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 2024-02-20.

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	11% 8% 4 7% 6% 4 5% 6% 6% 7% 37%	78761
	Night	11% 8% 3 6% 5% 3 5% 5% 5% 7% 41%	80436
Transparency	Day	44% 8% 11% 17% 16% 4	78484
	Night	41% 7% 12% 19% 17% 4	80232
Seeing	Day	17% 13% 23% 21% 17% 10%	13829
	Night	16% 11% 21% 28% 21% 4	23965

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	14% 11% 6% 6% 6% 3 4 5% 5% 6% 34%	2836
	11th to 20th	Day	14% 8% 6% 10% 5% 2 4 3 4 5% 39%	2840
	21st to end	Day	17% 15% 6% 6% 4 2 3 3 4 5% 35%	3197
February	1st to 10th	Day	13% 11% 4 7% 6% 3 4 5% 5% 6% 35%	1900
	11th to 20th	Day	16% 8% 5% 8% 6% 3 4 5% 5% 6% 35%	1838
	21st to end	Day	18% 11% 3 7% 5% 4 4 4 4 5% 35%	1480
March	1st to 10th	Day	12% 8% 3 6% 5% 3 5% 5% 6% 8% 40%	1842
	11th to 20th	Day	15% 9% 4 6% 7% 3 5% 5% 6% 6% 35%	1980
	21st to end	Day	12% 10% 3 8% 6% 4 5% 4 6% 7% 36%	2178
April	1st to 10th	Day	10% 7% 2 6% 6% 4 5% 5% 6% 7% 42%	2052
	11th to 20th	Day	12% 7% 3 6% 5% 3 5% 5% 5% 7% 43%	2134
	21st to end	Day	10% 7% 3 5% 5% 4 4 5% 7% 7% 43%	2317
May	1st to 10th	Day	11% 7% 3 6% 4 3 6% 6% 5% 8% 41%	2340
	11th to 20th	Day	12% 7% 4 7% 7% 4 6% 6% 6% 7% 35%	2301
	21st to end	Day	9% 5% 3 8% 7% 4 7% 6% 6% 9% 36%	2531
June	1st to 10th	Day	9% 7% 3 7% 7% 4 7% 7% 7% 9% 31%	2340
	11th to 20th	Day	5% 5% 3 6% 7% 5% 8% 9% 8% 10% 36%	2340
	21st to end	Day	7% 6% 3 6% 7% 4 8% 7% 8% 11% 33%	2340
July	1st to 10th	Day	9% 6% 4 8% 9% 5% 9% 8% 8% 11% 24%	2340
	11th to 20th	Day	9% 6% 3 8% 9% 5% 10% 8% 9% 10% 24%	2340
	21st to end	Day	7% 6% 3 8% 10% 6% 8% 8% 9% 10% 25%	2547
August	1st to 10th	Day	8% 5% 3 7% 8% 6% 8% 9% 9% 11% 26%	2327
	11th to 20th	Day	10% 7% 3 7% 9% 5% 7% 7% 7% 10% 29%	2189
	21st to end	Day	13% 7% 3 7% 10% 5% 6% 7% 6% 8% 28%	2376
September	1st to 10th	Day	10% 7% 3 7% 8% 4 6% 6% 6% 8% 33%	1998
	11th to 20th	Day	13% 7% 3 6% 6% 4 5% 6% 6% 9% 35%	1980
	21st to end	Day	13% 5% 2 5% 5% 4 5% 5% 5% 8% 43%	1980
October	1st to 10th	Day	10% 5% 3 4 5% 3 4 4 4 6% 51%	1980
	11th to 20th	Day	11% 7% 2 4 4 2 3 4 5% 6% 52%	1872
	21st to end	Day	11% 7% 2 5% 4 3 3 4 4 5% 52%	1967
November	1st to 10th	Day	10% 5% 3 4 3 2 3 4 4 6% 55%	1672
	11th to 20th	Day	11% 6% 2 6% 4 3 4 4 5% 6% 49%	1710
	21st to end	Day	12% 9% 2 5% 5% 3 4 5% 5% 7% 44%	1710
December	1st to 10th	Day	16% 10% 5% 7% 5% 3 5% 5% 5% 5% 34%	1710
	11th to 20th	Day	13% 8% 5% 6% 5% 4 5% 4 5% 6% 39%	2153
	21st to end	Day	15% 9% 6% 7% 6% 3 5% 5% 5% 7% 33%	3124
January	1st to 10th	Night	14% 12% 5% 7% 5% 2 5% 4 4 5% 36%	4109
	11th to 20th	Night	10% 10% 5% 8% 6% 3 4 4 5% 6% 38%	4120
	21st to end	Night	16% 17% 5% 7% 5% 2 4 3 3 4 34%	4454
February	1st to 10th	Night	13% 8% 5% 6% 6% 3 4 5% 5% 6% 40%	2280
	11th to 20th	Night	17% 10% 5% 8% 6% 3 5% 4 4 4 36%	2213
	21st to end	Night	18% 11% 4 7% 6% 3 5% 4 5% 5% 33%	1776
March	1st to 10th	Night	11% 8% 4 6% 6% 3 5% 4 4 6% 43%	2117
	11th to 20th	Night	14% 8% 4 6% 4 3 5% 5% 6% 7% 37%	1980
	21st to end	Night	11% 10% 3 8% 6% 3 5% 3 5% 6% 40%	2178
April	1st to 10th	Night	9% 6% 2 5% 4 3 5% 5% 5% 9% 47%	1922
	11th to 20th	Night	10% 7% 3 5% 4 3 4 4 5% 8% 48%	1775
	21st to end	Night	10% 6% 3 5% 4 3 4 4 5% 7% 49%	1642
May	1st to 10th	Night	9% 6% 3 5% 5% 4 5% 5% 5% 8% 46%	1620
	11th to 20th	Night	8% 6% 3 6% 5% 4 6% 6% 7% 9% 39%	1592
	21st to end	Night	6% 6% 3 5% 6% 3 5% 6% 8% 11% 42%	1744
June	1st to 10th	Night	6% 4 3 7% 7% 4 8% 6% 8% 12% 36%	1620
	11th to 20th	Night	4 3 2 4 5% 4 6% 6% 9% 14% 45%	1620
	21st to end	Night	4 4 2 5% 5% 4 6% 7% 7% 11% 45%	1620
July	1st to 10th	Night	8% 5% 3 6% 6% 5% 7% 7% 8% 12% 33%	1620
	11th to 20th	Night	7% 4 2 5% 6% 5% 6% 6% 9% 14% 37%	1620
	21st to end	Night	5% 5% 3 5% 5% 4 8% 7% 10% 12% 36%	1771
August	1st to 10th	Night	5% 4 3 5% 6% 4 6% 7% 8% 12% 39%	1611
	11th to 20th	Night	7% 5% 3 5% 7% 4 6% 5% 6% 11% 40%	1708
	21st to end	Night	10% 6% 3 6% 6% 3 6% 6% 7% 10% 36%	1980
September	1st to 10th	Night	8% 5% 3 6% 6% 4 5% 6% 7% 9% 40%	1942
	11th to 20th	Night	9% 6% 3 6% 5% 4 5% 5% 6% 9% 41%	1980
	21st to end	Night	8% 5% 3 5% 4 3 5% 5% 5% 7% 51%	1980
October	1st to 10th	Night	10% 5% 2 3 3 2 3 3 4 6% 59%	1980
	11th to 20th	Night	10% 6% 2 6% 4 2 4 4 4 5% 52%	2086
	21st to end	Night	10% 6% 3 5% 5% 2 4 3 4 5% 53%	2386
November	1st to 10th	Night	11% 6% 2 4 4 2 4 4 4 6% 53%	2406
	11th to 20th	Night	11% 8% 3 5% 4 2 3 3 4 6% 50%	2470
	21st to end	Night	12% 8% 3 5% 5% 3 4 6% 5% 6% 43%	2470
December	1st to 10th	Night	15% 10% 4 7% 6% 3 5% 4 5% 7% 33%	2470
	11th to 20th	Night	12% 12% 5% 7% 4 2 4 4 4 5% 41%	3042
	21st to end	Night	15% 11% 5% 8% 7% 4 5% 5% 5% 7% 30%	4532

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	49% 4 8% 13% 23% 3	2837
	11th to 20th	Day	47% 5% 7% 14% 22% 4	2840
	21st to end	Day	52% 4 6% 15% 19% 3	3197
February	1st to 10th	Day	50% 5% 7% 18% 18% 4	1900
	11th to 20th	Day	50% 5% 6% 16% 17% 5%	1848
	21st to end	Day	51% 4 7% 13% 18% 6%	1480
March	1st to 10th	Day	42% 7% 9% 15% 21% 8%	1842
	11th to 20th	Day	49% 7% 11% 14% 16% 4	1980
	21st to end	Day	47% 7% 10% 21% 14% 2	2178
April	1st to 10th	Day	40% 6% 12% 20% 18% 4	2052
	11th to 20th	Day	40% 5% 10% 17% 23% 4	2134
	21st to end	Day	38% 6% 12% 26% 14% 2	2317
May	1st to 10th	Day	40% 8% 11% 22% 15% 3	2340
	11th to 20th	Day	45% 10% 12% 19% 12% 1	2305
	21st to end	Day	41% 10% 13% 21% 13% 2	2531
June	1st to 10th	Day	45% 11% 15% 20% 8% 1	2340
	11th to 20th	Day	39% 11% 17% 21% 10% 1	2340
	21st to end	Day	40% 11% 17% 18% 11% 2	2340
July	1st to 10th	Day	47% 13% 17% 17% 5% 1	2275
	11th to 20th	Day	47% 13% 18% 11% 8% 2	2271
	21st to end	Day	47% 14% 17% 15% 6%	2405
August	1st to 10th	Day	45% 14% 18% 17% 5% 1	2314
	11th to 20th	Day	48% 11% 16% 16% 9% 1	2189
	21st to end	Day	52% 11% 12% 14% 8% 3	2376
September	1st to 10th	Day	44% 10% 12% 16% 14% 4	1998
	11th to 20th	Day	43% 10% 12% 18% 16% 1	1980
	21st to end	Day	39% 7% 12% 16% 21% 6%	1980
October	1st to 10th	Day	34% 7% 9% 17% 27% 7%	1980
	11th to 20th	Day	32% 6% 10% 22% 22% 9%	1872
	21st to end	Day	35% 4 7% 20% 27% 8%	1967
November	1st to 10th	Day	31% 4 8% 16% 32% 10%	1672
	11th to 20th	Day	36% 5% 7% 19% 25% 10%	1710
	21st to end	Day	41% 4 7% 17% 25% 5%	1710
December	1st to 10th	Day	51% 5% 7% 17% 16% 4	1710
	11th to 20th	Day	45% 5% 9% 14% 22% 5%	2150
	21st to end	Day	50% 5% 9% 19% 16% 2	3124
January	1st to 10th	Night	49% 4 8% 15% 22% 3	4109
	11th to 20th	Night	45% 7% 8% 15% 16% 9%	4120
	21st to end	Night	55% 3 6% 12% 20% 4	4454
February	1st to 10th	Night	45% 4 9% 17% 20% 5%	2280
	11th to 20th	Night	52% 5% 6% 16% 17% 5%	2214
	21st to end	Night	53% 5% 8% 15% 15% 5%	1776
March	1st to 10th	Night	43% 5% 9% 16% 20% 8%	2117
	11th to 20th	Night	45% 6% 12% 18% 16% 4	1980
	21st to end	Night	46% 5% 11% 22% 14% 2	2178
April	1st to 10th	Night	34% 6% 12% 21% 22% 4	1922
	11th to 20th	Night	35% 5% 10% 22% 20% 8%	1775
	21st to end	Night	35% 7% 11% 28% 18% 2	1642
May	1st to 10th	Night	35% 8% 15% 23% 17% 2	1620
	11th to 20th	Night	38% 11% 16% 22% 11% 1	1593
	21st to end	Night	33% 11% 16% 26% 11% 2	1745
June	1st to 10th	Night	38% 11% 18% 21% 9% 2	1620
	11th to 20th	Night	26% 11% 26% 26% 10% 1	1620
	21st to end	Night	31% 11% 21% 19% 14% 3	1620
July	1st to 10th	Night	38% 14% 18% 18% 10% 1	1575
	11th to 20th	Night	32% 13% 28% 15% 9% 4	1566
	21st to end	Night	34% 17% 19% 21% 8% 1	1672
August	1st to 10th	Night	34% 13% 22% 23% 7%	1600
	11th to 20th	Night	37% 11% 20% 18% 14% 1	1708
	21st to end	Night	40% 11% 19% 20% 9% 2	1980
September	1st to 10th	Night	37% 10% 16% 18% 14% 4	1942
	11th to 20th	Night	37% 11% 14% 20% 18% 1	1980
	21st to end	Night	31% 9% 10% 22% 22% 6%	1980
October	1st to 10th	Night	28% 5% 12% 21% 27% 7%	1980
	11th to 20th	Night	34% 5% 10% 21% 22% 8%	2086
	21st to end	Night	34% 4 6% 21% 27% 9%	2386
November	1st to 10th	Night	33% 5% 7% 21% 25% 9%	2406
	11th to 20th	Night	36% 3 7% 20% 24% 10%	2470
	21st to end	Night	41% 5% 8% 20% 22% 5%	2470
December	1st to 10th	Night	49% 6% 10% 15% 15% 5%	2470
	11th to 20th	Night	44% 5% 8% 13% 25% 4	3044
	21st to end	Night	51% 5% 10% 18% 13% 2	4532

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% 26% 34% 13% 1	270
	11th to 20th	Day	30% 23% 29% 14% 4	270
	21st to end	Day	24% 32% 29% 11% 4	297
February	1st to 10th	Day	28% 23% 35% 11% 3	270
	11th to 20th	Day	34% 32% 26% 8%	267
	21st to end	Day	35% 30% 27% 5% 2	198
March	1st to 10th	Day	26% 21% 34% 15% 5% 1	282
	11th to 20th	Day	25% 22% 28% 17% 7% 1	420
	21st to end	Day	24% 23% 30% 16% 7% 1	462
April	1st to 10th	Day	23% 16% 28% 21% 10% 2	420
	11th to 20th	Day	18% 18% 30% 20% 12% 1	412
	21st to end	Day	20% 15% 26% 21% 13% 4	420
May	1st to 10th	Day	15% 16% 31% 21% 12% 6%	423
	11th to 20th	Day	14% 9% 22% 30% 15% 10%	447
	21st to end	Day	12% 6% 19% 28% 21% 13%	485
June	1st to 10th	Day	11% 5% 21% 28% 20% 15%	450
	11th to 20th	Day	7% 5% 18% 26% 25% 20%	450
	21st to end	Day	9% 5% 23% 24% 22% 17%	450
July	1st to 10th	Day	11% 4 11% 23% 28% 23%	445
	11th to 20th	Day	9% 3 10% 26% 28% 24%	444
	21st to end	Day	8% 3 9% 24% 29% 27%	488
August	1st to 10th	Day	11% 4 15% 21% 24% 24%	446
	11th to 20th	Day	10% 3 15% 24% 28% 20%	439
	21st to end	Day	15% 3 12% 20% 28% 22%	495
September	1st to 10th	Day	8% 4 16% 23% 33% 16%	450
	11th to 20th	Day	14% 6% 13% 22% 30% 15%	450
	21st to end	Day	13% 7% 14% 29% 27% 10%	450
October	1st to 10th	Day	15% 7% 20% 27% 22% 8%	450
	11th to 20th	Day	17% 10% 24% 25% 19% 5%	450
	21st to end	Day	18% 13% 22% 27% 17% 3	482
November	1st to 10th	Day	19% 15% 28% 24% 11% 3	270
	11th to 20th	Day	21% 19% 34% 19% 8%	270
	21st to end	Day	15% 21% 36% 20% 7% 1	270
December	1st to 10th	Day	27% 26% 25% 17% 3 1	270
	11th to 20th	Day	24% 20% 30% 20% 6% 1	270
	21st to end	Day	24% 24% 32% 14% 5%	297
January	1st to 10th	Night	24% 21% 28% 21% 5%	760
	11th to 20th	Night	22% 22% 28% 22% 6%	760
	21st to end	Night	22% 20% 31% 25% 3	836
February	1st to 10th	Night	23% 16% 27% 29% 5%	760
	11th to 20th	Night	27% 21% 30% 19% 2	742
	21st to end	Night	27% 21% 29% 21% 2	592
March	1st to 10th	Night	18% 20% 33% 25% 4	720
	11th to 20th	Night	21% 18% 29% 23% 8% 1	720
	21st to end	Night	19% 15% 29% 27% 9%	792
April	1st to 10th	Night	15% 16% 26% 31% 11% 1	662
	11th to 20th	Night	15% 16% 26% 29% 13% 1	533
	21st to end	Night	14% 9% 25% 35% 17% 1	540
May	1st to 10th	Night	11% 9% 25% 35% 17% 2	540
	11th to 20th	Night	11% 7% 21% 32% 24% 6%	531
	21st to end	Night	9% 4 12% 33% 35% 7%	584
June	1st to 10th	Night	8% 3 12% 34% 37% 6%	540
	11th to 20th	Night	4 2 13% 31% 36% 15%	540
	21st to end	Night	4 2 9% 34% 41% 10%	540
July	1st to 10th	Night	9% 3 5% 22% 47% 13%	525
	11th to 20th	Night	8% 1 8% 22% 45% 16%	522
	21st to end	Night	6% 2 6% 21% 52% 13%	591
August	1st to 10th	Night	8% 3 4 27% 44% 15%	537
	11th to 20th	Night	8% 1 8% 25% 48% 9%	534
	21st to end	Night	13% 2 9% 22% 43% 11%	594
September	1st to 10th	Night	11% 3 9% 27% 42% 9%	682
	11th to 20th	Night	12% 3 13% 28% 38% 5%	720
	21st to end	Night	10% 2 14% 37% 33% 3	720
October	1st to 10th	Night	12% 7% 18% 31% 24% 7%	720
	11th to 20th	Night	14% 9% 24% 30% 22% 2	720
	21st to end	Night	16% 10% 19% 36% 17% 2	792
November	1st to 10th	Night	16% 9% 21% 32% 19% 4	740
	11th to 20th	Night	18% 13% 26% 30% 13% 2	760
	21st to end	Night	19% 15% 25% 29% 13% 1	760
December	1st to 10th	Night	24% 18% 24% 26% 8% 1	760
	11th to 20th	Night	20% 15% 28% 28% 8% 1	760
	21st to end	Night	24% 17% 26% 27% 6%	836

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