The Hughesville Sky-view Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Hughesville Sky-view Observatory clear sky chart from 2005-11-06 to 2024-07-16.

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% 6% 2 6% 4 4 4 4 6% 8% 42%	89769
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	89666
Transparency	Day	39% 7% 11% 24% 16% 3	89528
	Night	39% 6% 11% 24% 17% 3	89511
Seeing	Day	18% 15% 29% 23% 10% 4	14620
	Night	18% 14% 29% 27% 11% 1	24130

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% 6% 2 4 3 3 2 4 5% 6% 48%	2580
	11th to 20th	Day	16% 9% 3 7% 4 4 4 3 5% 5% 41%	2840
	21st to end	Day	17% 11% 3 7% 5% 4 4 3 5% 6% 36%	3124
February	1st to 10th	Day	14% 8% 3 6% 4 5% 5% 5% 5% 6% 39%	1710
	11th to 20th	Day	18% 7% 2 5% 4 3 4 3 5% 6% 43%	1748
	21st to end	Day	16% 10% 3 6% 4 5% 4 3 4 6% 38%	1570
March	1st to 10th	Day	22% 8% 2 5% 4 3 4 3 5% 7% 36%	3338
	11th to 20th	Day	11% 4 1 4 4 4 4 3 5% 7% 52%	3480
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 6% 39%	3905
April	1st to 10th	Day	12% 7% 2 5% 5% 4 4 4 5% 8% 44%	2280
	11th to 20th	Day	12% 7% 2 5% 4 4 4 3 5% 7% 48%	2254
	21st to end	Day	16% 7% 2 5% 4 4 4 4 4 7% 42%	2280
May	1st to 10th	Day	23% 8% 3 6% 4 5% 5% 4 6% 9% 29%	3925
	11th to 20th	Day	21% 6% 2 6% 5% 4 5% 4 6% 8% 32%	4302
	21st to end	Day	10% 5% 2 5% 4 5% 5% 4 7% 10% 44%	4823
June	1st to 10th	Day	11% 4 2 5% 5% 5% 5% 4 6% 10% 42%	2660
	11th to 20th	Day	10% 5% 1 5% 4 5% 5% 5% 7% 9% 43%	2660
	21st to end	Day	9% 3 2 5% 6% 5% 6% 5% 7% 11% 42%	2660
July	1st to 10th	Day	8% 6% 3 7% 4 6% 5% 5% 7% 10% 41%	2660
	11th to 20th	Day	5% 4 2 5% 6% 5% 5% 5% 8% 12% 44%	2531
	21st to end	Day	9% 5% 2 6% 5% 6% 6% 6% 9% 9% 36%	2547
August	1st to 10th	Day	9% 6% 3 7% 5% 5% 7% 5% 7% 10% 35%	2327
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 5% 7% 10% 38%	2177
	21st to end	Day	9% 6% 2 6% 5% 4 6% 5% 7% 9% 42%	2376
September	1st to 10th	Day	14% 5% 2 6% 4 4 4 4 5% 8% 45%	2160
	11th to 20th	Day	11% 6% 2 5% 4 4 4 3 6% 9% 46%	2160
	21st to end	Day	17% 9% 3 5% 4 4 4 4 5% 6% 39%	1908
October	1st to 10th	Day	16% 5% 2 4 4 4 4 3 5% 6% 46%	1800
	11th to 20th	Day	17% 4 2 5% 3 4 3 3 4 5% 51%	1800
	21st to end	Day	13% 6% 2 7% 3 4 3 3 5% 6% 47%	1980
November	1st to 10th	Day	12% 5% 1 4 4 3 3 3 5% 7% 53%	1743
	11th to 20th	Day	14% 6% 1 4 3 3 4 3 6% 5% 51%	1710
	21st to end	Day	14% 6% 2 5% 3 4 3 3 4 6% 50%	1549
December	1st to 10th	Day	16% 6% 2 5% 3 4 4 4 5% 8% 41%	1520
	11th to 20th	Day	15% 8% 2 5% 3 3 4 3 4 5% 48%	1910
	21st to end	Day	16% 8% 2 7% 4 4 4 4 6% 7% 38%	2772
January	1st to 10th	Night	14% 8% 3 6% 3 4 4 3 4 6% 46%	4365
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 5% 5% 46%	4120
	21st to end	Night	19% 9% 3 6% 4 3 3 3 4 5% 42%	4532
February	1st to 10th	Night	15% 7% 2 6% 3 4 4 4 5% 6% 43%	2470
	11th to 20th	Night	18% 8% 3 6% 3 3 4 2 4 5% 44%	2315
	21st to end	Night	17% 9% 2 4 3 3 4 3 4 7% 43%	1884
March	1st to 10th	Night	21% 8% 3 7% 4 3 3 3 5% 5% 38%	3512
	11th to 20th	Night	12% 5% 2 4 3 4 4 3 5% 8% 50%	3480
	21st to end	Night	16% 8% 3 6% 4 3 3 2 4 5% 47%	3725
April	1st to 10th	Night	15% 8% 1 5% 4 4 4 3 5% 8% 42%	1900
	11th to 20th	Night	13% 5% 2 6% 4 3 4 3 5% 6% 49%	1875
	21st to end	Night	18% 5% 2 5% 4 4 4 3 6% 8% 42%	1900
May	1st to 10th	Night	21% 10% 3 6% 4 4 4 4 6% 7% 32%	2984
	11th to 20th	Night	21% 9% 2 6% 5% 4 3 3 6% 8% 33%	2576
	21st to end	Night	10% 5% 2 6% 4 5% 4 4 7% 10% 43%	2732
June	1st to 10th	Night	10% 6% 2 5% 4 3 4 5% 7% 11% 41%	1520
	11th to 20th	Night	10% 6% 3 6% 5% 4 4 5% 6% 10% 40%	1520
	21st to end	Night	9% 5% 2 5% 5% 3 6% 5% 8% 11% 42%	1520
July	1st to 10th	Night	7% 5% 3 7% 5% 5% 5% 4 8% 11% 40%	1520
	11th to 20th	Night	5% 5% 2 6% 5% 5% 5% 5% 6% 10% 45%	1546
	21st to end	Night	7% 4 2 6% 7% 5% 5% 5% 8% 11% 39%	1771
August	1st to 10th	Night	8% 5% 2 7% 4 5% 6% 6% 6% 9% 41%	1611
	11th to 20th	Night	10% 6% 3 8% 5% 5% 5% 6% 7% 8% 36%	1705
	21st to end	Night	10% 6% 3 7% 5% 4 4 4 6% 9% 42%	1980
September	1st to 10th	Night	13% 6% 3 5% 4 4 4 3 5% 8% 45%	1800
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	1800
	21st to end	Night	18% 8% 2 6% 4 4 3 4 6% 7% 39%	2047
October	1st to 10th	Night	16% 6% 2 6% 4 4 4 4 4 6% 45%	2160
	11th to 20th	Night	15% 6% 2 6% 4 3 3 3 4 5% 50%	2160
	21st to end	Night	15% 5% 2 5% 4 4 4 3 4 7% 48%	2376
November	1st to 10th	Night	12% 7% 2 5% 3 3 3 2 4 5% 53%	2332
	11th to 20th	Night	15% 7% 2 5% 3 4 3 2 5% 5% 49%	2470
	21st to end	Night	12% 5% 1 4 4 4 4 4 5% 7% 50%	2629
December	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 5% 7% 42%	2660
	11th to 20th	Night	17% 6% 2 5% 4 4 4 3 5% 7% 44%	3285
	21st to end	Night	15% 8% 2 6% 4 5% 4 4 6% 8% 37%	4884

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	36% 5% 7% 31% 17% 4	2581
	11th to 20th	Day	43% 4 10% 21% 16% 5%	2840
	21st to end	Day	46% 7% 11% 21% 12% 2	3124
February	1st to 10th	Day	44% 6% 11% 25% 12% 2	1710
	11th to 20th	Day	41% 5% 8% 24% 18% 4	1757
	21st to end	Day	47% 4 12% 17% 16% 4	1570
March	1st to 10th	Day	47% 5% 9% 22% 14% 4	3338
	11th to 20th	Day	30% 6% 8% 28% 23% 5%	3480
	21st to end	Day	45% 5% 10% 20% 17% 4	3905
April	1st to 10th	Day	37% 7% 11% 22% 18% 6%	2280
	11th to 20th	Day	35% 5% 10% 22% 21% 6%	2254
	21st to end	Day	41% 5% 10% 22% 16% 5%	2280
May	1st to 10th	Day	50% 8% 11% 18% 11% 2	3960
	11th to 20th	Day	46% 9% 13% 22% 9% 1	4306
	21st to end	Day	32% 8% 14% 25% 17% 3	4837
June	1st to 10th	Day	35% 7% 14% 27% 15% 1	2660
	11th to 20th	Day	34% 9% 14% 24% 17% 2	2660
	21st to end	Day	33% 8% 15% 25% 17% 2	2660
July	1st to 10th	Day	36% 9% 14% 22% 15% 3	2590
	11th to 20th	Day	29% 9% 18% 27% 14% 2	2456
	21st to end	Day	37% 10% 14% 21% 17% 1	2405
August	1st to 10th	Day	40% 9% 14% 25% 11%	2314
	11th to 20th	Day	39% 8% 16% 22% 14% 1	2177
	21st to end	Day	36% 8% 14% 24% 14% 4	2376
September	1st to 10th	Day	38% 6% 13% 21% 18% 4	2160
	11th to 20th	Day	34% 6% 10% 26% 20% 4	2160
	21st to end	Day	45% 6% 8% 21% 17% 3	1908
October	1st to 10th	Day	38% 6% 9% 25% 19% 3	1800
	11th to 20th	Day	36% 4 8% 26% 22% 4	1800
	21st to end	Day	37% 5% 7% 26% 21% 4	1980
November	1st to 10th	Day	32% 4 11% 28% 21% 5%	1743
	11th to 20th	Day	34% 4 11% 23% 22% 5%	1710
	21st to end	Day	36% 3 10% 28% 20% 3	1549
December	1st to 10th	Day	41% 6% 13% 25% 12% 4	1520
	11th to 20th	Day	38% 4 9% 31% 14% 3	1906
	21st to end	Day	43% 7% 12% 26% 12% 1	2772
January	1st to 10th	Night	39% 4 8% 26% 18% 4	4365
	11th to 20th	Night	41% 3 9% 24% 19% 4	4120
	21st to end	Night	45% 4 7% 26% 16% 1	4532
February	1st to 10th	Night	41% 4 11% 26% 16% 2	2470
	11th to 20th	Night	44% 3 8% 21% 19% 6%	2317
	21st to end	Night	41% 4 11% 22% 16% 5%	1884
March	1st to 10th	Night	47% 5% 8% 24% 14% 2	3512
	11th to 20th	Night	30% 6% 10% 28% 22% 4	3480
	21st to end	Night	41% 5% 8% 21% 20% 6%	3725
April	1st to 10th	Night	41% 5% 9% 20% 21% 4	1900
	11th to 20th	Night	35% 5% 11% 21% 21% 5%	1875
	21st to end	Night	39% 6% 11% 25% 14% 5%	1900
May	1st to 10th	Night	50% 7% 11% 20% 10% 2	3014
	11th to 20th	Night	48% 8% 13% 21% 10% 1	2577
	21st to end	Night	33% 8% 17% 25% 15% 3	2739
June	1st to 10th	Night	35% 9% 13% 25% 16% 2	1520
	11th to 20th	Night	37% 7% 14% 25% 14% 3	1520
	21st to end	Night	34% 7% 18% 20% 19% 3	1520
July	1st to 10th	Night	36% 9% 19% 19% 13% 4	1480
	11th to 20th	Night	32% 9% 18% 25% 15% 2	1498
	21st to end	Night	34% 9% 16% 27% 14%	1672
August	1st to 10th	Night	36% 9% 18% 22% 14% 1	1600
	11th to 20th	Night	42% 9% 15% 21% 12% 1	1705
	21st to end	Night	38% 7% 15% 23% 15% 3	1980
September	1st to 10th	Night	38% 5% 13% 22% 17% 6%	1800
	11th to 20th	Night	32% 6% 11% 25% 22% 3	1800
	21st to end	Night	44% 6% 10% 20% 17% 3	2047
October	1st to 10th	Night	40% 5% 10% 24% 18% 4	2160
	11th to 20th	Night	37% 4 8% 27% 21% 3	2160
	21st to end	Night	36% 4 8% 26% 22% 4	2376
November	1st to 10th	Night	35% 4 9% 26% 21% 6%	2332
	11th to 20th	Night	38% 3 9% 21% 22% 6%	2470
	21st to end	Night	33% 4 11% 26% 22% 4	2629
December	1st to 10th	Night	42% 4 11% 25% 15% 3	2660
	11th to 20th	Night	40% 4 9% 23% 19% 4	3288
	21st to end	Night	42% 8% 14% 23% 11% 1	4884

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	25% 30% 29% 11% 4 1	198
	11th to 20th	Day	28% 29% 29% 12% 2	270
	21st to end	Day	22% 32% 34% 9% 2	297
February	1st to 10th	Day	21% 29% 36% 11% 3	270
	11th to 20th	Day	31% 25% 33% 9% 1	355
	21st to end	Day	30% 26% 31% 12% 2	382
March	1st to 10th	Day	23% 28% 32% 14% 2 1	460
	11th to 20th	Day	26% 26% 31% 13% 3 1	460
	21st to end	Day	23% 23% 35% 15% 4 1	506
April	1st to 10th	Day	20% 26% 36% 13% 5%	460
	11th to 20th	Day	18% 20% 36% 17% 7% 2	452
	21st to end	Day	23% 20% 34% 17% 5% 1	460
May	1st to 10th	Day	25% 18% 30% 17% 8% 2	463
	11th to 20th	Day	22% 15% 32% 22% 7% 1	487
	21st to end	Day	19% 8% 28% 29% 13% 4	529
June	1st to 10th	Day	12% 12% 30% 27% 16% 3	490
	11th to 20th	Day	13% 8% 33% 28% 15% 3	490
	21st to end	Day	11% 9% 31% 33% 13% 3	490
July	1st to 10th	Day	11% 4 22% 36% 20% 7%	485
	11th to 20th	Day	4 3 20% 43% 22% 8%	465
	21st to end	Day	11% 3 25% 34% 19% 7%	488
August	1st to 10th	Day	11% 7% 21% 34% 20% 7%	446
	11th to 20th	Day	12% 4 19% 36% 21% 8%	439
	21st to end	Day	11% 5% 23% 32% 18% 12%	495
September	1st to 10th	Day	16% 6% 21% 27% 16% 14%	450
	11th to 20th	Day	13% 6% 27% 30% 13% 11%	450
	21st to end	Day	26% 11% 27% 23% 10% 4	450
October	1st to 10th	Day	20% 10% 26% 24% 16% 4	450
	11th to 20th	Day	18% 16% 28% 25% 12% 2	450
	21st to end	Day	17% 16% 38% 18% 8% 2	495
November	1st to 10th	Day	17% 15% 34% 20% 10% 3	401
	11th to 20th	Day	19% 23% 29% 19% 8% 1	370
	21st to end	Day	19% 24% 31% 17% 10%	209
December	1st to 10th	Day	22% 25% 37% 12% 4 1	180
	11th to 20th	Day	24% 27% 27% 18% 4	180
	21st to end	Day	25% 24% 28% 19% 4 1	198
January	1st to 10th	Night	22% 23% 34% 17% 3	760
	11th to 20th	Night	22% 21% 31% 22% 4	760
	21st to end	Night	22% 22% 37% 18% 2	836
February	1st to 10th	Night	19% 21% 35% 22% 3	760
	11th to 20th	Night	25% 27% 34% 13% 2	743
	21st to end	Night	25% 22% 34% 16% 3	628
March	1st to 10th	Night	20% 22% 34% 21% 3	760
	11th to 20th	Night	23% 20% 35% 17% 5% 1	760
	21st to end	Night	20% 19% 40% 18% 4	836
April	1st to 10th	Night	21% 23% 34% 18% 3	760
	11th to 20th	Night	15% 16% 36% 26% 7%	751
	21st to end	Night	20% 14% 33% 24% 8%	760
May	1st to 10th	Night	20% 11% 35% 24% 10% 1	679
	11th to 20th	Night	17% 9% 33% 32% 8%	429
	21st to end	Night	14% 6% 25% 36% 17% 2	411
June	1st to 10th	Night	12% 4 27% 41% 16% 1	380
	11th to 20th	Night	12% 5% 25% 41% 15% 2	380
	21st to end	Night	9% 5% 27% 43% 13% 2	380
July	1st to 10th	Night	9% 4 20% 41% 24% 2	370
	11th to 20th	Night	7% 2 15% 43% 29% 4	418
	21st to end	Night	9% 3 22% 38% 25% 4	591
August	1st to 10th	Night	9% 2 16% 44% 26% 3	537
	11th to 20th	Night	12% 4 17% 41% 24% 2	641
	21st to end	Night	11% 4 18% 34% 27% 5%	792
September	1st to 10th	Night	17% 3 17% 34% 24% 4	720
	11th to 20th	Night	11% 4 16% 39% 25% 4	720
	21st to end	Night	23% 5% 25% 28% 18% 1	720
October	1st to 10th	Night	20% 7% 21% 31% 17% 5%	720
	11th to 20th	Night	18% 13% 25% 27% 15% 2	720
	21st to end	Night	20% 14% 30% 23% 12% 1	792
November	1st to 10th	Night	14% 13% 33% 27% 11% 2	740
	11th to 20th	Night	19% 18% 31% 24% 8% 1	760
	21st to end	Night	16% 20% 29% 25% 9% 1	760
December	1st to 10th	Night	24% 18% 30% 18% 9% 1	760
	11th to 20th	Night	20% 17% 37% 21% 5%	760
	21st to end	Night	20% 18% 31% 28% 4	836

Page generated at 2024-07-13 10:19:53. Version ac07

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