G-2 Farms Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the G-2 Farms Observatory clear sky chart from 2005-11-06 to 2025-05-26.

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	15% 11% 4 10% 5% 5% 4 4 5% 7% 30%	114140
	Night	15% 13% 5% 10% 5% 5% 4 3 5% 6% 29%	115172
Transparency	Day	52% 6% 12% 18% 10% 1	117752
	Night	54% 6% 12% 17% 10% 1	119687
Seeing	Day	19% 12% 28% 23% 13% 5%	15756
	Night	21% 10% 28% 28% 11% 1	25168

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	13% 17% 7% 29% 7% 5% 3 2 2 3 12%	3496
	11th to 20th	Day	11% 21% 10% 25% 8% 7% 3 2 2 3 7%	3968
	21st to end	Day	19% 19% 9% 14% 6% 6% 5% 3 3 3 13%	4466
February	1st to 10th	Day	16% 17% 5% 16% 8% 6% 4 3 4 4 17%	1800
	11th to 20th	Day	14% 15% 7% 15% 10% 6% 4 3 4 4 18%	1768
	21st to end	Day	16% 18% 6% 12% 6% 5% 4 3 4 5% 22%	1650
March	1st to 10th	Day	17% 12% 7% 13% 7% 4 3 3 4 5% 25%	4774
	11th to 20th	Day	12% 13% 6% 10% 4 4 4 4 5% 7% 30%	4980
	21st to end	Day	20% 14% 5% 10% 4 4 3 3 4 4 28%	5465
April	1st to 10th	Day	17% 15% 4 8% 4 4 4 3 6% 7% 29%	2270
	11th to 20th	Day	19% 11% 3 5% 4 3 4 4 5% 8% 35%	2572
	21st to end	Day	19% 11% 3 8% 4 4 4 3 5% 6% 35%	2600
May	1st to 10th	Day	18% 8% 3 6% 4 4 4 4 6% 8% 36%	4212
	11th to 20th	Day	17% 10% 3 7% 5% 4 5% 4 6% 8% 31%	4211
	21st to end	Day	14% 5% 2 5% 4 3 4 3 5% 7% 47%	4860
June	1st to 10th	Day	12% 7% 2 6% 4 5% 5% 4 6% 9% 39%	2701
	11th to 20th	Day	10% 7% 2 6% 4 6% 5% 5% 6% 7% 42%	2850
	21st to end	Day	13% 5% 2 7% 5% 4 4 4 6% 8% 41%	2850
July	1st to 10th	Day	11% 5% 2 7% 5% 5% 5% 4 7% 9% 40%	4736
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 45%	4290
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 9% 42%	4466
August	1st to 10th	Day	14% 6% 2 5% 5% 5% 5% 5% 7% 8% 38%	4104
	11th to 20th	Day	10% 7% 2 7% 4 5% 6% 5% 8% 11% 35%	4044
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 4 7% 8% 42%	4504
September	1st to 10th	Day	11% 8% 3 6% 5% 5% 5% 4 5% 7% 41%	2206
	11th to 20th	Day	11% 5% 2 6% 3 4 4 5% 6% 8% 46%	2090
	21st to end	Day	17% 7% 2 7% 4 5% 5% 4 6% 8% 35%	2090
October	1st to 10th	Day	15% 7% 3 7% 5% 4 4 5% 6% 7% 35%	1952
	11th to 20th	Day	21% 12% 3 9% 5% 5% 4 4 6% 6% 26%	1900
	21st to end	Day	26% 13% 3 9% 4 4 5% 4 5% 6% 20%	2029
November	1st to 10th	Day	15% 15% 3 9% 6% 5% 3 4 6% 6% 29%	1762
	11th to 20th	Day	16% 18% 4 9% 6% 4 5% 4 6% 6% 22%	1659
	21st to end	Day	19% 22% 7% 10% 7% 5% 4 4 4 5% 14%	1600
December	1st to 10th	Day	19% 22% 9% 15% 6% 4 4 4 4 3 9%	2600
	11th to 20th	Day	21% 22% 8% 13% 6% 4 3 3 3 3 12%	2990
	21st to end	Day	26% 23% 7% 13% 5% 4 4 2 4 4 8%	3625
January	1st to 10th	Night	13% 18% 9% 25% 7% 5% 3 2 3 3 12%	6468
	11th to 20th	Night	13% 18% 9% 19% 10% 6% 5% 3 4 4 9%	5977
	21st to end	Night	17% 17% 7% 14% 5% 6% 5% 3 4 5% 15%	6490
February	1st to 10th	Night	17% 16% 5% 13% 9% 5% 5% 3 4 5% 17%	2600
	11th to 20th	Night	16% 15% 6% 11% 8% 6% 5% 4 5% 6% 19%	2515
	21st to end	Night	17% 12% 6% 13% 7% 5% 4 4 5% 5% 22%	1980
March	1st to 10th	Night	15% 13% 4 10% 6% 4 4 3 5% 6% 31%	5079
	11th to 20th	Night	10% 10% 5% 9% 6% 4 4 4 6% 8% 34%	4980
	21st to end	Night	18% 12% 3 9% 5% 5% 4 3 4 4 34%	5467
April	1st to 10th	Night	19% 12% 3 7% 5% 4 4 3 6% 6% 31%	2140
	11th to 20th	Night	18% 9% 3 7% 4 4 4 4 5% 7% 36%	1785
	21st to end	Night	16% 11% 3 8% 5% 4 4 4 6% 7% 33%	1800
May	1st to 10th	Night	17% 8% 3 7% 4 4 4 3 5% 7% 38%	2903
	11th to 20th	Night	11% 9% 3 8% 5% 5% 4 4 6% 7% 36%	2902
	21st to end	Night	12% 5% 2 4 3 3 4 3 6% 7% 50%	2810
June	1st to 10th	Night	12% 7% 3 6% 5% 5% 4 3 6% 8% 43%	1474
	11th to 20th	Night	8% 6% 2 7% 5% 5% 5% 4 8% 9% 41%	1330
	21st to end	Night	10% 5% 2 5% 5% 4 4 4 5% 7% 48%	1330
July	1st to 10th	Night	7% 4 2 5% 3 5% 4 3 6% 10% 50%	2230
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 6% 8% 52%	2671
	21st to end	Night	6% 6% 3 6% 5% 4 5% 5% 7% 8% 47%	3087
August	1st to 10th	Night	11% 6% 2 6% 4 4 5% 4 6% 7% 44%	2825
	11th to 20th	Night	12% 8% 3 6% 3 3 4 3 6% 7% 45%	2785
	21st to end	Night	10% 6% 2 6% 4 4 4 4 5% 7% 48%	3124
September	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 5% 7% 46%	1966
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 5% 7% 52%	2090
	21st to end	Night	16% 8% 3 7% 4 5% 4 3 5% 6% 39%	2090
October	1st to 10th	Night	15% 8% 2 8% 4 4 4 3 6% 7% 39%	2227
	11th to 20th	Night	22% 11% 3 7% 4 4 4 3 4 6% 32%	2280
	21st to end	Night	25% 12% 3 8% 4 5% 4 3 5% 6% 25%	2565
November	1st to 10th	Night	16% 13% 3 8% 4 4 3 4 5% 5% 35%	2536
	11th to 20th	Night	17% 17% 4 10% 5% 5% 4 4 5% 6% 22%	2740
	21st to end	Night	21% 19% 6% 10% 6% 5% 4 4 4 5% 18%	2800
December	1st to 10th	Night	14% 24% 11% 15% 6% 5% 5% 4 4 4 9%	4580
	11th to 20th	Night	15% 25% 9% 12% 7% 5% 4 2 3 4 15%	5205
	21st to end	Night	23% 20% 7% 12% 5% 4 4 3 4 5% 12%	7341

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	78% 5% 9% 7% 1	3497
	11th to 20th	Day	84% 4 7% 3 2	3968
	21st to end	Day	74% 5% 10% 5% 6%	4466
February	1st to 10th	Day	69% 6% 9% 11% 4	1800
	11th to 20th	Day	68% 5% 8% 12% 6%	1777
	21st to end	Day	64% 6% 11% 12% 6% 1	1650
March	1st to 10th	Day	62% 4 13% 16% 4	4774
	11th to 20th	Day	52% 5% 16% 18% 7% 1	4980
	21st to end	Day	60% 4 11% 16% 9% 1	5465
April	1st to 10th	Day	54% 7% 11% 19% 9% 1	2270
	11th to 20th	Day	47% 6% 14% 19% 13% 1	2572
	21st to end	Day	50% 6% 12% 19% 12% 2	2600
May	1st to 10th	Day	45% 6% 13% 21% 12% 3	4250
	11th to 20th	Day	47% 10% 13% 20% 8% 1	4215
	21st to end	Day	36% 8% 11% 20% 20% 5%	4874
June	1st to 10th	Day	40% 8% 13% 25% 13% 2	2701
	11th to 20th	Day	38% 9% 11% 22% 18% 2	2850
	21st to end	Day	40% 8% 12% 24% 16% 1	2850
July	1st to 10th	Day	39% 7% 13% 23% 16% 2	4662
	11th to 20th	Day	34% 7% 12% 33% 13% 1	4215
	21st to end	Day	36% 9% 14% 20% 20% 1	4324
August	1st to 10th	Day	41% 8% 13% 23% 15% 1	4091
	11th to 20th	Day	41% 8% 15% 26% 10%	4083
	21st to end	Day	38% 6% 13% 29% 13% 1	4504
September	1st to 10th	Day	41% 8% 13% 25% 13% 1	2206
	11th to 20th	Day	34% 8% 13% 29% 16%	2090
	21st to end	Day	46% 8% 12% 24% 10% 1	2090
October	1st to 10th	Day	40% 8% 13% 23% 16% 1	3238
	11th to 20th	Day	44% 6% 12% 22% 16%	3140
	21st to end	Day	53% 6% 16% 19% 6%	3318
November	1st to 10th	Day	54% 7% 11% 19% 8% 1	1762
	11th to 20th	Day	59% 7% 14% 12% 7% 1	1659
	21st to end	Day	72% 5% 9% 11% 2	1600
December	1st to 10th	Day	76% 8% 10% 6% 1	2600
	11th to 20th	Day	76% 5% 9% 7% 3	2986
	21st to end	Day	80% 5% 8% 6% 1	3625
January	1st to 10th	Night	76% 5% 8% 9% 2	6468
	11th to 20th	Night	78% 7% 8% 6% 2	5977
	21st to end	Night	69% 5% 11% 9% 6%	6490
February	1st to 10th	Night	68% 6% 9% 12% 4	2600
	11th to 20th	Night	63% 6% 11% 14% 5%	2517
	21st to end	Night	62% 7% 11% 14% 6%	1980
March	1st to 10th	Night	53% 5% 13% 18% 9% 1	5079
	11th to 20th	Night	45% 6% 18% 20% 10% 1	4980
	21st to end	Night	53% 5% 11% 17% 13% 1	5467
April	1st to 10th	Night	53% 5% 10% 18% 13% 1	2140
	11th to 20th	Night	48% 5% 10% 19% 17% 2	1785
	21st to end	Night	49% 6% 10% 16% 15% 3	1800
May	1st to 10th	Night	45% 6% 10% 19% 15% 5%	2930
	11th to 20th	Night	43% 10% 11% 23% 10% 3	2903
	21st to end	Night	32% 7% 13% 23% 22% 4	2817
June	1st to 10th	Night	38% 7% 11% 25% 17% 2	1474
	11th to 20th	Night	35% 8% 12% 24% 18% 3	1330
	21st to end	Night	36% 6% 12% 26% 19% 1	1330
July	1st to 10th	Night	30% 6% 12% 28% 18% 7%	2195
	11th to 20th	Night	29% 6% 13% 32% 18% 2	2623
	21st to end	Night	32% 8% 16% 20% 21% 2	2988
August	1st to 10th	Night	38% 7% 12% 26% 17% 1	2814
	11th to 20th	Night	37% 8% 13% 29% 13% 1	2812
	21st to end	Night	34% 7% 12% 31% 15% 1	3124
September	1st to 10th	Night	36% 8% 13% 26% 16% 2	1966
	11th to 20th	Night	31% 6% 12% 29% 20% 2	2090
	21st to end	Night	45% 7% 12% 23% 13% 1	2090
October	1st to 10th	Night	33% 4 11% 26% 24% 1	3721
	11th to 20th	Night	46% 5% 16% 19% 14% 1	3779
	21st to end	Night	48% 6% 14% 22% 10%	4213
November	1st to 10th	Night	49% 6% 12% 22% 11% 1	2536
	11th to 20th	Night	59% 7% 13% 14% 6% 1	2740
	21st to end	Night	67% 6% 13% 10% 3	2800
December	1st to 10th	Night	76% 7% 10% 5% 2	4580
	11th to 20th	Night	72% 4 11% 9% 4 1	5208
	21st to end	Night	75% 5% 10% 8% 2	7341

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	23% 24% 30% 17% 5% 1	273
	11th to 20th	Day	19% 21% 40% 15% 3 1	300
	21st to end	Day	29% 14% 36% 18% 2 1	330
February	1st to 10th	Day	25% 22% 37% 12% 4	300
	11th to 20th	Day	25% 24% 36% 15%	300
	21st to end	Day	28% 26% 33% 12% 2	249
March	1st to 10th	Day	25% 16% 39% 14% 5%	425
	11th to 20th	Day	23% 16% 32% 24% 5% 1	500
	21st to end	Day	29% 14% 30% 21% 5% 1	550
April	1st to 10th	Day	22% 19% 31% 21% 6%	500
	11th to 20th	Day	28% 14% 26% 19% 10% 3	492
	21st to end	Day	24% 13% 32% 22% 7% 2	500
May	1st to 10th	Day	22% 14% 25% 27% 10% 3	503
	11th to 20th	Day	18% 8% 29% 24% 17% 5%	527
	21st to end	Day	16% 7% 24% 28% 18% 7%	549
June	1st to 10th	Day	12% 7% 34% 29% 14% 5%	531
	11th to 20th	Day	12% 9% 28% 34% 13% 4	680
	21st to end	Day	15% 8% 28% 31% 15% 4	680
July	1st to 10th	Day	11% 7% 23% 28% 24% 8%	671
	11th to 20th	Day	13% 6% 27% 28% 19% 7%	583
	21st to end	Day	8% 4 22% 33% 24% 9%	532
August	1st to 10th	Day	13% 5% 17% 26% 26% 14%	486
	11th to 20th	Day	13% 5% 20% 26% 22% 14%	479
	21st to end	Day	12% 5% 19% 31% 23% 10%	539
September	1st to 10th	Day	12% 7% 23% 26% 21% 11%	490
	11th to 20th	Day	10% 3 21% 24% 29% 13%	490
	21st to end	Day	19% 10% 23% 24% 16% 8%	490
October	1st to 10th	Day	18% 10% 26% 23% 18% 5%	490
	11th to 20th	Day	23% 15% 31% 22% 9% 1	490
	21st to end	Day	30% 13% 33% 20% 4	478
November	1st to 10th	Day	22% 20% 29% 18% 9% 2	300
	11th to 20th	Day	30% 18% 31% 14% 5% 2	229
	21st to end	Day	27% 19% 37% 14% 4	200
December	1st to 10th	Day	27% 21% 30% 16% 5% 1	200
	11th to 20th	Day	27% 26% 30% 14% 5%	200
	21st to end	Day	31% 20% 34% 13% 3	220
January	1st to 10th	Night	25% 16% 37% 15% 5% 1	1000
	11th to 20th	Night	30% 15% 31% 21% 4	838
	21st to end	Night	22% 12% 36% 23% 7%	880
February	1st to 10th	Night	24% 13% 38% 22% 2	800
	11th to 20th	Night	24% 15% 30% 25% 5%	783
	21st to end	Night	24% 16% 37% 20% 3	660
March	1st to 10th	Night	20% 14% 35% 25% 6%	800
	11th to 20th	Night	18% 14% 36% 25% 7% 1	800
	21st to end	Night	24% 12% 28% 27% 8% 1	880
April	1st to 10th	Night	24% 15% 31% 27% 5%	800
	11th to 20th	Night	22% 11% 31% 25% 10% 1	601
	21st to end	Night	20% 10% 32% 29% 8% 1	600
May	1st to 10th	Night	21% 7% 29% 31% 11% 1	600
	11th to 20th	Night	15% 6% 28% 38% 12% 2	591
	21st to end	Night	13% 3 26% 41% 15% 1	443
June	1st to 10th	Night	15% 3 29% 38% 14% 1	380
	11th to 20th	Night	12% 4 25% 44% 14%	380
	21st to end	Night	11% 5% 22% 46% 16%	380
July	1st to 10th	Night	6% 2 21% 46% 24% 2	377
	11th to 20th	Night	10% 3 19% 41% 24% 3	552
	21st to end	Night	9% 2 16% 47% 24% 1	624
August	1st to 10th	Night	10% 1 12% 44% 30% 3	567
	11th to 20th	Night	10% 2 14% 38% 32% 4	564
	21st to end	Night	12% 3 17% 37% 29% 2	627
September	1st to 10th	Night	11% 5% 21% 35% 24% 4	755
	11th to 20th	Night	13% 3 17% 35% 28% 4	760
	21st to end	Night	19% 6% 21% 32% 16% 5%	760
October	1st to 10th	Night	18% 7% 27% 29% 17% 1	760
	11th to 20th	Night	28% 11% 24% 27% 10% 1	760
	21st to end	Night	30% 10% 31% 25% 4	836
November	1st to 10th	Night	22% 11% 28% 28% 9% 1	780
	11th to 20th	Night	25% 15% 34% 20% 6% 1	800
	21st to end	Night	30% 12% 30% 23% 4	800
December	1st to 10th	Night	31% 17% 31% 17% 4	800
	11th to 20th	Night	25% 19% 35% 18% 3	800
	21st to end	Night	30% 14% 32% 20% 3	1030

Page generated at 2025-05-23 09:20:59. Version ac07

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