Pelican Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pelican Lake Observatory clear sky chart from 2005-11-06 to 2026-01-17.

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% 9% 3 8% 5% 4 5% 4 6% 7% 36%	127934
	Night	11% 10% 4 9% 6% 5% 5% 4 5% 6% 35%	124023
Transparency	Day	44% 7% 14% 24% 10% 1	131475
	Night	47% 6% 13% 22% 11% 1	128559
Seeing	Day	15% 10% 31% 27% 14% 3	17725
	Night	15% 9% 33% 31% 11% 1	27715

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	6% 13% 6% 14% 9% 6% 5% 3 5% 6% 26%	3248
	11th to 20th	Day	6% 10% 6% 16% 9% 7% 8% 8% 9% 6% 15%	3441
	21st to end	Day	4 13% 9% 17% 7% 6% 5% 4 4 7% 23%	4467
February	1st to 10th	Day	7% 15% 5% 11% 7% 5% 5% 4 6% 7% 28%	1800
	11th to 20th	Day	8% 10% 4 8% 7% 7% 5% 5% 7% 5% 35%	1754
	21st to end	Day	9% 12% 4 11% 7% 6% 5% 3 5% 6% 31%	1485
March	1st to 10th	Day	10% 9% 3 8% 5% 4 5% 3 6% 9% 39%	4890
	11th to 20th	Day	9% 9% 3 9% 5% 5% 5% 4 6% 8% 36%	4980
	21st to end	Day	22% 13% 3 8% 4 4 4 3 4 6% 30%	5462
April	1st to 10th	Day	17% 12% 3 8% 5% 4 4 3 5% 6% 34%	2398
	11th to 20th	Day	17% 13% 4 7% 4 5% 4 3 5% 5% 32%	2477
	21st to end	Day	22% 9% 3 6% 5% 4 4 4 4 5% 33%	2600
May	1st to 10th	Day	15% 7% 2 5% 3 3 4 3 5% 6% 48%	6133
	11th to 20th	Day	16% 10% 2 6% 4 3 4 3 5% 6% 41%	6319
	21st to end	Day	14% 8% 3 6% 4 4 5% 4 5% 8% 38%	6935
June	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	2923
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 4 5% 7% 37%	3000
	21st to end	Day	11% 6% 2 5% 5% 6% 7% 5% 7% 10% 38%	3000
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 5% 8% 10% 44%	6800
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 6% 10% 48%	6695
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 7% 10% 46%	6888
August	1st to 10th	Day	12% 5% 2 5% 4 5% 4 4 7% 8% 44%	4234
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 7% 9% 42%	4171
	21st to end	Day	14% 7% 2 6% 4 5% 4 4 5% 7% 42%	4580
September	1st to 10th	Day	10% 5% 2 6% 4 4 4 4 6% 9% 45%	2400
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 3 6% 7% 41%	2321
	21st to end	Day	15% 7% 2 6% 4 4 4 3 5% 6% 43%	2135
October	1st to 10th	Day	17% 8% 3 6% 3 4 4 3 6% 7% 39%	2000
	11th to 20th	Day	16% 14% 4 7% 4 3 4 2 4 5% 36%	2000
	21st to end	Day	19% 13% 5% 7% 4 3 4 4 4 6% 30%	2156
November	1st to 10th	Day	12% 13% 5% 11% 6% 4 4 3 5% 6% 31%	1647
	11th to 20th	Day	13% 16% 6% 13% 6% 5% 3 3 5% 5% 26%	1680
	21st to end	Day	12% 12% 6% 12% 7% 5% 5% 4 6% 6% 25%	1680
December	1st to 10th	Day	9% 13% 5% 15% 14% 8% 5% 3 4 6% 18%	2690
	11th to 20th	Day	8% 18% 8% 11% 5% 5% 4 4 5% 6% 26%	2970
	21st to end	Day	17% 18% 6% 20% 7% 5% 3 2 3 4 14%	3575
January	1st to 10th	Night	6% 9% 5% 16% 11% 6% 5% 4 5% 6% 28%	6937
	11th to 20th	Night	6% 12% 5% 11% 8% 7% 9% 8% 8% 6% 20%	6656
	21st to end	Night	6% 15% 10% 13% 6% 5% 6% 4 5% 6% 24%	6508
February	1st to 10th	Night	6% 11% 5% 10% 7% 5% 5% 5% 6% 7% 33%	2600
	11th to 20th	Night	6% 9% 4 9% 6% 5% 5% 5% 6% 8% 37%	2533
	21st to end	Night	10% 12% 5% 9% 6% 6% 5% 3 6% 6% 32%	2145
March	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 6% 47%	5007
	11th to 20th	Night	10% 10% 3 10% 6% 5% 5% 4 6% 7% 33%	4980
	21st to end	Night	21% 14% 5% 10% 4 3 4 3 4 5% 28%	5467
April	1st to 10th	Night	15% 11% 3 7% 5% 4 4 3 4 6% 36%	2001
	11th to 20th	Night	17% 12% 4 7% 4 4 4 2 4 6% 36%	1869
	21st to end	Night	20% 10% 3 7% 4 3 3 4 5% 6% 36%	1800
May	1st to 10th	Night	13% 7% 2 6% 3 4 3 2 4 5% 50%	3781
	11th to 20th	Night	14% 7% 3 6% 3 3 4 3 5% 5% 48%	3596
	21st to end	Night	15% 8% 2 6% 5% 5% 4 4 6% 7% 39%	3942
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 7% 9% 45%	1472
	11th to 20th	Night	11% 5% 2 6% 5% 5% 4 5% 6% 8% 44%	1400
	21st to end	Night	12% 6% 2 5% 4 3 4 4 6% 7% 47%	1400
July	1st to 10th	Night	8% 4 1 5% 4 4 5% 4 8% 10% 47%	3178
	11th to 20th	Night	7% 3 1 4 3 3 3 3 6% 9% 57%	3265
	21st to end	Night	8% 5% 2 5% 5% 4 5% 4 6% 9% 47%	3981
August	1st to 10th	Night	10% 6% 2 5% 4 4 4 3 6% 8% 49%	2926
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 6% 7% 49%	2888
	21st to end	Night	12% 7% 2 5% 3 4 4 4 6% 8% 45%	3325
September	1st to 10th	Night	9% 4 2 4 4 4 4 5% 5% 8% 51%	2000
	11th to 20th	Night	10% 5% 2 5% 5% 4 4 2 6% 8% 50%	2075
	21st to end	Night	13% 5% 2 5% 5% 3 3 2 4 7% 50%	2245
October	1st to 10th	Night	15% 7% 2 6% 4 3 4 3 6% 6% 45%	2400
	11th to 20th	Night	15% 10% 4 8% 4 4 4 3 5% 6% 37%	2400
	21st to end	Night	18% 11% 4 8% 4 4 4 3 6% 5% 33%	2678
November	1st to 10th	Night	13% 11% 4 8% 6% 4 5% 3 4 7% 34%	2871
	11th to 20th	Night	15% 12% 5% 10% 5% 4 4 4 5% 6% 30%	2940
	21st to end	Night	11% 10% 5% 12% 8% 5% 4 4 6% 6% 29%	2940
December	1st to 10th	Night	6% 11% 6% 16% 11% 10% 6% 4 5% 6% 18%	4720
	11th to 20th	Night	10% 15% 7% 14% 7% 5% 4 5% 6% 6% 22%	5452
	21st to end	Night	20% 19% 6% 17% 5% 4 3 2 3 4 16%	7645

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	58% 6% 8% 16% 12%	3249
	11th to 20th	Day	61% 7% 7% 18% 6%	3441
	21st to end	Day	60% 7% 11% 16% 6%	4467
February	1st to 10th	Day	54% 5% 10% 21% 9% 1	1800
	11th to 20th	Day	48% 7% 13% 21% 9% 1	1763
	21st to end	Day	52% 6% 13% 17% 11% 1	1485
March	1st to 10th	Day	40% 7% 15% 23% 11% 3	4890
	11th to 20th	Day	43% 6% 15% 26% 9%	4980
	21st to end	Day	56% 6% 10% 20% 8% 1	5464
April	1st to 10th	Day	51% 5% 10% 19% 12% 2	2398
	11th to 20th	Day	52% 7% 12% 18% 11% 1	2477
	21st to end	Day	52% 6% 10% 21% 11%	2600
May	1st to 10th	Day	35% 6% 14% 25% 17% 1	6171
	11th to 20th	Day	42% 7% 12% 21% 13% 5%	6323
	21st to end	Day	40% 9% 12% 26% 12% 1	6949
June	1st to 10th	Day	36% 9% 18% 27% 9% 1	2923
	11th to 20th	Day	44% 8% 14% 21% 12% 1	3000
	21st to end	Day	38% 10% 17% 26% 9% 1	3000
July	1st to 10th	Day	31% 10% 21% 28% 10%	6726
	11th to 20th	Day	31% 7% 17% 34% 10% 1	6614
	21st to end	Day	31% 8% 19% 30% 12%	6692
August	1st to 10th	Day	35% 7% 16% 28% 13% 1	4220
	11th to 20th	Day	37% 8% 16% 30% 8%	4210
	21st to end	Day	40% 8% 15% 26% 10% 1	4579
September	1st to 10th	Day	34% 8% 15% 32% 10%	2400
	11th to 20th	Day	39% 8% 20% 25% 8%	2321
	21st to end	Day	40% 7% 12% 32% 8% 1	2135
October	1st to 10th	Day	34% 5% 14% 31% 15% 1	3260
	11th to 20th	Day	44% 5% 10% 22% 17% 1	3240
	21st to end	Day	52% 5% 12% 24% 6%	3459
November	1st to 10th	Day	53% 7% 11% 18% 10% 1	1647
	11th to 20th	Day	59% 5% 13% 16% 7% 1	1680
	21st to end	Day	55% 8% 13% 16% 5% 1	1680
December	1st to 10th	Day	67% 6% 11% 12% 3 1	2690
	11th to 20th	Day	58% 5% 9% 19% 9%	2967
	21st to end	Day	75% 5% 6% 10% 4	3575
January	1st to 10th	Night	56% 6% 10% 16% 11%	6937
	11th to 20th	Night	57% 8% 11% 13% 10%	6656
	21st to end	Night	58% 6% 13% 18% 4	6508
February	1st to 10th	Night	48% 6% 12% 22% 11% 1	2600
	11th to 20th	Night	43% 7% 13% 24% 12% 1	2534
	21st to end	Night	51% 8% 10% 20% 10% 1	2145
March	1st to 10th	Night	36% 6% 17% 21% 16% 3	5007
	11th to 20th	Night	47% 8% 12% 22% 12%	4980
	21st to end	Night	60% 4 10% 17% 9% 1	5467
April	1st to 10th	Night	48% 6% 10% 19% 15% 1	2001
	11th to 20th	Night	50% 6% 8% 20% 16% 1	1869
	21st to end	Night	48% 6% 11% 21% 13% 2	1800
May	1st to 10th	Night	34% 7% 13% 28% 17% 1	3808
	11th to 20th	Night	37% 7% 12% 22% 18% 5%	3597
	21st to end	Night	42% 8% 11% 25% 14% 1	3950
June	1st to 10th	Night	32% 10% 20% 27% 10% 2	1472
	11th to 20th	Night	35% 9% 16% 23% 16% 1	1400
	21st to end	Night	35% 7% 16% 29% 12% 1	1400
July	1st to 10th	Night	29% 10% 19% 29% 11%	3145
	11th to 20th	Night	23% 7% 20% 37% 12% 2	3226
	21st to end	Night	32% 8% 18% 28% 13% 1	3866
August	1st to 10th	Night	33% 7% 16% 26% 15% 3	2916
	11th to 20th	Night	33% 7% 15% 34% 11% 1	2915
	21st to end	Night	35% 8% 18% 28% 11% 1	3325
September	1st to 10th	Night	30% 7% 17% 34% 11% 1	2000
	11th to 20th	Night	31% 7% 18% 31% 11%	2075
	21st to end	Night	34% 6% 12% 35% 12%	2245
October	1st to 10th	Night	28% 4 9% 36% 19% 4	3920
	11th to 20th	Night	40% 5% 10% 24% 19% 1	3899
	21st to end	Night	47% 6% 13% 22% 10%	4326
November	1st to 10th	Night	49% 6% 12% 23% 9% 1	2871
	11th to 20th	Night	54% 7% 13% 17% 8% 1	2940
	21st to end	Night	53% 7% 16% 18% 5% 1	2940
December	1st to 10th	Night	65% 7% 12% 12% 3	4720
	11th to 20th	Night	62% 5% 10% 15% 7% 1	5454
	21st to end	Night	73% 4 6% 12% 4	7645

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% 10% 38% 31% 9% 2	330
	11th to 20th	Day	17% 9% 34% 33% 7%	318
	21st to end	Day	12% 10% 38% 24% 13% 3	330
February	1st to 10th	Day	17% 14% 41% 21% 7%	300
	11th to 20th	Day	15% 15% 37% 23% 8% 2	300
	21st to end	Day	11% 14% 40% 32% 3	249
March	1st to 10th	Day	15% 13% 41% 23% 6% 1	300
	11th to 20th	Day	16% 7% 38% 24% 12% 2	300
	21st to end	Day	24% 14% 30% 18% 11% 2	330
April	1st to 10th	Day	24% 13% 32% 24% 7% 1	498
	11th to 20th	Day	25% 13% 28% 24% 10% 1	595
	21st to end	Day	24% 12% 29% 23% 12% 1	700
May	1st to 10th	Day	19% 14% 30% 23% 11% 3	703
	11th to 20th	Day	20% 10% 29% 27% 11% 3	725
	21st to end	Day	17% 9% 26% 31% 14% 3	789
June	1st to 10th	Day	11% 8% 31% 30% 17% 3	730
	11th to 20th	Day	17% 9% 35% 26% 11% 2	730
	21st to end	Day	13% 8% 32% 27% 16% 4	730
July	1st to 10th	Day	7% 5% 24% 29% 27% 8%	721
	11th to 20th	Day	9% 6% 30% 25% 20% 8%	718
	21st to end	Day	6% 5% 26% 32% 22% 8%	794
August	1st to 10th	Day	12% 5% 23% 30% 24% 6%	726
	11th to 20th	Day	12% 6% 21% 30% 24% 6%	715
	21st to end	Day	11% 9% 24% 32% 19% 5%	747
September	1st to 10th	Day	10% 7% 29% 31% 18% 5%	530
	11th to 20th	Day	11% 7% 28% 32% 16% 5%	451
	21st to end	Day	17% 11% 32% 22% 12% 6%	330
October	1st to 10th	Day	19% 11% 31% 25% 9% 5%	330
	11th to 20th	Day	18% 15% 37% 24% 5% 1	330
	21st to end	Day	26% 14% 37% 16% 6% 1	363
November	1st to 10th	Day	18% 15% 35% 24% 8% 1	330
	11th to 20th	Day	20% 16% 42% 18% 4	330
	21st to end	Day	20% 11% 41% 22% 6%	330
December	1st to 10th	Day	15% 9% 41% 26% 8% 1	330
	11th to 20th	Day	18% 19% 35% 25% 4	330
	21st to end	Day	24% 10% 36% 22% 6% 1	363
January	1st to 10th	Night	11% 12% 36% 31% 9% 2	1050
	11th to 20th	Night	15% 10% 36% 30% 8% 1	1031
	21st to end	Night	16% 10% 38% 28% 8% 1	1100
February	1st to 10th	Night	12% 9% 39% 31% 9% 1	1000
	11th to 20th	Night	10% 10% 44% 26% 9% 1	979
	21st to end	Night	16% 8% 36% 29% 10% 1	825
March	1st to 10th	Night	14% 11% 36% 30% 8% 1	640
	11th to 20th	Night	16% 10% 42% 27% 6% 1	600
	21st to end	Night	21% 10% 27% 30% 10% 2	660
April	1st to 10th	Night	20% 9% 36% 29% 6%	600
	11th to 20th	Night	22% 8% 32% 28% 8% 1	593
	21st to end	Night	24% 6% 31% 30% 9% 1	600
May	1st to 10th	Night	18% 10% 34% 29% 8% 1	600
	11th to 20th	Night	16% 8% 31% 36% 8% 1	591
	21st to end	Night	14% 8% 26% 38% 13%	650
June	1st to 10th	Night	13% 6% 29% 38% 14% 1	600
	11th to 20th	Night	12% 5% 33% 41% 8%	600
	21st to end	Night	14% 6% 24% 40% 16% 1	600
July	1st to 10th	Night	5% 2 23% 42% 26% 2	585
	11th to 20th	Night	7% 3 27% 42% 19% 1	582
	21st to end	Night	5% 3 23% 45% 22% 2	657
August	1st to 10th	Night	9% 3 17% 47% 21% 2	597
	11th to 20th	Night	12% 4 20% 38% 25% 2	594
	21st to end	Night	12% 5% 24% 37% 20% 2	660
September	1st to 10th	Night	10% 6% 24% 40% 19% 2	600
	11th to 20th	Night	12% 6% 30% 32% 20% 1	600
	21st to end	Night	14% 7% 33% 29% 15% 2	645
October	1st to 10th	Night	18% 10% 31% 30% 11% 1	800
	11th to 20th	Night	20% 12% 34% 28% 6% 1	800
	21st to end	Night	23% 12% 32% 28% 6%	896
November	1st to 10th	Night	18% 10% 33% 30% 9%	1025
	11th to 20th	Night	19% 12% 35% 25% 8% 1	1050
	21st to end	Night	17% 13% 39% 25% 6%	1050
December	1st to 10th	Night	15% 11% 34% 31% 8% 1	1050
	11th to 20th	Night	19% 12% 37% 25% 7%	1050
	21st to end	Night	24% 11% 33% 25% 6% 1	1155

Page generated at 2026-01-14 00:14:24. Version ac07

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