Maple Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maple Ridge Observatory clear sky chart from 2005-11-06 to 2024-04-10.

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	14% 11% 4 8% 7% 4 5% 5% 5% 7% 31%	82706
	Night	14% 11% 5% 9% 7% 4 5% 5% 5% 6% 30%	86100
Transparency	Day	52% 7% 12% 19% 10% 1	82411
	Night	53% 7% 13% 18% 8% 1	85931
Seeing	Day	20% 16% 33% 21% 8% 3	14607
	Night	20% 13% 32% 25% 9% 1	24278

By Month

Percentage Cloud Cover NE (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% 17% 8% 12% 9% 4 5% 5% 4 5% 15%	2467
	11th to 20th	Day	14% 16% 7% 16% 13% 5% 5% 5% 4 5% 13%	2530
	21st to end	Day	18% 21% 7% 11% 8% 4 5% 4 4 6% 11%	2814
February	1st to 10th	Day	11% 16% 6% 11% 11% 5% 7% 4 5% 5% 18%	1710
	11th to 20th	Day	11% 13% 6% 12% 9% 5% 5% 6% 5% 5% 22%	1745
	21st to end	Day	11% 16% 7% 11% 9% 5% 5% 5% 4 5% 22%	1570
March	1st to 10th	Day	13% 13% 3 8% 7% 4 5% 5% 5% 6% 33%	3145
	11th to 20th	Day	10% 13% 7% 10% 7% 4 5% 4 6% 6% 27%	3480
	21st to end	Day	17% 12% 4 9% 8% 3 5% 5% 5% 6% 27%	3815
April	1st to 10th	Day	18% 14% 5% 7% 7% 3 4 4 4 6% 28%	2244
	11th to 20th	Day	18% 11% 4 6% 5% 2 4 4 6% 6% 34%	2303
	21st to end	Day	17% 11% 4 6% 5% 3 4 4 5% 6% 35%	2340
May	1st to 10th	Day	17% 8% 3 6% 6% 3 5% 5% 6% 6% 36%	2340
	11th to 20th	Day	17% 7% 3 6% 5% 4 4 4 6% 7% 37%	2301
	21st to end	Day	11% 5% 2 5% 5% 3 5% 5% 6% 9% 44%	2837
June	1st to 10th	Day	13% 6% 3 5% 5% 3 5% 5% 6% 8% 42%	2700
	11th to 20th	Day	12% 6% 2 5% 6% 2 5% 6% 6% 8% 42%	2700
	21st to end	Day	13% 5% 2 6% 6% 3 5% 5% 5% 8% 42%	2700
July	1st to 10th	Day	9% 5% 2 5% 5% 3 4 5% 6% 9% 48%	2663
	11th to 20th	Day	11% 6% 2 5% 5% 3 6% 5% 6% 10% 40%	2520
	21st to end	Day	10% 5% 3 5% 6% 4 5% 5% 7% 9% 42%	2735
August	1st to 10th	Day	12% 5% 2 5% 5% 4 6% 6% 6% 9% 40%	2327
	11th to 20th	Day	10% 6% 2 5% 5% 4 4 6% 6% 9% 43%	2303
	21st to end	Day	13% 7% 3 5% 5% 3 5% 5% 6% 7% 41%	2574
September	1st to 10th	Day	12% 7% 3 7% 4 4 4 5% 6% 7% 41%	2082
	11th to 20th	Day	14% 5% 1 5% 4 3 5% 5% 6% 8% 43%	1980
	21st to end	Day	17% 8% 2 7% 6% 3 4 5% 6% 7% 34%	1980
October	1st to 10th	Day	18% 9% 3 7% 6% 3 4 4 5% 7% 34%	1918
	11th to 20th	Day	22% 12% 4 8% 6% 3 5% 5% 4 7% 24%	1785
	21st to end	Day	21% 16% 5% 8% 7% 4 5% 6% 5% 5% 17%	1782
November	1st to 10th	Day	14% 13% 5% 8% 7% 4 6% 5% 6% 6% 27%	1672
	11th to 20th	Day	13% 13% 6% 11% 8% 5% 5% 5% 5% 7% 22%	1630
	21st to end	Day	19% 17% 8% 8% 8% 3 5% 5% 4 6% 18%	1520
December	1st to 10th	Day	13% 16% 8% 13% 9% 5% 6% 5% 6% 5% 14%	1392
	11th to 20th	Day	16% 16% 6% 11% 9% 5% 6% 5% 5% 5% 15%	1671
	21st to end	Day	24% 23% 10% 13% 6% 3 4 4 2 3 7%	2431
January	1st to 10th	Night	15% 14% 7% 14% 9% 4 6% 4 5% 5% 17%	4483
	11th to 20th	Night	12% 13% 7% 16% 12% 5% 6% 5% 5% 5% 14%	4440
	21st to end	Night	13% 19% 8% 13% 11% 5% 5% 4 4 4 13%	4852
February	1st to 10th	Night	11% 15% 6% 10% 9% 5% 7% 5% 5% 6% 21%	2470
	11th to 20th	Night	12% 13% 5% 10% 9% 5% 5% 5% 5% 7% 24%	2318
	21st to end	Night	16% 14% 5% 10% 7% 4 5% 5% 4 6% 24%	1884
March	1st to 10th	Night	14% 9% 4 6% 5% 3 4 4 5% 6% 40%	3692
	11th to 20th	Night	9% 11% 4 7% 6% 3 4 5% 5% 7% 38%	3479
	21st to end	Night	13% 11% 5% 9% 7% 3 4 5% 5% 6% 31%	3817
April	1st to 10th	Night	19% 11% 4 6% 5% 3 5% 5% 5% 6% 31%	1942
	11th to 20th	Night	18% 8% 3 5% 5% 3 3 5% 6% 7% 37%	1605
	21st to end	Night	17% 8% 4 7% 5% 3 5% 5% 4 7% 35%	1620
May	1st to 10th	Night	13% 7% 3 6% 7% 5% 6% 5% 6% 7% 35%	1620
	11th to 20th	Night	16% 7% 3 5% 5% 3 4 5% 6% 7% 39%	1592
	21st to end	Night	11% 4 3 4 4 3 5% 5% 6% 8% 47%	1433
June	1st to 10th	Night	13% 6% 2 5% 5% 4 3 5% 5% 8% 44%	1260
	11th to 20th	Night	9% 5% 2 6% 5% 3 6% 6% 8% 9% 42%	1260
	21st to end	Night	13% 5% 2 5% 4 2 4 5% 6% 8% 46%	1260
July	1st to 10th	Night	7% 3 2 4 4 2 4 6% 5% 8% 56%	1293
	11th to 20th	Night	7% 5% 2 4 6% 3 5% 5% 6% 9% 48%	1440
	21st to end	Night	8% 4 2 5% 6% 3 3 5% 6% 7% 51%	1582
August	1st to 10th	Night	8% 5% 2 5% 5% 2 4 5% 6% 8% 51%	1611
	11th to 20th	Night	10% 4 2 4 4 2 4 4 6% 8% 52%	1598
	21st to end	Night	12% 5% 3 4 5% 3 4 5% 5% 7% 47%	1782
September	1st to 10th	Night	11% 5% 2 5% 5% 3 4 5% 5% 7% 48%	1857
	11th to 20th	Night	12% 4 2 5% 4 3 3 5% 5% 7% 48%	1980
	21st to end	Night	17% 6% 2 6% 4 3 5% 5% 4 7% 39%	1980
October	1st to 10th	Night	16% 7% 3 6% 5% 3 5% 4 5% 6% 40%	2041
	11th to 20th	Night	19% 12% 4 7% 6% 3 4 4 5% 7% 29%	2173
	21st to end	Night	25% 12% 4 7% 6% 4 5% 4 4 5% 24%	2574
November	1st to 10th	Night	13% 12% 4 6% 7% 3 5% 5% 5% 8% 32%	2406
	11th to 20th	Night	15% 14% 5% 8% 6% 5% 6% 6% 5% 7% 23%	2550
	21st to end	Night	19% 17% 6% 9% 6% 3 4 4 5% 6% 20%	2660
December	1st to 10th	Night	15% 14% 8% 10% 7% 4 5% 5% 6% 7% 20%	2784
	11th to 20th	Night	14% 15% 8% 14% 10% 4 5% 5% 5% 6% 15%	3526
	21st to end	Night	23% 24% 9% 11% 6% 3 4 3 4 4 8%	5236

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	69% 9% 12% 9% 1	2468
	11th to 20th	Day	74% 7% 8% 10% 1	2530
	21st to end	Day	73% 7% 11% 6% 2	2814
February	1st to 10th	Day	65% 7% 10% 15% 4	1710
	11th to 20th	Day	62% 6% 11% 13% 8%	1754
	21st to end	Day	63% 6% 10% 15% 6% 1	1570
March	1st to 10th	Day	51% 6% 13% 20% 8% 1	3148
	11th to 20th	Day	54% 7% 13% 19% 6% 2	3480
	21st to end	Day	57% 6% 12% 16% 8% 1	3815
April	1st to 10th	Day	57% 5% 10% 17% 9% 1	2244
	11th to 20th	Day	50% 4 10% 19% 15% 2	2303
	21st to end	Day	49% 5% 12% 15% 14% 3	2340
May	1st to 10th	Day	46% 5% 10% 23% 13% 3	2340
	11th to 20th	Day	46% 6% 10% 20% 15% 3	2305
	21st to end	Day	36% 8% 15% 24% 15% 2	2837
June	1st to 10th	Day	38% 7% 12% 26% 14% 3	2700
	11th to 20th	Day	38% 7% 12% 24% 17% 2	2700
	21st to end	Day	40% 7% 12% 25% 14% 2	2700
July	1st to 10th	Day	31% 7% 14% 27% 20% 2	2591
	11th to 20th	Day	37% 7% 14% 26% 14% 2	2445
	21st to end	Day	38% 8% 14% 23% 16% 2	2583
August	1st to 10th	Day	38% 7% 17% 25% 11% 1	2314
	11th to 20th	Day	35% 8% 16% 27% 13% 1	2303
	21st to end	Day	40% 7% 14% 25% 12% 1	2574
September	1st to 10th	Day	40% 7% 12% 27% 13% 1	2082
	11th to 20th	Day	37% 7% 15% 30% 10% 1	1980
	21st to end	Day	47% 6% 16% 22% 7%	1980
October	1st to 10th	Day	49% 7% 13% 21% 11% 1	1918
	11th to 20th	Day	60% 7% 10% 17% 5%	1785
	21st to end	Day	67% 7% 9% 12% 5%	1782
November	1st to 10th	Day	56% 6% 11% 20% 7%	1672
	11th to 20th	Day	59% 8% 15% 13% 6%	1630
	21st to end	Day	67% 6% 15% 10% 2	1520
December	1st to 10th	Day	68% 9% 12% 8% 3	1392
	11th to 20th	Day	67% 8% 10% 12% 3	1671
	21st to end	Day	84% 5% 6% 4 1	2431
January	1st to 10th	Night	64% 9% 13% 11% 3	4483
	11th to 20th	Night	71% 9% 9% 10% 2	4440
	21st to end	Night	73% 7% 10% 7% 3	4852
February	1st to 10th	Night	63% 6% 11% 15% 6%	2470
	11th to 20th	Night	58% 8% 12% 16% 6%	2320
	21st to end	Night	59% 7% 12% 16% 7%	1884
March	1st to 10th	Night	44% 6% 16% 23% 10% 1	3702
	11th to 20th	Night	43% 6% 16% 24% 9% 1	3480
	21st to end	Night	50% 7% 13% 20% 8% 1	3817
April	1st to 10th	Night	52% 7% 10% 18% 13% 1	1942
	11th to 20th	Night	46% 4 8% 24% 16% 3	1605
	21st to end	Night	48% 7% 10% 17% 15% 3	1620
May	1st to 10th	Night	46% 7% 12% 18% 14% 3	1620
	11th to 20th	Night	42% 6% 8% 22% 18% 3	1593
	21st to end	Night	34% 8% 13% 25% 15% 4	1434
June	1st to 10th	Night	38% 6% 12% 26% 17% 2	1260
	11th to 20th	Night	34% 8% 15% 24% 17% 2	1260
	21st to end	Night	37% 7% 13% 25% 15% 4	1260
July	1st to 10th	Night	25% 7% 15% 28% 22% 2	1257
	11th to 20th	Night	31% 7% 14% 30% 17% 1	1392
	21st to end	Night	31% 7% 18% 26% 17% 1	1494
August	1st to 10th	Night	30% 6% 18% 31% 13% 2	1600
	11th to 20th	Night	29% 7% 18% 32% 13% 1	1598
	21st to end	Night	36% 7% 17% 25% 13% 2	1782
September	1st to 10th	Night	33% 8% 13% 28% 16% 2	1857
	11th to 20th	Night	34% 6% 16% 33% 10% 1	1980
	21st to end	Night	44% 7% 17% 24% 9%	1980
October	1st to 10th	Night	44% 7% 13% 25% 11%	2041
	11th to 20th	Night	54% 6% 13% 20% 6% 1	2173
	21st to end	Night	62% 6% 10% 17% 5%	2574
November	1st to 10th	Night	49% 7% 13% 23% 7% 1	2406
	11th to 20th	Night	58% 9% 13% 15% 6%	2550
	21st to end	Night	64% 8% 14% 11% 3	2660
December	1st to 10th	Night	63% 7% 14% 13% 3	2784
	11th to 20th	Night	68% 8% 11% 8% 4	3525
	21st to end	Night	79% 7% 7% 5% 3	5236

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	24% 17% 33% 20% 4	254
	11th to 20th	Day	23% 20% 39% 14% 4	270
	21st to end	Day	27% 17% 37% 14% 4 1	297
February	1st to 10th	Day	23% 25% 37% 13% 2	270
	11th to 20th	Day	21% 33% 34% 10% 1	270
	21st to end	Day	28% 33% 28% 10%	225
March	1st to 10th	Day	26% 27% 31% 13% 2 1	285
	11th to 20th	Day	23% 18% 37% 16% 5% 1	460
	21st to end	Day	30% 17% 33% 14% 6% 1	506
April	1st to 10th	Day	26% 21% 31% 17% 5% 1	457
	11th to 20th	Day	28% 19% 27% 16% 9% 2	412
	21st to end	Day	26% 17% 33% 15% 7% 2	420
May	1st to 10th	Day	21% 21% 31% 18% 6% 3	423
	11th to 20th	Day	18% 15% 37% 19% 8% 3	447
	21st to end	Day	13% 13% 35% 29% 7% 4	654
June	1st to 10th	Day	14% 14% 40% 22% 8% 1	630
	11th to 20th	Day	16% 15% 37% 22% 8% 2	630
	21st to end	Day	15% 11% 38% 26% 7% 2	630
July	1st to 10th	Day	9% 10% 33% 33% 12% 2	621
	11th to 20th	Day	12% 10% 35% 29% 10% 4	618
	21st to end	Day	11% 8% 36% 30% 12% 4	676
August	1st to 10th	Day	13% 10% 26% 29% 15% 7%	446
	11th to 20th	Day	10% 8% 24% 33% 17% 10%	439
	21st to end	Day	15% 11% 28% 26% 16% 3	495
September	1st to 10th	Day	14% 9% 36% 21% 13% 7%	450
	11th to 20th	Day	13% 10% 27% 30% 14% 6%	450
	21st to end	Day	22% 13% 25% 23% 13% 5%	450
October	1st to 10th	Day	25% 14% 28% 19% 13% 1	450
	11th to 20th	Day	27% 19% 33% 16% 4 1	435
	21st to end	Day	29% 26% 32% 9% 4	297
November	1st to 10th	Day	22% 20% 36% 16% 6%	270
	11th to 20th	Day	24% 27% 31% 13% 4	232
	21st to end	Day	31% 19% 34% 15% 1	180
December	1st to 10th	Day	26% 22% 33% 14% 3 1	180
	11th to 20th	Day	26% 27% 33% 11% 3	180
	21st to end	Day	31% 23% 31% 11% 4	198
January	1st to 10th	Night	21% 17% 38% 19% 4 1	950
	11th to 20th	Night	24% 17% 32% 20% 6%	950
	21st to end	Night	17% 13% 38% 25% 5% 1	1026
February	1st to 10th	Night	19% 19% 38% 19% 4	760
	11th to 20th	Night	20% 19% 34% 22% 5%	743
	21st to end	Night	25% 18% 36% 19% 3	628
March	1st to 10th	Night	17% 15% 39% 23% 6% 1	760
	11th to 20th	Night	20% 17% 35% 23% 5%	760
	21st to end	Night	20% 14% 33% 25% 7%	836
April	1st to 10th	Night	24% 14% 36% 21% 5% 1	612
	11th to 20th	Night	24% 11% 32% 25% 8% 2	533
	21st to end	Night	20% 12% 32% 25% 9% 1	540
May	1st to 10th	Night	17% 9% 35% 27% 10% 2	540
	11th to 20th	Night	20% 7% 28% 33% 11% 1	531
	21st to end	Night	12% 9% 28% 36% 15% 1	445
June	1st to 10th	Night	15% 7% 34% 32% 12%	360
	11th to 20th	Night	11% 7% 33% 35% 14% 1	360
	21st to end	Night	14% 8% 29% 34% 13% 1	360
July	1st to 10th	Night	7% 3 29% 43% 18%	382
	11th to 20th	Night	10% 3 25% 39% 21% 3	522
	21st to end	Night	9% 4 29% 36% 20% 1	591
August	1st to 10th	Night	10% 2 23% 41% 22% 2	537
	11th to 20th	Night	11% 4 21% 33% 26% 5%	534
	21st to end	Night	14% 6% 25% 34% 20% 2	594
September	1st to 10th	Night	12% 6% 28% 31% 18% 5%	613
	11th to 20th	Night	14% 7% 27% 32% 16% 4	720
	21st to end	Night	21% 8% 25% 27% 15% 4	720
October	1st to 10th	Night	20% 10% 29% 28% 13% 1	720
	11th to 20th	Night	25% 14% 32% 22% 6%	720
	21st to end	Night	33% 14% 28% 20% 4 1	792
November	1st to 10th	Night	20% 16% 33% 21% 8% 1	740
	11th to 20th	Night	23% 19% 35% 18% 5%	760
	21st to end	Night	29% 14% 37% 17% 3	760
December	1st to 10th	Night	22% 20% 36% 17% 5%	884
	11th to 20th	Night	23% 20% 37% 15% 4 1	950
	21st to end	Night	27% 17% 35% 16% 4	1045

Page generated at 2024-04-07 09:28:09. Version ac07

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