Magazine Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Magazine Mountain clear sky chart from 2005-11-06 to 2024-01-31.

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% 6% 2 5% 5% 3 5% 4 5% 7% 45%	74796
	Night	12% 5% 2 4 4 2 4 4 5% 7% 51%	75337
Transparency	Day	39% 4 10% 24% 19% 4	74520
	Night	34% 3 10% 25% 22% 6%	75133
Seeing	Day	15% 9% 21% 26% 22% 8%	14283
	Night	15% 8% 20% 34% 21% 2	24258

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	17% 8% 2 4 3 2 3 3 3 6% 48%	1707
	11th to 20th	Day	14% 6% 2 5% 5% 3 4 4 5% 5% 46%	1710
	21st to end	Day	16% 7% 2 4 4 2 3 3 4 5% 50%	1872
February	1st to 10th	Day	20% 8% 3 5% 3 3 3 3 3 6% 44%	1620
	11th to 20th	Day	17% 8% 3 6% 4 2 4 4 4 5% 43%	1615
	21st to end	Day	20% 8% 3 6% 5% 3 3 3 4 5% 38%	1606
March	1st to 10th	Day	17% 7% 2 5% 4 2 4 3 4 6% 46%	1980
	11th to 20th	Day	20% 8% 3 5% 5% 3 4 3 3 4 42%	1980
	21st to end	Day	18% 8% 3 6% 6% 3 4 4 5% 6% 37%	2178
April	1st to 10th	Day	13% 6% 2 6% 6% 3 5% 3 5% 7% 44%	2101
	11th to 20th	Day	17% 5% 3 5% 5% 2 4 4 4 6% 44%	2134
	21st to end	Day	18% 7% 2 5% 6% 4 4 4 4 6% 41%	2160
May	1st to 10th	Day	17% 7% 4 5% 6% 3 4 4 5% 6% 40%	2246
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 6% 5% 6% 41%	2302
	21st to end	Day	11% 6% 2 7% 7% 4 6% 6% 6% 8% 37%	2531
June	1st to 10th	Day	9% 6% 2 6% 5% 3 5% 5% 7% 9% 41%	2340
	11th to 20th	Day	6% 3 3 5% 7% 4 7% 7% 6% 9% 44%	2340
	21st to end	Day	5% 3 2 4 5% 4 5% 6% 6% 10% 50%	2340
July	1st to 10th	Day	8% 6% 3 6% 7% 4 7% 6% 7% 9% 38%	2340
	11th to 20th	Day	5% 3 2 4 6% 5% 6% 8% 7% 9% 46%	2340
	21st to end	Day	6% 4 2 5% 6% 5% 6% 7% 8% 11% 40%	2546
August	1st to 10th	Day	7% 4 3 5% 6% 4 6% 6% 8% 10% 41%	2328
	11th to 20th	Day	11% 5% 2 5% 6% 3 4 5% 6% 10% 43%	2217
	21st to end	Day	8% 3 2 4 5% 4 6% 5% 7% 9% 47%	2376
September	1st to 10th	Day	11% 5% 2 5% 4 3 4 4 6% 8% 50%	2160
	11th to 20th	Day	12% 5% 2 4 5% 3 4 5% 5% 7% 48%	2062
	21st to end	Day	9% 5% 2 4 5% 2 5% 4 4 6% 54%	1926
October	1st to 10th	Day	8% 4 2 5% 5% 3 5% 4 4 6% 56%	1800
	11th to 20th	Day	14% 6% 2 4 3 2 3 4 4 5% 55%	1800
	21st to end	Day	19% 6% 2 4 3 3 3 3 4 4 50%	1980
November	1st to 10th	Day	11% 5% 2 4 4 2 4 4 4 6% 56%	1858
	11th to 20th	Day	11% 5% 2 5% 3 2 3 4 4 6% 55%	1900
	21st to end	Day	17% 7% 2 5% 4 2 3 3 3 5% 48%	1660
December	1st to 10th	Day	17% 5% 2 4 4 4 2 3 5% 6% 47%	1520
	11th to 20th	Day	13% 8% 4 6% 5% 3 5% 4 4 5% 43%	2086
	21st to end	Day	17% 10% 3 6% 6% 3 5% 4 4 5% 36%	3135
January	1st to 10th	Night	16% 6% 3 4 3 2 3 3 4 6% 52%	2458
	11th to 20th	Night	15% 6% 2 4 4 2 2 2 4 6% 51%	2470
	21st to end	Night	16% 5% 2 4 3 2 3 3 4 5% 53%	2711
February	1st to 10th	Night	18% 8% 3 5% 5% 2 3 3 5% 6% 44%	2340
	11th to 20th	Night	16% 8% 2 5% 4 2 3 3 4 6% 46%	2230
	21st to end	Night	19% 7% 3 5% 3 2 3 4 3 5% 46%	1664
March	1st to 10th	Night	16% 6% 3 5% 4 3 4 3 4 6% 47%	1980
	11th to 20th	Night	18% 8% 3 5% 4 3 4 4 3 5% 43%	1980
	21st to end	Night	18% 6% 3 5% 4 3 4 3 4 6% 44%	2178
April	1st to 10th	Night	13% 5% 2 5% 5% 3 4 4 5% 7% 50%	1857
	11th to 20th	Night	12% 6% 3 4 4 2 5% 5% 5% 5% 49%	1775
	21st to end	Night	15% 6% 3 4 5% 2 4 4 5% 6% 46%	1800
May	1st to 10th	Night	13% 4 3 5% 4 3 5% 4 5% 8% 47%	1710
	11th to 20th	Night	13% 6% 2 5% 4 3 4 5% 6% 7% 45%	1593
	21st to end	Night	8% 6% 3 5% 5% 3 4 5% 6% 10% 46%	1745
June	1st to 10th	Night	5% 4 2 4 4 3 4 5% 6% 9% 55%	1620
	11th to 20th	Night	4 3 1 3 3 2 3 3 7% 11% 59%	1620
	21st to end	Night	4 2 2 3 3 2 4 4 6% 8% 64%	1620
July	1st to 10th	Night	3 3 2 4 4 4 5% 6% 8% 12% 47%	1620
	11th to 20th	Night	4 3 1 3 4 2 5% 5% 7% 10% 58%	1620
	21st to end	Night	3 3 1 3 5% 3 4 5% 8% 11% 54%	1772
August	1st to 10th	Night	4 3 2 5% 6% 4 4 5% 8% 11% 49%	1611
	11th to 20th	Night	8% 4 2 4 4 3 4 5% 5% 10% 51%	1683
	21st to end	Night	6% 4 2 4 4 3 5% 5% 7% 8% 51%	1980
September	1st to 10th	Night	8% 4 2 3 4 2 4 4 5% 6% 58%	1800
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 5% 7% 52%	1894
	21st to end	Night	8% 4 1 3 4 2 3 4 6% 7% 58%	2015
October	1st to 10th	Night	8% 4 1 4 4 2 3 4 5% 6% 60%	2160
	11th to 20th	Night	13% 4 2 3 3 2 3 3 4 4 59%	2160
	21st to end	Night	17% 6% 2 4 3 2 2 3 4 4 54%	2376
November	1st to 10th	Night	12% 4 2 3 4 2 4 3 3 6% 57%	2220
	11th to 20th	Night	12% 4 2 4 3 2 4 3 5% 5% 58%	2280
	21st to end	Night	15% 5% 2 4 4 2 4 3 4 6% 51%	2505
December	1st to 10th	Night	17% 6% 2 4 4 3 4 3 3 6% 48%	2660
	11th to 20th	Night	16% 7% 2 5% 5% 3 3 3 3 5% 47%	3098
	21st to end	Night	17% 7% 3 6% 5% 2 4 5% 4 6% 41%	4532

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	40% 2 8% 24% 20% 6%	1708
	11th to 20th	Day	41% 3 9% 24% 21% 3	1710
	21st to end	Day	39% 2 7% 26% 22% 5%	1872
February	1st to 10th	Day	46% 2 10% 21% 17% 4	1620
	11th to 20th	Day	44% 4 6% 24% 18% 4	1624
	21st to end	Day	50% 2 6% 16% 18% 8%	1606
March	1st to 10th	Day	42% 2 7% 21% 18% 11%	1980
	11th to 20th	Day	47% 3 8% 22% 15% 5%	1980
	21st to end	Day	48% 3 9% 24% 14% 2	2178
April	1st to 10th	Day	42% 3 9% 22% 20% 4	2101
	11th to 20th	Day	41% 3 9% 23% 18% 6%	2134
	21st to end	Day	45% 4 7% 22% 19% 2	2160
May	1st to 10th	Day	46% 4 9% 20% 18% 3	2246
	11th to 20th	Day	42% 5% 13% 24% 15% 1	2306
	21st to end	Day	43% 6% 12% 24% 14% 1	2531
June	1st to 10th	Day	38% 6% 14% 26% 15% 2	2340
	11th to 20th	Day	35% 6% 14% 25% 18% 2	2340
	21st to end	Day	28% 7% 13% 27% 21% 4	2340
July	1st to 10th	Day	40% 6% 14% 27% 12% 1	2276
	11th to 20th	Day	31% 6% 13% 29% 19% 2	2271
	21st to end	Day	34% 7% 16% 30% 11% 1	2405
August	1st to 10th	Day	36% 6% 15% 29% 13% 1	2314
	11th to 20th	Day	36% 6% 12% 26% 19% 2	2217
	21st to end	Day	33% 5% 16% 26% 15% 4	2376
September	1st to 10th	Day	34% 4 10% 26% 18% 7%	2160
	11th to 20th	Day	35% 5% 10% 23% 22% 5%	2062
	21st to end	Day	31% 4 9% 21% 27% 7%	1926
October	1st to 10th	Day	30% 3 8% 22% 28% 8%	1800
	11th to 20th	Day	33% 3 5% 20% 28% 11%	1800
	21st to end	Day	39% 3 7% 23% 20% 9%	1980
November	1st to 10th	Day	32% 3 7% 27% 24% 7%	1858
	11th to 20th	Day	31% 3 7% 24% 27% 8%	1900
	21st to end	Day	41% 2 7% 19% 26% 5%	1660
December	1st to 10th	Day	38% 2 10% 25% 19% 5%	1520
	11th to 20th	Day	44% 2 5% 20% 25% 5%	2084
	21st to end	Day	49% 3 7% 20% 15% 5%	3135
January	1st to 10th	Night	37% 2 7% 23% 26% 5%	2458
	11th to 20th	Night	37% 2 10% 24% 22% 5%	2470
	21st to end	Night	35% 2 7% 25% 26% 6%	2711
February	1st to 10th	Night	43% 3 7% 25% 17% 5%	2340
	11th to 20th	Night	41% 3 8% 23% 20% 6%	2231
	21st to end	Night	43% 2 6% 20% 20% 9%	1664
March	1st to 10th	Night	40% 3 8% 17% 22% 11%	1980
	11th to 20th	Night	45% 3 8% 21% 17% 7%	1980
	21st to end	Night	43% 2 8% 25% 17% 4	2178
April	1st to 10th	Night	35% 3 11% 23% 21% 8%	1857
	11th to 20th	Night	36% 3 8% 24% 20% 9%	1775
	21st to end	Night	38% 4 9% 24% 22% 2	1800
May	1st to 10th	Night	37% 5% 11% 23% 18% 5%	1710
	11th to 20th	Night	37% 4 14% 26% 17% 2	1594
	21st to end	Night	33% 6% 17% 28% 14% 1	1746
June	1st to 10th	Night	25% 5% 15% 33% 20% 3	1620
	11th to 20th	Night	20% 5% 13% 36% 23% 3	1620
	21st to end	Night	19% 4 14% 30% 26% 7%	1620
July	1st to 10th	Night	26% 7% 20% 27% 18% 2	1575
	11th to 20th	Night	20% 5% 16% 33% 22% 3	1566
	21st to end	Night	23% 6% 17% 35% 17% 2	1673
August	1st to 10th	Night	27% 5% 17% 36% 14% 1	1601
	11th to 20th	Night	29% 4 15% 28% 22% 2	1683
	21st to end	Night	29% 5% 15% 27% 20% 4	1980
September	1st to 10th	Night	28% 4 9% 29% 22% 8%	1800
	11th to 20th	Night	31% 5% 10% 23% 24% 6%	1894
	21st to end	Night	26% 4 8% 24% 31% 8%	2015
October	1st to 10th	Night	25% 3 12% 24% 25% 10%	2160
	11th to 20th	Night	30% 2 6% 19% 32% 12%	2160
	21st to end	Night	35% 2 7% 21% 24% 11%	2376
November	1st to 10th	Night	30% 3 7% 24% 26% 10%	2220
	11th to 20th	Night	30% 3 6% 25% 27% 10%	2280
	21st to end	Night	36% 3 7% 22% 27% 6%	2505
December	1st to 10th	Night	40% 2 8% 21% 22% 6%	2660
	11th to 20th	Night	41% 3 6% 22% 22% 6%	3099
	21st to end	Night	43% 3 7% 25% 18% 4	4532

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	24% 14% 33% 20% 8%	270
	11th to 20th	Day	21% 20% 34% 19% 6%	270
	21st to end	Day	22% 20% 32% 18% 7% 1	294
February	1st to 10th	Day	25% 15% 36% 16% 8%	240
	11th to 20th	Day	25% 20% 35% 16% 3 1	240
	21st to end	Day	35% 18% 30% 14% 3	198
March	1st to 10th	Day	24% 17% 32% 21% 5%	240
	11th to 20th	Day	30% 22% 31% 16% 2	240
	21st to end	Day	22% 21% 37% 16% 3 1	264
April	1st to 10th	Day	20% 16% 32% 20% 10% 2	361
	11th to 20th	Day	24% 13% 29% 23% 10% 1	412
	21st to end	Day	22% 11% 33% 24% 8% 2	420
May	1st to 10th	Day	19% 12% 29% 28% 12%	509
	11th to 20th	Day	16% 7% 26% 27% 20% 4	625
	21st to end	Day	11% 6% 23% 33% 19% 7%	679
June	1st to 10th	Day	11% 4 16% 26% 33% 10%	630
	11th to 20th	Day	6% 3 15% 33% 32% 10%	630
	21st to end	Day	5% 3 15% 37% 30% 11%	630
July	1st to 10th	Day	6% 2 11% 30% 34% 17%	621
	11th to 20th	Day	5% 2 11% 28% 34% 20%	618
	21st to end	Day	6% 2 6% 27% 40% 19%	684
August	1st to 10th	Day	7% 2 8% 34% 38% 12%	626
	11th to 20th	Day	12% 3 7% 28% 38% 12%	531
	21st to end	Day	10% 2 4 22% 41% 20%	495
September	1st to 10th	Day	10% 2 6% 22% 43% 16%	450
	11th to 20th	Day	9% 2 11% 27% 37% 14%	352
	21st to end	Day	12% 4 13% 35% 28% 9%	270
October	1st to 10th	Day	6% 4 23% 36% 27% 4	270
	11th to 20th	Day	13% 12% 30% 28% 14% 2	270
	21st to end	Day	28% 15% 22% 21% 11% 2	297
November	1st to 10th	Day	16% 8% 30% 28% 16% 3	270
	11th to 20th	Day	14% 14% 36% 25% 10% 1	270
	21st to end	Day	24% 17% 22% 22% 13% 1	270
December	1st to 10th	Day	20% 14% 34% 20% 8% 2	270
	11th to 20th	Day	24% 15% 30% 24% 7%	270
	21st to end	Day	23% 16% 36% 18% 6%	297
January	1st to 10th	Night	20% 13% 26% 35% 6%	950
	11th to 20th	Night	20% 14% 29% 32% 6%	950
	21st to end	Night	18% 12% 33% 31% 5%	1043
February	1st to 10th	Night	23% 12% 27% 34% 5%	900
	11th to 20th	Night	21% 13% 33% 30% 2	836
	21st to end	Night	24% 14% 31% 30% 2	480
March	1st to 10th	Night	19% 10% 25% 41% 5%	540
	11th to 20th	Night	22% 10% 26% 35% 6% 1	540
	21st to end	Night	22% 9% 28% 33% 8% 1	594
April	1st to 10th	Night	15% 11% 30% 37% 8%	540
	11th to 20th	Night	13% 13% 27% 34% 12% 1	533
	21st to end	Night	18% 9% 31% 30% 11%	540
May	1st to 10th	Night	14% 6% 25% 41% 14% 1	540
	11th to 20th	Night	15% 7% 20% 36% 21% 2	531
	21st to end	Night	9% 6% 16% 38% 27% 4	584
June	1st to 10th	Night	6% 3 9% 33% 46% 3	540
	11th to 20th	Night	5% 1 7% 44% 39% 3	540
	21st to end	Night	4 2 7% 35% 47% 6%	540
July	1st to 10th	Night	4 1 6% 30% 50% 9%	525
	11th to 20th	Night	4 1 5% 32% 48% 11%	522
	21st to end	Night	3 1 2 29% 52% 12%	591
August	1st to 10th	Night	4 2 5% 32% 52% 6%	537
	11th to 20th	Night	10% 1 6% 31% 44% 7%	534
	21st to end	Night	7% 3 3 27% 52% 8%	594
September	1st to 10th	Night	10% 1 5% 29% 49% 5%	540
	11th to 20th	Night	11% 2 7% 33% 43% 5%	540
	21st to end	Night	10% 1 10% 36% 38% 4	575
October	1st to 10th	Night	9% 4 11% 38% 35% 4	720
	11th to 20th	Night	14% 6% 22% 40% 18%	720
	21st to end	Night	20% 8% 22% 32% 17% 2	792
November	1st to 10th	Night	13% 6% 19% 43% 19% 1	740
	11th to 20th	Night	14% 9% 25% 39% 14%	760
	21st to end	Night	20% 10% 23% 34% 13%	902
December	1st to 10th	Night	21% 9% 26% 36% 8%	950
	11th to 20th	Night	23% 10% 22% 38% 7%	950
	21st to end	Night	21% 15% 24% 34% 6%	1045

Page generated at 2024-01-28 04:26:36. Version ac07

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