Nicholia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nicholia clear sky chart from 2005-11-06 to 2024-10-25.

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	3 7% 3 8% 6% 5% 5% 5% 6% 7% 43%	101190
	Night	2 6% 3 8% 6% 5% 5% 5% 7% 8% 45%	97784
Transparency	Day	34% 8% 13% 20% 17% 8%	100934
	Night	32% 8% 14% 23% 16% 7%	97629
Seeing	Day	8% 15% 32% 29% 13% 3	15125
	Night	5% 8% 27% 39% 17% 3	24592

By Month

Percentage Cloud Cover SW (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	5% 5% 16% 10% 8% 9% 7% 8% 8% 25%	2504
	11th to 20th	Day	1 6% 3 10% 10% 8% 8% 5% 7% 9% 34%	2540
	21st to end	Day	1 13% 5% 13% 8% 6% 6% 4 5% 7% 33%	2960
February	1st to 10th	Day	1 7% 4 13% 8% 6% 8% 6% 8% 8% 33%	1710
	11th to 20th	Day	1 7% 4 11% 9% 8% 8% 6% 7% 9% 30%	1717
	21st to end	Day	7% 4 12% 10% 8% 8% 7% 7% 9% 26%	1570
March	1st to 10th	Day	1 4 4 11% 6% 7% 7% 5% 7% 8% 41%	3221
	11th to 20th	Day	1 8% 3 8% 5% 4 5% 4 8% 5% 48%	3490
	21st to end	Day	1 12% 7% 14% 9% 8% 8% 6% 8% 8% 20%	3825
April	1st to 10th	Day	3 12% 4 10% 7% 6% 6% 5% 8% 9% 30%	2199
	11th to 20th	Day	2 10% 3 8% 7% 6% 6% 6% 7% 8% 37%	2437
	21st to end	Day	4 10% 4 8% 6% 7% 6% 5% 8% 8% 33%	2470
May	1st to 10th	Day	3 11% 4 9% 6% 6% 7% 6% 8% 8% 33%	4110
	11th to 20th	Day	4 7% 3 7% 5% 5% 4 4 6% 8% 46%	4071
	21st to end	Day	6% 12% 4 8% 5% 5% 4 4 5% 7% 39%	4868
June	1st to 10th	Day	7% 8% 3 8% 6% 5% 5% 5% 8% 10% 34%	2850
	11th to 20th	Day	8% 9% 3 7% 5% 5% 4 3 6% 8% 42%	2850
	21st to end	Day	3 4 2 5% 5% 5% 4 4 6% 7% 56%	2850
July	1st to 10th	Day	2 3 1 4 3 3 3 3 5% 6% 67%	4648
	11th to 20th	Day	4 4 2 5% 4 5% 5% 4 6% 7% 54%	4420
	21st to end	Day	4 5% 2 6% 5% 5% 5% 5% 7% 6% 50%	4644
August	1st to 10th	Day	5% 5% 2 7% 5% 5% 6% 5% 7% 7% 44%	4092
	11th to 20th	Day	3 2 1 4 4 4 4 4 5% 6% 62%	4028
	21st to end	Day	3 5% 2 5% 4 4 5% 3 4 5% 60%	4521
September	1st to 10th	Day	5% 4 2 5% 2 4 3 3 5% 6% 62%	2203
	11th to 20th	Day	7% 8% 3 5% 3 5% 5% 3 6% 6% 50%	2090
	21st to end	Day	7% 6% 2 5% 4 3 3 3 4 7% 56%	2090
October	1st to 10th	Day	7% 9% 3 8% 6% 4 4 5% 6% 6% 43%	2024
	11th to 20th	Day	4 8% 3 7% 4 5% 4 4 5% 6% 52%	1900
	21st to end	Day	3 8% 3 9% 5% 5% 6% 4 6% 9% 43%	1855
November	1st to 10th	Day	3 9% 4 9% 7% 6% 5% 5% 6% 8% 38%	1674
	11th to 20th	Day	1 7% 4 11% 7% 6% 5% 6% 7% 8% 39%	1625
	21st to end	Day	1 8% 3 10% 5% 6% 6% 6% 6% 7% 41%	1520
December	1st to 10th	Day	1 6% 3 11% 8% 7% 7% 7% 7% 7% 36%	1487
	11th to 20th	Day	1 8% 5% 12% 9% 9% 7% 5% 8% 8% 28%	1685
	21st to end	Day	1 9% 4 11% 8% 5% 6% 4 7% 8% 36%	2442
January	1st to 10th	Night	4 3 14% 9% 7% 7% 6% 8% 10% 33%	4470
	11th to 20th	Night	6% 4 13% 11% 9% 8% 5% 7% 8% 29%	4420
	21st to end	Night	1 10% 5% 13% 8% 7% 5% 5% 6% 7% 33%	4698
February	1st to 10th	Night	1 8% 4 11% 9% 7% 7% 6% 6% 9% 32%	2470
	11th to 20th	Night	1 7% 3 10% 7% 5% 7% 5% 8% 9% 36%	2349
	21st to end	Night	1 7% 2 10% 8% 9% 7% 7% 9% 9% 31%	1884
March	1st to 10th	Night	1 7% 4 10% 5% 5% 5% 4 8% 9% 43%	3652
	11th to 20th	Night	1 5% 2 8% 5% 4 5% 5% 7% 6% 51%	3490
	21st to end	Night	1 7% 4 10% 7% 7% 7% 7% 8% 10% 31%	3828
April	1st to 10th	Night	2 10% 3 8% 6% 6% 7% 5% 7% 8% 37%	1977
	11th to 20th	Night	3 6% 2 7% 7% 7% 6% 4 8% 10% 39%	1691
	21st to end	Night	4 9% 4 9% 6% 6% 4 4 7% 8% 40%	1710
May	1st to 10th	Night	3 9% 5% 8% 5% 5% 5% 4 6% 8% 42%	2860
	11th to 20th	Night	4 7% 3 6% 5% 4 5% 4 6% 8% 50%	2834
	21st to end	Night	6% 8% 4 8% 5% 4 5% 5% 7% 8% 39%	2704
June	1st to 10th	Night	5% 6% 3 8% 7% 5% 5% 4 7% 10% 41%	1330
	11th to 20th	Night	7% 5% 3 6% 5% 4 5% 4 5% 7% 49%	1330
	21st to end	Night	2 3 2 4 3 4 5% 3 5% 7% 61%	1330
July	1st to 10th	Night	1 1 1 2 2 3 3 3 5% 6% 73%	2307
	11th to 20th	Night	2 2 1 2 2 3 3 3 5% 7% 68%	2540
	21st to end	Night	2 2 1 4 3 4 4 3 5% 7% 66%	2909
August	1st to 10th	Night	3 3 1 4 4 4 6% 5% 7% 8% 55%	2847
	11th to 20th	Night	1 2 1 3 3 4 4 4 6% 6% 66%	2811
	21st to end	Night	2 2 1 3 3 3 3 3 5% 6% 68%	3146
September	1st to 10th	Night	4 4 1 3 2 3 4 3 5% 6% 65%	1973
	11th to 20th	Night	5% 4 1 6% 4 4 4 4 5% 7% 57%	2090
	21st to end	Night	6% 6% 2 4 3 3 3 3 4 6% 61%	2090
October	1st to 10th	Night	5% 6% 2 5% 4 4 5% 4 6% 9% 51%	2156
	11th to 20th	Night	3 6% 2 6% 4 4 4 4 5% 8% 54%	2280
	21st to end	Night	2 6% 2 7% 5% 6% 5% 5% 8% 9% 45%	2601
November	1st to 10th	Night	3 9% 3 8% 6% 6% 5% 4 7% 9% 40%	2405
	11th to 20th	Night	1 7% 4 8% 6% 6% 6% 5% 8% 9% 40%	2534
	21st to end	Night	1 6% 3 8% 6% 6% 5% 5% 8% 8% 43%	2660
December	1st to 10th	Night	1 6% 3 9% 8% 7% 7% 7% 9% 10% 34%	2688
	11th to 20th	Night	1 7% 4 11% 8% 7% 7% 6% 8% 10% 30%	3506
	21st to end	Night	1 7% 4 12% 9% 7% 7% 5% 7% 7% 34%	5214

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	46% 15% 15% 14% 9% 1	2504
	11th to 20th	Day	42% 9% 18% 16% 11% 3	2540
	21st to end	Day	49% 7% 15% 19% 7% 2	2960
February	1st to 10th	Day	40% 13% 21% 18% 8%	1710
	11th to 20th	Day	41% 12% 20% 17% 9% 2	1726
	21st to end	Day	42% 13% 18% 17% 7% 3	1570
March	1st to 10th	Day	33% 10% 18% 18% 19% 2	3221
	11th to 20th	Day	30% 7% 22% 30% 10% 1	3490
	21st to end	Day	51% 12% 19% 15% 3	3825
April	1st to 10th	Day	42% 10% 20% 19% 8%	2199
	11th to 20th	Day	37% 8% 19% 24% 12% 1	2440
	21st to end	Day	39% 8% 18% 26% 8%	2470
May	1st to 10th	Day	36% 10% 17% 24% 11% 2	4110
	11th to 20th	Day	30% 8% 14% 31% 12% 6%	4074
	21st to end	Day	39% 9% 13% 31% 7% 1	4868
June	1st to 10th	Day	41% 8% 18% 25% 7%	2850
	11th to 20th	Day	39% 6% 9% 21% 17% 8%	2850
	21st to end	Day	25% 5% 9% 24% 30% 7%	2850
July	1st to 10th	Day	17% 4 5% 14% 27% 33%	4576
	11th to 20th	Day	25% 5% 5% 12% 21% 32%	4345
	21st to end	Day	28% 7% 5% 11% 29% 21%	4497
August	1st to 10th	Day	33% 7% 6% 14% 28% 11%	4078
	11th to 20th	Day	19% 6% 5% 19% 36% 15%	4067
	21st to end	Day	24% 5% 5% 20% 28% 17%	4520
September	1st to 10th	Day	22% 5% 6% 20% 30% 17%	2203
	11th to 20th	Day	31% 6% 9% 20% 24% 8%	2090
	21st to end	Day	27% 4 11% 26% 23% 8%	2090
October	1st to 10th	Day	38% 6% 13% 22% 17% 4	2024
	11th to 20th	Day	30% 6% 16% 29% 15% 3	1900
	21st to end	Day	34% 8% 16% 25% 15% 2	1855
November	1st to 10th	Day	41% 9% 15% 20% 14% 2	1674
	11th to 20th	Day	37% 10% 18% 25% 9% 2	1625
	21st to end	Day	36% 8% 19% 21% 11% 4	1520
December	1st to 10th	Day	39% 11% 17% 17% 10% 4	1487
	11th to 20th	Day	46% 11% 18% 16% 8% 1	1684
	21st to end	Day	40% 11% 12% 18% 9% 8%	2442
January	1st to 10th	Night	38% 12% 13% 22% 13% 1	4470
	11th to 20th	Night	44% 13% 10% 19% 9% 4	4420
	21st to end	Night	48% 8% 15% 17% 9% 2	4698
February	1st to 10th	Night	42% 11% 18% 19% 10% 1	2470
	11th to 20th	Night	37% 11% 20% 20% 9% 2	2350
	21st to end	Night	39% 12% 16% 21% 8% 3	1884
March	1st to 10th	Night	32% 10% 15% 22% 17% 5%	3652
	11th to 20th	Night	26% 7% 18% 34% 14% 1	3490
	21st to end	Night	37% 12% 20% 27% 4 1	3828
April	1st to 10th	Night	38% 10% 17% 22% 11% 1	1977
	11th to 20th	Night	34% 8% 19% 27% 11% 2	1691
	21st to end	Night	38% 8% 17% 29% 8%	1710
May	1st to 10th	Night	32% 8% 17% 28% 14% 2	2860
	11th to 20th	Night	27% 9% 12% 37% 14% 1	2835
	21st to end	Night	33% 11% 14% 29% 12%	2704
June	1st to 10th	Night	34% 8% 18% 30% 10%	1330
	11th to 20th	Night	31% 7% 12% 23% 19% 7%	1330
	21st to end	Night	20% 5% 10% 25% 30% 10%	1330
July	1st to 10th	Night	11% 4 6% 15% 29% 35%	2270
	11th to 20th	Night	14% 4 5% 15% 25% 38%	2492
	21st to end	Night	17% 5% 4 19% 33% 23%	2818
August	1st to 10th	Night	21% 9% 7% 19% 32% 13%	2838
	11th to 20th	Night	16% 5% 6% 25% 30% 17%	2838
	21st to end	Night	16% 4 7% 24% 33% 16%	3146
September	1st to 10th	Night	19% 5% 7% 21% 30% 18%	1973
	11th to 20th	Night	25% 5% 10% 25% 24% 10%	2090
	21st to end	Night	24% 4 9% 27% 29% 6%	2090
October	1st to 10th	Night	27% 6% 15% 29% 19% 4	2156
	11th to 20th	Night	26% 6% 15% 33% 18% 2	2280
	21st to end	Night	30% 8% 19% 27% 16% 1	2601
November	1st to 10th	Night	37% 7% 16% 24% 14% 3	2405
	11th to 20th	Night	35% 9% 19% 24% 10% 3	2534
	21st to end	Night	34% 8% 16% 24% 14% 5%	2660
December	1st to 10th	Night	37% 12% 19% 19% 10% 4	2688
	11th to 20th	Night	42% 10% 19% 16% 12% 1	3507
	21st to end	Night	41% 9% 13% 18% 9% 9%	5214

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	4 13% 28% 36% 12% 6%	180
	11th to 20th	Day	2 10% 37% 31% 14% 6%	180
	21st to end	Day	7% 12% 34% 29% 15% 2	247
February	1st to 10th	Day	3 23% 45% 23% 6% 1	270
	11th to 20th	Day	4 18% 37% 27% 11% 3	322
	21st to end	Day	3 17% 37% 32% 10% 1	382
March	1st to 10th	Day	4 17% 40% 31% 8%	460
	11th to 20th	Day	6% 13% 30% 38% 12% 2	460
	21st to end	Day	8% 17% 34% 29% 11% 1	506
April	1st to 10th	Day	8% 18% 32% 28% 12% 2	460
	11th to 20th	Day	5% 22% 40% 22% 10% 2	452
	21st to end	Day	9% 18% 30% 28% 12% 3	460
May	1st to 10th	Day	7% 18% 29% 30% 14% 2	463
	11th to 20th	Day	15% 14% 28% 27% 14% 2	488
	21st to end	Day	15% 10% 24% 30% 16% 5%	669
June	1st to 10th	Day	8% 12% 28% 30% 16% 6%	680
	11th to 20th	Day	15% 19% 28% 25% 11% 2	680
	21st to end	Day	6% 12% 31% 33% 17% 3	680
July	1st to 10th	Day	5% 11% 30% 30% 19% 4	620
	11th to 20th	Day	4 13% 38% 33% 10% 2	484
	21st to end	Day	5% 11% 35% 31% 14% 4	531
August	1st to 10th	Day	8% 11% 29% 33% 15% 3	487
	11th to 20th	Day	4 12% 28% 31% 18% 6%	477
	21st to end	Day	7% 12% 33% 29% 17% 4	539
September	1st to 10th	Day	7% 12% 34% 26% 15% 6%	490
	11th to 20th	Day	11% 15% 29% 27% 13% 5%	490
	21st to end	Day	11% 15% 33% 24% 15% 2	490
October	1st to 10th	Day	11% 13% 32% 26% 13% 4	424
	11th to 20th	Day	7% 21% 22% 25% 18% 8%	300
	21st to end	Day	8% 20% 32% 31% 7% 1	311
November	1st to 10th	Day	8% 19% 32% 27% 12% 2	270
	11th to 20th	Day	4 16% 32% 36% 9% 3	270
	21st to end	Day	5% 11% 31% 38% 13% 2	270
December	1st to 10th	Day	5% 7% 35% 32% 16% 5%	255
	11th to 20th	Day	7% 12% 35% 32% 12% 2	180
	21st to end	Day	4 16% 35% 29% 14% 2	198
January	1st to 10th	Night	3 8% 30% 43% 13% 2	798
	11th to 20th	Night	3 13% 29% 39% 13% 3	760
	21st to end	Night	4 11% 30% 40% 13% 2	836
February	1st to 10th	Night	3 13% 37% 36% 9% 2	760
	11th to 20th	Night	3 10% 36% 37% 12% 2	744
	21st to end	Night	4 8% 34% 39% 14% 2	628
March	1st to 10th	Night	3 8% 34% 42% 11% 1	760
	11th to 20th	Night	5% 8% 32% 36% 17% 3	760
	21st to end	Night	6% 13% 26% 38% 14% 2	836
April	1st to 10th	Night	6% 13% 31% 34% 13% 3	751
	11th to 20th	Night	6% 11% 36% 34% 12% 1	563
	21st to end	Night	9% 9% 28% 35% 15% 3	570
May	1st to 10th	Night	5% 11% 29% 35% 18% 3	570
	11th to 20th	Night	10% 5% 22% 36% 24% 3	561
	21st to end	Night	15% 8% 21% 30% 22% 3	525
June	1st to 10th	Night	8% 5% 21% 40% 23% 3	380
	11th to 20th	Night	8% 8% 26% 40% 17% 1	380
	21st to end	Night	2 2 19% 46% 28% 2	380
July	1st to 10th	Night	3 2 14% 46% 31% 3	370
	11th to 20th	Night	2 2 15% 55% 24% 2	368
	21st to end	Night	3 1 13% 48% 31% 4	502
August	1st to 10th	Night	5% 2 16% 46% 27% 3	567
	11th to 20th	Night	2 3 15% 47% 28% 3	564
	21st to end	Night	4 5% 20% 39% 28% 4	627
September	1st to 10th	Night	6% 3 18% 38% 29% 6%	721
	11th to 20th	Night	6% 5% 15% 36% 31% 7%	760
	21st to end	Night	9% 6% 19% 36% 22% 7%	760
October	1st to 10th	Night	7% 6% 26% 38% 20% 4	760
	11th to 20th	Night	7% 8% 22% 38% 19% 5%	760
	21st to end	Night	7% 10% 27% 37% 14% 5%	812
November	1st to 10th	Night	6% 7% 27% 41% 16% 3	740
	11th to 20th	Night	5% 9% 33% 41% 10% 1	824
	21st to end	Night	3 11% 32% 37% 15% 3	950
December	1st to 10th	Night	5% 11% 32% 41% 10% 2	950
	11th to 20th	Night	4 7% 33% 43% 11% 1	950
	21st to end	Night	5% 13% 36% 35% 10% 2	1045

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