Mahoney State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mahoney State Park clear sky chart from 2005-11-06 to 2025-06-10.

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	11% 7% 3 7% 4 4 4 3 5% 7% 45%	119463
	Night	10% 7% 2 6% 4 4 4 3 5% 7% 48%	118984
Transparency	Day	37% 6% 13% 25% 17% 2	123143
	Night	35% 5% 13% 26% 19% 3	123434
Seeing	Day	14% 9% 30% 30% 14% 3	16569
	Night	13% 9% 33% 34% 10% 1	26520

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	10% 12% 5% 15% 7% 6% 4 3 4 6% 28%	4077
	11th to 20th	Day	7% 9% 4 10% 5% 5% 6% 4 5% 5% 42%	4080
	21st to end	Day	6% 10% 4 11% 6% 5% 4 3 5% 7% 39%	4488
February	1st to 10th	Day	10% 12% 5% 8% 6% 5% 4 3 6% 7% 34%	1800
	11th to 20th	Day	10% 10% 3 9% 5% 3 5% 4 5% 7% 40%	1800
	21st to end	Day	11% 8% 3 6% 4 4 4 3 6% 7% 45%	1650
March	1st to 10th	Day	15% 8% 3 6% 3 2 2 2 3 4 52%	4851
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 4 7% 52%	4980
	21st to end	Day	17% 11% 4 8% 4 4 5% 4 6% 7% 31%	5462
April	1st to 10th	Day	15% 9% 2 6% 4 3 4 3 4 6% 44%	2250
	11th to 20th	Day	15% 8% 3 5% 4 4 4 4 4 6% 41%	2497
	21st to end	Day	19% 7% 3 6% 4 4 4 3 5% 6% 38%	2600
May	1st to 10th	Day	12% 8% 3 6% 4 4 4 3 5% 7% 45%	5862
	11th to 20th	Day	13% 7% 2 5% 3 3 3 2 4 6% 50%	5862
	21st to end	Day	17% 7% 3 6% 4 4 4 4 6% 7% 37%	6523
June	1st to 10th	Day	7% 5% 2 5% 4 4 5% 5% 6% 9% 49%	2787
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 7% 8% 47%	2660
	21st to end	Day	6% 5% 2 5% 5% 5% 4 4 6% 8% 50%	2650
July	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 45%	4120
	11th to 20th	Day	7% 4 2 5% 4 4 4 3 6% 8% 53%	4120
	21st to end	Day	4 3 1 4 4 4 4 4 7% 10% 54%	4465
August	1st to 10th	Day	6% 4 2 5% 4 5% 5% 5% 7% 11% 46%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	4041
	21st to end	Day	6% 5% 2 7% 4 4 5% 4 5% 8% 51%	4468
September	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 4 6% 54%	2193
	11th to 20th	Day	10% 5% 2 5% 3 4 3 3 5% 7% 54%	2090
	21st to end	Day	10% 4 1 4 3 3 3 3 4 6% 58%	2090
October	1st to 10th	Day	13% 6% 2 4 3 3 3 3 4 6% 52%	1952
	11th to 20th	Day	11% 6% 1 5% 4 3 3 3 3 4 57%	1900
	21st to end	Day	12% 8% 2 6% 3 3 4 3 5% 6% 47%	2090
November	1st to 10th	Day	9% 8% 2 4 3 3 4 3 5% 6% 53%	1779
	11th to 20th	Day	10% 6% 3 7% 5% 4 4 3 4 5% 49%	1765
	21st to end	Day	11% 9% 3 6% 4 3 3 4 5% 7% 44%	1600
December	1st to 10th	Day	5% 5% 2 6% 5% 5% 4 4 4 5% 54%	2610
	11th to 20th	Day	8% 9% 3 10% 5% 5% 4 3 6% 6% 42%	3008
	21st to end	Day	16% 11% 5% 13% 4 4 3 3 4 6% 31%	4189
January	1st to 10th	Night	10% 10% 4 18% 8% 5% 4 4 5% 6% 26%	5888
	11th to 20th	Night	6% 8% 3 8% 5% 4 6% 4 6% 7% 42%	5900
	21st to end	Night	9% 11% 5% 9% 5% 4 4 3 4 6% 42%	6490
February	1st to 10th	Night	10% 11% 4 8% 6% 4 5% 4 5% 5% 39%	2600
	11th to 20th	Night	9% 9% 3 8% 5% 5% 5% 4 6% 6% 42%	2503
	21st to end	Night	9% 8% 2 6% 3 4 3 3 5% 6% 51%	1980
March	1st to 10th	Night	13% 6% 2 6% 4 3 3 3 4 6% 52%	4995
	11th to 20th	Night	10% 6% 2 4 2 3 3 3 4 6% 57%	4980
	21st to end	Night	14% 11% 2 7% 4 4 4 4 5% 8% 36%	5467
April	1st to 10th	Night	12% 8% 2 5% 4 4 3 3 6% 6% 47%	2150
	11th to 20th	Night	11% 8% 2 6% 4 3 4 3 5% 8% 47%	1848
	21st to end	Night	17% 7% 2 6% 3 3 4 3 4 5% 46%	1800
May	1st to 10th	Night	13% 6% 2 4 4 3 4 3 4 6% 50%	4053
	11th to 20th	Night	13% 4 2 4 3 3 2 3 5% 6% 55%	4053
	21st to end	Night	17% 7% 2 6% 4 3 3 3 5% 7% 43%	4336
June	1st to 10th	Night	6% 4 2 5% 5% 4 4 4 6% 8% 54%	1597
	11th to 20th	Night	7% 4 2 4 3 4 4 5% 8% 10% 50%	1520
	21st to end	Night	4 3 1 4 3 4 4 4 7% 9% 57%	1524
July	1st to 10th	Night	7% 6% 2 6% 3 3 4 4 5% 8% 52%	2850
	11th to 20th	Night	4 3 1 3 2 2 4 3 6% 8% 63%	2850
	21st to end	Night	3 2 1 3 3 3 4 4 7% 11% 59%	3098
August	1st to 10th	Night	3 3 1 3 4 3 4 3 5% 10% 59%	2836
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 8% 51%	2798
	21st to end	Night	7% 4 2 5% 3 3 4 3 5% 8% 56%	3197
September	1st to 10th	Night	8% 4 2 4 3 2 3 3 5% 7% 61%	1984
	11th to 20th	Night	8% 3 1 3 3 2 3 3 5% 8% 59%	2090
	21st to end	Night	9% 5% 1 4 3 3 4 2 4 5% 60%	2090
October	1st to 10th	Night	12% 5% 2 4 3 4 4 4 5% 6% 51%	2208
	11th to 20th	Night	12% 5% 1 4 3 3 3 2 4 6% 57%	2280
	21st to end	Night	13% 7% 2 4 3 3 3 3 4 5% 52%	2508
November	1st to 10th	Night	9% 4 1 4 3 3 3 4 5% 7% 56%	2516
	11th to 20th	Night	9% 7% 2 6% 4 3 3 2 5% 6% 53%	2632
	21st to end	Night	11% 7% 3 5% 3 3 3 3 4 6% 52%	2800
December	1st to 10th	Night	5% 5% 2 6% 4 4 4 3 5% 7% 55%	4580
	11th to 20th	Night	9% 8% 3 8% 4 3 4 3 5% 7% 46%	5199
	21st to end	Night	16% 13% 5% 10% 4 3 3 3 4 5% 34%	6784

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	57% 6% 11% 19% 7%	4078
	11th to 20th	Day	43% 5% 13% 20% 16% 2	4080
	21st to end	Day	45% 6% 13% 23% 12% 1	4488
February	1st to 10th	Day	48% 7% 16% 18% 10% 1	1800
	11th to 20th	Day	44% 6% 12% 21% 14% 3	1809
	21st to end	Day	37% 6% 14% 25% 16% 3	1650
March	1st to 10th	Day	38% 4 8% 27% 18% 6%	4851
	11th to 20th	Day	33% 5% 8% 26% 23% 5%	4980
	21st to end	Day	50% 8% 20% 16% 5% 1	5464
April	1st to 10th	Day	41% 5% 13% 25% 14% 2	2250
	11th to 20th	Day	41% 7% 13% 23% 13% 3	2497
	21st to end	Day	46% 7% 11% 23% 13% 1	2600
May	1st to 10th	Day	36% 7% 12% 25% 18% 2	5900
	11th to 20th	Day	36% 5% 9% 22% 24% 4	5866
	21st to end	Day	43% 8% 12% 22% 15% 1	6537
June	1st to 10th	Day	30% 8% 17% 29% 13% 2	2787
	11th to 20th	Day	32% 8% 13% 30% 15% 1	2660
	21st to end	Day	31% 8% 15% 28% 14% 4	2650
July	1st to 10th	Day	37% 4 15% 29% 13% 1	4056
	11th to 20th	Day	29% 5% 13% 32% 18% 3	4051
	21st to end	Day	23% 6% 19% 29% 21% 2	4325
August	1st to 10th	Day	30% 8% 16% 27% 17% 2	4090
	11th to 20th	Day	38% 6% 15% 25% 15% 1	4080
	21st to end	Day	31% 6% 16% 25% 17% 6%	4467
September	1st to 10th	Day	31% 5% 11% 29% 18% 5%	2193
	11th to 20th	Day	30% 5% 12% 32% 19% 1	2090
	21st to end	Day	28% 5% 10% 31% 25% 1	2090
October	1st to 10th	Day	21% 4 7% 19% 47% 3	3238
	11th to 20th	Day	21% 3 13% 30% 26% 7%	3140
	21st to end	Day	35% 4 10% 28% 21% 3	3428
November	1st to 10th	Day	32% 4 15% 27% 19% 3	1779
	11th to 20th	Day	36% 7% 13% 24% 19% 1	1765
	21st to end	Day	39% 5% 12% 29% 13% 1	1600
December	1st to 10th	Day	33% 3 17% 28% 17% 1	2610
	11th to 20th	Day	43% 5% 17% 25% 10%	3005
	21st to end	Day	55% 5% 12% 21% 7% 1	4189
January	1st to 10th	Night	57% 7% 10% 15% 10%	5888
	11th to 20th	Night	39% 6% 14% 23% 17% 1	5900
	21st to end	Night	43% 5% 14% 20% 16% 2	6490
February	1st to 10th	Night	46% 5% 14% 20% 13% 2	2600
	11th to 20th	Night	41% 6% 15% 21% 15% 3	2504
	21st to end	Night	33% 6% 11% 25% 20% 5%	1980
March	1st to 10th	Night	34% 5% 8% 28% 23% 3	4995
	11th to 20th	Night	29% 4 7% 25% 28% 7%	4980
	21st to end	Night	45% 8% 18% 22% 6% 1	5467
April	1st to 10th	Night	37% 6% 11% 26% 17% 3	2150
	11th to 20th	Night	35% 7% 12% 26% 17% 3	1848
	21st to end	Night	40% 6% 13% 23% 17% 1	1800
May	1st to 10th	Night	35% 5% 10% 26% 21% 2	4080
	11th to 20th	Night	31% 5% 12% 20% 27% 5%	4054
	21st to end	Night	41% 7% 12% 23% 16% 2	4344
June	1st to 10th	Night	26% 8% 14% 32% 16% 3	1597
	11th to 20th	Night	26% 9% 15% 27% 19% 5%	1520
	21st to end	Night	22% 8% 15% 31% 21% 3	1524
July	1st to 10th	Night	31% 5% 14% 30% 17% 3	2805
	11th to 20th	Night	19% 5% 15% 36% 22% 3	2796
	21st to end	Night	18% 7% 17% 31% 24% 2	2999
August	1st to 10th	Night	22% 5% 16% 35% 20% 2	2826
	11th to 20th	Night	33% 4 16% 28% 18% 2	2825
	21st to end	Night	27% 5% 16% 26% 17% 9%	3197
September	1st to 10th	Night	25% 4 12% 28% 23% 7%	1984
	11th to 20th	Night	23% 7% 13% 34% 20% 4	2090
	21st to end	Night	27% 4 8% 28% 28% 5%	2090
October	1st to 10th	Night	20% 4 7% 16% 47% 6%	3689
	11th to 20th	Night	22% 2 8% 30% 30% 8%	3779
	21st to end	Night	33% 3 9% 30% 23% 2	4120
November	1st to 10th	Night	27% 6% 14% 25% 24% 4	2516
	11th to 20th	Night	32% 4 12% 29% 19% 3	2632
	21st to end	Night	35% 4 12% 28% 19% 2	2800
December	1st to 10th	Night	29% 4 16% 34% 17% 1	4580
	11th to 20th	Night	38% 5% 15% 29% 13%	5201
	21st to end	Night	53% 5% 11% 23% 8% 1	6784

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	17% 14% 38% 22% 8% 2	300
	11th to 20th	Day	19% 14% 35% 25% 6% 1	300
	21st to end	Day	12% 15% 45% 20% 7% 2	330
February	1st to 10th	Day	17% 17% 43% 21% 2	300
	11th to 20th	Day	16% 15% 39% 22% 6% 1	300
	21st to end	Day	15% 19% 38% 23% 5%	249
March	1st to 10th	Day	17% 15% 41% 23% 4 1	300
	11th to 20th	Day	27% 8% 35% 21% 7% 2	300
	21st to end	Day	30% 16% 35% 17% 2	330
April	1st to 10th	Day	20% 17% 41% 18% 4	350
	11th to 20th	Day	21% 16% 37% 20% 6%	615
	21st to end	Day	22% 18% 30% 21% 8% 2	700
May	1st to 10th	Day	18% 12% 32% 26% 11% 2	703
	11th to 20th	Day	17% 10% 31% 27% 13% 2	725
	21st to end	Day	18% 9% 29% 28% 15% 2	789
June	1st to 10th	Day	7% 5% 24% 35% 24% 5%	726
	11th to 20th	Day	10% 6% 28% 36% 16% 4	680
	21st to end	Day	7% 7% 31% 36% 15% 3	680
July	1st to 10th	Day	9% 4 15% 33% 29% 9%	671
	11th to 20th	Day	5% 4 22% 40% 22% 7%	668
	21st to end	Day	6% 1 18% 42% 29% 4	739
August	1st to 10th	Day	6% 2 21% 43% 24% 4	676
	11th to 20th	Day	9% 2 18% 42% 25% 4	665
	21st to end	Day	9% 2 23% 35% 26% 5%	710
September	1st to 10th	Day	12% 4 27% 36% 17% 4	403
	11th to 20th	Day	7% 3 30% 36% 20% 5%	300
	21st to end	Day	14% 8% 31% 28% 16% 4	300
October	1st to 10th	Day	20% 6% 26% 29% 14% 6%	300
	11th to 20th	Day	11% 16% 40% 22% 10% 1	300
	21st to end	Day	18% 14% 38% 20% 8% 2	330
November	1st to 10th	Day	17% 13% 35% 25% 9% 2	300
	11th to 20th	Day	16% 16% 38% 22% 8%	300
	21st to end	Day	20% 13% 33% 25% 8% 1	300
December	1st to 10th	Day	8% 13% 41% 30% 6% 2	300
	11th to 20th	Day	15% 15% 34% 29% 7%	300
	21st to end	Day	20% 14% 40% 21% 4 1	330
January	1st to 10th	Night	12% 11% 36% 34% 6%	1000
	11th to 20th	Night	14% 13% 37% 30% 6%	1000
	21st to end	Night	16% 8% 39% 32% 5%	1100
February	1st to 10th	Night	16% 10% 41% 29% 4	1000
	11th to 20th	Night	13% 10% 44% 28% 5%	949
	21st to end	Night	14% 13% 44% 25% 5%	660
March	1st to 10th	Night	14% 13% 39% 27% 7%	639
	11th to 20th	Night	18% 10% 38% 27% 6%	600
	21st to end	Night	21% 11% 40% 22% 5%	660
April	1st to 10th	Night	16% 16% 40% 24% 5%	600
	11th to 20th	Night	15% 14% 39% 28% 3 1	593
	21st to end	Night	19% 11% 35% 27% 7%	600
May	1st to 10th	Night	17% 10% 34% 31% 9%	600
	11th to 20th	Night	15% 9% 31% 36% 9% 1	591
	21st to end	Night	18% 7% 30% 31% 14% 1	650
June	1st to 10th	Night	7% 3 26% 46% 17%	599
	11th to 20th	Night	8% 4 32% 43% 13% 1	570
	21st to end	Night	5% 4 32% 46% 14%	570
July	1st to 10th	Night	8% 2 17% 43% 30% 1	555
	11th to 20th	Night	3 2 17% 51% 26% 1	552
	21st to end	Night	3 14% 55% 25% 1	624
August	1st to 10th	Night	4 2 20% 49% 23% 2	567
	11th to 20th	Night	8% 2 16% 49% 24% 1	564
	21st to end	Night	8% 2 22% 41% 25% 3	627
September	1st to 10th	Night	9% 3 23% 43% 20% 2	570
	11th to 20th	Night	10% 1 30% 41% 17% 1	570
	21st to end	Night	11% 5% 31% 35% 16% 1	570
October	1st to 10th	Night	14% 8% 30% 35% 12% 2	688
	11th to 20th	Night	15% 10% 36% 32% 8%	760
	21st to end	Night	18% 10% 31% 32% 9%	836
November	1st to 10th	Night	11% 10% 33% 37% 9% 1	956
	11th to 20th	Night	13% 12% 39% 31% 6%	1000
	21st to end	Night	15% 11% 35% 30% 8% 1	1000
December	1st to 10th	Night	12% 11% 39% 32% 6%	1000
	11th to 20th	Night	16% 9% 35% 33% 6%	1000
	21st to end	Night	20% 12% 33% 31% 5%	1100

Page generated at 2025-06-07 09:28:18. Version ac07

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