Oak Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oak Hills 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	16% 10% 3 8% 5% 4 4 4 5% 7% 33%	101548
	Night	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	97418
Transparency	Day	49% 6% 12% 21% 11% 1	101306
	Night	50% 6% 12% 20% 11% 1	97280
Seeing	Day	23% 15% 31% 19% 9% 3	14468
	Night	22% 13% 30% 25% 9% 1	23650

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% 5% 10% 5% 5% 4 3 4 5% 28%	2517
	11th to 20th	Day	13% 17% 7% 13% 6% 6% 5% 3 4 4 22%	2520
	21st to end	Day	19% 19% 6% 14% 6% 5% 3 2 3 3 19%	3069
February	1st to 10th	Day	14% 17% 4 10% 7% 5% 5% 3 5% 6% 23%	1710
	11th to 20th	Day	13% 15% 4 11% 7% 5% 5% 3 4 4 29%	1663
	21st to end	Day	19% 13% 5% 8% 7% 6% 4 3 4 5% 24%	1523
March	1st to 10th	Day	22% 12% 4 9% 5% 4 3 3 4 7% 29%	3266
	11th to 20th	Day	10% 17% 4 10% 6% 4 5% 4 5% 5% 31%	3480
	21st to end	Day	14% 10% 3 6% 4 3 3 3 4 6% 44%	3928
April	1st to 10th	Day	20% 13% 4 8% 5% 4 4 2 3 5% 32%	2280
	11th to 20th	Day	21% 8% 3 5% 4 4 3 3 5% 5% 37%	2254
	21st to end	Day	21% 10% 3 8% 6% 3 4 3 4 5% 32%	2422
May	1st to 10th	Day	20% 8% 2 7% 5% 4 5% 4 5% 6% 33%	4354
	11th to 20th	Day	16% 10% 3 8% 5% 5% 4 3 6% 8% 32%	4398
	21st to end	Day	13% 6% 2 6% 4 4 5% 4 5% 8% 42%	4837
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 5% 7% 7% 29%	2660
	11th to 20th	Day	15% 6% 2 5% 5% 5% 4 5% 7% 9% 37%	2660
	21st to end	Day	17% 8% 3 6% 5% 4 5% 4 6% 8% 34%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 6% 4 7% 10% 36%	4440
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 5% 7% 10% 41%	4440
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 4 7% 9% 41%	4814
August	1st to 10th	Day	16% 8% 3 7% 4 5% 5% 4 6% 8% 35%	4140
	11th to 20th	Day	17% 7% 2 7% 4 5% 4 4 7% 9% 35%	4044
	21st to end	Day	12% 6% 2 7% 4 4 5% 4 7% 9% 40%	4212
September	1st to 10th	Day	12% 7% 3 7% 4 4 5% 3 6% 8% 42%	2280
	11th to 20th	Day	11% 6% 2 6% 3 3 4 4 5% 8% 49%	2280
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 8% 38%	1997
October	1st to 10th	Day	19% 9% 3 7% 4 4 4 3 5% 7% 35%	1900
	11th to 20th	Day	21% 9% 3 8% 4 5% 5% 4 5% 7% 29%	1900
	21st to end	Day	25% 11% 4 7% 5% 5% 5% 3 4 6% 26%	2024
November	1st to 10th	Day	15% 9% 3 8% 5% 5% 4 5% 6% 6% 34%	1638
	11th to 20th	Day	17% 13% 4 9% 5% 4 4 3 5% 6% 30%	1520
	21st to end	Day	22% 13% 5% 8% 5% 4 4 4 5% 6% 24%	1520
December	1st to 10th	Day	20% 16% 5% 10% 5% 5% 5% 4 5% 6% 19%	1520
	11th to 20th	Day	18% 17% 5% 9% 4 4 4 3 4 5% 27%	1906
	21st to end	Day	28% 17% 4 11% 5% 4 3 2 3 4 20%	2772
January	1st to 10th	Night	19% 14% 6% 11% 7% 5% 5% 3 5% 5% 21%	4429
	11th to 20th	Night	14% 14% 5% 12% 8% 6% 6% 4 6% 5% 21%	4440
	21st to end	Night	19% 16% 7% 11% 6% 5% 4 3 5% 4 20%	4582
February	1st to 10th	Night	14% 15% 4 11% 6% 5% 5% 4 5% 5% 25%	2470
	11th to 20th	Night	13% 15% 6% 9% 6% 5% 4 4 5% 5% 28%	2403
	21st to end	Night	16% 12% 4 8% 5% 4 5% 4 6% 6% 30%	1930
March	1st to 10th	Night	19% 11% 3 8% 5% 4 4 3 5% 5% 32%	3570
	11th to 20th	Night	17% 15% 4 9% 5% 4 4 4 5% 6% 27%	3479
	21st to end	Night	15% 10% 3 6% 3 4 4 3 5% 6% 40%	3703
April	1st to 10th	Night	19% 12% 3 8% 4 3 4 3 4 6% 35%	1900
	11th to 20th	Night	18% 8% 2 7% 4 4 5% 3 5% 5% 38%	1875
	21st to end	Night	19% 8% 4 7% 4 5% 5% 3 5% 7% 34%	1774
May	1st to 10th	Night	21% 10% 3 6% 4 4 4 4 5% 7% 34%	2584
	11th to 20th	Night	17% 9% 2 7% 4 4 4 4 6% 6% 38%	2495
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 4 7% 45%	2738
June	1st to 10th	Night	15% 7% 2 8% 6% 5% 5% 4 5% 8% 35%	1520
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 4 5% 8% 44%	1520
	21st to end	Night	14% 7% 2 6% 5% 5% 3 4 6% 8% 39%	1520
July	1st to 10th	Night	9% 5% 2 7% 6% 6% 5% 5% 6% 8% 41%	2520
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 6% 8% 47%	2520
	21st to end	Night	10% 6% 2 5% 4 4 4 4 6% 8% 48%	2739
August	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 7% 44%	2786
	11th to 20th	Night	14% 6% 2 5% 4 3 4 4 6% 7% 45%	2785
	21st to end	Night	10% 4 2 6% 4 4 6% 4 7% 10% 44%	3411
September	1st to 10th	Night	12% 6% 2 6% 4 3 5% 3 5% 7% 47%	1900
	11th to 20th	Night	12% 4 2 5% 4 4 3 4 5% 6% 52%	1900
	21st to end	Night	17% 6% 2 6% 5% 4 5% 4 5% 6% 43%	2180
October	1st to 10th	Night	15% 8% 2 7% 4 4 4 4 5% 7% 39%	2280
	11th to 20th	Night	20% 9% 3 8% 6% 5% 4 3 5% 6% 32%	2280
	21st to end	Night	22% 10% 4 8% 5% 5% 4 3 5% 6% 29%	2574
November	1st to 10th	Night	18% 9% 3 6% 4 5% 3 3 5% 7% 36%	2459
	11th to 20th	Night	18% 10% 3 8% 5% 4 5% 3 5% 6% 32%	2660
	21st to end	Night	20% 13% 3 8% 5% 5% 4 4 6% 5% 27%	2660
December	1st to 10th	Night	21% 15% 5% 9% 5% 5% 5% 4 6% 7% 20%	2660
	11th to 20th	Night	19% 16% 4 9% 5% 4 3 3 4 5% 28%	3288
	21st to end	Night	30% 16% 4 9% 5% 4 4 3 4 5% 16%	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	56% 8% 15% 13% 6% 2	2518
	11th to 20th	Day	66% 5% 12% 10% 7%	2520
	21st to end	Day	71% 4 8% 10% 5% 1	3069
February	1st to 10th	Day	61% 6% 11% 16% 5% 1	1710
	11th to 20th	Day	61% 4 9% 15% 11% 1	1672
	21st to end	Day	62% 5% 9% 11% 11% 1	1523
March	1st to 10th	Day	56% 4 13% 16% 10% 1	3269
	11th to 20th	Day	53% 5% 15% 16% 10% 2	3480
	21st to end	Day	41% 4 9% 26% 16% 4	3928
April	1st to 10th	Day	55% 4 8% 18% 12% 3	2280
	11th to 20th	Day	48% 5% 8% 22% 15% 2	2254
	21st to end	Day	54% 5% 8% 17% 13% 3	2422
May	1st to 10th	Day	50% 6% 9% 22% 11% 2	4368
	11th to 20th	Day	47% 9% 12% 20% 10% 2	4402
	21st to end	Day	38% 7% 13% 24% 15% 2	4837
June	1st to 10th	Day	49% 9% 11% 17% 13% 1	2660
	11th to 20th	Day	41% 8% 11% 24% 14% 2	2660
	21st to end	Day	45% 7% 14% 19% 13% 1	2660
July	1st to 10th	Day	41% 6% 14% 25% 13% 1	4370
	11th to 20th	Day	36% 7% 14% 33% 10%	4365
	21st to end	Day	38% 7% 14% 29% 11%	4661
August	1st to 10th	Day	45% 6% 15% 22% 12% 1	4126
	11th to 20th	Day	44% 6% 14% 27% 9% 1	4083
	21st to end	Day	40% 5% 13% 31% 10% 1	4212
September	1st to 10th	Day	38% 9% 12% 27% 12% 1	2280
	11th to 20th	Day	33% 6% 13% 31% 15% 1	2280
	21st to end	Day	44% 8% 12% 27% 10%	1997
October	1st to 10th	Day	49% 7% 11% 21% 12% 1	1900
	11th to 20th	Day	53% 6% 14% 18% 7% 1	1900
	21st to end	Day	60% 5% 10% 17% 8%	2024
November	1st to 10th	Day	48% 7% 15% 20% 9% 1	1638
	11th to 20th	Day	55% 5% 12% 17% 10% 1	1520
	21st to end	Day	59% 8% 12% 12% 8%	1520
December	1st to 10th	Day	65% 7% 11% 11% 6%	1520
	11th to 20th	Day	61% 5% 15% 12% 7%	1906
	21st to end	Day	70% 5% 7% 14% 5%	2772
January	1st to 10th	Night	62% 9% 12% 12% 5%	4429
	11th to 20th	Night	63% 9% 12% 11% 5% 1	4440
	21st to end	Night	66% 7% 10% 11% 6% 1	4582
February	1st to 10th	Night	59% 7% 11% 16% 6% 1	2470
	11th to 20th	Night	57% 4 11% 19% 9% 1	2405
	21st to end	Night	52% 7% 12% 19% 10% 1	1930
March	1st to 10th	Night	54% 5% 8% 22% 11% 1	3580
	11th to 20th	Night	56% 6% 14% 16% 8% 1	3480
	21st to end	Night	41% 4 11% 22% 19% 3	3703
April	1st to 10th	Night	51% 4 8% 21% 14% 2	1900
	11th to 20th	Night	48% 6% 9% 20% 17% 1	1875
	21st to end	Night	49% 6% 10% 16% 16% 3	1774
May	1st to 10th	Night	50% 5% 11% 18% 13% 3	2590
	11th to 20th	Night	44% 8% 12% 24% 10% 2	2496
	21st to end	Night	38% 7% 13% 20% 20% 2	2739
June	1st to 10th	Night	44% 8% 13% 22% 13% 1	1520
	11th to 20th	Night	38% 5% 13% 22% 20% 2	1520
	21st to end	Night	41% 8% 14% 22% 13% 2	1520
July	1st to 10th	Night	39% 6% 14% 23% 17% 2	2480
	11th to 20th	Night	37% 5% 12% 33% 13%	2472
	21st to end	Night	34% 6% 17% 30% 12% 1	2651
August	1st to 10th	Night	38% 6% 14% 28% 14% 1	2776
	11th to 20th	Night	38% 5% 15% 31% 11% 1	2812
	21st to end	Night	34% 7% 14% 33% 11% 1	3411
September	1st to 10th	Night	36% 7% 15% 27% 14% 1	1900
	11th to 20th	Night	31% 7% 14% 31% 16% 1	1900
	21st to end	Night	42% 7% 11% 28% 12% 1	2180
October	1st to 10th	Night	45% 7% 10% 23% 14% 1	2280
	11th to 20th	Night	52% 6% 13% 20% 8%	2280
	21st to end	Night	55% 6% 12% 16% 10%	2574
November	1st to 10th	Night	47% 5% 14% 21% 11% 1	2459
	11th to 20th	Night	51% 6% 12% 19% 10% 2	2660
	21st to end	Night	56% 8% 13% 16% 6%	2660
December	1st to 10th	Night	63% 7% 12% 14% 5%	2660
	11th to 20th	Night	60% 5% 11% 16% 8% 1	3288
	21st to end	Night	70% 6% 9% 11% 4	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	27% 23% 28% 18% 3 1	180
	11th to 20th	Day	28% 20% 33% 15% 4	180
	21st to end	Day	28% 21% 33% 14% 4	283
February	1st to 10th	Day	32% 26% 31% 9% 2	270
	11th to 20th	Day	28% 26% 38% 6% 1	270
	21st to end	Day	38% 18% 32% 10% 2	335
March	1st to 10th	Day	27% 18% 35% 14% 5%	460
	11th to 20th	Day	28% 21% 32% 15% 4 1	460
	21st to end	Day	33% 20% 28% 13% 6% 1	506
April	1st to 10th	Day	30% 18% 34% 12% 5% 1	460
	11th to 20th	Day	34% 20% 22% 13% 8% 3	452
	21st to end	Day	28% 20% 33% 10% 7% 2	460
May	1st to 10th	Day	26% 15% 30% 19% 8% 3	463
	11th to 20th	Day	20% 14% 34% 21% 8% 3	487
	21st to end	Day	16% 17% 34% 19% 10% 3	529
June	1st to 10th	Day	24% 13% 33% 22% 6% 2	490
	11th to 20th	Day	16% 15% 33% 23% 12% 2	490
	21st to end	Day	22% 13% 33% 19% 9% 3	490
July	1st to 10th	Day	13% 9% 30% 32% 13% 4	485
	11th to 20th	Day	15% 9% 29% 28% 14% 4	484
	21st to end	Day	13% 8% 37% 27% 12% 3	532
August	1st to 10th	Day	14% 10% 27% 29% 14% 6%	486
	11th to 20th	Day	13% 8% 27% 29% 17% 6%	479
	21st to end	Day	15% 10% 32% 23% 12% 8%	539
September	1st to 10th	Day	15% 12% 30% 24% 12% 7%	490
	11th to 20th	Day	13% 9% 23% 24% 19% 12%	490
	21st to end	Day	20% 11% 27% 24% 12% 5%	490
October	1st to 10th	Day	24% 18% 24% 18% 11% 6%	490
	11th to 20th	Day	26% 18% 31% 17% 7% 2	490
	21st to end	Day	30% 19% 30% 18% 4	504
November	1st to 10th	Day	29% 16% 27% 19% 8% 1	326
	11th to 20th	Day	31% 19% 32% 13% 4 1	180
	21st to end	Day	27% 19% 36% 13% 3 2	180
December	1st to 10th	Day	31% 17% 35% 14% 3 1	180
	11th to 20th	Day	37% 21% 28% 10% 3 1	180
	21st to end	Day	37% 21% 31% 10% 2	198
January	1st to 10th	Night	29% 18% 30% 20% 4	760
	11th to 20th	Night	27% 17% 31% 20% 5%	760
	21st to end	Night	21% 14% 35% 24% 4 1	836
February	1st to 10th	Night	22% 19% 37% 20% 2	760
	11th to 20th	Night	23% 17% 38% 18% 4	743
	21st to end	Night	26% 19% 32% 20% 3	628
March	1st to 10th	Night	22% 18% 36% 21% 4	760
	11th to 20th	Night	25% 19% 30% 22% 3 1	760
	21st to end	Night	23% 14% 35% 20% 7% 1	836
April	1st to 10th	Night	26% 16% 33% 22% 4	760
	11th to 20th	Night	24% 20% 29% 18% 8% 1	751
	21st to end	Night	23% 14% 28% 24% 11%	634
May	1st to 10th	Night	24% 9% 28% 27% 10% 2	424
	11th to 20th	Night	16% 11% 33% 32% 9%	374
	21st to end	Night	13% 9% 34% 32% 11% 1	411
June	1st to 10th	Night	16% 8% 34% 32% 10%	380
	11th to 20th	Night	14% 7% 33% 34% 11% 1	380
	21st to end	Night	17% 6% 28% 38% 11% 1	380
July	1st to 10th	Night	6% 9% 29% 39% 16% 1	370
	11th to 20th	Night	13% 4 28% 35% 20% 1	368
	21st to end	Night	12% 3 26% 44% 14%	416
August	1st to 10th	Night	11% 4 27% 32% 24% 2	541
	11th to 20th	Night	11% 6% 21% 35% 24% 3	564
	21st to end	Night	12% 5% 29% 33% 18% 2	797
September	1st to 10th	Night	15% 6% 30% 30% 16% 3	760
	11th to 20th	Night	14% 6% 23% 26% 28% 4	760
	21st to end	Night	19% 9% 23% 28% 18% 3	760
October	1st to 10th	Night	19% 13% 26% 25% 16% 2	760
	11th to 20th	Night	25% 12% 30% 24% 9% 1	760
	21st to end	Night	28% 13% 30% 23% 6%	836
November	1st to 10th	Night	25% 12% 28% 26% 9%	745
	11th to 20th	Night	24% 16% 32% 19% 7% 1	760
	21st to end	Night	29% 15% 29% 21% 6%	760
December	1st to 10th	Night	31% 17% 30% 19% 3	760
	11th to 20th	Night	28% 16% 34% 18% 3 1	760
	21st to end	Night	37% 14% 30% 17% 3	836

Page generated at 2024-10-30 01:22:55. Version ac07

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