Jasper House Viewpoint
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jasper House Viewpoint clear sky chart from 2005-11-06 to 2024-03-01.

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	8% 9% 4 9% 8% 5% 7% 7% 7% 8% 28%	77693
	Night	5% 8% 4 9% 8% 4 6% 7% 8% 9% 32%	81660
Transparency	Day	52% 13% 15% 14% 6% 1	77389
	Night	47% 13% 16% 16% 7% 1	81544
Seeing	Day	19% 21% 31% 20% 7% 1	15085
	Night	13% 19% 35% 23% 9% 1	23640

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	2 5% 6% 13% 11% 6% 7% 8% 8% 11% 24%	1899
	11th to 20th	Day	1 6% 4 10% 6% 4 6% 7% 10% 10% 36%	2124
	21st to end	Day	3 7% 5% 9% 9% 5% 8% 8% 9% 11% 27%	2794
February	1st to 10th	Day	2 8% 5% 10% 10% 5% 8% 8% 8% 9% 26%	1520
	11th to 20th	Day	2 10% 6% 11% 8% 6% 6% 7% 7% 9% 29%	1555
	21st to end	Day	1 6% 5% 11% 10% 7% 8% 10% 7% 7% 28%	1551
March	1st to 10th	Day	1 7% 5% 9% 9% 6% 8% 9% 8% 9% 29%	1801
	11th to 20th	Day	1 6% 4 8% 8% 5% 8% 8% 9% 11% 31%	1833
	21st to end	Day	2 13% 7% 15% 10% 5% 6% 7% 7% 9% 19%	2376
April	1st to 10th	Day	3 11% 7% 13% 10% 7% 9% 8% 8% 8% 17%	2160
	11th to 20th	Day	5% 13% 8% 11% 10% 5% 5% 6% 7% 7% 22%	2256
	21st to end	Day	8% 13% 5% 11% 9% 4 7% 6% 6% 9% 23%	2483
May	1st to 10th	Day	10% 17% 5% 11% 10% 5% 6% 5% 6% 6% 20%	2520
	11th to 20th	Day	10% 11% 4 8% 6% 3 6% 5% 6% 8% 30%	2603
	21st to end	Day	21% 12% 5% 7% 7% 4 5% 5% 5% 7% 23%	2944
June	1st to 10th	Day	19% 10% 3 8% 8% 5% 7% 5% 6% 7% 21%	2880
	11th to 20th	Day	22% 12% 5% 9% 9% 5% 6% 6% 5% 6% 16%	2880
	21st to end	Day	14% 9% 5% 8% 8% 5% 7% 6% 7% 6% 26%	2880
July	1st to 10th	Day	16% 9% 3 7% 7% 3 7% 7% 6% 8% 26%	2880
	11th to 20th	Day	13% 8% 3 7% 7% 4 7% 6% 6% 8% 30%	2880
	21st to end	Day	11% 6% 3 7% 8% 5% 7% 6% 7% 8% 32%	2791
August	1st to 10th	Day	11% 8% 3 8% 7% 4 7% 6% 7% 8% 30%	2507
	11th to 20th	Day	10% 6% 3 6% 7% 4 6% 6% 6% 10% 35%	2475
	21st to end	Day	12% 8% 3 7% 7% 5% 6% 5% 7% 8% 31%	2557
September	1st to 10th	Day	12% 9% 3 7% 6% 4 5% 5% 6% 7% 35%	2160
	11th to 20th	Day	11% 8% 4 6% 5% 3 5% 6% 7% 7% 38%	2102
	21st to end	Day	9% 10% 4 8% 7% 4 5% 6% 7% 7% 35%	1980
October	1st to 10th	Day	6% 12% 4 8% 7% 5% 6% 6% 7% 7% 32%	1832
	11th to 20th	Day	6% 8% 3 6% 8% 5% 7% 7% 8% 10% 32%	1652
	21st to end	Day	4 10% 4 10% 8% 5% 6% 7% 6% 9% 33%	1782
November	1st to 10th	Day	2 9% 4 11% 9% 5% 8% 7% 7% 9% 27%	1528
	11th to 20th	Day	2 6% 4 7% 7% 5% 7% 7% 6% 12% 37%	1330
	21st to end	Day	2 8% 5% 10% 8% 4 6% 6% 9% 11% 31%	1330
December	1st to 10th	Day	3 7% 4 11% 11% 4 8% 7% 7% 9% 29%	1316
	11th to 20th	Day	2 5% 4 9% 9% 6% 8% 8% 7% 10% 32%	1442
	21st to end	Day	1 5% 3 7% 8% 5% 6% 7% 7% 11% 39%	2090
January	1st to 10th	Night	2 7% 6% 13% 9% 5% 6% 6% 8% 10% 28%	5046
	11th to 20th	Night	1 6% 3 9% 7% 5% 8% 9% 8% 13% 32%	4801
	21st to end	Night	1 7% 4 10% 8% 6% 8% 9% 9% 11% 27%	4862
February	1st to 10th	Night	3 8% 4 10% 11% 5% 8% 9% 7% 8% 26%	2660
	11th to 20th	Night	2 8% 5% 10% 9% 4 8% 7% 8% 9% 29%	2510
	21st to end	Night	1 7% 6% 11% 9% 5% 7% 8% 8% 9% 29%	1902
March	1st to 10th	Night	1 7% 5% 9% 9% 5% 8% 7% 9% 9% 32%	2165
	11th to 20th	Night	2 7% 4 8% 7% 3 7% 8% 10% 10% 34%	2125
	21st to end	Night	2 10% 6% 12% 7% 5% 7% 6% 7% 9% 29%	1980
April	1st to 10th	Night	2 10% 7% 12% 8% 5% 7% 8% 8% 8% 26%	1800
	11th to 20th	Night	6% 12% 5% 9% 9% 5% 5% 5% 6% 9% 31%	1654
	21st to end	Night	8% 12% 5% 9% 6% 4 5% 5% 5% 8% 33%	1476
May	1st to 10th	Night	10% 12% 5% 8% 7% 4 7% 6% 6% 8% 29%	1440
	11th to 20th	Night	9% 9% 3 6% 7% 3 5% 5% 6% 7% 39%	1289
	21st to end	Night	18% 10% 4 5% 5% 3 5% 5% 5% 7% 33%	1327
June	1st to 10th	Night	15% 10% 5% 6% 5% 4 5% 5% 7% 7% 32%	1080
	11th to 20th	Night	19% 9% 4 7% 8% 4 7% 7% 8% 7% 20%	1080
	21st to end	Night	10% 7% 3 6% 7% 5% 6% 5% 7% 7% 35%	1080
July	1st to 10th	Night	16% 6% 2 4 5% 4 6% 6% 7% 9% 33%	1080
	11th to 20th	Night	14% 7% 3 5% 5% 4 5% 5% 8% 8% 36%	1080
	21st to end	Night	9% 6% 3 5% 6% 5% 5% 6% 7% 8% 41%	1522
August	1st to 10th	Night	11% 7% 4 6% 6% 4 5% 5% 8% 9% 34%	1432
	11th to 20th	Night	11% 6% 2 5% 6% 2 6% 5% 5% 8% 44%	1424
	21st to end	Night	12% 6% 3 5% 5% 4 6% 6% 8% 9% 36%	1797
September	1st to 10th	Night	12% 9% 3 7% 6% 3 6% 5% 5% 8% 38%	1800
	11th to 20th	Night	11% 9% 3 6% 6% 4 5% 6% 5% 7% 39%	1858
	21st to end	Night	8% 8% 3 6% 5% 4 5% 7% 7% 8% 39%	1980
October	1st to 10th	Night	6% 13% 4 7% 6% 4 5% 6% 6% 8% 34%	2124
	11th to 20th	Night	6% 8% 3 6% 7% 4 5% 7% 9% 9% 36%	2308
	21st to end	Night	2 8% 5% 11% 10% 4 7% 6% 8% 9% 30%	2574
November	1st to 10th	Night	3 10% 5% 10% 8% 5% 6% 7% 8% 8% 30%	2529
	11th to 20th	Night	2 8% 4 9% 7% 4 6% 6% 8% 11% 35%	2850
	21st to end	Night	1 8% 5% 8% 9% 6% 6% 6% 8% 11% 31%	2850
December	1st to 10th	Night	3 6% 4 10% 8% 5% 7% 6% 7% 9% 34%	2859
	11th to 20th	Night	1 8% 5% 10% 9% 6% 7% 7% 8% 10% 29%	3750
	21st to end	Night	5% 4 8% 8% 4 7% 7% 8% 11% 37%	5566

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	50% 16% 18% 12% 3 1	1899
	11th to 20th	Day	43% 13% 12% 13% 15% 4	2144
	21st to end	Day	42% 24% 18% 11% 4	2794
February	1st to 10th	Day	51% 15% 13% 10% 10% 2	1520
	11th to 20th	Day	55% 11% 12% 15% 7% 1	1563
	21st to end	Day	53% 12% 12% 15% 7% 2	1551
March	1st to 10th	Day	48% 14% 16% 15% 6%	1801
	11th to 20th	Day	45% 14% 16% 17% 7%	1833
	21st to end	Day	61% 14% 13% 9% 4	2376
April	1st to 10th	Day	62% 14% 14% 8% 2	2160
	11th to 20th	Day	60% 10% 14% 13% 3	2256
	21st to end	Day	59% 12% 13% 13% 3	2483
May	1st to 10th	Day	63% 11% 12% 11% 3	2520
	11th to 20th	Day	51% 11% 16% 14% 8%	2607
	21st to end	Day	62% 9% 14% 11% 4	2945
June	1st to 10th	Day	62% 11% 10% 12% 4 1	2880
	11th to 20th	Day	69% 10% 10% 8% 3	2880
	21st to end	Day	57% 13% 13% 12% 5% 1	2880
July	1st to 10th	Day	54% 11% 14% 16% 5%	2801
	11th to 20th	Day	51% 13% 14% 16% 5% 1	2793
	21st to end	Day	48% 10% 17% 19% 5% 1	2635
August	1st to 10th	Day	51% 14% 14% 15% 5%	2490
	11th to 20th	Day	43% 13% 18% 18% 6% 1	2475
	21st to end	Day	49% 11% 14% 18% 7% 1	2557
September	1st to 10th	Day	48% 11% 16% 20% 4 1	2160
	11th to 20th	Day	45% 11% 15% 19% 8% 1	2102
	21st to end	Day	48% 12% 16% 15% 8% 2	1980
October	1st to 10th	Day	49% 12% 17% 18% 5%	1832
	11th to 20th	Day	46% 14% 17% 18% 4	1652
	21st to end	Day	49% 12% 16% 17% 6%	1782
November	1st to 10th	Day	52% 12% 16% 14% 5% 1	1528
	11th to 20th	Day	42% 15% 22% 15% 6% 1	1330
	21st to end	Day	48% 16% 17% 11% 5% 4	1330
December	1st to 10th	Day	53% 12% 11% 15% 7% 1	1316
	11th to 20th	Day	46% 14% 16% 14% 8% 1	1444
	21st to end	Day	36% 15% 19% 18% 12% 1	2090
January	1st to 10th	Night	51% 12% 16% 13% 6% 1	5046
	11th to 20th	Night	44% 13% 11% 12% 17% 4	4843
	21st to end	Night	45% 23% 16% 12% 5% 1	4862
February	1st to 10th	Night	54% 12% 12% 12% 8% 1	2660
	11th to 20th	Night	50% 12% 15% 14% 6% 1	2512
	21st to end	Night	49% 11% 13% 18% 7% 2	1902
March	1st to 10th	Night	46% 14% 16% 16% 7% 1	2165
	11th to 20th	Night	42% 14% 17% 19% 7%	2126
	21st to end	Night	51% 12% 16% 15% 5% 1	1980
April	1st to 10th	Night	54% 13% 17% 14% 3	1800
	11th to 20th	Night	51% 11% 16% 16% 6%	1654
	21st to end	Night	50% 12% 15% 17% 5% 1	1476
May	1st to 10th	Night	52% 12% 17% 15% 4	1440
	11th to 20th	Night	44% 12% 14% 19% 11%	1289
	21st to end	Night	50% 10% 16% 18% 5%	1327
June	1st to 10th	Night	52% 10% 16% 14% 7% 1	1080
	11th to 20th	Night	60% 14% 13% 9% 4	1080
	21st to end	Night	47% 12% 20% 15% 5% 1	1080
July	1st to 10th	Night	44% 13% 16% 20% 6% 1	1050
	11th to 20th	Night	44% 14% 20% 18% 5% 1	1044
	21st to end	Night	38% 11% 24% 23% 5%	1438
August	1st to 10th	Night	43% 12% 22% 20% 3	1424
	11th to 20th	Night	38% 11% 23% 21% 6%	1424
	21st to end	Night	41% 13% 19% 19% 8%	1797
September	1st to 10th	Night	45% 11% 15% 22% 6% 1	1800
	11th to 20th	Night	44% 10% 17% 20% 8% 1	1858
	21st to end	Night	41% 13% 19% 18% 7%	1980
October	1st to 10th	Night	47% 12% 15% 20% 5%	2124
	11th to 20th	Night	43% 14% 17% 21% 4	2308
	21st to end	Night	51% 13% 15% 14% 6%	2574
November	1st to 10th	Night	51% 12% 17% 15% 4 1	2529
	11th to 20th	Night	46% 14% 19% 14% 6% 1	2850
	21st to end	Night	49% 14% 15% 14% 6% 2	2850
December	1st to 10th	Night	48% 11% 15% 17% 8% 1	2859
	11th to 20th	Night	50% 15% 15% 14% 5%	3747
	21st to end	Night	36% 17% 18% 20% 8% 1	5566

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% 29% 34% 21% 4 2	180
	11th to 20th	Day	16% 23% 34% 20% 5% 3	180
	21st to end	Day	18% 30% 35% 11% 5% 1	198
February	1st to 10th	Day	19% 27% 34% 13% 5% 1	180
	11th to 20th	Day	15% 21% 42% 17% 4 1	255
	21st to end	Day	16% 25% 36% 18% 4 1	373
March	1st to 10th	Day	17% 28% 31% 16% 7% 1	421
	11th to 20th	Day	17% 26% 35% 15% 4 2	420
	21st to end	Day	16% 29% 31% 16% 7% 2	462
April	1st to 10th	Day	22% 22% 32% 18% 5%	420
	11th to 20th	Day	19% 21% 32% 18% 9% 1	412
	21st to end	Day	20% 26% 30% 15% 8% 2	420
May	1st to 10th	Day	19% 20% 33% 23% 5%	423
	11th to 20th	Day	18% 13% 30% 28% 9% 2	574
	21st to end	Day	24% 12% 25% 25% 12% 3	706
June	1st to 10th	Day	22% 20% 31% 20% 6%	810
	11th to 20th	Day	27% 19% 28% 19% 6% 1	810
	21st to end	Day	18% 17% 27% 24% 12% 2	810
July	1st to 10th	Day	22% 14% 30% 25% 8% 1	796
	11th to 20th	Day	19% 18% 31% 22% 10% 1	792
	21st to end	Day	15% 16% 30% 27% 9% 3	537
August	1st to 10th	Day	17% 13% 30% 28% 9% 3	447
	11th to 20th	Day	14% 22% 35% 21% 6% 1	437
	21st to end	Day	16% 22% 35% 20% 7%	495
September	1st to 10th	Day	21% 24% 30% 20% 4 1	450
	11th to 20th	Day	19% 21% 34% 20% 5%	450
	21st to end	Day	27% 26% 26% 16% 5% 1	450
October	1st to 10th	Day	22% 22% 32% 17% 7% 1	450
	11th to 20th	Day	19% 28% 31% 17% 5% 1	302
	21st to end	Day	16% 27% 34% 18% 4 1	297
November	1st to 10th	Day	23% 33% 27% 14% 3	210
	11th to 20th	Day	19% 32% 32% 14% 3 1	180
	21st to end	Day	24% 26% 26% 16% 6% 2	180
December	1st to 10th	Day	14% 29% 27% 15% 12% 3	180
	11th to 20th	Day	14% 28% 39% 13% 6% 1	180
	21st to end	Day	13% 23% 42% 14% 6% 3	198
January	1st to 10th	Night	12% 22% 46% 15% 4 1	1040
	11th to 20th	Night	11% 26% 41% 15% 5% 1	928
	21st to end	Night	13% 29% 36% 17% 6%	836
February	1st to 10th	Night	15% 22% 31% 25% 7%	760
	11th to 20th	Night	11% 18% 38% 28% 5%	744
	21st to end	Night	10% 16% 38% 24% 11% 1	628
March	1st to 10th	Night	8% 21% 37% 24% 8% 1	722
	11th to 20th	Night	8% 22% 40% 21% 8% 1	720
	21st to end	Night	10% 17% 34% 27% 10% 1	792
April	1st to 10th	Night	11% 16% 32% 30% 9% 1	720
	11th to 20th	Night	12% 16% 36% 26% 11%	586
	21st to end	Night	15% 17% 29% 29% 9% 1	396
May	1st to 10th	Night	16% 8% 25% 39% 11%	360
	11th to 20th	Night	12% 8% 28% 35% 16% 1	354
	21st to end	Night	22% 9% 25% 26% 18% 1	389
June	1st to 10th	Night	22% 9% 28% 26% 14% 1	360
	11th to 20th	Night	24% 10% 23% 28% 14% 1	360
	21st to end	Night	14% 11% 28% 28% 18% 1	360
July	1st to 10th	Night	18% 6% 23% 37% 15% 1	350
	11th to 20th	Night	19% 11% 19% 31% 18% 1	348
	21st to end	Night	11% 8% 20% 33% 26% 1	394
August	1st to 10th	Night	15% 6% 19% 33% 23% 3	358
	11th to 20th	Night	15% 7% 24% 33% 19% 2	356
	21st to end	Night	16% 11% 31% 30% 11% 1	609
September	1st to 10th	Night	19% 13% 28% 29% 11% 1	720
	11th to 20th	Night	18% 11% 28% 28% 14% 2	720
	21st to end	Night	17% 23% 28% 22% 9% 1	720
October	1st to 10th	Night	17% 17% 32% 25% 9% 1	720
	11th to 20th	Night	15% 18% 38% 24% 5% 1	720
	21st to end	Night	14% 22% 38% 19% 6% 1	792
November	1st to 10th	Night	14% 25% 38% 19% 3	740
	11th to 20th	Night	14% 29% 39% 15% 3	950
	21st to end	Night	11% 28% 40% 15% 5% 1	950
December	1st to 10th	Night	12% 25% 37% 20% 6%	954
	11th to 20th	Night	9% 26% 43% 17% 5% 1	1040
	21st to end	Night	10% 23% 44% 16% 6% 1	1144

Page generated at 2024-02-27 04:30:12. Version ac07

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