Independence Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Independence Mountain clear sky chart from 2005-11-06 to 2025-10-04.

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	2 5% 2 7% 5% 5% 5% 5% 7% 8% 49%	135481
	Night	2 4 2 6% 4 4 5% 4 7% 9% 53%	131348
Transparency	Day	29% 9% 14% 22% 18% 7%	130366
	Night	27% 9% 16% 25% 17% 5%	127468
Seeing	Day	8% 20% 32% 25% 12% 2	16915
	Night	5% 14% 36% 31% 13% 1	26888

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	3 4 14% 7% 5% 6% 5% 7% 11% 38%	3638
	11th to 20th	Day	3 3 10% 9% 7% 6% 5% 7% 9% 41%	3847
	21st to end	Day	5% 3 9% 6% 6% 6% 4 7% 9% 46%	4510
February	1st to 10th	Day	5% 4 10% 9% 7% 6% 5% 8% 8% 39%	1800
	11th to 20th	Day	5% 4 11% 8% 6% 6% 6% 7% 8% 39%	1817
	21st to end	Day	5% 4 10% 7% 6% 7% 4 6% 8% 43%	1650
March	1st to 10th	Day	7% 4 9% 5% 4 5% 4 6% 7% 49%	4638
	11th to 20th	Day	1 7% 3 8% 4 4 5% 5% 7% 9% 47%	5000
	21st to end	Day	1 6% 3 8% 5% 5% 7% 5% 8% 10% 43%	5678
April	1st to 10th	Day	1 8% 3 7% 5% 5% 5% 5% 6% 8% 46%	2400
	11th to 20th	Day	2 11% 3 8% 7% 6% 6% 5% 7% 9% 37%	2371
	21st to end	Day	3 9% 3 7% 5% 5% 6% 5% 6% 10% 41%	2400
May	1st to 10th	Day	4 10% 3 7% 5% 6% 6% 6% 8% 9% 36%	5959
	11th to 20th	Day	3 7% 2 7% 5% 5% 6% 5% 7% 10% 43%	6298
	21st to end	Day	2 5% 2 5% 4 5% 5% 5% 7% 10% 49%	6925
June	1st to 10th	Day	4 4 2 4 4 5% 5% 5% 7% 10% 51%	2800
	11th to 20th	Day	4 3 1 4 4 4 4 4 6% 7% 59%	2800
	21st to end	Day	3 2 2 4 3 4 5% 5% 7% 7% 59%	2800
July	1st to 10th	Day	2 2 1 4 4 5% 5% 5% 7% 8% 57%	6339
	11th to 20th	Day	2 3 1 5% 5% 6% 6% 6% 7% 9% 49%	6340
	21st to end	Day	4 4 1 5% 4 5% 6% 5% 7% 9% 50%	6641
August	1st to 10th	Day	2 3 1 5% 5% 5% 6% 5% 8% 10% 48%	5779
	11th to 20th	Day	3 3 1 5% 5% 6% 5% 5% 8% 8% 52%	5607
	21st to end	Day	5% 4 2 7% 6% 6% 6% 4 6% 8% 46%	5984
September	1st to 10th	Day	4 3 2 4 4 3 4 4 4 6% 61%	2400
	11th to 20th	Day	4 4 2 4 4 3 4 4 7% 7% 58%	2400
	21st to end	Day	5% 6% 1 5% 3 3 3 2 3 6% 63%	2145
October	1st to 10th	Day	3 4 1 3 3 2 3 3 4 4 70%	3200
	11th to 20th	Day	2 5% 1 4 5% 5% 6% 4 6% 8% 54%	3150
	21st to end	Day	3 7% 2 5% 3 3 3 3 4 6% 61%	3407
November	1st to 10th	Day	1 5% 2 5% 4 4 5% 4 6% 7% 56%	1763
	11th to 20th	Day	1 7% 3 7% 4 3 4 4 6% 7% 53%	1745
	21st to end	Day	1 6% 2 8% 5% 4 4 4 4 8% 54%	1600
December	1st to 10th	Day	3 2 6% 4 3 4 3 6% 8% 61%	2620
	11th to 20th	Day	4 3 8% 4 4 4 4 5% 9% 56%	3026
	21st to end	Day	1 8% 4 10% 6% 5% 7% 5% 7% 8% 40%	4004
January	1st to 10th	Night	3 3 12% 7% 5% 6% 6% 9% 11% 38%	6327
	11th to 20th	Night	4 3 9% 6% 7% 6% 6% 8% 9% 43%	6174
	21st to end	Night	1 5% 3 7% 6% 6% 6% 5% 9% 13% 39%	6468
February	1st to 10th	Night	4 3 8% 7% 6% 7% 5% 8% 9% 42%	2600
	11th to 20th	Night	5% 3 8% 6% 6% 5% 6% 7% 10% 44%	2468
	21st to end	Night	5% 3 9% 5% 5% 5% 4 7% 8% 48%	1980
March	1st to 10th	Night	6% 3 9% 4 4 5% 4 7% 8% 49%	5225
	11th to 20th	Night	1 7% 3 6% 4 3 4 3 6% 10% 54%	5000
	21st to end	Night	1 7% 3 9% 5% 4 5% 4 7% 9% 46%	5273
April	1st to 10th	Night	1 7% 2 5% 4 4 4 5% 6% 8% 54%	2000
	11th to 20th	Night	3 8% 3 6% 4 5% 5% 4 6% 9% 48%	1977
	21st to end	Night	3 7% 3 6% 3 3 3 4 6% 7% 54%	2000
May	1st to 10th	Night	5% 8% 2 5% 5% 4 5% 4 6% 9% 48%	4014
	11th to 20th	Night	4 5% 2 5% 4 4 4 4 7% 10% 50%	3617
	21st to end	Night	2 5% 1 4 3 4 5% 4 6% 8% 56%	3972
June	1st to 10th	Night	3 2 1 3 2 4 4 4 6% 10% 62%	1600
	11th to 20th	Night	3 2 1 3 4 4 4 3 5% 7% 65%	1600
	21st to end	Night	2 3 1 3 2 2 3 2 6% 7% 68%	1600
July	1st to 10th	Night	3 2 1 3 3 4 4 4 6% 7% 62%	3640
	11th to 20th	Night	1 1 2 3 4 5% 5% 9% 11% 58%	3640
	21st to end	Night	1 2 1 4 3 4 5% 5% 7% 9% 59%	4215
August	1st to 10th	Night	2 2 1 3 4 4 5% 4 8% 10% 59%	4033
	11th to 20th	Night	1 2 1 3 3 4 5% 5% 7% 10% 58%	4239
	21st to end	Night	4 3 1 6% 7% 5% 5% 4 6% 8% 51%	4993
September	1st to 10th	Night	4 3 1 3 3 2 4 3 4 7% 66%	2000
	11th to 20th	Night	4 3 1 4 4 3 3 3 5% 8% 63%	2000
	21st to end	Night	5% 3 1 3 2 2 3 2 4 6% 67%	2251
October	1st to 10th	Night	3 3 1 3 2 1 2 2 4 4 75%	3836
	11th to 20th	Night	2 3 1 3 3 3 3 4 6% 9% 64%	3778
	21st to end	Night	2 5% 2 5% 3 3 3 3 5% 7% 63%	4120
November	1st to 10th	Night	2 4 2 5% 3 3 4 3 6% 8% 59%	2533
	11th to 20th	Night	1 5% 2 5% 4 5% 4 4 6% 7% 57%	2650
	21st to end	Night	1 5% 2 5% 5% 4 4 4 6% 10% 55%	2800
December	1st to 10th	Night	3 2 6% 4 3 4 5% 6% 9% 58%	4570
	11th to 20th	Night	3 2 6% 4 4 4 5% 7% 10% 56%	5181
	21st to end	Night	1 7% 4 10% 6% 6% 6% 5% 7% 12% 39%	6974

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	38% 11% 18% 19% 13% 1	3639
	11th to 20th	Day	40% 10% 16% 15% 15% 4	3847
	21st to end	Day	33% 11% 17% 17% 19% 3	4510
February	1st to 10th	Day	43% 13% 16% 17% 10% 2	1800
	11th to 20th	Day	41% 11% 17% 21% 8% 2	1826
	21st to end	Day	36% 12% 19% 17% 14% 2	1650
March	1st to 10th	Day	30% 9% 17% 20% 18% 6%	4638
	11th to 20th	Day	28% 10% 18% 30% 13% 1	5000
	21st to end	Day	34% 13% 20% 24% 7% 1	5678
April	1st to 10th	Day	35% 11% 16% 20% 14% 4	2400
	11th to 20th	Day	40% 11% 15% 18% 14% 2	2374
	21st to end	Day	36% 11% 16% 27% 10%	2400
May	1st to 10th	Day	40% 11% 13% 19% 15% 2	5959
	11th to 20th	Day	29% 12% 16% 23% 19% 2	6302
	21st to end	Day	25% 9% 12% 27% 24% 3	6926
June	1st to 10th	Day	24% 10% 17% 23% 19% 7%	2800
	11th to 20th	Day	21% 7% 11% 19% 26% 16%	2800
	21st to end	Day	20% 6% 11% 20% 28% 14%	2800
July	1st to 10th	Day	20% 5% 10% 16% 24% 25%	6271
	11th to 20th	Day	26% 7% 11% 22% 21% 12%	6265
	21st to end	Day	27% 7% 11% 17% 21% 17%	6450
August	1st to 10th	Day	29% 11% 13% 20% 15% 12%	4208
	11th to 20th	Day	29% 9% 13% 17% 22% 10%	4054
	21st to end	Day	24% 7% 12% 19% 24% 15%	4311
September	1st to 10th	Day	21% 6% 11% 20% 27% 15%	2400
	11th to 20th	Day	23% 7% 13% 22% 25% 11%	2400
	21st to end	Day	22% 5% 9% 29% 30% 5%	2145
October	1st to 10th	Day	18% 5% 8% 20% 32% 16%	3200
	11th to 20th	Day	26% 6% 12% 33% 20% 3	3150
	21st to end	Day	26% 5% 12% 37% 18% 2	3407
November	1st to 10th	Day	25% 9% 16% 27% 21% 1	1763
	11th to 20th	Day	30% 8% 17% 26% 16% 2	1745
	21st to end	Day	30% 7% 19% 29% 14% 2	1600
December	1st to 10th	Day	22% 9% 19% 35% 14%	2620
	11th to 20th	Day	27% 8% 21% 34% 11%	3024
	21st to end	Day	39% 12% 12% 20% 14% 3	4004
January	1st to 10th	Night	39% 12% 18% 19% 11% 1	6327
	11th to 20th	Night	37% 11% 17% 16% 16% 3	6174
	21st to end	Night	32% 15% 20% 15% 16% 2	6468
February	1st to 10th	Night	38% 16% 19% 18% 9% 2	2600
	11th to 20th	Night	36% 13% 18% 22% 10% 1	2469
	21st to end	Night	34% 10% 18% 19% 15% 4	1980
March	1st to 10th	Night	31% 9% 16% 22% 18% 5%	5225
	11th to 20th	Night	24% 9% 16% 27% 22% 2	5000
	21st to end	Night	32% 11% 20% 31% 6%	5273
April	1st to 10th	Night	29% 10% 17% 22% 17% 4	2000
	11th to 20th	Night	33% 10% 16% 25% 15% 1	1977
	21st to end	Night	29% 10% 15% 30% 16%	2000
May	1st to 10th	Night	31% 11% 16% 27% 13% 1	4011
	11th to 20th	Night	24% 13% 19% 27% 14% 3	3618
	21st to end	Night	23% 10% 15% 30% 21% 1	3972
June	1st to 10th	Night	18% 9% 22% 27% 19% 6%	1600
	11th to 20th	Night	18% 7% 12% 21% 26% 16%	1600
	21st to end	Night	14% 6% 11% 23% 28% 17%	1600
July	1st to 10th	Night	20% 5% 11% 18% 20% 26%	3600
	11th to 20th	Night	15% 8% 18% 32% 17% 10%	3592
	21st to end	Night	19% 7% 16% 23% 20% 15%	4095
August	1st to 10th	Night	20% 8% 22% 22% 16% 12%	2928
	11th to 20th	Night	22% 10% 19% 20% 18% 12%	3068
	21st to end	Night	23% 7% 13% 19% 27% 11%	3597
September	1st to 10th	Night	19% 5% 13% 20% 27% 16%	2000
	11th to 20th	Night	20% 6% 12% 24% 25% 12%	2000
	21st to end	Night	20% 5% 10% 28% 33% 6%	2251
October	1st to 10th	Night	14% 5% 6% 23% 38% 14%	3836
	11th to 20th	Night	18% 6% 15% 36% 22% 3	3778
	21st to end	Night	22% 5% 14% 37% 18% 2	4120
November	1st to 10th	Night	25% 9% 15% 28% 22% 2	2533
	11th to 20th	Night	26% 10% 18% 27% 16% 3	2650
	21st to end	Night	26% 9% 16% 32% 15% 2	2800
December	1st to 10th	Night	24% 9% 20% 33% 13% 1	4570
	11th to 20th	Night	24% 10% 21% 36% 10%	5182
	21st to end	Night	37% 12% 16% 20% 13% 2	6974

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	6% 29% 32% 22% 11% 1	300
	11th to 20th	Day	8% 30% 33% 24% 6%	300
	21st to end	Day	4 27% 43% 20% 7%	330
February	1st to 10th	Day	9% 43% 33% 12% 2	300
	11th to 20th	Day	10% 40% 31% 18% 2	300
	21st to end	Day	12% 37% 35% 14% 2	249
March	1st to 10th	Day	7% 37% 33% 19% 3 1	360
	11th to 20th	Day	10% 28% 37% 20% 5%	500
	21st to end	Day	11% 36% 35% 14% 3	550
April	1st to 10th	Day	11% 37% 32% 16% 3	500
	11th to 20th	Day	14% 36% 32% 15% 2	492
	21st to end	Day	12% 28% 35% 18% 5% 2	500
May	1st to 10th	Day	14% 27% 31% 19% 8% 1	575
	11th to 20th	Day	11% 15% 32% 26% 14% 1	725
	21st to end	Day	11% 17% 28% 28% 14% 3	789
June	1st to 10th	Day	5% 12% 29% 30% 21% 4	730
	11th to 20th	Day	6% 15% 35% 30% 13% 2	730
	21st to end	Day	4 12% 30% 33% 20% 2	730
July	1st to 10th	Day	5% 5% 25% 35% 26% 4	721
	11th to 20th	Day	4 4 27% 36% 24% 5%	718
	21st to end	Day	7% 5% 24% 34% 25% 4	685
August	1st to 10th	Day	7% 6% 38% 30% 16% 3	527
	11th to 20th	Day	4 7% 30% 36% 19% 5%	517
	21st to end	Day	6% 8% 27% 36% 19% 5%	583
September	1st to 10th	Day	6% 10% 30% 29% 18% 6%	530
	11th to 20th	Day	6% 16% 34% 28% 13% 3	530
	21st to end	Day	5% 18% 29% 25% 17% 5%	375
October	1st to 10th	Day	7% 18% 27% 27% 16% 5%	309
	11th to 20th	Day	7% 28% 29% 23% 9% 3	300
	21st to end	Day	11% 28% 35% 20% 5% 1	330
November	1st to 10th	Day	11% 30% 29% 22% 7% 1	300
	11th to 20th	Day	10% 27% 37% 21% 5%	300
	21st to end	Day	5% 24% 46% 21% 4	300
December	1st to 10th	Day	10% 29% 31% 22% 6% 2	300
	11th to 20th	Day	8% 30% 41% 18% 3	300
	21st to end	Day	10% 33% 32% 21% 3 1	330
January	1st to 10th	Night	4 24% 40% 23% 8% 1	1000
	11th to 20th	Night	4 23% 47% 20% 5% 1	925
	21st to end	Night	2 18% 51% 24% 5%	880
February	1st to 10th	Night	4 26% 49% 15% 5%	800
	11th to 20th	Night	3 24% 44% 26% 3	784
	21st to end	Night	4 26% 49% 18% 3	660
March	1st to 10th	Night	3 19% 44% 27% 6% 1	800
	11th to 20th	Night	5% 12% 44% 31% 8%	800
	21st to end	Night	5% 17% 46% 24% 7% 1	793
April	1st to 10th	Night	7% 18% 42% 29% 4	600
	11th to 20th	Night	8% 17% 41% 26% 7% 1	593
	21st to end	Night	7% 14% 36% 31% 11% 1	600
May	1st to 10th	Night	10% 10% 36% 31% 13% 1	600
	11th to 20th	Night	8% 7% 29% 37% 17% 1	591
	21st to end	Night	6% 9% 30% 37% 18% 1	650
June	1st to 10th	Night	4 7% 22% 43% 24% 1	600
	11th to 20th	Night	3 8% 32% 44% 13%	600
	21st to end	Night	4 4 20% 48% 23% 1	600
July	1st to 10th	Night	5% 2 13% 44% 35% 2	585
	11th to 20th	Night	2 1 14% 48% 33% 2	582
	21st to end	Night	1 1 10% 47% 39% 2	657
August	1st to 10th	Night	4 2 13% 48% 32% 1	597
	11th to 20th	Night	2 2 14% 49% 31% 3	594
	21st to end	Night	2 3 14% 45% 33% 3	660
September	1st to 10th	Night	5% 2 18% 46% 27% 2	600
	11th to 20th	Night	6% 3 22% 46% 21% 3	600
	21st to end	Night	6% 6% 27% 34% 24% 4	696
October	1st to 10th	Night	7% 8% 33% 34% 17% 2	772
	11th to 20th	Night	5% 15% 35% 32% 13% 1	760
	21st to end	Night	7% 16% 40% 27% 8% 1	836
November	1st to 10th	Night	6% 18% 44% 25% 6% 1	973
	11th to 20th	Night	6% 23% 47% 21% 4	1000
	21st to end	Night	4 17% 48% 26% 5%	1000
December	1st to 10th	Night	7% 23% 44% 22% 4 1	1000
	11th to 20th	Night	4 22% 50% 21% 3	1000
	21st to end	Night	6% 27% 41% 20% 5%	1100

Page generated at 2025-09-30 23:39:08. Version ac07

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