Poudre Canyon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poudre Canyon Observatory clear sky chart from 2005-11-06 to 2024-11-10.

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	5% 5% 2 5% 4 4 4 4 6% 8% 52%	105297
	Night	5% 6% 2 5% 3 3 4 3 5% 7% 57%	102580
Transparency	Day	27% 6% 12% 24% 22% 9%	105040
	Night	24% 6% 11% 26% 24% 9%	102427
Seeing	Day	11% 12% 34% 28% 12% 3	15677
	Night	9% 10% 35% 32% 12% 2	25684

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% 2 8% 4 4 3 3 4 7% 59%	2538
	11th to 20th	Day	1 5% 3 8% 5% 4 5% 4 6% 9% 52%	2572
	21st to end	Day	1 5% 2 6% 4 4 4 3 5% 7% 59%	3146
February	1st to 10th	Day	1 6% 3 7% 4 4 4 4 6% 6% 54%	1710
	11th to 20th	Day	1 6% 2 5% 4 4 3 3 6% 9% 57%	1791
	21st to end	Day	1 7% 3 8% 4 3 3 3 5% 7% 57%	1570
March	1st to 10th	Day	3 11% 4 6% 3 3 4 3 5% 6% 52%	3130
	11th to 20th	Day	6% 11% 4 7% 4 3 4 3 5% 6% 48%	3456
	21st to end	Day	5% 9% 3 5% 4 4 5% 4 7% 9% 46%	4055
April	1st to 10th	Day	6% 7% 2 4 4 4 4 3 6% 9% 52%	2280
	11th to 20th	Day	9% 9% 3 7% 4 4 5% 4 5% 8% 42%	2251
	21st to end	Day	10% 8% 2 5% 4 4 5% 5% 7% 9% 41%	2280
May	1st to 10th	Day	11% 9% 3 6% 5% 5% 5% 4 6% 8% 39%	4125
	11th to 20th	Day	10% 7% 2 5% 5% 5% 6% 5% 7% 10% 40%	4388
	21st to end	Day	6% 5% 2 5% 4 4 5% 5% 8% 9% 46%	4825
June	1st to 10th	Day	5% 3 1 5% 4 4 6% 5% 9% 10% 48%	2660
	11th to 20th	Day	7% 3 1 4 4 3 5% 5% 8% 8% 52%	2660
	21st to end	Day	3 3 1 5% 4 4 6% 5% 8% 9% 50%	2660
July	1st to 10th	Day	6% 3 2 5% 4 4 5% 4 6% 8% 53%	4430
	11th to 20th	Day	2 3 1 5% 5% 6% 6% 6% 9% 9% 48%	4430
	21st to end	Day	4 4 1 5% 4 5% 5% 4 7% 9% 52%	4773
August	1st to 10th	Day	10% 4 2 5% 5% 5% 6% 5% 8% 10% 40%	4092
	11th to 20th	Day	3 3 2 5% 5% 5% 6% 5% 8% 9% 49%	3786
	21st to end	Day	4 3 1 5% 4 5% 5% 4 6% 8% 54%	4180
September	1st to 10th	Day	5% 5% 1 3 3 4 4 4 6% 7% 58%	2280
	11th to 20th	Day	6% 3 1 4 3 4 4 4 6% 8% 57%	2270
	21st to end	Day	7% 4 1 3 3 3 3 3 4 5% 64%	2085
October	1st to 10th	Day	5% 4 1 3 2 2 2 2 3 5% 71%	3170
	11th to 20th	Day	5% 3 2 4 3 3 4 3 5% 7% 59%	3150
	21st to end	Day	4 6% 2 3 2 2 3 3 5% 7% 63%	3295
November	1st to 10th	Day	3 5% 1 4 2 3 4 3 4 8% 64%	1754
	11th to 20th	Day	2 5% 2 3 3 3 3 3 6% 7% 63%	1710
	21st to end	Day	2 6% 2 6% 3 2 3 3 6% 7% 59%	1555
December	1st to 10th	Day	1 5% 3 5% 4 3 4 4 5% 9% 58%	1520
	11th to 20th	Day	3 6% 1 4 3 3 3 4 5% 8% 59%	1926
	21st to end	Day	2 7% 4 8% 5% 4 4 3 5% 6% 53%	2794
January	1st to 10th	Night	1 6% 3 7% 4 4 3 3 5% 7% 56%	4417
	11th to 20th	Night	1 5% 3 6% 4 4 4 3 6% 7% 58%	4428
	21st to end	Night	2 7% 2 6% 4 3 4 3 4 6% 57%	4521
February	1st to 10th	Night	1 7% 2 6% 3 3 4 3 6% 8% 56%	2470
	11th to 20th	Night	1 7% 3 6% 5% 4 4 3 4 7% 56%	2274
	21st to end	Night	2 9% 3 6% 4 2 3 2 4 5% 59%	1884
March	1st to 10th	Night	3 10% 3 6% 3 3 3 3 5% 7% 56%	3734
	11th to 20th	Night	7% 11% 2 5% 3 3 3 3 5% 5% 54%	3521
	21st to end	Night	5% 8% 3 5% 4 4 4 3 6% 7% 51%	3589
April	1st to 10th	Night	4 7% 2 4 4 4 3 4 5% 8% 56%	1900
	11th to 20th	Night	9% 8% 1 6% 4 3 3 3 4 7% 52%	1877
	21st to end	Night	13% 8% 2 5% 3 2 4 3 5% 7% 48%	1900
May	1st to 10th	Night	13% 6% 2 6% 4 4 5% 4 5% 6% 45%	2840
	11th to 20th	Night	13% 5% 2 5% 3 3 4 4 6% 8% 47%	2517
	21st to end	Night	8% 6% 2 4 3 4 4 4 6% 7% 54%	2762
June	1st to 10th	Night	7% 3 1 3 4 4 3 3 7% 10% 57%	1520
	11th to 20th	Night	6% 3 1 3 2 3 4 4 6% 7% 61%	1520
	21st to end	Night	5% 3 1 3 2 2 4 3 6% 9% 63%	1520
July	1st to 10th	Night	5% 2 1 3 3 4 5% 4 7% 7% 61%	2540
	11th to 20th	Night	2 2 1 4 4 4 5% 5% 7% 11% 56%	2540
	21st to end	Night	3 2 1 4 3 4 5% 4 6% 7% 60%	2786
August	1st to 10th	Night	11% 5% 1 4 3 3 4 4 8% 9% 47%	2847
	11th to 20th	Night	3 4 2 5% 4 5% 5% 5% 7% 10% 51%	3051
	21st to end	Night	2 2 1 4 3 3 4 4 7% 10% 58%	3487
September	1st to 10th	Night	6% 4 1 4 3 3 4 3 5% 6% 61%	1900
	11th to 20th	Night	7% 3 1 3 2 2 3 2 5% 6% 66%	1909
	21st to end	Night	7% 4 1 3 3 3 3 2 4 5% 65%	2092
October	1st to 10th	Night	6% 3 1 3 2 2 2 2 3 5% 72%	3800
	11th to 20th	Night	7% 6% 2 4 3 3 3 3 4 6% 59%	3778
	21st to end	Night	5% 6% 2 4 3 2 3 3 4 6% 63%	4231
November	1st to 10th	Night	3 5% 1 3 3 2 3 3 4 7% 65%	2529
	11th to 20th	Night	2 5% 1 5% 2 3 3 2 4 8% 64%	2470
	21st to end	Night	3 6% 3 4 3 2 3 3 6% 6% 61%	2622
December	1st to 10th	Night	1 5% 3 6% 3 3 3 3 4 7% 62%	2660
	11th to 20th	Night	3 5% 2 4 4 3 3 3 6% 11% 56%	3271
	21st to end	Night	3 8% 3 7% 4 4 4 3 5% 7% 53%	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	25% 4 14% 29% 20% 8%	2539
	11th to 20th	Day	26% 7% 16% 27% 17% 7%	2572
	21st to end	Day	23% 4 16% 30% 22% 5%	3146
February	1st to 10th	Day	28% 4 14% 29% 19% 6%	1710
	11th to 20th	Day	23% 5% 11% 31% 24% 6%	1801
	21st to end	Day	28% 4 10% 26% 25% 9%	1570
March	1st to 10th	Day	28% 7% 8% 23% 28% 5%	3130
	11th to 20th	Day	34% 6% 16% 29% 13% 3	3456
	21st to end	Day	30% 6% 14% 34% 13% 2	4055
April	1st to 10th	Day	28% 6% 13% 26% 19% 10%	2280
	11th to 20th	Day	37% 7% 10% 21% 19% 6%	2254
	21st to end	Day	35% 7% 12% 27% 17% 2	2280
May	1st to 10th	Day	38% 9% 11% 22% 13% 7%	4125
	11th to 20th	Day	35% 7% 16% 24% 14% 4	4392
	21st to end	Day	25% 11% 14% 24% 21% 4	4825
June	1st to 10th	Day	28% 7% 20% 23% 17% 6%	2660
	11th to 20th	Day	26% 6% 12% 21% 21% 13%	2660
	21st to end	Day	25% 6% 11% 25% 21% 12%	2660
July	1st to 10th	Day	25% 6% 10% 15% 27% 17%	4361
	11th to 20th	Day	26% 7% 12% 21% 19% 15%	4355
	21st to end	Day	26% 5% 11% 18% 22% 18%	4622
August	1st to 10th	Day	35% 7% 15% 19% 15% 9%	4078
	11th to 20th	Day	27% 7% 13% 17% 21% 15%	3823
	21st to end	Day	25% 6% 11% 19% 26% 13%	4179
September	1st to 10th	Day	24% 4 10% 20% 28% 15%	2280
	11th to 20th	Day	24% 4 8% 23% 27% 14%	2270
	21st to end	Day	24% 3 7% 21% 36% 10%	2085
October	1st to 10th	Day	17% 3 7% 17% 34% 23%	3170
	11th to 20th	Day	23% 5% 10% 28% 26% 8%	3150
	21st to end	Day	21% 3 8% 30% 31% 7%	3295
November	1st to 10th	Day	20% 4 11% 29% 27% 10%	1754
	11th to 20th	Day	19% 4 8% 31% 31% 7%	1710
	21st to end	Day	23% 3 9% 29% 27% 8%	1555
December	1st to 10th	Day	23% 5% 13% 33% 18% 8%	1520
	11th to 20th	Day	22% 5% 11% 30% 29% 3	1924
	21st to end	Day	30% 6% 8% 24% 24% 8%	2794
January	1st to 10th	Night	25% 6% 11% 28% 25% 5%	4417
	11th to 20th	Night	19% 10% 15% 24% 23% 10%	4428
	21st to end	Night	27% 5% 13% 34% 18% 4	4521
February	1st to 10th	Night	25% 6% 12% 30% 21% 5%	2470
	11th to 20th	Night	26% 7% 8% 31% 22% 5%	2274
	21st to end	Night	27% 3 7% 26% 26% 11%	1884
March	1st to 10th	Night	26% 6% 6% 24% 33% 5%	3734
	11th to 20th	Night	29% 6% 13% 24% 24% 3	3521
	21st to end	Night	28% 7% 13% 34% 15% 3	3589
April	1st to 10th	Night	26% 6% 12% 27% 22% 8%	1900
	11th to 20th	Night	32% 6% 12% 25% 19% 6%	1877
	21st to end	Night	35% 6% 8% 29% 20% 2	1900
May	1st to 10th	Night	33% 10% 9% 24% 15% 8%	2840
	11th to 20th	Night	31% 7% 18% 26% 14% 3	2518
	21st to end	Night	24% 9% 18% 23% 20% 5%	2762
June	1st to 10th	Night	24% 5% 23% 27% 15% 7%	1520
	11th to 20th	Night	21% 6% 12% 23% 21% 17%	1520
	21st to end	Night	18% 6% 10% 26% 28% 13%	1520
July	1st to 10th	Night	20% 6% 10% 23% 26% 15%	2500
	11th to 20th	Night	20% 5% 14% 27% 21% 13%	2492
	21st to end	Night	21% 5% 12% 28% 19% 15%	2699
August	1st to 10th	Night	30% 7% 17% 22% 19% 5%	2838
	11th to 20th	Night	25% 8% 15% 22% 18% 12%	3080
	21st to end	Night	19% 5% 14% 25% 27% 11%	3487
September	1st to 10th	Night	23% 4 10% 20% 24% 19%	1900
	11th to 20th	Night	20% 3 9% 27% 26% 15%	1909
	21st to end	Night	22% 3 6% 26% 30% 13%	2092
October	1st to 10th	Night	17% 3 7% 20% 31% 23%	3800
	11th to 20th	Night	26% 4 8% 27% 27% 8%	3778
	21st to end	Night	22% 3 6% 26% 32% 10%	4231
November	1st to 10th	Night	19% 4 11% 27% 27% 11%	2529
	11th to 20th	Night	19% 4 9% 31% 29% 8%	2470
	21st to end	Night	23% 4 9% 26% 28% 9%	2622
December	1st to 10th	Night	23% 4 14% 27% 23% 9%	2660
	11th to 20th	Night	21% 5% 10% 33% 26% 4	3272
	21st to end	Night	29% 6% 10% 25% 24% 7%	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	11% 12% 38% 27% 8% 4	270
	11th to 20th	Day	9% 21% 46% 19% 6%	270
	21st to end	Day	9% 20% 45% 20% 5% 1	297
February	1st to 10th	Day	10% 27% 43% 18% 2	270
	11th to 20th	Day	9% 21% 48% 19% 3	270
	21st to end	Day	12% 21% 46% 19% 2	225
March	1st to 10th	Day	12% 15% 41% 27% 5%	270
	11th to 20th	Day	15% 16% 38% 24% 6% 1	439
	21st to end	Day	16% 20% 40% 19% 4 1	506
April	1st to 10th	Day	15% 24% 36% 20% 5%	460
	11th to 20th	Day	19% 21% 40% 15% 4 1	452
	21st to end	Day	21% 17% 34% 22% 5% 1	460
May	1st to 10th	Day	19% 15% 34% 23% 8% 1	601
	11th to 20th	Day	20% 8% 30% 25% 13% 3	675
	21st to end	Day	12% 11% 27% 30% 18% 2	734
June	1st to 10th	Day	6% 9% 27% 34% 18% 5%	680
	11th to 20th	Day	9% 8% 37% 30% 15% 1	680
	21st to end	Day	5% 8% 31% 32% 19% 5%	680
July	1st to 10th	Day	9% 4 21% 34% 25% 7%	671
	11th to 20th	Day	3 4 24% 40% 23% 6%	668
	21st to end	Day	6% 4 20% 38% 26% 6%	722
August	1st to 10th	Day	8% 5% 28% 38% 17% 4	487
	11th to 20th	Day	4 5% 32% 37% 19% 3	477
	21st to end	Day	7% 6% 30% 36% 18% 4	539
September	1st to 10th	Day	9% 6% 31% 36% 14% 4	490
	11th to 20th	Day	7% 7% 32% 33% 18% 3	480
	21st to end	Day	10% 8% 32% 29% 15% 6%	300
October	1st to 10th	Day	11% 8% 31% 28% 16% 6%	300
	11th to 20th	Day	8% 16% 41% 25% 8% 3	300
	21st to end	Day	10% 14% 43% 26% 6% 1	330
November	1st to 10th	Day	8% 15% 45% 20% 7% 5%	297
	11th to 20th	Day	12% 13% 44% 23% 6% 1	270
	21st to end	Day	11% 16% 45% 24% 3 1	270
December	1st to 10th	Day	11% 19% 41% 23% 5% 1	270
	11th to 20th	Day	12% 14% 52% 19% 3	270
	21st to end	Day	9% 20% 47% 18% 4 1	297
January	1st to 10th	Night	8% 16% 43% 24% 7% 2	950
	11th to 20th	Night	11% 20% 44% 18% 6% 1	948
	21st to end	Night	6% 17% 45% 25% 6%	836
February	1st to 10th	Night	7% 19% 51% 19% 4 1	760
	11th to 20th	Night	7% 17% 47% 25% 3	744
	21st to end	Night	7% 17% 52% 22% 2	628
March	1st to 10th	Night	8% 13% 48% 26% 5% 1	760
	11th to 20th	Night	8% 13% 37% 34% 7% 1	760
	21st to end	Night	10% 14% 42% 28% 5% 1	700
April	1st to 10th	Night	11% 13% 44% 28% 4	570
	11th to 20th	Night	14% 12% 38% 28% 7% 1	563
	21st to end	Night	18% 11% 30% 31% 9% 1	570
May	1st to 10th	Night	17% 9% 30% 31% 11% 2	570
	11th to 20th	Night	19% 6% 22% 36% 15% 2	561
	21st to end	Night	10% 6% 27% 34% 21% 1	617
June	1st to 10th	Night	6% 4 19% 48% 20% 2	570
	11th to 20th	Night	7% 5% 25% 49% 13% 1	570
	21st to end	Night	7% 2 19% 46% 22% 2	570
July	1st to 10th	Night	9% 3 11% 43% 32% 3	555
	11th to 20th	Night	2 2 11% 54% 28% 3	552
	21st to end	Night	5% 3 9% 44% 36% 3	624
August	1st to 10th	Night	6% 4 12% 48% 28% 2	567
	11th to 20th	Night	4 3 13% 52% 23% 3	564
	21st to end	Night	4 2 12% 49% 29% 4	627
September	1st to 10th	Night	7% 3 17% 46% 22% 5%	570
	11th to 20th	Night	8% 4 21% 43% 19% 5%	570
	21st to end	Night	9% 2 28% 41% 18% 2	572
October	1st to 10th	Night	11% 7% 30% 36% 14% 3	760
	11th to 20th	Night	9% 7% 36% 35% 11% 1	760
	21st to end	Night	11% 12% 40% 29% 7% 2	898
November	1st to 10th	Night	8% 7% 47% 28% 8% 2	973
	11th to 20th	Night	9% 15% 45% 26% 4 1	950
	21st to end	Night	8% 13% 43% 30% 6% 1	950
December	1st to 10th	Night	7% 17% 48% 23% 4	950
	11th to 20th	Night	9% 13% 51% 22% 5% 1	950
	21st to end	Night	9% 15% 47% 22% 5% 1	1045

Page generated at 2024-11-07 04:55:48. Version ac07

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