Sundre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sundre clear sky chart from 2005-11-06 to 2024-02-05.

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	10% 8% 4 7% 7% 4 6% 6% 7% 8% 34%	77678
	Night	7% 9% 4 8% 7% 4 5% 6% 6% 8% 36%	81127
Transparency	Day	44% 9% 16% 20% 9% 2	77384
	Night	43% 9% 15% 21% 10% 2	81001
Seeing	Day	14% 9% 28% 30% 16% 4	14230
	Night	11% 6% 31% 35% 14% 2	23485

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	3 8% 8% 13% 7% 3 5% 5% 6% 9% 34%	2219
	11th to 20th	Day	3 9% 3 9% 7% 4 7% 7% 8% 8% 35%	2235
	21st to end	Day	4 7% 4 7% 6% 3 5% 6% 6% 11% 41%	2794
February	1st to 10th	Day	5% 11% 6% 9% 9% 4 5% 5% 6% 10% 30%	1472
	11th to 20th	Day	4 12% 4 12% 8% 5% 6% 6% 7% 8% 28%	1522
	21st to end	Day	3 10% 7% 10% 9% 5% 7% 7% 7% 7% 29%	1453
March	1st to 10th	Day	4 10% 6% 10% 8% 4 6% 6% 6% 9% 31%	1800
	11th to 20th	Day	4 9% 5% 8% 7% 3 6% 6% 8% 10% 35%	1929
	21st to end	Day	7% 13% 6% 10% 7% 4 6% 7% 6% 7% 26%	2241
April	1st to 10th	Day	8% 12% 6% 10% 9% 5% 6% 7% 6% 8% 24%	2196
	11th to 20th	Day	11% 16% 6% 9% 6% 3 6% 5% 6% 8% 26%	2310
	21st to end	Day	12% 11% 4 7% 7% 4 5% 6% 6% 9% 29%	2340
May	1st to 10th	Day	14% 11% 5% 7% 7% 4 6% 7% 6% 8% 26%	2515
	11th to 20th	Day	11% 7% 3 7% 7% 3 6% 6% 7% 9% 35%	2654
	21st to end	Day	21% 8% 4 6% 6% 4 5% 5% 7% 8% 26%	2917
June	1st to 10th	Day	19% 7% 4 6% 7% 4 6% 6% 7% 7% 26%	2700
	11th to 20th	Day	21% 9% 4 7% 8% 4 6% 6% 7% 6% 23%	2700
	21st to end	Day	12% 5% 3 7% 6% 4 6% 7% 8% 9% 34%	2700
July	1st to 10th	Day	12% 5% 3 6% 6% 4 7% 7% 7% 9% 35%	2700
	11th to 20th	Day	13% 4 2 6% 5% 3 6% 6% 8% 8% 39%	2700
	21st to end	Day	9% 4 3 4 5% 3 5% 6% 8% 10% 43%	2876
August	1st to 10th	Day	13% 5% 2 6% 5% 3 5% 6% 7% 9% 40%	2507
	11th to 20th	Day	10% 4 2 5% 5% 3 5% 5% 6% 10% 45%	2368
	21st to end	Day	12% 4 2 5% 5% 3 5% 5% 7% 9% 43%	2574
September	1st to 10th	Day	13% 7% 2 5% 5% 3 3 5% 5% 7% 44%	2227
	11th to 20th	Day	14% 9% 3 5% 4 3 4 4 4 5% 44%	1993
	21st to end	Day	10% 8% 3 6% 7% 3 5% 4 5% 8% 42%	1980
October	1st to 10th	Day	13% 9% 3 6% 5% 3 5% 5% 6% 7% 39%	1920
	11th to 20th	Day	10% 9% 3 7% 6% 3 6% 5% 8% 6% 38%	1625
	21st to end	Day	7% 9% 5% 7% 9% 4 5% 6% 7% 10% 33%	1782
November	1st to 10th	Day	7% 14% 5% 9% 6% 5% 6% 5% 5% 6% 32%	1558
	11th to 20th	Day	5% 11% 5% 9% 6% 3 4 6% 6% 8% 38%	1387
	21st to end	Day	5% 11% 5% 8% 6% 3 4 6% 6% 9% 36%	1330
December	1st to 10th	Day	6% 10% 5% 10% 7% 5% 7% 5% 6% 7% 31%	1330
	11th to 20th	Day	3 10% 5% 10% 8% 5% 6% 6% 6% 8% 31%	1682
	21st to end	Day	3 9% 4 8% 8% 4 5% 5% 6% 8% 40%	2442
January	1st to 10th	Night	3 13% 6% 11% 9% 5% 6% 7% 6% 8% 27%	4726
	11th to 20th	Night	2 8% 5% 11% 9% 4 6% 7% 6% 7% 34%	4693
	21st to end	Night	3 10% 5% 8% 7% 5% 6% 6% 7% 9% 34%	4862
February	1st to 10th	Night	6% 9% 5% 11% 9% 6% 6% 5% 7% 7% 30%	2582
	11th to 20th	Night	4 12% 5% 11% 9% 4 7% 6% 6% 8% 28%	2324
	21st to end	Night	3 9% 5% 10% 8% 5% 6% 5% 5% 7% 37%	1800
March	1st to 10th	Night	4 10% 5% 8% 7% 5% 7% 7% 7% 9% 30%	2160
	11th to 20th	Night	5% 10% 5% 8% 6% 4 5% 5% 7% 9% 36%	2029
	21st to end	Night	6% 11% 6% 9% 7% 4 6% 5% 6% 9% 31%	2111
April	1st to 10th	Night	8% 11% 5% 9% 8% 4 6% 5% 6% 8% 30%	1764
	11th to 20th	Night	10% 13% 6% 10% 7% 3 4 5% 4 7% 30%	1601
	21st to end	Night	11% 10% 5% 8% 7% 4 7% 5% 6% 8% 31%	1620
May	1st to 10th	Night	14% 14% 3 7% 5% 3 4 6% 5% 7% 32%	1440
	11th to 20th	Night	10% 7% 3 6% 5% 3 6% 4 6% 9% 40%	1239
	21st to end	Night	20% 8% 2 5% 5% 3 4 6% 6% 8% 33%	1358
June	1st to 10th	Night	19% 8% 3 6% 6% 3 5% 5% 6% 6% 33%	1260
	11th to 20th	Night	17% 7% 5% 7% 7% 5% 6% 6% 6% 8% 27%	1260
	21st to end	Night	9% 6% 2 4 6% 4 6% 6% 8% 9% 39%	1260
July	1st to 10th	Night	11% 6% 2 5% 5% 3 5% 5% 8% 10% 40%	1260
	11th to 20th	Night	12% 5% 2 4 6% 3 5% 6% 8% 9% 40%	1260
	21st to end	Night	8% 4 1 4 4 2 5% 5% 8% 8% 53%	1438
August	1st to 10th	Night	10% 5% 2 5% 6% 4 5% 6% 6% 8% 43%	1432
	11th to 20th	Night	9% 4 2 4 5% 2 4 6% 7% 9% 47%	1531
	21st to end	Night	10% 5% 2 5% 5% 3 4 3 5% 8% 48%	1782
September	1st to 10th	Night	12% 5% 2 6% 5% 3 4 4 5% 8% 47%	1732
	11th to 20th	Night	15% 7% 2 5% 4 2 4 4 7% 7% 42%	1966
	21st to end	Night	11% 6% 3 5% 5% 3 5% 5% 5% 8% 44%	1980
October	1st to 10th	Night	11% 9% 3 6% 6% 3 4 4 4 8% 41%	2039
	11th to 20th	Night	8% 8% 3 6% 6% 4 5% 5% 6% 10% 39%	2331
	21st to end	Night	8% 9% 4 8% 7% 4 5% 6% 6% 8% 35%	2574
November	1st to 10th	Night	8% 13% 5% 8% 6% 3 5% 6% 6% 7% 33%	2501
	11th to 20th	Night	4 9% 5% 8% 7% 4 6% 6% 6% 9% 36%	2788
	21st to end	Night	4 9% 5% 9% 7% 4 5% 6% 6% 9% 34%	2850
December	1st to 10th	Night	5% 11% 5% 10% 7% 4 5% 5% 6% 8% 35%	2850
	11th to 20th	Night	3 10% 5% 9% 9% 5% 6% 7% 7% 9% 31%	3510
	21st to end	Night	3 9% 4 7% 6% 3 5% 5% 7% 7% 43%	5214

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	44% 7% 12% 22% 12% 2	2219
	11th to 20th	Day	43% 9% 9% 16% 19% 4	2256
	21st to end	Day	34% 10% 15% 32% 8% 1	2794
February	1st to 10th	Day	48% 8% 15% 18% 9% 3	1472
	11th to 20th	Day	50% 9% 15% 16% 9% 1	1531
	21st to end	Day	50% 8% 12% 17% 12% 1	1453
March	1st to 10th	Day	48% 9% 16% 17% 9% 1	1800
	11th to 20th	Day	41% 8% 16% 22% 11% 1	1930
	21st to end	Day	53% 12% 16% 14% 6% 1	2241
April	1st to 10th	Day	55% 9% 16% 13% 7%	2196
	11th to 20th	Day	55% 7% 11% 17% 8% 1	2310
	21st to end	Day	51% 9% 15% 18% 6% 1	2340
May	1st to 10th	Day	53% 10% 17% 14% 5%	2515
	11th to 20th	Day	43% 10% 15% 21% 10% 1	2658
	21st to end	Day	53% 9% 16% 15% 6%	2918
June	1st to 10th	Day	53% 9% 15% 16% 5% 1	2700
	11th to 20th	Day	59% 9% 14% 12% 5% 1	2700
	21st to end	Day	42% 11% 19% 20% 7% 1	2700
July	1st to 10th	Day	42% 11% 19% 19% 8% 1	2626
	11th to 20th	Day	39% 12% 19% 22% 7% 1	2619
	21st to end	Day	33% 11% 20% 26% 10% 1	2716
August	1st to 10th	Day	38% 10% 20% 24% 7%	2490
	11th to 20th	Day	32% 10% 23% 25% 9% 2	2368
	21st to end	Day	35% 11% 18% 25% 10% 2	2574
September	1st to 10th	Day	37% 8% 19% 22% 10% 3	2227
	11th to 20th	Day	41% 7% 14% 25% 10% 2	1993
	21st to end	Day	39% 8% 17% 22% 12% 2	1980
October	1st to 10th	Day	42% 9% 14% 23% 11% 1	1920
	11th to 20th	Day	42% 8% 18% 20% 10% 2	1625
	21st to end	Day	45% 9% 14% 19% 12% 2	1782
November	1st to 10th	Day	52% 8% 12% 17% 10% 1	1558
	11th to 20th	Day	43% 9% 14% 22% 11% 2	1387
	21st to end	Day	42% 9% 17% 20% 9% 4	1330
December	1st to 10th	Day	49% 8% 11% 16% 13% 3	1330
	11th to 20th	Day	46% 10% 15% 17% 9% 2	1684
	21st to end	Day	37% 8% 10% 20% 19% 6%	2442
January	1st to 10th	Night	51% 10% 11% 17% 9% 2	4726
	11th to 20th	Night	46% 8% 10% 17% 13% 7%	4734
	21st to end	Night	40% 11% 15% 21% 11% 1	4862
February	1st to 10th	Night	50% 9% 10% 18% 11% 3	2582
	11th to 20th	Night	50% 8% 13% 17% 11% 1	2325
	21st to end	Night	46% 5% 11% 22% 14% 2	1800
March	1st to 10th	Night	45% 10% 14% 22% 8% 1	2160
	11th to 20th	Night	42% 7% 16% 19% 14% 1	2029
	21st to end	Night	47% 10% 17% 18% 8% 1	2111
April	1st to 10th	Night	49% 8% 13% 19% 10% 1	1764
	11th to 20th	Night	53% 7% 13% 18% 8% 1	1601
	21st to end	Night	50% 8% 15% 19% 6% 2	1620
May	1st to 10th	Night	50% 7% 16% 18% 9% 1	1440
	11th to 20th	Night	39% 9% 16% 24% 12%	1239
	21st to end	Night	47% 8% 16% 21% 6% 1	1358
June	1st to 10th	Night	49% 8% 15% 18% 10%	1260
	11th to 20th	Night	54% 9% 14% 15% 6% 2	1260
	21st to end	Night	38% 12% 19% 24% 6% 1	1260
July	1st to 10th	Night	36% 10% 20% 25% 7% 1	1225
	11th to 20th	Night	36% 12% 20% 22% 9% 1	1218
	21st to end	Night	26% 10% 19% 31% 13% 1	1358
August	1st to 10th	Night	36% 12% 18% 27% 7%	1424
	11th to 20th	Night	30% 10% 25% 25% 9% 1	1531
	21st to end	Night	33% 8% 17% 27% 12% 2	1782
September	1st to 10th	Night	35% 7% 17% 25% 13% 3	1732
	11th to 20th	Night	38% 8% 16% 22% 12% 4	1966
	21st to end	Night	36% 7% 17% 22% 14% 4	1980
October	1st to 10th	Night	41% 7% 16% 23% 10% 2	2039
	11th to 20th	Night	39% 9% 17% 22% 10% 2	2331
	21st to end	Night	44% 9% 15% 22% 9% 1	2574
November	1st to 10th	Night	48% 8% 11% 20% 12% 2	2501
	11th to 20th	Night	42% 10% 15% 19% 12% 2	2788
	21st to end	Night	42% 9% 15% 20% 10% 4	2850
December	1st to 10th	Night	46% 7% 13% 20% 11% 4	2850
	11th to 20th	Night	45% 11% 15% 20% 7% 1	3507
	21st to end	Night	36% 8% 13% 22% 15% 6%	5214

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	5% 9% 26% 34% 18% 9%	180
	11th to 20th	Day	7% 8% 31% 32% 17% 5%	180
	21st to end	Day	8% 11% 29% 35% 14% 4	198
February	1st to 10th	Day	12% 11% 35% 27% 10% 6%	168
	11th to 20th	Day	11% 8% 40% 28% 12%	216
	21st to end	Day	6% 10% 29% 35% 17% 3	319
March	1st to 10th	Day	9% 14% 36% 24% 13% 4	420
	11th to 20th	Day	8% 14% 35% 27% 11% 5%	420
	21st to end	Day	13% 15% 32% 25% 10% 5%	462
April	1st to 10th	Day	13% 15% 33% 25% 11% 2	420
	11th to 20th	Day	17% 13% 25% 29% 13% 3	412
	21st to end	Day	17% 12% 27% 28% 12% 3	420
May	1st to 10th	Day	19% 12% 25% 25% 16% 3	459
	11th to 20th	Day	16% 8% 21% 33% 17% 5%	625
	21st to end	Day	21% 5% 20% 29% 21% 4	679
June	1st to 10th	Day	17% 9% 27% 32% 12% 3	630
	11th to 20th	Day	25% 9% 24% 27% 12% 3	630
	21st to end	Day	14% 6% 23% 30% 20% 7%	630
July	1st to 10th	Day	15% 5% 20% 31% 24% 5%	621
	11th to 20th	Day	16% 4 24% 32% 20% 3	618
	21st to end	Day	8% 5% 26% 34% 19% 6%	622
August	1st to 10th	Day	13% 5% 28% 31% 16% 7%	447
	11th to 20th	Day	11% 5% 26% 34% 19% 4	437
	21st to end	Day	11% 6% 30% 29% 18% 6%	495
September	1st to 10th	Day	17% 7% 31% 28% 12% 5%	450
	11th to 20th	Day	19% 7% 21% 31% 17% 4	450
	21st to end	Day	16% 11% 28% 29% 12% 3	450
October	1st to 10th	Day	15% 10% 26% 25% 17% 7%	390
	11th to 20th	Day	16% 9% 33% 24% 14% 4	270
	21st to end	Day	14% 14% 33% 26% 11% 2	297
November	1st to 10th	Day	17% 9% 28% 31% 11% 3	270
	11th to 20th	Day	14% 13% 30% 31% 11% 1	207
	21st to end	Day	5% 9% 39% 27% 14% 6%	180
December	1st to 10th	Day	7% 8% 34% 31% 16% 4	180
	11th to 20th	Day	5% 11% 43% 28% 9% 3	180
	21st to end	Day	6% 7% 29% 33% 19% 7%	198
January	1st to 10th	Night	8% 9% 36% 34% 12% 1	950
	11th to 20th	Night	8% 8% 37% 36% 10% 1	944
	21st to end	Night	9% 10% 36% 32% 11% 2	836
February	1st to 10th	Night	9% 10% 32% 32% 14% 4	738
	11th to 20th	Night	9% 8% 35% 36% 12% 1	704
	21st to end	Night	5% 4 33% 35% 19% 4	592
March	1st to 10th	Night	8% 4 37% 35% 13% 3	720
	11th to 20th	Night	9% 6% 36% 36% 12% 2	720
	21st to end	Night	11% 6% 34% 31% 15% 3	792
April	1st to 10th	Night	11% 7% 33% 33% 15% 1	684
	11th to 20th	Night	14% 8% 34% 32% 11% 1	533
	21st to end	Night	16% 10% 27% 36% 11%	540
May	1st to 10th	Night	20% 8% 24% 34% 13% 1	397
	11th to 20th	Night	13% 3 26% 41% 16% 1	354
	21st to end	Night	22% 4 17% 37% 20% 1	389
June	1st to 10th	Night	21% 6% 21% 37% 14% 1	360
	11th to 20th	Night	21% 4 22% 37% 15% 1	360
	21st to end	Night	9% 2 23% 38% 26% 2	360
July	1st to 10th	Night	16% 2 14% 43% 24% 1	350
	11th to 20th	Night	15% 2 20% 41% 20% 1	348
	21st to end	Night	9% 2 16% 45% 26% 2	394
August	1st to 10th	Night	13% 3 12% 37% 32% 3	358
	11th to 20th	Night	10% 3 16% 44% 24% 3	463
	21st to end	Night	10% 3 20% 44% 22% 1	594
September	1st to 10th	Night	15% 3 21% 39% 18% 3	652
	11th to 20th	Night	18% 4 18% 36% 21% 3	720
	21st to end	Night	14% 5% 29% 36% 14% 2	720
October	1st to 10th	Night	17% 4 27% 34% 16% 2	720
	11th to 20th	Night	12% 5% 35% 33% 13% 2	720
	21st to end	Night	11% 9% 33% 36% 10% 1	792
November	1st to 10th	Night	14% 9% 35% 30% 10% 2	836
	11th to 20th	Night	9% 10% 44% 28% 7% 1	950
	21st to end	Night	8% 7% 39% 36% 9% 2	950
December	1st to 10th	Night	9% 7% 39% 32% 11% 2	950
	11th to 20th	Night	7% 7% 39% 35% 11% 1	950
	21st to end	Night	9% 6% 37% 33% 13% 2	1045

Page generated at 2024-02-02 03:20:30. Version ac07

Copyright 2024 Attilla Danko