Twin Pond
Clear Sky Chart
History

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

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	8% 6% 2 5% 4 3 4 3 5% 7% 54%	105308
	Night	7% 6% 2 5% 3 3 3 3 5% 7% 55%	102481
Transparency	Day	29% 5% 12% 27% 21% 5%	105064
	Night	28% 5% 13% 26% 22% 6%	102315
Seeing	Day	12% 6% 29% 33% 17% 3	15680
	Night	11% 7% 33% 38% 10% 1	25580

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	7% 9% 2 7% 4 3 4 4 5% 7% 49%	2538
	11th to 20th	Day	7% 10% 3 7% 5% 4 4 4 5% 6% 45%	2706
	21st to end	Day	6% 10% 4 6% 4 3 2 3 3 6% 54%	3135
February	1st to 10th	Day	7% 10% 2 8% 5% 3 4 4 6% 7% 44%	1814
	11th to 20th	Day	5% 7% 3 6% 5% 5% 5% 4 6% 7% 49%	1849
	21st to end	Day	6% 7% 2 6% 4 3 4 3 5% 7% 56%	1570
March	1st to 10th	Day	10% 6% 1 4 3 2 3 2 4 5% 60%	3149
	11th to 20th	Day	9% 6% 2 4 3 3 4 2 3 5% 59%	3480
	21st to end	Day	9% 8% 2 5% 4 4 3 4 6% 7% 49%	3814
April	1st to 10th	Day	9% 5% 2 4 4 3 3 3 5% 7% 55%	2232
	11th to 20th	Day	10% 7% 2 5% 4 4 3 4 6% 7% 48%	2300
	21st to end	Day	15% 5% 2 5% 4 4 3 3 5% 7% 47%	2470
May	1st to 10th	Day	11% 6% 2 5% 3 4 4 4 5% 8% 48%	4120
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 5% 8% 49%	4082
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 46%	4489
June	1st to 10th	Day	5% 3 1 3 3 2 4 3 5% 8% 61%	2497
	11th to 20th	Day	6% 5% 1 4 4 4 4 4 5% 8% 56%	2660
	21st to end	Day	4 3 1 3 3 3 5% 4 6% 8% 60%	2660
July	1st to 10th	Day	7% 5% 2 5% 4 4 4 4 6% 8% 51%	4430
	11th to 20th	Day	3 3 1 4 3 3 5% 4 7% 11% 55%	4316
	21st to end	Day	4 4 1 3 3 3 4 4 7% 10% 57%	4466
August	1st to 10th	Day	11% 6% 2 5% 4 3 3 3 5% 8% 48%	4103
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 49%	4041
	21st to end	Day	4 3 1 4 4 3 3 3 5% 8% 62%	4194
September	1st to 10th	Day	10% 4 2 4 3 3 3 2 5% 5% 59%	2187
	11th to 20th	Day	7% 5% 1 5% 3 3 3 2 5% 7% 58%	2090
	21st to end	Day	7% 4 2 5% 3 3 3 3 4 6% 61%	2090
October	1st to 10th	Day	9% 3 1 3 2 2 2 2 3 4 71%	3480
	11th to 20th	Day	5% 3 1 4 3 3 4 3 4 6% 65%	3186
	21st to end	Day	7% 5% 1 4 2 2 2 2 4 6% 64%	3166
November	1st to 10th	Day	7% 4 1 4 3 3 3 3 4 6% 61%	1763
	11th to 20th	Day	6% 5% 1 4 3 3 3 2 4 6% 64%	1710
	21st to end	Day	10% 6% 2 4 3 2 3 3 4 6% 58%	1710
December	1st to 10th	Day	6% 7% 3 4 3 3 3 4 5% 7% 54%	1710
	11th to 20th	Day	7% 7% 3 5% 3 3 3 3 5% 6% 55%	2161
	21st to end	Day	11% 14% 3 10% 4 4 4 2 4 5% 38%	2940
January	1st to 10th	Night	6% 9% 5% 13% 4 3 3 2 4 5% 47%	4417
	11th to 20th	Night	5% 6% 3 7% 4 4 4 3 5% 7% 53%	4245
	21st to end	Night	8% 9% 3 6% 3 3 3 3 4 5% 51%	4532
February	1st to 10th	Night	8% 9% 3 7% 5% 4 4 3 5% 5% 48%	2384
	11th to 20th	Night	5% 8% 2 6% 5% 4 4 4 6% 7% 49%	2218
	21st to end	Night	5% 6% 2 7% 4 4 3 2 4 5% 57%	1884
March	1st to 10th	Night	10% 5% 1 3 3 2 3 3 5% 5% 61%	3714
	11th to 20th	Night	7% 5% 2 5% 3 3 3 3 7% 8% 56%	3480
	21st to end	Night	11% 7% 2 5% 3 4 4 4 5% 7% 48%	3817
April	1st to 10th	Night	9% 6% 2 5% 2 3 3 4 6% 8% 52%	1943
	11th to 20th	Night	12% 6% 3 5% 4 4 4 3 6% 7% 49%	1827
	21st to end	Night	14% 5% 2 5% 4 4 3 3 4 7% 49%	1710
May	1st to 10th	Night	15% 7% 2 5% 4 4 4 4 6% 5% 45%	2850
	11th to 20th	Night	10% 7% 2 6% 4 4 4 3 6% 7% 48%	2823
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 7% 10% 44%	3098
June	1st to 10th	Night	4 3 1 4 3 4 3 4 8% 10% 56%	1678
	11th to 20th	Night	6% 4 1 4 3 4 4 4 6% 10% 54%	1520
	21st to end	Night	4 4 2 5% 4 4 4 5% 7% 9% 54%	1520
July	1st to 10th	Night	8% 3 2 5% 4 4 4 4 6% 8% 52%	2540
	11th to 20th	Night	4 3 1 4 3 5% 5% 5% 7% 11% 51%	2650
	21st to end	Night	4 4 1 3 2 3 4 4 7% 9% 59%	3097
August	1st to 10th	Night	7% 3 2 5% 3 3 4 5% 7% 11% 48%	2836
	11th to 20th	Night	9% 5% 2 5% 3 3 4 3 5% 8% 52%	2798
	21st to end	Night	2 3 2 5% 3 4 4 4 7% 10% 55%	3469
September	1st to 10th	Night	6% 4 1 3 3 3 4 3 4 8% 62%	1991
	11th to 20th	Night	7% 3 1 4 3 3 3 4 5% 7% 60%	2090
	21st to end	Night	6% 4 1 4 3 3 2 3 5% 5% 64%	2090
October	1st to 10th	Night	6% 2 1 2 2 2 2 2 3 4 73%	3480
	11th to 20th	Night	6% 3 1 3 2 3 2 2 4 6% 68%	3701
	21st to end	Night	6% 3 1 3 2 2 3 2 4 7% 67%	4373
November	1st to 10th	Night	6% 3 1 3 2 3 2 3 4 6% 66%	2535
	11th to 20th	Night	7% 5% 1 3 2 3 3 3 4 6% 64%	2477
	21st to end	Night	8% 6% 2 4 3 3 3 2 4 6% 59%	2470
December	1st to 10th	Night	5% 6% 2 5% 4 3 3 3 5% 7% 57%	2470
	11th to 20th	Night	7% 4 1 4 3 3 3 3 4 6% 60%	3036
	21st to end	Night	11% 13% 3 6% 3 3 3 3 4 5% 45%	4718

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	35% 5% 14% 29% 15% 2	2539
	11th to 20th	Day	39% 7% 13% 24% 12% 5%	2706
	21st to end	Day	34% 4 16% 30% 15% 2	3135
February	1st to 10th	Day	39% 5% 15% 23% 14% 4	1814
	11th to 20th	Day	34% 5% 15% 25% 16% 5%	1859
	21st to end	Day	29% 4 11% 25% 23% 7%	1570
March	1st to 10th	Day	28% 3 8% 22% 30% 9%	3149
	11th to 20th	Day	29% 5% 9% 27% 25% 4	3480
	21st to end	Day	33% 8% 21% 29% 9% 1	3814
April	1st to 10th	Day	28% 5% 12% 27% 22% 5%	2232
	11th to 20th	Day	34% 5% 14% 25% 17% 5%	2303
	21st to end	Day	36% 6% 12% 27% 17% 2	2470
May	1st to 10th	Day	32% 8% 13% 27% 12% 9%	4120
	11th to 20th	Day	32% 8% 15% 28% 15% 1	4086
	21st to end	Day	33% 10% 15% 23% 18% 3	4489
June	1st to 10th	Day	20% 7% 19% 35% 15% 4	2497
	11th to 20th	Day	25% 6% 13% 28% 20% 7%	2660
	21st to end	Day	21% 8% 11% 28% 25% 7%	2660
July	1st to 10th	Day	31% 5% 10% 25% 22% 7%	4361
	11th to 20th	Day	22% 5% 14% 28% 26% 5%	4241
	21st to end	Day	22% 5% 14% 25% 24% 10%	4325
August	1st to 10th	Day	34% 4 13% 27% 19% 3	4090
	11th to 20th	Day	33% 5% 17% 23% 19% 3	4080
	21st to end	Day	22% 4 13% 27% 25% 9%	4193
September	1st to 10th	Day	28% 4 8% 25% 25% 10%	2187
	11th to 20th	Day	27% 4 9% 27% 27% 6%	2090
	21st to end	Day	26% 3 9% 29% 27% 6%	2090
October	1st to 10th	Day	20% 2 5% 21% 41% 11%	3480
	11th to 20th	Day	22% 3 10% 36% 20% 10%	3186
	21st to end	Day	23% 2 7% 28% 33% 6%	3166
November	1st to 10th	Day	25% 4 10% 28% 26% 6%	1763
	11th to 20th	Day	24% 2 9% 29% 31% 5%	1710
	21st to end	Day	29% 3 9% 26% 28% 5%	1710
December	1st to 10th	Day	29% 5% 15% 28% 21% 3	1710
	11th to 20th	Day	30% 3 12% 36% 17% 1	2159
	21st to end	Day	48% 5% 9% 20% 15% 3	2940
January	1st to 10th	Night	40% 4 13% 26% 15% 2	4417
	11th to 20th	Night	30% 6% 15% 26% 20% 3	4245
	21st to end	Night	36% 5% 13% 27% 17% 2	4532
February	1st to 10th	Night	37% 5% 14% 22% 16% 6%	2384
	11th to 20th	Night	33% 5% 12% 28% 18% 3	2218
	21st to end	Night	30% 4 9% 22% 24% 11%	1884
March	1st to 10th	Night	26% 4 8% 22% 29% 11%	3714
	11th to 20th	Night	24% 5% 10% 25% 28% 7%	3480
	21st to end	Night	34% 6% 18% 31% 9% 1	3817
April	1st to 10th	Night	29% 6% 13% 22% 24% 5%	1943
	11th to 20th	Night	34% 5% 13% 23% 19% 4	1827
	21st to end	Night	34% 7% 13% 26% 19% 2	1710
May	1st to 10th	Night	35% 9% 12% 22% 14% 7%	2850
	11th to 20th	Night	33% 8% 16% 25% 18% 1	2824
	21st to end	Night	31% 10% 18% 24% 14% 3	3099
June	1st to 10th	Night	21% 8% 18% 30% 19% 3	1678
	11th to 20th	Night	25% 7% 14% 27% 20% 6%	1520
	21st to end	Night	24% 8% 14% 25% 24% 6%	1520
July	1st to 10th	Night	31% 5% 15% 21% 23% 5%	2500
	11th to 20th	Night	25% 5% 16% 27% 22% 5%	2602
	21st to end	Night	20% 5% 17% 24% 25% 11%	2999
August	1st to 10th	Night	28% 5% 16% 25% 23% 4	2826
	11th to 20th	Night	32% 4 18% 26% 17% 3	2825
	21st to end	Night	24% 4 15% 29% 19% 9%	3469
September	1st to 10th	Night	22% 6% 10% 25% 27% 11%	1991
	11th to 20th	Night	24% 6% 9% 24% 28% 9%	2090
	21st to end	Night	23% 3 11% 24% 32% 8%	2090
October	1st to 10th	Night	17% 3 6% 17% 44% 12%	3480
	11th to 20th	Night	19% 2 10% 26% 29% 13%	3701
	21st to end	Night	20% 2 9% 26% 35% 7%	4373
November	1st to 10th	Night	20% 3 11% 28% 28% 10%	2535
	11th to 20th	Night	23% 3 10% 28% 29% 8%	2477
	21st to end	Night	27% 3 9% 27% 26% 8%	2470
December	1st to 10th	Night	28% 5% 12% 29% 22% 4	2470
	11th to 20th	Night	26% 4 10% 37% 21% 2	3037
	21st to end	Night	41% 5% 12% 27% 14% 2	4718

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	10% 6% 39% 30% 13% 2	270
	11th to 20th	Day	14% 10% 34% 30% 11%	270
	21st to end	Day	12% 5% 43% 31% 9% 1	297
February	1st to 10th	Day	18% 9% 40% 26% 7%	270
	11th to 20th	Day	10% 11% 41% 26% 9% 3	270
	21st to end	Day	8% 12% 54% 20% 4	225
March	1st to 10th	Day	14% 9% 42% 26% 9%	270
	11th to 20th	Day	20% 10% 33% 26% 10% 2	270
	21st to end	Day	19% 10% 43% 21% 6% 1	297
April	1st to 10th	Day	15% 16% 37% 26% 5% 1	412
	11th to 20th	Day	16% 14% 39% 24% 6%	501
	21st to end	Day	18% 12% 38% 21% 8% 1	650
May	1st to 10th	Day	15% 7% 31% 32% 12% 2	653
	11th to 20th	Day	18% 7% 29% 28% 15% 3	675
	21st to end	Day	16% 7% 31% 34% 11% 2	734
June	1st to 10th	Day	5% 3 25% 36% 21% 9%	680
	11th to 20th	Day	6% 4 34% 35% 19% 3	680
	21st to end	Day	6% 3 32% 39% 18% 2	680
July	1st to 10th	Day	8% 2 20% 37% 27% 6%	671
	11th to 20th	Day	4 2 15% 44% 29% 5%	668
	21st to end	Day	8% 1 14% 41% 31% 6%	739
August	1st to 10th	Day	11% 1 14% 38% 30% 5%	676
	11th to 20th	Day	8% 1 17% 43% 27% 3	665
	21st to end	Day	8% 1 20% 40% 27% 5%	553
September	1st to 10th	Day	12% 3 19% 39% 22% 5%	397
	11th to 20th	Day	6% 4 25% 38% 22% 6%	300
	21st to end	Day	10% 5% 27% 31% 21% 6%	300
October	1st to 10th	Day	20% 4 17% 35% 16% 7%	300
	11th to 20th	Day	6% 10% 39% 27% 13% 4	300
	21st to end	Day	19% 8% 33% 25% 13% 3	330
November	1st to 10th	Day	15% 8% 32% 32% 10% 3	300
	11th to 20th	Day	13% 7% 40% 25% 13% 1	270
	21st to end	Day	19% 8% 32% 27% 12% 2	270
December	1st to 10th	Day	7% 7% 41% 31% 11% 2	270
	11th to 20th	Day	13% 10% 39% 29% 9%	270
	21st to end	Day	20% 9% 34% 29% 8%	297
January	1st to 10th	Night	10% 7% 35% 40% 7% 1	950
	11th to 20th	Night	10% 9% 36% 37% 8% 1	950
	21st to end	Night	11% 7% 42% 34% 6%	1045
February	1st to 10th	Night	13% 7% 40% 33% 7%	864
	11th to 20th	Night	8% 10% 41% 37% 5%	744
	21st to end	Night	9% 11% 42% 34% 4	628
March	1st to 10th	Night	13% 12% 37% 33% 5%	753
	11th to 20th	Night	15% 8% 35% 33% 8% 1	570
	21st to end	Night	17% 12% 39% 27% 5%	627
April	1st to 10th	Night	13% 13% 42% 29% 3	570
	11th to 20th	Night	17% 13% 38% 28% 4	563
	21st to end	Night	17% 9% 34% 33% 8%	570
May	1st to 10th	Night	15% 6% 36% 36% 6% 1	570
	11th to 20th	Night	16% 7% 31% 35% 9% 1	561
	21st to end	Night	13% 8% 34% 34% 10% 1	617
June	1st to 10th	Night	6% 5% 35% 39% 14% 1	570
	11th to 20th	Night	8% 4 39% 38% 11%	570
	21st to end	Night	6% 5% 33% 43% 12%	570
July	1st to 10th	Night	9% 1 23% 45% 21% 1	555
	11th to 20th	Night	4 1 24% 52% 18% 1	552
	21st to end	Night	7% 17% 49% 25% 1	624
August	1st to 10th	Night	8% 1 17% 52% 21%	567
	11th to 20th	Night	11% 1 20% 47% 20% 1	564
	21st to end	Night	4 1 23% 48% 23% 1	627
September	1st to 10th	Night	8% 2 28% 47% 13% 1	570
	11th to 20th	Night	9% 3 31% 40% 16% 1	570
	21st to end	Night	9% 5% 30% 39% 16% 1	570
October	1st to 10th	Night	11% 6% 31% 38% 13%	570
	11th to 20th	Night	12% 7% 37% 37% 8%	708
	21st to end	Night	14% 9% 30% 34% 12% 1	988
November	1st to 10th	Night	8% 8% 31% 43% 9%	975
	11th to 20th	Night	10% 8% 38% 35% 8%	953
	21st to end	Night	12% 7% 31% 39% 10% 1	950
December	1st to 10th	Night	9% 8% 38% 38% 7%	950
	11th to 20th	Night	12% 8% 34% 37% 7%	950
	21st to end	Night	14% 9% 33% 37% 7%	1045

Page generated at 2024-11-08 05:44:45. Version ac07

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