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 2024-11-02.

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 8% 5% 5% 4 4 5% 7% 32%	101497
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 31%	97451
Transparency	Day	51% 7% 12% 19% 11% 1	101294
	Night	53% 6% 12% 18% 10% 1	97325
Seeing	Day	19% 11% 28% 24% 13% 5%	15110
	Night	21% 10% 28% 29% 11% 1	24380

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	17% 21% 7% 14% 7% 5% 4 3 3 4 15%	2434
	11th to 20th	Day	13% 22% 9% 20% 8% 6% 3 3 3 3 10%	2774
	21st to end	Day	23% 22% 10% 12% 6% 5% 4 2 3 3 10%	3124
February	1st to 10th	Day	15% 18% 5% 15% 9% 6% 4 3 4 4 16%	1710
	11th to 20th	Day	14% 14% 7% 15% 10% 6% 4 3 4 4 19%	1677
	21st to end	Day	16% 17% 6% 12% 6% 4 4 3 4 5% 22%	1570
March	1st to 10th	Day	19% 15% 6% 10% 6% 4 3 3 3 5% 26%	3330
	11th to 20th	Day	13% 14% 7% 11% 5% 4 4 3 5% 6% 29%	3480
	21st to end	Day	18% 12% 4 9% 5% 4 4 3 4 5% 31%	3815
April	1st to 10th	Day	16% 15% 4 8% 4 4 4 3 6% 7% 29%	2156
	11th to 20th	Day	19% 11% 3 5% 4 3 4 4 5% 7% 35%	2442
	21st to end	Day	19% 11% 3 8% 4 4 4 3 5% 6% 34%	2470
May	1st to 10th	Day	18% 7% 3 6% 4 4 4 4 6% 8% 36%	4082
	11th to 20th	Day	17% 10% 3 7% 5% 4 5% 4 6% 8% 31%	4081
	21st to end	Day	13% 5% 2 5% 4 3 4 3 5% 7% 47%	4791
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 5% 6% 29%	1681
	11th to 20th	Day	16% 18% 4 9% 6% 4 5% 4 6% 6% 22%	1577
	21st to end	Day	20% 21% 7% 9% 7% 5% 4 4 4 5% 15%	1520
December	1st to 10th	Day	17% 21% 8% 14% 7% 4 4 5% 5% 4 12%	1520
	11th to 20th	Day	19% 19% 9% 15% 6% 4 4 3 4 4 13%	1910
	21st to end	Day	28% 22% 7% 11% 5% 4 3 2 4 5% 8%	2541
January	1st to 10th	Night	16% 20% 9% 15% 7% 6% 4 2 3 4 13%	4520
	11th to 20th	Night	15% 18% 8% 17% 9% 6% 4 3 4 4 11%	4183
	21st to end	Night	22% 18% 8% 15% 6% 5% 4 2 4 4 12%	4532
February	1st to 10th	Night	17% 16% 5% 13% 9% 6% 5% 3 4 5% 17%	2470
	11th to 20th	Night	15% 16% 6% 11% 8% 6% 5% 4 5% 6% 19%	2386
	21st to end	Night	17% 12% 6% 12% 7% 5% 4 4 5% 5% 22%	1884
March	1st to 10th	Night	16% 14% 4 9% 5% 3 3 3 5% 6% 31%	3523
	11th to 20th	Night	11% 11% 5% 9% 6% 5% 4 4 5% 6% 33%	3480
	21st to end	Night	16% 11% 4 9% 5% 5% 4 3 4 4 36%	3817
April	1st to 10th	Night	19% 12% 3 7% 5% 4 4 3 6% 6% 32%	2033
	11th to 20th	Night	18% 8% 3 7% 4 4 4 4 5% 7% 36%	1695
	21st to end	Night	16% 11% 3 8% 5% 4 4 4 5% 7% 33%	1710
May	1st to 10th	Night	17% 8% 3 7% 4 3 4 3 5% 7% 38%	2813
	11th to 20th	Night	12% 9% 3 8% 5% 5% 4 4 6% 7% 36%	2812
	21st to end	Night	12% 5% 2 4 3 3 4 3 6% 7% 51%	2763
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%	2431
	11th to 20th	Night	16% 17% 4 10% 5% 5% 4 4 6% 6% 22%	2603
	21st to end	Night	21% 19% 5% 10% 6% 5% 4 3 5% 5% 19%	2660
December	1st to 10th	Night	19% 22% 8% 11% 6% 4 4 4 4 4 13%	2660
	11th to 20th	Night	15% 22% 9% 12% 6% 5% 5% 3 4 5% 16%	3285
	21st to end	Night	27% 22% 8% 11% 5% 4 4 3 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	61% 5% 9% 20% 4	3330
	11th to 20th	Day	55% 5% 15% 16% 7% 1	3480
	21st to end	Day	54% 5% 12% 17% 11% 1	3815
April	1st to 10th	Day	53% 7% 11% 19% 9% 1	2156
	11th to 20th	Day	47% 6% 14% 18% 14% 1	2442
	21st to end	Day	51% 6% 11% 19% 12% 2	2470
May	1st to 10th	Day	45% 6% 13% 21% 13% 3	4120
	11th to 20th	Day	47% 10% 13% 20% 8% 1	4085
	21st to end	Day	35% 8% 11% 20% 20% 5%	4805
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	46% 7% 13% 20% 13% 1	1952
	11th to 20th	Day	56% 7% 13% 15% 9%	1900
	21st to end	Day	63% 6% 13% 13% 6%	2029
November	1st to 10th	Day	54% 7% 11% 19% 7% 1	1681
	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	53% 6% 12% 22% 6%	3523
	11th to 20th	Night	47% 7% 17% 18% 11% 1	3480
	21st to end	Night	50% 5% 11% 19% 13% 1	3817
April	1st to 10th	Night	52% 5% 10% 19% 13% 1	2033
	11th to 20th	Night	47% 5% 10% 20% 16% 2	1695
	21st to end	Night	49% 6% 10% 16% 15% 3	1710
May	1st to 10th	Night	44% 6% 10% 19% 16% 4	2840
	11th to 20th	Night	43% 10% 11% 23% 10% 3	2813
	21st to end	Night	32% 7% 13% 23% 22% 4	2770
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	44% 6% 11% 21% 17% 1	2227
	11th to 20th	Night	52% 6% 13% 19% 9% 1	2280
	21st to end	Night	59% 6% 11% 15% 9% 1	2565
November	1st to 10th	Night	49% 6% 12% 22% 11% 1	2431
	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	23% 15% 32% 24% 5% 1	460
	21st to end	Day	29% 14% 30% 22% 5% 1	506
April	1st to 10th	Day	20% 19% 32% 22% 7%	460
	11th to 20th	Day	29% 13% 27% 19% 9% 3	452
	21st to end	Day	24% 14% 30% 23% 7% 2	460
May	1st to 10th	Day	22% 13% 23% 28% 10% 4	463
	11th to 20th	Day	18% 8% 28% 24% 17% 5%	487
	21st to end	Day	14% 7% 24% 29% 18% 8%	529
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% 28% 18% 10% 2	273
	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% 14% 35% 25% 7% 1	760
	21st to end	Night	23% 11% 28% 28% 9% 1	836
April	1st to 10th	Night	24% 14% 31% 27% 5%	760
	11th to 20th	Night	23% 11% 31% 24% 10% 1	571
	21st to end	Night	21% 9% 32% 30% 8% 1	570
May	1st to 10th	Night	21% 7% 29% 31% 12% 1	570
	11th to 20th	Night	16% 5% 27% 38% 12% 2	561
	21st to end	Night	12% 3 26% 41% 16% 1	430
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% 12% 28% 29% 9% 1	748
	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 2024-10-30 13:19:22. Version ac07

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