Bald Butte Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bald Butte Observing Site clear sky chart from 2005-11-06 to 2024-03-08.

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	12% 9% 3 6% 6% 3 5% 5% 5% 7% 39%	78207
	Night	14% 9% 4 7% 6% 3 5% 5% 5% 6% 37%	81336
Transparency	Day	46% 3 12% 21% 14% 4	77910
	Night	49% 3 12% 20% 12% 4	81154
Seeing	Day	16% 5% 19% 27% 23% 10%	13638
	Night	19% 5% 16% 36% 22% 4	23129

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	14% 17% 7% 10% 8% 4 6% 5% 6% 6% 16%	2539
	11th to 20th	Day	17% 15% 6% 10% 6% 4 5% 5% 6% 6% 20%	2540
	21st to end	Day	22% 16% 5% 10% 8% 4 5% 4 4 6% 17%	2794
February	1st to 10th	Day	17% 17% 5% 8% 6% 4 5% 5% 5% 7% 21%	1535
	11th to 20th	Day	16% 16% 5% 7% 8% 3 5% 5% 5% 6% 23%	1816
	21st to end	Day	14% 18% 5% 8% 7% 4 5% 6% 5% 6% 23%	1570
March	1st to 10th	Day	17% 13% 4 8% 7% 4 5% 5% 4 7% 26%	1871
	11th to 20th	Day	15% 10% 5% 8% 8% 5% 6% 6% 6% 7% 25%	1859
	21st to end	Day	16% 14% 6% 9% 7% 4 7% 5% 6% 5% 21%	2336
April	1st to 10th	Day	14% 10% 4 8% 8% 4 7% 6% 6% 8% 26%	2160
	11th to 20th	Day	12% 11% 4 8% 6% 4 4 5% 6% 7% 33%	2182
	21st to end	Day	13% 9% 3 7% 7% 4 6% 5% 6% 8% 33%	2340
May	1st to 10th	Day	9% 7% 3 5% 6% 3 5% 6% 6% 8% 43%	2415
	11th to 20th	Day	12% 7% 3 6% 6% 4 5% 6% 6% 8% 35%	2477
	21st to end	Day	12% 8% 4 7% 6% 3 6% 5% 7% 9% 34%	2723
June	1st to 10th	Day	14% 8% 3 6% 6% 4 5% 5% 6% 7% 35%	2587
	11th to 20th	Day	13% 7% 2 6% 6% 4 5% 5% 6% 8% 39%	2700
	21st to end	Day	6% 5% 2 4 4 3 4 4 4 6% 60%	2587
July	1st to 10th	Day	3 2 2 2 2 2 3 4 5% 5% 70%	2520
	11th to 20th	Day	3 2 1 3 2 1 3 3 4 5% 71%	2520
	21st to end	Day	1 1 1 2 2 1 2 3 3 5% 79%	2741
August	1st to 10th	Day	4 3 1 3 3 2 2 3 4 6% 69%	2507
	11th to 20th	Day	4 2 2 3 3 2 3 3 4 8% 68%	2333
	21st to end	Day	5% 4 1 3 3 2 3 4 5% 6% 62%	2414
September	1st to 10th	Day	4 2 1 3 3 2 2 3 3 7% 68%	2160
	11th to 20th	Day	7% 4 2 5% 4 3 4 5% 6% 8% 52%	2044
	21st to end	Day	9% 5% 2 5% 5% 3 3 5% 5% 8% 50%	1980
October	1st to 10th	Day	14% 8% 3 6% 5% 2 4 3 4 6% 44%	1936
	11th to 20th	Day	12% 6% 2 6% 6% 3 4 6% 6% 7% 41%	1697
	21st to end	Day	16% 10% 3 7% 6% 3 4 5% 5% 6% 33%	1782
November	1st to 10th	Day	23% 9% 4 6% 8% 4 5% 4 4 7% 26%	1674
	11th to 20th	Day	20% 10% 4 9% 8% 5% 7% 5% 5% 5% 22%	1675
	21st to end	Day	17% 12% 5% 8% 7% 4 6% 6% 6% 6% 23%	1466
December	1st to 10th	Day	18% 13% 5% 10% 8% 3 5% 5% 5% 6% 19%	1330
	11th to 20th	Day	18% 18% 5% 9% 8% 5% 5% 6% 4 4 18%	1685
	21st to end	Day	16% 14% 4 9% 7% 3 4 4 6% 7% 24%	2712
January	1st to 10th	Night	21% 14% 6% 10% 8% 5% 5% 4 5% 6% 17%	4406
	11th to 20th	Night	18% 14% 5% 8% 6% 3 4 5% 6% 6% 24%	4420
	21st to end	Night	21% 13% 5% 9% 8% 4 5% 4 5% 6% 20%	4862
February	1st to 10th	Night	18% 16% 4 8% 6% 3 5% 4 6% 5% 24%	2641
	11th to 20th	Night	15% 13% 5% 8% 6% 3 4 5% 5% 6% 31%	2252
	21st to end	Night	15% 14% 5% 9% 6% 4 6% 5% 5% 5% 25%	1884
March	1st to 10th	Night	15% 12% 5% 8% 6% 5% 5% 6% 5% 7% 28%	2249
	11th to 20th	Night	15% 9% 4 7% 8% 4 5% 5% 5% 7% 31%	2100
	21st to end	Night	16% 11% 4 7% 6% 4 6% 7% 6% 7% 26%	2016
April	1st to 10th	Night	14% 10% 4 6% 6% 4 6% 6% 6% 8% 31%	1800
	11th to 20th	Night	15% 9% 4 6% 6% 3 4 3 5% 6% 38%	1725
	21st to end	Night	12% 9% 3 7% 6% 4 5% 5% 5% 7% 37%	1620
May	1st to 10th	Night	9% 5% 2 6% 5% 4 5% 5% 5% 7% 47%	1543
	11th to 20th	Night	11% 5% 3 7% 4 3 6% 6% 7% 8% 39%	1416
	21st to end	Night	12% 6% 4 7% 5% 4 5% 6% 6% 9% 38%	1552
June	1st to 10th	Night	11% 5% 3 6% 5% 4 6% 5% 6% 8% 41%	1364
	11th to 20th	Night	11% 7% 3 5% 6% 2 6% 5% 7% 6% 42%	1260
	21st to end	Night	6% 4 2 5% 4 3 4 4 5% 5% 57%	1365
July	1st to 10th	Night	3 2 1 2 3 2 3 4 5% 6% 69%	1440
	11th to 20th	Night	2 1 1 3 2 1 3 3 5% 8% 71%	1440
	21st to end	Night	2 2 1 3 2 2 2 3 3 5% 75%	1576
August	1st to 10th	Night	3 3 1 2 3 2 2 4 5% 8% 67%	1432
	11th to 20th	Night	2 2 1 3 3 3 4 4 4 5% 68%	1568
	21st to end	Night	5% 3 2 3 3 2 3 3 4 7% 65%	1939
September	1st to 10th	Night	5% 3 1 2 3 2 3 4 4 7% 66%	1800
	11th to 20th	Night	6% 4 1 4 4 3 4 5% 5% 6% 56%	1915
	21st to end	Night	9% 6% 2 5% 4 3 3 4 5% 7% 52%	1980
October	1st to 10th	Night	10% 5% 3 5% 5% 2 4 4 6% 6% 49%	2022
	11th to 20th	Night	13% 6% 3 5% 6% 3 5% 4 4 6% 45%	2263
	21st to end	Night	17% 6% 3 6% 5% 3 5% 4 6% 5% 40%	2574
November	1st to 10th	Night	19% 10% 4 8% 6% 4 4 5% 5% 7% 29%	2405
	11th to 20th	Night	21% 10% 3 7% 7% 3 5% 4 5% 6% 29%	2503
	21st to end	Night	18% 10% 4 7% 6% 3 4 5% 6% 6% 31%	2690
December	1st to 10th	Night	17% 12% 3 7% 7% 4 5% 5% 5% 7% 27%	2850
	11th to 20th	Night	20% 15% 5% 9% 7% 4 6% 5% 5% 6% 17%	3506
	21st to end	Night	17% 12% 4 7% 7% 4 5% 5% 5% 7% 27%	4958

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% 3 14% 11% 1	2539
	11th to 20th	Day	65% 3 12% 15% 5%	2540
	21st to end	Day	71% 3 14% 10% 2 1	2794
February	1st to 10th	Day	64% 5% 15% 12% 5%	1535
	11th to 20th	Day	63% 3 12% 15% 5%	1826
	21st to end	Day	62% 4 9% 19% 6% 1	1570
March	1st to 10th	Day	59% 4 12% 19% 6%	1871
	11th to 20th	Day	58% 4 13% 20% 5%	1859
	21st to end	Day	64% 4 15% 14% 4	2336
April	1st to 10th	Day	55% 5% 15% 19% 7%	2160
	11th to 20th	Day	50% 4 13% 20% 13% 1	2185
	21st to end	Day	50% 4 11% 24% 10% 1	2340
May	1st to 10th	Day	39% 3 12% 33% 12% 1	2415
	11th to 20th	Day	47% 4 15% 24% 11% 1	2480
	21st to end	Day	47% 3 15% 26% 8% 1	2724
June	1st to 10th	Day	48% 4 12% 25% 10% 1	2587
	11th to 20th	Day	44% 3 13% 26% 12% 2	2700
	21st to end	Day	27% 3 10% 32% 24% 4	2587
July	1st to 10th	Day	17% 3 8% 26% 32% 15%	2451
	11th to 20th	Day	17% 2 7% 19% 36% 19%	2445
	21st to end	Day	10% 2 2 20% 46% 19%	2589
August	1st to 10th	Day	18% 1 6% 23% 38% 13%	2490
	11th to 20th	Day	18% 2 8% 26% 33% 12%	2333
	21st to end	Day	23% 3 7% 31% 28% 8%	2414
September	1st to 10th	Day	18% 3 9% 31% 27% 12%	2160
	11th to 20th	Day	31% 3 12% 26% 22% 6%	2044
	21st to end	Day	33% 3 16% 30% 14% 3	1980
October	1st to 10th	Day	43% 3 11% 28% 14% 1	1936
	11th to 20th	Day	41% 3 14% 29% 13% 1	1697
	21st to end	Day	51% 3 15% 23% 8%	1782
November	1st to 10th	Day	58% 4 14% 19% 4 1	1674
	11th to 20th	Day	63% 5% 13% 14% 3 1	1675
	21st to end	Day	60% 5% 14% 15% 5% 1	1466
December	1st to 10th	Day	65% 5% 11% 15% 3 1	1330
	11th to 20th	Day	71% 3 14% 10% 2	1684
	21st to end	Day	60% 2 17% 16% 4	2712
January	1st to 10th	Night	70% 2 12% 14% 1 1	4406
	11th to 20th	Night	61% 2 14% 17% 5% 1	4420
	21st to end	Night	66% 3 16% 13% 2	4862
February	1st to 10th	Night	62% 4 14% 14% 5% 1	2641
	11th to 20th	Night	56% 3 16% 18% 7%	2253
	21st to end	Night	60% 3 12% 17% 6% 1	1884
March	1st to 10th	Night	56% 4 12% 20% 8% 1	2249
	11th to 20th	Night	52% 3 11% 27% 7%	2100
	21st to end	Night	57% 5% 14% 20% 5%	2016
April	1st to 10th	Night	50% 4 13% 24% 9%	1800
	11th to 20th	Night	48% 3 10% 23% 14% 3	1725
	21st to end	Night	47% 4 12% 21% 14% 2	1620
May	1st to 10th	Night	38% 2 8% 31% 19% 2	1543
	11th to 20th	Night	41% 4 12% 27% 14% 3	1416
	21st to end	Night	43% 4 16% 27% 11% 1	1552
June	1st to 10th	Night	41% 5% 10% 28% 15% 1	1364
	11th to 20th	Night	41% 3 9% 27% 16% 4	1260
	21st to end	Night	28% 3 8% 27% 27% 7%	1365
July	1st to 10th	Night	17% 2 5% 21% 34% 21%	1400
	11th to 20th	Night	13% 3 6% 19% 32% 26%	1392
	21st to end	Night	13% 2 2 13% 38% 32%	1488
August	1st to 10th	Night	17% 3 4 17% 39% 20%	1424
	11th to 20th	Night	19% 2 6% 19% 35% 18%	1568
	21st to end	Night	20% 3 6% 24% 33% 14%	1939
September	1st to 10th	Night	19% 2 6% 27% 29% 16%	1800
	11th to 20th	Night	29% 3 7% 25% 27% 9%	1915
	21st to end	Night	33% 2 12% 28% 16% 8%	1980
October	1st to 10th	Night	36% 2 11% 33% 17% 1	2022
	11th to 20th	Night	41% 3 11% 26% 17% 2	2263
	21st to end	Night	45% 4 12% 24% 14% 1	2574
November	1st to 10th	Night	55% 3 12% 23% 6% 1	2405
	11th to 20th	Night	57% 2 15% 19% 5% 1	2503
	21st to end	Night	53% 3 15% 22% 6%	2690
December	1st to 10th	Night	57% 6% 15% 18% 4 1	2850
	11th to 20th	Night	69% 3 13% 13% 2	3507
	21st to end	Night	60% 2 18% 15% 6%	4958

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	28% 7% 22% 20% 18% 4	180
	11th to 20th	Day	28% 3 23% 27% 12% 7%	180
	21st to end	Day	29% 4 26% 28% 13% 1	198
February	1st to 10th	Day	28% 9% 29% 25% 8% 2	195
	11th to 20th	Day	28% 11% 18% 27% 14% 3	439
	21st to end	Day	23% 10% 23% 29% 12% 3	382
March	1st to 10th	Day	21% 9% 26% 27% 14% 4	449
	11th to 20th	Day	20% 7% 18% 28% 20% 7%	420
	21st to end	Day	20% 10% 27% 25% 16% 3	462
April	1st to 10th	Day	21% 9% 20% 26% 18% 6%	420
	11th to 20th	Day	19% 9% 28% 23% 14% 7%	412
	21st to end	Day	15% 8% 22% 29% 20% 6%	420
May	1st to 10th	Day	15% 4 20% 27% 27% 6%	423
	11th to 20th	Day	19% 4 16% 25% 19% 17%	448
	21st to end	Day	14% 3 15% 23% 28% 17%	485
June	1st to 10th	Day	15% 4 15% 26% 26% 14%	517
	11th to 20th	Day	16% 6% 23% 28% 21% 7%	630
	21st to end	Day	7% 3 16% 28% 32% 14%	517
July	1st to 10th	Day	4 2 14% 30% 37% 14%	446
	11th to 20th	Day	4 3 19% 30% 30% 14%	444
	21st to end	Day	2 2 17% 28% 35% 17%	487
August	1st to 10th	Day	6% 2 15% 27% 29% 20%	447
	11th to 20th	Day	4 3 9% 27% 35% 23%	437
	21st to end	Day	9% 3 17% 24% 29% 17%	495
September	1st to 10th	Day	6% 2 19% 26% 32% 15%	450
	11th to 20th	Day	10% 4 15% 27% 27% 17%	450
	21st to end	Day	12% 6% 18% 30% 27% 8%	450
October	1st to 10th	Day	16% 7% 15% 29% 25% 8%	450
	11th to 20th	Day	14% 7% 17% 30% 23% 9%	347
	21st to end	Day	25% 5% 20% 32% 15% 4	297
November	1st to 10th	Day	25% 5% 27% 31% 11%	270
	11th to 20th	Day	24% 8% 25% 25% 16% 3	253
	21st to end	Day	23% 3 23% 33% 15% 3	180
December	1st to 10th	Day	31% 5% 21% 24% 14% 6%	180
	11th to 20th	Day	32% 7% 24% 24% 8% 3	180
	21st to end	Day	32% 7% 24% 26% 9% 4	198
January	1st to 10th	Night	31% 8% 17% 29% 13% 2	760
	11th to 20th	Night	26% 7% 16% 33% 15% 4	760
	21st to end	Night	22% 5% 17% 36% 18% 2	836
February	1st to 10th	Night	27% 8% 19% 34% 11% 2	760
	11th to 20th	Night	23% 6% 18% 34% 16% 2	744
	21st to end	Night	23% 10% 17% 34% 14% 2	628
March	1st to 10th	Night	21% 4 19% 35% 18% 3	750
	11th to 20th	Night	18% 7% 19% 32% 22% 2	720
	21st to end	Night	23% 5% 19% 37% 15% 2	792
April	1st to 10th	Night	20% 5% 14% 38% 20% 3	720
	11th to 20th	Night	19% 5% 21% 34% 16% 3	657
	21st to end	Night	16% 4 18% 37% 21% 3	540
May	1st to 10th	Night	12% 3 21% 35% 25% 3	463
	11th to 20th	Night	13% 3 11% 33% 30% 10%	354
	21st to end	Night	14% 3 13% 32% 32% 6%	389
June	1st to 10th	Night	12% 4 13% 36% 28% 7%	360
	11th to 20th	Night	12% 6% 23% 32% 23% 4	360
	21st to end	Night	8% 2 13% 40% 33% 5%	360
July	1st to 10th	Night	4 1 11% 38% 39% 7%	350
	11th to 20th	Night	3 1 16% 44% 33% 3	348
	21st to end	Night	2 2 11% 37% 42% 6%	394
August	1st to 10th	Night	5% 2 9% 36% 41% 7%	358
	11th to 20th	Night	3 1 8% 35% 43% 10%	500
	21st to end	Night	6% 2 14% 38% 36% 4	751
September	1st to 10th	Night	6% 1 13% 42% 30% 8%	720
	11th to 20th	Night	9% 2 10% 34% 38% 8%	720
	21st to end	Night	13% 2 14% 38% 29% 5%	720
October	1st to 10th	Night	14% 2 13% 43% 25% 4	720
	11th to 20th	Night	18% 5% 12% 34% 26% 5%	720
	21st to end	Night	20% 4 18% 37% 17% 5%	792
November	1st to 10th	Night	25% 5% 15% 39% 16% 1	740
	11th to 20th	Night	26% 6% 17% 34% 14% 2	760
	21st to end	Night	22% 6% 15% 33% 20% 4	790
December	1st to 10th	Night	24% 4 15% 38% 16% 2	950
	11th to 20th	Night	29% 5% 16% 36% 13% 1	950
	21st to end	Night	33% 8% 19% 29% 10% 1	893

Page generated at 2024-03-05 04:24:03. Version ac07

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