Greg's Happy Place
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greg's Happy Place clear sky chart from 2005-11-06 to 2025-12-18.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 31%	126559
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 32%	124463
Transparency	Day	50% 6% 10% 21% 12% 2	130190
	Night	51% 5% 10% 20% 12% 2	128901
Seeing	Day	22% 16% 27% 20% 11% 4	16145
	Night	21% 13% 27% 26% 12% 1	26144

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	15% 20% 7% 22% 5% 3 3 2 3 5% 16%	4056
	11th to 20th	Day	12% 23% 9% 14% 8% 5% 4 2 3 3 17%	4060
	21st to end	Day	20% 19% 7% 10% 8% 6% 4 3 4 4 15%	4466
February	1st to 10th	Day	20% 17% 5% 10% 6% 4 3 3 4 4 24%	1800
	11th to 20th	Day	16% 14% 6% 13% 5% 4 4 3 5% 6% 24%	1808
	21st to end	Day	19% 16% 4 9% 5% 4 3 2 4 6% 29%	1650
March	1st to 10th	Day	16% 14% 6% 9% 4 4 4 3 4 5% 29%	4888
	11th to 20th	Day	12% 8% 3 9% 5% 5% 5% 4 5% 6% 39%	4980
	21st to end	Day	19% 10% 4 8% 5% 4 4 4 6% 6% 30%	5465
April	1st to 10th	Day	15% 14% 4 8% 5% 4 4 3 5% 7% 30%	2247
	11th to 20th	Day	15% 10% 3 8% 5% 5% 5% 3 5% 7% 35%	2483
	21st to end	Day	18% 8% 2 8% 5% 4 5% 4 5% 7% 33%	2600
May	1st to 10th	Day	20% 9% 3 9% 5% 5% 5% 5% 6% 6% 26%	5862
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 8% 29%	5861
	21st to end	Day	17% 7% 2 7% 5% 5% 5% 4 7% 8% 31%	6433
June	1st to 10th	Day	12% 8% 3 6% 5% 5% 5% 5% 7% 8% 36%	2755
	11th to 20th	Day	12% 7% 2 8% 5% 5% 5% 5% 7% 9% 35%	2800
	21st to end	Day	11% 6% 2 6% 5% 6% 6% 5% 8% 9% 36%	2692
July	1st to 10th	Day	10% 7% 2 7% 5% 5% 5% 4 6% 9% 41%	5900
	11th to 20th	Day	11% 7% 2 8% 5% 6% 6% 5% 7% 10% 34%	5900
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 4 7% 9% 36%	6424
August	1st to 10th	Day	12% 6% 2 7% 6% 6% 6% 5% 8% 9% 33%	4234
	11th to 20th	Day	11% 6% 3 7% 5% 5% 6% 6% 7% 9% 36%	4174
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 7% 10% 44%	4543
September	1st to 10th	Day	14% 6% 2 5% 4 3 4 4 5% 7% 46%	2310
	11th to 20th	Day	8% 6% 2 6% 4 5% 4 4 5% 8% 48%	2200
	21st to end	Day	19% 8% 3 7% 5% 4 4 4 4 7% 35%	2200
October	1st to 10th	Day	12% 7% 3 5% 5% 4 5% 5% 5% 6% 45%	2053
	11th to 20th	Day	16% 9% 2 7% 5% 4 5% 4 5% 5% 38%	2000
	21st to end	Day	22% 10% 3 6% 4 4 4 3 4 6% 35%	2200
November	1st to 10th	Day	11% 10% 3 6% 4 4 4 3 4 6% 45%	1907
	11th to 20th	Day	17% 14% 4 7% 5% 4 4 3 5% 6% 32%	1890
	21st to end	Day	18% 14% 6% 10% 5% 3 4 3 4 6% 26%	1689
December	1st to 10th	Day	19% 13% 5% 15% 5% 4 4 3 4 4 24%	2680
	11th to 20th	Day	23% 17% 6% 11% 5% 3 3 2 4 4 22%	3046
	21st to end	Day	21% 21% 5% 12% 6% 6% 4 3 4 5% 15%	4303
January	1st to 10th	Night	15% 18% 8% 22% 6% 4 4 3 3 4 15%	5889
	11th to 20th	Night	15% 19% 8% 15% 8% 6% 5% 3 3 4 14%	5900
	21st to end	Night	21% 16% 6% 13% 6% 4 4 2 3 4 22%	6490
February	1st to 10th	Night	19% 14% 5% 11% 5% 5% 4 3 4 5% 25%	2600
	11th to 20th	Night	19% 15% 4 12% 5% 5% 4 4 4 5% 23%	2476
	21st to end	Night	19% 14% 5% 11% 5% 5% 4 3 5% 4 25%	1980
March	1st to 10th	Night	21% 12% 4 8% 4 4 3 2 4 5% 32%	4963
	11th to 20th	Night	11% 10% 4 8% 4 4 4 3 6% 7% 38%	4980
	21st to end	Night	17% 10% 3 8% 5% 4 4 3 5% 6% 34%	5467
April	1st to 10th	Night	19% 13% 3 6% 4 3 5% 3 5% 6% 32%	2152
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 4 5% 8% 35%	1882
	21st to end	Night	14% 9% 3 8% 4 4 4 3 5% 9% 37%	1800
May	1st to 10th	Night	26% 13% 3 8% 5% 4 5% 3 5% 5% 24%	4033
	11th to 20th	Night	16% 10% 3 6% 4 4 4 4 6% 9% 36%	4032
	21st to end	Night	16% 8% 2 7% 4 5% 5% 4 6% 9% 34%	4421
June	1st to 10th	Night	8% 7% 3 7% 4 4 5% 4 5% 8% 44%	1640
	11th to 20th	Night	10% 6% 2 6% 4 5% 4 4 7% 12% 40%	1600
	21st to end	Night	10% 5% 2 5% 6% 5% 5% 4 7% 8% 44%	1698
July	1st to 10th	Night	10% 8% 3 7% 4 4 4 4 6% 8% 42%	4058
	11th to 20th	Night	12% 7% 2 6% 5% 5% 5% 4 7% 9% 38%	4057
	21st to end	Night	7% 7% 3 7% 5% 5% 5% 4 7% 8% 41%	4427
August	1st to 10th	Night	9% 7% 4 7% 5% 5% 5% 5% 7% 9% 36%	2915
	11th to 20th	Night	13% 8% 2 7% 4 4 5% 4 4 7% 43%	2875
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 8% 9% 45%	3322
September	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 5% 6% 52%	2087
	11th to 20th	Night	9% 4 1 4 3 3 4 3 6% 8% 53%	2200
	21st to end	Night	15% 7% 2 7% 5% 3 5% 3 5% 6% 42%	2200
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	2345
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 4 5% 6% 41%	2400
	21st to end	Night	22% 9% 2 6% 4 3 4 3 5% 7% 37%	2640
November	1st to 10th	Night	12% 9% 2 6% 4 4 3 3 5% 7% 46%	2607
	11th to 20th	Night	17% 12% 3 8% 5% 4 4 3 5% 6% 33%	2730
	21st to end	Night	19% 15% 4 8% 5% 4 4 4 4 6% 28%	2927
December	1st to 10th	Night	18% 13% 7% 14% 5% 5% 5% 4 5% 6% 20%	4720
	11th to 20th	Night	19% 19% 7% 11% 4 3 3 3 4 5% 22%	5304
	21st to end	Night	21% 19% 6% 10% 5% 4 4 3 4 5% 18%	6646

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	72% 4 9% 10% 5%	4057
	11th to 20th	Day	74% 3 6% 9% 6% 2	4060
	21st to end	Day	73% 3 6% 11% 6%	4466
February	1st to 10th	Day	64% 4 9% 14% 9% 1	1800
	11th to 20th	Day	62% 4 8% 17% 8% 1	1817
	21st to end	Day	59% 3 10% 17% 8% 3	1650
March	1st to 10th	Day	57% 4 8% 23% 8% 1	4888
	11th to 20th	Day	44% 4 10% 29% 10% 2	4980
	21st to end	Day	53% 4 8% 20% 13% 1	5465
April	1st to 10th	Day	53% 5% 10% 18% 10% 3	2247
	11th to 20th	Day	49% 5% 11% 17% 15% 2	2483
	21st to end	Day	50% 6% 9% 21% 12% 2	2600
May	1st to 10th	Day	55% 7% 9% 18% 8% 3	5897
	11th to 20th	Day	51% 7% 10% 21% 11% 1	5865
	21st to end	Day	47% 8% 12% 21% 10% 3	6447
June	1st to 10th	Day	42% 8% 13% 23% 13% 1	2755
	11th to 20th	Day	43% 9% 12% 23% 12% 1	2800
	21st to end	Day	41% 9% 13% 22% 14% 1	2692
July	1st to 10th	Day	39% 6% 11% 27% 16% 2	5835
	11th to 20th	Day	43% 8% 13% 23% 12%	5831
	21st to end	Day	42% 7% 11% 20% 18% 2	6240
August	1st to 10th	Day	44% 8% 14% 24% 10%	4221
	11th to 20th	Day	40% 8% 11% 29% 12%	4213
	21st to end	Day	33% 8% 12% 31% 13% 2	4543
September	1st to 10th	Day	37% 5% 11% 22% 21% 4	2310
	11th to 20th	Day	34% 5% 13% 27% 18% 3	2200
	21st to end	Day	49% 5% 9% 21% 16% 1	2200
October	1st to 10th	Day	30% 5% 9% 33% 22% 1	3339
	11th to 20th	Day	42% 5% 12% 22% 16% 5%	3240
	21st to end	Day	38% 4 11% 26% 19% 1	3538
November	1st to 10th	Day	40% 4 10% 26% 16% 3	1907
	11th to 20th	Day	53% 4 10% 20% 11% 2	1890
	21st to end	Day	60% 3 10% 17% 8% 1	1689
December	1st to 10th	Day	64% 4 13% 15% 4	2680
	11th to 20th	Day	67% 3 11% 15% 5%	3042
	21st to end	Day	73% 4 8% 11% 4	4303
January	1st to 10th	Night	74% 4 6% 12% 4	5889
	11th to 20th	Night	74% 4 8% 10% 5%	5900
	21st to end	Night	67% 3 9% 14% 6% 2	6490
February	1st to 10th	Night	63% 4 9% 16% 8% 1	2600
	11th to 20th	Night	63% 4 8% 16% 8% 1	2478
	21st to end	Night	62% 4 9% 15% 9% 2	1980
March	1st to 10th	Night	55% 4 7% 23% 11% 1	4963
	11th to 20th	Night	44% 5% 11% 29% 9% 3	4980
	21st to end	Night	50% 4 9% 21% 13% 2	5467
April	1st to 10th	Night	52% 5% 10% 18% 13% 2	2152
	11th to 20th	Night	45% 6% 12% 17% 16% 3	1882
	21st to end	Night	45% 5% 12% 22% 15% 2	1800
May	1st to 10th	Night	60% 6% 9% 14% 8% 4	4060
	11th to 20th	Night	46% 7% 9% 25% 12% 1	4033
	21st to end	Night	44% 8% 12% 24% 9% 3	4429
June	1st to 10th	Night	37% 7% 11% 24% 18% 3	1640
	11th to 20th	Night	36% 8% 14% 23% 16% 2	1600
	21st to end	Night	36% 8% 12% 24% 17% 2	1698
July	1st to 10th	Night	39% 6% 9% 25% 18% 3	4015
	11th to 20th	Night	40% 9% 16% 23% 12% 1	4006
	21st to end	Night	38% 7% 11% 20% 21% 3	4297
August	1st to 10th	Night	42% 9% 13% 24% 11% 1	2904
	11th to 20th	Night	40% 6% 9% 24% 20% 1	2902
	21st to end	Night	31% 8% 14% 31% 14% 2	3322
September	1st to 10th	Night	34% 5% 10% 22% 23% 6%	2087
	11th to 20th	Night	28% 6% 13% 27% 25% 2	2200
	21st to end	Night	43% 6% 10% 21% 19% 1	2200
October	1st to 10th	Night	32% 4 8% 27% 27% 2	3839
	11th to 20th	Night	36% 5% 11% 23% 17% 8%	3899
	21st to end	Night	35% 3 8% 28% 24% 3	4252
November	1st to 10th	Night	39% 4 11% 24% 19% 4	2607
	11th to 20th	Night	53% 4 9% 20% 12% 3	2730
	21st to end	Night	58% 4 10% 20% 7% 1	2927
December	1st to 10th	Night	65% 5% 10% 17% 4 1	4720
	11th to 20th	Night	65% 3 14% 14% 3	5307
	21st to end	Night	68% 5% 9% 13% 5%	6646

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	32% 26% 29% 9% 4	300
	11th to 20th	Day	35% 29% 29% 6% 1	300
	21st to end	Day	33% 32% 29% 5% 2	330
February	1st to 10th	Day	33% 27% 30% 8% 2	300
	11th to 20th	Day	41% 25% 28% 5% 1	300
	21st to end	Day	35% 29% 31% 5%	249
March	1st to 10th	Day	29% 24% 29% 15% 3	477
	11th to 20th	Day	31% 22% 30% 12% 4 1	500
	21st to end	Day	34% 20% 30% 13% 3 1	550
April	1st to 10th	Day	31% 21% 28% 14% 5% 1	500
	11th to 20th	Day	26% 22% 26% 16% 7% 3	492
	21st to end	Day	25% 21% 32% 15% 6% 2	500
May	1st to 10th	Day	27% 22% 27% 16% 6% 2	503
	11th to 20th	Day	21% 17% 32% 18% 9% 4	527
	21st to end	Day	17% 12% 26% 24% 15% 5%	573
June	1st to 10th	Day	15% 11% 30% 28% 12% 3	530
	11th to 20th	Day	15% 13% 25% 29% 12% 5%	530
	21st to end	Day	15% 10% 30% 26% 16% 4	530
July	1st to 10th	Day	14% 7% 22% 27% 18% 11%	525
	11th to 20th	Day	11% 8% 26% 30% 17% 9%	524
	21st to end	Day	13% 9% 22% 30% 17% 9%	576
August	1st to 10th	Day	13% 5% 22% 31% 21% 9%	526
	11th to 20th	Day	13% 8% 20% 32% 18% 9%	519
	21st to end	Day	9% 6% 26% 28% 22% 9%	583
September	1st to 10th	Day	15% 9% 22% 26% 20% 8%	530
	11th to 20th	Day	10% 4 18% 31% 27% 11%	530
	21st to end	Day	24% 11% 25% 21% 14% 4	530
October	1st to 10th	Day	13% 11% 27% 27% 18% 4	530
	11th to 20th	Day	21% 15% 31% 22% 9% 2	530
	21st to end	Day	28% 16% 32% 16% 7%	583
November	1st to 10th	Day	21% 19% 35% 16% 7% 2	385
	11th to 20th	Day	32% 18% 32% 12% 5% 1	330
	21st to end	Day	31% 23% 34% 10% 2	224
December	1st to 10th	Day	31% 25% 31% 8% 4 1	220
	11th to 20th	Day	32% 24% 30% 12% 2	214
	21st to end	Day	39% 20% 31% 9% 1	295
January	1st to 10th	Night	29% 22% 32% 14% 3	800
	11th to 20th	Night	31% 21% 30% 16% 2	800
	21st to end	Night	27% 23% 30% 17% 2	880
February	1st to 10th	Night	30% 17% 31% 21% 2	800
	11th to 20th	Night	30% 22% 32% 15% 1	783
	21st to end	Night	28% 19% 33% 17% 2	660
March	1st to 10th	Night	26% 18% 32% 21% 4	800
	11th to 20th	Night	25% 19% 29% 21% 5% 1	800
	21st to end	Night	27% 17% 32% 19% 5%	880
April	1st to 10th	Night	27% 17% 30% 21% 6%	800
	11th to 20th	Night	20% 16% 35% 19% 10% 1	698
	21st to end	Night	20% 10% 36% 27% 6% 1	600
May	1st to 10th	Night	21% 14% 26% 27% 11% 1	600
	11th to 20th	Night	20% 8% 27% 31% 13% 1	591
	21st to end	Night	11% 5% 23% 37% 21% 2	650
June	1st to 10th	Night	10% 5% 28% 38% 18%	440
	11th to 20th	Night	13% 5% 24% 41% 18% 1	400
	21st to end	Night	11% 4 23% 39% 22% 2	498
July	1st to 10th	Night	11% 4 16% 38% 25% 6%	585
	11th to 20th	Night	9% 4 19% 34% 30% 4	582
	21st to end	Night	9% 4 17% 39% 29% 2	657
August	1st to 10th	Night	8% 3 16% 41% 28% 3	597
	11th to 20th	Night	11% 3 15% 37% 29% 5%	594
	21st to end	Night	10% 3 18% 31% 31% 6%	720
September	1st to 10th	Night	12% 5% 20% 30% 28% 5%	800
	11th to 20th	Night	9% 4 16% 38% 29% 5%	800
	21st to end	Night	18% 7% 24% 28% 19% 3	800
October	1st to 10th	Night	16% 8% 20% 32% 21% 4	800
	11th to 20th	Night	21% 11% 30% 27% 10% 1	800
	21st to end	Night	26% 12% 29% 25% 7% 1	880
November	1st to 10th	Night	18% 13% 29% 29% 11%	820
	11th to 20th	Night	26% 17% 29% 21% 6% 1	840
	21st to end	Night	30% 14% 30% 22% 4	840
December	1st to 10th	Night	31% 18% 29% 18% 4	840
	11th to 20th	Night	28% 18% 31% 18% 4	829
	21st to end	Night	33% 16% 32% 18% 2	880

Page generated at 2025-12-15 01:13:56. Version ac07

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