Flaming Gorge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flaming Gorge Observatory clear sky chart from 2005-11-06 to 2025-01-07.

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 6% 2 6% 5% 5% 5% 4 7% 8% 50%	108849
	Night	3 6% 2 5% 4 4 4 4 6% 8% 54%	108962
Transparency	Day	16% 47% 6% 13% 11% 6%	108608
	Night	16% 45% 8% 15% 12% 5%	108792
Seeing	Day	7% 11% 26% 31% 19% 5%	15655
	Night	5% 7% 27% 39% 19% 2	25921

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 7% 3 9% 5% 6% 6% 6% 9% 10% 39%	2793
	11th to 20th	Day	1 5% 4 8% 7% 5% 6% 5% 8% 9% 43%	2860
	21st to end	Day	1 9% 4 10% 5% 5% 12% 7% 6% 8% 34%	3146
February	1st to 10th	Day	2 7% 3 7% 5% 5% 5% 5% 7% 10% 45%	1710
	11th to 20th	Day	1 6% 3 8% 4 5% 5% 5% 7% 9% 46%	1665
	21st to end	Day	2 6% 2 7% 5% 7% 5% 6% 7% 9% 45%	1537
March	1st to 10th	Day	1 9% 4 8% 5% 5% 5% 4 8% 9% 41%	3444
	11th to 20th	Day	4 12% 3 6% 4 5% 5% 5% 7% 11% 39%	3490
	21st to end	Day	2 9% 4 10% 8% 7% 6% 5% 7% 9% 33%	3825
April	1st to 10th	Day	3 8% 3 6% 5% 5% 4 5% 7% 10% 44%	2213
	11th to 20th	Day	7% 9% 3 7% 5% 4 5% 5% 6% 8% 42%	2252
	21st to end	Day	5% 7% 2 6% 5% 4 6% 6% 8% 9% 42%	2470
May	1st to 10th	Day	6% 10% 3 6% 5% 5% 6% 5% 7% 8% 40%	4110
	11th to 20th	Day	5% 5% 2 5% 4 5% 5% 5% 7% 8% 49%	4098
	21st to end	Day	5% 6% 2 5% 5% 4 6% 5% 7% 9% 48%	4825
June	1st to 10th	Day	3 4 2 4 5% 5% 6% 5% 7% 9% 50%	2660
	11th to 20th	Day	4 5% 2 5% 3 4 4 4 6% 7% 56%	2660
	21st to end	Day	3 3 2 5% 4 5% 4 4 6% 8% 57%	2660
July	1st to 10th	Day	2 2 1 3 3 4 4 3 5% 5% 67%	4430
	11th to 20th	Day	3 3 2 5% 5% 6% 7% 6% 8% 9% 47%	4113
	21st to end	Day	3 4 1 5% 4 4 6% 4 6% 8% 53%	4454
August	1st to 10th	Day	3 3 2 5% 5% 5% 6% 5% 8% 9% 48%	4092
	11th to 20th	Day	3 3 1 6% 5% 6% 6% 5% 7% 8% 50%	4028
	21st to end	Day	2 2 1 4 4 4 5% 4 5% 7% 60%	4318
September	1st to 10th	Day	4 3 1 4 3 4 4 4 6% 5% 60%	2280
	11th to 20th	Day	4 3 1 4 4 3 4 3 6% 8% 60%	2128
	21st to end	Day	5% 3 1 4 3 4 3 2 5% 5% 66%	2086
October	1st to 10th	Day	4 4 1 3 2 2 3 2 5% 5% 69%	3170
	11th to 20th	Day	8% 5% 2 4 3 3 3 2 4 8% 57%	3150
	21st to end	Day	5% 6% 2 3 2 3 4 3 5% 7% 60%	3438
November	1st to 10th	Day	4 6% 2 4 3 3 3 4 5% 9% 58%	1884
	11th to 20th	Day	2 6% 1 4 4 3 4 4 5% 8% 58%	1610
	21st to end	Day	1 5% 3 7% 4 4 5% 4 6% 8% 53%	1600
December	1st to 10th	Day	4 2 3 3 3 3 5% 9% 11% 57%	2620
	11th to 20th	Day	1 5% 2 4 4 3 4 4 8% 12% 53%	3026
	21st to end	Day	2 8% 4 10% 6% 6% 5% 5% 7% 10% 37%	4004
January	1st to 10th	Night	1 9% 4 8% 5% 5% 4 4 8% 9% 42%	4311
	11th to 20th	Night	1 5% 3 8% 6% 5% 6% 4 7% 11% 43%	4110
	21st to end	Night	1 10% 3 10% 6% 7% 9% 5% 5% 6% 37%	4521
February	1st to 10th	Night	1 6% 3 6% 4 4 5% 5% 8% 9% 49%	2470
	11th to 20th	Night	1 6% 3 6% 5% 4 5% 4 7% 10% 48%	2402
	21st to end	Night	1 7% 3 7% 4 4 4 4 7% 9% 50%	1913
March	1st to 10th	Night	1 6% 2 8% 5% 4 5% 4 7% 8% 49%	3430
	11th to 20th	Night	2 11% 3 6% 3 3 4 5% 6% 9% 47%	3490
	21st to end	Night	3 12% 3 9% 7% 6% 6% 5% 6% 6% 38%	3828
April	1st to 10th	Night	4 7% 3 5% 4 4 4 5% 6% 8% 51%	1967
	11th to 20th	Night	5% 10% 3 6% 4 3 5% 4 6% 7% 46%	1872
	21st to end	Night	4 6% 2 5% 3 4 5% 5% 7% 8% 49%	1710
May	1st to 10th	Night	7% 8% 2 6% 5% 5% 4 3 5% 7% 46%	2860
	11th to 20th	Night	5% 6% 2 6% 3 4 4 4 6% 9% 50%	2807
	21st to end	Night	4 5% 1 4 4 3 4 4 6% 9% 56%	2762
June	1st to 10th	Night	2 2 1 3 4 4 4 5% 7% 10% 57%	1520
	11th to 20th	Night	4 3 1 3 3 3 3 3 7% 9% 62%	1520
	21st to end	Night	2 3 1 2 2 3 4 3 6% 6% 68%	1520
July	1st to 10th	Night	2 2 1 2 2 3 2 3 5% 5% 73%	2540
	11th to 20th	Night	2 2 1 3 3 3 5% 5% 7% 10% 59%	2852
	21st to end	Night	1 1 1 3 3 4 5% 5% 9% 9% 59%	3109
August	1st to 10th	Night	1 2 1 3 3 3 4 4 7% 9% 64%	2847
	11th to 20th	Night	2 2 2 4 4 4 5% 4 7% 7% 58%	2811
	21st to end	Night	1 1 1 3 2 3 4 3 5% 7% 71%	3349
September	1st to 10th	Night	3 2 1 2 2 2 3 3 4 7% 72%	1900
	11th to 20th	Night	2 2 1 2 3 3 3 3 5% 7% 69%	2048
	21st to end	Night	3 3 1 3 3 3 3 3 3 5% 70%	2092
October	1st to 10th	Night	2 3 1 2 2 2 3 2 4 5% 73%	3800
	11th to 20th	Night	6% 5% 2 4 3 3 3 3 4 6% 61%	3778
	21st to end	Night	6% 7% 2 4 3 3 3 3 5% 8% 58%	4120
November	1st to 10th	Night	3 6% 2 4 3 4 4 3 5% 9% 57%	2410
	11th to 20th	Night	2 5% 1 5% 3 4 4 4 6% 9% 58%	2768
	21st to end	Night	2 7% 3 5% 4 3 4 4 6% 7% 56%	2800
December	1st to 10th	Night	1 3 2 5% 4 3 5% 6% 9% 8% 55%	4570
	11th to 20th	Night	1 6% 2 6% 4 3 5% 4 7% 10% 53%	5181
	21st to end	Night	2 8% 4 8% 5% 5% 5% 5% 8% 10% 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	28% 41% 9% 14% 8% 1	2794
	11th to 20th	Day	25% 46% 8% 13% 8%	2860
	21st to end	Day	21% 46% 16% 13% 4	3146
February	1st to 10th	Day	13% 67% 8% 8% 4 1	1710
	11th to 20th	Day	10% 65% 4 13% 7%	1674
	21st to end	Day	13% 65% 5% 11% 6% 1	1537
March	1st to 10th	Day	22% 43% 7% 16% 10% 2	3444
	11th to 20th	Day	22% 45% 14% 14% 5% 1	3490
	21st to end	Day	26% 48% 8% 14% 3 1	3825
April	1st to 10th	Day	12% 66% 7% 8% 6%	2213
	11th to 20th	Day	15% 66% 5% 8% 6%	2255
	21st to end	Day	15% 66% 4 9% 6%	2470
May	1st to 10th	Day	25% 46% 6% 11% 10% 2	4110
	11th to 20th	Day	17% 43% 5% 20% 14% 1	4101
	21st to end	Day	16% 45% 6% 18% 15% 1	4825
June	1st to 10th	Day	9% 66% 4 9% 10% 2	2660
	11th to 20th	Day	10% 65% 3 9% 9% 4	2660
	21st to end	Day	10% 63% 2 7% 11% 7%	2660
July	1st to 10th	Day	7% 36% 2 6% 11% 39%	4361
	11th to 20th	Day	17% 37% 4 9% 16% 17%	4043
	21st to end	Day	16% 36% 4 8% 16% 20%	4314
August	1st to 10th	Day	15% 39% 6% 13% 15% 13%	4078
	11th to 20th	Day	18% 40% 7% 15% 15% 6%	4067
	21st to end	Day	12% 38% 5% 12% 17% 16%	4317
September	1st to 10th	Day	10% 60% 3 8% 13% 6%	2280
	11th to 20th	Day	8% 61% 3 9% 13% 6%	2128
	21st to end	Day	10% 59% 2 10% 13% 6%	2086
October	1st to 10th	Day	9% 36% 3 11% 22% 19%	3170
	11th to 20th	Day	18% 38% 4 16% 18% 5%	3150
	21st to end	Day	16% 37% 6% 23% 17% 2	3438
November	1st to 10th	Day	12% 56% 7% 14% 10% 1	1884
	11th to 20th	Day	12% 57% 5% 16% 9% 1	1610
	21st to end	Day	16% 57% 6% 14% 8% 1	1600
December	1st to 10th	Day	11% 38% 13% 29% 8% 1	2620
	11th to 20th	Day	14% 34% 20% 22% 11% 1	3024
	21st to end	Day	30% 29% 7% 17% 11% 5%	4004
January	1st to 10th	Night	25% 38% 10% 14% 11% 1	4311
	11th to 20th	Night	24% 42% 12% 16% 6%	4110
	21st to end	Night	21% 46% 17% 11% 5% 1	4521
February	1st to 10th	Night	12% 66% 8% 9% 3 1	2470
	11th to 20th	Night	10% 65% 5% 10% 8% 1	2403
	21st to end	Night	11% 64% 6% 12% 7% 1	1913
March	1st to 10th	Night	19% 41% 7% 21% 11% 2	3430
	11th to 20th	Night	20% 48% 11% 14% 7%	3490
	21st to end	Night	28% 44% 7% 13% 6% 1	3828
April	1st to 10th	Night	12% 65% 6% 10% 6% 1	1967
	11th to 20th	Night	15% 67% 3 10% 4	1872
	21st to end	Night	14% 66% 5% 11% 5%	1710
May	1st to 10th	Night	23% 44% 6% 9% 14% 5%	2860
	11th to 20th	Night	19% 41% 8% 18% 10% 4	2808
	21st to end	Night	15% 40% 5% 23% 18%	2762
June	1st to 10th	Night	6% 65% 4 11% 11% 3	1520
	11th to 20th	Night	7% 65% 3 11% 11% 3	1520
	21st to end	Night	7% 63% 3 8% 12% 8%	1520
July	1st to 10th	Night	7% 35% 3 5% 12% 38%	2500
	11th to 20th	Night	11% 36% 4 14% 18% 17%	2799
	21st to end	Night	10% 36% 7% 10% 21% 17%	3011
August	1st to 10th	Night	9% 37% 5% 16% 18% 15%	2838
	11th to 20th	Night	17% 39% 8% 14% 17% 6%	2838
	21st to end	Night	8% 37% 6% 13% 22% 14%	3349
September	1st to 10th	Night	5% 60% 3 12% 14% 6%	1900
	11th to 20th	Night	6% 60% 4 12% 14% 5%	2048
	21st to end	Night	9% 59% 2 10% 14% 5%	2092
October	1st to 10th	Night	7% 36% 4 10% 30% 14%	3800
	11th to 20th	Night	18% 39% 4 17% 15% 7%	3778
	21st to end	Night	19% 38% 7% 23% 12% 2	4120
November	1st to 10th	Night	11% 57% 7% 15% 9% 1	2410
	11th to 20th	Night	11% 58% 4 18% 7% 1	2768
	21st to end	Night	16% 58% 6% 13% 7% 1	2800
December	1st to 10th	Night	14% 39% 13% 24% 10% 1	4570
	11th to 20th	Night	15% 35% 17% 25% 8% 1	5182
	21st to end	Night	27% 30% 11% 16% 10% 5%	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	4 11% 26% 36% 19% 3	288
	11th to 20th	Day	6% 13% 27% 38% 16%	270
	21st to end	Day	5% 6% 30% 38% 17% 4	297
February	1st to 10th	Day	7% 19% 43% 22% 7% 1	270
	11th to 20th	Day	4 10% 39% 33% 13% 2	270
	21st to end	Day	5% 13% 31% 42% 8% 1	306
March	1st to 10th	Day	6% 14% 38% 31% 10% 2	460
	11th to 20th	Day	9% 12% 30% 32% 16% 2	460
	21st to end	Day	11% 18% 33% 26% 12%	506
April	1st to 10th	Day	10% 20% 26% 25% 17% 2	460
	11th to 20th	Day	13% 19% 33% 25% 9% 1	452
	21st to end	Day	13% 18% 27% 24% 15% 3	460
May	1st to 10th	Day	10% 19% 31% 25% 13% 3	463
	11th to 20th	Day	11% 14% 27% 28% 14% 5%	502
	21st to end	Day	11% 10% 23% 28% 22% 6%	734
June	1st to 10th	Day	5% 9% 22% 32% 25% 6%	680
	11th to 20th	Day	6% 13% 26% 31% 20% 2	680
	21st to end	Day	4 9% 25% 34% 23% 6%	680
July	1st to 10th	Day	4 3 18% 34% 31% 10%	671
	11th to 20th	Day	6% 5% 26% 29% 25% 10%	486
	21st to end	Day	4 3 19% 31% 31% 12%	531
August	1st to 10th	Day	5% 5% 20% 34% 25% 11%	487
	11th to 20th	Day	6% 5% 22% 32% 26% 9%	477
	21st to end	Day	5% 6% 23% 30% 24% 11%	539
September	1st to 10th	Day	7% 8% 22% 28% 22% 13%	490
	11th to 20th	Day	8% 11% 27% 28% 18% 8%	490
	21st to end	Day	7% 13% 21% 26% 26% 8%	486
October	1st to 10th	Day	8% 9% 20% 26% 28% 9%	300
	11th to 20th	Day	8% 13% 18% 29% 25% 7%	300
	21st to end	Day	8% 14% 26% 34% 16% 2	330
November	1st to 10th	Day	7% 22% 24% 27% 15% 5%	300
	11th to 20th	Day	7% 12% 26% 39% 11% 5%	300
	21st to end	Day	5% 10% 23% 41% 17% 4	300
December	1st to 10th	Day	5% 10% 26% 38% 19% 2	300
	11th to 20th	Day	3 11% 26% 45% 14% 1	300
	21st to end	Day	7% 10% 38% 28% 14% 3	330
January	1st to 10th	Night	6% 10% 31% 36% 16% 2	868
	11th to 20th	Night	5% 12% 32% 34% 15% 2	760
	21st to end	Night	6% 8% 33% 39% 12% 2	836
February	1st to 10th	Night	5% 12% 39% 34% 9% 2	760
	11th to 20th	Night	4 8% 38% 38% 12% 1	744
	21st to end	Night	4 6% 39% 43% 6%	628
March	1st to 10th	Night	6% 8% 33% 41% 10% 2	760
	11th to 20th	Night	5% 8% 27% 43% 16% 1	760
	21st to end	Night	6% 9% 37% 37% 10%	836
April	1st to 10th	Night	8% 11% 32% 38% 10%	637
	11th to 20th	Night	12% 12% 29% 35% 10% 1	563
	21st to end	Night	8% 12% 30% 36% 14% 1	570
May	1st to 10th	Night	9% 10% 28% 36% 14% 2	570
	11th to 20th	Night	9% 4 20% 41% 23% 3	561
	21st to end	Night	7% 5% 26% 36% 24% 2	617
June	1st to 10th	Night	3 6% 21% 39% 27% 2	570
	11th to 20th	Night	6% 6% 28% 42% 17%	570
	21st to end	Night	3 3 16% 46% 30% 2	570
July	1st to 10th	Night	4 1 13% 39% 39% 3	555
	11th to 20th	Night	3 1 12% 46% 35% 3	552
	21st to end	Night	4 1 7% 42% 42% 5%	624
August	1st to 10th	Night	4 1 12% 43% 37% 3	567
	11th to 20th	Night	4 1 12% 44% 36% 2	564
	21st to end	Night	2 1 14% 41% 37% 4	627
September	1st to 10th	Night	4 3 15% 41% 32% 5%	570
	11th to 20th	Night	3 3 19% 43% 26% 6%	718
	21st to end	Night	5% 4 19% 37% 26% 8%	760
October	1st to 10th	Night	6% 5% 25% 38% 24% 3	760
	11th to 20th	Night	6% 7% 26% 38% 20% 4	760
	21st to end	Night	8% 7% 29% 38% 17% 3	836
November	1st to 10th	Night	6% 9% 29% 38% 17% 3	780
	11th to 20th	Night	5% 11% 34% 36% 12% 2	968
	21st to end	Night	6% 10% 28% 38% 16% 2	1000
December	1st to 10th	Night	4 7% 32% 43% 12% 1	1000
	11th to 20th	Night	6% 8% 36% 40% 10% 1	1000
	21st to end	Night	6% 11% 38% 34% 9% 2	1100

Page generated at 2025-01-04 01:24:01. Version ac07

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