Black Bear Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Bear Hollow Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	101223
	Night	15% 9% 3 7% 5% 4 4 4 5% 7% 36%	97676
Transparency	Day	47% 8% 12% 21% 11% 1	101025
	Night	45% 8% 12% 21% 12% 2	97545
Seeing	Day	23% 16% 26% 20% 11% 4	14808
	Night	20% 14% 26% 28% 11% 1	24317

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% 15% 5% 11% 6% 4 4 4 4 4 28%	2613
	11th to 20th	Day	12% 18% 8% 14% 8% 4 5% 3 4 4 21%	2840
	21st to end	Day	18% 16% 9% 10% 5% 5% 4 3 4 5% 20%	3124
February	1st to 10th	Day	15% 15% 4 10% 6% 5% 5% 3 5% 5% 28%	1710
	11th to 20th	Day	13% 10% 6% 13% 5% 5% 4 4 5% 6% 28%	1663
	21st to end	Day	17% 13% 4 10% 4 4 4 4 5% 5% 31%	1558
March	1st to 10th	Day	20% 13% 4 8% 5% 4 4 3 5% 6% 29%	3435
	11th to 20th	Day	12% 9% 4 8% 5% 5% 5% 3 5% 8% 36%	3480
	21st to end	Day	16% 10% 3 7% 5% 4 4 3 5% 5% 38%	3815
April	1st to 10th	Day	15% 12% 3 8% 5% 5% 4 3 5% 7% 32%	2273
	11th to 20th	Day	14% 11% 3 7% 6% 4 4 3 5% 5% 37%	2254
	21st to end	Day	20% 8% 3 7% 4 4 4 4 5% 5% 35%	2359
May	1st to 10th	Day	27% 8% 2 7% 5% 4 4 4 5% 6% 28%	4082
	11th to 20th	Day	24% 9% 3 6% 4 4 4 4 5% 7% 29%	4237
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 6% 9% 39%	4823
June	1st to 10th	Day	13% 6% 2 6% 6% 5% 6% 5% 7% 8% 36%	2660
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 4 8% 9% 35%	2660
	21st to end	Day	11% 4 2 7% 6% 5% 5% 5% 7% 10% 38%	2660
July	1st to 10th	Day	7% 5% 2 7% 6% 6% 6% 5% 7% 10% 40%	4440
	11th to 20th	Day	6% 6% 3 7% 5% 5% 6% 5% 8% 10% 39%	4263
	21st to end	Day	11% 8% 3 8% 6% 5% 5% 4 6% 7% 37%	4466
August	1st to 10th	Day	17% 6% 2 7% 5% 6% 6% 5% 7% 9% 31%	4104
	11th to 20th	Day	10% 7% 2 7% 6% 6% 6% 4 7% 9% 35%	4015
	21st to end	Day	13% 5% 2 5% 4 4 4 5% 6% 8% 43%	4180
September	1st to 10th	Day	17% 5% 2 5% 4 4 4 4 5% 7% 43%	2280
	11th to 20th	Day	15% 6% 2 5% 3 3 4 3 5% 7% 46%	2237
	21st to end	Day	20% 8% 3 6% 5% 4 4 4 5% 7% 35%	2006
October	1st to 10th	Day	18% 6% 2 6% 4 5% 5% 3 5% 6% 40%	1900
	11th to 20th	Day	17% 8% 3 7% 4 5% 5% 4 4 6% 39%	1900
	21st to end	Day	17% 8% 3 6% 4 3 4 2 5% 7% 39%	2090
November	1st to 10th	Day	11% 7% 2 7% 5% 4 4 3 6% 6% 45%	1801
	11th to 20th	Day	15% 10% 4 7% 4 4 5% 3 6% 7% 36%	1573
	21st to end	Day	16% 13% 3 8% 5% 3 4 4 5% 7% 32%	1520
December	1st to 10th	Day	18% 13% 4 9% 6% 5% 5% 5% 6% 6% 24%	1520
	11th to 20th	Day	16% 13% 5% 8% 5% 4 4 4 4 5% 30%	1910
	21st to end	Day	20% 14% 6% 10% 6% 6% 5% 4 5% 5% 20%	2772
January	1st to 10th	Night	12% 14% 6% 10% 6% 5% 4 4 5% 6% 27%	4329
	11th to 20th	Night	15% 14% 5% 13% 7% 5% 4 3 4 5% 26%	4120
	21st to end	Night	21% 15% 6% 10% 6% 4 4 4 4 4 23%	4532
February	1st to 10th	Night	14% 12% 3 8% 5% 5% 5% 4 6% 6% 31%	2470
	11th to 20th	Night	15% 11% 3 10% 4 6% 5% 4 6% 6% 30%	2403
	21st to end	Night	16% 11% 3 9% 5% 4 5% 4 6% 6% 31%	1892
March	1st to 10th	Night	21% 11% 3 7% 4 4 3 3 5% 6% 33%	3418
	11th to 20th	Night	12% 8% 6% 7% 5% 4 3 3 5% 6% 41%	3480
	21st to end	Night	13% 9% 2 6% 5% 3 4 3 5% 6% 43%	3817
April	1st to 10th	Night	15% 12% 5% 8% 5% 4 5% 4 5% 6% 32%	1906
	11th to 20th	Night	13% 8% 2 7% 4 4 4 4 5% 9% 40%	1875
	21st to end	Night	18% 5% 2 5% 5% 4 4 4 6% 7% 40%	1838
May	1st to 10th	Night	26% 9% 3 7% 5% 3 4 3 4 7% 27%	2813
	11th to 20th	Night	26% 10% 2 6% 4 4 4 3 5% 6% 30%	2655
	21st to end	Night	12% 6% 2 7% 5% 5% 5% 4 7% 9% 39%	2732
June	1st to 10th	Night	11% 7% 2 6% 4 4 5% 3 5% 8% 45%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 4 8% 8% 40%	1520
	21st to end	Night	10% 4 2 5% 5% 4 4 4 8% 11% 44%	1520
July	1st to 10th	Night	7% 6% 2 6% 5% 5% 6% 5% 8% 9% 42%	2520
	11th to 20th	Night	6% 4 2 6% 5% 5% 6% 5% 7% 10% 45%	2679
	21st to end	Night	11% 8% 3 8% 5% 4 5% 4 5% 7% 40%	3087
August	1st to 10th	Night	16% 7% 2 7% 5% 4 4 4 6% 8% 37%	2825
	11th to 20th	Night	12% 7% 2 6% 4 5% 3 4 6% 8% 43%	2785
	21st to end	Night	14% 5% 2 5% 4 4 4 3 5% 8% 46%	3471
September	1st to 10th	Night	15% 5% 2 6% 3 4 3 3 5% 7% 46%	1900
	11th to 20th	Night	11% 6% 2 5% 3 3 4 2 5% 7% 51%	1939
	21st to end	Night	19% 7% 2 5% 4 4 4 4 5% 7% 41%	2173
October	1st to 10th	Night	16% 7% 2 5% 4 4 4 3 5% 6% 44%	2280
	11th to 20th	Night	15% 6% 2 5% 4 4 4 4 5% 8% 43%	2280
	21st to end	Night	18% 7% 2 5% 4 3 4 4 5% 7% 41%	2508
November	1st to 10th	Night	10% 8% 3 6% 4 4 4 3 4 6% 49%	2297
	11th to 20th	Night	15% 10% 3 7% 5% 4 5% 4 5% 7% 37%	2603
	21st to end	Night	15% 9% 3 7% 5% 6% 5% 4 5% 6% 35%	2660
December	1st to 10th	Night	17% 12% 4 8% 7% 5% 4 4 6% 8% 26%	2660
	11th to 20th	Night	17% 10% 3 8% 6% 5% 5% 4 5% 5% 31%	3285
	21st to end	Night	18% 13% 5% 9% 5% 5% 5% 4 6% 7% 22%	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	55% 8% 11% 19% 5% 2	2614
	11th to 20th	Day	64% 8% 9% 10% 9% 1	2840
	21st to end	Day	65% 6% 10% 14% 4 1	3124
February	1st to 10th	Day	57% 6% 13% 17% 7% 1	1710
	11th to 20th	Day	55% 6% 11% 19% 8% 1	1672
	21st to end	Day	53% 7% 12% 17% 8% 3	1558
March	1st to 10th	Day	52% 8% 12% 20% 7% 1	3435
	11th to 20th	Day	42% 9% 14% 23% 10% 2	3480
	21st to end	Day	46% 8% 11% 22% 12% 1	3815
April	1st to 10th	Day	50% 7% 12% 17% 12% 2	2273
	11th to 20th	Day	46% 7% 10% 19% 16% 3	2254
	21st to end	Day	49% 7% 10% 21% 12% 2	2359
May	1st to 10th	Day	54% 9% 8% 19% 10% 1	4120
	11th to 20th	Day	52% 8% 12% 19% 7% 2	4241
	21st to end	Day	36% 11% 15% 22% 14% 2	4837
June	1st to 10th	Day	43% 9% 13% 21% 14% 1	2660
	11th to 20th	Day	42% 10% 14% 19% 13% 1	2660
	21st to end	Day	38% 9% 14% 25% 13% 1	2660
July	1st to 10th	Day	38% 9% 14% 26% 10% 3	4370
	11th to 20th	Day	36% 9% 15% 24% 15% 1	4189
	21st to end	Day	43% 7% 10% 22% 16% 1	4324
August	1st to 10th	Day	48% 9% 15% 20% 8%	4091
	11th to 20th	Day	44% 7% 10% 27% 11% 1	4054
	21st to end	Day	37% 7% 13% 27% 15% 2	4180
September	1st to 10th	Day	40% 7% 10% 21% 18% 3	2280
	11th to 20th	Day	36% 5% 11% 26% 19% 2	2237
	21st to end	Day	48% 6% 13% 16% 16% 1	2006
October	1st to 10th	Day	44% 7% 11% 21% 15% 2	1900
	11th to 20th	Day	44% 7% 12% 24% 12% 1	1900
	21st to end	Day	43% 6% 13% 21% 15% 1	2090
November	1st to 10th	Day	38% 6% 14% 21% 16% 5%	1801
	11th to 20th	Day	46% 6% 12% 22% 11% 3	1573
	21st to end	Day	50% 7% 13% 22% 8% 1	1520
December	1st to 10th	Day	57% 8% 14% 14% 5%	1520
	11th to 20th	Day	54% 6% 12% 22% 5%	1906
	21st to end	Day	62% 9% 11% 12% 5%	2772
January	1st to 10th	Night	54% 8% 12% 18% 8% 1	4329
	11th to 20th	Night	56% 9% 13% 14% 7% 1	4120
	21st to end	Night	62% 7% 9% 17% 5% 1	4532
February	1st to 10th	Night	51% 7% 12% 21% 8% 1	2470
	11th to 20th	Night	52% 6% 10% 18% 12% 1	2405
	21st to end	Night	51% 7% 11% 18% 10% 2	1892
March	1st to 10th	Night	50% 6% 11% 23% 8% 1	3418
	11th to 20th	Night	39% 9% 12% 29% 10% 1	3480
	21st to end	Night	40% 7% 11% 22% 17% 2	3817
April	1st to 10th	Night	51% 7% 10% 17% 13% 1	1906
	11th to 20th	Night	41% 8% 12% 21% 16% 3	1875
	21st to end	Night	41% 8% 11% 23% 13% 3	1838
May	1st to 10th	Night	56% 8% 7% 17% 10% 2	2840
	11th to 20th	Night	51% 10% 12% 17% 8% 1	2656
	21st to end	Night	34% 12% 16% 24% 10% 3	2739
June	1st to 10th	Night	36% 8% 12% 27% 14% 2	1520
	11th to 20th	Night	38% 9% 14% 25% 12% 2	1520
	21st to end	Night	32% 9% 17% 26% 15% 1	1520
July	1st to 10th	Night	35% 10% 16% 21% 13% 4	2480
	11th to 20th	Night	32% 10% 16% 25% 16% 1	2631
	21st to end	Night	40% 9% 13% 18% 19% 2	2988
August	1st to 10th	Night	43% 9% 16% 23% 8%	2814
	11th to 20th	Night	38% 7% 12% 28% 13% 1	2812
	21st to end	Night	36% 6% 13% 30% 13% 2	3471
September	1st to 10th	Night	38% 7% 12% 22% 18% 3	1900
	11th to 20th	Night	32% 7% 10% 30% 20% 2	1939
	21st to end	Night	42% 6% 11% 23% 16% 2	2173
October	1st to 10th	Night	40% 7% 13% 23% 15% 1	2280
	11th to 20th	Night	38% 7% 12% 26% 14% 2	2280
	21st to end	Night	41% 6% 10% 25% 15% 1	2508
November	1st to 10th	Night	36% 5% 13% 24% 18% 4	2297
	11th to 20th	Night	45% 7% 11% 21% 14% 3	2603
	21st to end	Night	47% 7% 13% 22% 10% 1	2660
December	1st to 10th	Night	54% 7% 15% 16% 7%	2660
	11th to 20th	Night	51% 7% 12% 21% 9% 1	3288
	21st to end	Night	57% 10% 15% 14% 4	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	36% 25% 25% 11% 2	207
	11th to 20th	Day	34% 27% 28% 9% 1	270
	21st to end	Day	28% 31% 29% 8% 3	297
February	1st to 10th	Day	33% 27% 29% 10% 1	270
	11th to 20th	Day	40% 28% 29% 3	270
	21st to end	Day	36% 25% 25% 12% 2	354
March	1st to 10th	Day	31% 23% 26% 17% 3	460
	11th to 20th	Day	32% 24% 25% 14% 4 1	460
	21st to end	Day	32% 22% 27% 13% 5% 1	506
April	1st to 10th	Day	29% 25% 25% 15% 5% 1	460
	11th to 20th	Day	23% 23% 26% 16% 9% 4	452
	21st to end	Day	32% 18% 27% 12% 8% 1	460
May	1st to 10th	Day	29% 19% 27% 14% 8% 3	463
	11th to 20th	Day	26% 17% 27% 16% 10% 4	487
	21st to end	Day	18% 14% 26% 22% 14% 6%	529
June	1st to 10th	Day	19% 17% 27% 20% 15% 3	490
	11th to 20th	Day	18% 11% 31% 24% 13% 3	490
	21st to end	Day	12% 14% 31% 25% 15% 3	490
July	1st to 10th	Day	11% 7% 24% 29% 20% 8%	485
	11th to 20th	Day	7% 8% 29% 30% 18% 8%	484
	21st to end	Day	14% 8% 27% 30% 16% 5%	532
August	1st to 10th	Day	13% 8% 23% 28% 20% 8%	486
	11th to 20th	Day	15% 7% 25% 25% 19% 10%	479
	21st to end	Day	14% 7% 22% 29% 17% 11%	539
September	1st to 10th	Day	20% 9% 19% 25% 18% 9%	490
	11th to 20th	Day	17% 5% 20% 30% 20% 8%	490
	21st to end	Day	29% 13% 22% 18% 12% 5%	490
October	1st to 10th	Day	23% 10% 22% 25% 16% 3	490
	11th to 20th	Day	23% 17% 26% 21% 13% 1	490
	21st to end	Day	21% 18% 32% 19% 9% 1	539
November	1st to 10th	Day	18% 16% 32% 21% 11% 2	428
	11th to 20th	Day	26% 23% 28% 15% 6% 1	233
	21st to end	Day	27% 23% 35% 12% 3 1	180
December	1st to 10th	Day	32% 28% 26% 10% 4 1	180
	11th to 20th	Day	30% 26% 28% 15% 2	180
	21st to end	Day	28% 24% 26% 18% 3	198
January	1st to 10th	Night	22% 23% 34% 18% 3	760
	11th to 20th	Night	27% 19% 30% 21% 3	760
	21st to end	Night	22% 23% 32% 20% 2	836
February	1st to 10th	Night	24% 19% 30% 24% 3	760
	11th to 20th	Night	25% 28% 30% 17% 1	743
	21st to end	Night	27% 21% 32% 19% 2	628
March	1st to 10th	Night	24% 19% 33% 21% 3	760
	11th to 20th	Night	27% 21% 26% 21% 4 1	760
	21st to end	Night	22% 18% 34% 20% 5%	836
April	1st to 10th	Night	24% 21% 29% 21% 4	760
	11th to 20th	Night	18% 17% 30% 26% 9%	751
	21st to end	Night	22% 15% 26% 30% 8%	698
May	1st to 10th	Night	23% 10% 24% 29% 14%	570
	11th to 20th	Night	22% 9% 26% 32% 11%	469
	21st to end	Night	15% 6% 22% 36% 18% 2	411
June	1st to 10th	Night	14% 5% 26% 36% 19% 1	380
	11th to 20th	Night	14% 5% 22% 39% 19% 1	380
	21st to end	Night	9% 5% 25% 46% 16%	380
July	1st to 10th	Night	11% 5% 17% 41% 23% 3	370
	11th to 20th	Night	8% 3 18% 40% 30% 3	462
	21st to end	Night	10% 3 19% 41% 25% 2	624
August	1st to 10th	Night	10% 2 16% 44% 27% 2	567
	11th to 20th	Night	12% 3 14% 41% 25% 4	564
	21st to end	Night	14% 4 16% 35% 27% 3	831
September	1st to 10th	Night	17% 4 18% 35% 23% 4	760
	11th to 20th	Night	13% 6% 18% 31% 29% 4	760
	21st to end	Night	22% 7% 22% 26% 20% 3	760
October	1st to 10th	Night	19% 8% 20% 31% 20% 2	760
	11th to 20th	Night	19% 14% 28% 28% 11% 1	760
	21st to end	Night	22% 13% 27% 28% 8%	836
November	1st to 10th	Night	15% 12% 29% 33% 10% 1	745
	11th to 20th	Night	22% 19% 26% 25% 7% 1	760
	21st to end	Night	22% 20% 27% 25% 6%	760
December	1st to 10th	Night	27% 19% 27% 21% 5%	760
	11th to 20th	Night	22% 18% 31% 26% 3	760
	21st to end	Night	23% 20% 28% 28% 2	836

Page generated at 2024-10-30 01:22:56. Version ac07

Copyright © 2024 Attilla Danko.