WHOPPER Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the WHOPPER Observatory clear sky chart from 2005-11-06 to 2024-12-09.

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	17% 7% 3 6% 4 4 4 4 5% 7% 38%	101655
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	98138
Transparency	Day	43% 6% 11% 23% 15% 2	105174
	Night	42% 5% 11% 23% 16% 2	102695
Seeing	Day	22% 17% 30% 20% 9% 2	15029
	Night	20% 16% 30% 24% 9% 1	24285

By Month

Percentage Cloud Cover NE (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% 9% 3 6% 4 4 3 3 4 4 45%	2517
	11th to 20th	Day	15% 10% 4 10% 6% 5% 4 3 5% 5% 31%	2520
	21st to end	Day	21% 10% 3 7% 4 5% 4 3 5% 5% 33%	3120
February	1st to 10th	Day	17% 9% 3 7% 4 5% 4 4 6% 6% 36%	1710
	11th to 20th	Day	15% 9% 3 7% 4 4 4 4 5% 6% 40%	1802
	21st to end	Day	20% 9% 3 7% 6% 3 4 4 4 4 36%	1570
March	1st to 10th	Day	26% 9% 3 6% 5% 3 3 3 4 5% 34%	3116
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 4 6% 8% 42%	3443
	21st to end	Day	21% 8% 2 5% 3 3 3 2 4 6% 42%	4064
April	1st to 10th	Day	18% 8% 3 7% 4 4 5% 4 5% 7% 37%	2280
	11th to 20th	Day	16% 8% 3 6% 5% 4 3 3 6% 7% 39%	2254
	21st to end	Day	17% 6% 2 7% 4 5% 5% 4 5% 6% 40%	2280
May	1st to 10th	Day	27% 8% 3 6% 4 4 4 4 5% 7% 28%	4143
	11th to 20th	Day	24% 9% 3 8% 5% 5% 4 4 4 6% 29%	4398
	21st to end	Day	13% 5% 2 6% 4 4 5% 4 7% 9% 42%	4837
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 5% 5% 6% 8% 36%	2660
	11th to 20th	Day	14% 6% 3 7% 4 5% 6% 4 7% 9% 35%	2660
	21st to end	Day	13% 6% 2 6% 4 5% 6% 4 6% 8% 40%	2660
July	1st to 10th	Day	8% 6% 3 8% 6% 6% 6% 5% 7% 10% 35%	4440
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 5% 7% 10% 39%	4440
	21st to end	Day	14% 9% 3 8% 5% 5% 5% 5% 7% 7% 32%	4814
August	1st to 10th	Day	21% 7% 2 6% 4 4 5% 5% 6% 8% 31%	4114
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 6% 8% 41%	3738
	21st to end	Day	12% 6% 2 5% 4 3 4 3 5% 8% 47%	4180
September	1st to 10th	Day	16% 5% 2 5% 5% 4 4 4 6% 7% 42%	2280
	11th to 20th	Day	13% 4 2 5% 4 3 4 3 5% 7% 50%	2239
	21st to end	Day	20% 6% 2 6% 4 4 4 4 4 5% 39%	2090
October	1st to 10th	Day	19% 5% 2 6% 4 4 4 4 5% 6% 40%	1916
	11th to 20th	Day	16% 6% 1 5% 4 4 4 3 5% 7% 46%	1900
	21st to end	Day	20% 5% 2 5% 4 4 4 4 5% 6% 41%	1992
November	1st to 10th	Day	14% 8% 2 4 3 3 3 2 4 5% 53%	1761
	11th to 20th	Day	18% 5% 1 5% 5% 3 4 4 5% 5% 45%	1800
	21st to end	Day	17% 7% 2 5% 4 4 4 4 4 7% 42%	1655
December	1st to 10th	Day	20% 7% 3 7% 4 4 4 4 5% 7% 35%	1584
	11th to 20th	Day	21% 7% 2 6% 3 5% 4 3 6% 6% 38%	1906
	21st to end	Day	18% 10% 4 9% 6% 5% 6% 4 5% 7% 26%	2772
January	1st to 10th	Night	16% 7% 3 6% 4 4 4 4 5% 6% 42%	4429
	11th to 20th	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 37%	4440
	21st to end	Night	24% 10% 3 5% 4 3 4 3 4 4 35%	4532
February	1st to 10th	Night	16% 9% 4 6% 4 4 3 3 5% 7% 39%	2470
	11th to 20th	Night	16% 8% 3 7% 5% 4 5% 3 4 6% 39%	2262
	21st to end	Night	19% 8% 2 5% 4 4 4 4 5% 5% 40%	1884
March	1st to 10th	Night	23% 10% 2 6% 3 3 4 3 4 5% 36%	3724
	11th to 20th	Night	11% 6% 2 7% 5% 4 4 4 5% 6% 47%	3511
	21st to end	Night	16% 10% 3 6% 4 4 4 2 4 5% 43%	3567
April	1st to 10th	Night	18% 7% 3 7% 5% 3 5% 4 5% 7% 36%	1900
	11th to 20th	Night	17% 7% 3 6% 4 4 4 3 6% 7% 39%	1875
	21st to end	Night	20% 6% 2 4 3 3 3 3 5% 7% 43%	1900
May	1st to 10th	Night	28% 8% 2 6% 4 3 4 3 5% 7% 29%	2823
	11th to 20th	Night	25% 9% 3 7% 4 4 4 4 5% 6% 29%	2495
	21st to end	Night	14% 6% 3 6% 4 4 5% 3 6% 9% 41%	2738
June	1st to 10th	Night	15% 6% 2 5% 4 4 5% 4 5% 8% 42%	1520
	11th to 20th	Night	13% 5% 2 5% 5% 4 4 4 7% 9% 41%	1520
	21st to end	Night	12% 5% 2 5% 4 4 4 4 7% 10% 44%	1520
July	1st to 10th	Night	10% 6% 2 7% 5% 5% 6% 4 8% 9% 37%	2520
	11th to 20th	Night	11% 6% 2 6% 4 4 6% 5% 8% 10% 37%	2520
	21st to end	Night	16% 7% 2 6% 4 4 4 5% 7% 8% 35%	2739
August	1st to 10th	Night	22% 7% 2 7% 5% 4 4 5% 6% 8% 30%	2812
	11th to 20th	Night	14% 7% 3 7% 5% 5% 4 4 5% 6% 40%	3058
	21st to end	Night	12% 5% 2 5% 3 4 4 4 5% 8% 49%	3476
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 4 6% 45%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 3 2 5% 7% 51%	1940
	21st to end	Night	18% 6% 3 5% 3 4 3 3 5% 6% 43%	2090
October	1st to 10th	Night	20% 7% 2 6% 4 3 3 3 4 6% 42%	2261
	11th to 20th	Night	17% 6% 1 5% 3 3 3 3 5% 6% 48%	2280
	21st to end	Night	21% 6% 2 4 3 3 3 3 5% 6% 44%	2604
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 4 6% 6% 51%	2537
	11th to 20th	Night	17% 8% 2 5% 3 3 4 3 4 5% 47%	2600
	21st to end	Night	14% 7% 3 6% 4 4 4 4 5% 7% 42%	2740
December	1st to 10th	Night	19% 7% 3 6% 4 5% 4 4 5% 5% 37%	2779
	11th to 20th	Night	18% 7% 2 5% 5% 4 4 4 5% 6% 38%	3288
	21st to end	Night	20% 10% 3 8% 4 4 3 3 4 6% 35%	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	42% 3 11% 29% 12% 3	2518
	11th to 20th	Day	52% 4 10% 20% 12% 2	2520
	21st to end	Day	53% 5% 9% 22% 9% 1	3120
February	1st to 10th	Day	46% 4 14% 22% 12% 2	1710
	11th to 20th	Day	45% 5% 9% 23% 15% 2	1811
	21st to end	Day	50% 3 10% 21% 11% 3	1570
March	1st to 10th	Day	52% 4 9% 26% 8% 2	3119
	11th to 20th	Day	37% 7% 11% 29% 14% 2	3443
	21st to end	Day	44% 4 8% 16% 23% 5%	4064
April	1st to 10th	Day	46% 5% 9% 20% 15% 5%	2280
	11th to 20th	Day	43% 5% 11% 21% 17% 3	2254
	21st to end	Day	44% 6% 9% 20% 16% 5%	2280
May	1st to 10th	Day	54% 6% 11% 16% 11% 2	4157
	11th to 20th	Day	56% 6% 10% 18% 9% 1	4402
	21st to end	Day	35% 8% 11% 26% 18% 3	4837
June	1st to 10th	Day	43% 6% 14% 22% 14% 1	2660
	11th to 20th	Day	43% 8% 13% 22% 10% 3	2660
	21st to end	Day	41% 7% 12% 24% 15% 1	2660
July	1st to 10th	Day	42% 9% 12% 21% 14% 2	4370
	11th to 20th	Day	38% 7% 16% 24% 13% 1	4365
	21st to end	Day	48% 6% 11% 17% 15% 1	4661
August	1st to 10th	Day	49% 7% 13% 21% 9%	4100
	11th to 20th	Day	38% 6% 13% 29% 13% 1	3774
	21st to end	Day	35% 6% 10% 30% 18% 2	4180
September	1st to 10th	Day	40% 7% 10% 21% 20% 3	2280
	11th to 20th	Day	34% 4 10% 24% 25% 4	2239
	21st to end	Day	46% 5% 8% 18% 20% 2	2090
October	1st to 10th	Day	39% 5% 8% 19% 23% 5%	3176
	11th to 20th	Day	29% 5% 10% 26% 26% 5%	3140
	21st to end	Day	28% 3 15% 24% 26% 4	3256
November	1st to 10th	Day	36% 3 12% 24% 21% 3	1761
	11th to 20th	Day	39% 4 10% 25% 19% 3	1800
	21st to end	Day	41% 3 15% 28% 11% 2	1655
December	1st to 10th	Day	47% 5% 15% 20% 12% 1	1584
	11th to 20th	Day	45% 5% 15% 23% 11% 1	1906
	21st to end	Day	54% 6% 11% 21% 8%	2772
January	1st to 10th	Night	40% 4 12% 29% 11% 3	4429
	11th to 20th	Night	47% 4 13% 24% 11% 2	4440
	21st to end	Night	51% 3 10% 23% 12% 2	4532
February	1st to 10th	Night	45% 5% 13% 24% 12% 2	2470
	11th to 20th	Night	46% 5% 9% 19% 17% 4	2264
	21st to end	Night	44% 4 8% 24% 17% 3	1884
March	1st to 10th	Night	50% 4 9% 24% 11% 2	3734
	11th to 20th	Night	37% 5% 13% 26% 18% 2	3512
	21st to end	Night	45% 4 6% 17% 22% 6%	3567
April	1st to 10th	Night	47% 5% 11% 20% 15% 4	1900
	11th to 20th	Night	44% 5% 9% 20% 20% 2	1875
	21st to end	Night	40% 5% 10% 22% 18% 4	1900
May	1st to 10th	Night	54% 6% 10% 19% 10% 1	2829
	11th to 20th	Night	53% 7% 13% 14% 10% 2	2496
	21st to end	Night	39% 8% 13% 24% 13% 2	2739
June	1st to 10th	Night	40% 6% 10% 22% 19% 1	1520
	11th to 20th	Night	38% 8% 15% 24% 13% 1	1520
	21st to end	Night	34% 9% 14% 27% 15% 1	1520
July	1st to 10th	Night	40% 9% 16% 18% 15% 2	2480
	11th to 20th	Night	39% 8% 15% 25% 12% 1	2472
	21st to end	Night	44% 8% 13% 16% 18% 2	2651
August	1st to 10th	Night	49% 8% 16% 16% 9% 1	2802
	11th to 20th	Night	42% 7% 13% 24% 13% 1	3088
	21st to end	Night	32% 6% 10% 31% 19% 1	3476
September	1st to 10th	Night	41% 5% 10% 22% 20% 2	1900
	11th to 20th	Night	34% 4 9% 22% 26% 4	1940
	21st to end	Night	42% 5% 8% 23% 22% 1	2090
October	1st to 10th	Night	41% 5% 9% 23% 20% 2	3768
	11th to 20th	Night	26% 5% 10% 28% 27% 4	3779
	21st to end	Night	29% 4 12% 31% 21% 3	4290
November	1st to 10th	Night	33% 5% 12% 24% 22% 4	2537
	11th to 20th	Night	41% 3 8% 24% 20% 4	2600
	21st to end	Night	39% 5% 13% 27% 14% 1	2740
December	1st to 10th	Night	46% 5% 12% 24% 12% 1	2779
	11th to 20th	Night	43% 5% 13% 20% 16% 3	3288
	21st to end	Night	50% 5% 12% 23% 10%	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	27% 27% 34% 10% 2 1	180
	11th to 20th	Day	31% 32% 26% 9% 1	180
	21st to end	Day	22% 30% 35% 8% 5%	295
February	1st to 10th	Day	25% 32% 32% 7% 3	270
	11th to 20th	Day	29% 28% 34% 8% 1	410
	21st to end	Day	33% 26% 25% 13% 2	382
March	1st to 10th	Day	26% 27% 29% 15% 3	460
	11th to 20th	Day	26% 28% 28% 14% 3 1	460
	21st to end	Day	30% 24% 31% 10% 5% 1	506
April	1st to 10th	Day	27% 24% 29% 15% 4 1	460
	11th to 20th	Day	24% 25% 30% 12% 8% 1	452
	21st to end	Day	26% 21% 35% 14% 3 2	460
May	1st to 10th	Day	31% 21% 30% 11% 7% 1	463
	11th to 20th	Day	22% 17% 34% 20% 6% 1	487
	21st to end	Day	20% 11% 28% 27% 12% 2	529
June	1st to 10th	Day	18% 17% 29% 22% 13% 1	490
	11th to 20th	Day	16% 15% 29% 25% 13% 2	490
	21st to end	Day	16% 14% 32% 25% 11% 2	490
July	1st to 10th	Day	13% 7% 28% 29% 18% 5%	485
	11th to 20th	Day	12% 5% 27% 35% 18% 3	484
	21st to end	Day	15% 7% 33% 29% 12% 3	532
August	1st to 10th	Day	14% 6% 30% 29% 16% 5%	486
	11th to 20th	Day	15% 6% 26% 30% 19% 4	479
	21st to end	Day	14% 9% 30% 27% 14% 7%	539
September	1st to 10th	Day	20% 11% 24% 26% 13% 6%	490
	11th to 20th	Day	14% 7% 29% 24% 15% 10%	490
	21st to end	Day	23% 12% 30% 20% 11% 4	490
October	1st to 10th	Day	25% 10% 29% 19% 13% 5%	490
	11th to 20th	Day	17% 19% 32% 21% 9% 2	490
	21st to end	Day	23% 18% 32% 17% 9% 1	486
November	1st to 10th	Day	18% 19% 28% 22% 10% 3	395
	11th to 20th	Day	24% 23% 32% 18% 4 1	400
	21st to end	Day	25% 24% 35% 13% 4	255
December	1st to 10th	Day	25% 32% 29% 9% 5%	196
	11th to 20th	Day	33% 28% 24% 12% 3	180
	21st to end	Day	29% 22% 29% 15% 5% 1	198
January	1st to 10th	Night	20% 26% 37% 14% 3	760
	11th to 20th	Night	27% 22% 30% 19% 2	760
	21st to end	Night	20% 25% 36% 18% 1	836
February	1st to 10th	Night	22% 22% 36% 19% 2	760
	11th to 20th	Night	22% 28% 37% 12% 1	743
	21st to end	Night	26% 23% 31% 17% 2	628
March	1st to 10th	Night	24% 24% 30% 19% 3	760
	11th to 20th	Night	23% 23% 33% 17% 3	760
	21st to end	Night	21% 23% 36% 15% 5%	836
April	1st to 10th	Night	21% 24% 35% 17% 4	760
	11th to 20th	Night	22% 18% 36% 19% 6%	751
	21st to end	Night	22% 16% 33% 23% 5%	760
May	1st to 10th	Night	26% 17% 29% 22% 6%	572
	11th to 20th	Night	22% 10% 38% 23% 8%	374
	21st to end	Night	18% 6% 27% 36% 12% 1	411
June	1st to 10th	Night	18% 8% 28% 33% 13% 1	380
	11th to 20th	Night	14% 8% 31% 36% 11%	380
	21st to end	Night	13% 3 30% 43% 11% 1	380
July	1st to 10th	Night	12% 5% 26% 38% 17% 2	370
	11th to 20th	Night	13% 3 26% 40% 18% 1	368
	21st to end	Night	13% 5% 26% 38% 16% 1	416
August	1st to 10th	Night	15% 1 19% 41% 22% 2	554
	11th to 20th	Night	14% 3 21% 36% 24% 2	723
	21st to end	Night	14% 5% 22% 35% 22% 2	836
September	1st to 10th	Night	19% 5% 26% 32% 16% 2	760
	11th to 20th	Night	16% 5% 23% 32% 21% 4	760
	21st to end	Night	23% 6% 24% 30% 14% 2	760
October	1st to 10th	Night	23% 10% 25% 26% 14% 2	760
	11th to 20th	Night	18% 12% 30% 30% 10%	760
	21st to end	Night	24% 15% 29% 23% 8%	836
November	1st to 10th	Night	17% 15% 32% 26% 9% 1	780
	11th to 20th	Night	22% 21% 29% 22% 6% 1	800
	21st to end	Night	19% 21% 35% 21% 5% 1	800
December	1st to 10th	Night	26% 21% 30% 18% 4	795
	11th to 20th	Night	21% 23% 33% 20% 3	760
	21st to end	Night	22% 23% 33% 20% 2	836

Page generated at 2024-12-06 03:54:48. Version ac07

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