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 2024-12-02.

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	9% 7% 1 3 2 2 2 2 3 5% 63%	105414
	Night	11% 8% 2 3 2 2 3 2 4 5% 58%	102946
Transparency	Day	26% 2 6% 18% 25% 22%	105162
	Night	30% 3 7% 17% 23% 20%	102787
Seeing	Day	16% 15% 32% 26% 10% 3	15183
	Night	16% 7% 20% 33% 21% 4	24505

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	16% 18% 3 6% 3 3 2 2 3 6% 39%	2539
	11th to 20th	Day	20% 13% 3 7% 4 3 4 3 3 4 36%	2700
	21st to end	Day	22% 14% 3 6% 4 3 3 3 4 6% 34%	3146
February	1st to 10th	Day	19% 11% 2 2 2 3 3 2 5% 6% 45%	1710
	11th to 20th	Day	15% 15% 2 4 3 3 3 3 5% 5% 43%	1800
	21st to end	Day	17% 17% 3 4 2 2 2 3 4 4 43%	1570
March	1st to 10th	Day	17% 27% 6% 6% 3 3 3 2 4 4 25%	3186
	11th to 20th	Day	13% 12% 1 3 2 2 2 2 3 4 55%	3490
	21st to end	Day	17% 23% 3 6% 3 3 3 3 5% 5% 29%	4006
April	1st to 10th	Day	16% 12% 2 5% 3 3 3 3 4 7% 41%	2280
	11th to 20th	Day	14% 9% 1 3 4 3 3 3 4 5% 49%	2249
	21st to end	Day	12% 7% 1 3 3 2 3 2 5% 6% 55%	2280
May	1st to 10th	Day	9% 6% 1 3 2 2 2 2 3 4 67%	3951
	11th to 20th	Day	5% 3 1 2 2 1 2 2 3 5% 74%	4377
	21st to end	Day	7% 3 1 3 2 2 2 2 3 5% 68%	4813
June	1st to 10th	Day	8% 4 1 4 4 3 3 3 5% 7% 58%	2660
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 5% 76%	2660
	21st to end	Day	3 1 1 2 1 1 2 1 3 4 81%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 92%	4420
	11th to 20th	Day	2 2 1 1 1 1 2 2 2 3 83%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4578
August	1st to 10th	Day	2 2 1 3 2 2 2 2 4 4 77%	4091
	11th to 20th	Day	1 1 1 1 1 1 2 3 89%	3759
	21st to end	Day	2 1 1 1 1 1 1 2 2 88%	4180
September	1st to 10th	Day	2 1 1 1 2 1 2 3 86%	2280
	11th to 20th	Day	5% 2 1 3 2 2 2 2 3 5% 73%	2280
	21st to end	Day	5% 3 1 2 2 1 1 2 3 4 76%	2064
October	1st to 10th	Day	5% 3 1 3 2 2 2 3 4 5% 72%	3180
	11th to 20th	Day	8% 2 1 2 2 2 2 2 4 5% 69%	3161
	21st to end	Day	6% 5% 1 4 4 3 4 3 4 6% 61%	3435
November	1st to 10th	Day	13% 8% 2 3 3 2 3 3 4 6% 52%	1764
	11th to 20th	Day	15% 5% 1 4 4 3 3 3 5% 7% 50%	1800
	21st to end	Day	12% 9% 2 4 3 3 3 3 5% 5% 51%	1675
December	1st to 10th	Day	19% 6% 2 4 2 2 4 3 6% 7% 45%	1528
	11th to 20th	Day	27% 13% 2 6% 3 3 2 3 4 6% 31%	1928
	21st to end	Day	14% 9% 2 6% 4 4 4 4 6% 8% 39%	2794
January	1st to 10th	Night	13% 15% 3 5% 3 3 4 3 5% 6% 40%	4406
	11th to 20th	Night	22% 10% 3 5% 4 4 4 3 4 6% 35%	4262
	21st to end	Night	19% 16% 2 6% 4 4 4 3 4 6% 32%	4521
February	1st to 10th	Night	17% 9% 3 4 3 3 2 2 4 5% 47%	2470
	11th to 20th	Night	13% 13% 1 4 3 3 4 3 5% 6% 44%	2267
	21st to end	Night	15% 13% 3 5% 2 3 3 2 3 6% 45%	1884
March	1st to 10th	Night	18% 25% 5% 4 3 2 2 3 4 5% 30%	3685
	11th to 20th	Night	16% 10% 1 2 2 2 2 2 3 4 56%	3490
	21st to end	Night	18% 21% 2 5% 3 3 4 3 5% 5% 30%	3646
April	1st to 10th	Night	15% 12% 2 4 3 3 2 3 5% 6% 44%	1900
	11th to 20th	Night	13% 9% 2 4 3 3 3 3 4 6% 50%	1879
	21st to end	Night	10% 7% 1 3 2 3 3 3 4 6% 59%	1900
May	1st to 10th	Night	6% 7% 1 2 2 2 3 2 4 5% 65%	3017
	11th to 20th	Night	5% 2 1 2 1 2 2 2 3 5% 74%	2516
	21st to end	Night	6% 3 1 2 2 2 2 2 4 5% 71%	2762
June	1st to 10th	Night	8% 5% 1 3 2 3 3 3 4 6% 62%	1520
	11th to 20th	Night	2 2 1 2 1 1 2 2 4 5% 78%	1520
	21st to end	Night	3 2 1 2 2 2 2 1 3 3 79%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 92%	2540
	11th to 20th	Night	2 2 1 3 2 2 2 1 2 3 80%	2540
	21st to end	Night	1 1 1 2 1 1 1 2 3 3 84%	2976
August	1st to 10th	Night	3 3 1 3 2 2 3 2 4 5% 73%	2848
	11th to 20th	Night	1 1 1 1 1 1 1 3 2 88%	3088
	21st to end	Night	2 2 1 1 1 1 1 1 2 87%	3498
September	1st to 10th	Night	1 1 1 1 1 1 2 2 4 85%	1900
	11th to 20th	Night	3 2 1 3 2 2 2 2 3 4 77%	1900
	21st to end	Night	3 3 1 2 2 2 2 2 4 4 76%	2110
October	1st to 10th	Night	4 3 1 3 2 2 2 2 2 3 77%	3800
	11th to 20th	Night	4 2 1 2 2 2 2 1 3 4 77%	3777
	21st to end	Night	10% 3 1 2 3 2 3 3 5% 6% 62%	4121
November	1st to 10th	Night	14% 7% 1 3 3 2 3 2 4 6% 54%	2535
	11th to 20th	Night	11% 6% 1 4 3 3 3 3 6% 7% 53%	2600
	21st to end	Night	12% 8% 1 4 2 3 3 3 4 5% 53%	2724
December	1st to 10th	Night	19% 7% 1 3 2 2 4 3 3 5% 50%	2686
	11th to 20th	Night	29% 11% 2 4 3 2 3 3 4 7% 32%	3276
	21st to end	Night	17% 12% 3 6% 4 4 4 3 4 6% 35%	4862

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	50% 2 7% 22% 17% 3	2539
	11th to 20th	Day	54% 3 8% 15% 13% 7%	2700
	21st to end	Day	53% 3 8% 18% 14% 5%	3146
February	1st to 10th	Day	42% 2 9% 18% 19% 10%	1710
	11th to 20th	Day	43% 3 8% 17% 20% 8%	1810
	21st to end	Day	46% 3 7% 22% 15% 7%	1570
March	1st to 10th	Day	62% 4 7% 11% 11% 4	3186
	11th to 20th	Day	35% 2 8% 31% 17% 7%	3490
	21st to end	Day	57% 4 12% 17% 8% 2	4006
April	1st to 10th	Day	43% 4 12% 21% 16% 3	2280
	11th to 20th	Day	36% 4 13% 23% 18% 6%	2252
	21st to end	Day	30% 3 14% 28% 21% 4	2280
May	1st to 10th	Day	23% 3 12% 28% 20% 15%	3951
	11th to 20th	Day	15% 2 8% 27% 36% 11%	4380
	21st to end	Day	19% 3 10% 38% 25% 4	4814
June	1st to 10th	Day	26% 3 12% 22% 28% 10%	2660
	11th to 20th	Day	13% 3 8% 21% 36% 19%	2660
	21st to end	Day	10% 1 2 16% 37% 33%	2660
July	1st to 10th	Day	4 1 1 6% 16% 73%	4351
	11th to 20th	Day	8% 2 1 7% 18% 63%	4345
	21st to end	Day	7% 1 1 5% 29% 56%	4433
August	1st to 10th	Day	12% 2 1 8% 24% 53%	4076
	11th to 20th	Day	5% 1 1 7% 42% 44%	3795
	21st to end	Day	7% 1 1 11% 44% 36%	4179
September	1st to 10th	Day	6% 1 2 9% 32% 49%	2280
	11th to 20th	Day	16% 2 4 20% 37% 20%	2280
	21st to end	Day	14% 1 5% 19% 34% 26%	2064
October	1st to 10th	Day	16% 3 3 12% 33% 33%	3180
	11th to 20th	Day	19% 2 4 18% 40% 17%	3161
	21st to end	Day	26% 2 5% 23% 30% 15%	3435
November	1st to 10th	Day	34% 3 7% 20% 22% 13%	1764
	11th to 20th	Day	35% 3 10% 18% 23% 10%	1800
	21st to end	Day	35% 3 7% 19% 22% 14%	1675
December	1st to 10th	Day	39% 4 7% 20% 19% 11%	1528
	11th to 20th	Day	57% 3 6% 14% 14% 7%	1928
	21st to end	Day	44% 3 12% 22% 14% 5%	2794
January	1st to 10th	Night	44% 4 10% 24% 14% 4	4406
	11th to 20th	Night	51% 3 9% 13% 14% 9%	4262
	21st to end	Night	55% 3 8% 14% 13% 7%	4521
February	1st to 10th	Night	41% 3 6% 19% 19% 12%	2470
	11th to 20th	Night	42% 3 7% 19% 21% 8%	2268
	21st to end	Night	42% 3 7% 22% 19% 6%	1884
March	1st to 10th	Night	59% 3 10% 13% 11% 4	3685
	11th to 20th	Night	34% 2 8% 23% 25% 8%	3490
	21st to end	Night	54% 5% 12% 19% 8% 3	3646
April	1st to 10th	Night	41% 5% 12% 21% 16% 5%	1900
	11th to 20th	Night	36% 5% 13% 23% 18% 6%	1879
	21st to end	Night	27% 4 12% 32% 20% 4	1900
May	1st to 10th	Night	23% 3 14% 23% 25% 11%	3017
	11th to 20th	Night	14% 2 9% 24% 34% 17%	2516
	21st to end	Night	16% 3 13% 38% 25% 5%	2762
June	1st to 10th	Night	23% 5% 12% 24% 24% 12%	1520
	11th to 20th	Night	11% 3 7% 23% 35% 21%	1520
	21st to end	Night	13% 1 3 13% 33% 36%	1520
July	1st to 10th	Night	3 1 1 6% 15% 73%	2500
	11th to 20th	Night	12% 2 2 7% 14% 63%	2492
	21st to end	Night	7% 2 2 5% 25% 59%	2883
August	1st to 10th	Night	15% 2 2 7% 24% 51%	2839
	11th to 20th	Night	5% 1 1 8% 40% 45%	3118
	21st to end	Night	9% 1 1 12% 36% 41%	3498
September	1st to 10th	Night	7% 1 3 8% 32% 50%	1900
	11th to 20th	Night	14% 2 5% 20% 39% 21%	1900
	21st to end	Night	13% 2 4 20% 33% 28%	2110
October	1st to 10th	Night	16% 2 3 11% 27% 41%	3800
	11th to 20th	Night	14% 1 4 23% 40% 18%	3777
	21st to end	Night	25% 2 4 22% 29% 18%	4121
November	1st to 10th	Night	33% 3 8% 20% 20% 16%	2535
	11th to 20th	Night	31% 3 11% 20% 24% 11%	2600
	21st to end	Night	34% 3 6% 18% 22% 16%	2724
December	1st to 10th	Night	38% 4 8% 17% 19% 14%	2686
	11th to 20th	Night	54% 3 6% 12% 18% 7%	3276
	21st to end	Night	50% 3 10% 16% 15% 6%	4862

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	43% 12% 20% 17% 7%	180
	11th to 20th	Day	29% 11% 27% 22% 9% 2	275
	21st to end	Day	28% 14% 21% 25% 10% 2	407
February	1st to 10th	Day	32% 15% 27% 19% 7% 1	370
	11th to 20th	Day	28% 19% 30% 18% 4 1	432
	21st to end	Day	29% 16% 33% 18% 3	382
March	1st to 10th	Day	39% 20% 24% 12% 4 1	460
	11th to 20th	Day	33% 17% 23% 16% 9% 2	460
	21st to end	Day	32% 21% 28% 15% 4	506
April	1st to 10th	Day	25% 24% 28% 17% 5% 1	460
	11th to 20th	Day	26% 21% 28% 21% 4 1	452
	21st to end	Day	17% 19% 31% 23% 8% 1	460
May	1st to 10th	Day	17% 24% 31% 20% 7% 2	463
	11th to 20th	Day	17% 18% 31% 22% 9% 3	488
	21st to end	Day	15% 14% 31% 25% 10% 5%	529
June	1st to 10th	Day	10% 16% 33% 26% 10% 6%	490
	11th to 20th	Day	9% 18% 36% 24% 9% 4	490
	21st to end	Day	3 15% 38% 28% 11% 6%	490
July	1st to 10th	Day	1 7% 47% 28% 11% 5%	486
	11th to 20th	Day	1 7% 41% 32% 12% 6%	484
	21st to end	Day	1 6% 42% 33% 14% 5%	531
August	1st to 10th	Day	4 9% 38% 32% 13% 4	487
	11th to 20th	Day	3 12% 36% 35% 11% 4	477
	21st to end	Day	2 8% 42% 35% 10% 2	539
September	1st to 10th	Day	4 10% 43% 29% 13% 2	490
	11th to 20th	Day	9% 13% 34% 33% 9% 2	490
	21st to end	Day	7% 12% 38% 34% 8% 1	490
October	1st to 10th	Day	6% 18% 33% 31% 10% 2	490
	11th to 20th	Day	10% 13% 29% 33% 12% 3	490
	21st to end	Day	14% 15% 28% 30% 11% 3	538
November	1st to 10th	Day	21% 10% 22% 26% 17% 4	300
	11th to 20th	Day	18% 12% 23% 31% 15% 2	300
	21st to end	Day	22% 11% 23% 27% 16% 1	237
December	1st to 10th	Day	26% 13% 21% 20% 15% 4	182
	11th to 20th	Day	26% 14% 24% 20% 13% 3	180
	21st to end	Day	28% 12% 25% 22% 12% 1	198
January	1st to 10th	Night	28% 6% 24% 24% 13% 4	760
	11th to 20th	Night	23% 11% 27% 29% 10% 1	760
	21st to end	Night	24% 12% 22% 23% 17% 2	836
February	1st to 10th	Night	24% 10% 27% 26% 12% 1	760
	11th to 20th	Night	24% 10% 21% 28% 15% 3	744
	21st to end	Night	25% 11% 24% 30% 9% 2	628
March	1st to 10th	Night	31% 9% 20% 25% 12% 2	760
	11th to 20th	Night	27% 8% 18% 26% 21% 1	760
	21st to end	Night	27% 9% 23% 27% 13% 1	836
April	1st to 10th	Night	22% 6% 22% 34% 15% 2	760
	11th to 20th	Night	19% 9% 21% 32% 15% 3	751
	21st to end	Night	14% 6% 20% 35% 20% 4	760
May	1st to 10th	Night	12% 11% 24% 31% 20% 3	675
	11th to 20th	Night	10% 5% 15% 41% 26% 3	374
	21st to end	Night	12% 4 15% 34% 29% 5%	411
June	1st to 10th	Night	9% 4 14% 38% 31% 4	380
	11th to 20th	Night	3 5% 19% 38% 32% 3	380
	21st to end	Night	3 2 15% 43% 32% 4	380
July	1st to 10th	Night	1 1 12% 37% 45% 4	370
	11th to 20th	Night	1 1 12% 44% 36% 5%	368
	21st to end	Night	2 1 11% 31% 46% 8%	543
August	1st to 10th	Night	3 1 13% 41% 35% 7%	567
	11th to 20th	Night	2 1 15% 40% 34% 8%	726
	21st to end	Night	3 1 10% 46% 36% 4	836
September	1st to 10th	Night	2 1 13% 45% 34% 5%	760
	11th to 20th	Night	4 2 15% 38% 32% 9%	760
	21st to end	Night	5% 4 20% 38% 24% 8%	760
October	1st to 10th	Night	8% 5% 19% 41% 23% 5%	760
	11th to 20th	Night	10% 6% 18% 36% 24% 5%	760
	21st to end	Night	12% 7% 21% 32% 22% 6%	836
November	1st to 10th	Night	19% 5% 18% 31% 22% 4	780
	11th to 20th	Night	14% 10% 24% 33% 16% 3	800
	21st to end	Night	18% 8% 27% 28% 17% 3	800
December	1st to 10th	Night	24% 10% 22% 30% 11% 2	768
	11th to 20th	Night	30% 8% 23% 26% 11% 2	760
	21st to end	Night	29% 11% 24% 25% 10%	836

Page generated at 2024-11-29 07:43:07. Version ac07

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