Goodwin Conservation Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goodwin Conservation Center clear sky chart from 2005-11-06 to 2024-11-10.

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	18% 7% 2 6% 4 4 4 4 5% 7% 38%	101252
	Night	18% 8% 2 6% 4 3 4 3 5% 6% 39%	97907
Transparency	Day	44% 5% 11% 22% 15% 2	104803
	Night	44% 5% 11% 22% 15% 2	102445
Seeing	Day	25% 16% 31% 19% 7% 2	15072
	Night	23% 15% 32% 23% 7% 1	24032

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	15% 8% 2 6% 4 4 4 3 5% 5% 45%	2517
	11th to 20th	Day	18% 7% 3 7% 5% 4 5% 4 5% 5% 37%	2520
	21st to end	Day	22% 12% 3 6% 4 3 4 2 4 5% 34%	2772
February	1st to 10th	Day	19% 8% 2 6% 4 4 5% 3 5% 6% 37%	1808
	11th to 20th	Day	15% 6% 2 6% 6% 4 5% 3 5% 7% 41%	1848
	21st to end	Day	21% 10% 3 6% 4 4 3 2 5% 5% 37%	1570
March	1st to 10th	Day	25% 12% 3 7% 3 3 3 2 3 5% 34%	3116
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 7% 8% 41%	3280
	21st to end	Day	21% 9% 2 6% 4 4 4 3 6% 6% 35%	4116
April	1st to 10th	Day	19% 9% 2 5% 5% 3 4 4 5% 7% 37%	2280
	11th to 20th	Day	19% 6% 2 5% 4 4 4 3 5% 7% 41%	2254
	21st to end	Day	21% 6% 3 6% 4 5% 4 3 4 6% 38%	2433
May	1st to 10th	Day	28% 8% 2 6% 4 4 3 3 5% 7% 29%	4106
	11th to 20th	Day	24% 8% 3 7% 4 4 4 3 4 7% 33%	4195
	21st to end	Day	16% 5% 1 5% 4 3 4 4 5% 9% 44%	4837
June	1st to 10th	Day	19% 6% 2 6% 5% 4 5% 4 6% 9% 35%	2660
	11th to 20th	Day	16% 6% 2 6% 5% 5% 5% 4 6% 9% 35%	2660
	21st to end	Day	16% 7% 2 7% 4 5% 4 4 7% 9% 35%	2660
July	1st to 10th	Day	14% 6% 3 6% 6% 6% 6% 5% 6% 9% 34%	4440
	11th to 20th	Day	15% 5% 2 6% 4 4 5% 4 6% 10% 38%	4440
	21st to end	Day	20% 7% 3 7% 5% 5% 5% 4 5% 6% 34%	4814
August	1st to 10th	Day	20% 8% 3 6% 5% 5% 5% 4 6% 8% 30%	4184
	11th to 20th	Day	13% 7% 2 6% 4 5% 5% 4 6% 8% 40%	3863
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 4 7% 9% 44%	4180
September	1st to 10th	Day	15% 6% 2 6% 5% 5% 4 3 5% 5% 45%	2280
	11th to 20th	Day	15% 5% 2 5% 3 3 3 3 5% 6% 50%	2114
	21st to end	Day	18% 7% 2 6% 3 4 4 3 5% 7% 41%	2090
October	1st to 10th	Day	23% 7% 2 6% 2 3 3 3 4 5% 41%	2090
	11th to 20th	Day	15% 6% 3 4 3 3 3 4 4 6% 49%	1859
	21st to end	Day	19% 7% 3 5% 5% 3 3 3 5% 6% 42%	1881
November	1st to 10th	Day	13% 8% 2 6% 4 4 3 2 4 5% 49%	1752
	11th to 20th	Day	19% 6% 1 4 3 3 4 3 5% 6% 46%	1710
	21st to end	Day	16% 7% 2 6% 3 4 4 4 4 7% 43%	1710
December	1st to 10th	Day	20% 7% 3 5% 4 4 4 4 6% 6% 37%	1535
	11th to 20th	Day	22% 7% 2 4 3 3 3 3 4 5% 45%	1906
	21st to end	Day	20% 11% 3 6% 4 3 4 3 4 6% 35%	2772
January	1st to 10th	Night	17% 6% 2 5% 3 3 4 3 4 6% 46%	4429
	11th to 20th	Night	17% 9% 4 8% 4 3 3 3 4 5% 41%	4440
	21st to end	Night	23% 12% 4 6% 5% 4 4 3 4 5% 31%	4884
February	1st to 10th	Night	17% 8% 3 6% 4 4 4 3 5% 5% 40%	2368
	11th to 20th	Night	16% 8% 2 6% 5% 4 4 4 5% 7% 40%	2218
	21st to end	Night	19% 10% 1 7% 5% 3 3 4 5% 5% 39%	1884
March	1st to 10th	Night	27% 11% 2 5% 4 3 3 3 5% 5% 33%	3724
	11th to 20th	Night	10% 8% 2 6% 5% 5% 5% 4 6% 8% 42%	3677
	21st to end	Night	23% 9% 2 5% 3 3 4 4 6% 5% 36%	3512
April	1st to 10th	Night	19% 7% 2 6% 5% 4 4 4 6% 6% 36%	1900
	11th to 20th	Night	19% 7% 3 6% 5% 3 4 3 5% 7% 38%	1875
	21st to end	Night	22% 7% 2 6% 3 3 3 3 4 6% 41%	1745
May	1st to 10th	Night	24% 10% 3 8% 4 4 4 4 5% 7% 28%	2834
	11th to 20th	Night	23% 9% 3 8% 5% 5% 5% 4 5% 8% 27%	2727
	21st to end	Night	18% 6% 2 5% 3 3 4 3 6% 7% 42%	2738
June	1st to 10th	Night	17% 7% 2 6% 4 3 4 5% 5% 7% 39%	1520
	11th to 20th	Night	18% 6% 2 6% 5% 3 4 3 6% 9% 38%	1520
	21st to end	Night	14% 7% 2 5% 5% 3 4 4 6% 9% 41%	1520
July	1st to 10th	Night	16% 6% 3 8% 5% 5% 5% 5% 6% 8% 34%	2520
	11th to 20th	Night	19% 6% 2 5% 4 3 4 4 7% 8% 38%	2520
	21st to end	Night	20% 9% 3 7% 5% 4 4 3 5% 6% 34%	2739
August	1st to 10th	Night	24% 7% 2 7% 4 4 5% 4 5% 7% 29%	2712
	11th to 20th	Night	12% 8% 3 7% 6% 5% 5% 5% 6% 7% 36%	2961
	21st to end	Night	9% 4 2 4 3 3 3 3 5% 7% 56%	3476
September	1st to 10th	Night	14% 6% 3 7% 4 4 4 5% 5% 6% 43%	1900
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 4 6% 52%	2065
	21st to end	Night	17% 7% 2 6% 4 4 4 3 4 6% 41%	2090
October	1st to 10th	Night	20% 7% 2 6% 4 3 3 3 4 6% 41%	2090
	11th to 20th	Night	15% 6% 2 5% 3 3 4 3 5% 6% 47%	2317
	21st to end	Night	21% 7% 2 6% 3 3 3 3 5% 5% 40%	2717
November	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2531
	11th to 20th	Night	19% 7% 2 5% 4 3 3 4 4 5% 45%	2470
	21st to end	Night	16% 6% 2 5% 4 3 4 3 5% 7% 45%	2470
December	1st to 10th	Night	21% 8% 2 6% 3 3 4 3 5% 6% 40%	2642
	11th to 20th	Night	21% 6% 2 5% 4 3 4 3 5% 6% 41%	3288
	21st to end	Night	22% 11% 3 6% 4 3 3 3 4 5% 38%	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	41% 5% 8% 32% 12% 2	2518
	11th to 20th	Day	48% 5% 10% 25% 11% 2	2520
	21st to end	Day	53% 4 9% 22% 10% 2	2772
February	1st to 10th	Day	48% 5% 13% 20% 14% 2	1808
	11th to 20th	Day	44% 5% 10% 22% 15% 3	1857
	21st to end	Day	50% 5% 10% 21% 13% 2	1570
March	1st to 10th	Day	55% 3 11% 16% 12% 2	3119
	11th to 20th	Day	38% 7% 13% 28% 13% 2	3280
	21st to end	Day	48% 5% 6% 17% 19% 5%	4116
April	1st to 10th	Day	47% 5% 10% 20% 15% 3	2280
	11th to 20th	Day	42% 5% 10% 21% 19% 3	2254
	21st to end	Day	47% 5% 9% 20% 16% 4	2433
May	1st to 10th	Day	54% 7% 13% 14% 11% 1	4120
	11th to 20th	Day	51% 7% 12% 18% 10% 2	4199
	21st to end	Day	36% 7% 12% 24% 19% 2	4837
June	1st to 10th	Day	46% 6% 12% 23% 12% 1	2660
	11th to 20th	Day	44% 7% 13% 22% 13% 2	2660
	21st to end	Day	43% 9% 12% 20% 15% 1	2660
July	1st to 10th	Day	47% 6% 11% 20% 15% 1	4370
	11th to 20th	Day	42% 6% 15% 23% 12% 2	4365
	21st to end	Day	50% 5% 11% 18% 14% 2	4661
August	1st to 10th	Day	51% 6% 15% 19% 8%	4170
	11th to 20th	Day	42% 5% 13% 29% 10% 1	3902
	21st to end	Day	36% 6% 11% 28% 17% 2	4180
September	1st to 10th	Day	40% 6% 10% 22% 20% 2	2280
	11th to 20th	Day	34% 5% 10% 24% 24% 3	2114
	21st to end	Day	43% 5% 8% 20% 21% 2	2090
October	1st to 10th	Day	40% 4 9% 20% 24% 4	3480
	11th to 20th	Day	31% 3 8% 25% 30% 4	3062
	21st to end	Day	34% 3 13% 27% 21% 3	3081
November	1st to 10th	Day	39% 5% 12% 21% 21% 2	1752
	11th to 20th	Day	38% 5% 11% 22% 20% 3	1710
	21st to end	Day	42% 4 10% 27% 13% 3	1710
December	1st to 10th	Day	47% 5% 13% 17% 16% 1	1535
	11th to 20th	Day	43% 4 14% 18% 18% 3	1906
	21st to end	Day	51% 5% 11% 22% 10% 1	2772
January	1st to 10th	Night	39% 3 11% 32% 12% 3	4429
	11th to 20th	Night	47% 4 11% 23% 12% 3	4440
	21st to end	Night	56% 4 9% 18% 11% 2	4884
February	1st to 10th	Night	45% 5% 12% 23% 12% 2	2368
	11th to 20th	Night	44% 5% 10% 20% 17% 4	2220
	21st to end	Night	47% 4 8% 23% 14% 4	1884
March	1st to 10th	Night	53% 5% 8% 21% 11% 2	3734
	11th to 20th	Night	39% 7% 15% 22% 15% 2	3678
	21st to end	Night	49% 4 6% 14% 22% 6%	3512
April	1st to 10th	Night	46% 6% 10% 20% 14% 3	1900
	11th to 20th	Night	46% 5% 9% 19% 18% 2	1875
	21st to end	Night	46% 5% 10% 21% 13% 5%	1745
May	1st to 10th	Night	54% 7% 14% 15% 8% 2	2840
	11th to 20th	Night	54% 9% 13% 14% 8% 2	2728
	21st to end	Night	40% 9% 15% 22% 14% 1	2739
June	1st to 10th	Night	44% 7% 12% 21% 15% 1	1520
	11th to 20th	Night	42% 7% 15% 24% 11% 1	1520
	21st to end	Night	40% 8% 14% 24% 13%	1520
July	1st to 10th	Night	47% 8% 12% 20% 12% 1	2480
	11th to 20th	Night	43% 6% 17% 24% 9% 1	2472
	21st to end	Night	50% 5% 12% 15% 16% 1	2651
August	1st to 10th	Night	55% 7% 11% 18% 8% 1	2702
	11th to 20th	Night	45% 7% 15% 25% 8%	2988
	21st to end	Night	28% 4 16% 31% 19% 1	3476
September	1st to 10th	Night	41% 7% 9% 24% 17% 1	1900
	11th to 20th	Night	34% 5% 10% 22% 27% 2	2065
	21st to end	Night	44% 6% 7% 20% 20% 3	2090
October	1st to 10th	Night	40% 4 12% 23% 19% 2	3480
	11th to 20th	Night	27% 4 8% 26% 32% 2	3853
	21st to end	Night	34% 3 13% 30% 19% 3	4467
November	1st to 10th	Night	37% 5% 11% 23% 21% 4	2531
	11th to 20th	Night	42% 4 10% 23% 19% 3	2470
	21st to end	Night	40% 4 14% 28% 13% 2	2470
December	1st to 10th	Night	46% 4 13% 21% 14% 1	2642
	11th to 20th	Night	45% 4 13% 19% 17% 2	3288
	21st to end	Night	50% 4 8% 25% 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	31% 23% 29% 15% 2	180
	11th to 20th	Day	38% 21% 29% 8% 3 1	180
	21st to end	Day	32% 21% 33% 10% 3 1	198
February	1st to 10th	Day	34% 24% 27% 14% 1	373
	11th to 20th	Day	33% 24% 32% 9% 2	456
	21st to end	Day	34% 22% 30% 10% 4	382
March	1st to 10th	Day	33% 20% 30% 14% 2	460
	11th to 20th	Day	33% 21% 31% 12% 3	460
	21st to end	Day	32% 21% 30% 10% 4 2	506
April	1st to 10th	Day	34% 24% 25% 12% 5% 1	460
	11th to 20th	Day	33% 19% 30% 14% 4	452
	21st to end	Day	32% 18% 31% 13% 4 2	460
May	1st to 10th	Day	35% 19% 27% 13% 5% 1	463
	11th to 20th	Day	25% 16% 37% 16% 5% 1	487
	21st to end	Day	23% 12% 32% 23% 7% 3	529
June	1st to 10th	Day	22% 13% 32% 21% 10% 2	490
	11th to 20th	Day	18% 15% 38% 21% 8% 1	490
	21st to end	Day	18% 14% 35% 22% 8% 2	490
July	1st to 10th	Day	19% 9% 28% 27% 14% 3	485
	11th to 20th	Day	15% 9% 30% 31% 12% 3	484
	21st to end	Day	16% 11% 34% 28% 9% 1	532
August	1st to 10th	Day	16% 9% 34% 27% 12% 3	486
	11th to 20th	Day	15% 10% 29% 29% 12% 5%	479
	21st to end	Day	11% 11% 32% 23% 15% 8%	539
September	1st to 10th	Day	19% 10% 28% 23% 14% 6%	490
	11th to 20th	Day	17% 12% 29% 20% 13% 9%	490
	21st to end	Day	22% 11% 36% 18% 9% 4	490
October	1st to 10th	Day	30% 13% 23% 21% 9% 5%	490
	11th to 20th	Day	21% 17% 30% 21% 8% 3	457
	21st to end	Day	27% 16% 30% 19% 6% 2	429
November	1st to 10th	Day	21% 17% 30% 20% 9% 3	392
	11th to 20th	Day	32% 19% 26% 17% 6%	370
	21st to end	Day	25% 18% 31% 19% 6% 1	370
December	1st to 10th	Day	28% 25% 29% 15% 4	195
	11th to 20th	Day	38% 22% 31% 7% 2	180
	21st to end	Day	31% 24% 28% 12% 3 2	198
January	1st to 10th	Night	24% 21% 36% 16% 3	760
	11th to 20th	Night	31% 19% 30% 18% 2	760
	21st to end	Night	25% 21% 32% 19% 3	836
February	1st to 10th	Night	26% 18% 34% 20% 2	760
	11th to 20th	Night	28% 24% 35% 12% 1	743
	21st to end	Night	31% 19% 32% 15% 3	628
March	1st to 10th	Night	28% 19% 33% 17% 3	760
	11th to 20th	Night	23% 23% 34% 17% 3	760
	21st to end	Night	28% 20% 34% 15% 3	836
April	1st to 10th	Night	26% 19% 33% 19% 2	760
	11th to 20th	Night	24% 20% 33% 20% 3	751
	21st to end	Night	27% 17% 36% 15% 5%	605
May	1st to 10th	Night	28% 16% 29% 21% 5%	570
	11th to 20th	Night	22% 17% 36% 21% 4	515
	21st to end	Night	21% 9% 32% 30% 7% 1	411
June	1st to 10th	Night	19% 7% 34% 31% 9%	380
	11th to 20th	Night	19% 10% 31% 33% 6% 1	380
	21st to end	Night	18% 6% 33% 35% 8% 1	380
July	1st to 10th	Night	16% 6% 28% 35% 15%	370
	11th to 20th	Night	15% 4 25% 41% 15%	368
	21st to end	Night	16% 6% 29% 39% 9%	416
August	1st to 10th	Night	12% 6% 32% 39% 10% 1	493
	11th to 20th	Night	14% 6% 26% 38% 15% 1	663
	21st to end	Night	15% 5% 24% 34% 20% 2	836
September	1st to 10th	Night	16% 6% 33% 32% 12% 1	760
	11th to 20th	Night	16% 10% 25% 30% 16% 3	760
	21st to end	Night	20% 8% 31% 26% 14% 2	760
October	1st to 10th	Night	25% 9% 28% 24% 11% 2	760
	11th to 20th	Night	19% 13% 32% 25% 9% 1	760
	21st to end	Night	29% 14% 30% 20% 8%	836
November	1st to 10th	Night	19% 14% 33% 25% 9% 1	779
	11th to 20th	Night	25% 18% 32% 19% 6% 1	760
	21st to end	Night	25% 17% 31% 21% 6%	760
December	1st to 10th	Night	30% 16% 30% 18% 5%	760
	11th to 20th	Night	27% 20% 31% 20% 3	760
	21st to end	Night	28% 17% 34% 17% 2	836

Page generated at 2024-11-07 06:55:49. Version ac07

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