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 2025-12-03.

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%	126727
	Night	18% 8% 2 6% 4 3 4 3 5% 6% 40%	123989
Transparency	Day	45% 5% 11% 22% 15% 3	130260
	Night	44% 4 11% 22% 16% 3	128543
Seeing	Day	25% 16% 30% 18% 7% 2	16428
	Night	23% 15% 31% 23% 7% 1	25389

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	12% 8% 3 7% 4 4 4 3 5% 6% 44%	3597
	11th to 20th	Day	15% 8% 2 6% 4 3 4 4 5% 5% 44%	3570
	21st to end	Day	18% 9% 2 6% 4 3 4 3 4 5% 42%	3960
February	1st to 10th	Day	18% 8% 2 6% 4 4 6% 3 5% 6% 37%	1904
	11th to 20th	Day	14% 7% 2 6% 6% 4 5% 3 6% 7% 39%	1948
	21st to end	Day	20% 10% 3 6% 4 4 3 2 5% 5% 38%	1650
March	1st to 10th	Day	22% 10% 3 6% 3 3 3 2 4 5% 39%	4476
	11th to 20th	Day	15% 8% 2 5% 4 4 4 4 6% 7% 40%	4696
	21st to end	Day	23% 9% 2 5% 3 4 5% 3 6% 6% 33%	5892
April	1st to 10th	Day	20% 9% 2 5% 5% 3 4 4 5% 7% 36%	2400
	11th to 20th	Day	18% 7% 2 5% 4 4 4 3 5% 6% 41%	2374
	21st to end	Day	21% 6% 2 6% 4 5% 4 3 5% 6% 38%	2561
May	1st to 10th	Day	31% 8% 2 6% 4 4 4 3 5% 7% 25%	5886
	11th to 20th	Day	22% 8% 3 7% 4 5% 4 3 5% 6% 33%	6031
	21st to end	Day	21% 7% 2 6% 4 4 5% 4 5% 8% 34%	6949
June	1st to 10th	Day	19% 6% 2 6% 5% 4 5% 4 6% 9% 34%	2800
	11th to 20th	Day	17% 6% 2 6% 5% 5% 4 4 6% 9% 35%	2800
	21st to end	Day	16% 7% 2 7% 4 5% 4 4 7% 9% 36%	2800
July	1st to 10th	Day	17% 7% 3 6% 5% 5% 5% 5% 6% 9% 32%	6360
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 10% 34%	6360
	21st to end	Day	17% 6% 2 6% 4 4 4 3 5% 7% 41%	6926
August	1st to 10th	Day	19% 8% 3 6% 5% 5% 5% 4 6% 8% 31%	4317
	11th to 20th	Day	13% 7% 2 6% 5% 4 5% 4 6% 8% 40%	3987
	21st to end	Day	7% 4 2 7% 5% 5% 5% 4 7% 9% 44%	4312
September	1st to 10th	Day	15% 5% 2 6% 5% 5% 4 3 5% 5% 45%	2400
	11th to 20th	Day	14% 5% 2 5% 3 4 3 3 5% 6% 51%	2225
	21st to end	Day	18% 7% 2 6% 3 4 5% 3 5% 7% 40%	2200
October	1st to 10th	Day	22% 7% 2 5% 2 3 3 3 4 5% 44%	2200
	11th to 20th	Day	16% 6% 3 4 3 3 3 3 4 7% 48%	1957
	21st to end	Day	19% 7% 3 5% 4 3 3 3 5% 6% 42%	1980
November	1st to 10th	Day	13% 8% 2 6% 4 4 4 3 4 5% 49%	1851
	11th to 20th	Day	17% 6% 2 4 3 3 4 3 5% 6% 48%	1890
	21st to end	Day	17% 7% 2 6% 4 4 4 3 4 6% 43%	1890
December	1st to 10th	Day	15% 7% 3 5% 3 3 3 3 5% 6% 46%	2632
	11th to 20th	Day	20% 7% 2 4 3 3 3 3 4 5% 47%	2986
	21st to end	Day	21% 10% 3 6% 4 3 3 3 4 5% 39%	3960
January	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 7% 46%	6349
	11th to 20th	Night	15% 8% 3 8% 4 3 3 3 4 5% 43%	6315
	21st to end	Night	17% 9% 3 6% 5% 4 4 3 5% 6% 39%	6996
February	1st to 10th	Night	17% 8% 3 6% 4 4 4 3 5% 5% 40%	2492
	11th to 20th	Night	17% 7% 2 6% 4 4 4 4 5% 7% 40%	2338
	21st to end	Night	18% 9% 2 7% 5% 3 3 4 5% 5% 39%	1980
March	1st to 10th	Night	22% 9% 2 5% 3 3 4 3 5% 6% 39%	5364
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 5% 7% 40%	5261
	21st to end	Night	23% 9% 2 5% 4 4 4 4 5% 5% 35%	5036
April	1st to 10th	Night	20% 7% 2 6% 5% 4 4 4 6% 6% 36%	2000
	11th to 20th	Night	19% 7% 3 6% 5% 3 4 3 5% 7% 38%	1975
	21st to end	Night	21% 7% 2 6% 4 3 3 3 4 6% 41%	1837
May	1st to 10th	Night	29% 10% 3 7% 3 4 3 3 5% 7% 26%	4054
	11th to 20th	Night	21% 9% 3 8% 5% 4 4 4 5% 8% 28%	3905
	21st to end	Night	22% 8% 2 7% 4 4 4 4 6% 6% 33%	3926
June	1st to 10th	Night	17% 7% 3 6% 4 3 4 5% 5% 7% 38%	1600
	11th to 20th	Night	19% 7% 2 6% 5% 3 4 3 6% 9% 37%	1600
	21st to end	Night	14% 7% 2 5% 5% 3 4 4 6% 9% 41%	1600
July	1st to 10th	Night	18% 7% 3 7% 4 4 4 4 6% 8% 35%	3600
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 6% 8% 35%	3600
	21st to end	Night	16% 7% 2 6% 4 4 4 3 4 5% 44%	3926
August	1st to 10th	Night	24% 7% 2 7% 4 4 5% 4 5% 7% 30%	2798
	11th to 20th	Night	12% 8% 3 7% 6% 4 5% 5% 6% 7% 37%	3057
	21st to end	Night	9% 4 2 4 3 3 3 3 5% 7% 56%	3586
September	1st to 10th	Night	14% 6% 3 6% 4 4 4 5% 5% 6% 44%	2000
	11th to 20th	Night	13% 6% 2 5% 3 3 3 2 4 6% 52%	2174
	21st to end	Night	18% 8% 3 6% 4 4 4 3 4 6% 41%	2200
October	1st to 10th	Night	19% 7% 2 5% 4 3 3 3 4 6% 43%	2200
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 5% 6% 47%	2439
	21st to end	Night	21% 7% 2 6% 3 3 3 3 5% 5% 40%	2860
November	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2667
	11th to 20th	Night	18% 7% 2 5% 3 3 3 4 4 5% 46%	2730
	21st to end	Night	16% 7% 2 5% 4 3 4 3 5% 7% 45%	2730
December	1st to 10th	Night	18% 7% 2 5% 3 3 3 2 4 5% 47%	4590
	11th to 20th	Night	25% 7% 3 5% 3 3 3 3 4 4 41%	5208
	21st to end	Night	19% 10% 3 6% 4 3 3 3 4 5% 42%	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	41% 4 6% 29% 17% 3	3598
	11th to 20th	Day	41% 4 10% 22% 16% 8%	3600
	21st to end	Day	45% 3 10% 23% 18% 2	3960
February	1st to 10th	Day	47% 4 13% 19% 14% 2	1904
	11th to 20th	Day	45% 5% 10% 22% 15% 3	1957
	21st to end	Day	48% 5% 10% 20% 15% 2	1650
March	1st to 10th	Day	49% 3 10% 15% 13% 10%	4479
	11th to 20th	Day	42% 5% 13% 27% 11% 2	4696
	21st to end	Day	50% 4 6% 16% 18% 6%	5892
April	1st to 10th	Day	47% 5% 10% 20% 15% 4	2400
	11th to 20th	Day	43% 5% 10% 20% 19% 3	2374
	21st to end	Day	46% 5% 9% 20% 16% 4	2561
May	1st to 10th	Day	58% 6% 14% 13% 8% 1	5897
	11th to 20th	Day	52% 5% 12% 18% 11% 1	6035
	21st to end	Day	47% 6% 11% 21% 13% 1	6949
June	1st to 10th	Day	46% 6% 12% 23% 12% 1	2800
	11th to 20th	Day	44% 6% 13% 21% 13% 2	2800
	21st to end	Day	43% 9% 12% 20% 15% 1	2800
July	1st to 10th	Day	50% 6% 10% 20% 13% 1	6290
	11th to 20th	Day	44% 5% 16% 23% 10% 1	6285
	21st to end	Day	43% 4 10% 24% 18% 1	6728
August	1st to 10th	Day	50% 6% 15% 20% 8% 1	4303
	11th to 20th	Day	42% 5% 13% 29% 10% 1	4026
	21st to end	Day	36% 6% 11% 28% 18% 2	4312
September	1st to 10th	Day	40% 6% 10% 23% 19% 2	2400
	11th to 20th	Day	34% 5% 10% 24% 24% 3	2225
	21st to end	Day	44% 5% 9% 20% 21% 2	2200
October	1st to 10th	Day	39% 4 9% 20% 24% 4	3590
	11th to 20th	Day	31% 3 8% 25% 30% 4	3160
	21st to end	Day	34% 3 13% 27% 21% 3	3180
November	1st to 10th	Day	39% 5% 12% 21% 22% 2	1851
	11th to 20th	Day	37% 5% 10% 23% 21% 4	1890
	21st to end	Day	44% 4 10% 28% 13% 3	1890
December	1st to 10th	Day	40% 3 15% 28% 13% 1	2632
	11th to 20th	Day	41% 3 14% 18% 19% 5%	2986
	21st to end	Day	48% 4 7% 20% 15% 5%	3960
January	1st to 10th	Night	38% 3 9% 31% 17% 2	6349
	11th to 20th	Night	44% 4 12% 21% 14% 5%	6360
	21st to end	Night	48% 3 10% 17% 17% 4	6996
February	1st to 10th	Night	46% 5% 12% 23% 12% 2	2492
	11th to 20th	Night	45% 5% 9% 20% 17% 4	2340
	21st to end	Night	47% 4 8% 22% 14% 4	1980
March	1st to 10th	Night	47% 4 9% 18% 15% 6%	5374
	11th to 20th	Night	45% 5% 16% 21% 11% 3	5262
	21st to end	Night	51% 4 5% 13% 23% 5%	5036
April	1st to 10th	Night	47% 6% 10% 20% 14% 4	2000
	11th to 20th	Night	46% 5% 9% 19% 18% 2	1975
	21st to end	Night	46% 5% 10% 21% 14% 5%	1837
May	1st to 10th	Night	58% 6% 15% 12% 9% 1	4060
	11th to 20th	Night	53% 7% 13% 16% 9% 3	3906
	21st to end	Night	50% 7% 13% 19% 10%	3927
June	1st to 10th	Night	45% 7% 12% 21% 15% 1	1600
	11th to 20th	Night	44% 7% 15% 24% 11% 1	1600
	21st to end	Night	39% 8% 14% 24% 13% 1	1600
July	1st to 10th	Night	47% 6% 12% 22% 12% 1	3560
	11th to 20th	Night	47% 5% 17% 21% 9% 1	3552
	21st to end	Night	42% 4 12% 24% 17% 1	3809
August	1st to 10th	Night	54% 7% 11% 18% 9% 1	2788
	11th to 20th	Night	44% 7% 15% 26% 8%	3084
	21st to end	Night	28% 4 16% 31% 19% 2	3586
September	1st to 10th	Night	41% 6% 9% 25% 18% 1	2000
	11th to 20th	Night	34% 5% 10% 23% 27% 2	2174
	21st to end	Night	45% 6% 7% 20% 19% 3	2200
October	1st to 10th	Night	39% 4 12% 23% 19% 3	3590
	11th to 20th	Night	27% 4 9% 26% 32% 2	3975
	21st to end	Night	34% 3 12% 30% 19% 2	4610
November	1st to 10th	Night	37% 5% 11% 23% 21% 4	2667
	11th to 20th	Night	41% 4 9% 22% 20% 4	2730
	21st to end	Night	40% 3 13% 28% 13% 2	2730
December	1st to 10th	Night	41% 3 12% 30% 13% 1	4590
	11th to 20th	Night	48% 3 12% 15% 20% 2	5208
	21st to end	Night	46% 3 7% 22% 17% 4	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	33% 24% 28% 14% 2	200
	11th to 20th	Day	38% 21% 31% 8% 3 1	200
	21st to end	Day	33% 22% 31% 10% 3 1	220
February	1st to 10th	Day	34% 25% 27% 13% 1	409
	11th to 20th	Day	35% 23% 31% 9% 1	496
	21st to end	Day	32% 24% 30% 10% 4	414
March	1st to 10th	Day	34% 21% 30% 13% 2	500
	11th to 20th	Day	33% 20% 31% 13% 3	500
	21st to end	Day	33% 21% 30% 9% 4 2	550
April	1st to 10th	Day	37% 23% 24% 11% 4 1	500
	11th to 20th	Day	34% 20% 29% 13% 3	492
	21st to end	Day	32% 18% 32% 13% 4 2	500
May	1st to 10th	Day	35% 19% 27% 13% 5% 1	503
	11th to 20th	Day	25% 16% 37% 15% 5% 1	527
	21st to end	Day	24% 13% 32% 22% 6% 3	573
June	1st to 10th	Day	22% 13% 33% 21% 10% 2	530
	11th to 20th	Day	19% 15% 37% 21% 7% 1	530
	21st to end	Day	18% 14% 35% 23% 8% 2	530
July	1st to 10th	Day	20% 10% 28% 27% 13% 3	525
	11th to 20th	Day	15% 10% 30% 30% 12% 3	524
	21st to end	Day	16% 11% 34% 29% 9% 1	576
August	1st to 10th	Day	15% 9% 33% 27% 13% 3	526
	11th to 20th	Day	15% 10% 29% 29% 14% 5%	519
	21st to end	Day	11% 12% 34% 22% 14% 7%	583
September	1st to 10th	Day	19% 10% 29% 23% 13% 6%	530
	11th to 20th	Day	16% 11% 29% 22% 13% 8%	530
	21st to end	Day	22% 10% 36% 18% 10% 4	530
October	1st to 10th	Day	28% 12% 23% 22% 9% 5%	530
	11th to 20th	Day	22% 17% 29% 21% 8% 3	494
	21st to end	Day	28% 16% 29% 19% 6% 2	462
November	1st to 10th	Day	21% 18% 30% 19% 9% 2	425
	11th to 20th	Day	30% 20% 27% 17% 5%	430
	21st to end	Day	28% 19% 29% 18% 5% 1	430
December	1st to 10th	Day	27% 25% 30% 15% 3	220
	11th to 20th	Day	40% 22% 29% 8% 3	200
	21st to end	Day	31% 22% 29% 12% 4 2	220
January	1st to 10th	Night	25% 21% 35% 16% 3	800
	11th to 20th	Night	31% 19% 30% 18% 2	800
	21st to end	Night	24% 20% 33% 19% 3	880
February	1st to 10th	Night	26% 19% 33% 20% 2	800
	11th to 20th	Night	29% 23% 35% 12% 1	783
	21st to end	Night	30% 20% 32% 15% 3	660
March	1st to 10th	Night	29% 20% 33% 16% 3	800
	11th to 20th	Night	24% 22% 33% 17% 3	800
	21st to end	Night	28% 20% 35% 14% 3	880
April	1st to 10th	Night	27% 19% 33% 19% 2	800
	11th to 20th	Night	25% 21% 33% 19% 3	791
	21st to end	Night	26% 17% 36% 15% 5%	637
May	1st to 10th	Night	29% 15% 30% 21% 5%	600
	11th to 20th	Night	21% 17% 37% 21% 4	542
	21st to end	Night	22% 9% 32% 29% 7% 1	433
June	1st to 10th	Night	20% 7% 34% 31% 9%	400
	11th to 20th	Night	21% 10% 31% 33% 6% 1	400
	21st to end	Night	18% 6% 33% 35% 8% 1	400
July	1st to 10th	Night	16% 6% 28% 36% 14%	390
	11th to 20th	Night	15% 4 25% 40% 15%	388
	21st to end	Night	15% 6% 30% 39% 10%	438
August	1st to 10th	Night	13% 5% 31% 39% 11% 1	519
	11th to 20th	Night	14% 5% 26% 38% 15% 1	699
	21st to end	Night	15% 5% 25% 34% 19% 2	880
September	1st to 10th	Night	16% 6% 33% 31% 13% 1	800
	11th to 20th	Night	16% 9% 25% 31% 16% 3	800
	21st to end	Night	21% 8% 30% 26% 14% 2	800
October	1st to 10th	Night	25% 9% 28% 24% 12% 2	800
	11th to 20th	Night	20% 14% 32% 24% 9% 1	800
	21st to end	Night	28% 14% 30% 20% 8%	880
November	1st to 10th	Night	20% 14% 33% 25% 8% 1	820
	11th to 20th	Night	25% 19% 33% 18% 6%	840
	21st to end	Night	26% 17% 30% 22% 5%	840
December	1st to 10th	Night	29% 17% 30% 18% 5%	809
	11th to 20th	Night	28% 19% 31% 19% 3	800
	21st to end	Night	28% 17% 34% 19% 3	880

Page generated at 2025-11-30 01:00:52. Version ac07

Copyright © 2025 Attilla Danko.