Mt Bachelor Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mt Bachelor Star Party clear sky chart from 2005-11-06 to 2024-03-18.

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	5% 9% 5% 8% 7% 4 5% 5% 5% 6% 41%	78630
	Night	4 9% 5% 9% 9% 5% 6% 6% 5% 6% 38%	81176
Transparency	Day	39% 9% 12% 19% 15% 6%	78333
	Night	40% 12% 13% 17% 14% 5%	80994
Seeing	Day	12% 20% 28% 24% 13% 3	13788
	Night	9% 15% 24% 31% 18% 2	23009

By Month

Percentage Cloud Cover SW (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	5% 13% 7% 17% 12% 7% 6% 5% 6% 5% 19%	2539
	11th to 20th	Day	7% 15% 6% 11% 14% 6% 5% 4 3 4 25%	2540
	21st to end	Day	4 18% 9% 14% 10% 4 6% 4 4 5% 23%	3054
February	1st to 10th	Day	5% 12% 7% 12% 10% 5% 7% 6% 4 6% 25%	1710
	11th to 20th	Day	5% 12% 6% 11% 10% 5% 6% 5% 5% 6% 29%	1665
	21st to end	Day	2 11% 9% 14% 12% 6% 7% 6% 5% 5% 23%	1560
March	1st to 10th	Day	4 14% 8% 12% 12% 4 6% 5% 6% 5% 23%	1943
	11th to 20th	Day	4 14% 7% 11% 10% 5% 6% 4 5% 7% 28%	2059
	21st to end	Day	6% 16% 9% 13% 10% 4 6% 5% 4 6% 20%	2258
April	1st to 10th	Day	8% 13% 9% 11% 10% 4 6% 7% 5% 5% 22%	2160
	11th to 20th	Day	6% 14% 8% 10% 8% 4 6% 5% 6% 6% 29%	2129
	21st to end	Day	3 13% 5% 9% 8% 4 6% 6% 5% 8% 34%	2232
May	1st to 10th	Day	7% 12% 4 7% 6% 3 5% 6% 6% 8% 39%	2488
	11th to 20th	Day	8% 11% 4 8% 8% 4 5% 5% 6% 7% 33%	2477
	21st to end	Day	10% 12% 5% 8% 8% 4 5% 6% 6% 8% 29%	2723
June	1st to 10th	Day	11% 10% 4 8% 6% 3 5% 5% 5% 7% 37%	2520
	11th to 20th	Day	6% 8% 3 7% 6% 2 5% 5% 5% 8% 44%	2520
	21st to end	Day	5% 4 2 5% 4 2 3 4 4 6% 61%	2520
July	1st to 10th	Day	2 2 2 3 3 2 3 3 3 6% 72%	2520
	11th to 20th	Day	3 2 2 3 2 2 2 3 3 5% 73%	2520
	21st to end	Day	2 2 1 1 2 1 3 3 3 4 78%	2741
August	1st to 10th	Day	2 2 1 3 3 2 3 4 6% 7% 68%	2358
	11th to 20th	Day	2 2 1 3 3 2 3 3 4 6% 72%	2298
	21st to end	Day	3 2 1 2 2 1 3 3 3 5% 74%	2376
September	1st to 10th	Day	2 3 1 3 3 2 3 3 4 4 73%	2160
	11th to 20th	Day	4 5% 2 6% 6% 3 5% 4 5% 6% 53%	2160
	21st to end	Day	6% 7% 2 5% 5% 3 5% 4 5% 6% 52%	1918
October	1st to 10th	Day	6% 10% 4 6% 6% 4 4 4 4 4 48%	1800
	11th to 20th	Day	5% 8% 4 7% 8% 4 6% 5% 4 5% 44%	1800
	21st to end	Day	7% 8% 5% 8% 7% 4 5% 5% 5% 6% 40%	1921
November	1st to 10th	Day	6% 10% 6% 11% 10% 4 7% 5% 6% 6% 29%	1674
	11th to 20th	Day	3 9% 6% 12% 10% 5% 7% 7% 5% 8% 27%	1525
	21st to end	Day	3 10% 6% 12% 11% 5% 7% 6% 6% 6% 29%	1520
December	1st to 10th	Day	5% 8% 5% 11% 9% 5% 7% 6% 6% 5% 32%	1520
	11th to 20th	Day	6% 13% 7% 12% 10% 4 6% 6% 7% 7% 22%	1928
	21st to end	Day	3 12% 9% 15% 12% 5% 6% 5% 5% 5% 23%	2794
January	1st to 10th	Night	4 14% 7% 12% 12% 7% 7% 7% 6% 7% 17%	4406
	11th to 20th	Night	4 13% 6% 13% 13% 8% 5% 5% 5% 5% 22%	4420
	21st to end	Night	5% 20% 7% 12% 11% 5% 5% 5% 5% 4 21%	4605
February	1st to 10th	Night	4 9% 6% 11% 11% 5% 7% 7% 5% 7% 26%	2470
	11th to 20th	Night	3 10% 5% 10% 10% 5% 7% 7% 5% 6% 30%	2402
	21st to end	Night	3 7% 7% 14% 12% 6% 7% 7% 6% 6% 25%	1894
March	1st to 10th	Night	4 9% 5% 13% 12% 6% 8% 8% 6% 6% 24%	2233
	11th to 20th	Night	2 9% 5% 11% 11% 6% 9% 7% 6% 8% 27%	2067
	21st to end	Night	4 11% 6% 13% 11% 6% 8% 8% 6% 7% 21%	2098
April	1st to 10th	Night	5% 10% 6% 12% 10% 4 8% 7% 6% 6% 26%	1800
	11th to 20th	Night	4 9% 6% 10% 9% 4 8% 6% 6% 7% 32%	1779
	21st to end	Night	4 10% 5% 9% 8% 4 7% 6% 5% 7% 35%	1725
May	1st to 10th	Night	5% 10% 4 6% 5% 3 4 6% 5% 8% 43%	1469
	11th to 20th	Night	6% 7% 4 6% 6% 4 6% 7% 8% 9% 37%	1416
	21st to end	Night	5% 8% 5% 7% 9% 4 5% 6% 5% 8% 37%	1552
June	1st to 10th	Night	10% 10% 5% 7% 5% 4 3 4 5% 9% 39%	1440
	11th to 20th	Night	5% 7% 3 5% 5% 2 5% 6% 6% 8% 48%	1440
	21st to end	Night	5% 4 2 3 4 2 3 4 5% 5% 64%	1440
July	1st to 10th	Night	2 3 1 2 2 1 2 3 4 7% 73%	1440
	11th to 20th	Night	2 2 1 2 1 1 2 3 3 5% 78%	1440
	21st to end	Night	1 2 2 1 1 2 2 3 4 80%	1576
August	1st to 10th	Night	2 2 1 2 2 1 2 3 4 8% 73%	1578
	11th to 20th	Night	1 3 1 2 3 1 2 2 3 5% 76%	1602
	21st to end	Night	2 2 1 2 2 2 2 3 4 5% 75%	1979
September	1st to 10th	Night	2 2 1 2 3 1 3 3 3 6% 77%	1800
	11th to 20th	Night	3 3 2 5% 5% 3 4 4 5% 6% 59%	1800
	21st to end	Night	4 5% 2 5% 5% 3 4 5% 5% 7% 56%	2038
October	1st to 10th	Night	4 7% 3 6% 7% 4 4 4 5% 6% 50%	2160
	11th to 20th	Night	5% 7% 3 6% 7% 4 5% 5% 5% 5% 48%	2160
	21st to end	Night	6% 9% 3 8% 9% 5% 5% 6% 6% 4 40%	2434
November	1st to 10th	Night	5% 9% 6% 11% 11% 5% 7% 6% 5% 6% 29%	2405
	11th to 20th	Night	3 9% 5% 10% 12% 6% 8% 8% 7% 7% 26%	2650
	21st to end	Night	2 6% 5% 11% 12% 5% 7% 7% 7% 7% 32%	2660
December	1st to 10th	Night	5% 8% 5% 10% 9% 6% 7% 7% 6% 7% 29%	2660
	11th to 20th	Night	5% 14% 6% 12% 11% 5% 7% 6% 5% 7% 22%	3276
	21st to end	Night	3 12% 7% 12% 11% 5% 6% 6% 5% 6% 26%	4862

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	51% 21% 13% 11% 4 1	2539
	11th to 20th	Day	56% 13% 9% 14% 4 3	2540
	21st to end	Day	53% 16% 10% 13% 6% 2	3054
February	1st to 10th	Day	52% 12% 14% 16% 7%	1710
	11th to 20th	Day	49% 13% 11% 14% 10% 2	1674
	21st to end	Day	54% 13% 13% 13% 6% 1	1560
March	1st to 10th	Day	53% 12% 14% 14% 7% 1	1943
	11th to 20th	Day	51% 11% 12% 19% 7% 1	2059
	21st to end	Day	60% 10% 13% 12% 5%	2258
April	1st to 10th	Day	57% 10% 11% 13% 7% 2	2160
	11th to 20th	Day	50% 10% 14% 14% 11% 3	2132
	21st to end	Day	42% 10% 16% 21% 9% 2	2232
May	1st to 10th	Day	37% 10% 15% 25% 12%	2488
	11th to 20th	Day	46% 9% 13% 22% 9% 1	2480
	21st to end	Day	47% 10% 17% 18% 8% 1	2724
June	1st to 10th	Day	43% 8% 14% 26% 9% 1	2520
	11th to 20th	Day	34% 8% 15% 29% 11% 3	2520
	21st to end	Day	22% 5% 12% 29% 23% 8%	2520
July	1st to 10th	Day	15% 5% 10% 22% 27% 22%	2451
	11th to 20th	Day	14% 4 9% 14% 32% 28%	2445
	21st to end	Day	11% 2 4 16% 41% 26%	2589
August	1st to 10th	Day	13% 6% 10% 27% 28% 16%	2341
	11th to 20th	Day	14% 4 8% 23% 34% 16%	2298
	21st to end	Day	14% 3 7% 24% 37% 15%	2376
September	1st to 10th	Day	14% 4 7% 24% 32% 20%	2160
	11th to 20th	Day	28% 6% 10% 22% 24% 10%	2160
	21st to end	Day	29% 6% 12% 24% 19% 10%	1918
October	1st to 10th	Day	37% 7% 9% 17% 23% 8%	1800
	11th to 20th	Day	38% 8% 12% 19% 19% 5%	1800
	21st to end	Day	39% 10% 13% 16% 19% 3	1921
November	1st to 10th	Day	48% 11% 13% 15% 13% 1	1674
	11th to 20th	Day	51% 13% 12% 14% 8% 2	1525
	21st to end	Day	48% 10% 14% 11% 15% 3	1520
December	1st to 10th	Day	44% 13% 12% 19% 10% 2	1520
	11th to 20th	Day	52% 14% 14% 13% 6% 1	1928
	21st to end	Day	52% 17% 11% 15% 4 1	2794
January	1st to 10th	Night	52% 20% 13% 11% 4 1	4406
	11th to 20th	Night	53% 15% 11% 12% 4 4	4420
	21st to end	Night	58% 12% 11% 10% 7% 2	4605
February	1st to 10th	Night	49% 14% 13% 14% 9% 1	2470
	11th to 20th	Night	45% 14% 16% 15% 7% 3	2404
	21st to end	Night	50% 15% 12% 14% 8% 2	1894
March	1st to 10th	Night	50% 13% 13% 16% 7% 1	2233
	11th to 20th	Night	45% 13% 15% 19% 7% 1	2067
	21st to end	Night	54% 13% 14% 15% 4	2098
April	1st to 10th	Night	50% 13% 16% 13% 7% 1	1800
	11th to 20th	Night	43% 13% 16% 16% 9% 2	1779
	21st to end	Night	44% 12% 16% 18% 9% 2	1725
May	1st to 10th	Night	35% 11% 15% 28% 10% 1	1469
	11th to 20th	Night	38% 10% 18% 23% 10% 2	1416
	21st to end	Night	40% 14% 17% 22% 8%	1552
June	1st to 10th	Night	40% 10% 12% 28% 8% 1	1440
	11th to 20th	Night	28% 9% 18% 31% 12% 2	1440
	21st to end	Night	20% 6% 12% 32% 24% 6%	1440
July	1st to 10th	Night	12% 6% 11% 25% 26% 20%	1400
	11th to 20th	Night	10% 2 10% 20% 29% 28%	1392
	21st to end	Night	9% 2 5% 17% 44% 23%	1488
August	1st to 10th	Night	11% 3 9% 30% 34% 12%	1570
	11th to 20th	Night	13% 4 7% 27% 36% 14%	1602
	21st to end	Night	11% 3 9% 26% 37% 14%	1979
September	1st to 10th	Night	10% 4 7% 26% 36% 17%	1800
	11th to 20th	Night	22% 8% 11% 21% 28% 10%	1800
	21st to end	Night	24% 7% 12% 23% 21% 12%	2038
October	1st to 10th	Night	32% 8% 10% 18% 24% 8%	2160
	11th to 20th	Night	33% 9% 14% 17% 20% 7%	2160
	21st to end	Night	38% 13% 12% 12% 19% 5%	2434
November	1st to 10th	Night	47% 13% 13% 12% 12% 3	2405
	11th to 20th	Night	49% 13% 13% 13% 9% 2	2650
	21st to end	Night	43% 13% 13% 13% 13% 6%	2660
December	1st to 10th	Night	44% 14% 13% 16% 11% 2	2660
	11th to 20th	Night	54% 14% 11% 11% 9% 1	3276
	21st to end	Night	45% 17% 15% 16% 6% 1	4862

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	22% 32% 24% 14% 7% 2	180
	11th to 20th	Day	30% 14% 23% 23% 8% 2	180
	21st to end	Day	15% 28% 24% 20% 12% 2	354
February	1st to 10th	Day	18% 28% 27% 19% 9%	370
	11th to 20th	Day	16% 38% 23% 16% 6% 1	365
	21st to end	Day	18% 30% 27% 19% 7%	377
March	1st to 10th	Day	17% 30% 29% 19% 5%	460
	11th to 20th	Day	18% 24% 28% 22% 8%	449
	21st to end	Day	21% 28% 30% 16% 5%	462
April	1st to 10th	Day	24% 23% 28% 13% 9% 2	420
	11th to 20th	Day	20% 29% 26% 16% 7% 2	412
	21st to end	Day	12% 30% 30% 18% 8% 2	420
May	1st to 10th	Day	15% 21% 31% 22% 8% 3	423
	11th to 20th	Day	20% 21% 26% 17% 13% 3	448
	21st to end	Day	14% 16% 31% 22% 13% 4	485
June	1st to 10th	Day	11% 23% 24% 24% 14% 4	450
	11th to 20th	Day	13% 23% 31% 21% 10% 2	450
	21st to end	Day	4 13% 29% 31% 19% 4	450
July	1st to 10th	Day	3 11% 37% 32% 14% 3	446
	11th to 20th	Day	3 10% 38% 28% 16% 5%	444
	21st to end	Day	1 10% 33% 33% 17% 6%	487
August	1st to 10th	Day	2 9% 30% 34% 17% 7%	447
	11th to 20th	Day	2 8% 26% 35% 20% 9%	437
	21st to end	Day	6% 9% 29% 34% 16% 6%	495
September	1st to 10th	Day	4 8% 30% 34% 19% 5%	450
	11th to 20th	Day	7% 14% 26% 36% 15% 3	450
	21st to end	Day	11% 18% 24% 30% 16% 1	450
October	1st to 10th	Day	11% 19% 26% 22% 21% 1	450
	11th to 20th	Day	12% 20% 21% 24% 20% 3	450
	21st to end	Day	13% 24% 26% 17% 16% 3	436
November	1st to 10th	Day	14% 21% 31% 22% 12% 1	270
	11th to 20th	Day	10% 26% 31% 21% 9% 3	183
	21st to end	Day	14% 26% 22% 26% 10% 2	180
December	1st to 10th	Day	13% 25% 22% 24% 10% 6%	180
	11th to 20th	Day	15% 28% 30% 19% 7% 1	180
	21st to end	Day	14% 28% 29% 18% 9% 2	198
January	1st to 10th	Night	17% 21% 30% 19% 11% 2	760
	11th to 20th	Night	15% 21% 25% 22% 16% 2	760
	21st to end	Night	12% 17% 27% 28% 12% 4	836
February	1st to 10th	Night	12% 21% 28% 29% 9% 1	760
	11th to 20th	Night	10% 21% 28% 28% 12% 1	744
	21st to end	Night	13% 21% 32% 26% 7%	628
March	1st to 10th	Night	12% 24% 27% 27% 9% 1	760
	11th to 20th	Night	7% 24% 27% 30% 12% 1	752
	21st to end	Night	11% 24% 30% 24% 11%	792
April	1st to 10th	Night	11% 21% 28% 27% 12% 1	720
	11th to 20th	Night	8% 21% 32% 24% 13% 3	711
	21st to end	Night	9% 17% 28% 32% 13% 1	645
May	1st to 10th	Night	8% 15% 24% 31% 20% 1	389
	11th to 20th	Night	9% 11% 20% 35% 23% 1	354
	21st to end	Night	10% 7% 25% 34% 22% 2	389
June	1st to 10th	Night	12% 9% 22% 36% 20% 2	360
	11th to 20th	Night	6% 9% 26% 41% 17% 1	360
	21st to end	Night	6% 3 16% 53% 22%	360
July	1st to 10th	Night	3 2 12% 55% 27% 1	350
	11th to 20th	Night	1 1 16% 59% 23% 1	348
	21st to end	Night	2 1 10% 56% 31% 1	394
August	1st to 10th	Night	3 1 9% 42% 41% 4	504
	11th to 20th	Night	2 1 8% 43% 40% 5%	534
	21st to end	Night	2 3 22% 43% 29% 1	791
September	1st to 10th	Night	2 4 19% 41% 31% 3	720
	11th to 20th	Night	4 5% 16% 36% 34% 4	720
	21st to end	Night	7% 8% 22% 34% 26% 3	720
October	1st to 10th	Night	7% 7% 30% 29% 24% 4	720
	11th to 20th	Night	8% 14% 21% 30% 23% 4	720
	21st to end	Night	11% 16% 26% 26% 16% 5%	792
November	1st to 10th	Night	9% 19% 30% 28% 11% 1	740
	11th to 20th	Night	12% 23% 26% 26% 13% 1	760
	21st to end	Night	8% 22% 24% 30% 13% 3	760
December	1st to 10th	Night	12% 16% 27% 29% 14% 2	760
	11th to 20th	Night	12% 23% 26% 27% 11% 1	760
	21st to end	Night	11% 31% 27% 22% 8% 1	836

Page generated at 2024-03-15 11:01:42. Version ac07

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