Colorado State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colorado State Forest clear sky chart from 2005-11-06 to 2024-11-04.

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	4 11% 5% 10% 5% 4 4 3 5% 6% 42%	105269
	Night	3 10% 5% 10% 5% 4 4 3 5% 6% 46%	102463
Transparency	Day	43% 5% 9% 21% 16% 5%	105017
	Night	39% 5% 11% 24% 17% 5%	102305
Seeing	Day	14% 26% 30% 19% 9% 2	15621
	Night	10% 22% 29% 27% 12% 1	25642

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 11% 7% 20% 13% 5% 3 2 3 5% 31%	2538
	11th to 20th	Day	1 16% 9% 17% 10% 7% 3 2 3 4 26%	2650
	21st to end	Day	1 14% 12% 18% 5% 3 3 1 3 4 36%	3146
February	1st to 10th	Day	1 22% 9% 16% 7% 4 2 2 3 6% 27%	1710
	11th to 20th	Day	2 16% 9% 18% 7% 4 2 2 3 5% 32%	1756
	21st to end	Day	1 15% 9% 16% 10% 4 2 2 5% 5% 30%	1570
March	1st to 10th	Day	1 11% 9% 18% 6% 4 4 3 4 4 35%	3185
	11th to 20th	Day	2 13% 7% 9% 4 3 2 3 4 7% 47%	3490
	21st to end	Day	2 21% 8% 20% 5% 4 4 3 4 5% 23%	3997
April	1st to 10th	Day	5% 17% 7% 11% 4 3 4 3 6% 5% 36%	2280
	11th to 20th	Day	5% 22% 5% 11% 5% 4 3 3 5% 6% 30%	2251
	21st to end	Day	6% 19% 7% 9% 5% 4 4 4 5% 6% 31%	2280
May	1st to 10th	Day	6% 21% 9% 13% 6% 5% 4 3 4 5% 24%	4118
	11th to 20th	Day	6% 9% 3 7% 5% 6% 6% 5% 7% 8% 38%	4388
	21st to end	Day	6% 14% 3 7% 4 4 5% 4 5% 7% 40%	4825
June	1st to 10th	Day	6% 6% 2 6% 5% 4 5% 5% 7% 8% 45%	2660
	11th to 20th	Day	7% 5% 2 5% 4 5% 4 4 5% 7% 53%	2660
	21st to end	Day	3 4 2 5% 5% 5% 5% 5% 7% 8% 52%	2660
July	1st to 10th	Day	6% 4 2 5% 4 5% 5% 4 7% 8% 51%	4430
	11th to 20th	Day	3 3 2 6% 6% 6% 7% 6% 8% 9% 44%	4430
	21st to end	Day	5% 5% 2 8% 6% 6% 7% 5% 7% 7% 42%	4657
August	1st to 10th	Day	7% 5% 3 8% 6% 7% 6% 5% 8% 9% 37%	4092
	11th to 20th	Day	7% 5% 2 7% 5% 6% 6% 5% 7% 7% 43%	3843
	21st to end	Day	6% 5% 2 6% 5% 4 5% 4 6% 8% 49%	4180
September	1st to 10th	Day	7% 4 2 6% 4 3 4 2 4 6% 58%	2280
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 5% 5% 53%	2280
	21st to end	Day	9% 7% 2 4 3 2 3 2 3 5% 61%	2052
October	1st to 10th	Day	4 7% 2 3 2 2 2 2 2 4 69%	3170
	11th to 20th	Day	5% 9% 3 7% 4 3 4 4 5% 8% 50%	3150
	21st to end	Day	4 16% 5% 6% 2 2 2 2 4 6% 50%	3376
November	1st to 10th	Day	3 12% 6% 7% 3 2 2 2 4 6% 53%	1700
	11th to 20th	Day	2 21% 5% 9% 4 2 2 2 3 5% 45%	1705
	21st to end	Day	2 13% 4 13% 5% 2 2 2 3 6% 48%	1520
December	1st to 10th	Day	2 17% 8% 16% 4 4 3 3 3 5% 34%	1520
	11th to 20th	Day	1 18% 6% 13% 5% 3 2 2 4 7% 39%	1926
	21st to end	Day	1 15% 8% 18% 6% 5% 3 3 4 6% 31%	2794
January	1st to 10th	Night	1 10% 7% 19% 10% 7% 4 3 4 5% 31%	4417
	11th to 20th	Night	1 15% 11% 18% 7% 8% 3 2 3 4 30%	4335
	21st to end	Night	1 14% 9% 19% 7% 4 3 2 3 4 34%	4521
February	1st to 10th	Night	1 18% 8% 19% 8% 4 3 2 4 4 27%	2470
	11th to 20th	Night	2 15% 10% 17% 6% 5% 3 2 4 5% 32%	2309
	21st to end	Night	1 13% 9% 18% 8% 4 2 2 4 5% 33%	1884
March	1st to 10th	Night	1 10% 9% 15% 6% 3 3 3 4 5% 40%	3677
	11th to 20th	Night	1 11% 5% 10% 4 3 3 2 4 6% 50%	3490
	21st to end	Night	1 16% 8% 15% 4 4 4 3 4 6% 33%	3649
April	1st to 10th	Night	3 16% 4 9% 5% 3 3 3 5% 5% 41%	1900
	11th to 20th	Night	4 17% 4 9% 5% 4 4 3 5% 6% 39%	1877
	21st to end	Night	5% 16% 5% 7% 4 3 4 3 4 5% 44%	1900
May	1st to 10th	Night	5% 15% 7% 10% 5% 5% 5% 3 4 7% 36%	2845
	11th to 20th	Night	4 8% 3 6% 4 4 6% 5% 6% 10% 44%	2517
	21st to end	Night	4 10% 2 4 4 4 5% 4 5% 6% 52%	2762
June	1st to 10th	Night	4 4 1 5% 3 3 4 4 7% 9% 57%	1520
	11th to 20th	Night	4 4 1 4 3 4 4 3 5% 8% 60%	1520
	21st to end	Night	4 3 1 3 3 2 3 3 6% 7% 63%	1520
July	1st to 10th	Night	3 2 1 4 3 3 4 4 6% 7% 63%	2540
	11th to 20th	Night	2 2 1 3 4 4 6% 5% 8% 11% 55%	2540
	21st to end	Night	2 2 1 4 4 5% 5% 4 6% 7% 60%	2903
August	1st to 10th	Night	3 3 1 4 4 5% 5% 6% 9% 10% 50%	2847
	11th to 20th	Night	4 4 2 5% 4 5% 7% 6% 8% 9% 47%	2994
	21st to end	Night	3 3 1 5% 4 5% 5% 5% 7% 9% 52%	3487
September	1st to 10th	Night	4 4 1 4 3 3 3 3 5% 7% 62%	1900
	11th to 20th	Night	5% 4 1 4 2 4 3 3 4 7% 63%	1900
	21st to end	Night	6% 6% 1 4 2 3 3 3 4 6% 63%	2124
October	1st to 10th	Night	3 6% 1 3 2 2 2 2 3 5% 72%	3800
	11th to 20th	Night	3 8% 2 4 2 3 3 2 5% 8% 59%	3778
	21st to end	Night	4 10% 3 6% 2 2 2 2 4 6% 58%	4148
November	1st to 10th	Night	3 14% 4 5% 2 2 2 2 4 6% 55%	2451
	11th to 20th	Night	3 17% 5% 10% 4 2 2 2 3 5% 47%	2474
	21st to end	Night	2 12% 6% 10% 5% 3 3 3 4 7% 46%	2660
December	1st to 10th	Night	2 18% 6% 13% 7% 5% 2 2 2 4 38%	2660
	11th to 20th	Night	1 13% 7% 13% 5% 4 3 2 5% 7% 39%	3271
	21st to end	Night	1 12% 7% 16% 8% 6% 4 3 4 5% 34%	4873

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	58% 4 9% 14% 14% 1	2539
	11th to 20th	Day	63% 3 14% 12% 7% 1	2650
	21st to end	Day	54% 4 10% 18% 12% 2	3146
February	1st to 10th	Day	61% 5% 8% 13% 12% 1	1710
	11th to 20th	Day	57% 3 8% 20% 8% 4	1765
	21st to end	Day	58% 3 10% 12% 14% 3	1570
March	1st to 10th	Day	54% 3 6% 22% 12% 2	3185
	11th to 20th	Day	41% 3 12% 34% 8% 1	3490
	21st to end	Day	64% 5% 8% 19% 4 1	3997
April	1st to 10th	Day	50% 5% 11% 18% 13% 3	2280
	11th to 20th	Day	57% 4 9% 18% 11% 1	2254
	21st to end	Day	56% 3 9% 23% 7%	2280
May	1st to 10th	Day	64% 5% 6% 14% 11% 1	4118
	11th to 20th	Day	43% 6% 11% 27% 13% 1	4392
	21st to end	Day	41% 6% 7% 26% 18% 1	4825
June	1st to 10th	Day	36% 7% 14% 24% 15% 5%	2660
	11th to 20th	Day	32% 4 10% 19% 25% 10%	2660
	21st to end	Day	30% 6% 8% 23% 24% 9%	2660
July	1st to 10th	Day	29% 6% 7% 14% 26% 17%	4361
	11th to 20th	Day	33% 8% 9% 21% 19% 11%	4355
	21st to end	Day	39% 6% 10% 16% 18% 11%	4510
August	1st to 10th	Day	41% 9% 14% 17% 13% 7%	4078
	11th to 20th	Day	39% 8% 9% 17% 21% 7%	3882
	21st to end	Day	35% 6% 9% 17% 21% 12%	4179
September	1st to 10th	Day	29% 5% 8% 19% 28% 12%	2280
	11th to 20th	Day	35% 4 7% 22% 24% 8%	2280
	21st to end	Day	29% 3 7% 31% 25% 5%	2052
October	1st to 10th	Day	23% 3 5% 26% 37% 7%	3170
	11th to 20th	Day	32% 4 9% 35% 17% 3	3150
	21st to end	Day	37% 4 8% 35% 15% 2	3376
November	1st to 10th	Day	36% 4 12% 26% 20% 2	1700
	11th to 20th	Day	43% 3 13% 22% 15% 4	1705
	21st to end	Day	40% 3 11% 28% 13% 4	1520
December	1st to 10th	Day	54% 3 16% 14% 10% 2	1520
	11th to 20th	Day	46% 4 10% 28% 11% 1	1924
	21st to end	Day	55% 5% 4 18% 15% 4	2794
January	1st to 10th	Night	56% 4 9% 19% 11% 2	4417
	11th to 20th	Night	60% 3 12% 12% 8% 4	4335
	21st to end	Night	56% 4 10% 16% 10% 4	4521
February	1st to 10th	Night	59% 6% 9% 15% 10% 2	2470
	11th to 20th	Night	54% 3 9% 20% 11% 2	2310
	21st to end	Night	55% 4 8% 15% 14% 4	1884
March	1st to 10th	Night	47% 4 7% 24% 14% 4	3677
	11th to 20th	Night	37% 3 14% 33% 10% 3	3490
	21st to end	Night	51% 6% 12% 25% 5% 1	3649
April	1st to 10th	Night	44% 6% 12% 20% 15% 3	1900
	11th to 20th	Night	47% 4 12% 24% 12% 1	1877
	21st to end	Night	44% 4 11% 29% 12%	1900
May	1st to 10th	Night	48% 6% 8% 25% 12% 1	2845
	11th to 20th	Night	35% 6% 15% 34% 10%	2518
	21st to end	Night	32% 6% 9% 31% 21% 1	2762
June	1st to 10th	Night	23% 5% 22% 30% 16% 4	1520
	11th to 20th	Night	24% 4 13% 23% 27% 10%	1520
	21st to end	Night	20% 4 10% 27% 26% 12%	1520
July	1st to 10th	Night	20% 6% 10% 19% 24% 21%	2500
	11th to 20th	Night	20% 7% 15% 29% 20% 9%	2492
	21st to end	Night	23% 5% 13% 23% 21% 15%	2812
August	1st to 10th	Night	26% 7% 23% 20% 19% 6%	2838
	11th to 20th	Night	29% 9% 17% 17% 18% 10%	3021
	21st to end	Night	28% 7% 13% 20% 24% 9%	3487
September	1st to 10th	Night	23% 4 12% 20% 30% 11%	1900
	11th to 20th	Night	23% 4 12% 25% 26% 9%	1900
	21st to end	Night	24% 4 8% 32% 28% 4	2124
October	1st to 10th	Night	19% 3 6% 26% 39% 7%	3800
	11th to 20th	Night	22% 4 12% 40% 19% 3	3778
	21st to end	Night	29% 3 10% 36% 20% 2	4148
November	1st to 10th	Night	31% 5% 12% 28% 21% 3	2451
	11th to 20th	Night	40% 4 13% 26% 14% 4	2474
	21st to end	Night	40% 4 10% 28% 13% 4	2660
December	1st to 10th	Night	51% 5% 13% 15% 12% 3	2660
	11th to 20th	Night	46% 3 11% 27% 13% 1	3272
	21st to end	Night	50% 5% 8% 18% 15% 4	4873

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	17% 32% 25% 15% 9% 1	270
	11th to 20th	Day	19% 41% 22% 14% 3 1	270
	21st to end	Day	8% 42% 31% 14% 6%	297
February	1st to 10th	Day	22% 50% 19% 7% 1 1	270
	11th to 20th	Day	23% 37% 28% 11% 1	270
	21st to end	Day	28% 41% 24% 6% 1	225
March	1st to 10th	Day	19% 45% 22% 10% 3	299
	11th to 20th	Day	18% 35% 30% 14% 3	460
	21st to end	Day	18% 46% 27% 8% 1	506
April	1st to 10th	Day	23% 40% 28% 7% 2	460
	11th to 20th	Day	27% 40% 26% 5% 2	452
	21st to end	Day	23% 33% 28% 11% 3 1	460
May	1st to 10th	Day	22% 30% 28% 13% 6%	548
	11th to 20th	Day	17% 18% 31% 22% 10% 2	675
	21st to end	Day	16% 21% 29% 21% 11% 2	734
June	1st to 10th	Day	9% 15% 31% 24% 18% 4	680
	11th to 20th	Day	10% 24% 33% 22% 9% 1	680
	21st to end	Day	6% 19% 34% 25% 13% 3	680
July	1st to 10th	Day	8% 9% 29% 31% 20% 3	671
	11th to 20th	Day	6% 9% 31% 31% 20% 4	668
	21st to end	Day	7% 7% 32% 30% 20% 4	656
August	1st to 10th	Day	10% 15% 37% 28% 9% 1	487
	11th to 20th	Day	6% 14% 38% 27% 11% 3	477
	21st to end	Day	9% 16% 33% 28% 12% 2	539
September	1st to 10th	Day	9% 19% 33% 24% 11% 4	490
	11th to 20th	Day	11% 22% 37% 19% 9% 2	490
	21st to end	Day	11% 26% 27% 20% 13% 4	321
October	1st to 10th	Day	15% 25% 27% 18% 12% 4	300
	11th to 20th	Day	14% 35% 27% 16% 6% 2	300
	21st to end	Day	21% 35% 27% 14% 3 1	330
November	1st to 10th	Day	20% 39% 23% 10% 6% 1	279
	11th to 20th	Day	18% 39% 27% 12% 3 1	270
	21st to end	Day	14% 35% 31% 17% 3	270
December	1st to 10th	Day	20% 36% 26% 11% 5% 1	270
	11th to 20th	Day	10% 41% 32% 12% 4	270
	21st to end	Day	18% 38% 31% 11% 2	297
January	1st to 10th	Night	11% 29% 29% 21% 9% 1	950
	11th to 20th	Night	11% 37% 27% 19% 5% 1	894
	21st to end	Night	7% 32% 33% 22% 5% 1	836
February	1st to 10th	Night	11% 38% 31% 15% 5%	760
	11th to 20th	Night	9% 38% 29% 21% 3	744
	21st to end	Night	13% 34% 37% 13% 2	628
March	1st to 10th	Night	9% 34% 31% 20% 6%	760
	11th to 20th	Night	8% 21% 39% 24% 8% 1	760
	21st to end	Night	9% 27% 40% 19% 5% 1	734
April	1st to 10th	Night	14% 26% 37% 20% 3	570
	11th to 20th	Night	15% 23% 36% 21% 5% 1	563
	21st to end	Night	12% 21% 33% 24% 8% 1	570
May	1st to 10th	Night	13% 14% 37% 26% 9% 1	570
	11th to 20th	Night	10% 9% 28% 38% 15% 1	561
	21st to end	Night	8% 14% 28% 32% 17% 1	617
June	1st to 10th	Night	6% 7% 27% 39% 19% 1	570
	11th to 20th	Night	8% 12% 32% 35% 13%	570
	21st to end	Night	7% 6% 23% 45% 19% 1	570
July	1st to 10th	Night	4 2 17% 41% 34% 1	555
	11th to 20th	Night	3 2 18% 41% 32% 3	552
	21st to end	Night	4 2 12% 47% 33% 3	624
August	1st to 10th	Night	6% 2 16% 47% 27% 2	567
	11th to 20th	Night	3 3 20% 42% 29% 3	564
	21st to end	Night	5% 4 17% 41% 31% 3	627
September	1st to 10th	Night	6% 5% 22% 41% 24% 2	570
	11th to 20th	Night	7% 6% 24% 42% 17% 4	570
	21st to end	Night	9% 8% 29% 32% 18% 4	626
October	1st to 10th	Night	9% 16% 29% 28% 15% 3	760
	11th to 20th	Night	11% 23% 25% 30% 9% 1	760
	21st to end	Night	15% 23% 32% 21% 8% 2	852
November	1st to 10th	Night	12% 29% 32% 20% 6% 1	943
	11th to 20th	Night	14% 33% 30% 18% 5% 1	950
	21st to end	Night	9% 29% 34% 22% 6% 1	950
December	1st to 10th	Night	16% 32% 30% 17% 5%	950
	11th to 20th	Night	10% 33% 33% 20% 4	950
	21st to end	Night	10% 36% 31% 17% 5%	1045

Page generated at 2024-11-01 20:47:50. Version ac07

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