Little Colorado River Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Little Colorado River Valley Observatory clear sky chart from 2005-11-06 to 2024-07-03.

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	3 4 1 4 4 4 4 3 5% 6% 62%	89874
	Night	3 4 2 4 3 3 4 3 5% 7% 63%	89523
Transparency	Day	20% 6% 8% 16% 27% 22%	89600
	Night	19% 6% 9% 19% 28% 19%	89318
Seeing	Day	6% 10% 21% 28% 23% 12%	14188
	Night	4 5% 23% 40% 24% 3	24296

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	1 6% 3 7% 4 4 4 3 5% 5% 59%	2858
	11th to 20th	Day	2 5% 2 4 3 3 4 3 5% 7% 61%	2860
	21st to end	Day	4 8% 2 7% 4 5% 5% 3 6% 8% 49%	3146
February	1st to 10th	Day	2 5% 2 4 3 3 3 3 4 7% 64%	1710
	11th to 20th	Day	3 6% 2 4 4 2 3 3 5% 7% 60%	1726
	21st to end	Day	3 6% 2 5% 3 4 4 3 5% 6% 59%	1712
March	1st to 10th	Day	1 4 1 4 3 3 4 3 5% 6% 65%	3444
	11th to 20th	Day	4 7% 2 7% 6% 4 5% 4 6% 7% 48%	3490
	21st to end	Day	2 3 2 4 3 3 4 4 5% 7% 62%	3825
April	1st to 10th	Day	1 3 1 3 3 3 3 3 5% 6% 68%	2154
	11th to 20th	Day	3 4 1 4 3 2 2 3 4 5% 70%	2251
	21st to end	Day	2 2 1 4 3 2 3 2 4 6% 70%	2280
May	1st to 10th	Day	2 1 2 2 2 2 2 4 4 79%	4075
	11th to 20th	Day	2 3 1 5% 4 3 3 3 5% 6% 65%	4071
	21st to end	Day	2 1 1 2 2 2 1 2 2 4 82%	4477
June	1st to 10th	Day	2 2 1 2 2 2 3 3 5% 6% 73%	2470
	11th to 20th	Day	2 1 2 2 2 3 2 3 4 80%	2470
	21st to end	Day	2 3 1 5% 4 4 4 4 5% 5% 63%	2470
July	1st to 10th	Day	4 2 2 5% 5% 5% 6% 6% 7% 9% 49%	2367
	11th to 20th	Day	3 4 1 6% 6% 6% 7% 6% 9% 10% 40%	2340
	21st to end	Day	5% 4 2 8% 7% 8% 8% 8% 9% 10% 30%	2545
August	1st to 10th	Day	5% 4 2 6% 6% 6% 6% 7% 8% 8% 41%	2328
	11th to 20th	Day	5% 4 2 6% 6% 6% 8% 6% 7% 9% 41%	2263
	21st to end	Day	4 3 2 4 5% 6% 6% 6% 8% 9% 48%	2376
September	1st to 10th	Day	6% 4 2 5% 5% 5% 6% 5% 5% 7% 51%	2125
	11th to 20th	Day	3 2 2 4 3 3 3 3 5% 6% 66%	1980
	21st to end	Day	3 2 1 4 2 3 3 2 4 5% 70%	1980
October	1st to 10th	Day	4 3 1 3 3 4 3 2 4 5% 69%	1821
	11th to 20th	Day	2 2 1 1 2 2 2 2 3 3 80%	1800
	21st to end	Day	2 2 1 3 2 2 2 2 3 5% 76%	1980
November	1st to 10th	Day	1 2 1 2 2 3 2 2 3 6% 76%	1859
	11th to 20th	Day	3 2 1 3 2 2 2 2 4 6% 73%	1886
	21st to end	Day	3 5% 2 4 4 3 3 3 4 4 66%	1710
December	1st to 10th	Day	3 5% 2 5% 3 2 3 2 5% 7% 62%	1710
	11th to 20th	Day	3 7% 3 7% 5% 4 5% 4 4 7% 53%	2169
	21st to end	Day	4 6% 2 6% 5% 4 4 3 4 5% 57%	3146
January	1st to 10th	Night	2 9% 4 7% 3 4 4 3 5% 6% 53%	4097
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 8% 69%	4110
	21st to end	Night	6% 11% 2 6% 5% 4 5% 4 5% 7% 47%	4521
February	1st to 10th	Night	2 6% 1 4 3 2 3 3 4 7% 65%	2470
	11th to 20th	Night	2 6% 2 5% 4 4 4 4 4 6% 59%	2339
	21st to end	Night	2 4 2 5% 3 2 3 3 5% 7% 64%	1740
March	1st to 10th	Night	1 3 1 3 3 2 3 3 4 6% 72%	3430
	11th to 20th	Night	5% 5% 2 6% 4 4 5% 3 5% 7% 54%	3490
	21st to end	Night	2 3 1 4 3 3 4 4 6% 8% 63%	3828
April	1st to 10th	Night	2 4 1 2 3 3 3 3 5% 6% 68%	2024
	11th to 20th	Night	3 3 1 4 2 3 3 3 4 6% 69%	1877
	21st to end	Night	2 3 1 2 2 2 3 3 4 6% 72%	1900
May	1st to 10th	Night	1 1 2 2 2 2 2 2 4 81%	2891
	11th to 20th	Night	2 3 1 4 3 3 2 3 4 6% 69%	2834
	21st to end	Night	1 1 1 1 1 1 2 1 2 3 86%	3110
June	1st to 10th	Night	2 2 1 3 2 3 3 3 5% 6% 69%	1710
	11th to 20th	Night	2 1 1 2 1 1 2 2 4 6% 79%	1710
	21st to end	Night	2 3 1 4 4 3 5% 4 5% 7% 62%	1710
July	1st to 10th	Night	5% 4 2 6% 5% 5% 7% 4 9% 9% 45%	1638
	11th to 20th	Night	4 5% 2 7% 5% 6% 7% 6% 9% 11% 37%	1620
	21st to end	Night	7% 5% 2 7% 7% 8% 7% 7% 12% 11% 28%	1773
August	1st to 10th	Night	4 4 2 5% 4 6% 6% 5% 9% 10% 45%	1611
	11th to 20th	Night	3 4 2 8% 7% 6% 7% 5% 8% 10% 39%	1636
	21st to end	Night	4 4 2 5% 5% 5% 7% 5% 9% 11% 44%	1980
September	1st to 10th	Night	4 4 2 7% 5% 5% 6% 5% 7% 9% 47%	1830
	11th to 20th	Night	3 3 1 3 3 3 3 3 5% 7% 65%	1980
	21st to end	Night	3 2 1 3 3 3 3 3 5% 6% 69%	1980
October	1st to 10th	Night	3 2 1 4 3 3 3 3 4 5% 69%	2137
	11th to 20th	Night	2 2 3 2 1 2 2 2 4 81%	2160
	21st to end	Night	2 2 3 2 2 2 2 3 5% 77%	2376
November	1st to 10th	Night	2 2 1 2 2 3 3 2 4 6% 72%	2220
	11th to 20th	Night	2 2 1 3 2 2 2 2 3 6% 76%	2289
	21st to end	Night	3 5% 1 3 3 3 3 3 5% 6% 66%	2470
December	1st to 10th	Night	4 4 1 5% 2 2 3 2 4 7% 64%	2470
	11th to 20th	Night	4 5% 2 5% 4 3 5% 4 6% 8% 54%	3041
	21st to end	Night	4 5% 2 5% 4 4 4 3 5% 7% 56%	4521

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	22% 7% 7% 29% 27% 7%	2859
	11th to 20th	Day	19% 7% 9% 31% 28% 5%	2860
	21st to end	Day	28% 8% 10% 23% 25% 6%	3146
February	1st to 10th	Day	20% 4 9% 19% 31% 17%	1710
	11th to 20th	Day	21% 4 7% 22% 25% 19%	1735
	21st to end	Day	23% 6% 5% 16% 28% 22%	1712
March	1st to 10th	Day	15% 5% 6% 17% 39% 16%	3444
	11th to 20th	Day	24% 11% 11% 19% 22% 12%	3490
	21st to end	Day	16% 7% 10% 20% 37% 10%	3825
April	1st to 10th	Day	16% 4 6% 16% 35% 24%	2154
	11th to 20th	Day	16% 3 4 12% 32% 32%	2254
	21st to end	Day	15% 4 5% 14% 35% 26%	2280
May	1st to 10th	Day	9% 2 5% 10% 33% 40%	4075
	11th to 20th	Day	15% 6% 9% 10% 29% 31%	4074
	21st to end	Day	9% 2 3 6% 23% 58%	4477
June	1st to 10th	Day	10% 4 5% 11% 28% 42%	2470
	11th to 20th	Day	10% 3 3 7% 21% 56%	2470
	21st to end	Day	20% 6% 6% 10% 22% 35%	2470
July	1st to 10th	Day	29% 8% 12% 14% 13% 24%	2303
	11th to 20th	Day	33% 12% 19% 18% 10% 9%	2271
	21st to end	Day	40% 16% 19% 15% 8% 3	2404
August	1st to 10th	Day	35% 12% 16% 11% 13% 13%	2313
	11th to 20th	Day	33% 12% 14% 14% 16% 10%	2263
	21st to end	Day	28% 12% 12% 18% 22% 8%	2376
September	1st to 10th	Day	30% 7% 10% 15% 19% 18%	2125
	11th to 20th	Day	18% 6% 9% 16% 28% 23%	1980
	21st to end	Day	17% 4 8% 14% 28% 29%	1980
October	1st to 10th	Day	19% 5% 8% 16% 26% 27%	1821
	11th to 20th	Day	11% 3 3 10% 33% 39%	1800
	21st to end	Day	13% 3 6% 15% 42% 22%	1980
November	1st to 10th	Day	11% 3 5% 23% 37% 21%	1859
	11th to 20th	Day	14% 3 5% 20% 37% 22%	1886
	21st to end	Day	22% 3 5% 17% 33% 20%	1710
December	1st to 10th	Day	21% 4 8% 23% 31% 14%	1710
	11th to 20th	Day	29% 7% 11% 22% 20% 11%	2168
	21st to end	Day	26% 6% 8% 20% 32% 7%	3146
January	1st to 10th	Night	28% 7% 9% 24% 25% 7%	4097
	11th to 20th	Night	12% 5% 11% 35% 31% 5%	4110
	21st to end	Night	31% 9% 9% 22% 23% 5%	4521
February	1st to 10th	Night	18% 4 9% 20% 31% 16%	2470
	11th to 20th	Night	23% 5% 7% 23% 24% 18%	2340
	21st to end	Night	18% 5% 6% 19% 33% 19%	1740
March	1st to 10th	Night	11% 4 7% 23% 39% 17%	3430
	11th to 20th	Night	18% 10% 12% 23% 26% 11%	3490
	21st to end	Night	13% 7% 11% 26% 34% 8%	3828
April	1st to 10th	Night	15% 3 7% 19% 36% 21%	2024
	11th to 20th	Night	17% 3 5% 13% 35% 27%	1877
	21st to end	Night	12% 4 8% 15% 36% 25%	1900
May	1st to 10th	Night	8% 3 4 12% 45% 28%	2891
	11th to 20th	Night	13% 5% 8% 13% 33% 29%	2835
	21st to end	Night	7% 2 4 7% 24% 58%	3110
June	1st to 10th	Night	14% 4 5% 10% 26% 42%	1710
	11th to 20th	Night	8% 3 5% 7% 22% 56%	1710
	21st to end	Night	19% 6% 8% 13% 18% 36%	1710
July	1st to 10th	Night	28% 10% 14% 15% 11% 22%	1593
	11th to 20th	Night	31% 14% 20% 18% 9% 8%	1566
	21st to end	Night	40% 16% 21% 14% 7% 2	1674
August	1st to 10th	Night	28% 13% 17% 15% 13% 14%	1602
	11th to 20th	Night	34% 12% 17% 14% 11% 12%	1636
	21st to end	Night	28% 11% 16% 20% 17% 8%	1980
September	1st to 10th	Night	29% 9% 15% 14% 18% 15%	1830
	11th to 20th	Night	17% 6% 8% 19% 27% 22%	1980
	21st to end	Night	14% 6% 8% 13% 30% 29%	1980
October	1st to 10th	Night	16% 6% 8% 17% 25% 28%	2137
	11th to 20th	Night	10% 2 4 13% 31% 40%	2160
	21st to end	Night	12% 3 6% 17% 38% 25%	2376
November	1st to 10th	Night	13% 3 5% 20% 37% 20%	2220
	11th to 20th	Night	12% 2 6% 21% 35% 24%	2289
	21st to end	Night	17% 5% 7% 19% 33% 20%	2470
December	1st to 10th	Night	21% 4 7% 24% 30% 14%	2470
	11th to 20th	Night	24% 7% 10% 22% 29% 8%	3041
	21st to end	Night	24% 6% 10% 21% 26% 14%	4521

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	5% 12% 24% 34% 19% 5%	270
	11th to 20th	Day	9% 11% 23% 24% 27% 7%	270
	21st to end	Day	4 10% 22% 30% 24% 9%	297
February	1st to 10th	Day	4 12% 23% 30% 23% 8%	270
	11th to 20th	Day	8% 15% 27% 34% 13% 2	331
	21st to end	Day	11% 23% 27% 25% 10% 3	382
March	1st to 10th	Day	10% 21% 29% 25% 12% 3	460
	11th to 20th	Day	8% 19% 25% 28% 14% 5%	460
	21st to end	Day	10% 24% 30% 22% 11% 3	506
April	1st to 10th	Day	6% 17% 29% 27% 17% 5%	460
	11th to 20th	Day	10% 17% 32% 24% 13% 4	452
	21st to end	Day	6% 17% 32% 23% 16% 5%	460
May	1st to 10th	Day	5% 12% 35% 26% 18% 4	463
	11th to 20th	Day	4 13% 26% 28% 22% 8%	488
	21st to end	Day	6% 13% 31% 26% 19% 5%	529
June	1st to 10th	Day	3 5% 24% 33% 26% 10%	490
	11th to 20th	Day	2 8% 24% 33% 20% 13%	490
	21st to end	Day	2 3 21% 39% 24% 11%	490
July	1st to 10th	Day	4 2 10% 31% 30% 23%	455
	11th to 20th	Day	4 1 6% 25% 30% 34%	444
	21st to end	Day	7% 1 7% 22% 28% 35%	487
August	1st to 10th	Day	6% 1 8% 23% 36% 26%	447
	11th to 20th	Day	5% 3 8% 24% 35% 24%	437
	21st to end	Day	3 1 7% 26% 33% 29%	495
September	1st to 10th	Day	8% 3 14% 23% 30% 22%	450
	11th to 20th	Day	4 2 16% 34% 32% 12%	450
	21st to end	Day	5% 5% 21% 26% 28% 15%	450
October	1st to 10th	Day	4 7% 18% 27% 29% 14%	291
	11th to 20th	Day	5% 7% 17% 28% 31% 13%	270
	21st to end	Day	5% 6% 18% 26% 34% 13%	297
November	1st to 10th	Day	5% 9% 20% 35% 23% 8%	270
	11th to 20th	Day	4 6% 12% 35% 29% 14%	270
	21st to end	Day	6% 11% 20% 33% 21% 9%	270
December	1st to 10th	Day	7% 8% 17% 34% 25% 9%	270
	11th to 20th	Day	5% 9% 23% 35% 22% 6%	270
	21st to end	Day	11% 12% 23% 36% 15% 4	297
January	1st to 10th	Night	6% 6% 22% 42% 20% 4	760
	11th to 20th	Night	4 6% 23% 41% 21% 4	760
	21st to end	Night	8% 5% 26% 39% 19% 3	836
February	1st to 10th	Night	4 7% 29% 41% 16% 3	760
	11th to 20th	Night	6% 8% 33% 41% 12% 1	744
	21st to end	Night	4 12% 36% 38% 9% 1	628
March	1st to 10th	Night	3 12% 35% 38% 12% 1	760
	11th to 20th	Night	5% 9% 30% 39% 16% 2	760
	21st to end	Night	4 10% 35% 38% 12% 1	836
April	1st to 10th	Night	3 8% 37% 39% 12% 1	694
	11th to 20th	Night	3 13% 39% 36% 10%	563
	21st to end	Night	3 8% 38% 35% 15% 1	570
May	1st to 10th	Night	4 5% 35% 44% 11% 1	570
	11th to 20th	Night	2 4 30% 43% 18% 2	561
	21st to end	Night	3 4 34% 43% 15% 1	617
June	1st to 10th	Night	3 3 25% 51% 18%	570
	11th to 20th	Night	2 2 27% 51% 17% 1	570
	21st to end	Night	2 2 19% 46% 29% 1	570
July	1st to 10th	Night	5% 1 9% 45% 38% 2	531
	11th to 20th	Night	5% 1 7% 34% 47% 5%	522
	21st to end	Night	8% 1 7% 22% 52% 10%	591
August	1st to 10th	Night	5% 1 4 29% 51% 9%	537
	11th to 20th	Night	4 9% 33% 46% 7%	534
	21st to end	Night	5% 1 6% 29% 52% 6%	594
September	1st to 10th	Night	4 2 11% 37% 44% 3	570
	11th to 20th	Night	3 1 9% 42% 41% 4	720
	21st to end	Night	3 2 15% 40% 37% 4	720
October	1st to 10th	Night	3 2 23% 46% 23% 3	720
	11th to 20th	Night	2 3 18% 48% 27% 3	720
	21st to end	Night	3 4 17% 41% 30% 5%	792
November	1st to 10th	Night	3 4 21% 42% 27% 3	740
	11th to 20th	Night	3 3 22% 43% 25% 4	760
	21st to end	Night	5% 7% 24% 37% 24% 3	760
December	1st to 10th	Night	7% 6% 20% 41% 23% 3	760
	11th to 20th	Night	6% 6% 27% 40% 19% 2	760
	21st to end	Night	7% 8% 26% 41% 15% 3	836

Page generated at 2024-06-29 19:08:54. Version ac07

Copyright © 2024 Attilla Danko.