Mountain Gate Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain Gate Park clear sky chart from 2005-11-06 to 2026-10-14.

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	2 4 2 5% 3 3 4 3 5% 7% 63%	157653
	Night	1 3 2 4 3 3 3 3 5% 7% 67%	151589
Transparency	Day	20% 6% 6% 19% 27% 22%	152649
	Night	18% 5% 8% 22% 28% 19%	147576
Seeing	Day	9% 22% 30% 24% 12% 3	17644
	Night	4 12% 28% 33% 17% 4	27000

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	1 3 1 5% 3 4 4 4 7% 11% 57%	4722
	11th to 20th	Day	3 1 3 3 3 4 3 5% 6% 69%	4876
	21st to end	Day	2 6% 3 9% 4 4 5% 3 6% 10% 49%	5843
February	1st to 10th	Day	6% 2 5% 3 4 3 3 7% 10% 57%	1951
	11th to 20th	Day	1 4 3 7% 5% 5% 4 4 6% 11% 51%	2050
	21st to end	Day	1 4 2 7% 4 4 5% 3 6% 8% 57%	1730
March	1st to 10th	Day	1 8% 4 10% 5% 5% 5% 4 7% 9% 43%	4618
	11th to 20th	Day	4 2 6% 3 4 4 4 6% 10% 58%	4964
	21st to end	Day	8% 3 6% 3 3 4 4 6% 7% 54%	6010
April	1st to 10th	Day	2 4 2 6% 4 4 4 4 5% 9% 55%	2520
	11th to 20th	Day	1 5% 2 4 3 5% 4 4 6% 7% 58%	2489
	21st to end	Day	2 6% 2 4 4 4 4 4 5% 7% 58%	2520
May	1st to 10th	Day	4 6% 2 4 3 3 3 2 4 6% 64%	7415
	11th to 20th	Day	2 3 2 4 3 2 3 2 4 5% 71%	7816
	21st to end	Day	4 6% 2 6% 3 4 4 3 5% 5% 59%	8992
June	1st to 10th	Day	3 4 2 4 4 3 4 4 5% 7% 59%	2940
	11th to 20th	Day	1 2 1 3 2 2 3 2 4 5% 74%	2940
	21st to end	Day	2 2 1 4 3 3 4 2 3 4 71%	2940
July	1st to 10th	Day	1 1 1 3 2 2 2 2 3 4 77%	8219
	11th to 20th	Day	3 4 2 6% 4 4 4 3 5% 6% 57%	8220
	21st to end	Day	2 2 1 3 3 4 4 3 4 5% 68%	8739
August	1st to 10th	Day	1 2 1 4 3 3 3 2 3 4 73%	7307
	11th to 20th	Day	2 2 1 4 3 3 3 2 4 5% 71%	7001
	21st to end	Day	2 3 2 6% 4 4 4 3 4 5% 63%	7750
September	1st to 10th	Day	1 2 1 3 3 2 3 3 3 5% 72%	2520
	11th to 20th	Day	3 3 1 3 3 3 3 2 3 6% 70%	2459
	21st to end	Day	2 2 1 3 2 2 2 2 3 5% 75%	2310
October	1st to 10th	Day	2 4 2 4 2 3 3 2 4 5% 70%	3512
	11th to 20th	Day	2 3 2 3 1 1 2 2 2 3 79%	3292
	21st to end	Day	1 2 1 4 2 3 3 3 5% 7% 70%	3444
November	1st to 10th	Day	1 4 2 4 2 2 3 4 5% 7% 64%	1854
	11th to 20th	Day	2 3 1 3 2 4 4 4 7% 7% 65%	1890
	21st to end	Day	4 1 4 2 3 4 3 6% 11% 62%	1890
December	1st to 10th	Day	3 1 2 2 2 3 3 6% 8% 69%	2710
	11th to 20th	Day	1 4 2 6% 5% 5% 5% 5% 7% 9% 51%	3108
	21st to end	Day	1 5% 3 7% 4 3 5% 5% 7% 13% 46%	4092
January	1st to 10th	Night	1 3 3 6% 3 3 4 3 7% 10% 57%	8172
	11th to 20th	Night	3 2 4 3 2 3 3 6% 7% 68%	8089
	21st to end	Night	1 5% 3 9% 4 4 4 4 6% 7% 53%	8371
February	1st to 10th	Night	1 4 3 7% 3 4 5% 4 6% 7% 57%	2667
	11th to 20th	Night	5% 2 5% 4 3 4 4 7% 11% 55%	2458
	21st to end	Night	1 3 2 7% 3 3 4 4 7% 9% 60%	2076
March	1st to 10th	Night	7% 4 8% 4 4 5% 5% 7% 8% 50%	5496
	11th to 20th	Night	4 3 6% 3 4 4 4 6% 8% 58%	5251
	21st to end	Night	5% 2 6% 5% 4 4 4 7% 9% 53%	5206
April	1st to 10th	Night	2 4 2 4 3 3 3 4 7% 9% 58%	2100
	11th to 20th	Night	1 5% 2 3 4 3 3 3 6% 7% 64%	2079
	21st to end	Night	3 5% 2 3 3 3 4 3 4 6% 64%	2100
May	1st to 10th	Night	4 4 1 3 2 2 2 2 3 5% 71%	5527
	11th to 20th	Night	1 3 1 3 2 1 2 2 3 5% 77%	5058
	21st to end	Night	2 3 1 3 3 3 2 2 4 6% 71%	5181
June	1st to 10th	Night	4 3 1 2 2 3 3 3 4 6% 68%	1680
	11th to 20th	Night	1 1 1 1 1 1 2 1 3 6% 81%	1680
	21st to end	Night	2 1 3 1 2 1 2 3 3 81%	1680
July	1st to 10th	Night	1 1 1 2 1 2 3 88%	4740
	11th to 20th	Night	2 2 1 3 3 3 4 3 3 6% 70%	4740
	21st to end	Night	1 1 2 2 2 2 2 3 5% 79%	5328
August	1st to 10th	Night	1 1 1 1 1 1 2 3 4 84%	5526
	11th to 20th	Night	1 1 1 1 2 2 2 4 5% 81%	5886
	21st to end	Night	2 2 1 3 2 2 2 2 3 6% 75%	6499
September	1st to 10th	Night	1 1 1 1 2 2 2 2 4 83%	2100
	11th to 20th	Night	2 2 1 2 3 2 2 2 3 4 78%	2160
	21st to end	Night	1 2 1 3 2 2 3 2 4 4 76%	2310
October	1st to 10th	Night	2 3 1 2 1 1 2 2 4 5% 77%	3903
	11th to 20th	Night	1 3 2 2 2 2 2 2 3 4 79%	3933
	21st to end	Night	1 4 2 4 2 2 2 2 4 6% 73%	4362
November	1st to 10th	Night	1 2 1 3 2 3 3 3 6% 8% 67%	2665
	11th to 20th	Night	1 4 2 3 3 3 3 3 5% 9% 64%	2730
	21st to end	Night	1 3 2 4 3 3 3 3 5% 8% 65%	2730
December	1st to 10th	Night	1 2 1 3 2 2 3 3 6% 8% 69%	4684
	11th to 20th	Night	1 3 1 5% 3 4 5% 4 8% 14% 50%	5316
	21st to end	Night	1 6% 3 8% 5% 5% 5% 5% 8% 11% 42%	7106

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	19% 7% 15% 32% 25% 3	4723
	11th to 20th	Day	17% 3 8% 18% 27% 28%	4876
	21st to end	Day	31% 6% 6% 19% 27% 11%	5843
February	1st to 10th	Day	23% 7% 11% 23% 25% 13%	1951
	11th to 20th	Day	27% 5% 10% 23% 27% 8%	2060
	21st to end	Day	26% 6% 11% 25% 23% 8%	1730
March	1st to 10th	Day	36% 7% 6% 22% 20% 9%	4618
	11th to 20th	Day	20% 7% 11% 34% 23% 4	4964
	21st to end	Day	27% 7% 12% 24% 25% 5%	6010
April	1st to 10th	Day	27% 6% 11% 26% 21% 8%	2520
	11th to 20th	Day	24% 7% 10% 27% 24% 9%	2492
	21st to end	Day	25% 7% 12% 28% 23% 5%	2520
May	1st to 10th	Day	21% 5% 7% 22% 35% 9%	7415
	11th to 20th	Day	15% 6% 4 22% 41% 12%	7819
	21st to end	Day	24% 8% 4 19% 37% 8%	8994
June	1st to 10th	Day	24% 5% 8% 22% 29% 11%	2940
	11th to 20th	Day	14% 3 5% 19% 35% 24%	2940
	21st to end	Day	18% 4 2 10% 34% 32%	2940
July	1st to 10th	Day	11% 4 2 4 17% 63%	8151
	11th to 20th	Day	23% 8% 2 8% 13% 45%	8145
	21st to end	Day	16% 6% 4 10% 22% 42%	8543
August	1st to 10th	Day	18% 6% 2 9% 19% 45%	5780
	11th to 20th	Day	17% 5% 2 18% 15% 43%	5517
	21st to end	Day	16% 5% 1 15% 30% 32%	6077
September	1st to 10th	Day	16% 4 3 9% 32% 37%	2520
	11th to 20th	Day	18% 4 3 17% 33% 26%	2459
	21st to end	Day	15% 3 2 18% 36% 26%	2310
October	1st to 10th	Day	16% 6% 3 11% 34% 30%	3512
	11th to 20th	Day	13% 3 3 14% 51% 18%	3292
	21st to end	Day	14% 5% 4 25% 37% 15%	3444
November	1st to 10th	Day	19% 5% 10% 24% 28% 14%	1854
	11th to 20th	Day	17% 5% 12% 24% 31% 11%	1890
	21st to end	Day	18% 5% 9% 26% 27% 14%	1890
December	1st to 10th	Day	13% 5% 9% 28% 32% 13%	2710
	11th to 20th	Day	27% 7% 16% 21% 19% 10%	3108
	21st to end	Day	27% 7% 18% 22% 21% 5%	4092
January	1st to 10th	Night	22% 5% 14% 28% 26% 4	8172
	11th to 20th	Night	17% 3 9% 17% 28% 26%	8089
	21st to end	Night	30% 5% 7% 20% 27% 13%	8371
February	1st to 10th	Night	24% 6% 11% 24% 21% 15%	2667
	11th to 20th	Night	24% 5% 9% 27% 26% 10%	2459
	21st to end	Night	21% 6% 13% 27% 24% 9%	2076
March	1st to 10th	Night	29% 7% 6% 20% 27% 10%	5496
	11th to 20th	Night	22% 7% 9% 40% 19% 3	5251
	21st to end	Night	23% 9% 16% 27% 19% 5%	5206
April	1st to 10th	Night	22% 7% 13% 30% 20% 8%	2100
	11th to 20th	Night	21% 5% 12% 28% 24% 10%	2079
	21st to end	Night	21% 4 14% 34% 24% 3	2100
May	1st to 10th	Night	17% 3 7% 30% 35% 7%	5525
	11th to 20th	Night	12% 4 5% 25% 41% 12%	5059
	21st to end	Night	15% 4 6% 27% 43% 5%	5182
June	1st to 10th	Night	18% 4 10% 28% 31% 9%	1680
	11th to 20th	Night	8% 2 7% 19% 39% 25%	1680
	21st to end	Night	11% 2 3 15% 34% 34%	1680
July	1st to 10th	Night	4 3 1 8% 19% 65%	4700
	11th to 20th	Night	15% 5% 2 7% 21% 50%	4692
	21st to end	Night	9% 3 2 17% 23% 45%	5213
August	1st to 10th	Night	9% 2 2 14% 30% 44%	4372
	11th to 20th	Night	7% 4 2 24% 19% 43%	4636
	21st to end	Night	10% 3 1 23% 31% 32%	5092
September	1st to 10th	Night	7% 2 1 15% 37% 37%	2100
	11th to 20th	Night	12% 3 4 20% 36% 25%	2160
	21st to end	Night	13% 3 2 21% 37% 24%	2310
October	1st to 10th	Night	12% 3 4 13% 43% 26%	3903
	11th to 20th	Night	11% 3 3 16% 48% 19%	3933
	21st to end	Night	15% 2 5% 21% 38% 19%	4362
November	1st to 10th	Night	15% 5% 8% 29% 28% 14%	2665
	11th to 20th	Night	17% 5% 9% 27% 31% 10%	2730
	21st to end	Night	18% 5% 11% 24% 30% 12%	2730
December	1st to 10th	Night	14% 5% 10% 27% 26% 18%	4684
	11th to 20th	Night	23% 7% 14% 24% 24% 8%	5316
	21st to end	Night	32% 8% 12% 20% 20% 8%	7106

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	13% 29% 30% 19% 9%	220
	11th to 20th	Day	8% 22% 31% 25% 11% 3	265
	21st to end	Day	6% 21% 32% 28% 10% 3	473
February	1st to 10th	Day	13% 25% 32% 20% 9% 2	463
	11th to 20th	Day	13% 30% 31% 19% 8% 1	535
	21st to end	Day	13% 26% 35% 21% 5%	446
March	1st to 10th	Day	16% 29% 32% 18% 4 1	540
	11th to 20th	Day	11% 31% 30% 17% 10%	540
	21st to end	Day	13% 30% 33% 19% 5%	594
April	1st to 10th	Day	12% 29% 30% 21% 8% 1	540
	11th to 20th	Day	18% 28% 28% 18% 8% 1	532
	21st to end	Day	13% 28% 29% 19% 9% 2	540
May	1st to 10th	Day	15% 26% 28% 20% 9% 3	543
	11th to 20th	Day	15% 25% 27% 20% 10% 3	568
	21st to end	Day	14% 19% 25% 24% 13% 5%	617
June	1st to 10th	Day	9% 22% 29% 21% 14% 5%	570
	11th to 20th	Day	10% 25% 31% 21% 10% 4	570
	21st to end	Day	7% 19% 32% 26% 11% 5%	570
July	1st to 10th	Day	4 20% 31% 27% 14% 5%	566
	11th to 20th	Day	5% 13% 25% 32% 18% 5%	564
	21st to end	Day	6% 13% 30% 29% 16% 7%	619
August	1st to 10th	Day	4 18% 29% 27% 18% 4	567
	11th to 20th	Day	7% 17% 27% 27% 18% 4	557
	21st to end	Day	5% 15% 34% 28% 16% 3	627
September	1st to 10th	Day	5% 16% 31% 30% 14% 4	570
	11th to 20th	Day	8% 22% 28% 27% 12% 2	570
	21st to end	Day	6% 16% 34% 30% 12% 2	570
October	1st to 10th	Day	7% 20% 30% 27% 15% 1	570
	11th to 20th	Day	8% 17% 28% 31% 11% 3	543
	21st to end	Day	7% 18% 33% 26% 13% 4	518
November	1st to 10th	Day	8% 18% 29% 23% 17% 5%	330
	11th to 20th	Day	7% 20% 28% 28% 12% 5%	330
	21st to end	Day	5% 19% 28% 31% 14% 3	330
December	1st to 10th	Day	8% 20% 23% 26% 18% 6%	225
	11th to 20th	Day	7% 24% 30% 22% 13% 4	220
	21st to end	Day	19% 19% 28% 24% 8% 2	242
January	1st to 10th	Night	6% 18% 33% 23% 13% 7%	840
	11th to 20th	Night	4 13% 32% 33% 13% 5%	840
	21st to end	Night	5% 12% 35% 30% 14% 5%	924
February	1st to 10th	Night	6% 15% 32% 30% 15% 3	840
	11th to 20th	Night	5% 18% 32% 27% 13% 5%	824
	21st to end	Night	6% 21% 29% 32% 10% 3	692
March	1st to 10th	Night	6% 18% 37% 26% 10% 3	840
	11th to 20th	Night	4 21% 29% 28% 15% 4	840
	21st to end	Night	5% 21% 36% 26% 11% 1	924
April	1st to 10th	Night	6% 15% 33% 33% 12% 2	840
	11th to 20th	Night	6% 19% 29% 29% 13% 4	831
	21st to end	Night	6% 14% 29% 31% 15% 4	840
May	1st to 10th	Night	8% 10% 32% 31% 14% 4	706
	11th to 20th	Night	7% 10% 26% 40% 15% 2	540
	21st to end	Night	7% 6% 22% 41% 22% 2	455
June	1st to 10th	Night	6% 8% 25% 41% 17% 3	420
	11th to 20th	Night	2 8% 30% 40% 18% 2	420
	21st to end	Night	2 6% 24% 44% 20% 3	420
July	1st to 10th	Night	1 4 23% 47% 22% 3	410
	11th to 20th	Night	2 2 25% 48% 22% 2	408
	21st to end	Night	2 4 20% 42% 28% 4	521
August	1st to 10th	Night	2 2 23% 41% 27% 5%	713
	11th to 20th	Night	1 5% 25% 41% 24% 4	832
	21st to end	Night	3 5% 23% 43% 23% 4	924
September	1st to 10th	Night	1 7% 23% 37% 27% 5%	840
	11th to 20th	Night	3 8% 22% 37% 24% 6%	840
	21st to end	Night	2 8% 26% 32% 26% 6%	840
October	1st to 10th	Night	5% 10% 20% 39% 21% 6%	840
	11th to 20th	Night	4 11% 20% 38% 21% 6%	812
	21st to end	Night	3 11% 25% 31% 20% 10%	880
November	1st to 10th	Night	3 13% 25% 31% 21% 7%	820
	11th to 20th	Night	5% 13% 31% 31% 14% 5%	840
	21st to end	Night	5% 14% 30% 30% 16% 5%	840
December	1st to 10th	Night	5% 13% 32% 33% 13% 5%	840
	11th to 20th	Night	5% 19% 32% 27% 13% 4	840
	21st to end	Night	8% 17% 36% 27% 10% 2	924

Page generated at 2026-10-11 02:06:26. Version ac07

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