Adirondack Astronomy Retreat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Adirondack Astronomy Retreat clear sky chart from 2005-11-06 to 2026-06-16.

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	14% 9% 3 9% 6% 5% 5% 4 6% 7% 32%	137671
	Night	14% 11% 4 10% 6% 5% 5% 4 5% 6% 30%	134371
Transparency	Day	48% 9% 12% 20% 10% 1	141142
	Night	50% 9% 12% 19% 10% 1	138989
Seeing	Day	21% 21% 31% 18% 6% 2	16689
	Night	19% 18% 31% 23% 8% 1	25718

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	9% 13% 6% 18% 8% 6% 5% 4 5% 5% 20%	4661
	11th to 20th	Day	9% 16% 7% 16% 7% 6% 5% 4 4 6% 19%	4650
	21st to end	Day	8% 10% 4 12% 10% 7% 7% 4 6% 7% 25%	5124
February	1st to 10th	Day	11% 13% 4 13% 7% 7% 5% 3 6% 7% 24%	1874
	11th to 20th	Day	8% 12% 5% 12% 8% 5% 5% 4 5% 6% 29%	1996
	21st to end	Day	13% 13% 4 11% 7% 5% 4 3 4 7% 29%	1730
March	1st to 10th	Day	16% 12% 4 12% 7% 6% 5% 4 5% 4 26%	4576
	11th to 20th	Day	10% 12% 4 9% 6% 6% 5% 5% 5% 6% 32%	4793
	21st to end	Day	16% 12% 3 9% 6% 4 5% 3 4 5% 32%	6102
April	1st to 10th	Day	17% 12% 3 9% 6% 4 4 3 5% 5% 32%	2520
	11th to 20th	Day	17% 9% 4 9% 5% 4 4 3 5% 6% 35%	2494
	21st to end	Day	19% 9% 3 7% 6% 5% 5% 4 4 6% 34%	2672
May	1st to 10th	Day	23% 9% 4 10% 5% 5% 5% 4 5% 6% 24%	7928
	11th to 20th	Day	15% 8% 3 9% 6% 5% 5% 4 6% 8% 32%	8221
	21st to end	Day	18% 7% 3 7% 5% 5% 4 4 6% 8% 33%	9060
June	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 30%	2940
	11th to 20th	Day	13% 6% 2 7% 5% 6% 5% 5% 7% 9% 37%	2870
	21st to end	Day	16% 7% 3 9% 5% 5% 6% 5% 7% 8% 30%	2800
July	1st to 10th	Day	9% 6% 2 6% 6% 6% 7% 6% 8% 10% 35%	6360
	11th to 20th	Day	9% 5% 3 7% 5% 5% 6% 5% 8% 11% 36%	6360
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 6% 9% 42%	6926
August	1st to 10th	Day	12% 7% 2 6% 5% 5% 6% 5% 7% 9% 36%	4563
	11th to 20th	Day	11% 6% 3 8% 5% 6% 6% 5% 8% 10% 34%	3997
	21st to end	Day	9% 5% 2 7% 5% 5% 5% 4 6% 9% 41%	4312
September	1st to 10th	Day	11% 6% 2 5% 3 4 4 3 6% 7% 48%	2400
	11th to 20th	Day	10% 6% 1 5% 4 4 3 4 5% 7% 50%	2300
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 7% 8% 40%	2200
October	1st to 10th	Day	17% 9% 3 7% 5% 4 4 4 6% 6% 36%	2093
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 5% 6% 7% 35%	1965
	21st to end	Day	19% 9% 3 10% 4 5% 4 4 5% 6% 30%	1980
November	1st to 10th	Day	13% 11% 3 9% 5% 6% 5% 4 5% 7% 34%	1851
	11th to 20th	Day	15% 11% 4 8% 5% 6% 5% 4 5% 6% 32%	1879
	21st to end	Day	15% 13% 4 8% 6% 5% 5% 4 6% 5% 29%	1680
December	1st to 10th	Day	12% 20% 7% 14% 7% 6% 5% 3 5% 5% 17%	2680
	11th to 20th	Day	17% 13% 4 8% 5% 4 5% 5% 6% 7% 26%	3066
	21st to end	Day	18% 12% 4 11% 6% 5% 5% 4 5% 6% 24%	4048
January	1st to 10th	Night	11% 15% 8% 18% 7% 6% 4 3 4 5% 20%	8234
	11th to 20th	Night	9% 17% 7% 18% 8% 6% 5% 4 4 4 17%	8235
	21st to end	Night	10% 11% 5% 12% 9% 7% 7% 5% 6% 7% 22%	9057
February	1st to 10th	Night	10% 12% 5% 14% 7% 6% 6% 4 6% 6% 25%	2741
	11th to 20th	Night	8% 12% 5% 14% 8% 5% 5% 4 5% 6% 29%	2510
	21st to end	Night	12% 11% 5% 11% 6% 5% 4 4 5% 5% 31%	2076
March	1st to 10th	Night	18% 12% 4 10% 7% 5% 5% 3 5% 5% 28%	5484
	11th to 20th	Night	13% 13% 4 9% 5% 5% 5% 3 5% 7% 32%	5383
	21st to end	Night	14% 13% 4 10% 6% 5% 4 3 4 5% 31%	5072
April	1st to 10th	Night	16% 10% 3 9% 6% 6% 4 3 6% 6% 31%	2100
	11th to 20th	Night	19% 9% 3 8% 5% 5% 4 4 4 5% 33%	2075
	21st to end	Night	18% 8% 3 8% 4 4 5% 3 4 6% 37%	1948
May	1st to 10th	Night	23% 11% 3 9% 5% 5% 5% 4 5% 7% 24%	5025
	11th to 20th	Night	16% 9% 3 10% 5% 5% 4 4 5% 6% 34%	4639
	21st to end	Night	16% 7% 3 8% 5% 5% 5% 4 6% 8% 33%	5114
June	1st to 10th	Night	17% 7% 3 6% 6% 4 5% 4 5% 7% 35%	1680
	11th to 20th	Night	15% 6% 2 6% 4 5% 4 4 5% 9% 39%	1640
	21st to end	Night	14% 6% 2 7% 5% 5% 5% 4 6% 8% 37%	1600
July	1st to 10th	Night	9% 5% 2 6% 5% 5% 5% 5% 8% 9% 40%	3600
	11th to 20th	Night	11% 6% 3 7% 5% 5% 5% 5% 6% 8% 41%	3600
	21st to end	Night	7% 6% 3 6% 5% 5% 5% 4 6% 7% 46%	3926
August	1st to 10th	Night	12% 7% 3 7% 6% 5% 6% 3 6% 7% 38%	2586
	11th to 20th	Night	10% 7% 3 9% 6% 6% 5% 4 5% 7% 39%	3002
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 9% 46%	3586
September	1st to 10th	Night	10% 5% 2 5% 5% 5% 4 4 6% 7% 49%	2000
	11th to 20th	Night	11% 6% 2 6% 4 4 3 3 5% 7% 51%	2100
	21st to end	Night	14% 5% 2 5% 5% 5% 4 4 5% 7% 44%	2200
October	1st to 10th	Night	17% 7% 2 7% 6% 5% 4 5% 5% 6% 37%	2304
	11th to 20th	Night	15% 8% 3 7% 4 5% 5% 4 6% 7% 37%	2434
	21st to end	Night	20% 10% 3 8% 5% 5% 4 3 5% 7% 30%	2860
November	1st to 10th	Night	16% 10% 3 8% 5% 4 4 4 5% 6% 35%	2667
	11th to 20th	Night	16% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	2735
	21st to end	Night	15% 13% 4 9% 5% 6% 5% 4 5% 6% 28%	2940
December	1st to 10th	Night	14% 18% 7% 13% 6% 6% 5% 4 6% 5% 17%	4720
	11th to 20th	Night	20% 13% 5% 10% 6% 5% 5% 3 4 5% 26%	5348
	21st to end	Night	19% 13% 5% 11% 6% 6% 6% 4 5% 6% 19%	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	58% 8% 14% 16% 4	4662
	11th to 20th	Day	62% 8% 7% 11% 9% 3	4680
	21st to end	Day	55% 9% 9% 15% 10% 2	5124
February	1st to 10th	Day	58% 10% 8% 16% 7% 2	1874
	11th to 20th	Day	53% 9% 12% 16% 9% 1	2005
	21st to end	Day	54% 8% 12% 14% 10% 2	1730
March	1st to 10th	Day	57% 9% 8% 12% 8% 6%	4579
	11th to 20th	Day	49% 12% 13% 16% 8% 4	4793
	21st to end	Day	51% 9% 6% 14% 17% 3	6102
April	1st to 10th	Day	53% 7% 10% 17% 11% 2	2520
	11th to 20th	Day	50% 8% 8% 18% 14% 2	2494
	21st to end	Day	52% 7% 9% 17% 12% 3	2672
May	1st to 10th	Day	59% 8% 8% 15% 9% 1	7940
	11th to 20th	Day	47% 11% 14% 18% 9% 1	8225
	21st to end	Day	48% 9% 11% 24% 8% 1	9061
June	1st to 10th	Day	50% 8% 13% 17% 10% 1	2940
	11th to 20th	Day	43% 10% 13% 20% 12% 2	2870
	21st to end	Day	49% 10% 12% 18% 9% 1	2800
July	1st to 10th	Day	40% 10% 16% 22% 11%	6290
	11th to 20th	Day	38% 11% 14% 26% 10% 1	6285
	21st to end	Day	37% 9% 13% 32% 8%	6728
August	1st to 10th	Day	43% 11% 16% 20% 9% 1	4549
	11th to 20th	Day	41% 12% 17% 23% 6%	4037
	21st to end	Day	37% 9% 18% 23% 11% 1	4312
September	1st to 10th	Day	34% 10% 12% 31% 12% 1	2400
	11th to 20th	Day	33% 7% 13% 29% 16% 1	2300
	21st to end	Day	40% 10% 16% 22% 11% 2	2200
October	1st to 10th	Day	37% 8% 13% 27% 14%	3405
	11th to 20th	Day	40% 8% 14% 23% 15%	3181
	21st to end	Day	40% 7% 13% 30% 9% 1	3180
November	1st to 10th	Day	49% 9% 13% 17% 11%	1851
	11th to 20th	Day	51% 8% 12% 15% 11% 2	1879
	21st to end	Day	54% 10% 14% 18% 5% 1	1680
December	1st to 10th	Day	67% 8% 8% 12% 4	2680
	11th to 20th	Day	54% 9% 11% 17% 9%	3066
	21st to end	Day	55% 8% 9% 18% 9% 1	4048
January	1st to 10th	Night	59% 7% 14% 13% 6% 1	8234
	11th to 20th	Night	65% 8% 7% 11% 7% 2	8280
	21st to end	Night	56% 8% 10% 13% 12% 1	9057
February	1st to 10th	Night	56% 10% 11% 13% 9% 1	2741
	11th to 20th	Night	54% 10% 10% 16% 9% 1	2512
	21st to end	Night	52% 10% 10% 17% 9% 2	2076
March	1st to 10th	Night	56% 7% 8% 13% 13% 3	5494
	11th to 20th	Night	48% 9% 17% 16% 9% 2	5384
	21st to end	Night	53% 7% 7% 18% 13% 2	5072
April	1st to 10th	Night	50% 8% 10% 17% 13% 1	2100
	11th to 20th	Night	51% 9% 11% 17% 12% 1	2075
	21st to end	Night	46% 9% 10% 18% 13% 3	1948
May	1st to 10th	Night	58% 9% 8% 14% 10% 1	5031
	11th to 20th	Night	47% 9% 11% 23% 10% 1	4640
	21st to end	Night	46% 9% 10% 22% 12% 1	5115
June	1st to 10th	Night	45% 10% 12% 20% 13% 1	1680
	11th to 20th	Night	41% 9% 14% 22% 13% 2	1640
	21st to end	Night	42% 10% 15% 22% 10% 1	1600
July	1st to 10th	Night	36% 8% 18% 26% 12%	3560
	11th to 20th	Night	35% 10% 13% 27% 14%	3552
	21st to end	Night	31% 10% 15% 33% 10%	3809
August	1st to 10th	Night	41% 11% 15% 23% 10%	2576
	11th to 20th	Night	39% 10% 16% 25% 9% 1	3028
	21st to end	Night	32% 8% 18% 29% 13% 1	3586
September	1st to 10th	Night	33% 11% 15% 28% 13% 1	2000
	11th to 20th	Night	32% 8% 15% 30% 14%	2100
	21st to end	Night	37% 10% 13% 24% 14% 2	2200
October	1st to 10th	Night	42% 8% 12% 26% 11% 1	3772
	11th to 20th	Night	37% 7% 12% 27% 15% 2	3957
	21st to end	Night	44% 8% 13% 25% 9% 1	4610
November	1st to 10th	Night	48% 10% 12% 19% 10% 2	2667
	11th to 20th	Night	49% 10% 11% 19% 9% 3	2735
	21st to end	Night	53% 11% 14% 17% 5%	2940
December	1st to 10th	Night	63% 9% 10% 15% 3	4720
	11th to 20th	Night	59% 7% 8% 13% 12% 1	5348
	21st to end	Night	59% 8% 9% 16% 7% 1	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	17% 30% 30% 18% 5%	220
	11th to 20th	Day	21% 33% 34% 10% 1	220
	21st to end	Day	20% 27% 38% 12% 3	242
February	1st to 10th	Day	30% 34% 29% 5% 1	322
	11th to 20th	Day	26% 30% 32% 11% 2	484
	21st to end	Day	28% 23% 35% 12% 2	446
March	1st to 10th	Day	26% 26% 32% 14% 2	540
	11th to 20th	Day	28% 30% 26% 13% 2 1	540
	21st to end	Day	27% 29% 27% 11% 4 1	594
April	1st to 10th	Day	32% 24% 27% 13% 4 1	540
	11th to 20th	Day	31% 26% 26% 12% 3 2	532
	21st to end	Day	30% 27% 25% 11% 5% 2	540
May	1st to 10th	Day	28% 25% 30% 10% 6% 1	543
	11th to 20th	Day	19% 22% 35% 19% 4 1	567
	21st to end	Day	18% 21% 33% 20% 6% 1	617
June	1st to 10th	Day	23% 18% 34% 18% 6% 1	570
	11th to 20th	Day	15% 20% 37% 19% 7% 1	550
	21st to end	Day	18% 21% 33% 20% 7% 2	530
July	1st to 10th	Day	14% 14% 33% 27% 11% 1	525
	11th to 20th	Day	11% 12% 37% 28% 10% 2	524
	21st to end	Day	14% 12% 36% 29% 7% 2	576
August	1st to 10th	Day	9% 11% 35% 28% 13% 3	526
	11th to 20th	Day	12% 9% 35% 26% 12% 6%	519
	21st to end	Day	11% 16% 32% 26% 10% 5%	583
September	1st to 10th	Day	15% 13% 31% 24% 10% 7%	530
	11th to 20th	Day	13% 13% 25% 22% 18% 9%	530
	21st to end	Day	15% 16% 32% 22% 11% 4	530
October	1st to 10th	Day	21% 18% 26% 21% 12% 3	530
	11th to 20th	Day	21% 21% 30% 21% 6% 1	511
	21st to end	Day	26% 21% 31% 19% 3	462
November	1st to 10th	Day	26% 21% 28% 19% 5%	425
	11th to 20th	Day	23% 29% 27% 16% 4 1	419
	21st to end	Day	31% 25% 31% 11% 2	220
December	1st to 10th	Day	24% 30% 29% 13% 4	220
	11th to 20th	Day	28% 30% 32% 10% 1	220
	21st to end	Day	27% 26% 34% 10% 3	242
January	1st to 10th	Night	19% 24% 39% 17% 2	840
	11th to 20th	Night	21% 24% 35% 17% 3	840
	21st to end	Night	12% 23% 41% 21% 4	924
February	1st to 10th	Night	16% 23% 39% 20% 2	840
	11th to 20th	Night	18% 26% 37% 18% 2	823
	21st to end	Night	19% 23% 36% 19% 3	692
March	1st to 10th	Night	23% 21% 34% 19% 3	840
	11th to 20th	Night	24% 26% 29% 16% 4	840
	21st to end	Night	22% 24% 30% 19% 5% 1	924
April	1st to 10th	Night	23% 25% 30% 20% 3	840
	11th to 20th	Night	24% 23% 29% 18% 5%	831
	21st to end	Night	22% 21% 30% 21% 5%	688
May	1st to 10th	Night	26% 15% 32% 21% 6%	551
	11th to 20th	Night	14% 19% 36% 24% 6% 1	414
	21st to end	Night	15% 15% 35% 26% 9%	455
June	1st to 10th	Night	19% 10% 32% 27% 11%	420
	11th to 20th	Night	16% 9% 29% 35% 10%	410
	21st to end	Night	16% 8% 32% 33% 10% 1	400
July	1st to 10th	Night	12% 6% 28% 39% 14% 1	390
	11th to 20th	Night	11% 4 26% 41% 16% 2	388
	21st to end	Night	10% 7% 27% 43% 13%	438
August	1st to 10th	Night	10% 6% 22% 44% 18% 1	398
	11th to 20th	Night	9% 7% 23% 39% 19% 2	668
	21st to end	Night	11% 7% 26% 36% 18% 1	880
September	1st to 10th	Night	11% 9% 29% 34% 15% 2	800
	11th to 20th	Night	13% 10% 24% 29% 21% 3	800
	21st to end	Night	14% 12% 30% 26% 16% 2	800
October	1st to 10th	Night	21% 14% 24% 26% 14% 1	800
	11th to 20th	Night	18% 19% 27% 28% 8% 1	800
	21st to end	Night	25% 18% 31% 23% 4	880
November	1st to 10th	Night	21% 19% 33% 20% 7%	820
	11th to 20th	Night	21% 22% 32% 16% 8% 1	840
	21st to end	Night	21% 24% 31% 18% 5%	840
December	1st to 10th	Night	22% 26% 33% 16% 4	840
	11th to 20th	Night	23% 23% 33% 18% 4	840
	21st to end	Night	25% 23% 33% 16% 3	924

Page generated at 2026-06-13 02:31:43. Version ac07

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