Sharbot Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sharbot Lake clear sky chart from 2005-11-06 to 2026-07-01.

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	16% 10% 4 8% 5% 5% 5% 4 5% 7% 32%	138379
	Night	16% 11% 4 9% 5% 5% 4 3 5% 6% 31%	133967
Transparency	Day	50% 6% 11% 21% 11% 1	141885
	Night	52% 6% 11% 20% 11% 1	138550
Seeing	Day	24% 17% 31% 18% 8% 2	16519
	Night	22% 14% 31% 23% 8% 1	25698

By Month

Percentage Cloud Cover NE (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% 16% 6% 12% 8% 6% 5% 3 5% 5% 22%	4661
	11th to 20th	Day	11% 21% 9% 14% 6% 5% 5% 4 3 4 18%	4650
	21st to end	Day	11% 16% 7% 16% 7% 7% 5% 3 4 4 19%	5577
February	1st to 10th	Day	14% 15% 4 12% 7% 6% 4 5% 5% 6% 23%	1890
	11th to 20th	Day	12% 15% 5% 11% 7% 5% 4 4 5% 4 28%	1843
	21st to end	Day	18% 15% 4 10% 6% 7% 4 4 5% 4 23%	1702
March	1st to 10th	Day	18% 14% 5% 9% 5% 4 4 3 4 6% 28%	4712
	11th to 20th	Day	11% 13% 4 9% 6% 5% 6% 4 5% 6% 31%	5090
	21st to end	Day	18% 12% 4 7% 4 4 3 3 4 4 38%	5809
April	1st to 10th	Day	20% 12% 3 8% 5% 4 4 3 4 6% 31%	2520
	11th to 20th	Day	22% 10% 3 6% 4 3 3 3 4 5% 36%	2494
	21st to end	Day	21% 10% 3 8% 5% 4 4 3 4 5% 32%	2650
May	1st to 10th	Day	22% 9% 3 8% 5% 5% 5% 4 5% 6% 29%	8213
	11th to 20th	Day	16% 7% 3 8% 5% 4 5% 3 5% 7% 35%	8221
	21st to end	Day	19% 9% 2 6% 4 4 4 3 5% 7% 36%	9060
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	2940
	11th to 20th	Day	15% 6% 2 6% 5% 4 6% 5% 7% 9% 36%	2940
	21st to end	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 33%	2940
July	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 5% 6% 9% 35%	6360
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 6% 9% 43%	6360
	21st to end	Day	9% 5% 2 6% 4 4 5% 5% 6% 9% 44%	6926
August	1st to 10th	Day	16% 7% 3 7% 5% 4 4 4 5% 7% 37%	4344
	11th to 20th	Day	17% 6% 3 6% 4 4 5% 4 7% 8% 36%	4174
	21st to end	Day	14% 5% 2 6% 4 5% 5% 5% 6% 9% 39%	4312
September	1st to 10th	Day	12% 7% 2 6% 4 5% 4 4 6% 8% 42%	2400
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 48%	2400
	21st to end	Day	19% 6% 2 6% 5% 4 4 3 5% 8% 39%	2113
October	1st to 10th	Day	20% 8% 2 7% 4 3 4 3 4 7% 37%	2000
	11th to 20th	Day	21% 10% 3 7% 5% 5% 5% 3 6% 6% 30%	2000
	21st to end	Day	25% 10% 4 8% 5% 5% 4 4 4 6% 26%	2095
November	1st to 10th	Day	16% 10% 4 8% 4 5% 5% 4 6% 6% 34%	1829
	11th to 20th	Day	16% 15% 4 8% 5% 6% 5% 3 5% 5% 29%	1680
	21st to end	Day	21% 17% 5% 9% 6% 4 4 3 4 5% 22%	1680
December	1st to 10th	Day	22% 17% 5% 11% 6% 5% 4 3 5% 5% 17%	2680
	11th to 20th	Day	17% 20% 6% 10% 6% 4 4 2 4 4 23%	3066
	21st to end	Day	23% 18% 5% 12% 6% 3 2 2 3 4 23%	4048
January	1st to 10th	Night	14% 14% 7% 14% 8% 5% 5% 3 4 4 21%	8234
	11th to 20th	Night	11% 18% 7% 15% 8% 6% 5% 3 4 5% 17%	8235
	21st to end	Night	13% 14% 6% 12% 7% 6% 5% 4 4 5% 24%	8600
February	1st to 10th	Night	12% 16% 5% 10% 6% 5% 5% 4 6% 6% 24%	2730
	11th to 20th	Night	12% 15% 5% 11% 5% 5% 4 3 4 6% 29%	2663
	21st to end	Night	13% 15% 5% 8% 5% 6% 4 4 5% 6% 28%	2103
March	1st to 10th	Night	19% 13% 4 9% 6% 5% 3 2 4 4 29%	5343
	11th to 20th	Night	13% 12% 3 7% 5% 5% 4 5% 7% 9% 30%	5089
	21st to end	Night	18% 10% 4 8% 5% 4 3 3 4 6% 35%	5365
April	1st to 10th	Night	21% 11% 3 8% 4 4 4 3 4 6% 33%	2100
	11th to 20th	Night	20% 8% 4 6% 5% 4 4 3 4 4 37%	2075
	21st to end	Night	20% 10% 3 7% 4 3 4 3 5% 6% 34%	1988
May	1st to 10th	Night	22% 10% 3 7% 5% 5% 5% 4 6% 7% 27%	4684
	11th to 20th	Night	14% 8% 3 7% 4 4 4 3 5% 7% 41%	4639
	21st to end	Night	19% 6% 2 6% 4 4 4 4 6% 8% 37%	5114
June	1st to 10th	Night	14% 8% 3 7% 6% 5% 6% 4 6% 8% 35%	1680
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 6% 8% 42%	1680
	21st to end	Night	17% 7% 2 7% 5% 5% 4 4 6% 8% 35%	1680
July	1st to 10th	Night	12% 6% 3 7% 6% 5% 5% 4 7% 9% 37%	3600
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 5% 8% 47%	3600
	21st to end	Night	9% 6% 2 6% 3 4 4 3 6% 7% 49%	3926
August	1st to 10th	Night	12% 6% 2 7% 4 4 4 3 6% 7% 44%	2801
	11th to 20th	Night	14% 6% 3 6% 4 4 4 3 5% 7% 45%	2875
	21st to end	Night	11% 5% 2 7% 5% 5% 5% 4 7% 8% 42%	3553
September	1st to 10th	Night	11% 6% 2 7% 4 4 3 4 5% 9% 47%	2000
	11th to 20th	Night	12% 4 2 5% 3 4 4 3 5% 7% 51%	2000
	21st to end	Night	17% 7% 2 6% 4 4 4 3 5% 6% 43%	2281
October	1st to 10th	Night	16% 7% 2 7% 4 5% 5% 3 5% 6% 41%	2400
	11th to 20th	Night	20% 9% 2 7% 5% 5% 5% 4 6% 6% 31%	2400
	21st to end	Night	22% 11% 3 8% 5% 4 4 3 4 6% 30%	2743
November	1st to 10th	Night	17% 11% 3 7% 4 4 4 3 5% 6% 36%	2688
	11th to 20th	Night	17% 11% 3 8% 5% 5% 5% 4 5% 5% 31%	2940
	21st to end	Night	21% 14% 4 9% 5% 4 5% 4 5% 5% 24%	2940
December	1st to 10th	Night	19% 16% 4 11% 6% 5% 5% 4 5% 6% 18%	4720
	11th to 20th	Night	22% 16% 4 9% 5% 4 4 3 4 5% 24%	5348
	21st to end	Night	26% 17% 4 11% 5% 4 3 3 3 4 20%	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	62% 6% 11% 14% 6% 1	4662
	11th to 20th	Day	69% 5% 8% 10% 8%	4680
	21st to end	Day	67% 6% 7% 10% 9% 1	5577
February	1st to 10th	Day	61% 6% 9% 17% 6% 1	1890
	11th to 20th	Day	59% 4 10% 17% 9% 1	1852
	21st to end	Day	64% 4 9% 12% 10% 1	1702
March	1st to 10th	Day	58% 3 10% 13% 14% 2	4715
	11th to 20th	Day	52% 6% 16% 14% 11% 2	5090
	21st to end	Day	51% 3 5% 21% 17% 3	5809
April	1st to 10th	Day	56% 5% 7% 17% 13% 3	2520
	11th to 20th	Day	50% 5% 7% 21% 16% 2	2494
	21st to end	Day	54% 5% 8% 16% 14% 3	2650
May	1st to 10th	Day	53% 7% 8% 19% 11% 2	8225
	11th to 20th	Day	47% 7% 11% 21% 13% 1	8225
	21st to end	Day	47% 6% 11% 23% 12% 1	9061
June	1st to 10th	Day	50% 7% 9% 19% 14% 1	2940
	11th to 20th	Day	43% 7% 11% 25% 13% 2	2940
	21st to end	Day	48% 7% 13% 20% 11% 1	2940
July	1st to 10th	Day	42% 7% 13% 25% 11% 1	6290
	11th to 20th	Day	35% 8% 13% 27% 16%	6285
	21st to end	Day	34% 8% 12% 35% 11%	6728
August	1st to 10th	Day	45% 7% 13% 23% 11% 1	4330
	11th to 20th	Day	43% 7% 13% 26% 9% 1	4213
	21st to end	Day	39% 7% 13% 30% 10%	4312
September	1st to 10th	Day	39% 6% 13% 29% 12% 1	2400
	11th to 20th	Day	35% 6% 11% 32% 15% 1	2400
	21st to end	Day	44% 5% 13% 26% 11%	2113
October	1st to 10th	Day	42% 7% 10% 32% 9%	3260
	11th to 20th	Day	45% 6% 14% 24% 11% 1	3240
	21st to end	Day	50% 6% 14% 22% 7%	3359
November	1st to 10th	Day	49% 6% 14% 21% 8% 1	1829
	11th to 20th	Day	55% 6% 11% 16% 10% 1	1680
	21st to end	Day	63% 7% 12% 9% 8%	1680
December	1st to 10th	Day	68% 7% 14% 9% 3	2680
	11th to 20th	Day	65% 5% 10% 13% 7%	3066
	21st to end	Day	67% 4 7% 15% 7%	4048
January	1st to 10th	Night	65% 6% 11% 13% 5%	8234
	11th to 20th	Night	68% 6% 9% 10% 7%	8280
	21st to end	Night	61% 5% 8% 13% 13% 1	8600
February	1st to 10th	Night	58% 5% 11% 18% 7% 1	2730
	11th to 20th	Night	57% 5% 10% 20% 8% 1	2665
	21st to end	Night	56% 4 10% 18% 10% 1	2103
March	1st to 10th	Night	59% 4 7% 16% 11% 4	5353
	11th to 20th	Night	49% 7% 17% 17% 8% 2	5090
	21st to end	Night	50% 6% 7% 21% 14% 2	5365
April	1st to 10th	Night	52% 4 6% 21% 14% 2	2100
	11th to 20th	Night	50% 5% 7% 20% 17% 1	2075
	21st to end	Night	51% 5% 7% 17% 16% 3	1988
May	1st to 10th	Night	54% 7% 8% 19% 10% 2	4690
	11th to 20th	Night	41% 7% 12% 23% 15% 1	4640
	21st to end	Night	44% 6% 12% 21% 16% 1	5115
June	1st to 10th	Night	45% 7% 11% 21% 13% 2	1680
	11th to 20th	Night	39% 6% 13% 22% 18% 2	1680
	21st to end	Night	46% 7% 12% 21% 12% 1	1680
July	1st to 10th	Night	41% 7% 15% 20% 16% 1	3560
	11th to 20th	Night	34% 7% 13% 32% 13%	3552
	21st to end	Night	33% 7% 12% 33% 14% 1	3809
August	1st to 10th	Night	38% 7% 14% 26% 13% 1	2791
	11th to 20th	Night	38% 6% 14% 31% 10% 1	2902
	21st to end	Night	35% 9% 16% 29% 11% 1	3553
September	1st to 10th	Night	35% 7% 13% 31% 14% 1	2000
	11th to 20th	Night	31% 6% 13% 35% 14% 1	2000
	21st to end	Night	41% 6% 10% 30% 12% 1	2281
October	1st to 10th	Night	38% 6% 11% 28% 16%	3920
	11th to 20th	Night	44% 5% 15% 25% 10%	3899
	21st to end	Night	49% 6% 13% 24% 8%	4429
November	1st to 10th	Night	48% 6% 13% 22% 10% 1	2688
	11th to 20th	Night	53% 6% 10% 19% 10% 1	2940
	21st to end	Night	60% 6% 12% 16% 5%	2940
December	1st to 10th	Night	65% 7% 13% 12% 3	4720
	11th to 20th	Night	62% 6% 8% 14% 9% 1	5348
	21st to end	Night	68% 5% 6% 12% 9%	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	23% 22% 38% 13% 3	220
	11th to 20th	Day	35% 17% 30% 14% 3 1	220
	21st to end	Day	23% 25% 33% 15% 3 1	325
February	1st to 10th	Day	32% 24% 31% 12% 2	330
	11th to 20th	Day	29% 26% 38% 6%	330
	21st to end	Day	33% 24% 32% 10% 2	418
March	1st to 10th	Day	28% 21% 34% 13% 3	540
	11th to 20th	Day	30% 23% 30% 13% 4	540
	21st to end	Day	35% 21% 26% 12% 5% 1	594
April	1st to 10th	Day	32% 24% 27% 12% 4 1	540
	11th to 20th	Day	34% 23% 21% 14% 6% 2	532
	21st to end	Day	30% 21% 31% 11% 6% 1	540
May	1st to 10th	Day	27% 17% 31% 17% 6% 2	543
	11th to 20th	Day	19% 19% 35% 18% 8% 1	567
	21st to end	Day	21% 17% 32% 18% 9% 3	617
June	1st to 10th	Day	22% 13% 37% 19% 7% 1	570
	11th to 20th	Day	16% 19% 35% 18% 11% 2	570
	21st to end	Day	21% 14% 32% 23% 8% 2	570
July	1st to 10th	Day	14% 8% 34% 27% 13% 3	525
	11th to 20th	Day	15% 12% 31% 26% 13% 3	524
	21st to end	Day	14% 9% 36% 26% 10% 4	576
August	1st to 10th	Day	13% 7% 32% 29% 14% 3	526
	11th to 20th	Day	15% 8% 28% 28% 16% 6%	519
	21st to end	Day	16% 11% 32% 22% 13% 6%	583
September	1st to 10th	Day	15% 13% 32% 22% 12% 6%	530
	11th to 20th	Day	12% 7% 25% 27% 17% 11%	530
	21st to end	Day	19% 12% 31% 21% 13% 4	530
October	1st to 10th	Day	24% 15% 28% 18% 11% 4	530
	11th to 20th	Day	26% 21% 31% 17% 5% 1	530
	21st to end	Day	28% 20% 29% 18% 4	525
November	1st to 10th	Day	28% 18% 29% 18% 7%	403
	11th to 20th	Day	28% 20% 33% 12% 5% 2	220
	21st to end	Day	32% 22% 31% 12% 2 1	220
December	1st to 10th	Day	33% 23% 31% 11% 2	220
	11th to 20th	Day	37% 24% 28% 8% 3	220
	21st to end	Day	34% 19% 33% 10% 5%	242
January	1st to 10th	Night	27% 20% 31% 18% 3	840
	11th to 20th	Night	29% 19% 30% 18% 4 1	840
	21st to end	Night	21% 18% 35% 22% 5%	924
February	1st to 10th	Night	22% 21% 34% 20% 3	840
	11th to 20th	Night	23% 20% 38% 16% 3	823
	21st to end	Night	24% 22% 34% 18% 3	692
March	1st to 10th	Night	26% 17% 35% 20% 3	840
	11th to 20th	Night	27% 19% 29% 21% 3 1	840
	21st to end	Night	23% 18% 34% 18% 6% 1	924
April	1st to 10th	Night	28% 18% 31% 20% 3	840
	11th to 20th	Night	25% 20% 28% 19% 7% 1	831
	21st to end	Night	26% 15% 29% 22% 8%	728
May	1st to 10th	Night	25% 12% 25% 27% 10% 2	431
	11th to 20th	Night	15% 11% 36% 30% 7%	414
	21st to end	Night	13% 11% 38% 26% 10%	455
June	1st to 10th	Night	15% 9% 31% 34% 9%	420
	11th to 20th	Night	14% 12% 35% 26% 11% 2	420
	21st to end	Night	18% 9% 27% 35% 11%	420
July	1st to 10th	Night	8% 7% 35% 35% 15%	390
	11th to 20th	Night	11% 6% 29% 39% 14% 1	388
	21st to end	Night	10% 6% 30% 42% 11% 1	438
August	1st to 10th	Night	13% 4 28% 34% 20% 1	522
	11th to 20th	Night	12% 5% 24% 35% 22% 2	594
	21st to end	Night	12% 8% 31% 30% 17% 2	860
September	1st to 10th	Night	14% 6% 32% 29% 18% 2	800
	11th to 20th	Night	13% 8% 23% 28% 25% 4	800
	21st to end	Night	21% 10% 23% 27% 17% 2	800
October	1st to 10th	Night	21% 11% 29% 22% 14% 2	800
	11th to 20th	Night	26% 13% 32% 21% 8%	800
	21st to end	Night	28% 15% 30% 22% 5%	880
November	1st to 10th	Night	26% 14% 31% 22% 7%	820
	11th to 20th	Night	25% 15% 34% 17% 8% 1	840
	21st to end	Night	31% 18% 28% 18% 5%	840
December	1st to 10th	Night	29% 19% 31% 19% 3	840
	11th to 20th	Night	27% 20% 33% 17% 2 1	840
	21st to end	Night	34% 16% 29% 17% 3	924

Page generated at 2026-06-28 02:10:49. Version ac07

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