Blackbird State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blackbird State Forest clear sky chart from 2005-11-06 to 2024-11-08.

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	14% 6% 2 6% 4 4 5% 4 6% 8% 42%	101266
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	97790
Transparency	Day	38% 7% 12% 24% 16% 3	104870
	Night	40% 6% 11% 23% 17% 3	102325
Seeing	Day	17% 12% 27% 24% 14% 5%	15056
	Night	18% 9% 30% 30% 12% 1	24393

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	14% 7% 2 4 4 3 3 3 5% 6% 49%	2517
	11th to 20th	Day	15% 9% 3 7% 4 5% 5% 3 4 5% 40%	2689
	21st to end	Day	19% 8% 3 6% 4 3 4 4 5% 6% 38%	3124
February	1st to 10th	Day	14% 7% 3 6% 4 4 4 4 6% 7% 41%	1710
	11th to 20th	Day	16% 7% 2 5% 4 4 5% 3 5% 7% 43%	1796
	21st to end	Day	17% 9% 3 6% 3 4 4 3 4 7% 40%	1570
March	1st to 10th	Day	24% 6% 2 4 3 4 4 3 4 6% 40%	3183
	11th to 20th	Day	9% 4 2 4 3 4 5% 4 6% 7% 52%	3480
	21st to end	Day	21% 6% 2 5% 4 4 4 3 4 5% 43%	4001
April	1st to 10th	Day	13% 7% 2 5% 4 4 5% 4 5% 7% 43%	2280
	11th to 20th	Day	12% 6% 2 5% 4 3 4 4 5% 8% 47%	2254
	21st to end	Day	16% 5% 2 6% 4 4 4 5% 5% 8% 41%	2280
May	1st to 10th	Day	25% 8% 3 6% 4 4 4 3 5% 7% 30%	3957
	11th to 20th	Day	23% 7% 3 6% 5% 4 4 4 5% 7% 31%	4398
	21st to end	Day	10% 5% 2 5% 4 4 4 3 7% 10% 46%	4823
June	1st to 10th	Day	10% 5% 2 6% 4 4 6% 5% 8% 11% 40%	2660
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 7% 9% 42%	2660
	21st to end	Day	9% 4 2 5% 4 3 5% 4 7% 11% 46%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 11% 41%	4440
	11th to 20th	Day	10% 5% 2 5% 5% 5% 5% 5% 8% 11% 40%	4440
	21st to end	Day	8% 6% 3 8% 6% 6% 6% 6% 8% 11% 33%	4605
August	1st to 10th	Day	15% 6% 2 6% 4 5% 5% 5% 7% 11% 34%	4104
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 3 7% 10% 43%	3739
	21st to end	Day	8% 5% 2 5% 5% 4 5% 4 6% 8% 48%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 5% 4 4 6% 7% 44%	2280
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 5% 7% 50%	2269
	21st to end	Day	19% 7% 3 6% 4 4 5% 3 5% 6% 38%	2062
October	1st to 10th	Day	17% 6% 1 4 3 4 4 3 5% 7% 46%	1900
	11th to 20th	Day	16% 4 2 4 3 3 4 3 5% 7% 50%	1900
	21st to end	Day	15% 6% 2 6% 4 3 3 2 4 5% 49%	2067
November	1st to 10th	Day	12% 5% 2 4 4 4 3 3 5% 7% 51%	1734
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 5% 7% 48%	1710
	21st to end	Day	14% 6% 3 5% 3 3 4 3 5% 6% 47%	1592
December	1st to 10th	Day	16% 6% 2 6% 4 4 5% 3 5% 7% 42%	1520
	11th to 20th	Day	18% 8% 2 5% 3 3 4 3 5% 7% 43%	1910
	21st to end	Day	14% 7% 2 6% 5% 5% 4 3 7% 7% 39%	2772
January	1st to 10th	Night	17% 7% 2 5% 4 3 4 3 4 5% 44%	4429
	11th to 20th	Night	18% 8% 2 5% 4 3 4 3 4 5% 44%	4266
	21st to end	Night	21% 9% 3 5% 3 3 4 3 5% 6% 38%	4532
February	1st to 10th	Night	16% 8% 2 6% 4 4 4 4 5% 6% 42%	2470
	11th to 20th	Night	17% 9% 2 6% 4 3 4 3 4 5% 43%	2270
	21st to end	Night	17% 8% 2 5% 3 4 5% 3 5% 5% 43%	1884
March	1st to 10th	Night	21% 9% 2 6% 4 3 4 3 4 6% 39%	3656
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 6% 6% 49%	3480
	21st to end	Night	16% 9% 3 7% 4 3 3 3 4 4 45%	3629
April	1st to 10th	Night	15% 8% 3 6% 4 3 3 4 4 7% 42%	1900
	11th to 20th	Night	13% 6% 2 7% 5% 4 5% 3 5% 6% 44%	1875
	21st to end	Night	19% 6% 2 5% 4 4 4 3 6% 6% 43%	1900
May	1st to 10th	Night	21% 8% 4 7% 5% 3 4 4 4 8% 31%	2965
	11th to 20th	Night	23% 9% 3 7% 4 5% 4 3 6% 5% 30%	2495
	21st to end	Night	11% 5% 2 6% 4 4 4 4 7% 10% 42%	2732
June	1st to 10th	Night	12% 7% 2 6% 4 3 4 4 6% 8% 44%	1520
	11th to 20th	Night	8% 6% 3 7% 6% 4 5% 4 6% 9% 41%	1520
	21st to end	Night	8% 6% 2 6% 4 4 5% 3 8% 11% 43%	1520
July	1st to 10th	Night	6% 5% 2 7% 5% 6% 6% 5% 8% 10% 39%	2520
	11th to 20th	Night	9% 6% 2 7% 4 5% 5% 5% 8% 12% 38%	2520
	21st to end	Night	12% 8% 3 7% 5% 5% 5% 5% 7% 9% 35%	2945
August	1st to 10th	Night	16% 7% 2 7% 4 5% 6% 4 7% 10% 32%	2825
	11th to 20th	Night	11% 6% 2 7% 5% 5% 4 4 7% 8% 40%	3058
	21st to end	Night	11% 5% 2 5% 4 3 4 4 5% 8% 49%	3476
September	1st to 10th	Night	14% 7% 3 6% 3 4 4 4 4 7% 45%	1900
	11th to 20th	Night	10% 5% 2 4 3 3 3 2 5% 8% 55%	1910
	21st to end	Night	18% 7% 2 7% 4 5% 4 3 6% 6% 39%	2114
October	1st to 10th	Night	17% 7% 2 6% 4 3 3 3 5% 6% 44%	2280
	11th to 20th	Night	15% 4 2 5% 3 3 3 2 5% 6% 52%	2280
	21st to end	Night	15% 6% 2 5% 3 3 4 3 5% 6% 50%	2529
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 4 6% 6% 53%	2505
	11th to 20th	Night	15% 8% 2 5% 4 3 3 3 5% 4 49%	2470
	21st to end	Night	12% 6% 1 5% 4 3 5% 4 5% 7% 48%	2586
December	1st to 10th	Night	17% 8% 2 6% 4 4 4 3 6% 6% 40%	2660
	11th to 20th	Night	16% 5% 2 6% 4 4 3 4 6% 8% 42%	3285
	21st to end	Night	15% 7% 3 7% 4 5% 5% 4 6% 8% 37%	4884

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	37% 4 10% 29% 16% 4	2518
	11th to 20th	Day	46% 5% 11% 21% 14% 4	2689
	21st to end	Day	45% 6% 13% 22% 12% 2	3124
February	1st to 10th	Day	41% 6% 14% 24% 13% 2	1710
	11th to 20th	Day	41% 5% 10% 25% 16% 3	1805
	21st to end	Day	46% 5% 10% 21% 14% 4	1570
March	1st to 10th	Day	44% 4 9% 27% 12% 4	3183
	11th to 20th	Day	29% 7% 9% 31% 20% 4	3480
	21st to end	Day	44% 5% 8% 20% 19% 4	4001
April	1st to 10th	Day	39% 7% 12% 20% 17% 5%	2280
	11th to 20th	Day	36% 6% 11% 24% 18% 6%	2254
	21st to end	Day	39% 7% 12% 19% 19% 4	2280
May	1st to 10th	Day	52% 7% 10% 19% 11% 2	3992
	11th to 20th	Day	50% 8% 14% 19% 8% 1	4402
	21st to end	Day	32% 8% 13% 27% 18% 2	4837
June	1st to 10th	Day	35% 9% 13% 24% 16% 2	2660
	11th to 20th	Day	36% 9% 13% 26% 14% 2	2660
	21st to end	Day	30% 9% 15% 24% 19% 2	2660
July	1st to 10th	Day	34% 12% 18% 20% 13% 3	4370
	11th to 20th	Day	35% 8% 18% 25% 12% 2	4365
	21st to end	Day	41% 9% 14% 19% 15% 1	4458
August	1st to 10th	Day	42% 8% 16% 25% 8%	4091
	11th to 20th	Day	35% 8% 14% 29% 14% 1	3775
	21st to end	Day	32% 7% 12% 29% 18% 3	4180
September	1st to 10th	Day	38% 8% 11% 20% 20% 4	2280
	11th to 20th	Day	32% 6% 11% 24% 24% 4	2269
	21st to end	Day	46% 6% 7% 19% 19% 2	2062
October	1st to 10th	Day	33% 5% 10% 19% 28% 5%	3160
	11th to 20th	Day	24% 4 9% 25% 29% 9%	3140
	21st to end	Day	24% 3 10% 29% 28% 6%	3381
November	1st to 10th	Day	33% 4 12% 28% 19% 3	1734
	11th to 20th	Day	36% 5% 10% 23% 23% 3	1710
	21st to end	Day	38% 4 11% 30% 15% 3	1592
December	1st to 10th	Day	41% 6% 15% 23% 13% 2	1520
	11th to 20th	Day	41% 5% 11% 29% 11% 3	1906
	21st to end	Day	42% 6% 15% 22% 14%	2772
January	1st to 10th	Night	42% 4 9% 26% 15% 4	4429
	11th to 20th	Night	43% 5% 10% 25% 15% 2	4266
	21st to end	Night	47% 4 8% 27% 13% 1	4532
February	1st to 10th	Night	43% 5% 12% 24% 15% 1	2470
	11th to 20th	Night	44% 4 8% 21% 18% 5%	2272
	21st to end	Night	42% 5% 10% 20% 17% 5%	1884
March	1st to 10th	Night	48% 4 9% 24% 13% 2	3656
	11th to 20th	Night	33% 6% 11% 29% 17% 4	3480
	21st to end	Night	43% 4 8% 17% 22% 5%	3629
April	1st to 10th	Night	42% 5% 9% 19% 20% 5%	1900
	11th to 20th	Night	40% 5% 11% 20% 18% 6%	1875
	21st to end	Night	40% 6% 10% 20% 18% 6%	1900
May	1st to 10th	Night	52% 7% 9% 20% 11% 2	2995
	11th to 20th	Night	54% 7% 11% 16% 10% 2	2496
	21st to end	Night	35% 9% 16% 21% 15% 4	2739
June	1st to 10th	Night	37% 7% 12% 23% 19% 2	1520
	11th to 20th	Night	38% 8% 14% 25% 14% 2	1520
	21st to end	Night	34% 8% 15% 23% 16% 3	1520
July	1st to 10th	Night	38% 11% 20% 18% 11% 2	2480
	11th to 20th	Night	36% 9% 19% 25% 8% 2	2472
	21st to end	Night	44% 8% 13% 20% 15% 1	2851
August	1st to 10th	Night	45% 10% 17% 19% 8%	2814
	11th to 20th	Night	39% 8% 12% 26% 14% 1	3088
	21st to end	Night	32% 7% 10% 29% 20% 2	3476
September	1st to 10th	Night	39% 6% 10% 22% 20% 4	1900
	11th to 20th	Night	30% 5% 11% 26% 25% 4	1910
	21st to end	Night	44% 7% 8% 19% 18% 4	2114
October	1st to 10th	Night	40% 6% 10% 22% 20% 4	3800
	11th to 20th	Night	24% 4 12% 24% 30% 7%	3779
	21st to end	Night	23% 3 12% 31% 25% 6%	4165
November	1st to 10th	Night	32% 5% 11% 25% 21% 6%	2505
	11th to 20th	Night	38% 4 10% 22% 20% 6%	2470
	21st to end	Night	35% 5% 11% 26% 19% 3	2586
December	1st to 10th	Night	44% 5% 11% 23% 14% 2	2660
	11th to 20th	Night	40% 5% 11% 21% 19% 4	3288
	21st to end	Night	43% 7% 14% 25% 10% 1	4884

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	19% 24% 35% 16% 6% 1	180
	11th to 20th	Day	25% 33% 24% 14% 3	229
	21st to end	Day	23% 23% 36% 11% 6% 1	297
February	1st to 10th	Day	22% 24% 34% 15% 4	270
	11th to 20th	Day	25% 23% 40% 11% 2	404
	21st to end	Day	25% 23% 30% 17% 4	382
March	1st to 10th	Day	19% 24% 32% 19% 5%	460
	11th to 20th	Day	22% 23% 33% 16% 5% 2	460
	21st to end	Day	24% 17% 33% 19% 7% 1	506
April	1st to 10th	Day	19% 22% 37% 15% 6% 2	460
	11th to 20th	Day	18% 17% 31% 22% 9% 3	452
	21st to end	Day	23% 15% 32% 21% 7% 2	460
May	1st to 10th	Day	26% 17% 26% 19% 9% 2	463
	11th to 20th	Day	21% 10% 31% 25% 11% 2	487
	21st to end	Day	17% 5% 23% 27% 21% 6%	529
June	1st to 10th	Day	11% 9% 30% 26% 17% 8%	490
	11th to 20th	Day	12% 9% 25% 30% 17% 7%	490
	21st to end	Day	10% 5% 25% 34% 21% 6%	490
July	1st to 10th	Day	9% 3 20% 32% 27% 9%	485
	11th to 20th	Day	6% 2 17% 35% 30% 9%	484
	21st to end	Day	9% 3 20% 36% 25% 7%	532
August	1st to 10th	Day	12% 2 19% 33% 24% 10%	486
	11th to 20th	Day	13% 4 13% 34% 25% 11%	479
	21st to end	Day	10% 3 20% 32% 22% 13%	539
September	1st to 10th	Day	17% 5% 21% 26% 19% 13%	490
	11th to 20th	Day	14% 4 20% 31% 20% 12%	490
	21st to end	Day	24% 8% 22% 28% 13% 5%	490
October	1st to 10th	Day	22% 7% 23% 25% 16% 6%	490
	11th to 20th	Day	16% 13% 27% 25% 16% 3	490
	21st to end	Day	17% 11% 33% 24% 12% 3	526
November	1st to 10th	Day	14% 12% 33% 24% 14% 3	386
	11th to 20th	Day	17% 19% 30% 22% 12%	370
	21st to end	Day	17% 18% 31% 21% 12%	252
December	1st to 10th	Day	18% 23% 36% 17% 7% 1	180
	11th to 20th	Day	27% 22% 30% 16% 5% 1	180
	21st to end	Day	23% 19% 30% 20% 8% 1	198
January	1st to 10th	Night	20% 17% 38% 22% 4	760
	11th to 20th	Night	22% 16% 32% 25% 4	760
	21st to end	Night	19% 15% 38% 26% 2	836
February	1st to 10th	Night	20% 13% 39% 26% 2	760
	11th to 20th	Night	22% 20% 41% 17% 1	743
	21st to end	Night	23% 17% 36% 21% 3	628
March	1st to 10th	Night	19% 14% 40% 23% 4	760
	11th to 20th	Night	21% 15% 38% 20% 5% 1	760
	21st to end	Night	21% 10% 40% 23% 5%	836
April	1st to 10th	Night	21% 15% 37% 21% 6%	760
	11th to 20th	Night	16% 13% 36% 29% 6%	751
	21st to end	Night	22% 11% 33% 27% 8%	760
May	1st to 10th	Night	21% 7% 33% 31% 8%	673
	11th to 20th	Night	20% 8% 31% 33% 7%	374
	21st to end	Night	15% 3 22% 40% 18% 1	411
June	1st to 10th	Night	15% 4 24% 41% 15% 1	380
	11th to 20th	Night	10% 3 25% 44% 18%	380
	21st to end	Night	10% 4 21% 48% 16%	380
July	1st to 10th	Night	10% 2 18% 44% 24% 2	370
	11th to 20th	Night	6% 1 16% 45% 30% 2	368
	21st to end	Night	8% 3 15% 47% 24% 2	534
August	1st to 10th	Night	11% 2 13% 46% 27% 2	567
	11th to 20th	Night	13% 2 15% 41% 28% 3	723
	21st to end	Night	13% 3 15% 40% 25% 4	836
September	1st to 10th	Night	17% 2 18% 36% 24% 4	760
	11th to 20th	Night	14% 4 16% 35% 28% 4	760
	21st to end	Night	22% 4 21% 33% 19% 1	760
October	1st to 10th	Night	22% 4 20% 32% 18% 4	760
	11th to 20th	Night	17% 7% 29% 33% 13% 1	760
	21st to end	Night	19% 8% 34% 28% 11% 1	836
November	1st to 10th	Night	13% 7% 36% 32% 11% 1	771
	11th to 20th	Night	20% 12% 30% 29% 8% 1	760
	21st to end	Night	15% 13% 35% 28% 9% 1	760
December	1st to 10th	Night	24% 12% 34% 21% 9% 1	760
	11th to 20th	Night	19% 13% 38% 25% 6%	760
	21st to end	Night	20% 11% 37% 30% 3	836

Page generated at 2024-11-05 08:15:49. Version ac07

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