Amos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Amos 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	17% 12% 4 10% 6% 5% 5% 4 5% 6% 26%	101772
	Night	16% 14% 5% 11% 6% 5% 5% 4 5% 6% 24%	97286
Transparency	Day	58% 6% 10% 18% 7% 1	105246
	Night	61% 5% 10% 16% 7% 1	101890
Seeing	Day	24% 16% 33% 19% 7% 2	15103
	Night	25% 13% 30% 23% 8% 1	23936

By Month

Percentage Cloud Cover NE (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	13% 23% 8% 14% 5% 9% 7% 5% 5% 4 7%	2208
	11th to 20th	Day	10% 14% 9% 18% 10% 5% 8% 6% 5% 4 12%	2240
	21st to end	Day	12% 18% 8% 18% 6% 6% 5% 3 5% 4 14%	2880
February	1st to 10th	Day	8% 15% 6% 12% 10% 8% 7% 4 6% 6% 16%	1710
	11th to 20th	Day	10% 18% 6% 14% 7% 6% 6% 5% 6% 5% 17%	1663
	21st to end	Day	12% 16% 7% 14% 6% 5% 4 5% 5% 6% 21%	1429
March	1st to 10th	Day	19% 16% 4 8% 5% 4 5% 4 4 5% 26%	3272
	11th to 20th	Day	11% 17% 7% 18% 5% 4 3 2 3 4 26%	3480
	21st to end	Day	10% 14% 5% 14% 7% 6% 5% 3 4 4 27%	3900
April	1st to 10th	Day	19% 17% 5% 9% 5% 5% 4 3 4 5% 24%	2280
	11th to 20th	Day	20% 12% 4 9% 4 4 4 2 4 6% 30%	2356
	21st to end	Day	20% 14% 3 7% 5% 3 5% 3 4 5% 30%	2498
May	1st to 10th	Day	17% 12% 4 8% 5% 4 5% 4 6% 7% 28%	4426
	11th to 20th	Day	16% 9% 3 7% 5% 5% 6% 4 7% 7% 30%	4398
	21st to end	Day	18% 8% 3 7% 5% 5% 4 4 5% 7% 34%	4859
June	1st to 10th	Day	23% 8% 2 7% 5% 4 5% 5% 6% 8% 28%	2850
	11th to 20th	Day	15% 8% 3 9% 5% 5% 5% 4 6% 7% 34%	2850
	21st to end	Day	20% 7% 3 6% 6% 4 5% 4 6% 7% 31%	2850
July	1st to 10th	Day	17% 7% 3 7% 5% 6% 6% 5% 7% 8% 29%	4760
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 4 7% 9% 34%	4760
	21st to end	Day	16% 7% 2 7% 5% 5% 5% 5% 6% 8% 34%	4851
August	1st to 10th	Day	17% 8% 2 7% 5% 5% 6% 5% 7% 9% 31%	4334
	11th to 20th	Day	18% 8% 3 7% 5% 4 5% 4 6% 7% 33%	4044
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	4386
September	1st to 10th	Day	20% 8% 3 7% 4 4 5% 5% 6% 6% 31%	2280
	11th to 20th	Day	21% 8% 3 7% 4 4 5% 4 6% 7% 31%	2272
	21st to end	Day	24% 11% 3 7% 5% 4 4 3 4 5% 30%	1987
October	1st to 10th	Day	22% 11% 3 7% 5% 4 4 3 5% 5% 30%	1900
	11th to 20th	Day	29% 21% 4 8% 4 3 3 3 3 4 18%	1900
	21st to end	Day	28% 17% 5% 9% 5% 5% 4 3 4 4 15%	1948
November	1st to 10th	Day	21% 21% 6% 10% 5% 5% 4 3 3 4 17%	1510
	11th to 20th	Day	21% 19% 8% 14% 7% 5% 4 3 4 4 13%	1520
	21st to end	Day	23% 26% 8% 12% 8% 5% 3 2 3 3 8%	1520
December	1st to 10th	Day	19% 21% 9% 17% 5% 4 4 3 4 4 11%	1520
	11th to 20th	Day	16% 19% 7% 12% 9% 6% 5% 4 4 4 13%	1700
	21st to end	Day	17% 20% 7% 20% 9% 5% 4 3 3 3 9%	2431
January	1st to 10th	Night	13% 18% 8% 17% 9% 7% 6% 4 4 3 10%	4748
	11th to 20th	Night	11% 16% 7% 17% 9% 7% 7% 6% 5% 5% 12%	4728
	21st to end	Night	9% 18% 10% 16% 8% 8% 6% 4 5% 5% 11%	4774
February	1st to 10th	Night	10% 17% 5% 11% 9% 6% 7% 4 5% 7% 18%	2470
	11th to 20th	Night	12% 16% 7% 13% 9% 5% 5% 4 4 6% 18%	2403
	21st to end	Night	10% 16% 5% 13% 7% 7% 6% 5% 5% 5% 20%	2024
March	1st to 10th	Night	16% 14% 5% 9% 5% 6% 5% 4 5% 5% 26%	3564
	11th to 20th	Night	13% 21% 6% 14% 6% 5% 5% 3 4 4 20%	3479
	21st to end	Night	14% 11% 4 12% 6% 6% 5% 3 5% 5% 28%	3732
April	1st to 10th	Night	21% 14% 4 10% 5% 4 3 2 4 5% 28%	1900
	11th to 20th	Night	18% 11% 4 8% 5% 4 5% 4 5% 6% 30%	1788
	21st to end	Night	19% 10% 4 8% 5% 3 4 3 4 5% 34%	1680
May	1st to 10th	Night	20% 9% 3 7% 5% 5% 5% 4 6% 6% 30%	2514
	11th to 20th	Night	17% 9% 4 7% 5% 4 4 4 5% 8% 34%	2495
	21st to end	Night	20% 7% 2 6% 4 4 5% 5% 7% 8% 31%	2712
June	1st to 10th	Night	20% 7% 4 8% 6% 5% 4 5% 6% 7% 29%	1330
	11th to 20th	Night	17% 8% 3 6% 4 4 3 4 5% 6% 38%	1330
	21st to end	Night	14% 7% 2 7% 5% 6% 5% 5% 6% 8% 36%	1330
July	1st to 10th	Night	17% 7% 2 6% 5% 3 5% 4 6% 9% 36%	2210
	11th to 20th	Night	17% 9% 4 7% 5% 5% 5% 4 5% 7% 32%	2210
	21st to end	Night	17% 7% 3 6% 4 4 4 4 5% 7% 39%	2702
August	1st to 10th	Night	12% 6% 3 7% 6% 5% 6% 5% 7% 7% 36%	2591
	11th to 20th	Night	15% 7% 3 7% 5% 5% 5% 4 5% 8% 36%	2785
	21st to end	Night	16% 7% 3 7% 4 5% 4 3 5% 7% 38%	3238
September	1st to 10th	Night	19% 9% 3 6% 5% 4 4 3 5% 6% 36%	1900
	11th to 20th	Night	21% 7% 2 6% 4 4 4 3 4 7% 37%	1905
	21st to end	Night	22% 9% 3 7% 4 3 4 2 5% 6% 35%	2192
October	1st to 10th	Night	21% 9% 3 8% 4 5% 5% 4 5% 6% 31%	2280
	11th to 20th	Night	26% 17% 5% 9% 5% 4 4 3 4 5% 19%	2280
	21st to end	Night	24% 19% 5% 9% 5% 4 4 3 4 5% 19%	2643
November	1st to 10th	Night	19% 18% 5% 10% 6% 6% 4 3 5% 5% 19%	2641
	11th to 20th	Night	20% 18% 5% 13% 8% 5% 3 3 5% 5% 16%	2660
	21st to end	Night	22% 21% 7% 14% 7% 5% 4 3 4 3 10%	2660
December	1st to 10th	Night	17% 22% 8% 16% 8% 5% 3 2 4 4 10%	2660
	11th to 20th	Night	17% 20% 6% 14% 9% 6% 5% 4 3 4 13%	3492
	21st to end	Night	18% 18% 10% 19% 8% 5% 3 2 3 3 11%	5236

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	80% 4 9% 6% 1	2209
	11th to 20th	Day	74% 3 7% 12% 3 1	2240
	21st to end	Day	73% 3 7% 12% 5%	2880
February	1st to 10th	Day	68% 4 6% 14% 7%	1710
	11th to 20th	Day	69% 4 8% 13% 6%	1672
	21st to end	Day	64% 4 8% 17% 7% 1	1429
March	1st to 10th	Day	61% 5% 7% 18% 9%	3275
	11th to 20th	Day	64% 3 5% 17% 9% 1	3480
	21st to end	Day	61% 4 5% 19% 9% 2	3900
April	1st to 10th	Day	64% 4 8% 12% 11% 1	2280
	11th to 20th	Day	57% 4 7% 18% 12% 2	2356
	21st to end	Day	57% 4 8% 16% 13% 2	2498
May	1st to 10th	Day	52% 8% 9% 21% 9% 1	4440
	11th to 20th	Day	50% 9% 12% 21% 8% 1	4402
	21st to end	Day	49% 6% 9% 21% 14% 1	4859
June	1st to 10th	Day	52% 7% 10% 21% 9% 1	2850
	11th to 20th	Day	48% 6% 8% 24% 12% 2	2850
	21st to end	Day	50% 7% 10% 23% 9% 1	2850
July	1st to 10th	Day	49% 8% 14% 24% 5%	4686
	11th to 20th	Day	44% 7% 17% 22% 10% 1	4679
	21st to end	Day	47% 6% 12% 27% 7%	4697
August	1st to 10th	Day	48% 7% 16% 24% 4	4320
	11th to 20th	Day	49% 7% 14% 22% 8%	4083
	21st to end	Day	44% 6% 11% 29% 10%	4386
September	1st to 10th	Day	51% 7% 13% 20% 8% 1	2280
	11th to 20th	Day	52% 7% 16% 20% 5%	2272
	21st to end	Day	57% 5% 11% 20% 7%	1987
October	1st to 10th	Day	60% 4 10% 20% 5% 1	3160
	11th to 20th	Day	66% 4 12% 13% 5%	3140
	21st to end	Day	70% 5% 12% 8% 5%	3175
November	1st to 10th	Day	71% 5% 12% 9% 4	1510
	11th to 20th	Day	77% 3 9% 8% 3	1520
	21st to end	Day	84% 4 7% 4 2	1520
December	1st to 10th	Day	77% 5% 6% 10% 2	1520
	11th to 20th	Day	73% 4 5% 14% 4	1700
	21st to end	Day	81% 4 6% 8% 2	2431
January	1st to 10th	Night	78% 5% 10% 6% 1	4748
	11th to 20th	Night	73% 5% 7% 9% 5%	4728
	21st to end	Night	75% 5% 6% 9% 5%	4774
February	1st to 10th	Night	66% 4 8% 14% 8%	2470
	11th to 20th	Night	68% 4 8% 14% 6%	2405
	21st to end	Night	66% 4 7% 15% 7% 1	2024
March	1st to 10th	Night	59% 4 9% 14% 13% 1	3574
	11th to 20th	Night	69% 4 8% 13% 6% 1	3480
	21st to end	Night	57% 4 7% 16% 13% 2	3732
April	1st to 10th	Night	60% 3 8% 14% 13% 1	1900
	11th to 20th	Night	53% 5% 9% 21% 11% 1	1788
	21st to end	Night	53% 4 7% 19% 15% 2	1680
May	1st to 10th	Night	50% 9% 10% 17% 12% 2	2520
	11th to 20th	Night	47% 7% 11% 22% 12% 1	2496
	21st to end	Night	47% 7% 12% 20% 13% 1	2713
June	1st to 10th	Night	53% 7% 7% 21% 11% 1	1330
	11th to 20th	Night	44% 7% 8% 23% 15% 3	1330
	21st to end	Night	45% 7% 12% 25% 12% 1	1330
July	1st to 10th	Night	45% 6% 13% 27% 8%	2175
	11th to 20th	Night	49% 6% 15% 21% 8% 1	2168
	21st to end	Night	46% 6% 14% 29% 6%	2616
August	1st to 10th	Night	43% 8% 15% 29% 5%	2581
	11th to 20th	Night	46% 7% 17% 25% 6%	2812
	21st to end	Night	45% 6% 14% 25% 9% 2	3238
September	1st to 10th	Night	48% 7% 14% 21% 10% 1	1900
	11th to 20th	Night	48% 6% 16% 23% 7%	1905
	21st to end	Night	51% 5% 12% 25% 7%	2192
October	1st to 10th	Night	54% 5% 13% 20% 7%	3800
	11th to 20th	Night	64% 4 10% 21% 2	3779
	21st to end	Night	64% 5% 14% 10% 6% 1	4354
November	1st to 10th	Night	66% 6% 13% 12% 2	2641
	11th to 20th	Night	72% 5% 10% 10% 3	2660
	21st to end	Night	79% 4 8% 8% 1	2660
December	1st to 10th	Night	80% 3 7% 7% 3	2660
	11th to 20th	Night	76% 3 6% 11% 3	3491
	21st to end	Night	81% 3 5% 8% 3	5236

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	20% 23% 41% 12% 4 1	180
	11th to 20th	Day	21% 16% 38% 20% 4 2	180
	21st to end	Day	15% 15% 41% 22% 6% 1	231
February	1st to 10th	Day	18% 28% 34% 16% 3 1	270
	11th to 20th	Day	22% 23% 37% 14% 3	270
	21st to end	Day	25% 23% 39% 10% 3	241
March	1st to 10th	Day	21% 20% 40% 15% 5%	460
	11th to 20th	Day	26% 17% 34% 17% 5%	460
	21st to end	Day	25% 19% 37% 13% 5% 1	506
April	1st to 10th	Day	26% 18% 31% 15% 8% 1	460
	11th to 20th	Day	27% 20% 29% 17% 6% 2	452
	21st to end	Day	29% 21% 28% 16% 5% 2	460
May	1st to 10th	Day	22% 17% 31% 22% 6% 2	463
	11th to 20th	Day	25% 16% 32% 18% 6% 2	487
	21st to end	Day	25% 16% 33% 20% 5% 1	538
June	1st to 10th	Day	27% 13% 33% 21% 6% 1	680
	11th to 20th	Day	21% 15% 35% 20% 6% 2	680
	21st to end	Day	21% 11% 33% 23% 10% 2	680
July	1st to 10th	Day	20% 12% 32% 25% 9% 1	671
	11th to 20th	Day	15% 15% 35% 23% 10% 1	668
	21st to end	Day	18% 10% 35% 24% 10% 3	556
August	1st to 10th	Day	22% 9% 30% 27% 8% 4	486
	11th to 20th	Day	18% 8% 28% 26% 13% 6%	479
	21st to end	Day	21% 13% 28% 21% 12% 5%	539
September	1st to 10th	Day	25% 12% 32% 20% 8% 4	490
	11th to 20th	Day	22% 10% 32% 22% 12% 2	490
	21st to end	Day	28% 13% 27% 18% 11% 2	490
October	1st to 10th	Day	28% 17% 27% 17% 9% 2	490
	11th to 20th	Day	37% 19% 27% 12% 4 1	490
	21st to end	Day	34% 17% 31% 15% 3 1	452
November	1st to 10th	Day	35% 23% 33% 8% 1	186
	11th to 20th	Day	31% 18% 37% 12% 2 1	180
	21st to end	Day	43% 18% 31% 5% 2 1	180
December	1st to 10th	Day	26% 18% 32% 17% 7% 1	180
	11th to 20th	Day	27% 16% 43% 9% 4 1	180
	21st to end	Day	32% 14% 32% 15% 5% 2	198
January	1st to 10th	Night	27% 12% 35% 20% 5% 1	950
	11th to 20th	Night	26% 14% 34% 21% 5%	931
	21st to end	Night	17% 12% 31% 27% 11% 1	836
February	1st to 10th	Night	18% 17% 35% 23% 6% 1	760
	11th to 20th	Night	23% 14% 33% 24% 6%	743
	21st to end	Night	18% 20% 37% 19% 5%	628
March	1st to 10th	Night	20% 19% 33% 22% 6% 1	760
	11th to 20th	Night	27% 19% 31% 20% 4 1	760
	21st to end	Night	21% 16% 37% 21% 5% 1	836
April	1st to 10th	Night	30% 14% 28% 21% 7%	760
	11th to 20th	Night	25% 17% 26% 26% 6%	664
	21st to end	Night	22% 14% 34% 23% 6% 1	540
May	1st to 10th	Night	21% 11% 34% 25% 8% 1	380
	11th to 20th	Night	24% 10% 28% 29% 7% 1	374
	21st to end	Night	25% 10% 31% 28% 5%	411
June	1st to 10th	Night	23% 9% 32% 27% 8% 1	380
	11th to 20th	Night	21% 9% 32% 28% 8% 1	380
	21st to end	Night	16% 8% 30% 33% 13% 1	380
July	1st to 10th	Night	20% 8% 29% 33% 9% 1	370
	11th to 20th	Night	16% 8% 26% 39% 11%	368
	21st to end	Night	15% 7% 25% 37% 15% 1	416
August	1st to 10th	Night	19% 6% 27% 28% 18% 2	424
	11th to 20th	Night	18% 6% 24% 31% 20% 1	564
	21st to end	Night	22% 8% 28% 26% 14% 2	689
September	1st to 10th	Night	24% 9% 29% 24% 11% 2	760
	11th to 20th	Night	25% 11% 27% 25% 12% 1	760
	21st to end	Night	26% 12% 23% 26% 12% 1	760
October	1st to 10th	Night	28% 13% 27% 24% 8% 1	760
	11th to 20th	Night	35% 14% 26% 18% 6% 1	760
	21st to end	Night	36% 11% 31% 17% 5%	836
November	1st to 10th	Night	29% 14% 34% 15% 6%	755
	11th to 20th	Night	31% 17% 31% 15% 6%	760
	21st to end	Night	33% 18% 30% 15% 3 1	760
December	1st to 10th	Night	31% 15% 29% 18% 5% 1	760
	11th to 20th	Night	27% 15% 32% 19% 6% 2	916
	21st to end	Night	30% 16% 27% 18% 6% 2	1045

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