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 2024-03-23.

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	17% 11% 4 7% 6% 3 5% 4 5% 7% 31%	78613
	Night	17% 11% 5% 8% 6% 3 5% 4 5% 6% 30%	81268
Transparency	Day	54% 3 10% 21% 11% 1	78321
	Night	55% 3 11% 20% 10% 1	81094
Seeing	Day	24% 13% 31% 20% 9% 3	13510
	Night	23% 11% 30% 25% 10% 1	22964

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% 18% 6% 12% 6% 3 4 4 3 4 23%	2517
	11th to 20th	Day	12% 17% 9% 15% 9% 5% 5% 5% 4 4 15%	2560
	21st to end	Day	19% 19% 8% 11% 7% 3 4 3 3 4 19%	3124
February	1st to 10th	Day	14% 16% 7% 11% 10% 4 5% 4 4 4 21%	1710
	11th to 20th	Day	13% 14% 7% 12% 7% 4 5% 4 4 4 26%	1663
	21st to end	Day	17% 15% 6% 9% 8% 4 5% 4 4 5% 23%	1470
March	1st to 10th	Day	16% 11% 5% 9% 7% 4 5% 4 5% 6% 28%	2044
	11th to 20th	Day	12% 16% 5% 8% 7% 4 4 5% 4 6% 29%	2090
	21st to end	Day	19% 11% 4 6% 5% 2 4 4 4 6% 36%	2218
April	1st to 10th	Day	21% 12% 4 7% 6% 3 5% 4 5% 6% 29%	2160
	11th to 20th	Day	22% 9% 3 5% 4 3 4 4 4 5% 37%	2158
	21st to end	Day	22% 10% 3 7% 5% 3 4 4 4 6% 32%	2340
May	1st to 10th	Day	19% 7% 3 6% 6% 3 5% 5% 5% 6% 34%	2425
	11th to 20th	Day	16% 8% 3 5% 5% 3 5% 4 4 7% 39%	2478
	21st to end	Day	14% 6% 2 6% 6% 4 5% 5% 5% 8% 40%	2725
June	1st to 10th	Day	20% 7% 3 6% 6% 3 5% 4 5% 8% 33%	2520
	11th to 20th	Day	15% 7% 2 5% 5% 3 6% 4 6% 10% 36%	2520
	21st to end	Day	17% 6% 3 6% 5% 4 5% 4 6% 8% 35%	2520
July	1st to 10th	Day	12% 4 2 5% 5% 3 5% 5% 6% 9% 43%	2520
	11th to 20th	Day	11% 6% 3 5% 6% 4 6% 6% 7% 8% 39%	2520
	21st to end	Day	12% 5% 2 6% 7% 4 6% 8% 7% 9% 35%	2702
August	1st to 10th	Day	12% 6% 2 6% 6% 4 7% 5% 7% 8% 37%	2327
	11th to 20th	Day	12% 6% 3 7% 6% 3 5% 5% 6% 9% 37%	2303
	21st to end	Day	14% 6% 2 5% 6% 3 6% 5% 6% 10% 37%	2444
September	1st to 10th	Day	15% 6% 2 5% 6% 3 4 5% 6% 9% 39%	2160
	11th to 20th	Day	13% 5% 2 5% 5% 3 5% 5% 5% 7% 45%	2131
	21st to end	Day	18% 6% 3 6% 5% 4 4 4 6% 7% 37%	1896
October	1st to 10th	Day	21% 9% 3 6% 5% 3 4 4 5% 7% 33%	1800
	11th to 20th	Day	26% 9% 3 8% 6% 3 4 5% 5% 5% 25%	1800
	21st to end	Day	28% 11% 4 8% 6% 3 4 4 4 5% 23%	1967
November	1st to 10th	Day	17% 10% 4 7% 5% 4 5% 5% 6% 7% 31%	1563
	11th to 20th	Day	18% 12% 5% 8% 6% 3 4 4 6% 7% 26%	1520
	21st to end	Day	22% 17% 5% 8% 6% 4 4 6% 5% 5% 18%	1520
December	1st to 10th	Day	19% 20% 8% 11% 7% 3 4 4 4 5% 15%	1520
	11th to 20th	Day	19% 15% 6% 10% 5% 3 3 4 4 4 25%	1906
	21st to end	Day	26% 20% 6% 10% 5% 2 3 3 3 5% 17%	2772
January	1st to 10th	Night	19% 19% 8% 11% 7% 3 4 4 4 4 17%	4429
	11th to 20th	Night	14% 13% 7% 14% 12% 5% 6% 5% 4 4 15%	4399
	21st to end	Night	19% 15% 9% 10% 8% 4 5% 4 4 5% 18%	4532
February	1st to 10th	Night	13% 16% 5% 10% 8% 4 7% 5% 5% 6% 20%	2470
	11th to 20th	Night	13% 13% 6% 10% 7% 4 5% 5% 4 6% 27%	2403
	21st to end	Night	16% 14% 4 7% 7% 4 5% 5% 5% 6% 27%	1983
March	1st to 10th	Night	15% 11% 5% 8% 7% 4 4 4 4 5% 32%	2120
	11th to 20th	Night	14% 13% 6% 8% 6% 3 4 4 5% 6% 32%	2089
	21st to end	Night	15% 8% 4 7% 6% 3 4 5% 4 7% 38%	2183
April	1st to 10th	Night	19% 11% 5% 6% 5% 4 4 4 5% 6% 31%	1800
	11th to 20th	Night	17% 9% 4 7% 5% 2 4 4 4 7% 37%	1767
	21st to end	Night	19% 10% 3 6% 6% 3 5% 5% 6% 5% 34%	1620
May	1st to 10th	Night	18% 7% 2 6% 5% 3 4 5% 5% 7% 38%	1535
	11th to 20th	Night	14% 5% 2 5% 5% 4 4 5% 6% 7% 44%	1415
	21st to end	Night	11% 5% 2 4 4 3 5% 4 4 8% 49%	1550
June	1st to 10th	Night	16% 7% 2 4 6% 3 5% 5% 6% 8% 38%	1440
	11th to 20th	Night	13% 6% 3 3 6% 4 5% 5% 5% 8% 44%	1440
	21st to end	Night	13% 7% 3 5% 6% 2 5% 5% 5% 8% 40%	1440
July	1st to 10th	Night	9% 4 3 6% 5% 3 5% 4 5% 7% 51%	1440
	11th to 20th	Night	11% 5% 1 5% 5% 3 4 4 6% 8% 47%	1440
	21st to end	Night	10% 5% 2 4 4 3 4 6% 6% 7% 49%	1614
August	1st to 10th	Night	10% 4 2 5% 5% 3 4 5% 5% 8% 49%	1611
	11th to 20th	Night	9% 5% 2 5% 5% 3 4 5% 6% 10% 45%	1598
	21st to end	Night	11% 5% 3 5% 6% 3 5% 5% 5% 7% 44%	1892
September	1st to 10th	Night	12% 5% 3 6% 5% 3 5% 5% 6% 8% 43%	1800
	11th to 20th	Night	13% 4 1 6% 4 2 4 4 5% 6% 50%	1826
	21st to end	Night	19% 6% 2 5% 4 2 5% 4 4 5% 43%	2062
October	1st to 10th	Night	19% 7% 3 7% 5% 3 4 5% 5% 7% 35%	2160
	11th to 20th	Night	23% 10% 4 7% 6% 3 4 4 4 6% 28%	2160
	21st to end	Night	23% 13% 4 6% 7% 3 4 5% 4 5% 26%	2388
November	1st to 10th	Night	19% 9% 3 7% 5% 3 4 4 4 7% 35%	2510
	11th to 20th	Night	19% 12% 4 7% 5% 4 4 4 5% 6% 29%	2660
	21st to end	Night	21% 12% 5% 8% 7% 4 5% 5% 6% 6% 22%	2660
December	1st to 10th	Night	21% 17% 7% 10% 6% 3 4 4 4 5% 17%	2660
	11th to 20th	Night	17% 19% 6% 10% 6% 3 4 4 3 5% 23%	3288
	21st to end	Night	27% 19% 6% 12% 6% 3 3 4 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	57% 3 12% 16% 10% 2	2047
	11th to 20th	Day	58% 2 9% 18% 10% 2	2090
	21st to end	Day	51% 3 6% 20% 15% 4	2218
April	1st to 10th	Day	57% 2 7% 20% 11% 3	2160
	11th to 20th	Day	50% 2 8% 23% 15% 1	2158
	21st to end	Day	55% 2 8% 20% 12% 3	2340
May	1st to 10th	Day	51% 3 8% 21% 14% 3	2425
	11th to 20th	Day	47% 3 7% 26% 16% 1	2482
	21st to end	Day	43% 4 14% 22% 14% 3	2725
June	1st to 10th	Day	50% 3 11% 21% 14% 1	2520
	11th to 20th	Day	44% 4 11% 26% 14% 2	2520
	21st to end	Day	47% 3 12% 24% 12% 1	2520
July	1st to 10th	Day	37% 4 11% 30% 16% 2	2450
	11th to 20th	Day	40% 5% 14% 30% 11% 1	2445
	21st to end	Day	43% 5% 12% 27% 11% 1	2551
August	1st to 10th	Day	42% 5% 14% 26% 11% 1	2314
	11th to 20th	Day	44% 4 15% 26% 10% 1	2303
	21st to end	Day	42% 5% 12% 28% 12% 1	2444
September	1st to 10th	Day	42% 4 12% 29% 11% 1	2160
	11th to 20th	Day	39% 3 13% 31% 14% 1	2131
	21st to end	Day	47% 4 14% 26% 10%	1896
October	1st to 10th	Day	52% 3 10% 21% 12% 1	1800
	11th to 20th	Day	61% 3 12% 17% 6% 1	1800
	21st to end	Day	65% 2 10% 17% 7%	1967
November	1st to 10th	Day	52% 3 14% 22% 8% 1	1563
	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	54% 3 10% 19% 12% 2	2130
	11th to 20th	Night	54% 2 11% 20% 11% 2	2090
	21st to end	Night	48% 3 8% 23% 16% 3	2183
April	1st to 10th	Night	54% 2 8% 22% 13% 2	1800
	11th to 20th	Night	49% 2 8% 23% 16% 2	1767
	21st to end	Night	51% 4 9% 18% 16% 2	1620
May	1st to 10th	Night	46% 3 10% 21% 17% 4	1535
	11th to 20th	Night	40% 3 9% 27% 18% 3	1416
	21st to end	Night	34% 4 15% 25% 18% 4	1551
June	1st to 10th	Night	44% 4 11% 25% 15% 1	1440
	11th to 20th	Night	39% 3 12% 25% 19% 2	1440
	21st to end	Night	43% 4 14% 25% 13% 2	1440
July	1st to 10th	Night	31% 5% 12% 30% 20% 3	1400
	11th to 20th	Night	35% 3 13% 33% 15%	1392
	21st to end	Night	33% 4 16% 33% 13% 1	1524
August	1st to 10th	Night	34% 5% 18% 29% 14% 1	1600
	11th to 20th	Night	35% 4 18% 28% 14% 1	1598
	21st to end	Night	38% 4 13% 31% 13% 1	1892
September	1st to 10th	Night	38% 5% 16% 27% 14% 1	1800
	11th to 20th	Night	36% 2 13% 36% 13% 1	1826
	21st to end	Night	44% 3 11% 31% 11%	2062
October	1st to 10th	Night	49% 4 11% 23% 14% 1	2160
	11th to 20th	Night	57% 4 11% 22% 6%	2160
	21st to end	Night	61% 4 11% 14% 10%	2388
November	1st to 10th	Night	51% 3 12% 25% 10%	2510
	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% 30% 14% 7% 1	470
April	1st to 10th	Day	27% 20% 30% 15% 7%	420
	11th to 20th	Day	33% 16% 23% 17% 7% 4	412
	21st to end	Day	28% 18% 32% 15% 6% 1	420
May	1st to 10th	Day	29% 13% 30% 18% 5% 5%	423
	11th to 20th	Day	21% 14% 35% 18% 10% 3	447
	21st to end	Day	19% 11% 35% 20% 9% 5%	485
June	1st to 10th	Day	24% 10% 35% 23% 8% 1	450
	11th to 20th	Day	19% 11% 31% 23% 12% 4	450
	21st to end	Day	20% 11% 32% 24% 10% 3	450
July	1st to 10th	Day	13% 6% 30% 31% 15% 5%	445
	11th to 20th	Day	15% 7% 30% 27% 15% 6%	444
	21st to end	Day	14% 8% 35% 29% 11% 4	488
August	1st to 10th	Day	15% 4 30% 29% 15% 7%	446
	11th to 20th	Day	15% 5% 23% 33% 17% 7%	439
	21st to end	Day	15% 8% 32% 25% 13% 8%	495
September	1st to 10th	Day	16% 9% 29% 24% 14% 8%	450
	11th to 20th	Day	13% 8% 28% 23% 20% 9%	450
	21st to end	Day	20% 12% 26% 24% 12% 6%	450
October	1st to 10th	Day	27% 13% 23% 18% 15% 4	450
	11th to 20th	Day	27% 18% 31% 16% 6% 1	450
	21st to end	Day	35% 17% 25% 18% 5%	489
November	1st to 10th	Day	27% 16% 30% 19% 7% 1	257
	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	24% 16% 34% 20% 4 1	760
	21st to end	Night	20% 12% 34% 25% 8% 1	801
April	1st to 10th	Night	26% 13% 33% 22% 5%	720
	11th to 20th	Night	24% 14% 31% 21% 9% 1	703
	21st to end	Night	23% 10% 31% 24% 11% 1	540
May	1st to 10th	Night	22% 7% 29% 26% 14% 2	455
	11th to 20th	Night	16% 8% 35% 32% 9%	354
	21st to end	Night	13% 7% 32% 35% 12% 1	389
June	1st to 10th	Night	17% 7% 34% 29% 13% 1	360
	11th to 20th	Night	17% 8% 25% 38% 12% 1	360
	21st to end	Night	16% 6% 25% 39% 13%	360
July	1st to 10th	Night	8% 5% 25% 43% 18% 1	350
	11th to 20th	Night	12% 3 28% 36% 20% 1	348
	21st to end	Night	10% 3 28% 41% 17% 1	434
August	1st to 10th	Night	12% 3 19% 38% 25% 3	537
	11th to 20th	Night	11% 3 19% 36% 28% 3	534
	21st to end	Night	13% 4 28% 31% 22% 2	704
September	1st to 10th	Night	13% 6% 30% 30% 19% 3	720
	11th to 20th	Night	14% 4 25% 33% 21% 4	720
	21st to end	Night	22% 8% 20% 29% 19% 3	720
October	1st to 10th	Night	22% 9% 27% 25% 15% 2	720
	11th to 20th	Night	30% 11% 30% 21% 8% 1	720
	21st to end	Night	30% 13% 30% 22% 4	792
November	1st to 10th	Night	25% 12% 26% 28% 8% 1	740
	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 2024-03-19 23:31:08. Version ac07

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