Manheim Township Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Manheim Township Planetarium clear sky chart from 2005-11-06 to 2025-05-11.

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% 7% 2 6% 4 4 5% 4 6% 8% 40%	113864
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	115054
Transparency	Day	40% 6% 12% 23% 16% 3	117487
	Night	40% 5% 12% 23% 17% 3	119595
Seeing	Day	19% 12% 26% 24% 14% 5%	15522
	Night	18% 9% 29% 31% 12% 1	25010

By Month

Percentage Cloud Cover NE (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	12% 6% 2 7% 5% 5% 5% 3 5% 6% 43%	3597
	11th to 20th	Day	13% 9% 4 10% 5% 4 4 3 5% 6% 37%	3841
	21st to end	Day	16% 7% 3 8% 5% 5% 5% 4 5% 6% 37%	4466
February	1st to 10th	Day	15% 9% 3 6% 4 5% 5% 5% 6% 7% 36%	1800
	11th to 20th	Day	16% 8% 2 6% 5% 4 4 3 5% 8% 39%	1839
	21st to end	Day	18% 10% 3 5% 4 4 4 4 5% 6% 38%	1650
March	1st to 10th	Day	20% 5% 1 4 4 4 5% 3 5% 6% 44%	4658
	11th to 20th	Day	10% 8% 3 6% 5% 4 5% 4 6% 7% 43%	4980
	21st to end	Day	17% 7% 2 6% 4 4 4 3 5% 6% 42%	5683
April	1st to 10th	Day	17% 7% 2 7% 4 4 5% 3 6% 7% 38%	2400
	11th to 20th	Day	15% 7% 2 5% 4 4 4 4 5% 7% 42%	2374
	21st to end	Day	17% 6% 2 5% 3 4 5% 4 7% 7% 41%	2400
May	1st to 10th	Day	27% 7% 2 6% 3 4 4 4 5% 7% 30%	4213
	11th to 20th	Day	24% 8% 3 7% 5% 4 4 4 5% 6% 29%	4398
	21st to end	Day	11% 6% 2 6% 3 4 4 4 6% 10% 45%	4837
June	1st to 10th	Day	12% 6% 2 5% 5% 5% 5% 4 7% 9% 40%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 5% 6% 5% 6% 9% 39%	2660
	21st to end	Day	10% 4 2 5% 5% 4 5% 5% 6% 11% 43%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 6% 8% 11% 39%	4440
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 10% 39%	4440
	21st to end	Day	10% 7% 2 8% 6% 5% 6% 5% 7% 8% 35%	4579
August	1st to 10th	Day	18% 6% 2 7% 5% 5% 6% 4 6% 9% 33%	4104
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 5% 7% 9% 41%	3831
	21st to end	Day	11% 5% 2 5% 3 4 4 3 5% 8% 48%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 3 4 6% 46%	2280
	11th to 20th	Day	11% 6% 2 5% 3 4 3 4 5% 8% 50%	2280
	21st to end	Day	20% 8% 2 5% 4 4 4 4 5% 6% 38%	2027
October	1st to 10th	Day	17% 6% 2 5% 3 3 4 3 5% 6% 44%	1900
	11th to 20th	Day	17% 5% 2 6% 3 4 4 2 4 7% 46%	1900
	21st to end	Day	16% 6% 2 5% 4 3 3 4 5% 7% 45%	2085
November	1st to 10th	Day	11% 7% 2 5% 3 3 2 3 4 8% 50%	1761
	11th to 20th	Day	15% 6% 2 4 4 4 4 4 5% 6% 47%	1795
	21st to end	Day	15% 7% 2 6% 4 3 5% 3 5% 6% 44%	1600
December	1st to 10th	Day	14% 8% 3 6% 4 4 3 4 6% 6% 43%	2600
	11th to 20th	Day	21% 9% 2 4 4 3 4 3 5% 7% 40%	2986
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	3960
January	1st to 10th	Night	12% 7% 2 6% 5% 5% 4 4 5% 7% 43%	6349
	11th to 20th	Night	14% 8% 2 5% 4 4 4 3 5% 7% 45%	6042
	21st to end	Night	16% 8% 2 5% 4 3 4 3 5% 6% 42%	6490
February	1st to 10th	Night	17% 9% 2 6% 4 5% 5% 3 5% 7% 38%	2600
	11th to 20th	Night	17% 8% 3 7% 5% 3 4 3 5% 5% 41%	2445
	21st to end	Night	16% 9% 2 6% 5% 5% 4 4 5% 5% 39%	1980
March	1st to 10th	Night	16% 9% 3 5% 4 4 3 3 4 5% 44%	5166
	11th to 20th	Night	10% 7% 2 6% 3 3 4 3 5% 6% 51%	4979
	21st to end	Night	14% 7% 3 7% 4 4 4 3 5% 6% 44%	5248
April	1st to 10th	Night	18% 7% 2 6% 5% 4 4 3 5% 8% 37%	2000
	11th to 20th	Night	15% 6% 2 6% 4 4 3 4 6% 8% 42%	1975
	21st to end	Night	17% 6% 2 5% 4 3 4 3 5% 7% 44%	2000
May	1st to 10th	Night	24% 7% 2 7% 5% 4 4 3 5% 7% 31%	2976
	11th to 20th	Night	23% 10% 4 8% 4 4 4 4 5% 7% 28%	2501
	21st to end	Night	11% 6% 2 6% 4 4 4 3 5% 11% 42%	2738
June	1st to 10th	Night	13% 6% 2 5% 4 4 5% 4 6% 8% 43%	1520
	11th to 20th	Night	12% 5% 2 5% 4 5% 4 5% 7% 11% 40%	1520
	21st to end	Night	10% 4 2 6% 4 4 6% 4 8% 10% 41%	1520
July	1st to 10th	Night	6% 5% 3 8% 6% 5% 6% 5% 7% 10% 40%	2520
	11th to 20th	Night	7% 5% 3 8% 6% 6% 6% 5% 8% 11% 37%	2520
	21st to end	Night	14% 6% 3 7% 4 4 4 5% 6% 8% 38%	2956
August	1st to 10th	Night	19% 6% 2 6% 4 5% 5% 4 6% 8% 34%	2825
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 6% 7% 42%	2966
	21st to end	Night	12% 6% 2 5% 4 4 4 3 6% 8% 46%	3476
September	1st to 10th	Night	13% 6% 3 6% 4 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	12% 6% 2 4 2 4 3 3 6% 7% 51%	1900
	21st to end	Night	19% 7% 2 5% 4 5% 5% 4 4 5% 40%	2147
October	1st to 10th	Night	20% 7% 2 6% 3 3 3 2 4 5% 44%	2280
	11th to 20th	Night	14% 6% 2 5% 3 4 3 3 5% 6% 49%	2280
	21st to end	Night	17% 5% 2 3 3 3 3 3 5% 7% 47%	2510
November	1st to 10th	Night	10% 5% 2 4 3 4 4 4 5% 7% 53%	2537
	11th to 20th	Night	15% 7% 3 5% 4 4 4 3 5% 6% 45%	2604
	21st to end	Night	14% 6% 2 5% 4 4 5% 4 5% 7% 44%	2800
December	1st to 10th	Night	12% 8% 2 7% 4 4 4 3 5% 7% 43%	4580
	11th to 20th	Night	22% 6% 2 5% 3 3 4 4 4 7% 40%	5208
	21st to end	Night	18% 8% 3 7% 4 4 5% 4 6% 6% 35%	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	41% 4 11% 25% 16% 2	3598
	11th to 20th	Day	47% 4 10% 19% 15% 5%	3874
	21st to end	Day	46% 5% 12% 22% 14% 1	4466
February	1st to 10th	Day	45% 5% 13% 24% 11% 1	1800
	11th to 20th	Day	45% 4 11% 24% 14% 2	1848
	21st to end	Day	48% 3 10% 23% 12% 3	1650
March	1st to 10th	Day	39% 5% 10% 24% 16% 7%	4661
	11th to 20th	Day	38% 5% 12% 27% 13% 5%	4980
	21st to end	Day	43% 4 9% 18% 21% 5%	5683
April	1st to 10th	Day	43% 6% 10% 20% 16% 5%	2400
	11th to 20th	Day	39% 6% 12% 22% 16% 4	2374
	21st to end	Day	40% 6% 10% 22% 17% 4	2400
May	1st to 10th	Day	52% 6% 10% 20% 10% 2	4225
	11th to 20th	Day	54% 7% 13% 18% 8% 1	4402
	21st to end	Day	33% 7% 14% 27% 16% 2	4837
June	1st to 10th	Day	38% 8% 14% 24% 15% 1	2660
	11th to 20th	Day	39% 8% 14% 25% 12% 3	2660
	21st to end	Day	34% 8% 16% 25% 16% 1	2660
July	1st to 10th	Day	35% 11% 15% 21% 14% 3	4370
	11th to 20th	Day	36% 9% 16% 25% 14% 1	4365
	21st to end	Day	44% 8% 11% 19% 17% 1	4433
August	1st to 10th	Day	47% 8% 12% 24% 9%	4091
	11th to 20th	Day	37% 7% 12% 28% 15% 1	3870
	21st to end	Day	33% 7% 11% 28% 20% 2	4180
September	1st to 10th	Day	40% 5% 11% 20% 19% 5%	2280
	11th to 20th	Day	32% 5% 10% 26% 22% 4	2280
	21st to end	Day	46% 5% 8% 18% 19% 3	2027
October	1st to 10th	Day	36% 5% 9% 19% 27% 5%	3160
	11th to 20th	Day	27% 4 13% 27% 22% 7%	3140
	21st to end	Day	25% 3 12% 28% 28% 4	3411
November	1st to 10th	Day	34% 3 14% 25% 20% 5%	1761
	11th to 20th	Day	38% 5% 11% 24% 20% 2	1795
	21st to end	Day	40% 5% 12% 29% 11% 2	1600
December	1st to 10th	Day	41% 4 18% 25% 11% 2	2600
	11th to 20th	Day	44% 4 13% 30% 8% 1	2986
	21st to end	Day	45% 7% 16% 18% 13% 1	3960
January	1st to 10th	Night	38% 6% 11% 25% 17% 4	6349
	11th to 20th	Night	38% 4 12% 23% 16% 6%	6084
	21st to end	Night	42% 4 11% 25% 16% 2	6490
February	1st to 10th	Night	45% 4 14% 25% 11% 2	2600
	11th to 20th	Night	45% 4 10% 22% 17% 3	2447
	21st to end	Night	45% 5% 9% 20% 16% 4	1980
March	1st to 10th	Night	41% 4 10% 24% 13% 8%	5176
	11th to 20th	Night	33% 5% 14% 30% 13% 5%	4980
	21st to end	Night	41% 4 8% 19% 25% 3	5248
April	1st to 10th	Night	45% 5% 10% 20% 17% 4	2000
	11th to 20th	Night	40% 4 11% 22% 19% 3	1975
	21st to end	Night	39% 6% 9% 23% 18% 5%	2000
May	1st to 10th	Night	53% 5% 9% 18% 13% 2	2983
	11th to 20th	Night	54% 8% 13% 14% 10% 1	2502
	21st to end	Night	37% 7% 14% 23% 14% 4	2739
June	1st to 10th	Night	38% 7% 11% 22% 20% 2	1520
	11th to 20th	Night	36% 9% 15% 24% 16% 2	1520
	21st to end	Night	35% 7% 14% 26% 16% 2	1520
July	1st to 10th	Night	38% 9% 17% 18% 13% 5%	2480
	11th to 20th	Night	38% 10% 15% 22% 13% 1	2472
	21st to end	Night	41% 8% 15% 18% 17% 1	2862
August	1st to 10th	Night	46% 8% 17% 21% 9% 1	2814
	11th to 20th	Night	40% 6% 13% 25% 15% 1	2993
	21st to end	Night	34% 7% 12% 28% 18% 1	3476
September	1st to 10th	Night	37% 7% 10% 21% 21% 4	1900
	11th to 20th	Night	32% 5% 9% 25% 25% 4	1900
	21st to end	Night	45% 6% 8% 18% 20% 3	2147
October	1st to 10th	Night	43% 5% 9% 20% 21% 2	3800
	11th to 20th	Night	26% 4 11% 28% 27% 4	3779
	21st to end	Night	26% 3 12% 32% 24% 3	4134
November	1st to 10th	Night	32% 4 12% 26% 21% 4	2537
	11th to 20th	Night	39% 4 9% 25% 18% 5%	2604
	21st to end	Night	38% 5% 13% 28% 15% 2	2800
December	1st to 10th	Night	40% 5% 14% 29% 12% 1	4580
	11th to 20th	Night	45% 4 13% 24% 12% 2	5208
	21st to end	Night	47% 6% 12% 19% 15% 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	28% 24% 30% 16% 2 2	200
	11th to 20th	Day	25% 29% 29% 13% 3	260
	21st to end	Day	23% 22% 34% 16% 4 1	330
February	1st to 10th	Day	24% 19% 38% 15% 4	300
	11th to 20th	Day	26% 25% 36% 12% 1	386
	21st to end	Day	28% 17% 33% 18% 3	414
March	1st to 10th	Day	19% 23% 30% 23% 5%	500
	11th to 20th	Day	21% 22% 34% 18% 4 1	500
	21st to end	Day	23% 18% 33% 20% 5% 1	550
April	1st to 10th	Day	24% 18% 31% 18% 6% 2	500
	11th to 20th	Day	20% 18% 29% 19% 11% 3	492
	21st to end	Day	23% 15% 30% 21% 9% 2	500
May	1st to 10th	Day	25% 15% 27% 20% 10% 3	503
	11th to 20th	Day	20% 12% 27% 23% 13% 5%	487
	21st to end	Day	18% 5% 23% 26% 19% 9%	529
June	1st to 10th	Day	16% 8% 28% 24% 18% 6%	490
	11th to 20th	Day	16% 8% 23% 28% 19% 6%	490
	21st to end	Day	13% 6% 23% 33% 18% 7%	490
July	1st to 10th	Day	12% 3 18% 27% 27% 13%	485
	11th to 20th	Day	5% 3 17% 35% 29% 11%	484
	21st to end	Day	13% 3 22% 32% 23% 7%	532
August	1st to 10th	Day	13% 5% 18% 29% 25% 11%	486
	11th to 20th	Day	12% 6% 17% 31% 23% 12%	479
	21st to end	Day	13% 4 16% 33% 21% 14%	539
September	1st to 10th	Day	19% 5% 18% 22% 24% 12%	490
	11th to 20th	Day	13% 4 19% 27% 23% 14%	490
	21st to end	Day	25% 10% 22% 22% 15% 7%	490
October	1st to 10th	Day	20% 8% 23% 25% 18% 7%	490
	11th to 20th	Day	17% 12% 25% 27% 15% 3	490
	21st to end	Day	16% 12% 33% 26% 10% 3	536
November	1st to 10th	Day	15% 11% 29% 29% 14% 3	395
	11th to 20th	Day	14% 17% 33% 26% 9% 1	395
	21st to end	Day	21% 22% 33% 16% 8% 1	200
December	1st to 10th	Day	23% 21% 35% 16% 4 2	200
	11th to 20th	Day	28% 19% 30% 17% 6% 1	200
	21st to end	Day	21% 17% 32% 22% 8%	220
January	1st to 10th	Night	17% 16% 43% 21% 3	800
	11th to 20th	Night	22% 15% 33% 26% 4	800
	21st to end	Night	18% 14% 42% 25% 2	880
February	1st to 10th	Night	21% 15% 37% 26% 2	800
	11th to 20th	Night	23% 18% 39% 19% 1	783
	21st to end	Night	21% 18% 37% 20% 3	660
March	1st to 10th	Night	19% 14% 39% 24% 4	800
	11th to 20th	Night	20% 16% 36% 23% 6% 1	800
	21st to end	Night	20% 12% 38% 25% 5%	880
April	1st to 10th	Night	21% 16% 37% 22% 4	800
	11th to 20th	Night	18% 12% 34% 29% 7%	791
	21st to end	Night	21% 9% 32% 30% 8%	800
May	1st to 10th	Night	21% 8% 28% 34% 8% 1	640
	11th to 20th	Night	21% 6% 28% 35% 10%	376
	21st to end	Night	14% 3 21% 42% 18% 1	411
June	1st to 10th	Night	15% 3 23% 39% 19%	380
	11th to 20th	Night	13% 2 23% 44% 18%	380
	21st to end	Night	10% 2 20% 52% 15% 1	380
July	1st to 10th	Night	10% 2 17% 44% 25% 2	370
	11th to 20th	Night	6% 1 14% 46% 30% 2	368
	21st to end	Night	12% 2 14% 44% 26% 1	545
August	1st to 10th	Night	12% 1 11% 46% 28% 2	567
	11th to 20th	Night	13% 3 13% 39% 30% 2	667
	21st to end	Night	14% 2 14% 40% 27% 3	836
September	1st to 10th	Night	15% 4 19% 36% 23% 4	760
	11th to 20th	Night	14% 3 14% 38% 28% 4	760
	21st to end	Night	21% 4 19% 34% 20% 2	760
October	1st to 10th	Night	23% 5% 20% 30% 18% 4	760
	11th to 20th	Night	18% 7% 27% 34% 13% 1	760
	21st to end	Night	19% 7% 32% 30% 12%	836
November	1st to 10th	Night	12% 7% 32% 36% 13% 1	780
	11th to 20th	Night	17% 13% 30% 31% 8% 1	800
	21st to end	Night	16% 15% 34% 29% 7%	800
December	1st to 10th	Night	23% 12% 34% 24% 6% 1	800
	11th to 20th	Night	19% 12% 38% 26% 5%	800
	21st to end	Night	20% 11% 36% 30% 3	880

Page generated at 2025-05-08 09:33:57. Version ac07

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