Fox Run Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fox Run Observatory clear sky chart from 2005-11-06 to 2026-10-29.

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% 10% 4 9% 5% 5% 5% 4 6% 7% 31%	150716
	Night	14% 11% 4 10% 6% 5% 5% 4 5% 6% 31%	141332
Transparency	Day	50% 6% 12% 20% 11% 1	154297
	Night	51% 6% 11% 19% 12% 1	145828
Seeing	Day	19% 12% 28% 24% 13% 5%	17484
	Night	19% 12% 30% 28% 11% 1	26368

By Month

Percentage Cloud Cover NE (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% 16% 8% 18% 7% 4 4 3 4 4 18%	4721
	11th to 20th	Day	9% 23% 10% 22% 9% 9% 5% 3 2 2 6%	5246
	21st to end	Day	13% 15% 6% 18% 10% 7% 6% 4 4 5% 12%	5780
February	1st to 10th	Day	15% 17% 7% 13% 8% 6% 5% 3 4 4 17%	1890
	11th to 20th	Day	14% 12% 7% 15% 8% 4 6% 4 6% 6% 18%	1843
	21st to end	Day	16% 17% 5% 10% 7% 5% 5% 3 6% 5% 20%	1658
March	1st to 10th	Day	19% 12% 5% 10% 6% 4 3 3 4 5% 27%	4994
	11th to 20th	Day	12% 12% 6% 9% 5% 5% 5% 4 6% 8% 29%	5090
	21st to end	Day	18% 13% 4 9% 6% 5% 5% 3 5% 5% 29%	5586
April	1st to 10th	Day	17% 14% 5% 9% 5% 4 4 3 6% 6% 27%	2436
	11th to 20th	Day	19% 10% 3 7% 4 4 4 4 5% 6% 34%	2634
	21st to end	Day	19% 10% 3 7% 4 5% 3 3 5% 6% 32%	2730
May	1st to 10th	Day	17% 9% 3 7% 5% 4 5% 4 6% 7% 33%	7642
	11th to 20th	Day	15% 10% 3 8% 5% 4 5% 4 5% 7% 34%	7959
	21st to end	Day	18% 6% 2 5% 4 4 4 3 5% 7% 43%	9060
June	1st to 10th	Day	13% 7% 2 5% 5% 5% 6% 5% 7% 8% 37%	2940
	11th to 20th	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 8% 38%	3070
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 6% 9% 39%	3150
July	1st to 10th	Day	10% 7% 2 7% 5% 4 5% 5% 7% 10% 38%	8861
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 7% 10% 47%	8101
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 6% 9% 45%	8340
August	1st to 10th	Day	17% 8% 2 6% 4 4 5% 4 5% 7% 37%	6014
	11th to 20th	Day	10% 7% 3 7% 5% 5% 5% 5% 8% 10% 35%	5951
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 9% 36%	6434
September	1st to 10th	Day	11% 6% 3 6% 5% 5% 5% 5% 6% 9% 40%	2520
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 5% 9% 43%	2326
	21st to end	Day	14% 8% 3 7% 5% 5% 5% 4 7% 9% 34%	2310
October	1st to 10th	Day	17% 9% 3 7% 4 4 5% 4 6% 6% 34%	2100
	11th to 20th	Day	21% 9% 3 9% 4 5% 4 4 5% 7% 29%	2100
	21st to end	Day	22% 13% 4 8% 5% 5% 5% 4 6% 7% 21%	2279
November	1st to 10th	Day	16% 13% 4 9% 5% 4 5% 4 6% 6% 29%	1797
	11th to 20th	Day	15% 15% 4 9% 6% 4 5% 4 6% 6% 24%	1680
	21st to end	Day	17% 17% 8% 13% 5% 5% 4 3 6% 6% 17%	1680
December	1st to 10th	Day	16% 24% 8% 14% 5% 5% 4 3 5% 5% 12%	2680
	11th to 20th	Day	20% 21% 5% 11% 6% 4 4 3 4 5% 16%	3066
	21st to end	Day	26% 18% 6% 13% 6% 5% 4 3 4 3 11%	4048
January	1st to 10th	Night	14% 14% 8% 16% 7% 6% 5% 4 5% 5% 16%	8156
	11th to 20th	Night	10% 18% 8% 19% 12% 7% 6% 4 4 4 9%	7639
	21st to end	Night	12% 13% 7% 16% 9% 6% 6% 4 5% 6% 15%	8401
February	1st to 10th	Night	14% 16% 5% 10% 9% 6% 5% 4 5% 6% 20%	2730
	11th to 20th	Night	14% 13% 6% 11% 7% 6% 5% 4 6% 7% 22%	2663
	21st to end	Night	14% 12% 5% 13% 6% 5% 5% 3 6% 6% 25%	2144
March	1st to 10th	Night	14% 10% 4 10% 6% 5% 5% 4 6% 6% 30%	5065
	11th to 20th	Night	9% 9% 4 9% 5% 4 5% 5% 7% 8% 34%	5089
	21st to end	Night	20% 10% 3 8% 4 4 4 3 5% 5% 35%	5588
April	1st to 10th	Night	19% 11% 3 7% 6% 4 4 4 5% 6% 31%	2184
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 5% 37%	1951
	21st to end	Night	15% 8% 3 8% 5% 5% 4 4 6% 7% 35%	1890
May	1st to 10th	Night	18% 8% 2 6% 4 4 4 4 5% 7% 38%	5257
	11th to 20th	Night	14% 9% 3 8% 5% 4 4 3 5% 6% 38%	4901
	21st to end	Night	17% 6% 2 5% 3 3 3 3 4 7% 46%	5114
June	1st to 10th	Night	12% 6% 2 5% 3 5% 4 4 7% 7% 45%	1680
	11th to 20th	Night	10% 5% 2 6% 5% 5% 4 4 8% 9% 42%	1542
	21st to end	Night	11% 5% 2 6% 5% 5% 4 3 5% 8% 46%	1470
July	1st to 10th	Night	7% 5% 2 6% 4 4 4 4 7% 9% 49%	4110
	11th to 20th	Night	8% 5% 2 5% 3 4 4 3 5% 9% 51%	4855
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 5% 7% 50%	5737
August	1st to 10th	Night	13% 8% 3 6% 4 4 4 3 5% 7% 43%	4135
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 6% 9% 46%	4095
	21st to end	Night	13% 6% 2 7% 4 4 4 4 6% 8% 43%	4644
September	1st to 10th	Night	8% 5% 2 7% 4 4 5% 4 6% 8% 47%	2100
	11th to 20th	Night	10% 5% 2 5% 3 3 3 4 5% 7% 54%	2289
	21st to end	Night	16% 7% 3 7% 4 5% 4 3 5% 6% 41%	2310
October	1st to 10th	Night	14% 7% 2 8% 5% 4 4 3 5% 7% 42%	2520
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 3 4 6% 35%	2520
	21st to end	Night	19% 10% 3 8% 6% 5% 4 4 6% 7% 29%	2737
November	1st to 10th	Night	15% 10% 3 7% 5% 4 4 4 6% 7% 34%	2718
	11th to 20th	Night	15% 14% 4 10% 6% 5% 5% 4 6% 7% 25%	2940
	21st to end	Night	19% 14% 4 9% 7% 4 4 4 6% 7% 22%	2940
December	1st to 10th	Night	14% 19% 8% 13% 6% 5% 5% 4 5% 6% 14%	4720
	11th to 20th	Night	15% 21% 7% 12% 7% 5% 4 3 4 4 18%	5348
	21st to end	Night	23% 19% 8% 13% 6% 5% 4 3 4 4 12%	7150

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	68% 6% 8% 9% 8% 1	4722
	11th to 20th	Day	83% 6% 4 4 3	5280
	21st to end	Day	72% 5% 10% 8% 5%	5780
February	1st to 10th	Day	69% 6% 7% 12% 5% 1	1890
	11th to 20th	Day	65% 6% 7% 14% 7% 2	1852
	21st to end	Day	65% 4 10% 13% 7% 1	1658
March	1st to 10th	Day	59% 4 13% 13% 9% 1	4997
	11th to 20th	Day	53% 5% 15% 19% 7% 3	5090
	21st to end	Day	57% 5% 9% 18% 10% 2	5586
April	1st to 10th	Day	56% 5% 9% 18% 11% 1	2436
	11th to 20th	Day	51% 5% 10% 21% 12% 1	2634
	21st to end	Day	52% 5% 10% 20% 11% 2	2730
May	1st to 10th	Day	48% 5% 13% 20% 10% 5%	7651
	11th to 20th	Day	48% 6% 12% 20% 14% 1	7963
	21st to end	Day	41% 4 10% 25% 16% 3	9061
June	1st to 10th	Day	41% 8% 11% 21% 17% 1	2940
	11th to 20th	Day	39% 7% 14% 24% 14% 1	3070
	21st to end	Day	41% 7% 13% 25% 14%	3150
July	1st to 10th	Day	39% 6% 16% 24% 14% 1	8788
	11th to 20th	Day	30% 6% 13% 35% 15% 1	8026
	21st to end	Day	34% 6% 14% 27% 18% 1	8156
August	1st to 10th	Day	45% 6% 13% 18% 15% 3	6001
	11th to 20th	Day	40% 7% 17% 28% 7%	5990
	21st to end	Day	41% 7% 14% 29% 8% 1	6434
September	1st to 10th	Day	39% 7% 15% 26% 11% 1	2520
	11th to 20th	Day	36% 6% 14% 29% 14% 1	2326
	21st to end	Day	46% 6% 13% 24% 11% 1	2310
October	1st to 10th	Day	42% 7% 12% 23% 14% 1	3360
	11th to 20th	Day	43% 6% 12% 21% 17%	3340
	21st to end	Day	53% 6% 15% 19% 7%	3605
November	1st to 10th	Day	54% 7% 11% 20% 8% 1	1797
	11th to 20th	Day	58% 7% 11% 15% 8% 1	1680
	21st to end	Day	68% 5% 10% 12% 5%	1680
December	1st to 10th	Day	75% 5% 10% 8% 3	2680
	11th to 20th	Day	71% 5% 9% 9% 6%	3066
	21st to end	Day	78% 6% 5% 6% 6%	4048
January	1st to 10th	Night	65% 8% 8% 12% 6%	8156
	11th to 20th	Night	77% 6% 6% 7% 4	7680
	21st to end	Night	67% 5% 10% 11% 7%	8401
February	1st to 10th	Night	64% 6% 9% 16% 5% 1	2730
	11th to 20th	Night	59% 6% 10% 16% 8% 1	2665
	21st to end	Night	60% 5% 11% 16% 8%	2144
March	1st to 10th	Night	52% 5% 15% 16% 11% 1	5075
	11th to 20th	Night	44% 6% 17% 20% 11% 2	5090
	21st to end	Night	51% 5% 8% 18% 16% 2	5588
April	1st to 10th	Night	54% 4 9% 18% 14% 1	2184
	11th to 20th	Night	48% 5% 8% 22% 16% 2	1951
	21st to end	Night	46% 5% 9% 21% 15% 2	1890
May	1st to 10th	Night	46% 5% 12% 16% 16% 6%	5264
	11th to 20th	Night	46% 6% 12% 20% 14% 2	4902
	21st to end	Night	38% 4 11% 26% 18% 2	5115
June	1st to 10th	Night	36% 7% 11% 26% 19% 2	1680
	11th to 20th	Night	36% 6% 13% 26% 17% 2	1542
	21st to end	Night	36% 6% 14% 26% 17% 1	1470
July	1st to 10th	Night	31% 6% 17% 26% 17% 3	4075
	11th to 20th	Night	31% 5% 10% 32% 21% 2	4807
	21st to end	Night	32% 6% 11% 28% 21% 2	5606
August	1st to 10th	Night	41% 5% 12% 22% 15% 5%	4124
	11th to 20th	Night	34% 7% 17% 31% 11% 1	4122
	21st to end	Night	38% 6% 14% 29% 12% 1	4644
September	1st to 10th	Night	34% 8% 13% 30% 14% 1	2100
	11th to 20th	Night	28% 6% 13% 32% 20% 1	2289
	21st to end	Night	43% 5% 12% 26% 13% 1	2310
October	1st to 10th	Night	33% 5% 10% 28% 23% 1	4040
	11th to 20th	Night	45% 5% 11% 23% 15%	4019
	21st to end	Night	42% 5% 17% 26% 10% 1	4349
November	1st to 10th	Night	47% 7% 12% 21% 12% 1	2718
	11th to 20th	Night	56% 7% 12% 16% 7% 1	2940
	21st to end	Night	61% 6% 15% 13% 5% 1	2940
December	1st to 10th	Night	71% 6% 10% 11% 2	4720
	11th to 20th	Night	69% 4 9% 12% 6%	5348
	21st to end	Night	76% 4 8% 7% 5%	7150

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% 19% 34% 16% 6% 1	231
	11th to 20th	Day	22% 20% 39% 15% 3 1	330
	21st to end	Day	26% 18% 34% 18% 4	363
February	1st to 10th	Day	24% 21% 35% 15% 5%	330
	11th to 20th	Day	24% 22% 35% 18% 2	330
	21st to end	Day	23% 27% 35% 13% 1	273
March	1st to 10th	Day	25% 15% 33% 21% 5%	516
	11th to 20th	Day	24% 18% 33% 19% 6% 1	540
	21st to end	Day	29% 13% 32% 19% 6% 1	594
April	1st to 10th	Day	22% 20% 29% 21% 6% 1	540
	11th to 20th	Day	28% 17% 25% 17% 10% 3	532
	21st to end	Day	24% 13% 31% 22% 9% 1	540
May	1st to 10th	Day	22% 13% 28% 25% 9% 4	543
	11th to 20th	Day	16% 11% 30% 23% 14% 6%	567
	21st to end	Day	16% 8% 29% 26% 15% 7%	617
June	1st to 10th	Day	13% 11% 30% 28% 15% 3	570
	11th to 20th	Day	13% 10% 29% 29% 16% 3	700
	21st to end	Day	14% 10% 27% 34% 12% 3	780
July	1st to 10th	Day	9% 7% 23% 31% 22% 8%	766
	11th to 20th	Day	12% 6% 24% 27% 23% 9%	564
	21st to end	Day	10% 4 23% 33% 20% 10%	620
August	1st to 10th	Day	12% 5% 19% 30% 22% 12%	566
	11th to 20th	Day	11% 6% 21% 27% 22% 13%	559
	21st to end	Day	15% 6% 20% 28% 20% 11%	627
September	1st to 10th	Day	11% 9% 24% 23% 20% 14%	570
	11th to 20th	Day	10% 5% 18% 26% 25% 15%	570
	21st to end	Day	17% 11% 21% 25% 19% 7%	570
October	1st to 10th	Day	19% 13% 25% 21% 14% 7%	570
	11th to 20th	Day	21% 14% 33% 22% 7% 2	570
	21st to end	Day	27% 13% 28% 25% 6% 1	614
November	1st to 10th	Day	24% 21% 29% 18% 6% 1	300
	11th to 20th	Day	26% 16% 34% 17% 5% 3	220
	21st to end	Day	27% 20% 30% 19% 4	220
December	1st to 10th	Day	29% 18% 30% 16% 6%	220
	11th to 20th	Day	30% 23% 26% 17% 4	220
	21st to end	Day	31% 21% 33% 12% 4	242
January	1st to 10th	Night	22% 19% 37% 17% 5%	840
	11th to 20th	Night	27% 18% 32% 19% 4	840
	21st to end	Night	20% 14% 38% 21% 6%	924
February	1st to 10th	Night	22% 17% 35% 23% 3	840
	11th to 20th	Night	22% 17% 36% 21% 4	823
	21st to end	Night	20% 18% 37% 21% 3	692
March	1st to 10th	Night	18% 17% 36% 24% 5%	840
	11th to 20th	Night	20% 16% 37% 21% 6%	840
	21st to end	Night	23% 12% 33% 23% 8% 1	924
April	1st to 10th	Night	23% 18% 31% 24% 4	840
	11th to 20th	Night	21% 12% 33% 23% 8% 1	707
	21st to end	Night	17% 13% 30% 33% 7%	630
May	1st to 10th	Night	17% 7% 32% 29% 14% 1	630
	11th to 20th	Night	17% 5% 29% 37% 12% 1	509
	21st to end	Night	13% 4 30% 35% 17%	455
June	1st to 10th	Night	14% 4 30% 40% 13%	420
	11th to 20th	Night	12% 7% 30% 39% 12%	420
	21st to end	Night	12% 6% 23% 45% 14%	420
July	1st to 10th	Night	6% 4 19% 49% 22% 1	410
	11th to 20th	Night	8% 4 25% 39% 23% 2	466
	21st to end	Night	10% 3 19% 46% 20% 1	690
August	1st to 10th	Night	9% 2 18% 42% 27% 3	627
	11th to 20th	Night	9% 4 16% 40% 29% 3	624
	21st to end	Night	14% 4 20% 34% 26% 2	740
September	1st to 10th	Night	10% 7% 21% 36% 21% 5%	840
	11th to 20th	Night	11% 5% 19% 33% 27% 5%	840
	21st to end	Night	19% 6% 19% 33% 18% 5%	840
October	1st to 10th	Night	17% 7% 28% 29% 16% 3	840
	11th to 20th	Night	22% 11% 28% 29% 9% 1	840
	21st to end	Night	24% 12% 29% 27% 6%	913
November	1st to 10th	Night	22% 12% 29% 28% 8% 1	820
	11th to 20th	Night	22% 16% 33% 21% 7% 1	840
	21st to end	Night	26% 14% 33% 21% 4	840
December	1st to 10th	Night	27% 17% 32% 19% 5%	840
	11th to 20th	Night	23% 20% 37% 16% 4	840
	21st to end	Night	30% 16% 33% 18% 3	924

Page generated at 2026-10-26 04:37:52. Version ac07

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