Amanda
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Amanda 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	15% 10% 4 8% 5% 5% 5% 4 6% 7% 33%	101177
	Night	15% 11% 4 8% 5% 4 4 3 5% 7% 35%	97795
Transparency	Day	48% 5% 10% 22% 13% 2	104882
	Night	47% 5% 10% 22% 14% 2	102216
Seeing	Day	20% 13% 26% 22% 14% 6%	14865
	Night	19% 10% 27% 29% 14% 2	24927

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	18% 20% 6% 12% 4 3 4 3 4 5% 20%	2836
	11th to 20th	Day	15% 21% 8% 12% 6% 9% 4 3 4 3 15%	2840
	21st to end	Day	27% 19% 9% 9% 5% 4 4 2 3 4 12%	3124
February	1st to 10th	Day	21% 13% 4 10% 6% 4 3 3 4 6% 25%	1710
	11th to 20th	Day	17% 14% 4 12% 5% 4 4 3 5% 5% 26%	1826
	21st to end	Day	20% 15% 4 9% 5% 3 3 2 4 5% 29%	1570
March	1st to 10th	Day	21% 16% 5% 9% 4 4 4 2 4 6% 24%	3279
	11th to 20th	Day	14% 9% 3 8% 5% 5% 5% 4 5% 6% 37%	3480
	21st to end	Day	19% 9% 4 8% 5% 3 5% 3 4 7% 33%	3815
April	1st to 10th	Day	15% 13% 4 7% 6% 4 4 3 5% 6% 33%	2116
	11th to 20th	Day	17% 10% 3 7% 4 4 4 4 5% 6% 37%	2399
	21st to end	Day	18% 9% 3 6% 5% 5% 5% 4 5% 7% 33%	2470
May	1st to 10th	Day	21% 10% 3 7% 5% 5% 4 3 5% 7% 29%	4082
	11th to 20th	Day	21% 8% 3 6% 5% 4 4 3 5% 7% 33%	4081
	21st to end	Day	10% 5% 2 8% 6% 5% 6% 5% 8% 10% 34%	4476
June	1st to 10th	Day	13% 7% 2 6% 5% 5% 5% 5% 7% 9% 38%	2470
	11th to 20th	Day	10% 6% 2 7% 6% 5% 6% 4 7% 9% 39%	2470
	21st to end	Day	11% 7% 2 5% 6% 5% 6% 4 8% 10% 36%	2470
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 4 4 6% 9% 39%	4120
	11th to 20th	Day	8% 5% 2 6% 4 4 6% 5% 7% 11% 42%	4120
	21st to end	Day	12% 7% 3 7% 5% 6% 6% 5% 7% 8% 34%	4466
August	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 10% 37%	4104
	11th to 20th	Day	9% 7% 2 6% 5% 5% 6% 5% 7% 9% 38%	4044
	21st to end	Day	6% 4 2 6% 4 5% 5% 4 7% 9% 49%	4450
September	1st to 10th	Day	14% 5% 2 4 3 3 5% 4 6% 8% 46%	2090
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 3 5% 8% 49%	2090
	21st to end	Day	19% 7% 3 6% 4 3 4 3 4 5% 42%	2090
October	1st to 10th	Day	12% 7% 3 6% 4 3 4 5% 6% 6% 44%	2031
	11th to 20th	Day	15% 7% 2 6% 5% 5% 3 3 5% 6% 43%	1900
	21st to end	Day	21% 8% 3 7% 4 3 3 3 4 6% 36%	2052
November	1st to 10th	Day	10% 7% 2 6% 4 3 3 3 5% 5% 50%	1699
	11th to 20th	Day	16% 13% 5% 7% 4 4 4 3 4 6% 34%	1710
	21st to end	Day	18% 11% 4 8% 5% 4 5% 3 4 7% 31%	1710
December	1st to 10th	Day	21% 17% 7% 9% 6% 4 4 3 4 5% 19%	1710
	11th to 20th	Day	18% 17% 5% 11% 5% 3 4 3 5% 5% 22%	2153
	21st to end	Day	18% 23% 8% 11% 6% 5% 5% 4 4 5% 12%	3124
January	1st to 10th	Night	14% 21% 8% 13% 6% 5% 3 3 4 4 19%	4109
	11th to 20th	Night	14% 18% 6% 17% 6% 5% 5% 3 4 5% 18%	4120
	21st to end	Night	26% 17% 8% 10% 7% 4 3 2 2 3 18%	4532
February	1st to 10th	Night	21% 13% 3 10% 5% 4 3 3 4 4 29%	2470
	11th to 20th	Night	18% 14% 3 9% 5% 5% 4 4 4 6% 28%	2237
	21st to end	Night	19% 15% 5% 9% 4 4 4 3 4 5% 27%	1884
March	1st to 10th	Night	21% 13% 3 6% 5% 4 3 3 4 6% 33%	3573
	11th to 20th	Night	14% 10% 3 5% 5% 5% 4 3 5% 7% 39%	3480
	21st to end	Night	18% 9% 3 6% 4 4 4 2 5% 6% 39%	3817
April	1st to 10th	Night	16% 9% 3 6% 4 4 4 4 5% 7% 37%	2081
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 4 7% 7% 38%	1728
	21st to end	Night	15% 8% 3 7% 5% 5% 4 4 6% 7% 37%	1710
May	1st to 10th	Night	24% 10% 3 7% 5% 4 4 4 5% 7% 26%	2813
	11th to 20th	Night	19% 8% 2 6% 3 3 3 3 5% 8% 39%	2812
	21st to end	Night	9% 5% 2 6% 4 4 4 4 7% 10% 42%	3079
June	1st to 10th	Night	9% 6% 2 5% 4 5% 5% 3 6% 10% 45%	1710
	11th to 20th	Night	9% 5% 2 5% 2 5% 5% 4 9% 10% 44%	1710
	21st to end	Night	10% 6% 2 5% 5% 4 4 5% 6% 10% 44%	1710
July	1st to 10th	Night	11% 6% 3 6% 3 4 4 4 6% 7% 46%	2840
	11th to 20th	Night	8% 4 2 5% 4 5% 5% 4 7% 9% 46%	2840
	21st to end	Night	8% 6% 3 8% 6% 5% 5% 5% 8% 8% 38%	3087
August	1st to 10th	Night	6% 7% 3 8% 5% 5% 5% 5% 7% 10% 39%	2825
	11th to 20th	Night	9% 8% 3 8% 4 4 4 3 5% 7% 44%	2785
	21st to end	Night	4 3 2 5% 3 5% 5% 4 7% 10% 52%	3183
September	1st to 10th	Night	12% 5% 2 4 3 3 5% 3 5% 7% 52%	2076
	11th to 20th	Night	9% 4 2 5% 3 3 4 3 5% 7% 55%	2090
	21st to end	Night	14% 7% 2 5% 4 3 3 3 4 6% 47%	2090
October	1st to 10th	Night	10% 6% 3 5% 4 4 4 3 5% 7% 50%	2147
	11th to 20th	Night	15% 8% 2 6% 4 3 4 3 5% 6% 44%	2280
	21st to end	Night	20% 8% 2 6% 4 3 4 3 5% 6% 40%	2541
November	1st to 10th	Night	14% 7% 2 5% 4 4 3 2 4 6% 49%	2452
	11th to 20th	Night	16% 11% 3 7% 5% 3 4 3 5% 6% 36%	2470
	21st to end	Night	19% 13% 3 7% 5% 4 4 3 5% 6% 31%	2470
December	1st to 10th	Night	21% 15% 6% 9% 5% 3 3 3 5% 5% 24%	2470
	11th to 20th	Night	18% 15% 6% 8% 4 4 4 2 5% 6% 28%	3042
	21st to end	Night	20% 21% 7% 10% 6% 4 4 3 4 5% 16%	4532

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	67% 5% 10% 12% 6%	2837
	11th to 20th	Day	74% 4 8% 10% 4	2840
	21st to end	Day	76% 4 7% 9% 3 1	3124
February	1st to 10th	Day	61% 4 11% 14% 9%	1710
	11th to 20th	Day	61% 4 9% 17% 9%	1836
	21st to end	Day	58% 4 10% 19% 8% 1	1570
March	1st to 10th	Day	61% 5% 8% 20% 5% 1	3279
	11th to 20th	Day	46% 6% 10% 27% 10% 1	3480
	21st to end	Day	50% 5% 10% 23% 11%	3815
April	1st to 10th	Day	52% 4 10% 20% 11% 2	2116
	11th to 20th	Day	47% 4 11% 20% 14% 4	2399
	21st to end	Day	51% 5% 10% 20% 11% 2	2470
May	1st to 10th	Day	54% 6% 9% 22% 8% 1	4120
	11th to 20th	Day	50% 7% 11% 19% 12% 1	4085
	21st to end	Day	41% 9% 15% 19% 14% 3	4489
June	1st to 10th	Day	42% 7% 11% 24% 15% 1	2470
	11th to 20th	Day	40% 8% 14% 21% 15% 1	2470
	21st to end	Day	42% 7% 14% 21% 14% 2	2470
July	1st to 10th	Day	42% 6% 11% 22% 17% 2	4055
	11th to 20th	Day	34% 7% 11% 31% 16% 1	4051
	21st to end	Day	45% 7% 11% 17% 17% 4	4324
August	1st to 10th	Day	39% 7% 14% 28% 10% 1	4091
	11th to 20th	Day	39% 6% 11% 29% 14% 1	4083
	21st to end	Day	31% 7% 14% 30% 15% 3	4450
September	1st to 10th	Day	35% 6% 10% 22% 22% 4	2090
	11th to 20th	Day	33% 5% 11% 26% 22% 3	2090
	21st to end	Day	45% 4 9% 21% 20% 1	2090
October	1st to 10th	Day	26% 4 8% 31% 29% 2	3369
	11th to 20th	Day	34% 3 10% 27% 22% 3	3140
	21st to end	Day	37% 3 10% 27% 20% 2	3366
November	1st to 10th	Day	36% 5% 9% 29% 18% 3	1699
	11th to 20th	Day	52% 4 7% 20% 14% 3	1710
	21st to end	Day	54% 4 10% 20% 11% 1	1710
December	1st to 10th	Day	67% 4 9% 15% 4	1710
	11th to 20th	Day	63% 4 8% 17% 7%	2150
	21st to end	Day	74% 5% 9% 8% 4	3124
January	1st to 10th	Night	69% 4 8% 14% 5%	4109
	11th to 20th	Night	69% 4 10% 12% 3 1	4120
	21st to end	Night	74% 3 6% 13% 3 1	4532
February	1st to 10th	Night	59% 4 10% 18% 8% 1	2470
	11th to 20th	Night	59% 4 8% 17% 11% 1	2238
	21st to end	Night	61% 4 9% 16% 9% 2	1884
March	1st to 10th	Night	53% 4 7% 24% 10% 1	3573
	11th to 20th	Night	43% 6% 10% 29% 11% 1	3480
	21st to end	Night	47% 4 7% 28% 13% 1	3817
April	1st to 10th	Night	46% 5% 11% 20% 15% 2	2081
	11th to 20th	Night	43% 6% 11% 17% 19% 4	1728
	21st to end	Night	45% 5% 9% 23% 15% 2	1710
May	1st to 10th	Night	56% 7% 9% 19% 8% 2	2840
	11th to 20th	Night	44% 7% 11% 26% 10% 2	2813
	21st to end	Night	34% 8% 15% 27% 13% 4	3087
June	1st to 10th	Night	35% 7% 12% 23% 20% 3	1710
	11th to 20th	Night	31% 8% 17% 23% 19% 2	1710
	21st to end	Night	33% 8% 14% 23% 19% 3	1710
July	1st to 10th	Night	37% 5% 12% 23% 18% 5%	2795
	11th to 20th	Night	33% 7% 12% 30% 16% 1	2786
	21st to end	Night	41% 8% 12% 20% 14% 5%	2988
August	1st to 10th	Night	38% 8% 15% 26% 11% 1	2814
	11th to 20th	Night	39% 6% 10% 24% 21% 1	2812
	21st to end	Night	26% 7% 15% 29% 20% 3	3183
September	1st to 10th	Night	33% 4 12% 23% 22% 6%	2076
	11th to 20th	Night	29% 5% 11% 25% 26% 3	2090
	21st to end	Night	39% 4 9% 21% 26% 1	2090
October	1st to 10th	Night	28% 4 6% 28% 30% 3	3576
	11th to 20th	Night	31% 3 9% 27% 24% 6%	3779
	21st to end	Night	33% 3 8% 26% 25% 5%	4177
November	1st to 10th	Night	38% 3 10% 25% 21% 3	2452
	11th to 20th	Night	49% 3 8% 21% 16% 2	2470
	21st to end	Night	55% 4 10% 19% 11% 1	2470
December	1st to 10th	Night	62% 4 9% 17% 7% 1	2470
	11th to 20th	Night	59% 3 11% 21% 6%	3044
	21st to end	Night	70% 5% 8% 12% 4	4532

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	25% 23% 37% 11% 4 1	270
	11th to 20th	Day	30% 22% 37% 9% 2	270
	21st to end	Day	32% 22% 31% 11% 4	297
February	1st to 10th	Day	31% 23% 31% 13% 2	270
	11th to 20th	Day	33% 27% 29% 9% 2	270
	21st to end	Day	32% 26% 35% 7%	225
March	1st to 10th	Day	24% 26% 29% 18% 4	364
	11th to 20th	Day	27% 20% 33% 15% 6%	460
	21st to end	Day	31% 17% 31% 17% 4	506
April	1st to 10th	Day	23% 17% 32% 16% 9% 2	460
	11th to 20th	Day	25% 16% 30% 19% 7% 4	452
	21st to end	Day	23% 17% 32% 19% 8% 1	460
May	1st to 10th	Day	27% 18% 28% 16% 8% 3	463
	11th to 20th	Day	21% 12% 28% 22% 12% 6%	487
	21st to end	Day	12% 9% 24% 28% 20% 7%	529
June	1st to 10th	Day	13% 7% 26% 29% 18% 7%	490
	11th to 20th	Day	13% 6% 24% 30% 21% 6%	490
	21st to end	Day	12% 7% 29% 29% 17% 7%	490
July	1st to 10th	Day	16% 3 17% 22% 21% 20%	485
	11th to 20th	Day	10% 5% 21% 27% 27% 10%	484
	21st to end	Day	13% 4 17% 29% 23% 14%	532
August	1st to 10th	Day	11% 4 16% 28% 27% 13%	486
	11th to 20th	Day	13% 4 23% 29% 20% 11%	479
	21st to end	Day	9% 4 17% 28% 28% 14%	539
September	1st to 10th	Day	12% 7% 16% 26% 27% 13%	490
	11th to 20th	Day	11% 2 14% 26% 31% 15%	490
	21st to end	Day	24% 8% 18% 26% 20% 5%	490
October	1st to 10th	Day	12% 8% 26% 29% 18% 8%	490
	11th to 20th	Day	16% 14% 31% 22% 14% 3	490
	21st to end	Day	24% 15% 32% 20% 8% 1	501
November	1st to 10th	Day	14% 16% 36% 22% 10% 2	279
	11th to 20th	Day	27% 21% 26% 18% 7% 1	270
	21st to end	Day	24% 20% 34% 19% 3	270
December	1st to 10th	Day	26% 21% 33% 13% 4 2	270
	11th to 20th	Day	26% 24% 34% 11% 5%	270
	21st to end	Day	30% 22% 31% 14% 3	297
January	1st to 10th	Night	23% 21% 34% 18% 5%	760
	11th to 20th	Night	28% 19% 30% 20% 2	760
	21st to end	Night	26% 16% 33% 23% 2	836
February	1st to 10th	Night	28% 13% 32% 25% 2	760
	11th to 20th	Night	27% 16% 35% 21% 1	743
	21st to end	Night	28% 15% 36% 19% 2	628
March	1st to 10th	Night	23% 15% 33% 24% 4	760
	11th to 20th	Night	21% 16% 33% 23% 6%	760
	21st to end	Night	25% 13% 31% 23% 7%	836
April	1st to 10th	Night	20% 14% 34% 25% 6%	751
	11th to 20th	Night	18% 10% 37% 23% 11% 1	563
	21st to end	Night	18% 9% 40% 26% 6% 1	570
May	1st to 10th	Night	20% 10% 32% 26% 13%	570
	11th to 20th	Night	19% 7% 25% 32% 16% 1	561
	21st to end	Night	9% 3 24% 36% 26% 2	617
June	1st to 10th	Night	10% 2 26% 40% 20% 1	570
	11th to 20th	Night	10% 2 21% 42% 24% 1	570
	21st to end	Night	11% 4 22% 39% 23% 2	570
July	1st to 10th	Night	10% 3 16% 37% 27% 7%	555
	11th to 20th	Night	6% 3 15% 37% 34% 5%	552
	21st to end	Night	9% 3 13% 38% 35% 2	624
August	1st to 10th	Night	7% 2 13% 40% 34% 3	567
	11th to 20th	Night	9% 2 11% 42% 32% 4	564
	21st to end	Night	8% 1 15% 33% 36% 7%	627
September	1st to 10th	Night	14% 3 16% 37% 27% 4	746
	11th to 20th	Night	10% 2 13% 36% 33% 6%	760
	21st to end	Night	18% 6% 21% 32% 21% 2	760
October	1st to 10th	Night	11% 6% 24% 33% 22% 4	760
	11th to 20th	Night	18% 9% 29% 30% 12% 2	760
	21st to end	Night	24% 11% 26% 29% 10%	836
November	1st to 10th	Night	19% 9% 25% 30% 16% 1	755
	11th to 20th	Night	22% 15% 28% 26% 9% 1	760
	21st to end	Night	26% 11% 27% 29% 6% 1	760
December	1st to 10th	Night	30% 16% 26% 24% 4	760
	11th to 20th	Night	26% 13% 32% 23% 5% 1	760
	21st to end	Night	28% 15% 31% 23% 3	836

Page generated at 2024-11-01 22:47:52. Version ac07

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