Stelle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stelle clear sky chart from 2005-11-06 to 2024-01-15.

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	14% 8% 4 6% 6% 3 5% 5% 5% 7% 37%	74829
	Night	14% 9% 4 6% 5% 3 4 4 5% 7% 39%	74978
Transparency	Day	45% 7% 12% 21% 13% 2	74530
	Night	45% 6% 12% 21% 14% 2	74798
Seeing	Day	16% 10% 28% 25% 16% 6%	14580
	Night	17% 10% 30% 30% 12% 1	24553

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	15% 14% 6% 8% 7% 4 6% 3 5% 6% 27%	1517
	11th to 20th	Day	16% 17% 7% 11% 7% 4 4 4 4 5% 21%	1477
	21st to end	Day	15% 15% 8% 9% 8% 4 4 4 4 6% 24%	1664
February	1st to 10th	Day	19% 12% 5% 7% 6% 4 6% 4 4 5% 27%	1681
	11th to 20th	Day	15% 11% 4 7% 7% 5% 5% 4 5% 7% 31%	1748
	21st to end	Day	16% 14% 6% 9% 5% 3 4 4 4 6% 30%	1480
March	1st to 10th	Day	15% 14% 6% 7% 6% 3 5% 4 5% 7% 30%	1800
	11th to 20th	Day	13% 11% 4 7% 5% 4 5% 6% 7% 8% 31%	1857
	21st to end	Day	22% 11% 5% 7% 5% 3 5% 5% 6% 5% 25%	2376
April	1st to 10th	Day	15% 10% 4 7% 5% 3 4 4 5% 7% 35%	2160
	11th to 20th	Day	16% 9% 3 5% 6% 4 4 5% 4 6% 37%	2134
	21st to end	Day	20% 8% 3 7% 6% 3 5% 5% 5% 7% 33%	2233
May	1st to 10th	Day	16% 9% 3 7% 7% 4 5% 5% 5% 8% 31%	2340
	11th to 20th	Day	20% 7% 3 5% 5% 3 4 5% 4 7% 35%	2379
	21st to end	Day	13% 6% 3 6% 5% 4 5% 6% 6% 8% 38%	2725
June	1st to 10th	Day	10% 5% 2 5% 6% 3 5% 6% 6% 8% 43%	2520
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 5% 7% 9% 44%	2520
	21st to end	Day	11% 4 3 6% 6% 3 6% 5% 7% 9% 39%	2520
July	1st to 10th	Day	9% 4 2 4 6% 3 4 6% 7% 12% 43%	2520
	11th to 20th	Day	9% 3 2 5% 6% 3 5% 5% 7% 9% 45%	2520
	21st to end	Day	7% 4 2 4 6% 4 5% 7% 7% 9% 44%	2743
August	1st to 10th	Day	6% 5% 2 5% 5% 4 5% 6% 7% 10% 46%	2408
	11th to 20th	Day	9% 5% 2 5% 6% 2 4 6% 6% 9% 46%	2125
	21st to end	Day	7% 4 2 5% 5% 3 5% 5% 6% 9% 50%	2376
September	1st to 10th	Day	12% 5% 2 6% 4 4 5% 5% 5% 8% 45%	2160
	11th to 20th	Day	12% 5% 1 5% 4 2 5% 4 5% 7% 51%	2044
	21st to end	Day	10% 5% 3 6% 5% 3 5% 4 5% 8% 47%	1980
October	1st to 10th	Day	12% 7% 3 6% 5% 3 4 5% 5% 7% 45%	1940
	11th to 20th	Day	17% 7% 2 5% 4 4 5% 5% 5% 6% 40%	1800
	21st to end	Day	19% 10% 3 5% 6% 3 5% 4 4 7% 35%	1788
November	1st to 10th	Day	12% 6% 2 5% 4 2 4 4 5% 7% 48%	1672
	11th to 20th	Day	17% 9% 4 7% 5% 3 4 4 5% 6% 37%	1710
	21st to end	Day	18% 10% 3 8% 5% 3 3 4 4 6% 37%	1691
December	1st to 10th	Day	15% 14% 4 9% 7% 4 4 4 4 5% 30%	1520
	11th to 20th	Day	14% 13% 6% 9% 7% 3 4 5% 5% 5% 28%	1918
	21st to end	Day	23% 17% 8% 14% 7% 3 4 3 3 4 15%	2783
January	1st to 10th	Night	14% 14% 5% 8% 7% 2 5% 4 5% 5% 33%	2648
	11th to 20th	Night	16% 13% 7% 9% 6% 3 5% 4 4 5% 28%	2589
	21st to end	Night	16% 13% 7% 8% 6% 3 5% 4 4 5% 28%	2691
February	1st to 10th	Night	19% 12% 5% 7% 7% 3 4 4 4 7% 28%	2277
	11th to 20th	Night	15% 10% 4 7% 5% 4 5% 4 5% 6% 35%	2098
	21st to end	Night	19% 11% 5% 7% 4 3 4 4 4 5% 32%	1776
March	1st to 10th	Night	15% 11% 4 6% 6% 4 4 4 5% 5% 36%	2160
	11th to 20th	Night	14% 8% 4 6% 5% 3 4 4 5% 8% 39%	2117
	21st to end	Night	19% 10% 4 7% 5% 3 5% 4 5% 7% 31%	1980
April	1st to 10th	Night	13% 8% 5% 6% 5% 4 4 6% 5% 7% 39%	1800
	11th to 20th	Night	17% 9% 3 4 5% 3 4 4 4 6% 40%	1775
	21st to end	Night	20% 7% 2 5% 5% 4 5% 5% 7% 7% 34%	1725
May	1st to 10th	Night	17% 8% 2 5% 5% 3 5% 5% 5% 9% 35%	1620
	11th to 20th	Night	16% 7% 2 5% 4 3 5% 4 6% 9% 40%	1510
	21st to end	Night	10% 6% 3 6% 6% 4 6% 5% 6% 8% 41%	1551
June	1st to 10th	Night	9% 6% 2 5% 4 3 4 3 4 7% 52%	1440
	11th to 20th	Night	7% 5% 3 6% 5% 3 3 4 5% 10% 50%	1440
	21st to end	Night	10% 4 3 5% 5% 4 5% 5% 6% 9% 44%	1440
July	1st to 10th	Night	7% 5% 2 4 4 3 6% 5% 7% 10% 47%	1440
	11th to 20th	Night	7% 3 2 4 5% 2 4 5% 5% 8% 56%	1440
	21st to end	Night	4 4 2 4 4 3 5% 5% 6% 9% 55%	1575
August	1st to 10th	Night	6% 3 1 5% 4 3 5% 5% 8% 9% 51%	1524
	11th to 20th	Night	6% 4 2 5% 4 3 5% 4 7% 9% 50%	1776
	21st to end	Night	7% 4 2 4 4 3 4 5% 5% 8% 54%	1980
September	1st to 10th	Night	12% 4 2 4 4 2 4 4 5% 7% 53%	1800
	11th to 20th	Night	8% 5% 2 3 4 2 3 4 5% 7% 56%	1898
	21st to end	Night	9% 5% 2 5% 5% 4 5% 5% 6% 8% 47%	1980
October	1st to 10th	Night	11% 5% 2 4 4 2 4 4 5% 6% 53%	2016
	11th to 20th	Night	15% 6% 2 5% 4 3 3 4 4 7% 47%	2160
	21st to end	Night	20% 8% 3 6% 5% 3 4 3 4 6% 38%	2566
November	1st to 10th	Night	12% 7% 2 5% 5% 2 4 4 5% 6% 49%	2406
	11th to 20th	Night	14% 8% 3 7% 5% 3 4 5% 4 6% 41%	2470
	21st to end	Night	18% 10% 4 6% 5% 3 4 3 4 6% 38%	2487
December	1st to 10th	Night	16% 10% 5% 8% 5% 4 4 4 5% 6% 33%	2660
	11th to 20th	Night	15% 13% 5% 8% 6% 3 4 4 3 5% 34%	3279
	21st to end	Night	23% 17% 7% 10% 7% 3 4 4 3 4 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	60% 4 11% 15% 10% 1	1518
	11th to 20th	Day	66% 5% 10% 13% 5% 1	1477
	21st to end	Day	63% 5% 10% 14% 7% 1	1664
February	1st to 10th	Day	60% 4 12% 16% 6% 2	1681
	11th to 20th	Day	53% 5% 12% 20% 8% 1	1758
	21st to end	Day	57% 4 10% 20% 6% 2	1480
March	1st to 10th	Day	54% 5% 13% 20% 7% 1	1800
	11th to 20th	Day	49% 6% 14% 21% 10% 1	1857
	21st to end	Day	60% 5% 12% 18% 5% 1	2376
April	1st to 10th	Day	48% 6% 13% 20% 13%	2160
	11th to 20th	Day	47% 6% 10% 22% 11% 4	2134
	21st to end	Day	51% 6% 12% 18% 10% 2	2233
May	1st to 10th	Day	50% 8% 12% 22% 8%	2340
	11th to 20th	Day	48% 8% 13% 19% 12% 1	2383
	21st to end	Day	42% 9% 12% 18% 17% 2	2725
June	1st to 10th	Day	36% 8% 12% 25% 17% 3	2520
	11th to 20th	Day	35% 7% 10% 22% 21% 4	2520
	21st to end	Day	39% 9% 15% 20% 14% 3	2520
July	1st to 10th	Day	34% 9% 14% 26% 14% 4	2451
	11th to 20th	Day	33% 9% 15% 26% 15% 2	2445
	21st to end	Day	33% 9% 15% 25% 16% 3	2591
August	1st to 10th	Day	30% 9% 16% 30% 13% 1	2393
	11th to 20th	Day	33% 7% 17% 24% 17% 1	2125
	21st to end	Day	28% 9% 13% 26% 18% 5%	2376
September	1st to 10th	Day	38% 6% 13% 24% 15% 4	2160
	11th to 20th	Day	32% 6% 11% 26% 20% 5%	2044
	21st to end	Day	34% 6% 10% 27% 21% 2	1980
October	1st to 10th	Day	39% 7% 12% 23% 17% 3	1940
	11th to 20th	Day	43% 6% 11% 23% 16% 1	1800
	21st to end	Day	49% 5% 12% 21% 11% 2	1788
November	1st to 10th	Day	36% 5% 14% 24% 18% 3	1672
	11th to 20th	Day	48% 5% 12% 21% 13% 1	1710
	21st to end	Day	51% 4 11% 22% 11% 1	1691
December	1st to 10th	Day	58% 5% 12% 18% 7% 1	1520
	11th to 20th	Day	56% 6% 10% 21% 6%	1915
	21st to end	Day	74% 4 9% 8% 4	2783
January	1st to 10th	Night	54% 5% 10% 18% 13% 1	2648
	11th to 20th	Night	59% 5% 14% 14% 8%	2589
	21st to end	Night	58% 4 12% 16% 8% 1	2691
February	1st to 10th	Night	57% 5% 11% 17% 9% 1	2277
	11th to 20th	Night	50% 4 12% 21% 11% 1	2099
	21st to end	Night	53% 5% 11% 17% 11% 3	1776
March	1st to 10th	Night	50% 6% 11% 22% 10% 1	2160
	11th to 20th	Night	43% 6% 13% 20% 15% 3	2117
	21st to end	Night	54% 5% 11% 19% 9% 1	1980
April	1st to 10th	Night	44% 6% 12% 23% 13% 2	1800
	11th to 20th	Night	44% 6% 8% 22% 16% 4	1775
	21st to end	Night	47% 7% 13% 19% 11% 3	1725
May	1st to 10th	Night	46% 7% 12% 24% 11%	1620
	11th to 20th	Night	42% 6% 15% 22% 15% 1	1511
	21st to end	Night	38% 11% 13% 19% 16% 4	1552
June	1st to 10th	Night	33% 6% 12% 27% 20% 4	1440
	11th to 20th	Night	31% 6% 13% 24% 23% 3	1440
	21st to end	Night	35% 9% 15% 22% 15% 4	1440
July	1st to 10th	Night	30% 8% 15% 28% 14% 5%	1400
	11th to 20th	Night	25% 6% 14% 30% 22% 2	1392
	21st to end	Night	25% 7% 16% 28% 20% 4	1487
August	1st to 10th	Night	27% 8% 17% 27% 18% 2	1515
	11th to 20th	Night	28% 7% 15% 25% 22% 3	1776
	21st to end	Night	27% 7% 13% 25% 22% 5%	1980
September	1st to 10th	Night	31% 6% 11% 26% 21% 6%	1800
	11th to 20th	Night	27% 7% 8% 28% 25% 5%	1898
	21st to end	Night	34% 7% 11% 25% 21% 3	1980
October	1st to 10th	Night	33% 6% 10% 25% 23% 3	2016
	11th to 20th	Night	37% 5% 9% 26% 21% 2	2160
	21st to end	Night	48% 4 9% 22% 15% 2	2566
November	1st to 10th	Night	35% 5% 11% 26% 18% 4	2406
	11th to 20th	Night	44% 5% 13% 21% 15% 2	2470
	21st to end	Night	49% 4 10% 24% 12% 1	2487
December	1st to 10th	Night	53% 4 13% 20% 9% 1	2660
	11th to 20th	Night	54% 5% 11% 19% 11% 1	3281
	21st to end	Night	73% 5% 8% 10% 4	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	23% 14% 33% 22% 7% 1	270
	11th to 20th	Day	24% 18% 39% 14% 6%	254
	21st to end	Day	19% 18% 34% 22% 7%	264
February	1st to 10th	Day	28% 15% 38% 15% 3	240
	11th to 20th	Day	26% 15% 34% 20% 5%	240
	21st to end	Day	29% 15% 41% 13% 2	198
March	1st to 10th	Day	23% 21% 36% 19% 1	240
	11th to 20th	Day	28% 12% 35% 20% 5%	261
	21st to end	Day	30% 14% 31% 17% 7% 1	462
April	1st to 10th	Day	21% 14% 33% 25% 6% 1	420
	11th to 20th	Day	20% 15% 33% 17% 12% 3	412
	21st to end	Day	24% 15% 30% 21% 7% 3	420
May	1st to 10th	Day	19% 13% 30% 26% 10% 3	423
	11th to 20th	Day	20% 9% 30% 24% 14% 4	525
	21st to end	Day	14% 7% 29% 24% 19% 8%	679
June	1st to 10th	Day	9% 6% 27% 33% 20% 6%	630
	11th to 20th	Day	11% 5% 29% 31% 20% 5%	630
	21st to end	Day	12% 8% 30% 30% 15% 5%	630
July	1st to 10th	Day	9% 4 17% 28% 24% 18%	621
	11th to 20th	Day	9% 3 20% 31% 23% 13%	618
	21st to end	Day	8% 2 20% 36% 25% 8%	684
August	1st to 10th	Day	5% 3 15% 33% 30% 14%	551
	11th to 20th	Day	10% 4 17% 28% 27% 15%	439
	21st to end	Day	5% 3 18% 30% 30% 14%	495
September	1st to 10th	Day	12% 7% 16% 28% 28% 9%	450
	11th to 20th	Day	10% 4 14% 30% 28% 13%	450
	21st to end	Day	11% 7% 28% 21% 23% 10%	450
October	1st to 10th	Day	13% 6% 29% 29% 17% 6%	410
	11th to 20th	Day	15% 22% 34% 22% 7%	270
	21st to end	Day	30% 16% 32% 17% 4 1	297
November	1st to 10th	Day	12% 13% 38% 22% 10% 5%	270
	11th to 20th	Day	24% 13% 36% 17% 9% 1	270
	21st to end	Day	26% 9% 36% 26% 4	270
December	1st to 10th	Day	17% 19% 37% 18% 9% 1	270
	11th to 20th	Day	17% 19% 35% 23% 5% 1	270
	21st to end	Day	23% 20% 39% 15% 4	297
January	1st to 10th	Night	20% 16% 38% 21% 5%	950
	11th to 20th	Night	23% 15% 36% 21% 5%	925
	21st to end	Night	21% 14% 35% 26% 3	990
February	1st to 10th	Night	25% 12% 39% 21% 3	837
	11th to 20th	Night	20% 16% 35% 26% 4	703
	21st to end	Night	26% 14% 38% 20% 3	592
March	1st to 10th	Night	20% 15% 36% 24% 5%	720
	11th to 20th	Night	18% 11% 38% 27% 6% 1	699
	21st to end	Night	23% 11% 37% 24% 5% 1	594
April	1st to 10th	Night	17% 14% 37% 26% 7%	540
	11th to 20th	Night	20% 12% 33% 27% 7%	533
	21st to end	Night	23% 9% 33% 27% 7% 1	540
May	1st to 10th	Night	21% 7% 34% 31% 7%	540
	11th to 20th	Night	20% 6% 29% 33% 12% 1	531
	21st to end	Night	10% 5% 30% 34% 20%	584
June	1st to 10th	Night	11% 4 25% 46% 13%	540
	11th to 20th	Night	9% 4 25% 45% 16% 1	540
	21st to end	Night	10% 4 26% 43% 16% 1	540
July	1st to 10th	Night	7% 2 14% 41% 31% 5%	525
	11th to 20th	Night	7% 1 18% 41% 29% 3	522
	21st to end	Night	5% 2 14% 48% 29% 2	591
August	1st to 10th	Night	5% 3 14% 42% 32% 4	537
	11th to 20th	Night	6% 2 13% 41% 33% 5%	534
	21st to end	Night	7% 2 16% 35% 38% 2	594
September	1st to 10th	Night	14% 3 16% 39% 26% 3	540
	11th to 20th	Night	8% 3 17% 37% 31% 4	638
	21st to end	Night	10% 7% 25% 32% 24% 3	720
October	1st to 10th	Night	13% 6% 23% 36% 20% 2	720
	11th to 20th	Night	18% 12% 33% 28% 10%	720
	21st to end	Night	24% 13% 33% 22% 7%	792
November	1st to 10th	Night	15% 10% 39% 26% 9% 1	740
	11th to 20th	Night	17% 14% 35% 27% 6% 1	760
	21st to end	Night	23% 11% 34% 25% 6%	777
December	1st to 10th	Night	21% 13% 38% 24% 4	950
	11th to 20th	Night	23% 10% 35% 26% 5%	950
	21st to end	Night	29% 14% 32% 22% 2	1045

Page generated at 2024-01-12 15:17:49. Version ac07

Copyright 2024 Attilla Danko