Marys Peak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marys Peak clear sky chart from 2005-11-06 to 2024-11-02.

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	15% 9% 3 8% 5% 4 4 3 5% 6% 37%	101500
	Night	16% 10% 3 8% 5% 4 4 3 4 5% 36%	97642
Transparency	Day	48% 5% 11% 17% 13% 5%	101247
	Night	50% 6% 11% 17% 11% 5%	97484
Seeing	Day	22% 12% 23% 25% 14% 3	14764
	Night	23% 9% 14% 31% 21% 2	23683

By Month

Percentage Cloud Cover SW (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	28% 19% 5% 15% 8% 5% 4 3 3 2 7%	2539
	11th to 20th	Day	34% 13% 4 10% 5% 5% 4 3 4 4 16%	2586
	21st to end	Day	27% 14% 4 12% 6% 5% 5% 4 5% 4 13%	3146
February	1st to 10th	Day	26% 15% 5% 12% 7% 4 4 4 4 4 14%	1710
	11th to 20th	Day	23% 15% 5% 12% 6% 4 4 4 4 5% 17%	1665
	21st to end	Day	22% 20% 4 12% 6% 4 4 3 3 4 17%	1465
March	1st to 10th	Day	16% 15% 6% 13% 7% 6% 5% 4 5% 5% 19%	3379
	11th to 20th	Day	18% 12% 4 9% 5% 4 4 2 3 4 35%	3490
	21st to end	Day	21% 16% 5% 12% 8% 6% 5% 4 5% 5% 14%	3845
April	1st to 10th	Day	22% 16% 6% 11% 7% 5% 4 3 4 4 16%	2280
	11th to 20th	Day	22% 13% 4 10% 6% 5% 5% 3 4 4 23%	2267
	21st to end	Day	20% 11% 4 9% 7% 5% 5% 4 6% 6% 23%	2470
May	1st to 10th	Day	19% 10% 3 9% 5% 3 4 4 5% 6% 32%	4229
	11th to 20th	Day	10% 7% 2 5% 3 3 4 3 6% 7% 50%	4377
	21st to end	Day	14% 8% 3 8% 6% 6% 7% 6% 7% 8% 28%	4813
June	1st to 10th	Day	20% 10% 3 8% 5% 3 4 4 5% 6% 32%	2660
	11th to 20th	Day	14% 9% 4 8% 6% 5% 5% 5% 7% 8% 30%	2660
	21st to end	Day	8% 6% 2 5% 4 4 4 3 5% 7% 52%	2660
July	1st to 10th	Day	3 2 1 3 2 2 3 2 3 5% 74%	4420
	11th to 20th	Day	4 3 1 2 2 2 2 2 4 4 74%	4420
	21st to end	Day	3 3 1 2 2 2 2 2 3 6% 75%	4670
August	1st to 10th	Day	2 3 1 4 3 3 3 3 4 7% 68%	4091
	11th to 20th	Day	5% 4 2 5% 3 3 4 4 7% 9% 53%	4026
	21st to end	Day	7% 5% 2 4 3 4 4 4 5% 7% 56%	4335
September	1st to 10th	Day	5% 3 1 4 3 3 3 3 5% 7% 63%	2280
	11th to 20th	Day	10% 6% 4 5% 4 4 4 4 6% 8% 45%	2231
	21st to end	Day	14% 7% 3 6% 3 3 4 3 5% 6% 46%	2028
October	1st to 10th	Day	15% 8% 3 7% 4 3 3 3 5% 5% 42%	1900
	11th to 20th	Day	15% 9% 4 9% 6% 6% 4 4 5% 7% 32%	1900
	21st to end	Day	19% 12% 4 10% 6% 4 5% 3 5% 6% 27%	2090
November	1st to 10th	Day	25% 12% 5% 10% 6% 5% 5% 3 4 6% 18%	1586
	11th to 20th	Day	26% 12% 4 9% 5% 6% 5% 4 6% 5% 18%	1520
	21st to end	Day	23% 13% 4 9% 7% 5% 4 3 5% 5% 21%	1520
December	1st to 10th	Day	23% 13% 4 10% 6% 5% 3 3 4 5% 24%	1520
	11th to 20th	Day	22% 13% 4 13% 7% 6% 6% 4 6% 7% 13%	1928
	21st to end	Day	26% 17% 6% 14% 8% 6% 5% 2 4 4 7%	2794
January	1st to 10th	Night	27% 19% 6% 15% 7% 5% 4 2 3 3 9%	4406
	11th to 20th	Night	30% 15% 5% 12% 6% 4 3 3 3 3 16%	4358
	21st to end	Night	31% 16% 5% 11% 4 3 4 3 4 4 15%	4521
February	1st to 10th	Night	20% 17% 5% 11% 7% 5% 4 5% 5% 5% 17%	2470
	11th to 20th	Night	19% 14% 4 10% 6% 5% 4 4 4 4 24%	2402
	21st to end	Night	21% 15% 4 10% 6% 6% 4 3 5% 5% 21%	1989
March	1st to 10th	Night	14% 14% 5% 12% 8% 7% 5% 4 5% 6% 20%	3493
	11th to 20th	Night	15% 10% 3 8% 4 4 4 3 4 5% 40%	3490
	21st to end	Night	20% 18% 5% 12% 7% 5% 5% 3 4 5% 17%	3808
April	1st to 10th	Night	21% 14% 3 10% 7% 4 5% 3 4 6% 22%	1900
	11th to 20th	Night	15% 12% 4 9% 5% 4 5% 4 6% 6% 30%	1857
	21st to end	Night	16% 9% 4 9% 6% 5% 5% 3 5% 7% 31%	1710
May	1st to 10th	Night	18% 9% 3 8% 5% 4 3 2 4 4 40%	2737
	11th to 20th	Night	7% 6% 2 5% 5% 4 3 3 4 5% 57%	2516
	21st to end	Night	9% 8% 3 8% 6% 6% 4 5% 6% 8% 38%	2762
June	1st to 10th	Night	15% 8% 2 6% 4 5% 5% 4 5% 5% 41%	1520
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 6% 8% 46%	1520
	21st to end	Night	6% 5% 2 4 3 2 4 3 6% 5% 60%	1520
July	1st to 10th	Night	2 2 2 1 1 2 1 3 4 82%	2540
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 5% 77%	2540
	21st to end	Night	2 2 1 2 2 1 2 2 3 6% 77%	2881
August	1st to 10th	Night	1 2 2 2 3 2 3 4 7% 73%	2848
	11th to 20th	Night	3 2 1 4 3 4 5% 4 6% 8% 60%	2812
	21st to end	Night	5% 3 2 5% 3 3 3 3 4 6% 63%	3337
September	1st to 10th	Night	4 3 1 3 3 3 2 3 5% 6% 68%	1900
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 5% 6% 54%	1947
	21st to end	Night	9% 5% 2 6% 4 3 4 3 5% 7% 52%	2152
October	1st to 10th	Night	11% 6% 3 5% 4 4 3 3 5% 7% 49%	2280
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 4 5% 8% 39%	2280
	21st to end	Night	17% 8% 4 9% 4 5% 5% 3 4 5% 36%	2508
November	1st to 10th	Night	24% 11% 3 8% 5% 5% 5% 4 4 6% 25%	2520
	11th to 20th	Night	25% 12% 4 10% 6% 5% 5% 3 4 4 21%	2660
	21st to end	Night	19% 9% 3 9% 6% 5% 5% 4 6% 6% 28%	2660
December	1st to 10th	Night	22% 12% 4 8% 6% 4 5% 4 4 5% 25%	2660
	11th to 20th	Night	22% 14% 5% 11% 6% 5% 5% 3 5% 5% 18%	3276
	21st to end	Night	22% 14% 5% 15% 9% 6% 5% 3 3 4 14%	4862

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	82% 4 7% 4 1 1	2539
	11th to 20th	Day	74% 2 9% 8% 5% 2	2586
	21st to end	Day	75% 4 8% 7% 5% 1	3146
February	1st to 10th	Day	73% 5% 9% 8% 4 1	1710
	11th to 20th	Day	69% 7% 10% 8% 5% 2	1674
	21st to end	Day	73% 4 8% 8% 5% 2	1465
March	1st to 10th	Day	66% 7% 13% 11% 3	3379
	11th to 20th	Day	54% 4 8% 23% 11% 1	3490
	21st to end	Day	75% 5% 10% 7% 4	3845
April	1st to 10th	Day	72% 6% 8% 10% 4	2280
	11th to 20th	Day	64% 6% 9% 12% 6% 2	2270
	21st to end	Day	61% 6% 12% 14% 6% 1	2470
May	1st to 10th	Day	53% 6% 11% 18% 12%	4229
	11th to 20th	Day	32% 6% 16% 30% 14% 1	4380
	21st to end	Day	51% 8% 25% 14% 2	4814
June	1st to 10th	Day	53% 5% 14% 20% 6% 1	2660
	11th to 20th	Day	51% 7% 18% 18% 5%	2660
	21st to end	Day	32% 5% 18% 28% 13% 4	2660
July	1st to 10th	Day	15% 4 8% 15% 26% 32%	4351
	11th to 20th	Day	16% 3 5% 19% 35% 22%	4345
	21st to end	Day	13% 4 9% 28% 39% 8%	4522
August	1st to 10th	Day	16% 4 10% 27% 30% 12%	4076
	11th to 20th	Day	26% 8% 16% 31% 16% 3	4065
	21st to end	Day	27% 6% 12% 25% 22% 8%	4334
September	1st to 10th	Day	21% 4 11% 31% 21% 12%	2280
	11th to 20th	Day	36% 7% 14% 21% 16% 6%	2231
	21st to end	Day	40% 5% 11% 23% 16% 6%	2028
October	1st to 10th	Day	43% 6% 10% 18% 19% 5%	1900
	11th to 20th	Day	51% 6% 12% 16% 14% 2	1900
	21st to end	Day	57% 5% 9% 15% 12% 2	2090
November	1st to 10th	Day	67% 6% 10% 12% 4 1	1586
	11th to 20th	Day	67% 6% 9% 9% 5% 3	1520
	21st to end	Day	64% 6% 8% 8% 11% 3	1520
December	1st to 10th	Day	64% 3 10% 12% 10% 2	1520
	11th to 20th	Day	70% 5% 13% 9% 3	1928
	21st to end	Day	77% 4 10% 5% 2 1	2794
January	1st to 10th	Night	80% 6% 7% 4 3 1	4406
	11th to 20th	Night	75% 3 6% 9% 4 3	4358
	21st to end	Night	74% 4 7% 8% 6% 2	4521
February	1st to 10th	Night	69% 7% 9% 11% 4 1	2470
	11th to 20th	Night	64% 6% 10% 12% 6% 2	2404
	21st to end	Night	67% 5% 7% 12% 7% 2	1989
March	1st to 10th	Night	63% 7% 12% 13% 4	3493
	11th to 20th	Night	48% 6% 11% 22% 11% 1	3490
	21st to end	Night	71% 5% 11% 11% 1	3808
April	1st to 10th	Night	65% 7% 11% 11% 5%	1900
	11th to 20th	Night	55% 7% 13% 16% 5% 3	1857
	21st to end	Night	54% 8% 11% 19% 6% 2	1710
May	1st to 10th	Night	47% 7% 14% 21% 9% 1	2737
	11th to 20th	Night	31% 7% 12% 33% 13% 4	2516
	21st to end	Night	42% 10% 30% 14% 3	2762
June	1st to 10th	Night	45% 6% 15% 28% 4 1	1520
	11th to 20th	Night	35% 9% 21% 27% 8% 1	1520
	21st to end	Night	25% 8% 17% 34% 12% 5%	1520
July	1st to 10th	Night	10% 6% 8% 18% 24% 35%	2500
	11th to 20th	Night	13% 4 7% 18% 26% 32%	2492
	21st to end	Night	10% 6% 10% 27% 37% 10%	2791
August	1st to 10th	Night	11% 5% 10% 30% 30% 14%	2839
	11th to 20th	Night	19% 10% 17% 35% 14% 5%	2839
	21st to end	Night	21% 7% 9% 31% 24% 8%	3337
September	1st to 10th	Night	19% 6% 10% 28% 25% 13%	1900
	11th to 20th	Night	32% 5% 13% 25% 15% 9%	1947
	21st to end	Night	32% 6% 14% 23% 16% 9%	2152
October	1st to 10th	Night	36% 7% 9% 24% 18% 7%	2280
	11th to 20th	Night	44% 7% 12% 18% 15% 4	2280
	21st to end	Night	51% 7% 9% 15% 13% 5%	2508
November	1st to 10th	Night	61% 7% 8% 14% 8% 1	2520
	11th to 20th	Night	67% 5% 9% 9% 7% 3	2660
	21st to end	Night	57% 7% 9% 10% 12% 5%	2660
December	1st to 10th	Night	60% 6% 9% 12% 12% 1	2660
	11th to 20th	Night	69% 4 10% 11% 5% 1	3276
	21st to end	Night	74% 5% 11% 7% 3 1	4862

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	43% 17% 19% 13% 8%	180
	11th to 20th	Day	40% 13% 18% 18% 9% 1	213
	21st to end	Day	36% 14% 15% 21% 12% 2	407
February	1st to 10th	Day	38% 12% 19% 21% 9% 1	370
	11th to 20th	Day	36% 17% 23% 17% 6% 1	365
	21st to end	Day	35% 19% 21% 17% 6% 1	332
March	1st to 10th	Day	37% 17% 22% 18% 6%	460
	11th to 20th	Day	32% 13% 23% 20% 10% 2	460
	21st to end	Day	35% 20% 19% 16% 8% 1	506
April	1st to 10th	Day	33% 20% 17% 19% 9% 2	460
	11th to 20th	Day	33% 19% 22% 17% 7% 3	452
	21st to end	Day	28% 18% 25% 20% 8% 2	460
May	1st to 10th	Day	22% 16% 27% 20% 13% 3	463
	11th to 20th	Day	26% 13% 19% 24% 13% 4	488
	21st to end	Day	20% 12% 22% 25% 17% 4	529
June	1st to 10th	Day	24% 9% 25% 24% 15% 3	490
	11th to 20th	Day	18% 18% 27% 26% 11% 1	490
	21st to end	Day	8% 9% 25% 38% 18% 3	490
July	1st to 10th	Day	7% 7% 27% 37% 18% 5%	486
	11th to 20th	Day	5% 7% 29% 35% 19% 5%	484
	21st to end	Day	3 5% 25% 38% 24% 5%	531
August	1st to 10th	Day	3 5% 24% 40% 22% 7%	487
	11th to 20th	Day	4 4 20% 36% 28% 8%	477
	21st to end	Day	8% 7% 27% 31% 22% 5%	539
September	1st to 10th	Day	8% 5% 27% 31% 23% 5%	490
	11th to 20th	Day	14% 8% 23% 32% 17% 5%	490
	21st to end	Day	19% 10% 23% 32% 12% 4	490
October	1st to 10th	Day	18% 12% 26% 24% 17% 4	490
	11th to 20th	Day	21% 12% 20% 24% 17% 4	490
	21st to end	Day	31% 14% 23% 19% 9% 4	539
November	1st to 10th	Day	30% 16% 23% 18% 12% 1	238
	11th to 20th	Day	31% 13% 23% 21% 11% 2	180
	21st to end	Day	35% 16% 18% 18% 13% 1	180
December	1st to 10th	Day	38% 12% 15% 21% 7% 7%	180
	11th to 20th	Day	37% 14% 23% 19% 7% 1	180
	21st to end	Day	37% 15% 18% 20% 10%	198
January	1st to 10th	Night	41% 11% 14% 19% 12% 1	760
	11th to 20th	Night	36% 11% 14% 21% 15% 3	760
	21st to end	Night	32% 8% 11% 31% 15% 3	836
February	1st to 10th	Night	31% 12% 14% 28% 14% 2	760
	11th to 20th	Night	29% 11% 15% 28% 15% 1	744
	21st to end	Night	33% 15% 12% 26% 13%	628
March	1st to 10th	Night	30% 13% 16% 28% 11% 1	760
	11th to 20th	Night	29% 10% 15% 29% 16% 2	760
	21st to end	Night	33% 13% 16% 23% 14% 1	836
April	1st to 10th	Night	30% 13% 13% 26% 16% 2	760
	11th to 20th	Night	24% 12% 18% 27% 16% 2	729
	21st to end	Night	21% 10% 17% 32% 18% 1	570
May	1st to 10th	Night	15% 10% 19% 34% 21% 1	499
	11th to 20th	Night	17% 6% 14% 37% 24% 2	374
	21st to end	Night	16% 8% 15% 35% 25% 2	411
June	1st to 10th	Night	19% 6% 14% 33% 27% 1	380
	11th to 20th	Night	14% 5% 16% 46% 18% 1	380
	21st to end	Night	10% 4 12% 46% 27%	380
July	1st to 10th	Night	4 3 10% 46% 37%	370
	11th to 20th	Night	5% 4 11% 55% 25% 1	368
	21st to end	Night	2 2 9% 46% 38% 3	487
August	1st to 10th	Night	2 2 9% 41% 40% 5%	567
	11th to 20th	Night	4 1 7% 36% 47% 4	564
	21st to end	Night	6% 4 15% 40% 32% 3	740
September	1st to 10th	Night	6% 4 13% 41% 32% 3	760
	11th to 20th	Night	10% 6% 13% 32% 33% 6%	760
	21st to end	Night	13% 6% 12% 40% 26% 4	760
October	1st to 10th	Night	16% 6% 16% 31% 26% 4	760
	11th to 20th	Night	20% 7% 11% 34% 23% 6%	760
	21st to end	Night	25% 11% 17% 26% 17% 4	836
November	1st to 10th	Night	31% 10% 13% 31% 14% 1	748
	11th to 20th	Night	34% 12% 15% 23% 14% 1	760
	21st to end	Night	22% 12% 17% 29% 17% 3	760
December	1st to 10th	Night	30% 8% 15% 27% 18% 3	760
	11th to 20th	Night	37% 10% 15% 24% 14% 1	760
	21st to end	Night	39% 12% 14% 24% 9% 1	836

Page generated at 2024-10-30 10:19:22. Version ac07

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