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 2025-08-05.

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% 4 9% 5% 4 4 3 5% 7% 32%	126121
	Night	16% 12% 4 9% 5% 5% 4 4 5% 6% 31%	121923
Transparency	Day	52% 4 11% 22% 11% 1	129688
	Night	53% 4 11% 20% 11% 1	126442
Seeing	Day	24% 14% 31% 20% 9% 3	15317
	Night	23% 12% 30% 25% 10% 1	24560

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	13% 15% 5% 12% 5% 4 6% 4 5% 7% 26%	3597
	11th to 20th	Day	10% 20% 8% 17% 7% 7% 5% 3 4 3 14%	3638
	21st to end	Day	13% 18% 8% 16% 7% 5% 4 3 4 4 18%	4466
February	1st to 10th	Day	13% 17% 6% 13% 9% 5% 5% 3 4 3 21%	1800
	11th to 20th	Day	13% 15% 6% 13% 7% 5% 4 3 4 4 25%	1753
	21st to end	Day	16% 16% 6% 11% 7% 5% 4 3 4 5% 23%	1545
March	1st to 10th	Day	19% 13% 5% 11% 5% 4 4 2 5% 6% 27%	4838
	11th to 20th	Day	12% 15% 4 10% 6% 5% 5% 4 6% 7% 26%	4980
	21st to end	Day	19% 13% 4 7% 4 3 3 3 3 5% 36%	5510
April	1st to 10th	Day	20% 13% 3 8% 5% 4 4 3 5% 6% 29%	2400
	11th to 20th	Day	22% 11% 2 6% 4 4 4 3 5% 4 36%	2402
	21st to end	Day	22% 10% 3 7% 5% 4 4 4 4 5% 32%	2600
May	1st to 10th	Day	21% 8% 3 7% 5% 4 4 3 5% 6% 33%	6113
	11th to 20th	Day	18% 10% 3 7% 5% 4 4 3 4 7% 35%	6318
	21st to end	Day	19% 9% 3 7% 5% 4 4 4 5% 7% 34%	6949
June	1st to 10th	Day	19% 8% 2 7% 6% 5% 4 4 6% 8% 32%	2800
	11th to 20th	Day	14% 8% 2 7% 4 5% 6% 4 6% 9% 35%	2800
	21st to end	Day	18% 7% 3 6% 5% 5% 4 4 6% 8% 34%	2800
July	1st to 10th	Day	13% 6% 3 7% 5% 4 5% 4 6% 10% 39%	6360
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 46%	6360
	21st to end	Day	7% 4 2 6% 4 4 5% 5% 7% 9% 46%	6803
August	1st to 10th	Day	16% 9% 3 6% 4 4 5% 4 6% 8% 35%	4156
	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	17% 10% 4 8% 5% 5% 4 4 6% 6% 31%	1647
	11th to 20th	Day	17% 14% 4 9% 5% 5% 4 4 6% 7% 27%	1600
	21st to end	Day	21% 19% 5% 9% 6% 5% 4 5% 5% 5% 17%	1600
December	1st to 10th	Day	18% 23% 7% 12% 6% 4 3 3 4 6% 14%	2600
	11th to 20th	Day	18% 19% 6% 14% 4 4 3 3 3 3 22%	2986
	21st to end	Day	23% 20% 5% 12% 4 4 3 2 3 4 20%	3960
January	1st to 10th	Night	15% 17% 6% 12% 6% 5% 5% 3 5% 5% 21%	6349
	11th to 20th	Night	12% 15% 7% 19% 9% 7% 6% 4 4 4 13%	6246
	21st to end	Night	13% 16% 9% 15% 6% 5% 4 3 4 5% 19%	6490
February	1st to 10th	Night	12% 16% 5% 11% 7% 6% 6% 4 5% 6% 21%	2600
	11th to 20th	Night	13% 14% 6% 11% 7% 5% 5% 3 5% 5% 26%	2533
	21st to end	Night	15% 15% 4 9% 6% 5% 5% 4 5% 6% 26%	2084
March	1st to 10th	Night	18% 13% 4 10% 5% 6% 4 3 4 5% 28%	4999
	11th to 20th	Night	10% 12% 5% 9% 6% 5% 6% 4 6% 7% 29%	4979
	21st to end	Night	20% 8% 3 7% 5% 4 4 4 5% 7% 33%	5422
April	1st to 10th	Night	19% 12% 4 7% 5% 5% 4 3 5% 6% 30%	2000
	11th to 20th	Night	17% 11% 3 8% 5% 3 3 4 4 6% 36%	1965
	21st to end	Night	19% 10% 3 7% 5% 5% 4 5% 6% 5% 33%	1800
May	1st to 10th	Night	23% 9% 3 7% 5% 4 4 3 5% 6% 33%	3828
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 7% 41%	3575
	21st to end	Night	18% 8% 2 6% 5% 5% 4 4 4 7% 38%	3926
June	1st to 10th	Night	16% 7% 2 6% 5% 4 5% 4 6% 8% 38%	1600
	11th to 20th	Night	13% 6% 2 4 5% 5% 4 4 5% 9% 43%	1600
	21st to end	Night	14% 7% 3 7% 5% 4 5% 4 5% 7% 39%	1600
July	1st to 10th	Night	11% 5% 3 7% 5% 5% 5% 4 7% 8% 40%	3600
	11th to 20th	Night	13% 6% 2 5% 3 4 3 4 5% 7% 49%	3600
	21st to end	Night	9% 6% 2 5% 4 4 4 4 5% 7% 51%	4033
August	1st to 10th	Night	12% 5% 2 6% 3 4 4 4 5% 8% 47%	2861
	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%	2646
	11th to 20th	Night	18% 13% 4 8% 5% 4 4 3 5% 6% 29%	2800
	21st to end	Night	20% 13% 4 10% 7% 5% 4 4 6% 6% 21%	2800
December	1st to 10th	Night	20% 19% 6% 11% 6% 4 5% 3 4 5% 16%	4580
	11th to 20th	Night	16% 20% 6% 15% 6% 4 4 3 4 5% 17%	5208
	21st to end	Night	24% 19% 5% 14% 5% 4 3 3 3 4 16%	6996

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	57% 3 10% 21% 8% 1	3598
	11th to 20th	Day	74% 2 7% 10% 6% 1	3668
	21st to end	Day	70% 2 7% 11% 9% 1	4466
February	1st to 10th	Day	67% 2 8% 17% 5% 1	1800
	11th to 20th	Day	63% 3 8% 14% 10% 1	1762
	21st to end	Day	64% 2 9% 15% 10% 1	1545
March	1st to 10th	Day	60% 2 10% 13% 14% 1	4841
	11th to 20th	Day	57% 3 13% 17% 8% 2	4980
	21st to end	Day	52% 2 6% 21% 16% 2	5510
April	1st to 10th	Day	56% 2 7% 20% 12% 2	2400
	11th to 20th	Day	52% 2 8% 21% 15% 1	2402
	21st to end	Day	55% 2 8% 20% 12% 3	2600
May	1st to 10th	Day	52% 2 8% 22% 10% 5%	6122
	11th to 20th	Day	51% 2 9% 18% 18% 1	6322
	21st to end	Day	50% 3 11% 22% 12% 2	6949
June	1st to 10th	Day	51% 3 10% 21% 15% 1	2800
	11th to 20th	Day	44% 4 11% 26% 13% 2	2800
	21st to end	Day	47% 4 12% 24% 12% 1	2800
July	1st to 10th	Day	39% 6% 14% 27% 12% 1	6290
	11th to 20th	Day	34% 5% 13% 30% 17%	6285
	21st to end	Day	32% 7% 13% 36% 12%	6607
August	1st to 10th	Day	46% 4 14% 24% 11% 1	4143
	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 13% 23% 8% 1	1647
	11th to 20th	Day	56% 3 14% 17% 9% 2	1600
	21st to end	Day	67% 4 10% 12% 5% 1	1600
December	1st to 10th	Day	72% 3 11% 9% 3	2600
	11th to 20th	Day	68% 4 7% 13% 7%	2986
	21st to end	Day	70% 3 6% 13% 8%	3960
January	1st to 10th	Night	65% 2 9% 16% 8%	6349
	11th to 20th	Night	72% 4 8% 10% 5% 1	6291
	21st to end	Night	67% 2 9% 10% 11% 1	6490
February	1st to 10th	Night	63% 3 9% 18% 6% 1	2600
	11th to 20th	Night	59% 2 9% 20% 9% 1	2535
	21st to end	Night	57% 2 10% 21% 9%	2084
March	1st to 10th	Night	58% 3 7% 16% 12% 4	5009
	11th to 20th	Night	53% 3 16% 18% 9% 1	4980
	21st to end	Night	50% 2 8% 21% 17% 2	5422
April	1st to 10th	Night	55% 2 8% 21% 12% 2	2000
	11th to 20th	Night	50% 3 8% 23% 15% 1	1965
	21st to end	Night	52% 4 9% 18% 16% 2	1800
May	1st to 10th	Night	54% 2 9% 17% 13% 5%	3835
	11th to 20th	Night	44% 2 13% 22% 17% 2	3576
	21st to end	Night	47% 3 12% 23% 14% 2	3927
June	1st to 10th	Night	44% 3 11% 25% 16% 2	1600
	11th to 20th	Night	39% 4 12% 26% 19% 2	1600
	21st to end	Night	44% 4 14% 24% 13% 2	1600
July	1st to 10th	Night	39% 7% 15% 23% 15% 1	3560
	11th to 20th	Night	34% 5% 12% 32% 17%	3552
	21st to end	Night	32% 6% 11% 37% 14% 1	3914
August	1st to 10th	Night	35% 5% 14% 27% 17% 1	2850
	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 11% 25% 10%	2646
	11th to 20th	Night	55% 4 12% 19% 9% 1	2800
	21st to end	Night	61% 5% 13% 16% 5%	2800
December	1st to 10th	Night	69% 5% 11% 12% 3	4580
	11th to 20th	Night	70% 3 10% 12% 6%	5208
	21st to end	Night	73% 2 7% 11% 7%	6996

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	25% 20% 36% 14% 6% 1	200
	11th to 20th	Day	27% 20% 33% 17% 3 1	215
	21st to end	Day	25% 19% 37% 13% 5% 1	330
February	1st to 10th	Day	32% 19% 36% 10% 3	300
	11th to 20th	Day	30% 24% 39% 5% 2	300
	21st to end	Day	34% 15% 38% 12% 1	309
March	1st to 10th	Day	28% 16% 37% 15% 4	500
	11th to 20th	Day	28% 16% 34% 18% 3 1	500
	21st to end	Day	33% 16% 31% 14% 6% 1	550
April	1st to 10th	Day	29% 20% 30% 14% 6%	500
	11th to 20th	Day	36% 15% 24% 16% 6% 3	492
	21st to end	Day	29% 18% 31% 14% 6% 1	500
May	1st to 10th	Day	28% 13% 32% 17% 6% 5%	503
	11th to 20th	Day	21% 13% 35% 19% 10% 3	527
	21st to end	Day	21% 12% 34% 19% 10% 4	573
June	1st to 10th	Day	24% 12% 34% 22% 8% 1	530
	11th to 20th	Day	18% 11% 34% 23% 11% 3	530
	21st to end	Day	22% 13% 32% 22% 9% 3	530
July	1st to 10th	Day	13% 7% 33% 30% 13% 4	525
	11th to 20th	Day	14% 8% 31% 28% 14% 5%	524
	21st to end	Day	12% 8% 36% 28% 12% 4	576
August	1st to 10th	Day	16% 5% 29% 29% 14% 7%	502
	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	28% 15% 31% 18% 7% 1	281
	11th to 20th	Day	33% 18% 35% 10% 4 2	200
	21st to end	Day	33% 16% 34% 16% 2 1	200
December	1st to 10th	Day	34% 19% 26% 19% 3	200
	11th to 20th	Day	37% 18% 29% 14% 2 1	200
	21st to end	Day	31% 21% 32% 11% 3 1	220
January	1st to 10th	Night	29% 18% 31% 17% 6%	800
	11th to 20th	Night	30% 14% 30% 20% 5%	800
	21st to end	Night	20% 14% 33% 25% 6% 1	880
February	1st to 10th	Night	24% 19% 36% 19% 2	800
	11th to 20th	Night	22% 17% 39% 17% 4	783
	21st to end	Night	25% 18% 32% 22% 4	660
March	1st to 10th	Night	26% 17% 34% 20% 3	800
	11th to 20th	Night	24% 16% 36% 20% 4 1	800
	21st to end	Night	21% 13% 34% 24% 8% 1	880
April	1st to 10th	Night	27% 14% 32% 22% 5%	800
	11th to 20th	Night	24% 15% 31% 20% 9% 1	781
	21st to end	Night	24% 11% 32% 23% 11% 1	600
May	1st to 10th	Night	23% 7% 29% 25% 13% 2	505
	11th to 20th	Night	16% 8% 35% 32% 9%	394
	21st to end	Night	15% 7% 30% 36% 11% 1	433
June	1st to 10th	Night	17% 7% 33% 30% 12% 1	400
	11th to 20th	Night	17% 8% 26% 38% 11% 1	400
	21st to end	Night	17% 6% 27% 38% 12%	400
July	1st to 10th	Night	8% 5% 26% 43% 16% 1	390
	11th to 20th	Night	12% 3 28% 36% 20% 1	388
	21st to end	Night	11% 4 27% 40% 16% 1	483
August	1st to 10th	Night	12% 3 19% 38% 25% 2	579
	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% 27% 8% 1	780
	11th to 20th	Night	28% 14% 33% 19% 6% 1	800
	21st to end	Night	30% 15% 29% 20% 6%	800
December	1st to 10th	Night	32% 16% 32% 14% 5%	800
	11th to 20th	Night	26% 17% 35% 18% 4 1	800
	21st to end	Night	34% 13% 31% 18% 3	880

Page generated at 2025-08-02 01:32:28. Version ac07

Copyright © 2025 Attilla Danko.