Oberlin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oberlin clear sky chart from 2005-11-06 to 2025-02-21.

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% 11% 4 9% 5% 5% 4 4 5% 7% 31%	109143
	Night	15% 12% 4 9% 5% 4 4 4 5% 6% 31%	109420
Transparency	Day	51% 6% 12% 19% 11% 1	112804
	Night	52% 6% 11% 19% 11% 1	113886
Seeing	Day	20% 14% 28% 22% 12% 4	15342
	Night	21% 11% 27% 27% 12% 1	25028

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% 20% 8% 22% 5% 4 4 2 3 5% 12%	4056
	11th to 20th	Day	14% 22% 7% 15% 8% 6% 6% 3 3 3 13%	4060
	21st to end	Day	22% 18% 10% 12% 7% 5% 3 3 3 3 13%	4466
February	1st to 10th	Day	17% 18% 5% 13% 6% 4 4 3 4 4 21%	1800
	11th to 20th	Day	15% 14% 7% 15% 8% 5% 4 3 4 5% 20%	1852
	21st to end	Day	18% 14% 4 12% 5% 5% 4 4 5% 5% 24%	1570
March	1st to 10th	Day	23% 14% 5% 8% 4 3 3 3 4 5% 26%	3302
	11th to 20th	Day	13% 15% 4 10% 5% 5% 4 3 4 5% 33%	3480
	21st to end	Day	20% 12% 6% 9% 5% 4 4 3 4 5% 28%	3815
April	1st to 10th	Day	14% 14% 4 8% 6% 4 5% 4 5% 6% 31%	2113
	11th to 20th	Day	17% 10% 3 7% 5% 5% 4 3 4 6% 35%	2442
	21st to end	Day	20% 10% 2 7% 5% 3 4 3 5% 6% 35%	2470
May	1st to 10th	Day	19% 10% 3 8% 5% 5% 4 3 5% 6% 32%	4082
	11th to 20th	Day	18% 8% 2 7% 5% 4 4 3 5% 7% 35%	4081
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 6% 8% 40%	4476
June	1st to 10th	Day	13% 7% 3 6% 5% 5% 5% 4 7% 8% 39%	2565
	11th to 20th	Day	11% 6% 2 7% 6% 5% 5% 4 6% 8% 40%	2744
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 10% 41%	2705
July	1st to 10th	Day	9% 6% 2 7% 6% 5% 5% 4 6% 10% 40%	4412
	11th to 20th	Day	9% 4 2 5% 5% 4 4 5% 7% 10% 45%	4120
	21st to end	Day	9% 6% 3 7% 5% 5% 6% 5% 6% 8% 41%	4466
August	1st to 10th	Day	11% 7% 2 7% 4 5% 5% 3 6% 8% 41%	4104
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 10% 39%	4044
	21st to end	Day	9% 5% 2 7% 4 5% 5% 4 7% 10% 42%	4510
September	1st to 10th	Day	13% 6% 2 5% 4 5% 5% 4 6% 7% 44%	2128
	11th to 20th	Day	10% 6% 3 6% 5% 4 5% 3 5% 9% 44%	2090
	21st to end	Day	18% 8% 2 6% 4 5% 4 4 5% 7% 39%	2090
October	1st to 10th	Day	13% 8% 2 7% 4 5% 4 4 6% 7% 40%	1994
	11th to 20th	Day	17% 8% 3 7% 3 5% 4 3 5% 6% 37%	1900
	21st to end	Day	20% 11% 3 8% 4 4 4 4 5% 7% 29%	2043
November	1st to 10th	Day	12% 11% 3 7% 4 5% 5% 4 5% 7% 38%	1762
	11th to 20th	Day	17% 16% 4 7% 5% 4 4 4 4 6% 30%	1800
	21st to end	Day	17% 19% 5% 9% 5% 5% 5% 4 6% 6% 21%	1655
December	1st to 10th	Day	17% 15% 5% 13% 6% 5% 5% 4 5% 6% 20%	2600
	11th to 20th	Day	20% 20% 7% 11% 5% 4 3 3 4 5% 18%	2990
	21st to end	Day	23% 22% 7% 11% 6% 5% 4 3 4 3 12%	4356
January	1st to 10th	Night	15% 18% 8% 20% 6% 5% 3 3 4 4 15%	5889
	11th to 20th	Night	11% 20% 9% 17% 8% 6% 6% 5% 4 4 11%	5900
	21st to end	Night	21% 16% 7% 13% 5% 4 3 3 3 4 20%	6490
February	1st to 10th	Night	20% 14% 5% 12% 6% 5% 3 4 4 5% 22%	2600
	11th to 20th	Night	16% 15% 5% 12% 6% 5% 6% 3 4 5% 23%	2432
	21st to end	Night	20% 14% 4 11% 6% 5% 4 3 4 5% 24%	1885
March	1st to 10th	Night	21% 15% 4 6% 4 3 3 2 4 5% 34%	3549
	11th to 20th	Night	14% 10% 3 6% 5% 4 4 4 5% 6% 38%	3480
	21st to end	Night	18% 11% 4 9% 4 4 4 3 5% 6% 33%	3817
April	1st to 10th	Night	15% 13% 3 7% 6% 4 4 3 6% 6% 33%	2082
	11th to 20th	Night	16% 9% 3 7% 5% 3 5% 4 7% 7% 34%	1687
	21st to end	Night	17% 9% 3 7% 4 4 5% 3 6% 6% 36%	1710
May	1st to 10th	Night	20% 10% 3 8% 5% 5% 5% 3 5% 7% 28%	2813
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 6% 8% 36%	2812
	21st to end	Night	9% 5% 2 5% 5% 4 4 4 6% 9% 48%	3079
June	1st to 10th	Night	12% 6% 3 6% 5% 4 4 3 6% 7% 45%	1610
	11th to 20th	Night	9% 5% 2 7% 4 5% 5% 4 7% 9% 42%	1428
	21st to end	Night	10% 6% 2 5% 4 5% 5% 5% 6% 8% 44%	1466
July	1st to 10th	Night	10% 4 2 6% 4 4 4 4 6% 9% 47%	2551
	11th to 20th	Night	9% 3 2 5% 4 4 4 4 7% 9% 49%	2840
	21st to end	Night	6% 5% 3 6% 4 5% 5% 4 7% 9% 45%	3087
August	1st to 10th	Night	11% 6% 3 8% 4 4 4 4 6% 8% 42%	2825
	11th to 20th	Night	9% 7% 3 7% 4 4 4 4 5% 6% 46%	2785
	21st to end	Night	7% 5% 2 6% 4 5% 6% 4 6% 7% 47%	3124
September	1st to 10th	Night	10% 5% 2 5% 5% 5% 5% 4 5% 7% 48%	2037
	11th to 20th	Night	10% 4 2 5% 4 4 3 4 5% 7% 53%	2090
	21st to end	Night	15% 7% 3 6% 5% 4 5% 3 5% 6% 41%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 5% 5% 4 4 6% 44%	2185
	11th to 20th	Night	19% 8% 2 7% 5% 4 4 3 5% 7% 36%	2280
	21st to end	Night	22% 11% 3 7% 4 5% 4 3 5% 6% 30%	2553
November	1st to 10th	Night	15% 10% 3 7% 4 4 4 4 6% 6% 38%	2536
	11th to 20th	Night	16% 14% 4 8% 5% 5% 4 3 5% 5% 30%	2600
	21st to end	Night	21% 15% 4 9% 5% 5% 4 3 5% 6% 23%	2741
December	1st to 10th	Night	15% 16% 7% 10% 5% 5% 5% 3 5% 6% 22%	4580
	11th to 20th	Night	18% 19% 7% 11% 5% 4 4 3 4 5% 20%	5205
	21st to end	Night	23% 19% 5% 11% 6% 5% 4 3 4 5% 14%	6582

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	76% 4 9% 8% 3	4057
	11th to 20th	Day	76% 5% 8% 5% 5%	4060
	21st to end	Day	79% 3 6% 9% 4	4466
February	1st to 10th	Day	66% 4 11% 13% 6%	1800
	11th to 20th	Day	66% 5% 9% 14% 5% 1	1861
	21st to end	Day	59% 7% 14% 12% 7% 1	1570
March	1st to 10th	Day	60% 6% 10% 20% 5%	3302
	11th to 20th	Day	52% 8% 13% 21% 6% 1	3480
	21st to end	Day	56% 7% 11% 16% 9% 1	3815
April	1st to 10th	Day	52% 7% 12% 18% 11% 1	2113
	11th to 20th	Day	50% 6% 12% 17% 13% 2	2442
	21st to end	Day	50% 7% 11% 20% 10% 2	2470
May	1st to 10th	Day	51% 7% 10% 21% 9% 1	4120
	11th to 20th	Day	45% 9% 13% 23% 8% 1	4085
	21st to end	Day	37% 10% 14% 19% 15% 5%	4489
June	1st to 10th	Day	41% 8% 11% 25% 13% 1	2565
	11th to 20th	Day	40% 8% 14% 21% 15% 2	2744
	21st to end	Day	37% 8% 14% 21% 16% 3	2705
July	1st to 10th	Day	40% 4 12% 23% 17% 2	4343
	11th to 20th	Day	33% 5% 13% 29% 18% 2	4051
	21st to end	Day	40% 5% 16% 17% 20% 2	4324
August	1st to 10th	Day	41% 6% 15% 24% 13%	4091
	11th to 20th	Day	39% 5% 13% 32% 10% 1	4083
	21st to end	Day	38% 5% 15% 29% 12% 2	4510
September	1st to 10th	Day	38% 8% 15% 20% 16% 3	2128
	11th to 20th	Day	38% 6% 14% 24% 17% 2	2090
	21st to end	Day	45% 7% 10% 20% 18%	2090
October	1st to 10th	Day	32% 5% 14% 30% 18% 1	3306
	11th to 20th	Day	44% 4 11% 21% 19% 1	3140
	21st to end	Day	42% 4 12% 24% 17% 1	3345
November	1st to 10th	Day	46% 5% 12% 23% 14% 1	1762
	11th to 20th	Day	56% 5% 11% 18% 9% 1	1800
	21st to end	Day	62% 7% 12% 13% 6%	1655
December	1st to 10th	Day	66% 4 13% 13% 3	2600
	11th to 20th	Day	70% 5% 9% 12% 4	2986
	21st to end	Day	79% 4 7% 8% 3	4356
January	1st to 10th	Night	74% 4 7% 11% 3	5889
	11th to 20th	Night	78% 4 7% 7% 3	5900
	21st to end	Night	70% 4 10% 10% 7%	6490
February	1st to 10th	Night	65% 5% 11% 13% 5% 1	2600
	11th to 20th	Night	62% 7% 10% 15% 6%	2434
	21st to end	Night	62% 6% 9% 13% 7% 2	1885
March	1st to 10th	Night	54% 5% 13% 20% 8%	3549
	11th to 20th	Night	43% 9% 17% 20% 10% 1	3480
	21st to end	Night	48% 9% 10% 24% 9% 1	3817
April	1st to 10th	Night	50% 6% 12% 16% 13% 2	2082
	11th to 20th	Night	47% 7% 12% 16% 15% 3	1687
	21st to end	Night	46% 6% 12% 19% 14% 3	1710
May	1st to 10th	Night	53% 8% 10% 18% 9% 2	2840
	11th to 20th	Night	42% 10% 13% 20% 13% 2	2813
	21st to end	Night	30% 9% 15% 26% 17% 3	3087
June	1st to 10th	Night	39% 7% 12% 25% 15% 3	1610
	11th to 20th	Night	35% 8% 16% 21% 18% 2	1428
	21st to end	Night	35% 7% 14% 25% 16% 2	1466
July	1st to 10th	Night	34% 5% 13% 25% 17% 6%	2511
	11th to 20th	Night	31% 6% 14% 28% 18% 3	2786
	21st to end	Night	33% 6% 16% 21% 21% 3	2988
August	1st to 10th	Night	40% 7% 13% 25% 15% 2	2814
	11th to 20th	Night	38% 6% 11% 30% 14% 1	2812
	21st to end	Night	35% 6% 15% 28% 14% 3	3124
September	1st to 10th	Night	36% 7% 13% 24% 16% 4	2037
	11th to 20th	Night	29% 7% 12% 27% 22% 2	2090
	21st to end	Night	43% 7% 11% 20% 18% 1	2090
October	1st to 10th	Night	32% 4 8% 30% 25% 1	3640
	11th to 20th	Night	45% 4 10% 21% 19% 1	3779
	21st to end	Night	42% 4 10% 26% 17% 2	4201
November	1st to 10th	Night	44% 7% 13% 21% 14% 2	2536
	11th to 20th	Night	55% 5% 12% 17% 9% 2	2600
	21st to end	Night	61% 5% 13% 15% 5% 1	2741
December	1st to 10th	Night	63% 4 11% 16% 4	4580
	11th to 20th	Night	67% 5% 11% 14% 3	5208
	21st to end	Night	73% 5% 10% 10% 2	6582

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	26% 21% 36% 11% 5% 1	300
	11th to 20th	Day	29% 29% 31% 7% 4	300
	21st to end	Day	28% 27% 28% 15% 1 1	330
February	1st to 10th	Day	32% 23% 34% 8% 3	300
	11th to 20th	Day	31% 22% 34% 12% 2	300
	21st to end	Day	29% 29% 34% 8% 1	225
March	1st to 10th	Day	27% 20% 34% 15% 5%	374
	11th to 20th	Day	25% 17% 33% 18% 5%	460
	21st to end	Day	30% 17% 31% 17% 4 1	506
April	1st to 10th	Day	23% 18% 32% 18% 7% 1	460
	11th to 20th	Day	25% 19% 27% 17% 9% 4	452
	21st to end	Day	26% 15% 32% 17% 8% 2	460
May	1st to 10th	Day	26% 14% 29% 22% 6% 3	463
	11th to 20th	Day	21% 10% 32% 22% 11% 5%	487
	21st to end	Day	13% 9% 26% 28% 19% 5%	529
June	1st to 10th	Day	12% 9% 30% 31% 15% 3	490
	11th to 20th	Day	13% 8% 28% 32% 17% 3	574
	21st to end	Day	12% 10% 30% 30% 15% 3	680
July	1st to 10th	Day	10% 5% 22% 30% 22% 10%	656
	11th to 20th	Day	12% 5% 23% 29% 21% 8%	484
	21st to end	Day	10% 5% 24% 31% 22% 8%	532
August	1st to 10th	Day	10% 5% 22% 29% 24% 10%	486
	11th to 20th	Day	14% 5% 23% 28% 22% 9%	479
	21st to end	Day	11% 6% 20% 28% 24% 12%	539
September	1st to 10th	Day	14% 7% 22% 23% 23% 11%	490
	11th to 20th	Day	11% 5% 17% 27% 27% 13%	490
	21st to end	Day	21% 11% 25% 21% 13% 8%	490
October	1st to 10th	Day	12% 9% 28% 24% 19% 7%	490
	11th to 20th	Day	19% 18% 31% 23% 7% 3	490
	21st to end	Day	28% 20% 29% 18% 5%	492
November	1st to 10th	Day	19% 20% 32% 18% 9% 2	300
	11th to 20th	Day	28% 22% 28% 16% 6%	300
	21st to end	Day	33% 22% 33% 11% 1	227
December	1st to 10th	Day	24% 25% 32% 15% 4 2	200
	11th to 20th	Day	25% 25% 37% 12% 2	200
	21st to end	Day	28% 24% 33% 12% 2	307
January	1st to 10th	Night	27% 20% 32% 17% 4	800
	11th to 20th	Night	30% 19% 32% 15% 4	800
	21st to end	Night	26% 16% 34% 20% 3	880
February	1st to 10th	Night	27% 17% 32% 21% 3	800
	11th to 20th	Night	25% 18% 32% 22% 3	783
	21st to end	Night	28% 17% 34% 18% 3	629
March	1st to 10th	Night	24% 14% 32% 23% 6%	760
	11th to 20th	Night	21% 16% 33% 24% 6% 1	760
	21st to end	Night	25% 11% 30% 25% 9%	836
April	1st to 10th	Night	21% 15% 33% 27% 4	758
	11th to 20th	Night	21% 12% 32% 25% 8% 1	563
	21st to end	Night	21% 7% 34% 30% 7% 1	570
May	1st to 10th	Night	20% 9% 28% 33% 9% 1	570
	11th to 20th	Night	20% 7% 26% 32% 14% 1	561
	21st to end	Night	11% 5% 22% 37% 23% 3	617
June	1st to 10th	Night	13% 4 25% 42% 15% 1	470
	11th to 20th	Night	10% 3 27% 44% 16% 1	380
	21st to end	Night	11% 4 25% 40% 19% 1	516
July	1st to 10th	Night	10% 2 15% 41% 29% 2	555
	11th to 20th	Night	9% 5% 18% 42% 23% 3	552
	21st to end	Night	9% 2 17% 42% 28% 2	624
August	1st to 10th	Night	10% 2 14% 43% 27% 4	567
	11th to 20th	Night	11% 3 16% 39% 27% 4	564
	21st to end	Night	9% 3 18% 34% 31% 4	627
September	1st to 10th	Night	13% 5% 17% 36% 25% 4	750
	11th to 20th	Night	11% 4 13% 35% 31% 5%	760
	21st to end	Night	17% 9% 22% 30% 19% 3	760
October	1st to 10th	Night	16% 8% 23% 31% 19% 2	760
	11th to 20th	Night	23% 13% 29% 25% 9% 1	760
	21st to end	Night	27% 16% 29% 22% 6%	836
November	1st to 10th	Night	21% 12% 32% 25% 9% 1	780
	11th to 20th	Night	26% 14% 34% 19% 6% 1	800
	21st to end	Night	30% 16% 29% 19% 6%	800
December	1st to 10th	Night	28% 18% 31% 18% 5%	800
	11th to 20th	Night	27% 16% 36% 18% 3	800
	21st to end	Night	29% 17% 31% 20% 3	880

Page generated at 2025-02-18 03:26:32. Version ac07

Copyright © 2025 Attilla Danko.