 69%	2397
	21st to end	Day	1 2 1 1 2 2 3 2 3 8% 73%	2546
August	1st to 10th	Day	1 3 1 2 3 2 3 4 5% 9% 67%	2328
	11th to 20th	Day	2 1 1 2 2 2 3 3 4 6% 75%	2298
	21st to end	Day	3 3 1 2 3 2 3 3 3 7% 69%	2426
September	1st to 10th	Day	4 3 1 3 2 2 2 2 3 7% 71%	2160
	11th to 20th	Day	6% 4 2 5% 4 3 4 4 6% 8% 56%	2066
	21st to end	Day	7% 5% 2 3 3 2 2 3 5% 7% 63%	1948
October	1st to 10th	Day	9% 4 2 3 3 2 3 3 4 6% 62%	1800
	11th to 20th	Day	14% 4 1 3 3 3 3 4 6% 8% 52%	1800
	21st to end	Day	14% 7% 2 4 4 3 4 4 5% 7% 45%	1980
November	1st to 10th	Day	22% 7% 2 5% 5% 3 4 4 6% 9% 33%	1821
	11th to 20th	Day	22% 8% 3 5% 5% 2 4 5% 5% 9% 31%	1520
	21st to end	Day	20% 7% 3 6% 6% 3 3 4 4 8% 36%	1520
December	1st to 10th	Day	21% 7% 3 5% 4 2 4 4 5% 8% 37%	1520
	11th to 20th	Day	29% 11% 3 7% 5% 2 4 4 4 6% 23%	1928
	21st to end	Day	30% 12% 4 7% 7% 4 4 4 3 4 21%	2794
January	1st to 10th	Night	28% 13% 4 7% 6% 3 4 5% 5% 5% 20%	4304
	11th to 20th	Night	31% 12% 4 8% 6% 3 3 3 3 5% 23%	4110
	21st to end	Night	40% 13% 3 4 3 2 3 3 3 4 22%	4521
February	1st to 10th	Night	20% 11% 4 6% 5% 3 4 4 4 6% 33%	2470
	11th to 20th	Night	23% 11% 3 7% 6% 3 4 3 4 6% 31%	2402
	21st to end	Night	21% 12% 3 4 4 2 4 4 4 8% 32%	1914
March	1st to 10th	Night	29% 12% 3 6% 4 2 4 4 5% 6% 26%	2090
	11th to 20th	Night	24% 11% 3 6% 5% 2 4 3 5% 8% 30%	2090
	21st to end	Night	26% 13% 4 6% 4 3 5% 4 4 5% 26%	2299
April	1st to 10th	Night	21% 12% 5% 5% 6% 4 4 4 4 8% 27%	1853
	11th to 20th	Night	18% 12% 3 6% 4 3 4 3 6% 6% 33%	1779
	21st to end	Night	17% 9% 3 5% 4 3 3 4 7% 8% 37%	1668
May	1st to 10th	Night	11% 10% 2 6% 5% 3 3 4 5% 8% 44%	1620
	11th to 20th	Night	12% 11% 4 6% 6% 3 5% 4 4 7% 37%	1532
	21st to end	Night	13% 11% 4 6% 6% 4 6% 5% 5% 6% 34%	1552
June	1st to 10th	Night	13% 10% 3 7% 4 3 5% 5% 7% 8% 37%	1440
	11th to 20th	Night	6% 6% 3 5% 4 2 5% 4 4 8% 52%	1440
	21st to end	Night	5% 4 2 4 4 2 5% 4 5% 7% 58%	1440
July	1st to 10th	Night	3 3 2 5% 4 3 4 3 4 9% 61%	1440
	11th to 20th	Night	2 2 1 4 3 3 4 3 3 7% 68%	1558
	21st to end	Night	1 2 1 2 3 3 5% 4 5% 9% 65%	1773
August	1st to 10th	Night	2 1 4 3 3 7% 4 4 9% 62%	1611
	11th to 20th	Night	2 2 1 3 4 2 4 3 3 8% 70%	1602
	21st to end	Night	2 2 1 3 3 3 5% 5% 4 8% 64%	1930
September	1st to 10th	Night	3 3 1 2 2 2 3 2 4 8% 72%	1800
	11th to 20th	Night	5% 4 2 3 3 3 4 3 4 9% 59%	1892
	21st to end	Night	7% 5% 2 3 3 2 3 4 5% 6% 59%	2011
October	1st to 10th	Night	8% 4 2 4 3 3 2 3 4 6% 62%	2160
	11th to 20th	Night	13% 5% 2 5% 4 2 3 3 3 7% 51%	2160
	21st to end	Night	14% 5% 2 4 3 3 4 3 5% 9% 47%	2376
November	1st to 10th	Night	19% 9% 2 6% 5% 3 5% 5% 4 6% 36%	2254
	11th to 20th	Night	21% 8% 3 7% 6% 4 4 4 5% 7% 29%	2660
	21st to end	Night	20% 7% 2 5% 5% 2 4 5% 5% 8% 37%	2660
December	1st to 10th	Night	23% 6% 2 5% 5% 3 3 4 6% 8% 35%	2660
	11th to 20th	Night	29% 11% 4 6% 5% 2 5% 4 5% 6% 23%	3276
	21st to end	Night	27% 12% 3 6% 5% 4 4 4 4 5% 26%	4862

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	62% 9% 9% 14% 3 3	2640
	11th to 20th	Day	64% 8% 6% 10% 7% 6%	2860
	21st to end	Day	59% 7% 10% 10% 9% 4	3146
February	1st to 10th	Day	50% 6% 11% 16% 11% 5%	1710
	11th to 20th	Day	51% 7% 10% 18% 12% 1	1674
	21st to end	Day	57% 5% 11% 17% 9% 2	1534
March	1st to 10th	Day	62% 7% 9% 13% 8% 1	2090
	11th to 20th	Day	54% 6% 13% 15% 11% 2	2090
	21st to end	Day	60% 9% 13% 12% 6% 1	2299
April	1st to 10th	Day	57% 8% 13% 13% 7% 1	2150
	11th to 20th	Day	52% 6% 15% 15% 8% 3	2132
	21st to end	Day	44% 8% 15% 20% 11% 1	2290
May	1st to 10th	Day	35% 10% 15% 26% 12% 2	2340
	11th to 20th	Day	41% 8% 15% 23% 10% 3	2364
	21st to end	Day	43% 11% 16% 24% 6%	2724
June	1st to 10th	Day	40% 10% 15% 22% 12% 2	2520
	11th to 20th	Day	24% 8% 16% 31% 16% 4	2520
	21st to end	Day	17% 6% 15% 30% 25% 7%	2520
July	1st to 10th	Day	14% 7% 13% 27% 22% 16%	2451
	11th to 20th	Day	13% 4 13% 25% 28% 16%	2324
	21st to end	Day	7% 3 12% 22% 38% 17%	2405
August	1st to 10th	Day	10% 6% 18% 29% 30% 7%	2312
	11th to 20th	Day	9% 4 13% 24% 37% 13%	2298
	21st to end	Day	12% 5% 15% 27% 31% 11%	2426
September	1st to 10th	Day	13% 4 9% 19% 33% 22%	2160
	11th to 20th	Day	23% 7% 15% 26% 25% 5%	2066
	21st to end	Day	20% 5% 13% 23% 21% 17%	1948
October	1st to 10th	Day	25% 5% 13% 22% 19% 17%	1800
	11th to 20th	Day	30% 5% 12% 21% 21% 10%	1800
	21st to end	Day	36% 8% 11% 19% 15% 12%	1980
November	1st to 10th	Day	47% 7% 12% 17% 12% 5%	1821
	11th to 20th	Day	49% 7% 14% 13% 9% 8%	1520
	21st to end	Day	48% 7% 10% 12% 13% 10%	1520
December	1st to 10th	Day	46% 6% 12% 14% 14% 8%	1520
	11th to 20th	Day	62% 8% 9% 9% 9% 3	1928
	21st to end	Day	66% 6% 6% 11% 8% 3	2794
January	1st to 10th	Night	63% 9% 12% 9% 4 2	4304
	11th to 20th	Night	64% 8% 8% 8% 6% 6%	4110
	21st to end	Night	67% 5% 6% 10% 8% 4	4521
February	1st to 10th	Night	51% 7% 12% 16% 10% 5%	2470
	11th to 20th	Night	54% 7% 11% 15% 10% 3	2404
	21st to end	Night	51% 7% 14% 17% 7% 3	1914
March	1st to 10th	Night	59% 6% 10% 16% 8%	2090
	11th to 20th	Night	53% 7% 14% 14% 11% 2	2090
	21st to end	Night	58% 10% 14% 12% 5% 1	2299
April	1st to 10th	Night	54% 10% 13% 15% 6% 2	1853
	11th to 20th	Night	49% 10% 16% 14% 8% 3	1779
	21st to end	Night	43% 10% 18% 20% 6% 2	1668
May	1st to 10th	Night	35% 11% 18% 21% 12% 3	1620
	11th to 20th	Night	42% 11% 15% 18% 12% 2	1533
	21st to end	Night	41% 15% 18% 19% 6%	1552
June	1st to 10th	Night	40% 10% 18% 21% 10% 1	1440
	11th to 20th	Night	24% 10% 19% 28% 15% 4	1440
	21st to end	Night	16% 8% 18% 28% 24% 6%	1440
July	1st to 10th	Night	14% 8% 17% 23% 21% 16%	1400
	11th to 20th	Night	13% 5% 15% 20% 32% 15%	1508
	21st to end	Night	7% 5% 16% 22% 34% 16%	1674
August	1st to 10th	Night	11% 9% 19% 30% 22% 9%	1602
	11th to 20th	Night	10% 4 15% 23% 34% 14%	1602
	21st to end	Night	11% 6% 17% 24% 28% 13%	1930
September	1st to 10th	Night	11% 5% 12% 19% 29% 24%	1800
	11th to 20th	Night	18% 8% 18% 28% 22% 6%	1892
	21st to end	Night	25% 5% 14% 20% 18% 17%	2011
October	1st to 10th	Night	25% 6% 13% 20% 21% 16%	2160
	11th to 20th	Night	32% 7% 11% 21% 21% 8%	2160
	21st to end	Night	32% 8% 15% 18% 14% 12%	2376
November	1st to 10th	Night	48% 9% 13% 13% 12% 5%	2254
	11th to 20th	Night	53% 9% 12% 12% 8% 6%	2660
	21st to end	Night	45% 7% 10% 16% 13% 9%	2660
December	1st to 10th	Night	47% 7% 11% 13% 16% 6%	2660
	11th to 20th	Night	62% 7% 7% 12% 11% 2	3276
	21st to end	Night	57% 11% 13% 12% 6% 2	4862

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	42% 15% 21% 16% 5% 1	242
	11th to 20th	Day	37% 9% 21% 20% 10% 4	370
	21st to end	Day	31% 10% 21% 24% 12% 3	407
February	1st to 10th	Day	27% 14% 26% 23% 7% 3	370
	11th to 20th	Day	37% 12% 23% 19% 8%	365
	21st to end	Day	34% 17% 25% 16% 7% 1	347
March	1st to 10th	Day	37% 17% 25% 16% 5% 1	460
	11th to 20th	Day	30% 13% 25% 21% 7% 3	460
	21st to end	Day	34% 17% 25% 17% 7%	506
April	1st to 10th	Day	32% 18% 26% 17% 6% 1	429
	11th to 20th	Day	33% 16% 22% 22% 5% 2	412
	21st to end	Day	24% 15% 32% 18% 9% 3	420
May	1st to 10th	Day	21% 16% 29% 22% 10% 2	423
	11th to 20th	Day	31% 14% 25% 20% 8% 3	448
	21st to end	Day	22% 16% 26% 24% 10% 2	485
June	1st to 10th	Day	20% 14% 27% 24% 13% 3	450
	11th to 20th	Day	12% 17% 31% 28% 10% 2	450
	21st to end	Day	5% 8% 33% 36% 14% 4	450
July	1st to 10th	Day	7% 6% 31% 39% 14% 3	446
	11th to 20th	Day	3 5% 32% 40% 15% 5%	444
	21st to end	Day	1 4 24% 44% 21% 6%	487
August	1st to 10th	Day	4 5% 27% 38% 19% 7%	447
	11th to 20th	Day	2 6% 21% 45% 19% 8%	437
	21st to end	Day	5% 5% 25% 42% 17% 7%	495
September	1st to 10th	Day	7% 6% 27% 35% 19% 7%	450
	11th to 20th	Day	8% 11% 21% 39% 17% 4	450
	21st to end	Day	11% 10% 24% 31% 19% 4	450
October	1st to 10th	Day	10% 12% 23% 29% 19% 6%	450
	11th to 20th	Day	17% 7% 16% 30% 23% 7%	450
	21st to end	Day	18% 9% 24% 27% 18% 3	495
November	1st to 10th	Day	23% 10% 22% 28% 13% 5%	427
	11th to 20th	Day	21% 9% 19% 23% 21% 8%	180
	21st to end	Day	22% 9% 13% 32% 21% 3	180
December	1st to 10th	Day	27% 15% 18% 19% 13% 7%	180
	11th to 20th	Day	37% 7% 17% 22% 13% 4	180
	21st to end	Day	34% 8% 21% 21% 14% 2	198
January	1st to 10th	Night	31% 7% 16% 27% 17% 3	760
	11th to 20th	Night	30% 6% 15% 28% 16% 5%	760
	21st to end	Night	32% 4 11% 29% 21% 4	836
February	1st to 10th	Night	26% 8% 14% 33% 17% 2	760
	11th to 20th	Night	28% 8% 16% 25% 19% 4	744
	21st to end	Night	28% 7% 19% 30% 15%	628
March	1st to 10th	Night	36% 10% 15% 24% 12% 3	760
	11th to 20th	Night	29% 7% 13% 26% 22% 3	760
	21st to end	Night	31% 10% 17% 27% 14% 2	836
April	1st to 10th	Night	28% 7% 17% 27% 17% 3	728
	11th to 20th	Night	24% 9% 19% 26% 18% 5%	711
	21st to end	Night	22% 6% 13% 32% 21% 5%	588
May	1st to 10th	Night	16% 8% 17% 30% 25% 5%	540
	11th to 20th	Night	18% 7% 11% 30% 27% 7%	470
	21st to end	Night	18% 8% 14% 32% 24% 4	389
June	1st to 10th	Night	18% 7% 12% 32% 29% 3	360
	11th to 20th	Night	8% 5% 18% 45% 23% 2	360
	21st to end	Night	7% 4 9% 38% 39% 3	360
July	1st to 10th	Night	4 3 9% 38% 42% 4	350
	11th to 20th	Night	3 5% 3 33% 46% 9%	464
	21st to end	Night	2 2 6% 27% 49% 15%	591
August	1st to 10th	Night	2 4 7% 26% 48% 13%	537
	11th to 20th	Night	3 2 7% 22% 54% 13%	534
	21st to end	Night	3 3 8% 31% 43% 12%	742
September	1st to 10th	Night	5% 1 9% 29% 44% 13%	720
	11th to 20th	Night	6% 4 9% 30% 39% 11%	720
	21st to end	Night	10% 4 11% 28% 35% 13%	720
October	1st to 10th	Night	10% 4 12% 30% 35% 9%	720
	11th to 20th	Night	15% 4 10% 28% 32% 11%	720
	21st to end	Night	16% 5% 11% 30% 28% 9%	792
November	1st to 10th	Night	22% 6% 16% 29% 21% 7%	740
	11th to 20th	Night	25% 8% 13% 31% 21% 4	760
	21st to end	Night	23% 5% 15% 32% 21% 3	760
December	1st to 10th	Night	26% 8% 14% 29% 20% 3	760
	11th to 20th	Night	33% 8% 17% 26% 14% 3	760
	21st to end	Night	39% 7% 14% 25% 12% 2	836

Page generated at 2024-03-31 03:08:53. Version ac07

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