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 2024-06-17.

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	13% 10% 4 8% 5% 5% 5% 4 6% 7% 35%	89343
	Night	12% 10% 4 9% 5% 5% 4 4 5% 6% 35%	89551
Transparency	Day	46% 8% 14% 22% 9% 1	89084
	Night	47% 7% 13% 22% 10% 1	89415
Seeing	Day	15% 9% 31% 27% 14% 3	15521
	Night	15% 8% 32% 32% 11% 1	25515

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	7% 16% 7% 15% 8% 6% 4 3 5% 7% 22%	2218
	11th to 20th	Day	6% 10% 6% 16% 11% 8% 9% 7% 6% 6% 16%	2373
	21st to end	Day	6% 15% 11% 17% 7% 6% 5% 4 4 7% 18%	3114
February	1st to 10th	Day	7% 15% 5% 11% 7% 5% 5% 4 6% 7% 29%	1710
	11th to 20th	Day	8% 11% 4 8% 7% 7% 5% 5% 7% 5% 35%	1664
	21st to end	Day	10% 13% 4 11% 7% 6% 5% 3 5% 6% 31%	1413
March	1st to 10th	Day	10% 11% 4 10% 6% 5% 5% 4 5% 7% 34%	3404
	11th to 20th	Day	9% 9% 4 10% 5% 4 4 4 6% 7% 38%	3480
	21st to end	Day	21% 13% 4 9% 5% 4 4 3 4 7% 27%	3814
April	1st to 10th	Day	17% 12% 3 8% 6% 4 4 3 5% 6% 33%	2278
	11th to 20th	Day	18% 13% 4 7% 4 5% 4 3 5% 6% 32%	2352
	21st to end	Day	22% 10% 3 6% 5% 4 4 4 4 5% 33%	2470
May	1st to 10th	Day	19% 8% 2 6% 4 4 4 4 5% 7% 37%	4269
	11th to 20th	Day	15% 8% 2 6% 4 4 4 3 6% 7% 41%	4399
	21st to end	Day	17% 7% 3 7% 5% 4 5% 4 6% 8% 34%	4824
June	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 42%	2777
	11th to 20th	Day	15% 7% 2 6% 5% 5% 5% 4 5% 7% 39%	2794
	21st to end	Day	10% 6% 2 5% 5% 6% 7% 5% 7% 10% 38%	2700
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 5% 7% 8% 50%	2700
	11th to 20th	Day	10% 5% 2 5% 4 5% 5% 4 7% 8% 45%	2660
	21st to end	Day	6% 4 2 5% 4 4 4 5% 7% 10% 50%	2734
August	1st to 10th	Day	9% 5% 2 5% 5% 5% 4 4 7% 8% 46%	2328
	11th to 20th	Day	11% 7% 2 7% 4 4 5% 3 6% 8% 44%	2301
	21st to end	Day	12% 5% 2 5% 4 4 4 4 5% 7% 48%	2524
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 6% 8% 45%	2160
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 3 6% 6% 41%	2089
	21st to end	Day	16% 7% 2 6% 4 4 5% 4 5% 6% 40%	1922
October	1st to 10th	Day	18% 9% 3 6% 4 4 4 3 5% 7% 37%	1800
	11th to 20th	Day	17% 15% 4 7% 4 4 4 2 4 5% 35%	1800
	21st to end	Day	19% 12% 5% 7% 4 3 4 4 4 6% 31%	1941
November	1st to 10th	Day	12% 13% 5% 10% 6% 4 4 3 5% 6% 32%	1487
	11th to 20th	Day	12% 16% 6% 13% 7% 5% 3 3 5% 5% 24%	1520
	21st to end	Day	13% 12% 5% 10% 7% 5% 5% 4 7% 7% 25%	1520
December	1st to 10th	Day	10% 15% 5% 12% 8% 6% 6% 3 4 6% 23%	1520
	11th to 20th	Day	10% 14% 7% 13% 7% 6% 6% 4 5% 5% 24%	1842
	21st to end	Day	21% 17% 6% 14% 6% 5% 3 2 4 4 18%	2442
January	1st to 10th	Night	9% 11% 5% 14% 9% 5% 4 4 6% 6% 27%	4737
	11th to 20th	Night	6% 13% 5% 13% 10% 8% 10% 5% 5% 6% 20%	4594
	21st to end	Night	8% 18% 11% 15% 5% 4 5% 3 4 5% 21%	4550
February	1st to 10th	Night	6% 10% 5% 10% 7% 5% 5% 5% 6% 7% 34%	2470
	11th to 20th	Night	6% 10% 4 9% 6% 5% 5% 5% 6% 7% 37%	2403
	21st to end	Night	10% 12% 5% 9% 6% 6% 5% 3 5% 6% 32%	2041
March	1st to 10th	Night	8% 9% 3 7% 5% 4 4 3 5% 7% 44%	3479
	11th to 20th	Night	9% 10% 3 10% 6% 5% 5% 4 5% 6% 37%	3480
	21st to end	Night	21% 15% 5% 10% 5% 3 3 3 4 4 27%	3817
April	1st to 10th	Night	15% 11% 3 7% 5% 4 4 3 4 6% 36%	1901
	11th to 20th	Night	18% 11% 4 7% 4 4 4 2 4 6% 36%	1775
	21st to end	Night	19% 10% 3 8% 4 3 3 4 5% 6% 36%	1710
May	1st to 10th	Night	17% 9% 3 7% 3 4 3 3 5% 6% 40%	2635
	11th to 20th	Night	15% 6% 3 6% 3 3 5% 4 5% 6% 45%	2506
	21st to end	Night	17% 8% 2 6% 5% 5% 5% 4 5% 7% 36%	2743
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 7% 9% 45%	1399
	11th to 20th	Night	10% 5% 2 5% 5% 5% 3 5% 6% 8% 45%	1309
	21st to end	Night	11% 6% 2 5% 4 3 5% 4 6% 7% 48%	1260
July	1st to 10th	Night	3 3 1 4 3 3 5% 4 7% 9% 57%	1260
	11th to 20th	Night	6% 4 2 5% 3 4 3 4 6% 7% 57%	1296
	21st to end	Night	4 3 1 4 4 3 5% 5% 6% 8% 58%	1582
August	1st to 10th	Night	7% 4 1 4 4 4 4 4 7% 9% 52%	1611
	11th to 20th	Night	11% 5% 2 5% 4 3 4 3 5% 5% 53%	1600
	21st to end	Night	11% 5% 1 3 3 3 4 3 5% 7% 54%	1831
September	1st to 10th	Night	9% 4 2 4 4 4 4 5% 4 8% 51%	1800
	11th to 20th	Night	10% 5% 2 5% 5% 4 4 3 6% 8% 50%	1867
	21st to end	Night	15% 5% 2 5% 5% 3 3 3 4 7% 48%	2020
October	1st to 10th	Night	16% 7% 2 6% 5% 4 4 3 6% 6% 42%	2160
	11th to 20th	Night	15% 10% 4 8% 4 4 4 3 5% 6% 36%	2160
	21st to end	Night	19% 11% 4 8% 4 4 4 3 6% 5% 33%	2409
November	1st to 10th	Night	13% 11% 4 8% 6% 4 5% 3 5% 7% 35%	2591
	11th to 20th	Night	15% 12% 5% 11% 5% 5% 4 4 5% 6% 28%	2660
	21st to end	Night	12% 10% 4 10% 7% 5% 4 4 6% 7% 31%	2660
December	1st to 10th	Night	9% 14% 6% 14% 7% 7% 5% 4 5% 6% 24%	2660
	11th to 20th	Night	11% 15% 6% 12% 7% 6% 5% 4 6% 7% 24%	3350
	21st to end	Night	22% 19% 5% 12% 5% 4 3 3 4 5% 19%	5225

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	61% 7% 10% 17% 5%	2219
	11th to 20th	Day	63% 9% 9% 15% 4	2373
	21st to end	Day	64% 8% 9% 14% 5%	3114
February	1st to 10th	Day	53% 5% 10% 22% 9% 1	1710
	11th to 20th	Day	48% 7% 14% 21% 9% 1	1673
	21st to end	Day	53% 6% 12% 16% 12% 1	1413
March	1st to 10th	Day	47% 9% 13% 21% 9%	3404
	11th to 20th	Day	42% 7% 14% 28% 9%	3480
	21st to end	Day	57% 7% 11% 20% 4	3814
April	1st to 10th	Day	51% 6% 11% 19% 12% 2	2278
	11th to 20th	Day	52% 7% 12% 18% 11% 1	2352
	21st to end	Day	52% 7% 10% 20% 10%	2470
May	1st to 10th	Day	43% 8% 15% 21% 12% 2	4307
	11th to 20th	Day	39% 8% 15% 25% 10% 3	4403
	21st to end	Day	43% 11% 15% 23% 8% 1	4837
June	1st to 10th	Day	36% 9% 18% 27% 10% 1	2777
	11th to 20th	Day	42% 8% 14% 22% 13% 1	2794
	21st to end	Day	37% 11% 18% 26% 8% 1	2700
July	1st to 10th	Day	28% 9% 17% 31% 15% 1	2626
	11th to 20th	Day	32% 10% 16% 26% 13% 2	2579
	21st to end	Day	27% 9% 19% 28% 15% 1	2582
August	1st to 10th	Day	34% 8% 17% 29% 10% 2	2314
	11th to 20th	Day	36% 9% 18% 27% 9% 1	2301
	21st to end	Day	34% 8% 14% 29% 14% 1	2524
September	1st to 10th	Day	35% 8% 14% 32% 11%	2160
	11th to 20th	Day	40% 9% 19% 25% 8%	2089
	21st to end	Day	43% 7% 13% 30% 7%	1922
October	1st to 10th	Day	46% 8% 15% 23% 7% 1	1800
	11th to 20th	Day	51% 6% 11% 22% 9% 2	1800
	21st to end	Day	54% 7% 12% 20% 7%	1941
November	1st to 10th	Day	52% 7% 12% 18% 10% 1	1487
	11th to 20th	Day	61% 5% 13% 13% 7% 1	1520
	21st to end	Day	54% 9% 14% 16% 5% 2	1520
December	1st to 10th	Day	61% 7% 13% 14% 5%	1520
	11th to 20th	Day	60% 8% 11% 17% 4	1839
	21st to end	Day	70% 6% 6% 12% 5%	2442
January	1st to 10th	Night	55% 7% 12% 20% 5%	4737
	11th to 20th	Night	61% 9% 13% 12% 5% 1	4594
	21st to end	Night	64% 6% 9% 17% 5%	4550
February	1st to 10th	Night	48% 6% 12% 23% 11% 1	2470
	11th to 20th	Night	44% 8% 13% 24% 11% 1	2404
	21st to end	Night	51% 8% 10% 20% 10% 1	2041
March	1st to 10th	Night	38% 7% 16% 22% 14% 2	3479
	11th to 20th	Night	43% 8% 12% 23% 13%	3480
	21st to end	Night	61% 5% 9% 17% 7% 1	3817
April	1st to 10th	Night	48% 6% 10% 19% 15% 1	1901
	11th to 20th	Night	49% 6% 7% 20% 16% 1	1775
	21st to end	Night	48% 6% 11% 21% 13% 2	1710
May	1st to 10th	Night	42% 8% 12% 25% 11% 2	2662
	11th to 20th	Night	36% 8% 12% 24% 17% 3	2507
	21st to end	Night	44% 9% 13% 21% 12% 1	2751
June	1st to 10th	Night	32% 10% 21% 26% 10% 2	1399
	11th to 20th	Night	34% 9% 16% 23% 17% 1	1309
	21st to end	Night	33% 8% 17% 29% 12% 2	1260
July	1st to 10th	Night	20% 10% 20% 33% 16% 1	1225
	11th to 20th	Night	26% 8% 16% 30% 16% 5%	1254
	21st to end	Night	21% 8% 20% 32% 17% 3	1494
August	1st to 10th	Night	27% 8% 18% 33% 10% 4	1601
	11th to 20th	Night	31% 8% 16% 30% 14% 1	1600
	21st to end	Night	28% 7% 15% 31% 18% 1	1831
September	1st to 10th	Night	30% 7% 16% 33% 13% 1	1800
	11th to 20th	Night	32% 8% 17% 31% 12%	1867
	21st to end	Night	36% 6% 13% 34% 11%	2020
October	1st to 10th	Night	42% 7% 13% 27% 11% 1	2160
	11th to 20th	Night	46% 8% 12% 24% 10%	2160
	21st to end	Night	51% 7% 12% 21% 8%	2409
November	1st to 10th	Night	48% 6% 12% 23% 9% 1	2591
	11th to 20th	Night	55% 7% 13% 15% 8% 1	2660
	21st to end	Night	50% 8% 17% 19% 5% 1	2660
December	1st to 10th	Night	59% 7% 13% 15% 4 1	2660
	11th to 20th	Night	58% 7% 12% 15% 6% 1	3352
	21st to end	Night	68% 5% 8% 13% 5%	5225

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	11% 9% 36% 32% 9% 3	270
	11th to 20th	Day	16% 8% 33% 34% 9%	270
	21st to end	Day	12% 7% 38% 25% 14% 3	297
February	1st to 10th	Day	16% 14% 40% 22% 7%	270
	11th to 20th	Day	17% 15% 36% 23% 7% 2	270
	21st to end	Day	12% 12% 39% 33% 3	225
March	1st to 10th	Day	15% 13% 40% 24% 6% 1	270
	11th to 20th	Day	17% 6% 38% 25% 12% 3	270
	21st to end	Day	23% 14% 29% 19% 12% 3	297
April	1st to 10th	Day	23% 13% 32% 24% 7% 1	458
	11th to 20th	Day	25% 12% 27% 24% 11% 1	550
	21st to end	Day	24% 11% 28% 24% 12% 1	650
May	1st to 10th	Day	20% 14% 30% 23% 10% 2	653
	11th to 20th	Day	19% 10% 30% 27% 11% 3	675
	21st to end	Day	17% 10% 27% 31% 13% 3	734
June	1st to 10th	Day	11% 7% 31% 30% 17% 3	680
	11th to 20th	Day	16% 9% 35% 27% 11% 2	662
	21st to end	Day	11% 7% 32% 28% 18% 5%	630
July	1st to 10th	Day	7% 4 24% 29% 28% 8%	621
	11th to 20th	Day	9% 6% 31% 26% 19% 8%	618
	21st to end	Day	6% 4 26% 32% 24% 8%	684
August	1st to 10th	Day	10% 4 23% 30% 27% 6%	626
	11th to 20th	Day	11% 6% 22% 31% 23% 7%	615
	21st to end	Day	11% 9% 23% 32% 20% 6%	643
September	1st to 10th	Day	11% 6% 28% 32% 19% 4	450
	11th to 20th	Day	12% 7% 29% 30% 17% 5%	379
	21st to end	Day	20% 12% 33% 21% 11% 3	270
October	1st to 10th	Day	21% 10% 28% 24% 10% 6%	270
	11th to 20th	Day	16% 13% 39% 25% 7% 1	270
	21st to end	Day	26% 12% 39% 16% 6% 1	297
November	1st to 10th	Day	17% 13% 36% 25% 9% 1	270
	11th to 20th	Day	19% 14% 43% 19% 4	270
	21st to end	Day	21% 11% 42% 21% 5%	270
December	1st to 10th	Day	15% 9% 41% 26% 9% 1	270
	11th to 20th	Day	17% 17% 35% 27% 4	270
	21st to end	Day	24% 10% 34% 24% 6% 1	297
January	1st to 10th	Night	12% 11% 36% 31% 9% 2	950
	11th to 20th	Night	16% 8% 36% 30% 8% 1	950
	21st to end	Night	17% 10% 36% 28% 8% 1	1045
February	1st to 10th	Night	11% 9% 39% 31% 10% 1	950
	11th to 20th	Night	10% 10% 43% 26% 10% 1	929
	21st to end	Night	16% 8% 36% 29% 10% 1	785
March	1st to 10th	Night	14% 11% 36% 29% 8% 1	608
	11th to 20th	Night	15% 9% 42% 27% 6% 1	570
	21st to end	Night	21% 10% 26% 30% 10% 2	627
April	1st to 10th	Night	19% 8% 37% 29% 6%	570
	11th to 20th	Night	23% 8% 31% 29% 9% 1	563
	21st to end	Night	23% 6% 31% 30% 9% 1	570
May	1st to 10th	Night	18% 10% 34% 29% 8% 1	570
	11th to 20th	Night	16% 8% 31% 36% 8% 1	561
	21st to end	Night	14% 8% 27% 38% 13%	617
June	1st to 10th	Night	12% 5% 29% 38% 14% 1	570
	11th to 20th	Night	11% 4 34% 42% 9%	561
	21st to end	Night	13% 6% 22% 41% 17% 1	540
July	1st to 10th	Night	4 2 23% 43% 26% 2	525
	11th to 20th	Night	7% 3 28% 42% 19% 1	522
	21st to end	Night	4 3 23% 45% 23% 2	591
August	1st to 10th	Night	8% 3 15% 50% 22% 2	537
	11th to 20th	Night	11% 4 20% 38% 25% 2	534
	21st to end	Night	12% 5% 23% 38% 21% 2	594
September	1st to 10th	Night	10% 5% 23% 41% 19% 1	540
	11th to 20th	Night	12% 6% 29% 32% 20% 1	540
	21st to end	Night	16% 7% 34% 28% 14% 2	580
October	1st to 10th	Night	19% 9% 30% 30% 11% 1	720
	11th to 20th	Night	20% 10% 34% 29% 6% 1	720
	21st to end	Night	23% 11% 32% 28% 6%	806
November	1st to 10th	Night	18% 9% 33% 31% 9%	925
	11th to 20th	Night	19% 12% 35% 25% 8% 1	950
	21st to end	Night	17% 12% 39% 25% 6%	950
December	1st to 10th	Night	15% 11% 33% 31% 8% 1	950
	11th to 20th	Night	20% 10% 37% 26% 7% 1	950
	21st to end	Night	25% 11% 33% 25% 5% 1	1045

Page generated at 2024-06-14 12:06:10. Version ac07

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