Edinboro University Planetarium and Observatory.
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edinboro University Planetarium and Observatory. clear sky chart from 2005-11-06 to 2025-01-07.

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	17% 13% 5% 9% 5% 4 4 3 5% 6% 28%	104858
	Night	17% 15% 5% 10% 5% 4 4 3 4 5% 27%	104127
Transparency	Day	56% 3 10% 20% 10% 1	108501
	Night	58% 3 10% 18% 9% 1	108623
Seeing	Day	26% 15% 29% 19% 8% 3	14715
	Night	26% 14% 27% 22% 9% 1	24398

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	18% 25% 13% 15% 5% 3 3 2 3 4 10%	2736
	11th to 20th	Day	12% 25% 10% 18% 8% 5% 3 1 3 4 12%	2840
	21st to end	Day	25% 20% 11% 18% 6% 4 3 2 2 2 7%	3124
February	1st to 10th	Day	17% 20% 7% 15% 10% 5% 3 2 3 4 15%	1710
	11th to 20th	Day	15% 18% 8% 16% 8% 5% 4 3 3 4 15%	1663
	21st to end	Day	17% 19% 4 14% 5% 3 4 3 4 5% 21%	1531
March	1st to 10th	Day	20% 13% 8% 9% 4 4 4 3 5% 6% 25%	3435
	11th to 20th	Day	11% 21% 8% 9% 4 3 4 3 4 5% 28%	3480
	21st to end	Day	21% 15% 4 11% 4 3 3 2 4 5% 27%	3815
April	1st to 10th	Day	17% 15% 4 7% 5% 4 4 3 5% 6% 30%	2199
	11th to 20th	Day	20% 14% 3 6% 4 4 4 3 5% 5% 32%	2324
	21st to end	Day	20% 14% 3 7% 4 3 4 3 4 6% 33%	2470
May	1st to 10th	Day	20% 9% 3 9% 5% 4 4 3 5% 6% 31%	4082
	11th to 20th	Day	19% 11% 3 8% 5% 4 4 3 6% 7% 30%	4132
	21st to end	Day	13% 6% 2 6% 4 5% 5% 4 6% 8% 41%	4823
June	1st to 10th	Day	17% 7% 2 6% 5% 4 4 4 6% 8% 36%	2660
	11th to 20th	Day	15% 7% 3 7% 5% 4 5% 3 6% 9% 36%	2660
	21st to end	Day	16% 6% 2 6% 4 5% 4 4 7% 8% 38%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 4 6% 10% 39%	4440
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 6% 9% 41%	4163
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 7% 39%	4466
August	1st to 10th	Day	15% 7% 2 7% 5% 6% 5% 5% 6% 9% 32%	4104
	11th to 20th	Day	15% 7% 3 8% 5% 5% 6% 5% 8% 8% 29%	4044
	21st to end	Day	12% 5% 3 7% 5% 4 5% 5% 7% 9% 38%	4354
September	1st to 10th	Day	18% 7% 3 6% 4 4 4 3 5% 8% 37%	2280
	11th to 20th	Day	12% 7% 2 6% 5% 4 5% 4 6% 7% 41%	2104
	21st to end	Day	21% 9% 3 7% 5% 4 4 4 5% 6% 32%	2085
October	1st to 10th	Day	18% 9% 2 7% 4 4 4 4 6% 7% 34%	1900
	11th to 20th	Day	23% 10% 3 8% 6% 4 4 3 5% 6% 28%	1900
	21st to end	Day	26% 14% 3 8% 5% 5% 5% 3 4 6% 22%	2090
November	1st to 10th	Day	14% 15% 3 8% 5% 4 4 4 5% 6% 31%	1829
	11th to 20th	Day	17% 22% 4 9% 4 3 4 3 4 6% 23%	1605
	21st to end	Day	19% 27% 7% 8% 5% 4 4 3 4 6% 14%	1600
December	1st to 10th	Day	18% 30% 15% 13% 4 3 3 2 2 2 7%	2600
	11th to 20th	Day	22% 26% 9% 12% 5% 3 3 2 4 4 11%	2990
	21st to end	Day	23% 26% 8% 14% 5% 4 3 2 2 3 9%	3960
January	1st to 10th	Night	17% 24% 12% 19% 4 4 3 2 3 3 10%	4338
	11th to 20th	Night	15% 22% 11% 19% 6% 4 4 3 3 3 10%	4120
	21st to end	Night	25% 21% 10% 16% 5% 3 3 2 2 2 10%	4532
February	1st to 10th	Night	18% 20% 5% 14% 8% 5% 3 2 3 4 17%	2470
	11th to 20th	Night	15% 18% 8% 15% 7% 6% 4 3 4 4 16%	2403
	21st to end	Night	19% 15% 6% 16% 6% 4 4 3 3 4 21%	1919
March	1st to 10th	Night	21% 17% 4 8% 5% 3 3 2 3 5% 28%	3418
	11th to 20th	Night	17% 17% 9% 9% 4 2 3 3 4 5% 28%	3480
	21st to end	Night	17% 14% 5% 10% 5% 3 3 3 3 3 34%	3817
April	1st to 10th	Night	18% 17% 4 6% 4 4 3 4 4 5% 29%	1981
	11th to 20th	Night	19% 11% 2 7% 5% 4 4 3 5% 6% 32%	1820
	21st to end	Night	15% 12% 3 7% 5% 4 4 4 5% 7% 33%	1710
May	1st to 10th	Night	25% 10% 2 7% 3 4 3 3 4 6% 32%	2813
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 3 5% 7% 35%	2759
	21st to end	Night	14% 5% 2 4 4 3 4 3 6% 11% 45%	2732
June	1st to 10th	Night	11% 6% 3 6% 5% 6% 5% 4 7% 8% 39%	1520
	11th to 20th	Night	11% 7% 3 7% 6% 4 4 4 7% 7% 42%	1520
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 6% 9% 40%	1520
July	1st to 10th	Night	12% 8% 3 7% 5% 3 4 3 5% 8% 41%	2520
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 6% 9% 44%	2793
	21st to end	Night	9% 6% 2 6% 4 5% 5% 4 6% 8% 44%	3087
August	1st to 10th	Night	12% 8% 3 8% 5% 5% 4 5% 5% 7% 38%	2825
	11th to 20th	Night	15% 8% 3 7% 4 4 5% 4 5% 6% 39%	2785
	21st to end	Night	9% 6% 3 7% 4 5% 5% 5% 7% 8% 42%	3270
September	1st to 10th	Night	14% 6% 2 6% 4 3 4 4 5% 7% 44%	1900
	11th to 20th	Night	12% 6% 2 5% 4 4 3 3 6% 6% 49%	2072
	21st to end	Night	19% 8% 2 7% 4 4 5% 3 5% 7% 35%	2094
October	1st to 10th	Night	19% 6% 2 6% 4 3 4 3 5% 7% 40%	2280
	11th to 20th	Night	22% 10% 2 8% 4 5% 5% 4 5% 5% 30%	2280
	21st to end	Night	26% 12% 3 6% 4 4 4 2 5% 5% 27%	2508
November	1st to 10th	Night	16% 13% 3 8% 4 4 4 3 6% 6% 32%	2468
	11th to 20th	Night	19% 20% 4 9% 4 4 5% 3 5% 5% 21%	2792
	21st to end	Night	19% 24% 6% 9% 4 4 3 3 4 5% 19%	2800
December	1st to 10th	Night	16% 23% 14% 13% 4 4 3 3 3 3 12%	4580
	11th to 20th	Night	19% 26% 10% 13% 4 4 3 2 3 4 14%	5205
	21st to end	Night	21% 25% 7% 12% 7% 4 3 3 4 4 11%	6996

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	82% 1 7% 7% 3	2737
	11th to 20th	Day	79% 1 7% 10% 3	2840
	21st to end	Day	87% 1 5% 5% 2	3124
February	1st to 10th	Day	77% 2 7% 10% 4	1710
	11th to 20th	Day	75% 3 5% 12% 6%	1672
	21st to end	Day	67% 2 9% 15% 5% 2	1531
March	1st to 10th	Day	62% 2 8% 24% 4	3435
	11th to 20th	Day	61% 2 15% 16% 5% 1	3480
	21st to end	Day	62% 1 6% 19% 11% 1	3815
April	1st to 10th	Day	56% 2 11% 18% 12% 1	2199
	11th to 20th	Day	54% 3 9% 21% 12% 2	2324
	21st to end	Day	55% 2 10% 20% 11% 3	2470
May	1st to 10th	Day	56% 2 7% 24% 10% 1	4120
	11th to 20th	Day	54% 2 11% 23% 9% 1	4136
	21st to end	Day	42% 3 13% 23% 16% 4	4837
June	1st to 10th	Day	46% 3 12% 25% 13% 1	2660
	11th to 20th	Day	45% 4 14% 24% 13% 1	2660
	21st to end	Day	43% 4 11% 27% 14% 1	2660
July	1st to 10th	Day	39% 5% 13% 25% 16% 2	4370
	11th to 20th	Day	38% 5% 12% 26% 17% 1	4092
	21st to end	Day	40% 7% 12% 24% 16% 1	4324
August	1st to 10th	Day	46% 6% 13% 24% 11%	4091
	11th to 20th	Day	47% 6% 15% 25% 6% 1	4083
	21st to end	Day	39% 6% 12% 29% 13% 1	4354
September	1st to 10th	Day	45% 4 12% 23% 14% 2	2280
	11th to 20th	Day	41% 4 12% 26% 17%	2104
	21st to end	Day	53% 3 10% 23% 11% 1	2085
October	1st to 10th	Day	40% 5% 14% 24% 17% 1	3160
	11th to 20th	Day	49% 4 12% 19% 13% 4	3140
	21st to end	Day	49% 4 14% 24% 9% 1	3428
November	1st to 10th	Day	55% 3 9% 20% 11% 2	1829
	11th to 20th	Day	64% 3 10% 14% 7% 2	1605
	21st to end	Day	75% 3 8% 9% 4 1	1600
December	1st to 10th	Day	86% 3 5% 5% 1	2600
	11th to 20th	Day	80% 2 6% 11% 1	2986
	21st to end	Day	84% 2 7% 7% 1	3960
January	1st to 10th	Night	83% 1 6% 8% 2	4338
	11th to 20th	Night	81% 1 7% 8% 2	4120
	21st to end	Night	84% 1 6% 8% 2	4532
February	1st to 10th	Night	74% 2 7% 12% 4	2470
	11th to 20th	Night	73% 2 7% 13% 4	2405
	21st to end	Night	69% 2 9% 12% 7% 1	1919
March	1st to 10th	Night	61% 2 9% 22% 6%	3418
	11th to 20th	Night	62% 1 12% 18% 7% 1	3480
	21st to end	Night	57% 1 7% 18% 14% 2	3817
April	1st to 10th	Night	58% 3 9% 17% 12% 1	1981
	11th to 20th	Night	53% 3 10% 19% 13% 3	1820
	21st to end	Night	51% 3 11% 21% 11% 3	1710
May	1st to 10th	Night	55% 2 8% 20% 12% 3	2840
	11th to 20th	Night	50% 3 11% 24% 11% 2	2760
	21st to end	Night	36% 3 12% 29% 16% 3	2739
June	1st to 10th	Night	41% 5% 12% 25% 15% 2	1520
	11th to 20th	Night	41% 3 13% 24% 17% 2	1520
	21st to end	Night	41% 5% 13% 24% 16% 1	1520
July	1st to 10th	Night	42% 4 11% 22% 18% 3	2480
	11th to 20th	Night	37% 5% 13% 27% 17% 2	2741
	21st to end	Night	37% 7% 12% 23% 21% 1	2988
August	1st to 10th	Night	43% 5% 10% 28% 12% 1	2814
	11th to 20th	Night	44% 6% 13% 28% 8% 1	2812
	21st to end	Night	36% 6% 15% 28% 13% 1	3270
September	1st to 10th	Night	38% 4 13% 27% 15% 3	1900
	11th to 20th	Night	36% 4 12% 27% 20% 1	2072
	21st to end	Night	50% 2 12% 22% 13% 1	2094
October	1st to 10th	Night	40% 5% 9% 24% 21% 1	3800
	11th to 20th	Night	49% 5% 11% 17% 15% 4	3779
	21st to end	Night	45% 3 14% 24% 14% 1	4120
November	1st to 10th	Night	53% 3 11% 22% 10% 2	2468
	11th to 20th	Night	65% 3 8% 14% 7% 3	2792
	21st to end	Night	70% 2 10% 14% 3 1	2800
December	1st to 10th	Night	77% 4 9% 8% 1	4580
	11th to 20th	Night	78% 2 8% 11% 2	5208
	21st to end	Night	78% 3 8% 10% 1	6996

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% 27% 28% 9% 2	243
	11th to 20th	Day	33% 30% 27% 6% 3 1	270
	21st to end	Day	34% 29% 28% 7% 2	297
February	1st to 10th	Day	38% 21% 35% 6%	270
	11th to 20th	Day	39% 24% 30% 6% 1	270
	21st to end	Day	44% 24% 27% 5%	234
March	1st to 10th	Day	33% 23% 32% 10% 3	460
	11th to 20th	Day	33% 20% 33% 11% 2 1	460
	21st to end	Day	38% 21% 25% 13% 2	506
April	1st to 10th	Day	31% 22% 30% 11% 5% 1	460
	11th to 20th	Day	35% 18% 26% 12% 8% 2	452
	21st to end	Day	30% 19% 31% 14% 4 1	460
May	1st to 10th	Day	31% 14% 33% 16% 4 2	463
	11th to 20th	Day	26% 14% 27% 21% 10% 2	487
	21st to end	Day	17% 9% 33% 24% 12% 5%	529
June	1st to 10th	Day	20% 12% 30% 25% 9% 3	490
	11th to 20th	Day	22% 9% 27% 27% 12% 2	490
	21st to end	Day	19% 10% 34% 24% 10% 2	490
July	1st to 10th	Day	12% 6% 28% 30% 17% 7%	485
	11th to 20th	Day	17% 7% 32% 27% 13% 5%	484
	21st to end	Day	11% 8% 35% 27% 16% 3	532
August	1st to 10th	Day	14% 8% 26% 29% 16% 7%	486
	11th to 20th	Day	18% 4 27% 31% 13% 7%	479
	21st to end	Day	15% 7% 28% 29% 16% 6%	539
September	1st to 10th	Day	21% 7% 26% 25% 17% 4	490
	11th to 20th	Day	12% 4 27% 30% 20% 7%	490
	21st to end	Day	26% 12% 27% 21% 10% 4	490
October	1st to 10th	Day	21% 14% 28% 21% 13% 3	490
	11th to 20th	Day	30% 17% 30% 15% 6% 2	490
	21st to end	Day	37% 16% 31% 14% 2	539
November	1st to 10th	Day	32% 18% 29% 16% 5% 1	367
	11th to 20th	Day	39% 19% 31% 8% 3	203
	21st to end	Day	38% 20% 37% 6%	200
December	1st to 10th	Day	41% 27% 26% 3 4 1	200
	11th to 20th	Day	43% 22% 27% 7% 2	200
	21st to end	Day	37% 22% 34% 7%	220
January	1st to 10th	Night	35% 24% 29% 9% 3	785
	11th to 20th	Night	37% 21% 27% 14% 2	760
	21st to end	Night	29% 23% 31% 15% 2	836
February	1st to 10th	Night	36% 19% 29% 14% 1	760
	11th to 20th	Night	30% 25% 30% 13% 2	743
	21st to end	Night	32% 21% 30% 14% 2	628
March	1st to 10th	Night	28% 21% 31% 16% 5%	760
	11th to 20th	Night	29% 19% 30% 18% 4	760
	21st to end	Night	28% 16% 31% 19% 5%	836
April	1st to 10th	Night	30% 16% 31% 19% 5%	760
	11th to 20th	Night	29% 11% 32% 20% 7% 1	696
	21st to end	Night	24% 11% 33% 27% 5%	570
May	1st to 10th	Night	26% 9% 27% 28% 9% 1	570
	11th to 20th	Night	19% 9% 31% 33% 8% 1	534
	21st to end	Night	13% 7% 30% 30% 19% 2	411
June	1st to 10th	Night	14% 4 32% 35% 14%	380
	11th to 20th	Night	13% 8% 26% 41% 12%	380
	21st to end	Night	14% 6% 29% 34% 16% 1	380
July	1st to 10th	Night	13% 3 19% 40% 20% 5%	370
	11th to 20th	Night	13% 3 21% 35% 23% 4	520
	21st to end	Night	13% 3 19% 38% 27% 1	624
August	1st to 10th	Night	11% 3 19% 39% 24% 3	567
	11th to 20th	Night	13% 4 16% 34% 28% 4	564
	21st to end	Night	15% 3 23% 31% 25% 3	708
September	1st to 10th	Night	18% 6% 18% 33% 22% 4	760
	11th to 20th	Night	14% 5% 20% 33% 24% 5%	760
	21st to end	Night	24% 9% 22% 27% 14% 4	760
October	1st to 10th	Night	21% 7% 29% 26% 16% 2	760
	11th to 20th	Night	29% 14% 27% 22% 8% 1	760
	21st to end	Night	35% 14% 29% 19% 3	836
November	1st to 10th	Night	26% 14% 29% 23% 8%	780
	11th to 20th	Night	35% 19% 28% 13% 5% 1	800
	21st to end	Night	35% 19% 30% 12% 4	800
December	1st to 10th	Night	37% 23% 27% 10% 3	800
	11th to 20th	Night	34% 26% 25% 13% 2	800
	21st to end	Night	37% 20% 30% 13% 1	880

Page generated at 2025-01-04 03:24:03. Version ac07

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