Maor Observatory at COG Farms
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maor Observatory at COG Farms 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	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	127374
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	124645
Transparency	Day	37% 7% 12% 19% 18% 7%	131137
	Night	36% 6% 11% 18% 20% 9%	128951
Seeing	Day	14% 10% 24% 24% 19% 8%	16665
	Night	14% 9% 23% 30% 20% 3	26742

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	16% 5% 2 4 3 3 3 3 3 5% 53%	4146
	11th to 20th	Day	14% 6% 2 4 3 2 2 2 4 7% 55%	4150
	21st to end	Day	16% 7% 2 6% 4 3 4 3 5% 6% 43%	4722
February	1st to 10th	Day	15% 9% 2 7% 5% 4 4 3 5% 6% 40%	2000
	11th to 20th	Day	19% 7% 2 6% 3 3 3 3 5% 6% 43%	1948
	21st to end	Day	15% 7% 3 6% 4 3 3 4 5% 8% 42%	1650
March	1st to 10th	Day	19% 8% 3 7% 4 4 4 3 5% 6% 38%	4756
	11th to 20th	Day	8% 4 2 5% 4 4 4 3 5% 7% 54%	4980
	21st to end	Day	16% 7% 3 5% 4 4 4 3 4 5% 46%	5465
April	1st to 10th	Day	11% 6% 2 6% 5% 4 4 3 5% 6% 49%	2200
	11th to 20th	Day	12% 5% 2 5% 4 3 3 3 5% 7% 51%	2309
	21st to end	Day	7% 4 1 5% 4 4 5% 3 6% 7% 53%	2589
May	1st to 10th	Day	11% 7% 2 7% 5% 4 4 4 6% 8% 42%	5862
	11th to 20th	Day	15% 7% 3 6% 4 5% 5% 5% 7% 9% 34%	5861
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 7% 8% 44%	6433
June	1st to 10th	Day	11% 5% 2 7% 5% 6% 7% 5% 8% 9% 35%	2600
	11th to 20th	Day	5% 5% 2 5% 5% 6% 6% 5% 8% 12% 41%	2600
	21st to end	Day	6% 6% 2 7% 6% 6% 6% 6% 8% 10% 37%	2600
July	1st to 10th	Day	11% 6% 2 8% 6% 7% 8% 7% 10% 12% 24%	5900
	11th to 20th	Day	4 3 2 6% 6% 6% 7% 6% 9% 14% 39%	5900
	21st to end	Day	7% 5% 3 8% 6% 7% 8% 6% 10% 12% 27%	6424
August	1st to 10th	Day	13% 6% 2 7% 6% 6% 6% 5% 9% 13% 28%	4234
	11th to 20th	Day	6% 4 2 6% 5% 5% 5% 5% 8% 9% 46%	3976
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 10% 45%	4196
September	1st to 10th	Day	10% 6% 2 6% 5% 6% 5% 5% 7% 9% 39%	2200
	11th to 20th	Day	12% 6% 2 7% 5% 4 5% 4 7% 8% 41%	2200
	21st to end	Day	12% 7% 3 6% 5% 5% 5% 5% 5% 6% 42%	2200
October	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 6% 51%	2200
	11th to 20th	Day	10% 4 1 4 3 2 3 3 5% 7% 58%	2054
	21st to end	Day	10% 4 1 4 4 3 3 3 5% 5% 57%	2200
November	1st to 10th	Day	12% 7% 2 4 3 3 4 3 4 5% 52%	1991
	11th to 20th	Day	13% 5% 2 4 3 2 3 3 4 5% 56%	1890
	21st to end	Day	14% 6% 2 5% 4 3 4 3 6% 7% 47%	1890
December	1st to 10th	Day	14% 7% 2 5% 3 3 3 3 4 5% 50%	3020
	11th to 20th	Day	15% 7% 2 5% 3 2 3 3 4 6% 48%	3463
	21st to end	Day	20% 7% 3 5% 3 3 3 3 4 5% 44%	4565
January	1st to 10th	Night	14% 5% 2 4 4 4 3 3 5% 5% 52%	6019
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 3 5% 6% 47%	6030
	21st to end	Night	18% 8% 2 6% 3 3 3 3 4 7% 42%	6474
February	1st to 10th	Night	15% 7% 3 6% 3 3 3 4 5% 7% 45%	2401
	11th to 20th	Night	20% 6% 2 5% 4 3 4 3 4 5% 45%	2338
	21st to end	Night	14% 7% 2 6% 3 5% 4 4 6% 6% 44%	1980
March	1st to 10th	Night	19% 7% 2 6% 4 4 4 3 5% 6% 40%	5081
	11th to 20th	Night	10% 5% 1 4 3 4 4 4 6% 8% 51%	4980
	21st to end	Night	15% 5% 2 5% 4 4 4 4 5% 6% 47%	5467
April	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 5% 6% 49%	2200
	11th to 20th	Night	10% 4 2 4 4 4 4 3 4 7% 53%	2055
	21st to end	Night	7% 4 1 5% 4 4 4 3 5% 8% 54%	1810
May	1st to 10th	Night	9% 6% 2 6% 4 5% 6% 5% 7% 11% 39%	4033
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 5% 8% 9% 36%	4032
	21st to end	Night	7% 5% 2 5% 4 4 4 4 8% 10% 46%	4421
June	1st to 10th	Night	9% 6% 3 6% 6% 6% 7% 5% 8% 10% 34%	1800
	11th to 20th	Night	6% 4 1 6% 4 5% 5% 5% 9% 12% 44%	1800
	21st to end	Night	6% 5% 3 6% 6% 7% 6% 5% 9% 11% 37%	1800
July	1st to 10th	Night	11% 7% 3 9% 6% 6% 7% 5% 8% 11% 26%	4058
	11th to 20th	Night	3 4 2 7% 6% 6% 6% 7% 11% 14% 34%	4057
	21st to end	Night	9% 7% 3 8% 7% 6% 7% 7% 9% 12% 26%	4427
August	1st to 10th	Night	12% 7% 3 8% 6% 6% 6% 5% 9% 11% 27%	2915
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 5% 8% 10% 44%	3068
	21st to end	Night	7% 5% 2 5% 4 4 4 4 7% 10% 49%	3666
September	1st to 10th	Night	9% 7% 2 7% 5% 6% 4 4 6% 10% 39%	2200
	11th to 20th	Night	11% 5% 3 7% 5% 5% 5% 4 4 7% 44%	2200
	21st to end	Night	11% 6% 2 6% 5% 4 4 4 7% 9% 43%	2200
October	1st to 10th	Night	10% 6% 2 5% 4 4 4 2 5% 7% 52%	2200
	11th to 20th	Night	11% 4 1 4 2 2 3 2 3 6% 60%	2345
	21st to end	Night	10% 5% 1 5% 3 3 4 3 4 6% 56%	2640
November	1st to 10th	Night	11% 6% 2 4 3 3 3 3 4 5% 55%	2523
	11th to 20th	Night	14% 5% 2 4 3 3 2 3 3 6% 55%	2730
	21st to end	Night	13% 6% 2 5% 4 4 4 3 5% 7% 48%	2730
December	1st to 10th	Night	14% 6% 2 4 3 3 3 3 3 5% 55%	4380
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 4 5% 50%	4952
	21st to end	Night	19% 8% 3 6% 3 4 3 3 4 5% 43%	6633

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	35% 3 4 17% 31% 9%	4147
	11th to 20th	Day	31% 3 4 16% 32% 14%	4150
	21st to end	Day	42% 4 6% 16% 21% 11%	4722
February	1st to 10th	Day	44% 5% 8% 16% 19% 8%	2000
	11th to 20th	Day	43% 4 5% 16% 24% 7%	1958
	21st to end	Day	40% 5% 6% 17% 21% 11%	1650
March	1st to 10th	Day	47% 5% 7% 11% 23% 8%	4756
	11th to 20th	Day	30% 4 8% 15% 21% 22%	4980
	21st to end	Day	41% 4 7% 19% 18% 11%	5465
April	1st to 10th	Day	35% 6% 10% 21% 18% 10%	2200
	11th to 20th	Day	32% 5% 8% 20% 23% 12%	2309
	21st to end	Day	30% 5% 11% 24% 25% 5%	2589
May	1st to 10th	Day	39% 6% 15% 22% 16% 2	5897
	11th to 20th	Day	43% 7% 19% 20% 10% 1	5865
	21st to end	Day	33% 10% 15% 21% 21% 1	6447
June	1st to 10th	Day	41% 10% 15% 19% 13% 2	2600
	11th to 20th	Day	32% 10% 18% 24% 16% 1	2600
	21st to end	Day	38% 10% 19% 17% 13% 2	2600
July	1st to 10th	Day	46% 13% 20% 16% 3 1	5835
	11th to 20th	Day	31% 13% 30% 22% 3 1	5831
	21st to end	Day	44% 15% 20% 18% 3	6240
August	1st to 10th	Day	44% 11% 19% 23% 3	4221
	11th to 20th	Day	30% 10% 16% 31% 12% 1	4015
	21st to end	Day	33% 8% 18% 28% 12% 1	4196
September	1st to 10th	Day	39% 10% 14% 18% 15% 4	2200
	11th to 20th	Day	39% 8% 11% 20% 19% 4	2200
	21st to end	Day	40% 6% 10% 20% 18% 6%	2200
October	1st to 10th	Day	33% 4 6% 14% 30% 14%	3590
	11th to 20th	Day	16% 3 5% 17% 27% 33%	3320
	21st to end	Day	21% 3 5% 18% 38% 15%	3538
November	1st to 10th	Day	34% 4 8% 13% 27% 14%	1991
	11th to 20th	Day	31% 3 7% 19% 25% 15%	1890
	21st to end	Day	36% 5% 9% 18% 23% 9%	1890
December	1st to 10th	Day	37% 4 6% 17% 26% 10%	3020
	11th to 20th	Day	38% 3 8% 22% 22% 8%	3460
	21st to end	Day	43% 3 6% 21% 24% 3	4565
January	1st to 10th	Night	33% 3 6% 17% 31% 10%	6019
	11th to 20th	Night	37% 4 5% 18% 27% 10%	6030
	21st to end	Night	43% 3 5% 13% 26% 8%	6474
February	1st to 10th	Night	40% 4 9% 17% 21% 10%	2401
	11th to 20th	Night	43% 3 6% 16% 22% 10%	2339
	21st to end	Night	40% 5% 7% 16% 18% 15%	1980
March	1st to 10th	Night	45% 5% 8% 15% 16% 12%	5081
	11th to 20th	Night	30% 5% 10% 12% 24% 20%	4980
	21st to end	Night	38% 4 7% 17% 20% 14%	5467
April	1st to 10th	Night	34% 6% 10% 19% 19% 12%	2200
	11th to 20th	Night	31% 4 7% 22% 23% 12%	2055
	21st to end	Night	29% 6% 10% 25% 22% 8%	1810
May	1st to 10th	Night	36% 8% 15% 23% 15% 3	4060
	11th to 20th	Night	40% 9% 16% 23% 10% 1	4033
	21st to end	Night	31% 7% 15% 25% 19% 3	4429
June	1st to 10th	Night	41% 10% 16% 18% 14% 1	1800
	11th to 20th	Night	30% 10% 19% 27% 13% 2	1800
	21st to end	Night	36% 12% 21% 16% 12% 4	1800
July	1st to 10th	Night	49% 12% 21% 14% 3 1	4015
	11th to 20th	Night	34% 14% 31% 17% 3	4006
	21st to end	Night	47% 14% 20% 16% 2	4297
August	1st to 10th	Night	47% 10% 21% 20% 3	2904
	11th to 20th	Night	31% 10% 19% 26% 12% 1	3095
	21st to end	Night	28% 8% 20% 31% 12% 1	3666
September	1st to 10th	Night	39% 10% 17% 17% 14% 4	2200
	11th to 20th	Night	40% 9% 11% 18% 18% 4	2200
	21st to end	Night	37% 7% 13% 17% 20% 5%	2200
October	1st to 10th	Night	34% 5% 7% 13% 27% 14%	3590
	11th to 20th	Night	17% 2 4 12% 31% 33%	3818
	21st to end	Night	20% 2 4 19% 33% 20%	4252
November	1st to 10th	Night	32% 4 8% 14% 28% 15%	2523
	11th to 20th	Night	32% 3 6% 17% 27% 15%	2730
	21st to end	Night	37% 5% 6% 18% 23% 11%	2730
December	1st to 10th	Night	33% 4 6% 19% 29% 8%	4380
	11th to 20th	Night	37% 4 10% 18% 22% 9%	4954
	21st to end	Night	44% 3 5% 21% 24% 3	6633

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	21% 23% 42% 13% 1	330
	11th to 20th	Day	22% 25% 34% 12% 6% 1	330
	21st to end	Day	24% 28% 34% 11% 3	363
February	1st to 10th	Day	18% 22% 41% 15% 3	300
	11th to 20th	Day	33% 18% 33% 14% 2	300
	21st to end	Day	22% 24% 40% 11% 3	249
March	1st to 10th	Day	19% 23% 29% 22% 7%	420
	11th to 20th	Day	19% 17% 37% 19% 8% 1	500
	21st to end	Day	21% 18% 34% 19% 7%	550
April	1st to 10th	Day	20% 18% 29% 23% 9% 1	500
	11th to 20th	Day	13% 16% 30% 25% 14% 2	492
	21st to end	Day	10% 13% 25% 33% 15% 4	500
May	1st to 10th	Day	9% 16% 28% 28% 14% 6%	503
	11th to 20th	Day	12% 6% 26% 28% 18% 10%	527
	21st to end	Day	12% 6% 17% 31% 23% 12%	573
June	1st to 10th	Day	12% 3 19% 28% 27% 10%	530
	11th to 20th	Day	6% 4 16% 25% 29% 19%	530
	21st to end	Day	7% 3 15% 32% 26% 17%	530
July	1st to 10th	Day	9% 2 10% 25% 32% 23%	525
	11th to 20th	Day	7% 2 7% 21% 38% 25%	524
	21st to end	Day	4 2 9% 28% 38% 19%	576
August	1st to 10th	Day	13% 3 12% 26% 29% 17%	526
	11th to 20th	Day	8% 3 7% 25% 39% 19%	519
	21st to end	Day	13% 3 14% 27% 28% 15%	583
September	1st to 10th	Day	12% 4 15% 27% 29% 15%	530
	11th to 20th	Day	13% 3 15% 34% 25% 10%	530
	21st to end	Day	16% 4 15% 31% 25% 10%	530
October	1st to 10th	Day	15% 6% 26% 28% 17% 7%	530
	11th to 20th	Day	10% 8% 23% 32% 21% 6%	530
	21st to end	Day	13% 9% 29% 28% 18% 3	583
November	1st to 10th	Day	19% 9% 27% 26% 17% 3	469
	11th to 20th	Day	14% 16% 40% 21% 8% 2	330
	21st to end	Day	15% 16% 37% 22% 9% 1	330
December	1st to 10th	Day	26% 19% 32% 15% 7% 1	330
	11th to 20th	Day	24% 18% 36% 15% 5% 2	330
	21st to end	Day	26% 13% 34% 21% 6% 1	363
January	1st to 10th	Night	21% 18% 32% 25% 4	840
	11th to 20th	Night	19% 16% 31% 24% 9%	840
	21st to end	Night	21% 18% 35% 23% 3	924
February	1st to 10th	Night	19% 14% 30% 30% 7%	801
	11th to 20th	Night	24% 16% 30% 26% 3	783
	21st to end	Night	16% 17% 37% 25% 4	660
March	1st to 10th	Night	15% 15% 34% 30% 6%	800
	11th to 20th	Night	16% 16% 31% 28% 10% 1	800
	21st to end	Night	15% 15% 34% 27% 9%	880
April	1st to 10th	Night	15% 13% 33% 28% 12% 1	800
	11th to 20th	Night	12% 12% 29% 31% 14% 1	673
	21st to end	Night	7% 8% 28% 39% 18% 1	600
May	1st to 10th	Night	9% 8% 25% 39% 18% 2	600
	11th to 20th	Night	9% 5% 24% 34% 23% 4	591
	21st to end	Night	11% 3 15% 39% 28% 4	650
June	1st to 10th	Night	11% 2 16% 37% 33% 3	600
	11th to 20th	Night	6% 2 13% 33% 36% 10%	600
	21st to end	Night	7% 2 11% 34% 38% 8%	600
July	1st to 10th	Night	9% 2 6% 31% 37% 15%	585
	11th to 20th	Night	6% 3 5% 25% 46% 15%	582
	21st to end	Night	6% 3 8% 31% 42% 9%	657
August	1st to 10th	Night	10% 2 8% 31% 38% 11%	597
	11th to 20th	Night	12% 1 7% 29% 41% 9%	594
	21st to end	Night	13% 2 10% 30% 35% 10%	701
September	1st to 10th	Night	10% 3 13% 31% 36% 8%	800
	11th to 20th	Night	13% 3 12% 33% 34% 4	800
	21st to end	Night	14% 3 17% 31% 33% 3	800
October	1st to 10th	Night	13% 3 24% 32% 23% 5%	800
	11th to 20th	Night	13% 7% 23% 31% 22% 4	800
	21st to end	Night	12% 9% 23% 33% 22% 1	880
November	1st to 10th	Night	14% 8% 22% 34% 20% 1	820
	11th to 20th	Night	17% 11% 25% 32% 13% 1	840
	21st to end	Night	15% 13% 29% 29% 14% 1	840
December	1st to 10th	Night	17% 14% 30% 27% 12% 1	840
	11th to 20th	Night	19% 11% 29% 29% 10% 1	840
	21st to end	Night	23% 14% 24% 31% 8%	924

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

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