Whiteway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiteway clear sky chart from 2005-11-06 to 2024-11-12.

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	22% 16% 5% 10% 5% 4 4 3 4 5% 21%	101700
	Night	23% 17% 6% 11% 5% 4 4 3 4 5% 19%	97622
Transparency	Day	65% 6% 11% 13% 5%	105199
	Night	67% 6% 10% 12% 4	102238
Seeing	Day	33% 20% 27% 15% 4 1	18170
	Night	32% 19% 29% 17% 4	24753

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	18% 18% 11% 17% 4 3 2 2 4 5% 17%	2216
	11th to 20th	Day	20% 18% 8% 17% 5% 4 3 3 3 3 16%	2501
	21st to end	Day	17% 18% 10% 17% 5% 3 4 2 3 5% 16%	2783
February	1st to 10th	Day	21% 15% 8% 12% 8% 5% 5% 3 4 4 14%	1636
	11th to 20th	Day	21% 20% 6% 13% 6% 4 4 3 4 4 13%	1682
	21st to end	Day	14% 19% 7% 17% 7% 5% 3 3 4 5% 15%	1570
March	1st to 10th	Day	25% 15% 7% 12% 6% 4 3 3 3 4 17%	3134
	11th to 20th	Day	20% 20% 11% 15% 5% 4 4 3 3 4 13%	3480
	21st to end	Day	25% 18% 9% 13% 5% 3 3 2 3 4 13%	3817
April	1st to 10th	Day	19% 19% 6% 12% 7% 4 4 3 4 4 18%	2298
	11th to 20th	Day	23% 19% 4 10% 5% 4 3 2 4 4 22%	2441
	21st to end	Day	21% 20% 5% 9% 5% 5% 4 3 4 5% 20%	2470
May	1st to 10th	Day	24% 23% 6% 8% 4 3 3 3 4 6% 17%	4105
	11th to 20th	Day	28% 17% 5% 8% 5% 4 3 3 4 5% 19%	4457
	21st to end	Day	22% 18% 5% 9% 5% 4 3 3 5% 6% 20%	5173
June	1st to 10th	Day	28% 17% 5% 10% 6% 4 3 3 4 4 16%	2850
	11th to 20th	Day	25% 13% 4 7% 6% 5% 4 3 5% 6% 23%	2850
	21st to end	Day	25% 14% 4 7% 5% 4 4 3 5% 6% 23%	2850
July	1st to 10th	Day	31% 12% 3 7% 4 4 4 3 5% 6% 21%	4750
	11th to 20th	Day	22% 13% 4 8% 5% 5% 4 4 5% 5% 25%	4704
	21st to end	Day	17% 9% 3 7% 4 4 4 3 5% 7% 36%	4815
August	1st to 10th	Day	27% 13% 4 7% 4 4 4 3 5% 7% 22%	4212
	11th to 20th	Day	18% 12% 4 9% 5% 5% 4 3 6% 6% 28%	4046
	21st to end	Day	20% 10% 3 7% 4 4 4 3 5% 8% 31%	4532
September	1st to 10th	Day	18% 10% 4 7% 5% 4 5% 4 6% 6% 31%	2270
	11th to 20th	Day	23% 9% 3 7% 4 4 5% 3 4 6% 31%	2090
	21st to end	Day	19% 11% 3 6% 5% 5% 3 4 6% 7% 32%	2090
October	1st to 10th	Day	22% 13% 4 7% 5% 4 4 3 4 6% 29%	2000
	11th to 20th	Day	23% 15% 4 9% 5% 5% 5% 3 4 5% 22%	1843
	21st to end	Day	24% 19% 4 9% 5% 5% 4 2 4 5% 19%	1881
November	1st to 10th	Day	20% 18% 4 10% 5% 4 3 3 4 5% 24%	1737
	11th to 20th	Day	23% 20% 5% 9% 5% 4 3 3 4 6% 18%	1528
	21st to end	Day	23% 23% 6% 8% 6% 3 3 2 4 4 18%	1449
December	1st to 10th	Day	24% 20% 6% 11% 5% 4 3 3 4 5% 15%	1330
	11th to 20th	Day	15% 25% 10% 12% 5% 4 3 2 3 5% 15%	1668
	21st to end	Day	21% 25% 7% 11% 5% 4 3 3 3 4 14%	2442
January	1st to 10th	Night	16% 22% 11% 13% 7% 5% 4 2 3 3 15%	4739
	11th to 20th	Night	17% 16% 8% 18% 6% 5% 4 3 4 4 15%	4467
	21st to end	Night	14% 15% 9% 18% 7% 5% 5% 3 4 4 16%	4884
February	1st to 10th	Night	21% 18% 8% 16% 7% 5% 3 2 4 4 13%	2542
	11th to 20th	Night	23% 19% 7% 14% 6% 4 3 3 3 5% 13%	2384
	21st to end	Night	14% 19% 6% 14% 6% 6% 4 3 4 5% 17%	1884
March	1st to 10th	Night	24% 15% 7% 12% 5% 4 4 3 4 4 19%	3706
	11th to 20th	Night	15% 16% 11% 17% 8% 5% 4 3 4 4 14%	3479
	21st to end	Night	31% 18% 8% 11% 4 3 3 3 3 3 15%	3815
April	1st to 10th	Night	22% 22% 8% 9% 4 3 3 2 3 4 19%	1877
	11th to 20th	Night	24% 18% 6% 9% 3 4 3 3 3 5% 22%	1688
	21st to end	Night	23% 23% 5% 8% 4 3 4 2 4 3 20%	1710
May	1st to 10th	Night	28% 22% 8% 8% 4 4 3 2 3 4 14%	2845
	11th to 20th	Night	29% 16% 4 10% 5% 4 4 3 4 4 16%	2443
	21st to end	Night	27% 18% 5% 8% 5% 4 4 2 4 4 17%	2412
June	1st to 10th	Night	28% 18% 4 8% 4 5% 3 3 3 5% 18%	1330
	11th to 20th	Night	26% 13% 5% 8% 5% 5% 4 3 6% 6% 20%	1330
	21st to end	Night	29% 13% 4 8% 4 4 4 3 4 7% 20%	1330
July	1st to 10th	Night	38% 13% 3 6% 4 3 4 2 3 5% 18%	2220
	11th to 20th	Night	32% 16% 4 8% 4 4 4 3 5% 5% 15%	2251
	21st to end	Night	20% 13% 3 7% 4 5% 4 3 4 5% 33%	2750
August	1st to 10th	Night	25% 14% 3 7% 4 4 4 4 6% 7% 22%	2726
	11th to 20th	Night	25% 12% 4 6% 3 4 3 2 5% 6% 29%	2791
	21st to end	Night	28% 9% 3 7% 4 4 4 3 4 6% 27%	3135
September	1st to 10th	Night	22% 11% 4 7% 4 4 4 3 5% 7% 29%	1907
	11th to 20th	Night	24% 13% 3 8% 4 4 4 3 4 6% 28%	2090
	21st to end	Night	21% 12% 4 8% 5% 4 4 3 4 6% 30%	2090
October	1st to 10th	Night	24% 13% 4 8% 4 4 3 3 4 6% 27%	2180
	11th to 20th	Night	25% 14% 3 8% 4 4 3 4 5% 6% 23%	2332
	21st to end	Night	26% 18% 4 8% 4 5% 4 3 3 4 21%	2717
November	1st to 10th	Night	23% 20% 4 7% 5% 4 3 3 4 5% 22%	2558
	11th to 20th	Night	23% 20% 6% 7% 5% 4 4 3 4 5% 20%	2675
	21st to end	Night	18% 21% 5% 9% 5% 5% 4 3 4 5% 19%	2729
December	1st to 10th	Night	22% 21% 7% 12% 6% 5% 4 2 3 4 16%	2850
	11th to 20th	Night	20% 24% 8% 14% 7% 4 3 2 3 3 11%	3531
	21st to end	Night	21% 21% 8% 10% 5% 4 4 3 3 4 18%	5225

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	71% 5% 6% 11% 6% 2	2217
	11th to 20th	Day	70% 9% 7% 9% 6% 1	2501
	21st to end	Day	70% 6% 6% 11% 6% 1	2783
February	1st to 10th	Day	74% 5% 9% 7% 5% 1	1636
	11th to 20th	Day	74% 5% 8% 8% 3	1689
	21st to end	Day	69% 7% 9% 7% 6% 1	1570
March	1st to 10th	Day	71% 6% 8% 10% 4 1	3138
	11th to 20th	Day	76% 7% 8% 7% 2	3480
	21st to end	Day	75% 5% 7% 10% 2 1	3817
April	1st to 10th	Day	72% 5% 7% 11% 4	2298
	11th to 20th	Day	67% 4 8% 12% 8% 1	2441
	21st to end	Day	68% 5% 8% 11% 8% 1	2470
May	1st to 10th	Day	70% 7% 10% 9% 4	4120
	11th to 20th	Day	68% 6% 11% 11% 3	4461
	21st to end	Day	66% 7% 8% 14% 5%	5173
June	1st to 10th	Day	73% 5% 8% 10% 4 1	2850
	11th to 20th	Day	63% 6% 12% 12% 6%	2850
	21st to end	Day	63% 7% 11% 14% 5%	2850
July	1st to 10th	Day	64% 6% 11% 14% 4	4675
	11th to 20th	Day	61% 7% 15% 12% 5%	4622
	21st to end	Day	48% 6% 19% 21% 5%	4662
August	1st to 10th	Day	63% 6% 13% 16% 3	4198
	11th to 20th	Day	57% 6% 14% 20% 3	4085
	21st to end	Day	53% 6% 16% 23% 3	4532
September	1st to 10th	Day	53% 8% 11% 20% 8%	2270
	11th to 20th	Day	54% 6% 12% 18% 9%	2090
	21st to end	Day	50% 8% 15% 20% 7% 1	2090
October	1st to 10th	Day	64% 6% 10% 15% 5%	3330
	11th to 20th	Day	61% 5% 14% 14% 7%	3056
	21st to end	Day	68% 5% 7% 15% 5%	3092
November	1st to 10th	Day	64% 7% 13% 12% 4	1737
	11th to 20th	Day	67% 7% 9% 12% 5%	1528
	21st to end	Day	70% 6% 11% 9% 4	1449
December	1st to 10th	Day	73% 5% 8% 10% 3	1330
	11th to 20th	Day	74% 6% 8% 8% 4	1667
	21st to end	Day	74% 7% 9% 9% 2	2442
January	1st to 10th	Night	72% 7% 6% 9% 5% 1	4739
	11th to 20th	Night	67% 11% 9% 9% 3	4467
	21st to end	Night	68% 8% 10% 10% 3 1	4884
February	1st to 10th	Night	75% 4 8% 8% 4 1	2542
	11th to 20th	Night	73% 6% 8% 10% 3	2388
	21st to end	Night	66% 9% 9% 11% 6%	1884
March	1st to 10th	Night	68% 7% 8% 13% 4 1	3715
	11th to 20th	Night	73% 7% 9% 8% 3	3480
	21st to end	Night	74% 6% 7% 11% 3	3815
April	1st to 10th	Night	70% 5% 8% 11% 6% 1	1877
	11th to 20th	Night	67% 4 8% 13% 7% 1	1688
	21st to end	Night	69% 5% 7% 12% 7%	1710
May	1st to 10th	Night	74% 6% 9% 7% 3	2850
	11th to 20th	Night	71% 6% 7% 11% 4	2444
	21st to end	Night	67% 9% 9% 10% 5%	2413
June	1st to 10th	Night	69% 5% 10% 11% 4	1330
	11th to 20th	Night	62% 8% 12% 13% 4	1330
	21st to end	Night	64% 6% 13% 13% 4	1330
July	1st to 10th	Night	70% 5% 8% 14% 3	2186
	11th to 20th	Night	72% 6% 9% 9% 3	2209
	21st to end	Night	53% 6% 16% 21% 3	2663
August	1st to 10th	Night	61% 6% 16% 14% 2	2715
	11th to 20th	Night	57% 5% 15% 18% 4	2818
	21st to end	Night	57% 6% 13% 21% 3	3134
September	1st to 10th	Night	54% 7% 11% 19% 7% 1	1907
	11th to 20th	Night	58% 6% 13% 14% 8% 1	2090
	21st to end	Night	54% 6% 13% 19% 7%	2090
October	1st to 10th	Night	62% 6% 14% 15% 3	3635
	11th to 20th	Night	59% 5% 16% 13% 7%	3868
	21st to end	Night	62% 5% 11% 16% 6%	4467
November	1st to 10th	Night	64% 6% 13% 12% 5%	2558
	11th to 20th	Night	66% 8% 11% 11% 4	2675
	21st to end	Night	65% 8% 12% 11% 4	2729
December	1st to 10th	Night	72% 7% 7% 11% 4	2850
	11th to 20th	Night	79% 4 6% 7% 3	3533
	21st to end	Night	68% 8% 9% 12% 2	5225

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	34% 26% 27% 11% 2	370
	11th to 20th	Day	34% 24% 28% 11% 2 1	370
	21st to end	Day	32% 26% 28% 11% 3	407
February	1st to 10th	Day	31% 24% 29% 13% 2	370
	11th to 20th	Day	34% 32% 23% 10% 2	366
	21st to end	Day	30% 29% 29% 9% 2	307
March	1st to 10th	Day	36% 28% 26% 8% 2	370
	11th to 20th	Day	31% 24% 26% 14% 4 2	370
	21st to end	Day	36% 23% 28% 9% 4 1	407
April	1st to 10th	Day	38% 25% 24% 10% 3	484
	11th to 20th	Day	37% 21% 25% 13% 4	639
	21st to end	Day	35% 24% 24% 14% 3	650
May	1st to 10th	Day	38% 20% 23% 13% 5% 1	653
	11th to 20th	Day	29% 18% 30% 17% 5% 1	674
	21st to end	Day	35% 17% 30% 15% 3 1	735
June	1st to 10th	Day	43% 15% 25% 13% 4 1	680
	11th to 20th	Day	34% 17% 28% 15% 5% 1	680
	21st to end	Day	33% 15% 30% 16% 5% 1	680
July	1st to 10th	Day	31% 15% 31% 15% 6% 1	670
	11th to 20th	Day	28% 14% 31% 20% 5% 1	668
	21st to end	Day	31% 16% 26% 19% 7%	740
August	1st to 10th	Day	32% 12% 28% 19% 7% 2	675
	11th to 20th	Day	27% 15% 28% 22% 6% 1	667
	21st to end	Day	30% 14% 26% 22% 7% 1	748
September	1st to 10th	Day	26% 13% 27% 25% 7% 1	516
	11th to 20th	Day	34% 20% 25% 17% 4 1	390
	21st to end	Day	26% 18% 34% 16% 6%	390
October	1st to 10th	Day	28% 19% 31% 17% 5%	390
	11th to 20th	Day	33% 20% 25% 15% 6% 1	390
	21st to end	Day	37% 23% 23% 13% 3 2	429
November	1st to 10th	Day	38% 21% 26% 11% 3 1	395
	11th to 20th	Day	37% 23% 21% 15% 4 1	373
	21st to end	Day	39% 25% 25% 9% 2	370
December	1st to 10th	Day	35% 21% 28% 12% 4	370
	11th to 20th	Day	37% 27% 25% 8% 2	370
	21st to end	Day	29% 24% 30% 12% 4 1	407
January	1st to 10th	Night	32% 25% 29% 11% 3	850
	11th to 20th	Night	34% 23% 28% 12% 3	850
	21st to end	Night	30% 23% 29% 16% 2	935
February	1st to 10th	Night	32% 26% 30% 11% 2	850
	11th to 20th	Night	36% 25% 27% 11% 1	824
	21st to end	Night	26% 25% 30% 16% 4	628
March	1st to 10th	Night	26% 30% 30% 12% 3	753
	11th to 20th	Night	25% 20% 27% 22% 6%	570
	21st to end	Night	34% 22% 28% 15% 2	627
April	1st to 10th	Night	33% 22% 26% 14% 4	570
	11th to 20th	Night	33% 18% 31% 14% 4	564
	21st to end	Night	36% 18% 28% 16% 3 1	570
May	1st to 10th	Night	34% 13% 30% 18% 4	570
	11th to 20th	Night	31% 15% 28% 20% 6%	562
	21st to end	Night	33% 16% 28% 19% 4	616
June	1st to 10th	Night	38% 14% 26% 18% 4	570
	11th to 20th	Night	32% 14% 28% 21% 5%	570
	21st to end	Night	34% 11% 32% 17% 5% 1	570
July	1st to 10th	Night	29% 12% 32% 23% 3 1	556
	11th to 20th	Night	32% 12% 35% 18% 3	552
	21st to end	Night	30% 12% 33% 20% 6%	623
August	1st to 10th	Night	30% 10% 30% 24% 7%	568
	11th to 20th	Night	28% 12% 30% 24% 6%	562
	21st to end	Night	29% 8% 32% 24% 6%	627
September	1st to 10th	Night	28% 8% 31% 26% 6%	570
	11th to 20th	Night	34% 12% 29% 19% 5% 1	570
	21st to end	Night	29% 14% 29% 23% 5%	570
October	1st to 10th	Night	31% 14% 29% 21% 5%	617
	11th to 20th	Night	34% 16% 27% 17% 6%	722
	21st to end	Night	36% 18% 25% 17% 4	946
November	1st to 10th	Night	34% 22% 25% 16% 3	880
	11th to 20th	Night	34% 18% 26% 17% 4	856
	21st to end	Night	33% 25% 28% 11% 4	850
December	1st to 10th	Night	33% 22% 27% 15% 4	850
	11th to 20th	Night	38% 26% 24% 10% 2	850
	21st to end	Night	30% 23% 29% 14% 3 1	935

Page generated at 2024-11-09 00:45:34. Version ac07

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