Loon Lake Road Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Loon Lake Road Observing Site clear sky chart from 2005-11-06 to 2025-07-06.

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	8% 11% 4 9% 6% 5% 5% 4 6% 7% 36%	123366
	Night	7% 11% 4 10% 6% 5% 5% 4 6% 7% 35%	124103
Transparency	Day	47% 7% 13% 19% 11% 2	123122
	Night	47% 8% 15% 20% 9% 2	123989
Seeing	Day	18% 19% 28% 21% 11% 3	16196
	Night	15% 15% 28% 26% 13% 2	24635

By Month

Percentage Cloud Cover NW (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	9% 19% 6% 15% 8% 6% 5% 4 6% 7% 16%	3179
	11th to 20th	Day	4 13% 5% 11% 6% 6% 6% 5% 8% 9% 28%	3502
	21st to end	Day	6% 15% 4 10% 7% 6% 6% 4 6% 6% 29%	4004
February	1st to 10th	Day	7% 19% 5% 11% 7% 6% 6% 6% 7% 8% 20%	1684
	11th to 20th	Day	5% 18% 6% 12% 7% 6% 5% 4 6% 7% 23%	1755
	21st to end	Day	6% 19% 6% 14% 7% 7% 6% 4 7% 5% 20%	1591
March	1st to 10th	Day	6% 13% 5% 12% 7% 5% 6% 5% 7% 7% 27%	4518
	11th to 20th	Day	3 13% 5% 11% 7% 6% 6% 4 7% 6% 31%	4863
	21st to end	Day	10% 17% 5% 12% 7% 5% 5% 4 7% 7% 22%	5833
April	1st to 10th	Day	8% 16% 6% 11% 7% 7% 7% 5% 6% 7% 21%	2400
	11th to 20th	Day	8% 13% 5% 10% 7% 6% 5% 5% 6% 6% 29%	2372
	21st to end	Day	8% 16% 5% 10% 6% 5% 5% 4 7% 7% 26%	2771
May	1st to 10th	Day	6% 13% 4 9% 5% 4 5% 3 5% 6% 41%	6320
	11th to 20th	Day	10% 13% 4 10% 7% 6% 6% 5% 7% 9% 24%	6277
	21st to end	Day	12% 13% 4 8% 5% 5% 5% 4 6% 8% 31%	6903
June	1st to 10th	Day	15% 10% 3 8% 6% 5% 5% 4 6% 6% 32%	3017
	11th to 20th	Day	15% 9% 3 9% 6% 5% 4 5% 6% 7% 30%	3200
	21st to end	Day	10% 7% 2 7% 6% 4 6% 4 6% 8% 40%	3127
July	1st to 10th	Day	5% 3 2 4 3 3 3 3 4 5% 64%	4816
	11th to 20th	Day	4 2 1 3 2 2 3 3 4 6% 71%	4613
	21st to end	Day	6% 3 2 4 3 3 3 3 5% 7% 61%	4790
August	1st to 10th	Day	3 2 1 4 3 4 4 3 5% 7% 63%	4401
	11th to 20th	Day	4 4 2 6% 4 5% 5% 5% 7% 8% 50%	4238
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 7% 8% 44%	4283
September	1st to 10th	Day	9% 6% 2 7% 4 4 4 3 4 6% 51%	2280
	11th to 20th	Day	11% 8% 2 8% 6% 5% 5% 3 4 6% 42%	2280
	21st to end	Day	12% 9% 2 8% 5% 5% 4 4 6% 7% 37%	2037
October	1st to 10th	Day	12% 10% 4 8% 4 4 5% 4 5% 6% 39%	3180
	11th to 20th	Day	17% 11% 4 8% 5% 4 4 4 5% 6% 31%	3114
	21st to end	Day	9% 15% 5% 11% 6% 5% 4 4 5% 6% 30%	3101
November	1st to 10th	Day	14% 16% 5% 11% 6% 7% 5% 5% 5% 6% 22%	1625
	11th to 20th	Day	11% 16% 5% 8% 7% 5% 5% 5% 6% 6% 26%	1600
	21st to end	Day	8% 17% 5% 9% 7% 5% 6% 5% 7% 7% 23%	1573
December	1st to 10th	Day	6% 13% 4 11% 6% 5% 6% 5% 7% 8% 29%	2290
	11th to 20th	Day	8% 17% 5% 13% 6% 6% 6% 5% 7% 8% 19%	2492
	21st to end	Day	6% 15% 6% 15% 10% 7% 7% 5% 7% 7% 16%	3337
January	1st to 10th	Night	9% 17% 6% 14% 7% 7% 6% 5% 6% 7% 16%	6766
	11th to 20th	Night	5% 14% 4 9% 6% 5% 5% 4 8% 7% 35%	6392
	21st to end	Night	6% 11% 4 11% 7% 6% 6% 5% 7% 7% 30%	6952
February	1st to 10th	Night	8% 19% 6% 14% 7% 4 5% 4 6% 6% 22%	2715
	11th to 20th	Night	5% 15% 5% 12% 7% 6% 5% 5% 6% 6% 30%	2532
	21st to end	Night	5% 14% 7% 12% 9% 6% 6% 4 6% 7% 23%	2038
March	1st to 10th	Night	2 10% 4 11% 6% 6% 6% 5% 9% 10% 32%	5376
	11th to 20th	Night	2 8% 4 11% 7% 6% 6% 5% 7% 8% 35%	5133
	21st to end	Night	9% 15% 5% 10% 7% 7% 7% 5% 6% 7% 23%	5141
April	1st to 10th	Night	5% 13% 5% 10% 6% 7% 5% 5% 5% 8% 31%	2000
	11th to 20th	Night	5% 12% 4 9% 6% 5% 7% 5% 6% 7% 33%	1979
	21st to end	Night	6% 10% 4 8% 6% 6% 6% 4 6% 9% 34%	1627
May	1st to 10th	Night	6% 10% 3 7% 5% 4 5% 4 6% 6% 45%	3640
	11th to 20th	Night	8% 12% 4 9% 5% 5% 5% 5% 7% 8% 32%	3616
	21st to end	Night	7% 10% 3 8% 6% 5% 6% 5% 7% 7% 36%	3972
June	1st to 10th	Night	10% 9% 3 6% 5% 6% 5% 6% 6% 9% 35%	1374
	11th to 20th	Night	10% 7% 3 7% 6% 5% 6% 4 7% 8% 37%	1200
	21st to end	Night	6% 7% 2 6% 5% 3 5% 4 7% 10% 47%	1268
July	1st to 10th	Night	3 3 1 4 2 2 3 3 4 5% 70%	2255
	11th to 20th	Night	3 2 1 2 2 3 2 3 4 5% 74%	2343
	21st to end	Night	3 2 1 4 2 2 3 2 5% 7% 69%	2762
August	1st to 10th	Night	2 2 1 3 2 3 5% 4 6% 9% 63%	2529
	11th to 20th	Night	3 3 1 4 3 4 4 4 7% 9% 59%	2589
	21st to end	Night	9% 6% 3 7% 4 4 5% 4 6% 7% 47%	3392
September	1st to 10th	Night	6% 5% 1 4 4 3 4 4 5% 7% 57%	1900
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 3 6% 8% 48%	1900
	21st to end	Night	10% 10% 3 7% 4 4 4 3 6% 9% 40%	2139
October	1st to 10th	Night	9% 9% 3 8% 4 4 5% 4 6% 6% 40%	3800
	11th to 20th	Night	17% 10% 3 8% 4 4 4 4 5% 6% 33%	3821
	21st to end	Night	9% 12% 5% 11% 5% 5% 5% 3 5% 5% 35%	4457
November	1st to 10th	Night	13% 15% 4 11% 5% 5% 5% 5% 5% 7% 25%	2670
	11th to 20th	Night	9% 15% 5% 11% 7% 6% 5% 5% 6% 6% 25%	2800
	21st to end	Night	9% 16% 5% 11% 7% 6% 5% 5% 6% 6% 25%	2805
December	1st to 10th	Night	7% 12% 3 8% 5% 5% 5% 5% 6% 8% 36%	4890
	11th to 20th	Night	6% 18% 7% 15% 7% 6% 6% 4 5% 6% 20%	5670
	21st to end	Night	5% 14% 6% 15% 7% 7% 7% 5% 7% 7% 20%	7660

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	65% 8% 11% 12% 3	3179
	11th to 20th	Day	51% 5% 17% 19% 4 3	3526
	21st to end	Day	53% 9% 15% 15% 8%	4004
February	1st to 10th	Day	60% 11% 11% 9% 8% 1	1684
	11th to 20th	Day	59% 10% 12% 11% 6% 1	1764
	21st to end	Day	63% 10% 9% 12% 5%	1591
March	1st to 10th	Day	53% 7% 11% 15% 13%	4518
	11th to 20th	Day	51% 7% 12% 21% 9%	4863
	21st to end	Day	60% 8% 11% 13% 8%	5833
April	1st to 10th	Day	59% 12% 13% 14% 2	2400
	11th to 20th	Day	54% 9% 11% 16% 9% 1	2372
	21st to end	Day	55% 9% 14% 14% 7%	2771
May	1st to 10th	Day	41% 8% 9% 28% 13% 1	6320
	11th to 20th	Day	53% 9% 17% 18% 3	6280
	21st to end	Day	49% 7% 14% 24% 5% 1	6904
June	1st to 10th	Day	51% 8% 12% 17% 8% 3	3017
	11th to 20th	Day	52% 10% 12% 18% 7%	3200
	21st to end	Day	42% 9% 15% 21% 11% 2	3127
July	1st to 10th	Day	24% 4 8% 20% 27% 16%	4742
	11th to 20th	Day	17% 5% 8% 22% 32% 16%	4532
	21st to end	Day	24% 3 13% 30% 21% 8%	4639
August	1st to 10th	Day	21% 5% 10% 27% 31% 6%	4384
	11th to 20th	Day	32% 4 24% 28% 10% 2	4280
	21st to end	Day	38% 5% 18% 25% 13% 1	4282
September	1st to 10th	Day	35% 6% 14% 26% 15% 4	2280
	11th to 20th	Day	43% 6% 11% 21% 15% 3	2280
	21st to end	Day	45% 8% 17% 17% 9% 3	2037
October	1st to 10th	Day	47% 5% 14% 27% 6%	3180
	11th to 20th	Day	55% 5% 9% 25% 6% 1	3114
	21st to end	Day	55% 6% 15% 18% 5%	3101
November	1st to 10th	Day	63% 10% 11% 11% 5%	1625
	11th to 20th	Day	58% 8% 13% 14% 5% 1	1600
	21st to end	Day	57% 10% 13% 14% 5% 2	1573
December	1st to 10th	Day	52% 9% 21% 12% 6%	2290
	11th to 20th	Day	61% 8% 15% 12% 3	2493
	21st to end	Day	64% 9% 13% 11% 2	3337
January	1st to 10th	Night	64% 9% 14% 11% 3	6766
	11th to 20th	Night	48% 6% 19% 17% 7% 3	6430
	21st to end	Night	51% 10% 16% 15% 8%	6952
February	1st to 10th	Night	62% 8% 11% 11% 6% 1	2715
	11th to 20th	Night	54% 10% 13% 14% 7% 2	2534
	21st to end	Night	59% 9% 11% 14% 6%	2038
March	1st to 10th	Night	41% 9% 15% 22% 12%	5376
	11th to 20th	Night	43% 8% 15% 24% 9%	5134
	21st to end	Night	57% 9% 12% 15% 7%	5141
April	1st to 10th	Night	49% 11% 20% 16% 4	2000
	11th to 20th	Night	47% 10% 16% 19% 8%	1979
	21st to end	Night	45% 9% 19% 19% 7%	1627
May	1st to 10th	Night	37% 7% 13% 30% 13%	3637
	11th to 20th	Night	46% 9% 20% 22% 3	3616
	21st to end	Night	43% 12% 18% 23% 4	3972
June	1st to 10th	Night	44% 9% 16% 20% 8% 3	1374
	11th to 20th	Night	42% 12% 18% 19% 9%	1200
	21st to end	Night	31% 10% 24% 23% 10% 1	1268
July	1st to 10th	Night	17% 6% 10% 31% 21% 16%	2220
	11th to 20th	Night	15% 3 11% 26% 36% 10%	2301
	21st to end	Night	17% 3 17% 31% 19% 14%	2674
August	1st to 10th	Night	19% 5% 13% 26% 34% 4	2521
	11th to 20th	Night	22% 5% 29% 32% 10% 3	2613
	21st to end	Night	36% 6% 20% 25% 12% 2	3392
September	1st to 10th	Night	26% 8% 16% 31% 15% 4	1900
	11th to 20th	Night	33% 10% 15% 21% 18% 5%	1900
	21st to end	Night	42% 9% 18% 20% 10% 2	2139
October	1st to 10th	Night	44% 5% 17% 27% 7%	3800
	11th to 20th	Night	53% 5% 11% 23% 8%	3821
	21st to end	Night	52% 5% 14% 23% 6%	4457
November	1st to 10th	Night	59% 10% 13% 12% 6% 1	2670
	11th to 20th	Night	58% 10% 14% 13% 5% 1	2800
	21st to end	Night	57% 11% 13% 12% 6% 1	2805
December	1st to 10th	Night	47% 8% 17% 22% 5% 1	4890
	11th to 20th	Night	65% 7% 12% 12% 2	5667
	21st to end	Night	59% 10% 12% 15% 4	7660

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	18% 24% 28% 15% 11% 5%	200
	11th to 20th	Day	14% 19% 34% 21% 12% 2	200
	21st to end	Day	14% 23% 32% 20% 10%	220
February	1st to 10th	Day	26% 24% 27% 17% 6% 1	284
	11th to 20th	Day	17% 22% 35% 17% 7% 2	395
	21st to end	Day	23% 23% 33% 15% 5% 1	385
March	1st to 10th	Day	22% 23% 28% 19% 7% 1	500
	11th to 20th	Day	20% 26% 25% 17% 10% 3	500
	21st to end	Day	23% 27% 22% 17% 9% 1	550
April	1st to 10th	Day	24% 25% 27% 17% 5% 1	500
	11th to 20th	Day	20% 25% 25% 19% 9% 3	492
	21st to end	Day	22% 23% 25% 18% 8% 3	500
May	1st to 10th	Day	17% 19% 34% 21% 8% 2	503
	11th to 20th	Day	19% 15% 25% 27% 12% 2	528
	21st to end	Day	22% 17% 26% 21% 10% 3	573
June	1st to 10th	Day	20% 20% 31% 19% 9% 1	747
	11th to 20th	Day	21% 19% 29% 19% 9% 2	930
	21st to end	Day	16% 14% 29% 23% 14% 3	857
July	1st to 10th	Day	11% 15% 33% 27% 12% 1	697
	11th to 20th	Day	9% 16% 31% 28% 14% 2	593
	21st to end	Day	8% 11% 31% 31% 16% 3	531
August	1st to 10th	Day	7% 11% 27% 31% 18% 6%	487
	11th to 20th	Day	7% 10% 30% 29% 18% 6%	477
	21st to end	Day	12% 15% 31% 25% 12% 5%	539
September	1st to 10th	Day	13% 16% 29% 22% 16% 4	490
	11th to 20th	Day	16% 15% 28% 24% 13% 3	490
	21st to end	Day	22% 19% 27% 19% 10% 3	490
October	1st to 10th	Day	23% 17% 25% 17% 14% 4	490
	11th to 20th	Day	25% 20% 22% 16% 13% 2	468
	21st to end	Day	25% 18% 28% 18% 9% 2	330
November	1st to 10th	Day	25% 22% 30% 18% 4 1	230
	11th to 20th	Day	30% 20% 23% 12% 13% 3	200
	21st to end	Day	22% 20% 28% 17% 9% 5%	200
December	1st to 10th	Day	22% 13% 23% 23% 14% 8%	200
	11th to 20th	Day	21% 23% 26% 17% 10% 4	200
	21st to end	Day	18% 16% 34% 22% 5% 4	220
January	1st to 10th	Night	23% 18% 30% 18% 9% 1	900
	11th to 20th	Night	16% 17% 31% 26% 9% 1	823
	21st to end	Night	15% 16% 32% 25% 10% 2	880
February	1st to 10th	Night	21% 18% 27% 23% 9% 2	800
	11th to 20th	Night	13% 16% 29% 28% 11% 2	784
	21st to end	Night	15% 19% 26% 24% 14% 1	660
March	1st to 10th	Night	14% 21% 24% 25% 14% 2	800
	11th to 20th	Night	13% 21% 33% 22% 10% 2	800
	21st to end	Night	16% 18% 28% 24% 12% 2	880
April	1st to 10th	Night	14% 18% 27% 28% 11% 2	800
	11th to 20th	Night	12% 17% 30% 26% 13% 1	791
	21st to end	Night	12% 15% 29% 30% 12% 2	427
May	1st to 10th	Night	14% 11% 28% 31% 14% 2	400
	11th to 20th	Night	11% 8% 27% 35% 18% 1	394
	21st to end	Night	16% 9% 27% 31% 15% 2	433
June	1st to 10th	Night	13% 14% 33% 29% 11% 1	400
	11th to 20th	Night	14% 14% 32% 28% 12%	400
	21st to end	Night	8% 11% 32% 30% 18% 2	400
July	1st to 10th	Night	7% 7% 24% 39% 20% 2	380
	11th to 20th	Night	6% 10% 29% 36% 18% 1	368
	21st to end	Night	4 7% 28% 37% 21% 2	416
August	1st to 10th	Night	4 5% 21% 39% 27% 4	378
	11th to 20th	Night	5% 4 25% 32% 28% 5%	429
	21st to end	Night	10% 8% 25% 32% 22% 2	769
September	1st to 10th	Night	9% 10% 27% 28% 22% 4	760
	11th to 20th	Night	12% 8% 23% 24% 26% 7%	760
	21st to end	Night	18% 14% 26% 22% 18% 3	760
October	1st to 10th	Night	15% 11% 26% 26% 18% 3	760
	11th to 20th	Night	21% 16% 23% 23% 15% 2	760
	21st to end	Night	20% 20% 25% 22% 11% 3	836
November	1st to 10th	Night	23% 17% 31% 22% 6% 1	780
	11th to 20th	Night	22% 21% 28% 19% 9% 1	800
	21st to end	Night	18% 20% 27% 22% 11% 2	805
December	1st to 10th	Night	16% 15% 29% 27% 12% 2	1000
	11th to 20th	Night	19% 20% 31% 22% 8% 1	1027
	21st to end	Night	18% 21% 32% 22% 7%	1075

Page generated at 2025-07-02 22:30:18. Version ac07

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