The SkyRunner Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The SkyRunner Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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% 6% 3 5% 5% 3 5% 5% 5% 7% 40%	78195
	Night	17% 6% 2 5% 4 3 4 4 5% 7% 42%	80755
Transparency	Day	43% 6% 11% 22% 15% 3	77900
	Night	42% 6% 11% 23% 16% 3	80584
Seeing	Day	21% 14% 31% 22% 10% 3	13912
	Night	20% 11% 31% 28% 9% 1	23219

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	15% 6% 2 4 4 3 4 4 5% 6% 47%	2517
	11th to 20th	Day	15% 8% 3 6% 7% 5% 6% 4 4 6% 35%	2520
	21st to end	Day	21% 11% 4 7% 5% 2 3 5% 4 5% 33%	3010
February	1st to 10th	Day	18% 6% 3 6% 5% 3 5% 4 5% 8% 38%	1701
	11th to 20th	Day	15% 7% 3 5% 5% 3 4 4 5% 6% 43%	1744
	21st to end	Day	20% 8% 2 5% 5% 2 5% 5% 4 5% 38%	1480
March	1st to 10th	Day	14% 6% 3 6% 6% 2 4 4 5% 7% 43%	1797
	11th to 20th	Day	15% 6% 2 6% 6% 4 5% 5% 5% 9% 38%	1905
	21st to end	Day	19% 8% 3 5% 5% 2 4 5% 4 6% 40%	2348
April	1st to 10th	Day	17% 8% 3 5% 5% 3 4 4 5% 6% 40%	2160
	11th to 20th	Day	16% 6% 3 5% 5% 3 4 5% 4 8% 42%	2134
	21st to end	Day	21% 6% 2 5% 4 3 4 4 5% 6% 40%	2178
May	1st to 10th	Day	24% 6% 2 5% 5% 3 4 5% 4 7% 35%	2340
	11th to 20th	Day	20% 5% 2 6% 5% 3 5% 5% 6% 8% 35%	2478
	21st to end	Day	16% 6% 2 5% 4 3 5% 5% 5% 8% 41%	2725
June	1st to 10th	Day	17% 6% 2 4 5% 4 5% 6% 7% 9% 36%	2520
	11th to 20th	Day	17% 6% 2 6% 5% 4 6% 6% 6% 9% 34%	2520
	21st to end	Day	12% 5% 2 6% 6% 4 5% 6% 6% 9% 39%	2520
July	1st to 10th	Day	11% 7% 3 6% 6% 4 6% 6% 6% 8% 39%	2520
	11th to 20th	Day	10% 5% 3 5% 5% 3 5% 7% 7% 10% 40%	2520
	21st to end	Day	12% 5% 3 6% 6% 4 6% 5% 7% 8% 37%	2744
August	1st to 10th	Day	11% 6% 2 5% 6% 5% 6% 6% 7% 9% 37%	2380
	11th to 20th	Day	13% 6% 3 6% 7% 4 5% 6% 6% 8% 37%	2126
	21st to end	Day	15% 5% 2 5% 5% 3 5% 6% 5% 8% 41%	2376
September	1st to 10th	Day	15% 5% 2 6% 6% 3 5% 5% 5% 6% 42%	2160
	11th to 20th	Day	14% 5% 2 3 4 3 3 5% 4 7% 49%	2089
	21st to end	Day	18% 5% 2 5% 5% 3 4 4 5% 7% 41%	1980
October	1st to 10th	Day	21% 6% 2 5% 4 3 4 3 5% 6% 41%	1868
	11th to 20th	Day	16% 6% 2 3 4 3 3 5% 5% 7% 46%	1800
	21st to end	Day	22% 4 2 5% 4 2 4 5% 4 7% 40%	1841
November	1st to 10th	Day	15% 5% 2 4 4 2 3 3 4 6% 52%	1671
	11th to 20th	Day	19% 6% 1 3 3 2 3 4 4 7% 47%	1710
	21st to end	Day	16% 6% 2 4 3 3 4 6% 5% 7% 44%	1615
December	1st to 10th	Day	20% 7% 2 5% 5% 3 3 4 5% 7% 38%	1520
	11th to 20th	Day	23% 4 2 4 3 2 4 3 4 7% 44%	1906
	21st to end	Day	18% 8% 4 8% 6% 4 4 6% 5% 8% 30%	2772
January	1st to 10th	Night	17% 5% 2 4 4 2 4 4 5% 6% 47%	4429
	11th to 20th	Night	16% 8% 3 7% 5% 2 4 5% 4 5% 42%	4440
	21st to end	Night	24% 10% 3 5% 4 2 4 4 4 6% 35%	4630
February	1st to 10th	Night	17% 8% 3 5% 4 2 4 3 5% 6% 42%	2464
	11th to 20th	Night	16% 7% 3 5% 5% 3 4 5% 5% 6% 41%	2102
	21st to end	Night	19% 7% 3 6% 4 4 4 4 4 5% 42%	1776
March	1st to 10th	Night	16% 6% 2 4 4 3 4 4 4 6% 46%	2150
	11th to 20th	Night	17% 8% 2 4 4 3 4 4 5% 6% 43%	2051
	21st to end	Night	17% 7% 3 5% 4 3 3 5% 5% 7% 41%	2006
April	1st to 10th	Night	18% 7% 3 5% 4 3 4 4 5% 7% 39%	1800
	11th to 20th	Night	19% 5% 2 4 5% 3 4 4 5% 7% 41%	1775
	21st to end	Night	21% 6% 2 5% 4 3 4 3 5% 6% 42%	1782
May	1st to 10th	Night	23% 6% 3 7% 6% 3 3 4 4 5% 35%	1620
	11th to 20th	Night	19% 7% 3 6% 4 2 4 5% 4 6% 40%	1431
	21st to end	Night	17% 5% 2 5% 4 3 3 4 6% 9% 41%	1550
June	1st to 10th	Night	17% 5% 3 3 4 3 4 5% 5% 8% 42%	1440
	11th to 20th	Night	15% 5% 2 5% 4 3 5% 5% 7% 10% 40%	1440
	21st to end	Night	11% 3 3 4 5% 3 4 5% 7% 10% 45%	1440
July	1st to 10th	Night	12% 4 3 5% 7% 4 5% 5% 6% 9% 41%	1440
	11th to 20th	Night	12% 6% 2 5% 4 3 6% 5% 8% 11% 39%	1440
	21st to end	Night	12% 4 2 4 4 3 5% 6% 7% 10% 42%	1574
August	1st to 10th	Night	10% 4 2 6% 4 4 5% 6% 5% 9% 44%	1537
	11th to 20th	Night	11% 6% 2 8% 7% 5% 6% 6% 6% 7% 37%	1774
	21st to end	Night	14% 6% 3 5% 4 3 5% 5% 5% 8% 43%	1980
September	1st to 10th	Night	16% 5% 2 5% 5% 3 4 4 5% 7% 43%	1800
	11th to 20th	Night	15% 5% 1 4 4 2 3 4 3 6% 53%	1870
	21st to end	Night	18% 6% 2 5% 4 3 3 4 5% 5% 47%	1980
October	1st to 10th	Night	22% 6% 3 5% 4 2 3 3 4 6% 42%	2088
	11th to 20th	Night	17% 5% 2 4 4 2 3 3 5% 7% 48%	2160
	21st to end	Night	22% 7% 2 4 4 2 3 4 4 6% 43%	2513
November	1st to 10th	Night	14% 5% 2 4 3 2 4 4 4 6% 50%	2407
	11th to 20th	Night	21% 6% 1 4 3 2 3 3 4 5% 48%	2470
	21st to end	Night	15% 4 2 5% 5% 3 4 4 5% 7% 47%	2564
December	1st to 10th	Night	20% 6% 3 4 5% 2 4 5% 5% 6% 40%	2660
	11th to 20th	Night	20% 7% 2 4 4 3 4 4 5% 5% 42%	3288
	21st to end	Night	20% 9% 3 6% 5% 4 4 4 4 6% 36%	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	38% 3 10% 32% 13% 3	2518
	11th to 20th	Day	49% 4 11% 21% 12% 2	2520
	21st to end	Day	54% 5% 8% 21% 10% 1	3010
February	1st to 10th	Day	45% 5% 13% 21% 13% 2	1701
	11th to 20th	Day	43% 4 9% 24% 17% 3	1753
	21st to end	Day	46% 4 11% 21% 14% 3	1480
March	1st to 10th	Day	40% 5% 13% 24% 15% 3	1800
	11th to 20th	Day	43% 6% 12% 22% 15% 2	1905
	21st to end	Day	47% 4 9% 18% 17% 5%	2348
April	1st to 10th	Day	44% 5% 10% 20% 16% 5%	2160
	11th to 20th	Day	42% 4 11% 21% 18% 4	2134
	21st to end	Day	44% 5% 10% 21% 16% 4	2178
May	1st to 10th	Day	49% 5% 9% 18% 16% 3	2340
	11th to 20th	Day	45% 7% 9% 21% 14% 3	2482
	21st to end	Day	41% 8% 14% 22% 14% 2	2725
June	1st to 10th	Day	41% 8% 14% 20% 15% 2	2520
	11th to 20th	Day	45% 8% 10% 23% 12% 2	2520
	21st to end	Day	39% 8% 13% 22% 16% 1	2520
July	1st to 10th	Day	42% 8% 10% 22% 16% 1	2450
	11th to 20th	Day	36% 8% 15% 24% 15% 2	2445
	21st to end	Day	43% 7% 11% 19% 17% 3	2591
August	1st to 10th	Day	40% 9% 13% 23% 15% 1	2366
	11th to 20th	Day	42% 8% 13% 23% 13% 1	2126
	21st to end	Day	40% 6% 10% 22% 18% 3	2376
September	1st to 10th	Day	42% 6% 10% 22% 17% 3	2160
	11th to 20th	Day	35% 5% 10% 23% 25% 2	2089
	21st to end	Day	43% 5% 9% 20% 19% 4	1980
October	1st to 10th	Day	43% 6% 9% 23% 16% 3	1868
	11th to 20th	Day	38% 5% 11% 26% 19% 2	1800
	21st to end	Day	44% 5% 9% 23% 17% 3	1841
November	1st to 10th	Day	36% 4 10% 25% 22% 3	1671
	11th to 20th	Day	38% 4 11% 23% 20% 4	1710
	21st to end	Day	38% 5% 13% 29% 12% 3	1615
December	1st to 10th	Day	45% 6% 15% 19% 14% 1	1520
	11th to 20th	Day	42% 3 15% 23% 13% 3	1906
	21st to end	Day	51% 7% 10% 24% 8%	2772
January	1st to 10th	Night	38% 4 11% 31% 12% 4	4429
	11th to 20th	Night	44% 5% 12% 24% 12% 2	4440
	21st to end	Night	52% 4 8% 22% 12% 2	4630
February	1st to 10th	Night	43% 5% 13% 24% 13% 2	2464
	11th to 20th	Night	44% 5% 10% 19% 17% 5%	2104
	21st to end	Night	46% 3 6% 25% 17% 3	1776
March	1st to 10th	Night	40% 5% 12% 24% 15% 5%	2160
	11th to 20th	Night	42% 4 12% 21% 17% 3	2052
	21st to end	Night	43% 5% 10% 18% 19% 6%	2006
April	1st to 10th	Night	44% 4 10% 21% 17% 4	1800
	11th to 20th	Night	43% 5% 9% 21% 20% 2	1775
	21st to end	Night	44% 5% 9% 20% 18% 4	1782
May	1st to 10th	Night	51% 5% 9% 18% 15% 2	1620
	11th to 20th	Night	46% 6% 9% 17% 19% 3	1432
	21st to end	Night	41% 7% 16% 21% 12% 3	1551
June	1st to 10th	Night	41% 7% 10% 21% 19% 2	1440
	11th to 20th	Night	39% 8% 15% 26% 11% 1	1440
	21st to end	Night	34% 9% 14% 26% 16% 1	1440
July	1st to 10th	Night	39% 9% 13% 20% 15% 3	1400
	11th to 20th	Night	38% 9% 13% 25% 13% 1	1392
	21st to end	Night	33% 9% 17% 21% 17% 3	1486
August	1st to 10th	Night	35% 11% 13% 23% 15% 2	1527
	11th to 20th	Night	43% 10% 13% 23% 11% 1	1774
	21st to end	Night	39% 8% 12% 20% 20% 2	1980
September	1st to 10th	Night	41% 6% 9% 26% 17% 1	1800
	11th to 20th	Night	34% 4 10% 25% 24% 3	1870
	21st to end	Night	39% 5% 7% 23% 23% 2	1980
October	1st to 10th	Night	45% 5% 11% 23% 14% 2	2088
	11th to 20th	Night	38% 4 12% 28% 17% 2	2160
	21st to end	Night	44% 4 10% 24% 16% 2	2513
November	1st to 10th	Night	35% 5% 11% 23% 22% 4	2407
	11th to 20th	Night	40% 3 9% 24% 19% 4	2470
	21st to end	Night	37% 5% 13% 29% 14% 2	2564
December	1st to 10th	Night	44% 6% 12% 23% 13% 2	2660
	11th to 20th	Night	44% 4 13% 20% 16% 3	3288
	21st to end	Night	48% 7% 11% 23% 11% 1	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	21% 30% 31% 16% 3	180
	11th to 20th	Day	30% 23% 36% 9% 2	180
	21st to end	Day	21% 22% 39% 10% 6% 2	267
February	1st to 10th	Day	30% 19% 38% 10% 3	267
	11th to 20th	Day	25% 21% 37% 16% 1	412
	21st to end	Day	29% 18% 33% 17% 3	346
March	1st to 10th	Day	21% 26% 31% 18% 3	420
	11th to 20th	Day	21% 22% 34% 18% 5% 1	420
	21st to end	Day	27% 21% 30% 15% 6% 1	462
April	1st to 10th	Day	24% 21% 31% 14% 7% 1	420
	11th to 20th	Day	22% 20% 33% 15% 8% 1	412
	21st to end	Day	30% 18% 32% 13% 4 2	420
May	1st to 10th	Day	31% 19% 29% 14% 5% 2	423
	11th to 20th	Day	22% 15% 36% 19% 7% 1	447
	21st to end	Day	21% 9% 26% 28% 13% 3	485
June	1st to 10th	Day	18% 11% 31% 24% 13% 2	450
	11th to 20th	Day	20% 12% 31% 26% 10% 1	450
	21st to end	Day	15% 10% 31% 27% 14% 2	450
July	1st to 10th	Day	14% 7% 25% 31% 18% 5%	445
	11th to 20th	Day	11% 4 28% 32% 21% 4	444
	21st to end	Day	13% 8% 28% 33% 16% 2	488
August	1st to 10th	Day	12% 5% 25% 36% 14% 7%	446
	11th to 20th	Day	15% 5% 23% 34% 18% 5%	439
	21st to end	Day	14% 6% 29% 27% 17% 7%	495
September	1st to 10th	Day	18% 8% 27% 24% 16% 7%	450
	11th to 20th	Day	16% 7% 29% 23% 14% 11%	450
	21st to end	Day	20% 10% 32% 21% 12% 6%	450
October	1st to 10th	Day	27% 8% 28% 20% 14% 4	450
	11th to 20th	Day	19% 16% 30% 23% 12% 1	450
	21st to end	Day	27% 13% 32% 18% 9% 1	426
November	1st to 10th	Day	17% 15% 30% 25% 11% 3	365
	11th to 20th	Day	24% 16% 32% 22% 5% 1	370
	21st to end	Day	17% 21% 35% 21% 4 2	275
December	1st to 10th	Day	26% 22% 32% 14% 6% 1	180
	11th to 20th	Day	31% 21% 34% 12% 2	180
	21st to end	Day	26% 18% 36% 14% 6% 1	198
January	1st to 10th	Night	19% 15% 42% 20% 3	760
	11th to 20th	Night	25% 15% 33% 24% 4	760
	21st to end	Night	20% 17% 36% 24% 3	836
February	1st to 10th	Night	22% 13% 37% 26% 2	759
	11th to 20th	Night	22% 18% 38% 21% 2	703
	21st to end	Night	24% 17% 35% 21% 3	592
March	1st to 10th	Night	22% 17% 36% 21% 4	720
	11th to 20th	Night	23% 14% 37% 22% 4 1	720
	21st to end	Night	21% 16% 36% 21% 5% 1	792
April	1st to 10th	Night	22% 17% 35% 21% 5%	720
	11th to 20th	Night	22% 14% 34% 23% 5%	711
	21st to end	Night	24% 14% 32% 24% 6%	702
May	1st to 10th	Night	23% 14% 33% 22% 7%	540
	11th to 20th	Night	24% 10% 32% 29% 6%	370
	21st to end	Night	20% 5% 21% 41% 12% 1	389
June	1st to 10th	Night	19% 4 27% 36% 14% 1	360
	11th to 20th	Night	16% 5% 29% 37% 13%	360
	21st to end	Night	11% 3 26% 48% 11%	360
July	1st to 10th	Night	13% 4 23% 39% 21% 1	350
	11th to 20th	Night	13% 4 20% 43% 19% 1	348
	21st to end	Night	15% 2 22% 44% 15% 1	394
August	1st to 10th	Night	11% 2 21% 43% 22% 2	463
	11th to 20th	Night	14% 4 20% 36% 25% 2	710
	21st to end	Night	16% 4 19% 37% 22% 2	792
September	1st to 10th	Night	18% 4 23% 36% 17% 2	720
	11th to 20th	Night	18% 4 22% 34% 18% 4	720
	21st to end	Night	21% 5% 25% 33% 15% 2	720
October	1st to 10th	Night	25% 8% 27% 24% 14% 3	720
	11th to 20th	Night	19% 10% 28% 30% 11%	720
	21st to end	Night	26% 10% 32% 23% 8%	792
November	1st to 10th	Night	16% 11% 31% 28% 13% 1	740
	11th to 20th	Night	23% 12% 33% 24% 8% 1	760
	21st to end	Night	19% 16% 33% 25% 7% 1	760
December	1st to 10th	Night	25% 13% 32% 24% 5% 1	760
	11th to 20th	Night	22% 13% 34% 26% 4	760
	21st to end	Night	23% 13% 35% 27% 2	836

Page generated at 2024-02-07 06:11:55. Version ac07

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