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 2024-04-10.

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	4 5% 2 4 4 3 4 5% 6% 8% 56%	83374
	Night	5% 6% 2 4 4 3 4 4 5% 7% 55%	85521
Transparency	Day	26% 7% 12% 21% 21% 14%	83099
	Night	27% 7% 11% 21% 21% 12%	85317
Seeing	Day	7% 10% 26% 32% 20% 4	14277
	Night	7% 5% 20% 37% 26% 4	24681

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% 3 5% 6% 3 7% 7% 8% 11% 40%	2858
	11th to 20th	Day	5% 6% 2 5% 6% 4 5% 6% 7% 11% 43%	2860
	21st to end	Day	7% 7% 2 4 4 3 4 5% 5% 7% 51%	3146
February	1st to 10th	Day	4 6% 2 5% 5% 3 4 6% 8% 10% 46%	1710
	11th to 20th	Day	6% 8% 3 5% 5% 2 4 5% 6% 8% 49%	1665
	21st to end	Day	7% 7% 3 4 4 4 5% 4 6% 6% 50%	1615
March	1st to 10th	Day	4 8% 4 5% 5% 2 4 4 4 7% 52%	3444
	11th to 20th	Day	5% 9% 3 7% 5% 3 5% 5% 6% 8% 43%	3490
	21st to end	Day	6% 11% 4 7% 6% 3 4 4 5% 7% 42%	3825
April	1st to 10th	Day	5% 5% 2 5% 4 2 3 4 5% 6% 59%	2188
	11th to 20th	Day	4 5% 2 4 5% 3 4 4 5% 7% 56%	2131
	21st to end	Day	4 5% 2 4 4 2 4 4 5% 8% 59%	2261
May	1st to 10th	Day	4 5% 2 4 4 3 5% 5% 6% 9% 53%	2340
	11th to 20th	Day	4 3 2 4 3 3 4 5% 5% 8% 59%	2301
	21st to end	Day	4 3 1 3 5% 2 4 5% 6% 8% 59%	2569
June	1st to 10th	Day	3 2 1 3 2 2 3 3 5% 8% 68%	2520
	11th to 20th	Day	2 3 1 2 3 1 3 3 4 4 73%	2520
	21st to end	Day	1 2 1 2 2 2 3 3 4 5% 74%	2490
July	1st to 10th	Day	2 2 2 3 3 2 4 6% 6% 8% 62%	2340
	11th to 20th	Day	3 3 1 3 4 4 4 6% 7% 9% 56%	2340
	21st to end	Day	4 3 1 4 5% 4 6% 7% 9% 11% 46%	2545
August	1st to 10th	Day	3 3 1 4 5% 4 5% 7% 8% 9% 51%	2328
	11th to 20th	Day	2 3 1 3 5% 3 4 4 6% 8% 61%	2299
	21st to end	Day	4 2 1 3 4 2 4 5% 6% 8% 61%	2412
September	1st to 10th	Day	4 3 1 3 3 2 3 4 6% 6% 65%	2160
	11th to 20th	Day	3 2 1 4 3 2 4 3 5% 6% 67%	2007
	21st to end	Day	3 2 1 2 3 2 2 3 3 5% 73%	1979
October	1st to 10th	Day	5% 4 1 3 3 2 3 4 5% 6% 65%	1800
	11th to 20th	Day	3 2 1 3 3 1 2 2 4 6% 73%	1800
	21st to end	Day	4 3 1 3 3 2 2 3 5% 6% 68%	1980
November	1st to 10th	Day	4 3 2 3 3 2 2 2 5% 7% 68%	1859
	11th to 20th	Day	5% 3 1 2 4 1 2 3 4 7% 67%	1671
	21st to end	Day	5% 5% 1 3 3 2 3 4 4 7% 63%	1520
December	1st to 10th	Day	6% 8% 2 5% 5% 2 3 5% 5% 7% 52%	1520
	11th to 20th	Day	6% 7% 3 6% 5% 4 5% 6% 7% 12% 38%	1926
	21st to end	Day	5% 8% 2 6% 5% 4 5% 6% 6% 8% 45%	2955
January	1st to 10th	Night	4 8% 4 6% 5% 3 4 4 5% 7% 48%	4097
	11th to 20th	Night	6% 8% 3 5% 5% 3 4 4 6% 10% 47%	4110
	21st to end	Night	7% 8% 3 6% 5% 3 4 4 5% 6% 50%	4521
February	1st to 10th	Night	3 6% 2 5% 4 3 4 5% 6% 9% 54%	2470
	11th to 20th	Night	6% 7% 2 5% 3 3 5% 3 6% 8% 52%	2402
	21st to end	Night	5% 8% 3 6% 4 3 4 5% 5% 8% 49%	1835
March	1st to 10th	Night	6% 9% 3 4 4 3 4 4 5% 7% 51%	3430
	11th to 20th	Night	6% 8% 2 5% 6% 2 4 5% 5% 8% 48%	3490
	21st to end	Night	7% 11% 3 7% 5% 3 5% 6% 6% 7% 41%	3828
April	1st to 10th	Night	5% 7% 3 6% 4 3 5% 4 5% 6% 54%	1979
	11th to 20th	Night	6% 6% 3 5% 4 3 5% 5% 4 6% 54%	1777
	21st to end	Night	6% 4 3 4 4 3 4 5% 6% 7% 55%	1695
May	1st to 10th	Night	6% 4 2 4 4 3 5% 5% 6% 7% 53%	1620
	11th to 20th	Night	4 5% 2 4 4 3 5% 5% 7% 7% 55%	1594
	21st to end	Night	5% 3 1 4 4 2 4 5% 6% 6% 61%	1702
June	1st to 10th	Night	2 3 2 4 3 2 3 5% 6% 8% 63%	1440
	11th to 20th	Night	3 3 1 3 4 2 4 4 5% 8% 64%	1440
	21st to end	Night	2 2 1 3 4 2 3 4 5% 6% 68%	1463
July	1st to 10th	Night	2 2 2 2 4 3 5% 6% 7% 9% 57%	1620
	11th to 20th	Night	2 3 2 4 5% 4 7% 7% 7% 10% 50%	1620
	21st to end	Night	3 3 2 6% 6% 3 6% 6% 9% 12% 44%	1773
August	1st to 10th	Night	3 2 2 4 4 4 5% 7% 8% 10% 52%	1611
	11th to 20th	Night	4 3 2 4 4 2 3 4 6% 10% 57%	1602
	21st to end	Night	2 4 1 3 4 2 5% 5% 7% 8% 58%	1944
September	1st to 10th	Night	4 3 1 2 3 1 5% 4 6% 7% 63%	1800
	11th to 20th	Night	4 2 2 3 4 2 3 4 4 7% 65%	1950
	21st to end	Night	4 3 1 2 3 1 3 3 3 4 72%	1980
October	1st to 10th	Night	7% 2 1 3 3 2 3 3 4 7% 65%	2160
	11th to 20th	Night	4 3 1 2 2 1 3 3 4 5% 73%	2160
	21st to end	Night	5% 4 1 3 3 2 2 3 3 5% 68%	2376
November	1st to 10th	Night	3 3 2 3 3 2 4 2 4 7% 67%	2220
	11th to 20th	Night	5% 4 1 3 3 1 3 3 4 6% 67%	2482
	21st to end	Night	6% 6% 2 4 3 2 3 3 4 6% 61%	2660
December	1st to 10th	Night	7% 6% 2 4 4 2 3 3 4 7% 57%	2660
	11th to 20th	Night	7% 6% 2 5% 5% 3 5% 6% 7% 9% 46%	3271
	21st to end	Night	6% 8% 3 6% 5% 2 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% 23% 24% 12%	2188
	11th to 20th	Day	28% 5% 11% 23% 23% 10%	2134
	21st to end	Day	25% 5% 10% 22% 30% 8%	2261
May	1st to 10th	Day	27% 7% 10% 18% 27% 10%	2340
	11th to 20th	Day	22% 7% 11% 21% 27% 13%	2304
	21st to end	Day	22% 7% 11% 15% 29% 16%	2569
June	1st to 10th	Day	15% 4 6% 16% 32% 28%	2520
	11th to 20th	Day	15% 3 5% 9% 23% 44%	2520
	21st to end	Day	13% 3 6% 10% 23% 45%	2490
July	1st to 10th	Day	20% 6% 10% 12% 16% 36%	2276
	11th to 20th	Day	23% 7% 12% 18% 16% 23%	2271
	21st to end	Day	26% 11% 16% 19% 13% 15%	2404
August	1st to 10th	Day	25% 11% 13% 15% 15% 21%	2313
	11th to 20th	Day	22% 7% 10% 15% 19% 27%	2299
	21st to end	Day	22% 6% 10% 19% 21% 22%	2412
September	1st to 10th	Day	20% 5% 8% 13% 22% 31%	2160
	11th to 20th	Day	18% 6% 9% 17% 21% 28%	2007
	21st to end	Day	17% 3 7% 13% 39% 21%	1979
October	1st to 10th	Day	22% 7% 10% 22% 25% 16%	1800
	11th to 20th	Day	15% 4 7% 21% 38% 15%	1800
	21st to end	Day	19% 6% 9% 28% 31% 8%	1980
November	1st to 10th	Day	19% 3 12% 28% 30% 8%	1859
	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	31% 6% 8% 18% 25% 12%	1979
	11th to 20th	Night	31% 5% 8% 19% 26% 11%	1777
	21st to end	Night	27% 6% 9% 20% 29% 10%	1695
May	1st to 10th	Night	29% 6% 9% 16% 29% 10%	1620
	11th to 20th	Night	26% 6% 9% 20% 27% 11%	1595
	21st to end	Night	22% 7% 11% 16% 30% 14%	1702
June	1st to 10th	Night	18% 4 6% 14% 31% 27%	1440
	11th to 20th	Night	18% 5% 7% 10% 17% 43%	1440
	21st to end	Night	15% 4 7% 10% 20% 44%	1463
July	1st to 10th	Night	21% 6% 10% 13% 14% 36%	1575
	11th to 20th	Night	25% 8% 11% 18% 17% 22%	1566
	21st to end	Night	29% 10% 17% 18% 14% 12%	1674
August	1st to 10th	Night	24% 8% 13% 18% 17% 19%	1602
	11th to 20th	Night	22% 6% 10% 18% 15% 29%	1602
	21st to end	Night	22% 7% 10% 16% 21% 25%	1944
September	1st to 10th	Night	20% 5% 8% 13% 18% 36%	1800
	11th to 20th	Night	19% 5% 11% 17% 19% 30%	1950
	21st to end	Night	17% 4 6% 11% 34% 28%	1980
October	1st to 10th	Night	21% 6% 8% 20% 25% 20%	2160
	11th to 20th	Night	16% 3 7% 17% 36% 21%	2160
	21st to end	Night	20% 3 7% 26% 33% 11%	2376
November	1st to 10th	Night	20% 3 9% 23% 32% 13%	2220
	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% 24% 11% 4	457
	11th to 20th	Day	13% 19% 37% 22% 7% 2	412
	21st to end	Day	12% 20% 30% 23% 13% 1	420
May	1st to 10th	Day	9% 13% 41% 26% 9% 1	423
	11th to 20th	Day	6% 13% 30% 30% 16% 4	448
	21st to end	Day	7% 15% 25% 30% 18% 5%	524
June	1st to 10th	Day	4 8% 24% 32% 29% 3	630
	11th to 20th	Day	4 10% 26% 33% 22% 5%	630
	21st to end	Day	3 6% 26% 37% 24% 3	600
July	1st to 10th	Day	2 5% 20% 39% 28% 6%	446
	11th to 20th	Day	3 1 18% 37% 35% 6%	444
	21st to end	Day	3 1 12% 37% 41% 6%	487
August	1st to 10th	Day	5% 4 17% 42% 28% 5%	447
	11th to 20th	Day	3 4 18% 38% 28% 9%	437
	21st to end	Day	4 3 21% 36% 29% 7%	495
September	1st to 10th	Day	4 5% 19% 34% 29% 9%	450
	11th to 20th	Day	3 11% 24% 33% 23% 6%	450
	21st to end	Day	6% 12% 21% 30% 23% 7%	449
October	1st to 10th	Day	12% 9% 21% 26% 24% 9%	270
	11th to 20th	Day	6% 12% 21% 30% 25% 6%	270
	21st to end	Day	8% 13% 26% 29% 23% 2	297
November	1st to 10th	Day	8% 14% 26% 29% 19% 4	270
	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% 35% 15% 1	649
	11th to 20th	Night	10% 12% 28% 33% 16% 2	533
	21st to end	Night	8% 14% 25% 31% 17% 5%	540
May	1st to 10th	Night	7% 10% 25% 39% 16% 3	540
	11th to 20th	Night	6% 5% 21% 39% 25% 4	531
	21st to end	Night	4 10% 26% 32% 25% 3	584
June	1st to 10th	Night	3 6% 20% 36% 33% 2	540
	11th to 20th	Night	5% 7% 21% 38% 26% 3	540
	21st to end	Night	2 3 16% 41% 34% 3	540
July	1st to 10th	Night	2 1 14% 31% 45% 6%	525
	11th to 20th	Night	2 1 10% 34% 47% 7%	522
	21st to end	Night	4 1 7% 32% 49% 8%	591
August	1st to 10th	Night	4 1 10% 36% 42% 6%	537
	11th to 20th	Night	4 2 10% 39% 37% 7%	534
	21st to end	Night	4 2 10% 39% 37% 9%	594
September	1st to 10th	Night	5% 1 11% 40% 35% 8%	540
	11th to 20th	Night	3 4 15% 36% 35% 7%	690
	21st to end	Night	5% 5% 15% 33% 31% 11%	720
October	1st to 10th	Night	7% 5% 20% 38% 26% 5%	720
	11th to 20th	Night	4 4 19% 38% 29% 6%	720
	21st to end	Night	7% 5% 20% 33% 29% 6%	792
November	1st to 10th	Night	5% 5% 19% 37% 29% 4	740
	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 2024-04-07 07:28:11. Version ac07

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