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 2024-01-31.

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 7% 6% 4 5% 5% 6% 7% 33%	74907
	Night	15% 9% 4 8% 6% 4 5% 5% 5% 7% 33%	75218
Transparency	Day	33% 39% 9% 12% 6% 1	74612
	Night	34% 39% 9% 12% 6% 1	75047
Seeing	Day	21% 21% 31% 18% 7% 2	13618
	Night	18% 18% 31% 23% 8% 1	22769

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% 14% 5% 9% 10% 4 6% 6% 7% 6% 22%	1517
	11th to 20th	Day	13% 12% 6% 12% 7% 4 5% 4 4 6% 27%	1520
	21st to end	Day	9% 11% 4 11% 9% 5% 7% 6% 5% 6% 26%	1664
February	1st to 10th	Day	12% 13% 5% 10% 9% 5% 7% 4 6% 7% 23%	1606
	11th to 20th	Day	9% 11% 6% 10% 9% 4 6% 5% 5% 6% 29%	1703
	21st to end	Day	14% 12% 6% 10% 7% 4 5% 4 4 6% 28%	1480
March	1st to 10th	Day	12% 10% 5% 10% 8% 5% 6% 5% 5% 5% 29%	1797
	11th to 20th	Day	13% 14% 4 8% 7% 4 5% 5% 4 5% 30%	1858
	21st to end	Day	14% 10% 4 8% 8% 3 4 4 3 5% 36%	2376
April	1st to 10th	Day	17% 11% 4 7% 6% 3 4 4 5% 5% 33%	2160
	11th to 20th	Day	16% 7% 3 7% 6% 3 4 4 5% 6% 37%	2134
	21st to end	Day	20% 9% 3 7% 6% 3 5% 5% 4 6% 32%	2290
May	1st to 10th	Day	17% 7% 4 7% 5% 4 5% 5% 5% 6% 33%	2421
	11th to 20th	Day	16% 8% 3 6% 6% 4 5% 5% 6% 7% 36%	2478
	21st to end	Day	13% 5% 2 5% 7% 4 5% 6% 6% 9% 37%	2725
June	1st to 10th	Day	19% 7% 3 6% 5% 4 5% 5% 6% 9% 29%	2520
	11th to 20th	Day	14% 6% 2 6% 5% 4 6% 5% 6% 8% 38%	2520
	21st to end	Day	16% 7% 3 8% 6% 4 6% 6% 6% 9% 30%	2520
July	1st to 10th	Day	11% 6% 2 5% 6% 5% 6% 6% 6% 9% 38%	2520
	11th to 20th	Day	9% 6% 3 6% 6% 4 7% 6% 8% 10% 35%	2520
	21st to end	Day	12% 5% 2 6% 6% 4 7% 6% 7% 9% 36%	2744
August	1st to 10th	Day	9% 5% 2 6% 7% 4 7% 6% 8% 9% 38%	2506
	11th to 20th	Day	9% 5% 2 7% 6% 4 6% 6% 7% 10% 38%	2216
	21st to end	Day	10% 5% 2 6% 6% 4 5% 6% 6% 8% 41%	2376
September	1st to 10th	Day	12% 6% 2 4 4 2 5% 5% 6% 8% 47%	2160
	11th to 20th	Day	11% 6% 2 4 5% 3 4 5% 5% 7% 49%	2070
	21st to end	Day	12% 5% 2 6% 6% 3 5% 5% 7% 8% 40%	1980
October	1st to 10th	Day	19% 10% 3 6% 6% 3 5% 5% 6% 6% 32%	1885
	11th to 20th	Day	14% 8% 3 7% 7% 4 5% 7% 6% 7% 33%	1769
	21st to end	Day	20% 9% 3 9% 6% 4 5% 5% 5% 6% 29%	1782
November	1st to 10th	Day	13% 11% 3 8% 6% 4 6% 5% 4 7% 34%	1671
	11th to 20th	Day	16% 9% 4 7% 6% 4 6% 5% 5% 6% 32%	1701
	21st to end	Day	15% 12% 4 7% 6% 4 6% 5% 6% 6% 30%	1520
December	1st to 10th	Day	17% 18% 6% 9% 7% 4 4 5% 4 5% 20%	1520
	11th to 20th	Day	19% 13% 5% 6% 6% 3 5% 5% 6% 7% 25%	1906
	21st to end	Day	22% 13% 5% 10% 7% 4 5% 4 5% 6% 20%	2772
January	1st to 10th	Night	14% 13% 5% 10% 8% 5% 6% 5% 6% 7% 22%	2649
	11th to 20th	Night	14% 13% 6% 12% 8% 5% 5% 5% 5% 5% 23%	2660
	21st to end	Night	9% 10% 6% 10% 8% 4 6% 5% 5% 7% 29%	2919
February	1st to 10th	Night	10% 11% 6% 12% 9% 4 7% 5% 6% 6% 23%	2350
	11th to 20th	Night	9% 11% 6% 11% 8% 4 5% 5% 5% 6% 30%	2143
	21st to end	Night	13% 10% 5% 10% 7% 4 5% 5% 5% 6% 30%	1776
March	1st to 10th	Night	13% 13% 5% 9% 7% 4 6% 5% 5% 5% 30%	2150
	11th to 20th	Night	15% 11% 5% 9% 7% 3 5% 4 5% 5% 32%	2098
	21st to end	Night	15% 10% 3 8% 6% 3 4 4 5% 5% 38%	1980
April	1st to 10th	Night	16% 9% 4 8% 7% 4 5% 4 6% 7% 31%	1800
	11th to 20th	Night	19% 7% 3 8% 6% 3 5% 4 4 6% 34%	1775
	21st to end	Night	19% 8% 3 7% 5% 4 5% 4 4 6% 35%	1670
May	1st to 10th	Night	20% 8% 3 6% 6% 4 4 5% 5% 7% 32%	1553
	11th to 20th	Night	16% 6% 3 7% 6% 3 4 4 5% 6% 40%	1415
	21st to end	Night	10% 6% 3 5% 5% 3 5% 5% 7% 9% 41%	1550
June	1st to 10th	Night	19% 6% 3 6% 6% 4 4 5% 5% 7% 35%	1440
	11th to 20th	Night	16% 6% 2 5% 4 3 5% 5% 5% 9% 40%	1440
	21st to end	Night	15% 5% 3 7% 6% 4 5% 6% 5% 8% 38%	1440
July	1st to 10th	Night	11% 5% 2 4 5% 3 4 5% 7% 9% 44%	1440
	11th to 20th	Night	10% 5% 2 5% 4 3 4 6% 7% 11% 43%	1440
	21st to end	Night	10% 4 3 5% 4 3 5% 5% 7% 9% 45%	1574
August	1st to 10th	Night	9% 3 2 4 6% 4 5% 5% 6% 9% 47%	1432
	11th to 20th	Night	8% 5% 2 7% 6% 4 5% 6% 5% 9% 43%	1664
	21st to end	Night	10% 5% 3 5% 5% 3 4 5% 6% 9% 44%	1980
September	1st to 10th	Night	11% 5% 2 3 6% 4 5% 5% 6% 7% 48%	1800
	11th to 20th	Night	12% 6% 2 5% 5% 3 3 3 5% 7% 50%	1890
	21st to end	Night	13% 5% 2 5% 5% 3 5% 4 5% 7% 45%	1980
October	1st to 10th	Night	18% 7% 2 6% 6% 4 5% 6% 5% 6% 35%	2073
	11th to 20th	Night	17% 8% 3 6% 5% 4 5% 5% 6% 7% 35%	2190
	21st to end	Night	21% 10% 3 7% 6% 3 4 4 5% 7% 29%	2574
November	1st to 10th	Night	16% 10% 4 7% 6% 3 5% 5% 5% 6% 36%	2407
	11th to 20th	Night	17% 8% 3 7% 6% 3 5% 5% 5% 7% 34%	2474
	21st to end	Night	15% 12% 5% 7% 6% 4 5% 5% 5% 7% 28%	2660
December	1st to 10th	Night	17% 15% 5% 10% 8% 5% 6% 5% 5% 5% 20%	2660
	11th to 20th	Night	19% 12% 5% 8% 7% 4 5% 4 5% 5% 26%	3288
	21st to end	Night	22% 13% 6% 10% 8% 4 4 4 4 5% 20%	4884

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	37% 42% 7% 11% 2	1518
	11th to 20th	Day	37% 44% 7% 7% 5%	1520
	21st to end	Day	37% 39% 10% 8% 6% 1	1664
February	1st to 10th	Day	37% 40% 7% 11% 4 1	1606
	11th to 20th	Day	35% 41% 10% 9% 4 1	1712
	21st to end	Day	39% 37% 9% 8% 6%	1480
March	1st to 10th	Day	35% 40% 9% 10% 5% 1	1800
	11th to 20th	Day	38% 38% 8% 9% 5% 1	1858
	21st to end	Day	32% 37% 7% 12% 10% 3	2376
April	1st to 10th	Day	33% 38% 8% 13% 7% 2	2160
	11th to 20th	Day	33% 37% 8% 11% 9% 1	2134
	21st to end	Day	36% 38% 7% 9% 7% 3	2290
May	1st to 10th	Day	32% 38% 7% 12% 9% 2	2421
	11th to 20th	Day	30% 39% 7% 11% 11% 2	2482
	21st to end	Day	27% 42% 10% 12% 8% 2	2725
June	1st to 10th	Day	34% 39% 11% 11% 5%	2520
	11th to 20th	Day	31% 40% 9% 12% 8% 1	2520
	21st to end	Day	35% 41% 9% 10% 5%	2520
July	1st to 10th	Day	29% 41% 10% 15% 5%	2450
	11th to 20th	Day	30% 41% 10% 14% 6%	2445
	21st to end	Day	26% 43% 10% 14% 6%	2591
August	1st to 10th	Day	27% 42% 11% 14% 6%	2492
	11th to 20th	Day	26% 39% 13% 15% 6%	2216
	21st to end	Day	29% 40% 8% 16% 7% 1	2376
September	1st to 10th	Day	26% 40% 8% 18% 7%	2160
	11th to 20th	Day	26% 38% 9% 18% 9%	2070
	21st to end	Day	28% 39% 11% 13% 8% 1	1980
October	1st to 10th	Day	34% 39% 8% 12% 7%	1885
	11th to 20th	Day	32% 41% 11% 12% 4	1769
	21st to end	Day	36% 40% 7% 10% 7% 1	1782
November	1st to 10th	Day	28% 43% 10% 12% 7%	1671
	11th to 20th	Day	32% 43% 9% 8% 5% 2	1701
	21st to end	Day	34% 42% 10% 12% 2	1520
December	1st to 10th	Day	41% 43% 6% 7% 2	1520
	11th to 20th	Day	42% 34% 9% 12% 4	1906
	21st to end	Day	46% 31% 8% 12% 3	2772
January	1st to 10th	Night	35% 45% 9% 9% 2	2649
	11th to 20th	Night	39% 43% 7% 7% 4	2660
	21st to end	Night	36% 39% 7% 10% 7% 1	2919
February	1st to 10th	Night	38% 40% 8% 7% 5% 1	2350
	11th to 20th	Night	36% 40% 7% 12% 4	2145
	21st to end	Night	39% 38% 8% 10% 5% 1	1776
March	1st to 10th	Night	39% 38% 8% 10% 5%	2160
	11th to 20th	Night	36% 38% 9% 12% 4	2099
	21st to end	Night	30% 38% 7% 13% 9% 3	1980
April	1st to 10th	Night	33% 39% 7% 12% 7% 2	1800
	11th to 20th	Night	34% 38% 10% 11% 7%	1775
	21st to end	Night	33% 38% 7% 12% 7% 2	1670
May	1st to 10th	Night	33% 38% 5% 11% 11% 2	1553
	11th to 20th	Night	30% 38% 7% 12% 10% 2	1416
	21st to end	Night	26% 40% 10% 14% 9% 1	1551
June	1st to 10th	Night	30% 42% 10% 13% 5% 1	1440
	11th to 20th	Night	28% 39% 10% 16% 6% 1	1440
	21st to end	Night	29% 42% 11% 12% 6%	1440
July	1st to 10th	Night	25% 42% 11% 15% 7%	1400
	11th to 20th	Night	23% 43% 11% 16% 7%	1392
	21st to end	Night	22% 43% 10% 17% 8%	1486
August	1st to 10th	Night	22% 41% 12% 17% 7%	1422
	11th to 20th	Night	25% 38% 10% 19% 8%	1664
	21st to end	Night	27% 39% 11% 15% 7%	1980
September	1st to 10th	Night	25% 40% 9% 19% 7%	1800
	11th to 20th	Night	24% 38% 11% 19% 7%	1890
	21st to end	Night	29% 39% 9% 15% 8% 1	1980
October	1st to 10th	Night	32% 39% 8% 14% 7%	2073
	11th to 20th	Night	34% 39% 9% 13% 4	2190
	21st to end	Night	35% 40% 9% 9% 6% 1	2574
November	1st to 10th	Night	31% 43% 8% 10% 6% 1	2407
	11th to 20th	Night	30% 43% 9% 11% 4 2	2474
	21st to end	Night	34% 43% 8% 11% 3	2660
December	1st to 10th	Night	42% 43% 8% 7% 2	2660
	11th to 20th	Night	41% 36% 8% 10% 5%	3288
	21st to end	Night	51% 28% 8% 12% 1	4884

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% 29% 18% 6% 1	180
	11th to 20th	Day	21% 33% 34% 10% 2 1	180
	21st to end	Day	18% 28% 40% 12% 2 1	196
February	1st to 10th	Day	34% 38% 25% 3	234
	11th to 20th	Day	25% 30% 33% 9% 2	371
	21st to end	Day	29% 23% 34% 12% 2	346
March	1st to 10th	Day	25% 26% 32% 15% 2	420
	11th to 20th	Day	24% 31% 27% 15% 3 1	420
	21st to end	Day	26% 28% 26% 13% 5% 2	462
April	1st to 10th	Day	28% 24% 28% 15% 5% 1	420
	11th to 20th	Day	28% 25% 26% 14% 4 2	412
	21st to end	Day	30% 25% 25% 12% 5% 2	420
May	1st to 10th	Day	25% 25% 31% 10% 7% 1	423
	11th to 20th	Day	20% 21% 35% 18% 4 2	447
	21st to end	Day	17% 20% 33% 22% 7% 1	485
June	1st to 10th	Day	26% 18% 34% 17% 5% 1	450
	11th to 20th	Day	17% 19% 36% 19% 7% 1	450
	21st to end	Day	18% 21% 32% 20% 8% 2	450
July	1st to 10th	Day	15% 13% 32% 28% 12% 1	445
	11th to 20th	Day	11% 12% 38% 28% 10% 1	444
	21st to end	Day	14% 10% 38% 28% 7% 2	488
August	1st to 10th	Day	9% 11% 35% 28% 13% 3	446
	11th to 20th	Day	11% 9% 36% 26% 12% 5%	439
	21st to end	Day	11% 17% 31% 25% 11% 5%	495
September	1st to 10th	Day	15% 13% 32% 22% 10% 7%	450
	11th to 20th	Day	15% 15% 25% 21% 16% 8%	450
	21st to end	Day	14% 16% 33% 21% 12% 4	450
October	1st to 10th	Day	23% 19% 25% 18% 12% 2	450
	11th to 20th	Day	20% 23% 29% 21% 6% 1	435
	21st to end	Day	27% 20% 30% 19% 3	396
November	1st to 10th	Day	23% 21% 28% 21% 6%	365
	11th to 20th	Day	24% 29% 27% 15% 4 1	361
	21st to end	Day	26% 28% 31% 13% 2	180
December	1st to 10th	Day	22% 33% 26% 14% 3 1	180
	11th to 20th	Day	28% 28% 34% 9% 1	180
	21st to end	Day	29% 28% 32% 9% 3	198
January	1st to 10th	Night	19% 23% 39% 17% 2	760
	11th to 20th	Night	21% 24% 35% 16% 3	760
	21st to end	Night	12% 22% 40% 21% 4	835
February	1st to 10th	Night	17% 23% 40% 18% 2	720
	11th to 20th	Night	17% 27% 37% 18% 2	703
	21st to end	Night	20% 23% 35% 19% 3	592
March	1st to 10th	Night	22% 21% 34% 21% 2	720
	11th to 20th	Night	23% 26% 30% 17% 5%	720
	21st to end	Night	21% 22% 31% 20% 5% 1	792
April	1st to 10th	Night	21% 24% 29% 22% 4	720
	11th to 20th	Night	22% 23% 28% 20% 6%	711
	21st to end	Night	23% 20% 29% 21% 6%	590
May	1st to 10th	Night	25% 15% 31% 21% 7%	473
	11th to 20th	Night	14% 18% 36% 25% 6% 1	354
	21st to end	Night	13% 15% 34% 27% 11%	389
June	1st to 10th	Night	20% 10% 31% 26% 12%	360
	11th to 20th	Night	17% 8% 28% 35% 11% 1	360
	21st to end	Night	16% 8% 31% 34% 10% 1	360
July	1st to 10th	Night	12% 6% 29% 36% 15% 1	350
	11th to 20th	Night	11% 3 27% 40% 17% 2	348
	21st to end	Night	10% 7% 26% 43% 13% 1	394
August	1st to 10th	Night	10% 5% 23% 43% 18% 1	358
	11th to 20th	Night	9% 7% 24% 39% 19% 3	600
	21st to end	Night	11% 8% 26% 35% 19% 2	792
September	1st to 10th	Night	12% 9% 28% 34% 15% 3	720
	11th to 20th	Night	13% 11% 26% 28% 18% 3	720
	21st to end	Night	13% 13% 30% 26% 16% 2	720
October	1st to 10th	Night	22% 15% 24% 24% 13% 1	720
	11th to 20th	Night	19% 18% 27% 28% 8% 1	720
	21st to end	Night	26% 18% 30% 21% 4	792
November	1st to 10th	Night	20% 19% 33% 20% 7% 1	740
	11th to 20th	Night	21% 23% 32% 16% 8% 1	760
	21st to end	Night	21% 25% 30% 17% 6% 1	760
December	1st to 10th	Night	22% 27% 32% 15% 4	760
	11th to 20th	Night	22% 23% 33% 19% 4	760
	21st to end	Night	25% 23% 34% 15% 3	836

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