Alberton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alberton 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	17% 10% 3 8% 5% 4 4 4 5% 7% 32%	102155
	Night	18% 11% 4 9% 5% 5% 4 3 5% 6% 29%	98039
Transparency	Day	28% 48% 8% 11% 5%	105706
	Night	30% 49% 7% 9% 4	102579
Seeing	Day	22% 8% 24% 29% 14% 3	17064
	Night	25% 10% 27% 27% 10% 1	24588

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	15% 13% 5% 15% 11% 6% 5% 4 4 5% 17%	2207
	11th to 20th	Day	13% 13% 5% 12% 7% 6% 6% 4 4 4 27%	2338
	21st to end	Day	10% 10% 5% 12% 7% 4 4 3 5% 6% 34%	3076
February	1st to 10th	Day	16% 13% 3 8% 6% 4 4 3 5% 6% 32%	1710
	11th to 20th	Day	15% 13% 5% 9% 7% 5% 3 3 5% 6% 30%	1663
	21st to end	Day	11% 12% 3 8% 5% 4 6% 4 5% 6% 35%	1413
March	1st to 10th	Day	19% 13% 5% 8% 4 6% 4 3 4 6% 29%	3388
	11th to 20th	Day	14% 16% 6% 13% 7% 5% 5% 3 4 6% 21%	3480
	21st to end	Day	25% 14% 4 7% 5% 4 4 3 4 6% 24%	3829
April	1st to 10th	Day	19% 11% 4 8% 4 4 4 4 5% 6% 31%	2280
	11th to 20th	Day	18% 10% 3 7% 4 3 4 3 4 8% 36%	2371
	21st to end	Day	21% 12% 3 7% 4 3 4 3 5% 6% 32%	2470
May	1st to 10th	Day	22% 14% 3 6% 4 3 4 4 5% 7% 29%	4316
	11th to 20th	Day	15% 8% 3 7% 4 4 4 3 5% 7% 40%	4398
	21st to end	Day	17% 8% 2 8% 5% 5% 5% 4 6% 8% 31%	4836
June	1st to 10th	Day	25% 9% 3 7% 4 4 5% 4 5% 7% 27%	2810
	11th to 20th	Day	18% 8% 3 7% 5% 4 5% 4 5% 7% 35%	2850
	21st to end	Day	24% 8% 3 6% 5% 5% 4 3 5% 6% 31%	2850
July	1st to 10th	Day	13% 7% 3 8% 5% 5% 5% 5% 7% 8% 34%	4760
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 6% 8% 38%	4674
	21st to end	Day	12% 7% 2 6% 5% 4 5% 4 6% 8% 42%	4815
August	1st to 10th	Day	16% 7% 3 8% 5% 4 5% 4 6% 7% 35%	4114
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 5% 6% 8% 39%	4045
	21st to end	Day	15% 5% 1 5% 3 3 4 4 5% 8% 47%	4409
September	1st to 10th	Day	16% 6% 2 4 3 4 4 4 6% 8% 43%	2280
	11th to 20th	Day	17% 7% 3 5% 4 4 4 4 4 5% 44%	2214
	21st to end	Day	17% 7% 2 6% 4 3 4 3 5% 7% 43%	2028
October	1st to 10th	Day	18% 8% 3 7% 4 5% 3 3 5% 8% 37%	1900
	11th to 20th	Day	19% 10% 4 9% 5% 5% 5% 3 5% 6% 29%	1900
	21st to end	Day	21% 13% 4 9% 5% 5% 5% 3 5% 6% 26%	2040
November	1st to 10th	Day	19% 14% 4 9% 5% 5% 4 3 5% 5% 27%	1565
	11th to 20th	Day	20% 15% 7% 10% 7% 5% 4 3 4 6% 20%	1600
	21st to end	Day	19% 16% 6% 12% 6% 5% 5% 4 5% 5% 18%	1600
December	1st to 10th	Day	21% 15% 6% 14% 8% 5% 3 3 4 3 17%	1600
	11th to 20th	Day	16% 18% 6% 14% 8% 6% 5% 3 3 3 18%	1874
	21st to end	Day	17% 14% 8% 17% 7% 5% 4 2 3 4 17%	2452
January	1st to 10th	Night	12% 12% 5% 16% 9% 5% 5% 4 5% 5% 21%	4748
	11th to 20th	Night	17% 13% 5% 11% 6% 4 5% 3 4 5% 27%	4630
	21st to end	Night	11% 13% 4 10% 9% 5% 5% 4 6% 6% 29%	4566
February	1st to 10th	Night	15% 14% 4 8% 5% 4 4 4 6% 6% 30%	2470
	11th to 20th	Night	16% 14% 5% 9% 5% 5% 4 4 5% 4 28%	2403
	21st to end	Night	13% 14% 3 8% 5% 5% 4 3 5% 6% 34%	2041
March	1st to 10th	Night	19% 13% 4 10% 6% 4 4 2 5% 4 27%	3450
	11th to 20th	Night	22% 18% 4 9% 6% 5% 4 3 4 4 20%	3479
	21st to end	Night	28% 12% 4 9% 5% 4 4 3 4 5% 23%	3802
April	1st to 10th	Night	21% 14% 3 9% 5% 4 4 3 4 5% 29%	1900
	11th to 20th	Night	21% 11% 3 6% 3 4 4 4 4 6% 33%	1758
	21st to end	Night	22% 11% 3 8% 4 4 4 3 5% 6% 30%	1710
May	1st to 10th	Night	26% 11% 3 7% 6% 4 4 3 5% 5% 26%	2629
	11th to 20th	Night	14% 7% 3 7% 4 4 4 4 5% 7% 40%	2506
	21st to end	Night	17% 9% 4 8% 6% 6% 5% 4 7% 7% 27%	2749
June	1st to 10th	Night	25% 10% 2 8% 5% 3 4 3 5% 7% 28%	1385
	11th to 20th	Night	18% 7% 3 7% 5% 5% 4 4 6% 6% 36%	1330
	21st to end	Night	22% 8% 4 9% 6% 4 5% 4 5% 6% 27%	1330
July	1st to 10th	Night	12% 8% 4 8% 6% 5% 5% 4 7% 7% 34%	2210
	11th to 20th	Night	15% 7% 3 7% 6% 6% 5% 4 7% 8% 31%	2260
	21st to end	Night	12% 6% 2 6% 4 4 4 5% 6% 8% 43%	2750
August	1st to 10th	Night	16% 7% 3 9% 6% 6% 5% 5% 6% 7% 28%	2814
	11th to 20th	Night	10% 6% 3 8% 6% 5% 5% 4 6% 8% 39%	2782
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 5% 7% 45%	3246
September	1st to 10th	Night	16% 5% 3 6% 4 3 5% 3 4 8% 42%	1900
	11th to 20th	Night	16% 7% 2 6% 3 3 3 3 4 6% 45%	1964
	21st to end	Night	17% 6% 2 7% 4 3 3 4 5% 6% 44%	2152
October	1st to 10th	Night	20% 7% 2 7% 4 4 4 3 5% 7% 38%	2280
	11th to 20th	Night	19% 10% 3 7% 5% 4 4 3 4 6% 34%	2280
	21st to end	Night	23% 12% 4 8% 5% 4 5% 3 4 5% 28%	2554
November	1st to 10th	Night	21% 14% 3 8% 5% 4 4 3 4 6% 29%	2733
	11th to 20th	Night	21% 15% 5% 9% 5% 5% 4 4 4 5% 23%	2800
	21st to end	Night	23% 15% 5% 11% 5% 5% 5% 3 5% 5% 20%	2800
December	1st to 10th	Night	22% 14% 6% 13% 6% 5% 4 3 4 4 18%	2800
	11th to 20th	Night	19% 19% 7% 14% 7% 4 3 2 4 4 18%	3540
	21st to end	Night	23% 13% 6% 14% 5% 5% 4 3 3 4 20%	5288

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	40% 46% 6% 4 3	2208
	11th to 20th	Day	31% 43% 8% 11% 6% 1	2338
	21st to end	Day	31% 44% 11% 7% 7%	3076
February	1st to 10th	Day	19% 65% 3 8% 4 1	1710
	11th to 20th	Day	19% 64% 4 8% 5%	1671
	21st to end	Day	15% 65% 3 9% 6% 1	1413
March	1st to 10th	Day	34% 42% 8% 13% 3 1	3392
	11th to 20th	Day	40% 45% 6% 5% 3 1	3480
	21st to end	Day	38% 42% 5% 9% 5% 1	3829
April	1st to 10th	Day	19% 66% 3 5% 5% 2	2280
	11th to 20th	Day	17% 66% 4 8% 4 1	2371
	21st to end	Day	20% 66% 4 4 5% 1	2470
May	1st to 10th	Day	32% 43% 8% 12% 4	4331
	11th to 20th	Day	25% 43% 10% 18% 3	4402
	21st to end	Day	29% 46% 9% 11% 6%	4836
June	1st to 10th	Day	19% 66% 5% 8% 2	2810
	11th to 20th	Day	16% 66% 5% 10% 3	2850
	21st to end	Day	18% 64% 5% 8% 5%	2850
July	1st to 10th	Day	31% 39% 14% 9% 8%	4685
	11th to 20th	Day	28% 38% 11% 19% 4	4593
	21st to end	Day	22% 39% 15% 18% 6%	4662
August	1st to 10th	Day	31% 40% 10% 15% 4	4100
	11th to 20th	Day	26% 40% 9% 15% 9%	4084
	21st to end	Day	22% 39% 10% 18% 9% 1	4409
September	1st to 10th	Day	13% 61% 7% 13% 6%	2280
	11th to 20th	Day	19% 61% 7% 9% 4	2214
	21st to end	Day	16% 61% 4 12% 6% 1	2028
October	1st to 10th	Day	29% 39% 11% 16% 5%	3160
	11th to 20th	Day	34% 38% 7% 16% 5%	3140
	21st to end	Day	29% 40% 15% 12% 4	3344
November	1st to 10th	Day	28% 56% 5% 7% 3	1565
	11th to 20th	Day	34% 58% 4 2 2	1600
	21st to end	Day	32% 58% 5% 3 2	1600
December	1st to 10th	Day	34% 58% 3 4 2	1600
	11th to 20th	Day	41% 47% 3 5% 4	1873
	21st to end	Day	44% 40% 8% 5% 3	2452
January	1st to 10th	Night	34% 48% 9% 7% 2	4748
	11th to 20th	Night	33% 43% 8% 10% 5%	4630
	21st to end	Night	34% 46% 9% 7% 3	4566
February	1st to 10th	Night	20% 65% 4 6% 5% 1	2470
	11th to 20th	Night	21% 64% 3 8% 5%	2406
	21st to end	Night	17% 65% 3 6% 7% 2	2041
March	1st to 10th	Night	35% 44% 5% 10% 5% 1	3459
	11th to 20th	Night	44% 44% 5% 4 3	3480
	21st to end	Night	41% 42% 4 8% 5% 1	3802
April	1st to 10th	Night	20% 64% 4 6% 4 1	1900
	11th to 20th	Night	19% 66% 3 7% 3 1	1758
	21st to end	Night	22% 65% 3 5% 4 2	1710
May	1st to 10th	Night	37% 44% 6% 8% 4	2634
	11th to 20th	Night	22% 44% 12% 17% 4	2507
	21st to end	Night	32% 47% 10% 7% 3	2750
June	1st to 10th	Night	19% 66% 4 8% 4	1385
	11th to 20th	Night	15% 66% 5% 10% 4	1330
	21st to end	Night	19% 64% 4 8% 4	1330
July	1st to 10th	Night	32% 39% 10% 10% 8%	2175
	11th to 20th	Night	31% 39% 12% 14% 4	2218
	21st to end	Night	20% 41% 16% 15% 8%	2663
August	1st to 10th	Night	37% 41% 9% 10% 3	2803
	11th to 20th	Night	25% 41% 11% 14% 8% 1	2809
	21st to end	Night	23% 40% 10% 16% 11%	3245
September	1st to 10th	Night	15% 61% 6% 14% 5%	1900
	11th to 20th	Night	19% 60% 6% 12% 3	1964
	21st to end	Night	16% 61% 5% 13% 5%	2152
October	1st to 10th	Night	33% 39% 10% 14% 4	3800
	11th to 20th	Night	30% 40% 7% 17% 6%	3779
	21st to end	Night	32% 38% 11% 13% 6%	4202
November	1st to 10th	Night	28% 56% 6% 7% 2	2733
	11th to 20th	Night	30% 59% 5% 4 2	2800
	21st to end	Night	33% 58% 5% 3 1	2800
December	1st to 10th	Night	33% 58% 3 5% 1	2800
	11th to 20th	Night	40% 47% 4 6% 2	3542
	21st to end	Night	44% 38% 8% 7% 2	5288

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	27% 17% 28% 23% 5%	180
	11th to 20th	Day	25% 19% 32% 20% 4 1	256
	21st to end	Day	16% 8% 39% 30% 7%	407
February	1st to 10th	Day	26% 12% 33% 21% 5% 2	370
	11th to 20th	Day	20% 15% 37% 22% 5%	366
	21st to end	Day	17% 11% 32% 29% 11% 1	307
March	1st to 10th	Day	21% 12% 31% 27% 9% 1	447
	11th to 20th	Day	14% 13% 32% 27% 13% 1	460
	21st to end	Day	26% 12% 27% 24% 9% 2	506
April	1st to 10th	Day	26% 10% 32% 23% 9%	460
	11th to 20th	Day	21% 7% 31% 30% 10% 2	452
	21st to end	Day	23% 11% 20% 29% 14% 2	460
May	1st to 10th	Day	30% 4 24% 26% 13% 3	583
	11th to 20th	Day	21% 6% 20% 29% 21% 3	674
	21st to end	Day	22% 3 26% 36% 12% 1	735
June	1st to 10th	Day	28% 4 20% 32% 13% 3	680
	11th to 20th	Day	21% 4 20% 34% 19% 3	680
	21st to end	Day	27% 3 15% 32% 18% 4	680
July	1st to 10th	Day	19% 3 20% 31% 23% 3	670
	11th to 20th	Day	14% 3 16% 37% 25% 4	668
	21st to end	Day	16% 4 12% 41% 22% 4	740
August	1st to 10th	Day	13% 2 16% 39% 25% 6%	495
	11th to 20th	Day	17% 4 15% 29% 27% 8%	479
	21st to end	Day	17% 3 19% 28% 25% 7%	539
September	1st to 10th	Day	14% 4 23% 37% 18% 4	490
	11th to 20th	Day	23% 7% 20% 27% 19% 5%	490
	21st to end	Day	21% 7% 24% 27% 16% 4	457
October	1st to 10th	Day	22% 8% 21% 27% 19% 3	390
	11th to 20th	Day	25% 11% 25% 23% 15% 1	390
	21st to end	Day	26% 13% 30% 22% 8% 1	429
November	1st to 10th	Day	28% 12% 29% 26% 4 1	395
	11th to 20th	Day	34% 15% 28% 18% 6% 1	400
	21st to end	Day	31% 15% 32% 19% 3	400
December	1st to 10th	Day	30% 14% 33% 19% 4	400
	11th to 20th	Day	27% 24% 30% 16% 3	325
	21st to end	Day	19% 20% 36% 23% 3	204
January	1st to 10th	Night	26% 14% 32% 22% 6%	850
	11th to 20th	Night	25% 13% 35% 21% 6%	850
	21st to end	Night	19% 13% 36% 24% 7% 1	845
February	1st to 10th	Night	24% 11% 34% 22% 8% 1	760
	11th to 20th	Night	24% 13% 35% 23% 4 1	743
	21st to end	Night	18% 9% 30% 32% 9% 1	628
March	1st to 10th	Night	23% 8% 34% 30% 5%	760
	11th to 20th	Night	21% 10% 31% 26% 9% 2	760
	21st to end	Night	26% 10% 28% 25% 10% 1	834
April	1st to 10th	Night	26% 10% 29% 26% 9%	570
	11th to 20th	Night	26% 6% 27% 29% 10% 2	564
	21st to end	Night	27% 6% 26% 27% 13% 1	570
May	1st to 10th	Night	29% 3 24% 28% 12% 4	570
	11th to 20th	Night	22% 3 23% 29% 19% 4	562
	21st to end	Night	19% 5% 28% 37% 9% 1	616
June	1st to 10th	Night	31% 3 19% 35% 11%	435
	11th to 20th	Night	21% 4 19% 35% 19% 1	380
	21st to end	Night	23% 2 17% 41% 14% 3	380
July	1st to 10th	Night	20% 2 19% 40% 16% 3	370
	11th to 20th	Night	14% 2 22% 41% 19% 2	392
	21st to end	Night	20% 3 17% 40% 18% 2	623
August	1st to 10th	Night	18% 2 18% 39% 22% 1	568
	11th to 20th	Night	20% 2 18% 35% 23% 2	562
	21st to end	Night	16% 3 17% 37% 23% 3	627
September	1st to 10th	Night	20% 6% 25% 34% 15% 1	570
	11th to 20th	Night	21% 7% 20% 33% 17% 2	634
	21st to end	Night	21% 8% 25% 33% 13% 1	760
October	1st to 10th	Night	24% 6% 26% 29% 13% 1	760
	11th to 20th	Night	25% 12% 27% 23% 12% 1	760
	21st to end	Night	32% 15% 27% 20% 5%	852
November	1st to 10th	Night	29% 15% 29% 21% 5% 1	880
	11th to 20th	Night	31% 17% 26% 18% 6% 1	900
	21st to end	Night	34% 15% 27% 20% 4	900
December	1st to 10th	Night	31% 14% 32% 18% 4	900
	11th to 20th	Night	29% 20% 32% 16% 3	900
	21st to end	Night	30% 16% 28% 21% 4 1	953

Page generated at 2024-12-21 05:13:47. Version ac07

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