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 2024-01-16.

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% 8% 43%	75047
	Night	13% 6% 2 5% 4 3 4 4 5% 7% 46%	74716
Transparency	Day	39% 6% 11% 21% 19% 5%	74771
	Night	37% 5% 10% 21% 21% 6%	74513
Seeing	Day	16% 9% 23% 24% 19% 9%	13874
	Night	15% 9% 23% 29% 20% 4	23643

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	20% 8% 3 5% 4 2 3 3 4 5% 45%	1517
	11th to 20th	Day	22% 9% 3 5% 5% 2 3 4 4 6% 38%	1704
	21st to end	Day	17% 6% 2 5% 4 2 4 4 4 5% 48%	1980
February	1st to 10th	Day	18% 9% 4 6% 5% 2 3 3 4 5% 40%	1800
	11th to 20th	Day	23% 7% 2 5% 4 3 3 4 4 5% 39%	1748
	21st to end	Day	22% 7% 3 5% 5% 3 3 3 4 5% 39%	1480
March	1st to 10th	Day	16% 6% 3 6% 5% 3 4 5% 4 6% 42%	1800
	11th to 20th	Day	17% 7% 3 5% 6% 3 5% 5% 6% 6% 37%	1862
	21st to end	Day	15% 6% 3 6% 5% 3 5% 4 5% 8% 40%	2376
April	1st to 10th	Day	13% 5% 2 4 4 3 4 4 5% 8% 47%	2160
	11th to 20th	Day	14% 7% 3 4 4 2 4 4 4 6% 48%	2134
	21st to end	Day	10% 5% 2 4 4 3 4 4 5% 9% 48%	2160
May	1st to 10th	Day	14% 5% 2 4 5% 2 4 4 4 7% 47%	2208
	11th to 20th	Day	10% 6% 3 6% 6% 4 5% 6% 6% 7% 43%	2301
	21st to end	Day	8% 4 3 6% 7% 3 6% 6% 7% 9% 42%	2531
June	1st to 10th	Day	9% 6% 2 6% 7% 4 6% 7% 7% 11% 37%	2340
	11th to 20th	Day	6% 3 2 5% 5% 4 6% 6% 7% 11% 44%	2502
	21st to end	Day	8% 4 2 5% 5% 4 6% 6% 6% 9% 46%	2520
July	1st to 10th	Day	8% 6% 3 7% 7% 5% 7% 7% 8% 10% 32%	2520
	11th to 20th	Day	9% 4 2 5% 7% 4 7% 7% 8% 12% 34%	2471
	21st to end	Day	7% 4 2 5% 6% 5% 8% 8% 8% 10% 36%	2367
August	1st to 10th	Day	5% 5% 2 4 8% 5% 6% 8% 9% 11% 37%	2148
	11th to 20th	Day	8% 6% 2 6% 7% 4 8% 7% 7% 10% 35%	2125
	21st to end	Day	12% 6% 2 6% 6% 4 6% 5% 7% 8% 38%	2376
September	1st to 10th	Day	9% 5% 2 6% 5% 3 5% 5% 6% 8% 45%	2160
	11th to 20th	Day	9% 5% 3 6% 6% 3 5% 5% 5% 7% 45%	2009
	21st to end	Day	11% 3 2 4 5% 3 4 4 4 7% 52%	1980
October	1st to 10th	Day	9% 5% 2 4 4 2 3 4 4 6% 55%	1980
	11th to 20th	Day	10% 5% 2 4 4 2 4 4 4 7% 55%	1872
	21st to end	Day	15% 5% 2 4 4 2 4 4 4 5% 53%	1930
November	1st to 10th	Day	10% 5% 2 4 5% 2 4 4 4 6% 55%	1672
	11th to 20th	Day	14% 5% 3 4 3 2 4 3 4 6% 53%	1710
	21st to end	Day	15% 7% 3 5% 4 2 4 5% 5% 6% 44%	1710
December	1st to 10th	Day	20% 9% 3 5% 5% 3 4 4 4 5% 38%	1710
	11th to 20th	Day	17% 8% 3 5% 4 3 3 4 4 5% 43%	2153
	21st to end	Day	16% 9% 3 6% 5% 3 4 5% 5% 6% 38%	3031
January	1st to 10th	Night	19% 7% 2 5% 5% 2 3 3 4 5% 45%	2648
	11th to 20th	Night	17% 10% 4 7% 4 2 4 3 3 6% 39%	2356
	21st to end	Night	17% 7% 2 6% 4 2 4 4 4 6% 45%	2376
February	1st to 10th	Night	19% 8% 3 6% 4 2 3 4 4 6% 42%	2160
	11th to 20th	Night	22% 7% 3 5% 4 2 3 3 4 4 43%	2098
	21st to end	Night	21% 7% 2 6% 5% 3 4 4 5% 6% 37%	1776
March	1st to 10th	Night	15% 8% 2 4 4 3 4 4 5% 6% 45%	2160
	11th to 20th	Night	16% 8% 3 5% 5% 3 4 4 6% 7% 40%	2111
	21st to end	Night	15% 7% 3 5% 5% 3 4 4 5% 6% 43%	1980
April	1st to 10th	Night	11% 5% 3 5% 5% 2 4 5% 5% 7% 48%	1800
	11th to 20th	Night	13% 5% 2 4 4 2 3 4 5% 8% 50%	1775
	21st to end	Night	11% 5% 2 4 5% 3 4 3 5% 7% 50%	1800
May	1st to 10th	Night	10% 5% 2 5% 4 2 4 4 5% 7% 53%	1751
	11th to 20th	Night	10% 6% 2 5% 5% 3 4 4 6% 9% 45%	1592
	21st to end	Night	6% 4 1 5% 4 4 5% 6% 7% 11% 49%	1744
June	1st to 10th	Night	6% 4 3 5% 5% 4 6% 5% 7% 10% 45%	1620
	11th to 20th	Night	4 4 2 3 5% 2 5% 5% 6% 11% 53%	1451
	21st to end	Night	5% 3 2 3 5% 3 5% 6% 6% 10% 51%	1440
July	1st to 10th	Night	5% 4 2 6% 5% 4 6% 7% 8% 11% 41%	1440
	11th to 20th	Night	6% 4 2 5% 5% 3 5% 6% 7% 12% 46%	1484
	21st to end	Night	5% 4 2 4 5% 4 7% 6% 8% 13% 41%	1946
August	1st to 10th	Night	3 3 2 4 5% 3 7% 7% 9% 13% 44%	1790
	11th to 20th	Night	5% 5% 2 5% 6% 4 6% 7% 8% 13% 41%	1776
	21st to end	Night	8% 5% 2 6% 6% 3 5% 4 7% 8% 45%	1980
September	1st to 10th	Night	11% 5% 3 4 4 2 3 4 5% 9% 49%	1800
	11th to 20th	Night	9% 6% 3 4 5% 3 4 5% 6% 8% 47%	1930
	21st to end	Night	8% 3 2 4 3 3 4 4 7% 8% 55%	1980
October	1st to 10th	Night	7% 4 2 4 3 2 4 4 4 6% 62%	1980
	11th to 20th	Night	12% 6% 2 4 4 2 4 3 4 6% 53%	2084
	21st to end	Night	16% 6% 2 4 3 1 3 3 4 5% 53%	2425
November	1st to 10th	Night	11% 4 2 5% 4 3 4 3 4 5% 57%	2406
	11th to 20th	Night	12% 5% 2 4 4 2 4 4 5% 5% 54%	2470
	21st to end	Night	16% 6% 2 4 4 2 3 5% 4 4 49%	2470
December	1st to 10th	Night	19% 7% 3 4 4 3 4 4 5% 6% 42%	2470
	11th to 20th	Night	16% 7% 2 5% 4 3 3 4 4 6% 47%	3042
	21st to end	Night	17% 9% 3 6% 5% 3 5% 5% 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	44% 3 7% 18% 23% 5%	1518
	11th to 20th	Day	49% 4 5% 19% 19% 4	1704
	21st to end	Day	40% 2 5% 24% 24% 5%	1980
February	1st to 10th	Day	47% 3 7% 19% 19% 4	1800
	11th to 20th	Day	48% 3 6% 18% 18% 6%	1758
	21st to end	Day	49% 3 6% 14% 22% 7%	1480
March	1st to 10th	Day	44% 4 7% 17% 18% 11%	1800
	11th to 20th	Day	47% 5% 10% 15% 18% 5%	1862
	21st to end	Day	43% 5% 10% 23% 17% 2	2376
April	1st to 10th	Day	36% 5% 10% 23% 19% 7%	2160
	11th to 20th	Day	38% 3 7% 23% 23% 7%	2134
	21st to end	Day	34% 4 10% 26% 24% 2	2160
May	1st to 10th	Day	37% 5% 10% 25% 18% 4	2208
	11th to 20th	Day	39% 6% 14% 23% 15% 2	2305
	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	43% 3 7% 19% 24% 4	2648
	11th to 20th	Night	49% 4 6% 18% 19% 5%	2356
	21st to end	Night	43% 3 4 21% 24% 6%	2376
February	1st to 10th	Night	45% 3 6% 20% 20% 6%	2160
	11th to 20th	Night	46% 3 5% 18% 20% 7%	2099
	21st to end	Night	48% 4 5% 16% 17% 9%	1776
March	1st to 10th	Night	40% 3 8% 17% 19% 13%	2160
	11th to 20th	Night	43% 5% 9% 18% 18% 6%	2111
	21st to end	Night	41% 4 8% 23% 20% 4	1980
April	1st to 10th	Night	37% 4 10% 23% 19% 7%	1800
	11th to 20th	Night	34% 4 8% 22% 23% 10%	1775
	21st to end	Night	34% 5% 9% 24% 23% 5%	1800
May	1st to 10th	Night	31% 4 11% 24% 25% 5%	1751
	11th to 20th	Night	35% 6% 16% 22% 17% 4	1593
	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	31% 18% 33% 14% 4	255
	21st to end	Day	24% 26% 33% 13% 3	264
February	1st to 10th	Day	29% 21% 33% 14% 3	240
	11th to 20th	Day	42% 18% 29% 11%	240
	21st to end	Day	35% 20% 34% 10% 1	198
March	1st to 10th	Day	27% 21% 33% 13% 5%	240
	11th to 20th	Day	26% 25% 28% 16% 4	262
	21st to end	Day	24% 16% 34% 18% 7%	462
April	1st to 10th	Day	20% 15% 34% 21% 9% 1	420
	11th to 20th	Day	20% 16% 28% 23% 10% 3	412
	21st to end	Day	15% 15% 30% 26% 13% 1	420
May	1st to 10th	Day	18% 10% 26% 28% 14% 4	423
	11th to 20th	Day	11% 4 30% 27% 18% 9%	447
	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%	861
	21st to end	Night	23% 14% 36% 25% 2	792
February	1st to 10th	Night	26% 13% 31% 25% 5%	720
	11th to 20th	Night	26% 16% 31% 25% 2	703
	21st to end	Night	25% 19% 34% 20% 2	592
March	1st to 10th	Night	20% 14% 32% 28% 5%	720
	11th to 20th	Night	19% 14% 32% 27% 7% 1	695
	21st to end	Night	20% 10% 35% 25% 10%	594
April	1st to 10th	Night	15% 13% 32% 27% 12% 1	540
	11th to 20th	Night	15% 11% 31% 29% 11% 2	533
	21st to end	Night	13% 9% 33% 31% 14% 1	540
May	1st to 10th	Night	11% 6% 29% 31% 22% 1	540
	11th to 20th	Night	12% 4 23% 35% 22% 5%	531
	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 2024-01-13 00:38:11. Version ac07

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