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 2024-11-11.

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% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	100987
	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 33%	98117
Transparency	Day	49% 6% 11% 21% 12% 1	104662
	Night	49% 5% 10% 21% 12% 2	102581
Seeing	Day	22% 15% 28% 20% 11% 4	14752
	Night	21% 12% 27% 26% 12% 2	24696

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	18% 20% 7% 12% 5% 3 3 2 4 5% 20%	2836
	11th to 20th	Day	13% 24% 8% 13% 7% 4 3 3 3 3 18%	2840
	21st to end	Day	25% 21% 9% 11% 6% 4 3 2 3 4 12%	3124
February	1st to 10th	Day	20% 18% 5% 10% 6% 4 3 3 4 4 24%	1710
	11th to 20th	Day	15% 14% 6% 13% 5% 4 3 3 5% 6% 24%	1715
	21st to end	Day	19% 16% 4 9% 5% 4 3 2 4 5% 29%	1570
March	1st to 10th	Day	21% 15% 5% 8% 4 4 4 3 4 5% 25%	3402
	11th to 20th	Day	13% 9% 4 10% 5% 5% 5% 3 5% 6% 35%	3480
	21st to end	Day	21% 9% 3 7% 5% 4 4 3 5% 6% 32%	3815
April	1st to 10th	Day	14% 13% 4 8% 5% 4 4 3 6% 7% 31%	2134
	11th to 20th	Day	15% 10% 3 8% 5% 4 4 3 5% 6% 35%	2357
	21st to end	Day	19% 8% 2 8% 5% 4 5% 4 5% 7% 31%	2470
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 4 4 6% 6% 27%	4082
	11th to 20th	Day	19% 10% 3 7% 5% 4 5% 3 6% 7% 32%	4081
	21st to end	Day	11% 6% 2 7% 6% 5% 5% 4 7% 10% 35%	4476
June	1st to 10th	Day	12% 8% 3 6% 5% 5% 5% 5% 7% 9% 36%	2617
	11th to 20th	Day	12% 7% 2 7% 5% 5% 5% 5% 7% 9% 35%	2660
	21st to end	Day	11% 6% 3 6% 5% 6% 6% 5% 8% 9% 35%	2558
July	1st to 10th	Day	9% 7% 2 7% 5% 5% 6% 5% 7% 9% 39%	4120
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 42%	4120
	21st to end	Day	12% 8% 3 8% 5% 6% 5% 4 8% 9% 34%	4466
August	1st to 10th	Day	12% 6% 2 7% 6% 6% 6% 5% 8% 9% 33%	4104
	11th to 20th	Day	11% 6% 3 7% 5% 5% 6% 6% 8% 9% 35%	4044
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 7% 10% 44%	4404
September	1st to 10th	Day	15% 6% 2 5% 4 3 4 4 5% 8% 46%	2195
	11th to 20th	Day	9% 7% 2 6% 4 5% 4 4 5% 8% 47%	2090
	21st to end	Day	19% 8% 3 7% 5% 4 4 4 4 7% 36%	2090
October	1st to 10th	Day	12% 7% 3 5% 5% 4 5% 4 5% 6% 43%	1951
	11th to 20th	Day	16% 9% 2 7% 5% 4 4 4 5% 5% 37%	1900
	21st to end	Day	22% 10% 3 6% 4 4 4 2 4 6% 35%	2090
November	1st to 10th	Day	11% 10% 3 6% 4 4 4 3 4 6% 46%	1814
	11th to 20th	Day	16% 14% 4 7% 5% 4 4 3 5% 5% 33%	1710
	21st to end	Day	18% 13% 5% 9% 5% 3 5% 4 4 6% 28%	1529
December	1st to 10th	Day	21% 18% 6% 11% 5% 4 4 4 4 4 19%	1520
	11th to 20th	Day	19% 16% 7% 13% 5% 4 4 3 4 5% 22%	1910
	21st to end	Day	23% 22% 6% 10% 5% 5% 4 3 4 5% 14%	3003
January	1st to 10th	Night	16% 20% 8% 13% 5% 5% 4 3 3 4 19%	4109
	11th to 20th	Night	16% 19% 7% 16% 5% 5% 5% 3 4 5% 15%	4120
	21st to end	Night	26% 18% 6% 14% 5% 3 2 2 3 3 17%	4532
February	1st to 10th	Night	19% 14% 5% 11% 5% 5% 4 3 3 4 26%	2470
	11th to 20th	Night	18% 15% 5% 12% 5% 5% 4 4 4 5% 24%	2349
	21st to end	Night	20% 14% 5% 11% 5% 5% 4 3 5% 4 25%	1884
March	1st to 10th	Night	22% 12% 4 7% 4 4 3 2 4 6% 32%	3449
	11th to 20th	Night	14% 11% 5% 9% 5% 4 4 3 5% 6% 34%	3480
	21st to end	Night	19% 9% 2 7% 4 4 4 3 5% 6% 37%	3817
April	1st to 10th	Night	18% 13% 3 6% 4 3 5% 3 5% 6% 33%	2045
	11th to 20th	Night	17% 8% 3 6% 4 4 4 4 5% 8% 36%	1787
	21st to end	Night	14% 9% 3 8% 4 4 4 3 5% 9% 37%	1710
May	1st to 10th	Night	28% 11% 3 7% 5% 3 4 4 5% 5% 26%	2813
	11th to 20th	Night	17% 11% 2 6% 4 4 4 4 4 6% 38%	2812
	21st to end	Night	10% 6% 3 7% 5% 5% 5% 4 7% 10% 40%	3079
June	1st to 10th	Night	8% 7% 3 6% 4 4 5% 4 5% 9% 44%	1558
	11th to 20th	Night	9% 6% 2 5% 4 5% 4 4 7% 13% 40%	1520
	21st to end	Night	11% 5% 2 5% 5% 5% 4 4 7% 8% 44%	1613
July	1st to 10th	Night	10% 8% 3 7% 4 4 4 4 6% 8% 43%	2840
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 46%	2840
	21st to end	Night	8% 7% 2 7% 6% 5% 5% 5% 7% 7% 41%	3087
August	1st to 10th	Night	9% 7% 4 8% 5% 5% 5% 5% 8% 9% 35%	2825
	11th to 20th	Night	13% 8% 2 7% 4 4 5% 4 4 7% 43%	2785
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 8% 10% 46%	3220
September	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 5% 6% 51%	1982
	11th to 20th	Night	9% 5% 1 5% 3 3 4 3 6% 8% 53%	2090
	21st to end	Night	15% 7% 2 7% 5% 3 4 3 5% 6% 42%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2228
	11th to 20th	Night	15% 8% 3 6% 5% 4 4 4 5% 6% 39%	2280
	21st to end	Night	22% 9% 2 6% 4 4 4 3 4 7% 36%	2508
November	1st to 10th	Night	12% 9% 2 6% 4 4 3 3 5% 7% 46%	2480
	11th to 20th	Night	17% 12% 3 8% 5% 4 4 3 5% 6% 33%	2477
	21st to end	Night	18% 14% 4 8% 5% 4 4 4 5% 6% 29%	2647
December	1st to 10th	Night	22% 15% 6% 11% 5% 4 4 4 4 5% 21%	2660
	11th to 20th	Night	17% 18% 6% 10% 5% 3 4 3 5% 6% 24%	3285
	21st to end	Night	22% 20% 7% 10% 5% 4 3 2 5% 5% 16%	4646

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	66% 5% 10% 13% 6%	2837
	11th to 20th	Day	71% 4 7% 12% 5% 1	2840
	21st to end	Day	77% 3 6% 10% 3 1	3124
February	1st to 10th	Day	64% 4 9% 14% 9% 1	1710
	11th to 20th	Day	62% 5% 9% 17% 8% 1	1724
	21st to end	Day	60% 3 9% 17% 8% 3	1570
March	1st to 10th	Day	61% 5% 9% 20% 6%	3402
	11th to 20th	Day	49% 5% 10% 25% 9% 1	3480
	21st to end	Day	52% 4 9% 20% 13% 1	3815
April	1st to 10th	Day	52% 5% 11% 19% 10% 3	2134
	11th to 20th	Day	49% 5% 11% 17% 16% 3	2357
	21st to end	Day	50% 6% 9% 20% 12% 2	2470
May	1st to 10th	Day	55% 6% 9% 21% 8% 1	4120
	11th to 20th	Day	50% 7% 10% 21% 11% 1	4085
	21st to end	Day	42% 9% 14% 21% 11% 3	4489
June	1st to 10th	Day	42% 8% 13% 23% 12% 1	2617
	11th to 20th	Day	42% 9% 12% 23% 12% 1	2660
	21st to end	Day	42% 8% 13% 22% 14% 1	2558
July	1st to 10th	Day	41% 7% 12% 22% 16% 2	4055
	11th to 20th	Day	36% 7% 11% 28% 16% 1	4051
	21st to end	Day	44% 7% 11% 18% 17% 3	4324
August	1st to 10th	Day	44% 8% 13% 23% 10%	4091
	11th to 20th	Day	41% 8% 11% 28% 12%	4083
	21st to end	Day	34% 7% 12% 31% 13% 2	4404
September	1st to 10th	Day	38% 5% 11% 22% 21% 4	2195
	11th to 20th	Day	35% 6% 12% 27% 17% 3	2090
	21st to end	Day	49% 5% 8% 21% 16% 1	2090
October	1st to 10th	Day	30% 5% 9% 33% 21% 1	3237
	11th to 20th	Day	42% 5% 12% 21% 15% 5%	3140
	21st to end	Day	38% 4 12% 26% 20% 1	3428
November	1st to 10th	Day	40% 4 9% 27% 16% 3	1814
	11th to 20th	Day	53% 4 10% 20% 11% 2	1710
	21st to end	Day	58% 4 11% 18% 8% 1	1529
December	1st to 10th	Day	68% 5% 9% 15% 4	1520
	11th to 20th	Day	66% 3 9% 17% 5%	1906
	21st to end	Day	73% 5% 10% 8% 3	3003
January	1st to 10th	Night	68% 5% 8% 14% 5%	4109
	11th to 20th	Night	72% 4 10% 11% 3	4120
	21st to end	Night	74% 2 6% 13% 3 1	4532
February	1st to 10th	Night	63% 4 9% 16% 8% 1	2470
	11th to 20th	Night	62% 4 8% 17% 8% 1	2351
	21st to end	Night	63% 4 9% 14% 9% 2	1884
March	1st to 10th	Night	54% 4 8% 23% 11% 1	3449
	11th to 20th	Night	49% 6% 10% 27% 7% 1	3480
	21st to end	Night	47% 4 9% 27% 12% 2	3817
April	1st to 10th	Night	51% 5% 10% 19% 13% 2	2045
	11th to 20th	Night	45% 6% 12% 17% 17% 3	1787
	21st to end	Night	45% 5% 12% 21% 15% 2	1710
May	1st to 10th	Night	58% 6% 8% 18% 8% 2	2840
	11th to 20th	Night	47% 6% 9% 25% 12% 1	2813
	21st to end	Night	35% 9% 14% 25% 12% 4	3087
June	1st to 10th	Night	37% 8% 11% 24% 18% 3	1558
	11th to 20th	Night	34% 9% 15% 24% 16% 2	1520
	21st to end	Night	36% 8% 13% 24% 17% 2	1613
July	1st to 10th	Night	38% 6% 10% 24% 17% 4	2795
	11th to 20th	Night	34% 8% 12% 28% 16% 1	2786
	21st to end	Night	39% 8% 10% 20% 19% 4	2988
August	1st to 10th	Night	43% 9% 13% 24% 11% 1	2814
	11th to 20th	Night	41% 6% 9% 23% 20% 1	2812
	21st to end	Night	31% 8% 14% 31% 14% 2	3220
September	1st to 10th	Night	35% 5% 10% 22% 22% 6%	1982
	11th to 20th	Night	28% 6% 13% 26% 25% 2	2090
	21st to end	Night	42% 6% 10% 22% 19% 1	2090
October	1st to 10th	Night	32% 4 8% 27% 26% 2	3722
	11th to 20th	Night	37% 5% 11% 23% 16% 8%	3779
	21st to end	Night	35% 3 8% 28% 24% 3	4120
November	1st to 10th	Night	39% 4 11% 24% 18% 4	2480
	11th to 20th	Night	52% 4 9% 20% 13% 2	2477
	21st to end	Night	56% 4 11% 20% 7% 1	2647
December	1st to 10th	Night	65% 5% 9% 15% 5% 1	2660
	11th to 20th	Night	62% 4 12% 18% 5%	3288
	21st to end	Night	70% 5% 9% 12% 3	4646

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% 25% 30% 10% 4	270
	11th to 20th	Day	35% 27% 30% 7% 1	270
	21st to end	Day	33% 31% 29% 4 2	297
February	1st to 10th	Day	33% 25% 31% 9% 2	270
	11th to 20th	Day	40% 26% 29% 5% 1	270
	21st to end	Day	37% 29% 28% 5%	225
March	1st to 10th	Day	29% 23% 29% 15% 4	438
	11th to 20th	Day	30% 22% 30% 13% 4 1	460
	21st to end	Day	33% 20% 30% 14% 3 1	506
April	1st to 10th	Day	28% 22% 28% 15% 6% 1	460
	11th to 20th	Day	26% 21% 27% 15% 8% 3	452
	21st to end	Day	25% 21% 32% 14% 5% 2	460
May	1st to 10th	Day	27% 22% 25% 16% 6% 3	463
	11th to 20th	Day	21% 16% 32% 17% 9% 4	487
	21st to end	Day	15% 11% 27% 26% 17% 5%	529
June	1st to 10th	Day	15% 10% 29% 29% 13% 3	490
	11th to 20th	Day	14% 13% 25% 29% 13% 6%	490
	21st to end	Day	15% 11% 31% 25% 14% 3	490
July	1st to 10th	Day	14% 7% 22% 27% 18% 12%	485
	11th to 20th	Day	11% 7% 27% 29% 17% 9%	484
	21st to end	Day	13% 8% 23% 30% 17% 10%	532
August	1st to 10th	Day	14% 5% 21% 30% 21% 9%	486
	11th to 20th	Day	14% 8% 21% 32% 16% 9%	479
	21st to end	Day	9% 6% 25% 29% 23% 9%	539
September	1st to 10th	Day	14% 8% 23% 27% 19% 8%	490
	11th to 20th	Day	10% 4 19% 31% 26% 10%	490
	21st to end	Day	24% 11% 25% 21% 14% 5%	490
October	1st to 10th	Day	14% 11% 29% 26% 17% 4	490
	11th to 20th	Day	22% 14% 29% 22% 10% 2	490
	21st to end	Day	29% 15% 31% 17% 8%	539
November	1st to 10th	Day	21% 19% 34% 16% 7% 3	352
	11th to 20th	Day	30% 17% 32% 14% 6% 1	270
	21st to end	Day	27% 24% 36% 11% 2	184
December	1st to 10th	Day	31% 24% 32% 7% 5% 1	180
	11th to 20th	Day	29% 25% 33% 11% 2	180
	21st to end	Day	38% 20% 31% 9% 2	265
January	1st to 10th	Night	29% 22% 32% 15% 3	760
	11th to 20th	Night	31% 20% 30% 16% 3	760
	21st to end	Night	27% 23% 30% 17% 2	836
February	1st to 10th	Night	29% 17% 30% 22% 2	760
	11th to 20th	Night	29% 22% 32% 15% 1	743
	21st to end	Night	29% 20% 33% 17% 2	628
March	1st to 10th	Night	25% 18% 32% 21% 4	760
	11th to 20th	Night	25% 19% 29% 21% 5% 1	760
	21st to end	Night	27% 17% 32% 19% 6%	836
April	1st to 10th	Night	26% 16% 31% 21% 6%	760
	11th to 20th	Night	20% 16% 35% 20% 10% 1	663
	21st to end	Night	20% 10% 37% 27% 6% 1	570
May	1st to 10th	Night	21% 13% 26% 27% 12% 1	570
	11th to 20th	Night	21% 8% 26% 31% 13% 1	561
	21st to end	Night	10% 5% 23% 37% 22% 3	617
June	1st to 10th	Night	10% 5% 28% 37% 19%	418
	11th to 20th	Night	12% 4 24% 41% 18% 1	380
	21st to end	Night	11% 4 23% 40% 20% 1	473
July	1st to 10th	Night	11% 4 17% 37% 25% 6%	555
	11th to 20th	Night	8% 4 20% 35% 29% 4	552
	21st to end	Night	9% 4 17% 39% 29% 2	624
August	1st to 10th	Night	9% 2 16% 41% 29% 3	567
	11th to 20th	Night	11% 3 15% 38% 27% 5%	564
	21st to end	Night	10% 3 19% 30% 31% 7%	684
September	1st to 10th	Night	13% 5% 19% 30% 28% 5%	760
	11th to 20th	Night	10% 4 17% 37% 28% 5%	760
	21st to end	Night	18% 7% 25% 27% 19% 3	760
October	1st to 10th	Night	16% 8% 21% 32% 20% 4	760
	11th to 20th	Night	21% 12% 29% 26% 11% 1	760
	21st to end	Night	27% 12% 28% 25% 8% 1	836
November	1st to 10th	Night	18% 13% 29% 29% 12%	780
	11th to 20th	Night	25% 17% 29% 22% 7% 1	763
	21st to end	Night	28% 14% 30% 23% 4 1	760
December	1st to 10th	Night	32% 17% 29% 18% 4	760
	11th to 20th	Night	28% 18% 32% 19% 4	760
	21st to end	Night	32% 16% 32% 18% 2	836

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