Mount Kobau Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Kobau Star Party 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	7% 9% 4 8% 7% 4 6% 6% 6% 7% 35%	83220
	Night	5% 9% 4 8% 7% 4 6% 6% 6% 7% 38%	85537
Transparency	Day	44% 5% 15% 22% 12% 2	82943
	Night	46% 5% 16% 21% 10% 2	85394
Seeing	Day	14% 18% 32% 25% 9% 2	14151
	Night	13% 8% 31% 32% 14% 1	22984

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	4 13% 7% 14% 11% 6% 10% 5% 6% 6% 19%	2539
	11th to 20th	Day	4 11% 4 9% 7% 4 8% 7% 7% 7% 32%	2516
	21st to end	Day	6% 16% 8% 16% 12% 5% 7% 4 4 5% 18%	2794
February	1st to 10th	Day	5% 11% 5% 9% 9% 6% 7% 8% 6% 8% 27%	1587
	11th to 20th	Day	4 11% 6% 8% 8% 5% 6% 6% 7% 9% 29%	1665
	21st to end	Day	3 12% 7% 12% 9% 6% 6% 8% 7% 7% 23%	1556
March	1st to 10th	Day	3 11% 7% 10% 7% 5% 8% 6% 6% 8% 29%	3138
	11th to 20th	Day	4 8% 3 6% 6% 4 6% 5% 5% 7% 46%	3335
	21st to end	Day	8% 16% 5% 12% 9% 5% 7% 5% 5% 5% 22%	4120
April	1st to 10th	Day	8% 15% 5% 8% 8% 5% 6% 6% 6% 7% 25%	2270
	11th to 20th	Day	8% 15% 5% 9% 9% 4 6% 5% 7% 7% 27%	2132
	21st to end	Day	7% 11% 4 8% 7% 5% 6% 6% 6% 8% 32%	2449
May	1st to 10th	Day	9% 9% 3 7% 6% 4 6% 6% 6% 8% 35%	2520
	11th to 20th	Day	12% 10% 3 8% 8% 4 6% 5% 6% 7% 31%	2477
	21st to end	Day	16% 10% 4 9% 7% 5% 7% 5% 5% 7% 27%	2723
June	1st to 10th	Day	16% 8% 4 7% 6% 4 6% 6% 5% 6% 31%	2589
	11th to 20th	Day	13% 9% 3 8% 8% 5% 6% 7% 5% 7% 28%	2815
	21st to end	Day	11% 6% 3 6% 7% 4 6% 6% 5% 8% 39%	2788
July	1st to 10th	Day	6% 6% 3 6% 7% 5% 6% 5% 6% 6% 45%	2653
	11th to 20th	Day	6% 4 3 5% 5% 2 5% 4 5% 6% 54%	2520
	21st to end	Day	4 3 2 3 4 2 4 5% 5% 6% 60%	2741
August	1st to 10th	Day	5% 3 2 5% 5% 3 4 4 6% 7% 56%	2507
	11th to 20th	Day	5% 3 2 3 4 3 5% 4 5% 8% 58%	2439
	21st to end	Day	6% 5% 2 5% 6% 4 6% 5% 6% 7% 48%	2397
September	1st to 10th	Day	7% 4 2 5% 5% 3 4 4 4 6% 56%	2160
	11th to 20th	Day	8% 6% 3 6% 7% 3 4 5% 4 7% 46%	2145
	21st to end	Day	8% 8% 3 6% 5% 4 4 5% 4 7% 46%	1959
October	1st to 10th	Day	9% 6% 4 7% 5% 4 6% 4 5% 6% 45%	1800
	11th to 20th	Day	8% 7% 4 7% 5% 4 5% 5% 6% 7% 41%	1764
	21st to end	Day	12% 8% 4 8% 7% 4 5% 5% 6% 6% 35%	1782
November	1st to 10th	Day	9% 12% 5% 9% 6% 3 7% 6% 7% 7% 27%	1603
	11th to 20th	Day	4 13% 5% 8% 8% 4 8% 5% 6% 7% 31%	1520
	21st to end	Day	4 10% 5% 10% 8% 5% 10% 7% 6% 7% 26%	1499
December	1st to 10th	Day	3 9% 6% 9% 7% 4 7% 7% 8% 8% 31%	1330
	11th to 20th	Day	3 8% 5% 9% 10% 6% 13% 9% 7% 7% 23%	1682
	21st to end	Day	4 11% 6% 11% 9% 7% 10% 7% 7% 7% 20%	2706
January	1st to 10th	Night	5% 11% 6% 14% 12% 7% 9% 6% 5% 6% 18%	4406
	11th to 20th	Night	4 12% 6% 9% 7% 3 5% 5% 5% 8% 35%	4382
	21st to end	Night	5% 12% 6% 16% 14% 7% 9% 5% 4 5% 17%	4862
February	1st to 10th	Night	5% 12% 5% 10% 9% 6% 6% 6% 7% 6% 28%	2589
	11th to 20th	Night	3 10% 4 7% 7% 5% 6% 6% 6% 8% 37%	2402
	21st to end	Night	4 10% 5% 12% 8% 4 6% 8% 8% 8% 28%	1897
March	1st to 10th	Night	3 8% 5% 7% 6% 4 6% 7% 9% 10% 36%	3736
	11th to 20th	Night	3 7% 3 6% 5% 3 5% 5% 5% 7% 51%	3630
	21st to end	Night	6% 12% 5% 8% 9% 5% 7% 6% 6% 8% 28%	3533
April	1st to 10th	Night	5% 10% 3 6% 7% 5% 7% 6% 6% 8% 36%	1900
	11th to 20th	Night	5% 10% 4 6% 6% 4 7% 6% 6% 6% 39%	1779
	21st to end	Night	6% 8% 3 6% 6% 3 6% 6% 6% 9% 40%	1507
May	1st to 10th	Night	7% 7% 2 5% 5% 4 5% 5% 5% 9% 47%	1440
	11th to 20th	Night	7% 5% 2 5% 7% 3 5% 5% 8% 11% 42%	1416
	21st to end	Night	11% 7% 3 5% 5% 3 5% 6% 5% 10% 39%	1552
June	1st to 10th	Night	10% 7% 2 6% 6% 4 5% 6% 7% 8% 39%	1364
	11th to 20th	Night	9% 7% 2 5% 4 3 7% 5% 6% 8% 45%	1139
	21st to end	Night	5% 3 1 4 4 3 5% 7% 7% 9% 53%	1164
July	1st to 10th	Night	4 2 2 3 4 3 5% 4 5% 6% 60%	1303
	11th to 20th	Night	3 3 2 3 3 2 3 5% 6% 8% 63%	1440
	21st to end	Night	3 2 1 2 2 2 2 3 4 6% 74%	1576
August	1st to 10th	Night	3 3 1 3 4 2 4 4 4 7% 63%	1432
	11th to 20th	Night	2 3 1 2 3 2 2 4 5% 7% 68%	1458
	21st to end	Night	4 3 1 2 3 2 5% 5% 6% 9% 60%	1958
September	1st to 10th	Night	5% 4 1 3 4 2 4 5% 4 7% 61%	1800
	11th to 20th	Night	6% 5% 1 4 4 3 3 4 5% 8% 57%	1814
	21st to end	Night	6% 6% 2 4 5% 3 4 5% 6% 8% 50%	1998
October	1st to 10th	Night	8% 6% 2 5% 6% 4 5% 5% 5% 6% 46%	2160
	11th to 20th	Night	8% 7% 3 6% 6% 4 5% 6% 6% 7% 43%	2196
	21st to end	Night	10% 8% 3 6% 5% 4 5% 6% 7% 8% 39%	2574
November	1st to 10th	Night	7% 12% 5% 8% 6% 5% 7% 5% 6% 7% 33%	2475
	11th to 20th	Night	6% 11% 4 8% 7% 5% 7% 6% 6% 8% 33%	2660
	21st to end	Night	3 11% 6% 12% 8% 5% 9% 7% 6% 6% 27%	2660
December	1st to 10th	Night	3 10% 6% 10% 8% 5% 6% 7% 6% 6% 32%	2849
	11th to 20th	Night	4 12% 6% 12% 8% 5% 12% 7% 6% 6% 21%	3510
	21st to end	Night	4 13% 7% 12% 10% 5% 8% 5% 5% 6% 24%	4976

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	71% 4 10% 9% 6%	2539
	11th to 20th	Day	53% 5% 18% 14% 4 6%	2540
	21st to end	Day	75% 3 9% 10% 3	2794
February	1st to 10th	Day	53% 7% 17% 17% 6% 1	1587
	11th to 20th	Day	48% 8% 19% 17% 7%	1674
	21st to end	Day	50% 8% 17% 16% 7% 1	1556
March	1st to 10th	Day	46% 7% 17% 19% 10% 1	3138
	11th to 20th	Day	33% 4 21% 35% 6%	3335
	21st to end	Day	54% 5% 17% 14% 9%	4120
April	1st to 10th	Day	49% 7% 16% 19% 8% 1	2270
	11th to 20th	Day	47% 6% 14% 21% 10% 2	2132
	21st to end	Day	42% 6% 15% 24% 11% 2	2449
May	1st to 10th	Day	38% 5% 17% 27% 11% 1	2520
	11th to 20th	Day	42% 5% 19% 24% 8% 1	2480
	21st to end	Day	49% 5% 14% 23% 8% 1	2724
June	1st to 10th	Day	47% 5% 14% 19% 11% 5%	2589
	11th to 20th	Day	46% 5% 16% 24% 9% 1	2815
	21st to end	Day	36% 5% 16% 25% 16% 3	2788
July	1st to 10th	Day	31% 5% 12% 25% 20% 7%	2581
	11th to 20th	Day	25% 4 10% 26% 27% 9%	2445
	21st to end	Day	17% 4 7% 27% 35% 9%	2589
August	1st to 10th	Day	23% 4 11% 30% 22% 10%	2490
	11th to 20th	Day	20% 3 13% 33% 25% 6%	2439
	21st to end	Day	27% 4 14% 34% 18% 2	2397
September	1st to 10th	Day	25% 3 15% 30% 23% 4	2160
	11th to 20th	Day	32% 6% 14% 25% 21% 4	2145
	21st to end	Day	34% 5% 18% 26% 15% 2	1959
October	1st to 10th	Day	35% 5% 16% 31% 12%	1800
	11th to 20th	Day	39% 6% 21% 24% 11%	1764
	21st to end	Day	48% 6% 16% 24% 6%	1782
November	1st to 10th	Day	53% 9% 16% 15% 7%	1603
	11th to 20th	Day	56% 7% 15% 15% 5% 2	1520
	21st to end	Day	58% 7% 15% 14% 6% 1	1499
December	1st to 10th	Day	57% 7% 16% 17% 3	1330
	11th to 20th	Day	68% 5% 13% 11% 4	1684
	21st to end	Day	66% 6% 11% 12% 4	2706
January	1st to 10th	Night	73% 3 11% 10% 3	4406
	11th to 20th	Night	51% 3 17% 18% 6% 4	4420
	21st to end	Night	78% 3 9% 7% 3	4862
February	1st to 10th	Night	57% 6% 16% 13% 6% 1	2589
	11th to 20th	Night	49% 6% 16% 20% 8%	2404
	21st to end	Night	49% 7% 18% 17% 8% 1	1897
March	1st to 10th	Night	41% 5% 21% 20% 12% 1	3736
	11th to 20th	Night	32% 4 20% 34% 9%	3631
	21st to end	Night	51% 5% 18% 19% 7%	3533
April	1st to 10th	Night	39% 7% 19% 24% 9% 1	1900
	11th to 20th	Night	37% 7% 19% 23% 13% 1	1779
	21st to end	Night	38% 5% 16% 28% 13% 1	1507
May	1st to 10th	Night	31% 4 19% 30% 15% 1	1440
	11th to 20th	Night	33% 4 25% 28% 10% 1	1416
	21st to end	Night	39% 6% 19% 28% 8% 1	1552
June	1st to 10th	Night	37% 5% 14% 29% 12% 3	1364
	11th to 20th	Night	34% 5% 18% 30% 13% 1	1139
	21st to end	Night	23% 5% 21% 28% 19% 4	1164
July	1st to 10th	Night	23% 3 14% 31% 20% 9%	1266
	11th to 20th	Night	18% 4 14% 28% 28% 8%	1392
	21st to end	Night	10% 3 9% 31% 37% 11%	1488
August	1st to 10th	Night	20% 4 10% 28% 28% 10%	1424
	11th to 20th	Night	14% 3 14% 34% 30% 6%	1458
	21st to end	Night	18% 3 14% 38% 22% 3	1958
September	1st to 10th	Night	21% 4 15% 32% 24% 5%	1800
	11th to 20th	Night	25% 3 15% 28% 24% 5%	1814
	21st to end	Night	29% 4 18% 32% 14% 3	1998
October	1st to 10th	Night	36% 4 17% 30% 12% 1	2160
	11th to 20th	Night	39% 5% 18% 26% 12%	2196
	21st to end	Night	44% 5% 18% 26% 7%	2574
November	1st to 10th	Night	51% 7% 18% 16% 7% 1	2475
	11th to 20th	Night	54% 7% 17% 15% 6% 2	2660
	21st to end	Night	62% 4 15% 13% 6%	2660
December	1st to 10th	Night	58% 5% 16% 17% 4	2849
	11th to 20th	Night	72% 5% 10% 9% 4	3507
	21st to end	Night	66% 4 12% 12% 5% 1	4976

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	17% 13% 33% 23% 12% 3	180
	11th to 20th	Day	22% 12% 29% 22% 13% 1	180
	21st to end	Day	27% 17% 26% 25% 5% 1	198
February	1st to 10th	Day	13% 21% 45% 19% 2	247
	11th to 20th	Day	16% 19% 40% 20% 5%	365
	21st to end	Day	11% 20% 40% 22% 7% 1	376
March	1st to 10th	Day	19% 23% 32% 20% 5% 1	460
	11th to 20th	Day	15% 22% 31% 20% 11% 2	460
	21st to end	Day	20% 24% 30% 18% 6% 1	506
April	1st to 10th	Day	23% 23% 30% 17% 5% 2	457
	11th to 20th	Day	19% 27% 26% 18% 7% 2	412
	21st to end	Day	13% 27% 30% 19% 8% 3	420
May	1st to 10th	Day	12% 23% 32% 23% 8% 2	423
	11th to 20th	Day	17% 15% 29% 24% 12% 3	448
	21st to end	Day	16% 14% 30% 26% 10% 3	485
June	1st to 10th	Day	17% 20% 33% 24% 6% 1	519
	11th to 20th	Day	14% 20% 30% 27% 8% 1	745
	21st to end	Day	7% 15% 36% 28% 12% 2	718
July	1st to 10th	Day	7% 15% 34% 33% 10% 1	576
	11th to 20th	Day	7% 18% 34% 30% 9% 2	444
	21st to end	Day	3 14% 36% 33% 11% 3	487
August	1st to 10th	Day	4 12% 31% 35% 13% 5%	447
	11th to 20th	Day	5% 12% 30% 33% 17% 3	437
	21st to end	Day	7% 18% 32% 29% 8% 6%	495
September	1st to 10th	Day	9% 17% 35% 25% 10% 4	450
	11th to 20th	Day	13% 17% 30% 25% 12% 4	450
	21st to end	Day	15% 20% 33% 20% 8% 3	450
October	1st to 10th	Day	14% 19% 32% 21% 11% 3	450
	11th to 20th	Day	16% 19% 27% 23% 11% 3	414
	21st to end	Day	22% 18% 30% 22% 6% 2	297
November	1st to 10th	Day	24% 15% 31% 25% 5%	237
	11th to 20th	Day	21% 17% 34% 20% 6% 2	180
	21st to end	Day	16% 18% 34% 20% 10% 2	180
December	1st to 10th	Day	21% 13% 24% 26% 12% 4	180
	11th to 20th	Day	19% 14% 36% 19% 9% 2	180
	21st to end	Day	17% 10% 36% 27% 8% 2	198
January	1st to 10th	Night	19% 10% 32% 28% 10% 2	760
	11th to 20th	Night	18% 8% 34% 29% 9% 2	760
	21st to end	Night	17% 7% 32% 31% 12% 1	836
February	1st to 10th	Night	17% 7% 35% 31% 9% 1	760
	11th to 20th	Night	12% 7% 35% 32% 13% 1	744
	21st to end	Night	13% 8% 32% 32% 14% 1	628
March	1st to 10th	Night	13% 9% 31% 32% 14% 1	760
	11th to 20th	Night	10% 11% 34% 29% 14% 1	760
	21st to end	Night	11% 11% 35% 32% 10% 1	836
April	1st to 10th	Night	13% 10% 31% 33% 13% 1	760
	11th to 20th	Night	10% 9% 39% 28% 12% 2	711
	21st to end	Night	8% 13% 38% 30% 9% 1	427
May	1st to 10th	Night	8% 9% 40% 32% 11% 1	360
	11th to 20th	Night	8% 6% 29% 34% 21% 2	354
	21st to end	Night	11% 7% 28% 39% 15%	389
June	1st to 10th	Night	11% 9% 36% 30% 14%	360
	11th to 20th	Night	12% 8% 32% 38% 10%	360
	21st to end	Night	6% 5% 34% 38% 17%	360
July	1st to 10th	Night	5% 5% 29% 44% 17% 1	350
	11th to 20th	Night	3 5% 37% 37% 18%	348
	21st to end	Night	2 6% 28% 44% 20% 1	394
August	1st to 10th	Night	5% 4 20% 46% 25% 1	358
	11th to 20th	Night	3 3 25% 43% 25% 2	390
	21st to end	Night	5% 5% 28% 38% 23% 2	770
September	1st to 10th	Night	5% 8% 27% 36% 23% 2	720
	11th to 20th	Night	9% 5% 20% 33% 30% 3	720
	21st to end	Night	11% 7% 27% 35% 18% 3	720
October	1st to 10th	Night	14% 8% 24% 33% 19% 2	720
	11th to 20th	Night	14% 8% 26% 35% 14% 3	720
	21st to end	Night	19% 8% 28% 31% 11% 2	792
November	1st to 10th	Night	21% 9% 31% 31% 7%	740
	11th to 20th	Night	21% 10% 32% 23% 12% 2	760
	21st to end	Night	19% 9% 31% 26% 12% 3	760
December	1st to 10th	Night	17% 6% 33% 32% 11% 1	949
	11th to 20th	Night	21% 10% 34% 28% 6% 1	950
	21st to end	Night	19% 11% 35% 29% 7%	898

Page generated at 2024-04-07 06:28:12. Version ac07

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