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 2026-08-15.

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% 6% 5% 5% 5% 6% 8% 36%	143300
	Night	10% 8% 3 8% 5% 5% 5% 4 6% 7% 40%	138610
Transparency	Day	44% 6% 12% 19% 15% 4	147076
	Night	41% 6% 12% 20% 17% 5%	142905
Seeing	Day	17% 13% 23% 22% 16% 9%	17183
	Night	16% 11% 21% 28% 20% 4	27164

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% 10% 5% 8% 5% 4 4 3 4 4 40%	5258
	11th to 20th	Day	9% 7% 5% 8% 3 3 3 2 3 4 53%	5280
	21st to end	Day	15% 15% 5% 9% 4 4 3 3 4 6% 33%	5937
February	1st to 10th	Day	11% 11% 4 8% 6% 4 4 4 5% 6% 36%	2100
	11th to 20th	Day	16% 10% 4 9% 6% 4 4 3 5% 6% 34%	2048
	21st to end	Day	15% 11% 3 8% 5% 4 4 4 5% 5% 36%	1730
March	1st to 10th	Day	16% 10% 4 7% 5% 5% 5% 4 5% 6% 34%	4708
	11th to 20th	Day	9% 7% 3 6% 5% 4 4 3 5% 7% 49%	5090
	21st to end	Day	13% 9% 3 7% 4 4 4 3 5% 6% 42%	5586
April	1st to 10th	Day	10% 7% 2 7% 6% 6% 5% 4 7% 7% 41%	2394
	11th to 20th	Day	10% 7% 3 7% 4 4 4 4 5% 7% 46%	2494
	21st to end	Day	10% 7% 3 7% 4 5% 4 4 7% 7% 42%	2704
May	1st to 10th	Day	13% 9% 3 8% 5% 5% 6% 5% 7% 8% 32%	7616
	11th to 20th	Day	11% 8% 3 9% 6% 6% 6% 5% 7% 8% 30%	7626
	21st to end	Day	11% 9% 4 12% 7% 6% 6% 4 6% 7% 28%	8391
June	1st to 10th	Day	9% 8% 3 8% 6% 6% 7% 6% 8% 10% 31%	2730
	11th to 20th	Day	5% 5% 3 6% 6% 7% 8% 7% 9% 10% 34%	2730
	21st to end	Day	7% 6% 3 6% 6% 7% 6% 6% 9% 12% 33%	2730
July	1st to 10th	Day	5% 5% 2 8% 7% 8% 8% 7% 10% 12% 30%	7680
	11th to 20th	Day	7% 7% 3 9% 8% 8% 9% 7% 10% 12% 20%	7680
	21st to end	Day	8% 8% 4 10% 8% 8% 8% 6% 9% 10% 21%	8340
August	1st to 10th	Day	6% 4 2 8% 6% 7% 8% 7% 9% 11% 32%	4364
	11th to 20th	Day	6% 5% 2 7% 6% 7% 6% 5% 8% 11% 36%	4007
	21st to end	Day	8% 5% 2 7% 7% 6% 6% 5% 6% 8% 41%	4312
September	1st to 10th	Day	10% 7% 3 8% 7% 6% 6% 4 7% 8% 34%	2220
	11th to 20th	Day	13% 7% 3 7% 6% 5% 5% 5% 7% 9% 35%	2200
	21st to end	Day	12% 5% 2 7% 4 5% 5% 4 6% 8% 40%	2200
October	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 4 6% 50%	2200
	11th to 20th	Day	10% 7% 2 4 3 3 3 3 5% 6% 54%	2080
	21st to end	Day	11% 7% 2 5% 4 4 3 3 4 5% 53%	2185
November	1st to 10th	Day	10% 6% 3 5% 3 3 4 3 5% 6% 53%	1852
	11th to 20th	Day	11% 6% 2 6% 4 3 4 3 5% 6% 50%	1890
	21st to end	Day	12% 9% 2 6% 4 3 4 4 5% 7% 44%	1890
December	1st to 10th	Day	13% 10% 3 7% 4 4 4 3 4 5% 44%	3020
	11th to 20th	Day	11% 10% 6% 10% 6% 6% 5% 3 5% 5% 35%	3463
	21st to end	Day	12% 9% 5% 9% 5% 4 4 4 5% 8% 36%	4565
January	1st to 10th	Night	13% 9% 4 10% 4 4 4 3 5% 5% 39%	7635
	11th to 20th	Night	11% 10% 3 8% 4 3 3 2 4 5% 46%	7680
	21st to end	Night	14% 13% 4 8% 5% 4 4 3 4 4 39%	8239
February	1st to 10th	Night	12% 9% 4 7% 5% 4 4 4 6% 6% 39%	2520
	11th to 20th	Night	17% 11% 3 9% 5% 4 4 3 4 4 35%	2458
	21st to end	Night	16% 11% 3 8% 5% 4 4 3 5% 6% 35%	2076
March	1st to 10th	Night	15% 13% 4 7% 5% 5% 5% 4 5% 6% 31%	5364
	11th to 20th	Night	10% 7% 2 5% 3 3 4 4 6% 7% 49%	5090
	21st to end	Night	10% 10% 3 7% 5% 5% 4 3 5% 6% 42%	5588
April	1st to 10th	Night	9% 6% 2 6% 4 4 5% 5% 5% 8% 45%	2242
	11th to 20th	Night	10% 7% 2 6% 4 3 4 2 5% 8% 48%	2075
	21st to end	Night	10% 7% 3 6% 4 4 4 3 5% 6% 48%	1915
May	1st to 10th	Night	10% 8% 3 8% 6% 6% 6% 4 7% 8% 32%	5237
	11th to 20th	Night	11% 10% 4 8% 5% 6% 5% 4 6% 9% 33%	5234
	21st to end	Night	11% 9% 4 10% 7% 6% 5% 4 6% 8% 29%	5761
June	1st to 10th	Night	6% 5% 3 8% 6% 6% 6% 4 8% 11% 36%	1890
	11th to 20th	Night	4 3 2 4 5% 5% 5% 5% 8% 13% 43%	1890
	21st to end	Night	4 4 2 6% 5% 5% 6% 6% 7% 11% 45%	1890
July	1st to 10th	Night	5% 5% 2 7% 5% 6% 7% 6% 8% 13% 35%	5278
	11th to 20th	Night	5% 6% 3 9% 6% 7% 7% 6% 9% 11% 31%	5277
	21st to end	Night	8% 7% 3 9% 6% 7% 7% 5% 8% 11% 28%	5736
August	1st to 10th	Night	6% 4 2 6% 5% 6% 6% 5% 8% 13% 40%	3005
	11th to 20th	Night	7% 6% 3 7% 6% 5% 5% 4 7% 9% 43%	3125
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	3586
September	1st to 10th	Night	8% 6% 3 7% 6% 5% 5% 4 7% 9% 39%	2158
	11th to 20th	Night	9% 7% 3 8% 4 5% 5% 4 6% 9% 41%	2200
	21st to end	Night	9% 6% 3 6% 4 4 4 4 6% 7% 48%	2200
October	1st to 10th	Night	10% 6% 2 4 3 3 4 2 4 6% 57%	2200
	11th to 20th	Night	9% 6% 2 6% 4 3 4 3 4 5% 55%	2318
	21st to end	Night	10% 7% 2 6% 4 3 3 3 5% 5% 54%	2652
November	1st to 10th	Night	10% 6% 3 5% 4 3 4 3 5% 6% 51%	2666
	11th to 20th	Night	10% 8% 3 6% 4 3 3 2 5% 6% 50%	2730
	21st to end	Night	11% 9% 3 7% 4 4 4 4 5% 6% 43%	2730
December	1st to 10th	Night	13% 8% 3 8% 5% 4 4 3 5% 5% 42%	4380
	11th to 20th	Night	14% 12% 4 8% 4 5% 4 4 4 5% 36%	4952
	21st to end	Night	12% 10% 5% 10% 5% 5% 5% 3 5% 6% 34%	6633

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	48% 2 8% 20% 20% 2	5259
	11th to 20th	Day	36% 3 4 13% 33% 10%	5280
	21st to end	Day	54% 2 5% 16% 15% 7%	5937
February	1st to 10th	Day	48% 4 6% 20% 18% 3	2100
	11th to 20th	Day	51% 5% 6% 17% 17% 5%	2058
	21st to end	Day	50% 4 7% 14% 20% 6%	1730
March	1st to 10th	Day	48% 6% 7% 13% 19% 8%	4708
	11th to 20th	Day	35% 4 6% 17% 22% 15%	5090
	21st to end	Day	43% 4 8% 26% 15% 4	5586
April	1st to 10th	Day	41% 6% 12% 20% 17% 4	2394
	11th to 20th	Day	38% 5% 9% 20% 24% 4	2494
	21st to end	Day	39% 6% 12% 27% 14% 2	2704
May	1st to 10th	Day	47% 7% 12% 22% 12% 1	7651
	11th to 20th	Day	48% 7% 16% 21% 8% 1	7630
	21st to end	Day	54% 7% 10% 17% 11% 1	8405
June	1st to 10th	Day	44% 11% 15% 21% 8% 1	2730
	11th to 20th	Day	39% 11% 18% 21% 11% 1	2730
	21st to end	Day	39% 11% 18% 20% 11% 2	2730
July	1st to 10th	Day	41% 8% 25% 20% 6%	7615
	11th to 20th	Day	51% 9% 25% 12% 3 1	7611
	21st to end	Day	53% 8% 18% 15% 6%	8156
August	1st to 10th	Day	40% 9% 15% 28% 7%	4351
	11th to 20th	Day	37% 8% 19% 22% 12% 1	4046
	21st to end	Day	39% 7% 11% 26% 16% 1	4311
September	1st to 10th	Day	43% 9% 12% 16% 16% 4	2220
	11th to 20th	Day	43% 9% 12% 19% 16% 1	2200
	21st to end	Day	40% 6% 13% 16% 20% 5%	2200
October	1st to 10th	Day	30% 5% 5% 15% 34% 11%	3590
	11th to 20th	Day	21% 4 6% 19% 28% 22%	3372
	21st to end	Day	29% 3 5% 26% 26% 12%	3511
November	1st to 10th	Day	32% 4 9% 16% 30% 9%	1852
	11th to 20th	Day	35% 4 7% 20% 25% 9%	1890
	21st to end	Day	40% 4 7% 19% 24% 5%	1890
December	1st to 10th	Day	43% 4 6% 17% 26% 6%	3020
	11th to 20th	Day	51% 3 9% 15% 17% 5%	3460
	21st to end	Day	46% 4 10% 25% 13% 2	4565
January	1st to 10th	Night	46% 2 12% 18% 19% 3	7636
	11th to 20th	Night	40% 4 5% 16% 26% 8%	7680
	21st to end	Night	49% 2 6% 16% 19% 7%	8239
February	1st to 10th	Night	45% 4 9% 19% 19% 4	2520
	11th to 20th	Night	52% 4 6% 16% 16% 5%	2459
	21st to end	Night	50% 5% 7% 16% 17% 5%	2076
March	1st to 10th	Night	50% 5% 8% 13% 20% 4	5364
	11th to 20th	Night	33% 4 8% 19% 22% 13%	5090
	21st to end	Night	43% 4 9% 24% 16% 4	5588
April	1st to 10th	Night	35% 6% 14% 21% 21% 4	2242
	11th to 20th	Night	35% 5% 10% 23% 21% 7%	2075
	21st to end	Night	36% 6% 12% 27% 17% 2	1915
May	1st to 10th	Night	45% 7% 16% 21% 10% 1	5264
	11th to 20th	Night	46% 6% 17% 21% 11%	5235
	21st to end	Night	50% 9% 13% 18% 9% 1	5771
June	1st to 10th	Night	39% 10% 18% 21% 11% 2	1890
	11th to 20th	Night	28% 10% 24% 25% 11% 1	1890
	21st to end	Night	31% 11% 21% 20% 13% 3	1890
July	1st to 10th	Night	38% 10% 27% 20% 5%	5235
	11th to 20th	Night	42% 11% 29% 14% 3 1	5226
	21st to end	Night	47% 10% 21% 15% 6% 1	5606
August	1st to 10th	Night	35% 8% 20% 30% 7%	2994
	11th to 20th	Night	35% 7% 21% 25% 12%	3152
	21st to end	Night	30% 7% 16% 29% 17% 1	3586
September	1st to 10th	Night	39% 10% 16% 17% 14% 4	2158
	11th to 20th	Night	38% 10% 14% 21% 17% 1	2200
	21st to end	Night	34% 8% 12% 21% 20% 6%	2200
October	1st to 10th	Night	27% 4 8% 19% 30% 11%	3590
	11th to 20th	Night	21% 3 6% 19% 33% 18%	3765
	21st to end	Night	25% 3 4 28% 28% 12%	4276
November	1st to 10th	Night	34% 4 8% 21% 24% 8%	2666
	11th to 20th	Night	36% 3 7% 20% 25% 10%	2730
	21st to end	Night	41% 5% 8% 20% 21% 5%	2730
December	1st to 10th	Night	43% 4 7% 17% 24% 5%	4380
	11th to 20th	Night	50% 5% 8% 14% 20% 4	4954
	21st to end	Night	48% 4 11% 23% 13% 1	6633

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% 27% 31% 13% 2	330
	11th to 20th	Day	31% 25% 28% 13% 4	330
	21st to end	Day	26% 31% 28% 12% 3	363
February	1st to 10th	Day	26% 24% 36% 11% 3	330
	11th to 20th	Day	36% 31% 23% 9% 1	330
	21st to end	Day	36% 27% 27% 7% 3	273
March	1st to 10th	Day	30% 19% 32% 14% 4 1	380
	11th to 20th	Day	25% 21% 29% 17% 6% 1	540
	21st to end	Day	23% 22% 31% 18% 6% 1	594
April	1st to 10th	Day	23% 17% 28% 20% 9% 2	540
	11th to 20th	Day	18% 18% 31% 21% 11% 2	532
	21st to end	Day	20% 13% 28% 23% 12% 4	540
May	1st to 10th	Day	17% 17% 30% 19% 11% 5%	543
	11th to 20th	Day	15% 11% 23% 28% 14% 8%	567
	21st to end	Day	13% 7% 23% 27% 18% 11%	617
June	1st to 10th	Day	11% 6% 22% 28% 20% 13%	570
	11th to 20th	Day	6% 6% 21% 27% 23% 17%	570
	21st to end	Day	9% 5% 22% 25% 22% 18%	570
July	1st to 10th	Day	9% 3 12% 25% 29% 23%	565
	11th to 20th	Day	9% 3 10% 27% 29% 23%	564
	21st to end	Day	9% 4 11% 25% 28% 23%	620
August	1st to 10th	Day	11% 5% 15% 24% 23% 21%	566
	11th to 20th	Day	10% 4 16% 25% 27% 19%	535
	21st to end	Day	13% 4 11% 21% 29% 21%	583
September	1st to 10th	Day	8% 3 18% 25% 31% 14%	530
	11th to 20th	Day	15% 5% 14% 22% 29% 15%	530
	21st to end	Day	14% 8% 15% 28% 26% 9%	530
October	1st to 10th	Day	14% 6% 20% 30% 22% 8%	530
	11th to 20th	Day	16% 9% 24% 26% 20% 5%	530
	21st to end	Day	18% 13% 23% 25% 17% 4	568
November	1st to 10th	Day	18% 14% 32% 22% 10% 3	330
	11th to 20th	Day	19% 21% 35% 17% 7% 1	330
	21st to end	Day	18% 22% 35% 18% 7% 1	330
December	1st to 10th	Day	28% 28% 24% 17% 2 1	330
	11th to 20th	Day	24% 21% 30% 19% 6% 1	330
	21st to end	Day	23% 23% 32% 14% 6% 1	363
January	1st to 10th	Night	25% 21% 28% 22% 5%	840
	11th to 20th	Night	22% 21% 29% 22% 6%	840
	21st to end	Night	21% 20% 32% 24% 2	924
February	1st to 10th	Night	23% 16% 27% 29% 5%	840
	11th to 20th	Night	28% 21% 30% 19% 2	823
	21st to end	Night	27% 21% 28% 21% 2	692
March	1st to 10th	Night	19% 19% 32% 25% 4	840
	11th to 20th	Night	20% 17% 29% 25% 7% 1	840
	21st to end	Night	19% 15% 31% 28% 8%	924
April	1st to 10th	Night	15% 17% 26% 31% 10% 1	772
	11th to 20th	Night	14% 15% 27% 30% 13%	623
	21st to end	Night	15% 8% 24% 36% 17% 1	630
May	1st to 10th	Night	11% 9% 25% 37% 16% 2	630
	11th to 20th	Night	12% 7% 22% 33% 22% 5%	621
	21st to end	Night	11% 5% 14% 33% 31% 6%	683
June	1st to 10th	Night	7% 3 14% 35% 36% 5%	630
	11th to 20th	Night	5% 3 13% 31% 36% 13%	630
	21st to end	Night	5% 2 9% 33% 42% 10%	630
July	1st to 10th	Night	9% 3 6% 21% 48% 14%	615
	11th to 20th	Night	8% 2 8% 22% 45% 16%	612
	21st to end	Night	8% 2 6% 23% 50% 12%	690
August	1st to 10th	Night	9% 3 4 28% 43% 13%	627
	11th to 20th	Night	9% 2 8% 26% 46% 9%	606
	21st to end	Night	13% 2 9% 23% 42% 11%	660
September	1st to 10th	Night	11% 3 9% 29% 40% 8%	758
	11th to 20th	Night	12% 3 13% 28% 39% 5%	800
	21st to end	Night	12% 3 14% 36% 33% 3	800
October	1st to 10th	Night	12% 7% 18% 32% 25% 7%	800
	11th to 20th	Night	13% 9% 23% 31% 22% 2	800
	21st to end	Night	16% 9% 19% 36% 17% 2	880
November	1st to 10th	Night	16% 8% 22% 32% 18% 3	820
	11th to 20th	Night	17% 12% 26% 30% 12% 1	840
	21st to end	Night	18% 16% 26% 27% 12% 1	840
December	1st to 10th	Night	24% 18% 25% 26% 7%	840
	11th to 20th	Night	21% 14% 28% 28% 8% 1	840
	21st to end	Night	24% 17% 26% 28% 6%	924

Page generated at 2026-08-12 03:37:14. Version ac07

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