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 2025-02-21.

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 6% 4 4 4 3 5% 7% 46%	108652
	Night	13% 6% 2 5% 3 3 3 3 5% 6% 51%	110104
Transparency	Day	37% 3 10% 24% 20% 5%	112300
	Night	33% 3 9% 25% 22% 7%	114596
Seeing	Day	15% 9% 22% 26% 21% 7%	15710
	Night	15% 8% 20% 34% 20% 2	25691

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	16% 8% 3 5% 4 3 3 2 3 5% 48%	4077
	11th to 20th	Day	8% 7% 2 6% 4 4 4 3 5% 5% 53%	4080
	21st to end	Day	22% 7% 2 4 3 2 3 2 3 5% 48%	4488
February	1st to 10th	Day	20% 9% 2 5% 3 4 3 3 3 5% 43%	1800
	11th to 20th	Day	18% 9% 2 6% 3 3 3 3 5% 5% 43%	1800
	21st to end	Day	19% 9% 3 7% 4 4 3 2 5% 5% 38%	1703
March	1st to 10th	Day	20% 9% 3 6% 4 3 3 2 4 5% 43%	3436
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 4 6% 46%	3480
	21st to end	Day	16% 8% 3 7% 4 3 3 3 4 6% 41%	3814
April	1st to 10th	Day	13% 6% 2 7% 5% 5% 4 3 5% 6% 44%	2218
	11th to 20th	Day	17% 5% 3 5% 4 3 4 3 4 6% 43%	2254
	21st to end	Day	18% 8% 2 6% 5% 4 4 3 4 6% 40%	2280
May	1st to 10th	Day	18% 8% 3 7% 5% 4 4 3 5% 6% 37%	3921
	11th to 20th	Day	13% 6% 2 7% 4 5% 5% 4 5% 7% 41%	4082
	21st to end	Day	16% 7% 3 8% 5% 6% 5% 4 6% 7% 34%	4477
June	1st to 10th	Day	9% 7% 2 7% 5% 5% 5% 4 7% 9% 41%	2470
	11th to 20th	Day	5% 4 2 6% 6% 6% 6% 6% 6% 9% 44%	2470
	21st to end	Day	4 4 1 5% 5% 5% 5% 5% 7% 10% 50%	2470
July	1st to 10th	Day	10% 5% 2 5% 5% 5% 5% 4 7% 9% 44%	4120
	11th to 20th	Day	5% 3 1 4 4 4 4 4 6% 8% 55%	4120
	21st to end	Day	9% 6% 3 7% 6% 6% 6% 5% 8% 10% 34%	4465
August	1st to 10th	Day	4 2 1 4 4 4 4 4 6% 9% 58%	4104
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 6% 10% 44%	3887
	21st to end	Day	5% 3 1 4 4 5% 5% 4 7% 9% 53%	4180
September	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 6% 7% 49%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 7% 47%	2176
	21st to end	Day	8% 5% 2 5% 4 3 4 3 5% 6% 53%	2033
October	1st to 10th	Day	8% 4 2 6% 4 4 3 3 4 6% 58%	1900
	11th to 20th	Day	13% 5% 2 4 2 2 3 3 3 5% 57%	1900
	21st to end	Day	18% 6% 2 5% 3 3 3 2 4 5% 50%	2090
November	1st to 10th	Day	13% 6% 2 4 3 3 4 3 4 5% 54%	1958
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 4 6% 55%	2000
	21st to end	Day	16% 7% 2 6% 3 3 3 3 3 6% 49%	1747
December	1st to 10th	Day	14% 7% 2 5% 3 4 3 2 4 5% 49%	2610
	11th to 20th	Day	15% 9% 3 7% 4 4 4 3 4 5% 43%	3274
	21st to end	Day	20% 10% 3 7% 4 3 4 2 4 5% 38%	4488
January	1st to 10th	Night	15% 6% 3 6% 4 3 3 3 4 6% 48%	5888
	11th to 20th	Night	10% 4 1 3 3 2 2 2 4 5% 63%	5900
	21st to end	Night	21% 7% 2 4 3 2 2 2 3 5% 48%	6490
February	1st to 10th	Night	18% 8% 2 6% 5% 2 3 3 5% 5% 43%	2600
	11th to 20th	Night	16% 8% 2 6% 4 3 3 3 4 6% 46%	2485
	21st to end	Night	18% 7% 3 5% 3 3 3 3 4 5% 47%	1766
March	1st to 10th	Night	21% 7% 3 5% 3 3 3 2 4 5% 43%	3419
	11th to 20th	Night	16% 7% 2 5% 3 3 3 3 4 5% 49%	3480
	21st to end	Night	14% 6% 3 6% 4 4 4 3 5% 7% 43%	3817
April	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 5% 7% 49%	1960
	11th to 20th	Night	12% 6% 3 5% 4 4 4 4 5% 6% 49%	1875
	21st to end	Night	16% 6% 2 5% 4 3 4 3 5% 6% 45%	1900
May	1st to 10th	Night	15% 7% 3 7% 4 4 4 3 4 7% 41%	2962
	11th to 20th	Night	13% 6% 2 6% 4 5% 4 4 6% 7% 43%	2823
	21st to end	Night	16% 7% 2 5% 5% 3 4 3 6% 7% 41%	3090
June	1st to 10th	Night	5% 4 1 5% 3 4 4 4 6% 10% 55%	1710
	11th to 20th	Night	4 4 1 3 3 2 4 3 7% 11% 59%	1710
	21st to end	Night	4 2 2 3 2 3 3 3 6% 8% 63%	1710
July	1st to 10th	Night	7% 4 2 5% 3 5% 5% 4 6% 9% 49%	2850
	11th to 20th	Night	5% 3 1 3 3 3 3 3 5% 8% 63%	2850
	21st to end	Night	6% 6% 2 7% 5% 5% 4 4 7% 9% 44%	3098
August	1st to 10th	Night	2 2 1 3 4 4 3 3 6% 9% 64%	2836
	11th to 20th	Night	5% 3 1 4 4 4 4 3 6% 8% 57%	2946
	21st to end	Night	4 3 1 4 3 3 5% 3 6% 9% 58%	3476
September	1st to 10th	Night	8% 5% 2 4 3 3 4 3 5% 6% 58%	1900
	11th to 20th	Night	11% 5% 2 6% 3 4 3 3 5% 7% 52%	2000
	21st to end	Night	8% 5% 1 4 3 3 3 3 6% 7% 57%	2127
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 5% 6% 61%	2280
	11th to 20th	Night	12% 5% 2 4 2 2 3 2 4 4 61%	2280
	21st to end	Night	16% 6% 2 4 3 2 2 2 4 4 55%	2508
November	1st to 10th	Night	13% 5% 2 4 3 2 3 3 3 6% 55%	2340
	11th to 20th	Night	12% 4 2 4 3 2 3 3 5% 5% 57%	2400
	21st to end	Night	14% 6% 2 5% 4 3 3 2 4 6% 52%	2638
December	1st to 10th	Night	13% 8% 2 5% 4 3 3 2 3 5% 52%	4580
	11th to 20th	Night	15% 10% 3 6% 4 3 3 2 4 4 48%	4920
	21st to end	Night	20% 9% 3 7% 4 3 3 3 4 5% 41%	6490

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	41% 1 8% 26% 21% 2	4078
	11th to 20th	Day	33% 3 9% 23% 27% 5%	4080
	21st to end	Day	42% 1 5% 19% 24% 9%	4488
February	1st to 10th	Day	47% 2 10% 20% 17% 4	1800
	11th to 20th	Day	44% 3 7% 23% 19% 5%	1809
	21st to end	Day	49% 2 6% 17% 18% 8%	1703
March	1st to 10th	Day	47% 1 6% 17% 17% 11%	3436
	11th to 20th	Day	41% 2 10% 23% 19% 4	3480
	21st to end	Day	45% 2 9% 25% 17% 1	3814
April	1st to 10th	Day	41% 3 9% 21% 21% 5%	2218
	11th to 20th	Day	42% 3 9% 22% 18% 6%	2254
	21st to end	Day	46% 4 7% 23% 18% 2	2280
May	1st to 10th	Day	50% 3 8% 22% 15% 2	3956
	11th to 20th	Day	41% 3 11% 27% 16% 1	4086
	21st to end	Day	49% 4 11% 20% 14% 2	4489
June	1st to 10th	Day	38% 6% 14% 26% 15% 2	2470
	11th to 20th	Day	34% 6% 14% 26% 19% 2	2470
	21st to end	Day	28% 7% 14% 28% 20% 4	2470
July	1st to 10th	Day	35% 5% 18% 29% 11% 2	4056
	11th to 20th	Day	25% 5% 10% 36% 21% 2	4051
	21st to end	Day	42% 6% 17% 25% 8% 1	4325
August	1st to 10th	Day	23% 4 15% 29% 23% 6%	4090
	11th to 20th	Day	36% 5% 15% 30% 13% 1	3926
	21st to end	Day	26% 5% 16% 35% 16% 2	4179
September	1st to 10th	Day	34% 4 10% 25% 18% 9%	2280
	11th to 20th	Day	36% 5% 10% 23% 21% 5%	2176
	21st to end	Day	31% 4 9% 21% 27% 7%	2033
October	1st to 10th	Day	17% 2 5% 13% 38% 25%	3160
	11th to 20th	Day	20% 2 3 19% 38% 18%	3140
	21st to end	Day	32% 3 7% 29% 23% 6%	3428
November	1st to 10th	Day	33% 3 7% 26% 23% 7%	1958
	11th to 20th	Day	31% 3 7% 23% 26% 9%	2000
	21st to end	Day	39% 2 7% 20% 26% 5%	1747
December	1st to 10th	Day	39% 2 7% 30% 19% 3	2610
	11th to 20th	Day	44% 3 6% 20% 24% 4	3272
	21st to end	Day	49% 3 6% 24% 14% 4	4488
January	1st to 10th	Night	38% 1 8% 28% 22% 3	5888
	11th to 20th	Night	25% 2 9% 23% 33% 8%	5900
	21st to end	Night	42% 1 7% 17% 26% 6%	6490
February	1st to 10th	Night	43% 3 7% 25% 17% 5%	2600
	11th to 20th	Night	41% 2 8% 23% 20% 6%	2486
	21st to end	Night	41% 2 7% 20% 21% 9%	1766
March	1st to 10th	Night	45% 2 8% 17% 18% 11%	3419
	11th to 20th	Night	39% 3 7% 28% 17% 7%	3480
	21st to end	Night	41% 3 10% 27% 17% 2	3817
April	1st to 10th	Night	35% 3 10% 22% 21% 9%	1960
	11th to 20th	Night	36% 3 8% 23% 20% 9%	1875
	21st to end	Night	39% 4 10% 24% 21% 2	1900
May	1st to 10th	Night	45% 4 10% 23% 14% 4	2992
	11th to 20th	Night	40% 3 14% 26% 15% 1	2824
	21st to end	Night	43% 4 14% 24% 13% 3	3099
June	1st to 10th	Night	25% 5% 15% 33% 19% 3	1710
	11th to 20th	Night	20% 5% 12% 35% 24% 3	1710
	21st to end	Night	19% 4 14% 31% 25% 6%	1710
July	1st to 10th	Night	30% 6% 20% 26% 17% 2	2805
	11th to 20th	Night	19% 4 11% 39% 25% 2	2796
	21st to end	Night	35% 6% 17% 28% 14% 1	2999
August	1st to 10th	Night	17% 4 15% 34% 26% 4	2826
	11th to 20th	Night	25% 4 19% 33% 17% 2	2973
	21st to end	Night	23% 5% 14% 32% 24% 3	3476
September	1st to 10th	Night	28% 4 9% 28% 22% 9%	1900
	11th to 20th	Night	32% 5% 10% 24% 23% 6%	2000
	21st to end	Night	27% 4 8% 23% 29% 8%	2127
October	1st to 10th	Night	15% 2 7% 14% 32% 30%	3800
	11th to 20th	Night	17% 1 3 16% 40% 22%	3779
	21st to end	Night	27% 3 5% 25% 29% 11%	4120
November	1st to 10th	Night	32% 3 7% 23% 25% 10%	2340
	11th to 20th	Night	29% 3 6% 25% 27% 11%	2400
	21st to end	Night	35% 3 7% 22% 27% 6%	2638
December	1st to 10th	Night	37% 2 7% 32% 19% 4	4580
	11th to 20th	Night	42% 2 5% 22% 21% 8%	4921
	21st to end	Night	45% 2 8% 26% 15% 4	6490

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% 15% 32% 20% 7%	300
	11th to 20th	Day	20% 21% 36% 18% 5%	300
	21st to end	Day	24% 21% 31% 17% 7% 1	330
February	1st to 10th	Day	28% 13% 36% 16% 6%	300
	11th to 20th	Day	27% 21% 32% 15% 4 1	300
	21st to end	Day	33% 22% 30% 12% 3	225
March	1st to 10th	Day	24% 16% 32% 22% 5%	270
	11th to 20th	Day	27% 22% 33% 16% 2	270
	21st to end	Day	23% 21% 37% 15% 3 1	297
April	1st to 10th	Day	22% 17% 31% 19% 9% 2	398
	11th to 20th	Day	24% 13% 31% 22% 9% 1	452
	21st to end	Day	23% 12% 32% 23% 8% 2	460
May	1st to 10th	Day	19% 13% 29% 27% 12%	554
	11th to 20th	Day	16% 7% 26% 28% 19% 4	675
	21st to end	Day	11% 7% 25% 33% 18% 7%	734
June	1st to 10th	Day	11% 4 16% 28% 32% 9%	680
	11th to 20th	Day	6% 3 15% 34% 32% 11%	680
	21st to end	Day	4 4 15% 37% 30% 10%	680
July	1st to 10th	Day	7% 2 11% 31% 33% 15%	671
	11th to 20th	Day	5% 2 12% 30% 33% 19%	668
	21st to end	Day	6% 2 9% 28% 38% 18%	739
August	1st to 10th	Day	7% 2 9% 34% 37% 12%	676
	11th to 20th	Day	13% 3 9% 28% 36% 12%	576
	21st to end	Day	9% 2 5% 23% 40% 21%	539
September	1st to 10th	Day	10% 1 8% 24% 41% 15%	490
	11th to 20th	Day	10% 3 12% 28% 34% 13%	386
	21st to end	Day	12% 6% 15% 34% 25% 8%	300
October	1st to 10th	Day	5% 4 24% 37% 26% 4	300
	11th to 20th	Day	12% 12% 29% 31% 15% 2	300
	21st to end	Day	27% 15% 24% 22% 11% 2	330
November	1st to 10th	Day	20% 7% 31% 25% 15% 2	300
	11th to 20th	Day	16% 13% 37% 24% 9% 1	300
	21st to end	Day	25% 17% 24% 21% 13% 1	300
December	1st to 10th	Day	21% 15% 34% 20% 8% 2	300
	11th to 20th	Day	25% 16% 29% 22% 7%	300
	21st to end	Day	27% 16% 34% 17% 6%	330
January	1st to 10th	Night	20% 14% 27% 34% 6%	1000
	11th to 20th	Night	19% 14% 30% 31% 6%	1000
	21st to end	Night	19% 12% 34% 30% 5%	1100
February	1st to 10th	Night	23% 12% 27% 33% 5%	1000
	11th to 20th	Night	22% 14% 32% 29% 2	931
	21st to end	Night	23% 14% 32% 29% 2	510
March	1st to 10th	Night	19% 10% 25% 41% 5%	570
	11th to 20th	Night	22% 10% 27% 35% 6% 1	570
	21st to end	Night	22% 9% 29% 33% 8%	627
April	1st to 10th	Night	16% 11% 29% 36% 7%	570
	11th to 20th	Night	14% 12% 28% 33% 12% 1	563
	21st to end	Night	18% 9% 31% 30% 11%	570
May	1st to 10th	Night	13% 6% 25% 42% 13% 1	570
	11th to 20th	Night	14% 7% 19% 38% 21% 2	561
	21st to end	Night	10% 6% 17% 38% 26% 4	617
June	1st to 10th	Night	6% 3 9% 35% 45% 3	570
	11th to 20th	Night	5% 1 7% 44% 39% 3	570
	21st to end	Night	4 2 7% 36% 46% 5%	570
July	1st to 10th	Night	5% 2 7% 31% 48% 8%	555
	11th to 20th	Night	4 1 5% 34% 46% 11%	552
	21st to end	Night	4 1 2 31% 51% 11%	624
August	1st to 10th	Night	4 2 6% 32% 51% 6%	567
	11th to 20th	Night	10% 1 7% 32% 44% 7%	564
	21st to end	Night	7% 3 4 27% 51% 8%	627
September	1st to 10th	Night	10% 1 5% 30% 48% 5%	570
	11th to 20th	Night	13% 2 7% 34% 41% 4	570
	21st to end	Night	11% 2 11% 37% 36% 4	607
October	1st to 10th	Night	9% 3 11% 38% 35% 3	760
	11th to 20th	Night	13% 6% 21% 40% 19% 1	760
	21st to end	Night	19% 8% 22% 33% 17% 1	836
November	1st to 10th	Night	16% 6% 19% 41% 18% 1	780
	11th to 20th	Night	14% 9% 25% 38% 13%	800
	21st to end	Night	19% 11% 23% 34% 12%	950
December	1st to 10th	Night	21% 10% 27% 35% 8%	1000
	11th to 20th	Night	24% 10% 22% 37% 7%	1000
	21st to end	Night	22% 15% 24% 33% 6%	1100

Page generated at 2025-02-18 02:26:26. Version ac07

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