Bee Sting Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bee Sting Hill Observatory clear sky chart from 2005-11-06 to 2025-04-11.

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	10% 8% 3 8% 5% 5% 5% 4 6% 7% 38%	113759
	Night	10% 8% 3 7% 5% 4 5% 4 6% 7% 41%	114553
Transparency	Day	42% 7% 10% 19% 17% 5%	117579
	Night	39% 6% 11% 20% 18% 5%	118871
Seeing	Day	17% 13% 23% 21% 16% 9%	15348
	Night	16% 11% 21% 28% 20% 4	25476

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% 11% 5% 7% 5% 3 4 3 4 4 42%	4056
	11th to 20th	Day	10% 8% 6% 10% 3 3 3 2 3 4 47%	4060
	21st to end	Day	14% 14% 5% 8% 4 4 3 3 4 6% 35%	4581
February	1st to 10th	Day	12% 11% 4 8% 6% 4 4 4 5% 6% 36%	2000
	11th to 20th	Day	16% 10% 4 9% 6% 4 4 3 5% 5% 34%	1948
	21st to end	Day	16% 11% 3 8% 4 4 4 3 4 5% 37%	1650
March	1st to 10th	Day	16% 10% 4 7% 5% 5% 5% 4 5% 6% 34%	4606
	11th to 20th	Day	9% 7% 3 6% 5% 4 3 3 5% 7% 49%	4980
	21st to end	Day	13% 9% 3 7% 4 4 4 3 5% 6% 42%	5465
April	1st to 10th	Day	10% 7% 2 7% 6% 5% 5% 4 6% 7% 41%	2280
	11th to 20th	Day	11% 8% 3 7% 4 4 4 4 5% 7% 43%	2254
	21st to end	Day	10% 8% 2 7% 4 5% 4 4 7% 7% 43%	2446
May	1st to 10th	Day	10% 8% 3 8% 5% 5% 6% 5% 6% 8% 35%	4082
	11th to 20th	Day	14% 10% 4 9% 5% 6% 5% 4 6% 7% 29%	4081
	21st to end	Day	7% 5% 2 8% 6% 5% 6% 5% 7% 10% 38%	4476
June	1st to 10th	Day	9% 8% 3 9% 6% 6% 7% 6% 8% 9% 31%	2470
	11th to 20th	Day	5% 5% 3 6% 6% 7% 8% 7% 8% 9% 36%	2470
	21st to end	Day	7% 6% 3 6% 6% 7% 6% 6% 8% 11% 33%	2470
July	1st to 10th	Day	6% 6% 2 9% 8% 8% 8% 7% 9% 11% 26%	4120
	11th to 20th	Day	8% 7% 2 9% 7% 8% 8% 6% 8% 10% 27%	4120
	21st to end	Day	10% 10% 4 12% 10% 9% 8% 6% 8% 7% 16%	4466
August	1st to 10th	Day	5% 4 2 7% 6% 7% 8% 7% 9% 11% 33%	4104
	11th to 20th	Day	6% 5% 2 7% 6% 7% 6% 5% 8% 12% 36%	3832
	21st to end	Day	8% 5% 2 7% 7% 6% 6% 5% 6% 8% 41%	4180
September	1st to 10th	Day	10% 7% 3 8% 7% 6% 6% 4 7% 8% 34%	2109
	11th to 20th	Day	13% 7% 3 7% 6% 5% 5% 4 7% 9% 34%	2090
	21st to end	Day	13% 5% 2 6% 4 5% 5% 4 6% 8% 41%	2090
October	1st to 10th	Day	10% 5% 2 6% 4 4 5% 3 4 6% 51%	2090
	11th to 20th	Day	10% 7% 2 4 3 3 3 3 5% 6% 53%	1976
	21st to end	Day	11% 7% 2 5% 4 4 3 3 4 5% 53%	2076
November	1st to 10th	Day	10% 6% 2 5% 3 3 4 3 5% 6% 53%	1762
	11th to 20th	Day	11% 6% 2 6% 4 3 4 3 5% 6% 48%	1800
	21st to end	Day	12% 9% 2 6% 4 4 4 4 5% 7% 44%	1800
December	1st to 10th	Day	13% 9% 3 7% 4 4 3 3 4 5% 45%	2930
	11th to 20th	Day	12% 10% 6% 10% 6% 6% 5% 3 5% 5% 34%	3373
	21st to end	Day	12% 9% 5% 9% 5% 4 4 4 5% 8% 35%	4466
January	1st to 10th	Night	11% 10% 4 10% 4 4 3 3 4 5% 41%	5889
	11th to 20th	Night	11% 10% 4 9% 5% 3 4 3 4 5% 43%	5900
	21st to end	Night	12% 13% 4 7% 4 4 4 3 4 5% 41%	6370
February	1st to 10th	Night	13% 9% 4 7% 5% 4 4 4 5% 5% 39%	2400
	11th to 20th	Night	17% 11% 4 9% 5% 4 4 3 4 4 35%	2338
	21st to end	Night	16% 11% 3 8% 4 4 4 3 5% 6% 36%	1980
March	1st to 10th	Night	16% 13% 4 7% 5% 5% 5% 4 5% 6% 31%	5246
	11th to 20th	Night	10% 7% 2 4 3 3 4 4 6% 7% 49%	4980
	21st to end	Night	10% 10% 3 7% 5% 5% 4 3 5% 6% 42%	5467
April	1st to 10th	Night	10% 7% 2 6% 4 4 5% 4 5% 8% 45%	2135
	11th to 20th	Night	11% 7% 2 6% 4 4 4 2 5% 8% 47%	1881
	21st to end	Night	10% 7% 3 6% 4 4 4 3 5% 7% 48%	1733
May	1st to 10th	Night	8% 8% 3 7% 5% 6% 6% 4 7% 8% 38%	2813
	11th to 20th	Night	11% 12% 4 8% 4 5% 4 4 5% 8% 33%	2812
	21st to end	Night	5% 5% 3 7% 5% 4 6% 5% 8% 11% 41%	3079
June	1st to 10th	Night	5% 5% 3 8% 6% 6% 6% 5% 8% 11% 35%	1710
	11th to 20th	Night	4 3 2 4 5% 5% 6% 5% 9% 14% 45%	1710
	21st to end	Night	4 5% 2 6% 6% 5% 6% 5% 7% 10% 44%	1710
July	1st to 10th	Night	7% 7% 3 8% 6% 6% 6% 6% 8% 13% 32%	2840
	11th to 20th	Night	6% 5% 2 6% 5% 5% 5% 5% 8% 11% 40%	2840
	21st to end	Night	10% 9% 4 10% 6% 7% 8% 6% 9% 9% 23%	3087
August	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 5% 8% 13% 41%	2825
	11th to 20th	Night	7% 6% 2 7% 6% 4 5% 4 7% 9% 44%	2993
	21st to end	Night	6% 4 2 5% 4 4 5% 4 6% 9% 49%	3476
September	1st to 10th	Night	8% 6% 2 7% 6% 5% 5% 4 7% 9% 39%	2050
	11th to 20th	Night	9% 7% 3 8% 4 5% 5% 4 6% 8% 40%	2090
	21st to end	Night	8% 6% 2 6% 3 4 4 4 5% 6% 50%	2090
October	1st to 10th	Night	9% 5% 2 4 3 3 3 2 4 6% 58%	2090
	11th to 20th	Night	9% 7% 2 6% 4 3 4 3 4 5% 54%	2202
	21st to end	Night	10% 6% 2 6% 4 3 3 3 4 5% 55%	2519
November	1st to 10th	Night	10% 6% 2 5% 4 3 4 3 5% 6% 51%	2536
	11th to 20th	Night	11% 9% 3 6% 4 3 3 3 4 6% 49%	2600
	21st to end	Night	11% 9% 3 6% 4 4 4 4 5% 6% 43%	2600
December	1st to 10th	Night	12% 8% 3 8% 5% 4 4 3 5% 5% 43%	4250
	11th to 20th	Night	14% 12% 4 9% 4 5% 4 4 4 5% 35%	4822
	21st to end	Night	13% 10% 5% 10% 5% 5% 5% 3 5% 6% 34%	6490

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	45% 3 6% 18% 26% 3	4057
	11th to 20th	Day	41% 4 5% 15% 30% 6%	4060
	21st to end	Day	51% 3 5% 17% 18% 6%	4581
February	1st to 10th	Day	49% 4 7% 19% 18% 3	2000
	11th to 20th	Day	51% 5% 6% 16% 17% 5%	1958
	21st to end	Day	50% 4 7% 13% 21% 6%	1650
March	1st to 10th	Day	48% 6% 6% 12% 19% 8%	4606
	11th to 20th	Day	35% 4 6% 16% 23% 15%	4980
	21st to end	Day	43% 4 8% 26% 15% 4	5465
April	1st to 10th	Day	41% 6% 12% 19% 18% 4	2280
	11th to 20th	Day	40% 5% 9% 17% 24% 4	2254
	21st to end	Day	38% 6% 12% 27% 14% 3	2446
May	1st to 10th	Day	43% 11% 11% 20% 13% 2	4120
	11th to 20th	Day	49% 10% 11% 21% 8% 1	4085
	21st to end	Day	38% 10% 13% 22% 16% 1	4489
June	1st to 10th	Day	45% 12% 15% 20% 8% 1	2470
	11th to 20th	Day	38% 11% 17% 22% 11% 1	2470
	21st to end	Day	40% 11% 17% 18% 12% 2	2470
July	1st to 10th	Day	45% 10% 20% 18% 5% 1	4055
	11th to 20th	Day	48% 9% 20% 16% 5% 1	4051
	21st to end	Day	62% 10% 14% 10% 4	4324
August	1st to 10th	Day	39% 9% 15% 29% 8%	4091
	11th to 20th	Day	37% 8% 19% 22% 13% 1	3871
	21st to end	Day	39% 7% 11% 26% 15% 2	4179
September	1st to 10th	Day	44% 10% 12% 16% 16% 4	2109
	11th to 20th	Day	44% 9% 12% 18% 16% 1	2090
	21st to end	Day	39% 6% 13% 16% 20% 5%	2090
October	1st to 10th	Day	29% 5% 5% 15% 35% 11%	3480
	11th to 20th	Day	21% 4 6% 19% 28% 22%	3268
	21st to end	Day	28% 3 6% 26% 26% 12%	3402
November	1st to 10th	Day	32% 4 8% 16% 31% 9%	1762
	11th to 20th	Day	36% 4 7% 19% 25% 9%	1800
	21st to end	Day	40% 4 7% 18% 25% 5%	1800
December	1st to 10th	Day	42% 4 6% 17% 26% 6%	2930
	11th to 20th	Day	52% 4 8% 16% 17% 4	3370
	21st to end	Day	47% 4 10% 25% 13% 2	4466
January	1st to 10th	Night	46% 3 7% 17% 24% 3	5889
	11th to 20th	Night	42% 6% 6% 16% 22% 8%	5900
	21st to end	Night	46% 3 5% 17% 23% 6%	6370
February	1st to 10th	Night	45% 4 9% 18% 20% 4	2400
	11th to 20th	Night	52% 4 6% 16% 16% 5%	2339
	21st to end	Night	49% 5% 7% 15% 17% 6%	1980
March	1st to 10th	Night	50% 5% 7% 13% 21% 4	5246
	11th to 20th	Night	33% 4 9% 19% 22% 14%	4980
	21st to end	Night	43% 4 8% 24% 16% 4	5467
April	1st to 10th	Night	35% 6% 13% 20% 21% 4	2135
	11th to 20th	Night	36% 5% 10% 21% 20% 7%	1881
	21st to end	Night	35% 7% 11% 28% 18% 2	1733
May	1st to 10th	Night	39% 12% 16% 21% 12% 1	2840
	11th to 20th	Night	45% 9% 14% 22% 9%	2813
	21st to end	Night	30% 12% 18% 26% 13% 1	3087
June	1st to 10th	Night	39% 11% 18% 20% 10% 1	1710
	11th to 20th	Night	26% 11% 25% 26% 11% 1	1710
	21st to end	Night	32% 11% 21% 19% 14% 4	1710
July	1st to 10th	Night	41% 12% 21% 20% 6%	2795
	11th to 20th	Night	34% 10% 27% 22% 5% 2	2786
	21st to end	Night	52% 14% 15% 13% 5% 1	2988
August	1st to 10th	Night	33% 8% 20% 31% 7%	2814
	11th to 20th	Night	35% 7% 20% 25% 12%	3020
	21st to end	Night	30% 7% 16% 29% 17% 1	3476
September	1st to 10th	Night	38% 10% 16% 18% 14% 4	2050
	11th to 20th	Night	39% 10% 13% 20% 17% 1	2090
	21st to end	Night	33% 8% 11% 21% 21% 6%	2090
October	1st to 10th	Night	27% 4 8% 18% 31% 12%	3480
	11th to 20th	Night	22% 3 6% 18% 33% 18%	3649
	21st to end	Night	24% 3 4 28% 28% 13%	4143
November	1st to 10th	Night	34% 5% 8% 21% 24% 9%	2536
	11th to 20th	Night	37% 3 6% 20% 24% 10%	2600
	21st to end	Night	41% 5% 8% 20% 22% 5%	2600
December	1st to 10th	Night	42% 4 7% 17% 24% 5%	4250
	11th to 20th	Night	50% 5% 8% 14% 19% 4	4824
	21st to end	Night	48% 4 11% 23% 13% 1	6490

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	28% 28% 31% 12% 1	300
	11th to 20th	Day	30% 24% 29% 13% 4	300
	21st to end	Day	24% 32% 28% 13% 4	330
February	1st to 10th	Day	26% 24% 36% 12% 3	300
	11th to 20th	Day	36% 30% 24% 9% 1	300
	21st to end	Day	35% 28% 27% 6% 3	249
March	1st to 10th	Day	31% 19% 30% 14% 4 1	348
	11th to 20th	Day	25% 21% 29% 18% 7% 1	500
	21st to end	Day	25% 23% 29% 16% 6% 1	550
April	1st to 10th	Day	25% 18% 28% 19% 9% 2	500
	11th to 20th	Day	19% 18% 30% 20% 12% 1	452
	21st to end	Day	19% 15% 28% 23% 12% 4	460
May	1st to 10th	Day	14% 16% 31% 20% 12% 6%	463
	11th to 20th	Day	15% 10% 22% 28% 15% 9%	487
	21st to end	Day	12% 6% 22% 28% 20% 12%	529
June	1st to 10th	Day	11% 6% 23% 27% 20% 14%	490
	11th to 20th	Day	7% 5% 18% 27% 24% 19%	490
	21st to end	Day	10% 4 23% 23% 22% 17%	490
July	1st to 10th	Day	11% 4 12% 24% 28% 22%	485
	11th to 20th	Day	9% 3 11% 27% 27% 23%	484
	21st to end	Day	9% 4 10% 24% 28% 25%	532
August	1st to 10th	Day	10% 5% 17% 23% 22% 23%	486
	11th to 20th	Day	10% 4 17% 24% 26% 19%	479
	21st to end	Day	14% 3 11% 20% 30% 23%	539
September	1st to 10th	Day	8% 3 16% 24% 33% 15%	490
	11th to 20th	Day	16% 5% 14% 22% 29% 14%	490
	21st to end	Day	15% 7% 15% 28% 26% 9%	490
October	1st to 10th	Day	14% 7% 20% 29% 22% 8%	490
	11th to 20th	Day	17% 10% 24% 25% 19% 5%	490
	21st to end	Day	16% 13% 22% 27% 18% 4	525
November	1st to 10th	Day	18% 14% 31% 23% 11% 3	300
	11th to 20th	Day	21% 20% 34% 18% 8%	300
	21st to end	Day	16% 22% 34% 19% 7% 1	300
December	1st to 10th	Day	27% 28% 25% 17% 2 1	300
	11th to 20th	Day	24% 20% 30% 20% 5% 1	300
	21st to end	Day	25% 23% 31% 15% 7%	330
January	1st to 10th	Night	25% 21% 28% 21% 5%	800
	11th to 20th	Night	22% 22% 29% 22% 6%	800
	21st to end	Night	21% 20% 32% 25% 2	880
February	1st to 10th	Night	23% 16% 27% 29% 5%	800
	11th to 20th	Night	28% 21% 30% 19% 2	783
	21st to end	Night	26% 21% 30% 21% 2	660
March	1st to 10th	Night	20% 20% 32% 25% 4	800
	11th to 20th	Night	20% 17% 30% 25% 7% 1	800
	21st to end	Night	19% 16% 29% 28% 8%	880
April	1st to 10th	Night	16% 18% 26% 30% 10% 1	735
	11th to 20th	Night	15% 16% 27% 30% 12% 1	565
	21st to end	Night	14% 9% 25% 35% 16% 1	570
May	1st to 10th	Night	11% 9% 25% 35% 17% 2	570
	11th to 20th	Night	12% 7% 21% 32% 23% 6%	561
	21st to end	Night	9% 4 13% 34% 34% 7%	617
June	1st to 10th	Night	8% 3 14% 34% 36% 5%	570
	11th to 20th	Night	4 2 12% 31% 37% 14%	570
	21st to end	Night	5% 2 9% 33% 41% 10%	570
July	1st to 10th	Night	9% 3 6% 22% 47% 13%	555
	11th to 20th	Night	8% 1 8% 22% 45% 16%	552
	21st to end	Night	8% 2 5% 23% 50% 12%	624
August	1st to 10th	Night	8% 2 4 28% 43% 14%	567
	11th to 20th	Night	9% 2 9% 26% 46% 8%	564
	21st to end	Night	13% 2 8% 22% 43% 11%	627
September	1st to 10th	Night	11% 3 9% 28% 41% 9%	720
	11th to 20th	Night	13% 3 14% 28% 38% 5%	760
	21st to end	Night	11% 2 14% 36% 33% 3	760
October	1st to 10th	Night	12% 7% 18% 32% 25% 7%	760
	11th to 20th	Night	13% 9% 24% 30% 22% 2	760
	21st to end	Night	16% 10% 18% 37% 18% 2	836
November	1st to 10th	Night	16% 8% 22% 32% 19% 3	780
	11th to 20th	Night	18% 12% 26% 30% 13% 2	800
	21st to end	Night	18% 16% 25% 28% 12% 1	800
December	1st to 10th	Night	24% 18% 24% 26% 8% 1	800
	11th to 20th	Night	20% 15% 28% 28% 8% 1	800
	21st to end	Night	24% 17% 26% 27% 6%	880

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