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 2024-11-05.

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% 9% 3 7% 5% 4 4 4 6% 8% 37%	101252
	Night	14% 9% 3 7% 4 4 4 3 5% 7% 39%	97846
Transparency	Day	43% 6% 12% 22% 14% 2	104831
	Night	44% 6% 11% 22% 15% 2	102395
Seeing	Day	16% 10% 28% 25% 16% 6%	15748
	Night	17% 10% 30% 30% 12% 1	25576

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	14% 13% 8% 13% 5% 5% 4 3 5% 6% 23%	2527
	11th to 20th	Day	13% 13% 5% 16% 8% 6% 3 6% 7% 4 17%	2530
	21st to end	Day	21% 22% 7% 11% 5% 3 3 2 3 5% 18%	2919
February	1st to 10th	Day	17% 12% 5% 8% 5% 6% 5% 3 4 6% 28%	1774
	11th to 20th	Day	14% 12% 4 8% 5% 6% 4 3 5% 6% 33%	1848
	21st to end	Day	15% 14% 5% 10% 4 4 3 3 5% 6% 30%	1570
March	1st to 10th	Day	17% 17% 5% 6% 4 3 4 3 4 6% 32%	3120
	11th to 20th	Day	9% 8% 3 7% 4 5% 5% 4 7% 8% 40%	3273
	21st to end	Day	18% 12% 5% 10% 5% 5% 5% 4 6% 6% 24%	4165
April	1st to 10th	Day	15% 12% 3 8% 5% 4 4 3 5% 7% 35%	2280
	11th to 20th	Day	16% 9% 3 6% 6% 4 4 4 4 7% 37%	2254
	21st to end	Day	20% 8% 2 8% 5% 4 4 3 5% 7% 34%	2358
May	1st to 10th	Day	17% 8% 2 7% 5% 5% 5% 4 6% 9% 31%	4082
	11th to 20th	Day	16% 7% 2 6% 4 4 4 4 6% 8% 39%	4229
	21st to end	Day	10% 5% 2 5% 4 4 4 4 6% 9% 45%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 5% 6% 8% 43%	2660
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 45%	2660
	21st to end	Day	11% 5% 2 7% 5% 4 6% 4 8% 9% 39%	2660
July	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 11% 33%	4440
	11th to 20th	Day	7% 4 2 5% 5% 5% 5% 4 7% 10% 46%	4440
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 6% 9% 41%	4813
August	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 6% 9% 47%	4226
	11th to 20th	Day	10% 6% 2 5% 4 3 5% 5% 7% 11% 44%	3729
	21st to end	Day	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 6% 7% 47%	2280
	11th to 20th	Day	11% 5% 1 5% 3 3 5% 3 5% 7% 51%	2157
	21st to end	Day	11% 5% 2 6% 5% 4 4 3 6% 8% 45%	2090
October	1st to 10th	Day	11% 7% 3 6% 4 4 4 4 5% 7% 46%	2047
	11th to 20th	Day	16% 7% 2 6% 4 4 5% 3 5% 6% 41%	1900
	21st to end	Day	18% 10% 2 7% 5% 4 4 3 5% 7% 35%	1887
November	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 5% 7% 48%	1708
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 3 5% 6% 37%	1710
	21st to end	Day	17% 11% 3 8% 4 3 3 4 4 5% 36%	1691
December	1st to 10th	Day	15% 15% 4 10% 7% 5% 4 3 4 5% 30%	1520
	11th to 20th	Day	14% 14% 5% 10% 6% 5% 4 4 5% 5% 28%	1918
	21st to end	Day	23% 17% 8% 15% 5% 4 3 2 3 4 15%	2783
January	1st to 10th	Night	15% 16% 7% 10% 5% 4 4 3 5% 4 27%	4428
	11th to 20th	Night	14% 19% 7% 12% 5% 4 5% 3 6% 4 19%	4440
	21st to end	Night	25% 16% 7% 9% 4 4 4 3 4 4 22%	4747
February	1st to 10th	Night	18% 13% 4 9% 6% 4 3 3 4 6% 30%	2404
	11th to 20th	Night	15% 10% 3 8% 5% 5% 5% 3 5% 6% 36%	2218
	21st to end	Night	18% 12% 4 8% 4 4 4 4 4 6% 33%	1884
March	1st to 10th	Night	17% 13% 3 6% 4 3 3 3 4 6% 39%	3733
	11th to 20th	Night	11% 7% 3 6% 5% 4 4 3 4 7% 46%	3701
	21st to end	Night	20% 10% 5% 10% 5% 5% 5% 4 5% 6% 27%	3466
April	1st to 10th	Night	13% 10% 3 7% 4 5% 4 4 5% 7% 39%	1900
	11th to 20th	Night	17% 9% 2 5% 4 4 4 3 4 6% 41%	1875
	21st to end	Night	19% 7% 2 6% 5% 5% 4 4 6% 8% 34%	1820
May	1st to 10th	Night	17% 8% 2 8% 4 5% 4 4 6% 9% 33%	2813
	11th to 20th	Night	15% 7% 2 6% 3 4 5% 3 6% 9% 39%	2665
	21st to end	Night	9% 7% 2 6% 5% 4 5% 4 6% 8% 44%	2743
June	1st to 10th	Night	9% 6% 2 5% 4 4 4 2 5% 7% 51%	1520
	11th to 20th	Night	7% 5% 3 6% 5% 4 3 3 5% 10% 50%	1520
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	1520
July	1st to 10th	Night	11% 5% 2 6% 4 5% 6% 4 6% 9% 41%	2530
	11th to 20th	Night	6% 4 1 5% 5% 3 4 4 6% 8% 56%	2530
	21st to end	Night	5% 5% 2 6% 5% 5% 5% 4 6% 9% 48%	2750
August	1st to 10th	Night	6% 4 1 6% 4 4 4 4 8% 8% 51%	2702
	11th to 20th	Night	6% 4 2 5% 4 4 5% 3 6% 9% 51%	3100
	21st to end	Night	7% 4 2 5% 3 4 4 3 5% 9% 53%	3476
September	1st to 10th	Night	11% 4 2 4 4 3 4 2 5% 7% 54%	1900
	11th to 20th	Night	7% 5% 2 4 3 3 4 4 5% 7% 56%	2004
	21st to end	Night	10% 5% 2 6% 4 5% 5% 3 6% 8% 46%	2090
October	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 5% 5% 54%	2128
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 4 7% 49%	2280
	21st to end	Night	19% 8% 3 6% 4 4 3 3 5% 6% 39%	2709
November	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 5% 6% 49%	2470
	11th to 20th	Night	13% 9% 3 8% 5% 4 4 4 4 6% 40%	2470
	21st to end	Night	18% 11% 3 7% 4 4 3 3 5% 5% 37%	2487
December	1st to 10th	Night	16% 11% 4 9% 5% 5% 4 3 5% 6% 33%	2660
	11th to 20th	Night	15% 14% 4 9% 5% 4 4 3 4 5% 34%	3279
	21st to end	Night	23% 18% 7% 12% 6% 5% 4 3 4 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	62% 5% 13% 15% 6%	2528
	11th to 20th	Day	66% 5% 9% 11% 8% 1	2530
	21st to end	Day	71% 4 7% 13% 4	2919
February	1st to 10th	Day	58% 5% 11% 17% 7% 2	1774
	11th to 20th	Day	51% 5% 11% 22% 9% 1	1858
	21st to end	Day	56% 4 11% 22% 6% 3	1570
March	1st to 10th	Day	55% 5% 10% 17% 12% 1	3120
	11th to 20th	Day	38% 7% 13% 28% 13% 1	3273
	21st to end	Day	57% 8% 15% 16% 3	4165
April	1st to 10th	Day	48% 6% 12% 20% 13%	2280
	11th to 20th	Day	47% 6% 10% 22% 12% 4	2254
	21st to end	Day	50% 6% 12% 18% 11% 2	2358
May	1st to 10th	Day	46% 9% 12% 24% 9%	4120
	11th to 20th	Day	42% 7% 12% 28% 10% 1	4233
	21st to end	Day	33% 8% 12% 20% 22% 5%	4837
June	1st to 10th	Day	36% 8% 12% 25% 17% 3	2660
	11th to 20th	Day	35% 7% 10% 23% 21% 4	2660
	21st to end	Day	39% 8% 14% 20% 15% 3	2660
July	1st to 10th	Day	43% 8% 13% 23% 11% 2	4371
	11th to 20th	Day	31% 8% 16% 28% 16% 1	4365
	21st to end	Day	37% 8% 17% 18% 18% 3	4662
August	1st to 10th	Day	31% 7% 18% 29% 14% 1	4211
	11th to 20th	Day	33% 6% 14% 29% 16% 1	3765
	21st to end	Day	30% 7% 13% 29% 17% 4	4179
September	1st to 10th	Day	36% 6% 12% 24% 18% 4	2280
	11th to 20th	Day	31% 6% 11% 26% 22% 5%	2157
	21st to end	Day	36% 6% 10% 27% 20% 2	2090
October	1st to 10th	Day	26% 5% 7% 26% 34% 2	3398
	11th to 20th	Day	30% 4 11% 23% 30% 1	3140
	21st to end	Day	41% 4 9% 24% 19% 2	3087
November	1st to 10th	Day	36% 5% 14% 24% 18% 3	1708
	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	58% 6% 11% 15% 9%	4428
	11th to 20th	Night	67% 4 10% 12% 7%	4440
	21st to end	Night	67% 4 10% 13% 6%	4747
February	1st to 10th	Night	55% 5% 11% 18% 10% 1	2404
	11th to 20th	Night	49% 4 12% 21% 12% 1	2219
	21st to end	Night	52% 5% 12% 18% 11% 3	1884
March	1st to 10th	Night	47% 6% 11% 24% 10% 2	3733
	11th to 20th	Night	37% 6% 10% 26% 19% 2	3701
	21st to end	Night	56% 8% 11% 19% 6% 1	3466
April	1st to 10th	Night	45% 6% 12% 22% 13% 2	1900
	11th to 20th	Night	43% 6% 8% 22% 16% 4	1875
	21st to end	Night	46% 7% 13% 20% 12% 3	1820
May	1st to 10th	Night	46% 8% 12% 21% 12% 1	2840
	11th to 20th	Night	40% 8% 17% 25% 10%	2666
	21st to end	Night	34% 9% 11% 21% 19% 5%	2751
June	1st to 10th	Night	33% 6% 12% 27% 19% 4	1520
	11th to 20th	Night	31% 6% 12% 24% 23% 3	1520
	21st to end	Night	35% 9% 15% 22% 15% 4	1520
July	1st to 10th	Night	38% 6% 14% 26% 11% 5%	2490
	11th to 20th	Night	25% 6% 13% 29% 25% 2	2482
	21st to end	Night	32% 7% 18% 20% 19% 5%	2662
August	1st to 10th	Night	28% 7% 19% 27% 18% 1	2693
	11th to 20th	Night	29% 6% 15% 28% 20% 2	3130
	21st to end	Night	28% 5% 13% 32% 19% 3	3476
September	1st to 10th	Night	30% 6% 10% 26% 22% 5%	1900
	11th to 20th	Night	26% 7% 8% 27% 26% 5%	2004
	21st to end	Night	36% 7% 11% 24% 20% 3	2090
October	1st to 10th	Night	20% 4 7% 32% 34% 3	3544
	11th to 20th	Night	27% 4 8% 25% 33% 2	3779
	21st to end	Night	37% 3 8% 25% 22% 4	4459
November	1st to 10th	Night	35% 5% 11% 27% 18% 4	2470
	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	23% 17% 41% 14% 6%	270
	21st to end	Day	22% 18% 32% 21% 7%	297
February	1st to 10th	Day	26% 14% 38% 17% 4	270
	11th to 20th	Day	24% 15% 34% 22% 5%	270
	21st to end	Day	27% 16% 40% 15% 3	225
March	1st to 10th	Day	23% 20% 37% 18% 1	270
	11th to 20th	Day	26% 15% 35% 19% 4	293
	21st to end	Day	29% 14% 32% 17% 7% 1	506
April	1st to 10th	Day	22% 15% 33% 23% 6% 1	460
	11th to 20th	Day	19% 17% 32% 18% 11% 3	452
	21st to end	Day	23% 15% 32% 21% 8% 2	460
May	1st to 10th	Day	18% 13% 30% 27% 10% 2	463
	11th to 20th	Day	19% 9% 29% 24% 15% 5%	570
	21st to end	Day	13% 8% 30% 23% 18% 8%	734
June	1st to 10th	Day	10% 7% 28% 32% 19% 5%	680
	11th to 20th	Day	10% 5% 30% 32% 19% 5%	680
	21st to end	Day	11% 8% 33% 29% 15% 4	680
July	1st to 10th	Day	10% 4 18% 29% 22% 17%	671
	11th to 20th	Day	8% 3 21% 32% 23% 14%	668
	21st to end	Day	8% 3 19% 37% 26% 8%	739
August	1st to 10th	Day	6% 3 16% 33% 29% 13%	596
	11th to 20th	Day	10% 4 18% 29% 26% 13%	479
	21st to end	Day	5% 3 17% 30% 32% 13%	539
September	1st to 10th	Day	11% 7% 15% 30% 27% 9%	490
	11th to 20th	Day	10% 4 14% 29% 30% 14%	490
	21st to end	Day	13% 7% 28% 21% 22% 9%	490
October	1st to 10th	Day	12% 7% 28% 29% 19% 6%	447
	11th to 20th	Day	14% 20% 32% 22% 10% 1	300
	21st to end	Day	29% 16% 31% 17% 5% 1	330
November	1st to 10th	Day	13% 13% 38% 22% 10% 5%	282
	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% 20% 5%	950
	21st to end	Night	22% 14% 35% 26% 3	1045
February	1st to 10th	Night	24% 12% 39% 22% 3	884
	11th to 20th	Night	19% 15% 36% 26% 4	743
	21st to end	Night	25% 14% 39% 20% 3	628
March	1st to 10th	Night	20% 15% 37% 24% 5%	760
	11th to 20th	Night	17% 12% 39% 26% 5% 1	737
	21st to end	Night	23% 11% 37% 24% 5%	627
April	1st to 10th	Night	17% 14% 37% 25% 6%	570
	11th to 20th	Night	20% 13% 33% 26% 7%	563
	21st to end	Night	23% 9% 34% 26% 7% 1	570
May	1st to 10th	Night	20% 7% 35% 31% 7%	570
	11th to 20th	Night	19% 6% 29% 33% 12% 1	561
	21st to end	Night	10% 6% 30% 34% 19%	617
June	1st to 10th	Night	11% 4 26% 46% 13%	570
	11th to 20th	Night	9% 4 26% 44% 15% 1	570
	21st to end	Night	10% 4 27% 42% 15% 1	570
July	1st to 10th	Night	8% 3 14% 41% 30% 5%	555
	11th to 20th	Night	7% 1 18% 41% 29% 3	552
	21st to end	Night	5% 2 14% 48% 29% 2	624
August	1st to 10th	Night	6% 3 14% 43% 31% 3	567
	11th to 20th	Night	6% 2 13% 43% 31% 4	564
	21st to end	Night	6% 2 16% 36% 38% 2	627
September	1st to 10th	Night	13% 2 15% 40% 26% 3	570
	11th to 20th	Night	8% 3 17% 38% 31% 4	674
	21st to end	Night	11% 7% 25% 32% 23% 2	760
October	1st to 10th	Night	13% 6% 23% 38% 19% 2	760
	11th to 20th	Night	17% 12% 33% 28% 10%	760
	21st to end	Night	23% 13% 33% 23% 8%	836
November	1st to 10th	Night	15% 10% 38% 26% 9% 1	760
	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 2024-11-03 01:11:19. Version ac07

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