Pit Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pit Road clear sky chart from 2005-11-06 to 2024-11-25.

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% 4 9% 5% 4 4 4 5% 6% 32%	101781
	Night	16% 12% 4 9% 5% 5% 4 3 5% 6% 30%	97707
Transparency	Day	50% 7% 12% 21% 10% 1	105303
	Night	52% 6% 12% 19% 9% 1	102274
Seeing	Day	22% 16% 30% 20% 9% 3	14448
	Night	22% 13% 30% 25% 9% 1	23608

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% 6% 14% 9% 5% 4 3 4 4 21%	2517
	11th to 20th	Day	13% 13% 7% 18% 7% 5% 4 3 4 6% 19%	2520
	21st to end	Day	15% 20% 8% 15% 7% 6% 3 2 3 3 18%	2973
February	1st to 10th	Day	12% 15% 6% 15% 8% 5% 5% 4 5% 5% 21%	1710
	11th to 20th	Day	12% 15% 6% 11% 6% 5% 4 4 6% 6% 25%	1663
	21st to end	Day	18% 15% 4 9% 6% 5% 5% 3 5% 5% 25%	1518
March	1st to 10th	Day	19% 15% 5% 10% 5% 4 4 3 3 5% 27%	3228
	11th to 20th	Day	11% 16% 6% 13% 6% 4 4 3 4 5% 27%	3480
	21st to end	Day	12% 8% 3 7% 5% 4 3 3 5% 6% 44%	3958
April	1st to 10th	Day	21% 14% 3 7% 5% 3 4 4 4 5% 30%	2280
	11th to 20th	Day	22% 10% 3 7% 4 3 3 3 4 5% 35%	2254
	21st to end	Day	23% 9% 3 8% 5% 4 3 3 4 6% 33%	2438
May	1st to 10th	Day	20% 8% 3 8% 5% 4 5% 3 6% 6% 32%	4426
	11th to 20th	Day	16% 9% 3 7% 5% 4 4 4 5% 8% 35%	4398
	21st to end	Day	16% 7% 2 7% 5% 4 4 4 6% 6% 38%	4837
June	1st to 10th	Day	20% 9% 3 8% 6% 4 4 4 6% 6% 30%	2660
	11th to 20th	Day	16% 6% 2 6% 4 4 4 5% 6% 7% 39%	2660
	21st to end	Day	17% 7% 2 7% 6% 5% 6% 5% 6% 7% 32%	2660
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 6% 5% 7% 8% 35%	4440
	11th to 20th	Day	12% 6% 2 6% 5% 4 6% 4 7% 8% 40%	4440
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 7% 47%	4814
August	1st to 10th	Day	13% 7% 3 8% 5% 5% 5% 4 6% 7% 34%	4245
	11th to 20th	Day	17% 6% 2 7% 4 4 4 4 6% 8% 37%	4044
	21st to end	Day	10% 5% 2 6% 5% 4 5% 4 8% 10% 40%	4222
September	1st to 10th	Day	13% 6% 3 7% 4 4 4 4 6% 8% 41%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 5% 4 3 5% 6% 45%	2280
	21st to end	Day	18% 7% 3 7% 4 4 4 3 5% 7% 37%	2004
October	1st to 10th	Day	20% 8% 3 8% 6% 4 5% 4 4 6% 34%	1900
	11th to 20th	Day	21% 11% 4 9% 5% 3 4 4 4 6% 27%	1900
	21st to end	Day	25% 12% 3 8% 5% 4 4 3 5% 6% 24%	1986
November	1st to 10th	Day	14% 13% 3 8% 4 4 4 3 4 7% 34%	1696
	11th to 20th	Day	16% 14% 5% 9% 6% 5% 5% 4 5% 6% 26%	1600
	21st to end	Day	21% 18% 4 11% 6% 6% 4 3 5% 5% 17%	1552
December	1st to 10th	Day	20% 20% 6% 11% 7% 4 5% 3 4 4 16%	1520
	11th to 20th	Day	20% 17% 4 10% 6% 4 3 3 4 6% 21%	1906
	21st to end	Day	26% 20% 5% 14% 5% 3 2 2 3 3 18%	2772
January	1st to 10th	Night	15% 18% 8% 14% 7% 5% 4 3 4 4 17%	4429
	11th to 20th	Night	12% 14% 4 15% 8% 6% 5% 4 5% 6% 20%	4440
	21st to end	Night	14% 21% 7% 12% 6% 6% 4 3 4 4 20%	4681
February	1st to 10th	Night	12% 15% 6% 13% 8% 5% 6% 4 4 5% 21%	2470
	11th to 20th	Night	12% 15% 6% 12% 6% 5% 5% 3 4 6% 26%	2403
	21st to end	Night	14% 13% 5% 10% 6% 5% 4 4 5% 6% 28%	1935
March	1st to 10th	Night	19% 12% 5% 8% 6% 4 4 2 4 4 31%	3610
	11th to 20th	Night	15% 17% 5% 10% 5% 5% 5% 4 5% 6% 23%	3479
	21st to end	Night	13% 8% 4 9% 5% 5% 3 4 5% 7% 36%	3673
April	1st to 10th	Night	20% 12% 4 8% 5% 4 4 2 4 6% 31%	1900
	11th to 20th	Night	20% 11% 3 6% 5% 4 4 3 5% 6% 35%	1875
	21st to end	Night	21% 10% 3 8% 5% 4 4 3 5% 5% 31%	1756
May	1st to 10th	Night	20% 10% 3 7% 4 4 4 3 4 7% 32%	2514
	11th to 20th	Night	18% 8% 2 7% 5% 5% 4 4 5% 7% 34%	2495
	21st to end	Night	12% 7% 3 7% 5% 5% 5% 3 5% 7% 40%	2738
June	1st to 10th	Night	16% 7% 3 7% 5% 5% 4 4 6% 8% 34%	1520
	11th to 20th	Night	14% 4 2 7% 4 4 4 4 6% 7% 43%	1520
	21st to end	Night	18% 7% 3 6% 4 5% 4 4 7% 7% 35%	1520
July	1st to 10th	Night	11% 6% 3 9% 6% 6% 5% 5% 6% 7% 36%	2520
	11th to 20th	Night	14% 6% 2 6% 4 4 6% 4 6% 8% 40%	2520
	21st to end	Night	9% 6% 2 6% 4 4 6% 4 7% 8% 45%	2739
August	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 5% 6% 8% 40%	2682
	11th to 20th	Night	16% 6% 2 6% 3 4 4 4 6% 7% 42%	2785
	21st to end	Night	13% 5% 2 6% 4 4 5% 4 6% 8% 43%	3402
September	1st to 10th	Night	11% 6% 3 7% 4 4 4 3 6% 6% 46%	1900
	11th to 20th	Night	15% 5% 2 5% 3 3 3 4 5% 6% 49%	1900
	21st to end	Night	17% 6% 3 7% 5% 4 4 3 4 7% 42%	2172
October	1st to 10th	Night	20% 7% 2 6% 4 4 4 4 4 4 40%	2280
	11th to 20th	Night	20% 11% 3 8% 5% 5% 5% 3 5% 5% 30%	2280
	21st to end	Night	23% 11% 4 8% 4 5% 5% 3 5% 5% 26%	2612
November	1st to 10th	Night	18% 12% 3 7% 4 5% 4 4 5% 6% 32%	2602
	11th to 20th	Night	17% 13% 4 9% 5% 5% 5% 4 5% 6% 27%	2800
	21st to end	Night	21% 16% 5% 11% 6% 4 4 3 4 6% 20%	2723
December	1st to 10th	Night	21% 18% 6% 10% 7% 5% 5% 3 4 4 17%	2660
	11th to 20th	Night	19% 18% 6% 10% 6% 4 4 3 3 4 24%	3288
	21st to end	Night	27% 19% 5% 13% 5% 4 3 2 3 3 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	66% 8% 12% 8% 6%	2518
	11th to 20th	Day	66% 6% 11% 12% 6% 1	2520
	21st to end	Day	72% 5% 7% 10% 5% 1	2973
February	1st to 10th	Day	64% 7% 8% 15% 4 1	1710
	11th to 20th	Day	57% 7% 13% 14% 8% 1	1672
	21st to end	Day	60% 5% 11% 13% 9% 2	1518
March	1st to 10th	Day	60% 5% 8% 16% 10% 1	3231
	11th to 20th	Day	58% 6% 12% 15% 9% 1	3480
	21st to end	Day	40% 5% 10% 24% 17% 4	3958
April	1st to 10th	Day	55% 5% 8% 18% 11% 3	2280
	11th to 20th	Day	51% 4 8% 21% 14% 2	2254
	21st to end	Day	53% 5% 7% 15% 16% 3	2438
May	1st to 10th	Day	49% 8% 9% 20% 11% 2	4440
	11th to 20th	Day	44% 9% 13% 22% 10% 1	4402
	21st to end	Day	44% 6% 12% 19% 15% 3	4837
June	1st to 10th	Day	52% 8% 9% 19% 11% 1	2660
	11th to 20th	Day	42% 7% 12% 23% 14% 2	2660
	21st to end	Day	47% 8% 12% 21% 12% 1	2660
July	1st to 10th	Day	43% 7% 14% 26% 10% 1	4370
	11th to 20th	Day	38% 8% 15% 30% 10%	4365
	21st to end	Day	35% 7% 13% 33% 12%	4661
August	1st to 10th	Day	47% 7% 14% 23% 9%	4231
	11th to 20th	Day	44% 7% 16% 26% 7%	4083
	21st to end	Day	37% 7% 15% 30% 11% 1	4222
September	1st to 10th	Day	39% 8% 14% 27% 11%	2280
	11th to 20th	Day	39% 6% 13% 31% 12%	2280
	21st to end	Day	46% 6% 15% 24% 9%	2004
October	1st to 10th	Day	51% 6% 9% 26% 7%	3160
	11th to 20th	Day	50% 5% 14% 23% 7%	3140
	21st to end	Day	54% 6% 18% 17% 4	3250
November	1st to 10th	Day	49% 6% 16% 22% 6% 1	1696
	11th to 20th	Day	58% 7% 14% 13% 7% 1	1600
	21st to end	Day	69% 7% 11% 8% 4 1	1552
December	1st to 10th	Day	72% 6% 10% 9% 3	1520
	11th to 20th	Day	63% 8% 10% 12% 7%	1906
	21st to end	Day	74% 3 7% 14% 2	2772
January	1st to 10th	Night	68% 7% 14% 9% 3	4429
	11th to 20th	Night	61% 9% 14% 12% 4	4440
	21st to end	Night	69% 5% 9% 10% 6%	4681
February	1st to 10th	Night	64% 6% 11% 14% 6% 1	2470
	11th to 20th	Night	59% 5% 11% 18% 6%	2405
	21st to end	Night	56% 6% 10% 18% 9% 1	1935
March	1st to 10th	Night	56% 6% 10% 19% 7% 1	3620
	11th to 20th	Night	58% 7% 14% 13% 7% 1	3480
	21st to end	Night	44% 7% 10% 21% 15% 3	3673
April	1st to 10th	Night	55% 4 9% 18% 12% 2	1900
	11th to 20th	Night	49% 5% 8% 22% 14% 2	1875
	21st to end	Night	54% 4 8% 16% 16% 2	1756
May	1st to 10th	Night	49% 8% 12% 20% 10% 3	2520
	11th to 20th	Night	44% 10% 14% 21% 10% 2	2496
	21st to end	Night	41% 7% 13% 21% 15% 2	2739
June	1st to 10th	Night	45% 8% 14% 22% 9% 1	1520
	11th to 20th	Night	38% 8% 11% 25% 16% 2	1520
	21st to end	Night	45% 7% 14% 20% 13% 1	1520
July	1st to 10th	Night	43% 9% 14% 19% 13% 1	2480
	11th to 20th	Night	39% 7% 13% 31% 9%	2472
	21st to end	Night	34% 8% 13% 31% 14%	2651
August	1st to 10th	Night	39% 7% 14% 25% 13% 1	2672
	11th to 20th	Night	40% 7% 16% 28% 9%	2812
	21st to end	Night	38% 6% 15% 28% 11% 2	3402
September	1st to 10th	Night	37% 8% 13% 28% 14% 1	1900
	11th to 20th	Night	35% 6% 15% 33% 10%	1900
	21st to end	Night	42% 6% 14% 28% 10%	2172
October	1st to 10th	Night	40% 5% 13% 30% 12%	3800
	11th to 20th	Night	48% 5% 16% 21% 9%	3779
	21st to end	Night	52% 6% 18% 17% 7%	4298
November	1st to 10th	Night	51% 6% 14% 19% 9%	2602
	11th to 20th	Night	57% 7% 13% 16% 7% 1	2800
	21st to end	Night	65% 6% 13% 13% 3	2723
December	1st to 10th	Night	70% 7% 9% 11% 4	2660
	11th to 20th	Night	64% 6% 10% 14% 7% 1	3288
	21st to end	Night	75% 4 7% 11% 3	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	19% 22% 33% 22% 3 1	180
	11th to 20th	Day	29% 16% 36% 14% 4 1	180
	21st to end	Day	23% 19% 33% 19% 6%	256
February	1st to 10th	Day	23% 28% 31% 14% 4	270
	11th to 20th	Day	24% 29% 38% 8% 1	270
	21st to end	Day	32% 22% 33% 12% 1	330
March	1st to 10th	Day	27% 19% 35% 15% 3 1	460
	11th to 20th	Day	25% 20% 33% 17% 4	460
	21st to end	Day	29% 21% 32% 13% 6%	506
April	1st to 10th	Day	30% 20% 28% 15% 6%	460
	11th to 20th	Day	33% 21% 21% 15% 9% 2	452
	21st to end	Day	32% 17% 31% 13% 5% 2	460
May	1st to 10th	Day	26% 14% 29% 20% 8% 2	463
	11th to 20th	Day	18% 18% 31% 20% 10% 3	487
	21st to end	Day	18% 18% 32% 21% 10% 2	529
June	1st to 10th	Day	22% 16% 31% 22% 8% 1	490
	11th to 20th	Day	18% 14% 28% 24% 13% 3	490
	21st to end	Day	19% 14% 32% 22% 11% 2	490
July	1st to 10th	Day	11% 7% 34% 33% 12% 3	485
	11th to 20th	Day	10% 11% 34% 28% 14% 3	484
	21st to end	Day	12% 9% 33% 30% 13% 4	532
August	1st to 10th	Day	15% 8% 28% 29% 14% 6%	486
	11th to 20th	Day	15% 6% 26% 29% 16% 8%	479
	21st to end	Day	13% 11% 29% 25% 15% 6%	539
September	1st to 10th	Day	16% 12% 28% 22% 14% 8%	490
	11th to 20th	Day	15% 11% 21% 24% 17% 13%	490
	21st to end	Day	17% 13% 28% 23% 13% 7%	490
October	1st to 10th	Day	25% 16% 22% 20% 13% 3	490
	11th to 20th	Day	27% 21% 31% 12% 8% 1	490
	21st to end	Day	29% 17% 30% 18% 5% 1	484
November	1st to 10th	Day	27% 17% 32% 18% 5% 1	330
	11th to 20th	Day	24% 27% 31% 13% 6% 1	200
	21st to end	Day	31% 22% 34% 8% 3 2	188
December	1st to 10th	Day	29% 14% 39% 14% 4	180
	11th to 20th	Day	28% 27% 32% 11% 2 1	180
	21st to end	Day	28% 23% 30% 15% 3 2	198
January	1st to 10th	Night	25% 19% 33% 19% 4	760
	11th to 20th	Night	29% 16% 28% 21% 6%	760
	21st to end	Night	18% 14% 36% 25% 6%	836
February	1st to 10th	Night	19% 18% 39% 21% 3	760
	11th to 20th	Night	20% 17% 40% 19% 4	743
	21st to end	Night	22% 20% 30% 25% 3	628
March	1st to 10th	Night	26% 17% 33% 21% 4	760
	11th to 20th	Night	23% 21% 31% 19% 5%	760
	21st to end	Night	21% 16% 34% 22% 7%	836
April	1st to 10th	Night	27% 15% 32% 21% 5%	760
	11th to 20th	Night	25% 17% 29% 21% 7%	751
	21st to end	Night	25% 14% 27% 25% 9% 1	616
May	1st to 10th	Night	23% 7% 30% 29% 10% 1	380
	11th to 20th	Night	20% 12% 29% 32% 7%	374
	21st to end	Night	15% 7% 38% 29% 10%	411
June	1st to 10th	Night	17% 7% 33% 35% 7% 1	380
	11th to 20th	Night	13% 10% 32% 33% 12%	380
	21st to end	Night	21% 8% 28% 29% 14%	380
July	1st to 10th	Night	10% 4 34% 37% 14% 1	370
	11th to 20th	Night	13% 5% 25% 42% 15%	368
	21st to end	Night	9% 5% 31% 41% 13% 1	416
August	1st to 10th	Night	11% 4 25% 39% 21% 1	476
	11th to 20th	Night	11% 3 23% 39% 21% 3	564
	21st to end	Night	13% 8% 27% 33% 18% 2	788
September	1st to 10th	Night	14% 7% 30% 30% 18% 2	760
	11th to 20th	Night	18% 6% 21% 30% 21% 4	760
	21st to end	Night	20% 11% 22% 26% 19% 2	760
October	1st to 10th	Night	24% 8% 29% 24% 14% 1	760
	11th to 20th	Night	27% 13% 31% 19% 10% 1	760
	21st to end	Night	29% 15% 28% 22% 6%	836
November	1st to 10th	Night	26% 16% 27% 24% 7% 1	780
	11th to 20th	Night	25% 18% 31% 17% 10% 1	800
	21st to end	Night	31% 17% 25% 22% 4	779
December	1st to 10th	Night	30% 18% 31% 16% 5%	760
	11th to 20th	Night	27% 18% 31% 20% 4 1	760
	21st to end	Night	32% 16% 29% 20% 3 1	836

Page generated at 2024-11-22 08:02:29. Version ac07

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