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 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	13% 9% 4 8% 5% 4 4 4 5% 7% 37%	105133
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 38%	104019
Transparency	Day	46% 3 12% 24% 13% 1	108673
	Night	46% 3 11% 24% 14% 2	108618
Seeing	Day	19% 16% 31% 21% 9% 3	16056
	Night	18% 14% 31% 26% 10% 1	25999

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% 13% 10% 15% 6% 4 4 2 4 5% 27%	2575
	11th to 20th	Day	11% 11% 5% 16% 5% 5% 5% 9% 7% 5% 20%	2530
	21st to end	Day	17% 21% 10% 10% 5% 3 3 3 4 6% 20%	3039
February	1st to 10th	Day	13% 13% 6% 8% 6% 4 6% 3 5% 6% 31%	1710
	11th to 20th	Day	14% 10% 4 7% 5% 5% 4 3 6% 5% 37%	1765
	21st to end	Day	13% 14% 4 9% 6% 4 4 3 5% 6% 32%	1570
March	1st to 10th	Day	14% 10% 4 7% 4 3 3 3 4 5% 42%	3120
	11th to 20th	Day	11% 7% 3 7% 5% 5% 4 4 5% 7% 43%	3442
	21st to end	Day	23% 14% 3 10% 6% 5% 4 3 5% 5% 22%	4062
April	1st to 10th	Day	18% 14% 3 7% 6% 4 3 4 4 6% 31%	2280
	11th to 20th	Day	17% 11% 3 7% 5% 4 4 4 4 6% 34%	2254
	21st to end	Day	21% 8% 3 7% 4 5% 5% 3 5% 6% 32%	2285
May	1st to 10th	Day	17% 8% 3 8% 5% 4 4 3 6% 7% 35%	4260
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 6% 41%	4399
	21st to end	Day	13% 7% 2 7% 4 5% 4 4 5% 7% 40%	4824
June	1st to 10th	Day	10% 5% 3 7% 5% 5% 5% 4 6% 9% 42%	2660
	11th to 20th	Day	11% 5% 3 5% 4 4 5% 4 6% 8% 44%	2660
	21st to end	Day	12% 7% 3 7% 4 5% 5% 5% 6% 8% 38%	2660
July	1st to 10th	Day	11% 7% 3 8% 6% 5% 6% 5% 7% 9% 33%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 6% 10% 51%	4440
	21st to end	Day	8% 6% 3 7% 5% 5% 6% 5% 7% 9% 39%	4813
August	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 4 7% 9% 41%	4214
	11th to 20th	Day	12% 5% 2 6% 3 4 4 4 7% 9% 43%	3836
	21st to end	Day	9% 5% 2 6% 4 4 4 4 6% 8% 48%	4180
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 5% 7% 46%	2280
	11th to 20th	Day	12% 4 1 4 3 3 3 4 4 7% 53%	2247
	21st to end	Day	13% 6% 3 5% 4 4 4 3 5% 8% 46%	2087
October	1st to 10th	Day	14% 6% 3 6% 3 3 3 3 4 6% 49%	1900
	11th to 20th	Day	19% 9% 2 7% 4 4 4 2 4 6% 38%	1900
	21st to end	Day	19% 9% 3 6% 4 3 4 2 4 6% 40%	1964
November	1st to 10th	Day	13% 8% 3 6% 5% 4 4 3 4 6% 44%	1762
	11th to 20th	Day	14% 14% 4 8% 5% 4 4 3 4 6% 34%	1775
	21st to end	Day	15% 14% 3 9% 4 4 3 3 3 5% 36%	1600
December	1st to 10th	Day	8% 10% 4 8% 4 3 4 3 6% 7% 42%	2610
	11th to 20th	Day	14% 15% 6% 13% 6% 6% 5% 3 5% 6% 22%	3008
	21st to end	Day	20% 24% 9% 11% 4 4 3 3 4 5% 13%	3982
January	1st to 10th	Night	13% 12% 8% 13% 6% 4 4 3 4 4 28%	4513
	11th to 20th	Night	13% 17% 6% 14% 5% 4 4 6% 7% 4 20%	4440
	21st to end	Night	17% 20% 7% 10% 6% 5% 3 2 4 4 21%	4628
February	1st to 10th	Night	12% 14% 4 9% 6% 5% 3 4 5% 6% 31%	2470
	11th to 20th	Night	11% 11% 3 9% 5% 4 4 3 4 5% 40%	2301
	21st to end	Night	15% 13% 4 8% 4 4 4 2 4 6% 36%	1884
March	1st to 10th	Night	19% 9% 3 5% 4 4 4 3 4 4 41%	3733
	11th to 20th	Night	10% 7% 2 6% 4 5% 4 3 4 7% 48%	3548
	21st to end	Night	25% 12% 4 10% 4 4 3 2 4 5% 26%	3567
April	1st to 10th	Night	16% 12% 3 6% 4 3 3 3 5% 5% 39%	1900
	11th to 20th	Night	17% 9% 3 7% 4 3 4 3 5% 5% 39%	1875
	21st to end	Night	18% 8% 2 7% 4 4 5% 4 5% 8% 35%	1895
May	1st to 10th	Night	18% 8% 3 7% 5% 4 4 5% 5% 7% 34%	2638
	11th to 20th	Night	14% 7% 3 6% 6% 5% 5% 4 5% 6% 41%	2506
	21st to end	Night	9% 6% 2 5% 4 3 5% 4 6% 8% 46%	2743
June	1st to 10th	Night	8% 5% 2 6% 5% 4 5% 3 8% 7% 47%	1520
	11th to 20th	Night	11% 6% 2 5% 4 3 5% 4 7% 9% 45%	1520
	21st to end	Night	10% 7% 2 6% 5% 4 4 4 6% 8% 44%	1520
July	1st to 10th	Night	14% 7% 3 7% 4 4 5% 4 5% 8% 40%	2530
	11th to 20th	Night	4 4 2 4 4 4 4 3 6% 8% 57%	2530
	21st to end	Night	6% 5% 2 5% 4 5% 6% 5% 6% 8% 48%	2750
August	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 8% 52%	2722
	11th to 20th	Night	8% 6% 2 5% 3 4 4 3 6% 6% 52%	2983
	21st to end	Night	9% 5% 2 5% 4 3 4 4 5% 9% 50%	3476
September	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 4 6% 56%	1900
	11th to 20th	Night	10% 4 2 5% 4 3 5% 3 6% 8% 51%	1914
	21st to end	Night	9% 5% 2 5% 4 4 5% 3 5% 7% 51%	2090
October	1st to 10th	Night	11% 6% 2 5% 3 4 4 2 4 6% 53%	2280
	11th to 20th	Night	15% 8% 2 6% 4 3 3 3 5% 6% 45%	2280
	21st to end	Night	18% 9% 3 6% 5% 4 4 3 4 6% 38%	2632
November	1st to 10th	Night	13% 7% 2 6% 3 3 3 3 4 6% 50%	2536
	11th to 20th	Night	14% 12% 3 8% 5% 5% 4 3 4 6% 36%	2620
	21st to end	Night	17% 10% 4 9% 4 3 3 3 5% 6% 37%	2800
December	1st to 10th	Night	9% 8% 3 7% 6% 4 5% 4 5% 6% 42%	4580
	11th to 20th	Night	16% 15% 5% 10% 5% 4 4 3 5% 5% 30%	5199
	21st to end	Night	21% 20% 7% 13% 5% 4 4 3 4 4 16%	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	62% 2 11% 17% 7%	2576
	11th to 20th	Day	60% 4 15% 13% 8% 1	2530
	21st to end	Day	67% 3 13% 11% 5%	3039
February	1st to 10th	Day	56% 2 13% 18% 10% 1	1710
	11th to 20th	Day	49% 3 12% 24% 11% 2	1774
	21st to end	Day	53% 4 10% 21% 10% 2	1570
March	1st to 10th	Day	46% 3 12% 26% 11% 3	3120
	11th to 20th	Day	39% 5% 12% 31% 12% 1	3442
	21st to end	Day	64% 3 13% 14% 5% 1	4062
April	1st to 10th	Day	53% 4 10% 22% 11%	2280
	11th to 20th	Day	51% 4 9% 22% 12% 2	2254
	21st to end	Day	53% 4 10% 19% 13% 2	2285
May	1st to 10th	Day	48% 4 11% 20% 16%	4298
	11th to 20th	Day	45% 2 10% 30% 13%	4403
	21st to end	Day	42% 5% 10% 24% 15% 4	4837
June	1st to 10th	Day	38% 5% 13% 26% 16% 1	2660
	11th to 20th	Day	37% 4 12% 24% 20% 2	2660
	21st to end	Day	43% 5% 13% 24% 13% 2	2660
July	1st to 10th	Day	46% 4 14% 25% 9% 2	4371
	11th to 20th	Day	29% 4 17% 32% 17% 1	4365
	21st to end	Day	40% 5% 16% 18% 19% 2	4662
August	1st to 10th	Day	38% 5% 15% 28% 14% 1	4199
	11th to 20th	Day	37% 3 13% 30% 16% 1	3874
	21st to end	Day	34% 3 13% 32% 16% 2	4179
September	1st to 10th	Day	37% 5% 10% 27% 20% 2	2280
	11th to 20th	Day	32% 3 11% 34% 18% 2	2247
	21st to end	Day	38% 3 10% 29% 18% 2	2087
October	1st to 10th	Day	24% 2 6% 36% 30% 1	3160
	11th to 20th	Day	34% 2 9% 26% 27% 3	3140
	21st to end	Day	42% 2 9% 29% 14% 3	3215
November	1st to 10th	Day	42% 3 15% 25% 13% 2	1762
	11th to 20th	Day	53% 2 12% 21% 10% 1	1775
	21st to end	Day	52% 3 15% 22% 8% 1	1600
December	1st to 10th	Day	42% 2 19% 30% 6% 1	2610
	11th to 20th	Day	64% 2 12% 14% 7% 1	3005
	21st to end	Day	76% 2 9% 8% 5%	3982
January	1st to 10th	Night	58% 4 11% 18% 9% 1	4513
	11th to 20th	Night	64% 3 11% 14% 8%	4440
	21st to end	Night	68% 2 8% 15% 6% 1	4628
February	1st to 10th	Night	53% 3 11% 19% 13% 1	2470
	11th to 20th	Night	47% 4 10% 24% 14% 1	2302
	21st to end	Night	50% 3 12% 21% 11% 3	1884
March	1st to 10th	Night	48% 2 11% 23% 12% 3	3733
	11th to 20th	Night	37% 4 9% 32% 16% 2	3548
	21st to end	Night	63% 2 10% 18% 6% 1	3567
April	1st to 10th	Night	46% 3 11% 24% 14% 2	1900
	11th to 20th	Night	48% 3 7% 20% 19% 3	1875
	21st to end	Night	47% 4 12% 22% 14% 2	1895
May	1st to 10th	Night	49% 4 11% 17% 17% 2	2665
	11th to 20th	Night	45% 4 12% 23% 15% 1	2507
	21st to end	Night	33% 6% 13% 26% 20% 3	2751
June	1st to 10th	Night	32% 5% 14% 27% 20% 2	1520
	11th to 20th	Night	34% 4 10% 25% 23% 3	1520
	21st to end	Night	38% 4 15% 24% 17% 3	1520
July	1st to 10th	Night	44% 3 15% 23% 12% 3	2490
	11th to 20th	Night	26% 3 16% 35% 18% 2	2482
	21st to end	Night	32% 6% 17% 21% 19% 5%	2662
August	1st to 10th	Night	31% 3 15% 33% 17% 2	2713
	11th to 20th	Night	32% 3 14% 33% 18% 1	3010
	21st to end	Night	32% 4 12% 30% 18% 4	3476
September	1st to 10th	Night	30% 4 10% 28% 25% 2	1900
	11th to 20th	Night	32% 4 10% 33% 18% 3	1914
	21st to end	Night	33% 4 9% 31% 20% 2	2090
October	1st to 10th	Night	24% 2 6% 36% 30% 2	3800
	11th to 20th	Night	33% 3 7% 25% 29% 3	3779
	21st to end	Night	45% 2 9% 26% 15% 3	4331
November	1st to 10th	Night	37% 3 11% 27% 19% 3	2536
	11th to 20th	Night	50% 3 10% 22% 13% 1	2620
	21st to end	Night	50% 3 12% 25% 10% 1	2800
December	1st to 10th	Night	43% 2 16% 30% 8% 1	4580
	11th to 20th	Night	57% 3 14% 19% 7%	5201
	21st to end	Night	74% 3 7% 12% 5%	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	22% 22% 33% 19% 4	288
	11th to 20th	Day	24% 27% 37% 9% 3 1	270
	21st to end	Day	27% 25% 35% 9% 4	297
February	1st to 10th	Day	24% 30% 33% 10% 1	270
	11th to 20th	Day	24% 32% 29% 12% 2	270
	21st to end	Day	32% 31% 28% 8% 1	225
March	1st to 10th	Day	23% 32% 35% 8% 2	270
	11th to 20th	Day	29% 26% 30% 13% 2 1	270
	21st to end	Day	33% 23% 29% 10% 3 2	442
April	1st to 10th	Day	30% 25% 27% 13% 4	460
	11th to 20th	Day	30% 22% 23% 18% 6% 1	452
	21st to end	Day	26% 21% 29% 18% 5% 1	460
May	1st to 10th	Day	22% 20% 33% 18% 6% 1	563
	11th to 20th	Day	24% 15% 30% 20% 8% 1	675
	21st to end	Day	17% 15% 30% 24% 9% 4	734
June	1st to 10th	Day	10% 13% 37% 26% 11% 4	680
	11th to 20th	Day	14% 14% 35% 25% 9% 3	680
	21st to end	Day	17% 13% 35% 22% 11% 3	680
July	1st to 10th	Day	10% 6% 27% 30% 18% 8%	671
	11th to 20th	Day	9% 10% 32% 28% 15% 6%	668
	21st to end	Day	9% 6% 31% 34% 15% 5%	739
August	1st to 10th	Day	6% 6% 28% 36% 19% 5%	676
	11th to 20th	Day	15% 7% 26% 25% 19% 7%	550
	21st to end	Day	11% 7% 25% 32% 19% 6%	539
September	1st to 10th	Day	16% 9% 29% 24% 16% 6%	490
	11th to 20th	Day	11% 6% 29% 30% 18% 6%	490
	21st to end	Day	16% 18% 25% 26% 12% 3	487
October	1st to 10th	Day	22% 14% 31% 23% 10%	300
	11th to 20th	Day	29% 26% 28% 14% 3	300
	21st to end	Day	35% 18% 32% 12% 2	330
November	1st to 10th	Day	22% 23% 36% 14% 3 2	300
	11th to 20th	Day	28% 22% 34% 12% 4	300
	21st to end	Day	29% 19% 40% 9% 3	300
December	1st to 10th	Day	20% 29% 35% 11% 4 1	300
	11th to 20th	Day	23% 20% 38% 15% 4	300
	21st to end	Day	31% 23% 34% 11% 1	330
January	1st to 10th	Night	18% 21% 35% 20% 4 1	981
	11th to 20th	Night	20% 20% 34% 20% 5%	950
	21st to end	Night	22% 18% 35% 21% 4	1045
February	1st to 10th	Night	23% 19% 34% 20% 5%	950
	11th to 20th	Night	17% 23% 35% 21% 3	826
	21st to end	Night	25% 21% 35% 16% 2	628
March	1st to 10th	Night	23% 20% 33% 19% 4 1	760
	11th to 20th	Night	20% 16% 34% 24% 6%	612
	21st to end	Night	26% 18% 33% 18% 4 1	627
April	1st to 10th	Night	24% 18% 33% 21% 4	570
	11th to 20th	Night	26% 16% 28% 24% 6%	563
	21st to end	Night	22% 14% 31% 26% 7% 1	570
May	1st to 10th	Night	19% 10% 38% 26% 6%	570
	11th to 20th	Night	21% 10% 32% 28% 9%	561
	21st to end	Night	13% 7% 33% 32% 13% 1	617
June	1st to 10th	Night	9% 6% 34% 42% 9%	570
	11th to 20th	Night	13% 6% 37% 33% 12%	570
	21st to end	Night	12% 7% 32% 34% 14% 1	570
July	1st to 10th	Night	9% 3 19% 39% 27% 4	555
	11th to 20th	Night	7% 4 26% 37% 23% 2	552
	21st to end	Night	9% 2 24% 40% 23% 1	624
August	1st to 10th	Night	6% 3 19% 42% 27% 3	567
	11th to 20th	Night	10% 2 17% 38% 28% 5%	564
	21st to end	Night	11% 3 21% 40% 22% 3	627
September	1st to 10th	Night	12% 6% 23% 35% 20% 5%	570
	11th to 20th	Night	11% 6% 25% 31% 23% 4	584
	21st to end	Night	12% 12% 28% 31% 16% 2	760
October	1st to 10th	Night	14% 10% 31% 29% 14% 2	760
	11th to 20th	Night	21% 14% 31% 23% 9%	760
	21st to end	Night	26% 16% 30% 21% 6% 1	836
November	1st to 10th	Night	19% 17% 34% 23% 7% 1	780
	11th to 20th	Night	23% 21% 33% 18% 5%	820
	21st to end	Night	22% 18% 34% 18% 7%	1000
December	1st to 10th	Night	22% 20% 33% 21% 5% 1	1000
	11th to 20th	Night	23% 17% 33% 22% 5%	1000
	21st to end	Night	28% 21% 31% 18% 3	1100

Page generated at 2025-01-04 02:23:57. Version ac07

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