Pigeon Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pigeon Lake Observatory clear sky chart from 2005-11-06 to 2024-11-28.

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% 8% 3 7% 5% 4 5% 4 6% 7% 38%	101620
	Night	13% 9% 3 7% 5% 4 4 4 5% 7% 39%	97976
Transparency	Day	43% 6% 12% 25% 13% 1	105152
	Night	44% 6% 11% 24% 14% 2	102585
Seeing	Day	16% 11% 31% 26% 12% 4	16014
	Night	17% 10% 31% 29% 12% 1	25888

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	11% 14% 4 8% 5% 4 6% 4 6% 7% 31%	2527
	11th to 20th	Day	12% 12% 5% 11% 6% 6% 6% 6% 7% 7% 22%	2530
	21st to end	Day	17% 16% 7% 12% 5% 4 4 3 4 5% 23%	2783
February	1st to 10th	Day	10% 12% 5% 10% 5% 4 4 3 6% 7% 33%	1672
	11th to 20th	Day	12% 11% 4 7% 5% 3 5% 4 5% 6% 38%	1840
	21st to end	Day	12% 13% 4 8% 5% 5% 5% 4 5% 7% 33%	1570
March	1st to 10th	Day	12% 9% 3 6% 4 5% 4 3 5% 7% 43%	3120
	11th to 20th	Day	11% 9% 4 8% 3 3 4 4 6% 7% 42%	3251
	21st to end	Day	21% 13% 4 10% 5% 3 4 3 4 5% 29%	4165
April	1st to 10th	Day	14% 14% 4 8% 5% 5% 5% 3 5% 6% 30%	2280
	11th to 20th	Day	19% 9% 3 7% 5% 5% 5% 4 5% 6% 34%	2254
	21st to end	Day	17% 9% 4 8% 5% 4 4 4 5% 6% 33%	2441
May	1st to 10th	Day	14% 8% 2 6% 5% 4 5% 4 6% 6% 40%	4113
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 6% 7% 46%	4399
	21st to end	Day	11% 6% 3 7% 5% 5% 4 4 6% 8% 42%	4824
June	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	12% 6% 2 5% 5% 5% 4 4 6% 8% 42%	2660
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 9% 44%	2660
July	1st to 10th	Day	13% 6% 2 6% 4 5% 6% 4 8% 10% 36%	4440
	11th to 20th	Day	5% 4 1 4 4 4 6% 5% 7% 10% 51%	4440
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 47%	4813
August	1st to 10th	Day	9% 6% 3 6% 4 4 5% 4 6% 9% 43%	4423
	11th to 20th	Day	11% 4 2 6% 5% 4 4 4 6% 8% 46%	3896
	21st to end	Day	10% 6% 2 7% 5% 4 5% 4 6% 7% 43%	4180
September	1st to 10th	Day	11% 5% 2 7% 5% 4 5% 3 6% 8% 44%	2280
	11th to 20th	Day	11% 4 2 5% 4 4 4 3 7% 8% 47%	2158
	21st to end	Day	12% 6% 3 7% 4 5% 5% 4 6% 7% 42%	2090
October	1st to 10th	Day	14% 6% 2 6% 4 4 5% 3 4 7% 45%	2028
	11th to 20th	Day	21% 8% 3 7% 6% 6% 5% 3 5% 7% 29%	1843
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 3 5% 6% 34%	1881
November	1st to 10th	Day	13% 8% 3 6% 3 4 5% 4 5% 8% 41%	1762
	11th to 20th	Day	11% 11% 4 10% 5% 5% 5% 5% 5% 7% 32%	1800
	21st to end	Day	17% 12% 3 8% 4 5% 4 3 5% 5% 35%	1616
December	1st to 10th	Day	13% 12% 4 8% 6% 6% 5% 3 6% 8% 30%	1520
	11th to 20th	Day	13% 14% 4 8% 5% 5% 5% 5% 6% 8% 29%	1918
	21st to end	Day	18% 20% 7% 11% 5% 4 4 3 4 5% 19%	2783
January	1st to 10th	Night	14% 14% 6% 9% 5% 4 4 2 3 5% 35%	4428
	11th to 20th	Night	12% 13% 4 12% 7% 5% 7% 5% 6% 7% 22%	4440
	21st to end	Night	15% 17% 6% 11% 4 5% 4 3 4 5% 26%	4884
February	1st to 10th	Night	11% 14% 4 9% 5% 5% 5% 3 4 5% 35%	2504
	11th to 20th	Night	10% 10% 3 8% 6% 4 4 4 5% 5% 39%	2224
	21st to end	Night	15% 14% 3 7% 4 3 3 3 4 5% 38%	1884
March	1st to 10th	Night	14% 8% 2 6% 4 4 3 3 5% 7% 43%	3733
	11th to 20th	Night	9% 8% 3 7% 5% 5% 5% 5% 6% 8% 41%	3724
	21st to end	Night	18% 10% 4 10% 5% 5% 4 3 4 5% 31%	3466
April	1st to 10th	Night	16% 12% 3 6% 4 4 4 3 6% 7% 35%	1900
	11th to 20th	Night	20% 9% 3 6% 4 4 3 4 5% 6% 39%	1875
	21st to end	Night	17% 8% 4 6% 5% 4 4 3 5% 6% 38%	1739
May	1st to 10th	Night	14% 6% 2 7% 5% 5% 4 4 5% 8% 39%	2768
	11th to 20th	Night	12% 5% 2 7% 5% 4 6% 4 7% 8% 39%	2506
	21st to end	Night	16% 7% 3 7% 4 4 3 4 5% 7% 40%	2743
June	1st to 10th	Night	10% 5% 2 6% 4 4 5% 4 6% 7% 46%	1520
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 5% 9% 46%	1520
	21st to end	Night	8% 5% 2 6% 4 3 5% 4 6% 9% 48%	1520
July	1st to 10th	Night	12% 7% 3 6% 4 5% 5% 3 5% 8% 43%	2530
	11th to 20th	Night	4 4 1 5% 3 3 5% 4 7% 9% 56%	2530
	21st to end	Night	5% 5% 3 6% 4 4 4 4 6% 8% 51%	2750
August	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 6% 8% 48%	2517
	11th to 20th	Night	10% 5% 2 6% 3 5% 4 4 5% 7% 50%	2929
	21st to end	Night	10% 6% 2 5% 3 4 5% 4 6% 7% 49%	3476
September	1st to 10th	Night	8% 5% 2 6% 4 3 4 3 5% 8% 53%	1900
	11th to 20th	Night	11% 4 2 4 4 4 3 3 5% 6% 55%	2001
	21st to end	Night	11% 7% 2 6% 4 4 4 3 6% 7% 46%	2090
October	1st to 10th	Night	12% 5% 2 6% 3 4 4 3 4 5% 50%	2148
	11th to 20th	Night	15% 8% 2 6% 4 4 5% 4 6% 6% 40%	2337
	21st to end	Night	16% 9% 3 6% 4 4 4 4 6% 8% 36%	2717
November	1st to 10th	Night	13% 6% 2 5% 5% 4 4 3 5% 7% 47%	2536
	11th to 20th	Night	15% 9% 3 8% 5% 5% 4 5% 6% 6% 34%	2600
	21st to end	Night	16% 10% 3 6% 4 5% 4 3 5% 5% 38%	2714
December	1st to 10th	Night	14% 11% 4 8% 6% 5% 4 4 6% 7% 32%	2660
	11th to 20th	Night	14% 11% 5% 9% 5% 5% 5% 4 5% 6% 31%	3279
	21st to end	Night	21% 18% 4 9% 5% 4 4 3 4 5% 22%	4884

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	52% 7% 16% 18% 7%	2528
	11th to 20th	Day	55% 8% 12% 20% 5%	2530
	21st to end	Day	64% 5% 9% 18% 5%	2783
February	1st to 10th	Day	51% 4 12% 21% 11% 1	1672
	11th to 20th	Day	47% 6% 11% 22% 13% 2	1850
	21st to end	Day	50% 5% 11% 21% 11% 2	1570
March	1st to 10th	Day	42% 5% 10% 24% 15% 3	3120
	11th to 20th	Day	41% 4 12% 26% 15% 2	3251
	21st to end	Day	58% 4 11% 19% 7% 1	4165
April	1st to 10th	Day	52% 7% 13% 18% 10%	2280
	11th to 20th	Day	50% 6% 9% 21% 13% 2	2254
	21st to end	Day	50% 6% 11% 19% 11% 2	2441
May	1st to 10th	Day	43% 7% 10% 23% 17% 1	4151
	11th to 20th	Day	35% 8% 10% 31% 14% 1	4403
	21st to end	Day	40% 7% 11% 22% 17% 4	4837
June	1st to 10th	Day	36% 6% 12% 28% 16% 2	2660
	11th to 20th	Day	38% 6% 14% 25% 15% 1	2660
	21st to end	Day	35% 8% 15% 26% 15% 2	2660
July	1st to 10th	Day	42% 6% 14% 26% 11% 2	4371
	11th to 20th	Day	26% 7% 16% 33% 15% 2	4365
	21st to end	Day	33% 8% 14% 23% 21% 3	4662
August	1st to 10th	Day	36% 7% 14% 30% 12% 1	4408
	11th to 20th	Day	35% 6% 12% 34% 11% 1	3935
	21st to end	Day	39% 5% 15% 24% 16% 1	4179
September	1st to 10th	Day	38% 8% 11% 27% 15% 1	2280
	11th to 20th	Day	33% 7% 14% 32% 13% 1	2158
	21st to end	Day	40% 6% 12% 30% 11%	2090
October	1st to 10th	Day	25% 3 9% 37% 24% 2	3366
	11th to 20th	Day	45% 4 9% 24% 18%	3046
	21st to end	Day	43% 4 11% 28% 13% 1	3081
November	1st to 10th	Day	41% 7% 13% 24% 14% 2	1762
	11th to 20th	Day	51% 6% 14% 20% 8% 1	1800
	21st to end	Day	51% 5% 14% 22% 7% 1	1616
December	1st to 10th	Day	51% 6% 16% 21% 6%	1520
	11th to 20th	Day	51% 6% 16% 17% 7% 3	1915
	21st to end	Day	68% 4 9% 13% 5%	2783
January	1st to 10th	Night	54% 4 10% 20% 11% 1	4428
	11th to 20th	Night	59% 9% 9% 15% 7%	4440
	21st to end	Night	60% 5% 11% 17% 6%	4884
February	1st to 10th	Night	51% 4 9% 21% 12% 2	2504
	11th to 20th	Night	46% 4 10% 24% 13% 2	2225
	21st to end	Night	48% 4 12% 20% 13% 2	1884
March	1st to 10th	Night	42% 5% 13% 28% 10% 2	3733
	11th to 20th	Night	39% 7% 11% 24% 18% 2	3724
	21st to end	Night	55% 5% 9% 20% 10% 2	3466
April	1st to 10th	Night	48% 6% 9% 19% 17% 1	1900
	11th to 20th	Night	46% 5% 7% 22% 16% 3	1875
	21st to end	Night	45% 5% 11% 22% 15% 2	1739
May	1st to 10th	Night	43% 7% 12% 19% 17% 2	2795
	11th to 20th	Night	39% 9% 11% 27% 13% 1	2507
	21st to end	Night	43% 7% 9% 19% 14% 7%	2751
June	1st to 10th	Night	35% 7% 11% 29% 17% 1	1520
	11th to 20th	Night	36% 5% 11% 26% 19% 2	1520
	21st to end	Night	32% 8% 16% 25% 17% 3	1520
July	1st to 10th	Night	40% 5% 14% 22% 12% 5%	2490
	11th to 20th	Night	24% 6% 16% 33% 19% 2	2482
	21st to end	Night	30% 7% 13% 24% 22% 3	2662
August	1st to 10th	Night	34% 6% 13% 27% 18% 2	2508
	11th to 20th	Night	32% 6% 12% 31% 18% 1	2956
	21st to end	Night	34% 5% 14% 23% 21% 3	3476
September	1st to 10th	Night	30% 7% 13% 26% 23% 2	1900
	11th to 20th	Night	30% 5% 10% 36% 17% 1	2001
	21st to end	Night	37% 5% 11% 29% 17% 1	2090
October	1st to 10th	Night	27% 3 8% 40% 21% 1	3590
	11th to 20th	Night	34% 4 14% 28% 18% 3	3873
	21st to end	Night	42% 4 11% 26% 17%	4467
November	1st to 10th	Night	38% 5% 12% 26% 18% 2	2536
	11th to 20th	Night	48% 5% 13% 19% 12% 2	2600
	21st to end	Night	47% 5% 16% 24% 8% 1	2714
December	1st to 10th	Night	52% 7% 13% 21% 7% 1	2660
	11th to 20th	Night	53% 6% 12% 17% 10% 1	3281
	21st to end	Night	65% 5% 9% 15% 6%	4884

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	19% 16% 32% 27% 6% 1	270
	11th to 20th	Day	19% 17% 36% 22% 4 1	270
	21st to end	Day	19% 13% 34% 28% 5% 1	297
February	1st to 10th	Day	14% 23% 41% 17% 5%	270
	11th to 20th	Day	17% 27% 36% 16% 5%	270
	21st to end	Day	22% 22% 40% 14% 2	225
March	1st to 10th	Day	21% 17% 46% 14% 1	270
	11th to 20th	Day	27% 14% 31% 19% 7% 2	303
	21st to end	Day	26% 13% 32% 22% 6% 1	506
April	1st to 10th	Day	25% 14% 33% 21% 7%	460
	11th to 20th	Day	25% 19% 28% 17% 8% 2	452
	21st to end	Day	22% 15% 29% 21% 11% 2	460
May	1st to 10th	Day	21% 11% 37% 20% 9% 2	481
	11th to 20th	Day	17% 12% 34% 24% 9% 3	675
	21st to end	Day	14% 10% 31% 26% 14% 5%	734
June	1st to 10th	Day	12% 10% 33% 32% 11% 3	680
	11th to 20th	Day	14% 8% 31% 32% 12% 3	680
	21st to end	Day	13% 7% 31% 34% 12% 4	680
July	1st to 10th	Day	8% 4 25% 36% 20% 8%	671
	11th to 20th	Day	9% 7% 28% 33% 17% 7%	668
	21st to end	Day	6% 4 31% 33% 18% 8%	739
August	1st to 10th	Day	8% 3 26% 39% 16% 8%	676
	11th to 20th	Day	11% 3 21% 32% 23% 10%	482
	21st to end	Day	13% 7% 20% 29% 22% 7%	539
September	1st to 10th	Day	14% 9% 24% 29% 17% 8%	490
	11th to 20th	Day	11% 3 22% 36% 19% 8%	490
	21st to end	Day	16% 12% 24% 25% 18% 4	490
October	1st to 10th	Day	19% 9% 30% 26% 13% 3	428
	11th to 20th	Day	22% 18% 30% 23% 8%	300
	21st to end	Day	19% 18% 40% 16% 5% 1	330
November	1st to 10th	Day	18% 14% 37% 21% 8% 2	300
	11th to 20th	Day	16% 23% 35% 19% 7%	300
	21st to end	Day	23% 16% 37% 20% 4	291
December	1st to 10th	Day	21% 19% 38% 17% 4	270
	11th to 20th	Day	23% 20% 36% 13% 6% 1	270
	21st to end	Day	28% 19% 36% 13% 5%	297
January	1st to 10th	Night	19% 15% 39% 23% 5%	950
	11th to 20th	Night	19% 16% 35% 24% 5% 1	950
	21st to end	Night	19% 11% 37% 26% 6%	1045
February	1st to 10th	Night	19% 16% 36% 24% 5% 1	950
	11th to 20th	Night	17% 16% 36% 24% 6%	749
	21st to end	Night	22% 15% 38% 21% 3	628
March	1st to 10th	Night	19% 13% 34% 24% 10% 1	760
	11th to 20th	Night	16% 12% 39% 26% 6% 1	756
	21st to end	Night	20% 8% 29% 32% 11% 1	627
April	1st to 10th	Night	20% 9% 40% 24% 6%	570
	11th to 20th	Night	24% 9% 31% 25% 9% 1	563
	21st to end	Night	20% 7% 30% 30% 11% 1	570
May	1st to 10th	Night	19% 6% 31% 34% 9% 1	570
	11th to 20th	Night	19% 7% 29% 33% 11% 1	561
	21st to end	Night	14% 5% 22% 39% 18% 2	617
June	1st to 10th	Night	12% 6% 25% 40% 16% 1	570
	11th to 20th	Night	14% 4 27% 35% 18% 2	570
	21st to end	Night	9% 4 25% 42% 20% 1	570
July	1st to 10th	Night	10% 2 16% 42% 28% 2	555
	11th to 20th	Night	6% 3 21% 39% 28% 3	552
	21st to end	Night	5% 2 22% 45% 25% 2	624
August	1st to 10th	Night	10% 2 15% 43% 28% 3	567
	11th to 20th	Night	9% 2 17% 38% 28% 6%	564
	21st to end	Night	12% 3 18% 39% 25% 4	627
September	1st to 10th	Night	10% 4 24% 31% 26% 5%	570
	11th to 20th	Night	12% 4 21% 33% 24% 6%	671
	21st to end	Night	14% 9% 24% 30% 19% 4	760
October	1st to 10th	Night	15% 8% 29% 27% 19% 2	760
	11th to 20th	Night	20% 11% 32% 27% 10%	760
	21st to end	Night	22% 11% 31% 26% 10%	836
November	1st to 10th	Night	16% 11% 38% 25% 9% 1	780
	11th to 20th	Night	22% 14% 35% 22% 6%	800
	21st to end	Night	23% 14% 36% 20% 7%	941
December	1st to 10th	Night	21% 15% 38% 21% 5% 1	950
	11th to 20th	Night	22% 14% 36% 20% 7% 1	950
	21st to end	Night	26% 14% 36% 20% 3	1045

Page generated at 2024-11-24 23:22:19. Version ac07

Copyright © 2024 Attilla Danko.