Dad's Nest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dad's Nest clear sky chart from 2005-11-06 to 2025-04-11.

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	16% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	113349
	Night	17% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	114924
Transparency	Day	48% 8% 12% 20% 11% 1	116873
	Night	50% 7% 12% 19% 11% 1	119564
Seeing	Day	23% 17% 29% 20% 9% 3	15221
	Night	22% 15% 29% 25% 8% 1	24449

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	11% 10% 5% 17% 7% 6% 7% 5% 5% 5% 22%	3597
	11th to 20th	Day	13% 13% 6% 13% 6% 6% 5% 5% 6% 6% 21%	3570
	21st to end	Day	15% 11% 4 11% 7% 6% 6% 4 5% 6% 27%	4126
February	1st to 10th	Day	13% 12% 4 11% 8% 7% 6% 4 6% 5% 24%	1800
	11th to 20th	Day	12% 11% 5% 13% 8% 6% 5% 4 5% 6% 26%	1884
	21st to end	Day	18% 13% 4 11% 5% 4 4 4 5% 5% 27%	1650
March	1st to 10th	Day	19% 12% 4 9% 5% 4 5% 3 4 5% 28%	4476
	11th to 20th	Day	14% 9% 3 8% 6% 5% 5% 4 5% 6% 35%	4787
	21st to end	Day	19% 11% 3 9% 5% 4 4 3 4 5% 35%	5916
April	1st to 10th	Day	18% 10% 3 8% 5% 4 4 4 4 6% 33%	2400
	11th to 20th	Day	17% 8% 3 7% 5% 5% 5% 4 5% 6% 36%	2254
	21st to end	Day	20% 8% 4 8% 5% 5% 4 3 5% 5% 32%	2351
May	1st to 10th	Day	24% 9% 3 7% 4 4 4 3 5% 6% 31%	4262
	11th to 20th	Day	18% 7% 3 7% 6% 5% 5% 4 6% 7% 32%	4398
	21st to end	Day	13% 5% 2 6% 5% 5% 5% 4 6% 9% 40%	4837
June	1st to 10th	Day	16% 7% 2 7% 6% 5% 5% 4 6% 9% 32%	2660
	11th to 20th	Day	17% 5% 2 6% 5% 5% 5% 5% 6% 9% 34%	2660
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 4 7% 9% 33%	2660
July	1st to 10th	Day	11% 5% 3 6% 5% 5% 5% 5% 7% 9% 38%	4440
	11th to 20th	Day	10% 5% 2 6% 4 6% 6% 6% 9% 12% 36%	4440
	21st to end	Day	14% 5% 2 7% 5% 5% 6% 5% 7% 7% 36%	4814
August	1st to 10th	Day	17% 5% 2 6% 5% 5% 5% 4 6% 9% 36%	4374
	11th to 20th	Day	15% 6% 2 6% 5% 5% 6% 5% 7% 9% 33%	3773
	21st to end	Day	14% 5% 2 5% 5% 5% 6% 4 7% 8% 40%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 5% 5% 4 6% 8% 43%	2280
	11th to 20th	Day	14% 4 2 5% 3 4 4 4 6% 7% 47%	2214
	21st to end	Day	17% 6% 2 6% 5% 4 4 4 6% 7% 39%	2090
October	1st to 10th	Day	22% 7% 2 8% 5% 5% 5% 3 4 7% 32%	1949
	11th to 20th	Day	16% 8% 2 7% 5% 4 4 4 5% 7% 38%	1900
	21st to end	Day	23% 9% 3 6% 4 4 4 4 7% 6% 30%	1905
November	1st to 10th	Day	14% 9% 3 6% 4 4 4 4 6% 8% 39%	1761
	11th to 20th	Day	15% 9% 2 7% 4 5% 6% 4 6% 7% 35%	1795
	21st to end	Day	18% 11% 4 7% 6% 5% 5% 4 6% 6% 29%	1600
December	1st to 10th	Day	18% 16% 7% 12% 6% 5% 4 3 6% 5% 19%	2600
	11th to 20th	Day	21% 11% 4 7% 5% 4 4 4 5% 6% 27%	2986
	21st to end	Day	21% 13% 6% 11% 5% 4 4 3 4 6% 24%	3960
January	1st to 10th	Night	13% 11% 4 12% 8% 6% 5% 4 5% 6% 25%	6349
	11th to 20th	Night	10% 13% 6% 14% 8% 7% 6% 4 6% 6% 19%	6315
	21st to end	Night	14% 12% 4 10% 5% 5% 6% 4 7% 7% 26%	6816
February	1st to 10th	Night	12% 12% 5% 9% 8% 5% 6% 4 7% 6% 26%	2600
	11th to 20th	Night	12% 10% 4 10% 7% 6% 5% 4 7% 7% 29%	2400
	21st to end	Night	15% 10% 3 11% 6% 4 4 4 6% 7% 29%	1980
March	1st to 10th	Night	20% 10% 4 9% 5% 5% 4 4 6% 6% 27%	5364
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 3 5% 7% 35%	5168
	21st to end	Night	19% 11% 4 10% 4 4 4 3 5% 5% 31%	5015
April	1st to 10th	Night	20% 9% 3 8% 5% 4 4 3 5% 7% 33%	2000
	11th to 20th	Night	18% 8% 2 7% 5% 4 4 4 5% 6% 36%	1882
	21st to end	Night	21% 7% 3 7% 5% 4 4 3 5% 5% 37%	1829
May	1st to 10th	Night	25% 7% 3 7% 4 5% 4 3 5% 7% 30%	2706
	11th to 20th	Night	18% 9% 3 8% 5% 4 4 3 5% 6% 33%	2495
	21st to end	Night	13% 6% 2 7% 5% 5% 5% 4 5% 8% 38%	2738
June	1st to 10th	Night	17% 6% 2 5% 6% 4 4 4 5% 8% 39%	1520
	11th to 20th	Night	16% 6% 3 4 4 4 5% 4 5% 8% 41%	1520
	21st to end	Night	15% 5% 2 5% 4 4 5% 4 5% 8% 43%	1520
July	1st to 10th	Night	10% 5% 3 6% 6% 5% 5% 5% 7% 7% 39%	2520
	11th to 20th	Night	14% 4 2 5% 4 4 5% 5% 6% 9% 42%	2520
	21st to end	Night	14% 6% 2 5% 4 5% 5% 4 6% 7% 43%	2739
August	1st to 10th	Night	21% 6% 2 6% 4 4 5% 4 6% 7% 37%	2551
	11th to 20th	Night	18% 6% 2 6% 4 4 4 3 5% 6% 41%	3024
	21st to end	Night	14% 4 1 5% 3 4 3 4 6% 9% 47%	3476
September	1st to 10th	Night	12% 4 2 5% 4 3 5% 4 6% 7% 47%	1900
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 4 6% 52%	1966
	21st to end	Night	17% 5% 2 5% 4 4 4 4 5% 7% 44%	2090
October	1st to 10th	Night	21% 6% 3 6% 5% 5% 5% 3 5% 6% 35%	2228
	11th to 20th	Night	17% 7% 2 7% 4 5% 3 4 6% 6% 39%	2280
	21st to end	Night	21% 10% 2 7% 5% 4 4 3 6% 7% 32%	2691
November	1st to 10th	Night	13% 8% 3 7% 5% 4 4 4 6% 6% 41%	2537
	11th to 20th	Night	19% 8% 2 6% 5% 4 5% 4 5% 6% 35%	2601
	21st to end	Night	15% 10% 3 8% 5% 4 4 4 6% 7% 34%	2800
December	1st to 10th	Night	15% 14% 5% 8% 5% 5% 5% 4 7% 8% 25%	4580
	11th to 20th	Night	24% 11% 4 8% 5% 4 4 4 5% 5% 27%	5208
	21st to end	Night	23% 14% 5% 8% 5% 4 3 3 4 4 26%	6996

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	59% 10% 8% 17% 5% 1	3598
	11th to 20th	Day	60% 9% 9% 10% 10% 2	3600
	21st to end	Day	55% 7% 9% 16% 11% 1	4126
February	1st to 10th	Day	59% 8% 11% 15% 6% 1	1800
	11th to 20th	Day	58% 8% 9% 15% 8% 2	1893
	21st to end	Day	57% 7% 10% 16% 9% 1	1650
March	1st to 10th	Day	58% 6% 8% 13% 10% 4	4479
	11th to 20th	Day	49% 7% 19% 14% 8% 3	4787
	21st to end	Day	52% 5% 7% 15% 18% 3	5916
April	1st to 10th	Day	52% 6% 9% 18% 12% 3	2400
	11th to 20th	Day	48% 7% 11% 19% 13% 2	2254
	21st to end	Day	53% 6% 9% 17% 12% 3	2351
May	1st to 10th	Day	53% 7% 10% 20% 9% 1	4276
	11th to 20th	Day	48% 10% 12% 20% 8% 1	4402
	21st to end	Day	38% 10% 14% 27% 11% 1	4837
June	1st to 10th	Day	47% 9% 14% 18% 10%	2660
	11th to 20th	Day	44% 8% 16% 19% 11% 1	2660
	21st to end	Day	45% 9% 14% 21% 10% 1	2660
July	1st to 10th	Day	40% 8% 14% 25% 13%	4370
	11th to 20th	Day	38% 9% 15% 29% 8%	4365
	21st to end	Day	44% 7% 15% 24% 10%	4661
August	1st to 10th	Day	45% 7% 16% 20% 11%	4360
	11th to 20th	Day	45% 9% 16% 24% 6%	3810
	21st to end	Day	40% 7% 14% 30% 9%	4180
September	1st to 10th	Day	37% 9% 14% 29% 11% 1	2280
	11th to 20th	Day	35% 8% 12% 27% 17% 1	2214
	21st to end	Day	43% 6% 12% 25% 12% 1	2090
October	1st to 10th	Day	46% 7% 9% 24% 14% 1	3235
	11th to 20th	Day	40% 6% 13% 25% 15% 2	3140
	21st to end	Day	37% 7% 14% 27% 12% 1	3117
November	1st to 10th	Day	41% 8% 15% 22% 13% 1	1761
	11th to 20th	Day	48% 8% 11% 18% 14% 2	1795
	21st to end	Day	53% 8% 16% 15% 6% 1	1600
December	1st to 10th	Day	65% 6% 12% 13% 3	2600
	11th to 20th	Day	56% 7% 11% 17% 8%	2986
	21st to end	Day	63% 6% 7% 14% 10% 1	3960
January	1st to 10th	Night	58% 9% 9% 14% 9%	6349
	11th to 20th	Night	60% 10% 10% 10% 8% 1	6360
	21st to end	Night	54% 6% 10% 12% 14% 2	6816
February	1st to 10th	Night	56% 8% 11% 18% 7% 1	2600
	11th to 20th	Night	53% 7% 12% 17% 10% 1	2402
	21st to end	Night	53% 7% 13% 17% 8% 2	1980
March	1st to 10th	Night	56% 7% 10% 13% 12% 2	5374
	11th to 20th	Night	47% 8% 18% 18% 8% 2	5169
	21st to end	Night	55% 5% 6% 17% 15% 2	5015
April	1st to 10th	Night	51% 6% 11% 19% 12% 1	2000
	11th to 20th	Night	47% 8% 11% 20% 13% 1	1882
	21st to end	Night	48% 7% 9% 18% 15% 3	1829
May	1st to 10th	Night	53% 7% 11% 16% 11% 2	2712
	11th to 20th	Night	50% 8% 14% 19% 8% 1	2496
	21st to end	Night	40% 11% 14% 18% 15% 1	2739
June	1st to 10th	Night	43% 7% 13% 24% 12% 2	1520
	11th to 20th	Night	40% 7% 15% 24% 13% 1	1520
	21st to end	Night	38% 10% 14% 25% 13%	1520
July	1st to 10th	Night	43% 7% 14% 21% 14% 1	2480
	11th to 20th	Night	40% 8% 15% 23% 15%	2472
	21st to end	Night	40% 9% 10% 29% 11% 1	2651
August	1st to 10th	Night	46% 9% 13% 23% 9%	2541
	11th to 20th	Night	44% 7% 15% 25% 9%	3053
	21st to end	Night	34% 7% 13% 36% 10%	3476
September	1st to 10th	Night	36% 8% 13% 29% 13% 1	1900
	11th to 20th	Night	34% 6% 12% 27% 20% 1	1966
	21st to end	Night	38% 7% 12% 26% 15% 2	2090
October	1st to 10th	Night	50% 7% 9% 21% 12% 1	3722
	11th to 20th	Night	36% 7% 13% 24% 18% 2	3779
	21st to end	Night	42% 6% 14% 29% 9% 1	4429
November	1st to 10th	Night	43% 7% 12% 22% 14% 2	2537
	11th to 20th	Night	48% 7% 12% 20% 13% 2	2601
	21st to end	Night	48% 8% 16% 19% 8% 1	2800
December	1st to 10th	Night	57% 9% 13% 16% 4	4580
	11th to 20th	Night	59% 6% 10% 15% 10% 1	5208
	21st to end	Night	61% 6% 8% 12% 11% 2	6996

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	27% 22% 33% 13% 5% 1	200
	11th to 20th	Day	30% 24% 33% 12% 2 1	200
	21st to end	Day	23% 27% 33% 12% 4	257
February	1st to 10th	Day	31% 31% 29% 8% 1	300
	11th to 20th	Day	31% 30% 29% 9% 2	432
	21st to end	Day	31% 23% 30% 14% 2	414
March	1st to 10th	Day	28% 23% 32% 15% 2	500
	11th to 20th	Day	31% 24% 28% 13% 4 1	500
	21st to end	Day	33% 24% 22% 15% 5% 1	550
April	1st to 10th	Day	34% 22% 24% 14% 5% 1	500
	11th to 20th	Day	32% 22% 22% 15% 7% 2	452
	21st to end	Day	29% 21% 30% 12% 6% 2	460
May	1st to 10th	Day	32% 16% 31% 12% 7% 2	463
	11th to 20th	Day	20% 15% 34% 23% 7% 1	487
	21st to end	Day	18% 13% 28% 24% 12% 3	529
June	1st to 10th	Day	19% 18% 28% 22% 11% 2	490
	11th to 20th	Day	17% 17% 30% 24% 11% 2	490
	21st to end	Day	18% 17% 32% 22% 9% 2	490
July	1st to 10th	Day	14% 9% 29% 28% 17% 3	485
	11th to 20th	Day	14% 8% 31% 30% 14% 3	484
	21st to end	Day	14% 8% 37% 28% 10% 2	532
August	1st to 10th	Day	10% 11% 27% 29% 18% 5%	486
	11th to 20th	Day	16% 9% 28% 27% 14% 7%	479
	21st to end	Day	12% 12% 27% 29% 14% 6%	539
September	1st to 10th	Day	17% 9% 23% 25% 18% 8%	490
	11th to 20th	Day	12% 9% 26% 20% 18% 14%	490
	21st to end	Day	19% 8% 28% 27% 12% 6%	490
October	1st to 10th	Day	26% 15% 27% 15% 13% 4	490
	11th to 20th	Day	22% 17% 27% 24% 9% 2	490
	21st to end	Day	30% 14% 27% 22% 6% 1	442
November	1st to 10th	Day	24% 16% 28% 18% 13% 1	395
	11th to 20th	Day	27% 21% 26% 21% 5% 1	395
	21st to end	Day	34% 22% 29% 14% 2	200
December	1st to 10th	Day	31% 24% 29% 12% 5%	200
	11th to 20th	Day	39% 17% 32% 10% 4	200
	21st to end	Day	29% 22% 30% 14% 5% 1	220
January	1st to 10th	Night	23% 23% 35% 18% 2	800
	11th to 20th	Night	26% 20% 31% 20% 3	800
	21st to end	Night	18% 23% 36% 22% 2	880
February	1st to 10th	Night	22% 22% 37% 19% 1	800
	11th to 20th	Night	23% 24% 36% 15% 2	783
	21st to end	Night	28% 19% 33% 18% 2	660
March	1st to 10th	Night	24% 21% 35% 18% 2	800
	11th to 20th	Night	26% 21% 31% 19% 3	800
	21st to end	Night	23% 19% 33% 20% 5%	880
April	1st to 10th	Night	27% 17% 33% 19% 4	800
	11th to 20th	Night	24% 17% 31% 21% 6%	754
	21st to end	Night	25% 17% 29% 22% 6%	689
May	1st to 10th	Night	27% 14% 29% 21% 9%	494
	11th to 20th	Night	19% 13% 29% 32% 6% 1	374
	21st to end	Night	18% 5% 26% 38% 13%	411
June	1st to 10th	Night	17% 9% 28% 32% 12% 1	380
	11th to 20th	Night	18% 9% 24% 37% 12%	380
	21st to end	Night	15% 7% 27% 38% 13%	380
July	1st to 10th	Night	12% 6% 23% 39% 19% 1	370
	11th to 20th	Night	14% 4 23% 39% 20% 1	368
	21st to end	Night	12% 4 25% 42% 17%	416
August	1st to 10th	Night	13% 3 23% 40% 21% 1	397
	11th to 20th	Night	16% 5% 22% 34% 20% 3	701
	21st to end	Night	17% 5% 21% 34% 21% 1	836
September	1st to 10th	Night	13% 7% 23% 36% 19% 1	760
	11th to 20th	Night	15% 6% 24% 28% 22% 4	760
	21st to end	Night	17% 8% 26% 31% 16% 2	760
October	1st to 10th	Night	24% 12% 22% 25% 15% 2	760
	11th to 20th	Night	21% 12% 27% 31% 9% 1	760
	21st to end	Night	26% 14% 31% 24% 5%	836
November	1st to 10th	Night	18% 15% 30% 29% 8%	780
	11th to 20th	Night	24% 18% 27% 24% 6% 2	800
	21st to end	Night	22% 20% 29% 23% 5%	800
December	1st to 10th	Night	25% 19% 35% 18% 3	800
	11th to 20th	Night	28% 20% 30% 19% 4	800
	21st to end	Night	27% 23% 29% 18% 3	880

Page generated at 2025-04-08 09:17:24. Version ac07

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