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 2024-02-05.

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	8% 9% 3 6% 5% 3 4 5% 5% 7% 46%	78194
	Night	9% 10% 4 6% 5% 3 4 4 5% 7% 42%	80684
Transparency	Day	37% 7% 12% 20% 17% 8%	77897
	Night	40% 8% 12% 20% 15% 5%	80502
Seeing	Day	11% 11% 25% 27% 19% 6%	13585
	Night	11% 8% 21% 36% 21% 3	22825

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	13% 15% 6% 9% 6% 4 6% 5% 7% 7% 22%	2539
	11th to 20th	Day	16% 18% 5% 7% 6% 3 5% 5% 6% 6% 22%	2540
	21st to end	Day	11% 15% 5% 8% 7% 3 5% 5% 5% 9% 27%	2967
February	1st to 10th	Day	8% 11% 5% 8% 6% 4 6% 5% 6% 10% 31%	1657
	11th to 20th	Day	8% 11% 6% 7% 6% 4 4 6% 6% 9% 33%	1604
	21st to end	Day	7% 14% 8% 8% 7% 4 4 7% 6% 9% 26%	1480
March	1st to 10th	Day	8% 11% 7% 9% 7% 5% 6% 7% 6% 7% 28%	1800
	11th to 20th	Day	9% 13% 4 8% 7% 4 5% 5% 5% 8% 31%	1971
	21st to end	Day	9% 15% 5% 10% 7% 4 7% 5% 5% 6% 28%	2291
April	1st to 10th	Day	10% 14% 6% 8% 7% 4 5% 5% 5% 6% 31%	2160
	11th to 20th	Day	10% 10% 5% 10% 6% 3 4 4 5% 7% 36%	2129
	21st to end	Day	9% 9% 3 6% 5% 2 4 6% 5% 8% 42%	2196
May	1st to 10th	Day	8% 9% 3 5% 5% 2 4 5% 6% 7% 46%	2520
	11th to 20th	Day	12% 8% 3 6% 5% 3 4 5% 5% 8% 40%	2477
	21st to end	Day	14% 8% 3 6% 5% 3 5% 4 4 7% 40%	2723
June	1st to 10th	Day	12% 8% 3 5% 5% 4 4 5% 6% 7% 42%	2520
	11th to 20th	Day	9% 5% 2 5% 4 3 4 4 4 7% 53%	2520
	21st to end	Day	5% 3 1 3 4 2 3 4 4 6% 65%	2520
July	1st to 10th	Day	3 2 1 2 2 2 3 4 4 5% 73%	2520
	11th to 20th	Day	2 2 1 2 3 2 3 3 3 5% 75%	2520
	21st to end	Day	2 1 1 1 2 1 2 3 3 5% 78%	2741
August	1st to 10th	Day	2 2 1 3 3 3 3 4 5% 6% 69%	2416
	11th to 20th	Day	3 2 1 3 3 2 2 3 3 5% 75%	2262
	21st to end	Day	2 2 1 2 2 1 3 2 3 4 76%	2376
September	1st to 10th	Day	2 2 2 2 2 2 3 3 5% 76%	2160
	11th to 20th	Day	5% 4 2 4 5% 2 3 4 4 7% 60%	2160
	21st to end	Day	7% 6% 2 4 3 2 4 3 5% 6% 58%	1939
October	1st to 10th	Day	11% 9% 3 5% 4 2 4 4 4 5% 50%	1800
	11th to 20th	Day	10% 7% 3 5% 5% 3 4 4 5% 8% 47%	1800
	21st to end	Day	11% 7% 3 6% 5% 3 5% 5% 4 5% 46%	1877
November	1st to 10th	Day	12% 11% 3 6% 7% 3 4 5% 5% 7% 37%	1674
	11th to 20th	Day	12% 10% 4 7% 7% 3 5% 6% 7% 8% 31%	1573
	21st to end	Day	9% 11% 4 7% 5% 4 5% 5% 7% 7% 36%	1520
December	1st to 10th	Day	9% 10% 4 6% 6% 3 6% 5% 5% 8% 38%	1520
	11th to 20th	Day	12% 12% 4 8% 8% 4 5% 6% 6% 9% 26%	1928
	21st to end	Day	9% 15% 5% 10% 6% 4 5% 5% 6% 8% 26%	2794
January	1st to 10th	Night	10% 17% 6% 9% 8% 4 6% 5% 6% 7% 21%	4406
	11th to 20th	Night	14% 20% 5% 8% 7% 3 4 5% 5% 6% 23%	4420
	21st to end	Night	12% 15% 4 9% 7% 4 6% 5% 6% 7% 26%	4693
February	1st to 10th	Night	8% 13% 6% 9% 6% 3 6% 5% 5% 8% 31%	2397
	11th to 20th	Night	8% 12% 4 8% 5% 3 5% 5% 6% 7% 36%	2241
	21st to end	Night	6% 15% 6% 9% 7% 3 6% 5% 6% 8% 28%	1776
March	1st to 10th	Night	9% 12% 5% 9% 5% 3 5% 5% 7% 7% 31%	2160
	11th to 20th	Night	8% 10% 4 9% 8% 5% 6% 6% 6% 8% 32%	1985
	21st to end	Night	8% 13% 6% 9% 8% 4 6% 5% 6% 7% 28%	2064
April	1st to 10th	Night	12% 14% 3 8% 6% 3 4 5% 6% 6% 32%	1800
	11th to 20th	Night	10% 13% 5% 7% 5% 3 4 4 4 6% 38%	1779
	21st to end	Night	9% 12% 4 6% 5% 3 4 5% 5% 7% 39%	1761
May	1st to 10th	Night	8% 9% 3 4 4 3 5% 5% 5% 7% 48%	1440
	11th to 20th	Night	11% 6% 2 6% 5% 3 6% 4 5% 9% 44%	1416
	21st to end	Night	13% 8% 3 6% 6% 3 4 4 5% 8% 40%	1552
June	1st to 10th	Night	12% 5% 3 5% 6% 3 4 5% 4 7% 46%	1440
	11th to 20th	Night	9% 8% 2 3 3 2 3 3 5% 7% 56%	1440
	21st to end	Night	4 3 2 3 3 2 3 4 4 6% 68%	1440
July	1st to 10th	Night	1 1 1 2 3 2 4 4 4 6% 72%	1440
	11th to 20th	Night	2 1 1 2 1 1 3 3 3 4 80%	1440
	21st to end	Night	1 1 1 2 2 1 1 3 4 3 81%	1576
August	1st to 10th	Night	1 2 1 2 2 2 3 3 5% 7% 72%	1520
	11th to 20th	Night	1 2 1 2 2 2 2 3 3 5% 78%	1638
	21st to end	Night	2 2 1 2 1 1 2 3 4 4 78%	1980
September	1st to 10th	Night	2 1 1 2 3 1 2 2 4 4 78%	1800
	11th to 20th	Night	5% 3 2 4 4 1 3 4 4 6% 64%	1800
	21st to end	Night	8% 6% 2 4 2 3 3 4 4 6% 59%	2017
October	1st to 10th	Night	8% 8% 3 4 4 2 3 3 4 5% 56%	2160
	11th to 20th	Night	10% 6% 2 4 4 2 3 3 4 7% 55%	2160
	21st to end	Night	11% 9% 3 6% 5% 3 5% 4 6% 6% 44%	2477
November	1st to 10th	Night	14% 11% 4 6% 6% 4 5% 5% 4 6% 36%	2405
	11th to 20th	Night	13% 10% 4 7% 7% 4 6% 5% 7% 6% 33%	2603
	21st to end	Night	9% 11% 4 6% 4 3 4 5% 5% 9% 40%	2660
December	1st to 10th	Night	10% 12% 4 8% 5% 2 5% 4 5% 7% 37%	2660
	11th to 20th	Night	9% 13% 5% 9% 7% 3 6% 6% 6% 8% 26%	3276
	21st to end	Night	9% 15% 5% 8% 7% 3 6% 5% 5% 6% 31%	4862

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	51% 12% 17% 16% 4 1	2539
	11th to 20th	Day	57% 11% 12% 14% 4 3	2540
	21st to end	Day	50% 14% 13% 16% 5% 1	2967
February	1st to 10th	Day	48% 8% 15% 19% 9%	1657
	11th to 20th	Day	45% 9% 15% 19% 10% 3	1613
	21st to end	Day	51% 11% 15% 14% 8% 1	1480
March	1st to 10th	Day	51% 9% 15% 15% 8% 1	1800
	11th to 20th	Day	48% 9% 13% 21% 9%	1971
	21st to end	Day	55% 9% 13% 16% 6%	2291
April	1st to 10th	Day	51% 7% 13% 16% 10% 2	2160
	11th to 20th	Day	47% 6% 15% 17% 12% 3	2132
	21st to end	Day	39% 7% 14% 24% 13% 2	2196
May	1st to 10th	Day	36% 7% 12% 27% 18% 1	2520
	11th to 20th	Day	42% 6% 12% 24% 13% 3	2480
	21st to end	Day	44% 8% 14% 22% 11% 2	2724
June	1st to 10th	Day	41% 7% 12% 28% 12% 1	2520
	11th to 20th	Day	30% 5% 12% 31% 18% 3	2520
	21st to end	Day	21% 4 10% 27% 28% 10%	2520
July	1st to 10th	Day	15% 4 8% 21% 26% 27%	2451
	11th to 20th	Day	13% 4 7% 12% 30% 34%	2445
	21st to end	Day	11% 2 5% 12% 36% 34%	2589
August	1st to 10th	Day	16% 4 9% 23% 30% 19%	2399
	11th to 20th	Day	14% 3 7% 20% 33% 23%	2262
	21st to end	Day	14% 2 6% 22% 38% 18%	2376
September	1st to 10th	Day	12% 3 7% 23% 33% 23%	2160
	11th to 20th	Day	25% 5% 9% 21% 26% 15%	2160
	21st to end	Day	28% 5% 9% 24% 23% 12%	1939
October	1st to 10th	Day	37% 7% 9% 17% 22% 9%	1800
	11th to 20th	Day	35% 6% 12% 22% 19% 7%	1800
	21st to end	Day	40% 7% 12% 20% 19% 3	1877
November	1st to 10th	Day	45% 7% 14% 21% 12% 1	1674
	11th to 20th	Day	47% 10% 17% 16% 9% 1	1573
	21st to end	Day	44% 9% 15% 15% 16% 1	1520
December	1st to 10th	Day	42% 12% 14% 20% 11% 1	1520
	11th to 20th	Day	52% 10% 15% 15% 8%	1928
	21st to end	Day	51% 11% 14% 19% 5% 1	2794
January	1st to 10th	Night	55% 13% 14% 13% 5% 1	4406
	11th to 20th	Night	55% 11% 12% 14% 5% 3	4420
	21st to end	Night	53% 12% 14% 13% 7% 1	4693
February	1st to 10th	Night	49% 10% 16% 15% 9% 1	2397
	11th to 20th	Night	45% 10% 15% 19% 9% 3	2243
	21st to end	Night	51% 10% 13% 17% 8% 1	1776
March	1st to 10th	Night	48% 10% 15% 18% 8% 2	2160
	11th to 20th	Night	46% 10% 14% 21% 7% 1	1985
	21st to end	Night	52% 10% 14% 18% 5%	2064
April	1st to 10th	Night	49% 9% 14% 18% 9% 1	1800
	11th to 20th	Night	46% 6% 15% 19% 12% 2	1779
	21st to end	Night	43% 9% 14% 23% 10% 1	1761
May	1st to 10th	Night	33% 6% 16% 29% 15% 1	1440
	11th to 20th	Night	37% 8% 15% 27% 10% 3	1416
	21st to end	Night	41% 8% 17% 24% 9% 1	1552
June	1st to 10th	Night	37% 9% 12% 30% 12%	1440
	11th to 20th	Night	28% 7% 15% 33% 15% 2	1440
	21st to end	Night	19% 4 12% 31% 26% 7%	1440
July	1st to 10th	Night	13% 5% 11% 25% 27% 20%	1400
	11th to 20th	Night	10% 3 7% 19% 33% 28%	1392
	21st to end	Night	10% 2 4 15% 41% 27%	1488
August	1st to 10th	Night	12% 3 9% 29% 33% 13%	1512
	11th to 20th	Night	11% 3 8% 26% 34% 18%	1638
	21st to end	Night	11% 3 7% 25% 38% 16%	1980
September	1st to 10th	Night	11% 2 6% 26% 36% 19%	1800
	11th to 20th	Night	19% 6% 10% 25% 27% 14%	1800
	21st to end	Night	26% 5% 8% 24% 22% 15%	2017
October	1st to 10th	Night	31% 5% 11% 20% 25% 8%	2160
	11th to 20th	Night	30% 6% 14% 23% 21% 6%	2160
	21st to end	Night	39% 8% 13% 16% 21% 3	2477
November	1st to 10th	Night	47% 8% 11% 17% 14% 3	2405
	11th to 20th	Night	47% 11% 13% 19% 10% 1	2603
	21st to end	Night	41% 8% 13% 17% 18% 3	2660
December	1st to 10th	Night	44% 11% 14% 19% 10% 2	2660
	11th to 20th	Night	51% 10% 13% 16% 9%	3276
	21st to end	Night	49% 11% 13% 19% 8% 1	4862

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	21% 16% 33% 17% 13% 1	180
	11th to 20th	Day	18% 16% 27% 22% 15% 2	180
	21st to end	Day	14% 11% 29% 27% 18% 1	306
February	1st to 10th	Day	14% 17% 24% 32% 13%	353
	11th to 20th	Day	12% 16% 34% 27% 10% 1	349
	21st to end	Day	14% 16% 29% 31% 10% 1	346
March	1st to 10th	Day	15% 13% 32% 29% 10% 1	420
	11th to 20th	Day	15% 15% 26% 27% 13% 4	420
	21st to end	Day	16% 19% 25% 28% 10% 2	462
April	1st to 10th	Day	21% 17% 25% 21% 11% 5%	420
	11th to 20th	Day	13% 18% 32% 21% 11% 5%	412
	21st to end	Day	14% 15% 30% 21% 17% 3	420
May	1st to 10th	Day	11% 17% 26% 26% 15% 5%	423
	11th to 20th	Day	21% 12% 23% 19% 18% 7%	448
	21st to end	Day	14% 9% 23% 26% 19% 9%	485
June	1st to 10th	Day	11% 9% 28% 24% 20% 8%	450
	11th to 20th	Day	10% 17% 27% 25% 17% 4	450
	21st to end	Day	4 8% 24% 28% 24% 13%	450
July	1st to 10th	Day	4 4 25% 33% 24% 10%	446
	11th to 20th	Day	2 7% 25% 29% 25% 11%	444
	21st to end	Day	2 5% 26% 28% 25% 14%	487
August	1st to 10th	Day	3 4 24% 26% 29% 13%	447
	11th to 20th	Day	2 4 19% 29% 28% 18%	437
	21st to end	Day	5% 7% 21% 27% 26% 13%	495
September	1st to 10th	Day	3 5% 20% 32% 30% 10%	450
	11th to 20th	Day	7% 8% 18% 31% 29% 7%	450
	21st to end	Day	10% 7% 23% 28% 26% 6%	450
October	1st to 10th	Day	13% 10% 21% 31% 18% 8%	450
	11th to 20th	Day	12% 12% 22% 26% 22% 6%	450
	21st to end	Day	14% 13% 27% 22% 19% 5%	392
November	1st to 10th	Day	14% 13% 24% 32% 14% 2	270
	11th to 20th	Day	14% 17% 24% 28% 14% 3	205
	21st to end	Day	13% 14% 21% 36% 14% 1	180
December	1st to 10th	Day	12% 14% 28% 27% 13% 6%	180
	11th to 20th	Day	18% 16% 29% 30% 7%	180
	21st to end	Day	14% 14% 28% 29% 14% 1	198
January	1st to 10th	Night	16% 13% 28% 28% 14% 2	760
	11th to 20th	Night	13% 15% 25% 26% 18% 3	760
	21st to end	Night	17% 9% 20% 35% 17% 3	836
February	1st to 10th	Night	14% 10% 28% 32% 15% 1	738
	11th to 20th	Night	13% 9% 24% 36% 16% 2	704
	21st to end	Night	11% 13% 28% 35% 12% 1	592
March	1st to 10th	Night	13% 11% 28% 33% 14% 1	720
	11th to 20th	Night	12% 9% 24% 37% 16% 2	720
	21st to end	Night	13% 11% 26% 34% 14% 1	792
April	1st to 10th	Night	18% 11% 22% 30% 18% 2	720
	11th to 20th	Night	13% 11% 26% 30% 17% 3	711
	21st to end	Night	13% 10% 23% 35% 17% 2	681
May	1st to 10th	Night	10% 7% 20% 41% 21% 1	360
	11th to 20th	Night	11% 7% 14% 41% 25% 2	354
	21st to end	Night	15% 5% 14% 38% 25% 2	389
June	1st to 10th	Night	12% 5% 18% 40% 24% 1	360
	11th to 20th	Night	9% 5% 24% 43% 19%	360
	21st to end	Night	5% 3 16% 50% 26% 1	360
July	1st to 10th	Night	2 1 12% 50% 33% 1	350
	11th to 20th	Night	2 1 15% 56% 24% 2	348
	21st to end	Night	1 16% 54% 28% 1	394
August	1st to 10th	Night	1 1 9% 48% 37% 4	446
	11th to 20th	Night	2 1 8% 36% 45% 8%	570
	21st to end	Night	3 2 15% 44% 33% 4	792
September	1st to 10th	Night	2 1 15% 42% 36% 4	720
	11th to 20th	Night	6% 3 11% 38% 35% 7%	720
	21st to end	Night	9% 4 13% 35% 32% 5%	720
October	1st to 10th	Night	11% 4 17% 37% 26% 5%	720
	11th to 20th	Night	11% 5% 18% 37% 25% 4	720
	21st to end	Night	12% 8% 20% 36% 18% 6%	792
November	1st to 10th	Night	16% 9% 21% 37% 15% 1	740
	11th to 20th	Night	16% 13% 22% 32% 15% 2	760
	21st to end	Night	14% 11% 21% 33% 17% 3	760
December	1st to 10th	Night	14% 10% 23% 31% 20% 2	760
	11th to 20th	Night	14% 14% 25% 32% 15% 1	760
	21st to end	Night	18% 17% 28% 27% 10%	836

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