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 2026-09-14.

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% 6% 2 6% 4 4 5% 4 6% 8% 39%	149227
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 41%	141827
Transparency	Day	40% 6% 12% 23% 15% 2	152806
	Night	40% 6% 12% 23% 16% 3	146336
Seeing	Day	18% 13% 26% 24% 14% 5%	17323
	Night	17% 10% 29% 31% 12% 1	26622

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	13% 6% 2 8% 5% 5% 5% 3 5% 6% 41%	4661
	11th to 20th	Day	13% 9% 3 8% 5% 4 4 3 5% 6% 40%	5005
	21st to end	Day	14% 6% 2 7% 5% 6% 6% 4 6% 7% 36%	5780
February	1st to 10th	Day	14% 8% 3 6% 4 5% 4 5% 6% 7% 37%	1890
	11th to 20th	Day	16% 9% 3 6% 4 4 4 4 5% 7% 38%	1934
	21st to end	Day	18% 10% 3 5% 4 4 4 4 4 5% 38%	1730
March	1st to 10th	Day	20% 5% 1 4 4 4 5% 3 5% 6% 43%	4762
	11th to 20th	Day	10% 8% 3 6% 5% 4 5% 4 6% 7% 43%	5090
	21st to end	Day	17% 7% 2 6% 4 4 4 3 5% 6% 42%	5808
April	1st to 10th	Day	17% 7% 2 7% 4 4 5% 4 6% 7% 38%	2520
	11th to 20th	Day	14% 7% 2 5% 4 4 4 4 5% 8% 43%	2494
	21st to end	Day	17% 6% 2 5% 3 4 5% 4 6% 7% 40%	2520
May	1st to 10th	Day	21% 7% 2 6% 3 4 4 4 6% 8% 34%	7574
	11th to 20th	Day	19% 6% 2 6% 4 3 4 4 6% 8% 36%	8221
	21st to end	Day	23% 6% 2 6% 3 4 4 3 5% 8% 36%	9060
June	1st to 10th	Day	11% 6% 2 5% 5% 5% 5% 4 7% 9% 41%	2940
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 5% 6% 9% 39%	2940
	21st to end	Day	10% 4 2 5% 5% 4 5% 4 6% 10% 43%	2940
July	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 4 7% 10% 39%	8280
	11th to 20th	Day	8% 6% 3 8% 5% 5% 6% 5% 8% 11% 35%	8280
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 4 7% 10% 39%	8562
August	1st to 10th	Day	15% 7% 3 8% 6% 6% 7% 5% 7% 9% 29%	6014
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 5% 7% 10% 39%	5648
	21st to end	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 45%	6080
September	1st to 10th	Day	14% 6% 2 5% 4 4 4 3 4 7% 46%	2520
	11th to 20th	Day	12% 6% 2 5% 3 4 3 4 5% 8% 49%	2436
	21st to end	Day	20% 8% 3 6% 4 4 4 4 5% 6% 37%	2134
October	1st to 10th	Day	17% 6% 2 5% 3 3 4 3 5% 7% 45%	2000
	11th to 20th	Day	17% 5% 2 6% 3 4 4 3 4 7% 46%	2000
	21st to end	Day	15% 6% 2 5% 3 3 3 4 5% 7% 45%	2195
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 5% 8% 51%	1851
	11th to 20th	Day	14% 6% 2 4 4 4 4 4 5% 6% 46%	1884
	21st to end	Day	15% 7% 2 6% 4 3 4 3 5% 6% 43%	1680
December	1st to 10th	Day	14% 8% 3 6% 4 4 3 4 6% 6% 42%	2680
	11th to 20th	Day	20% 8% 2 4 4 3 4 3 5% 7% 40%	3066
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 5% 7% 35%	4048
January	1st to 10th	Night	11% 7% 3 7% 5% 5% 5% 4 6% 8% 40%	8234
	11th to 20th	Night	13% 8% 2 6% 4 4 4 3 5% 7% 44%	7878
	21st to end	Night	14% 8% 2 5% 4 3 4 3 5% 7% 45%	8401
February	1st to 10th	Night	16% 9% 2 6% 4 5% 5% 3 5% 7% 39%	2730
	11th to 20th	Night	17% 8% 3 7% 5% 3 4 3 5% 5% 40%	2570
	21st to end	Night	15% 9% 2 6% 5% 4 3 4 5% 5% 40%	2076
March	1st to 10th	Night	17% 9% 3 5% 4 4 3 3 4 5% 44%	5282
	11th to 20th	Night	10% 7% 2 6% 3 4 4 3 5% 6% 51%	5089
	21st to end	Night	14% 7% 3 7% 4 4 4 3 5% 6% 43%	5365
April	1st to 10th	Night	18% 7% 2 6% 5% 4 4 3 5% 8% 38%	2100
	11th to 20th	Night	14% 6% 2 6% 4 4 3 4 6% 8% 42%	2075
	21st to end	Night	17% 6% 2 5% 4 3 4 3 5% 7% 44%	2100
May	1st to 10th	Night	20% 7% 3 7% 5% 4 5% 4 6% 8% 32%	5353
	11th to 20th	Night	20% 8% 3 7% 3 3 4 4 6% 9% 34%	4639
	21st to end	Night	24% 7% 2 6% 4 4 3 3 4 7% 35%	5114
June	1st to 10th	Night	13% 5% 2 5% 4 4 5% 4 6% 8% 44%	1680
	11th to 20th	Night	13% 5% 2 5% 4 5% 4 5% 7% 11% 39%	1680
	21st to end	Night	10% 5% 3 6% 4 4 6% 4 8% 10% 41%	1680
July	1st to 10th	Night	10% 6% 3 8% 5% 5% 5% 5% 6% 10% 38%	4680
	11th to 20th	Night	7% 7% 3 9% 6% 6% 6% 5% 8% 11% 32%	4680
	21st to end	Night	11% 6% 3 6% 5% 5% 5% 5% 6% 9% 41%	5497
August	1st to 10th	Night	16% 7% 3 7% 6% 6% 6% 4 7% 9% 30%	4135
	11th to 20th	Night	13% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	4352
	21st to end	Night	11% 6% 2 6% 4 4 5% 3 6% 8% 43%	5045
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 6% 46%	2100
	11th to 20th	Night	12% 6% 2 4 3 4 3 3 6% 7% 50%	2031
	21st to end	Night	19% 7% 3 6% 4 5% 5% 4 5% 6% 38%	2260
October	1st to 10th	Night	19% 7% 2 6% 3 3 3 2 4 5% 45%	2400
	11th to 20th	Night	14% 7% 2 5% 3 4 3 3 5% 6% 49%	2400
	21st to end	Night	17% 5% 2 4 3 3 3 3 5% 7% 48%	2642
November	1st to 10th	Night	10% 5% 2 4 3 4 4 4 5% 7% 53%	2667
	11th to 20th	Night	15% 7% 3 5% 4 4 4 3 5% 7% 45%	2734
	21st to end	Night	14% 6% 2 5% 4 4 5% 4 5% 7% 44%	2940
December	1st to 10th	Night	12% 8% 2 7% 4 4 4 4 5% 7% 43%	4720
	11th to 20th	Night	22% 6% 2 5% 3 3 4 4 4 7% 40%	5348
	21st to end	Night	18% 8% 3 7% 4 4 5% 4 6% 6% 35%	7150

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	43% 4 12% 25% 14% 2	4662
	11th to 20th	Day	44% 4 9% 20% 17% 6%	5038
	21st to end	Day	44% 6% 12% 24% 13% 1	5780
February	1st to 10th	Day	44% 5% 13% 25% 11% 2	1890
	11th to 20th	Day	46% 4 11% 23% 14% 2	1943
	21st to end	Day	48% 3 10% 24% 11% 3	1730
March	1st to 10th	Day	40% 5% 10% 23% 16% 6%	4765
	11th to 20th	Day	38% 5% 12% 27% 13% 5%	5090
	21st to end	Day	43% 5% 9% 18% 20% 5%	5808
April	1st to 10th	Day	43% 6% 10% 20% 16% 5%	2520
	11th to 20th	Day	38% 6% 13% 22% 16% 4	2494
	21st to end	Day	41% 7% 10% 22% 17% 4	2520
May	1st to 10th	Day	46% 6% 12% 21% 13% 1	7583
	11th to 20th	Day	44% 6% 12% 25% 13% 1	8225
	21st to end	Day	46% 6% 10% 22% 15% 2	9061
June	1st to 10th	Day	37% 8% 13% 23% 17% 1	2940
	11th to 20th	Day	39% 8% 14% 24% 13% 3	2940
	21st to end	Day	35% 8% 15% 25% 16% 1	2940
July	1st to 10th	Day	39% 10% 13% 21% 16% 2	8210
	11th to 20th	Day	39% 9% 14% 26% 11% 1	8205
	21st to end	Day	37% 7% 12% 22% 21% 1	8374
August	1st to 10th	Day	49% 10% 13% 19% 9%	6001
	11th to 20th	Day	38% 8% 15% 27% 12% 1	5687
	21st to end	Day	33% 8% 13% 27% 18% 2	6080
September	1st to 10th	Day	38% 5% 12% 21% 19% 4	2520
	11th to 20th	Day	33% 5% 10% 26% 22% 4	2436
	21st to end	Day	47% 5% 9% 18% 19% 3	2134
October	1st to 10th	Day	35% 5% 9% 19% 27% 5%	3260
	11th to 20th	Day	28% 4 13% 27% 22% 7%	3240
	21st to end	Day	25% 3 12% 28% 28% 3	3521
November	1st to 10th	Day	33% 3 14% 25% 21% 4	1851
	11th to 20th	Day	38% 5% 11% 24% 20% 2	1884
	21st to end	Day	41% 5% 12% 29% 11% 2	1680
December	1st to 10th	Day	41% 4 18% 25% 11% 2	2680
	11th to 20th	Day	44% 4 13% 30% 8% 1	3066
	21st to end	Day	45% 7% 16% 19% 12% 1	4048
January	1st to 10th	Night	41% 6% 14% 24% 13% 3	8234
	11th to 20th	Night	39% 4 11% 22% 19% 6%	7920
	21st to end	Night	38% 4 10% 28% 18% 2	8401
February	1st to 10th	Night	45% 4 13% 24% 12% 2	2730
	11th to 20th	Night	45% 4 10% 21% 17% 2	2572
	21st to end	Night	45% 5% 9% 21% 15% 4	2076
March	1st to 10th	Night	42% 4 10% 24% 13% 8%	5292
	11th to 20th	Night	33% 5% 14% 29% 13% 5%	5090
	21st to end	Night	41% 4 8% 19% 24% 3	5365
April	1st to 10th	Night	44% 5% 10% 20% 17% 4	2100
	11th to 20th	Night	40% 4 12% 22% 19% 3	2075
	21st to end	Night	39% 6% 9% 23% 18% 5%	2100
May	1st to 10th	Night	49% 6% 11% 18% 13% 2	5360
	11th to 20th	Night	45% 7% 13% 24% 10% 1	4640
	21st to end	Night	50% 5% 9% 20% 13% 2	5115
June	1st to 10th	Night	37% 7% 11% 23% 21% 2	1680
	11th to 20th	Night	37% 9% 14% 23% 16% 2	1680
	21st to end	Night	35% 8% 14% 25% 16% 2	1680
July	1st to 10th	Night	41% 9% 13% 19% 14% 3	4640
	11th to 20th	Night	43% 10% 14% 22% 10% 1	4632
	21st to end	Night	36% 9% 14% 22% 18% 1	5371
August	1st to 10th	Night	49% 8% 15% 18% 10%	4124
	11th to 20th	Night	41% 8% 15% 24% 11% 1	4379
	21st to end	Night	36% 7% 12% 28% 16% 1	5045
September	1st to 10th	Night	37% 7% 10% 22% 21% 4	2100
	11th to 20th	Night	33% 5% 10% 25% 24% 3	2031
	21st to end	Night	46% 6% 8% 18% 19% 3	2260
October	1st to 10th	Night	42% 5% 9% 20% 22% 2	3920
	11th to 20th	Night	26% 4 11% 28% 27% 4	3899
	21st to end	Night	26% 3 11% 32% 25% 3	4266
November	1st to 10th	Night	32% 4 12% 27% 21% 4	2667
	11th to 20th	Night	39% 4 9% 24% 19% 5%	2734
	21st to end	Night	38% 5% 13% 27% 15% 1	2940
December	1st to 10th	Night	39% 5% 14% 29% 12% 1	4720
	11th to 20th	Night	44% 3 13% 24% 12% 3	5348
	21st to end	Night	47% 6% 12% 19% 15% 1	7150

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% 23% 31% 16% 2 1	220
	11th to 20th	Day	26% 30% 29% 12% 3	286
	21st to end	Day	23% 24% 33% 15% 4 1	363
February	1st to 10th	Day	22% 20% 38% 15% 5% 1	330
	11th to 20th	Day	27% 23% 35% 14% 1	421
	21st to end	Day	28% 17% 35% 17% 3	446
March	1st to 10th	Day	21% 23% 30% 22% 5%	540
	11th to 20th	Day	22% 22% 33% 18% 4 1	540
	21st to end	Day	22% 18% 34% 18% 5% 1	594
April	1st to 10th	Day	24% 18% 31% 18% 7% 2	540
	11th to 20th	Day	19% 18% 30% 20% 10% 3	532
	21st to end	Day	23% 14% 29% 21% 10% 2	540
May	1st to 10th	Day	24% 16% 29% 20% 9% 3	543
	11th to 20th	Day	19% 13% 28% 24% 12% 4	567
	21st to end	Day	22% 6% 24% 24% 18% 7%	617
June	1st to 10th	Day	14% 8% 28% 25% 18% 6%	570
	11th to 20th	Day	17% 10% 25% 26% 18% 5%	570
	21st to end	Day	13% 7% 23% 31% 19% 7%	570
July	1st to 10th	Day	13% 4 16% 27% 28% 12%	565
	11th to 20th	Day	5% 4 18% 34% 28% 11%	564
	21st to end	Day	12% 4 22% 33% 23% 7%	620
August	1st to 10th	Day	12% 5% 19% 28% 25% 11%	566
	11th to 20th	Day	12% 6% 17% 31% 23% 11%	559
	21st to end	Day	12% 4 17% 33% 20% 13%	627
September	1st to 10th	Day	17% 6% 19% 24% 23% 11%	570
	11th to 20th	Day	13% 4 18% 27% 24% 13%	542
	21st to end	Day	24% 9% 22% 24% 15% 6%	530
October	1st to 10th	Day	19% 8% 22% 25% 18% 8%	530
	11th to 20th	Day	18% 13% 26% 26% 14% 3	530
	21st to end	Day	16% 13% 33% 26% 9% 3	580
November	1st to 10th	Day	14% 13% 29% 28% 14% 2	425
	11th to 20th	Day	16% 18% 32% 25% 8%	424
	21st to end	Day	22% 21% 34% 15% 7% 1	220
December	1st to 10th	Day	23% 21% 35% 15% 4 2	220
	11th to 20th	Day	27% 19% 31% 17% 6%	220
	21st to end	Day	22% 19% 31% 20% 7%	242
January	1st to 10th	Night	16% 16% 43% 22% 3	840
	11th to 20th	Night	22% 16% 33% 25% 3	840
	21st to end	Night	17% 15% 42% 24% 2	924
February	1st to 10th	Night	20% 15% 38% 26% 2	840
	11th to 20th	Night	23% 17% 39% 20% 1	823
	21st to end	Night	21% 18% 38% 21% 3	692
March	1st to 10th	Night	20% 13% 39% 24% 4	840
	11th to 20th	Night	20% 16% 35% 23% 5% 1	840
	21st to end	Night	20% 12% 38% 24% 5%	924
April	1st to 10th	Night	21% 16% 36% 22% 4	840
	11th to 20th	Night	17% 12% 34% 30% 7%	831
	21st to end	Night	20% 9% 32% 31% 8%	840
May	1st to 10th	Night	21% 8% 29% 33% 8% 1	672
	11th to 20th	Night	20% 6% 29% 36% 9%	414
	21st to end	Night	16% 5% 21% 41% 16% 1	455
June	1st to 10th	Night	14% 4 24% 40% 19%	420
	11th to 20th	Night	13% 3 24% 43% 16%	420
	21st to end	Night	10% 3 20% 50% 16%	420
July	1st to 10th	Night	10% 3 17% 42% 26% 2	410
	11th to 20th	Night	6% 1 14% 47% 29% 2	408
	21st to end	Night	11% 2 14% 44% 27% 2	603
August	1st to 10th	Night	12% 2 11% 44% 30% 2	627
	11th to 20th	Night	12% 3 13% 39% 30% 2	738
	21st to end	Night	14% 3 14% 41% 25% 3	924
September	1st to 10th	Night	14% 5% 19% 36% 23% 3	840
	11th to 20th	Night	14% 3 14% 39% 27% 3	813
	21st to end	Night	21% 4 19% 35% 20% 2	800
October	1st to 10th	Night	22% 5% 20% 30% 19% 4	800
	11th to 20th	Night	18% 7% 27% 34% 13% 1	800
	21st to end	Night	19% 6% 33% 30% 12%	880
November	1st to 10th	Night	13% 8% 31% 36% 12% 1	820
	11th to 20th	Night	17% 14% 30% 30% 7% 1	840
	21st to end	Night	16% 15% 34% 28% 7%	840
December	1st to 10th	Night	22% 13% 35% 25% 5% 1	840
	11th to 20th	Night	18% 13% 38% 26% 5%	840
	21st to end	Night	20% 11% 37% 30% 3	924

Page generated at 2026-09-11 04:11:55. Version ac07

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