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 2026-09-29.

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% 11% 4 9% 5% 5% 4 4 5% 7% 32%	149479
	Night	15% 12% 5% 10% 5% 5% 4 3 5% 6% 30%	141964
Transparency	Day	51% 6% 11% 19% 11% 1	153047
	Night	53% 6% 11% 18% 11% 1	146454
Seeing	Day	19% 12% 28% 24% 13% 5%	17617
	Night	20% 10% 28% 29% 11% 1	26815

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	15% 17% 7% 29% 7% 5% 3 2 2 3 10%	4530
	11th to 20th	Day	11% 22% 11% 26% 9% 7% 3 2 2 2 6%	5162
	21st to end	Day	15% 18% 8% 14% 8% 7% 6% 3 4 4 13%	5780
February	1st to 10th	Day	15% 17% 5% 16% 8% 6% 5% 3 4 4 17%	1890
	11th to 20th	Day	14% 14% 7% 15% 10% 6% 4 3 4 4 18%	1859
	21st to end	Day	16% 18% 6% 12% 6% 5% 4 3 5% 5% 21%	1730
March	1st to 10th	Day	17% 12% 7% 13% 7% 4 3 3 4 5% 25%	4880
	11th to 20th	Day	12% 13% 6% 10% 4 4 4 4 5% 7% 30%	5090
	21st to end	Day	20% 14% 6% 10% 4 4 3 3 4 4 28%	5586
April	1st to 10th	Day	17% 15% 4 8% 5% 4 4 3 6% 7% 28%	2383
	11th to 20th	Day	19% 11% 3 5% 4 3 4 4 5% 7% 34%	2702
	21st to end	Day	18% 11% 3 8% 4 4 4 3 5% 6% 35%	2730
May	1st to 10th	Day	17% 8% 3 7% 4 4 4 4 5% 7% 37%	7616
	11th to 20th	Day	16% 10% 3 6% 4 4 5% 4 6% 8% 35%	7626
	21st to end	Day	16% 8% 2 6% 4 3 4 3 4 6% 45%	8986
June	1st to 10th	Day	12% 7% 2 6% 4 5% 5% 4 6% 8% 40%	2985
	11th to 20th	Day	10% 7% 2 7% 4 6% 5% 5% 6% 7% 41%	3150
	21st to end	Day	12% 5% 2 7% 5% 4 5% 4 6% 8% 41%	3150
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 4 6% 9% 40%	8828
	11th to 20th	Day	8% 4 2 6% 4 4 4 4 6% 10% 47%	8004
	21st to end	Day	9% 5% 2 6% 5% 4 5% 4 6% 9% 45%	8340
August	1st to 10th	Day	15% 8% 2 6% 4 4 5% 4 6% 7% 39%	6014
	11th to 20th	Day	9% 6% 3 7% 4 5% 6% 5% 8% 10% 37%	5951
	21st to end	Day	11% 6% 3 8% 5% 5% 5% 4 7% 9% 37%	6551
September	1st to 10th	Day	10% 7% 2 6% 5% 5% 5% 4 6% 7% 41%	2438
	11th to 20th	Day	11% 5% 2 6% 3 4 4 5% 6% 8% 46%	2310
	21st to end	Day	16% 7% 2 7% 4 5% 5% 4 6% 8% 36%	2288
October	1st to 10th	Day	15% 7% 3 7% 5% 4 4 5% 6% 7% 37%	2055
	11th to 20th	Day	20% 11% 3 9% 5% 4 4 4 6% 6% 27%	2000
	21st to end	Day	25% 13% 3 8% 4 4 5% 4 5% 6% 22%	2136
November	1st to 10th	Day	16% 15% 3 8% 6% 5% 3 4 6% 6% 28%	1852
	11th to 20th	Day	16% 18% 4 9% 6% 4 5% 4 6% 6% 22%	1742
	21st to end	Day	19% 23% 7% 10% 7% 5% 4 3 4 5% 14%	1680
December	1st to 10th	Day	19% 22% 9% 15% 6% 4 4 4 4 3 9%	2680
	11th to 20th	Day	21% 22% 8% 13% 6% 4 4 3 3 3 12%	3070
	21st to end	Day	26% 22% 7% 13% 5% 4 4 3 4 4 8%	3705
January	1st to 10th	Night	14% 18% 9% 26% 7% 5% 4 2 3 3 10%	8378
	11th to 20th	Night	11% 20% 9% 19% 10% 6% 5% 3 4 4 10%	7785
	21st to end	Night	14% 15% 7% 14% 8% 7% 6% 3 5% 5% 16%	8401
February	1st to 10th	Night	16% 16% 5% 13% 9% 6% 5% 4 4 5% 18%	2730
	11th to 20th	Night	15% 15% 6% 11% 8% 6% 5% 4 5% 6% 20%	2644
	21st to end	Night	17% 13% 6% 13% 7% 5% 4 4 5% 5% 21%	2076
March	1st to 10th	Night	15% 13% 3 10% 6% 4 4 3 5% 6% 30%	5193
	11th to 20th	Night	11% 10% 5% 9% 6% 5% 4 4 6% 8% 33%	5090
	21st to end	Night	18% 12% 3 9% 5% 5% 4 3 4 4 34%	5588
April	1st to 10th	Night	19% 12% 3 8% 5% 4 4 3 6% 6% 30%	2247
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 5% 7% 35%	1875
	21st to end	Night	15% 11% 3 8% 5% 4 4 4 5% 7% 34%	1890
May	1st to 10th	Night	18% 8% 3 8% 4 4 4 3 5% 7% 36%	5237
	11th to 20th	Night	14% 10% 3 8% 5% 4 4 4 5% 7% 38%	5234
	21st to end	Night	18% 7% 2 4 3 3 4 3 5% 6% 44%	5167
June	1st to 10th	Night	12% 6% 3 6% 4 4 4 3 6% 8% 44%	1629
	11th to 20th	Night	9% 6% 2 7% 5% 5% 5% 4 8% 9% 41%	1470
	21st to end	Night	10% 5% 2 5% 5% 4 5% 4 5% 7% 48%	1470
July	1st to 10th	Night	8% 5% 2 6% 4 5% 4 3 6% 9% 47%	4142
	11th to 20th	Night	8% 5% 2 5% 4 4 3 4 7% 9% 50%	4952
	21st to end	Night	9% 6% 2 6% 4 4 4 4 5% 7% 49%	5736
August	1st to 10th	Night	14% 7% 2 6% 4 4 5% 4 5% 6% 42%	4135
	11th to 20th	Night	11% 8% 3 7% 4 4 4 4 6% 7% 43%	4095
	21st to end	Night	12% 7% 3 7% 5% 4 4 4 5% 7% 42%	4532
September	1st to 10th	Night	9% 6% 3 6% 4 4 5% 4 5% 8% 46%	2174
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 5% 7% 53%	2310
	21st to end	Night	16% 8% 3 7% 4 5% 4 3 4 6% 40%	2289
October	1st to 10th	Night	14% 8% 2 8% 4 4 4 3 6% 7% 41%	2344
	11th to 20th	Night	22% 10% 3 8% 4 4 4 3 4 6% 33%	2400
	21st to end	Night	24% 12% 3 8% 4 5% 4 3 5% 6% 26%	2700
November	1st to 10th	Night	16% 13% 3 8% 4 4 3 4 5% 5% 34%	2666
	11th to 20th	Night	16% 17% 4 10% 5% 5% 4 4 6% 6% 22%	2877
	21st to end	Night	21% 19% 5% 10% 5% 4 4 4 4 5% 18%	2940
December	1st to 10th	Night	14% 23% 11% 15% 6% 5% 5% 4 4 4 9%	4720
	11th to 20th	Night	15% 24% 8% 12% 7% 5% 4 2 3 4 15%	5345
	21st to end	Night	23% 20% 8% 12% 5% 4 4 3 4 5% 12%	7503

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	80% 5% 8% 6% 1	4531
	11th to 20th	Day	86% 4 5% 3 1	5162
	21st to end	Day	74% 5% 11% 5% 6%	5780
February	1st to 10th	Day	69% 6% 9% 11% 4	1890
	11th to 20th	Day	68% 5% 9% 13% 6%	1868
	21st to end	Day	64% 6% 11% 12% 6% 1	1730
March	1st to 10th	Day	62% 4 13% 16% 4	4880
	11th to 20th	Day	53% 5% 16% 18% 7% 1	5090
	21st to end	Day	60% 4 11% 16% 9% 1	5586
April	1st to 10th	Day	54% 7% 10% 19% 9% 1	2383
	11th to 20th	Day	48% 5% 13% 19% 13% 1	2702
	21st to end	Day	50% 6% 11% 20% 12% 2	2730
May	1st to 10th	Day	45% 5% 12% 22% 11% 4	7651
	11th to 20th	Day	45% 8% 11% 22% 13% 2	7630
	21st to end	Day	41% 5% 8% 22% 20% 3	9001
June	1st to 10th	Day	39% 7% 12% 25% 14% 2	2985
	11th to 20th	Day	40% 8% 11% 22% 17% 1	3150
	21st to end	Day	40% 8% 12% 24% 16% 1	3150
July	1st to 10th	Day	40% 6% 12% 25% 16% 1	8754
	11th to 20th	Day	31% 6% 11% 33% 17% 1	7929
	21st to end	Day	34% 7% 13% 24% 21% 1	8156
August	1st to 10th	Day	43% 6% 13% 18% 17% 3	6001
	11th to 20th	Day	40% 8% 15% 30% 8%	5990
	21st to end	Day	42% 6% 14% 27% 10% 1	6551
September	1st to 10th	Day	40% 8% 13% 25% 12% 1	2438
	11th to 20th	Day	34% 8% 13% 29% 16%	2310
	21st to end	Day	45% 7% 12% 24% 12% 1	2288
October	1st to 10th	Day	39% 7% 12% 24% 17% 1	3341
	11th to 20th	Day	44% 6% 12% 22% 17%	3240
	21st to end	Day	53% 6% 16% 18% 7%	3425
November	1st to 10th	Day	54% 7% 11% 19% 7% 1	1852
	11th to 20th	Day	59% 7% 14% 12% 6% 1	1742
	21st to end	Day	73% 5% 9% 11% 2	1680
December	1st to 10th	Day	76% 8% 10% 6% 1	2680
	11th to 20th	Day	76% 5% 9% 7% 3	3066
	21st to end	Day	80% 5% 8% 6% 1	3705
January	1st to 10th	Night	78% 5% 8% 7% 2	8379
	11th to 20th	Night	77% 6% 8% 6% 3	7785
	21st to end	Night	69% 6% 10% 10% 6%	8401
February	1st to 10th	Night	67% 6% 9% 13% 5%	2730
	11th to 20th	Night	63% 6% 11% 14% 6%	2646
	21st to end	Night	63% 6% 11% 14% 6%	2076
March	1st to 10th	Night	53% 5% 13% 18% 9% 1	5193
	11th to 20th	Night	46% 6% 18% 20% 10% 1	5090
	21st to end	Night	54% 5% 11% 17% 13% 1	5588
April	1st to 10th	Night	53% 5% 10% 18% 13% 1	2247
	11th to 20th	Night	48% 5% 10% 20% 16% 2	1875
	21st to end	Night	48% 6% 10% 17% 15% 3	1890
May	1st to 10th	Night	48% 6% 10% 16% 15% 6%	5264
	11th to 20th	Night	45% 8% 10% 23% 12% 3	5235
	21st to end	Night	41% 5% 10% 23% 18% 3	5174
June	1st to 10th	Night	36% 7% 11% 24% 19% 3	1629
	11th to 20th	Night	35% 8% 12% 25% 17% 2	1470
	21st to end	Night	36% 6% 12% 26% 19% 1	1470
July	1st to 10th	Night	33% 6% 13% 28% 16% 4	4109
	11th to 20th	Night	30% 6% 11% 30% 22% 2	4907
	21st to end	Night	34% 6% 11% 22% 24% 2	5606
August	1st to 10th	Night	41% 6% 11% 21% 15% 5%	4124
	11th to 20th	Night	38% 8% 14% 28% 12% 1	4122
	21st to end	Night	40% 7% 12% 29% 12% 1	4532
September	1st to 10th	Night	36% 8% 13% 27% 15% 2	2174
	11th to 20th	Night	30% 6% 13% 30% 20% 1	2310
	21st to end	Night	44% 7% 11% 22% 14% 1	2289
October	1st to 10th	Night	33% 4 11% 27% 24% 1	3838
	11th to 20th	Night	46% 5% 15% 19% 15% 1	3899
	21st to end	Night	48% 6% 14% 22% 10%	4348
November	1st to 10th	Night	49% 6% 11% 22% 11% 1	2666
	11th to 20th	Night	58% 7% 13% 14% 6% 1	2877
	21st to end	Night	68% 6% 13% 10% 3	2940
December	1st to 10th	Night	76% 7% 10% 5% 2	4720
	11th to 20th	Night	72% 4 11% 9% 4 1	5348
	21st to end	Night	75% 5% 10% 8% 2	7503

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% 25% 30% 16% 4 1	300
	11th to 20th	Day	20% 23% 39% 14% 3 1	330
	21st to end	Day	28% 16% 36% 18% 2 1	363
February	1st to 10th	Day	24% 22% 36% 14% 4	330
	11th to 20th	Day	25% 23% 36% 15% 1	330
	21st to end	Day	27% 28% 33% 11% 1	273
March	1st to 10th	Day	26% 16% 38% 14% 5%	461
	11th to 20th	Day	24% 18% 31% 23% 4 1	540
	21st to end	Day	29% 15% 31% 20% 4 1	594
April	1st to 10th	Day	23% 19% 31% 20% 6%	540
	11th to 20th	Day	28% 14% 26% 19% 9% 3	532
	21st to end	Day	23% 14% 31% 23% 7% 2	540
May	1st to 10th	Day	21% 14% 26% 27% 9% 3	543
	11th to 20th	Day	18% 8% 30% 23% 16% 5%	567
	21st to end	Day	16% 7% 26% 27% 17% 7%	617
June	1st to 10th	Day	12% 8% 35% 28% 13% 4	615
	11th to 20th	Day	13% 10% 29% 31% 12% 4	780
	21st to end	Day	14% 8% 29% 32% 14% 3	780
July	1st to 10th	Day	11% 7% 23% 28% 23% 8%	771
	11th to 20th	Day	13% 6% 27% 29% 19% 6%	674
	21st to end	Day	9% 4 22% 33% 24% 8%	620
August	1st to 10th	Day	12% 5% 17% 28% 25% 13%	566
	11th to 20th	Day	12% 6% 21% 27% 22% 13%	559
	21st to end	Day	12% 6% 20% 31% 22% 9%	627
September	1st to 10th	Day	12% 7% 23% 25% 22% 12%	570
	11th to 20th	Day	10% 4 21% 24% 28% 13%	570
	21st to end	Day	18% 9% 22% 25% 17% 8%	562
October	1st to 10th	Day	18% 10% 25% 25% 18% 5%	530
	11th to 20th	Day	22% 15% 31% 22% 9% 1	530
	21st to end	Day	29% 13% 34% 20% 3 1	519
November	1st to 10th	Day	24% 20% 30% 17% 8% 2	330
	11th to 20th	Day	31% 19% 30% 14% 5% 2	252
	21st to end	Day	28% 19% 36% 14% 4	220
December	1st to 10th	Day	28% 21% 29% 17% 5% 1	220
	11th to 20th	Day	27% 27% 29% 13% 5%	220
	21st to end	Day	32% 19% 34% 13% 2	242
January	1st to 10th	Night	25% 17% 37% 15% 5% 1	1050
	11th to 20th	Night	29% 16% 31% 20% 4	880
	21st to end	Night	21% 13% 37% 22% 6%	924
February	1st to 10th	Night	23% 13% 37% 23% 3	840
	11th to 20th	Night	24% 16% 30% 26% 5%	823
	21st to end	Night	25% 16% 36% 19% 3	692
March	1st to 10th	Night	20% 14% 35% 25% 6%	840
	11th to 20th	Night	20% 14% 35% 24% 6% 1	840
	21st to end	Night	23% 12% 29% 27% 8% 1	924
April	1st to 10th	Night	24% 14% 31% 26% 5%	840
	11th to 20th	Night	22% 12% 31% 25% 10% 1	631
	21st to end	Night	20% 10% 31% 31% 7% 1	630
May	1st to 10th	Night	20% 7% 30% 31% 11% 1	630
	11th to 20th	Night	16% 6% 28% 38% 11% 2	621
	21st to end	Night	14% 4 27% 39% 14% 1	476
June	1st to 10th	Night	15% 3 30% 38% 14%	420
	11th to 20th	Night	12% 5% 25% 45% 13%	420
	21st to end	Night	11% 5% 23% 45% 16%	420
July	1st to 10th	Night	6% 2 20% 48% 24% 2	418
	11th to 20th	Night	10% 3 20% 41% 24% 3	612
	21st to end	Night	9% 2 16% 48% 23% 1	690
August	1st to 10th	Night	10% 1 13% 44% 30% 3	627
	11th to 20th	Night	10% 2 14% 41% 30% 4	624
	21st to end	Night	12% 2 17% 39% 28% 2	693
September	1st to 10th	Night	11% 5% 21% 35% 24% 4	835
	11th to 20th	Night	12% 3 17% 36% 28% 4	840
	21st to end	Night	19% 6% 21% 33% 17% 4	833
October	1st to 10th	Night	18% 7% 27% 30% 18% 1	800
	11th to 20th	Night	27% 11% 26% 27% 9% 1	800
	21st to end	Night	29% 10% 32% 25% 4	880
November	1st to 10th	Night	22% 12% 29% 28% 8% 1	820
	11th to 20th	Night	25% 15% 33% 20% 6% 1	840
	21st to end	Night	30% 12% 31% 23% 4	840
December	1st to 10th	Night	31% 17% 31% 18% 4	840
	11th to 20th	Night	25% 20% 35% 17% 3	840
	21st to end	Night	30% 15% 32% 20% 3	1082

Page generated at 2026-09-26 04:18:39. Version ac07

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