Neuenschwander Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Neuenschwander Observatory clear sky chart from 2005-11-06 to 2026-03-03.

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% 10% 4 9% 5% 5% 5% 4 5% 7% 33%	130633
	Night	14% 11% 5% 10% 5% 5% 4 3 5% 6% 31%	130745
Transparency	Day	49% 6% 12% 21% 12% 1	134201
	Night	52% 5% 11% 19% 12% 1	135251
Seeing	Day	17% 11% 28% 24% 15% 6%	17461
	Night	19% 9% 29% 29% 12% 1	27432

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	13% 19% 9% 20% 6% 4 4 3 4 4 13%	4691
	11th to 20th	Day	11% 15% 7% 14% 10% 9% 6% 5% 6% 5% 13%	4710
	21st to end	Day	17% 16% 6% 14% 9% 6% 5% 3 4 4 15%	5284
February	1st to 10th	Day	15% 14% 6% 12% 9% 6% 4 3 5% 5% 20%	1974
	11th to 20th	Day	15% 12% 5% 14% 7% 5% 5% 4 5% 6% 22%	2048
	21st to end	Day	15% 16% 6% 11% 6% 5% 4 3 5% 6% 22%	1730
March	1st to 10th	Day	15% 12% 5% 13% 6% 4 4 3 4 6% 29%	4500
	11th to 20th	Day	11% 11% 5% 8% 5% 4 4 4 6% 8% 35%	4883
	21st to end	Day	17% 15% 7% 10% 6% 5% 5% 3 5% 6% 21%	5597
April	1st to 10th	Day	19% 13% 3 7% 5% 4 4 4 5% 6% 29%	2400
	11th to 20th	Day	17% 10% 3 6% 5% 4 4 4 5% 6% 36%	2427
	21st to end	Day	17% 10% 3 7% 4 4 4 3 5% 7% 35%	2600
May	1st to 10th	Day	20% 9% 3 7% 5% 4 5% 3 5% 7% 31%	5862
	11th to 20th	Day	14% 7% 3 6% 4 5% 5% 4 5% 10% 37%	5861
	21st to end	Day	15% 7% 2 6% 4 4 5% 3 6% 8% 40%	6741
June	1st to 10th	Day	10% 6% 3 6% 5% 5% 5% 5% 6% 8% 42%	2800
	11th to 20th	Day	11% 6% 1 6% 5% 5% 4 4 7% 8% 44%	2800
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 7% 8% 41%	2800
July	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 4 7% 10% 40%	6360
	11th to 20th	Day	8% 5% 2 6% 4 5% 5% 4 7% 11% 44%	6360
	21st to end	Day	8% 6% 2 7% 5% 4 5% 4 7% 10% 42%	6818
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	4234
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 6% 8% 44%	4174
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 10% 46%	4353
September	1st to 10th	Day	11% 6% 3 6% 5% 4 5% 4 5% 8% 45%	2345
	11th to 20th	Day	10% 3 2 5% 3 4 5% 4 7% 9% 49%	2200
	21st to end	Day	13% 7% 3 7% 4 4 4 3 6% 7% 41%	2200
October	1st to 10th	Day	13% 6% 2 7% 5% 4 4 3 6% 7% 44%	2200
	11th to 20th	Day	17% 9% 2 8% 5% 5% 4 4 6% 6% 34%	1985
	21st to end	Day	20% 11% 3 7% 5% 5% 6% 4 5% 7% 28%	1980
November	1st to 10th	Day	12% 10% 4 6% 5% 3 5% 4 6% 7% 38%	1852
	11th to 20th	Day	16% 17% 4 11% 6% 4 3 3 4 5% 27%	1890
	21st to end	Day	21% 15% 6% 10% 6% 4 3 3 4 5% 23%	1890
December	1st to 10th	Day	11% 17% 8% 15% 6% 4 4 3 5% 6% 22%	2926
	11th to 20th	Day	17% 20% 9% 14% 7% 5% 3 3 3 5% 15%	3088
	21st to end	Day	26% 19% 8% 13% 6% 4 3 2 4 4 11%	4070
January	1st to 10th	Night	12% 17% 9% 19% 6% 5% 4 3 4 4 17%	8232
	11th to 20th	Night	10% 16% 8% 19% 8% 8% 5% 4 5% 4 12%	8280
	21st to end	Night	16% 14% 7% 14% 8% 6% 5% 3 4 5% 18%	8920
February	1st to 10th	Night	16% 15% 5% 11% 8% 5% 4 4 4 5% 23%	2643
	11th to 20th	Night	15% 14% 4 12% 7% 6% 4 3 4 7% 25%	2458
	21st to end	Night	18% 13% 5% 10% 6% 5% 4 3 4 4 28%	2076
March	1st to 10th	Night	15% 11% 4 9% 5% 4 3 3 5% 7% 34%	5398
	11th to 20th	Night	11% 8% 3 7% 5% 4 4 4 5% 7% 42%	5077
	21st to end	Night	18% 11% 4 9% 4 4 4 3 4 5% 32%	5362
April	1st to 10th	Night	17% 9% 3 6% 5% 4 5% 3 5% 7% 36%	2000
	11th to 20th	Night	19% 8% 2 6% 5% 4 4 4 4 6% 37%	1920
	21st to end	Night	17% 8% 4 7% 4 3 5% 4 5% 7% 38%	1800
May	1st to 10th	Night	19% 10% 3 8% 4 4 4 3 5% 6% 31%	4033
	11th to 20th	Night	17% 8% 2 6% 4 3 4 3 5% 7% 42%	4032
	21st to end	Night	16% 6% 2 7% 4 3 4 3 5% 7% 42%	4125
June	1st to 10th	Night	10% 4 2 5% 4 4 4 4 7% 9% 47%	1600
	11th to 20th	Night	9% 5% 3 6% 5% 4 4 5% 7% 8% 44%	1600
	21st to end	Night	9% 4 2 5% 5% 5% 5% 5% 7% 9% 45%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 7% 9% 46%	3618
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	3617
	21st to end	Night	10% 5% 3 5% 4 4 4 4 7% 9% 45%	4033
August	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 7% 8% 46%	2915
	11th to 20th	Night	9% 5% 2 5% 4 5% 4 4 6% 8% 48%	2875
	21st to end	Night	9% 6% 2 6% 4 4 4 4 6% 8% 48%	3542
September	1st to 10th	Night	10% 6% 2 5% 4 3 4 3 6% 6% 51%	2034
	11th to 20th	Night	9% 4 2 5% 4 3 4 3 4 8% 55%	2200
	21st to end	Night	14% 7% 2 6% 4 3 4 3 4 6% 45%	2200
October	1st to 10th	Night	13% 6% 2 6% 3 4 3 3 5% 7% 48%	2200
	11th to 20th	Night	16% 10% 4 7% 4 4 4 3 5% 6% 37%	2408
	21st to end	Night	21% 8% 3 7% 4 4 4 3 5% 6% 34%	2860
November	1st to 10th	Night	14% 10% 3 7% 5% 4 4 2 5% 6% 39%	2666
	11th to 20th	Night	15% 15% 3 8% 5% 4 4 4 6% 7% 28%	2730
	21st to end	Night	18% 18% 5% 8% 5% 4 4 3 4 6% 25%	2730
December	1st to 10th	Night	13% 15% 7% 16% 7% 5% 5% 3 4 6% 20%	4472
	11th to 20th	Night	16% 20% 9% 14% 7% 4 4 3 4 5% 14%	5339
	21st to end	Night	26% 21% 6% 11% 5% 4 4 3 4 5% 11%	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	74% 6% 9% 10% 2	4692
	11th to 20th	Day	71% 5% 9% 8% 6%	4710
	21st to end	Day	73% 4 8% 10% 5%	5284
February	1st to 10th	Day	65% 5% 11% 11% 7% 1	1974
	11th to 20th	Day	62% 5% 10% 14% 8% 1	2058
	21st to end	Day	62% 5% 11% 14% 6% 1	1730
March	1st to 10th	Day	57% 4 12% 18% 8%	4500
	11th to 20th	Day	46% 5% 16% 24% 8% 1	4883
	21st to end	Day	63% 6% 9% 15% 7%	5599
April	1st to 10th	Day	55% 6% 10% 19% 10%	2400
	11th to 20th	Day	47% 6% 12% 22% 12% 2	2427
	21st to end	Day	48% 5% 13% 19% 14% 2	2600
May	1st to 10th	Day	51% 6% 10% 19% 14%	5897
	11th to 20th	Day	42% 6% 15% 23% 13% 1	5865
	21st to end	Day	41% 6% 10% 23% 19% 1	6755
June	1st to 10th	Day	37% 8% 12% 26% 16% 2	2800
	11th to 20th	Day	36% 6% 14% 25% 18% 2	2800
	21st to end	Day	39% 8% 14% 22% 16% 2	2800
July	1st to 10th	Day	38% 6% 12% 25% 17% 2	6291
	11th to 20th	Day	33% 6% 14% 30% 16% 1	6285
	21st to end	Day	35% 7% 15% 23% 18% 2	6623
August	1st to 10th	Day	33% 8% 16% 26% 16% 1	4221
	11th to 20th	Day	36% 8% 11% 29% 16% 1	4213
	21st to end	Day	33% 6% 13% 30% 15% 2	4352
September	1st to 10th	Day	36% 6% 15% 23% 17% 3	2345
	11th to 20th	Day	31% 6% 11% 30% 21% 1	2200
	21st to end	Day	41% 4 12% 24% 18% 1	2200
October	1st to 10th	Day	29% 4 9% 38% 19% 1	3590
	11th to 20th	Day	40% 5% 11% 24% 20%	3214
	21st to end	Day	47% 5% 11% 24% 12% 2	3180
November	1st to 10th	Day	43% 6% 12% 25% 13% 1	1852
	11th to 20th	Day	59% 4 10% 18% 8% 1	1890
	21st to end	Day	64% 5% 10% 16% 5%	1890
December	1st to 10th	Day	64% 5% 14% 13% 3	2926
	11th to 20th	Day	74% 4 10% 10% 2	3085
	21st to end	Day	78% 4 6% 8% 3	4070
January	1st to 10th	Night	71% 5% 7% 13% 4	8233
	11th to 20th	Night	74% 5% 9% 8% 4	8280
	21st to end	Night	69% 4 11% 9% 6%	8920
February	1st to 10th	Night	63% 6% 11% 13% 6% 1	2643
	11th to 20th	Night	60% 4 9% 19% 8%	2459
	21st to end	Night	59% 4 12% 17% 7% 1	2076
March	1st to 10th	Night	50% 4 13% 24% 8% 1	5398
	11th to 20th	Night	40% 5% 13% 27% 13% 1	5077
	21st to end	Night	53% 5% 10% 18% 12% 1	5362
April	1st to 10th	Night	48% 5% 12% 20% 14% 2	2000
	11th to 20th	Night	48% 6% 9% 18% 18% 2	1920
	21st to end	Night	46% 5% 11% 20% 15% 3	1800
May	1st to 10th	Night	52% 6% 9% 18% 14% 1	4060
	11th to 20th	Night	42% 6% 11% 24% 16% 2	4033
	21st to end	Night	41% 5% 11% 22% 19% 2	4133
June	1st to 10th	Night	32% 6% 12% 28% 19% 3	1600
	11th to 20th	Night	36% 7% 15% 22% 18% 2	1600
	21st to end	Night	33% 8% 17% 22% 18% 3	1600
July	1st to 10th	Night	33% 6% 13% 27% 17% 5%	3580
	11th to 20th	Night	31% 6% 16% 24% 21% 2	3572
	21st to end	Night	35% 6% 14% 21% 22% 3	3916
August	1st to 10th	Night	32% 7% 15% 30% 15% 1	2904
	11th to 20th	Night	32% 6% 13% 31% 16% 1	2902
	21st to end	Night	35% 6% 10% 30% 18% 2	3542
September	1st to 10th	Night	32% 6% 11% 26% 21% 4	2034
	11th to 20th	Night	29% 5% 8% 32% 25% 2	2200
	21st to end	Night	39% 5% 10% 27% 17% 1	2200
October	1st to 10th	Night	25% 5% 8% 34% 27% 1	3590
	11th to 20th	Night	41% 4 10% 23% 22% 1	3918
	21st to end	Night	39% 4 9% 30% 17% 1	4610
November	1st to 10th	Night	46% 4 10% 23% 15% 1	2666
	11th to 20th	Night	53% 6% 13% 18% 8% 2	2730
	21st to end	Night	60% 5% 11% 19% 5%	2730
December	1st to 10th	Night	66% 5% 14% 11% 4	4472
	11th to 20th	Night	74% 4 9% 9% 3	5341
	21st to end	Night	76% 4 9% 8% 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	20% 18% 33% 20% 7% 1	330
	11th to 20th	Day	22% 17% 40% 16% 4 1	330
	21st to end	Day	26% 16% 31% 21% 6%	363
February	1st to 10th	Day	22% 15% 37% 18% 5% 2	330
	11th to 20th	Day	25% 18% 32% 22% 4	330
	21st to end	Day	21% 25% 38% 13% 3	273
March	1st to 10th	Day	18% 20% 42% 16% 4	306
	11th to 20th	Day	22% 16% 32% 22% 7% 1	455
	21st to end	Day	31% 15% 28% 18% 7% 1	550
April	1st to 10th	Day	24% 13% 33% 22% 7% 1	500
	11th to 20th	Day	26% 16% 31% 15% 9% 3	492
	21st to end	Day	25% 12% 30% 22% 9% 3	500
May	1st to 10th	Day	21% 13% 30% 23% 10% 3	503
	11th to 20th	Day	21% 10% 25% 25% 13% 6%	527
	21st to end	Day	16% 7% 25% 26% 17% 8%	699
June	1st to 10th	Day	13% 7% 27% 30% 17% 6%	730
	11th to 20th	Day	13% 6% 27% 30% 19% 5%	730
	21st to end	Day	12% 7% 28% 30% 17% 6%	730
July	1st to 10th	Day	8% 4 20% 31% 23% 14%	721
	11th to 20th	Day	12% 4 23% 27% 23% 12%	718
	21st to end	Day	7% 3 21% 32% 26% 11%	750
August	1st to 10th	Day	7% 4 17% 29% 26% 17%	526
	11th to 20th	Day	13% 4 17% 26% 27% 12%	519
	21st to end	Day	10% 4 17% 28% 28% 13%	583
September	1st to 10th	Day	13% 6% 20% 25% 22% 14%	530
	11th to 20th	Day	8% 3 16% 24% 31% 18%	530
	21st to end	Day	15% 11% 19% 27% 19% 9%	530
October	1st to 10th	Day	15% 6% 28% 27% 18% 7%	530
	11th to 20th	Day	19% 14% 28% 29% 8% 1	470
	21st to end	Day	27% 12% 37% 17% 6% 1	363
November	1st to 10th	Day	17% 16% 35% 22% 9% 2	330
	11th to 20th	Day	25% 21% 31% 16% 7%	330
	21st to end	Day	30% 14% 38% 15% 4	330
December	1st to 10th	Day	22% 22% 35% 14% 7% 1	330
	11th to 20th	Day	23% 16% 38% 18% 3 1	330
	21st to end	Day	26% 21% 36% 15% 2	363
January	1st to 10th	Night	21% 14% 36% 23% 6%	1050
	11th to 20th	Night	24% 14% 36% 20% 5% 1	1050
	21st to end	Night	22% 11% 36% 27% 4	1108
February	1st to 10th	Night	25% 10% 38% 24% 3	840
	11th to 20th	Night	21% 14% 36% 26% 3	823
	21st to end	Night	24% 12% 39% 22% 3	692
March	1st to 10th	Night	20% 13% 34% 26% 7% 1	809
	11th to 20th	Night	19% 10% 38% 25% 7% 1	800
	21st to end	Night	24% 11% 31% 28% 6%	839
April	1st to 10th	Night	19% 11% 35% 28% 7% 1	600
	11th to 20th	Night	24% 9% 33% 27% 6% 1	593
	21st to end	Night	22% 6% 33% 29% 9% 1	600
May	1st to 10th	Night	22% 6% 32% 31% 9% 1	600
	11th to 20th	Night	24% 4 26% 30% 16%	591
	21st to end	Night	13% 5% 24% 38% 17% 2	650
June	1st to 10th	Night	11% 4 24% 45% 16% 1	600
	11th to 20th	Night	11% 4 25% 43% 17% 1	600
	21st to end	Night	9% 2 23% 41% 23% 2	600
July	1st to 10th	Night	9% 3 15% 41% 27% 5%	585
	11th to 20th	Night	9% 2 18% 42% 25% 4	582
	21st to end	Night	7% 2 16% 45% 29% 2	657
August	1st to 10th	Night	9% 2 9% 46% 30% 4	597
	11th to 20th	Night	10% 2 13% 39% 31% 4	594
	21st to end	Night	11% 1 17% 33% 35% 4	660
September	1st to 10th	Night	12% 3 16% 35% 29% 5%	634
	11th to 20th	Night	10% 4 14% 36% 33% 4	800
	21st to end	Night	17% 6% 23% 30% 21% 4	800
October	1st to 10th	Night	16% 5% 23% 35% 19% 1	800
	11th to 20th	Night	22% 10% 29% 30% 9% 1	800
	21st to end	Night	25% 11% 31% 25% 8%	880
November	1st to 10th	Night	20% 12% 30% 28% 10% 1	820
	11th to 20th	Night	23% 14% 34% 24% 5% 1	840
	21st to end	Night	27% 11% 33% 25% 4	840
December	1st to 10th	Night	25% 16% 33% 20% 5%	893
	11th to 20th	Night	24% 14% 38% 21% 4	1050
	21st to end	Night	32% 13% 34% 18% 3	1155

Page generated at 2026-02-28 01:40:19. Version ac07

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