Moab Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moab Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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 5% 2 4 3 3 4 4 6% 8% 58%	104908
	Night	5% 5% 2 5% 4 4 4 4 6% 7% 56%	102882
Transparency	Day	23% 7% 11% 20% 23% 17%	104673
	Night	26% 7% 11% 20% 22% 15%	102706
Seeing	Day	7% 10% 26% 32% 21% 4	15107
	Night	7% 6% 21% 38% 25% 4	25363

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 7% 2 6% 5% 4 7% 5% 8% 11% 40%	2858
	11th to 20th	Day	5% 6% 2 6% 5% 5% 5% 5% 8% 11% 43%	2860
	21st to end	Day	6% 7% 2 5% 4 4 5% 3 5% 7% 51%	3146
February	1st to 10th	Day	4 6% 2 6% 4 4 4 5% 9% 10% 45%	1710
	11th to 20th	Day	6% 8% 2 6% 5% 3 4 4 6% 8% 49%	1665
	21st to end	Day	7% 8% 3 4 4 5% 5% 3 6% 6% 50%	1615
March	1st to 10th	Day	3 9% 3 6% 4 3 4 4 4 7% 52%	3444
	11th to 20th	Day	5% 10% 3 8% 4 4 5% 4 7% 8% 43%	3490
	21st to end	Day	6% 12% 3 8% 6% 4 4 3 6% 6% 42%	3825
April	1st to 10th	Day	5% 5% 2 5% 4 3 3 3 5% 6% 59%	2199
	11th to 20th	Day	4 5% 2 5% 5% 4 4 4 5% 7% 56%	2251
	21st to end	Day	4 5% 2 4 4 3 4 3 5% 7% 59%	2387
May	1st to 10th	Day	5% 5% 2 5% 4 4 4 3 5% 8% 54%	4110
	11th to 20th	Day	3 3 1 4 3 3 4 4 6% 7% 62%	4071
	21st to end	Day	4 4 1 3 3 3 4 3 5% 7% 62%	4558
June	1st to 10th	Day	3 2 1 3 2 3 3 3 5% 8% 68%	2660
	11th to 20th	Day	2 3 1 3 3 2 3 3 4 5% 73%	2660
	21st to end	Day	2 2 1 3 2 2 3 3 4 5% 73%	2628
July	1st to 10th	Day	2 2 1 2 2 2 2 3 4 5% 76%	4110
	11th to 20th	Day	2 2 1 3 3 4 4 5% 8% 11% 58%	4110
	21st to end	Day	2 2 1 3 3 3 4 4 6% 9% 62%	4454
August	1st to 10th	Day	2 2 1 4 3 5% 5% 5% 8% 11% 53%	4092
	11th to 20th	Day	2 2 1 4 3 4 4 4 6% 8% 61%	4028
	21st to end	Day	4 2 1 3 3 4 4 4 7% 9% 60%	4242
September	1st to 10th	Day	4 3 1 3 3 3 3 3 6% 6% 65%	2280
	11th to 20th	Day	3 2 1 4 3 3 4 2 5% 6% 68%	2118
	21st to end	Day	3 2 1 3 2 2 2 3 3 5% 73%	2088
October	1st to 10th	Day	3 2 1 2 1 2 2 2 3 4 79%	3170
	11th to 20th	Day	5% 3 1 5% 3 3 4 3 6% 9% 58%	3150
	21st to end	Day	3 3 1 2 2 2 2 3 5% 10% 67%	3438
November	1st to 10th	Day	4 4 1 3 3 3 2 2 5% 7% 67%	1899
	11th to 20th	Day	5% 4 1 3 3 2 2 2 4 7% 67%	1671
	21st to end	Day	5% 6% 1 4 2 3 3 3 4 7% 63%	1520
December	1st to 10th	Day	6% 8% 2 6% 5% 2 4 4 5% 7% 51%	1520
	11th to 20th	Day	6% 8% 2 7% 5% 5% 5% 5% 8% 12% 37%	1926
	21st to end	Day	5% 9% 2 7% 4 5% 5% 4 6% 9% 44%	2955
January	1st to 10th	Night	4 8% 4 7% 4 4 4 3 5% 7% 48%	4097
	11th to 20th	Night	5% 9% 2 6% 4 4 4 4 5% 10% 47%	4110
	21st to end	Night	7% 8% 3 6% 4 4 4 4 5% 6% 50%	4521
February	1st to 10th	Night	3 7% 2 5% 3 4 4 4 6% 9% 53%	2470
	11th to 20th	Night	5% 7% 2 5% 3 4 4 3 6% 8% 52%	2402
	21st to end	Night	5% 8% 2 7% 4 4 3 4 5% 7% 49%	1835
March	1st to 10th	Night	6% 9% 2 5% 4 4 4 3 5% 7% 51%	3430
	11th to 20th	Night	6% 8% 2 6% 5% 3 4 4 5% 8% 48%	3490
	21st to end	Night	7% 11% 3 8% 4 4 5% 4 6% 6% 41%	3828
April	1st to 10th	Night	5% 7% 2 6% 4 4 4 3 5% 6% 54%	1979
	11th to 20th	Night	5% 7% 3 5% 4 5% 4 3 4 6% 54%	1877
	21st to end	Night	7% 5% 2 5% 3 4 4 3 7% 7% 54%	1789
May	1st to 10th	Night	7% 6% 1 4 4 4 4 4 5% 6% 54%	2860
	11th to 20th	Night	4 4 2 5% 3 5% 5% 4 8% 8% 52%	2834
	21st to end	Night	6% 3 1 4 3 3 4 3 5% 6% 63%	3024
June	1st to 10th	Night	3 3 1 4 3 3 3 4 6% 8% 62%	1520
	11th to 20th	Night	3 4 1 4 3 3 4 3 5% 8% 64%	1520
	21st to end	Night	2 2 1 4 4 2 3 4 6% 7% 67%	1545
July	1st to 10th	Night	1 2 1 2 2 3 4 3 5% 7% 70%	2860
	11th to 20th	Night	1 2 1 4 4 5% 8% 6% 9% 12% 46%	2860
	21st to end	Night	2 2 2 5% 4 4 4 4 8% 10% 54%	3109
August	1st to 10th	Night	3 2 2 6% 5% 6% 6% 6% 9% 10% 44%	2847
	11th to 20th	Night	3 3 2 5% 4 4 4 3 7% 9% 55%	2811
	21st to end	Night	2 3 1 4 4 3 4 4 7% 8% 59%	3425
September	1st to 10th	Night	4 3 1 3 3 2 4 3 6% 7% 63%	1900
	11th to 20th	Night	4 2 1 3 4 3 3 3 4 7% 66%	2059
	21st to end	Night	4 3 1 3 2 2 3 3 3 4 73%	2090
October	1st to 10th	Night	4 2 1 2 2 2 2 2 4 5% 75%	3800
	11th to 20th	Night	5% 4 1 5% 3 3 4 3 5% 7% 58%	3778
	21st to end	Night	5% 4 1 3 2 3 3 3 3 6% 68%	4120
November	1st to 10th	Night	3 4 1 3 3 3 3 2 5% 7% 67%	2280
	11th to 20th	Night	5% 4 1 3 3 2 3 2 4 5% 67%	2482
	21st to end	Night	6% 6% 2 4 3 2 3 3 5% 5% 61%	2660
December	1st to 10th	Night	7% 6% 2 5% 3 3 3 3 4 7% 57%	2660
	11th to 20th	Night	7% 7% 2 6% 4 4 5% 5% 7% 9% 45%	3271
	21st to end	Night	6% 9% 3 7% 4 3 4 4 6% 8% 47%	4739

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	32% 11% 20% 28% 8% 1	2859
	11th to 20th	Day	30% 12% 21% 29% 7% 1	2860
	21st to end	Day	31% 10% 17% 28% 12% 2	3146
February	1st to 10th	Day	32% 10% 20% 20% 15% 3	1710
	11th to 20th	Day	33% 7% 15% 23% 19% 3	1674
	21st to end	Day	33% 7% 9% 24% 22% 5%	1615
March	1st to 10th	Day	28% 7% 11% 27% 23% 3	3444
	11th to 20th	Day	37% 10% 13% 23% 12% 4	3490
	21st to end	Day	39% 8% 10% 22% 18% 3	3825
April	1st to 10th	Day	27% 5% 9% 24% 24% 12%	2199
	11th to 20th	Day	27% 6% 11% 23% 23% 11%	2254
	21st to end	Day	24% 5% 10% 22% 30% 8%	2387
May	1st to 10th	Day	24% 8% 9% 17% 33% 9%	4110
	11th to 20th	Day	17% 7% 9% 21% 34% 13%	4074
	21st to end	Day	19% 7% 8% 14% 37% 15%	4558
June	1st to 10th	Day	15% 4 6% 16% 31% 27%	2660
	11th to 20th	Day	15% 3 5% 8% 24% 44%	2660
	21st to end	Day	13% 3 6% 10% 24% 44%	2628
July	1st to 10th	Day	13% 3 6% 7% 10% 60%	4046
	11th to 20th	Day	16% 5% 9% 18% 28% 25%	4041
	21st to end	Day	16% 7% 10% 17% 18% 32%	4314
August	1st to 10th	Day	20% 8% 13% 26% 16% 17%	4078
	11th to 20th	Day	21% 7% 11% 15% 23% 23%	4067
	21st to end	Day	20% 6% 10% 18% 24% 22%	4241
September	1st to 10th	Day	19% 5% 8% 13% 24% 30%	2280
	11th to 20th	Day	18% 6% 9% 16% 22% 29%	2118
	21st to end	Day	16% 3 7% 13% 39% 22%	2088
October	1st to 10th	Day	12% 4 6% 13% 28% 38%	3170
	11th to 20th	Day	23% 4 8% 21% 35% 9%	3150
	21st to end	Day	16% 4 9% 30% 36% 6%	3438
November	1st to 10th	Day	19% 3 12% 28% 30% 8%	1899
	11th to 20th	Day	20% 4 9% 34% 30% 3	1671
	21st to end	Day	24% 6% 14% 28% 24% 4	1520
December	1st to 10th	Day	32% 7% 17% 26% 14% 4	1520
	11th to 20th	Day	38% 10% 21% 21% 9%	1924
	21st to end	Day	35% 10% 14% 13% 23% 6%	2955
January	1st to 10th	Night	32% 9% 18% 27% 13% 1	4097
	11th to 20th	Night	30% 13% 19% 26% 10% 1	4110
	21st to end	Night	34% 9% 14% 29% 12% 2	4521
February	1st to 10th	Night	28% 9% 18% 26% 17% 3	2470
	11th to 20th	Night	30% 9% 13% 25% 20% 4	2403
	21st to end	Night	32% 6% 10% 26% 21% 5%	1835
March	1st to 10th	Night	30% 8% 9% 27% 21% 6%	3430
	11th to 20th	Night	32% 9% 12% 25% 17% 4	3490
	21st to end	Night	37% 10% 10% 20% 19% 2	3828
April	1st to 10th	Night	30% 6% 8% 19% 24% 12%	1979
	11th to 20th	Night	31% 5% 8% 19% 25% 12%	1877
	21st to end	Night	27% 6% 9% 20% 29% 9%	1789
May	1st to 10th	Night	26% 7% 9% 16% 30% 12%	2860
	11th to 20th	Night	20% 9% 10% 21% 31% 9%	2835
	21st to end	Night	19% 7% 8% 15% 34% 18%	3024
June	1st to 10th	Night	18% 4 6% 14% 31% 27%	1520
	11th to 20th	Night	18% 5% 7% 10% 18% 42%	1520
	21st to end	Night	16% 4 7% 11% 21% 43%	1545
July	1st to 10th	Night	14% 4 7% 9% 9% 56%	2815
	11th to 20th	Night	21% 6% 10% 15% 24% 22%	2806
	21st to end	Night	22% 6% 11% 12% 20% 28%	3011
August	1st to 10th	Night	30% 8% 12% 21% 13% 17%	2838
	11th to 20th	Night	25% 6% 11% 14% 16% 28%	2838
	21st to end	Night	21% 6% 9% 17% 19% 27%	3425
September	1st to 10th	Night	20% 5% 8% 13% 20% 35%	1900
	11th to 20th	Night	19% 4 11% 16% 19% 31%	2059
	21st to end	Night	17% 4 5% 11% 33% 30%	2090
October	1st to 10th	Night	13% 3 5% 12% 24% 42%	3800
	11th to 20th	Night	24% 4 8% 14% 37% 12%	3778
	21st to end	Night	20% 3 5% 29% 35% 9%	4120
November	1st to 10th	Night	20% 3 9% 23% 33% 12%	2280
	11th to 20th	Night	21% 4 8% 28% 34% 5%	2482
	21st to end	Night	26% 5% 9% 22% 29% 9%	2660
December	1st to 10th	Night	28% 8% 13% 27% 19% 5%	2660
	11th to 20th	Night	35% 9% 15% 24% 16% 1	3272
	21st to end	Night	33% 8% 15% 16% 20% 7%	4739

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% 11% 27% 30% 16% 5%	270
	11th to 20th	Day	10% 10% 26% 37% 16% 1	270
	21st to end	Day	6% 4 30% 38% 19% 3	297
February	1st to 10th	Day	8% 10% 34% 34% 12% 2	270
	11th to 20th	Day	12% 10% 37% 27% 13% 1	270
	21st to end	Day	11% 19% 31% 29% 9% 1	341
March	1st to 10th	Day	10% 16% 30% 30% 12% 1	460
	11th to 20th	Day	8% 14% 33% 28% 15% 2	460
	21st to end	Day	16% 20% 34% 23% 7% 1	506
April	1st to 10th	Day	12% 16% 33% 25% 11% 3	460
	11th to 20th	Day	12% 19% 37% 23% 8% 2	452
	21st to end	Day	11% 20% 31% 24% 13% 1	460
May	1st to 10th	Day	10% 14% 40% 25% 9% 1	463
	11th to 20th	Day	6% 13% 30% 31% 17% 4	488
	21st to end	Day	7% 16% 24% 30% 18% 4	571
June	1st to 10th	Day	3 8% 25% 33% 29% 3	680
	11th to 20th	Day	4 11% 26% 33% 20% 5%	680
	21st to end	Day	3 6% 27% 37% 24% 3	648
July	1st to 10th	Day	2 4 20% 40% 28% 6%	486
	11th to 20th	Day	3 2 17% 36% 36% 7%	484
	21st to end	Day	3 2 14% 37% 39% 6%	531
August	1st to 10th	Day	5% 3 17% 40% 29% 6%	487
	11th to 20th	Day	4 4 18% 38% 28% 8%	477
	21st to end	Day	4 4 22% 34% 29% 7%	539
September	1st to 10th	Day	4 4 18% 33% 30% 10%	490
	11th to 20th	Day	4 11% 24% 33% 22% 5%	490
	21st to end	Day	6% 11% 20% 31% 24% 8%	488
October	1st to 10th	Day	11% 8% 19% 25% 24% 14%	300
	11th to 20th	Day	6% 12% 22% 29% 24% 6%	300
	21st to end	Day	8% 12% 24% 28% 25% 3	330
November	1st to 10th	Day	8% 14% 26% 29% 19% 4	282
	11th to 20th	Day	3 9% 33% 33% 19% 4	270
	21st to end	Day	8% 10% 25% 32% 22% 2	270
December	1st to 10th	Day	9% 10% 27% 34% 19% 2	270
	11th to 20th	Day	10% 7% 27% 38% 14% 4	270
	21st to end	Day	11% 12% 28% 36% 12% 2	297
January	1st to 10th	Night	8% 5% 17% 41% 24% 5%	760
	11th to 20th	Night	7% 5% 21% 38% 25% 4	760
	21st to end	Night	10% 3 21% 41% 20% 4	836
February	1st to 10th	Night	6% 4 28% 41% 17% 3	760
	11th to 20th	Night	8% 6% 29% 38% 17% 2	744
	21st to end	Night	9% 8% 28% 41% 13% 1	628
March	1st to 10th	Night	9% 9% 25% 39% 16% 2	760
	11th to 20th	Night	6% 6% 24% 36% 25% 1	760
	21st to end	Night	7% 11% 29% 36% 16% 2	836
April	1st to 10th	Night	9% 10% 29% 34% 15% 1	649
	11th to 20th	Night	9% 12% 29% 33% 15% 2	563
	21st to end	Night	7% 14% 25% 33% 16% 5%	570
May	1st to 10th	Night	7% 10% 26% 38% 15% 2	570
	11th to 20th	Night	5% 5% 22% 40% 24% 4	561
	21st to end	Night	5% 10% 26% 33% 24% 3	617
June	1st to 10th	Night	3 6% 20% 37% 32% 2	570
	11th to 20th	Night	5% 7% 22% 38% 25% 3	570
	21st to end	Night	2 3 17% 42% 32% 3	570
July	1st to 10th	Night	2 1 16% 32% 43% 6%	555
	11th to 20th	Night	2 1 9% 34% 47% 7%	552
	21st to end	Night	4 8% 33% 47% 7%	624
August	1st to 10th	Night	4 1 10% 36% 43% 6%	567
	11th to 20th	Night	4 2 11% 40% 36% 6%	564
	21st to end	Night	4 2 11% 38% 36% 9%	627
September	1st to 10th	Night	5% 1 11% 40% 35% 8%	570
	11th to 20th	Night	3 4 16% 35% 34% 7%	729
	21st to end	Night	5% 5% 15% 34% 31% 10%	760
October	1st to 10th	Night	7% 5% 19% 38% 27% 4	760
	11th to 20th	Night	5% 4 18% 39% 28% 6%	760
	21st to end	Night	7% 6% 20% 33% 28% 6%	836
November	1st to 10th	Night	5% 5% 19% 38% 28% 4	760
	11th to 20th	Night	5% 4 22% 41% 22% 5%	802
	21st to end	Night	9% 6% 20% 36% 23% 5%	950
December	1st to 10th	Night	9% 4 20% 44% 20% 2	950
	11th to 20th	Night	12% 5% 21% 39% 22% 2	950
	21st to end	Night	13% 6% 23% 39% 17% 3	963

Page generated at 2024-11-03 00:11:08. Version ac07

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