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 2025-04-11.

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% 44%	116873
	Night	2 6% 3 8% 6% 5% 5% 5% 7% 8% 46%	120221
Transparency	Day	33% 8% 13% 21% 18% 8%	116617
	Night	31% 9% 13% 24% 17% 6%	120066
Seeing	Day	8% 15% 32% 29% 13% 3	15632
	Night	5% 8% 28% 39% 17% 3	25308

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	4 4 15% 10% 8% 8% 6% 7% 9% 29%	3590
	11th to 20th	Day	5% 2 8% 9% 7% 7% 5% 7% 8% 42%	3640
	21st to end	Day	9% 4 10% 6% 5% 5% 4 5% 6% 47%	4254
February	1st to 10th	Day	1 7% 4 13% 8% 6% 8% 6% 8% 7% 33%	1800
	11th to 20th	Day	1 6% 4 11% 9% 7% 8% 6% 7% 9% 30%	1810
	21st to end	Day	7% 4 12% 10% 8% 8% 7% 7% 9% 28%	1650
March	1st to 10th	Day	6% 4 9% 6% 6% 6% 5% 7% 9% 43%	4640
	11th to 20th	Day	1 9% 4 10% 5% 4 5% 4 8% 7% 43%	5000
	21st to end	Day	1 11% 6% 13% 8% 8% 8% 6% 8% 8% 23%	5486
April	1st to 10th	Day	3 11% 4 9% 7% 6% 6% 5% 8% 9% 32%	2316
	11th to 20th	Day	2 10% 3 8% 7% 6% 6% 6% 7% 8% 37%	2439
	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	4 6% 2 6% 5% 4 3 3 4 5% 59%	3372
	11th to 20th	Day	2 6% 2 5% 3 3 3 3 5% 6% 60%	3150
	21st to end	Day	2 7% 3 8% 4 5% 7% 4 5% 7% 47%	3145
November	1st to 10th	Day	3 9% 4 9% 7% 6% 5% 5% 6% 8% 38%	1764
	11th to 20th	Day	1 7% 4 11% 7% 6% 5% 6% 7% 8% 38%	1710
	21st to end	Day	1 8% 3 10% 5% 6% 6% 6% 6% 8% 41%	1600
December	1st to 10th	Day	1 4 2 7% 5% 5% 4 5% 5% 6% 56%	2559
	11th to 20th	Day	1 8% 6% 14% 8% 8% 7% 5% 8% 8% 29%	2645
	21st to end	Day	1 9% 4 12% 8% 6% 7% 4 7% 7% 34%	3498
January	1st to 10th	Night	4 3 12% 8% 6% 7% 6% 8% 10% 36%	6398
	11th to 20th	Night	4 3 10% 10% 8% 7% 5% 7% 8% 40%	6320
	21st to end	Night	1 7% 4 9% 7% 6% 5% 4 5% 6% 47%	6710
February	1st to 10th	Night	1 9% 4 11% 9% 7% 7% 6% 6% 9% 32%	2600
	11th to 20th	Night	1 7% 3 10% 7% 5% 7% 5% 7% 9% 37%	2476
	21st to end	Night	1 6% 2 10% 8% 9% 7% 7% 9% 9% 33%	1980
March	1st to 10th	Night	6% 4 11% 5% 5% 5% 4 6% 9% 45%	5253
	11th to 20th	Night	1 9% 3 8% 5% 5% 6% 5% 8% 7% 43%	5000
	21st to end	Night	1 7% 4 10% 7% 6% 7% 6% 8% 11% 33%	5489
April	1st to 10th	Night	2 10% 3 8% 7% 6% 7% 5% 7% 8% 38%	2080
	11th to 20th	Night	3 6% 2 7% 7% 7% 6% 4 9% 9% 39%	1695
	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	3 4 1 4 3 3 3 3 5% 7% 64%	3604
	11th to 20th	Night	3 6% 3 6% 4 4 4 3 5% 6% 56%	3778
	21st to end	Night	2 6% 3 7% 5% 5% 5% 5% 8% 8% 46%	4396
November	1st to 10th	Night	2 8% 3 9% 6% 6% 5% 4 7% 9% 40%	2535
	11th to 20th	Night	1 7% 4 8% 6% 6% 6% 5% 8% 9% 40%	2668
	21st to end	Night	1 6% 3 8% 6% 6% 6% 5% 8% 8% 43%	2800
December	1st to 10th	Night	1 4 2 6% 6% 5% 4 4 6% 8% 55%	4624
	11th to 20th	Night	1 7% 4 12% 8% 7% 8% 6% 8% 10% 29%	5546
	21st to end	Night	1 7% 4 12% 8% 8% 7% 6% 8% 8% 31%	7458

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	42% 14% 14% 17% 13% 1	3590
	11th to 20th	Day	32% 11% 16% 24% 13% 4	3640
	21st to end	Day	36% 6% 13% 19% 19% 6%	4254
February	1st to 10th	Day	40% 13% 20% 17% 9% 1	1800
	11th to 20th	Day	40% 12% 19% 17% 9% 2	1819
	21st to end	Day	41% 14% 17% 17% 8% 3	1650
March	1st to 10th	Day	32% 8% 16% 21% 17% 6%	4640
	11th to 20th	Day	32% 9% 16% 29% 14%	5000
	21st to end	Day	47% 13% 18% 19% 3	5486
April	1st to 10th	Day	40% 10% 20% 20% 9%	2316
	11th to 20th	Day	37% 7% 19% 24% 12% 1	2442
	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	28% 4 8% 21% 31% 8%	3372
	11th to 20th	Day	23% 5% 15% 32% 20% 5%	3150
	21st to end	Day	31% 8% 12% 24% 23% 2	3145
November	1st to 10th	Day	41% 9% 14% 20% 15% 2	1764
	11th to 20th	Day	36% 10% 19% 25% 9% 2	1710
	21st to end	Day	36% 8% 19% 22% 11% 4	1600
December	1st to 10th	Day	25% 8% 19% 26% 19% 3	2559
	11th to 20th	Day	46% 10% 18% 18% 7%	2644
	21st to end	Day	43% 11% 11% 18% 11% 6%	3498
January	1st to 10th	Night	35% 12% 11% 24% 17% 1	6398
	11th to 20th	Night	34% 13% 9% 26% 14% 4	6320
	21st to end	Night	36% 7% 11% 18% 20% 8%	6710
February	1st to 10th	Night	42% 11% 17% 18% 11% 1	2600
	11th to 20th	Night	37% 11% 20% 20% 10% 3	2477
	21st to end	Night	38% 12% 16% 22% 9% 3	1980
March	1st to 10th	Night	32% 8% 12% 23% 15% 9%	5253
	11th to 20th	Night	31% 9% 14% 31% 14% 1	5000
	21st to end	Night	35% 13% 18% 29% 5%	5489
April	1st to 10th	Night	38% 10% 16% 23% 12% 1	2080
	11th to 20th	Night	34% 8% 19% 27% 11% 2	1695
	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	18% 5% 10% 27% 32% 8%	3604
	11th to 20th	Night	27% 6% 13% 25% 23% 6%	3778
	21st to end	Night	30% 7% 14% 29% 19% 1	4396
November	1st to 10th	Night	36% 7% 15% 24% 15% 2	2535
	11th to 20th	Night	35% 9% 19% 24% 10% 2	2668
	21st to end	Night	34% 8% 15% 25% 14% 4	2800
December	1st to 10th	Night	24% 8% 22% 26% 18% 3	4624
	11th to 20th	Night	44% 11% 18% 18% 8%	5547
	21st to end	Night	41% 11% 13% 19% 10% 6%	7458

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	5% 13% 30% 36% 11% 6%	200
	11th to 20th	Day	3 12% 38% 29% 14% 5%	200
	21st to end	Day	7% 12% 34% 31% 14% 2	275
February	1st to 10th	Day	5% 23% 44% 22% 5% 1	300
	11th to 20th	Day	5% 18% 37% 27% 11% 3	355
	21st to end	Day	3 17% 37% 32% 10% 1	414
March	1st to 10th	Day	4 18% 39% 30% 7% 1	500
	11th to 20th	Day	7% 13% 31% 36% 11% 2	500
	21st to end	Day	8% 18% 33% 29% 11% 1	550
April	1st to 10th	Day	7% 18% 32% 27% 13% 2	500
	11th to 20th	Day	5% 22% 40% 22% 10% 2	453
	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	9% 22% 31% 31% 7% 1	330
November	1st to 10th	Day	8% 20% 33% 26% 11% 2	300
	11th to 20th	Day	6% 17% 33% 34% 8% 3	300
	21st to end	Day	5% 11% 31% 38% 12% 2	300
December	1st to 10th	Day	4 8% 33% 31% 17% 6%	283
	11th to 20th	Day	7% 14% 36% 31% 12% 2	200
	21st to end	Day	4 18% 35% 29% 13% 2	220
January	1st to 10th	Night	3 9% 31% 43% 13% 2	840
	11th to 20th	Night	3 13% 30% 38% 13% 3	800
	21st to end	Night	4 11% 30% 39% 13% 2	880
February	1st to 10th	Night	4 13% 38% 35% 9% 2	800
	11th to 20th	Night	4 10% 37% 37% 11% 2	784
	21st to end	Night	4 8% 34% 39% 13% 2	660
March	1st to 10th	Night	3 9% 34% 42% 11% 1	800
	11th to 20th	Night	6% 9% 32% 35% 16% 3	800
	21st to end	Night	7% 13% 28% 38% 14% 1	880
April	1st to 10th	Night	6% 13% 31% 34% 13% 3	790
	11th to 20th	Night	5% 11% 36% 34% 12% 1	565
	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% 29% 37% 13% 5%	836
November	1st to 10th	Night	6% 8% 28% 40% 15% 3	780
	11th to 20th	Night	6% 9% 34% 41% 9% 1	868
	21st to end	Night	3 11% 34% 36% 14% 2	1000
December	1st to 10th	Night	4 11% 32% 41% 10% 2	1000
	11th to 20th	Night	4 8% 35% 42% 10% 1	1000
	21st to end	Night	5% 13% 37% 34% 9% 2	1100

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