Hamilton Branch State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hamilton Branch State Park 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	13% 6% 2 6% 4 4 4 4 6% 8% 42%	101163
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 43%	97962
Transparency	Day	20% 48% 7% 11% 10% 4	104918
	Night	21% 48% 6% 10% 11% 5%	102346
Seeing	Day	15% 9% 24% 25% 19% 8%	15210
	Night	15% 9% 23% 31% 19% 3	25250

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	16% 6% 2 5% 3 4 4 3 6% 7% 44%	2836
	11th to 20th	Day	13% 5% 2 5% 3 3 3 2 4 6% 53%	2840
	21st to end	Day	20% 7% 2 6% 4 3 3 3 4 5% 43%	3124
February	1st to 10th	Day	16% 6% 2 6% 4 4 4 5% 6% 7% 39%	1824
	11th to 20th	Day	20% 8% 2 5% 3 3 3 3 4 6% 43%	1848
	21st to end	Day	18% 5% 2 7% 3 4 4 3 4 6% 42%	1570
March	1st to 10th	Day	21% 9% 3 8% 4 3 3 2 4 5% 38%	3425
	11th to 20th	Day	11% 5% 2 4 4 3 4 3 5% 7% 53%	3480
	21st to end	Day	19% 6% 2 5% 4 4 4 3 4 5% 42%	3815
April	1st to 10th	Day	10% 5% 2 5% 4 4 5% 4 5% 7% 50%	2090
	11th to 20th	Day	11% 5% 2 7% 4 4 4 3 6% 7% 48%	2182
	21st to end	Day	8% 4 2 5% 4 4 5% 4 5% 8% 52%	2470
May	1st to 10th	Day	9% 6% 2 7% 4 4 4 4 6% 10% 43%	4082
	11th to 20th	Day	16% 7% 3 7% 4 4 4 4 5% 6% 39%	4081
	21st to end	Day	7% 4 2 4 4 5% 5% 4 7% 11% 48%	4476
June	1st to 10th	Day	9% 7% 2 6% 6% 6% 5% 5% 8% 11% 36%	2470
	11th to 20th	Day	6% 5% 1 6% 4 5% 6% 6% 8% 10% 44%	2470
	21st to end	Day	6% 4 2 5% 6% 6% 6% 6% 8% 11% 41%	2470
July	1st to 10th	Day	11% 6% 3 8% 6% 6% 7% 5% 9% 10% 30%	4120
	11th to 20th	Day	6% 5% 2 6% 6% 6% 7% 6% 8% 14% 35%	4120
	21st to end	Day	9% 8% 3 8% 6% 7% 7% 7% 10% 13% 23%	4466
August	1st to 10th	Day	17% 7% 3 7% 6% 5% 6% 6% 7% 11% 27%	4104
	11th to 20th	Day	10% 5% 2 5% 4 5% 6% 5% 9% 11% 38%	4044
	21st to end	Day	6% 5% 2 5% 4 5% 4 4 7% 10% 49%	4072
September	1st to 10th	Day	8% 4 2 6% 5% 5% 6% 5% 7% 9% 41%	2090
	11th to 20th	Day	14% 6% 3 6% 5% 5% 4 3 6% 8% 40%	2090
	21st to end	Day	15% 7% 2 5% 4 4 4 3 6% 7% 43%	2090
October	1st to 10th	Day	12% 7% 2 6% 3 3 3 2 4 6% 52%	2055
	11th to 20th	Day	12% 4 1 4 2 3 2 3 4 6% 60%	1900
	21st to end	Day	11% 5% 2 5% 3 4 4 2 4 4 58%	2090
November	1st to 10th	Day	14% 5% 2 6% 3 3 3 3 4 6% 51%	1957
	11th to 20th	Day	14% 6% 2 4 3 3 3 2 5% 6% 54%	1715
	21st to end	Day	15% 5% 2 5% 4 4 3 4 5% 6% 48%	1710
December	1st to 10th	Day	17% 7% 2 7% 5% 4 3 4 6% 6% 38%	1710
	11th to 20th	Day	17% 4 1 5% 4 3 3 3 5% 6% 49%	2153
	21st to end	Day	20% 8% 2 5% 3 3 4 3 5% 7% 41%	3124
January	1st to 10th	Night	17% 5% 2 6% 4 3 3 3 4 6% 46%	4109
	11th to 20th	Night	11% 6% 2 5% 4 4 5% 4 7% 7% 46%	4120
	21st to end	Night	20% 8% 2 6% 4 3 3 3 3 3 44%	4532
February	1st to 10th	Night	16% 7% 2 5% 4 3 4 4 5% 6% 45%	2352
	11th to 20th	Night	19% 6% 2 6% 4 4 3 3 4 5% 45%	2218
	21st to end	Night	14% 7% 2 6% 3 4 4 4 5% 6% 44%	1884
March	1st to 10th	Night	21% 9% 3 6% 4 3 4 3 4 6% 36%	3428
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 6% 7% 52%	3480
	21st to end	Night	18% 6% 2 6% 4 3 4 4 5% 6% 42%	3817
April	1st to 10th	Night	11% 5% 2 4 4 3 4 4 6% 7% 49%	2090
	11th to 20th	Night	11% 6% 2 4 4 3 3 3 4 7% 52%	1961
	21st to end	Night	8% 5% 1 5% 4 4 4 3 6% 7% 53%	1710
May	1st to 10th	Night	10% 6% 3 7% 4 5% 5% 4 6% 10% 41%	2813
	11th to 20th	Night	14% 6% 3 5% 4 4 5% 4 5% 8% 41%	2812
	21st to end	Night	6% 3 2 5% 4 5% 4 4 6% 11% 49%	3079
June	1st to 10th	Night	10% 7% 2 7% 4 6% 6% 5% 7% 12% 32%	1710
	11th to 20th	Night	7% 5% 2 6% 5% 6% 5% 5% 7% 12% 41%	1710
	21st to end	Night	6% 6% 2 6% 5% 5% 7% 6% 9% 12% 35%	1710
July	1st to 10th	Night	14% 8% 3 9% 6% 5% 6% 5% 7% 10% 28%	2840
	11th to 20th	Night	7% 6% 2 7% 6% 6% 6% 7% 11% 13% 30%	2840
	21st to end	Night	12% 8% 3 10% 7% 6% 7% 6% 8% 12% 22%	3087
August	1st to 10th	Night	15% 7% 3 8% 6% 7% 7% 6% 8% 11% 23%	2825
	11th to 20th	Night	9% 5% 2 7% 5% 5% 5% 6% 8% 11% 37%	2785
	21st to end	Night	6% 4 2 5% 4 4 4 5% 7% 10% 48%	3545
September	1st to 10th	Night	10% 5% 3 6% 5% 4 6% 4 8% 9% 39%	2090
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 3 5% 8% 39%	2090
	21st to end	Night	15% 5% 2 6% 4 4 4 4 5% 7% 46%	2090
October	1st to 10th	Night	11% 6% 2 6% 2 4 4 3 5% 7% 51%	2123
	11th to 20th	Night	11% 4 2 5% 3 3 3 2 4 5% 58%	2280
	21st to end	Night	10% 4 1 4 4 4 4 2 3 6% 58%	2508
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 6% 53%	2341
	11th to 20th	Night	13% 7% 3 4 3 3 3 2 4 5% 52%	2469
	21st to end	Night	14% 5% 2 4 4 4 4 4 5% 7% 49%	2470
December	1st to 10th	Night	17% 6% 3 6% 3 3 4 3 6% 6% 44%	2470
	11th to 20th	Night	17% 5% 2 5% 3 3 3 2 4 5% 52%	3042
	21st to end	Night	19% 8% 3 6% 4 4 4 4 5% 6% 38%	4532

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	23% 38% 5% 14% 14% 5%	2837
	11th to 20th	Day	19% 37% 3 14% 19% 8%	2840
	21st to end	Day	27% 40% 2 10% 17% 5%	3124
February	1st to 10th	Day	15% 66% 3 8% 6% 2	1824
	11th to 20th	Day	16% 64% 2 7% 8% 2	1858
	21st to end	Day	18% 65% 3 3 6% 4	1570
March	1st to 10th	Day	37% 42% 4 6% 4 6%	3425
	11th to 20th	Day	15% 41% 4 10% 21% 9%	3480
	21st to end	Day	28% 40% 3 11% 15% 3	3815
April	1st to 10th	Day	12% 66% 4 6% 9% 3	2090
	11th to 20th	Day	16% 66% 4 5% 5% 3	2182
	21st to end	Day	12% 65% 4 9% 8% 1	2470
May	1st to 10th	Day	24% 44% 7% 17% 7% 1	4120
	11th to 20th	Day	29% 41% 5% 15% 9% 1	4085
	21st to end	Day	14% 43% 12% 13% 17% 1	4489
June	1st to 10th	Day	15% 68% 6% 6% 3 2	2470
	11th to 20th	Day	9% 68% 7% 9% 7%	2470
	21st to end	Day	13% 66% 8% 8% 5% 1	2470
July	1st to 10th	Day	30% 41% 13% 14% 2	4055
	11th to 20th	Day	21% 43% 20% 15% 1	4051
	21st to end	Day	35% 44% 11% 7% 2	4324
August	1st to 10th	Day	35% 41% 12% 11% 1	4091
	11th to 20th	Day	18% 43% 11% 15% 12% 1	4083
	21st to end	Day	10% 40% 10% 24% 14% 3	4072
September	1st to 10th	Day	13% 63% 7% 7% 7% 2	2090
	11th to 20th	Day	18% 62% 4 7% 7% 1	2090
	21st to end	Day	17% 62% 7% 8% 5% 1	2090
October	1st to 10th	Day	18% 38% 4 10% 22% 8%	3419
	11th to 20th	Day	7% 37% 2 9% 19% 27%	3140
	21st to end	Day	12% 37% 3 17% 22% 10%	3428
November	1st to 10th	Day	19% 57% 3 6% 10% 4	1957
	11th to 20th	Day	16% 59% 4 8% 9% 4	1715
	21st to end	Day	14% 60% 3 9% 11% 3	1710
December	1st to 10th	Day	21% 60% 3 7% 6% 3	1710
	11th to 20th	Day	17% 48% 3 10% 16% 7%	2150
	21st to end	Day	28% 38% 5% 13% 15% 1	3124
January	1st to 10th	Night	26% 38% 4 11% 15% 7%	4109
	11th to 20th	Night	21% 38% 4 15% 17% 5%	4120
	21st to end	Night	29% 40% 2 7% 18% 5%	4532
February	1st to 10th	Night	13% 64% 4 8% 8% 3	2352
	11th to 20th	Night	18% 64% 3 7% 8% 2	2219
	21st to end	Night	17% 65% 3 5% 5% 5%	1884
March	1st to 10th	Night	35% 43% 7% 8% 5% 2	3428
	11th to 20th	Night	17% 40% 3 7% 20% 13%	3480
	21st to end	Night	28% 41% 4 10% 9% 8%	3817
April	1st to 10th	Night	14% 66% 4 5% 7% 4	2090
	11th to 20th	Night	15% 65% 4 7% 5% 4	1961
	21st to end	Night	10% 66% 4 10% 7% 2	1710
May	1st to 10th	Night	22% 45% 9% 14% 8% 1	2840
	11th to 20th	Night	24% 41% 8% 15% 11% 1	2813
	21st to end	Night	13% 43% 9% 16% 16% 2	3087
June	1st to 10th	Night	16% 68% 6% 6% 3 1	1710
	11th to 20th	Night	10% 67% 8% 8% 6% 1	1710
	21st to end	Night	11% 68% 9% 8% 4	1710
July	1st to 10th	Night	33% 41% 14% 10% 2	2795
	11th to 20th	Night	25% 45% 16% 12% 1	2786
	21st to end	Night	39% 43% 10% 5% 2 1	2988
August	1st to 10th	Night	38% 42% 11% 7% 1	2814
	11th to 20th	Night	20% 44% 15% 14% 6% 1	2812
	21st to end	Night	11% 40% 12% 22% 14% 2	3545
September	1st to 10th	Night	14% 64% 7% 8% 6% 2	2090
	11th to 20th	Night	19% 61% 5% 7% 6% 1	2090
	21st to end	Night	15% 62% 6% 10% 6% 1	2090
October	1st to 10th	Night	19% 39% 6% 11% 21% 4	3539
	11th to 20th	Night	7% 36% 2 9% 17% 28%	3779
	21st to end	Night	11% 37% 3 14% 22% 14%	4120
November	1st to 10th	Night	19% 56% 3 7% 11% 4	2341
	11th to 20th	Night	15% 59% 3 7% 10% 6%	2469
	21st to end	Night	14% 60% 4 8% 11% 3	2470
December	1st to 10th	Night	20% 60% 4 7% 7% 2	2470
	11th to 20th	Night	17% 48% 2 9% 18% 5%	3044
	21st to end	Night	32% 38% 4 13% 13% 1	4532

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	20% 20% 41% 16% 3	270
	11th to 20th	Day	24% 20% 32% 20% 3	270
	21st to end	Day	23% 24% 37% 11% 4 1	297
February	1st to 10th	Day	23% 17% 38% 18% 4	270
	11th to 20th	Day	35% 17% 32% 16% 1	270
	21st to end	Day	26% 20% 39% 13% 3	225
March	1st to 10th	Day	21% 17% 31% 22% 8%	450
	11th to 20th	Day	19% 15% 41% 19% 7%	460
	21st to end	Day	21% 17% 36% 17% 9%	506
April	1st to 10th	Day	19% 13% 31% 25% 11%	460
	11th to 20th	Day	15% 13% 33% 23% 14% 2	452
	21st to end	Day	12% 12% 30% 27% 16% 4	460
May	1st to 10th	Day	11% 12% 31% 26% 15% 4	463
	11th to 20th	Day	15% 6% 23% 31% 16% 9%	487
	21st to end	Day	15% 4 18% 27% 24% 12%	529
June	1st to 10th	Day	11% 2 18% 30% 29% 9%	490
	11th to 20th	Day	7% 4 19% 28% 27% 16%	490
	21st to end	Day	7% 3 15% 35% 28% 12%	490
July	1st to 10th	Day	7% 3 11% 24% 32% 23%	485
	11th to 20th	Day	7% 2 9% 27% 37% 18%	484
	21st to end	Day	5% 3 8% 32% 38% 14%	532
August	1st to 10th	Day	11% 4 14% 27% 28% 15%	486
	11th to 20th	Day	11% 2 13% 25% 33% 16%	479
	21st to end	Day	11% 2 13% 27% 30% 17%	539
September	1st to 10th	Day	9% 2 13% 30% 33% 12%	490
	11th to 20th	Day	19% 4 12% 26% 28% 11%	490
	21st to end	Day	17% 6% 19% 25% 24% 10%	490
October	1st to 10th	Day	15% 6% 24% 29% 18% 9%	490
	11th to 20th	Day	12% 8% 23% 30% 21% 7%	490
	21st to end	Day	14% 8% 25% 27% 22% 4	539
November	1st to 10th	Day	21% 8% 25% 25% 17% 4	495
	11th to 20th	Day	19% 12% 41% 20% 7% 1	275
	21st to end	Day	13% 13% 35% 26% 12% 1	270
December	1st to 10th	Day	25% 16% 34% 19% 6% 1	270
	11th to 20th	Day	23% 16% 34% 19% 7% 1	270
	21st to end	Day	29% 15% 32% 15% 4 3	297
January	1st to 10th	Night	21% 16% 31% 26% 5%	760
	11th to 20th	Night	19% 17% 30% 26% 8%	760
	21st to end	Night	21% 18% 34% 23% 3	836
February	1st to 10th	Night	18% 16% 31% 29% 6%	760
	11th to 20th	Night	22% 15% 35% 25% 3	743
	21st to end	Night	20% 19% 30% 28% 3	628
March	1st to 10th	Night	17% 14% 34% 30% 5%	760
	11th to 20th	Night	17% 13% 36% 26% 8% 1	760
	21st to end	Night	17% 15% 32% 28% 8%	836
April	1st to 10th	Night	15% 15% 33% 28% 10%	760
	11th to 20th	Night	15% 14% 26% 31% 14%	737
	21st to end	Night	9% 8% 28% 39% 16%	570
May	1st to 10th	Night	11% 8% 26% 37% 17% 1	570
	11th to 20th	Night	10% 5% 26% 37% 21% 2	561
	21st to end	Night	11% 2 13% 40% 30% 4	617
June	1st to 10th	Night	12% 4 17% 36% 27% 4	570
	11th to 20th	Night	7% 3 14% 35% 32% 10%	570
	21st to end	Night	8% 3 13% 35% 34% 7%	570
July	1st to 10th	Night	11% 3 9% 31% 36% 10%	555
	11th to 20th	Night	9% 2 6% 32% 45% 7%	552
	21st to end	Night	9% 2 10% 31% 41% 7%	624
August	1st to 10th	Night	10% 2 7% 35% 37% 9%	567
	11th to 20th	Night	11% 2 10% 33% 39% 5%	564
	21st to end	Night	11% 2 13% 33% 36% 6%	725
September	1st to 10th	Night	11% 4 10% 34% 36% 6%	760
	11th to 20th	Night	14% 4 14% 27% 38% 3	760
	21st to end	Night	16% 4 17% 31% 28% 4	760
October	1st to 10th	Night	14% 4 19% 33% 25% 5%	760
	11th to 20th	Night	13% 6% 22% 34% 22% 3	760
	21st to end	Night	11% 8% 22% 33% 23% 2	836
November	1st to 10th	Night	14% 8% 25% 30% 20% 3	780
	11th to 20th	Night	16% 11% 30% 30% 12% 1	763
	21st to end	Night	17% 11% 27% 28% 16% 1	760
December	1st to 10th	Night	20% 13% 25% 31% 9% 1	760
	11th to 20th	Night	19% 11% 27% 29% 13% 1	760
	21st to end	Night	26% 14% 25% 28% 8%	836

Page generated at 2024-11-08 06:44:48. Version ac07

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