Observation Tower at The Beech
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observation Tower at The Beech clear sky chart from 2005-11-06 to 2024-08-30.

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	17% 8% 2 7% 5% 5% 5% 4 6% 7% 35%	95646
	Night	17% 8% 3 7% 5% 4 4 4 5% 6% 37%	93412
Transparency	Day	46% 8% 13% 19% 12% 2	95365
	Night	46% 8% 13% 20% 12% 2	93247
Seeing	Day	23% 19% 29% 19% 9% 2	14636
	Night	21% 16% 28% 26% 9% 1	23427

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	14% 8% 3 8% 5% 6% 5% 4 7% 6% 36%	2517
	11th to 20th	Day	14% 8% 3 8% 6% 4 5% 5% 6% 7% 34%	2520
	21st to end	Day	13% 12% 3 8% 5% 5% 4 4 5% 7% 34%	2772
February	1st to 10th	Day	13% 10% 3 7% 6% 5% 6% 5% 5% 6% 35%	1654
	11th to 20th	Day	10% 10% 3 9% 4 5% 5% 3 6% 7% 38%	1848
	21st to end	Day	15% 10% 3 7% 7% 5% 5% 4 6% 5% 34%	1570
March	1st to 10th	Day	21% 15% 3 8% 4 4 4 3 4 5% 28%	3116
	11th to 20th	Day	14% 10% 3 8% 5% 4 4 4 6% 6% 36%	3367
	21st to end	Day	21% 8% 3 7% 4 4 3 3 5% 7% 35%	3996
April	1st to 10th	Day	17% 11% 3 7% 5% 4 4 4 4 6% 35%	2280
	11th to 20th	Day	17% 6% 2 6% 4 5% 5% 4 6% 7% 38%	2321
	21st to end	Day	22% 8% 3 7% 4 5% 5% 3 4 6% 33%	2470
May	1st to 10th	Day	23% 11% 4 8% 5% 4 5% 4 6% 6% 26%	4106
	11th to 20th	Day	18% 7% 3 9% 6% 6% 5% 4 5% 6% 30%	4257
	21st to end	Day	14% 5% 2 6% 5% 5% 5% 4 7% 10% 37%	4837
June	1st to 10th	Day	22% 7% 2 6% 5% 5% 5% 5% 6% 7% 29%	2660
	11th to 20th	Day	17% 6% 2 6% 5% 4 4 5% 6% 7% 38%	2660
	21st to end	Day	22% 7% 3 8% 5% 5% 4 4 6% 7% 29%	2660
July	1st to 10th	Day	14% 5% 2 6% 5% 6% 6% 5% 8% 10% 33%	4440
	11th to 20th	Day	12% 5% 1 6% 5% 5% 6% 5% 8% 10% 36%	4440
	21st to end	Day	19% 6% 2 6% 4 5% 5% 4 6% 7% 36%	4814
August	1st to 10th	Day	14% 5% 2 6% 5% 5% 7% 5% 7% 8% 36%	2528
	11th to 20th	Day	14% 6% 2 6% 5% 5% 6% 5% 6% 8% 36%	2434
	21st to end	Day	12% 4 2 4 4 4 5% 5% 7% 10% 44%	2543
September	1st to 10th	Day	12% 5% 1 5% 4 4 5% 5% 5% 9% 46%	2149
	11th to 20th	Day	13% 4 1 5% 4 4 3 2 4 6% 53%	1980
	21st to end	Day	16% 5% 2 5% 3 4 4 4 5% 9% 44%	1980
October	1st to 10th	Day	19% 7% 3 6% 4 4 4 3 4 6% 38%	1980
	11th to 20th	Day	18% 6% 2 6% 4 4 5% 4 5% 7% 40%	1714
	21st to end	Day	24% 10% 3 6% 5% 4 4 4 4 5% 32%	1782
November	1st to 10th	Day	16% 7% 2 5% 4 4 4 3 5% 7% 44%	1671
	11th to 20th	Day	19% 5% 2 5% 5% 4 4 5% 6% 8% 38%	1710
	21st to end	Day	19% 10% 2 5% 3 3 4 4 6% 7% 39%	1672
December	1st to 10th	Day	17% 11% 4 8% 5% 4 5% 5% 6% 5% 31%	1520
	11th to 20th	Day	21% 10% 3 5% 4 4 4 3 4 5% 37%	1906
	21st to end	Day	21% 11% 3 6% 5% 4 4 5% 5% 6% 30%	2772
January	1st to 10th	Night	14% 10% 3 8% 4 3 4 4 5% 6% 38%	4429
	11th to 20th	Night	11% 11% 4 13% 8% 6% 5% 4 5% 7% 27%	4440
	21st to end	Night	15% 11% 5% 12% 5% 5% 5% 4 4 6% 28%	4884
February	1st to 10th	Night	12% 9% 4 7% 6% 5% 5% 5% 6% 6% 34%	2523
	11th to 20th	Night	9% 10% 4 6% 5% 5% 5% 4 5% 7% 41%	2218
	21st to end	Night	12% 10% 4 7% 5% 4 4 4 5% 6% 39%	1884
March	1st to 10th	Night	23% 12% 3 5% 4 4 4 4 5% 5% 31%	3724
	11th to 20th	Night	12% 8% 4 9% 7% 6% 6% 5% 5% 6% 32%	3591
	21st to end	Night	22% 9% 3 7% 4 4 4 3 5% 7% 32%	3635
April	1st to 10th	Night	18% 10% 3 6% 4 4 4 3 5% 5% 37%	1900
	11th to 20th	Night	17% 8% 2 7% 4 4 4 3 6% 6% 37%	1806
	21st to end	Night	22% 8% 2 6% 4 4 3 4 5% 6% 36%	1710
May	1st to 10th	Night	23% 11% 3 8% 4 4 4 4 5% 6% 28%	2834
	11th to 20th	Night	18% 9% 3 7% 6% 5% 5% 5% 6% 7% 29%	2665
	21st to end	Night	15% 6% 2 6% 4 3 4 4 6% 9% 41%	2738
June	1st to 10th	Night	20% 8% 3 6% 4 4 4 4 6% 6% 36%	1520
	11th to 20th	Night	18% 6% 2 4 3 4 4 4 6% 8% 40%	1520
	21st to end	Night	20% 6% 2 7% 4 5% 4 3 6% 8% 35%	1520
July	1st to 10th	Night	12% 5% 2 5% 5% 5% 5% 5% 8% 9% 40%	2520
	11th to 20th	Night	16% 5% 2 6% 4 4 3 4 5% 7% 45%	2520
	21st to end	Night	17% 5% 2 5% 4 4 5% 3 7% 7% 42%	2739
August	1st to 10th	Night	16% 6% 2 5% 3 3 5% 3 6% 6% 44%	1611
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 4 7% 8% 40%	1686
	21st to end	Night	14% 5% 1 5% 3 3 4 3 6% 7% 47%	2019
September	1st to 10th	Night	13% 4 1 4 3 4 4 3 5% 8% 51%	1809
	11th to 20th	Night	15% 5% 2 4 3 3 2 3 5% 6% 52%	1980
	21st to end	Night	16% 6% 2 5% 4 4 3 3 4 7% 47%	1980
October	1st to 10th	Night	20% 6% 3 5% 4 4 4 4 6% 6% 38%	1980
	11th to 20th	Night	17% 7% 2 6% 4 5% 4 4 6% 7% 39%	2241
	21st to end	Night	24% 7% 2 6% 5% 3 4 4 5% 7% 34%	2574
November	1st to 10th	Night	16% 6% 2 5% 5% 4 5% 3 4 6% 42%	2407
	11th to 20th	Night	16% 7% 3 6% 5% 5% 5% 3 4 6% 40%	2470
	21st to end	Night	15% 8% 2 6% 5% 4 4 4 5% 6% 41%	2503
December	1st to 10th	Night	18% 12% 3 7% 4 5% 4 4 5% 6% 32%	2660
	11th to 20th	Night	19% 10% 2 6% 4 4 4 4 5% 5% 36%	3288
	21st to end	Night	20% 10% 3 7% 4 4 4 4 5% 6% 33%	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	44% 8% 15% 23% 10% 1	2518
	11th to 20th	Day	47% 9% 16% 18% 9% 2	2520
	21st to end	Day	48% 8% 12% 19% 11% 1	2772
February	1st to 10th	Day	48% 8% 11% 19% 11% 2	1654
	11th to 20th	Day	46% 7% 13% 17% 14% 3	1857
	21st to end	Day	50% 6% 12% 16% 11% 4	1570
March	1st to 10th	Day	60% 6% 8% 10% 13% 2	3119
	11th to 20th	Day	46% 9% 13% 15% 13% 4	3367
	21st to end	Day	49% 5% 8% 15% 19% 4	3996
April	1st to 10th	Day	51% 5% 10% 17% 13% 4	2280
	11th to 20th	Day	45% 8% 11% 21% 13% 2	2321
	21st to end	Day	52% 7% 9% 17% 12% 4	2470
May	1st to 10th	Day	57% 9% 9% 16% 7% 1	4120
	11th to 20th	Day	52% 9% 14% 15% 9% 1	4261
	21st to end	Day	39% 10% 14% 21% 15% 1	4837
June	1st to 10th	Day	51% 8% 13% 19% 8% 1	2660
	11th to 20th	Day	44% 8% 13% 19% 14% 2	2660
	21st to end	Day	53% 10% 11% 16% 10% 1	2660
July	1st to 10th	Day	43% 8% 16% 22% 11%	4370
	11th to 20th	Day	39% 9% 16% 28% 8%	4365
	21st to end	Day	45% 8% 11% 22% 14% 1	4661
August	1st to 10th	Day	42% 11% 15% 21% 10%	2514
	11th to 20th	Day	43% 10% 15% 22% 9%	2434
	21st to end	Day	34% 9% 16% 24% 16% 1	2543
September	1st to 10th	Day	34% 9% 16% 25% 16%	2149
	11th to 20th	Day	34% 6% 9% 31% 17% 3	1980
	21st to end	Day	37% 7% 14% 24% 16% 1	1980
October	1st to 10th	Day	47% 7% 10% 21% 13% 1	1980
	11th to 20th	Day	44% 7% 16% 23% 9% 1	1714
	21st to end	Day	53% 8% 11% 15% 11% 2	1782
November	1st to 10th	Day	40% 7% 15% 21% 14% 2	1671
	11th to 20th	Day	43% 9% 15% 15% 15% 3	1710
	21st to end	Day	45% 7% 17% 19% 10% 1	1672
December	1st to 10th	Day	54% 6% 13% 18% 8% 1	1520
	11th to 20th	Day	50% 5% 10% 15% 17% 2	1906
	21st to end	Day	55% 8% 10% 17% 8% 2	2772
January	1st to 10th	Night	44% 8% 14% 22% 9% 2	4429
	11th to 20th	Night	53% 9% 16% 13% 7% 2	4440
	21st to end	Night	55% 7% 10% 16% 10% 2	4884
February	1st to 10th	Night	46% 9% 14% 16% 13% 3	2523
	11th to 20th	Night	43% 6% 14% 20% 14% 2	2220
	21st to end	Night	45% 5% 13% 20% 12% 4	1884
March	1st to 10th	Night	54% 6% 12% 16% 9% 3	3734
	11th to 20th	Night	50% 10% 12% 16% 10% 2	3592
	21st to end	Night	52% 6% 8% 14% 17% 3	3635
April	1st to 10th	Night	49% 5% 11% 18% 16% 2	1900
	11th to 20th	Night	46% 8% 10% 21% 14% 1	1806
	21st to end	Night	48% 7% 12% 16% 14% 3	1710
May	1st to 10th	Night	55% 9% 10% 16% 8% 1	2840
	11th to 20th	Night	50% 11% 13% 17% 7% 2	2666
	21st to end	Night	39% 10% 17% 20% 13% 1	2739
June	1st to 10th	Night	48% 9% 14% 18% 10%	1520
	11th to 20th	Night	42% 7% 14% 23% 12% 2	1520
	21st to end	Night	47% 10% 13% 19% 10% 1	1520
July	1st to 10th	Night	40% 7% 20% 21% 11% 1	2480
	11th to 20th	Night	39% 6% 15% 28% 11%	2472
	21st to end	Night	40% 8% 13% 26% 12%	2651
August	1st to 10th	Night	40% 9% 14% 27% 9%	1601
	11th to 20th	Night	41% 9% 16% 22% 12%	1686
	21st to end	Night	35% 8% 14% 27% 15% 1	2019
September	1st to 10th	Night	31% 9% 14% 31% 14%	1809
	11th to 20th	Night	33% 7% 11% 31% 16% 1	1980
	21st to end	Night	37% 7% 13% 28% 14% 2	1980
October	1st to 10th	Night	44% 8% 13% 21% 13% 1	1980
	11th to 20th	Night	43% 9% 14% 24% 9% 1	2241
	21st to end	Night	51% 6% 12% 17% 12% 1	2574
November	1st to 10th	Night	42% 7% 13% 23% 13% 1	2407
	11th to 20th	Night	44% 6% 13% 20% 14% 2	2470
	21st to end	Night	43% 7% 17% 21% 11% 1	2503
December	1st to 10th	Night	53% 7% 12% 18% 9% 1	2660
	11th to 20th	Night	49% 6% 12% 16% 16% 1	3288
	21st to end	Night	52% 7% 13% 19% 9% 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	24% 22% 30% 21% 3	180
	11th to 20th	Day	27% 23% 33% 14% 3 1	180
	21st to end	Day	19% 24% 34% 16% 7%	198
February	1st to 10th	Day	26% 27% 29% 16% 3	296
	11th to 20th	Day	24% 32% 30% 12% 2	456
	21st to end	Day	27% 24% 28% 17% 3	382
March	1st to 10th	Day	25% 23% 33% 14% 5%	460
	11th to 20th	Day	25% 26% 30% 13% 5% 1	460
	21st to end	Day	27% 25% 25% 14% 6% 2	506
April	1st to 10th	Day	30% 24% 25% 14% 6% 2	460
	11th to 20th	Day	28% 26% 24% 13% 7% 1	452
	21st to end	Day	32% 24% 26% 11% 5% 2	460
May	1st to 10th	Day	32% 21% 27% 14% 3 2	463
	11th to 20th	Day	22% 20% 34% 14% 7% 2	487
	21st to end	Day	21% 18% 32% 21% 7% 2	529
June	1st to 10th	Day	22% 18% 34% 17% 9% 1	490
	11th to 20th	Day	18% 16% 30% 23% 9% 2	490
	21st to end	Day	25% 14% 32% 20% 8% 2	490
July	1st to 10th	Day	18% 13% 32% 23% 12% 2	485
	11th to 20th	Day	14% 10% 33% 28% 11% 3	484
	21st to end	Day	16% 10% 35% 24% 12% 2	532
August	1st to 10th	Day	17% 8% 29% 26% 15% 4	486
	11th to 20th	Day	17% 14% 25% 24% 14% 6%	479
	21st to end	Day	13% 11% 32% 24% 15% 5%	532
September	1st to 10th	Day	16% 12% 27% 24% 17% 4	450
	11th to 20th	Day	20% 14% 25% 18% 15% 9%	450
	21st to end	Day	15% 18% 26% 24% 10% 6%	450
October	1st to 10th	Day	22% 18% 23% 21% 12% 4	450
	11th to 20th	Day	23% 18% 27% 19% 12% 1	378
	21st to end	Day	36% 16% 23% 19% 6% 1	396
November	1st to 10th	Day	24% 20% 22% 24% 9% 1	365
	11th to 20th	Day	28% 19% 25% 19% 8% 1	370
	21st to end	Day	26% 24% 24% 18% 7%	332
December	1st to 10th	Day	23% 22% 31% 19% 6%	180
	11th to 20th	Day	33% 21% 33% 8% 4	180
	21st to end	Day	29% 25% 26% 15% 5% 1	198
January	1st to 10th	Night	18% 23% 30% 25% 4	760
	11th to 20th	Night	23% 21% 30% 23% 3	760
	21st to end	Night	16% 23% 35% 22% 3	836
February	1st to 10th	Night	18% 22% 34% 23% 3	760
	11th to 20th	Night	16% 27% 36% 18% 3	743
	21st to end	Night	21% 21% 30% 25% 4	628
March	1st to 10th	Night	23% 21% 32% 21% 2	760
	11th to 20th	Night	23% 22% 28% 21% 6% 1	760
	21st to end	Night	23% 20% 30% 21% 6% 1	836
April	1st to 10th	Night	27% 18% 28% 22% 4	760
	11th to 20th	Night	22% 17% 30% 25% 6%	682
	21st to end	Night	26% 19% 29% 21% 5%	570
May	1st to 10th	Night	26% 12% 28% 27% 6% 1	570
	11th to 20th	Night	22% 11% 31% 27% 9%	479
	21st to end	Night	19% 8% 25% 37% 10% 1	411
June	1st to 10th	Night	24% 11% 24% 31% 10% 1	380
	11th to 20th	Night	18% 8% 24% 33% 17%	380
	21st to end	Night	21% 6% 22% 39% 12%	380
July	1st to 10th	Night	16% 4 24% 40% 16% 1	370
	11th to 20th	Night	15% 3 23% 40% 17% 2	368
	21st to end	Night	18% 4 17% 42% 19% 1	416
August	1st to 10th	Night	18% 4 20% 38% 18% 1	477
	11th to 20th	Night	18% 5% 25% 34% 17% 2	562
	21st to end	Night	15% 6% 22% 33% 22% 2	771
September	1st to 10th	Night	16% 5% 24% 35% 19% 2	720
	11th to 20th	Night	17% 11% 23% 25% 20% 4	720
	21st to end	Night	18% 9% 25% 30% 16% 2	720
October	1st to 10th	Night	25% 10% 19% 30% 14% 1	720
	11th to 20th	Night	22% 12% 28% 23% 13% 2	720
	21st to end	Night	30% 15% 26% 25% 4	792
November	1st to 10th	Night	20% 18% 26% 25% 9% 1	740
	11th to 20th	Night	21% 18% 28% 23% 8% 1	760
	21st to end	Night	21% 21% 25% 26% 5% 1	760
December	1st to 10th	Night	25% 19% 32% 19% 4	760
	11th to 20th	Night	22% 23% 30% 20% 5%	760
	21st to end	Night	23% 22% 30% 22% 3	836

Page generated at 2024-08-27 09:49:36. Version ac07

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