Lead Parachute Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lead Parachute Observatory clear sky chart from 2005-11-06 to 2024-12-09.

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% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	101741
	Night	16% 12% 4 8% 5% 4 4 3 5% 6% 32%	98051
Transparency	Day	50% 7% 12% 20% 10% 1	105342
	Night	50% 7% 12% 19% 10% 1	102538
Seeing	Day	24% 18% 29% 17% 8% 3	14796
	Night	22% 17% 28% 23% 9% 1	24179

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	14% 19% 9% 10% 5% 4 3 3 4 5% 25%	2517
	11th to 20th	Day	11% 16% 9% 18% 7% 5% 4 3 4 4 20%	2684
	21st to end	Day	20% 17% 10% 11% 6% 4 4 3 3 4 18%	3124
February	1st to 10th	Day	14% 16% 5% 11% 8% 5% 5% 4 5% 5% 22%	1710
	11th to 20th	Day	12% 13% 6% 12% 8% 5% 5% 4 4 5% 26%	1663
	21st to end	Day	16% 15% 4 11% 6% 3 4 3 5% 5% 28%	1567
March	1st to 10th	Day	20% 16% 5% 9% 4 4 3 2 4 6% 28%	3326
	11th to 20th	Day	10% 16% 5% 9% 5% 4 5% 3 4 6% 33%	3480
	21st to end	Day	15% 11% 3 10% 5% 5% 5% 4 5% 5% 32%	3900
April	1st to 10th	Day	15% 15% 3 8% 5% 4 5% 3 5% 6% 30%	2280
	11th to 20th	Day	17% 12% 3 8% 4 5% 4 4 6% 6% 32%	2254
	21st to end	Day	20% 10% 3 7% 4 4 4 3 5% 6% 34%	2341
May	1st to 10th	Day	26% 9% 3 6% 4 4 4 3 4 6% 31%	4191
	11th to 20th	Day	23% 9% 3 8% 5% 4 4 3 6% 7% 27%	4398
	21st to end	Day	13% 7% 2 6% 4 5% 5% 3 6% 8% 40%	4837
June	1st to 10th	Day	16% 7% 2 7% 5% 5% 5% 4 6% 8% 33%	2660
	11th to 20th	Day	14% 7% 3 8% 5% 4 5% 5% 7% 8% 35%	2660
	21st to end	Day	13% 6% 2 7% 5% 6% 6% 4 7% 8% 35%	2660
July	1st to 10th	Day	9% 6% 2 8% 5% 5% 7% 6% 8% 9% 35%	4440
	11th to 20th	Day	7% 5% 3 7% 6% 6% 6% 5% 8% 10% 36%	4440
	21st to end	Day	11% 6% 3 8% 6% 6% 6% 4 7% 8% 34%	4603
August	1st to 10th	Day	20% 8% 3 7% 4 5% 5% 4 6% 8% 30%	4104
	11th to 20th	Day	15% 8% 3 7% 5% 6% 6% 5% 7% 9% 29%	3985
	21st to end	Day	12% 8% 3 7% 4 4 5% 4 6% 9% 37%	4180
September	1st to 10th	Day	18% 6% 2 6% 4 4 5% 4 6% 6% 40%	2280
	11th to 20th	Day	15% 7% 2 6% 4 4 5% 3 4 7% 44%	2280
	21st to end	Day	22% 8% 3 5% 5% 4 5% 4 4 6% 35%	1996
October	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 2 5% 8% 33%	1900
	11th to 20th	Day	19% 10% 3 8% 5% 4 4 4 5% 6% 32%	1900
	21st to end	Day	20% 13% 3 8% 4 4 4 3 5% 7% 28%	2090
November	1st to 10th	Day	13% 11% 3 8% 4 4 4 3 4 5% 40%	1771
	11th to 20th	Day	15% 16% 4 8% 5% 4 5% 3 6% 6% 29%	1658
	21st to end	Day	16% 17% 4 8% 6% 4 4 3 5% 8% 26%	1600
December	1st to 10th	Day	18% 16% 7% 13% 7% 4 4 3 5% 5% 20%	1584
	11th to 20th	Day	19% 15% 6% 9% 5% 4 4 2 5% 6% 24%	1906
	21st to end	Day	22% 21% 5% 11% 5% 4 4 3 4 4 16%	2772
January	1st to 10th	Night	14% 16% 7% 11% 5% 5% 4 4 5% 6% 23%	4429
	11th to 20th	Night	12% 18% 7% 14% 5% 4 5% 3 4 6% 21%	4275
	21st to end	Night	21% 16% 6% 13% 7% 5% 5% 3 4 4 17%	4532
February	1st to 10th	Night	12% 15% 5% 10% 6% 5% 6% 4 5% 6% 26%	2470
	11th to 20th	Night	11% 14% 6% 11% 7% 4 6% 4 5% 6% 26%	2403
	21st to end	Night	15% 12% 4 13% 5% 5% 5% 3 4 5% 27%	1885
March	1st to 10th	Night	20% 15% 4 8% 4 4 4 3 4 4 28%	3510
	11th to 20th	Night	13% 18% 6% 8% 5% 4 4 3 4 6% 28%	3479
	21st to end	Night	14% 12% 3 8% 4 4 4 2 4 5% 38%	3732
April	1st to 10th	Night	17% 13% 4 9% 5% 4 3 4 4 5% 30%	1900
	11th to 20th	Night	17% 11% 3 7% 5% 4 4 3 6% 6% 35%	1875
	21st to end	Night	16% 11% 3 7% 4 4 4 4 5% 6% 38%	1856
May	1st to 10th	Night	28% 10% 3 6% 3 4 3 2 4 5% 32%	2747
	11th to 20th	Night	24% 9% 3 7% 5% 5% 4 3 5% 5% 30%	2495
	21st to end	Night	13% 6% 2 7% 5% 5% 4 4 6% 8% 40%	2738
June	1st to 10th	Night	13% 7% 3 7% 4 4 4 4 6% 8% 40%	1520
	11th to 20th	Night	11% 6% 2 7% 5% 4 5% 4 6% 9% 40%	1520
	21st to end	Night	12% 5% 3 6% 4 5% 6% 4 7% 7% 42%	1520
July	1st to 10th	Night	9% 8% 3 7% 5% 4 4 4 6% 8% 40%	2520
	11th to 20th	Night	8% 5% 2 5% 4 4 5% 5% 7% 10% 44%	2520
	21st to end	Night	12% 7% 3 7% 5% 4 4 3 5% 6% 44%	2946
August	1st to 10th	Night	18% 8% 2 7% 5% 5% 5% 3 5% 7% 36%	2825
	11th to 20th	Night	17% 6% 2 6% 4 4 4 3 5% 8% 40%	2812
	21st to end	Night	12% 6% 2 6% 4 4 5% 5% 6% 7% 42%	3476
September	1st to 10th	Night	15% 6% 2 6% 5% 3 4 3 5% 6% 45%	1900
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 7% 50%	1900
	21st to end	Night	18% 7% 2 7% 5% 4 3 4 5% 6% 38%	2180
October	1st to 10th	Night	17% 8% 3 6% 5% 3 5% 3 5% 6% 39%	2280
	11th to 20th	Night	17% 9% 2 7% 4 4 4 4 4 7% 37%	2280
	21st to end	Night	21% 11% 3 7% 4 4 4 3 5% 7% 31%	2508
November	1st to 10th	Night	11% 10% 3 7% 4 4 5% 3 5% 6% 42%	2527
	11th to 20th	Night	17% 14% 3 8% 5% 5% 5% 3 5% 6% 30%	2740
	21st to end	Night	15% 15% 4 7% 5% 5% 5% 4 6% 6% 27%	2800
December	1st to 10th	Night	15% 17% 6% 10% 6% 5% 5% 4 6% 6% 20%	2779
	11th to 20th	Night	17% 15% 5% 11% 6% 5% 4 3 5% 4 25%	3288
	21st to end	Night	21% 15% 8% 10% 6% 4 4 4 5% 5% 17%	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	62% 5% 11% 16% 4 2	2518
	11th to 20th	Day	68% 5% 7% 13% 5% 1	2684
	21st to end	Day	70% 6% 8% 13% 3 1	3124
February	1st to 10th	Day	63% 5% 11% 13% 7% 1	1710
	11th to 20th	Day	59% 6% 8% 18% 9%	1672
	21st to end	Day	57% 5% 9% 18% 8% 2	1567
March	1st to 10th	Day	57% 6% 9% 21% 6% 1	3329
	11th to 20th	Day	50% 7% 12% 19% 8% 3	3480
	21st to end	Day	50% 7% 9% 21% 12% 2	3900
April	1st to 10th	Day	54% 5% 8% 20% 10% 2	2280
	11th to 20th	Day	51% 7% 10% 18% 13% 1	2254
	21st to end	Day	50% 6% 9% 18% 14% 3	2341
May	1st to 10th	Day	53% 6% 8% 22% 10% 1	4203
	11th to 20th	Day	54% 9% 12% 17% 7% 1	4402
	21st to end	Day	39% 8% 13% 24% 14% 1	4837
June	1st to 10th	Day	47% 8% 11% 20% 13% 1	2660
	11th to 20th	Day	44% 9% 14% 20% 12% 1	2660
	21st to end	Day	43% 9% 12% 25% 11% 1	2660
July	1st to 10th	Day	41% 7% 17% 23% 11% 1	4370
	11th to 20th	Day	38% 9% 16% 25% 12%	4365
	21st to end	Day	44% 8% 14% 21% 13% 1	4456
August	1st to 10th	Day	50% 8% 13% 19% 10%	4091
	11th to 20th	Day	47% 8% 15% 23% 7%	4024
	21st to end	Day	41% 7% 12% 31% 8% 1	4180
September	1st to 10th	Day	43% 6% 12% 24% 13% 2	2280
	11th to 20th	Day	39% 7% 11% 25% 17% 1	2280
	21st to end	Day	48% 6% 11% 19% 14% 1	1996
October	1st to 10th	Day	43% 5% 13% 20% 18% 1	3160
	11th to 20th	Day	45% 5% 11% 20% 17% 3	3140
	21st to end	Day	40% 5% 16% 26% 12% 1	3428
November	1st to 10th	Day	46% 6% 11% 20% 14% 3	1771
	11th to 20th	Day	54% 6% 11% 18% 8% 2	1658
	21st to end	Day	58% 6% 13% 17% 6% 1	1600
December	1st to 10th	Day	66% 6% 11% 11% 6%	1584
	11th to 20th	Day	61% 5% 16% 13% 5%	1906
	21st to end	Day	70% 6% 8% 13% 2	2772
January	1st to 10th	Night	60% 8% 10% 16% 6% 1	4429
	11th to 20th	Night	64% 6% 11% 13% 6% 1	4275
	21st to end	Night	71% 5% 7% 12% 4 1	4532
February	1st to 10th	Night	57% 6% 12% 17% 7% 1	2470
	11th to 20th	Night	57% 7% 9% 17% 9% 1	2405
	21st to end	Night	59% 5% 9% 15% 10% 2	1885
March	1st to 10th	Night	58% 6% 11% 16% 8% 1	3520
	11th to 20th	Night	54% 9% 13% 18% 6% 1	3480
	21st to end	Night	47% 7% 8% 21% 15% 2	3732
April	1st to 10th	Night	55% 7% 10% 17% 12% 1	1900
	11th to 20th	Night	48% 6% 12% 18% 14% 1	1875
	21st to end	Night	46% 6% 11% 20% 15% 2	1856
May	1st to 10th	Night	55% 5% 9% 22% 8% 1	2754
	11th to 20th	Night	53% 10% 13% 15% 8% 1	2496
	21st to end	Night	38% 12% 13% 19% 15% 4	2739
June	1st to 10th	Night	41% 7% 13% 24% 15% 1	1520
	11th to 20th	Night	39% 9% 14% 24% 13% 2	1520
	21st to end	Night	38% 8% 13% 26% 13% 1	1520
July	1st to 10th	Night	41% 8% 13% 22% 15% 1	2480
	11th to 20th	Night	32% 9% 20% 25% 14%	2472
	21st to end	Night	39% 7% 13% 21% 19% 1	2852
August	1st to 10th	Night	46% 8% 15% 22% 8%	2814
	11th to 20th	Night	41% 7% 16% 26% 9%	2839
	21st to end	Night	38% 8% 14% 30% 10% 1	3476
September	1st to 10th	Night	40% 6% 12% 26% 14% 2	1900
	11th to 20th	Night	33% 7% 14% 27% 18% 2	1900
	21st to end	Night	45% 6% 12% 23% 14% 1	2180
October	1st to 10th	Night	46% 6% 12% 20% 16% 1	3800
	11th to 20th	Night	40% 5% 12% 22% 16% 5%	3779
	21st to end	Night	39% 5% 17% 26% 12% 1	4120
November	1st to 10th	Night	42% 6% 13% 23% 14% 2	2527
	11th to 20th	Night	54% 6% 11% 18% 9% 2	2740
	21st to end	Night	55% 7% 14% 18% 6% 1	2800
December	1st to 10th	Night	62% 8% 12% 14% 4	2779
	11th to 20th	Night	63% 6% 10% 15% 6%	3288
	21st to end	Night	67% 8% 10% 12% 2	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	34% 23% 30% 8% 4 1	180
	11th to 20th	Day	35% 30% 27% 7% 1	227
	21st to end	Day	28% 30% 32% 7% 2	297
February	1st to 10th	Day	32% 32% 29% 5% 1	270
	11th to 20th	Day	37% 28% 32% 2	270
	21st to end	Day	37% 25% 28% 8% 2	379
March	1st to 10th	Day	33% 24% 28% 12% 2	460
	11th to 20th	Day	32% 26% 26% 12% 3	460
	21st to end	Day	35% 24% 25% 10% 3 2	506
April	1st to 10th	Day	33% 23% 27% 12% 4 1	460
	11th to 20th	Day	28% 27% 25% 11% 6% 4	452
	21st to end	Day	31% 20% 29% 14% 4 2	460
May	1st to 10th	Day	31% 19% 27% 12% 7% 3	463
	11th to 20th	Day	26% 16% 31% 15% 9% 3	487
	21st to end	Day	19% 12% 31% 22% 12% 4	529
June	1st to 10th	Day	18% 19% 31% 21% 10% 1	490
	11th to 20th	Day	19% 12% 31% 26% 11% 1	490
	21st to end	Day	16% 14% 37% 23% 8% 2	490
July	1st to 10th	Day	11% 10% 32% 28% 15% 5%	485
	11th to 20th	Day	8% 11% 32% 29% 14% 6%	484
	21st to end	Day	12% 9% 37% 27% 11% 5%	532
August	1st to 10th	Day	13% 9% 28% 29% 15% 7%	486
	11th to 20th	Day	15% 11% 27% 27% 13% 8%	479
	21st to end	Day	15% 11% 28% 23% 14% 9%	539
September	1st to 10th	Day	19% 11% 25% 23% 14% 8%	490
	11th to 20th	Day	14% 9% 27% 20% 21% 9%	490
	21st to end	Day	27% 14% 26% 18% 13% 3	490
October	1st to 10th	Day	25% 12% 23% 20% 14% 5%	490
	11th to 20th	Day	27% 16% 32% 16% 7% 2	490
	21st to end	Day	30% 21% 27% 17% 5%	539
November	1st to 10th	Day	24% 24% 25% 17% 10% 1	400
	11th to 20th	Day	34% 22% 27% 12% 4 1	258
	21st to end	Day	31% 31% 31% 6% 2	200
December	1st to 10th	Day	31% 28% 32% 6% 3 1	196
	11th to 20th	Day	38% 27% 27% 8% 1	180
	21st to end	Day	35% 29% 30% 5% 1	198
January	1st to 10th	Night	23% 28% 35% 12% 3	760
	11th to 20th	Night	26% 24% 30% 16% 3	760
	21st to end	Night	23% 27% 31% 18% 2	836
February	1st to 10th	Night	26% 25% 31% 17% 1	760
	11th to 20th	Night	29% 25% 34% 12% 1	743
	21st to end	Night	31% 22% 29% 16% 2	628
March	1st to 10th	Night	26% 27% 29% 15% 2	760
	11th to 20th	Night	29% 24% 26% 17% 3	760
	21st to end	Night	25% 23% 30% 17% 5% 1	836
April	1st to 10th	Night	27% 22% 30% 18% 3	760
	11th to 20th	Night	24% 20% 30% 18% 7% 1	751
	21st to end	Night	23% 16% 31% 24% 7%	716
May	1st to 10th	Night	27% 12% 23% 27% 11%	523
	11th to 20th	Night	18% 13% 30% 28% 9% 1	374
	21st to end	Night	12% 10% 29% 33% 15% 1	411
June	1st to 10th	Night	14% 9% 27% 35% 14% 1	380
	11th to 20th	Night	16% 9% 23% 38% 14%	380
	21st to end	Night	12% 6% 31% 40% 11%	380
July	1st to 10th	Night	9% 7% 26% 38% 18% 2	370
	11th to 20th	Night	9% 4 23% 41% 21% 2	368
	21st to end	Night	12% 6% 18% 41% 20% 2	535
August	1st to 10th	Night	10% 4 25% 38% 22% 2	567
	11th to 20th	Night	14% 5% 19% 34% 26% 3	578
	21st to end	Night	12% 7% 21% 35% 23% 3	836
September	1st to 10th	Night	17% 9% 23% 31% 17% 3	760
	11th to 20th	Night	14% 6% 21% 28% 25% 5%	760
	21st to end	Night	21% 10% 25% 26% 14% 3	760
October	1st to 10th	Night	21% 12% 23% 25% 16% 2	760
	11th to 20th	Night	23% 17% 28% 23% 8% 1	760
	21st to end	Night	28% 15% 30% 21% 5%	836
November	1st to 10th	Night	18% 19% 31% 23% 8%	780
	11th to 20th	Night	28% 20% 29% 16% 6% 2	800
	21st to end	Night	26% 20% 32% 19% 3 1	800
December	1st to 10th	Night	28% 25% 30% 12% 4	795
	11th to 20th	Night	27% 21% 32% 17% 3	760
	21st to end	Night	28% 23% 33% 14% 1	836

Page generated at 2024-12-06 03:54:50. Version ac07

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