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 2024-12-24.

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	9% 4 1 3 2 2 2 2 3 5% 66%	105551
	Night	12% 4 1 3 2 2 3 2 4 5% 60%	103307
Transparency	Day	23% 3 7% 18% 24% 25%	105302
	Night	28% 3 8% 18% 22% 22%	103145
Seeing	Day	11% 6% 20% 32% 24% 6%	15291
	Night	13% 3 11% 37% 31% 6%	24663

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 1 2 93%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 1 3 3 85%	4420
	21st to end	Day	1 1 1 1 1 1 2 3 88%	4489
August	1st to 10th	Day	2 1 1 2 1 2 2 2 3 4 80%	4091
	11th to 20th	Day	1 1 1 1 1 2 2 89%	3782
	21st to end	Day	2 1 1 1 1 1 1 1 2 90%	4180
September	1st to 10th	Day	2 1 1 1 1 2 3 89%	2280
	11th to 20th	Day	4 2 1 2 2 2 2 2 3 3 77%	2280
	21st to end	Day	4 2 1 2 1 1 2 2 2 4 80%	2053
October	1st to 10th	Day	3 2 1 3 2 2 1 2 4 5% 75%	3180
	11th to 20th	Day	5% 2 1 2 2 2 3 2 4 4 74%	3161
	21st to end	Day	5% 4 2 4 3 3 3 2 4 7% 64%	3448
November	1st to 10th	Day	12% 4 1 3 3 4 3 3 5% 7% 55%	1797
	11th to 20th	Day	14% 4 1 4 4 4 3 3 5% 7% 52%	1800
	21st to end	Day	14% 4 1 3 3 3 3 3 4 6% 54%	1664
December	1st to 10th	Day	16% 4 2 6% 4 3 3 3 3 6% 50%	1600
	11th to 20th	Day	31% 9% 2 6% 3 2 3 3 4 6% 32%	2008
	21st to end	Day	17% 7% 2 5% 4 4 5% 4 7% 8% 36%	2818
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 2 93%	2540
	11th to 20th	Night	2 2 1 1 1 1 2 1 2 3 83%	2540
	21st to end	Night	1 1 1 1 1 1 2 3 4 85%	3069
August	1st to 10th	Night	3 2 1 2 2 2 2 3 4 5% 76%	2848
	11th to 20th	Night	1 1 1 1 1 1 2 3 88%	3066
	21st to end	Night	3 1 2 1 1 1 2 1 88%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 88%	1900
	11th to 20th	Night	3 2 1 2 1 2 2 2 2 4 78%	1900
	21st to end	Night	2 1 1 1 2 2 2 2 3 3 80%	2123
October	1st to 10th	Night	3 2 1 3 2 2 2 1 3 3 78%	3800
	11th to 20th	Night	4 1 1 2 1 1 2 2 2 4 79%	3777
	21st to end	Night	8% 2 1 3 3 3 3 3 4 6% 64%	4121
November	1st to 10th	Night	14% 5% 1 3 2 3 3 3 5% 7% 55%	2502
	11th to 20th	Night	12% 4 1 3 3 3 3 3 5% 7% 56%	2600
	21st to end	Night	15% 4 1 3 3 3 3 2 4 6% 57%	2733
December	1st to 10th	Night	19% 4 1 4 2 3 3 3 4 6% 52%	2800
	11th to 20th	Night	32% 7% 2 4 2 2 3 2 5% 7% 33%	3416
	21st to end	Night	21% 6% 3 7% 5% 5% 4 3 5% 6% 34%	4910

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	3 1 1 5% 15% 75%	4351
	11th to 20th	Day	7% 2 2 7% 16% 67%	4345
	21st to end	Day	5% 2 1 5% 24% 64%	4347
August	1st to 10th	Day	9% 2 2 7% 22% 57%	4076
	11th to 20th	Day	4 1 1 7% 35% 52%	3819
	21st to end	Day	6% 1 1 8% 38% 45%	4179
September	1st to 10th	Day	4 1 2 8% 28% 57%	2280
	11th to 20th	Day	13% 3 4 21% 36% 23%	2280
	21st to end	Day	11% 2 4 19% 34% 31%	2053
October	1st to 10th	Day	13% 2 4 12% 24% 45%	3180
	11th to 20th	Day	14% 4 4 20% 38% 19%	3161
	21st to end	Day	21% 3 7% 19% 34% 16%	3448
November	1st to 10th	Day	27% 5% 9% 22% 23% 13%	1797
	11th to 20th	Day	33% 4 10% 23% 22% 8%	1800
	21st to end	Day	31% 4 10% 20% 23% 13%	1664
December	1st to 10th	Day	37% 3 9% 21% 20% 10%	1600
	11th to 20th	Day	55% 4 9% 14% 14% 5%	2008
	21st to end	Day	44% 5% 18% 19% 10% 4	2818
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	3 1 1 6% 15% 74%	2500
	11th to 20th	Night	9% 2 2 7% 15% 65%	2492
	21st to end	Night	6% 2 1 5% 27% 59%	2973
August	1st to 10th	Night	13% 2 1 8% 23% 53%	2839
	11th to 20th	Night	5% 1 1 8% 37% 48%	3095
	21st to end	Night	8% 1 2 10% 34% 46%	3498
September	1st to 10th	Night	5% 2 1 7% 29% 56%	1900
	11th to 20th	Night	13% 2 4 19% 39% 23%	1900
	21st to end	Night	11% 2 4 18% 30% 35%	2123
October	1st to 10th	Night	14% 2 3 10% 19% 51%	3800
	11th to 20th	Night	12% 2 5% 25% 32% 24%	3777
	21st to end	Night	21% 3 5% 18% 32% 21%	4121
November	1st to 10th	Night	29% 4 9% 22% 19% 17%	2502
	11th to 20th	Night	29% 4 10% 26% 22% 10%	2600
	21st to end	Night	31% 3 7% 22% 22% 15%	2733
December	1st to 10th	Night	35% 4 10% 21% 19% 13%	2800
	11th to 20th	Night	52% 3 7% 16% 15% 6%	3416
	21st to end	Night	51% 4 13% 18% 10% 4	4910

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% 44% 38% 7%	484
	21st to end	Day	1 12% 44% 33% 10%	531
August	1st to 10th	Day	3 2 13% 42% 33% 7%	487
	11th to 20th	Day	1 2 18% 40% 29% 10%	477
	21st to end	Day	1 1 12% 41% 37% 8%	539
September	1st to 10th	Day	2 2 16% 45% 29% 7%	490
	11th to 20th	Day	6% 4 21% 37% 28% 5%	490
	21st to end	Day	3 3 21% 39% 27% 6%	490
October	1st to 10th	Day	3 7% 22% 32% 30% 6%	490
	11th to 20th	Day	7% 5% 17% 32% 31% 8%	490
	21st to end	Day	11% 6% 19% 31% 27% 7%	539
November	1st to 10th	Day	17% 5% 16% 28% 27% 7%	333
	11th to 20th	Day	13% 4 20% 30% 25% 9%	300
	21st to end	Day	15% 5% 18% 30% 24% 8%	232
December	1st to 10th	Day	19% 6% 16% 26% 23% 12%	200
	11th to 20th	Day	20% 8% 23% 23% 18% 10%	200
	21st to end	Day	21% 9% 22% 25% 19% 5%	204
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	1 5% 43% 48% 3	368
	21st to end	Night	1 3 34% 54% 8%	597
August	1st to 10th	Night	3 1 4 40% 48% 5%	567
	11th to 20th	Night	1 5% 44% 43% 7%	716
	21st to end	Night	2 4 36% 53% 5%	836
September	1st to 10th	Night	2 5% 38% 49% 6%	760
	11th to 20th	Night	4 1 9% 36% 42% 8%	760
	21st to end	Night	3 2 10% 40% 35% 11%	760
October	1st to 10th	Night	6% 2 9% 40% 34% 8%	760
	11th to 20th	Night	8% 2 9% 36% 39% 6%	760
	21st to end	Night	7% 2 13% 36% 29% 13%	836
November	1st to 10th	Night	15% 3 11% 33% 30% 9%	780
	11th to 20th	Night	14% 3 13% 39% 25% 7%	800
	21st to end	Night	16% 2 14% 38% 23% 7%	800
December	1st to 10th	Night	19% 3 13% 37% 22% 7%	800
	11th to 20th	Night	29% 3 11% 33% 20% 4	800
	21st to end	Night	26% 4 16% 32% 18% 4	850

Page generated at 2024-12-21 01:13:49. Version ac07

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