Adams Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Adams Observing Site clear sky chart from 2005-11-06 to 2025-05-11.

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	15% 9% 3 7% 5% 4 4 4 5% 7% 36%	114198
	Night	15% 10% 3 7% 4 4 4 3 5% 7% 37%	114752
Transparency	Day	46% 5% 9% 23% 15% 2	117929
	Night	45% 5% 9% 22% 16% 3	119159
Seeing	Day	24% 10% 25% 22% 13% 6%	15432
	Night	21% 9% 23% 28% 16% 2	25565

By Month

Percentage Cloud Cover SE (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	16% 19% 7% 12% 5% 4 3 3 4 5% 23%	4056
	11th to 20th	Day	14% 17% 7% 13% 5% 3 3 2 3 4 29%	4060
	21st to end	Day	21% 14% 4 7% 5% 4 4 3 5% 5% 28%	4466
February	1st to 10th	Day	20% 12% 4 10% 5% 4 4 2 4 5% 30%	1885
	11th to 20th	Day	20% 11% 4 10% 4 4 5% 2 5% 5% 29%	1948
	21st to end	Day	20% 12% 3 7% 5% 3 4 3 5% 6% 32%	1650
March	1st to 10th	Day	18% 13% 3 7% 4 4 4 3 4 5% 34%	4618
	11th to 20th	Day	13% 8% 3 6% 4 4 4 3 6% 8% 42%	4980
	21st to end	Day	16% 8% 2 8% 5% 4 5% 3 6% 7% 36%	5465
April	1st to 10th	Day	16% 9% 3 8% 5% 4 4 3 5% 7% 37%	2279
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 4 5% 6% 39%	2453
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 4 5% 7% 36%	2600
May	1st to 10th	Day	19% 10% 3 8% 6% 5% 5% 4 5% 6% 28%	4212
	11th to 20th	Day	18% 10% 3 7% 4 4 4 4 5% 7% 34%	4081
	21st to end	Day	11% 6% 3 7% 5% 6% 6% 5% 8% 10% 34%	4476
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 7% 41%	2470
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 4 7% 9% 41%	2470
	21st to end	Day	10% 5% 2 6% 6% 5% 6% 5% 6% 9% 39%	2470
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 7% 10% 39%	4120
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 4 8% 11% 40%	4120
	21st to end	Day	16% 10% 4 9% 6% 6% 6% 5% 6% 7% 25%	4466
August	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 7% 10% 42%	4104
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 11% 38%	4044
	21st to end	Day	6% 3 1 4 4 5% 4 4 6% 9% 54%	4261
September	1st to 10th	Day	13% 5% 2 6% 4 4 5% 3 5% 8% 45%	2114
	11th to 20th	Day	12% 6% 2 5% 3 4 4 4 5% 8% 47%	2090
	21st to end	Day	18% 5% 3 6% 3 4 3 3 4 6% 44%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 4 3 2 6% 8% 51%	2090
	11th to 20th	Day	15% 6% 2 6% 3 3 4 3 4 5% 50%	1901
	21st to end	Day	21% 7% 2 6% 3 3 4 3 4 6% 42%	2028
November	1st to 10th	Day	12% 7% 1 5% 3 4 3 3 4 4 53%	1762
	11th to 20th	Day	15% 10% 3 7% 3 4 4 3 5% 5% 41%	1800
	21st to end	Day	18% 11% 3 7% 5% 3 3 3 4 6% 38%	1800
December	1st to 10th	Day	19% 12% 3 8% 4 3 3 2 4 3 37%	2930
	11th to 20th	Day	21% 15% 5% 8% 4 5% 4 3 4 4 28%	3373
	21st to end	Day	19% 16% 5% 10% 6% 5% 4 3 4 6% 21%	4466
January	1st to 10th	Night	16% 15% 6% 15% 6% 4 4 3 5% 5% 21%	5889
	11th to 20th	Night	18% 16% 6% 11% 4 3 3 3 4 4 28%	5900
	21st to end	Night	19% 11% 5% 7% 5% 4 4 2 5% 5% 34%	6490
February	1st to 10th	Night	21% 13% 4 8% 5% 5% 4 3 4 5% 29%	2512
	11th to 20th	Night	22% 11% 4 9% 5% 4 4 3 4 5% 30%	2338
	21st to end	Night	23% 12% 3 9% 4 4 4 3 4 5% 30%	1980
March	1st to 10th	Night	18% 12% 3 6% 4 4 4 3 5% 6% 37%	5220
	11th to 20th	Night	13% 7% 2 6% 3 3 4 3 5% 7% 47%	4980
	21st to end	Night	14% 9% 3 8% 6% 5% 5% 4 6% 7% 33%	5467
April	1st to 10th	Night	16% 7% 2 5% 4 4 4 4 6% 7% 40%	2137
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 6% 7% 44%	1894
	21st to end	Night	16% 7% 2 7% 5% 4 4 4 5% 7% 38%	1800
May	1st to 10th	Night	20% 11% 3 8% 5% 5% 6% 4 5% 6% 27%	2903
	11th to 20th	Night	19% 8% 2 6% 4 4 3 4 5% 8% 37%	2818
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 9% 43%	3079
June	1st to 10th	Night	8% 6% 2 5% 4 4 4 5% 8% 9% 45%	1710
	11th to 20th	Night	5% 4 1 6% 5% 5% 5% 5% 7% 9% 47%	1710
	21st to end	Night	8% 5% 2 5% 4 4 5% 5% 7% 11% 44%	1710
July	1st to 10th	Night	7% 5% 2 6% 4 5% 5% 4 7% 10% 44%	2840
	11th to 20th	Night	7% 5% 2 6% 4 5% 4 4 7% 9% 46%	2840
	21st to end	Night	13% 9% 4 8% 5% 5% 5% 4 6% 8% 34%	3087
August	1st to 10th	Night	7% 5% 2 7% 4 4 5% 4 7% 10% 43%	2825
	11th to 20th	Night	9% 6% 3 8% 4 5% 5% 4 7% 9% 42%	2785
	21st to end	Night	4 4 1 4 3 4 3 4 5% 9% 58%	3378
September	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 5% 8% 48%	2047
	11th to 20th	Night	9% 6% 2 6% 4 4 4 3 6% 6% 50%	2090
	21st to end	Night	12% 6% 2 7% 6% 4 4 3 3 6% 47%	2090
October	1st to 10th	Night	11% 4 2 4 3 4 3 3 5% 7% 54%	2090
	11th to 20th	Night	15% 6% 2 5% 3 4 3 3 5% 7% 48%	2278
	21st to end	Night	18% 7% 2 5% 4 3 3 3 4 5% 44%	2567
November	1st to 10th	Night	13% 7% 2 5% 4 4 3 3 4 5% 50%	2536
	11th to 20th	Night	17% 8% 3 6% 4 3 3 4 5% 6% 42%	2600
	21st to end	Night	18% 11% 3 4 4 4 3 4 4 6% 38%	2600
December	1st to 10th	Night	19% 13% 4 7% 4 3 3 2 4 5% 36%	4250
	11th to 20th	Night	20% 12% 6% 8% 4 4 3 3 4 5% 31%	4822
	21st to end	Night	19% 18% 4 10% 5% 5% 5% 3 5% 6% 20%	6490

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	64% 4 7% 17% 7% 1	4057
	11th to 20th	Day	62% 2 4 17% 12% 2	4060
	21st to end	Day	59% 3 7% 22% 7% 2	4466
February	1st to 10th	Day	58% 3 8% 19% 11% 1	1885
	11th to 20th	Day	58% 4 7% 18% 11% 2	1958
	21st to end	Day	54% 3 8% 22% 11% 3	1650
March	1st to 10th	Day	53% 4 5% 17% 15% 5%	4618
	11th to 20th	Day	40% 4 9% 25% 19% 2	4980
	21st to end	Day	47% 5% 9% 25% 13% 1	5465
April	1st to 10th	Day	48% 4 9% 24% 13% 3	2279
	11th to 20th	Day	46% 4 8% 22% 16% 4	2453
	21st to end	Day	47% 6% 10% 23% 12% 2	2600
May	1st to 10th	Day	54% 7% 9% 21% 9% 1	4250
	11th to 20th	Day	50% 6% 9% 22% 12% 1	4085
	21st to end	Day	40% 10% 13% 18% 16% 3	4489
June	1st to 10th	Day	39% 7% 11% 26% 16% 1	2470
	11th to 20th	Day	38% 6% 14% 22% 18% 2	2470
	21st to end	Day	40% 7% 13% 21% 16% 3	2470
July	1st to 10th	Day	40% 7% 14% 23% 15% 1	4055
	11th to 20th	Day	37% 6% 11% 33% 13% 1	4051
	21st to end	Day	56% 6% 9% 17% 10% 2	4324
August	1st to 10th	Day	35% 7% 14% 31% 12% 1	4091
	11th to 20th	Day	39% 5% 11% 30% 15% 1	4083
	21st to end	Day	26% 5% 15% 31% 21% 3	4260
September	1st to 10th	Day	37% 5% 12% 21% 18% 6%	2114
	11th to 20th	Day	36% 3 11% 25% 22% 3	2090
	21st to end	Day	41% 4 8% 25% 21% 2	2090
October	1st to 10th	Day	23% 3 7% 26% 38% 2	3480
	11th to 20th	Day	27% 4 8% 29% 30% 2	3141
	21st to end	Day	31% 3 8% 30% 22% 5%	3317
November	1st to 10th	Day	36% 3 8% 27% 23% 4	1762
	11th to 20th	Day	46% 2 7% 22% 19% 4	1800
	21st to end	Day	50% 3 8% 21% 17% 2	1800
December	1st to 10th	Day	53% 3 6% 22% 16%	2930
	11th to 20th	Day	61% 3 8% 17% 10% 1	3370
	21st to end	Day	64% 5% 9% 16% 5% 1	4466
January	1st to 10th	Night	66% 4 7% 15% 8% 1	5889
	11th to 20th	Night	61% 3 4 17% 11% 3	5900
	21st to end	Night	54% 2 7% 23% 12% 2	6490
February	1st to 10th	Night	58% 3 9% 19% 9% 1	2512
	11th to 20th	Night	58% 3 7% 19% 12% 1	2339
	21st to end	Night	58% 3 9% 15% 11% 3	1980
March	1st to 10th	Night	50% 3 5% 24% 15% 4	5220
	11th to 20th	Night	37% 5% 8% 28% 21% 1	4980
	21st to end	Night	50% 5% 8% 22% 14% 1	5467
April	1st to 10th	Night	42% 6% 10% 23% 18% 2	2137
	11th to 20th	Night	39% 5% 10% 22% 18% 6%	1894
	21st to end	Night	45% 5% 11% 23% 14% 2	1800
May	1st to 10th	Night	56% 7% 9% 19% 8% 2	2930
	11th to 20th	Night	45% 7% 12% 24% 11% 1	2819
	21st to end	Night	34% 9% 13% 24% 18% 4	3087
June	1st to 10th	Night	32% 8% 15% 26% 16% 4	1710
	11th to 20th	Night	31% 8% 15% 24% 19% 3	1710
	21st to end	Night	34% 7% 15% 25% 15% 5%	1710
July	1st to 10th	Night	35% 8% 14% 23% 17% 3	2795
	11th to 20th	Night	33% 6% 13% 30% 16% 2	2786
	21st to end	Night	48% 6% 9% 21% 14% 2	2988
August	1st to 10th	Night	35% 7% 14% 31% 12% 1	2814
	11th to 20th	Night	38% 5% 10% 28% 17% 1	2812
	21st to end	Night	22% 6% 15% 32% 22% 4	3378
September	1st to 10th	Night	34% 6% 11% 23% 19% 7%	2047
	11th to 20th	Night	33% 4 10% 24% 25% 4	2090
	21st to end	Night	39% 5% 7% 22% 24% 3	2090
October	1st to 10th	Night	25% 4 7% 24% 36% 3	3480
	11th to 20th	Night	26% 3 7% 25% 34% 4	3777
	21st to end	Night	31% 3 7% 23% 29% 7%	4228
November	1st to 10th	Night	38% 4 7% 24% 23% 4	2536
	11th to 20th	Night	44% 3 7% 20% 22% 5%	2600
	21st to end	Night	48% 4 8% 24% 15% 2	2600
December	1st to 10th	Night	53% 3 10% 22% 13% 1	4250
	11th to 20th	Night	56% 3 9% 20% 10% 1	4824
	21st to end	Night	65% 5% 8% 15% 7%	6490

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	33% 21% 30% 13% 3 1	300
	11th to 20th	Day	42% 17% 29% 11%	300
	21st to end	Day	35% 23% 29% 10% 3	330
February	1st to 10th	Day	33% 21% 33% 11% 2	300
	11th to 20th	Day	44% 21% 28% 5% 2	300
	21st to end	Day	35% 16% 39% 8% 1	249
March	1st to 10th	Day	36% 18% 29% 13% 5%	360
	11th to 20th	Day	29% 20% 30% 16% 4	500
	21st to end	Day	35% 15% 29% 15% 5%	550
April	1st to 10th	Day	30% 16% 28% 16% 8% 2	500
	11th to 20th	Day	25% 16% 30% 19% 6% 4	492
	21st to end	Day	26% 16% 32% 19% 6% 2	500
May	1st to 10th	Day	29% 15% 27% 17% 9% 3	503
	11th to 20th	Day	23% 8% 29% 21% 13% 5%	487
	21st to end	Day	15% 6% 25% 27% 18% 8%	529
June	1st to 10th	Day	16% 5% 24% 30% 17% 8%	490
	11th to 20th	Day	13% 5% 22% 33% 18% 9%	490
	21st to end	Day	14% 6% 26% 27% 18% 10%	490
July	1st to 10th	Day	18% 2 16% 24% 20% 20%	485
	11th to 20th	Day	14% 3 18% 30% 20% 14%	484
	21st to end	Day	16% 3 17% 29% 22% 14%	532
August	1st to 10th	Day	15% 2 17% 26% 26% 13%	486
	11th to 20th	Day	14% 4 16% 31% 23% 12%	479
	21st to end	Day	11% 3 13% 31% 27% 16%	539
September	1st to 10th	Day	16% 2 14% 26% 29% 13%	490
	11th to 20th	Day	14% 3 13% 27% 31% 12%	490
	21st to end	Day	23% 7% 20% 23% 21% 7%	490
October	1st to 10th	Day	15% 4 21% 31% 22% 7%	490
	11th to 20th	Day	18% 12% 26% 25% 13% 5%	490
	21st to end	Day	28% 8% 29% 24% 10% 1	477
November	1st to 10th	Day	19% 9% 37% 24% 7% 3	300
	11th to 20th	Day	31% 12% 33% 17% 7% 1	300
	21st to end	Day	30% 15% 34% 15% 5% 1	300
December	1st to 10th	Day	34% 18% 29% 14% 5% 1	300
	11th to 20th	Day	34% 14% 31% 16% 5%	300
	21st to end	Day	37% 16% 30% 13% 4	330
January	1st to 10th	Night	29% 19% 29% 19% 5%	800
	11th to 20th	Night	34% 17% 27% 20% 2	800
	21st to end	Night	26% 18% 32% 22% 2	880
February	1st to 10th	Night	31% 14% 31% 22% 3	800
	11th to 20th	Night	34% 17% 31% 16% 2	783
	21st to end	Night	33% 14% 34% 17% 2	660
March	1st to 10th	Night	28% 15% 29% 23% 6%	800
	11th to 20th	Night	28% 16% 28% 20% 7% 1	800
	21st to end	Night	23% 15% 31% 25% 7%	880
April	1st to 10th	Night	24% 12% 29% 26% 9%	737
	11th to 20th	Night	20% 12% 28% 28% 10% 1	593
	21st to end	Night	21% 8% 33% 29% 9% 1	600
May	1st to 10th	Night	23% 7% 26% 29% 13% 3	600
	11th to 20th	Night	18% 4 21% 35% 20% 1	563
	21st to end	Night	11% 2 19% 35% 28% 5%	617
June	1st to 10th	Night	12% 3 17% 42% 24% 3	570
	11th to 20th	Night	7% 3 14% 41% 30% 5%	570
	21st to end	Night	12% 2 17% 38% 26% 5%	570
July	1st to 10th	Night	14% 1 12% 29% 33% 11%	555
	11th to 20th	Night	8% 1 11% 36% 38% 5%	552
	21st to end	Night	13% 2 9% 33% 37% 6%	624
August	1st to 10th	Night	10% 2 7% 35% 40% 7%	567
	11th to 20th	Night	11% 2 8% 37% 36% 7%	564
	21st to end	Night	11% 1 9% 31% 40% 8%	627
September	1st to 10th	Night	14% 2 9% 34% 36% 6%	717
	11th to 20th	Night	15% 2 11% 31% 35% 6%	760
	21st to end	Night	15% 5% 19% 31% 28% 2	760
October	1st to 10th	Night	13% 4 18% 32% 28% 5%	760
	11th to 20th	Night	19% 7% 24% 30% 17% 3	760
	21st to end	Night	23% 9% 26% 28% 13% 1	836
November	1st to 10th	Night	18% 8% 25% 31% 16% 2	780
	11th to 20th	Night	24% 12% 28% 26% 10%	800
	21st to end	Night	27% 10% 23% 29% 9% 1	800
December	1st to 10th	Night	32% 13% 27% 24% 5%	800
	11th to 20th	Night	25% 15% 28% 26% 6% 1	800
	21st to end	Night	32% 13% 26% 25% 4	880

Page generated at 2025-05-08 09:33:58. Version ac07

Copyright © 2025 Attilla Danko.