Dover-Foxcroft
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dover-Foxcroft clear sky chart from 2005-11-06 to 2026-04-02.

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	18% 9% 3 7% 5% 4 4 4 5% 7% 34%	130569
	Night	17% 9% 3 7% 5% 4 5% 4 5% 6% 34%	131293
Transparency	Day	48% 5% 12% 20% 12% 2	134062
	Night	48% 5% 12% 21% 12% 1	135875
Seeing	Day	26% 17% 30% 19% 7% 2	17395
	Night	23% 14% 31% 25% 7%	25894

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	12% 12% 4 10% 5% 5% 5% 4 5% 6% 34%	4661
	11th to 20th	Day	15% 11% 4 9% 5% 5% 4 4 5% 7% 32%	4650
	21st to end	Day	8% 8% 3 7% 5% 5% 5% 4 6% 6% 41%	5124
February	1st to 10th	Day	14% 12% 4 7% 6% 5% 5% 4 5% 8% 31%	1864
	11th to 20th	Day	13% 11% 5% 10% 6% 5% 4 3 5% 5% 33%	1967
	21st to end	Day	14% 11% 4 9% 5% 6% 5% 4 5% 5% 34%	1730
March	1st to 10th	Day	23% 14% 4 8% 5% 4 4 3 4 4 27%	4576
	11th to 20th	Day	20% 12% 3 8% 5% 4 5% 3 4 5% 32%	5079
	21st to end	Day	25% 11% 3 6% 4 4 4 3 4 6% 29%	5624
April	1st to 10th	Day	23% 11% 3 6% 5% 4 4 3 4 6% 30%	2412
	11th to 20th	Day	20% 9% 3 6% 5% 4 5% 3 4 6% 35%	2536
	21st to end	Day	23% 11% 2 6% 4 3 4 3 4 6% 34%	2600
May	1st to 10th	Day	28% 10% 3 7% 5% 5% 4 4 5% 5% 24%	5886
	11th to 20th	Day	24% 9% 3 7% 5% 4 5% 4 5% 6% 29%	5952
	21st to end	Day	20% 8% 3 7% 5% 5% 5% 5% 6% 8% 31%	7174
June	1st to 10th	Day	24% 8% 3 7% 4 4 4 4 6% 8% 29%	3000
	11th to 20th	Day	18% 7% 2 7% 4 5% 4 4 5% 7% 37%	3000
	21st to end	Day	24% 8% 3 7% 5% 4 4 4 6% 6% 29%	3000
July	1st to 10th	Day	15% 6% 3 8% 5% 5% 6% 5% 8% 10% 30%	6557
	11th to 20th	Day	17% 6% 3 6% 4 5% 4 4 6% 8% 36%	6360
	21st to end	Day	13% 6% 2 6% 5% 4 4 4 6% 9% 41%	6926
August	1st to 10th	Day	17% 6% 3 6% 5% 5% 6% 4 6% 9% 33%	4247
	11th to 20th	Day	16% 8% 4 7% 5% 4 5% 4 6% 8% 33%	4175
	21st to end	Day	14% 6% 2 6% 4 4 4 4 6% 8% 41%	4623
September	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 8% 45%	2325
	11th to 20th	Day	14% 5% 2 5% 4 3 4 4 5% 5% 51%	2200
	21st to end	Day	17% 5% 3 6% 4 4 4 4 4 8% 42%	2200
October	1st to 10th	Day	18% 6% 2 6% 5% 4 4 3 4 7% 40%	2159
	11th to 20th	Day	20% 10% 2 6% 4 4 3 3 5% 7% 36%	1945
	21st to end	Day	23% 11% 4 7% 4 4 4 3 5% 6% 30%	1980
November	1st to 10th	Day	17% 9% 3 8% 4 4 4 3 6% 7% 36%	1851
	11th to 20th	Day	19% 9% 2 5% 3 4 5% 4 5% 7% 37%	1853
	21st to end	Day	22% 8% 3 5% 5% 4 4 3 5% 6% 36%	1680
December	1st to 10th	Day	17% 12% 3 7% 5% 4 5% 4 5% 7% 31%	2384
	11th to 20th	Day	19% 8% 2 5% 4 4 5% 4 5% 5% 40%	2688
	21st to end	Day	20% 10% 3 6% 4 4 5% 3 5% 6% 33%	3581
January	1st to 10th	Night	11% 11% 4 11% 6% 5% 5% 4 5% 6% 32%	8234
	11th to 20th	Night	14% 13% 4 10% 7% 6% 7% 5% 6% 6% 23%	8235
	21st to end	Night	8% 9% 3 8% 5% 6% 7% 5% 7% 6% 36%	9057
February	1st to 10th	Night	13% 11% 4 9% 5% 4 5% 5% 6% 7% 31%	2755
	11th to 20th	Night	11% 11% 4 9% 7% 4 4 3 5% 6% 36%	2535
	21st to end	Night	14% 12% 3 7% 5% 5% 4 4 4 6% 35%	2076
March	1st to 10th	Night	25% 11% 4 8% 5% 4 4 3 4 5% 27%	5484
	11th to 20th	Night	17% 10% 3 8% 5% 5% 5% 4 5% 6% 30%	5100
	21st to end	Night	25% 11% 2 6% 4 4 5% 3 6% 7% 28%	5546
April	1st to 10th	Night	22% 12% 3 7% 5% 3 3 3 4 4 34%	2011
	11th to 20th	Night	19% 8% 3 6% 5% 6% 4 4 5% 6% 34%	1812
	21st to end	Night	25% 9% 3 6% 4 3 3 3 5% 5% 34%	1800
May	1st to 10th	Night	27% 11% 3 7% 4 4 3 3 4 6% 26%	4054
	11th to 20th	Night	23% 9% 3 7% 5% 5% 5% 4 5% 7% 27%	3971
	21st to end	Night	18% 7% 3 8% 4 4 4 3 6% 8% 36%	3711
June	1st to 10th	Night	21% 9% 3 7% 4 5% 5% 3 6% 7% 30%	1400
	11th to 20th	Night	17% 7% 3 7% 4 5% 5% 4 6% 8% 37%	1400
	21st to end	Night	24% 8% 3 6% 4 4 4 4 5% 6% 32%	1400
July	1st to 10th	Night	13% 6% 2 7% 5% 6% 5% 5% 6% 9% 35%	3393
	11th to 20th	Night	18% 7% 2 8% 4 3 4 3 5% 8% 37%	3600
	21st to end	Night	11% 5% 2 5% 4 5% 4 4 7% 9% 45%	3926
August	1st to 10th	Night	21% 7% 3 7% 5% 5% 5% 4 5% 5% 33%	2868
	11th to 20th	Night	16% 10% 2 7% 5% 5% 5% 4 6% 7% 34%	2872
	21st to end	Night	13% 7% 2 5% 4 4 4 3 5% 7% 46%	3272
September	1st to 10th	Night	13% 5% 1 4 3 3 4 4 4 7% 51%	2075
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 4 6% 52%	2200
	21st to end	Night	18% 7% 3 5% 4 3 4 3 4 6% 43%	2200
October	1st to 10th	Night	19% 5% 2 7% 3 3 4 3 5% 6% 42%	2240
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 3 6% 6% 40%	2450
	21st to end	Night	24% 10% 2 6% 4 4 4 3 5% 5% 33%	2860
November	1st to 10th	Night	18% 9% 2 6% 4 5% 5% 3 5% 6% 37%	2667
	11th to 20th	Night	17% 7% 2 7% 5% 4 4 4 6% 7% 37%	2763
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 7% 7% 33%	2940
December	1st to 10th	Night	16% 11% 3 8% 5% 4 6% 4 6% 7% 30%	5025
	11th to 20th	Night	22% 9% 2 6% 4 4 4 3 4 6% 35%	5741
	21st to end	Night	21% 11% 3 7% 3 4 3 3 4 5% 35%	7620

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	51% 4 12% 22% 10% 2	4662
	11th to 20th	Day	51% 3 10% 24% 10% 2	4680
	21st to end	Day	42% 4 11% 20% 19% 4	5124
February	1st to 10th	Day	51% 5% 9% 20% 12% 3	1864
	11th to 20th	Day	52% 4 11% 18% 13% 2	1975
	21st to end	Day	51% 4 11% 18% 12% 5%	1730
March	1st to 10th	Day	61% 4 7% 9% 14% 5%	4579
	11th to 20th	Day	54% 6% 13% 16% 10% 2	5079
	21st to end	Day	55% 4 5% 17% 16% 3	5624
April	1st to 10th	Day	55% 4 9% 15% 12% 4	2412
	11th to 20th	Day	49% 6% 9% 21% 14% 1	2536
	21st to end	Day	52% 4 8% 19% 13% 4	2600
May	1st to 10th	Day	60% 7% 10% 15% 7% 1	5897
	11th to 20th	Day	55% 7% 12% 18% 7% 3	5956
	21st to end	Day	48% 8% 12% 17% 13% 2	7174
June	1st to 10th	Day	52% 7% 14% 19% 9% 1	3000
	11th to 20th	Day	46% 5% 12% 21% 15% 2	3000
	21st to end	Day	53% 7% 11% 18% 9% 2	3000
July	1st to 10th	Day	46% 7% 18% 20% 9%	6487
	11th to 20th	Day	43% 7% 14% 24% 12% 1	6285
	21st to end	Day	40% 5% 13% 29% 12% 1	6728
August	1st to 10th	Day	46% 7% 14% 26% 6%	4233
	11th to 20th	Day	47% 7% 16% 22% 8%	4214
	21st to end	Day	39% 6% 13% 25% 15% 1	4623
September	1st to 10th	Day	36% 6% 14% 27% 16% 1	2325
	11th to 20th	Day	35% 4 10% 31% 19% 2	2200
	21st to end	Day	41% 6% 10% 28% 15% 1	2200
October	1st to 10th	Day	53% 5% 10% 21% 11%	3510
	11th to 20th	Day	40% 4 14% 28% 13% 1	3148
	21st to end	Day	41% 4 16% 20% 18% 1	3180
November	1st to 10th	Day	46% 6% 15% 19% 13% 1	1851
	11th to 20th	Day	45% 6% 12% 21% 13% 3	1853
	21st to end	Day	48% 6% 15% 21% 9% 1	1680
December	1st to 10th	Day	49% 5% 17% 15% 13% 1	2384
	11th to 20th	Day	44% 4 13% 17% 16% 5%	2688
	21st to end	Day	51% 4 11% 18% 12% 4	3581
January	1st to 10th	Night	51% 4 13% 19% 12% 1	8234
	11th to 20th	Night	56% 6% 12% 15% 9% 2	8280
	21st to end	Night	45% 4 11% 20% 17% 3	9057
February	1st to 10th	Night	49% 7% 11% 19% 12% 2	2755
	11th to 20th	Night	47% 5% 11% 20% 15% 2	2538
	21st to end	Night	50% 5% 8% 20% 14% 3	2076
March	1st to 10th	Night	60% 3 7% 13% 12% 5%	5494
	11th to 20th	Night	51% 7% 18% 16% 8% 1	5101
	21st to end	Night	55% 4 6% 19% 15% 2	5546
April	1st to 10th	Night	54% 4 7% 16% 16% 3	2011
	11th to 20th	Night	49% 6% 9% 20% 15% 2	1812
	21st to end	Night	52% 5% 10% 16% 14% 3	1800
May	1st to 10th	Night	58% 6% 13% 14% 8% 1	4060
	11th to 20th	Night	53% 8% 13% 19% 7% 1	3972
	21st to end	Night	46% 7% 14% 21% 12%	3712
June	1st to 10th	Night	52% 7% 12% 21% 9% 1	1400
	11th to 20th	Night	44% 8% 15% 20% 12% 2	1400
	21st to end	Night	52% 6% 13% 18% 10% 1	1400
July	1st to 10th	Night	43% 8% 18% 23% 9%	3353
	11th to 20th	Night	46% 7% 12% 28% 8%	3552
	21st to end	Night	34% 7% 17% 31% 10% 1	3809
August	1st to 10th	Night	52% 7% 11% 22% 7%	2858
	11th to 20th	Night	48% 7% 17% 19% 9% 1	2899
	21st to end	Night	37% 6% 14% 25% 17% 1	3272
September	1st to 10th	Night	33% 6% 14% 32% 15%	2075
	11th to 20th	Night	34% 6% 10% 30% 19% 1	2200
	21st to end	Night	42% 5% 10% 27% 15% 1	2200
October	1st to 10th	Night	44% 5% 12% 24% 14%	3656
	11th to 20th	Night	36% 4 13% 31% 16% 1	3986
	21st to end	Night	41% 4 13% 25% 14% 2	4610
November	1st to 10th	Night	46% 6% 13% 23% 12% 1	2667
	11th to 20th	Night	45% 6% 11% 22% 14% 2	2763
	21st to end	Night	47% 7% 15% 18% 11% 1	2940
December	1st to 10th	Night	50% 4 13% 24% 8%	5025
	11th to 20th	Night	48% 4 9% 19% 18% 2	5742
	21st to end	Night	52% 4 10% 17% 15% 1	7620

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	30% 22% 31% 14% 3	220
	11th to 20th	Day	34% 21% 31% 10% 2 1	220
	21st to end	Day	21% 22% 39% 16% 2	242
February	1st to 10th	Day	27% 17% 34% 17% 4	404
	11th to 20th	Day	25% 27% 34% 11% 3	492
	21st to end	Day	26% 24% 32% 15% 2	446
March	1st to 10th	Day	32% 23% 31% 12% 1	540
	11th to 20th	Day	29% 26% 29% 13% 3 1	540
	21st to end	Day	31% 24% 25% 13% 5% 1	594
April	1st to 10th	Day	37% 21% 26% 10% 5% 1	504
	11th to 20th	Day	34% 23% 28% 9% 5% 1	492
	21st to end	Day	32% 20% 29% 14% 3 1	500
May	1st to 10th	Day	34% 16% 30% 15% 4 1	503
	11th to 20th	Day	27% 18% 31% 18% 4 1	527
	21st to end	Day	24% 17% 33% 20% 6%	668
June	1st to 10th	Day	28% 14% 30% 19% 8% 1	730
	11th to 20th	Day	24% 14% 28% 21% 11% 2	730
	21st to end	Day	27% 11% 28% 23% 8% 1	730
July	1st to 10th	Day	21% 10% 35% 22% 10% 1	618
	11th to 20th	Day	19% 10% 37% 22% 10% 2	524
	21st to end	Day	16% 10% 35% 28% 9% 3	576
August	1st to 10th	Day	16% 9% 34% 29% 10% 2	526
	11th to 20th	Day	17% 10% 28% 27% 14% 4	519
	21st to end	Day	19% 12% 30% 25% 11% 3	583
September	1st to 10th	Day	16% 13% 31% 26% 12% 3	530
	11th to 20th	Day	18% 12% 27% 21% 15% 7%	530
	21st to end	Day	19% 15% 28% 23% 10% 6%	530
October	1st to 10th	Day	19% 15% 26% 22% 14% 3	507
	11th to 20th	Day	27% 16% 31% 16% 8% 2	420
	21st to end	Day	31% 17% 28% 20% 3	462
November	1st to 10th	Day	27% 19% 26% 20% 7%	425
	11th to 20th	Day	29% 16% 34% 13% 7% 1	430
	21st to end	Day	32% 20% 25% 18% 5%	430
December	1st to 10th	Day	29% 16% 34% 17% 4	241
	11th to 20th	Day	35% 25% 27% 11% 2	220
	21st to end	Day	31% 22% 26% 16% 5%	242
January	1st to 10th	Night	22% 19% 34% 23% 2	840
	11th to 20th	Night	25% 17% 32% 21% 3	840
	21st to end	Night	17% 20% 37% 21% 4	924
February	1st to 10th	Night	22% 18% 35% 22% 4	840
	11th to 20th	Night	21% 25% 35% 17% 2	823
	21st to end	Night	25% 17% 33% 23% 2	692
March	1st to 10th	Night	26% 16% 37% 19% 2	840
	11th to 20th	Night	24% 19% 33% 20% 4	840
	21st to end	Night	24% 19% 31% 20% 5%	924
April	1st to 10th	Night	30% 18% 32% 18% 2	805
	11th to 20th	Night	24% 17% 35% 19% 5%	628
	21st to end	Night	33% 15% 29% 20% 5%	600
May	1st to 10th	Night	28% 12% 32% 25% 4	600
	11th to 20th	Night	26% 12% 34% 21% 7%	569
	21st to end	Night	21% 8% 33% 32% 5% 1	433
June	1st to 10th	Night	23% 10% 31% 30% 6%	400
	11th to 20th	Night	20% 8% 32% 32% 9%	400
	21st to end	Night	28% 7% 26% 31% 8%	400
July	1st to 10th	Night	17% 4 33% 36% 10%	390
	11th to 20th	Night	20% 4 24% 39% 13%	388
	21st to end	Night	18% 4 26% 40% 11%	438
August	1st to 10th	Night	18% 6% 26% 33% 16%	563
	11th to 20th	Night	18% 6% 26% 36% 14% 1	592
	21st to end	Night	16% 6% 28% 35% 14% 1	683
September	1st to 10th	Night	15% 8% 28% 36% 12% 1	800
	11th to 20th	Night	19% 7% 25% 31% 16% 2	800
	21st to end	Night	20% 10% 31% 27% 12% 1	800
October	1st to 10th	Night	23% 8% 27% 30% 12%	800
	11th to 20th	Night	23% 13% 30% 24% 10% 1	800
	21st to end	Night	30% 14% 31% 21% 4	880
November	1st to 10th	Night	25% 15% 31% 22% 7%	820
	11th to 20th	Night	23% 15% 31% 23% 8% 1	858
	21st to end	Night	28% 15% 29% 23% 5%	950
December	1st to 10th	Night	28% 13% 33% 21% 5%	950
	11th to 20th	Night	26% 19% 29% 21% 3	950
	21st to end	Night	29% 19% 31% 18% 4	1034

Page generated at 2026-03-30 02:18:42. Version ac07

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