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 2024-02-05.

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	17% 10% 4 7% 6% 3 5% 5% 5% 6% 32%	78103
	Night	17% 11% 4 7% 6% 3 4 4 5% 6% 32%	80750
Transparency	Day	52% 6% 11% 19% 11% 1	77808
	Night	53% 6% 11% 19% 10% 1	80579
Seeing	Day	24% 16% 31% 18% 8% 3	13417
	Night	22% 14% 31% 23% 9% 1	22748

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	14% 17% 6% 9% 8% 4 5% 4 4 4 24%	2517
	11th to 20th	Day	13% 16% 7% 12% 8% 4 5% 5% 4 4 22%	2520
	21st to end	Day	18% 19% 7% 12% 8% 4 4 3 3 4 18%	3005
February	1st to 10th	Day	15% 15% 5% 11% 7% 5% 5% 6% 4 6% 22%	1656
	11th to 20th	Day	13% 15% 6% 9% 8% 4 5% 5% 4 4 29%	1573
	21st to end	Day	20% 14% 4 8% 6% 5% 5% 5% 5% 3 24%	1456
March	1st to 10th	Day	15% 11% 6% 10% 9% 3 5% 4 4 4 29%	1846
	11th to 20th	Day	15% 13% 5% 7% 7% 4 5% 4 3 5% 31%	1980
	21st to end	Day	20% 11% 4 6% 4 2 3 3 4 4 39%	2258
April	1st to 10th	Day	20% 11% 4 7% 5% 3 4 4 4 6% 32%	2160
	11th to 20th	Day	21% 8% 3 5% 5% 3 4 4 4 5% 39%	2134
	21st to end	Day	22% 10% 3 7% 6% 3 4 4 4 5% 32%	2271
May	1st to 10th	Day	19% 8% 2 7% 6% 3 5% 4 5% 6% 34%	2510
	11th to 20th	Day	16% 6% 3 6% 6% 3 5% 4 4 7% 39%	2478
	21st to end	Day	13% 6% 2 6% 5% 3 6% 5% 5% 7% 40%	2725
June	1st to 10th	Day	21% 8% 3 6% 5% 3 6% 5% 6% 7% 30%	2520
	11th to 20th	Day	16% 5% 2 6% 5% 3 5% 6% 6% 9% 38%	2520
	21st to end	Day	17% 7% 3 7% 6% 4 5% 5% 6% 7% 33%	2520
July	1st to 10th	Day	11% 6% 3 5% 5% 4 6% 5% 6% 9% 40%	2520
	11th to 20th	Day	13% 6% 2 6% 6% 3 6% 6% 6% 10% 37%	2520
	21st to end	Day	12% 5% 3 6% 6% 4 6% 7% 7% 9% 36%	2744
August	1st to 10th	Day	11% 6% 2 6% 6% 4 6% 6% 6% 8% 39%	2392
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 6% 7% 7% 38%	2303
	21st to end	Day	14% 6% 2 5% 6% 3 5% 5% 6% 8% 39%	2376
September	1st to 10th	Day	13% 7% 2 6% 5% 3 4 5% 6% 8% 42%	2160
	11th to 20th	Day	13% 5% 3 5% 4 3 5% 4 5% 7% 47%	2160
	21st to end	Day	18% 6% 2 6% 6% 3 4 4 5% 7% 39%	1903
October	1st to 10th	Day	21% 8% 3 7% 5% 2 4 4 5% 6% 36%	1800
	11th to 20th	Day	22% 9% 3 6% 6% 4 5% 5% 6% 6% 28%	1800
	21st to end	Day	27% 10% 4 7% 6% 3 4 5% 3 6% 25%	1886
November	1st to 10th	Day	15% 9% 3 7% 6% 4 5% 5% 6% 6% 35%	1652
	11th to 20th	Day	18% 13% 4 7% 6% 4 6% 4 4 5% 29%	1520
	21st to end	Day	21% 15% 6% 8% 6% 3 5% 4 4 6% 22%	1520
December	1st to 10th	Day	22% 17% 6% 8% 8% 3 4 4 5% 5% 18%	1520
	11th to 20th	Day	20% 13% 7% 8% 7% 2 5% 4 5% 5% 25%	1906
	21st to end	Day	28% 17% 6% 11% 6% 2 3 2 2 3 20%	2772
January	1st to 10th	Night	18% 14% 7% 11% 8% 4 5% 4 5% 5% 20%	4429
	11th to 20th	Night	13% 14% 5% 11% 9% 5% 6% 5% 5% 6% 20%	4440
	21st to end	Night	19% 16% 7% 10% 8% 5% 5% 3 3 4 20%	4647
February	1st to 10th	Night	14% 16% 5% 9% 7% 4 5% 5% 6% 7% 23%	2399
	11th to 20th	Night	14% 13% 6% 8% 6% 3 5% 4 4 6% 30%	2273
	21st to end	Night	14% 14% 5% 8% 6% 4 4 4 5% 6% 30%	1799
March	1st to 10th	Night	16% 11% 5% 8% 7% 3 4 4 5% 6% 32%	2096
	11th to 20th	Night	17% 12% 5% 7% 5% 4 3 4 4 6% 34%	1979
	21st to end	Night	16% 9% 4 7% 5% 2 4 4 4 4 41%	2098
April	1st to 10th	Night	21% 9% 4 6% 5% 3 3 4 4 6% 35%	1800
	11th to 20th	Night	19% 7% 3 5% 6% 3 5% 4 5% 5% 38%	1775
	21st to end	Night	19% 10% 4 6% 6% 3 4 4 5% 6% 33%	1705
May	1st to 10th	Night	21% 7% 2 5% 5% 3 3 4 6% 5% 37%	1450
	11th to 20th	Night	15% 6% 3 5% 4 3 4 4 5% 7% 44%	1415
	21st to end	Night	11% 5% 2 5% 4 3 4 4 6% 8% 46%	1550
June	1st to 10th	Night	15% 7% 3 6% 6% 3 6% 5% 5% 8% 34%	1440
	11th to 20th	Night	13% 6% 3 5% 5% 3 4 4 5% 8% 42%	1440
	21st to end	Night	16% 6% 2 6% 6% 4 5% 5% 6% 8% 36%	1440
July	1st to 10th	Night	9% 4 3 5% 5% 3 4 4 6% 8% 46%	1440
	11th to 20th	Night	11% 6% 2 5% 5% 3 5% 5% 6% 9% 44%	1440
	21st to end	Night	10% 5% 2 5% 4 4 4 5% 7% 9% 46%	1574
August	1st to 10th	Night	11% 6% 2 6% 5% 3 3 5% 6% 7% 46%	1543
	11th to 20th	Night	10% 6% 3 6% 5% 3 5% 5% 6% 8% 45%	1598
	21st to end	Night	11% 5% 2 6% 5% 3 5% 5% 5% 7% 46%	1962
September	1st to 10th	Night	12% 6% 2 7% 4 3 3 5% 5% 9% 45%	1800
	11th to 20th	Night	13% 4 2 4 4 3 4 4 5% 8% 50%	1800
	21st to end	Night	17% 6% 2 5% 5% 3 4 4 5% 6% 44%	2052
October	1st to 10th	Night	17% 7% 3 6% 6% 4 5% 4 5% 6% 38%	2160
	11th to 20th	Night	21% 9% 3 6% 5% 4 5% 5% 6% 6% 30%	2160
	21st to end	Night	23% 11% 3 7% 6% 3 4 4 4 6% 29%	2468
November	1st to 10th	Night	18% 9% 3 6% 4 3 4 5% 5% 6% 37%	2426
	11th to 20th	Night	18% 10% 3 7% 6% 4 5% 5% 5% 6% 31%	2660
	21st to end	Night	22% 12% 4 8% 6% 3 5% 5% 5% 6% 25%	2660
December	1st to 10th	Night	19% 16% 5% 10% 7% 3 5% 5% 5% 5% 19%	2660
	11th to 20th	Night	20% 16% 5% 7% 6% 3 4 3 3 4 27%	3288
	21st to end	Night	29% 17% 4 9% 6% 3 4 4 3 5% 16%	4884

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	61% 6% 14% 11% 6% 1	2518
	11th to 20th	Day	64% 7% 9% 12% 8%	2520
	21st to end	Day	71% 5% 8% 10% 5% 1	3005
February	1st to 10th	Day	63% 6% 9% 16% 5% 1	1656
	11th to 20th	Day	59% 5% 10% 15% 10% 1	1582
	21st to end	Day	64% 3 9% 12% 11% 1	1456
March	1st to 10th	Day	59% 4 10% 15% 10% 2	1849
	11th to 20th	Day	57% 5% 10% 14% 12% 2	1980
	21st to end	Day	51% 3 7% 19% 14% 6%	2258
April	1st to 10th	Day	55% 5% 6% 18% 13% 3	2160
	11th to 20th	Day	48% 5% 7% 22% 16% 2	2134
	21st to end	Day	54% 5% 8% 15% 14% 4	2271
May	1st to 10th	Day	50% 6% 9% 17% 15% 4	2510
	11th to 20th	Day	45% 5% 9% 23% 15% 3	2482
	21st to end	Day	42% 8% 14% 21% 13% 3	2725
June	1st to 10th	Day	51% 7% 9% 19% 12% 1	2520
	11th to 20th	Day	42% 7% 10% 25% 14% 2	2520
	21st to end	Day	48% 7% 13% 19% 12% 1	2520
July	1st to 10th	Day	39% 7% 11% 27% 15% 1	2450
	11th to 20th	Day	40% 8% 15% 26% 11%	2445
	21st to end	Day	42% 9% 13% 24% 11% 1	2591
August	1st to 10th	Day	41% 9% 14% 25% 11%	2378
	11th to 20th	Day	41% 8% 16% 24% 10% 1	2303
	21st to end	Day	41% 7% 13% 27% 12% 1	2376
September	1st to 10th	Day	40% 7% 13% 27% 13% 1	2160
	11th to 20th	Day	36% 6% 11% 30% 15% 1	2160
	21st to end	Day	44% 6% 13% 27% 10%	1903
October	1st to 10th	Day	49% 6% 10% 22% 12% 1	1800
	11th to 20th	Day	54% 7% 13% 18% 7% 1	1800
	21st to end	Day	60% 5% 10% 17% 7%	1886
November	1st to 10th	Day	48% 6% 16% 21% 8% 1	1652
	11th to 20th	Day	56% 6% 12% 16% 10% 1	1520
	21st to end	Day	63% 8% 12% 9% 8%	1520
December	1st to 10th	Day	67% 7% 11% 10% 5% 1	1520
	11th to 20th	Day	62% 5% 14% 11% 7%	1906
	21st to end	Day	71% 4 6% 14% 4	2772
January	1st to 10th	Night	64% 7% 13% 12% 4	4429
	11th to 20th	Night	64% 7% 13% 11% 5%	4440
	21st to end	Night	69% 5% 10% 10% 6% 1	4647
February	1st to 10th	Night	61% 5% 11% 16% 6% 1	2399
	11th to 20th	Night	56% 4 10% 20% 9% 1	2275
	21st to end	Night	56% 4 10% 18% 11% 1	1799
March	1st to 10th	Night	54% 4 11% 17% 12% 1	2106
	11th to 20th	Night	52% 4 10% 20% 12% 2	1980
	21st to end	Night	47% 5% 7% 21% 16% 4	2098
April	1st to 10th	Night	51% 4 7% 22% 15% 2	1800
	11th to 20th	Night	48% 5% 8% 20% 18% 1	1775
	21st to end	Night	52% 5% 8% 16% 16% 3	1705
May	1st to 10th	Night	48% 5% 7% 19% 18% 4	1450
	11th to 20th	Night	40% 6% 9% 25% 17% 3	1416
	21st to end	Night	35% 7% 17% 19% 20% 3	1551
June	1st to 10th	Night	47% 8% 12% 22% 11% 2	1440
	11th to 20th	Night	39% 7% 12% 21% 19% 2	1440
	21st to end	Night	45% 7% 14% 21% 12% 1	1440
July	1st to 10th	Night	33% 7% 12% 26% 19% 3	1400
	11th to 20th	Night	36% 6% 13% 30% 13%	1392
	21st to end	Night	33% 8% 16% 29% 13% 1	1486
August	1st to 10th	Night	36% 8% 16% 27% 12% 1	1533
	11th to 20th	Night	37% 7% 15% 28% 12% 1	1598
	21st to end	Night	35% 8% 14% 30% 13% 1	1962
September	1st to 10th	Night	36% 7% 13% 29% 14% 1	1800
	11th to 20th	Night	33% 6% 13% 34% 13% 1	1800
	21st to end	Night	41% 6% 10% 32% 10% 1	2052
October	1st to 10th	Night	47% 5% 11% 22% 14% 1	2160
	11th to 20th	Night	53% 6% 13% 19% 8% 1	2160
	21st to end	Night	57% 6% 12% 15% 10%	2468
November	1st to 10th	Night	48% 6% 14% 21% 11% 1	2426
	11th to 20th	Night	52% 6% 10% 19% 10% 2	2660
	21st to end	Night	59% 6% 13% 16% 6%	2660
December	1st to 10th	Night	66% 6% 11% 13% 4	2660
	11th to 20th	Night	61% 5% 10% 15% 8% 1	3288
	21st to end	Night	71% 6% 8% 12% 3	4884

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	25% 24% 33% 13% 4 1	180
	11th to 20th	Day	36% 16% 29% 15% 3 1	180
	21st to end	Day	25% 22% 33% 15% 4 1	265
February	1st to 10th	Day	35% 26% 28% 9% 2	252
	11th to 20th	Day	30% 28% 38% 4	240
	21st to end	Day	36% 22% 30% 10% 2	322
March	1st to 10th	Day	26% 22% 34% 15% 4	420
	11th to 20th	Day	27% 23% 31% 14% 4	420
	21st to end	Day	34% 21% 26% 12% 6% 1	462
April	1st to 10th	Day	30% 22% 28% 14% 5% 1	420
	11th to 20th	Day	31% 24% 21% 15% 8% 2	412
	21st to end	Day	31% 20% 30% 12% 6% 1	420
May	1st to 10th	Day	28% 15% 31% 17% 7% 2	423
	11th to 20th	Day	19% 18% 36% 17% 9% 2	447
	21st to end	Day	19% 16% 33% 19% 11% 3	485
June	1st to 10th	Day	24% 12% 36% 19% 8% 2	450
	11th to 20th	Day	16% 19% 31% 21% 12% 2	450
	21st to end	Day	20% 13% 32% 24% 9% 2	450
July	1st to 10th	Day	14% 8% 31% 29% 15% 3	445
	11th to 20th	Day	16% 11% 31% 25% 14% 3	444
	21st to end	Day	15% 8% 36% 26% 10% 4	488
August	1st to 10th	Day	13% 8% 33% 28% 15% 4	446
	11th to 20th	Day	14% 7% 29% 28% 16% 7%	439
	21st to end	Day	16% 12% 30% 22% 13% 7%	495
September	1st to 10th	Day	14% 13% 32% 22% 13% 6%	450
	11th to 20th	Day	14% 8% 27% 24% 16% 10%	450
	21st to end	Day	19% 12% 31% 20% 13% 4	450
October	1st to 10th	Day	26% 15% 27% 16% 11% 5%	450
	11th to 20th	Day	29% 20% 29% 17% 5% 1	450
	21st to end	Day	30% 19% 28% 18% 4	448
November	1st to 10th	Day	25% 17% 30% 19% 8%	346
	11th to 20th	Day	29% 21% 30% 13% 4 3	180
	21st to end	Day	30% 22% 32% 13% 2 1	180
December	1st to 10th	Day	33% 22% 31% 12% 2	180
	11th to 20th	Day	36% 23% 29% 10% 2 1	180
	21st to end	Day	34% 20% 33% 10% 3 1	198
January	1st to 10th	Night	28% 20% 30% 18% 4	760
	11th to 20th	Night	29% 18% 30% 18% 4 1	760
	21st to end	Night	20% 17% 35% 23% 5%	836
February	1st to 10th	Night	23% 22% 35% 18% 2	739
	11th to 20th	Night	22% 20% 38% 17% 4	703
	21st to end	Night	24% 21% 35% 17% 3	592
March	1st to 10th	Night	25% 16% 36% 21% 3	720
	11th to 20th	Night	27% 19% 29% 21% 4 1	720
	21st to end	Night	22% 17% 34% 19% 7% 1	792
April	1st to 10th	Night	28% 17% 32% 20% 3	720
	11th to 20th	Night	24% 20% 29% 19% 7% 1	711
	21st to end	Night	26% 15% 28% 22% 9%	625
May	1st to 10th	Night	25% 11% 25% 27% 11% 2	370
	11th to 20th	Night	16% 10% 36% 31% 7%	354
	21st to end	Night	12% 11% 39% 26% 12% 1	389
June	1st to 10th	Night	16% 8% 33% 33% 9% 1	360
	11th to 20th	Night	14% 12% 33% 27% 13% 2	360
	21st to end	Night	17% 9% 26% 36% 13%	360
July	1st to 10th	Night	8% 6% 33% 36% 17%	350
	11th to 20th	Night	11% 4 30% 39% 15% 1	348
	21st to end	Night	10% 6% 30% 42% 11% 1	394
August	1st to 10th	Night	14% 4 27% 34% 21% 1	469
	11th to 20th	Night	11% 4 25% 35% 22% 3	534
	21st to end	Night	12% 7% 32% 29% 17% 2	774
September	1st to 10th	Night	14% 6% 32% 29% 17% 2	720
	11th to 20th	Night	14% 8% 24% 28% 21% 4	720
	21st to end	Night	20% 11% 23% 26% 18% 2	720
October	1st to 10th	Night	23% 12% 28% 21% 14% 2	720
	11th to 20th	Night	27% 13% 31% 21% 7%	720
	21st to end	Night	29% 15% 29% 22% 5%	792
November	1st to 10th	Night	26% 12% 31% 22% 8%	740
	11th to 20th	Night	26% 16% 33% 17% 8% 1	760
	21st to end	Night	31% 17% 28% 19% 5%	760
December	1st to 10th	Night	29% 20% 30% 18% 3	760
	11th to 20th	Night	26% 19% 33% 18% 3 1	760
	21st to end	Night	35% 16% 30% 17% 2	836

Page generated at 2024-02-02 05:20:31. Version ac07

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