Moonridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moonridge Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	127464
	Night	14% 6% 2 6% 4 4 4 4 6% 7% 42%	124536
Transparency	Day	39% 6% 12% 23% 16% 3	131061
	Night	39% 6% 12% 24% 17% 3	129008
Seeing	Day	19% 14% 26% 23% 14% 5%	16461
	Night	17% 11% 29% 30% 12% 1	26119

By Month

Percentage Cloud Cover SE (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	14% 5% 2 5% 4 4 5% 4 6% 6% 45%	3881
	11th to 20th	Day	13% 8% 3 6% 4 4 4 3 4 5% 45%	4150
	21st to end	Day	14% 8% 3 7% 4 3 5% 3 6% 6% 42%	4565
February	1st to 10th	Day	13% 10% 3 7% 4 5% 5% 4 6% 6% 38%	1800
	11th to 20th	Day	17% 8% 2 7% 5% 3 4 3 5% 7% 38%	1768
	21st to end	Day	16% 9% 2 5% 5% 4 4 3 5% 6% 40%	1650
March	1st to 10th	Day	17% 7% 2 6% 4 5% 5% 3 5% 6% 41%	4935
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 5% 7% 48%	4980
	21st to end	Day	15% 6% 2 7% 4 5% 5% 4 5% 7% 39%	5499
April	1st to 10th	Day	14% 7% 3 7% 5% 4 5% 3 5% 8% 38%	2400
	11th to 20th	Day	13% 7% 3 5% 4 4 5% 4 5% 7% 44%	2374
	21st to end	Day	17% 7% 2 6% 4 4 4 4 6% 6% 41%	2412
May	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 5% 7% 9% 30%	5862
	11th to 20th	Day	23% 6% 2 6% 4 4 4 4 6% 9% 30%	6061
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 7% 9% 38%	6934
June	1st to 10th	Day	12% 5% 2 4 5% 4 5% 5% 7% 9% 43%	2800
	11th to 20th	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 8% 40%	2800
	21st to end	Day	9% 4 1 6% 4 5% 5% 4 7% 10% 45%	2800
July	1st to 10th	Day	7% 4 2 6% 5% 5% 6% 4 7% 10% 44%	6360
	11th to 20th	Day	9% 5% 3 7% 6% 6% 7% 5% 8% 11% 33%	6048
	21st to end	Day	8% 6% 3 6% 6% 5% 6% 4 7% 10% 40%	6424
August	1st to 10th	Day	16% 5% 2 7% 4 5% 5% 5% 7% 9% 35%	4234
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 4 7% 9% 41%	4057
	21st to end	Day	11% 5% 2 5% 4 4 4 4 5% 7% 48%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 3 4 4 5% 6% 47%	2400
	11th to 20th	Day	13% 5% 2 6% 3 4 4 3 6% 7% 48%	2390
	21st to end	Day	22% 6% 3 6% 4 4 4 3 5% 6% 37%	2091
October	1st to 10th	Day	16% 5% 2 5% 3 3 3 3 4 7% 48%	2000
	11th to 20th	Day	16% 4 3 5% 3 4 4 3 5% 6% 49%	2000
	21st to end	Day	14% 5% 2 5% 4 4 4 3 5% 6% 50%	2200
November	1st to 10th	Day	11% 6% 2 4 3 3 3 4 5% 7% 51%	1988
	11th to 20th	Day	15% 6% 2 5% 3 3 4 4 6% 6% 47%	1811
	21st to end	Day	14% 6% 3 6% 3 5% 4 4 5% 7% 44%	1680
December	1st to 10th	Day	12% 6% 2 5% 4 4 5% 4 5% 7% 46%	2680
	11th to 20th	Day	18% 8% 3 6% 4 4 4 3 5% 7% 40%	3070
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 7% 8% 34%	4048
January	1st to 10th	Night	10% 7% 2 5% 4 4 4 3 5% 7% 46%	6282
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 5% 6% 48%	6030
	21st to end	Night	14% 8% 3 6% 3 3 4 3 5% 6% 46%	6633
February	1st to 10th	Night	14% 7% 3 6% 4 4 4 3 6% 7% 40%	2601
	11th to 20th	Night	17% 8% 3 6% 4 4 5% 3 5% 5% 41%	2518
	21st to end	Night	17% 9% 2 6% 5% 4 4 4 5% 5% 40%	1975
March	1st to 10th	Night	16% 6% 2 6% 4 3 3 3 4 6% 46%	4918
	11th to 20th	Night	10% 5% 2 6% 4 5% 4 4 5% 7% 48%	4980
	21st to end	Night	11% 8% 2 5% 5% 5% 5% 4 5% 6% 44%	5432
April	1st to 10th	Night	15% 8% 2 6% 5% 4 4 4 6% 6% 38%	2000
	11th to 20th	Night	13% 5% 2 7% 5% 4 4 4 6% 8% 43%	1975
	21st to end	Night	16% 5% 2 5% 3 4 4 4 5% 8% 44%	2000
May	1st to 10th	Night	21% 9% 3 8% 5% 5% 5% 3 6% 8% 29%	4038
	11th to 20th	Night	25% 8% 2 6% 3 4 4 4 6% 8% 30%	3817
	21st to end	Night	17% 7% 2 7% 4 4 5% 5% 7% 8% 34%	3920
June	1st to 10th	Night	11% 5% 2 6% 4 4 5% 4 7% 8% 44%	1600
	11th to 20th	Night	12% 6% 2 6% 4 4 4 5% 7% 9% 41%	1600
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 7% 11% 44%	1600
July	1st to 10th	Night	7% 6% 3 7% 6% 6% 6% 5% 7% 10% 39%	3598
	11th to 20th	Night	8% 7% 3 9% 7% 6% 6% 6% 9% 10% 30%	3891
	21st to end	Night	8% 6% 2 6% 4 5% 6% 5% 7% 10% 42%	4427
August	1st to 10th	Night	15% 5% 2 8% 5% 6% 6% 4 7% 9% 33%	2915
	11th to 20th	Night	9% 8% 3 6% 5% 5% 5% 4 7% 8% 39%	2957
	21st to end	Night	12% 5% 2 5% 3 4 4 4 6% 8% 47%	3586
September	1st to 10th	Night	15% 5% 2 5% 4 4 4 4 6% 7% 45%	2000
	11th to 20th	Night	12% 5% 2 6% 3 4 4 2 3 6% 52%	2007
	21st to end	Night	21% 7% 2 7% 4 4 3 2 5% 6% 39%	2308
October	1st to 10th	Night	19% 5% 2 5% 3 3 3 3 4 6% 48%	2400
	11th to 20th	Night	14% 5% 1 4 3 3 4 3 4 6% 53%	2400
	21st to end	Night	15% 5% 2 5% 3 3 3 3 5% 6% 51%	2640
November	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 4 6% 54%	2529
	11th to 20th	Night	14% 6% 2 4 4 3 4 4 5% 6% 48%	2804
	21st to end	Night	13% 4 2 6% 4 4 5% 4 5% 7% 46%	2940
December	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 6% 8% 50%	4720
	11th to 20th	Night	19% 7% 2 5% 4 4 4 4 5% 7% 39%	5345
	21st to end	Night	15% 8% 2 7% 4 5% 6% 5% 6% 8% 33%	7150

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	36% 4 8% 27% 18% 6%	3882
	11th to 20th	Day	41% 4 8% 21% 18% 8%	4150
	21st to end	Day	41% 4 11% 26% 14% 3	4565
February	1st to 10th	Day	44% 6% 13% 23% 12% 2	1800
	11th to 20th	Day	46% 5% 10% 22% 15% 2	1777
	21st to end	Day	45% 5% 11% 20% 15% 4	1650
March	1st to 10th	Day	42% 5% 9% 21% 16% 7%	4935
	11th to 20th	Day	33% 5% 10% 26% 19% 6%	4980
	21st to end	Day	43% 6% 10% 18% 18% 5%	5499
April	1st to 10th	Day	41% 7% 13% 18% 18% 4	2400
	11th to 20th	Day	37% 6% 11% 22% 19% 5%	2374
	21st to end	Day	42% 7% 9% 23% 16% 3	2412
May	1st to 10th	Day	47% 9% 14% 19% 10% 2	5897
	11th to 20th	Day	47% 7% 12% 23% 9% 1	6065
	21st to end	Day	40% 7% 14% 21% 16% 1	6949
June	1st to 10th	Day	35% 9% 15% 24% 16% 1	2800
	11th to 20th	Day	37% 9% 15% 22% 14% 2	2800
	21st to end	Day	32% 9% 15% 26% 17% 2	2800
July	1st to 10th	Day	34% 10% 15% 22% 15% 4	6290
	11th to 20th	Day	41% 10% 16% 24% 9% 1	5975
	21st to end	Day	38% 7% 10% 23% 22% 1	6240
August	1st to 10th	Day	44% 8% 15% 24% 9% 1	4221
	11th to 20th	Day	37% 8% 12% 27% 15% 1	4096
	21st to end	Day	34% 7% 13% 27% 18% 2	4312
September	1st to 10th	Day	37% 6% 11% 20% 21% 4	2400
	11th to 20th	Day	35% 6% 9% 27% 21% 3	2390
	21st to end	Day	47% 5% 10% 18% 17% 2	2091
October	1st to 10th	Day	36% 4 8% 20% 28% 5%	3260
	11th to 20th	Day	27% 3 9% 28% 24% 9%	3240
	21st to end	Day	24% 3 11% 30% 28% 5%	3538
November	1st to 10th	Day	32% 4 13% 25% 21% 4	1988
	11th to 20th	Day	36% 4 11% 23% 22% 4	1811
	21st to end	Day	39% 5% 12% 28% 15% 2	1680
December	1st to 10th	Day	37% 5% 13% 29% 12% 4	2680
	11th to 20th	Day	44% 5% 13% 26% 10% 2	3066
	21st to end	Day	45% 6% 17% 19% 13% 1	4048
January	1st to 10th	Night	34% 4 9% 26% 23% 3	6282
	11th to 20th	Night	37% 3 9% 24% 21% 7%	6030
	21st to end	Night	38% 3 9% 30% 17% 2	6633
February	1st to 10th	Night	42% 5% 14% 24% 14% 2	2601
	11th to 20th	Night	44% 5% 10% 22% 15% 4	2520
	21st to end	Night	44% 4 12% 21% 14% 5%	1975
March	1st to 10th	Night	39% 4 9% 26% 14% 8%	4918
	11th to 20th	Night	33% 6% 10% 27% 18% 5%	4980
	21st to end	Night	39% 4 10% 22% 19% 5%	5432
April	1st to 10th	Night	43% 7% 10% 19% 17% 4	2000
	11th to 20th	Night	38% 6% 12% 20% 18% 6%	1975
	21st to end	Night	38% 6% 12% 26% 14% 4	2000
May	1st to 10th	Night	53% 7% 11% 17% 8% 4	4065
	11th to 20th	Night	49% 7% 11% 21% 10% 1	3818
	21st to end	Night	44% 8% 14% 23% 9% 2	3927
June	1st to 10th	Night	35% 9% 11% 25% 17% 3	1600
	11th to 20th	Night	37% 9% 15% 24% 14% 2	1600
	21st to end	Night	33% 7% 16% 24% 18% 2	1600
July	1st to 10th	Night	38% 10% 16% 18% 14% 4	3560
	11th to 20th	Night	45% 11% 18% 16% 9% 1	3844
	21st to end	Night	35% 8% 13% 23% 19% 1	4297
August	1st to 10th	Night	45% 8% 16% 21% 9% 1	2904
	11th to 20th	Night	39% 7% 12% 26% 14% 1	2984
	21st to end	Night	34% 6% 13% 29% 16% 2	3586
September	1st to 10th	Night	36% 7% 12% 21% 19% 5%	2000
	11th to 20th	Night	34% 5% 10% 26% 23% 2	2007
	21st to end	Night	47% 5% 11% 18% 17% 2	2308
October	1st to 10th	Night	39% 4 10% 22% 22% 3	3920
	11th to 20th	Night	25% 4 11% 23% 31% 7%	3899
	21st to end	Night	23% 3 10% 32% 27% 5%	4252
November	1st to 10th	Night	32% 4 11% 26% 23% 5%	2529
	11th to 20th	Night	35% 4 9% 25% 21% 5%	2804
	21st to end	Night	36% 5% 13% 25% 18% 3	2940
December	1st to 10th	Night	33% 4 14% 30% 17% 1	4720
	11th to 20th	Night	45% 4 12% 20% 16% 3	5348
	21st to end	Night	44% 8% 16% 18% 14% 1	7150

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	28% 29% 27% 13% 3	267
	11th to 20th	Day	28% 30% 29% 11% 2	330
	21st to end	Day	24% 28% 35% 9% 3 1	363
February	1st to 10th	Day	21% 31% 34% 11% 3	300
	11th to 20th	Day	36% 30% 28% 6% 1	315
	21st to end	Day	29% 19% 33% 16% 3	414
March	1st to 10th	Day	23% 25% 27% 21% 3	500
	11th to 20th	Day	25% 22% 31% 16% 5% 2	500
	21st to end	Day	22% 21% 33% 18% 5% 1	550
April	1st to 10th	Day	23% 25% 25% 18% 7% 1	500
	11th to 20th	Day	18% 19% 29% 19% 12% 3	492
	21st to end	Day	25% 18% 26% 20% 9% 3	500
May	1st to 10th	Day	24% 16% 28% 19% 9% 3	503
	11th to 20th	Day	21% 15% 25% 21% 14% 4	527
	21st to end	Day	19% 9% 24% 23% 20% 5%	573
June	1st to 10th	Day	14% 9% 27% 25% 18% 7%	530
	11th to 20th	Day	14% 8% 27% 29% 18% 5%	530
	21st to end	Day	9% 7% 26% 31% 20% 7%	530
July	1st to 10th	Day	11% 5% 17% 28% 28% 12%	525
	11th to 20th	Day	7% 3 19% 30% 31% 10%	524
	21st to end	Day	11% 4 20% 32% 25% 8%	576
August	1st to 10th	Day	13% 4 20% 26% 24% 13%	526
	11th to 20th	Day	13% 4 21% 29% 22% 11%	519
	21st to end	Day	9% 4 21% 30% 22% 14%	583
September	1st to 10th	Day	18% 6% 19% 24% 23% 10%	530
	11th to 20th	Day	15% 4 18% 31% 22% 12%	530
	21st to end	Day	27% 9% 22% 25% 14% 4	530
October	1st to 10th	Day	17% 8% 20% 28% 20% 8%	530
	11th to 20th	Day	18% 13% 26% 28% 12% 3	530
	21st to end	Day	16% 14% 34% 24% 10% 3	583
November	1st to 10th	Day	16% 13% 32% 25% 10% 3	498
	11th to 20th	Day	21% 17% 32% 21% 8% 1	351
	21st to end	Day	20% 24% 30% 20% 5%	220
December	1st to 10th	Day	20% 24% 36% 16% 3 1	220
	11th to 20th	Day	22% 23% 28% 21% 6%	220
	21st to end	Day	23% 21% 31% 18% 7%	242
January	1st to 10th	Night	18% 21% 40% 18% 3	840
	11th to 20th	Night	23% 17% 32% 24% 3	840
	21st to end	Night	18% 18% 42% 20% 2	924
February	1st to 10th	Night	17% 18% 37% 26% 2	801
	11th to 20th	Night	24% 22% 35% 17% 2	783
	21st to end	Night	24% 18% 37% 18% 3	660
March	1st to 10th	Night	21% 17% 37% 22% 3	800
	11th to 20th	Night	24% 19% 31% 21% 5% 1	800
	21st to end	Night	20% 17% 38% 21% 4 1	880
April	1st to 10th	Night	19% 19% 35% 23% 4	800
	11th to 20th	Night	17% 13% 35% 28% 7%	791
	21st to end	Night	19% 12% 32% 30% 7%	800
May	1st to 10th	Night	22% 7% 26% 34% 11%	605
	11th to 20th	Night	21% 7% 24% 37% 10% 1	506
	21st to end	Night	15% 5% 24% 39% 17% 1	433
June	1st to 10th	Night	11% 3 25% 39% 22% 1	400
	11th to 20th	Night	14% 5% 19% 41% 20% 1	400
	21st to end	Night	9% 4 22% 45% 20% 1	400
July	1st to 10th	Night	11% 3 16% 39% 28% 3	390
	11th to 20th	Night	8% 1 12% 42% 34% 3	511
	21st to end	Night	8% 2 15% 43% 29% 2	657
August	1st to 10th	Night	11% 2 11% 44% 28% 3	597
	11th to 20th	Night	10% 4 13% 40% 31% 3	637
	21st to end	Night	14% 3 16% 39% 26% 3	880
September	1st to 10th	Night	16% 2 19% 35% 26% 3	800
	11th to 20th	Night	13% 3 18% 36% 27% 3	800
	21st to end	Night	23% 5% 19% 31% 20% 1	800
October	1st to 10th	Night	21% 6% 21% 30% 21% 3	800
	11th to 20th	Night	16% 11% 27% 32% 13% 1	800
	21st to end	Night	18% 9% 32% 30% 10%	880
November	1st to 10th	Night	13% 10% 33% 32% 10% 1	820
	11th to 20th	Night	17% 15% 32% 28% 7% 1	840
	21st to end	Night	16% 16% 33% 28% 7%	840
December	1st to 10th	Night	20% 15% 35% 24% 6%	840
	11th to 20th	Night	20% 12% 39% 25% 4	840
	21st to end	Night	20% 13% 35% 30% 2	924

Page generated at 2026-01-29 01:21:40. Version ac07

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