Auburn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Auburn clear sky chart from 2005-11-06 to 2024-07-16.

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	11% 4 1 3 2 2 3 2 4 5% 62%	89845
	Night	13% 5% 1 4 3 3 3 2 4 5% 57%	89800
Transparency	Day	26% 3 8% 20% 24% 19%	89558
	Night	30% 3 8% 19% 21% 18%	89608
Seeing	Day	11% 6% 20% 32% 24% 6%	14730
	Night	13% 3 11% 37% 31% 6%	24053

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	27% 8% 2 4 2 3 3 2 4 5% 38%	2539
	11th to 20th	Day	27% 8% 3 7% 4 4 4 2 3 4 33%	2768
	21st to end	Day	26% 9% 3 6% 3 3 4 3 4 7% 31%	3146
February	1st to 10th	Day	22% 5% 2 5% 2 3 3 4 5% 5% 45%	1710
	11th to 20th	Day	19% 6% 1 5% 4 3 3 3 4 5% 47%	1787
	21st to end	Day	19% 7% 2 5% 3 3 2 3 4 6% 47%	1570
March	1st to 10th	Day	21% 12% 4 7% 5% 4 4 3 5% 4 30%	3227
	11th to 20th	Day	16% 4 1 3 3 3 2 2 4 6% 56%	3490
	21st to end	Day	19% 8% 2 6% 4 4 5% 4 6% 8% 34%	3975
April	1st to 10th	Day	16% 6% 2 3 4 3 4 4 5% 6% 47%	2280
	11th to 20th	Day	13% 4 1 4 3 2 3 3 5% 6% 55%	2249
	21st to end	Day	9% 4 2 2 2 2 3 3 4 8% 61%	2280
May	1st to 10th	Day	8% 2 1 3 2 1 2 2 3 4 72%	3889
	11th to 20th	Day	3 2 1 2 2 1 2 2 2 4 80%	4377
	21st to end	Day	4 2 1 2 2 2 2 2 4 5% 75%	4813
June	1st to 10th	Day	6% 3 1 3 3 3 2 3 4 6% 67%	2660
	11th to 20th	Day	2 2 2 1 2 2 2 3 4 81%	2660
	21st to end	Day	2 1 1 1 1 1 2 1 2 3 84%	2660
July	1st to 10th	Day	1 1 1 1 2 2 3 88%	2660
	11th to 20th	Day	1 1 1 1 1 1 2 2 2 3 86%	2593
	21st to end	Day	1 1 1 2 1 2 2 2 3 4 83%	2567
August	1st to 10th	Day	3 1 2 1 1 1 2 2 3 84%	2328
	11th to 20th	Day	1 1 1 1 1 1 2 3 3 87%	2156
	21st to end	Day	1 1 1 1 1 1 1 2 92%	2376
September	1st to 10th	Day	2 1 1 1 1 1 2 3 88%	2160
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 3 77%	2160
	21st to end	Day	4 2 1 2 1 2 2 2 2 4 79%	1946
October	1st to 10th	Day	5% 2 1 2 3 2 2 2 4 6% 71%	1800
	11th to 20th	Day	7% 2 1 2 2 2 4 3 5% 4 69%	1800
	21st to end	Day	8% 4 2 4 2 3 3 2 4 5% 65%	1980
November	1st to 10th	Day	13% 4 1 3 3 4 3 3 5% 7% 54%	1706
	11th to 20th	Day	14% 3 1 4 4 4 3 3 5% 7% 53%	1710
	21st to end	Day	13% 4 1 3 3 3 3 3 4 7% 55%	1581
December	1st to 10th	Day	17% 4 2 6% 4 3 3 3 3 6% 49%	1520
	11th to 20th	Day	31% 9% 2 6% 4 2 3 3 4 5% 32%	1928
	21st to end	Day	17% 7% 2 5% 4 4 5% 4 7% 8% 36%	2794
January	1st to 10th	Night	19% 9% 3 5% 3 3 3 3 5% 6% 41%	4406
	11th to 20th	Night	25% 7% 2 6% 4 4 5% 4 4 5% 35%	4194
	21st to end	Night	27% 7% 3 7% 4 4 4 3 4 5% 32%	4521
February	1st to 10th	Night	20% 5% 2 4 3 3 3 2 4 4 50%	2470
	11th to 20th	Night	17% 5% 2 5% 3 3 4 3 5% 7% 46%	2279
	21st to end	Night	18% 6% 1 4 3 3 3 3 3 5% 50%	1884
March	1st to 10th	Night	26% 12% 2 6% 4 4 3 2 4 4 32%	3643
	11th to 20th	Night	19% 5% 1 3 2 2 2 2 3 4 57%	3490
	21st to end	Night	22% 7% 3 5% 4 4 4 3 5% 7% 35%	3676
April	1st to 10th	Night	14% 6% 2 5% 4 3 3 4 4 5% 49%	1900
	11th to 20th	Night	13% 5% 1 5% 3 3 3 3 4 6% 55%	1879
	21st to end	Night	8% 3 1 3 2 2 4 2 5% 6% 64%	1900
May	1st to 10th	Night	6% 4 1 3 2 2 2 3 4 5% 69%	3084
	11th to 20th	Night	4 1 1 2 1 1 2 2 3 5% 80%	2516
	21st to end	Night	3 1 2 1 1 2 2 3 5% 78%	2762
June	1st to 10th	Night	6% 3 1 3 3 3 2 4 4 6% 66%	1520
	11th to 20th	Night	1 1 1 2 2 2 2 2 2 6% 80%	1520
	21st to end	Night	2 1 1 1 1 2 2 2 3 3 83%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 3 89%	1520
	11th to 20th	Night	1 1 1 1 1 2 1 2 3 86%	1488
	21st to end	Night	1 2 2 2 1 2 2 4 4 80%	1747
August	1st to 10th	Night	2 2 1 2 2 2 2 2 3 3 79%	1611
	11th to 20th	Night	1 1 1 2 1 1 2 2 3 4 83%	1746
	21st to end	Night	1 1 1 1 1 1 2 1 2 2 87%	1980
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 88%	1800
	11th to 20th	Night	3 2 2 1 1 2 1 3 5% 79%	1800
	21st to end	Night	3 1 1 1 2 2 2 2 4 4 79%	2011
October	1st to 10th	Night	6% 3 1 3 2 2 3 2 3 3 73%	2160
	11th to 20th	Night	7% 2 1 3 2 1 2 2 3 5% 72%	2160
	21st to end	Night	7% 2 1 3 2 2 2 2 4 6% 69%	2376
November	1st to 10th	Night	14% 5% 1 3 2 3 3 2 5% 7% 55%	2373
	11th to 20th	Night	12% 4 1 3 3 3 3 3 5% 7% 56%	2470
	21st to end	Night	14% 4 1 3 3 3 3 2 4 6% 57%	2596
December	1st to 10th	Night	20% 5% 1 4 2 3 3 3 4 5% 51%	2660
	11th to 20th	Night	31% 7% 2 4 2 2 3 2 5% 7% 33%	3276
	21st to end	Night	20% 6% 3 7% 5% 5% 4 3 5% 6% 35%	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	50% 3 10% 24% 11% 3	2539
	11th to 20th	Day	57% 3 9% 13% 11% 8%	2768
	21st to end	Day	54% 3 11% 16% 11% 5%	3146
February	1st to 10th	Day	40% 4 10% 20% 17% 10%	1710
	11th to 20th	Day	39% 4 10% 19% 20% 8%	1796
	21st to end	Day	40% 4 10% 23% 17% 7%	1570
March	1st to 10th	Day	56% 5% 10% 15% 12% 3	3227
	11th to 20th	Day	31% 3 10% 32% 15% 10%	3490
	21st to end	Day	45% 7% 14% 21% 10% 2	3975
April	1st to 10th	Day	37% 5% 11% 25% 16% 6%	2280
	11th to 20th	Day	29% 4 13% 26% 21% 6%	2252
	21st to end	Day	23% 4 13% 29% 26% 4	2280
May	1st to 10th	Day	17% 3 9% 30% 25% 16%	3889
	11th to 20th	Day	12% 2 5% 26% 43% 12%	4380
	21st to end	Day	13% 3 11% 36% 30% 6%	4814
June	1st to 10th	Day	19% 3 10% 26% 29% 12%	2660
	11th to 20th	Day	9% 2 7% 20% 36% 25%	2660
	21st to end	Day	8% 1 2 13% 35% 40%	2660
July	1st to 10th	Day	5% 1 2 8% 25% 58%	2591
	11th to 20th	Day	7% 2 3 10% 24% 54%	2518
	21st to end	Day	8% 2 1 7% 24% 57%	2424
August	1st to 10th	Day	8% 2 3 11% 29% 48%	2312
	11th to 20th	Day	5% 1 1 10% 33% 49%	2156
	21st to end	Day	4 1 1 10% 35% 48%	2376
September	1st to 10th	Day	5% 1 2 8% 28% 56%	2160
	11th to 20th	Day	13% 3 4 21% 35% 24%	2160
	21st to end	Day	12% 2 4 19% 34% 29%	1946
October	1st to 10th	Day	17% 3 6% 19% 28% 28%	1800
	11th to 20th	Day	18% 4 6% 20% 24% 28%	1800
	21st to end	Day	23% 3 7% 19% 26% 22%	1980
November	1st to 10th	Day	29% 5% 9% 21% 22% 14%	1706
	11th to 20th	Day	33% 4 10% 23% 23% 8%	1710
	21st to end	Day	30% 4 10% 20% 24% 11%	1581
December	1st to 10th	Day	39% 4 9% 20% 19% 9%	1520
	11th to 20th	Day	55% 4 9% 13% 14% 5%	1928
	21st to end	Day	44% 5% 18% 19% 10% 4	2794
January	1st to 10th	Night	44% 4 15% 23% 10% 4	4406
	11th to 20th	Night	51% 4 13% 11% 11% 10%	4194
	21st to end	Night	55% 3 11% 13% 12% 6%	4521
February	1st to 10th	Night	39% 2 7% 21% 20% 11%	2470
	11th to 20th	Night	37% 4 8% 22% 21% 9%	2281
	21st to end	Night	35% 5% 9% 24% 20% 7%	1884
March	1st to 10th	Night	56% 5% 9% 15% 11% 4	3643
	11th to 20th	Night	33% 3 7% 27% 19% 11%	3490
	21st to end	Night	47% 6% 11% 22% 10% 4	3676
April	1st to 10th	Night	36% 5% 12% 20% 20% 6%	1900
	11th to 20th	Night	31% 5% 12% 26% 16% 10%	1879
	21st to end	Night	22% 5% 12% 32% 23% 7%	1900
May	1st to 10th	Night	17% 5% 13% 22% 25% 18%	3084
	11th to 20th	Night	11% 2 7% 26% 41% 14%	2516
	21st to end	Night	11% 3 12% 38% 30% 6%	2762
June	1st to 10th	Night	19% 5% 10% 27% 28% 11%	1520
	11th to 20th	Night	9% 3 6% 21% 33% 28%	1520
	21st to end	Night	9% 2 3 12% 33% 41%	1520
July	1st to 10th	Night	4 2 2 11% 26% 56%	1480
	11th to 20th	Night	7% 2 2 11% 22% 56%	1440
	21st to end	Night	9% 3 2 8% 24% 54%	1650
August	1st to 10th	Night	12% 2 2 14% 26% 45%	1602
	11th to 20th	Night	8% 2 1 10% 32% 48%	1746
	21st to end	Night	7% 1 1 10% 30% 51%	1980
September	1st to 10th	Night	6% 2 2 8% 29% 55%	1800
	11th to 20th	Night	12% 2 5% 19% 40% 24%	1800
	21st to end	Night	11% 2 4 19% 30% 34%	2011
October	1st to 10th	Night	18% 3 5% 17% 27% 30%	2160
	11th to 20th	Night	17% 3 4 19% 25% 31%	2160
	21st to end	Night	18% 2 6% 21% 27% 25%	2376
November	1st to 10th	Night	30% 4 9% 22% 18% 17%	2373
	11th to 20th	Night	28% 4 9% 26% 22% 10%	2470
	21st to end	Night	30% 3 7% 22% 22% 15%	2596
December	1st to 10th	Night	36% 4 10% 19% 18% 13%	2660
	11th to 20th	Night	52% 3 7% 16% 15% 7%	3276
	21st to end	Night	51% 4 13% 18% 11% 4	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	41% 6% 19% 17% 15% 2	180
	11th to 20th	Day	23% 6% 18% 28% 20% 4	317
	21st to end	Day	23% 8% 21% 24% 19% 5%	407
February	1st to 10th	Day	25% 7% 21% 24% 20% 3	370
	11th to 20th	Day	21% 13% 24% 24% 15% 3	425
	21st to end	Day	20% 12% 24% 29% 13% 2	382
March	1st to 10th	Day	28% 12% 27% 22% 10% 2	460
	11th to 20th	Day	23% 13% 24% 22% 14% 4	460
	21st to end	Day	20% 13% 32% 22% 12% 1	506
April	1st to 10th	Day	19% 11% 29% 24% 13% 3	460
	11th to 20th	Day	15% 12% 29% 26% 15% 3	452
	21st to end	Day	9% 10% 23% 29% 23% 6%	460
May	1st to 10th	Day	9% 10% 30% 28% 18% 5%	463
	11th to 20th	Day	7% 9% 25% 28% 24% 8%	488
	21st to end	Day	7% 7% 19% 31% 27% 9%	529
June	1st to 10th	Day	5% 7% 20% 35% 25% 8%	490
	11th to 20th	Day	4 6% 24% 38% 23% 5%	490
	21st to end	Day	1 4 18% 41% 27% 9%	490
July	1st to 10th	Day	1 1 13% 47% 31% 7%	486
	11th to 20th	Day	1 11% 43% 38% 7%	465
	21st to end	Day	1 12% 43% 34% 10%	487
August	1st to 10th	Day	3 2 13% 42% 33% 7%	447
	11th to 20th	Day	1 1 16% 41% 31% 10%	437
	21st to end	Day	1 12% 42% 37% 8%	495
September	1st to 10th	Day	2 2 14% 46% 30% 7%	450
	11th to 20th	Day	6% 3 20% 38% 28% 5%	450
	21st to end	Day	4 4 22% 38% 28% 5%	450
October	1st to 10th	Day	4 7% 24% 30% 29% 6%	450
	11th to 20th	Day	7% 4 15% 32% 33% 8%	450
	21st to end	Day	11% 6% 17% 30% 28% 7%	495
November	1st to 10th	Day	18% 5% 14% 27% 29% 7%	302
	11th to 20th	Day	11% 4 18% 29% 27% 10%	270
	21st to end	Day	12% 4 19% 32% 26% 8%	209
December	1st to 10th	Day	21% 6% 15% 26% 22% 11%	180
	11th to 20th	Day	17% 9% 23% 23% 17% 11%	180
	21st to end	Day	20% 9% 22% 24% 20% 5%	198
January	1st to 10th	Night	25% 3 14% 29% 22% 8%	760
	11th to 20th	Night	18% 3 12% 39% 22% 6%	760
	21st to end	Night	22% 3 14% 33% 22% 6%	836
February	1st to 10th	Night	22% 3 13% 34% 23% 4	760
	11th to 20th	Night	19% 4 15% 36% 21% 5%	744
	21st to end	Night	20% 5% 15% 41% 16% 3	628
March	1st to 10th	Night	26% 6% 13% 31% 19% 4	760
	11th to 20th	Night	22% 4 15% 29% 26% 4	760
	21st to end	Night	21% 5% 17% 36% 19% 3	836
April	1st to 10th	Night	16% 4 13% 41% 24% 3	760
	11th to 20th	Night	13% 5% 15% 35% 26% 6%	751
	21st to end	Night	8% 4 13% 39% 29% 6%	760
May	1st to 10th	Night	10% 4 17% 39% 27% 4	703
	11th to 20th	Night	7% 2 10% 39% 38% 3	374
	21st to end	Night	7% 2 10% 40% 38% 2	411
June	1st to 10th	Night	6% 3 12% 38% 36% 5%	380
	11th to 20th	Night	3 1 13% 43% 38% 3	380
	21st to end	Night	2 1 6% 44% 42% 3	380
July	1st to 10th	Night	1 4 42% 52% 2	370
	11th to 20th	Night	2 4 43% 48% 3	360
	21st to end	Night	1 3 33% 55% 8%	565
August	1st to 10th	Night	3 1 4 39% 48% 5%	537
	11th to 20th	Night	1 4 42% 45% 8%	678
	21st to end	Night	1 3 37% 54% 5%	792
September	1st to 10th	Night	2 5% 36% 51% 7%	720
	11th to 20th	Night	4 1 8% 36% 43% 8%	720
	21st to end	Night	3 2 10% 38% 36% 11%	720
October	1st to 10th	Night	6% 2 10% 40% 33% 9%	720
	11th to 20th	Night	8% 2 8% 36% 39% 6%	720
	21st to end	Night	7% 2 13% 34% 30% 13%	792
November	1st to 10th	Night	15% 3 10% 33% 30% 9%	740
	11th to 20th	Night	13% 3 11% 40% 27% 7%	760
	21st to end	Night	15% 2 14% 38% 24% 8%	760
December	1st to 10th	Night	20% 3 12% 36% 21% 7%	760
	11th to 20th	Night	29% 3 11% 33% 20% 4	760
	21st to end	Night	26% 3 16% 32% 18% 4	836

Page generated at 2024-07-13 07:19:52. Version ac07

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