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 2026-04-02.

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	16% 7% 3 6% 4 4 4 4 5% 7% 38%	131468
	Night	17% 8% 3 6% 4 4 4 3 5% 7% 40%	130376
Transparency	Day	43% 6% 11% 22% 16% 2	134969
	Night	42% 5% 11% 23% 16% 3	134949
Seeing	Day	23% 18% 30% 19% 9% 2	16669
	Night	21% 16% 30% 24% 8% 1	26014

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	14% 8% 2 8% 4 5% 4 3 5% 6% 41%	4661
	11th to 20th	Day	14% 9% 4 9% 5% 4 4 3 4 5% 39%	4650
	21st to end	Day	15% 6% 2 7% 4 5% 5% 4 6% 6% 39%	5776
February	1st to 10th	Day	15% 9% 3 7% 4 5% 4 4 6% 6% 38%	1890
	11th to 20th	Day	16% 9% 3 8% 4 4 4 4 5% 6% 38%	1998
	21st to end	Day	19% 10% 3 7% 5% 4 4 4 4 4 37%	1730
March	1st to 10th	Day	21% 8% 3 5% 4 3 4 3 4 5% 40%	4576
	11th to 20th	Day	12% 6% 3 8% 5% 5% 4 4 6% 7% 41%	5038
	21st to end	Day	18% 7% 2 5% 4 4 4 3 6% 7% 41%	5955
April	1st to 10th	Day	18% 8% 3 7% 4 4 5% 4 5% 6% 36%	2412
	11th to 20th	Day	17% 8% 3 6% 5% 4 3 3 5% 7% 38%	2374
	21st to end	Day	16% 6% 2 7% 4 5% 5% 4 5% 6% 40%	2400
May	1st to 10th	Day	26% 8% 3 6% 4 4 4 4 5% 8% 27%	5937
	11th to 20th	Day	23% 9% 3 7% 4 4 3 3 4 7% 32%	6318
	21st to end	Day	20% 6% 2 6% 4 4 5% 4 6% 8% 34%	6949
June	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 5% 6% 8% 36%	2800
	11th to 20th	Day	15% 6% 3 7% 4 5% 6% 4 6% 9% 35%	2800
	21st to end	Day	13% 6% 2 6% 4 5% 5% 4 6% 8% 40%	2800
July	1st to 10th	Day	9% 7% 3 7% 6% 5% 6% 4 7% 10% 36%	6360
	11th to 20th	Day	11% 7% 3 7% 5% 6% 6% 6% 8% 10% 31%	6360
	21st to end	Day	13% 7% 2 6% 4 5% 5% 4 7% 9% 38%	6926
August	1st to 10th	Day	21% 7% 2 6% 4 4 5% 4 6% 8% 32%	4244
	11th to 20th	Day	13% 7% 2 6% 4 5% 5% 4 6% 8% 41%	3858
	21st to end	Day	12% 6% 2 5% 4 3 4 3 5% 8% 47%	4312
September	1st to 10th	Day	15% 5% 2 5% 5% 4 4 4 6% 7% 43%	2400
	11th to 20th	Day	13% 4 2 5% 4 3 4 3 5% 7% 50%	2357
	21st to end	Day	19% 6% 3 6% 5% 4 5% 4 4 5% 38%	2200
October	1st to 10th	Day	19% 5% 2 6% 4 4 4 4 5% 6% 42%	2017
	11th to 20th	Day	16% 6% 2 5% 4 4 4 3 5% 7% 45%	2000
	21st to end	Day	20% 5% 2 5% 3 4 4 4 5% 6% 41%	2097
November	1st to 10th	Day	13% 7% 2 4 3 3 3 2 4 5% 52%	1851
	11th to 20th	Day	17% 5% 2 5% 4 4 4 4 5% 6% 44%	1890
	21st to end	Day	17% 7% 2 6% 4 4 4 4 4 7% 41%	1738
December	1st to 10th	Day	16% 8% 3 6% 4 4 4 4 5% 6% 40%	2680
	11th to 20th	Day	22% 9% 2 5% 3 4 4 3 5% 6% 38%	3066
	21st to end	Day	18% 8% 3 7% 6% 5% 5% 3 5% 7% 32%	4048
January	1st to 10th	Night	13% 8% 3 7% 4 5% 4 4 5% 7% 40%	8234
	11th to 20th	Night	14% 9% 3 7% 5% 4 5% 4 5% 7% 38%	8235
	21st to end	Night	15% 8% 2 5% 4 4 4 3 5% 6% 44%	8401
February	1st to 10th	Night	15% 9% 4 6% 4 4 3 3 5% 7% 39%	2730
	11th to 20th	Night	17% 9% 3 7% 5% 4 5% 3 4 6% 37%	2506
	21st to end	Night	18% 9% 2 5% 4 4 4 4 5% 6% 40%	2076
March	1st to 10th	Night	19% 8% 2 6% 4 4 3 3 4 5% 41%	5484
	11th to 20th	Night	13% 6% 3 6% 4 4 4 3 4 6% 48%	5136
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 5% 5% 40%	5218
April	1st to 10th	Night	18% 7% 3 7% 5% 3 5% 4 5% 6% 35%	2011
	11th to 20th	Night	18% 7% 3 6% 4 4 4 3 6% 7% 38%	1975
	21st to end	Night	20% 6% 2 4 3 3 3 3 5% 7% 43%	2000
May	1st to 10th	Night	28% 9% 2 6% 4 4 4 4 6% 7% 27%	4043
	11th to 20th	Night	23% 9% 3 7% 4 4 4 3 5% 6% 31%	3575
	21st to end	Night	22% 6% 2 6% 4 4 4 3 5% 7% 36%	3926
June	1st to 10th	Night	15% 6% 2 5% 4 4 5% 4 5% 8% 41%	1600
	11th to 20th	Night	14% 6% 2 5% 5% 4 4 4 7% 9% 40%	1600
	21st to end	Night	12% 5% 2 5% 4 4 4 4 7% 10% 44%	1600
July	1st to 10th	Night	11% 7% 3 7% 5% 5% 5% 4 7% 9% 37%	3600
	11th to 20th	Night	14% 8% 3 8% 4 5% 6% 4 8% 9% 31%	3600
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 8% 44%	3926
August	1st to 10th	Night	21% 7% 2 7% 5% 4 4 4 6% 8% 31%	2902
	11th to 20th	Night	14% 7% 3 7% 5% 5% 4 4 5% 6% 41%	3157
	21st to end	Night	12% 5% 2 4 4 3 4 3 5% 7% 50%	3586
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 4 6% 45%	2000
	11th to 20th	Night	12% 6% 2 5% 4 4 4 2 5% 7% 51%	2042
	21st to end	Night	18% 7% 3 5% 3 4 3 3 5% 7% 42%	2200
October	1st to 10th	Night	19% 6% 2 6% 4 2 3 3 4 6% 44%	2380
	11th to 20th	Night	17% 6% 1 5% 3 3 3 3 5% 6% 48%	2400
	21st to end	Night	20% 6% 2 5% 3 3 3 3 5% 6% 45%	2741
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 4 6% 6% 51%	2667
	11th to 20th	Night	16% 8% 2 5% 3 3 4 3 4 5% 46%	2730
	21st to end	Night	14% 7% 3 6% 4 4 4 4 5% 7% 42%	2877
December	1st to 10th	Night	13% 8% 3 7% 4 4 4 3 5% 5% 44%	4720
	11th to 20th	Night	23% 8% 2 4 4 3 4 3 4 5% 39%	5348
	21st to end	Night	20% 11% 3 7% 3 4 3 3 4 5% 37%	7150

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	41% 4 12% 27% 16% 2	4662
	11th to 20th	Day	45% 4 9% 21% 16% 5%	4680
	21st to end	Day	44% 5% 12% 23% 16% 1	5776
February	1st to 10th	Day	44% 4 14% 23% 12% 2	1890
	11th to 20th	Day	47% 4 9% 23% 15% 2	2007
	21st to end	Day	49% 3 11% 22% 12% 3	1730
March	1st to 10th	Day	44% 4 9% 23% 13% 7%	4579
	11th to 20th	Day	40% 6% 12% 27% 11% 4	5038
	21st to end	Day	42% 5% 11% 14% 23% 5%	5955
April	1st to 10th	Day	48% 5% 8% 20% 15% 5%	2412
	11th to 20th	Day	43% 5% 11% 20% 17% 3	2374
	21st to end	Day	44% 5% 9% 21% 16% 5%	2400
May	1st to 10th	Day	54% 6% 13% 15% 10% 1	5948
	11th to 20th	Day	52% 5% 8% 21% 12% 1	6322
	21st to end	Day	45% 7% 10% 23% 14% 2	6949
June	1st to 10th	Day	43% 6% 14% 22% 15% 1	2800
	11th to 20th	Day	44% 8% 13% 22% 11% 2	2800
	21st to end	Day	41% 7% 12% 24% 15% 1	2800
July	1st to 10th	Day	42% 9% 12% 21% 15% 1	6290
	11th to 20th	Day	42% 9% 17% 21% 10% 1	6285
	21st to end	Day	40% 6% 12% 21% 21% 1	6728
August	1st to 10th	Day	48% 7% 13% 22% 10% 1	4230
	11th to 20th	Day	38% 6% 13% 29% 13% 1	3894
	21st to end	Day	34% 6% 10% 30% 18% 2	4312
September	1st to 10th	Day	39% 7% 10% 21% 20% 3	2400
	11th to 20th	Day	33% 4 10% 24% 25% 3	2357
	21st to end	Day	47% 6% 8% 18% 19% 2	2200
October	1st to 10th	Day	38% 5% 8% 20% 24% 5%	3277
	11th to 20th	Day	29% 4 10% 26% 25% 5%	3240
	21st to end	Day	28% 3 14% 25% 26% 4	3361
November	1st to 10th	Day	36% 4 12% 23% 22% 3	1851
	11th to 20th	Day	39% 4 10% 25% 18% 3	1890
	21st to end	Day	42% 3 14% 28% 11% 2	1738
December	1st to 10th	Day	42% 5% 15% 26% 12% 1	2680
	11th to 20th	Day	46% 4 14% 24% 12% 1	3066
	21st to end	Day	48% 5% 10% 21% 14% 1	4048
January	1st to 10th	Night	39% 5% 14% 24% 15% 3	8234
	11th to 20th	Night	43% 4 12% 21% 15% 5%	8280
	21st to end	Night	41% 3 9% 22% 21% 3	8401
February	1st to 10th	Night	44% 5% 12% 24% 12% 2	2730
	11th to 20th	Night	47% 5% 9% 19% 16% 4	2508
	21st to end	Night	44% 4 9% 24% 17% 3	2076
March	1st to 10th	Night	43% 5% 10% 22% 12% 8%	5494
	11th to 20th	Night	38% 4 15% 25% 15% 4	5137
	21st to end	Night	45% 4 6% 16% 23% 5%	5218
April	1st to 10th	Night	48% 4 10% 19% 14% 4	2011
	11th to 20th	Night	45% 5% 9% 20% 19% 2	1975
	21st to end	Night	40% 5% 10% 23% 18% 5%	2000
May	1st to 10th	Night	55% 6% 12% 16% 10% 2	4049
	11th to 20th	Night	52% 7% 12% 15% 13% 2	3576
	21st to end	Night	46% 7% 12% 23% 11% 2	3927
June	1st to 10th	Night	41% 6% 10% 22% 20% 1	1600
	11th to 20th	Night	40% 8% 15% 24% 12% 1	1600
	21st to end	Night	34% 9% 14% 26% 16% 1	1600
July	1st to 10th	Night	42% 8% 15% 18% 15% 2	3560
	11th to 20th	Night	46% 8% 14% 20% 10% 1	3552
	21st to end	Night	36% 7% 13% 23% 20% 1	3809
August	1st to 10th	Night	49% 8% 16% 17% 10% 1	2892
	11th to 20th	Night	42% 7% 13% 25% 13% 1	3187
	21st to end	Night	32% 6% 10% 32% 20% 1	3586
September	1st to 10th	Night	41% 5% 10% 22% 20% 2	2000
	11th to 20th	Night	34% 5% 9% 22% 26% 4	2042
	21st to end	Night	42% 5% 8% 22% 21% 1	2200
October	1st to 10th	Night	41% 5% 9% 23% 21% 2	3887
	11th to 20th	Night	27% 4 10% 28% 27% 4	3899
	21st to end	Night	29% 4 12% 31% 21% 3	4427
November	1st to 10th	Night	33% 5% 12% 24% 22% 4	2667
	11th to 20th	Night	41% 3 8% 24% 20% 3	2730
	21st to end	Night	40% 5% 12% 27% 15% 1	2877
December	1st to 10th	Night	40% 4 13% 31% 10% 1	4720
	11th to 20th	Night	46% 4 10% 23% 15% 2	5348
	21st to end	Night	48% 4 10% 20% 16% 3	7150

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	30% 29% 30% 9% 1	220
	11th to 20th	Day	35% 31% 25% 8% 1	220
	21st to end	Day	26% 32% 31% 7% 4	361
February	1st to 10th	Day	26% 32% 31% 7% 3	330
	11th to 20th	Day	32% 27% 32% 8% 1	486
	21st to end	Day	32% 28% 25% 13% 2	446
March	1st to 10th	Day	29% 26% 30% 13% 2	540
	11th to 20th	Day	28% 26% 29% 13% 3 1	540
	21st to end	Day	29% 25% 31% 10% 4 1	594
April	1st to 10th	Day	28% 26% 28% 14% 4 1	504
	11th to 20th	Day	26% 25% 29% 12% 7% 1	492
	21st to end	Day	27% 20% 34% 14% 3 2	500
May	1st to 10th	Day	31% 21% 30% 11% 6% 1	503
	11th to 20th	Day	23% 17% 33% 19% 6% 1	527
	21st to end	Day	22% 12% 28% 25% 12% 2	573
June	1st to 10th	Day	19% 16% 29% 22% 12% 2	530
	11th to 20th	Day	19% 15% 29% 23% 12% 2	530
	21st to end	Day	17% 13% 31% 26% 11% 2	530
July	1st to 10th	Day	13% 7% 29% 30% 17% 5%	525
	11th to 20th	Day	12% 5% 27% 34% 18% 4	524
	21st to end	Day	15% 7% 33% 30% 12% 3	576
August	1st to 10th	Day	14% 6% 29% 30% 16% 5%	526
	11th to 20th	Day	14% 6% 27% 29% 19% 4	519
	21st to end	Day	13% 8% 32% 26% 14% 7%	583
September	1st to 10th	Day	19% 11% 25% 26% 14% 5%	530
	11th to 20th	Day	14% 6% 29% 26% 15% 9%	530
	21st to end	Day	23% 12% 30% 21% 11% 4	530
October	1st to 10th	Day	24% 9% 29% 19% 14% 5%	530
	11th to 20th	Day	19% 20% 31% 20% 8% 2	530
	21st to end	Day	23% 18% 33% 16% 9% 1	525
November	1st to 10th	Day	19% 20% 28% 22% 9% 2	425
	11th to 20th	Day	24% 23% 31% 18% 3 1	430
	21st to end	Day	26% 25% 33% 12% 4	278
December	1st to 10th	Day	27% 30% 30% 9% 5%	220
	11th to 20th	Day	35% 27% 23% 11% 3	220
	21st to end	Day	30% 21% 29% 14% 5% 1	242
January	1st to 10th	Night	21% 25% 36% 14% 3	840
	11th to 20th	Night	28% 22% 29% 18% 2	840
	21st to end	Night	20% 26% 37% 17% 1	924
February	1st to 10th	Night	23% 21% 36% 19% 2	840
	11th to 20th	Night	25% 26% 37% 12% 1	823
	21st to end	Night	25% 23% 33% 16% 2	692
March	1st to 10th	Night	25% 24% 30% 19% 3	840
	11th to 20th	Night	24% 23% 32% 18% 3	840
	21st to end	Night	22% 23% 36% 15% 4	924
April	1st to 10th	Night	22% 24% 34% 16% 3	805
	11th to 20th	Night	23% 18% 35% 18% 6%	791
	21st to end	Night	23% 17% 32% 23% 5%	800
May	1st to 10th	Night	27% 16% 29% 23% 6%	602
	11th to 20th	Night	22% 10% 37% 23% 8%	394
	21st to end	Night	20% 6% 27% 35% 12% 1	433
June	1st to 10th	Night	18% 8% 28% 34% 13% 1	400
	11th to 20th	Night	15% 8% 31% 35% 11%	400
	21st to end	Night	13% 3 29% 43% 11% 1	400
July	1st to 10th	Night	13% 5% 26% 38% 17% 2	390
	11th to 20th	Night	13% 3 26% 39% 19% 1	388
	21st to end	Night	13% 5% 27% 39% 16% 1	438
August	1st to 10th	Night	14% 2 19% 41% 22% 2	584
	11th to 20th	Night	14% 3 21% 37% 24% 2	762
	21st to end	Night	14% 5% 22% 36% 21% 2	880
September	1st to 10th	Night	19% 5% 26% 32% 16% 2	800
	11th to 20th	Night	15% 5% 22% 34% 20% 4	800
	21st to end	Night	23% 6% 24% 31% 14% 2	800
October	1st to 10th	Night	23% 10% 25% 26% 15% 2	800
	11th to 20th	Night	20% 13% 29% 29% 10%	800
	21st to end	Night	24% 16% 30% 23% 8%	880
November	1st to 10th	Night	18% 15% 31% 26% 9% 1	820
	11th to 20th	Night	23% 21% 29% 21% 5%	840
	21st to end	Night	20% 20% 34% 21% 5%	840
December	1st to 10th	Night	25% 21% 31% 18% 4	840
	11th to 20th	Night	23% 22% 32% 19% 3	840
	21st to end	Night	24% 22% 32% 20% 2	924

Page generated at 2026-03-30 02:18:46. Version ac07

Copyright © 2026 Attilla Danko.