Deep Sky Hermitage
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deep Sky Hermitage clear sky chart from 2005-11-06 to 2026-07-16.

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	6% 8% 3 6% 4 4 4 3 5% 7% 51%	147272
	Night	7% 9% 3 7% 4 4 4 3 5% 6% 47%	142728
Transparency	Day	31% 6% 10% 22% 20% 10%	142069
	Night	35% 7% 12% 22% 17% 7%	138929
Seeing	Day	11% 12% 25% 27% 18% 6%	16759
	Night	11% 8% 21% 37% 20% 2	25817

By Month

Percentage Cloud Cover SW (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	11% 17% 5% 11% 6% 5% 6% 4 7% 7% 21%	4722
	11th to 20th	Day	9% 11% 3 5% 3 3 3 3 4 6% 51%	4740
	21st to end	Day	6% 10% 4 8% 5% 4 5% 5% 7% 9% 37%	5525
February	1st to 10th	Day	8% 12% 4 9% 6% 5% 5% 4 6% 10% 30%	1890
	11th to 20th	Day	8% 13% 4 9% 6% 5% 4 5% 6% 9% 31%	1879
	21st to end	Day	6% 16% 7% 9% 6% 5% 5% 5% 6% 8% 28%	1730
March	1st to 10th	Day	7% 11% 5% 10% 5% 5% 5% 5% 6% 8% 34%	4618
	11th to 20th	Day	5% 13% 5% 10% 5% 6% 4 4 4 6% 38%	5100
	21st to end	Day	8% 15% 5% 11% 7% 6% 6% 4 6% 6% 27%	5907
April	1st to 10th	Day	9% 14% 5% 8% 6% 5% 5% 4 5% 7% 32%	2520
	11th to 20th	Day	9% 10% 4 10% 5% 5% 4 4 5% 6% 38%	2489
	21st to end	Day	8% 10% 3 6% 4 4 4 4 5% 8% 43%	2563
May	1st to 10th	Day	7% 7% 2 5% 3 3 3 4 6% 7% 54%	8195
	11th to 20th	Day	6% 6% 2 5% 3 4 4 3 5% 7% 54%	8160
	21st to end	Day	7% 7% 2 5% 3 3 4 3 5% 8% 52%	8992
June	1st to 10th	Day	11% 8% 2 6% 4 4 4 4 5% 6% 45%	2940
	11th to 20th	Day	8% 5% 2 5% 4 3 4 3 5% 6% 55%	2940
	21st to end	Day	4 4 1 4 3 3 3 3 4 6% 65%	2940
July	1st to 10th	Day	2 2 1 2 1 2 2 2 3 4 80%	6459
	11th to 20th	Day	1 1 1 2 2 2 2 2 2 3 82%	6391
	21st to end	Day	1 1 1 2 2 2 2 2 4 5% 77%	6880
August	1st to 10th	Day	2 3 1 4 3 3 3 4 5% 7% 66%	5979
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 5% 74%	5695
	21st to end	Day	4 4 2 4 3 3 3 3 4 5% 64%	5984
September	1st to 10th	Day	2 2 1 3 2 3 3 2 4 6% 73%	2400
	11th to 20th	Day	5% 4 2 5% 4 3 4 3 4 6% 60%	2400
	21st to end	Day	7% 6% 2 4 3 3 3 3 5% 6% 60%	2153
October	1st to 10th	Day	6% 6% 2 4 3 2 3 2 4 5% 63%	3280
	11th to 20th	Day	6% 5% 2 6% 5% 4 5% 4 6% 9% 48%	3261
	21st to end	Day	10% 9% 3 8% 5% 5% 6% 4 5% 6% 39%	3368
November	1st to 10th	Day	11% 12% 3 8% 6% 4 4 4 5% 7% 36%	1854
	11th to 20th	Day	11% 11% 3 9% 6% 5% 5% 5% 7% 7% 30%	1738
	21st to end	Day	8% 13% 4 8% 4 5% 5% 4 7% 7% 35%	1680
December	1st to 10th	Day	7% 8% 3 5% 3 3 4 4 5% 7% 52%	2700
	11th to 20th	Day	11% 14% 5% 12% 7% 6% 5% 5% 6% 8% 23%	3108
	21st to end	Day	10% 16% 4 11% 6% 6% 6% 5% 6% 8% 23%	4092
January	1st to 10th	Night	10% 17% 5% 12% 6% 6% 5% 4 6% 7% 20%	8172
	11th to 20th	Night	7% 12% 3 5% 4 3 3 3 4 6% 51%	8220
	21st to end	Night	7% 10% 3 9% 6% 6% 5% 4 5% 7% 36%	8672
February	1st to 10th	Night	8% 15% 5% 10% 5% 5% 4 4 5% 7% 31%	2730
	11th to 20th	Night	8% 13% 4 9% 5% 6% 5% 4 6% 7% 34%	2626
	21st to end	Night	6% 15% 5% 10% 7% 4 5% 5% 7% 8% 29%	2076
March	1st to 10th	Night	5% 12% 4 8% 5% 5% 5% 5% 9% 9% 34%	5496
	11th to 20th	Night	6% 10% 4 8% 5% 5% 4 4 5% 6% 43%	5115
	21st to end	Night	7% 15% 4 10% 6% 6% 6% 4 6% 7% 30%	5309
April	1st to 10th	Night	10% 15% 3 9% 5% 4 4 4 6% 7% 34%	2100
	11th to 20th	Night	9% 13% 4 7% 4 5% 3 4 5% 6% 39%	2079
	21st to end	Night	8% 12% 3 7% 5% 4 4 4 5% 7% 41%	2053
May	1st to 10th	Night	6% 9% 3 5% 3 3 3 3 4 7% 55%	4723
	11th to 20th	Night	6% 7% 2 6% 4 4 4 3 4 7% 53%	4700
	21st to end	Night	10% 7% 2 5% 3 3 2 2 4 6% 55%	5181
June	1st to 10th	Night	11% 6% 2 5% 6% 4 4 3 5% 6% 48%	1680
	11th to 20th	Night	8% 7% 2 4 3 3 3 3 5% 6% 56%	1680
	21st to end	Night	4 3 2 3 3 2 3 4 4 5% 67%	1680
July	1st to 10th	Night	1 2 1 3 2 2 2 2 3 4 78%	3720
	11th to 20th	Night	1 1 1 2 1 1 1 1 2 3 85%	3680
	21st to end	Night	2 3 1 3 2 2 2 2 3 3 75%	3970
August	1st to 10th	Night	3 3 1 5% 3 3 4 4 5% 7% 62%	3807
	11th to 20th	Night	1 2 1 3 2 2 2 2 4 5% 77%	4144
	21st to end	Night	3 4 1 4 3 3 3 2 4 5% 69%	5015
September	1st to 10th	Night	2 2 1 3 2 2 2 2 4 4 75%	2000
	11th to 20th	Night	4 3 1 5% 3 2 4 3 5% 6% 63%	2000
	21st to end	Night	7% 5% 2 4 2 3 3 3 5% 6% 61%	2243
October	1st to 10th	Night	5% 6% 2 4 2 2 2 2 3 4 68%	3920
	11th to 20th	Night	8% 7% 2 6% 4 3 4 3 5% 8% 52%	3897
	21st to end	Night	8% 7% 3 8% 5% 5% 6% 4 6% 7% 42%	4435
November	1st to 10th	Night	13% 11% 3 8% 5% 5% 4 4 5% 6% 36%	2665
	11th to 20th	Night	13% 11% 4 8% 5% 5% 6% 4 7% 6% 31%	2878
	21st to end	Night	9% 12% 4 6% 4 4 4 4 5% 8% 40%	2940
December	1st to 10th	Night	6% 8% 2 6% 4 3 3 3 4 7% 54%	4700
	11th to 20th	Night	11% 15% 4 11% 7% 5% 6% 5% 6% 7% 22%	5316
	21st to end	Night	11% 15% 4 10% 6% 5% 5% 4 5% 7% 28%	7106

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	56% 10% 14% 16% 5%	4723
	11th to 20th	Day	33% 7% 8% 19% 25% 8%	4740
	21st to end	Day	38% 9% 10% 14% 21% 6%	5525
February	1st to 10th	Day	48% 8% 14% 19% 10% 1	1890
	11th to 20th	Day	46% 9% 15% 18% 9% 3	1888
	21st to end	Day	49% 10% 15% 15% 9% 2	1730
March	1st to 10th	Day	40% 8% 13% 21% 13% 4	4618
	11th to 20th	Day	42% 9% 12% 26% 11%	5100
	21st to end	Day	49% 13% 14% 18% 6%	5907
April	1st to 10th	Day	48% 8% 13% 19% 10% 1	2520
	11th to 20th	Day	45% 6% 14% 17% 15% 3	2492
	21st to end	Day	38% 7% 14% 25% 14% 3	2563
May	1st to 10th	Day	26% 5% 9% 28% 28% 3	8195
	11th to 20th	Day	27% 6% 13% 28% 24% 3	8163
	21st to end	Day	29% 7% 13% 32% 18% 2	8994
June	1st to 10th	Day	37% 7% 10% 28% 15% 2	2940
	11th to 20th	Day	28% 5% 11% 29% 22% 5%	2940
	21st to end	Day	21% 4 10% 26% 28% 11%	2940
July	1st to 10th	Day	10% 2 4 15% 28% 40%	6391
	11th to 20th	Day	9% 2 4 8% 21% 55%	6316
	21st to end	Day	10% 3 5% 25% 35% 22%	6681
August	1st to 10th	Day	18% 3 6% 16% 32% 25%	4350
	11th to 20th	Day	14% 3 6% 24% 35% 18%	4118
	21st to end	Day	16% 3 7% 26% 26% 22%	4311
September	1st to 10th	Day	13% 3 7% 22% 33% 22%	2400
	11th to 20th	Day	25% 5% 9% 22% 25% 14%	2400
	21st to end	Day	26% 5% 9% 25% 23% 12%	2153
October	1st to 10th	Day	24% 5% 10% 19% 26% 17%	3280
	11th to 20th	Day	30% 7% 16% 25% 18% 4	3261
	21st to end	Day	42% 6% 10% 22% 18% 2	3368
November	1st to 10th	Day	45% 7% 14% 21% 12% 1	1854
	11th to 20th	Day	49% 9% 17% 15% 9% 1	1738
	21st to end	Day	44% 9% 15% 16% 15% 1	1680
December	1st to 10th	Day	32% 8% 11% 22% 25% 3	2700
	11th to 20th	Day	57% 9% 14% 15% 6% 1	3108
	21st to end	Day	54% 10% 13% 18% 5%	4092
January	1st to 10th	Night	56% 11% 15% 14% 4	8172
	11th to 20th	Night	32% 7% 8% 22% 23% 9%	8220
	21st to end	Night	45% 8% 9% 12% 19% 6%	8672
February	1st to 10th	Night	50% 10% 14% 16% 10% 1	2730
	11th to 20th	Night	46% 10% 14% 18% 9% 3	2628
	21st to end	Night	48% 10% 13% 18% 9% 1	2076
March	1st to 10th	Night	38% 8% 13% 24% 13% 4	5496
	11th to 20th	Night	35% 9% 13% 28% 14% 1	5115
	21st to end	Night	47% 14% 14% 19% 6%	5309
April	1st to 10th	Night	46% 8% 16% 20% 9% 1	2100
	11th to 20th	Night	44% 6% 15% 21% 13% 1	2079
	21st to end	Night	41% 9% 14% 24% 12% 1	2053
May	1st to 10th	Night	27% 5% 12% 27% 27% 1	4721
	11th to 20th	Night	29% 7% 16% 33% 15% 1	4700
	21st to end	Night	27% 7% 21% 31% 13%	5182
June	1st to 10th	Night	36% 8% 11% 30% 14% 1	1680
	11th to 20th	Night	27% 6% 13% 31% 19% 4	1680
	21st to end	Night	19% 4 12% 30% 27% 8%	1680
July	1st to 10th	Night	13% 2 6% 20% 28% 31%	3680
	11th to 20th	Night	8% 2 5% 13% 26% 47%	3632
	21st to end	Night	15% 2 4 29% 30% 21%	3857
August	1st to 10th	Night	17% 3 7% 19% 34% 19%	2764
	11th to 20th	Night	11% 3 7% 38% 30% 11%	2995
	21st to end	Night	13% 4 9% 28% 27% 19%	3608
September	1st to 10th	Night	13% 3 6% 25% 34% 19%	2000
	11th to 20th	Night	20% 6% 10% 26% 26% 13%	2000
	21st to end	Night	25% 5% 8% 24% 23% 14%	2243
October	1st to 10th	Night	22% 3 8% 21% 32% 14%	3920
	11th to 20th	Night	31% 6% 18% 23% 19% 4	3897
	21st to end	Night	38% 7% 11% 26% 16% 2	4435
November	1st to 10th	Night	47% 8% 12% 17% 13% 3	2665
	11th to 20th	Night	48% 10% 13% 19% 10% 1	2878
	21st to end	Night	40% 8% 13% 18% 18% 3	2940
December	1st to 10th	Night	29% 8% 10% 24% 26% 3	4700
	11th to 20th	Night	56% 9% 13% 15% 6%	5316
	21st to end	Night	51% 11% 14% 17% 7% 1	7106

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	22% 16% 33% 18% 10%	220
	11th to 20th	Day	15% 14% 28% 25% 16% 2	220
	21st to end	Day	13% 10% 30% 28% 17% 1	362
February	1st to 10th	Day	15% 18% 24% 31% 12% 1	430
	11th to 20th	Day	12% 17% 33% 27% 10% 1	444
	21st to end	Day	15% 17% 29% 30% 8% 1	446
March	1st to 10th	Day	14% 15% 33% 28% 9% 1	540
	11th to 20th	Day	16% 16% 28% 25% 12% 4	540
	21st to end	Day	17% 20% 26% 27% 9% 1	594
April	1st to 10th	Day	19% 16% 24% 25% 12% 4	540
	11th to 20th	Day	12% 17% 32% 24% 11% 4	532
	21st to end	Day	12% 14% 29% 25% 17% 3	540
May	1st to 10th	Day	11% 16% 27% 25% 16% 4	543
	11th to 20th	Day	20% 14% 23% 20% 16% 7%	568
	21st to end	Day	12% 10% 23% 25% 20% 9%	617
June	1st to 10th	Day	10% 11% 27% 24% 20% 8%	570
	11th to 20th	Day	8% 17% 26% 24% 20% 5%	570
	21st to end	Day	5% 9% 24% 27% 24% 12%	570
July	1st to 10th	Day	4 5% 24% 32% 25% 10%	566
	11th to 20th	Day	2 8% 26% 28% 26% 10%	545
	21st to end	Day	2 5% 26% 28% 24% 15%	575
August	1st to 10th	Day	3 5% 24% 26% 29% 13%	527
	11th to 20th	Day	3 5% 20% 28% 28% 17%	517
	21st to end	Day	5% 8% 21% 27% 27% 13%	583
September	1st to 10th	Day	3 5% 20% 32% 30% 10%	530
	11th to 20th	Day	7% 8% 18% 30% 29% 8%	530
	21st to end	Day	10% 8% 22% 28% 28% 5%	530
October	1st to 10th	Day	13% 10% 21% 31% 19% 7%	530
	11th to 20th	Day	12% 12% 23% 28% 20% 5%	530
	21st to end	Day	16% 14% 26% 23% 16% 4	468
November	1st to 10th	Day	16% 14% 25% 29% 13% 2	330
	11th to 20th	Day	17% 18% 25% 25% 12% 2	250
	21st to end	Day	13% 14% 22% 37% 13% 1	220
December	1st to 10th	Day	12% 15% 27% 27% 13% 5%	220
	11th to 20th	Day	19% 18% 30% 26% 7%	220
	21st to end	Day	17% 17% 27% 26% 11% 1	242
January	1st to 10th	Night	16% 14% 29% 27% 13% 2	840
	11th to 20th	Night	11% 14% 27% 28% 17% 3	840
	21st to end	Night	16% 8% 23% 35% 15% 2	924
February	1st to 10th	Night	13% 12% 27% 34% 14% 1	840
	11th to 20th	Night	12% 10% 27% 36% 14% 2	824
	21st to end	Night	13% 13% 28% 34% 10% 1	692
March	1st to 10th	Night	12% 12% 29% 33% 13% 1	840
	11th to 20th	Night	13% 9% 26% 35% 15% 2	840
	21st to end	Night	13% 12% 27% 34% 13% 1	924
April	1st to 10th	Night	17% 10% 23% 31% 18% 2	840
	11th to 20th	Night	12% 11% 26% 32% 16% 3	831
	21st to end	Night	12% 10% 23% 37% 16% 2	793
May	1st to 10th	Night	10% 6% 20% 43% 20% 1	420
	11th to 20th	Night	10% 8% 16% 40% 24% 2	414
	21st to end	Night	14% 5% 15% 40% 24% 2	455
June	1st to 10th	Night	12% 5% 19% 42% 22%	420
	11th to 20th	Night	8% 5% 23% 46% 18%	420
	21st to end	Night	5% 3 15% 51% 24% 1	420
July	1st to 10th	Night	2 1 12% 51% 31% 1	410
	11th to 20th	Night	2 2 15% 56% 24% 2	398
	21st to end	Night	1 16% 55% 27% 1	438
August	1st to 10th	Night	2 1 9% 48% 36% 4	496
	11th to 20th	Night	2 1 9% 39% 43% 7%	634
	21st to end	Night	3 2 15% 44% 32% 3	880
September	1st to 10th	Night	2 1 15% 43% 35% 3	800
	11th to 20th	Night	6% 2 12% 40% 33% 7%	800
	21st to end	Night	9% 4 14% 36% 33% 5%	800
October	1st to 10th	Night	11% 4 17% 39% 25% 5%	800
	11th to 20th	Night	11% 5% 17% 40% 23% 4	800
	21st to end	Night	12% 8% 22% 36% 16% 5%	880
November	1st to 10th	Night	16% 9% 23% 37% 14% 1	820
	11th to 20th	Night	17% 14% 22% 31% 14% 2	840
	21st to end	Night	14% 12% 22% 33% 17% 3	840
December	1st to 10th	Night	13% 10% 24% 32% 19% 2	840
	11th to 20th	Night	15% 14% 27% 30% 13% 1	840
	21st to end	Night	19% 17% 29% 26% 9%	924

Page generated at 2026-07-13 00:14:47. Version ac07

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