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 2025-02-06.

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	13% 9% 3 9% 6% 5% 5% 4 6% 7% 32%	108375
	Night	14% 11% 4 10% 6% 5% 5% 4 5% 6% 31%	109868
Transparency	Day	47% 10% 13% 20% 10% 1	111892
	Night	49% 9% 12% 19% 10% 1	114515
Seeing	Day	21% 21% 31% 18% 7% 2	14907
	Night	18% 18% 31% 24% 8% 1	24043

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% 6% 17% 7% 5% 5% 4 5% 5% 21%	3597
	11th to 20th	Day	10% 14% 7% 17% 7% 6% 5% 4 5% 6% 21%	3570
	21st to end	Day	10% 11% 5% 11% 7% 6% 7% 4 6% 7% 27%	3960
February	1st to 10th	Day	11% 13% 4 12% 7% 7% 5% 4 6% 6% 24%	1740
	11th to 20th	Day	8% 12% 5% 12% 8% 5% 5% 4 5% 6% 29%	1800
	21st to end	Day	13% 13% 4 11% 7% 5% 4 3 4 7% 29%	1570
March	1st to 10th	Day	19% 13% 4 11% 7% 5% 4 4 5% 4 23%	3116
	11th to 20th	Day	10% 16% 5% 10% 6% 6% 5% 5% 5% 5% 26%	3274
	21st to end	Day	13% 10% 3 8% 6% 4 5% 3 4 6% 37%	4166
April	1st to 10th	Day	17% 12% 3 8% 6% 4 4 3 5% 5% 32%	2280
	11th to 20th	Day	17% 8% 3 9% 5% 4 4 3 5% 6% 36%	2254
	21st to end	Day	19% 9% 3 8% 6% 5% 5% 4 4 6% 33%	2418
May	1st to 10th	Day	18% 9% 3 9% 5% 5% 5% 4 5% 7% 29%	4257
	11th to 20th	Day	14% 9% 3 8% 6% 5% 4 4 7% 9% 31%	4398
	21st to end	Day	12% 5% 2 6% 6% 6% 5% 5% 7% 9% 38%	4837
June	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	2660
	11th to 20th	Day	13% 6% 2 7% 5% 6% 5% 4 7% 8% 37%	2660
	21st to end	Day	16% 8% 3 8% 5% 5% 6% 5% 7% 8% 29%	2660
July	1st to 10th	Day	10% 6% 2 6% 6% 6% 6% 5% 7% 9% 38%	4440
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 9% 11% 36%	4440
	21st to end	Day	11% 5% 3 7% 5% 5% 6% 5% 6% 8% 39%	4814
August	1st to 10th	Day	13% 7% 2 6% 5% 5% 6% 5% 7% 9% 35%	4423
	11th to 20th	Day	11% 6% 2 8% 5% 6% 6% 5% 8% 10% 34%	3872
	21st to end	Day	10% 5% 2 7% 5% 5% 5% 4 6% 9% 41%	4180
September	1st to 10th	Day	11% 6% 2 5% 3 4 5% 4 6% 7% 47%	2280
	11th to 20th	Day	11% 6% 1 5% 4 4 3 4 5% 7% 49%	2185
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 7% 8% 40%	2090
October	1st to 10th	Day	18% 10% 3 7% 5% 4 5% 4 6% 6% 33%	1989
	11th to 20th	Day	14% 8% 3 8% 5% 5% 5% 5% 6% 7% 34%	1867
	21st to end	Day	19% 9% 3 10% 4 5% 4 4 5% 6% 31%	1881
November	1st to 10th	Day	12% 11% 3 9% 5% 6% 5% 4 5% 7% 34%	1761
	11th to 20th	Day	15% 10% 3 8% 5% 6% 5% 4 5% 6% 32%	1790
	21st to end	Day	15% 13% 4 8% 6% 5% 5% 4 6% 6% 29%	1600
December	1st to 10th	Day	12% 20% 7% 14% 7% 6% 5% 3 5% 5% 17%	2600
	11th to 20th	Day	17% 13% 4 8% 5% 4 5% 5% 6% 7% 26%	2986
	21st to end	Day	18% 12% 4 11% 6% 5% 5% 4 5% 6% 24%	3960
January	1st to 10th	Night	12% 15% 9% 18% 6% 5% 4 3 4 5% 19%	6349
	11th to 20th	Night	8% 15% 8% 18% 8% 6% 5% 4 5% 5% 18%	6315
	21st to end	Night	12% 13% 6% 11% 7% 6% 6% 4 6% 6% 22%	6996
February	1st to 10th	Night	10% 13% 5% 14% 7% 6% 6% 4 6% 6% 24%	2547
	11th to 20th	Night	8% 12% 5% 13% 8% 5% 5% 4 5% 6% 30%	2266
	21st to end	Night	13% 11% 5% 10% 6% 6% 4 4 5% 5% 31%	1884
March	1st to 10th	Night	20% 12% 3 9% 6% 4 4 3 4 5% 29%	3724
	11th to 20th	Night	13% 15% 4 10% 6% 5% 5% 3 5% 5% 30%	3682
	21st to end	Night	12% 11% 3 10% 5% 5% 4 3 4 5% 37%	3466
April	1st to 10th	Night	15% 10% 3 9% 6% 6% 4 3 6% 6% 31%	1900
	11th to 20th	Night	19% 8% 3 9% 6% 5% 4 4 4 6% 33%	1875
	21st to end	Night	19% 8% 3 8% 4 4 5% 3 4 6% 36%	1762
May	1st to 10th	Night	19% 10% 3 9% 6% 5% 5% 4 6% 8% 26%	2711
	11th to 20th	Night	17% 10% 4 10% 5% 4 4 3 4 6% 34%	2495
	21st to end	Night	11% 6% 2 7% 5% 5% 6% 4 7% 9% 39%	2738
June	1st to 10th	Night	18% 7% 3 7% 6% 4 5% 4 5% 7% 34%	1520
	11th to 20th	Night	15% 6% 2 5% 4 5% 4 4 5% 9% 39%	1520
	21st to end	Night	15% 7% 2 7% 5% 5% 5% 4 6% 8% 36%	1520
July	1st to 10th	Night	10% 5% 2 7% 5% 6% 5% 5% 7% 8% 39%	2520
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 6% 9% 44%	2520
	21st to end	Night	8% 6% 3 7% 5% 5% 5% 4 6% 7% 42%	2739
August	1st to 10th	Night	12% 7% 3 7% 6% 5% 6% 3 5% 7% 38%	2506
	11th to 20th	Night	10% 6% 3 8% 6% 6% 5% 4 5% 7% 39%	2908
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 9% 46%	3476
September	1st to 10th	Night	10% 5% 2 5% 5% 5% 4 4 6% 7% 49%	1900
	11th to 20th	Night	11% 6% 2 6% 4 4 3 3 5% 7% 50%	1995
	21st to end	Night	13% 5% 2 5% 5% 5% 4 4 6% 7% 44%	2090
October	1st to 10th	Night	17% 7% 2 7% 6% 5% 5% 5% 5% 6% 35%	2189
	11th to 20th	Night	16% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	2312
	21st to end	Night	20% 10% 3 8% 5% 4 4 3 4 7% 30%	2717
November	1st to 10th	Night	15% 10% 3 8% 5% 4 4 4 5% 6% 35%	2537
	11th to 20th	Night	16% 9% 3 8% 5% 5% 5% 4 5% 6% 35%	2605
	21st to end	Night	15% 13% 4 9% 5% 6% 5% 4 5% 7% 28%	2800
December	1st to 10th	Night	14% 18% 7% 13% 6% 6% 5% 4 5% 5% 17%	4580
	11th to 20th	Night	20% 13% 4 10% 6% 5% 5% 3 4 5% 26%	5208
	21st to end	Night	19% 13% 5% 11% 7% 6% 5% 4 5% 6% 20%	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	57% 8% 13% 18% 4	3598
	11th to 20th	Day	60% 9% 8% 11% 8% 3	3600
	21st to end	Day	53% 10% 10% 15% 10% 2	3960
February	1st to 10th	Day	58% 10% 9% 16% 6% 2	1740
	11th to 20th	Day	54% 10% 12% 15% 9% 1	1809
	21st to end	Day	54% 8% 12% 13% 10% 2	1570
March	1st to 10th	Day	60% 11% 9% 12% 7% 1	3119
	11th to 20th	Day	53% 15% 10% 12% 8% 2	3274
	21st to end	Day	46% 9% 8% 16% 17% 3	4166
April	1st to 10th	Day	52% 7% 10% 17% 11% 2	2280
	11th to 20th	Day	48% 9% 9% 18% 14% 2	2254
	21st to end	Day	53% 8% 10% 16% 11% 3	2418
May	1st to 10th	Day	53% 10% 11% 18% 8% 1	4271
	11th to 20th	Day	46% 13% 15% 15% 9% 1	4402
	21st to end	Day	39% 11% 13% 25% 10% 1	4837
June	1st to 10th	Day	51% 9% 14% 16% 9% 1	2660
	11th to 20th	Day	43% 10% 13% 20% 12% 2	2660
	21st to end	Day	50% 10% 12% 18% 9% 1	2660
July	1st to 10th	Day	39% 10% 15% 24% 11%	4370
	11th to 20th	Day	39% 11% 15% 28% 7%	4365
	21st to end	Day	41% 10% 13% 27% 9%	4661
August	1st to 10th	Day	43% 11% 16% 20% 9% 1	4409
	11th to 20th	Day	41% 12% 18% 23% 6%	3912
	21st to end	Day	37% 9% 19% 23% 11% 1	4180
September	1st to 10th	Day	35% 10% 13% 30% 12% 1	2280
	11th to 20th	Day	34% 7% 14% 29% 15% 1	2185
	21st to end	Day	40% 10% 16% 22% 10% 2	2090
October	1st to 10th	Day	38% 9% 13% 27% 13%	3301
	11th to 20th	Day	40% 8% 14% 23% 14%	3083
	21st to end	Day	40% 7% 13% 30% 9% 1	3081
November	1st to 10th	Day	49% 9% 14% 18% 10%	1761
	11th to 20th	Day	50% 8% 12% 15% 12% 3	1790
	21st to end	Day	53% 10% 14% 18% 5% 1	1600
December	1st to 10th	Day	68% 8% 8% 12% 3	2600
	11th to 20th	Day	54% 9% 11% 16% 9%	2986
	21st to end	Day	55% 8% 9% 18% 9% 1	3960
January	1st to 10th	Night	59% 7% 15% 13% 5%	6349
	11th to 20th	Night	63% 10% 8% 11% 6% 1	6360
	21st to end	Night	58% 9% 9% 12% 12% 1	6996
February	1st to 10th	Night	57% 10% 12% 12% 8% 1	2547
	11th to 20th	Night	53% 10% 10% 16% 10% 1	2268
	21st to end	Night	52% 11% 10% 17% 9% 2	1884
March	1st to 10th	Night	55% 10% 10% 14% 9% 1	3734
	11th to 20th	Night	52% 9% 12% 16% 9% 1	3683
	21st to end	Night	47% 9% 9% 18% 14% 4	3466
April	1st to 10th	Night	50% 9% 10% 17% 12% 1	1900
	11th to 20th	Night	50% 9% 12% 17% 11% 1	1875
	21st to end	Night	47% 10% 10% 17% 12% 3	1762
May	1st to 10th	Night	54% 11% 9% 16% 9% 1	2717
	11th to 20th	Night	47% 11% 12% 19% 10% 1	2496
	21st to end	Night	38% 12% 14% 20% 15% 1	2739
June	1st to 10th	Night	45% 11% 13% 19% 10% 1	1520
	11th to 20th	Night	40% 9% 14% 22% 13% 2	1520
	21st to end	Night	43% 11% 15% 21% 10% 1	1520
July	1st to 10th	Night	40% 8% 16% 23% 13% 1	2480
	11th to 20th	Night	34% 11% 14% 30% 11%	2472
	21st to end	Night	35% 11% 16% 26% 11% 1	2651
August	1st to 10th	Night	41% 11% 15% 23% 9%	2496
	11th to 20th	Night	39% 11% 17% 24% 9%	2934
	21st to end	Night	32% 9% 18% 28% 13% 1	3476
September	1st to 10th	Night	33% 11% 15% 27% 13% 1	1900
	11th to 20th	Night	32% 8% 15% 30% 14%	1995
	21st to end	Night	37% 10% 13% 25% 13% 2	2090
October	1st to 10th	Night	43% 8% 12% 26% 10%	3657
	11th to 20th	Night	37% 7% 12% 27% 15% 2	3835
	21st to end	Night	44% 8% 13% 25% 9% 1	4467
November	1st to 10th	Night	48% 10% 12% 18% 10% 2	2537
	11th to 20th	Night	49% 10% 11% 18% 9% 3	2605
	21st to end	Night	52% 11% 15% 17% 5%	2800
December	1st to 10th	Night	64% 9% 10% 14% 3	4580
	11th to 20th	Night	59% 7% 8% 13% 12% 1	5208
	21st to end	Night	59% 8% 9% 16% 7% 1	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	18% 32% 29% 16% 5% 1	200
	11th to 20th	Day	21% 32% 35% 11% 2 1	200
	21st to end	Day	20% 27% 39% 11% 2	220
February	1st to 10th	Day	31% 39% 26% 3 1	278
	11th to 20th	Day	25% 31% 33% 9% 1	408
	21st to end	Day	30% 22% 34% 12% 2	382
March	1st to 10th	Day	27% 25% 31% 15% 3	460
	11th to 20th	Day	25% 32% 26% 14% 3 1	460
	21st to end	Day	27% 28% 26% 12% 5% 2	506
April	1st to 10th	Day	29% 24% 27% 15% 4 1	460
	11th to 20th	Day	30% 26% 25% 13% 4 2	452
	21st to end	Day	30% 26% 25% 12% 5% 2	460
May	1st to 10th	Day	24% 25% 32% 10% 7% 1	463
	11th to 20th	Day	20% 20% 34% 19% 5% 2	487
	21st to end	Day	17% 21% 33% 22% 6% 1	529
June	1st to 10th	Day	24% 18% 34% 18% 6% 1	490
	11th to 20th	Day	16% 19% 36% 20% 8% 1	490
	21st to end	Day	19% 21% 32% 20% 7% 1	490
July	1st to 10th	Day	14% 13% 33% 28% 11% 1	485
	11th to 20th	Day	11% 13% 37% 28% 10% 1	484
	21st to end	Day	14% 11% 36% 29% 7% 2	532
August	1st to 10th	Day	10% 11% 35% 28% 12% 3	486
	11th to 20th	Day	12% 9% 36% 27% 12% 5%	479
	21st to end	Day	11% 17% 31% 25% 11% 6%	539
September	1st to 10th	Day	15% 14% 32% 23% 10% 7%	490
	11th to 20th	Day	14% 14% 24% 22% 17% 9%	490
	21st to end	Day	14% 16% 32% 22% 12% 4	490
October	1st to 10th	Day	22% 19% 26% 20% 11% 2	490
	11th to 20th	Day	20% 22% 29% 21% 7% 1	473
	21st to end	Day	27% 20% 31% 19% 3	429
November	1st to 10th	Day	25% 21% 29% 20% 6%	395
	11th to 20th	Day	24% 28% 26% 16% 4 1	390
	21st to end	Day	30% 26% 31% 12% 2	200
December	1st to 10th	Day	23% 31% 28% 14% 5% 1	200
	11th to 20th	Day	29% 28% 33% 10% 1	200
	21st to end	Day	27% 26% 33% 11% 3	220
January	1st to 10th	Night	19% 24% 38% 17% 2	800
	11th to 20th	Night	21% 24% 35% 17% 3	800
	21st to end	Night	12% 22% 41% 21% 4	880
February	1st to 10th	Night	16% 24% 40% 18% 2	781
	11th to 20th	Night	17% 27% 37% 17% 2	743
	21st to end	Night	20% 24% 34% 19% 3	628
March	1st to 10th	Night	23% 21% 33% 21% 3	760
	11th to 20th	Night	23% 26% 29% 17% 4	760
	21st to end	Night	21% 23% 30% 19% 5% 1	836
April	1st to 10th	Night	21% 24% 29% 22% 3	760
	11th to 20th	Night	23% 24% 28% 19% 6%	751
	21st to end	Night	23% 21% 29% 22% 6%	622
May	1st to 10th	Night	25% 15% 32% 21% 7%	499
	11th to 20th	Night	15% 18% 36% 24% 6% 1	374
	21st to end	Night	13% 16% 34% 27% 10%	411
June	1st to 10th	Night	19% 10% 32% 26% 12%	380
	11th to 20th	Night	16% 9% 28% 36% 11% 1	380
	21st to end	Night	16% 8% 32% 33% 9% 1	380
July	1st to 10th	Night	12% 6% 29% 37% 15% 1	370
	11th to 20th	Night	11% 4 27% 40% 17% 2	368
	21st to end	Night	10% 7% 26% 43% 13%	416
August	1st to 10th	Night	11% 6% 22% 43% 17% 1	378
	11th to 20th	Night	9% 7% 24% 39% 18% 3	634
	21st to end	Night	11% 8% 26% 35% 18% 1	836
September	1st to 10th	Night	11% 9% 29% 33% 15% 2	760
	11th to 20th	Night	13% 10% 25% 28% 20% 4	760
	21st to end	Night	13% 12% 30% 26% 16% 2	760
October	1st to 10th	Night	22% 15% 25% 24% 14% 1	760
	11th to 20th	Night	19% 18% 26% 28% 8% 1	760
	21st to end	Night	25% 18% 31% 22% 4	836
November	1st to 10th	Night	20% 19% 34% 20% 7% 1	780
	11th to 20th	Night	20% 23% 32% 16% 8% 2	800
	21st to end	Night	21% 25% 30% 18% 6% 1	800
December	1st to 10th	Night	22% 27% 31% 16% 4	800
	11th to 20th	Night	22% 23% 33% 19% 4	800
	21st to end	Night	24% 23% 34% 16% 3	880

Page generated at 2025-02-03 03:05:55. Version ac07

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