Blue Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Canyon clear sky chart from 2005-11-06 to 2026-03-03.

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	9% 7% 1 3 2 2 2 2 3 5% 64%	139806
	Night	10% 8% 2 3 2 2 3 2 4 5% 59%	138761
Transparency	Day	26% 2 6% 18% 25% 22%	134752
	Night	31% 2 6% 17% 23% 21%	134799
Seeing	Day	16% 15% 32% 25% 9% 3	16733
	Night	16% 7% 21% 33% 20% 3	26152

By Month

Percentage Cloud Cover SW (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	18% 15% 2 4 2 2 3 3 4 6% 41%	4722
	11th to 20th	Day	11% 7% 2 4 3 3 3 2 3 4 59%	5040
	21st to end	Day	14% 8% 2 5% 3 3 4 3 5% 7% 45%	5843
February	1st to 10th	Day	20% 11% 2 2 2 3 3 2 5% 5% 45%	1890
	11th to 20th	Day	15% 15% 2 4 3 3 3 3 5% 5% 41%	1996
	21st to end	Day	17% 15% 3 4 2 2 3 3 4 5% 43%	1730
March	1st to 10th	Day	15% 25% 5% 6% 3 3 3 3 4 5% 30%	4600
	11th to 20th	Day	14% 15% 2 4 3 2 2 2 3 4 47%	5000
	21st to end	Day	19% 22% 3 5% 3 3 3 3 4 5% 32%	5745
April	1st to 10th	Day	16% 12% 2 5% 3 3 3 3 5% 7% 41%	2400
	11th to 20th	Day	14% 9% 1 4 4 3 3 3 4 5% 50%	2369
	21st to end	Day	12% 7% 1 3 3 2 3 2 5% 6% 55%	2400
May	1st to 10th	Day	6% 5% 1 3 2 2 2 2 3 5% 70%	5643
	11th to 20th	Day	6% 4 1 3 2 2 2 2 3 5% 70%	6277
	21st to end	Day	5% 2 1 2 1 2 2 2 3 4 76%	6902
June	1st to 10th	Day	8% 4 1 4 4 3 3 3 5% 6% 60%	2800
	11th to 20th	Day	3 2 1 2 2 2 2 2 4 5% 76%	2800
	21st to end	Day	3 1 1 2 1 1 2 1 2 4 82%	2800
July	1st to 10th	Day	1 1 1 1 1 1 2 93%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 88%	6320
	21st to end	Day	1 1 1 2 2 2 2 1 3 3 82%	6577
August	1st to 10th	Day	1 1 1 2 1 2 1 2 3 3 83%	5777
	11th to 20th	Day	1 1 1 1 1 1 1 2 91%	5412
	21st to end	Day	2 1 1 2 2 2 2 2 3 3 81%	5984
September	1st to 10th	Day	2 1 1 1 2 2 1 2 4 84%	2400
	11th to 20th	Day	5% 2 1 3 2 2 2 2 3 5% 73%	2400
	21st to end	Day	5% 3 1 2 2 1 1 2 3 4 76%	2172
October	1st to 10th	Day	5% 3 1 3 2 1 2 3 4 5% 71%	3280
	11th to 20th	Day	8% 3 1 3 2 2 2 2 4 5% 69%	3261
	21st to end	Day	7% 5% 1 4 4 3 4 3 4 6% 61%	3545
November	1st to 10th	Day	13% 8% 2 3 3 2 3 3 4 6% 53%	1854
	11th to 20th	Day	16% 6% 1 4 4 3 3 3 5% 7% 48%	1890
	21st to end	Day	11% 9% 2 4 3 3 3 3 5% 5% 53%	1758
December	1st to 10th	Day	11% 4 1 3 2 3 3 3 6% 6% 57%	2700
	11th to 20th	Day	25% 12% 2 5% 3 3 3 3 5% 6% 32%	3108
	21st to end	Day	23% 10% 2 5% 3 4 4 4 5% 7% 33%	4092
January	1st to 10th	Night	17% 13% 3 5% 3 3 4 3 5% 6% 38%	8172
	11th to 20th	Night	12% 5% 1 3 2 2 3 2 4 6% 59%	7919
	21st to end	Night	12% 11% 3 6% 4 4 4 3 4 6% 44%	8371
February	1st to 10th	Night	18% 8% 3 4 3 3 2 3 4 5% 47%	2730
	11th to 20th	Night	13% 14% 2 5% 3 3 5% 3 5% 6% 42%	2511
	21st to end	Night	16% 12% 3 5% 2 3 3 3 3 6% 46%	2076
March	1st to 10th	Night	16% 22% 4 5% 3 2 2 2 4 6% 33%	5323
	11th to 20th	Night	18% 16% 2 3 2 2 2 2 3 4 46%	5000
	21st to end	Night	17% 20% 3 5% 3 3 4 3 5% 5% 32%	5229
April	1st to 10th	Night	14% 12% 2 4 3 3 2 3 6% 6% 45%	2000
	11th to 20th	Night	12% 9% 2 4 3 3 3 3 4 6% 50%	1979
	21st to end	Night	10% 7% 1 3 2 3 3 2 4 5% 59%	2000
May	1st to 10th	Night	4 5% 1 3 2 2 3 2 4 5% 69%	4327
	11th to 20th	Night	4 4 1 3 2 2 2 2 3 5% 72%	3616
	21st to end	Night	4 2 1 2 2 2 2 1 3 4 77%	3972
June	1st to 10th	Night	8% 4 1 3 2 3 3 3 5% 7% 63%	1600
	11th to 20th	Night	2 2 1 2 1 1 2 2 4 5% 78%	1600
	21st to end	Night	3 2 1 2 2 2 2 1 3 3 80%	1600
July	1st to 10th	Night	1 1 1 1 1 1 93%	3640
	11th to 20th	Night	2 2 1 2 1 1 2 1 2 3 85%	3640
	21st to end	Night	1 1 1 3 2 2 2 2 4 5% 77%	4283
August	1st to 10th	Night	2 2 1 2 1 2 2 1 3 4 80%	4035
	11th to 20th	Night	1 1 1 1 1 1 2 3 90%	4454
	21st to end	Night	3 2 1 2 1 2 2 2 2 3 80%	5015
September	1st to 10th	Night	2 1 1 1 1 2 2 2 4 84%	2000
	11th to 20th	Night	4 2 1 3 2 2 2 2 3 4 76%	2000
	21st to end	Night	3 3 1 2 2 2 2 2 4 4 75%	2222
October	1st to 10th	Night	4 3 1 3 2 2 2 2 2 3 77%	3920
	11th to 20th	Night	4 3 1 2 2 2 2 1 3 4 76%	3897
	21st to end	Night	10% 3 1 2 3 2 3 3 5% 6% 62%	4253
November	1st to 10th	Night	14% 7% 1 3 3 2 3 2 4 6% 54%	2665
	11th to 20th	Night	12% 6% 1 5% 3 3 3 3 5% 7% 51%	2730
	21st to end	Night	12% 8% 1 4 2 3 3 3 4 6% 54%	2860
December	1st to 10th	Night	11% 5% 1 2 2 2 3 2 4 6% 62%	4700
	11th to 20th	Night	23% 14% 2 4 3 3 4 4 6% 8% 29%	5316
	21st to end	Night	24% 14% 3 5% 4 4 4 3 4 5% 31%	7106

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	47% 2 11% 17% 16% 7%	4723
	11th to 20th	Day	32% 2 4 12% 21% 29%	5040
	21st to end	Day	40% 2 5% 18% 20% 15%	5843
February	1st to 10th	Day	42% 2 9% 17% 18% 11%	1890
	11th to 20th	Day	45% 3 8% 18% 19% 7%	2006
	21st to end	Day	45% 3 8% 22% 14% 8%	1730
March	1st to 10th	Day	58% 3 5% 13% 16% 6%	4600
	11th to 20th	Day	44% 2 9% 27% 13% 5%	5000
	21st to end	Day	56% 3 11% 18% 10% 1	5745
April	1st to 10th	Day	43% 4 12% 22% 16% 3	2400
	11th to 20th	Day	35% 4 13% 23% 18% 6%	2372
	21st to end	Day	30% 3 14% 28% 21% 4	2400
May	1st to 10th	Day	20% 2 9% 27% 28% 15%	5643
	11th to 20th	Day	19% 2 9% 29% 33% 8%	6280
	21st to end	Day	14% 2 7% 30% 39% 7%	6904
June	1st to 10th	Day	25% 3 11% 23% 29% 9%	2800
	11th to 20th	Day	12% 3 8% 21% 36% 21%	2800
	21st to end	Day	10% 1 2 16% 39% 33%	2800
July	1st to 10th	Day	3 1 1 6% 21% 68%	6251
	11th to 20th	Day	6% 1 1 5% 14% 73%	6245
	21st to end	Day	10% 1 1 16% 30% 42%	6387
August	1st to 10th	Day	12% 2 1 8% 25% 52%	4206
	11th to 20th	Day	5% 1 1 7% 42% 44%	3916
	21st to end	Day	7% 1 1 11% 45% 35%	4311
September	1st to 10th	Day	7% 1 2 11% 32% 46%	2400
	11th to 20th	Day	16% 2 4 20% 37% 20%	2400
	21st to end	Day	15% 1 5% 18% 35% 26%	2172
October	1st to 10th	Day	17% 2 3 12% 33% 32%	3280
	11th to 20th	Day	19% 2 4 18% 40% 17%	3261
	21st to end	Day	26% 2 5% 23% 30% 14%	3545
November	1st to 10th	Day	33% 3 8% 20% 23% 13%	1854
	11th to 20th	Day	37% 3 9% 18% 22% 10%	1890
	21st to end	Day	33% 3 6% 20% 24% 14%	1758
December	1st to 10th	Day	28% 3 6% 22% 26% 16%	2700
	11th to 20th	Day	54% 2 7% 15% 14% 8%	3108
	21st to end	Day	52% 3 10% 19% 12% 4	4092
January	1st to 10th	Night	48% 3 11% 17% 15% 6%	8172
	11th to 20th	Night	29% 2 5% 10% 22% 31%	7919
	21st to end	Night	44% 2 5% 12% 18% 20%	8371
February	1st to 10th	Night	41% 2 6% 19% 19% 14%	2730
	11th to 20th	Night	44% 3 7% 19% 20% 8%	2512
	21st to end	Night	42% 3 8% 22% 19% 8%	2076
March	1st to 10th	Night	54% 3 7% 17% 13% 7%	5323
	11th to 20th	Night	44% 2 8% 22% 19% 6%	5000
	21st to end	Night	54% 4 12% 19% 9% 2	5229
April	1st to 10th	Night	40% 4 12% 22% 17% 5%	2000
	11th to 20th	Night	35% 4 13% 23% 18% 7%	1979
	21st to end	Night	28% 4 12% 33% 20% 4	2000
May	1st to 10th	Night	20% 2 11% 26% 30% 11%	4324
	11th to 20th	Night	17% 2 8% 31% 30% 12%	3616
	21st to end	Night	13% 2 9% 30% 37% 9%	3972
June	1st to 10th	Night	22% 5% 12% 26% 25% 11%	1600
	11th to 20th	Night	10% 3 6% 22% 35% 23%	1600
	21st to end	Night	12% 1 3 13% 35% 35%	1600
July	1st to 10th	Night	3 1 1 6% 22% 67%	3600
	11th to 20th	Night	8% 2 1 5% 14% 70%	3592
	21st to end	Night	12% 2 2 13% 26% 45%	4161
August	1st to 10th	Night	14% 2 2 7% 25% 50%	2929
	11th to 20th	Night	5% 1 1 8% 40% 44%	3217
	21st to end	Night	9% 1 1 12% 36% 40%	3608
September	1st to 10th	Night	8% 1 2 9% 32% 47%	2000
	11th to 20th	Night	14% 2 5% 20% 39% 20%	2000
	21st to end	Night	14% 2 4 19% 33% 27%	2222
October	1st to 10th	Night	16% 2 3 11% 28% 40%	3920
	11th to 20th	Night	15% 1 3 23% 39% 18%	3897
	21st to end	Night	25% 2 4 22% 30% 17%	4253
November	1st to 10th	Night	32% 3 8% 21% 20% 16%	2665
	11th to 20th	Night	33% 3 11% 20% 23% 11%	2730
	21st to end	Night	33% 3 6% 19% 23% 15%	2860
December	1st to 10th	Night	26% 2 6% 21% 23% 22%	4700
	11th to 20th	Night	53% 3 5% 12% 19% 7%	5316
	21st to end	Night	57% 3 8% 15% 11% 6%	7106

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	44% 13% 19% 16% 8%	220
	11th to 20th	Day	26% 12% 28% 22% 10% 2	325
	21st to end	Day	26% 14% 22% 26% 11% 1	473
February	1st to 10th	Day	32% 16% 25% 19% 8% 1	430
	11th to 20th	Day	30% 20% 30% 16% 4 1	508
	21st to end	Day	29% 16% 33% 18% 4	446
March	1st to 10th	Day	38% 20% 24% 13% 4 1	509
	11th to 20th	Day	35% 17% 22% 16% 8% 2	500
	21st to end	Day	33% 20% 27% 15% 4 1	550
April	1st to 10th	Day	26% 23% 28% 17% 5% 1	500
	11th to 20th	Day	24% 21% 29% 20% 4 1	492
	21st to end	Day	17% 19% 32% 23% 8% 1	500
May	1st to 10th	Day	17% 23% 30% 21% 7% 2	503
	11th to 20th	Day	18% 18% 31% 21% 8% 3	528
	21st to end	Day	14% 14% 31% 25% 10% 5%	573
June	1st to 10th	Day	9% 15% 34% 26% 10% 6%	530
	11th to 20th	Day	9% 18% 36% 24% 9% 4	530
	21st to end	Day	3 15% 38% 27% 11% 6%	530
July	1st to 10th	Day	2 9% 46% 27% 11% 5%	526
	11th to 20th	Day	1 6% 43% 31% 12% 6%	524
	21st to end	Day	1 6% 41% 32% 13% 6%	575
August	1st to 10th	Day	4 9% 39% 32% 13% 4	527
	11th to 20th	Day	3 11% 36% 36% 11% 4	517
	21st to end	Day	2 8% 41% 35% 11% 2	583
September	1st to 10th	Day	3 12% 43% 28% 12% 2	530
	11th to 20th	Day	8% 12% 35% 33% 9% 2	530
	21st to end	Day	8% 13% 37% 34% 8% 1	530
October	1st to 10th	Day	8% 18% 32% 30% 10% 2	530
	11th to 20th	Day	11% 14% 28% 32% 12% 2	530
	21st to end	Day	14% 14% 27% 30% 11% 3	582
November	1st to 10th	Day	20% 10% 22% 27% 17% 4	330
	11th to 20th	Day	20% 12% 23% 29% 14% 2	330
	21st to end	Day	21% 11% 24% 28% 14% 2	260
December	1st to 10th	Day	23% 13% 22% 22% 15% 5%	220
	11th to 20th	Day	26% 14% 22% 21% 14% 3	220
	21st to end	Day	33% 12% 25% 20% 10% 1	242
January	1st to 10th	Night	30% 6% 25% 22% 12% 4	840
	11th to 20th	Night	21% 12% 29% 28% 9% 1	840
	21st to end	Night	24% 12% 24% 23% 15% 2	924
February	1st to 10th	Night	25% 10% 28% 25% 11% 1	840
	11th to 20th	Night	24% 10% 23% 27% 13% 2	824
	21st to end	Night	24% 10% 28% 29% 8% 2	692
March	1st to 10th	Night	31% 9% 21% 26% 11% 2	808
	11th to 20th	Night	28% 8% 18% 26% 20% 1	800
	21st to end	Night	27% 9% 23% 27% 12% 1	880
April	1st to 10th	Night	21% 7% 23% 34% 14% 2	800
	11th to 20th	Night	18% 9% 23% 32% 15% 3	791
	21st to end	Night	15% 6% 20% 36% 20% 4	800
May	1st to 10th	Night	12% 10% 24% 32% 19% 3	710
	11th to 20th	Night	10% 5% 18% 40% 25% 3	394
	21st to end	Night	12% 4 16% 36% 28% 5%	433
June	1st to 10th	Night	9% 4 15% 40% 30% 4	400
	11th to 20th	Night	3 5% 20% 39% 31% 3	400
	21st to end	Night	3 2 15% 45% 31% 4	400
July	1st to 10th	Night	1 1 14% 38% 43% 3	390
	11th to 20th	Night	1 1 12% 46% 35% 5%	388
	21st to end	Night	2 1 11% 34% 44% 8%	572
August	1st to 10th	Night	3 1 14% 43% 34% 6%	597
	11th to 20th	Night	1 1 15% 41% 34% 8%	765
	21st to end	Night	2 1 10% 48% 35% 4	880
September	1st to 10th	Night	2 1 14% 45% 33% 5%	800
	11th to 20th	Night	5% 2 15% 39% 31% 8%	800
	21st to end	Night	5% 4 21% 38% 24% 8%	800
October	1st to 10th	Night	8% 5% 20% 40% 22% 4	800
	11th to 20th	Night	11% 6% 20% 36% 24% 5%	800
	21st to end	Night	12% 7% 22% 33% 21% 6%	880
November	1st to 10th	Night	19% 5% 19% 32% 21% 4	820
	11th to 20th	Night	16% 10% 24% 32% 15% 3	840
	21st to end	Night	17% 8% 29% 28% 16% 3	840
December	1st to 10th	Night	23% 11% 24% 30% 10% 2	840
	11th to 20th	Night	30% 8% 24% 27% 10% 2	840
	21st to end	Night	33% 10% 24% 23% 9%	924

Page generated at 2026-02-27 22:40:21. Version ac07

Copyright © 2026 Attilla Danko.