Sulligent
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sulligent clear sky chart from 2005-11-06 to 2024-05-13.

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% 7% 2 6% 4 4 5% 4 5% 7% 42%	84104
	Night	14% 7% 2 5% 4 4 4 3 5% 7% 45%	85400
Transparency	Day	40% 5% 10% 21% 19% 5%	83828
	Night	38% 5% 9% 20% 21% 6%	85197
Seeing	Day	16% 10% 23% 24% 19% 8%	14284
	Night	16% 9% 23% 29% 20% 4	24064

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	16% 14% 3 5% 3 3 3 3 4 6% 40%	2527
	11th to 20th	Day	21% 7% 3 6% 4 2 3 2 3 4 45%	2915
	21st to end	Day	23% 10% 2 5% 3 2 2 2 3 5% 43%	3476
February	1st to 10th	Day	18% 9% 4 6% 4 3 3 3 5% 5% 40%	1900
	11th to 20th	Day	22% 7% 2 6% 4 4 3 3 3 5% 40%	1848
	21st to end	Day	21% 8% 3 6% 4 4 3 3 5% 5% 40%	1570
March	1st to 10th	Day	23% 9% 3 7% 4 3 4 4 4 6% 32%	3120
	11th to 20th	Day	15% 7% 2 5% 4 3 4 4 6% 8% 42%	3292
	21st to end	Day	14% 8% 3 7% 5% 4 5% 4 5% 7% 39%	4165
April	1st to 10th	Day	13% 6% 2 5% 4 4 4 4 5% 8% 46%	2280
	11th to 20th	Day	14% 7% 3 5% 3 3 3 3 4 6% 47%	2254
	21st to end	Day	10% 6% 2 5% 4 4 4 3 6% 9% 48%	2280
May	1st to 10th	Day	14% 5% 2 5% 4 3 4 4 5% 7% 47%	2331
	11th to 20th	Day	10% 7% 2 7% 5% 4 5% 5% 6% 7% 43%	2329
	21st to end	Day	8% 5% 2 7% 6% 4 6% 5% 7% 8% 42%	2531
June	1st to 10th	Day	9% 6% 2 7% 6% 6% 6% 5% 8% 10% 36%	2340
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 11% 44%	2502
	21st to end	Day	8% 4 2 6% 4 5% 6% 5% 6% 8% 45%	2520
July	1st to 10th	Day	8% 6% 3 8% 7% 6% 6% 6% 8% 10% 32%	2520
	11th to 20th	Day	9% 5% 2 6% 6% 6% 6% 5% 8% 12% 34%	2471
	21st to end	Day	7% 4 2 6% 6% 7% 7% 7% 8% 10% 36%	2367
August	1st to 10th	Day	5% 5% 2 6% 6% 6% 6% 6% 9% 11% 37%	2148
	11th to 20th	Day	8% 6% 2 7% 6% 5% 8% 5% 8% 10% 35%	2125
	21st to end	Day	11% 6% 2 7% 5% 6% 6% 4 7% 8% 38%	2376
September	1st to 10th	Day	9% 5% 2 7% 5% 4 5% 4 6% 8% 45%	2160
	11th to 20th	Day	9% 5% 3 7% 5% 4 5% 4 5% 7% 45%	2009
	21st to end	Day	11% 4 2 5% 4 4 4 3 4 7% 52%	1980
October	1st to 10th	Day	9% 6% 2 5% 3 3 3 3 5% 6% 54%	1980
	11th to 20th	Day	10% 5% 1 5% 3 3 4 3 4 7% 55%	1872
	21st to end	Day	15% 5% 1 4 3 3 4 3 4 5% 53%	1930
November	1st to 10th	Day	10% 5% 1 5% 4 3 4 3 4 5% 55%	1672
	11th to 20th	Day	14% 5% 3 4 3 3 4 3 4 6% 52%	1710
	21st to end	Day	15% 8% 2 5% 3 3 4 3 5% 6% 44%	1710
December	1st to 10th	Day	20% 10% 3 6% 5% 4 4 3 4 5% 38%	1710
	11th to 20th	Day	17% 8% 3 6% 4 4 3 3 4 5% 42%	2153
	21st to end	Day	16% 10% 3 7% 4 4 4 4 5% 6% 37%	3031
January	1st to 10th	Night	19% 12% 2 5% 3 3 3 3 4 5% 40%	4428
	11th to 20th	Night	17% 9% 3 7% 3 3 2 2 3 5% 45%	4041
	21st to end	Night	22% 13% 2 6% 3 2 2 2 3 4 42%	4180
February	1st to 10th	Night	19% 9% 3 6% 3 3 3 3 4 5% 41%	2280
	11th to 20th	Night	22% 8% 2 5% 4 3 3 3 4 4 43%	2218
	21st to end	Night	20% 8% 2 6% 5% 4 3 3 5% 6% 38%	1884
March	1st to 10th	Night	22% 11% 3 6% 4 4 3 3 4 5% 36%	3733
	11th to 20th	Night	13% 8% 2 5% 3 3 4 3 5% 7% 45%	3695
	21st to end	Night	18% 9% 3 7% 4 4 4 3 4 5% 40%	3466
April	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 5% 7% 47%	1900
	11th to 20th	Night	13% 5% 2 5% 3 4 3 4 6% 7% 49%	1875
	21st to end	Night	11% 6% 2 4 5% 4 4 2 5% 7% 50%	1900
May	1st to 10th	Night	10% 5% 2 6% 4 3 3 3 6% 8% 51%	1848
	11th to 20th	Night	10% 6% 2 5% 5% 4 4 3 7% 9% 45%	1619
	21st to end	Night	5% 4 1 5% 4 6% 5% 5% 7% 10% 48%	1744
June	1st to 10th	Night	6% 5% 2 6% 5% 5% 5% 5% 8% 9% 44%	1620
	11th to 20th	Night	4 4 2 4 4 3 4 4 6% 11% 53%	1451
	21st to end	Night	5% 4 1 4 5% 4 6% 4 7% 10% 50%	1440
July	1st to 10th	Night	4 5% 2 6% 5% 6% 6% 6% 9% 10% 41%	1440
	11th to 20th	Night	6% 4 1 5% 5% 4 5% 5% 8% 12% 45%	1484
	21st to end	Night	5% 4 2 5% 5% 6% 6% 5% 8% 12% 41%	1946
August	1st to 10th	Night	3 3 1 4 5% 5% 7% 5% 9% 12% 44%	1790
	11th to 20th	Night	5% 5% 2 6% 5% 5% 6% 6% 8% 13% 40%	1776
	21st to end	Night	8% 5% 2 6% 5% 4 6% 3 7% 8% 45%	1980
September	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 9% 49%	1800
	11th to 20th	Night	9% 6% 2 5% 4 4 4 4 6% 8% 47%	1930
	21st to end	Night	8% 3 1 4 3 4 4 3 7% 8% 55%	1980
October	1st to 10th	Night	7% 4 2 4 2 3 4 3 4 5% 62%	1980
	11th to 20th	Night	12% 6% 1 5% 2 3 3 2 4 6% 53%	2084
	21st to end	Night	16% 6% 2 4 2 2 3 2 4 5% 53%	2425
November	1st to 10th	Night	11% 5% 1 5% 3 4 3 2 4 5% 56%	2406
	11th to 20th	Night	12% 6% 2 4 3 3 4 3 5% 5% 53%	2470
	21st to end	Night	16% 6% 2 4 4 3 3 4 5% 4 49%	2470
December	1st to 10th	Night	19% 8% 2 5% 3 4 4 3 5% 6% 42%	2470
	11th to 20th	Night	16% 8% 2 6% 3 3 4 3 4 6% 47%	3042
	21st to end	Night	17% 9% 3 7% 4 5% 5% 4 7% 6% 34%	4605

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	46% 3 5% 19% 22% 4	2528
	11th to 20th	Day	44% 3 5% 23% 22% 3	2915
	21st to end	Day	46% 2 6% 20% 20% 6%	3476
February	1st to 10th	Day	47% 3 7% 19% 19% 5%	1900
	11th to 20th	Day	48% 3 5% 18% 19% 7%	1858
	21st to end	Day	48% 3 6% 14% 21% 7%	1570
March	1st to 10th	Day	53% 3 8% 11% 15% 9%	3120
	11th to 20th	Day	41% 4 8% 22% 18% 7%	3292
	21st to end	Day	45% 4 9% 19% 18% 5%	4165
April	1st to 10th	Day	37% 4 10% 22% 19% 8%	2280
	11th to 20th	Day	38% 3 7% 22% 22% 7%	2254
	21st to end	Day	34% 4 10% 26% 23% 3	2280
May	1st to 10th	Day	37% 5% 10% 25% 18% 4	2331
	11th to 20th	Day	39% 6% 14% 24% 15% 2	2333
	21st to end	Day	37% 8% 14% 24% 15% 2	2531
June	1st to 10th	Day	39% 8% 13% 21% 16% 2	2340
	11th to 20th	Day	32% 8% 14% 26% 18% 2	2502
	21st to end	Day	34% 8% 16% 22% 17% 4	2520
July	1st to 10th	Day	41% 10% 19% 18% 10% 2	2451
	11th to 20th	Day	39% 10% 20% 19% 9% 2	2396
	21st to end	Day	38% 10% 21% 21% 10% 1	2235
August	1st to 10th	Day	36% 11% 20% 24% 9% 1	2136
	11th to 20th	Day	41% 9% 16% 20% 12% 2	2125
	21st to end	Day	40% 9% 15% 21% 10% 5%	2376
September	1st to 10th	Day	37% 7% 13% 20% 19% 4	2160
	11th to 20th	Day	38% 7% 11% 16% 22% 6%	2009
	21st to end	Day	32% 5% 9% 23% 21% 9%	1980
October	1st to 10th	Day	30% 4 8% 23% 26% 9%	1980
	11th to 20th	Day	30% 4 7% 23% 28% 9%	1872
	21st to end	Day	35% 3 5% 18% 30% 9%	1930
November	1st to 10th	Day	31% 4 6% 20% 29% 10%	1672
	11th to 20th	Day	34% 4 6% 20% 25% 11%	1710
	21st to end	Day	40% 4 6% 20% 23% 7%	1710
December	1st to 10th	Day	49% 4 6% 16% 19% 6%	1710
	11th to 20th	Day	45% 3 5% 18% 23% 5%	2150
	21st to end	Day	47% 4 7% 21% 19% 2	3031
January	1st to 10th	Night	47% 3 5% 16% 26% 3	4428
	11th to 20th	Night	44% 3 5% 21% 20% 7%	4041
	21st to end	Night	49% 3 2 20% 21% 5%	4180
February	1st to 10th	Night	45% 3 6% 20% 20% 6%	2280
	11th to 20th	Night	47% 3 5% 18% 20% 8%	2219
	21st to end	Night	48% 4 5% 16% 18% 10%	1884
March	1st to 10th	Night	50% 4 8% 14% 15% 9%	3733
	11th to 20th	Night	37% 5% 8% 21% 20% 10%	3695
	21st to end	Night	47% 4 6% 19% 21% 3	3466
April	1st to 10th	Night	37% 4 10% 22% 20% 7%	1900
	11th to 20th	Night	35% 4 8% 21% 23% 10%	1875
	21st to end	Night	34% 5% 9% 24% 23% 5%	1900
May	1st to 10th	Night	31% 4 12% 24% 24% 5%	1848
	11th to 20th	Night	35% 6% 15% 23% 17% 4	1620
	21st to end	Night	27% 9% 15% 27% 19% 3	1745
June	1st to 10th	Night	34% 9% 12% 23% 19% 3	1620
	11th to 20th	Night	24% 6% 17% 30% 19% 4	1451
	21st to end	Night	28% 9% 18% 21% 21% 4	1440
July	1st to 10th	Night	33% 11% 21% 21% 11% 3	1400
	11th to 20th	Night	29% 9% 21% 27% 12% 2	1436
	21st to end	Night	31% 9% 25% 24% 9% 2	1838
August	1st to 10th	Night	27% 10% 20% 31% 11% 1	1778
	11th to 20th	Night	33% 11% 20% 20% 11% 4	1776
	21st to end	Night	34% 9% 17% 23% 11% 5%	1980
September	1st to 10th	Night	32% 7% 15% 22% 19% 6%	1800
	11th to 20th	Night	34% 6% 13% 18% 22% 7%	1930
	21st to end	Night	27% 5% 9% 25% 24% 9%	1980
October	1st to 10th	Night	25% 4 8% 24% 25% 14%	1980
	11th to 20th	Night	33% 4 6% 19% 28% 11%	2084
	21st to end	Night	35% 3 5% 17% 29% 11%	2425
November	1st to 10th	Night	31% 3 6% 19% 27% 13%	2406
	11th to 20th	Night	33% 3 7% 18% 28% 12%	2470
	21st to end	Night	39% 3 6% 21% 23% 9%	2470
December	1st to 10th	Night	44% 3 8% 19% 21% 4	2470
	11th to 20th	Night	40% 3 6% 19% 26% 6%	3044
	21st to end	Night	47% 5% 7% 19% 19% 3	4605

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% 23% 32% 15% 3	270
	11th to 20th	Day	33% 17% 32% 14% 4	270
	21st to end	Day	26% 25% 33% 13% 3	297
February	1st to 10th	Day	28% 21% 33% 13% 4	270
	11th to 20th	Day	40% 17% 30% 12% 1	270
	21st to end	Day	36% 23% 32% 8% 1	225
March	1st to 10th	Day	28% 21% 33% 13% 5%	270
	11th to 20th	Day	25% 24% 31% 17% 3	294
	21st to end	Day	24% 16% 35% 18% 7%	506
April	1st to 10th	Day	23% 16% 32% 20% 8% 1	460
	11th to 20th	Day	21% 17% 28% 23% 9% 2	452
	21st to end	Day	15% 14% 32% 26% 13% 1	460
May	1st to 10th	Day	17% 10% 27% 28% 14% 3	463
	11th to 20th	Day	11% 4 30% 28% 18% 9%	456
	21st to end	Day	10% 4 25% 30% 21% 11%	485
June	1st to 10th	Day	12% 5% 17% 30% 25% 12%	450
	11th to 20th	Day	7% 3 17% 31% 28% 15%	612
	21st to end	Day	9% 3 16% 29% 29% 14%	630
July	1st to 10th	Day	6% 3 12% 31% 32% 16%	621
	11th to 20th	Day	9% 2 9% 24% 33% 23%	569
	21st to end	Day	8% 1 8% 26% 36% 22%	488
August	1st to 10th	Day	7% 2 12% 22% 35% 22%	446
	11th to 20th	Day	10% 2 10% 31% 31% 17%	439
	21st to end	Day	15% 3 9% 22% 31% 20%	495
September	1st to 10th	Day	9% 4 9% 33% 34% 11%	450
	11th to 20th	Day	8% 4 13% 27% 33% 15%	450
	21st to end	Day	13% 2 15% 30% 31% 8%	450
October	1st to 10th	Day	11% 4 22% 33% 22% 8%	450
	11th to 20th	Day	12% 10% 33% 30% 14% 1	342
	21st to end	Day	23% 11% 29% 26% 10% 1	297
November	1st to 10th	Day	17% 9% 31% 27% 13% 3	270
	11th to 20th	Day	14% 17% 38% 24% 6% 1	270
	21st to end	Day	18% 19% 34% 17% 10% 1	270
December	1st to 10th	Day	31% 19% 27% 20% 3 1	270
	11th to 20th	Day	21% 22% 34% 17% 7%	270
	21st to end	Day	28% 19% 36% 14% 4	297
January	1st to 10th	Night	24% 17% 32% 21% 5%	950
	11th to 20th	Night	23% 18% 28% 23% 8%	882
	21st to end	Night	23% 14% 36% 25% 2	836
February	1st to 10th	Night	26% 13% 31% 25% 5%	760
	11th to 20th	Night	26% 16% 30% 25% 3	743
	21st to end	Night	24% 21% 34% 19% 2	628
March	1st to 10th	Night	21% 15% 31% 28% 5%	760
	11th to 20th	Night	19% 14% 33% 26% 7% 1	733
	21st to end	Night	20% 10% 36% 24% 10%	627
April	1st to 10th	Night	16% 14% 32% 27% 12% 1	570
	11th to 20th	Night	16% 10% 32% 29% 11% 2	563
	21st to end	Night	12% 9% 33% 30% 13% 1	570
May	1st to 10th	Night	10% 7% 29% 30% 22% 2	570
	11th to 20th	Night	12% 4 23% 35% 21% 5%	540
	21st to end	Night	7% 3 16% 34% 34% 6%	584
June	1st to 10th	Night	7% 2 14% 37% 32% 7%	540
	11th to 20th	Night	5% 2 10% 33% 41% 10%	540
	21st to end	Night	5% 2 11% 30% 40% 11%	540
July	1st to 10th	Night	5% 2 6% 28% 45% 14%	525
	11th to 20th	Night	6% 1 7% 27% 41% 18%	522
	21st to end	Night	6% 1 8% 25% 43% 16%	591
August	1st to 10th	Night	5% 5% 26% 48% 15%	537
	11th to 20th	Night	7% 1 7% 33% 40% 12%	534
	21st to end	Night	10% 1 9% 28% 40% 12%	594
September	1st to 10th	Night	11% 2 11% 33% 37% 5%	540
	11th to 20th	Night	10% 4 14% 30% 37% 6%	670
	21st to end	Night	9% 2 15% 33% 37% 4	720
October	1st to 10th	Night	10% 3 19% 32% 30% 5%	720
	11th to 20th	Night	16% 6% 23% 35% 18% 1	720
	21st to end	Night	20% 7% 20% 32% 19% 2	792
November	1st to 10th	Night	13% 8% 21% 37% 18% 3	740
	11th to 20th	Night	13% 12% 29% 32% 13% 1	760
	21st to end	Night	20% 9% 29% 28% 12% 2	760
December	1st to 10th	Night	23% 12% 28% 28% 8%	760
	11th to 20th	Night	22% 13% 30% 26% 8%	760
	21st to end	Night	25% 14% 31% 26% 4	883

Page generated at 2024-05-10 11:39:05. Version ac07

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