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 2024-03-18.

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	16% 11% 5% 8% 6% 3 5% 5% 5% 7% 30%	78774
	Night	16% 12% 5% 8% 6% 3 4 4 5% 6% 28%	81025
Transparency	Day	53% 7% 12% 18% 10% 1	78480
	Night	56% 6% 11% 17% 9% 1	80839
Seeing	Day	19% 11% 28% 24% 13% 5%	14162
	Night	21% 10% 28% 29% 11% 1	23656

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	18% 20% 8% 13% 8% 5% 4 4 3 4 15%	2434
	11th to 20th	Day	13% 20% 11% 18% 10% 4 5% 3 3 4 10%	2774
	21st to end	Day	23% 21% 11% 11% 7% 3 5% 3 3 3 10%	3124
February	1st to 10th	Day	16% 16% 5% 13% 10% 5% 5% 4 4 4 16%	1710
	11th to 20th	Day	14% 13% 8% 13% 11% 5% 5% 3 3 5% 19%	1677
	21st to end	Day	17% 16% 7% 11% 6% 3 4 4 4 5% 23%	1570
March	1st to 10th	Day	16% 13% 6% 10% 8% 3 4 5% 4 6% 26%	2019
	11th to 20th	Day	14% 12% 7% 10% 5% 3 4 5% 4 6% 31%	2058
	21st to end	Day	20% 11% 4 8% 6% 3 4 4 5% 5% 29%	2178
April	1st to 10th	Day	17% 13% 5% 7% 5% 3 4 4 6% 7% 29%	2042
	11th to 20th	Day	20% 10% 3 5% 4 3 4 4 5% 8% 34%	2312
	21st to end	Day	20% 10% 4 7% 4 3 4 4 5% 6% 34%	2340
May	1st to 10th	Day	17% 8% 3 6% 5% 3 5% 5% 5% 8% 34%	2340
	11th to 20th	Day	18% 8% 3 5% 5% 3 4 5% 5% 7% 37%	2301
	21st to end	Day	13% 5% 3 5% 6% 2 5% 6% 6% 8% 42%	2707
June	1st to 10th	Day	12% 6% 3 5% 5% 4 5% 5% 6% 9% 40%	2558
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 5% 6% 7% 43%	2700
	21st to end	Day	13% 5% 3 6% 5% 3 5% 5% 6% 8% 42%	2700
July	1st to 10th	Day	9% 4 2 5% 5% 3 5% 4 6% 9% 49%	2690
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 6% 6% 10% 42%	2440
	21st to end	Day	10% 5% 2 6% 5% 4 6% 6% 7% 10% 41%	2547
August	1st to 10th	Day	10% 5% 2 5% 6% 4 6% 6% 7% 9% 40%	2327
	11th to 20th	Day	10% 6% 3 6% 5% 4 5% 6% 8% 9% 37%	2303
	21st to end	Day	13% 6% 3 6% 5% 3 4 5% 6% 8% 42%	2560
September	1st to 10th	Day	11% 8% 3 5% 6% 4 5% 6% 6% 8% 40%	2090
	11th to 20th	Day	12% 5% 2 5% 5% 3 5% 5% 6% 8% 44%	1980
	21st to end	Day	17% 7% 2 5% 5% 4 5% 5% 5% 8% 36%	1980
October	1st to 10th	Day	16% 7% 3 7% 6% 3 5% 5% 6% 7% 35%	1850
	11th to 20th	Day	22% 11% 3 8% 6% 3 5% 5% 6% 6% 25%	1800
	21st to end	Day	27% 13% 3 7% 6% 4 5% 5% 5% 5% 20%	1923
November	1st to 10th	Day	16% 14% 3 8% 6% 3 5% 5% 5% 7% 29%	1672
	11th to 20th	Day	16% 16% 5% 8% 6% 3 5% 5% 7% 6% 22%	1577
	21st to end	Day	20% 20% 8% 8% 8% 4 5% 4 4 5% 15%	1520
December	1st to 10th	Day	17% 19% 9% 13% 8% 3 4 6% 5% 4 12%	1520
	11th to 20th	Day	19% 17% 11% 13% 7% 3 4 5% 4 4 13%	1910
	21st to end	Day	29% 22% 8% 9% 6% 3 4 3 4 5% 8%	2541
January	1st to 10th	Night	17% 19% 10% 13% 9% 5% 4 3 3 4 13%	4520
	11th to 20th	Night	16% 18% 9% 15% 10% 5% 4 4 4 4 11%	4183
	21st to end	Night	22% 17% 9% 13% 7% 3 5% 3 4 4 12%	4532
February	1st to 10th	Night	17% 14% 6% 11% 11% 4 6% 4 4 5% 17%	2470
	11th to 20th	Night	16% 14% 6% 10% 9% 5% 5% 5% 4 6% 19%	2386
	21st to end	Night	18% 11% 7% 11% 8% 4 5% 5% 5% 6% 22%	1884
March	1st to 10th	Night	15% 11% 5% 9% 8% 3 4 4 5% 7% 29%	2161
	11th to 20th	Night	14% 11% 5% 8% 6% 2 5% 4 5% 6% 34%	2068
	21st to end	Night	18% 11% 5% 8% 6% 3 4 4 4 5% 33%	2178
April	1st to 10th	Night	19% 10% 4 6% 5% 3 5% 4 6% 7% 32%	1926
	11th to 20th	Night	18% 8% 2 6% 5% 3 4 5% 5% 7% 37%	1605
	21st to end	Night	16% 11% 3 7% 6% 3 4 5% 5% 7% 34%	1620
May	1st to 10th	Night	17% 7% 3 6% 5% 3 4 5% 5% 7% 36%	1620
	11th to 20th	Night	13% 6% 3 6% 6% 4 4 5% 6% 8% 39%	1592
	21st to end	Night	10% 4 2 4 4 2 4 4 6% 8% 50%	1567
June	1st to 10th	Night	12% 6% 3 5% 5% 3 5% 4 6% 8% 44%	1397
	11th to 20th	Night	9% 6% 2 6% 5% 4 4 6% 7% 10% 42%	1260
	21st to end	Night	10% 5% 3 4 5% 3 5% 4 5% 7% 49%	1260
July	1st to 10th	Night	6% 3 2 4 4 3 4 4 6% 9% 55%	1266
	11th to 20th	Night	9% 5% 2 4 4 3 4 5% 6% 8% 49%	1516
	21st to end	Night	8% 4 3 5% 6% 3 5% 5% 7% 8% 47%	1771
August	1st to 10th	Night	8% 4 2 5% 6% 3 5% 6% 7% 8% 46%	1611
	11th to 20th	Night	9% 5% 2 5% 5% 3 5% 5% 6% 8% 48%	1598
	21st to end	Night	10% 6% 2 5% 4 3 4 4 5% 8% 49%	1782
September	1st to 10th	Night	10% 6% 4 6% 5% 3 4 5% 5% 8% 45%	1862
	11th to 20th	Night	12% 5% 2 5% 4 2 4 4 5% 7% 51%	1980
	21st to end	Night	16% 7% 3 6% 5% 4 5% 4 5% 6% 41%	1980
October	1st to 10th	Night	15% 8% 3 7% 6% 3 4 4 6% 6% 38%	2109
	11th to 20th	Night	23% 11% 3 6% 5% 3 4 4 4 6% 31%	2160
	21st to end	Night	26% 11% 4 8% 6% 3 4 4 4 6% 24%	2430
November	1st to 10th	Night	16% 11% 4 7% 5% 3 4 4 5% 6% 35%	2406
	11th to 20th	Night	17% 16% 5% 9% 6% 4 5% 5% 5% 7% 22%	2603
	21st to end	Night	21% 18% 6% 9% 6% 3 4 5% 4 5% 19%	2660
December	1st to 10th	Night	19% 20% 9% 11% 6% 3 5% 5% 4 5% 13%	2660
	11th to 20th	Night	15% 21% 9% 11% 7% 4 4 4 4 5% 16%	3285
	21st to end	Night	27% 21% 8% 10% 7% 3 4 4 3 4 10%	5117

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	71% 7% 12% 9% 2	2435
	11th to 20th	Day	79% 6% 8% 5% 2	2774
	21st to end	Day	79% 5% 8% 5% 3	3124
February	1st to 10th	Day	70% 6% 9% 11% 4	1710
	11th to 20th	Day	68% 5% 8% 13% 6%	1686
	21st to end	Day	63% 6% 11% 12% 6% 1	1570
March	1st to 10th	Day	60% 5% 12% 16% 6% 1	2019
	11th to 20th	Day	55% 5% 10% 18% 10% 2	2058
	21st to end	Day	57% 5% 9% 17% 10% 1	2178
April	1st to 10th	Day	53% 7% 10% 19% 9% 1	2042
	11th to 20th	Day	47% 5% 14% 18% 14% 1	2312
	21st to end	Day	51% 6% 12% 18% 11% 2	2340
May	1st to 10th	Day	47% 7% 11% 22% 12% 2	2340
	11th to 20th	Day	47% 6% 10% 20% 14% 3	2305
	21st to end	Day	39% 8% 13% 23% 15% 2	2707
June	1st to 10th	Day	39% 8% 13% 25% 13% 2	2558
	11th to 20th	Day	39% 9% 11% 22% 17% 2	2700
	21st to end	Day	39% 8% 12% 24% 17% 1	2700
July	1st to 10th	Day	32% 8% 10% 28% 20% 3	2616
	11th to 20th	Day	37% 8% 13% 27% 14% 1	2365
	21st to end	Day	37% 9% 13% 24% 15% 2	2405
August	1st to 10th	Day	37% 9% 14% 27% 11% 1	2314
	11th to 20th	Day	40% 9% 15% 23% 12% 1	2303
	21st to end	Day	39% 6% 14% 25% 14% 1	2560
September	1st to 10th	Day	42% 8% 14% 23% 13% 1	2090
	11th to 20th	Day	35% 9% 13% 29% 14%	1980
	21st to end	Day	45% 8% 12% 24% 10% 1	1980
October	1st to 10th	Day	47% 7% 13% 20% 13% 1	1850
	11th to 20th	Day	57% 7% 14% 15% 7%	1800
	21st to end	Day	64% 6% 12% 12% 6%	1923
November	1st to 10th	Day	54% 7% 11% 19% 8% 1	1672
	11th to 20th	Day	59% 7% 15% 12% 6% 1	1577
	21st to end	Day	72% 6% 9% 11% 2	1520
December	1st to 10th	Day	72% 8% 10% 8% 2	1520
	11th to 20th	Day	75% 5% 9% 8% 2	1906
	21st to end	Day	81% 5% 10% 4	2541
January	1st to 10th	Night	73% 6% 10% 8% 2	4520
	11th to 20th	Night	76% 8% 8% 6% 2	4183
	21st to end	Night	75% 6% 9% 7% 2	4532
February	1st to 10th	Night	68% 6% 9% 12% 4	2470
	11th to 20th	Night	63% 6% 11% 14% 5%	2388
	21st to end	Night	62% 7% 11% 14% 6%	1884
March	1st to 10th	Night	56% 5% 11% 19% 9% 1	2161
	11th to 20th	Night	51% 5% 13% 20% 11% 1	2068
	21st to end	Night	55% 4 8% 20% 11% 2	2178
April	1st to 10th	Night	52% 5% 10% 19% 13% 1	1926
	11th to 20th	Night	46% 5% 11% 20% 17% 2	1605
	21st to end	Night	49% 6% 10% 17% 15% 3	1620
May	1st to 10th	Night	46% 6% 9% 22% 13% 3	1620
	11th to 20th	Night	42% 6% 11% 22% 14% 5%	1593
	21st to end	Night	32% 7% 14% 26% 17% 4	1568
June	1st to 10th	Night	37% 7% 12% 26% 17% 2	1397
	11th to 20th	Night	34% 9% 12% 24% 18% 3	1260
	21st to end	Night	35% 6% 13% 26% 19% 1	1260
July	1st to 10th	Night	27% 6% 10% 29% 23% 5%	1231
	11th to 20th	Night	32% 7% 13% 28% 17% 3	1468
	21st to end	Night	32% 9% 17% 22% 17% 3	1672
August	1st to 10th	Night	33% 9% 13% 30% 14% 1	1600
	11th to 20th	Night	32% 9% 14% 30% 13% 2	1598
	21st to end	Night	34% 7% 14% 28% 16% 2	1782
September	1st to 10th	Night	36% 8% 13% 25% 15% 3	1862
	11th to 20th	Night	32% 6% 12% 30% 18% 1	1980
	21st to end	Night	43% 7% 12% 23% 13% 1	1980
October	1st to 10th	Night	45% 6% 11% 21% 16% 1	2109
	11th to 20th	Night	53% 6% 13% 20% 8% 1	2160
	21st to end	Night	61% 6% 11% 14% 8% 1	2430
November	1st to 10th	Night	49% 6% 12% 22% 11% 1	2406
	11th to 20th	Night	58% 8% 13% 14% 6% 1	2603
	21st to end	Night	67% 6% 14% 10% 3	2660
December	1st to 10th	Night	72% 7% 11% 8% 2	2660
	11th to 20th	Night	70% 5% 13% 10% 2	3288
	21st to end	Night	79% 5% 10% 5% 1	5117

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	24% 23% 27% 18% 5% 2	245
	11th to 20th	Day	21% 19% 41% 14% 4 1	270
	21st to end	Day	29% 13% 35% 19% 3 1	297
February	1st to 10th	Day	25% 21% 38% 12% 4	270
	11th to 20th	Day	24% 23% 37% 16%	270
	21st to end	Day	28% 28% 31% 11% 2	225
March	1st to 10th	Day	26% 16% 38% 15% 6%	389
	11th to 20th	Day	22% 14% 33% 24% 5% 1	449
	21st to end	Day	29% 13% 30% 21% 5% 1	462
April	1st to 10th	Day	20% 19% 31% 23% 7%	420
	11th to 20th	Day	28% 12% 26% 20% 10% 4	412
	21st to end	Day	25% 13% 30% 22% 7% 2	420
May	1st to 10th	Day	22% 13% 23% 27% 10% 4	423
	11th to 20th	Day	19% 8% 29% 23% 16% 5%	447
	21st to end	Day	14% 7% 23% 29% 18% 8%	485
June	1st to 10th	Day	12% 6% 33% 30% 14% 5%	488
	11th to 20th	Day	13% 9% 27% 33% 14% 4	630
	21st to end	Day	14% 7% 27% 32% 15% 4	630
July	1st to 10th	Day	11% 6% 21% 28% 25% 9%	621
	11th to 20th	Day	14% 6% 25% 30% 19% 7%	538
	21st to end	Day	8% 4 23% 34% 22% 9%	488
August	1st to 10th	Day	12% 5% 16% 26% 27% 15%	446
	11th to 20th	Day	12% 5% 19% 26% 23% 15%	439
	21st to end	Day	13% 6% 19% 30% 22% 10%	495
September	1st to 10th	Day	12% 6% 23% 26% 22% 11%	450
	11th to 20th	Day	11% 3 22% 23% 28% 12%	450
	21st to end	Day	19% 9% 23% 24% 16% 9%	450
October	1st to 10th	Day	20% 10% 25% 22% 18% 5%	450
	11th to 20th	Day	24% 16% 32% 21% 7%	450
	21st to end	Day	32% 12% 34% 18% 4	438
November	1st to 10th	Day	21% 20% 29% 18% 10% 2	270
	11th to 20th	Day	30% 18% 31% 14% 6% 2	207
	21st to end	Day	27% 18% 37% 15% 3	180
December	1st to 10th	Day	27% 22% 31% 14% 6% 1	180
	11th to 20th	Day	25% 27% 31% 13% 4	180
	21st to end	Day	31% 21% 34% 13% 2	198
January	1st to 10th	Night	26% 16% 37% 15% 6% 1	950
	11th to 20th	Night	30% 14% 30% 22% 4	797
	21st to end	Night	23% 11% 35% 24% 7%	836
February	1st to 10th	Night	24% 13% 37% 23% 2	760
	11th to 20th	Night	24% 15% 30% 26% 5%	743
	21st to end	Night	25% 16% 35% 20% 3	628
March	1st to 10th	Night	19% 12% 36% 26% 6%	760
	11th to 20th	Night	19% 13% 35% 25% 7% 1	752
	21st to end	Night	24% 11% 27% 28% 9% 1	792
April	1st to 10th	Night	23% 14% 30% 28% 5%	720
	11th to 20th	Night	22% 11% 30% 25% 11% 1	541
	21st to end	Night	21% 9% 31% 30% 8% 1	540
May	1st to 10th	Night	21% 6% 29% 31% 12% 1	540
	11th to 20th	Night	16% 5% 28% 38% 11% 2	531
	21st to end	Night	12% 3 26% 42% 16% 1	407
June	1st to 10th	Night	15% 3 29% 38% 15% 1	360
	11th to 20th	Night	12% 3 25% 44% 14%	360
	21st to end	Night	11% 5% 21% 46% 17%	360
July	1st to 10th	Night	5% 1 20% 47% 25% 2	356
	11th to 20th	Night	11% 3 18% 41% 24% 3	522
	21st to end	Night	9% 2 17% 47% 24% 1	591
August	1st to 10th	Night	10% 1 11% 45% 30% 3	537
	11th to 20th	Night	9% 2 14% 39% 32% 4	534
	21st to end	Night	12% 3 18% 36% 29% 2	594
September	1st to 10th	Night	11% 5% 20% 36% 24% 4	715
	11th to 20th	Night	13% 3 18% 34% 27% 4	720
	21st to end	Night	18% 7% 22% 31% 17% 5%	720
October	1st to 10th	Night	19% 7% 26% 29% 18% 2	720
	11th to 20th	Night	28% 11% 25% 26% 9% 1	720
	21st to end	Night	31% 10% 31% 24% 3	792
November	1st to 10th	Night	21% 11% 28% 29% 9% 1	740
	11th to 20th	Night	24% 15% 34% 20% 6% 1	760
	21st to end	Night	29% 12% 31% 24% 5%	760
December	1st to 10th	Night	31% 17% 30% 17% 4	760
	11th to 20th	Night	25% 19% 35% 18% 3	760
	21st to end	Night	31% 14% 33% 20% 2	978

Page generated at 2024-03-15 14:01:39. Version ac07

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