Peppermill Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peppermill Skies Observatory clear sky chart from 2005-11-06 to 2026-02-16.

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	15% 7% 2 6% 4 4 4 4 6% 8% 41%	130650
	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	130179
Transparency	Day	42% 5% 12% 23% 16% 2	134190
	Night	43% 3 11% 23% 17% 3	134726
Seeing	Day	19% 11% 29% 27% 12% 2	16600
	Night	20% 11% 31% 28% 9% 1	25813

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	13% 6% 2 5% 3 4 4 3 5% 7% 48%	4661
	11th to 20th	Day	16% 8% 2 6% 3 4 4 3 4 5% 46%	4650
	21st to end	Day	16% 7% 3 7% 4 3 4 3 5% 7% 42%	5441
February	1st to 10th	Day	16% 7% 3 6% 4 4 4 3 5% 7% 41%	1948
	11th to 20th	Day	14% 7% 1 7% 4 4 4 2 5% 6% 45%	1998
	21st to end	Day	18% 9% 2 6% 4 4 4 3 5% 5% 40%	1650
March	1st to 10th	Day	20% 8% 2 5% 3 3 3 3 4 5% 44%	4476
	11th to 20th	Day	11% 7% 2 5% 4 4 4 4 6% 8% 43%	4690
	21st to end	Day	18% 7% 2 6% 4 4 3 3 5% 7% 42%	5970
April	1st to 10th	Day	17% 8% 2 5% 5% 4 4 3 5% 8% 39%	2400
	11th to 20th	Day	16% 7% 2 5% 4 4 4 3 4 7% 43%	2374
	21st to end	Day	18% 6% 2 4 3 4 4 3 6% 7% 42%	2465
May	1st to 10th	Day	27% 9% 2 5% 3 3 4 4 5% 8% 30%	5886
	11th to 20th	Day	21% 9% 2 6% 4 3 3 3 5% 6% 38%	6152
	21st to end	Day	19% 7% 2 5% 3 4 4 3 6% 9% 38%	6949
June	1st to 10th	Day	17% 5% 2 5% 4 3 4 4 6% 9% 41%	2800
	11th to 20th	Day	14% 7% 2 5% 4 5% 5% 4 6% 9% 39%	2800
	21st to end	Day	10% 6% 3 5% 5% 4 4 4 6% 9% 44%	2800
July	1st to 10th	Day	9% 7% 3 7% 5% 5% 5% 5% 7% 10% 36%	6360
	11th to 20th	Day	9% 7% 3 7% 5% 5% 6% 5% 8% 11% 35%	6360
	21st to end	Day	12% 7% 2 7% 4 4 4 4 6% 8% 41%	6926
August	1st to 10th	Day	16% 7% 2 7% 5% 5% 5% 4 7% 9% 34%	4322
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 7% 8% 44%	3850
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 10% 48%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 4 5% 3 5% 7% 46%	2400
	11th to 20th	Day	12% 6% 2 4 3 4 4 3 5% 7% 51%	2281
	21st to end	Day	18% 7% 2 7% 5% 4 4 3 5% 6% 40%	2200
October	1st to 10th	Day	19% 7% 2 4 3 3 3 3 5% 7% 44%	2140
	11th to 20th	Day	15% 5% 2 5% 3 4 4 3 5% 7% 47%	2000
	21st to end	Day	19% 5% 2 6% 4 4 4 3 4 6% 43%	2000
November	1st to 10th	Day	14% 5% 2 5% 3 3 3 4 4 6% 50%	1851
	11th to 20th	Day	16% 7% 2 5% 4 3 3 2 5% 7% 48%	1890
	21st to end	Day	15% 8% 3 5% 3 4 4 4 5% 7% 44%	1854
December	1st to 10th	Day	14% 7% 3 6% 4 4 3 3 6% 8% 43%	2680
	11th to 20th	Day	20% 8% 3 4 2 2 2 2 4 5% 47%	3066
	21st to end	Day	17% 9% 3 8% 4 4 4 3 4 6% 38%	4048
January	1st to 10th	Night	13% 8% 3 6% 3 3 3 2 4 6% 47%	8234
	11th to 20th	Night	16% 8% 3 7% 3 3 3 3 4 5% 45%	8235
	21st to end	Night	16% 7% 3 7% 4 4 4 3 5% 6% 41%	8724
February	1st to 10th	Night	16% 9% 3 5% 4 4 4 3 5% 6% 41%	2671
	11th to 20th	Night	18% 8% 3 5% 4 4 4 4 5% 6% 40%	2399
	21st to end	Night	19% 7% 3 4 4 4 4 3 6% 5% 42%	1980
March	1st to 10th	Night	19% 9% 2 6% 3 3 3 3 4 5% 43%	5364
	11th to 20th	Night	14% 10% 3 6% 5% 4 3 3 5% 6% 42%	5263
	21st to end	Night	20% 9% 3 6% 4 3 4 3 5% 5% 39%	4962
April	1st to 10th	Night	19% 7% 3 6% 4 5% 4 4 5% 6% 37%	2000
	11th to 20th	Night	19% 7% 3 5% 4 3 4 3 4 7% 40%	1975
	21st to end	Night	17% 7% 3 6% 5% 3 3 3 5% 5% 43%	1933
May	1st to 10th	Night	26% 10% 3 7% 4 4 4 3 4 8% 27%	4054
	11th to 20th	Night	22% 9% 3 6% 4 4 4 3 5% 6% 34%	3770
	21st to end	Night	22% 8% 3 6% 3 3 4 3 5% 7% 36%	3926
June	1st to 10th	Night	16% 7% 2 6% 4 5% 3 4 5% 8% 40%	1600
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 7% 9% 39%	1600
	21st to end	Night	10% 6% 2 7% 5% 4 6% 5% 7% 9% 40%	1600
July	1st to 10th	Night	10% 9% 3 8% 5% 5% 5% 5% 6% 9% 34%	3600
	11th to 20th	Night	11% 10% 3 9% 5% 5% 5% 5% 6% 9% 32%	3600
	21st to end	Night	13% 7% 3 6% 4 4 4 4 6% 9% 41%	3926
August	1st to 10th	Night	21% 7% 3 6% 4 5% 5% 4 7% 7% 32%	2792
	11th to 20th	Night	13% 7% 3 7% 4 4 5% 4 6% 8% 39%	3197
	21st to end	Night	8% 4 1 5% 4 4 4 4 5% 8% 52%	3586
September	1st to 10th	Night	13% 5% 2 6% 5% 4 5% 4 6% 7% 44%	2000
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 7% 51%	2118
	21st to end	Night	17% 6% 3 6% 5% 4 4 3 4 7% 42%	2200
October	1st to 10th	Night	17% 8% 3 6% 4 4 3 3 4 6% 42%	2255
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 6% 49%	2400
	21st to end	Night	20% 6% 3 6% 4 3 3 3 4 6% 42%	2838
November	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 5% 6% 49%	2667
	11th to 20th	Night	17% 6% 2 5% 3 2 3 3 4 6% 48%	2730
	21st to end	Night	15% 6% 2 5% 4 4 4 3 5% 6% 46%	2762
December	1st to 10th	Night	16% 7% 2 5% 3 4 3 3 4 6% 47%	4720
	11th to 20th	Night	23% 9% 2 5% 3 3 3 3 4 4 43%	5348
	21st to end	Night	17% 9% 3 6% 4 4 4 3 4 5% 41%	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	37% 3 9% 31% 18% 2	4662
	11th to 20th	Day	42% 3 8% 23% 18% 6%	4680
	21st to end	Day	44% 3 10% 27% 16% 1	5441
February	1st to 10th	Day	44% 5% 12% 23% 15% 2	1948
	11th to 20th	Day	41% 4 9% 27% 17% 2	2007
	21st to end	Day	46% 4 10% 22% 15% 3	1650
March	1st to 10th	Day	43% 5% 10% 18% 15% 9%	4479
	11th to 20th	Day	38% 6% 13% 28% 13% 2	4690
	21st to end	Day	44% 4 9% 14% 23% 6%	5970
April	1st to 10th	Day	45% 5% 8% 21% 16% 4	2400
	11th to 20th	Day	42% 5% 10% 22% 17% 3	2374
	21st to end	Day	42% 5% 10% 22% 18% 4	2465
May	1st to 10th	Day	54% 4 17% 15% 10% 1	5897
	11th to 20th	Day	49% 5% 11% 20% 14% 2	6156
	21st to end	Day	44% 6% 11% 24% 14% 1	6949
June	1st to 10th	Day	40% 7% 13% 23% 16% 2	2800
	11th to 20th	Day	41% 7% 13% 25% 13% 2	2800
	21st to end	Day	38% 7% 15% 23% 16% 1	2800
July	1st to 10th	Day	43% 7% 13% 21% 15% 1	6290
	11th to 20th	Day	43% 4 20% 22% 10% 1	6285
	21st to end	Day	42% 5% 11% 22% 19% 2	6728
August	1st to 10th	Day	47% 5% 16% 22% 9% 1	4308
	11th to 20th	Day	38% 5% 13% 34% 10% 1	3886
	21st to end	Day	33% 4 13% 28% 21% 2	4312
September	1st to 10th	Day	38% 5% 13% 22% 20% 2	2400
	11th to 20th	Day	34% 4 11% 25% 25% 2	2281
	21st to end	Day	45% 4 10% 19% 19% 2	2200
October	1st to 10th	Day	37% 4 10% 20% 24% 5%	3491
	11th to 20th	Day	27% 3 10% 23% 32% 5%	3240
	21st to end	Day	30% 3 14% 26% 24% 3	3212
November	1st to 10th	Day	36% 3 14% 23% 22% 2	1851
	11th to 20th	Day	38% 3 10% 23% 23% 3	1890
	21st to end	Day	40% 4 14% 28% 12% 2	1854
December	1st to 10th	Day	40% 3 15% 28% 13% 1	2680
	11th to 20th	Day	42% 3 13% 23% 17% 3	3066
	21st to end	Day	47% 5% 8% 22% 15% 3	4048
January	1st to 10th	Night	39% 2 11% 25% 21% 3	8234
	11th to 20th	Night	42% 2 10% 22% 18% 6%	8280
	21st to end	Night	45% 2 8% 22% 19% 4	8724
February	1st to 10th	Night	44% 4 12% 24% 13% 2	2671
	11th to 20th	Night	44% 4 9% 22% 17% 4	2401
	21st to end	Night	44% 4 7% 24% 17% 4	1980
March	1st to 10th	Night	45% 3 10% 20% 14% 8%	5374
	11th to 20th	Night	44% 3 13% 25% 12% 4	5264
	21st to end	Night	48% 3 5% 14% 24% 5%	4962
April	1st to 10th	Night	48% 4 9% 18% 17% 3	2000
	11th to 20th	Night	45% 5% 10% 19% 21% 2	1975
	21st to end	Night	44% 4 8% 21% 18% 5%	1933
May	1st to 10th	Night	58% 4 13% 14% 10% 1	4060
	11th to 20th	Night	52% 4 13% 15% 13% 2	3771
	21st to end	Night	50% 4 12% 22% 11% 2	3927
June	1st to 10th	Night	44% 5% 9% 21% 20% 1	1600
	11th to 20th	Night	41% 6% 14% 26% 12% 1	1600
	21st to end	Night	39% 8% 12% 25% 14% 2	1600
July	1st to 10th	Night	48% 6% 12% 22% 11% 1	3560
	11th to 20th	Night	51% 4 14% 21% 9% 1	3552
	21st to end	Night	41% 4 14% 24% 16% 1	3809
August	1st to 10th	Night	50% 6% 17% 18% 9% 1	2782
	11th to 20th	Night	42% 5% 14% 30% 9% 1	3227
	21st to end	Night	30% 5% 11% 34% 19% 1	3586
September	1st to 10th	Night	39% 6% 10% 26% 19% 1	2000
	11th to 20th	Night	35% 4 10% 25% 23% 3	2118
	21st to end	Night	44% 5% 8% 21% 19% 3	2200
October	1st to 10th	Night	41% 3 10% 24% 20% 3	3684
	11th to 20th	Night	25% 3 10% 28% 30% 4	3899
	21st to end	Night	32% 3 13% 29% 21% 3	4576
November	1st to 10th	Night	36% 4 11% 24% 21% 4	2667
	11th to 20th	Night	39% 3 8% 24% 20% 5%	2730
	21st to end	Night	38% 4 12% 30% 15% 1	2762
December	1st to 10th	Night	40% 3 12% 30% 13% 2	4720
	11th to 20th	Night	47% 3 9% 24% 15% 3	5348
	21st to end	Night	45% 4 9% 21% 17% 4	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	25% 22% 32% 17% 3	220
	11th to 20th	Day	21% 30% 32% 13% 3	220
	21st to end	Day	21% 18% 40% 15% 4 1	300
February	1st to 10th	Day	23% 15% 44% 16% 3	388
	11th to 20th	Day	22% 20% 37% 19% 2	516
	21st to end	Day	23% 20% 33% 18% 5%	414
March	1st to 10th	Day	17% 20% 36% 23% 4	500
	11th to 20th	Day	18% 14% 39% 24% 4 1	500
	21st to end	Day	24% 15% 36% 18% 6% 1	550
April	1st to 10th	Day	24% 17% 35% 16% 8% 1	500
	11th to 20th	Day	21% 15% 32% 23% 8%	492
	21st to end	Day	24% 13% 32% 24% 5% 1	500
May	1st to 10th	Day	28% 12% 30% 22% 7% 1	503
	11th to 20th	Day	21% 10% 28% 31% 10% 1	527
	21st to end	Day	19% 5% 21% 33% 20% 3	573
June	1st to 10th	Day	19% 5% 24% 33% 17% 2	530
	11th to 20th	Day	17% 8% 27% 34% 12% 2	530
	21st to end	Day	13% 5% 27% 33% 19% 2	530
July	1st to 10th	Day	14% 4 19% 37% 23% 4	525
	11th to 20th	Day	10% 4 21% 37% 23% 5%	524
	21st to end	Day	13% 5% 21% 41% 17% 3	576
August	1st to 10th	Day	13% 3 19% 37% 21% 6%	526
	11th to 20th	Day	14% 4 20% 35% 23% 4	519
	21st to end	Day	12% 5% 23% 36% 19% 6%	583
September	1st to 10th	Day	18% 6% 22% 27% 20% 6%	530
	11th to 20th	Day	14% 3 22% 32% 19% 9%	530
	21st to end	Day	23% 4 28% 27% 15% 4	530
October	1st to 10th	Day	23% 8% 23% 24% 16% 6%	530
	11th to 20th	Day	17% 13% 29% 26% 13% 2	530
	21st to end	Day	21% 13% 31% 23% 10% 2	473
November	1st to 10th	Day	16% 15% 26% 31% 10% 2	425
	11th to 20th	Day	19% 21% 31% 22% 6%	430
	21st to end	Day	22% 17% 31% 23% 7% 1	394
December	1st to 10th	Day	23% 18% 35% 18% 6%	220
	11th to 20th	Day	31% 20% 28% 16% 5%	220
	21st to end	Day	26% 16% 39% 12% 8%	242
January	1st to 10th	Night	20% 18% 39% 19% 4	840
	11th to 20th	Night	26% 17% 32% 23% 2	840
	21st to end	Night	20% 17% 40% 20% 2	924
February	1st to 10th	Night	21% 15% 39% 23% 2	840
	11th to 20th	Night	24% 17% 40% 18% 1	804
	21st to end	Night	23% 17% 36% 19% 4	660
March	1st to 10th	Night	22% 16% 36% 21% 5%	800
	11th to 20th	Night	20% 13% 39% 22% 5% 1	800
	21st to end	Night	22% 14% 39% 20% 5%	880
April	1st to 10th	Night	23% 13% 36% 23% 5%	800
	11th to 20th	Night	22% 13% 32% 27% 5%	791
	21st to end	Night	21% 10% 35% 28% 6% 1	733
May	1st to 10th	Night	24% 8% 33% 27% 7% 1	600
	11th to 20th	Night	22% 9% 34% 28% 6%	485
	21st to end	Night	22% 5% 20% 36% 16% 2	433
June	1st to 10th	Night	20% 5% 26% 34% 15%	400
	11th to 20th	Night	19% 4 21% 42% 15% 1	400
	21st to end	Night	12% 4 23% 47% 13% 1	400
July	1st to 10th	Night	13% 3 23% 42% 18% 2	390
	11th to 20th	Night	13% 6% 17% 43% 19% 3	388
	21st to end	Night	15% 2 18% 47% 17% 1	438
August	1st to 10th	Night	12% 2 20% 45% 20% 1	513
	11th to 20th	Night	15% 3 17% 38% 25% 2	790
	21st to end	Night	13% 5% 17% 38% 23% 3	880
September	1st to 10th	Night	16% 3 24% 35% 18% 4	800
	11th to 20th	Night	16% 4 19% 35% 20% 6%	800
	21st to end	Night	21% 3 24% 33% 17% 2	800
October	1st to 10th	Night	22% 7% 25% 27% 16% 3	800
	11th to 20th	Night	18% 11% 29% 29% 12% 1	800
	21st to end	Night	23% 11% 34% 25% 8%	880
November	1st to 10th	Night	15% 11% 33% 27% 11% 2	820
	11th to 20th	Night	21% 15% 33% 22% 8%	840
	21st to end	Night	18% 17% 33% 25% 7% 1	840
December	1st to 10th	Night	25% 16% 34% 19% 5% 1	840
	11th to 20th	Night	24% 15% 36% 22% 3	840
	21st to end	Night	23% 15% 38% 21% 3	924

Page generated at 2026-02-13 01:42:16. Version ac07

Copyright © 2026 Attilla Danko.