Hawk's Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawk's Hollow Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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% 10% 4 9% 5% 5% 4 4 5% 7% 34%	127329
	Night	14% 12% 5% 10% 5% 4 4 3 5% 6% 31%	124916
Transparency	Day	48% 5% 12% 21% 12% 1	130855
	Night	53% 5% 11% 19% 11% 1	129464
Seeing	Day	17% 12% 29% 24% 12% 5%	17478
	Night	19% 9% 28% 31% 12% 1	27439

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% 20% 7% 20% 7% 6% 4 3 4 4 12%	3697
	11th to 20th	Day	11% 15% 7% 21% 15% 11% 4 3 3 4 6%	3700
	21st to end	Day	16% 18% 8% 20% 8% 5% 6% 2 2 3 12%	4070
February	1st to 10th	Day	12% 17% 6% 15% 10% 6% 5% 4 4 4 17%	1835
	11th to 20th	Day	13% 14% 6% 15% 9% 5% 5% 3 4 5% 20%	1948
	21st to end	Day	15% 16% 6% 13% 4 5% 5% 4 5% 6% 22%	1650
March	1st to 10th	Day	14% 11% 4 12% 5% 5% 4 3 5% 6% 31%	4480
	11th to 20th	Day	11% 9% 4 8% 5% 5% 5% 4 6% 8% 36%	4831
	21st to end	Day	19% 14% 6% 9% 5% 4 3 3 4 6% 27%	5691
April	1st to 10th	Day	19% 14% 4 7% 5% 4 4 3 5% 6% 30%	2400
	11th to 20th	Day	17% 11% 3 7% 4 4 4 3 6% 6% 36%	2423
	21st to end	Day	17% 9% 3 7% 5% 4 4 4 5% 7% 35%	2600
May	1st to 10th	Day	18% 8% 2 6% 4 4 4 3 5% 8% 38%	5862
	11th to 20th	Day	14% 7% 2 7% 4 4 4 4 6% 8% 39%	5898
	21st to end	Day	15% 6% 2 5% 4 4 4 3 5% 7% 43%	6935
June	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 9% 44%	2800
	11th to 20th	Day	11% 6% 2 5% 5% 5% 4 3 5% 8% 47%	2800
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 11% 42%	2800
July	1st to 10th	Day	10% 6% 3 6% 4 4 5% 4 7% 9% 41%	6360
	11th to 20th	Day	8% 5% 2 6% 4 4 4 5% 6% 8% 47%	6360
	21st to end	Day	8% 6% 2 6% 4 4 5% 4 6% 10% 46%	6924
August	1st to 10th	Day	11% 5% 2 6% 4 3 5% 4 7% 10% 42%	4299
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 4 5% 8% 46%	4174
	21st to end	Day	7% 6% 2 7% 4 4 5% 4 7% 8% 46%	4348
September	1st to 10th	Day	10% 5% 3 7% 4 5% 5% 3 5% 8% 45%	2375
	11th to 20th	Day	10% 5% 2 5% 3 4 5% 3 6% 9% 48%	2200
	21st to end	Day	12% 7% 3 7% 6% 4 5% 3 5% 8% 41%	2200
October	1st to 10th	Day	15% 7% 2 7% 4 4 4 3 4 6% 44%	2200
	11th to 20th	Day	20% 10% 4 8% 4 6% 5% 4 5% 7% 27%	1943
	21st to end	Day	22% 11% 3 9% 6% 6% 5% 3 5% 7% 24%	1980
November	1st to 10th	Day	13% 11% 3 8% 5% 5% 5% 4 5% 7% 35%	1852
	11th to 20th	Day	16% 18% 5% 11% 6% 5% 4 3 5% 5% 22%	1890
	21st to end	Day	20% 17% 6% 10% 4 4 4 3 4 7% 20%	1890
December	1st to 10th	Day	10% 24% 9% 15% 6% 6% 4 3 4 5% 13%	2756
	11th to 20th	Day	15% 24% 12% 15% 7% 4 4 3 3 3 11%	3088
	21st to end	Day	23% 23% 6% 13% 6% 4 3 3 3 4 12%	4070
January	1st to 10th	Night	11% 20% 9% 21% 7% 4 4 2 3 3 15%	6488
	11th to 20th	Night	12% 17% 9% 23% 12% 8% 4 2 3 2 7%	6500
	21st to end	Night	16% 19% 8% 14% 7% 7% 5% 3 4 4 13%	7150
February	1st to 10th	Night	13% 18% 5% 14% 10% 5% 4 3 4 5% 19%	2561
	11th to 20th	Night	13% 16% 6% 13% 6% 5% 4 4 4 5% 23%	2338
	21st to end	Night	16% 15% 4 10% 6% 5% 5% 4 5% 6% 25%	1980
March	1st to 10th	Night	15% 9% 3 9% 4 5% 4 3 5% 7% 35%	5373
	11th to 20th	Night	11% 8% 3 6% 4 4 4 3 6% 9% 43%	5128
	21st to end	Night	18% 12% 5% 7% 5% 4 4 3 5% 6% 31%	5268
April	1st to 10th	Night	16% 11% 3 7% 5% 4 4 4 4 6% 36%	2000
	11th to 20th	Night	19% 9% 3 6% 4 3 4 4 5% 5% 37%	1925
	21st to end	Night	16% 9% 3 7% 4 4 3 4 5% 7% 38%	1800
May	1st to 10th	Night	17% 9% 3 8% 4 4 4 4 5% 6% 35%	4033
	11th to 20th	Night	15% 8% 3 7% 4 4 4 3 5% 6% 42%	3993
	21st to end	Night	17% 6% 3 6% 4 4 4 4 4 6% 42%	3942
June	1st to 10th	Night	10% 6% 2 5% 5% 4 4 5% 5% 9% 46%	1600
	11th to 20th	Night	9% 7% 2 6% 5% 4 5% 3 7% 10% 42%	1600
	21st to end	Night	9% 5% 2 5% 5% 5% 5% 5% 7% 9% 44%	1600
July	1st to 10th	Night	9% 5% 2 7% 5% 3 5% 5% 7% 9% 43%	3618
	11th to 20th	Night	7% 5% 2 5% 4 5% 4 3 6% 7% 52%	3617
	21st to end	Night	9% 6% 2 6% 4 5% 3 3 5% 8% 49%	3947
August	1st to 10th	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	2852
	11th to 20th	Night	11% 5% 2 6% 3 3 4 4 6% 7% 49%	2875
	21st to end	Night	8% 6% 2 8% 5% 4 5% 4 6% 7% 46%	3547
September	1st to 10th	Night	8% 6% 2 6% 3 4 4 3 5% 7% 51%	2005
	11th to 20th	Night	10% 4 2 5% 3 4 3 3 4 6% 56%	2200
	21st to end	Night	13% 8% 3 6% 5% 4 4 3 5% 6% 44%	2200
October	1st to 10th	Night	17% 5% 2 4 3 4 4 3 4 7% 48%	2200
	11th to 20th	Night	20% 10% 3 8% 4 4 3 3 5% 6% 34%	2453
	21st to end	Night	22% 10% 3 6% 4 4 4 3 5% 6% 33%	2860
November	1st to 10th	Night	15% 12% 3 8% 4 4 4 3 5% 6% 36%	2666
	11th to 20th	Night	16% 16% 5% 11% 5% 4 4 4 6% 7% 23%	2730
	21st to end	Night	18% 18% 6% 9% 4 4 3 3 4 6% 23%	2730
December	1st to 10th	Night	11% 23% 9% 14% 5% 4 4 3 4 6% 17%	4648
	11th to 20th	Night	17% 23% 9% 15% 8% 4 3 3 4 4 11%	5339
	21st to end	Night	25% 22% 6% 10% 5% 4 4 3 4 4 13%	7150

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	74% 7% 9% 9% 1	3698
	11th to 20th	Day	82% 5% 7% 4 1	3700
	21st to end	Day	78% 5% 8% 7% 2	4070
February	1st to 10th	Day	70% 6% 9% 13% 3	1835
	11th to 20th	Day	66% 5% 9% 13% 6%	1958
	21st to end	Day	62% 6% 12% 14% 6%	1650
March	1st to 10th	Day	53% 4 15% 19% 8% 1	4480
	11th to 20th	Day	45% 5% 17% 23% 9% 1	4831
	21st to end	Day	60% 4 10% 16% 10% 1	5693
April	1st to 10th	Day	55% 5% 10% 19% 10% 1	2400
	11th to 20th	Day	47% 5% 10% 23% 13% 2	2423
	21st to end	Day	47% 6% 12% 19% 14% 2	2600
May	1st to 10th	Day	44% 5% 12% 21% 16% 2	5897
	11th to 20th	Day	41% 5% 14% 21% 16% 2	5902
	21st to end	Day	39% 5% 11% 26% 18% 1	6949
June	1st to 10th	Day	35% 6% 13% 28% 16% 2	2800
	11th to 20th	Day	35% 6% 13% 25% 19% 2	2800
	21st to end	Day	35% 7% 15% 23% 18% 2	2800
July	1st to 10th	Day	38% 5% 12% 26% 16% 2	6291
	11th to 20th	Day	32% 5% 13% 29% 20% 1	6285
	21st to end	Day	33% 5% 14% 26% 20% 2	6728
August	1st to 10th	Day	36% 6% 12% 30% 15% 1	4284
	11th to 20th	Day	35% 6% 12% 29% 17% 1	4213
	21st to end	Day	34% 5% 14% 28% 17% 2	4347
September	1st to 10th	Day	37% 6% 14% 27% 14% 2	2375
	11th to 20th	Day	32% 6% 13% 31% 18% 1	2200
	21st to end	Day	40% 5% 13% 25% 17%	2200
October	1st to 10th	Day	30% 3 8% 38% 20% 1	3590
	11th to 20th	Day	42% 5% 12% 25% 15%	3133
	21st to end	Day	50% 5% 12% 23% 9% 1	3180
November	1st to 10th	Day	47% 8% 12% 21% 12%	1852
	11th to 20th	Day	64% 5% 10% 15% 5% 1	1890
	21st to end	Day	64% 6% 12% 13% 4	1890
December	1st to 10th	Day	73% 7% 10% 8% 2	2756
	11th to 20th	Day	79% 4 7% 8% 1	3085
	21st to end	Day	77% 4 6% 11% 2	4070
January	1st to 10th	Night	75% 4 7% 10% 4	6488
	11th to 20th	Night	84% 4 5% 4 2	6500
	21st to end	Night	76% 5% 10% 7% 2	7150
February	1st to 10th	Night	69% 5% 9% 12% 5%	2561
	11th to 20th	Night	63% 6% 8% 16% 6%	2339
	21st to end	Night	60% 6% 12% 15% 6% 1	1980
March	1st to 10th	Night	47% 5% 13% 25% 9% 1	5373
	11th to 20th	Night	38% 5% 15% 29% 11% 2	5128
	21st to end	Night	53% 6% 10% 17% 13% 1	5268
April	1st to 10th	Night	49% 6% 11% 21% 14% 1	2000
	11th to 20th	Night	48% 5% 8% 18% 17% 3	1925
	21st to end	Night	44% 5% 12% 20% 16% 3	1800
May	1st to 10th	Night	48% 6% 12% 16% 14% 3	4060
	11th to 20th	Night	43% 6% 10% 22% 16% 4	3994
	21st to end	Night	43% 5% 8% 22% 20% 2	3950
June	1st to 10th	Night	35% 6% 10% 29% 17% 3	1600
	11th to 20th	Night	36% 6% 14% 24% 18% 2	1600
	21st to end	Night	34% 7% 15% 25% 16% 2	1600
July	1st to 10th	Night	36% 5% 13% 28% 13% 5%	3580
	11th to 20th	Night	31% 5% 13% 27% 22% 2	3572
	21st to end	Night	35% 5% 12% 22% 23% 2	3832
August	1st to 10th	Night	33% 5% 13% 31% 17% 1	2843
	11th to 20th	Night	33% 6% 10% 32% 17% 1	2902
	21st to end	Night	36% 5% 10% 28% 18% 2	3547
September	1st to 10th	Night	31% 8% 12% 28% 18% 3	2005
	11th to 20th	Night	29% 5% 11% 33% 20% 2	2200
	21st to end	Night	40% 6% 12% 26% 15% 1	2200
October	1st to 10th	Night	28% 4 9% 36% 22% 2	3590
	11th to 20th	Night	42% 3 13% 23% 19%	4002
	21st to end	Night	43% 4 9% 27% 16%	4610
November	1st to 10th	Night	49% 6% 9% 23% 12% 1	2666
	11th to 20th	Night	59% 6% 12% 16% 6% 1	2730
	21st to end	Night	62% 6% 13% 15% 3	2730
December	1st to 10th	Night	70% 5% 12% 10% 2	4648
	11th to 20th	Night	78% 5% 8% 7% 2	5341
	21st to end	Night	74% 4 9% 9% 3	7150

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	21% 16% 33% 23% 5% 2	330
	11th to 20th	Day	21% 20% 41% 15% 4	330
	21st to end	Day	27% 16% 31% 21% 5% 1	363
February	1st to 10th	Day	19% 28% 28% 21% 2 2	300
	11th to 20th	Day	21% 22% 36% 17% 4	300
	21st to end	Day	25% 27% 35% 10% 2 1	249
March	1st to 10th	Day	22% 22% 41% 11% 4	300
	11th to 20th	Day	23% 16% 29% 23% 8% 1	429
	21st to end	Day	28% 17% 29% 19% 6% 1	550
April	1st to 10th	Day	27% 15% 31% 22% 5% 1	500
	11th to 20th	Day	25% 20% 28% 19% 5% 3	492
	21st to end	Day	23% 14% 31% 20% 11% 2	500
May	1st to 10th	Day	22% 14% 31% 22% 8% 2	503
	11th to 20th	Day	17% 11% 30% 24% 14% 4	538
	21st to end	Day	15% 11% 26% 27% 15% 5%	789
June	1st to 10th	Day	12% 9% 34% 28% 12% 5%	730
	11th to 20th	Day	13% 9% 30% 30% 13% 5%	730
	21st to end	Day	13% 9% 32% 29% 12% 4	730
July	1st to 10th	Day	8% 6% 27% 31% 21% 8%	721
	11th to 20th	Day	11% 6% 26% 31% 18% 8%	718
	21st to end	Day	10% 4 29% 33% 18% 7%	794
August	1st to 10th	Day	10% 4 21% 27% 25% 14%	566
	11th to 20th	Day	11% 5% 20% 30% 24% 11%	519
	21st to end	Day	10% 5% 21% 30% 24% 11%	583
September	1st to 10th	Day	14% 4 23% 28% 20% 10%	530
	11th to 20th	Day	8% 4 18% 27% 28% 14%	530
	21st to end	Day	15% 11% 20% 27% 19% 8%	530
October	1st to 10th	Day	15% 12% 25% 26% 18% 4	530
	11th to 20th	Day	22% 15% 31% 27% 6%	418
	21st to end	Day	29% 13% 39% 13% 4 2	363
November	1st to 10th	Day	23% 16% 31% 23% 6% 1	330
	11th to 20th	Day	24% 22% 34% 15% 5%	330
	21st to end	Day	25% 18% 42% 11% 4	330
December	1st to 10th	Day	25% 24% 28% 14% 8% 1	330
	11th to 20th	Day	22% 22% 37% 15% 4	330
	21st to end	Day	27% 23% 33% 12% 4 1	363
January	1st to 10th	Night	21% 15% 33% 24% 7%	1050
	11th to 20th	Night	25% 14% 33% 24% 5%	1050
	21st to end	Night	22% 11% 31% 32% 5%	1155
February	1st to 10th	Night	22% 10% 37% 27% 4	841
	11th to 20th	Night	20% 13% 35% 25% 6%	783
	21st to end	Night	23% 13% 40% 20% 3	660
March	1st to 10th	Night	19% 11% 36% 26% 7% 1	800
	11th to 20th	Night	16% 13% 35% 29% 7% 1	800
	21st to end	Night	21% 11% 31% 28% 8% 1	797
April	1st to 10th	Night	19% 10% 35% 30% 6%	600
	11th to 20th	Night	23% 10% 33% 26% 7% 1	593
	21st to end	Night	20% 10% 30% 32% 8% 1	600
May	1st to 10th	Night	18% 8% 31% 34% 9% 1	600
	11th to 20th	Night	19% 5% 29% 35% 12%	591
	21st to end	Night	14% 4 25% 36% 19% 2	650
June	1st to 10th	Night	11% 5% 27% 40% 17%	600
	11th to 20th	Night	12% 5% 28% 40% 15%	600
	21st to end	Night	11% 4 24% 42% 19% 1	600
July	1st to 10th	Night	8% 3 16% 43% 28% 2	585
	11th to 20th	Night	8% 4 18% 43% 25% 3	582
	21st to end	Night	8% 1 17% 45% 28% 1	657
August	1st to 10th	Night	9% 2 15% 45% 27% 2	597
	11th to 20th	Night	12% 2 13% 43% 25% 4	594
	21st to end	Night	10% 3 15% 40% 29% 3	660
September	1st to 10th	Night	10% 4 18% 39% 25% 4	605
	11th to 20th	Night	10% 4 16% 36% 28% 4	800
	21st to end	Night	14% 7% 21% 32% 21% 4	800
October	1st to 10th	Night	18% 6% 22% 36% 18% 1	800
	11th to 20th	Night	26% 11% 24% 29% 10% 1	800
	21st to end	Night	28% 10% 30% 25% 7%	880
November	1st to 10th	Night	21% 11% 30% 28% 9%	820
	11th to 20th	Night	24% 15% 32% 23% 6% 1	840
	21st to end	Night	27% 11% 31% 26% 4	840
December	1st to 10th	Night	26% 14% 30% 23% 6%	1004
	11th to 20th	Night	25% 14% 35% 22% 4	1050
	21st to end	Night	32% 11% 36% 20% 2	1155

Page generated at 2026-01-29 01:21:41. Version ac07

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