Ames
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ames clear sky chart from 2005-11-06 to 2024-11-04.

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% 8% 3 8% 5% 4 5% 4 6% 7% 39%	101433
	Night	12% 8% 3 8% 4 4 4 3 5% 7% 42%	97684
Transparency	Day	42% 6% 13% 23% 14% 1	105073
	Night	40% 6% 13% 24% 15% 2	102184
Seeing	Day	15% 10% 29% 28% 14% 3	15863
	Night	15% 9% 33% 32% 11% 1	25701

By Month

Percentage Cloud Cover SE (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	7% 12% 6% 21% 8% 6% 6% 4 4 5% 20%	2527
	11th to 20th	Day	8% 14% 5% 11% 8% 7% 8% 3 7% 6% 23%	2822
	21st to end	Day	13% 16% 8% 16% 7% 5% 4 3 5% 6% 18%	3135
February	1st to 10th	Day	10% 14% 5% 10% 6% 5% 5% 4 5% 8% 28%	1710
	11th to 20th	Day	11% 10% 4 7% 5% 6% 5% 4 6% 6% 36%	1664
	21st to end	Day	13% 10% 3 11% 5% 4 5% 3 5% 6% 35%	1508
March	1st to 10th	Day	16% 9% 3 7% 4 4 4 3 3 5% 42%	3436
	11th to 20th	Day	11% 7% 3 8% 5% 4 4 3 5% 6% 45%	3480
	21st to end	Day	22% 14% 6% 9% 5% 4 4 4 5% 5% 22%	3814
April	1st to 10th	Day	18% 10% 3 6% 5% 4 4 4 5% 6% 34%	2269
	11th to 20th	Day	17% 9% 3 7% 6% 5% 3 3 5% 7% 35%	2254
	21st to end	Day	21% 8% 3 6% 3 4 5% 3 5% 6% 34%	2424
May	1st to 10th	Day	19% 8% 3 7% 5% 4 6% 4 6% 8% 32%	4082
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 39%	4351
	21st to end	Day	14% 6% 2 6% 4 4 4 4 5% 8% 42%	4824
June	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 3 6% 8% 45%	2660
	11th to 20th	Day	9% 6% 2 5% 5% 4 4 4 7% 10% 43%	2660
	21st to end	Day	9% 7% 2 6% 6% 5% 5% 5% 7% 8% 40%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 8% 10% 37%	4440
	11th to 20th	Day	5% 3 1 4 3 4 4 4 6% 7% 58%	4417
	21st to end	Day	5% 4 2 6% 5% 5% 6% 5% 7% 10% 45%	4465
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 6% 9% 46%	4104
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 8% 39%	4041
	21st to end	Day	7% 5% 2 7% 5% 5% 4 4 6% 8% 48%	4276
September	1st to 10th	Day	11% 5% 2 4 4 4 3 4 4 7% 53%	2280
	11th to 20th	Day	10% 5% 1 6% 4 4 4 4 7% 7% 49%	2216
	21st to end	Day	12% 4 2 6% 4 3 5% 3 5% 7% 49%	2019
October	1st to 10th	Day	14% 6% 3 6% 4 4 4 2 5% 6% 48%	1900
	11th to 20th	Day	15% 7% 3 6% 4 4 3 4 4 5% 45%	1900
	21st to end	Day	15% 8% 3 7% 4 3 3 3 5% 7% 42%	2090
November	1st to 10th	Day	10% 7% 2 6% 5% 4 5% 4 6% 7% 45%	1744
	11th to 20th	Day	13% 9% 4 6% 5% 3 4 5% 5% 8% 38%	1520
	21st to end	Day	15% 11% 3 6% 3 4 4 3 4 7% 39%	1520
December	1st to 10th	Day	11% 11% 3 10% 5% 5% 5% 4 5% 8% 33%	1520
	11th to 20th	Day	12% 9% 4 10% 6% 5% 4 4 5% 6% 34%	1918
	21st to end	Day	21% 16% 7% 14% 5% 3 4 3 4 5% 18%	2783
January	1st to 10th	Night	10% 12% 5% 22% 7% 4 4 3 4 5% 24%	4428
	11th to 20th	Night	10% 14% 5% 10% 6% 5% 7% 4 8% 7% 24%	4144
	21st to end	Night	14% 16% 6% 15% 5% 4 4 3 4 7% 22%	4532
February	1st to 10th	Night	10% 13% 4 11% 7% 4 4 4 4 7% 32%	2470
	11th to 20th	Night	11% 9% 3 7% 4 5% 5% 3 6% 6% 40%	2403
	21st to end	Night	11% 9% 5% 9% 5% 4 3 3 4 6% 41%	1959
March	1st to 10th	Night	14% 9% 2 6% 3 3 4 3 4 6% 47%	3422
	11th to 20th	Night	11% 6% 2 5% 4 3 3 3 5% 7% 50%	3480
	21st to end	Night	22% 12% 5% 13% 5% 5% 4 3 4 5% 22%	3817
April	1st to 10th	Night	14% 8% 3 6% 5% 4 3 4 4 7% 41%	1910
	11th to 20th	Night	15% 9% 2 7% 4 5% 4 3 4 6% 41%	1875
	21st to end	Night	16% 7% 2 7% 4 4 4 3 5% 6% 43%	1753
May	1st to 10th	Night	18% 7% 2 6% 3 4 4 3 6% 6% 40%	2823
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 4 6% 48%	2552
	21st to end	Night	12% 6% 3 6% 5% 4 4 3 6% 7% 45%	2743
June	1st to 10th	Night	6% 4 2 6% 4 5% 4 4 6% 7% 51%	1520
	11th to 20th	Night	7% 5% 2 5% 5% 4 3 3 6% 10% 49%	1520
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 5% 8% 50%	1520
July	1st to 10th	Night	8% 5% 2 5% 4 4 5% 4 8% 9% 46%	2530
	11th to 20th	Night	4 3 1 4 3 3 4 3 6% 9% 61%	2550
	21st to end	Night	5% 3 1 5% 4 5% 5% 5% 8% 10% 49%	3098
August	1st to 10th	Night	5% 4 2 5% 4 4 4 4 5% 10% 53%	2836
	11th to 20th	Night	9% 5% 2 5% 4 3 3 3 4 8% 56%	2798
	21st to end	Night	8% 5% 2 5% 3 3 3 3 4 7% 55%	3383
September	1st to 10th	Night	9% 5% 2 5% 3 3 3 2 4 5% 58%	1900
	11th to 20th	Night	10% 5% 2 4 3 3 4 2 5% 6% 56%	1962
	21st to end	Night	9% 5% 1 4 3 3 3 3 5% 6% 59%	2142
October	1st to 10th	Night	11% 7% 2 5% 3 3 3 3 4 6% 53%	2280
	11th to 20th	Night	15% 6% 2 6% 3 3 3 3 4 6% 49%	2280
	21st to end	Night	15% 9% 2 5% 3 3 4 3 4 6% 44%	2508
November	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 7% 53%	2403
	11th to 20th	Night	12% 9% 2 7% 4 4 4 4 5% 6% 42%	2660
	21st to end	Night	14% 9% 2 7% 4 3 4 3 5% 5% 43%	2660
December	1st to 10th	Night	9% 12% 4 9% 5% 5% 5% 4 6% 6% 35%	2660
	11th to 20th	Night	11% 10% 4 9% 6% 4 5% 3 5% 6% 37%	3279
	21st to end	Night	19% 16% 7% 14% 5% 4 3 3 4 4 23%	4884

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	63% 8% 11% 12% 6%	2528
	11th to 20th	Day	59% 5% 10% 20% 5%	2822
	21st to end	Day	67% 6% 11% 12% 4	3135
February	1st to 10th	Day	54% 5% 14% 18% 8% 1	1710
	11th to 20th	Day	47% 6% 11% 22% 11% 2	1673
	21st to end	Day	50% 5% 14% 17% 11% 3	1508
March	1st to 10th	Day	44% 6% 11% 24% 14% 2	3436
	11th to 20th	Day	38% 7% 12% 26% 14% 3	3480
	21st to end	Day	62% 7% 12% 13% 4 1	3814
April	1st to 10th	Day	48% 6% 12% 24% 10% 1	2269
	11th to 20th	Day	48% 6% 11% 21% 13% 1	2254
	21st to end	Day	48% 6% 11% 23% 12% 1	2424
May	1st to 10th	Day	48% 8% 14% 17% 12% 1	4120
	11th to 20th	Day	41% 8% 12% 26% 12% 1	4355
	21st to end	Day	39% 7% 13% 22% 17% 1	4837
June	1st to 10th	Day	35% 8% 16% 23% 16% 2	2660
	11th to 20th	Day	33% 7% 15% 23% 20% 2	2660
	21st to end	Day	38% 8% 15% 24% 14% 2	2660
July	1st to 10th	Day	39% 8% 16% 27% 8% 2	4371
	11th to 20th	Day	24% 6% 15% 34% 20% 2	4342
	21st to end	Day	30% 9% 18% 24% 17% 2	4325
August	1st to 10th	Day	33% 7% 16% 28% 15% 1	4090
	11th to 20th	Day	42% 6% 14% 25% 13% 1	4080
	21st to end	Day	33% 6% 16% 26% 17% 2	4275
September	1st to 10th	Day	31% 6% 12% 27% 20% 4	2280
	11th to 20th	Day	32% 6% 14% 30% 17% 1	2216
	21st to end	Day	34% 6% 11% 31% 19% 1	2019
October	1st to 10th	Day	23% 3 6% 29% 37% 2	3160
	11th to 20th	Day	29% 3 9% 30% 25% 4	3140
	21st to end	Day	39% 4 10% 29% 15% 3	3428
November	1st to 10th	Day	36% 6% 16% 22% 18% 2	1744
	11th to 20th	Day	42% 5% 15% 21% 15% 1	1520
	21st to end	Day	46% 4 15% 24% 10% 1	1520
December	1st to 10th	Day	48% 5% 17% 19% 9% 2	1520
	11th to 20th	Day	49% 5% 19% 20% 6% 1	1915
	21st to end	Day	68% 5% 9% 13% 4 1	2783
January	1st to 10th	Night	62% 5% 11% 13% 9%	4428
	11th to 20th	Night	55% 5% 13% 15% 10% 1	4144
	21st to end	Night	61% 6% 12% 14% 6% 1	4532
February	1st to 10th	Night	52% 4 12% 21% 10% 1	2470
	11th to 20th	Night	43% 6% 12% 25% 13% 2	2404
	21st to end	Night	45% 4 11% 21% 15% 3	1959
March	1st to 10th	Night	37% 6% 11% 28% 17% 2	3422
	11th to 20th	Night	33% 5% 12% 32% 15% 4	3480
	21st to end	Night	62% 8% 15% 9% 4 1	3817
April	1st to 10th	Night	41% 6% 12% 25% 14% 2	1910
	11th to 20th	Night	44% 5% 10% 21% 17% 3	1875
	21st to end	Night	42% 5% 13% 23% 14% 2	1753
May	1st to 10th	Night	42% 7% 12% 20% 18% 1	2850
	11th to 20th	Night	36% 7% 11% 27% 15% 4	2553
	21st to end	Night	37% 7% 13% 23% 17% 3	2751
June	1st to 10th	Night	30% 7% 16% 27% 16% 4	1520
	11th to 20th	Night	30% 7% 13% 22% 23% 5%	1520
	21st to end	Night	30% 7% 15% 28% 17% 3	1520
July	1st to 10th	Night	31% 7% 16% 32% 13% 2	2490
	11th to 20th	Night	20% 6% 19% 34% 20% 2	2502
	21st to end	Night	26% 10% 19% 25% 18% 2	2999
August	1st to 10th	Night	27% 6% 17% 33% 15% 2	2826
	11th to 20th	Night	30% 5% 17% 31% 16% 1	2825
	21st to end	Night	28% 6% 16% 28% 17% 5%	3383
September	1st to 10th	Night	28% 4 11% 27% 25% 4	1900
	11th to 20th	Night	29% 4 12% 34% 20% 1	1962
	21st to end	Night	27% 5% 10% 31% 24% 3	2142
October	1st to 10th	Night	22% 3 6% 25% 41% 3	3800
	11th to 20th	Night	27% 3 8% 28% 26% 7%	3779
	21st to end	Night	41% 4 10% 25% 17% 2	4120
November	1st to 10th	Night	32% 4 16% 26% 19% 4	2403
	11th to 20th	Night	40% 5% 15% 25% 13% 2	2660
	21st to end	Night	43% 4 12% 27% 13% 1	2660
December	1st to 10th	Night	47% 6% 14% 23% 9% 1	2660
	11th to 20th	Night	45% 6% 14% 27% 7%	3281
	21st to end	Night	65% 6% 9% 14% 6%	4884

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	19% 11% 36% 25% 8% 2	270
	11th to 20th	Day	19% 11% 44% 22% 4	270
	21st to end	Day	18% 11% 36% 29% 5% 1	297
February	1st to 10th	Day	17% 19% 39% 20% 4 1	270
	11th to 20th	Day	16% 16% 36% 26% 6%	270
	21st to end	Day	20% 14% 46% 17% 4	225
March	1st to 10th	Day	17% 16% 41% 18% 7% 1	270
	11th to 20th	Day	23% 13% 36% 21% 7%	270
	21st to end	Day	34% 14% 30% 17% 5%	297
April	1st to 10th	Day	25% 16% 34% 20% 5%	449
	11th to 20th	Day	24% 14% 33% 19% 8% 1	452
	21st to end	Day	25% 15% 29% 21% 8% 2	604
May	1st to 10th	Day	22% 13% 33% 22% 9% 1	653
	11th to 20th	Day	21% 13% 29% 23% 12% 2	675
	21st to end	Day	17% 8% 27% 30% 15% 3	734
June	1st to 10th	Day	8% 8% 26% 32% 23% 4	680
	11th to 20th	Day	12% 6% 29% 36% 15% 3	680
	21st to end	Day	10% 8% 31% 32% 15% 3	680
July	1st to 10th	Day	9% 4 17% 34% 26% 10%	671
	11th to 20th	Day	6% 2 26% 35% 23% 7%	668
	21st to end	Day	6% 2 22% 39% 26% 5%	739
August	1st to 10th	Day	8% 5% 19% 37% 26% 5%	676
	11th to 20th	Day	14% 3 17% 36% 23% 6%	665
	21st to end	Day	11% 3 21% 35% 23% 7%	596
September	1st to 10th	Day	13% 5% 23% 32% 21% 6%	490
	11th to 20th	Day	9% 4 23% 38% 21% 6%	426
	21st to end	Day	12% 10% 27% 32% 15% 4	300
October	1st to 10th	Day	16% 6% 31% 25% 17% 4	300
	11th to 20th	Day	17% 19% 34% 22% 7% 1	300
	21st to end	Day	20% 14% 37% 21% 6% 3	330
November	1st to 10th	Day	17% 10% 39% 23% 9% 2	279
	11th to 20th	Day	17% 21% 33% 20% 9% 1	270
	21st to end	Day	22% 12% 38% 23% 4 1	270
December	1st to 10th	Day	11% 14% 44% 21% 9% 1	270
	11th to 20th	Day	14% 15% 34% 26% 10% 1	270
	21st to end	Day	24% 18% 40% 16% 2	297
January	1st to 10th	Night	14% 12% 37% 29% 7%	950
	11th to 20th	Night	17% 12% 36% 28% 6% 1	950
	21st to end	Night	17% 13% 35% 29% 6%	1045
February	1st to 10th	Night	18% 10% 38% 29% 5%	950
	11th to 20th	Night	16% 12% 39% 27% 5%	929
	21st to end	Night	17% 13% 41% 23% 5% 1	703
March	1st to 10th	Night	18% 11% 38% 24% 7% 1	573
	11th to 20th	Night	18% 9% 38% 27% 8%	570
	21st to end	Night	24% 11% 38% 19% 7% 1	627
April	1st to 10th	Night	19% 14% 40% 23% 4	570
	11th to 20th	Night	18% 12% 36% 27% 6% 1	563
	21st to end	Night	19% 11% 36% 26% 8% 1	570
May	1st to 10th	Night	19% 8% 34% 30% 8% 1	570
	11th to 20th	Night	16% 9% 33% 31% 10% 1	561
	21st to end	Night	15% 7% 27% 36% 14%	617
June	1st to 10th	Night	8% 4 28% 41% 19%	570
	11th to 20th	Night	11% 4 28% 44% 12% 1	570
	21st to end	Night	9% 5% 31% 38% 16%	570
July	1st to 10th	Night	7% 1 15% 46% 29% 2	555
	11th to 20th	Night	5% 1 23% 44% 26% 2	552
	21st to end	Night	6% 2 17% 50% 24% 1	624
August	1st to 10th	Night	7% 4 16% 47% 25% 2	567
	11th to 20th	Night	8% 2 16% 46% 24% 3	564
	21st to end	Night	10% 2 22% 41% 24% 2	627
September	1st to 10th	Night	13% 4 21% 38% 22% 2	570
	11th to 20th	Night	12% 3 24% 39% 20% 2	570
	21st to end	Night	12% 5% 31% 36% 14% 1	622
October	1st to 10th	Night	14% 8% 32% 31% 14% 1	760
	11th to 20th	Night	17% 12% 34% 30% 7%	760
	21st to end	Night	21% 9% 34% 28% 7%	836
November	1st to 10th	Night	14% 9% 38% 30% 8%	791
	11th to 20th	Night	16% 15% 40% 22% 6%	950
	21st to end	Night	17% 13% 36% 27% 8%	950
December	1st to 10th	Night	15% 12% 37% 28% 7%	950
	11th to 20th	Night	19% 8% 35% 31% 6%	950
	21st to end	Night	23% 12% 37% 22% 5%	1045

Page generated at 2024-11-01 21:47:49. Version ac07

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