Corydon Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Corydon Ridge Observatory clear sky chart from 2005-11-06 to 2024-04-25.

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	15% 8% 3 6% 5% 3 5% 5% 5% 7% 39%	83440
	Night	15% 8% 3 6% 5% 3 4 4 5% 7% 40%	85710
Transparency	Day	45% 4 11% 23% 15% 2	83153
	Night	45% 3 10% 23% 16% 3	85518
Seeing	Day	20% 10% 26% 24% 14% 6%	14583
	Night	19% 10% 26% 28% 16% 2	24509

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	15% 14% 6% 8% 5% 3 4 4 5% 7% 29%	2527
	11th to 20th	Day	19% 9% 3 11% 7% 3 4 4 3 5% 30%	2530
	21st to end	Day	27% 13% 8% 6% 4 2 3 3 4 5% 23%	3169
February	1st to 10th	Day	18% 11% 4 9% 5% 2 3 3 4 7% 33%	1900
	11th to 20th	Day	16% 9% 4 6% 6% 3 4 4 5% 7% 36%	1848
	21st to end	Day	18% 12% 5% 6% 5% 2 5% 5% 5% 7% 30%	1570
March	1st to 10th	Day	25% 15% 3 5% 4 2 3 3 3 5% 32%	3120
	11th to 20th	Day	14% 7% 3 5% 5% 2 4 3 5% 7% 45%	3381
	21st to end	Day	14% 7% 3 6% 5% 4 5% 5% 6% 8% 37%	3937
April	1st to 10th	Day	15% 7% 3 6% 5% 3 5% 4 6% 7% 40%	2280
	11th to 20th	Day	17% 9% 3 5% 6% 3 4 5% 4 6% 39%	2254
	21st to end	Day	18% 5% 3 5% 6% 4 3 5% 5% 6% 39%	2343
May	1st to 10th	Day	18% 7% 3 5% 6% 3 4 5% 6% 7% 35%	2340
	11th to 20th	Day	18% 7% 3 6% 5% 4 6% 5% 4 7% 36%	2301
	21st to end	Day	10% 5% 3 6% 8% 4 7% 6% 7% 9% 36%	2531
June	1st to 10th	Day	11% 4 3 6% 6% 3 4 4 6% 8% 46%	2438
	11th to 20th	Day	7% 4 2 5% 6% 3 6% 6% 7% 9% 45%	2520
	21st to end	Day	9% 4 3 4 5% 4 6% 6% 7% 11% 42%	2520
July	1st to 10th	Day	12% 6% 3 5% 6% 4 6% 6% 6% 9% 36%	2520
	11th to 20th	Day	8% 5% 2 4 6% 4 6% 6% 6% 9% 44%	2520
	21st to end	Day	9% 5% 2 6% 5% 3 6% 6% 7% 10% 40%	2561
August	1st to 10th	Day	9% 5% 2 6% 5% 3 5% 6% 7% 10% 42%	2327
	11th to 20th	Day	9% 6% 3 5% 6% 4 6% 5% 7% 9% 40%	2169
	21st to end	Day	8% 4 2 5% 5% 3 5% 6% 6% 9% 47%	2376
September	1st to 10th	Day	14% 5% 2 4 5% 3 5% 4 5% 6% 46%	2111
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 6% 8% 47%	1980
	21st to end	Day	12% 5% 2 5% 4 3 4 4 5% 5% 51%	1980
October	1st to 10th	Day	11% 5% 2 4 4 3 3 4 4 6% 54%	1980
	11th to 20th	Day	14% 5% 3 5% 5% 3 4 4 4 7% 47%	1896
	21st to end	Day	18% 7% 3 5% 5% 3 4 4 5% 5% 41%	1782
November	1st to 10th	Day	12% 4 2 5% 4 3 3 4 4 6% 53%	1672
	11th to 20th	Day	17% 9% 3 4 4 2 4 3 5% 6% 43%	1710
	21st to end	Day	20% 8% 3 5% 4 2 4 3 5% 7% 40%	1710
December	1st to 10th	Day	22% 11% 5% 5% 6% 2 4 3 4 5% 33%	1710
	11th to 20th	Day	15% 13% 5% 7% 6% 4 4 3 4 6% 32%	2144
	21st to end	Day	20% 17% 5% 7% 6% 3 4 4 4 6% 24%	2783
January	1st to 10th	Night	16% 14% 6% 7% 5% 3 4 5% 5% 6% 28%	4428
	11th to 20th	Night	17% 13% 6% 10% 9% 3 5% 3 4 4 28%	4440
	21st to end	Night	25% 13% 5% 6% 5% 3 4 4 4 5% 27%	4482
February	1st to 10th	Night	22% 10% 4 8% 6% 3 4 4 5% 5% 30%	2280
	11th to 20th	Night	18% 8% 4 8% 6% 3 4 4 4 5% 36%	2218
	21st to end	Night	22% 10% 4 7% 5% 3 4 4 4 6% 31%	1884
March	1st to 10th	Night	24% 14% 3 5% 4 3 3 3 4 4 33%	3733
	11th to 20th	Night	14% 7% 2 5% 4 2 3 4 4 5% 49%	3577
	21st to end	Night	15% 7% 3 7% 6% 3 4 4 4 6% 41%	3722
April	1st to 10th	Night	12% 6% 2 5% 5% 3 5% 5% 5% 9% 42%	1900
	11th to 20th	Night	16% 8% 3 5% 5% 2 5% 4 5% 7% 42%	1875
	21st to end	Night	17% 6% 3 5% 5% 3 4 4 5% 7% 40%	1714
May	1st to 10th	Night	16% 6% 3 6% 6% 2 5% 5% 6% 7% 38%	1620
	11th to 20th	Night	14% 4 2 6% 6% 4 5% 6% 5% 8% 40%	1592
	21st to end	Night	7% 5% 2 5% 6% 5% 6% 6% 8% 10% 40%	1744
June	1st to 10th	Night	9% 4 2 5% 5% 3 4 4 6% 10% 48%	1517
	11th to 20th	Night	7% 4 3 4 4 2 5% 5% 6% 9% 51%	1440
	21st to end	Night	5% 3 1 3 4 3 5% 6% 7% 12% 51%	1440
July	1st to 10th	Night	9% 5% 3 5% 5% 3 5% 5% 6% 9% 45%	1440
	11th to 20th	Night	6% 4 2 4 4 3 4 4 7% 11% 50%	1440
	21st to end	Night	8% 5% 1 4 5% 3 5% 5% 7% 9% 47%	1753
August	1st to 10th	Night	7% 3 3 4 4 2 4 5% 7% 10% 51%	1611
	11th to 20th	Night	6% 4 2 4 5% 4 5% 7% 6% 10% 46%	1729
	21st to end	Night	6% 4 1 3 4 2 3 4 6% 12% 55%	1980
September	1st to 10th	Night	13% 3 2 4 5% 3 4 4 5% 7% 51%	1830
	11th to 20th	Night	11% 5% 1 4 4 2 3 4 6% 9% 51%	1980
	21st to end	Night	12% 4 2 5% 4 2 3 3 4 7% 54%	1980
October	1st to 10th	Night	8% 5% 1 4 4 2 3 3 5% 6% 58%	1980
	11th to 20th	Night	13% 7% 2 4 5% 3 4 4 5% 6% 47%	2061
	21st to end	Night	18% 7% 2 5% 4 3 3 3 4 6% 45%	2574
November	1st to 10th	Night	13% 5% 3 4 4 3 3 4 4 5% 52%	2406
	11th to 20th	Night	15% 7% 3 5% 5% 3 3 4 4 6% 45%	2470
	21st to end	Night	18% 10% 3 5% 4 3 4 4 4 6% 40%	2470
December	1st to 10th	Night	20% 10% 4 6% 5% 3 4 4 4 6% 35%	2470
	11th to 20th	Night	18% 11% 4 8% 4 2 4 4 4 6% 34%	3046
	21st to end	Night	20% 16% 5% 8% 8% 4 5% 4 4 4 21%	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% 3 11% 20% 9% 1	2528
	11th to 20th	Day	59% 2 9% 20% 9% 1	2530
	21st to end	Day	65% 2 8% 20% 5% 1	3169
February	1st to 10th	Day	54% 2 8% 23% 11% 2	1900
	11th to 20th	Day	50% 3 9% 23% 13% 2	1858
	21st to end	Day	54% 3 10% 20% 11% 3	1570
March	1st to 10th	Day	58% 2 6% 19% 11% 4	3120
	11th to 20th	Day	39% 4 10% 28% 18% 2	3381
	21st to end	Day	44% 4 14% 23% 13% 1	3937
April	1st to 10th	Day	44% 3 12% 24% 17% 1	2280
	11th to 20th	Day	47% 3 8% 23% 16% 3	2254
	21st to end	Day	46% 4 10% 25% 13% 3	2343
May	1st to 10th	Day	48% 4 12% 23% 11% 1	2340
	11th to 20th	Day	49% 4 12% 20% 14% 1	2305
	21st to end	Day	43% 6% 16% 20% 14% 1	2531
June	1st to 10th	Day	37% 4 10% 28% 19% 3	2438
	11th to 20th	Day	35% 4 14% 26% 18% 2	2520
	21st to end	Day	36% 6% 14% 22% 19% 4	2520
July	1st to 10th	Day	44% 5% 12% 22% 14% 3	2451
	11th to 20th	Day	35% 5% 14% 27% 15% 4	2445
	21st to end	Day	37% 5% 15% 25% 15% 2	2419
August	1st to 10th	Day	35% 5% 14% 27% 17% 1	2314
	11th to 20th	Day	39% 4 12% 27% 16% 2	2169
	21st to end	Day	33% 5% 13% 26% 18% 6%	2376
September	1st to 10th	Day	38% 3 11% 25% 18% 5%	2111
	11th to 20th	Day	35% 5% 11% 25% 21% 3	1980
	21st to end	Day	35% 4 7% 26% 24% 3	1980
October	1st to 10th	Day	33% 3 7% 28% 25% 4	1980
	11th to 20th	Day	38% 2 8% 25% 23% 4	1896
	21st to end	Day	45% 2 9% 25% 16% 3	1782
November	1st to 10th	Day	34% 2 8% 30% 21% 5%	1672
	11th to 20th	Day	43% 2 8% 24% 18% 5%	1710
	21st to end	Day	47% 2 7% 24% 18% 1	1710
December	1st to 10th	Day	55% 2 10% 21% 11% 1	1710
	11th to 20th	Day	55% 3 7% 22% 12% 1	2141
	21st to end	Day	62% 3 9% 16% 8% 1	2783
January	1st to 10th	Night	57% 3 10% 18% 11% 1	4428
	11th to 20th	Night	61% 2 8% 19% 9% 1	4440
	21st to end	Night	60% 2 7% 19% 10% 1	4482
February	1st to 10th	Night	57% 3 9% 22% 8% 1	2280
	11th to 20th	Night	52% 2 8% 23% 14% 1	2219
	21st to end	Night	55% 3 10% 17% 11% 3	1884
March	1st to 10th	Night	56% 2 6% 21% 12% 2	3733
	11th to 20th	Night	39% 2 11% 27% 19% 3	3577
	21st to end	Night	45% 3 11% 26% 15% 1	3722
April	1st to 10th	Night	40% 4 11% 25% 17% 3	1900
	11th to 20th	Night	44% 2 9% 21% 19% 5%	1875
	21st to end	Night	45% 2 10% 24% 16% 3	1714
May	1st to 10th	Night	46% 4 10% 26% 12% 3	1620
	11th to 20th	Night	44% 5% 13% 21% 17% 1	1593
	21st to end	Night	37% 6% 16% 22% 16% 3	1745
June	1st to 10th	Night	32% 4 11% 28% 20% 4	1517
	11th to 20th	Night	29% 4 17% 24% 20% 5%	1440
	21st to end	Night	26% 5% 18% 25% 18% 7%	1440
July	1st to 10th	Night	36% 5% 13% 26% 17% 3	1400
	11th to 20th	Night	29% 4 15% 29% 18% 6%	1392
	21st to end	Night	32% 5% 13% 30% 17% 2	1655
August	1st to 10th	Night	29% 5% 17% 29% 18% 3	1600
	11th to 20th	Night	32% 6% 15% 28% 17% 2	1729
	21st to end	Night	24% 4 17% 30% 21% 5%	1980
September	1st to 10th	Night	34% 3 10% 26% 21% 6%	1830
	11th to 20th	Night	32% 3 8% 29% 24% 5%	1980
	21st to end	Night	32% 2 7% 27% 27% 5%	1980
October	1st to 10th	Night	28% 3 10% 26% 28% 5%	1980
	11th to 20th	Night	39% 3 6% 24% 24% 4	2061
	21st to end	Night	43% 2 7% 23% 21% 4	2574
November	1st to 10th	Night	36% 3 8% 24% 24% 5%	2406
	11th to 20th	Night	41% 3 7% 23% 21% 6%	2470
	21st to end	Night	48% 2 8% 23% 18% 1	2470
December	1st to 10th	Night	52% 2 11% 22% 12% 1	2470
	11th to 20th	Night	53% 3 9% 21% 13% 2	3048
	21st to end	Night	66% 3 8% 14% 7% 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	27% 17% 33% 18% 4	270
	11th to 20th	Day	29% 25% 31% 13% 3	270
	21st to end	Day	31% 27% 28% 12% 2	297
February	1st to 10th	Day	27% 21% 37% 12% 2	270
	11th to 20th	Day	30% 26% 33% 9% 2	270
	21st to end	Day	34% 20% 35% 8% 2	225
March	1st to 10th	Day	29% 21% 36% 11% 2	270
	11th to 20th	Day	27% 20% 34% 12% 6% 1	400
	21st to end	Day	29% 16% 34% 15% 5% 1	506
April	1st to 10th	Day	24% 17% 29% 21% 8% 1	460
	11th to 20th	Day	26% 15% 27% 22% 7% 3	452
	21st to end	Day	24% 15% 35% 15% 10% 1	437
May	1st to 10th	Day	25% 11% 33% 21% 5% 5%	423
	11th to 20th	Day	22% 9% 29% 26% 10% 4	447
	21st to end	Day	14% 6% 24% 27% 18% 11%	485
June	1st to 10th	Day	15% 5% 24% 30% 17% 9%	548
	11th to 20th	Day	8% 6% 25% 34% 19% 8%	630
	21st to end	Day	11% 4 27% 28% 20% 9%	630
July	1st to 10th	Day	16% 2 15% 26% 24% 17%	621
	11th to 20th	Day	10% 3 20% 33% 23% 12%	618
	21st to end	Day	11% 1 15% 36% 25% 12%	502
August	1st to 10th	Day	12% 3 16% 29% 24% 16%	446
	11th to 20th	Day	16% 2 18% 32% 22% 10%	439
	21st to end	Day	10% 2 15% 31% 26% 16%	495
September	1st to 10th	Day	15% 3 16% 30% 27% 9%	450
	11th to 20th	Day	11% 3 16% 31% 29% 12%	450
	21st to end	Day	16% 7% 18% 27% 22% 10%	450
October	1st to 10th	Day	13% 5% 23% 37% 16% 6%	450
	11th to 20th	Day	17% 14% 33% 24% 9% 3	428
	21st to end	Day	29% 12% 36% 18% 5% 1	297
November	1st to 10th	Day	17% 13% 33% 23% 10% 3	270
	11th to 20th	Day	28% 15% 31% 20% 5% 1	270
	21st to end	Day	26% 14% 36% 17% 7%	270
December	1st to 10th	Day	28% 19% 30% 17% 6% 1	270
	11th to 20th	Day	25% 16% 39% 14% 5% 1	270
	21st to end	Day	36% 18% 31% 12% 3	297
January	1st to 10th	Night	23% 18% 32% 23% 4	950
	11th to 20th	Night	28% 16% 33% 19% 3	950
	21st to end	Night	24% 17% 35% 21% 2	842
February	1st to 10th	Night	29% 14% 32% 23% 2	760
	11th to 20th	Night	25% 18% 35% 20% 2	743
	21st to end	Night	30% 16% 35% 18% 2	628
March	1st to 10th	Night	25% 16% 31% 23% 5%	760
	11th to 20th	Night	25% 15% 33% 22% 6%	760
	21st to end	Night	24% 12% 30% 28% 5% 1	779
April	1st to 10th	Night	17% 12% 34% 28% 9%	570
	11th to 20th	Night	20% 11% 31% 26% 10% 1	563
	21st to end	Night	20% 9% 33% 29% 8% 1	555
May	1st to 10th	Night	19% 7% 34% 27% 13% 1	540
	11th to 20th	Night	17% 6% 21% 34% 18% 4	531
	21st to end	Night	9% 2 23% 33% 27% 6%	584
June	1st to 10th	Night	12% 2 21% 36% 27% 3	540
	11th to 20th	Night	7% 4 17% 43% 26% 2	540
	21st to end	Night	5% 2 21% 39% 29% 4	540
July	1st to 10th	Night	12% 1 10% 30% 36% 10%	525
	11th to 20th	Night	8% 2 9% 36% 39% 7%	522
	21st to end	Night	10% 1 12% 36% 33% 7%	591
August	1st to 10th	Night	10% 1 9% 35% 40% 6%	537
	11th to 20th	Night	7% 1 12% 39% 34% 6%	534
	21st to end	Night	8% 1 11% 33% 42% 6%	594
September	1st to 10th	Night	13% 1 12% 33% 35% 5%	570
	11th to 20th	Night	12% 3 15% 30% 34% 5%	720
	21st to end	Night	13% 6% 19% 29% 29% 4	720
October	1st to 10th	Night	11% 5% 21% 33% 26% 5%	720
	11th to 20th	Night	17% 9% 27% 28% 16% 2	720
	21st to end	Night	23% 9% 32% 24% 10% 1	792
November	1st to 10th	Night	16% 10% 29% 26% 17% 1	740
	11th to 20th	Night	19% 15% 30% 25% 11% 1	760
	21st to end	Night	24% 14% 23% 28% 11%	760
December	1st to 10th	Night	25% 14% 30% 25% 6%	760
	11th to 20th	Night	24% 14% 29% 25% 7% 1	764
	21st to end	Night	32% 13% 29% 23% 4	1045

Page generated at 2024-04-22 09:25:46. Version ac07

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