Dolan Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dolan Lake clear sky chart from 2005-11-06 to 2025-02-06.

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	12% 7% 3 7% 5% 4 4 4 5% 7% 42%	108378
	Night	14% 7% 3 6% 4 4 4 3 5% 6% 43%	110042
Transparency	Day	40% 5% 11% 25% 17% 3	112022
	Night	40% 4 10% 24% 18% 3	114526
Seeing	Day	15% 8% 23% 26% 19% 9%	15809
	Night	16% 7% 26% 32% 16% 2	25750

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	15% 11% 4 11% 5% 5% 5% 3 5% 5% 32%	3617
	11th to 20th	Day	12% 7% 4 10% 6% 5% 5% 3 5% 6% 38%	3638
	21st to end	Day	19% 13% 4 7% 4 3 3 2 4 5% 35%	4488
February	1st to 10th	Day	16% 10% 5% 7% 4 3 4 3 5% 6% 37%	1909
	11th to 20th	Day	15% 10% 4 8% 5% 3 4 3 5% 6% 37%	1848
	21st to end	Day	14% 10% 3 9% 5% 5% 4 3 5% 5% 36%	1570
March	1st to 10th	Day	21% 13% 3 6% 4 4 3 2 3 5% 35%	3120
	11th to 20th	Day	13% 7% 2 5% 3 3 4 3 5% 6% 48%	3294
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	4165
April	1st to 10th	Day	11% 6% 3 5% 4 5% 4 4 6% 8% 44%	2280
	11th to 20th	Day	14% 8% 2 7% 4 4 4 3 5% 7% 41%	2254
	21st to end	Day	18% 7% 2 6% 4 4 5% 3 5% 6% 40%	2280
May	1st to 10th	Day	14% 7% 3 7% 5% 5% 6% 5% 7% 9% 31%	4068
	11th to 20th	Day	18% 8% 3 6% 4 4 4 3 6% 8% 37%	4081
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 4 6% 7% 42%	4748
June	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 45%	2660
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 5% 7% 9% 48%	2660
	21st to end	Day	6% 5% 2 5% 5% 4 5% 4 7% 9% 46%	2660
July	1st to 10th	Day	12% 4 2 6% 4 5% 5% 4 6% 10% 43%	4440
	11th to 20th	Day	5% 4 2 5% 5% 5% 5% 4 7% 11% 48%	4440
	21st to end	Day	8% 7% 3 8% 6% 6% 7% 6% 8% 9% 32%	4813
August	1st to 10th	Day	5% 3 1 4 4 4 4 4 6% 10% 54%	3816
	11th to 20th	Day	8% 5% 2 7% 5% 5% 5% 5% 7% 10% 43%	3729
	21st to end	Day	5% 4 1 5% 4 4 4 4 6% 8% 55%	4180
September	1st to 10th	Day	10% 6% 2 6% 4 4 3 5% 5% 7% 48%	2280
	11th to 20th	Day	7% 6% 2 6% 4 3 5% 4 6% 7% 49%	2157
	21st to end	Day	10% 5% 2 6% 3 3 3 3 4 7% 52%	2090
October	1st to 10th	Day	10% 4 1 5% 4 3 4 2 5% 6% 57%	2069
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 4 7% 51%	1900
	21st to end	Day	17% 6% 2 6% 4 3 3 3 4 6% 46%	1957
November	1st to 10th	Day	8% 5% 2 4 5% 4 4 4 5% 5% 53%	1762
	11th to 20th	Day	14% 7% 2 7% 4 4 4 3 5% 6% 46%	1800
	21st to end	Day	17% 9% 3 7% 4 3 3 3 4 5% 41%	1800
December	1st to 10th	Day	10% 11% 2 7% 3 3 3 2 4 5% 50%	2815
	11th to 20th	Day	13% 9% 4 10% 5% 4 4 4 5% 7% 35%	3008
	21st to end	Day	27% 15% 4 9% 5% 4 4 2 4 4 23%	3982
January	1st to 10th	Night	16% 11% 4 9% 4 4 4 3 5% 6% 33%	6348
	11th to 20th	Night	15% 10% 3 9% 4 4 5% 3 4 5% 37%	6339
	21st to end	Night	19% 9% 4 7% 4 3 4 3 4 6% 37%	6490
February	1st to 10th	Night	18% 11% 4 7% 5% 4 3 5% 4 6% 32%	2380
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 3 4 5% 41%	2218
	21st to end	Night	18% 10% 2 9% 4 5% 3 4 5% 5% 36%	1884
March	1st to 10th	Night	21% 10% 2 7% 4 4 4 3 4 5% 36%	3733
	11th to 20th	Night	12% 7% 2 5% 4 3 4 3 4 6% 50%	3694
	21st to end	Night	17% 7% 3 7% 5% 4 4 4 5% 6% 38%	3466
April	1st to 10th	Night	11% 7% 2 6% 5% 4 4 4 4 7% 46%	1900
	11th to 20th	Night	16% 7% 2 4 4 4 4 4 6% 6% 44%	1875
	21st to end	Night	18% 7% 2 6% 5% 4 4 3 5% 6% 38%	1900
May	1st to 10th	Night	15% 8% 2 7% 5% 4 4 4 6% 7% 38%	2827
	11th to 20th	Night	13% 8% 2 7% 4 4 4 3 5% 6% 43%	2812
	21st to end	Night	8% 5% 3 6% 5% 5% 5% 5% 7% 10% 41%	2813
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 5% 8% 49%	1520
	11th to 20th	Night	5% 3 2 5% 4 4 4 4 6% 9% 55%	1520
	21st to end	Night	4 3 1 4 4 4 4 5% 8% 10% 53%	1520
July	1st to 10th	Night	10% 6% 2 5% 3 4 4 4 6% 8% 48%	2530
	11th to 20th	Night	5% 3 1 5% 3 4 3 4 5% 8% 59%	2530
	21st to end	Night	8% 7% 3 9% 6% 5% 6% 5% 8% 9% 35%	2750
August	1st to 10th	Night	4 3 1 5% 3 3 4 3 5% 9% 59%	3096
	11th to 20th	Night	6% 5% 1 6% 4 4 4 4 6% 8% 52%	3100
	21st to end	Night	4 3 2 5% 3 3 4 3 5% 9% 58%	3476
September	1st to 10th	Night	9% 5% 2 6% 4 3 4 3 4 5% 55%	1900
	11th to 20th	Night	7% 4 2 6% 4 4 4 4 5% 8% 53%	2004
	21st to end	Night	11% 5% 2 5% 3 3 4 3 5% 7% 52%	2090
October	1st to 10th	Night	7% 4 2 5% 3 3 3 2 5% 6% 59%	2108
	11th to 20th	Night	13% 4 2 5% 3 3 3 2 4 5% 55%	2280
	21st to end	Night	18% 7% 2 5% 4 3 3 2 4 5% 46%	2641
November	1st to 10th	Night	11% 6% 2 4 3 3 3 3 5% 5% 55%	2536
	11th to 20th	Night	13% 5% 2 6% 3 3 3 3 5% 6% 50%	2600
	21st to end	Night	18% 7% 3 6% 4 3 3 3 4 6% 45%	2600
December	1st to 10th	Night	17% 9% 3 6% 4 3 3 2 4 4 44%	4367
	11th to 20th	Night	17% 7% 3 6% 4 4 4 3 5% 6% 42%	5199
	21st to end	Night	26% 14% 4 8% 5% 4 4 3 3 4 25%	6996

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	56% 3 11% 21% 8% 1	3618
	11th to 20th	Day	48% 4 7% 26% 14% 2	3638
	21st to end	Day	52% 3 10% 17% 13% 6%	4488
February	1st to 10th	Day	48% 5% 12% 22% 12% 2	1909
	11th to 20th	Day	49% 4 9% 21% 14% 3	1858
	21st to end	Day	49% 4 9% 19% 13% 4	1570
March	1st to 10th	Day	53% 4 6% 19% 15% 5%	3120
	11th to 20th	Day	36% 4 11% 28% 15% 5%	3294
	21st to end	Day	44% 6% 14% 23% 13% 1	4165
April	1st to 10th	Day	37% 5% 13% 27% 16% 1	2280
	11th to 20th	Day	42% 6% 11% 23% 15% 3	2254
	21st to end	Day	43% 6% 10% 26% 12% 2	2280
May	1st to 10th	Day	45% 11% 13% 22% 9% 1	4106
	11th to 20th	Day	43% 8% 10% 25% 12% 1	4085
	21st to end	Day	38% 9% 10% 19% 23% 1	4761
June	1st to 10th	Day	34% 8% 12% 25% 18% 3	2660
	11th to 20th	Day	30% 8% 11% 26% 22% 3	2660
	21st to end	Day	32% 8% 15% 23% 16% 6%	2660
July	1st to 10th	Day	36% 6% 12% 26% 16% 3	4371
	11th to 20th	Day	29% 6% 12% 34% 17% 2	4365
	21st to end	Day	45% 6% 16% 22% 9% 1	4662
August	1st to 10th	Day	26% 5% 14% 38% 16% 1	3802
	11th to 20th	Day	35% 5% 14% 26% 18% 1	3765
	21st to end	Day	26% 5% 13% 35% 18% 3	4179
September	1st to 10th	Day	35% 6% 9% 27% 19% 5%	2280
	11th to 20th	Day	33% 5% 10% 25% 24% 3	2157
	21st to end	Day	32% 5% 8% 25% 26% 4	2090
October	1st to 10th	Day	18% 3 5% 25% 43% 6%	3433
	11th to 20th	Day	25% 3 7% 23% 36% 7%	3140
	21st to end	Day	32% 3 5% 25% 30% 4	3208
November	1st to 10th	Day	32% 4 10% 29% 18% 6%	1762
	11th to 20th	Day	40% 4 7% 25% 19% 5%	1800
	21st to end	Day	46% 3 9% 25% 15% 2	1800
December	1st to 10th	Day	38% 3 13% 29% 16% 1	2815
	11th to 20th	Day	48% 4 10% 25% 12% 1	3005
	21st to end	Day	65% 3 11% 13% 7%	3982
January	1st to 10th	Night	52% 2 11% 25% 9% 1	6348
	11th to 20th	Night	49% 4 7% 22% 15% 3	6339
	21st to end	Night	50% 2 9% 18% 19% 1	6490
February	1st to 10th	Night	53% 4 9% 21% 11% 1	2380
	11th to 20th	Night	46% 5% 8% 23% 16% 2	2219
	21st to end	Night	49% 5% 10% 18% 14% 3	1884
March	1st to 10th	Night	51% 4 7% 18% 17% 3	3733
	11th to 20th	Night	35% 6% 12% 22% 19% 6%	3694
	21st to end	Night	45% 7% 11% 25% 11% 1	3466
April	1st to 10th	Night	37% 5% 12% 26% 17% 3	1900
	11th to 20th	Night	39% 6% 9% 23% 19% 5%	1875
	21st to end	Night	45% 6% 10% 22% 15% 3	1900
May	1st to 10th	Night	42% 9% 16% 24% 9% 1	2854
	11th to 20th	Night	41% 8% 11% 24% 15% 1	2813
	21st to end	Night	34% 9% 14% 25% 17% 2	2821
June	1st to 10th	Night	32% 6% 13% 25% 22% 3	1520
	11th to 20th	Night	25% 6% 13% 25% 25% 6%	1520
	21st to end	Night	24% 7% 17% 26% 19% 7%	1520
July	1st to 10th	Night	34% 6% 10% 27% 18% 5%	2490
	11th to 20th	Night	23% 6% 11% 38% 20% 3	2482
	21st to end	Night	44% 5% 16% 22% 12% 1	2662
August	1st to 10th	Night	23% 5% 15% 39% 18% 1	3086
	11th to 20th	Night	30% 5% 13% 29% 22% 2	3130
	21st to end	Night	23% 5% 12% 35% 22% 3	3476
September	1st to 10th	Night	31% 6% 7% 28% 22% 7%	1900
	11th to 20th	Night	30% 6% 8% 27% 25% 5%	2004
	21st to end	Night	32% 4 9% 23% 25% 7%	2090
October	1st to 10th	Night	17% 3 5% 16% 49% 9%	3511
	11th to 20th	Night	23% 2 5% 24% 39% 7%	3779
	21st to end	Night	32% 2 7% 25% 25% 9%	4340
November	1st to 10th	Night	32% 4 10% 24% 24% 6%	2536
	11th to 20th	Night	36% 3 7% 24% 24% 6%	2600
	21st to end	Night	42% 3 9% 25% 19% 2	2600
December	1st to 10th	Night	44% 3 8% 26% 18% 1	4367
	11th to 20th	Night	44% 3 12% 23% 17% 1	5201
	21st to end	Night	63% 3 10% 16% 6% 2	6996

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% 14% 30% 23% 7% 1	300
	11th to 20th	Day	24% 17% 34% 20% 5%	300
	21st to end	Day	21% 17% 41% 16% 5%	330
February	1st to 10th	Day	24% 12% 44% 17% 4	285
	11th to 20th	Day	26% 18% 38% 14% 3 1	270
	21st to end	Day	29% 15% 34% 19% 4	225
March	1st to 10th	Day	20% 17% 38% 20% 4 1	270
	11th to 20th	Day	23% 20% 32% 20% 5%	279
	21st to end	Day	25% 14% 31% 20% 9% 1	506
April	1st to 10th	Day	16% 15% 33% 25% 10% 1	460
	11th to 20th	Day	19% 14% 27% 24% 14% 1	452
	21st to end	Day	21% 11% 32% 24% 10% 3	460
May	1st to 10th	Day	19% 11% 27% 29% 10% 4	463
	11th to 20th	Day	18% 6% 24% 27% 17% 7%	487
	21st to end	Day	12% 3 25% 29% 22% 10%	684
June	1st to 10th	Day	12% 5% 17% 28% 26% 13%	680
	11th to 20th	Day	7% 2 18% 33% 30% 10%	680
	21st to end	Day	9% 2 23% 33% 25% 9%	680
July	1st to 10th	Day	12% 2 11% 24% 26% 25%	671
	11th to 20th	Day	6% 3 14% 30% 32% 16%	668
	21st to end	Day	9% 2 11% 32% 31% 16%	739
August	1st to 10th	Day	9% 2 9% 29% 31% 20%	503
	11th to 20th	Day	13% 1 15% 27% 31% 12%	479
	21st to end	Day	8% 1 9% 23% 37% 22%	539
September	1st to 10th	Day	12% 1 12% 25% 34% 16%	490
	11th to 20th	Day	9% 3 8% 27% 35% 19%	490
	21st to end	Day	12% 5% 22% 26% 22% 13%	490
October	1st to 10th	Day	10% 3 18% 36% 21% 12%	469
	11th to 20th	Day	12% 11% 36% 23% 13% 6%	300
	21st to end	Day	23% 10% 31% 25% 11% 1	330
November	1st to 10th	Day	11% 7% 34% 25% 19% 5%	300
	11th to 20th	Day	15% 16% 30% 24% 12% 3	300
	21st to end	Day	24% 12% 30% 22% 11% 1	300
December	1st to 10th	Day	18% 18% 33% 20% 8% 3	300
	11th to 20th	Day	21% 12% 37% 23% 7%	300
	21st to end	Day	29% 17% 31% 17% 5%	330
January	1st to 10th	Night	20% 14% 36% 27% 4	1000
	11th to 20th	Night	24% 14% 37% 21% 4	1000
	21st to end	Night	20% 10% 41% 26% 3	1100
February	1st to 10th	Night	23% 12% 37% 25% 3	820
	11th to 20th	Night	20% 14% 38% 26% 2	743
	21st to end	Night	22% 15% 39% 23% 2	628
March	1st to 10th	Night	21% 12% 34% 29% 4	760
	11th to 20th	Night	20% 10% 34% 28% 7% 1	717
	21st to end	Night	23% 10% 29% 30% 7% 1	627
April	1st to 10th	Night	14% 11% 35% 32% 8%	570
	11th to 20th	Night	19% 9% 29% 30% 13% 1	563
	21st to end	Night	21% 7% 32% 31% 8% 1	570
May	1st to 10th	Night	15% 8% 28% 37% 12%	570
	11th to 20th	Night	16% 4 23% 32% 22% 2	561
	21st to end	Night	8% 2 18% 43% 25% 4	617
June	1st to 10th	Night	11% 2 17% 41% 26% 3	570
	11th to 20th	Night	6% 3 15% 46% 29% 2	570
	21st to end	Night	5% 2 17% 41% 32% 3	570
July	1st to 10th	Night	11% 1 8% 31% 39% 9%	555
	11th to 20th	Night	6% 1 9% 36% 42% 5%	552
	21st to end	Night	8% 2 11% 37% 36% 6%	624
August	1st to 10th	Night	7% 1 5% 42% 38% 7%	567
	11th to 20th	Night	6% 1 10% 39% 38% 5%	564
	21st to end	Night	7% 1 6% 37% 43% 7%	627
September	1st to 10th	Night	12% 1 10% 33% 37% 6%	570
	11th to 20th	Night	9% 2 11% 31% 41% 6%	674
	21st to end	Night	14% 2 18% 32% 28% 6%	760
October	1st to 10th	Night	9% 3 18% 38% 27% 6%	760
	11th to 20th	Night	16% 6% 28% 31% 16% 3	760
	21st to end	Night	21% 7% 31% 30% 11% 1	836
November	1st to 10th	Night	14% 6% 28% 37% 13% 1	780
	11th to 20th	Night	15% 9% 31% 34% 11% 1	800
	21st to end	Night	22% 9% 29% 29% 10% 1	800
December	1st to 10th	Night	23% 8% 32% 30% 6%	865
	11th to 20th	Night	24% 8% 30% 32% 6% 1	1000
	21st to end	Night	26% 12% 34% 23% 4	1100

Page generated at 2025-02-03 02:05:53. Version ac07

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