Stargate Colorado Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stargate Colorado Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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 4 2 4 4 3 4 5% 6% 8% 56%	74817
	Night	3 4 2 4 3 2 4 4 5% 7% 60%	75022
Transparency	Day	16% 38% 6% 14% 17% 9%	74530
	Night	15% 37% 7% 15% 18% 9%	74832
Seeing	Day	7% 16% 30% 28% 15% 4	14231
	Night	6% 11% 34% 35% 13% 1	24398

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 3 2 3 3 2 3 3 5% 8% 67%	1518
	11th to 20th	Day	2 5% 2 3 3 2 3 4 5% 6% 66%	1615
	21st to end	Day	2 5% 2 3 3 2 3 4 5% 7% 65%	1782
February	1st to 10th	Day	1 4 3 6% 3 2 2 3 4 8% 63%	1710
	11th to 20th	Day	1 3 3 3 3 3 5% 4 5% 9% 60%	1749
	21st to end	Day	2 5% 2 5% 4 2 4 4 6% 6% 60%	1480
March	1st to 10th	Day	2 6% 3 4 4 3 3 4 5% 7% 61%	1800
	11th to 20th	Day	5% 6% 2 5% 4 3 3 3 5% 8% 57%	1934
	21st to end	Day	5% 6% 2 4 3 2 4 4 6% 9% 55%	2330
April	1st to 10th	Day	3 5% 2 4 3 2 4 4 6% 8% 60%	2160
	11th to 20th	Day	6% 6% 2 5% 4 3 4 4 5% 8% 54%	2131
	21st to end	Day	5% 6% 3 4 3 3 4 5% 5% 9% 53%	2160
May	1st to 10th	Day	6% 6% 3 4 4 3 4 6% 6% 8% 53%	2214
	11th to 20th	Day	6% 6% 2 4 4 3 6% 6% 7% 9% 47%	2302
	21st to end	Day	4 4 2 4 5% 3 4 6% 7% 8% 53%	2724
June	1st to 10th	Day	4 3 2 3 3 3 6% 8% 8% 10% 48%	2520
	11th to 20th	Day	3 3 1 2 3 3 5% 6% 8% 9% 57%	2520
	21st to end	Day	5% 3 1 4 5% 3 6% 7% 8% 9% 47%	2520
July	1st to 10th	Day	5% 3 2 4 6% 4 7% 8% 8% 10% 44%	2520
	11th to 20th	Day	3 3 1 4 5% 3 8% 7% 9% 11% 47%	2520
	21st to end	Day	6% 3 2 4 7% 5% 7% 9% 10% 11% 34%	2598
August	1st to 10th	Day	6% 3 2 5% 6% 4 9% 9% 8% 9% 39%	2213
	11th to 20th	Day	6% 4 2 5% 6% 4 7% 7% 7% 10% 44%	2123
	21st to end	Day	4 3 2 4 5% 3 5% 7% 7% 11% 48%	2376
September	1st to 10th	Day	5% 5% 2 4 5% 4 5% 5% 6% 8% 52%	2160
	11th to 20th	Day	5% 3 1 4 4 2 4 4 6% 7% 59%	2111
	21st to end	Day	4 3 2 4 4 2 3 4 5% 5% 65%	1980
October	1st to 10th	Day	6% 4 1 3 4 2 4 4 5% 8% 59%	1879
	11th to 20th	Day	2 2 1 2 3 2 3 3 3 6% 74%	1800
	21st to end	Day	5% 5% 2 3 2 1 2 3 3 4 69%	1949
November	1st to 10th	Day	1 3 1 3 2 1 3 3 3 6% 74%	1673
	11th to 20th	Day	1 3 2 4 4 2 4 3 4 7% 68%	1710
	21st to end	Day	3 5% 2 4 3 2 3 4 3 7% 64%	1710
December	1st to 10th	Day	1 4 3 4 2 2 2 3 5% 9% 65%	1606
	11th to 20th	Day	2 5% 2 5% 4 2 3 5% 5% 7% 61%	1926
	21st to end	Day	1 4 3 5% 4 2 3 4 6% 7% 60%	2794
January	1st to 10th	Night	1 4 2 4 3 2 3 4 5% 6% 64%	2647
	11th to 20th	Night	3 5% 2 4 3 2 3 4 4 5% 66%	2490
	21st to end	Night	2 4 2 4 3 2 3 4 4 6% 65%	2574
February	1st to 10th	Night	1 6% 2 5% 3 2 3 3 4 6% 65%	2249
	11th to 20th	Night	2 5% 3 4 4 2 3 5% 6% 7% 59%	2098
	21st to end	Night	2 5% 1 4 4 2 3 3 3 6% 67%	1776
March	1st to 10th	Night	2 5% 2 4 4 2 4 4 5% 7% 61%	2160
	11th to 20th	Night	4 6% 2 5% 3 2 3 4 4 7% 61%	2023
	21st to end	Night	3 4 3 3 4 3 4 4 6% 7% 60%	2026
April	1st to 10th	Night	3 4 2 3 3 2 3 3 5% 6% 66%	1800
	11th to 20th	Night	5% 6% 2 4 4 2 3 4 5% 8% 58%	1777
	21st to end	Night	7% 6% 1 4 4 2 3 4 4 8% 57%	1800
May	1st to 10th	Night	6% 5% 3 3 3 2 3 5% 5% 7% 58%	1746
	11th to 20th	Night	9% 7% 3 6% 4 3 5% 5% 5% 8% 47%	1589
	21st to end	Night	5% 5% 1 3 2 1 4 4 6% 9% 60%	1552
June	1st to 10th	Night	4 4 2 3 4 2 4 5% 7% 10% 56%	1440
	11th to 20th	Night	2 3 1 3 4 2 5% 4 7% 7% 61%	1440
	21st to end	Night	5% 4 2 4 5% 3 5% 6% 8% 11% 48%	1440
July	1st to 10th	Night	4 4 3 4 5% 4 7% 6% 8% 10% 44%	1440
	11th to 20th	Night	6% 3 1 3 4 3 6% 7% 8% 10% 50%	1440
	21st to end	Night	6% 5% 3 5% 6% 4 6% 7% 8% 12% 38%	1716
August	1st to 10th	Night	5% 3 2 4 6% 4 7% 7% 8% 10% 44%	1726
	11th to 20th	Night	7% 4 2 4 5% 4 5% 8% 8% 9% 44%	1778
	21st to end	Night	4 3 2 3 3 3 5% 6% 10% 11% 50%	1980
September	1st to 10th	Night	5% 3 2 4 4 2 5% 5% 7% 9% 55%	1800
	11th to 20th	Night	5% 3 1 3 3 2 3 3 5% 8% 62%	1849
	21st to end	Night	4 4 1 4 3 2 3 4 5% 6% 64%	1980
October	1st to 10th	Night	6% 4 2 2 3 2 3 3 4 6% 64%	2078
	11th to 20th	Night	2 2 1 2 1 1 2 3 4 6% 76%	2160
	21st to end	Night	5% 5% 2 4 3 1 3 3 4 5% 66%	2389
November	1st to 10th	Night	1 2 1 3 2 1 3 3 4 7% 73%	2405
	11th to 20th	Night	1 3 2 3 2 2 2 3 4 6% 73%	2470
	21st to end	Night	2 4 2 4 3 2 3 4 5% 7% 64%	2470
December	1st to 10th	Night	2 4 2 4 3 2 3 4 6% 8% 62%	2570
	11th to 20th	Night	1 4 2 4 4 3 4 4 5% 8% 63%	3271
	21st to end	Night	2 5% 2 5% 3 2 4 4 5% 7% 60%	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	11% 39% 4 18% 23% 6%	1519
	11th to 20th	Day	12% 40% 5% 12% 23% 8%	1615
	21st to end	Day	13% 37% 4 17% 22% 7%	1782
February	1st to 10th	Day	17% 35% 5% 17% 17% 8%	1710
	11th to 20th	Day	17% 37% 4 16% 18% 9%	1759
	21st to end	Day	15% 36% 3 12% 20% 14%	1480
March	1st to 10th	Day	17% 35% 5% 14% 19% 9%	1800
	11th to 20th	Day	19% 36% 4 16% 20% 6%	1934
	21st to end	Day	17% 37% 6% 14% 18% 8%	2330
April	1st to 10th	Day	15% 37% 4 13% 17% 13%	2160
	11th to 20th	Day	18% 35% 3 16% 18% 11%	2134
	21st to end	Day	16% 37% 7% 14% 19% 7%	2160
May	1st to 10th	Day	17% 38% 6% 13% 16% 9%	2214
	11th to 20th	Day	21% 40% 9% 13% 12% 5%	2306
	21st to end	Day	18% 40% 6% 10% 14% 12%	2724
June	1st to 10th	Day	17% 40% 9% 11% 13% 9%	2520
	11th to 20th	Day	14% 38% 6% 11% 15% 16%	2520
	21st to end	Day	21% 38% 6% 12% 12% 11%	2520
July	1st to 10th	Day	21% 41% 8% 12% 10% 8%	2451
	11th to 20th	Day	15% 41% 10% 18% 13% 4	2445
	21st to end	Day	23% 43% 12% 15% 6% 1	2454
August	1st to 10th	Day	23% 41% 9% 11% 10% 6%	2198
	11th to 20th	Day	23% 37% 7% 14% 14% 5%	2123
	21st to end	Day	18% 39% 8% 15% 15% 5%	2376
September	1st to 10th	Day	18% 38% 5% 14% 16% 9%	2160
	11th to 20th	Day	17% 37% 7% 11% 16% 12%	2111
	21st to end	Day	12% 37% 4 14% 23% 10%	1980
October	1st to 10th	Day	14% 39% 6% 15% 17% 10%	1879
	11th to 20th	Day	10% 35% 3 12% 27% 13%	1800
	21st to end	Day	11% 36% 4 15% 24% 10%	1949
November	1st to 10th	Day	8% 40% 3 15% 22% 12%	1673
	11th to 20th	Day	9% 39% 4 18% 20% 9%	1710
	21st to end	Day	12% 39% 3 11% 23% 12%	1710
December	1st to 10th	Day	12% 40% 8% 16% 17% 7%	1606
	11th to 20th	Day	16% 33% 7% 16% 20% 9%	1924
	21st to end	Day	16% 25% 5% 21% 21% 12%	2794
January	1st to 10th	Night	12% 40% 5% 17% 20% 6%	2647
	11th to 20th	Night	13% 40% 4 16% 20% 8%	2490
	21st to end	Night	13% 36% 5% 18% 22% 6%	2574
February	1st to 10th	Night	17% 35% 6% 17% 17% 8%	2249
	11th to 20th	Night	17% 36% 6% 17% 15% 8%	2098
	21st to end	Night	12% 35% 3 14% 24% 11%	1776
March	1st to 10th	Night	16% 36% 5% 14% 21% 8%	2160
	11th to 20th	Night	16% 36% 6% 15% 20% 6%	2023
	21st to end	Night	15% 37% 5% 14% 21% 8%	2026
April	1st to 10th	Night	13% 36% 5% 16% 19% 12%	1800
	11th to 20th	Night	17% 35% 5% 16% 17% 10%	1777
	21st to end	Night	17% 36% 8% 14% 16% 9%	1800
May	1st to 10th	Night	16% 37% 6% 14% 16% 10%	1746
	11th to 20th	Night	23% 39% 8% 13% 12% 5%	1590
	21st to end	Night	15% 39% 8% 12% 13% 14%	1552
June	1st to 10th	Night	15% 39% 9% 16% 11% 11%	1440
	11th to 20th	Night	13% 37% 5% 14% 16% 16%	1440
	21st to end	Night	20% 39% 8% 10% 12% 10%	1440
July	1st to 10th	Night	21% 41% 9% 12% 10% 7%	1400
	11th to 20th	Night	17% 40% 13% 17% 8% 5%	1392
	21st to end	Night	21% 42% 16% 15% 5%	1621
August	1st to 10th	Night	18% 41% 14% 11% 9% 6%	1717
	11th to 20th	Night	23% 37% 10% 20% 7% 3	1778
	21st to end	Night	15% 40% 11% 18% 12% 5%	1980
September	1st to 10th	Night	17% 37% 8% 17% 15% 7%	1800
	11th to 20th	Night	17% 37% 7% 12% 18% 10%	1849
	21st to end	Night	14% 37% 4 15% 22% 8%	1980
October	1st to 10th	Night	13% 37% 7% 15% 19% 10%	2078
	11th to 20th	Night	7% 35% 4 14% 27% 13%	2160
	21st to end	Night	13% 36% 4 15% 21% 11%	2389
November	1st to 10th	Night	8% 40% 5% 17% 19% 12%	2405
	11th to 20th	Night	8% 38% 4 17% 23% 9%	2470
	21st to end	Night	10% 39% 5% 13% 21% 12%	2470
December	1st to 10th	Night	14% 39% 8% 16% 16% 8%	2570
	11th to 20th	Night	15% 33% 6% 13% 26% 6%	3272
	21st to end	Night	18% 26% 8% 19% 20% 10%	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	7% 16% 38% 27% 12% 1	270
	11th to 20th	Day	10% 19% 35% 25% 7% 3	257
	21st to end	Day	4 23% 36% 26% 10% 1	264
February	1st to 10th	Day	1 24% 40% 25% 8% 1	240
	11th to 20th	Day	6% 31% 37% 21% 5%	240
	21st to end	Day	17% 28% 31% 21% 4	198
March	1st to 10th	Day	8% 25% 39% 20% 8%	240
	11th to 20th	Day	11% 27% 35% 20% 7% 1	374
	21st to end	Day	17% 36% 31% 13% 3	462
April	1st to 10th	Day	10% 30% 38% 16% 5% 1	420
	11th to 20th	Day	15% 33% 35% 13% 3 1	412
	21st to end	Day	13% 32% 36% 15% 3	420
May	1st to 10th	Day	9% 26% 37% 21% 6% 1	477
	11th to 20th	Day	11% 16% 33% 26% 12% 2	625
	21st to end	Day	9% 19% 35% 25% 10% 2	679
June	1st to 10th	Day	5% 13% 27% 30% 20% 4	630
	11th to 20th	Day	5% 12% 35% 30% 16% 3	630
	21st to end	Day	6% 6% 34% 29% 21% 4	630
July	1st to 10th	Day	5% 6% 20% 33% 30% 6%	621
	11th to 20th	Day	4 1 16% 37% 34% 9%	618
	21st to end	Day	4 2 14% 36% 33% 11%	540
August	1st to 10th	Day	5% 4 21% 34% 26% 10%	447
	11th to 20th	Day	4 4 26% 41% 20% 5%	437
	21st to end	Day	5% 3 23% 44% 21% 5%	495
September	1st to 10th	Day	5% 5% 26% 40% 19% 6%	450
	11th to 20th	Day	4 10% 29% 31% 20% 4	401
	21st to end	Day	7% 11% 24% 31% 23% 4	270
October	1st to 10th	Day	8% 20% 24% 24% 17% 7%	270
	11th to 20th	Day	5% 16% 29% 27% 16% 6%	270
	21st to end	Day	12% 17% 26% 28% 14% 3	297
November	1st to 10th	Day	4 21% 31% 28% 14% 2	270
	11th to 20th	Day	5% 15% 34% 28% 14% 4	270
	21st to end	Day	9% 18% 33% 26% 11% 4	270
December	1st to 10th	Day	5% 21% 35% 27% 10% 1	270
	11th to 20th	Day	6% 17% 41% 28% 7% 1	270
	21st to end	Day	10% 22% 38% 25% 5%	297
January	1st to 10th	Night	5% 11% 34% 37% 11% 1	950
	11th to 20th	Night	7% 12% 35% 34% 9% 2	816
	21st to end	Night	5% 11% 36% 38% 10% 1	792
February	1st to 10th	Night	5% 14% 42% 31% 8%	720
	11th to 20th	Night	5% 20% 43% 24% 7%	704
	21st to end	Night	6% 18% 43% 30% 3	592
March	1st to 10th	Night	6% 18% 39% 31% 5%	720
	11th to 20th	Night	8% 14% 38% 31% 8% 1	720
	21st to end	Night	8% 22% 39% 26% 6%	640
April	1st to 10th	Night	6% 20% 46% 24% 3	540
	11th to 20th	Night	9% 23% 37% 28% 4	533
	21st to end	Night	12% 16% 38% 26% 8%	540
May	1st to 10th	Night	9% 14% 35% 33% 8% 1	540
	11th to 20th	Night	12% 10% 33% 33% 11% 1	531
	21st to end	Night	9% 14% 39% 30% 8% 1	584
June	1st to 10th	Night	6% 9% 36% 32% 16% 1	540
	11th to 20th	Night	4 8% 43% 35% 9%	540
	21st to end	Night	5% 5% 29% 41% 17% 2	540
July	1st to 10th	Night	4 6% 23% 41% 23% 2	525
	11th to 20th	Night	6% 2 22% 42% 25% 3	522
	21st to end	Night	7% 2 19% 37% 32% 4	591
August	1st to 10th	Night	4 1 16% 37% 35% 6%	537
	11th to 20th	Night	7% 2 25% 38% 26% 2	534
	21st to end	Night	3 2 26% 40% 26% 3	594
September	1st to 10th	Night	6% 5% 26% 42% 20% 2	540
	11th to 20th	Night	6% 6% 29% 39% 18% 2	540
	21st to end	Night	5% 11% 30% 35% 17% 2	540
October	1st to 10th	Night	9% 13% 33% 31% 13% 2	638
	11th to 20th	Night	3 7% 34% 39% 15% 2	720
	21st to end	Night	8% 8% 30% 38% 14% 3	805
November	1st to 10th	Night	4 12% 30% 39% 14% 1	925
	11th to 20th	Night	4 12% 36% 36% 11% 2	950
	21st to end	Night	6% 13% 30% 36% 13% 2	950
December	1st to 10th	Night	4 11% 38% 36% 9% 1	950
	11th to 20th	Night	5% 12% 38% 35% 10%	950
	21st to end	Night	8% 15% 35% 35% 6% 1	1045

Page generated at 2024-01-13 17:28:34. Version ac07

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