Massbach Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Massbach Ridge clear sky chart from 2005-11-06 to 2026-05-02.

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	13% 9% 4 8% 5% 5% 4 4 5% 7% 37%	132031
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 38%	130737
Transparency	Day	46% 3 12% 25% 13% 1	135526
	Night	46% 3 11% 23% 14% 2	135315
Seeing	Day	20% 17% 31% 21% 9% 3	17827
	Night	19% 14% 31% 26% 10% 1	27803

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	8% 12% 8% 15% 7% 6% 6% 3 5% 5% 25%	4691
	11th to 20th	Day	6% 11% 6% 13% 4 5% 5% 7% 7% 6% 30%	4710
	21st to end	Day	9% 13% 6% 9% 6% 4 4 3 5% 6% 34%	5632
February	1st to 10th	Day	12% 13% 6% 9% 6% 4 6% 3 4 6% 30%	1890
	11th to 20th	Day	13% 11% 4 7% 5% 5% 4 3 5% 5% 37%	1957
	21st to end	Day	13% 14% 4 9% 6% 4 4 3 5% 6% 33%	1730
March	1st to 10th	Day	16% 9% 3 6% 4 3 3 2 4 5% 45%	4580
	11th to 20th	Day	12% 7% 3 6% 4 4 4 3 5% 9% 43%	5037
	21st to end	Day	21% 13% 4 9% 5% 5% 4 3 5% 5% 26%	5951
April	1st to 10th	Day	18% 14% 3 7% 5% 4 3 4 4 6% 31%	2520
	11th to 20th	Day	17% 11% 3 7% 5% 5% 5% 4 5% 6% 33%	2494
	21st to end	Day	20% 8% 3 7% 4 5% 5% 3 5% 7% 33%	2525
May	1st to 10th	Day	15% 8% 3 7% 5% 4 4 3 6% 7% 37%	6123
	11th to 20th	Day	15% 7% 2 7% 4 4 5% 3 6% 6% 42%	6319
	21st to end	Day	13% 7% 2 8% 5% 5% 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	10% 5% 2 7% 5% 5% 5% 4 6% 9% 42%	2800
	11th to 20th	Day	11% 6% 3 6% 4 5% 5% 4 6% 9% 43%	2800
	21st to end	Day	12% 7% 3 7% 4 5% 5% 5% 6% 8% 39%	2800
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 9% 36%	6360
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 4 6% 9% 45%	6360
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 4 7% 9% 36%	6924
August	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 4 7% 9% 41%	4348
	11th to 20th	Day	12% 5% 2 6% 3 4 4 4 7% 9% 43%	3960
	21st to end	Day	8% 5% 2 6% 4 5% 4 4 6% 8% 48%	4312
September	1st to 10th	Day	12% 5% 2 6% 4 4 5% 4 5% 7% 46%	2400
	11th to 20th	Day	12% 4 1 4 3 3 3 4 4 7% 54%	2365
	21st to end	Day	12% 6% 3 5% 4 4 4 3 5% 8% 46%	2197
October	1st to 10th	Day	13% 6% 2 6% 3 3 3 3 4 6% 49%	2000
	11th to 20th	Day	18% 9% 2 7% 4 4 4 3 5% 6% 38%	2000
	21st to end	Day	19% 9% 3 6% 4 3 4 2 4 6% 40%	2067
November	1st to 10th	Day	12% 8% 3 6% 5% 4 4 3 4 6% 44%	1852
	11th to 20th	Day	14% 14% 4 8% 5% 4 4 3 4 6% 34%	1864
	21st to end	Day	14% 14% 4 9% 4 4 3 3 3 5% 36%	1680
December	1st to 10th	Day	8% 10% 4 9% 4 4 4 3 6% 7% 41%	2690
	11th to 20th	Day	14% 15% 6% 13% 6% 6% 5% 3 5% 6% 22%	3088
	21st to end	Day	21% 24% 9% 11% 4 4 3 3 4 5% 13%	4070
January	1st to 10th	Night	11% 12% 7% 14% 6% 4 4 3 4 4 31%	8232
	11th to 20th	Night	8% 14% 6% 15% 7% 7% 5% 5% 6% 5% 22%	8280
	21st to end	Night	11% 14% 5% 9% 6% 5% 4 3 5% 6% 33%	8568
February	1st to 10th	Night	12% 14% 5% 10% 6% 5% 3 4 5% 6% 32%	2730
	11th to 20th	Night	11% 11% 3 9% 5% 5% 4 3 4 5% 40%	2549
	21st to end	Night	14% 12% 4 8% 4 4 4 2 4 6% 37%	2076
March	1st to 10th	Night	17% 9% 4 6% 4 4 3 3 4 4 42%	5493
	11th to 20th	Night	10% 7% 2 6% 4 4 4 3 4 7% 49%	5188
	21st to end	Night	21% 13% 5% 11% 5% 4 4 3 4 4 26%	5218
April	1st to 10th	Night	17% 12% 3 6% 4 3 3 3 5% 5% 39%	2100
	11th to 20th	Night	18% 9% 3 7% 4 3 4 3 5% 5% 39%	2075
	21st to end	Night	17% 9% 2 7% 4 4 4 4 5% 8% 34%	2094
May	1st to 10th	Night	18% 7% 3 6% 4 4 4 4 5% 7% 37%	3789
	11th to 20th	Night	12% 6% 2 6% 5% 4 5% 4 5% 7% 44%	3596
	21st to end	Night	14% 7% 2 6% 4 4 4 4 6% 8% 42%	3942
June	1st to 10th	Night	8% 5% 2 6% 5% 4 5% 4 8% 7% 48%	1600
	11th to 20th	Night	11% 6% 2 5% 4 4 5% 4 8% 9% 44%	1600
	21st to end	Night	10% 7% 2 6% 5% 4 4 4 6% 7% 45%	1600
July	1st to 10th	Night	13% 6% 2 7% 4 4 5% 4 6% 9% 40%	3618
	11th to 20th	Night	7% 5% 2 5% 4 4 4 3 6% 9% 52%	3617
	21st to end	Night	9% 6% 2 6% 4 5% 5% 4 6% 8% 46%	3947
August	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 8% 52%	2808
	11th to 20th	Night	8% 7% 2 5% 3 4 4 3 6% 6% 52%	3079
	21st to end	Night	9% 5% 2 5% 4 3 4 4 5% 9% 50%	3586
September	1st to 10th	Night	9% 5% 2 5% 3 3 4 3 5% 6% 56%	2000
	11th to 20th	Night	10% 4 1 5% 4 3 5% 3 6% 8% 50%	2015
	21st to end	Night	9% 5% 2 5% 4 4 5% 3 5% 7% 51%	2200
October	1st to 10th	Night	11% 6% 2 5% 3 4 4 2 4 6% 54%	2400
	11th to 20th	Night	16% 8% 2 6% 4 3 3 3 5% 6% 45%	2400
	21st to end	Night	18% 9% 3 6% 5% 4 4 3 4 5% 38%	2771
November	1st to 10th	Night	13% 7% 2 6% 3 3 3 3 4 6% 49%	2666
	11th to 20th	Night	14% 13% 3 8% 5% 4 3 3 4 6% 36%	2751
	21st to end	Night	17% 11% 4 9% 4 3 3 3 5% 6% 36%	2940
December	1st to 10th	Night	9% 8% 3 8% 6% 5% 5% 4 5% 6% 41%	4720
	11th to 20th	Night	15% 15% 5% 10% 5% 4 4 3 5% 5% 30%	5339
	21st to end	Night	21% 20% 7% 13% 5% 4 4 3 4 4 16%	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	63% 2 12% 16% 7% 1	4692
	11th to 20th	Day	51% 3 11% 17% 16% 2	4710
	21st to end	Day	52% 2 15% 22% 8%	5632
February	1st to 10th	Day	56% 2 12% 18% 10% 1	1890
	11th to 20th	Day	49% 3 11% 24% 10% 2	1966
	21st to end	Day	53% 3 10% 22% 10% 2	1730
March	1st to 10th	Day	44% 2 11% 29% 10% 4	4580
	11th to 20th	Day	39% 4 12% 32% 12% 1	5037
	21st to end	Day	60% 3 12% 15% 8% 1	5953
April	1st to 10th	Day	54% 4 10% 22% 11%	2520
	11th to 20th	Day	52% 4 10% 21% 11% 2	2494
	21st to end	Day	51% 3 10% 21% 13% 1	2525
May	1st to 10th	Day	46% 3 9% 22% 19%	6158
	11th to 20th	Day	43% 3 10% 29% 14% 1	6323
	21st to end	Day	44% 5% 11% 26% 11% 3	6949
June	1st to 10th	Day	38% 5% 13% 27% 16% 1	2800
	11th to 20th	Day	38% 4 13% 24% 20% 2	2800
	21st to end	Day	42% 5% 13% 25% 13% 2	2800
July	1st to 10th	Day	42% 3 15% 28% 10% 1	6291
	11th to 20th	Day	37% 3 15% 30% 15% 1	6285
	21st to end	Day	43% 4 16% 20% 15% 1	6728
August	1st to 10th	Day	38% 4 15% 28% 13% 1	4333
	11th to 20th	Day	37% 3 13% 30% 15% 1	3998
	21st to end	Day	34% 3 13% 32% 16% 2	4311
September	1st to 10th	Day	36% 5% 10% 29% 19% 2	2400
	11th to 20th	Day	32% 3 11% 34% 18% 2	2365
	21st to end	Day	37% 3 10% 29% 19% 1	2197
October	1st to 10th	Day	24% 2 6% 36% 31% 1	3260
	11th to 20th	Day	34% 2 9% 26% 26% 3	3240
	21st to end	Day	42% 2 9% 29% 15% 3	3318
November	1st to 10th	Day	41% 3 14% 26% 14% 2	1852
	11th to 20th	Day	53% 2 12% 22% 10% 1	1864
	21st to end	Day	53% 3 14% 22% 8%	1680
December	1st to 10th	Day	43% 2 18% 30% 6% 1	2690
	11th to 20th	Day	64% 2 12% 14% 7% 1	3085
	21st to end	Day	76% 2 9% 8% 5%	4070
January	1st to 10th	Night	57% 2 14% 18% 8%	8233
	11th to 20th	Night	62% 3 10% 12% 13% 1	8280
	21st to end	Night	53% 2 12% 23% 11%	8568
February	1st to 10th	Night	54% 2 11% 20% 12% 1	2730
	11th to 20th	Night	48% 4 10% 25% 13% 1	2550
	21st to end	Night	49% 3 12% 21% 11% 3	2076
March	1st to 10th	Night	48% 2 10% 23% 12% 5%	5493
	11th to 20th	Night	36% 3 9% 34% 14% 4	5188
	21st to end	Night	62% 2 9% 18% 8% 1	5218
April	1st to 10th	Night	47% 3 10% 24% 13% 2	2100
	11th to 20th	Night	48% 3 7% 20% 18% 4	2075
	21st to end	Night	47% 3 12% 22% 13% 2	2094
May	1st to 10th	Night	46% 4 11% 17% 19% 2	3816
	11th to 20th	Night	40% 4 13% 23% 17% 3	3597
	21st to end	Night	40% 4 10% 28% 15% 2	3950
June	1st to 10th	Night	32% 5% 13% 28% 20% 2	1600
	11th to 20th	Night	35% 5% 11% 24% 22% 3	1600
	21st to end	Night	38% 4 14% 24% 17% 3	1600
July	1st to 10th	Night	42% 3 14% 25% 14% 2	3580
	11th to 20th	Night	31% 3 14% 31% 19% 1	3572
	21st to end	Night	36% 5% 18% 22% 16% 3	3832
August	1st to 10th	Night	31% 3 15% 33% 17% 1	2799
	11th to 20th	Night	33% 3 14% 33% 17% 1	3106
	21st to end	Night	32% 4 12% 31% 18% 4	3586
September	1st to 10th	Night	30% 4 10% 29% 25% 2	2000
	11th to 20th	Night	32% 4 10% 34% 18% 3	2015
	21st to end	Night	33% 4 9% 30% 21% 2	2200
October	1st to 10th	Night	24% 2 6% 36% 30% 2	3920
	11th to 20th	Night	34% 3 7% 24% 29% 3	3899
	21st to end	Night	45% 2 9% 25% 16% 3	4470
November	1st to 10th	Night	37% 3 11% 28% 19% 3	2666
	11th to 20th	Night	50% 3 11% 23% 13% 1	2751
	21st to end	Night	51% 2 11% 25% 10% 1	2940
December	1st to 10th	Night	44% 2 15% 29% 9% 1	4720
	11th to 20th	Night	57% 3 14% 19% 7% 1	5341
	21st to end	Night	74% 3 7% 12% 5%	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	21% 22% 34% 19% 4	330
	11th to 20th	Day	24% 28% 36% 9% 2 1	330
	21st to end	Day	26% 27% 35% 9% 3	363
February	1st to 10th	Day	25% 29% 34% 11% 2	330
	11th to 20th	Day	23% 33% 31% 11% 2	330
	21st to end	Day	33% 30% 30% 7% 1	273
March	1st to 10th	Day	25% 30% 35% 7% 2	330
	11th to 20th	Day	31% 25% 30% 12% 2 1	330
	21st to end	Day	32% 25% 29% 10% 2 1	524
April	1st to 10th	Day	32% 24% 28% 13% 4	540
	11th to 20th	Day	30% 22% 24% 17% 6% 1	532
	21st to end	Day	25% 20% 30% 18% 5% 1	540
May	1st to 10th	Day	21% 20% 33% 18% 7% 1	612
	11th to 20th	Day	24% 15% 29% 21% 8% 2	725
	21st to end	Day	18% 15% 31% 24% 8% 4	789
June	1st to 10th	Day	11% 13% 36% 26% 11% 4	730
	11th to 20th	Day	14% 13% 35% 26% 9% 3	730
	21st to end	Day	17% 12% 36% 22% 11% 3	730
July	1st to 10th	Day	11% 6% 27% 30% 18% 8%	721
	11th to 20th	Day	10% 10% 32% 27% 15% 6%	718
	21st to end	Day	9% 6% 31% 33% 15% 5%	794
August	1st to 10th	Day	6% 5% 28% 35% 20% 5%	726
	11th to 20th	Day	15% 7% 25% 27% 19% 7%	594
	21st to end	Day	10% 8% 25% 32% 19% 5%	583
September	1st to 10th	Day	15% 9% 28% 24% 16% 7%	530
	11th to 20th	Day	10% 6% 27% 32% 20% 5%	530
	21st to end	Day	15% 17% 25% 27% 13% 3	527
October	1st to 10th	Day	20% 13% 32% 24% 11%	330
	11th to 20th	Day	29% 25% 29% 15% 2	330
	21st to end	Day	34% 18% 33% 12% 2	363
November	1st to 10th	Day	22% 24% 36% 14% 3 2	330
	11th to 20th	Day	28% 23% 32% 12% 4	330
	21st to end	Day	29% 19% 39% 9% 3	330
December	1st to 10th	Day	19% 28% 36% 12% 4 1	330
	11th to 20th	Day	24% 20% 37% 14% 4	330
	21st to end	Day	31% 23% 34% 10% 1	363
January	1st to 10th	Night	18% 21% 34% 21% 5% 1	1050
	11th to 20th	Night	21% 21% 34% 20% 4	1050
	21st to end	Night	22% 18% 36% 20% 4	1155
February	1st to 10th	Night	22% 20% 33% 20% 5%	1050
	11th to 20th	Night	18% 23% 35% 21% 3	914
	21st to end	Night	23% 21% 36% 17% 2	692
March	1st to 10th	Night	23% 20% 33% 20% 4	840
	11th to 20th	Night	21% 16% 33% 24% 6%	676
	21st to end	Night	25% 18% 35% 17% 4 1	693
April	1st to 10th	Night	25% 18% 33% 20% 3	630
	11th to 20th	Night	26% 15% 29% 24% 6%	623
	21st to end	Night	23% 13% 31% 26% 7% 1	630
May	1st to 10th	Night	19% 10% 38% 27% 6%	603
	11th to 20th	Night	21% 10% 31% 28% 9%	591
	21st to end	Night	15% 7% 32% 32% 13% 1	650
June	1st to 10th	Night	9% 6% 33% 42% 10%	600
	11th to 20th	Night	13% 6% 36% 34% 12%	600
	21st to end	Night	13% 7% 32% 35% 13% 1	600
July	1st to 10th	Night	9% 2 19% 39% 27% 3	585
	11th to 20th	Night	8% 4 26% 38% 23% 2	582
	21st to end	Night	8% 3 25% 40% 23% 1	657
August	1st to 10th	Night	7% 3 19% 43% 26% 3	597
	11th to 20th	Night	10% 2 16% 39% 28% 5%	594
	21st to end	Night	11% 3 20% 42% 22% 3	660
September	1st to 10th	Night	11% 6% 23% 35% 20% 5%	600
	11th to 20th	Night	10% 6% 25% 31% 24% 4	615
	21st to end	Night	12% 12% 26% 31% 18% 2	800
October	1st to 10th	Night	14% 10% 32% 29% 14% 2	800
	11th to 20th	Night	22% 14% 32% 23% 9%	800
	21st to end	Night	26% 15% 31% 22% 6% 1	880
November	1st to 10th	Night	19% 16% 35% 23% 6% 1	820
	11th to 20th	Night	23% 21% 34% 18% 4	861
	21st to end	Night	23% 18% 34% 18% 6%	1050
December	1st to 10th	Night	22% 20% 33% 20% 5%	1050
	11th to 20th	Night	23% 18% 33% 21% 4	1050
	21st to end	Night	29% 20% 31% 17% 3	1155

Page generated at 2026-04-29 01:21:47. Version ac07

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