DeepSkyEye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DeepSkyEye Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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	22% 10% 4 7% 6% 3 4 4 4 6% 30%	78472
	Night	22% 11% 4 8% 6% 3 4 4 5% 6% 26%	80685
Transparency	Day	55% 5% 11% 17% 10% 1	78178
	Night	58% 5% 11% 17% 8% 1	80514
Seeing	Day	30% 18% 30% 15% 5% 1	15715
	Night	29% 15% 29% 21% 6%	23698

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	21% 15% 7% 15% 8% 3 4 4 4 4 16%	2249
	11th to 20th	Day	20% 16% 7% 16% 8% 4 3 4 4 4 14%	2818
	21st to end	Day	22% 14% 7% 14% 8% 2 4 3 3 4 19%	3124
February	1st to 10th	Day	20% 17% 8% 12% 9% 4 3 4 4 5% 14%	1710
	11th to 20th	Day	18% 15% 7% 14% 11% 3 4 4 3 4 17%	1654
	21st to end	Day	13% 16% 8% 10% 7% 4 4 4 4 5% 25%	1435
March	1st to 10th	Day	19% 13% 7% 11% 8% 3 3 3 3 4 25%	1933
	11th to 20th	Day	19% 13% 6% 8% 6% 3 3 3 4 5% 30%	1980
	21st to end	Day	20% 13% 6% 7% 5% 3 3 3 4 5% 31%	2178
April	1st to 10th	Day	26% 13% 5% 5% 5% 3 4 3 4 5% 28%	2071
	11th to 20th	Day	23% 9% 3 5% 4 2 4 5% 5% 6% 36%	2284
	21st to end	Day	25% 11% 2 5% 4 2 3 4 4 6% 34%	2340
May	1st to 10th	Day	27% 10% 3 6% 5% 3 4 3 4 5% 29%	2340
	11th to 20th	Day	22% 7% 3 5% 4 3 4 4 4 7% 38%	2379
	21st to end	Day	25% 8% 3 5% 4 3 4 3 5% 8% 32%	2724
June	1st to 10th	Day	28% 7% 2 5% 5% 3 3 4 4 6% 33%	2561
	11th to 20th	Day	23% 7% 3 5% 5% 3 4 3 4 6% 37%	2700
	21st to end	Day	27% 8% 2 6% 4 2 4 4 5% 6% 31%	2700
July	1st to 10th	Day	23% 7% 3 5% 4 2 4 4 6% 7% 36%	2700
	11th to 20th	Day	22% 7% 2 5% 6% 3 4 5% 6% 9% 32%	2517
	21st to end	Day	23% 8% 3 5% 5% 3 5% 4 5% 7% 32%	2548
August	1st to 10th	Day	20% 6% 2 4 5% 3 5% 6% 6% 7% 36%	2327
	11th to 20th	Day	22% 6% 2 6% 5% 4 4 5% 4 6% 35%	2304
	21st to end	Day	20% 6% 2 4 4 3 3 4 5% 7% 42%	2538
September	1st to 10th	Day	18% 5% 1 5% 3 3 4 4 5% 6% 46%	2152
	11th to 20th	Day	17% 6% 3 5% 5% 3 3 3 4 6% 44%	1980
	21st to end	Day	22% 7% 2 5% 4 2 3 3 4 6% 42%	1980
October	1st to 10th	Day	21% 7% 2 5% 4 3 4 4 5% 7% 38%	1816
	11th to 20th	Day	21% 8% 3 5% 5% 4 5% 4 5% 6% 34%	1800
	21st to end	Day	23% 10% 3 7% 6% 4 4 4 5% 6% 29%	1949
November	1st to 10th	Day	23% 9% 3 6% 6% 3 3 4 4 6% 33%	1638
	11th to 20th	Day	22% 14% 5% 7% 6% 3 4 5% 4 6% 23%	1520
	21st to end	Day	20% 18% 6% 9% 7% 3 5% 3 3 6% 19%	1520
December	1st to 10th	Day	26% 18% 5% 9% 7% 3 4 3 3 5% 16%	1520
	11th to 20th	Day	28% 15% 6% 9% 6% 4 5% 4 4 5% 14%	1906
	21st to end	Day	23% 14% 9% 10% 7% 3 3 4 3 5% 19%	2577
January	1st to 10th	Night	17% 15% 7% 19% 8% 4 5% 4 3 4 14%	4702
	11th to 20th	Night	20% 16% 8% 15% 8% 4 4 3 3 4 14%	4122
	21st to end	Night	20% 15% 6% 14% 8% 4 6% 4 4 4 16%	4532
February	1st to 10th	Night	20% 16% 6% 12% 9% 4 4 5% 4 4 16%	2470
	11th to 20th	Night	19% 13% 6% 11% 10% 5% 5% 5% 5% 5% 17%	2397
	21st to end	Night	13% 12% 6% 10% 8% 4 7% 6% 5% 6% 24%	1816
March	1st to 10th	Night	18% 11% 5% 10% 9% 4 4 4 4 5% 26%	2012
	11th to 20th	Night	20% 9% 5% 8% 7% 4 5% 5% 4 6% 26%	1979
	21st to end	Night	18% 10% 4 7% 6% 3 5% 4 5% 6% 33%	2178
April	1st to 10th	Night	24% 13% 3 6% 5% 3 4 4 4 6% 28%	1887
	11th to 20th	Night	24% 9% 3 4 5% 3 5% 4 5% 7% 32%	1622
	21st to end	Night	26% 9% 3 5% 4 3 4 5% 5% 7% 31%	1620
May	1st to 10th	Night	23% 9% 4 6% 5% 3 5% 3 5% 6% 31%	1620
	11th to 20th	Night	25% 10% 3 5% 5% 3 3 4 5% 7% 31%	1511
	21st to end	Night	22% 10% 4 7% 4 3 4 4 5% 6% 32%	1550
June	1st to 10th	Night	28% 8% 4 5% 4 2 4 5% 5% 7% 29%	1412
	11th to 20th	Night	22% 8% 4 6% 4 3 3 4 5% 6% 33%	1260
	21st to end	Night	28% 10% 3 5% 5% 2 4 4 4 6% 27%	1260
July	1st to 10th	Night	23% 10% 4 4 6% 2 4 5% 7% 8% 29%	1260
	11th to 20th	Night	23% 10% 4 6% 6% 3 5% 6% 6% 6% 26%	1417
	21st to end	Night	24% 8% 3 7% 6% 3 4 5% 5% 7% 28%	1770
August	1st to 10th	Night	21% 9% 3 5% 5% 2 3 3 6% 9% 35%	1612
	11th to 20th	Night	23% 12% 4 6% 5% 2 3 3 5% 7% 31%	1596
	21st to end	Night	18% 8% 3 5% 4 3 3 4 5% 6% 40%	1818
September	1st to 10th	Night	19% 7% 2 4 4 2 4 4 6% 7% 41%	1806
	11th to 20th	Night	21% 6% 2 4 4 2 3 3 5% 7% 43%	1980
	21st to end	Night	23% 8% 2 4 4 2 3 4 4 7% 38%	1980
October	1st to 10th	Night	22% 6% 2 5% 4 4 3 4 5% 6% 39%	2142
	11th to 20th	Night	18% 9% 2 5% 5% 3 4 4 5% 7% 39%	2160
	21st to end	Night	26% 10% 3 6% 4 3 4 4 4 6% 30%	2404
November	1st to 10th	Night	20% 8% 3 6% 5% 3 4 5% 5% 6% 33%	2437
	11th to 20th	Night	20% 12% 4 8% 7% 3 4 5% 6% 6% 24%	2660
	21st to end	Night	20% 14% 5% 8% 7% 3 4 4 5% 6% 24%	2660
December	1st to 10th	Night	26% 15% 5% 8% 6% 4 4 5% 5% 6% 16%	2660
	11th to 20th	Night	28% 14% 6% 9% 6% 3 5% 4 4 5% 16%	3293
	21st to end	Night	24% 15% 6% 10% 6% 3 4 3 4 4 21%	5080

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	69% 6% 14% 10% 2	2250
	11th to 20th	Day	70% 7% 11% 10% 3	2818
	21st to end	Day	69% 4 9% 12% 6%	3124
February	1st to 10th	Day	72% 5% 10% 8% 5%	1710
	11th to 20th	Day	70% 4 9% 12% 5%	1662
	21st to end	Day	60% 5% 11% 16% 7% 1	1435
March	1st to 10th	Day	63% 3 10% 15% 8% 1	1937
	11th to 20th	Day	56% 5% 9% 17% 12% 1	1980
	21st to end	Day	55% 5% 8% 18% 12% 2	2178
April	1st to 10th	Day	60% 5% 8% 14% 12% 1	2071
	11th to 20th	Day	49% 7% 10% 22% 12% 1	2284
	21st to end	Day	52% 5% 8% 19% 13% 2	2340
May	1st to 10th	Day	59% 4 8% 19% 9% 2	2340
	11th to 20th	Day	48% 6% 9% 20% 14% 2	2383
	21st to end	Day	52% 5% 13% 17% 12% 1	2724
June	1st to 10th	Day	53% 5% 9% 21% 11% 1	2561
	11th to 20th	Day	50% 5% 11% 18% 14% 2	2700
	21st to end	Day	54% 7% 12% 16% 9% 1	2700
July	1st to 10th	Day	47% 6% 16% 18% 12% 2	2625
	11th to 20th	Day	50% 7% 14% 20% 9% 1	2437
	21st to end	Day	51% 8% 14% 19% 8% 1	2406
August	1st to 10th	Day	46% 8% 14% 19% 12% 1	2314
	11th to 20th	Day	48% 8% 14% 19% 10% 1	2304
	21st to end	Day	42% 5% 12% 23% 17% 1	2538
September	1st to 10th	Day	39% 6% 12% 23% 19% 2	2152
	11th to 20th	Day	42% 5% 9% 24% 17% 3	1980
	21st to end	Day	46% 4 7% 23% 19% 2	1980
October	1st to 10th	Day	46% 5% 10% 26% 12% 2	1816
	11th to 20th	Day	50% 6% 10% 23% 10%	1800
	21st to end	Day	55% 5% 9% 18% 11% 1	1949
November	1st to 10th	Day	52% 5% 12% 20% 9% 1	1638
	11th to 20th	Day	61% 4 12% 17% 6%	1520
	21st to end	Day	66% 5% 12% 14% 2	1520
December	1st to 10th	Day	70% 4 10% 13% 3	1520
	11th to 20th	Day	71% 5% 9% 10% 4	1905
	21st to end	Day	65% 7% 15% 10% 4	2577
January	1st to 10th	Night	71% 4 11% 11% 2	4702
	11th to 20th	Night	71% 6% 9% 10% 3	4122
	21st to end	Night	70% 5% 10% 11% 5%	4532
February	1st to 10th	Night	69% 4 12% 10% 4	2470
	11th to 20th	Night	67% 5% 8% 14% 6%	2400
	21st to end	Night	57% 6% 13% 16% 7% 1	1816
March	1st to 10th	Night	60% 4 10% 15% 9% 2	2021
	11th to 20th	Night	59% 4 10% 14% 12% 1	1980
	21st to end	Night	51% 5% 10% 20% 13% 2	2178
April	1st to 10th	Night	57% 4 9% 15% 12% 3	1887
	11th to 20th	Night	52% 4 8% 22% 12% 1	1622
	21st to end	Night	53% 5% 10% 19% 11% 1	1620
May	1st to 10th	Night	55% 4 9% 20% 10% 1	1620
	11th to 20th	Night	53% 4 8% 22% 11% 1	1512
	21st to end	Night	53% 5% 13% 19% 9% 1	1551
June	1st to 10th	Night	55% 4 10% 23% 7% 1	1412
	11th to 20th	Night	51% 5% 12% 20% 11% 1	1260
	21st to end	Night	58% 6% 10% 15% 10% 1	1260
July	1st to 10th	Night	50% 8% 15% 18% 8%	1225
	11th to 20th	Night	56% 6% 14% 16% 8% 1	1374
	21st to end	Night	52% 6% 15% 18% 7% 1	1672
August	1st to 10th	Night	47% 6% 13% 24% 10%	1600
	11th to 20th	Night	54% 6% 13% 19% 9%	1596
	21st to end	Night	44% 6% 12% 24% 13% 1	1818
September	1st to 10th	Night	42% 6% 9% 27% 14% 2	1806
	11th to 20th	Night	43% 4 7% 28% 16% 2	1980
	21st to end	Night	47% 5% 7% 22% 18% 2	1980
October	1st to 10th	Night	47% 5% 11% 21% 14% 2	2142
	11th to 20th	Night	45% 4 12% 28% 11%	2160
	21st to end	Night	54% 4 10% 20% 11% 1	2404
November	1st to 10th	Night	50% 6% 14% 20% 10%	2437
	11th to 20th	Night	57% 5% 13% 18% 7%	2660
	21st to end	Night	60% 6% 15% 15% 5%	2660
December	1st to 10th	Night	66% 5% 14% 12% 3	2660
	11th to 20th	Night	68% 5% 10% 13% 4	3295
	21st to end	Night	64% 5% 11% 16% 3	5080

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	41% 22% 28% 6% 2	180
	11th to 20th	Day	37% 21% 28% 12% 2	361
	21st to end	Day	25% 26% 35% 11% 2	407
February	1st to 10th	Day	35% 20% 32% 11% 3	370
	11th to 20th	Day	38% 26% 25% 10% 2	363
	21st to end	Day	31% 23% 31% 12% 2	326
March	1st to 10th	Day	32% 25% 31% 9% 3	420
	11th to 20th	Day	36% 25% 25% 8% 5% 1	420
	21st to end	Day	30% 25% 27% 12% 5% 1	462
April	1st to 10th	Day	41% 24% 25% 7% 3	420
	11th to 20th	Day	33% 23% 31% 11% 2	412
	21st to end	Day	36% 18% 29% 12% 5% 1	420
May	1st to 10th	Day	34% 28% 26% 9% 3 1	423
	11th to 20th	Day	28% 22% 29% 16% 4	525
	21st to end	Day	32% 15% 30% 18% 4 1	680
June	1st to 10th	Day	33% 16% 28% 18% 5%	630
	11th to 20th	Day	25% 16% 33% 20% 6% 1	630
	21st to end	Day	33% 13% 30% 19% 5% 1	630
July	1st to 10th	Day	27% 11% 29% 23% 9% 1	620
	11th to 20th	Day	24% 10% 34% 23% 8% 1	551
	21st to end	Day	25% 11% 37% 21% 5% 1	488
August	1st to 10th	Day	21% 11% 37% 23% 7% 1	446
	11th to 20th	Day	26% 11% 34% 18% 8% 2	439
	21st to end	Day	24% 13% 31% 20% 10% 2	495
September	1st to 10th	Day	19% 14% 35% 24% 6% 1	450
	11th to 20th	Day	24% 16% 33% 16% 6% 5%	450
	21st to end	Day	24% 16% 33% 17% 7% 4	450
October	1st to 10th	Day	27% 12% 31% 18% 9% 2	367
	11th to 20th	Day	26% 16% 32% 18% 6% 3	360
	21st to end	Day	29% 22% 27% 14% 7% 1	396
November	1st to 10th	Day	27% 20% 29% 15% 8% 1	365
	11th to 20th	Day	37% 19% 28% 11% 4 1	370
	21st to end	Day	34% 20% 32% 9% 3 1	370
December	1st to 10th	Day	35% 22% 29% 11% 2	370
	11th to 20th	Day	43% 25% 22% 9% 2	370
	21st to end	Day	40% 24% 22% 9% 4 1	279
January	1st to 10th	Night	32% 21% 29% 15% 2	835
	11th to 20th	Night	36% 17% 29% 15% 3	760
	21st to end	Night	28% 23% 30% 17% 3	836
February	1st to 10th	Night	34% 18% 30% 17% 1	760
	11th to 20th	Night	32% 24% 25% 15% 2	742
	21st to end	Night	23% 22% 34% 16% 4	592
March	1st to 10th	Night	27% 20% 33% 16% 3	720
	11th to 20th	Night	27% 21% 27% 19% 6%	720
	21st to end	Night	25% 18% 33% 17% 6% 1	792
April	1st to 10th	Night	34% 17% 32% 15% 2	627
	11th to 20th	Night	28% 19% 34% 16% 3	534
	21st to end	Night	33% 14% 28% 19% 6%	540
May	1st to 10th	Night	28% 15% 36% 17% 4	540
	11th to 20th	Night	29% 13% 33% 21% 4	532
	21st to end	Night	24% 14% 35% 22% 4 1	583
June	1st to 10th	Night	32% 9% 33% 21% 5%	512
	11th to 20th	Night	23% 8% 33% 30% 6% 1	360
	21st to end	Night	32% 4 31% 26% 7%	360
July	1st to 10th	Night	26% 5% 33% 28% 8%	350
	11th to 20th	Night	22% 8% 35% 26% 9%	441
	21st to end	Night	25% 5% 35% 30% 6%	590
August	1st to 10th	Night	22% 6% 31% 32% 9% 1	538
	11th to 20th	Night	27% 6% 29% 30% 8%	532
	21st to end	Night	20% 8% 29% 31% 11% 1	594
September	1st to 10th	Night	22% 8% 30% 30% 11%	546
	11th to 20th	Night	25% 9% 27% 23% 14% 2	720
	21st to end	Night	25% 12% 26% 24% 11% 2	720
October	1st to 10th	Night	26% 10% 26% 25% 11% 1	720
	11th to 20th	Night	24% 15% 28% 24% 9% 1	720
	21st to end	Night	31% 17% 26% 21% 5%	792
November	1st to 10th	Night	28% 13% 26% 24% 8% 1	755
	11th to 20th	Night	31% 18% 26% 20% 5%	850
	21st to end	Night	31% 21% 25% 17% 5%	850
December	1st to 10th	Night	36% 18% 28% 15% 3	850
	11th to 20th	Night	37% 22% 25% 14% 2	850
	21st to end	Night	36% 21% 23% 17% 3	935

Page generated at 2024-02-17 07:28:41. Version ac07

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