Paul Plishner Radio Astronomy and Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Paul Plishner Radio Astronomy and Science Center clear sky chart from 2005-11-06 to 2024-11-01.

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	4 4 1 4 3 3 4 3 6% 8% 59%	101121
	Night	5% 5% 2 5% 4 4 4 4 6% 7% 55%	98046
Transparency	Day	22% 5% 11% 24% 26% 12%	100863
	Night	27% 5% 11% 23% 24% 10%	97895
Seeing	Day	7% 6% 23% 33% 24% 8%	15524
	Night	7% 6% 30% 41% 14% 1	25471

By Month

Percentage Cloud Cover SW (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	2 5% 2 7% 4 3 4 3 5% 7% 58%	2538
	11th to 20th	Day	3 5% 2 5% 3 5% 6% 5% 6% 8% 54%	2540
	21st to end	Day	4 6% 2 6% 3 3 3 3 5% 7% 58%	3096
February	1st to 10th	Day	4 6% 2 5% 4 5% 4 3 5% 7% 54%	1867
	11th to 20th	Day	2 6% 2 7% 5% 3 4 3 5% 6% 56%	1849
	21st to end	Day	3 5% 2 6% 5% 4 4 4 5% 5% 59%	1570
March	1st to 10th	Day	2 4 1 5% 4 3 3 3 4 7% 64%	3130
	11th to 20th	Day	6% 6% 1 4 3 3 3 3 5% 7% 60%	3266
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 8% 54%	4165
April	1st to 10th	Day	5% 5% 1 4 3 3 4 3 7% 7% 59%	2280
	11th to 20th	Day	7% 5% 2 5% 4 4 3 4 6% 8% 53%	2251
	21st to end	Day	6% 6% 2 5% 4 4 4 4 6% 7% 53%	2289
May	1st to 10th	Day	8% 5% 1 4 4 3 3 3 5% 6% 57%	4120
	11th to 20th	Day	5% 4 1 5% 3 3 4 3 6% 8% 56%	4082
	21st to end	Day	4 3 1 3 3 3 3 3 6% 8% 63%	4749
June	1st to 10th	Day	4 2 1 3 3 3 4 4 8% 12% 57%	2660
	11th to 20th	Day	5% 3 1 3 3 3 3 3 6% 7% 63%	2660
	21st to end	Day	3 3 1 5% 3 4 4 4 7% 9% 57%	2660
July	1st to 10th	Day	4 3 1 4 4 4 5% 4 7% 9% 55%	4430
	11th to 20th	Day	2 1 1 3 2 3 4 4 6% 11% 63%	4430
	21st to end	Day	4 2 1 3 3 3 4 4 7% 10% 60%	4802
August	1st to 10th	Day	6% 4 2 4 3 4 4 4 7% 10% 52%	3871
	11th to 20th	Day	4 2 1 3 3 3 4 3 6% 9% 61%	3726
	21st to end	Day	3 2 1 3 3 3 4 4 7% 11% 59%	4180
September	1st to 10th	Day	4 3 1 3 3 3 4 3 6% 7% 63%	2280
	11th to 20th	Day	5% 2 1 3 2 3 3 3 4 6% 67%	2162
	21st to end	Day	6% 3 2 3 2 2 3 3 4 6% 67%	2090
October	1st to 10th	Day	7% 3 1 4 2 3 2 3 5% 6% 63%	2083
	11th to 20th	Day	4 3 1 3 3 2 3 2 4 5% 70%	1900
	21st to end	Day	6% 6% 1 4 2 2 2 2 3 4 68%	1934
November	1st to 10th	Day	3 4 2 3 2 2 2 2 5% 6% 70%	1673
	11th to 20th	Day	3 3 2 4 2 3 2 3 4 6% 68%	1710
	21st to end	Day	5% 5% 2 4 3 3 2 3 4 6% 63%	1710
December	1st to 10th	Day	2 7% 2 5% 4 3 3 3 4 6% 59%	1648
	11th to 20th	Day	4 6% 2 4 2 2 3 3 5% 8% 59%	1926
	21st to end	Day	5% 8% 2 7% 4 4 4 3 6% 7% 52%	2794
January	1st to 10th	Night	3 6% 2 5% 3 4 5% 4 6% 8% 55%	4417
	11th to 20th	Night	2 4 2 5% 3 3 3 4 6% 8% 59%	4430
	21st to end	Night	3 6% 2 5% 4 3 4 3 5% 7% 58%	4588
February	1st to 10th	Night	5% 5% 3 6% 5% 4 3 2 4 6% 57%	2310
	11th to 20th	Night	4 7% 3 7% 4 3 4 4 6% 8% 51%	2218
	21st to end	Night	4 5% 2 5% 3 3 3 3 5% 7% 60%	1884
March	1st to 10th	Night	3 5% 2 4 3 3 3 3 4 6% 64%	3734
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 5% 7% 54%	3702
	21st to end	Night	6% 5% 2 5% 3 4 4 3 6% 8% 54%	3477
April	1st to 10th	Night	6% 6% 2 5% 3 3 4 3 5% 8% 56%	1900
	11th to 20th	Night	9% 5% 2 5% 3 4 5% 3 6% 7% 51%	1877
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 7% 49%	1889
May	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 4 6% 49%	2850
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 5% 8% 47%	2823
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 5% 7% 7% 46%	2835
June	1st to 10th	Night	4 3 1 3 4 4 5% 5% 8% 9% 54%	1520
	11th to 20th	Night	4 4 2 4 3 4 4 5% 7% 8% 56%	1520
	21st to end	Night	5% 6% 2 4 3 4 5% 5% 7% 9% 50%	1520
July	1st to 10th	Night	6% 4 2 5% 4 5% 6% 5% 8% 10% 45%	2540
	11th to 20th	Night	4 4 2 6% 4 4 6% 4 7% 10% 50%	2540
	21st to end	Night	5% 4 2 5% 4 5% 5% 5% 7% 7% 51%	2761
August	1st to 10th	Night	11% 5% 2 8% 6% 6% 7% 5% 7% 9% 33%	3061
	11th to 20th	Night	6% 4 2 7% 5% 5% 6% 5% 8% 10% 41%	3113
	21st to end	Night	3 2 1 6% 5% 6% 7% 6% 10% 11% 44%	3487
September	1st to 10th	Night	6% 3 1 4 3 4 3 3 6% 9% 57%	1900
	11th to 20th	Night	5% 3 1 3 3 3 4 3 5% 9% 60%	2016
	21st to end	Night	6% 3 2 4 3 2 3 2 4 5% 64%	2090
October	1st to 10th	Night	8% 3 1 4 3 4 3 3 5% 6% 60%	2095
	11th to 20th	Night	4 3 1 3 1 2 3 2 4 6% 70%	2280
	21st to end	Night	5% 6% 1 4 3 3 3 3 3 5% 65%	2643
November	1st to 10th	Night	3 3 1 3 2 3 3 2 4 6% 70%	2412
	11th to 20th	Night	3 4 1 4 2 3 3 2 3 4 70%	2470
	21st to end	Night	4 6% 2 4 2 3 3 3 5% 6% 63%	2470
December	1st to 10th	Night	3 5% 2 5% 3 3 3 3 5% 7% 60%	2530
	11th to 20th	Night	4 6% 2 5% 3 3 4 3 5% 7% 58%	3271
	21st to end	Night	4 7% 2 6% 4 4 4 3 6% 7% 53%	4873

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	26% 5% 9% 30% 24% 6%	2539
	11th to 20th	Day	26% 5% 13% 25% 22% 9%	2540
	21st to end	Day	26% 3 12% 30% 24% 4	3096
February	1st to 10th	Day	29% 5% 10% 25% 22% 9%	1867
	11th to 20th	Day	28% 4 8% 26% 26% 8%	1859
	21st to end	Day	26% 3 8% 20% 27% 16%	1570
March	1st to 10th	Day	21% 3 6% 18% 32% 19%	3130
	11th to 20th	Day	23% 5% 9% 27% 31% 5%	3266
	21st to end	Day	25% 6% 11% 32% 20% 6%	4165
April	1st to 10th	Day	23% 5% 9% 23% 26% 14%	2280
	11th to 20th	Day	27% 5% 11% 25% 20% 13%	2254
	21st to end	Day	29% 5% 11% 24% 23% 8%	2289
May	1st to 10th	Day	25% 5% 11% 26% 18% 14%	4120
	11th to 20th	Day	24% 6% 15% 26% 23% 7%	4086
	21st to end	Day	18% 5% 14% 23% 24% 15%	4749
June	1st to 10th	Day	18% 6% 16% 29% 22% 9%	2660
	11th to 20th	Day	19% 4 9% 22% 25% 20%	2660
	21st to end	Day	21% 5% 11% 23% 25% 15%	2660
July	1st to 10th	Day	23% 7% 9% 18% 30% 13%	4361
	11th to 20th	Day	14% 6% 15% 23% 31% 12%	4355
	21st to end	Day	18% 6% 13% 21% 24% 17%	4651
August	1st to 10th	Day	25% 7% 18% 29% 15% 5%	3857
	11th to 20th	Day	19% 6% 14% 23% 27% 10%	3762
	21st to end	Day	18% 6% 12% 31% 22% 11%	4179
September	1st to 10th	Day	20% 5% 9% 24% 26% 17%	2280
	11th to 20th	Day	18% 4 8% 19% 29% 22%	2162
	21st to end	Day	18% 4 7% 18% 36% 17%	2090
October	1st to 10th	Day	21% 4 9% 20% 31% 15%	2083
	11th to 20th	Day	17% 3 7% 19% 35% 18%	1900
	21st to end	Day	22% 2 7% 24% 30% 16%	1934
November	1st to 10th	Day	16% 3 9% 25% 29% 17%	1673
	11th to 20th	Day	18% 3 7% 29% 31% 12%	1710
	21st to end	Day	24% 3 7% 18% 33% 16%	1710
December	1st to 10th	Day	26% 4 10% 25% 28% 7%	1648
	11th to 20th	Day	22% 3 9% 24% 34% 7%	1924
	21st to end	Day	32% 4 9% 23% 25% 7%	2794
January	1st to 10th	Night	25% 6% 11% 29% 25% 4	4417
	11th to 20th	Night	21% 5% 15% 27% 23% 9%	4430
	21st to end	Night	26% 4 12% 28% 25% 4	4588
February	1st to 10th	Night	30% 3 10% 23% 26% 9%	2310
	11th to 20th	Night	29% 5% 10% 26% 23% 7%	2218
	21st to end	Night	24% 3 7% 21% 29% 15%	1884
March	1st to 10th	Night	20% 4 7% 19% 28% 22%	3734
	11th to 20th	Night	28% 5% 13% 21% 22% 10%	3702
	21st to end	Night	24% 6% 14% 29% 21% 5%	3477
April	1st to 10th	Night	25% 6% 9% 23% 25% 13%	1900
	11th to 20th	Night	29% 6% 12% 24% 19% 10%	1877
	21st to end	Night	31% 5% 14% 24% 20% 6%	1889
May	1st to 10th	Night	32% 8% 17% 17% 16% 10%	2850
	11th to 20th	Night	35% 7% 16% 22% 14% 7%	2824
	21st to end	Night	31% 8% 13% 20% 18% 9%	2836
June	1st to 10th	Night	21% 8% 22% 26% 16% 7%	1520
	11th to 20th	Night	24% 6% 13% 23% 19% 15%	1520
	21st to end	Night	28% 7% 11% 21% 22% 11%	1520
July	1st to 10th	Night	30% 8% 10% 23% 25% 4	2500
	11th to 20th	Night	28% 7% 16% 19% 25% 5%	2492
	21st to end	Night	31% 6% 11% 18% 23% 11%	2674
August	1st to 10th	Night	44% 8% 14% 20% 9% 5%	3052
	11th to 20th	Night	34% 9% 15% 22% 16% 4	3143
	21st to end	Night	29% 8% 13% 26% 17% 7%	3487
September	1st to 10th	Night	24% 5% 12% 23% 22% 15%	1900
	11th to 20th	Night	20% 5% 10% 21% 25% 19%	2016
	21st to end	Night	22% 4 6% 19% 33% 15%	2090
October	1st to 10th	Night	24% 4 11% 19% 26% 15%	2095
	11th to 20th	Night	16% 4 7% 22% 29% 22%	2280
	21st to end	Night	23% 4 8% 21% 28% 17%	2643
November	1st to 10th	Night	16% 2 8% 25% 29% 19%	2412
	11th to 20th	Night	19% 3 6% 25% 34% 14%	2470
	21st to end	Night	23% 3 7% 20% 30% 16%	2470
December	1st to 10th	Night	23% 4 12% 28% 25% 9%	2530
	11th to 20th	Night	26% 4 7% 22% 35% 6%	3272
	21st to end	Night	30% 4 9% 24% 27% 5%	4873

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	6% 6% 23% 46% 17% 4	270
	11th to 20th	Day	11% 8% 25% 37% 16% 3	270
	21st to end	Day	8% 5% 25% 38% 21% 4	297
February	1st to 10th	Day	7% 8% 36% 36% 13% 1	270
	11th to 20th	Day	4 4 38% 39% 13% 1	270
	21st to end	Day	4 10% 38% 38% 8% 1	225
March	1st to 10th	Day	4 10% 27% 40% 16% 3	270
	11th to 20th	Day	11% 9% 31% 24% 19% 6%	292
	21st to end	Day	12% 13% 31% 31% 11% 2	506
April	1st to 10th	Day	9% 12% 35% 28% 13% 4	460
	11th to 20th	Day	11% 17% 31% 27% 12% 2	452
	21st to end	Day	11% 14% 31% 29% 12% 3	469
May	1st to 10th	Day	10% 12% 29% 30% 17% 2	653
	11th to 20th	Day	10% 8% 27% 31% 19% 6%	675
	21st to end	Day	8% 10% 28% 29% 20% 4	734
June	1st to 10th	Day	4 5% 21% 30% 29% 11%	680
	11th to 20th	Day	5% 6% 26% 33% 25% 5%	680
	21st to end	Day	5% 4 21% 33% 30% 7%	680
July	1st to 10th	Day	6% 2 17% 33% 33% 10%	671
	11th to 20th	Day	3 1 10% 33% 40% 14%	668
	21st to end	Day	6% 2 9% 29% 38% 16%	739
August	1st to 10th	Day	4 2 11% 33% 37% 13%	538
	11th to 20th	Day	3 2 17% 36% 30% 11%	477
	21st to end	Day	3 1 15% 35% 31% 14%	539
September	1st to 10th	Day	4 1 17% 35% 28% 15%	490
	11th to 20th	Day	3 2 16% 31% 32% 15%	372
	21st to end	Day	9% 3 17% 24% 28% 19%	300
October	1st to 10th	Day	9% 5% 18% 26% 23% 19%	300
	11th to 20th	Day	4 4 23% 32% 26% 10%	300
	21st to end	Day	11% 7% 24% 29% 22% 7%	330
November	1st to 10th	Day	4 4 24% 38% 21% 9%	270
	11th to 20th	Day	4 7% 21% 37% 26% 4	270
	21st to end	Day	9% 9% 24% 33% 20% 6%	270
December	1st to 10th	Day	4 6% 24% 44% 19% 3	270
	11th to 20th	Day	9% 5% 26% 38% 21% 1	270
	21st to end	Day	8% 9% 33% 37% 11% 1	297
January	1st to 10th	Night	6% 5% 28% 46% 14% 2	950
	11th to 20th	Night	6% 5% 31% 43% 15% 1	950
	21st to end	Night	6% 5% 28% 49% 11% 1	877
February	1st to 10th	Night	7% 5% 34% 44% 9%	760
	11th to 20th	Night	7% 8% 40% 36% 9%	744
	21st to end	Night	7% 9% 39% 39% 6%	628
March	1st to 10th	Night	7% 7% 38% 38% 9% 1	760
	11th to 20th	Night	10% 8% 33% 37% 12% 1	736
	21st to end	Night	10% 11% 42% 31% 6%	627
April	1st to 10th	Night	9% 12% 44% 29% 5%	570
	11th to 20th	Night	12% 12% 43% 28% 4	563
	21st to end	Night	13% 12% 34% 32% 9%	570
May	1st to 10th	Night	13% 11% 36% 30% 10%	570
	11th to 20th	Night	11% 9% 31% 35% 12% 1	561
	21st to end	Night	11% 11% 39% 31% 8%	617
June	1st to 10th	Night	4 6% 32% 44% 12% 1	570
	11th to 20th	Night	5% 6% 42% 40% 8%	570
	21st to end	Night	6% 4 32% 46% 12% 1	570
July	1st to 10th	Night	6% 3 24% 47% 20% 1	555
	11th to 20th	Night	5% 1 16% 53% 24% 1	552
	21st to end	Night	8% 3 15% 45% 27% 2	624
August	1st to 10th	Night	7% 3 21% 38% 31% 1	567
	11th to 20th	Night	6% 3 24% 48% 19% 1	564
	21st to end	Night	4 1 19% 50% 25% 2	627
September	1st to 10th	Night	7% 2 24% 47% 20% 1	570
	11th to 20th	Night	6% 3 25% 44% 20% 1	570
	21st to end	Night	6% 5% 27% 42% 19% 1	570
October	1st to 10th	Night	11% 7% 28% 37% 17% 1	575
	11th to 20th	Night	4 7% 28% 40% 19% 2	760
	21st to end	Night	8% 8% 25% 38% 18% 2	971
November	1st to 10th	Night	4 4 27% 44% 20% 1	928
	11th to 20th	Night	6% 7% 25% 44% 18% 1	950
	21st to end	Night	8% 7% 24% 43% 17% 1	950
December	1st to 10th	Night	5% 6% 30% 45% 13% 1	950
	11th to 20th	Night	7% 7% 28% 43% 15% 1	950
	21st to end	Night	8% 10% 30% 41% 11%	1045

Page generated at 2024-10-29 09:20:49. Version ac07

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