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 2024-01-17.

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	14% 9% 4 6% 5% 3 5% 5% 5% 7% 37%	74806
	Night	14% 9% 4 6% 5% 3 4 4 5% 6% 39%	75050
Transparency	Day	47% 4 12% 23% 13% 1	74506
	Night	46% 3 12% 23% 14% 2	74870
Seeing	Day	19% 16% 31% 21% 9% 3	14697
	Night	18% 14% 31% 26% 10% 1	24692

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	11% 11% 6% 9% 8% 3 5% 5% 5% 7% 30%	1517
	11th to 20th	Day	13% 13% 7% 13% 6% 3 3 5% 5% 6% 25%	1488
	21st to end	Day	13% 15% 8% 12% 7% 3 4 5% 4 5% 24%	1728
February	1st to 10th	Day	14% 13% 7% 8% 7% 4 5% 4 5% 5% 30%	1620
	11th to 20th	Day	14% 10% 5% 7% 6% 3 5% 4 6% 5% 35%	1670
	21st to end	Day	14% 14% 4 9% 6% 3 4 4 5% 6% 31%	1480
March	1st to 10th	Day	15% 11% 6% 6% 6% 3 4 4 5% 6% 34%	1800
	11th to 20th	Day	13% 10% 4 6% 6% 2 4 4 4 9% 39%	1956
	21st to end	Day	21% 12% 4 6% 6% 3 5% 5% 5% 6% 28%	2315
April	1st to 10th	Day	18% 12% 4 6% 6% 3 4 5% 4 7% 31%	2160
	11th to 20th	Day	18% 10% 4 6% 6% 3 5% 4 4 6% 34%	2134
	21st to end	Day	21% 8% 3 6% 6% 4 5% 4 5% 7% 32%	2164
May	1st to 10th	Day	18% 9% 3 7% 6% 4 5% 4 7% 7% 29%	2434
	11th to 20th	Day	20% 9% 3 5% 6% 4 5% 5% 5% 6% 33%	2479
	21st to end	Day	15% 7% 3 7% 6% 4 5% 5% 5% 7% 35%	2725
June	1st to 10th	Day	10% 5% 3 5% 6% 4 6% 5% 6% 9% 41%	2520
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 5% 6% 8% 45%	2520
	21st to end	Day	12% 6% 3 6% 5% 3 5% 6% 6% 8% 38%	2520
July	1st to 10th	Day	8% 4 2 5% 5% 3 5% 5% 6% 9% 46%	2520
	11th to 20th	Day	8% 4 3 5% 5% 3 5% 6% 6% 10% 45%	2520
	21st to end	Day	7% 5% 2 6% 5% 4 6% 6% 6% 10% 44%	2743
August	1st to 10th	Day	6% 4 3 6% 6% 4 6% 7% 8% 11% 40%	2396
	11th to 20th	Day	11% 6% 2 5% 4 4 4 5% 6% 10% 44%	2193
	21st to end	Day	10% 5% 2 4 4 3 5% 4 6% 7% 48%	2376
September	1st to 10th	Day	13% 5% 2 5% 5% 3 5% 5% 5% 7% 44%	2160
	11th to 20th	Day	13% 5% 1 4 4 2 3 4 4 7% 53%	2129
	21st to end	Day	13% 6% 3 4 5% 3 4 4 5% 8% 46%	1978
October	1st to 10th	Day	15% 7% 3 6% 4 2 4 4 4 6% 47%	1800
	11th to 20th	Day	20% 9% 3 6% 5% 3 4 3 4 6% 37%	1800
	21st to end	Day	20% 8% 3 5% 5% 3 4 3 4 6% 39%	1861
November	1st to 10th	Day	12% 8% 3 6% 6% 3 4 4 4 6% 45%	1672
	11th to 20th	Day	14% 12% 5% 8% 5% 3 4 4 4 7% 34%	1687
	21st to end	Day	15% 12% 4 8% 4 3 3 4 3 5% 38%	1520
December	1st to 10th	Day	15% 14% 4 8% 5% 4 4 4 5% 6% 32%	1520
	11th to 20th	Day	15% 12% 6% 9% 7% 3 4 4 4 7% 30%	1918
	21st to end	Day	22% 21% 9% 9% 5% 3 4 3 4 5% 15%	2783
January	1st to 10th	Night	12% 11% 6% 8% 7% 3 5% 4 4 5% 35%	2648
	11th to 20th	Night	13% 15% 5% 10% 8% 3 4 5% 5% 6% 26%	2617
	21st to end	Night	15% 13% 7% 10% 6% 4 5% 4 6% 6% 25%	2628
February	1st to 10th	Night	13% 13% 5% 8% 7% 4 4 4 5% 6% 31%	2340
	11th to 20th	Night	12% 10% 4 8% 6% 4 4 4 4 5% 39%	2176
	21st to end	Night	16% 12% 4 7% 5% 3 4 4 4 6% 35%	1776
March	1st to 10th	Night	17% 11% 4 6% 6% 3 4 4 4 6% 35%	2160
	11th to 20th	Night	12% 8% 4 6% 6% 4 5% 4 4 7% 41%	2020
	21st to end	Night	21% 11% 5% 7% 6% 3 4 4 4 6% 30%	2039
April	1st to 10th	Night	16% 10% 5% 6% 5% 3 3 4 5% 6% 39%	1800
	11th to 20th	Night	18% 9% 4 6% 5% 3 4 3 4 6% 38%	1775
	21st to end	Night	17% 8% 3 6% 5% 3 5% 5% 5% 9% 34%	1796
May	1st to 10th	Night	15% 7% 3 6% 5% 3 5% 6% 7% 8% 35%	1523
	11th to 20th	Night	18% 7% 3 6% 6% 3 5% 4 5% 6% 38%	1416
	21st to end	Night	11% 6% 3 4 5% 2 5% 6% 7% 10% 41%	1551
June	1st to 10th	Night	8% 4 2 6% 6% 3 5% 5% 7% 8% 48%	1440
	11th to 20th	Night	11% 5% 2 4 4 3 5% 5% 7% 9% 46%	1440
	21st to end	Night	10% 6% 2 5% 5% 3 5% 5% 6% 8% 45%	1440
July	1st to 10th	Night	6% 3 2 5% 4 2 5% 4 5% 11% 54%	1440
	11th to 20th	Night	6% 4 2 3 4 3 3 3 6% 9% 57%	1440
	21st to end	Night	6% 5% 2 4 4 3 4 5% 7% 8% 52%	1575
August	1st to 10th	Night	6% 4 2 4 5% 3 4 6% 5% 9% 52%	1539
	11th to 20th	Night	7% 5% 2 4 4 2 4 3 5% 7% 55%	1707
	21st to end	Night	9% 4 2 4 4 2 3 4 5% 8% 55%	1980
September	1st to 10th	Night	10% 5% 2 4 4 2 4 4 5% 6% 54%	1800
	11th to 20th	Night	11% 4 2 3 4 2 4 4 5% 8% 51%	1813
	21st to end	Night	10% 5% 2 5% 4 3 4 4 5% 7% 51%	1980
October	1st to 10th	Night	12% 6% 3 4 4 3 4 2 4 6% 52%	2160
	11th to 20th	Night	17% 7% 3 5% 5% 2 3 3 5% 6% 44%	2160
	21st to end	Night	19% 9% 3 5% 6% 3 4 4 4 6% 38%	2493
November	1st to 10th	Night	12% 6% 2 5% 4 3 3 4 4 6% 51%	2406
	11th to 20th	Night	14% 11% 4 7% 6% 4 4 4 4 6% 36%	2489
	21st to end	Night	17% 8% 4 7% 4 3 3 3 5% 6% 38%	2660
December	1st to 10th	Night	14% 11% 5% 9% 7% 3 4 5% 5% 6% 31%	2660
	11th to 20th	Night	14% 12% 6% 9% 5% 3 4 5% 5% 6% 32%	3279
	21st to end	Night	21% 17% 7% 11% 6% 3 5% 4 4 4 18%	4884

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	54% 3 14% 17% 12% 1	1518
	11th to 20th	Day	60% 3 14% 17% 6% 1	1488
	21st to end	Day	62% 4 12% 13% 8% 1	1728
February	1st to 10th	Day	58% 2 13% 18% 8% 1	1620
	11th to 20th	Day	50% 3 12% 22% 11% 2	1679
	21st to end	Day	55% 3 9% 21% 10% 2	1480
March	1st to 10th	Day	51% 4 15% 21% 9% 1	1800
	11th to 20th	Day	45% 3 13% 24% 13% 1	1956
	21st to end	Day	57% 4 10% 19% 8% 1	2315
April	1st to 10th	Day	53% 4 10% 22% 11%	2160
	11th to 20th	Day	51% 4 9% 21% 12% 2	2134
	21st to end	Day	53% 4 10% 19% 13% 2	2164
May	1st to 10th	Day	52% 5% 13% 21% 8% 1	2434
	11th to 20th	Day	52% 3 10% 22% 12%	2483
	21st to end	Day	48% 4 12% 20% 15% 2	2725
June	1st to 10th	Day	38% 5% 13% 27% 16% 1	2520
	11th to 20th	Day	37% 4 12% 24% 20% 2	2520
	21st to end	Day	42% 5% 14% 24% 13% 1	2520
July	1st to 10th	Day	34% 5% 16% 28% 15% 3	2451
	11th to 20th	Day	34% 5% 15% 29% 16% 2	2445
	21st to end	Day	34% 5% 16% 26% 15% 3	2591
August	1st to 10th	Day	35% 5% 15% 31% 12% 1	2381
	11th to 20th	Day	36% 5% 13% 28% 17% 1	2193
	21st to end	Day	34% 4 12% 28% 18% 3	2376
September	1st to 10th	Day	38% 5% 10% 27% 19% 2	2160
	11th to 20th	Day	32% 3 11% 34% 17% 2	2129
	21st to end	Day	38% 3 10% 30% 18% 1	1978
October	1st to 10th	Day	40% 3 10% 29% 17% 1	1800
	11th to 20th	Day	50% 3 9% 23% 14% 1	1800
	21st to end	Day	48% 2 12% 23% 13% 1	1861
November	1st to 10th	Day	41% 3 15% 25% 14% 2	1672
	11th to 20th	Day	52% 2 13% 21% 10% 1	1687
	21st to end	Day	51% 3 15% 22% 8% 1	1520
December	1st to 10th	Day	53% 2 15% 20% 8% 2	1520
	11th to 20th	Day	56% 3 16% 16% 9% 1	1915
	21st to end	Day	74% 2 10% 9% 5%	2783
January	1st to 10th	Night	52% 4 11% 19% 13% 1	2648
	11th to 20th	Night	59% 3 15% 15% 8% 1	2617
	21st to end	Night	60% 3 11% 15% 9% 1	2628
February	1st to 10th	Night	55% 2 11% 19% 12% 1	2340
	11th to 20th	Night	48% 4 10% 23% 13% 1	2177
	21st to end	Night	51% 3 12% 20% 11% 3	1776
March	1st to 10th	Night	51% 3 12% 22% 10% 1	2160
	11th to 20th	Night	45% 3 11% 21% 17% 2	2020
	21st to end	Night	57% 2 10% 20% 9% 2	2039
April	1st to 10th	Night	46% 3 11% 23% 14% 2	1800
	11th to 20th	Night	49% 3 7% 20% 18% 4	1775
	21st to end	Night	47% 4 12% 22% 13% 2	1796
May	1st to 10th	Night	45% 5% 14% 23% 12%	1523
	11th to 20th	Night	48% 4 10% 21% 15% 1	1417
	21st to end	Night	37% 5% 16% 23% 17% 2	1552
June	1st to 10th	Night	32% 5% 14% 26% 21% 2	1440
	11th to 20th	Night	34% 5% 10% 24% 23% 4	1440
	21st to end	Night	37% 4 15% 25% 17% 3	1440
July	1st to 10th	Night	27% 4 15% 33% 17% 3	1400
	11th to 20th	Night	25% 4 13% 33% 21% 4	1392
	21st to end	Night	28% 5% 16% 28% 18% 5%	1487
August	1st to 10th	Night	29% 4 16% 34% 14% 3	1530
	11th to 20th	Night	29% 3 14% 33% 20% 1	1707
	21st to end	Night	28% 3 11% 31% 21% 5%	1980
September	1st to 10th	Night	31% 4 11% 27% 24% 2	1800
	11th to 20th	Night	32% 4 10% 33% 18% 3	1813
	21st to end	Night	33% 4 10% 31% 20% 2	1980
October	1st to 10th	Night	34% 3 9% 29% 22% 2	2160
	11th to 20th	Night	41% 3 9% 25% 19% 2	2160
	21st to end	Night	48% 3 11% 25% 12% 1	2493
November	1st to 10th	Night	36% 3 11% 27% 20% 3	2406
	11th to 20th	Night	50% 3 11% 22% 13% 1	2489
	21st to end	Night	48% 3 12% 26% 11% 1	2660
December	1st to 10th	Night	54% 3 12% 22% 8% 1	2660
	11th to 20th	Night	53% 4 14% 20% 9% 1	3281
	21st to end	Night	71% 3 8% 13% 5%	4884

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	22% 23% 31% 20% 4	270
	11th to 20th	Day	25% 26% 36% 9% 3 1	258
	21st to end	Day	25% 27% 36% 8% 4	264
February	1st to 10th	Day	25% 32% 33% 8% 2	240
	11th to 20th	Day	26% 33% 27% 11% 3	240
	21st to end	Day	36% 32% 26% 6% 1	198
March	1st to 10th	Day	24% 33% 33% 9% 2	240
	11th to 20th	Day	27% 27% 28% 15% 2 1	240
	21st to end	Day	34% 23% 28% 11% 3 2	401
April	1st to 10th	Day	28% 25% 28% 14% 4	420
	11th to 20th	Day	29% 22% 24% 18% 7% 1	412
	21st to end	Day	26% 20% 29% 18% 6% 1	420
May	1st to 10th	Day	22% 20% 34% 17% 6% 1	517
	11th to 20th	Day	25% 15% 30% 20% 8% 1	625
	21st to end	Day	17% 15% 29% 25% 10% 5%	679
June	1st to 10th	Day	9% 12% 37% 27% 11% 4	630
	11th to 20th	Day	14% 13% 34% 26% 9% 3	630
	21st to end	Day	17% 13% 33% 22% 11% 3	630
July	1st to 10th	Day	10% 6% 26% 30% 19% 9%	621
	11th to 20th	Day	9% 9% 33% 28% 15% 6%	618
	21st to end	Day	8% 7% 32% 33% 15% 5%	684
August	1st to 10th	Day	5% 5% 27% 36% 20% 6%	626
	11th to 20th	Day	16% 7% 24% 26% 20% 8%	507
	21st to end	Day	11% 8% 25% 31% 18% 6%	495
September	1st to 10th	Day	17% 10% 28% 24% 14% 6%	450
	11th to 20th	Day	12% 6% 30% 29% 17% 6%	450
	21st to end	Day	16% 19% 24% 26% 13% 3	448
October	1st to 10th	Day	23% 14% 31% 23% 9%	270
	11th to 20th	Day	31% 27% 28% 11% 2	270
	21st to end	Day	36% 18% 32% 11% 2	297
November	1st to 10th	Day	20% 23% 37% 16% 3 2	270
	11th to 20th	Day	26% 23% 36% 11% 4	270
	21st to end	Day	27% 19% 42% 9% 3	270
December	1st to 10th	Day	21% 28% 34% 11% 4 1	270
	11th to 20th	Day	21% 21% 37% 16% 4	270
	21st to end	Day	32% 24% 34% 9% 1	297
January	1st to 10th	Night	19% 20% 35% 21% 5% 1	950
	11th to 20th	Night	21% 20% 34% 20% 5%	935
	21st to end	Night	22% 18% 36% 20% 4	990
February	1st to 10th	Night	24% 19% 33% 19% 5%	900
	11th to 20th	Night	18% 23% 35% 21% 3	781
	21st to end	Night	26% 21% 34% 17% 2 1	592
March	1st to 10th	Night	23% 20% 33% 20% 4 1	720
	11th to 20th	Night	19% 16% 33% 25% 6%	580
	21st to end	Night	25% 19% 33% 18% 5% 1	594
April	1st to 10th	Night	23% 18% 34% 21% 4	540
	11th to 20th	Night	26% 15% 28% 24% 6%	533
	21st to end	Night	22% 13% 31% 25% 8% 1	540
May	1st to 10th	Night	19% 9% 38% 27% 6%	540
	11th to 20th	Night	22% 10% 31% 28% 9%	531
	21st to end	Night	14% 7% 33% 31% 14% 1	584
June	1st to 10th	Night	9% 6% 32% 43% 10%	540
	11th to 20th	Night	13% 6% 35% 34% 12%	540
	21st to end	Night	12% 6% 32% 35% 14% 1	540
July	1st to 10th	Night	7% 2 19% 39% 28% 4	525
	11th to 20th	Night	7% 4 26% 38% 22% 2	522
	21st to end	Night	9% 2 25% 41% 22% 1	591
August	1st to 10th	Night	6% 3 18% 43% 28% 3	537
	11th to 20th	Night	9% 2 17% 37% 29% 6%	534
	21st to end	Night	11% 3 22% 40% 22% 3	594
September	1st to 10th	Night	12% 6% 24% 34% 19% 5%	540
	11th to 20th	Night	11% 6% 26% 31% 22% 4	553
	21st to end	Night	12% 13% 27% 30% 16% 2	720
October	1st to 10th	Night	14% 10% 31% 28% 14% 2	720
	11th to 20th	Night	22% 15% 31% 23% 9%	720
	21st to end	Night	27% 15% 31% 20% 6% 1	792
November	1st to 10th	Night	17% 17% 34% 24% 7% 1	740
	11th to 20th	Night	22% 22% 33% 18% 5%	779
	21st to end	Night	22% 18% 34% 19% 7%	950
December	1st to 10th	Night	23% 19% 33% 20% 5% 1	950
	11th to 20th	Night	23% 17% 33% 22% 5%	950
	21st to end	Night	27% 22% 31% 18% 2	1045

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