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 2024-11-05.

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	14% 8% 3 6% 4 4 4 4 5% 7% 39%	101055
	Night	14% 8% 3 6% 4 4 4 3 5% 7% 41%	97993
Transparency	Day	42% 4 11% 25% 16% 2	104740
	Night	43% 3 10% 24% 18% 3	102448
Seeing	Day	19% 10% 26% 24% 14% 6%	15387
	Night	19% 10% 26% 28% 16% 2	25149

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	14% 15% 6% 9% 4 4 4 3 5% 7% 29%	2527
	11th to 20th	Day	19% 10% 3 12% 6% 4 4 3 3 5% 30%	2530
	21st to end	Day	27% 14% 7% 7% 4 3 3 2 5% 5% 23%	3169
February	1st to 10th	Day	18% 12% 4 10% 5% 3 2 2 4 7% 33%	1900
	11th to 20th	Day	16% 9% 4 6% 5% 4 5% 3 5% 7% 36%	1848
	21st to end	Day	18% 13% 5% 7% 4 3 5% 3 5% 6% 30%	1570
March	1st to 10th	Day	25% 15% 3 6% 4 3 3 2 3 5% 32%	3120
	11th to 20th	Day	13% 7% 3 6% 4 4 3 3 5% 7% 45%	3381
	21st to end	Day	14% 8% 2 7% 4 5% 5% 4 6% 8% 37%	3937
April	1st to 10th	Day	14% 7% 3 6% 5% 4 5% 3 6% 7% 40%	2280
	11th to 20th	Day	16% 10% 3 6% 5% 4 4 4 4 6% 39%	2254
	21st to end	Day	18% 6% 2 6% 5% 5% 4 4 5% 6% 38%	2419
May	1st to 10th	Day	20% 9% 2 7% 5% 4 5% 5% 7% 8% 29%	4082
	11th to 20th	Day	20% 7% 2 6% 3 4 4 3 4 6% 39%	4081
	21st to end	Day	11% 6% 3 7% 6% 5% 6% 4 7% 7% 38%	4476
June	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 6% 8% 45%	2574
	11th to 20th	Day	7% 5% 2 6% 6% 5% 5% 4 7% 9% 45%	2660
	21st to end	Day	8% 5% 2 5% 5% 5% 6% 5% 7% 10% 42%	2660
July	1st to 10th	Day	14% 6% 2 6% 4 4 5% 5% 6% 8% 40%	4440
	11th to 20th	Day	7% 4 1 5% 4 4 5% 4 7% 9% 49%	4440
	21st to end	Day	12% 8% 3 10% 6% 6% 7% 5% 8% 8% 27%	4480
August	1st to 10th	Day	8% 4 1 6% 4 4 4 4 7% 10% 49%	4104
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 6% 7% 10% 40%	3799
	21st to end	Day	6% 3 2 4 4 4 4 4 6% 10% 55%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 4 5% 3 5% 6% 47%	2228
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 47%	2090
	21st to end	Day	13% 5% 2 6% 4 4 4 3 5% 5% 49%	2090
October	1st to 10th	Day	11% 4 2 5% 3 3 4 3 4 6% 55%	2090
	11th to 20th	Day	13% 5% 3 6% 4 4 4 3 4 7% 48%	2000
	21st to end	Day	17% 7% 3 6% 4 4 4 3 6% 5% 42%	1881
November	1st to 10th	Day	11% 4 2 5% 4 3 4 3 4 6% 53%	1708
	11th to 20th	Day	16% 10% 3 4 3 3 3 3 5% 6% 43%	1710
	21st to end	Day	20% 8% 3 6% 3 4 3 3 5% 6% 40%	1710
December	1st to 10th	Day	21% 13% 4 6% 5% 3 4 2 4 5% 33%	1710
	11th to 20th	Day	15% 14% 5% 8% 5% 6% 3 3 4 6% 32%	2144
	21st to end	Day	20% 18% 5% 8% 5% 4 4 3 4 6% 23%	2783
January	1st to 10th	Night	16% 15% 6% 8% 5% 4 4 4 5% 6% 28%	4428
	11th to 20th	Night	16% 13% 5% 11% 7% 5% 4 3 4 4 28%	4440
	21st to end	Night	25% 14% 5% 7% 4 3 4 3 4 5% 27%	4482
February	1st to 10th	Night	21% 11% 4 9% 5% 4 4 3 5% 5% 30%	2280
	11th to 20th	Night	17% 9% 4 8% 5% 4 4 3 4 5% 36%	2218
	21st to end	Night	22% 10% 3 8% 4 4 4 4 4 6% 31%	1884
March	1st to 10th	Night	24% 15% 3 6% 3 3 3 3 4 5% 33%	3733
	11th to 20th	Night	14% 8% 2 6% 3 3 3 3 5% 5% 49%	3577
	21st to end	Night	15% 7% 2 7% 5% 4 4 3 5% 6% 41%	3722
April	1st to 10th	Night	12% 7% 2 6% 4 4 5% 4 5% 9% 42%	1900
	11th to 20th	Night	16% 8% 2 6% 4 3 4 3 5% 7% 42%	1875
	21st to end	Night	17% 7% 3 6% 5% 4 3 4 5% 7% 39%	1759
May	1st to 10th	Night	19% 10% 3 8% 5% 4 5% 4 6% 7% 30%	2813
	11th to 20th	Night	18% 5% 2 6% 4 4 4 4 5% 7% 43%	2812
	21st to end	Night	9% 5% 2 6% 5% 6% 5% 4 7% 9% 42%	3079
June	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 7% 10% 47%	1601
	11th to 20th	Night	7% 4 2 5% 4 3 4 5% 6% 9% 51%	1520
	21st to end	Night	5% 3 1 4 3 4 5% 5% 7% 12% 51%	1520
July	1st to 10th	Night	9% 5% 2 7% 4 4 4 4 5% 8% 48%	2530
	11th to 20th	Night	6% 4 2 4 3 4 4 3 6% 10% 55%	2530
	21st to end	Night	10% 7% 2 9% 7% 6% 6% 5% 8% 8% 31%	3056
August	1st to 10th	Night	6% 4 2 4 3 3 4 4 6% 9% 55%	2825
	11th to 20th	Night	6% 5% 2 5% 4 5% 5% 5% 6% 9% 48%	3027
	21st to end	Night	4 3 1 3 2 2 3 3 5% 10% 64%	3476
September	1st to 10th	Night	12% 4 2 5% 4 4 3 3 5% 7% 51%	1932
	11th to 20th	Night	10% 5% 1 5% 3 3 3 3 6% 9% 51%	2090
	21st to end	Night	13% 5% 2 6% 4 3 3 2 4 7% 52%	2090
October	1st to 10th	Night	8% 5% 1 5% 3 3 3 3 4 6% 59%	2090
	11th to 20th	Night	13% 7% 2 5% 4 4 4 3 5% 6% 49%	2177
	21st to end	Night	17% 7% 1 6% 3 3 3 2 4 6% 46%	2717
November	1st to 10th	Night	12% 6% 2 5% 4 4 3 3 4 5% 51%	2470
	11th to 20th	Night	15% 8% 2 6% 4 3 3 3 4 6% 45%	2470
	21st to end	Night	18% 10% 3 5% 4 4 4 3 4 6% 40%	2470
December	1st to 10th	Night	20% 10% 4 7% 4 4 3 3 4 6% 35%	2470
	11th to 20th	Night	18% 12% 4 8% 4 4 4 3 4 5% 34%	3046
	21st to end	Night	20% 17% 5% 9% 6% 6% 5% 3 4 5% 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% 12% 3	2419
May	1st to 10th	Day	52% 4 14% 19% 9% 1	4120
	11th to 20th	Day	47% 3 11% 24% 14% 1	4085
	21st to end	Day	43% 5% 12% 17% 21% 1	4489
June	1st to 10th	Day	37% 4 11% 27% 18% 3	2574
	11th to 20th	Day	34% 4 14% 26% 20% 2	2660
	21st to end	Day	35% 6% 14% 22% 19% 4	2660
July	1st to 10th	Day	41% 5% 12% 23% 17% 2	4371
	11th to 20th	Day	30% 5% 12% 36% 15% 2	4365
	21st to end	Day	52% 6% 13% 18% 10% 1	4338
August	1st to 10th	Day	29% 5% 14% 36% 15% 1	4091
	11th to 20th	Day	36% 5% 12% 30% 16% 1	3837
	21st to end	Day	25% 5% 13% 38% 16% 3	4179
September	1st to 10th	Day	37% 3 10% 24% 20% 5%	2228
	11th to 20th	Day	35% 5% 11% 25% 21% 3	2090
	21st to end	Day	38% 4 7% 25% 23% 3	2090
October	1st to 10th	Day	21% 2 5% 29% 40% 3	3480
	11th to 20th	Day	27% 3 10% 27% 31% 3	3294
	21st to end	Day	33% 2 9% 27% 23% 6%	3081
November	1st to 10th	Day	34% 2 8% 30% 21% 5%	1708
	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% 15% 3	1759
May	1st to 10th	Night	54% 4 12% 22% 7% 2	2840
	11th to 20th	Night	42% 5% 14% 28% 11% 1	2813
	21st to end	Night	37% 5% 14% 23% 17% 3	3087
June	1st to 10th	Night	33% 4 11% 29% 20% 4	1601
	11th to 20th	Night	29% 4 17% 24% 21% 5%	1520
	21st to end	Night	26% 5% 18% 25% 18% 7%	1520
July	1st to 10th	Night	35% 6% 10% 27% 19% 3	2490
	11th to 20th	Night	25% 4 12% 38% 18% 3	2482
	21st to end	Night	48% 6% 13% 20% 11% 1	2958
August	1st to 10th	Night	25% 5% 14% 39% 15% 1	2814
	11th to 20th	Night	30% 6% 14% 32% 18% 1	3055
	21st to end	Night	17% 4 15% 37% 23% 4	3476
September	1st to 10th	Night	34% 3 10% 25% 22% 6%	1932
	11th to 20th	Night	31% 3 8% 28% 25% 5%	2090
	21st to end	Night	34% 3 8% 26% 25% 5%	2090
October	1st to 10th	Night	20% 3 6% 19% 49% 4	3480
	11th to 20th	Night	25% 2 5% 25% 38% 4	3622
	21st to end	Night	31% 2 7% 23% 30% 7%	4467
November	1st to 10th	Night	36% 3 8% 24% 25% 5%	2470
	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% 16% 9% 1	460
May	1st to 10th	Day	25% 11% 32% 22% 6% 5%	463
	11th to 20th	Day	22% 9% 28% 25% 10% 5%	487
	21st to end	Day	14% 6% 26% 26% 17% 10%	529
June	1st to 10th	Day	15% 6% 26% 29% 16% 9%	594
	11th to 20th	Day	8% 6% 25% 35% 19% 8%	680
	21st to end	Day	11% 5% 29% 28% 19% 9%	680
July	1st to 10th	Day	16% 3 16% 25% 23% 16%	671
	11th to 20th	Day	9% 3 22% 33% 22% 11%	668
	21st to end	Day	11% 2 16% 36% 23% 11%	546
August	1st to 10th	Day	12% 3 17% 29% 24% 16%	486
	11th to 20th	Day	15% 3 20% 31% 21% 10%	479
	21st to end	Day	10% 2 14% 32% 26% 17%	539
September	1st to 10th	Day	14% 3 17% 31% 26% 9%	490
	11th to 20th	Day	11% 2 16% 32% 28% 11%	490
	21st to end	Day	18% 8% 19% 26% 20% 10%	490
October	1st to 10th	Day	12% 5% 23% 37% 18% 6%	490
	11th to 20th	Day	17% 14% 31% 23% 11% 4	466
	21st to end	Day	26% 12% 38% 18% 5% 1	330
November	1st to 10th	Day	16% 13% 34% 24% 10% 3	282
	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	570
May	1st to 10th	Night	19% 8% 33% 27% 13% 1	570
	11th to 20th	Night	17% 6% 21% 35% 18% 4	561
	21st to end	Night	9% 3 23% 34% 26% 6%	617
June	1st to 10th	Night	12% 2 21% 36% 26% 3	570
	11th to 20th	Night	8% 4 17% 44% 25% 2	570
	21st to end	Night	5% 2 21% 39% 28% 4	570
July	1st to 10th	Night	12% 1 12% 30% 35% 10%	555
	11th to 20th	Night	8% 2 10% 37% 37% 6%	552
	21st to end	Night	10% 1 13% 36% 33% 7%	624
August	1st to 10th	Night	10% 1 10% 35% 39% 6%	567
	11th to 20th	Night	7% 2 12% 40% 33% 6%	564
	21st to end	Night	7% 1 10% 32% 42% 7%	627
September	1st to 10th	Night	13% 2 12% 33% 35% 5%	602
	11th to 20th	Night	12% 3 15% 31% 34% 5%	760
	21st to end	Night	14% 6% 19% 30% 28% 4	760
October	1st to 10th	Night	10% 5% 20% 33% 27% 5%	760
	11th to 20th	Night	16% 10% 27% 28% 17% 3	760
	21st to end	Night	22% 9% 33% 24% 11%	836
November	1st to 10th	Night	15% 10% 30% 27% 16% 1	760
	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 2024-11-03 02:11:17. Version ac07

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