Solarity Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Solarity Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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	13% 6% 3 5% 5% 3 5% 5% 5% 7% 42%	79282
	Night	13% 6% 2 5% 5% 3 4 4 5% 7% 46%	80213
Transparency	Day	40% 6% 11% 20% 18% 5%	79009
	Night	38% 5% 10% 20% 20% 6%	80006
Seeing	Day	16% 10% 22% 23% 19% 10%	13754
	Night	15% 8% 22% 29% 22% 4	23621

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	18% 11% 4 6% 5% 2 4 4 4 6% 38%	2836
	11th to 20th	Day	18% 7% 4 6% 4 2 3 2 3 4 47%	3004
	21st to end	Day	24% 9% 3 4 3 2 2 2 3 6% 42%	3476
February	1st to 10th	Day	20% 9% 3 6% 4 2 4 3 4 6% 39%	1900
	11th to 20th	Day	22% 7% 4 5% 4 2 3 4 4 5% 40%	1848
	21st to end	Day	22% 8% 3 5% 4 2 4 4 4 5% 39%	1570
March	1st to 10th	Day	17% 7% 3 5% 4 3 4 4 4 6% 43%	1850
	11th to 20th	Day	18% 7% 4 6% 6% 3 4 5% 5% 6% 37%	1871
	21st to end	Day	14% 6% 3 7% 5% 3 5% 5% 5% 7% 40%	2330
April	1st to 10th	Day	11% 4 3 5% 5% 3 4 5% 6% 7% 47%	2160
	11th to 20th	Day	13% 6% 2 5% 5% 3 4 4 5% 7% 46%	2134
	21st to end	Day	10% 4 2 5% 5% 3 4 5% 5% 9% 48%	2160
May	1st to 10th	Day	12% 5% 2 5% 5% 3 4 5% 6% 7% 47%	2276
	11th to 20th	Day	10% 6% 3 5% 5% 4 6% 5% 6% 9% 42%	2301
	21st to end	Day	8% 4 2 5% 7% 3 6% 6% 7% 9% 43%	2531
June	1st to 10th	Day	10% 5% 3 5% 7% 4 6% 6% 8% 10% 36%	2340
	11th to 20th	Day	5% 4 2 5% 5% 3 6% 7% 8% 10% 46%	2340
	21st to end	Day	8% 4 2 6% 6% 3 7% 6% 6% 9% 43%	2472
July	1st to 10th	Day	8% 4 3 7% 8% 5% 9% 7% 7% 10% 31%	2454
	11th to 20th	Day	8% 5% 3 5% 6% 5% 7% 8% 9% 12% 32%	2340
	21st to end	Day	7% 4 2 6% 6% 4 8% 8% 11% 12% 32%	2460
August	1st to 10th	Day	7% 4 3 5% 7% 4 7% 8% 10% 11% 35%	2148
	11th to 20th	Day	8% 6% 2 7% 7% 4 7% 7% 7% 11% 34%	2125
	21st to end	Day	12% 6% 2 7% 7% 4 7% 6% 7% 10% 33%	2376
September	1st to 10th	Day	10% 5% 2 6% 6% 4 6% 6% 6% 8% 41%	2142
	11th to 20th	Day	12% 7% 2 5% 5% 3 5% 5% 6% 7% 42%	1980
	21st to end	Day	11% 4 2 5% 5% 2 4 4 4 6% 52%	1980
October	1st to 10th	Day	10% 4 2 5% 4 3 4 3 5% 7% 53%	1980
	11th to 20th	Day	10% 4 2 5% 4 3 3 4 5% 7% 54%	1951
	21st to end	Day	15% 4 2 4 4 2 4 3 4 6% 53%	1868
November	1st to 10th	Day	12% 4 2 5% 4 3 3 4 3 5% 55%	1672
	11th to 20th	Day	13% 5% 2 4 3 3 4 4 4 6% 52%	1710
	21st to end	Day	16% 6% 2 5% 4 3 4 5% 4 7% 45%	1710
December	1st to 10th	Day	22% 9% 3 5% 4 2 4 4 4 6% 37%	1710
	11th to 20th	Day	18% 8% 3 6% 5% 3 4 4 3 4 44%	2153
	21st to end	Day	18% 9% 4 6% 6% 3 4 4 4 6% 36%	3124
January	1st to 10th	Night	18% 11% 2 5% 5% 3 3 4 4 5% 40%	4109
	11th to 20th	Night	19% 8% 3 5% 4 2 2 3 4 5% 44%	3951
	21st to end	Night	22% 11% 3 4 4 2 4 3 4 3 40%	4180
February	1st to 10th	Night	19% 7% 3 5% 4 2 3 3 5% 5% 43%	2280
	11th to 20th	Night	22% 6% 3 5% 4 2 3 3 4 5% 43%	2218
	21st to end	Night	22% 6% 2 5% 5% 3 4 4 5% 5% 39%	1884
March	1st to 10th	Night	17% 6% 2 5% 4 3 3 4 5% 7% 45%	2227
	11th to 20th	Night	16% 6% 3 5% 4 3 5% 5% 5% 7% 42%	2088
	21st to end	Night	14% 6% 3 6% 6% 3 4 4 4 7% 44%	2039
April	1st to 10th	Night	11% 5% 2 4 4 3 4 5% 5% 8% 48%	1800
	11th to 20th	Night	14% 5% 2 5% 3 3 3 4 5% 7% 50%	1775
	21st to end	Night	10% 5% 3 4 3 2 4 4 5% 8% 52%	1800
May	1st to 10th	Night	10% 3 2 4 5% 3 4 3 4 9% 52%	1680
	11th to 20th	Night	9% 5% 3 6% 5% 3 5% 4 6% 8% 46%	1592
	21st to end	Night	7% 4 1 5% 5% 2 5% 5% 7% 11% 48%	1744
June	1st to 10th	Night	6% 5% 3 5% 6% 4 5% 6% 8% 9% 43%	1620
	11th to 20th	Night	4 3 1 4 4 3 5% 4 6% 12% 53%	1620
	21st to end	Night	6% 4 3 5% 6% 4 5% 5% 6% 9% 48%	1473
July	1st to 10th	Night	7% 4 2 5% 6% 4 7% 6% 6% 11% 41%	1494
	11th to 20th	Night	5% 4 2 5% 6% 4 6% 6% 8% 12% 42%	1620
	21st to end	Night	6% 5% 3 5% 6% 4 6% 7% 8% 11% 39%	1852
August	1st to 10th	Night	3 3 1 4 7% 4 7% 8% 8% 15% 42%	1790
	11th to 20th	Night	7% 4 2 6% 5% 3 6% 6% 8% 11% 42%	1776
	21st to end	Night	10% 6% 3 5% 5% 4 4 5% 6% 9% 42%	1980
September	1st to 10th	Night	8% 5% 3 5% 5% 3 4 4 5% 8% 49%	1800
	11th to 20th	Night	10% 6% 2 5% 6% 3 5% 4 6% 8% 45%	1979
	21st to end	Night	6% 5% 2 4 5% 3 3 5% 5% 8% 54%	1980
October	1st to 10th	Night	9% 5% 2 3 3 2 3 4 3 4 61%	1980
	11th to 20th	Night	11% 5% 2 5% 4 2 4 4 5% 6% 53%	2006
	21st to end	Night	15% 5% 2 4 3 2 2 3 3 5% 55%	2486
November	1st to 10th	Night	11% 4 2 4 4 2 3 3 4 5% 56%	2406
	11th to 20th	Night	13% 5% 2 4 4 3 3 3 4 7% 53%	2470
	21st to end	Night	15% 5% 2 5% 4 3 5% 4 5% 6% 48%	2470
December	1st to 10th	Night	20% 6% 3 4 4 2 5% 4 4 7% 40%	2470
	11th to 20th	Night	18% 6% 2 5% 4 2 3 3 4 5% 48%	3042
	21st to end	Night	19% 8% 3 6% 5% 3 5% 5% 6% 7% 33%	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	48% 3 6% 19% 20% 4	2837
	11th to 20th	Day	43% 3 5% 24% 22% 3	3004
	21st to end	Day	47% 2 7% 20% 20% 5%	3476
February	1st to 10th	Day	47% 3 7% 19% 19% 5%	1900
	11th to 20th	Day	48% 3 6% 18% 19% 7%	1858
	21st to end	Day	48% 4 6% 14% 22% 7%	1570
March	1st to 10th	Day	43% 3 9% 15% 19% 11%	1850
	11th to 20th	Day	48% 5% 10% 16% 18% 4	1871
	21st to end	Day	43% 5% 10% 22% 18% 2	2330
April	1st to 10th	Day	36% 4 11% 23% 18% 8%	2160
	11th to 20th	Day	38% 4 7% 21% 23% 7%	2134
	21st to end	Day	34% 5% 9% 26% 22% 3	2160
May	1st to 10th	Day	37% 4 11% 24% 20% 4	2276
	11th to 20th	Day	38% 7% 14% 23% 16% 2	2305
	21st to end	Day	36% 8% 14% 24% 17% 2	2531
June	1st to 10th	Day	40% 9% 14% 19% 17% 1	2340
	11th to 20th	Day	31% 8% 16% 27% 16% 2	2340
	21st to end	Day	36% 9% 16% 22% 12% 5%	2472
July	1st to 10th	Day	42% 10% 18% 19% 9% 2	2388
	11th to 20th	Day	40% 11% 22% 17% 8% 2	2271
	21st to end	Day	37% 13% 20% 19% 9% 1	2322
August	1st to 10th	Day	36% 11% 19% 25% 8% 1	2136
	11th to 20th	Day	41% 11% 15% 20% 11% 3	2125
	21st to end	Day	45% 9% 13% 20% 9% 4	2376
September	1st to 10th	Day	37% 8% 13% 19% 17% 5%	2142
	11th to 20th	Day	39% 8% 12% 16% 20% 5%	1980
	21st to end	Day	33% 5% 9% 22% 23% 8%	1980
October	1st to 10th	Day	31% 5% 8% 22% 26% 9%	1980
	11th to 20th	Day	31% 4 8% 22% 27% 8%	1951
	21st to end	Day	34% 4 4 18% 31% 9%	1868
November	1st to 10th	Day	33% 3 7% 19% 29% 9%	1672
	11th to 20th	Day	34% 4 6% 19% 26% 10%	1710
	21st to end	Day	39% 5% 6% 18% 24% 7%	1710
December	1st to 10th	Day	49% 4 7% 15% 20% 5%	1710
	11th to 20th	Day	46% 3 6% 19% 22% 5%	2150
	21st to end	Day	49% 3 8% 21% 18% 2	3124
January	1st to 10th	Night	48% 3 5% 16% 25% 3	4109
	11th to 20th	Night	44% 3 5% 22% 18% 7%	3951
	21st to end	Night	50% 3 3 19% 19% 5%	4180
February	1st to 10th	Night	44% 3 6% 20% 21% 6%	2280
	11th to 20th	Night	47% 3 5% 18% 19% 8%	2219
	21st to end	Night	46% 5% 6% 15% 19% 9%	1884
March	1st to 10th	Night	40% 3 7% 17% 21% 12%	2227
	11th to 20th	Night	41% 5% 11% 17% 19% 6%	2088
	21st to end	Night	41% 4 8% 24% 19% 4	2039
April	1st to 10th	Night	35% 4 12% 23% 20% 6%	1800
	11th to 20th	Night	36% 3 7% 22% 21% 12%	1775
	21st to end	Night	31% 5% 10% 27% 23% 5%	1800
May	1st to 10th	Night	30% 6% 11% 23% 26% 4	1680
	11th to 20th	Night	36% 6% 17% 21% 17% 4	1593
	21st to end	Night	29% 8% 15% 26% 18% 4	1745
June	1st to 10th	Night	34% 10% 13% 22% 19% 2	1620
	11th to 20th	Night	24% 7% 18% 28% 19% 4	1620
	21st to end	Night	32% 8% 14% 23% 20% 3	1473
July	1st to 10th	Night	35% 9% 22% 20% 10% 3	1451
	11th to 20th	Night	30% 10% 23% 22% 12% 2	1566
	21st to end	Night	34% 12% 23% 20% 10% 1	1749
August	1st to 10th	Night	27% 11% 23% 28% 10% 1	1778
	11th to 20th	Night	33% 12% 20% 18% 13% 4	1776
	21st to end	Night	37% 9% 17% 21% 11% 5%	1980
September	1st to 10th	Night	34% 7% 16% 21% 18% 5%	1800
	11th to 20th	Night	35% 7% 13% 18% 21% 6%	1979
	21st to end	Night	28% 7% 9% 23% 25% 9%	1980
October	1st to 10th	Night	28% 4 6% 23% 26% 13%	1980
	11th to 20th	Night	33% 3 7% 20% 26% 11%	2006
	21st to end	Night	34% 3 5% 16% 31% 11%	2486
November	1st to 10th	Night	31% 3 7% 18% 28% 14%	2406
	11th to 20th	Night	32% 3 7% 18% 28% 12%	2470
	21st to end	Night	38% 4 7% 20% 23% 8%	2470
December	1st to 10th	Night	44% 4 8% 18% 21% 4	2470
	11th to 20th	Night	40% 3 7% 18% 26% 6%	3044
	21st to end	Night	47% 4 7% 20% 19% 3	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	29% 22% 31% 13% 4	270
	11th to 20th	Day	30% 20% 30% 14% 6%	270
	21st to end	Day	25% 24% 38% 10% 3 1	297
February	1st to 10th	Day	29% 19% 34% 14% 5%	270
	11th to 20th	Day	36% 19% 29% 14% 2 1	270
	21st to end	Day	34% 24% 34% 8%	225
March	1st to 10th	Day	26% 19% 36% 12% 5% 2	255
	11th to 20th	Day	26% 21% 31% 15% 6% 1	311
	21st to end	Day	22% 17% 32% 20% 9%	462
April	1st to 10th	Day	17% 18% 27% 25% 11% 2	420
	11th to 20th	Day	18% 16% 26% 24% 14% 2	412
	21st to end	Day	14% 13% 29% 28% 14% 2	420
May	1st to 10th	Day	15% 10% 27% 27% 14% 7%	423
	11th to 20th	Day	9% 7% 27% 26% 19% 11%	447
	21st to end	Day	10% 6% 20% 29% 20% 16%	485
June	1st to 10th	Day	13% 3 17% 27% 27% 13%	450
	11th to 20th	Day	7% 3 15% 28% 26% 22%	450
	21st to end	Day	10% 3 16% 27% 29% 16%	582
July	1st to 10th	Day	8% 1 10% 27% 32% 22%	558
	11th to 20th	Day	8% 1 9% 21% 30% 31%	444
	21st to end	Day	6% 2 9% 20% 37% 26%	488
August	1st to 10th	Day	10% 3 11% 21% 29% 27%	446
	11th to 20th	Day	10% 1 10% 30% 33% 17%	439
	21st to end	Day	13% 3 9% 22% 32% 21%	495
September	1st to 10th	Day	9% 4 11% 28% 35% 13%	450
	11th to 20th	Day	11% 4 12% 25% 32% 16%	450
	21st to end	Day	13% 3 15% 25% 34% 10%	450
October	1st to 10th	Day	13% 3 23% 28% 25% 8%	450
	11th to 20th	Day	11% 9% 28% 35% 16% 1	421
	21st to end	Day	20% 13% 23% 27% 14% 2	297
November	1st to 10th	Day	21% 7% 30% 26% 11% 4	270
	11th to 20th	Day	15% 17% 40% 21% 7%	270
	21st to end	Day	16% 18% 34% 24% 7% 1	270
December	1st to 10th	Day	30% 17% 30% 18% 4 1	270
	11th to 20th	Day	24% 19% 33% 16% 7% 1	270
	21st to end	Day	31% 15% 31% 18% 4 1	297
January	1st to 10th	Night	23% 14% 33% 24% 5%	760
	11th to 20th	Night	25% 15% 28% 26% 7%	760
	21st to end	Night	22% 15% 33% 27% 3	836
February	1st to 10th	Night	23% 13% 30% 30% 5%	760
	11th to 20th	Night	27% 13% 30% 26% 3	743
	21st to end	Night	26% 16% 33% 23% 2	628
March	1st to 10th	Night	20% 15% 29% 30% 5%	743
	11th to 20th	Night	19% 13% 32% 26% 9% 1	720
	21st to end	Night	19% 12% 31% 27% 11%	653
April	1st to 10th	Night	14% 13% 30% 29% 13% 1	540
	11th to 20th	Night	15% 10% 32% 26% 15% 2	533
	21st to end	Night	12% 9% 28% 34% 16% 1	540
May	1st to 10th	Night	11% 4 28% 32% 22% 3	540
	11th to 20th	Night	11% 4 24% 31% 27% 4	531
	21st to end	Night	8% 2 12% 34% 36% 8%	584
June	1st to 10th	Night	8% 2 10% 34% 37% 7%	540
	11th to 20th	Night	4 1 11% 26% 44% 14%	540
	21st to end	Night	8% 1 8% 28% 44% 11%	540
July	1st to 10th	Night	6% 1 6% 26% 47% 15%	525
	11th to 20th	Night	7% 1 5% 24% 42% 21%	522
	21st to end	Night	7% 1 7% 24% 43% 17%	591
August	1st to 10th	Night	5% 4 26% 48% 17%	537
	11th to 20th	Night	7% 1 7% 31% 45% 10%	534
	21st to end	Night	14% 2 6% 26% 42% 11%	594
September	1st to 10th	Night	8% 1 11% 30% 41% 8%	540
	11th to 20th	Night	11% 3 13% 29% 38% 7%	719
	21st to end	Night	8% 2 15% 32% 38% 5%	720
October	1st to 10th	Night	10% 4 18% 31% 30% 6%	720
	11th to 20th	Night	13% 7% 23% 34% 21% 2	720
	21st to end	Night	18% 7% 19% 33% 20% 2	792
November	1st to 10th	Night	13% 7% 21% 34% 21% 3	740
	11th to 20th	Night	14% 10% 29% 33% 13% 2	760
	21st to end	Night	19% 8% 28% 31% 13% 1	760
December	1st to 10th	Night	22% 12% 25% 30% 10%	760
	11th to 20th	Night	24% 11% 28% 27% 10%	760
	21st to end	Night	25% 12% 29% 27% 6%	836

Page generated at 2024-03-03 05:28:59. Version ac07

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