Buckhorn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buckhorn Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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	16% 11% 3 8% 5% 4 4 4 5% 7% 32%	101529
	Night	16% 11% 4 8% 5% 4 4 4 5% 6% 32%	97493
Transparency	Day	51% 3 11% 23% 11% 1	105114
	Night	52% 3 11% 22% 11% 1	101996
Seeing	Day	24% 13% 31% 20% 9% 3	14410
	Night	22% 11% 30% 25% 10% 1	23659

By Month

Percentage Cloud Cover NE (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% 19% 6% 14% 5% 4 4 3 3 4 23%	2517
	11th to 20th	Day	12% 18% 8% 17% 7% 6% 5% 4 5% 3 15%	2560
	21st to end	Day	18% 20% 8% 13% 6% 4 3 3 3 4 18%	3124
February	1st to 10th	Day	13% 17% 6% 13% 9% 5% 5% 3 4 4 21%	1710
	11th to 20th	Day	13% 15% 6% 12% 7% 5% 4 3 4 4 26%	1663
	21st to end	Day	16% 16% 6% 10% 7% 5% 4 3 5% 5% 23%	1470
March	1st to 10th	Day	20% 13% 4 10% 5% 4 4 2 5% 6% 27%	3366
	11th to 20th	Day	11% 19% 5% 10% 6% 5% 4 4 5% 6% 26%	3480
	21st to end	Day	14% 9% 3 7% 4 3 4 3 4 6% 42%	3846
April	1st to 10th	Day	20% 13% 3 8% 5% 4 4 3 5% 6% 29%	2280
	11th to 20th	Day	23% 10% 2 5% 4 4 4 3 4 5% 36%	2280
	21st to end	Day	22% 10% 3 7% 4 4 3 4 4 6% 32%	2470
May	1st to 10th	Day	20% 7% 3 7% 5% 4 4 3 5% 7% 34%	4263
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 3 5% 8% 33%	4398
	21st to end	Day	15% 6% 2 6% 4 4 4 4 5% 7% 42%	4837
June	1st to 10th	Day	19% 8% 2 6% 6% 5% 4 4 6% 8% 32%	2660
	11th to 20th	Day	14% 7% 2 7% 4 5% 6% 4 6% 9% 35%	2660
	21st to end	Day	18% 6% 3 6% 5% 5% 4 4 6% 8% 34%	2660
July	1st to 10th	Day	12% 5% 2 6% 5% 4 6% 4 7% 10% 37%	4440
	11th to 20th	Day	12% 5% 2 5% 4 5% 5% 4 6% 8% 44%	4440
	21st to end	Day	9% 5% 2 6% 5% 4 5% 5% 8% 9% 42%	4733
August	1st to 10th	Day	16% 9% 3 7% 4 5% 5% 4 6% 8% 35%	4104
	11th to 20th	Day	15% 7% 3 7% 5% 4 5% 4 6% 9% 34%	4044
	21st to end	Day	10% 5% 2 7% 5% 4 5% 4 6% 10% 41%	4290
September	1st to 10th	Day	15% 6% 2 6% 5% 4 4 4 6% 9% 39%	2280
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 3 5% 7% 46%	2249
	21st to end	Day	18% 6% 3 7% 4 5% 4 3 6% 7% 37%	2001
October	1st to 10th	Day	20% 10% 3 7% 5% 4 4 3 5% 7% 33%	1900
	11th to 20th	Day	25% 10% 3 9% 5% 4 4 4 5% 5% 26%	1900
	21st to end	Day	27% 12% 4 9% 5% 4 4 3 4 5% 24%	2076
November	1st to 10th	Day	16% 10% 4 8% 5% 5% 4 4 6% 6% 32%	1590
	11th to 20th	Day	18% 14% 4 9% 5% 4 3 4 6% 7% 26%	1520
	21st to end	Day	21% 18% 5% 8% 6% 5% 4 5% 5% 5% 18%	1520
December	1st to 10th	Day	19% 22% 7% 12% 6% 4 4 3 4 5% 15%	1520
	11th to 20th	Day	19% 17% 5% 11% 4 4 3 4 4 4 25%	1906
	21st to end	Day	26% 21% 6% 12% 4 3 3 2 3 4 17%	2772
January	1st to 10th	Night	18% 20% 7% 12% 6% 4 4 3 4 4 17%	4429
	11th to 20th	Night	13% 14% 6% 16% 10% 7% 6% 4 4 4 15%	4399
	21st to end	Night	19% 16% 9% 11% 6% 5% 5% 3 4 5% 18%	4532
February	1st to 10th	Night	13% 17% 5% 11% 8% 6% 6% 4 5% 6% 20%	2470
	11th to 20th	Night	13% 15% 6% 10% 7% 5% 5% 3 5% 5% 27%	2403
	21st to end	Night	15% 15% 4 8% 6% 5% 5% 4 5% 6% 27%	1983
March	1st to 10th	Night	19% 12% 4 9% 5% 5% 4 3 4 5% 29%	3471
	11th to 20th	Night	13% 16% 7% 9% 5% 4 4 3 5% 5% 27%	3479
	21st to end	Night	15% 7% 3 7% 5% 4 4 4 6% 8% 38%	3786
April	1st to 10th	Night	19% 12% 4 6% 5% 5% 4 3 5% 6% 30%	1900
	11th to 20th	Night	17% 10% 3 8% 5% 3 3 3 4 7% 36%	1866
	21st to end	Night	19% 10% 3 6% 5% 5% 4 5% 6% 5% 33%	1710
May	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 5% 6% 37%	2678
	11th to 20th	Night	16% 8% 2 7% 5% 5% 4 4 6% 6% 36%	2495
	21st to end	Night	11% 7% 2 5% 5% 4 4 3 4 8% 46%	2738
June	1st to 10th	Night	16% 8% 2 5% 5% 4 5% 4 6% 8% 37%	1520
	11th to 20th	Night	12% 6% 2 4 6% 5% 4 4 5% 8% 44%	1520
	21st to end	Night	14% 7% 3 7% 5% 4 5% 4 5% 7% 39%	1520
July	1st to 10th	Night	9% 4 3 7% 6% 5% 4 4 7% 7% 44%	2520
	11th to 20th	Night	14% 6% 1 5% 3 4 3 4 5% 6% 48%	2520
	21st to end	Night	9% 6% 2 5% 4 4 4 4 6% 7% 50%	2818
August	1st to 10th	Night	12% 5% 2 6% 3 4 4 4 5% 8% 47%	2825
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 5% 8% 43%	2785
	21st to end	Night	11% 5% 2 6% 4 4 4 3 5% 8% 47%	3332
September	1st to 10th	Night	11% 6% 2 6% 4 4 5% 3 6% 8% 44%	1900
	11th to 20th	Night	12% 4 1 6% 4 3 4 3 5% 6% 52%	1928
	21st to end	Night	19% 6% 2 6% 4 4 5% 3 5% 5% 42%	2177
October	1st to 10th	Night	18% 7% 3 7% 4 4 4 4 5% 7% 37%	2280
	11th to 20th	Night	21% 10% 3 8% 5% 5% 4 4 4 6% 30%	2280
	21st to end	Night	22% 13% 3 8% 5% 4 4 4 5% 5% 26%	2521
November	1st to 10th	Night	19% 10% 3 7% 5% 4 4 3 4 6% 35%	2556
	11th to 20th	Night	19% 13% 4 7% 5% 4 4 3 6% 6% 29%	2660
	21st to end	Night	20% 13% 4 9% 7% 5% 4 4 6% 6% 22%	2660
December	1st to 10th	Night	21% 19% 6% 11% 6% 4 4 3 5% 5% 17%	2660
	11th to 20th	Night	17% 20% 5% 11% 5% 4 3 3 3 5% 23%	3288
	21st to end	Night	27% 20% 5% 13% 5% 4 3 3 3 4 13%	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	66% 2 12% 12% 7% 1	2518
	11th to 20th	Day	72% 2 8% 11% 6% 1	2560
	21st to end	Day	73% 1 7% 12% 6% 1	3124
February	1st to 10th	Day	68% 2 8% 17% 4 1	1710
	11th to 20th	Day	63% 3 8% 15% 11% 1	1672
	21st to end	Day	64% 2 9% 15% 10% 1	1470
March	1st to 10th	Day	59% 2 11% 16% 11% 1	3369
	11th to 20th	Day	60% 2 11% 18% 9% 2	3480
	21st to end	Day	45% 2 7% 25% 18% 3	3846
April	1st to 10th	Day	57% 2 7% 20% 11% 3	2280
	11th to 20th	Day	52% 2 8% 22% 15% 1	2280
	21st to end	Day	55% 2 8% 20% 12% 3	2470
May	1st to 10th	Day	51% 2 8% 26% 12% 2	4275
	11th to 20th	Day	51% 2 11% 24% 11% 1	4402
	21st to end	Day	42% 2 13% 24% 15% 3	4837
June	1st to 10th	Day	51% 3 10% 20% 14% 1	2660
	11th to 20th	Day	45% 4 11% 26% 13% 2	2660
	21st to end	Day	48% 3 12% 23% 12% 1	2660
July	1st to 10th	Day	40% 6% 16% 25% 13% 1	4370
	11th to 20th	Day	35% 5% 15% 34% 10%	4365
	21st to end	Day	35% 7% 11% 33% 12%	4582
August	1st to 10th	Day	47% 4 14% 24% 11% 1	4091
	11th to 20th	Day	45% 5% 14% 27% 8%	4083
	21st to end	Day	37% 6% 11% 35% 11% 1	4290
September	1st to 10th	Day	42% 4 12% 30% 12% 1	2280
	11th to 20th	Day	37% 3 13% 31% 15% 1	2249
	21st to end	Day	47% 4 13% 25% 11%	2001
October	1st to 10th	Day	44% 5% 12% 28% 11% 1	3160
	11th to 20th	Day	50% 4 12% 22% 12% 1	3140
	21st to end	Day	57% 4 13% 20% 6%	3402
November	1st to 10th	Day	52% 3 14% 23% 8% 1	1590
	11th to 20th	Day	57% 3 14% 16% 8% 2	1520
	21st to end	Day	67% 4 10% 13% 6% 1	1520
December	1st to 10th	Day	73% 3 8% 11% 5%	1520
	11th to 20th	Day	64% 5% 9% 12% 10%	1906
	21st to end	Day	73% 1 7% 14% 5%	2772
January	1st to 10th	Night	71% 2 9% 13% 5%	4429
	11th to 20th	Night	72% 2 9% 12% 5% 1	4399
	21st to end	Night	69% 2 10% 12% 6% 1	4532
February	1st to 10th	Night	63% 3 9% 17% 6% 1	2470
	11th to 20th	Night	59% 2 9% 20% 9%	2405
	21st to end	Night	57% 2 10% 20% 9% 1	1983
March	1st to 10th	Night	57% 2 8% 21% 10% 1	3481
	11th to 20th	Night	60% 1 12% 18% 8% 1	3480
	21st to end	Night	44% 2 8% 25% 19% 2	3786
April	1st to 10th	Night	54% 2 8% 22% 12% 2	1900
	11th to 20th	Night	50% 2 8% 23% 16% 2	1866
	21st to end	Night	52% 3 9% 17% 17% 2	1710
May	1st to 10th	Night	50% 2 10% 20% 15% 2	2685
	11th to 20th	Night	49% 2 12% 25% 11% 2	2496
	21st to end	Night	39% 2 13% 25% 19% 2	2739
June	1st to 10th	Night	44% 3 11% 25% 15% 2	1520
	11th to 20th	Night	38% 4 12% 25% 19% 2	1520
	21st to end	Night	44% 4 14% 24% 13% 1	1520
July	1st to 10th	Night	35% 6% 15% 26% 16% 1	2480
	11th to 20th	Night	36% 4 11% 34% 15%	2472
	21st to end	Night	33% 6% 13% 34% 14%	2728
August	1st to 10th	Night	36% 5% 14% 27% 17% 1	2814
	11th to 20th	Night	38% 5% 19% 26% 12% 1	2812
	21st to end	Night	33% 5% 13% 36% 12% 2	3332
September	1st to 10th	Night	37% 5% 15% 28% 14% 1	1900
	11th to 20th	Night	34% 2 12% 36% 15% 1	1928
	21st to end	Night	44% 3 11% 30% 12%	2177
October	1st to 10th	Night	37% 3 11% 30% 18%	3800
	11th to 20th	Night	46% 5% 14% 26% 9%	3779
	21st to end	Night	51% 5% 14% 22% 7%	4145
November	1st to 10th	Night	51% 3 12% 25% 10%	2556
	11th to 20th	Night	56% 4 13% 18% 9% 2	2660
	21st to end	Night	61% 5% 13% 15% 5%	2660
December	1st to 10th	Night	69% 3 10% 13% 5%	2660
	11th to 20th	Night	65% 2 10% 15% 7%	3288
	21st to end	Night	77% 1 7% 11% 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	27% 18% 34% 14% 7% 1	180
	11th to 20th	Day	28% 19% 33% 16% 3 1	193
	21st to end	Day	26% 17% 37% 14% 5% 1	297
February	1st to 10th	Day	32% 18% 37% 10% 3	270
	11th to 20th	Day	28% 23% 41% 6% 1	270
	21st to end	Day	34% 16% 37% 12% 1	282
March	1st to 10th	Day	26% 16% 38% 16% 4	460
	11th to 20th	Day	28% 16% 34% 18% 3 1	460
	21st to end	Day	32% 16% 31% 14% 7% 1	506
April	1st to 10th	Day	28% 19% 31% 14% 7%	460
	11th to 20th	Day	36% 15% 23% 16% 6% 3	452
	21st to end	Day	29% 18% 31% 14% 7% 1	460
May	1st to 10th	Day	28% 12% 31% 17% 6% 5%	463
	11th to 20th	Day	21% 13% 34% 18% 11% 3	487
	21st to end	Day	19% 12% 36% 20% 10% 4	529
June	1st to 10th	Day	24% 11% 34% 23% 8% 1	490
	11th to 20th	Day	18% 10% 33% 24% 12% 3	490
	21st to end	Day	22% 13% 31% 22% 9% 3	490
July	1st to 10th	Day	13% 7% 32% 30% 14% 4	485
	11th to 20th	Day	14% 7% 31% 27% 14% 5%	484
	21st to end	Day	13% 8% 34% 29% 12% 4	532
August	1st to 10th	Day	17% 5% 29% 29% 14% 7%	486
	11th to 20th	Day	15% 5% 24% 32% 16% 6%	479
	21st to end	Day	14% 7% 32% 26% 12% 8%	539
September	1st to 10th	Day	17% 10% 28% 24% 14% 7%	490
	11th to 20th	Day	12% 7% 26% 22% 21% 12%	490
	21st to end	Day	21% 12% 25% 25% 12% 6%	490
October	1st to 10th	Day	27% 14% 24% 17% 15% 4	490
	11th to 20th	Day	26% 19% 31% 17% 7% 2	490
	21st to end	Day	34% 18% 26% 17% 5%	532
November	1st to 10th	Day	27% 15% 30% 19% 7% 1	266
	11th to 20th	Day	33% 18% 33% 10% 3 2	180
	21st to end	Day	33% 14% 36% 14% 2 1	180
December	1st to 10th	Day	34% 18% 26% 20% 2	180
	11th to 20th	Day	35% 18% 29% 14% 2 1	180
	21st to end	Day	33% 22% 32% 10% 2 1	198
January	1st to 10th	Night	29% 17% 30% 17% 6%	760
	11th to 20th	Night	31% 14% 30% 20% 5%	760
	21st to end	Night	20% 14% 33% 25% 6% 1	836
February	1st to 10th	Night	24% 18% 36% 20% 2	760
	11th to 20th	Night	21% 17% 39% 18% 4	743
	21st to end	Night	26% 18% 31% 21% 4	628
March	1st to 10th	Night	25% 17% 34% 21% 3	760
	11th to 20th	Night	25% 15% 34% 20% 4 1	760
	21st to end	Night	20% 13% 34% 24% 8% 1	836
April	1st to 10th	Night	27% 13% 33% 22% 5%	760
	11th to 20th	Night	25% 14% 32% 20% 9% 1	742
	21st to end	Night	23% 10% 31% 24% 11% 1	570
May	1st to 10th	Night	22% 7% 29% 26% 13% 2	480
	11th to 20th	Night	16% 8% 34% 32% 9%	374
	21st to end	Night	13% 7% 31% 36% 12% 1	411
June	1st to 10th	Night	18% 7% 33% 29% 13% 1	380
	11th to 20th	Night	16% 8% 25% 39% 11% 1	380
	21st to end	Night	17% 6% 26% 38% 13%	380
July	1st to 10th	Night	8% 5% 25% 43% 17% 1	370
	11th to 20th	Night	12% 3 28% 35% 20% 1	368
	21st to end	Night	10% 4 27% 41% 17% 2	459
August	1st to 10th	Night	12% 3 20% 38% 25% 2	567
	11th to 20th	Night	12% 4 19% 35% 27% 3	564
	21st to end	Night	12% 4 27% 32% 22% 2	744
September	1st to 10th	Night	13% 6% 29% 30% 19% 3	760
	11th to 20th	Night	13% 3 23% 32% 23% 5%	760
	21st to end	Night	22% 8% 19% 29% 19% 3	760
October	1st to 10th	Night	21% 10% 27% 25% 16% 2	760
	11th to 20th	Night	29% 11% 29% 22% 8% 1	760
	21st to end	Night	30% 13% 30% 22% 5%	836
November	1st to 10th	Night	25% 12% 26% 28% 8% 1	755
	11th to 20th	Night	28% 13% 33% 19% 6% 1	760
	21st to end	Night	29% 15% 29% 21% 6%	760
December	1st to 10th	Night	33% 16% 32% 14% 5%	760
	11th to 20th	Night	26% 16% 35% 18% 4 1	760
	21st to end	Night	35% 13% 31% 18% 3	836

Page generated at 2024-11-01 22:47:43. Version ac07

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