NAA Caton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the NAA Caton clear sky chart from 2005-11-06 to 2024-01-16.

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	14% 8% 4 6% 6% 3 5% 5% 5% 7% 37%	74826
	Night	15% 8% 4 6% 5% 3 4 4 5% 7% 39%	74989
Transparency	Day	47% 3 12% 23% 13% 2	74527
	Night	46% 3 11% 23% 15% 2	74809
Seeing	Day	17% 7% 26% 27% 16% 6%	14630
	Night	18% 8% 28% 32% 13% 1	24607

By Month

Percentage Cloud Cover SE (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% 11% 5% 9% 8% 4 6% 4 4 6% 27%	1517
	11th to 20th	Day	14% 15% 6% 11% 6% 4 5% 5% 5% 5% 23%	1480
	21st to end	Day	16% 15% 8% 10% 8% 3 4 4 4 6% 23%	1660
February	1st to 10th	Day	18% 13% 5% 8% 5% 4 6% 5% 4 5% 26%	1644
	11th to 20th	Day	16% 10% 5% 7% 7% 4 4 4 4 5% 34%	1748
	21st to end	Day	17% 12% 6% 10% 5% 2 3 4 5% 6% 29%	1480
March	1st to 10th	Day	17% 12% 4 7% 7% 3 4 5% 4 6% 32%	1800
	11th to 20th	Day	15% 8% 4 7% 6% 3 5% 5% 6% 8% 33%	1862
	21st to end	Day	20% 10% 5% 8% 7% 4 5% 4 5% 6% 25%	2376
April	1st to 10th	Day	17% 11% 4 8% 5% 3 4 4 6% 7% 31%	2160
	11th to 20th	Day	17% 9% 3 6% 5% 3 4 5% 5% 7% 36%	2134
	21st to end	Day	21% 7% 3 6% 6% 4 4 5% 4 7% 33%	2232
May	1st to 10th	Day	18% 7% 4 6% 6% 3 5% 6% 6% 8% 31%	2340
	11th to 20th	Day	19% 8% 2 7% 5% 3 4 4 5% 8% 35%	2430
	21st to end	Day	14% 6% 3 6% 5% 3 5% 6% 7% 8% 37%	2725
June	1st to 10th	Day	10% 6% 2 4 6% 3 5% 5% 6% 7% 47%	2520
	11th to 20th	Day	9% 5% 2 5% 6% 3 5% 4 6% 8% 46%	2520
	21st to end	Day	11% 6% 3 6% 6% 4 5% 6% 7% 9% 37%	2520
July	1st to 10th	Day	8% 3 2 4 5% 4 5% 5% 6% 9% 48%	2520
	11th to 20th	Day	10% 4 2 3 4 3 5% 6% 6% 9% 48%	2520
	21st to end	Day	7% 4 2 6% 6% 4 6% 6% 7% 8% 45%	2743
August	1st to 10th	Day	7% 5% 3 5% 5% 3 4 6% 7% 12% 43%	2446
	11th to 20th	Day	9% 5% 2 5% 5% 4 6% 5% 6% 9% 43%	2125
	21st to end	Day	9% 4 2 4 4 3 6% 5% 6% 10% 48%	2376
September	1st to 10th	Day	11% 6% 2 4 5% 3 5% 4 5% 8% 47%	2160
	11th to 20th	Day	11% 4 2 4 4 2 4 4 5% 8% 52%	2060
	21st to end	Day	9% 6% 3 7% 4 3 4 5% 6% 8% 46%	1980
October	1st to 10th	Day	12% 6% 3 6% 5% 3 4 4 4 7% 46%	1913
	11th to 20th	Day	18% 8% 3 6% 5% 3 5% 4 6% 7% 36%	1800
	21st to end	Day	20% 8% 3 6% 5% 2 3 4 5% 7% 36%	1794
November	1st to 10th	Day	12% 8% 3 5% 5% 2 4 4 4 7% 46%	1672
	11th to 20th	Day	16% 10% 4 7% 5% 3 5% 4 5% 6% 34%	1710
	21st to end	Day	19% 10% 4 8% 5% 3 4 4 4 5% 36%	1638
December	1st to 10th	Day	15% 11% 4 8% 6% 4 5% 4 5% 6% 32%	1520
	11th to 20th	Day	15% 12% 5% 8% 6% 4 6% 5% 5% 6% 29%	1918
	21st to end	Day	23% 21% 9% 11% 7% 3 4 3 2 4 14%	2783
January	1st to 10th	Night	15% 12% 5% 8% 6% 3 4 4 4 5% 34%	2648
	11th to 20th	Night	15% 14% 7% 9% 6% 3 4 4 4 6% 27%	2591
	21st to end	Night	15% 13% 7% 10% 6% 4 3 5% 5% 6% 27%	2692
February	1st to 10th	Night	17% 14% 6% 8% 6% 3 4 3 3 6% 30%	2313
	11th to 20th	Night	15% 10% 5% 6% 6% 3 5% 4 4 5% 37%	2098
	21st to end	Night	19% 10% 4 9% 5% 2 4 3 4 5% 36%	1776
March	1st to 10th	Night	16% 11% 4 6% 5% 3 5% 4 4 5% 36%	2160
	11th to 20th	Night	13% 8% 3 6% 5% 3 5% 4 5% 6% 42%	2112
	21st to end	Night	21% 10% 5% 7% 5% 3 4 4 5% 5% 31%	1980
April	1st to 10th	Night	16% 8% 4 6% 5% 4 3 4 5% 6% 39%	1800
	11th to 20th	Night	20% 7% 3 5% 5% 3 4 4 4 6% 40%	1775
	21st to end	Night	19% 7% 3 7% 5% 3 5% 5% 6% 7% 35%	1728
May	1st to 10th	Night	17% 7% 3 6% 4 4 4 5% 6% 9% 36%	1620
	11th to 20th	Night	16% 5% 2 5% 5% 3 4 5% 6% 8% 41%	1462
	21st to end	Night	11% 6% 3 4 5% 4 5% 6% 6% 9% 40%	1551
June	1st to 10th	Night	10% 3 2 5% 4 3 4 4 6% 7% 51%	1440
	11th to 20th	Night	9% 4 2 5% 5% 3 5% 5% 7% 9% 47%	1440
	21st to end	Night	10% 4 3 6% 6% 3 5% 5% 6% 7% 43%	1440
July	1st to 10th	Night	7% 5% 2 5% 4 2 5% 5% 7% 9% 49%	1440
	11th to 20th	Night	7% 4 1 4 5% 3 5% 5% 5% 7% 54%	1440
	21st to end	Night	4 3 2 4 3 3 5% 6% 8% 9% 53%	1575
August	1st to 10th	Night	5% 4 2 6% 4 3 5% 6% 6% 9% 50%	1488
	11th to 20th	Night	8% 3 2 4 4 2 3 5% 5% 9% 53%	1776
	21st to end	Night	8% 4 1 4 3 3 4 4 6% 8% 55%	1980
September	1st to 10th	Night	11% 5% 3 4 4 1 3 3 4 7% 54%	1800
	11th to 20th	Night	9% 4 2 4 4 3 3 4 5% 7% 55%	1881
	21st to end	Night	9% 4 2 6% 5% 3 5% 5% 6% 8% 48%	1980
October	1st to 10th	Night	11% 5% 2 4 5% 3 3 4 5% 7% 51%	2044
	11th to 20th	Night	19% 6% 3 4 4 2 3 4 5% 6% 45%	2160
	21st to end	Night	21% 8% 4 5% 4 2 3 3 4 6% 39%	2560
November	1st to 10th	Night	13% 6% 3 5% 4 2 3 3 5% 6% 50%	2406
	11th to 20th	Night	16% 7% 3 7% 6% 3 5% 4 5% 6% 38%	2470
	21st to end	Night	18% 8% 4 6% 6% 3 4 3 4 6% 39%	2540
December	1st to 10th	Night	17% 9% 4 8% 5% 3 4 4 4 6% 34%	2660
	11th to 20th	Night	16% 11% 5% 8% 7% 3 4 3 4 5% 33%	3279
	21st to end	Night	24% 16% 7% 9% 6% 4 5% 4 4 5% 16%	4884

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	58% 3 11% 18% 10%	1518
	11th to 20th	Day	63% 3 12% 15% 6% 1	1480
	21st to end	Day	64% 3 11% 14% 9%	1660
February	1st to 10th	Day	61% 3 10% 16% 8% 2	1644
	11th to 20th	Day	53% 3 11% 22% 9% 2	1758
	21st to end	Day	58% 3 10% 21% 8% 2	1480
March	1st to 10th	Day	55% 3 12% 23% 7% 1	1800
	11th to 20th	Day	50% 3 14% 23% 10% 1	1862
	21st to end	Day	60% 4 10% 20% 5% 1	2376
April	1st to 10th	Day	52% 3 10% 23% 11%	2160
	11th to 20th	Day	48% 3 10% 23% 12% 3	2134
	21st to end	Day	53% 3 12% 17% 13% 2	2232
May	1st to 10th	Day	51% 4 13% 23% 8% 1	2340
	11th to 20th	Day	50% 4 10% 25% 12% 1	2434
	21st to end	Day	44% 4 12% 21% 16% 2	2725
June	1st to 10th	Day	37% 3 11% 29% 18% 2	2520
	11th to 20th	Day	37% 4 10% 25% 21% 3	2520
	21st to end	Day	43% 5% 13% 23% 15% 2	2520
July	1st to 10th	Day	32% 4 15% 30% 16% 3	2451
	11th to 20th	Day	32% 5% 16% 29% 16% 3	2445
	21st to end	Day	35% 4 16% 27% 16% 2	2591
August	1st to 10th	Day	34% 4 17% 31% 13% 2	2431
	11th to 20th	Day	36% 4 14% 28% 17% 1	2125
	21st to end	Day	31% 5% 11% 29% 21% 4	2376
September	1st to 10th	Day	37% 3 12% 25% 17% 5%	2160
	11th to 20th	Day	31% 2 11% 31% 21% 4	2060
	21st to end	Day	36% 3 9% 29% 21% 2	1980
October	1st to 10th	Day	39% 3 11% 26% 18% 2	1913
	11th to 20th	Day	48% 2 10% 24% 15% 2	1800
	21st to end	Day	49% 3 11% 24% 10% 3	1794
November	1st to 10th	Day	40% 2 14% 25% 16% 3	1672
	11th to 20th	Day	52% 2 10% 24% 11% 1	1710
	21st to end	Day	53% 3 10% 24% 10%	1638
December	1st to 10th	Day	55% 2 13% 21% 8% 1	1520
	11th to 20th	Day	57% 2 12% 20% 8% 1	1915
	21st to end	Day	78% 1 7% 10% 4	2783
January	1st to 10th	Night	53% 3 10% 21% 13% 1	2648
	11th to 20th	Night	60% 2 14% 15% 9%	2591
	21st to end	Night	59% 2 11% 17% 10% 1	2692
February	1st to 10th	Night	59% 2 10% 19% 10% 2	2313
	11th to 20th	Night	50% 3 9% 24% 12% 1	2099
	21st to end	Night	53% 3 10% 20% 12% 3	1776
March	1st to 10th	Night	52% 2 11% 23% 11% 1	2160
	11th to 20th	Night	44% 3 12% 22% 17% 3	2112
	21st to end	Night	56% 2 11% 20% 10% 1	1980
April	1st to 10th	Night	46% 3 11% 24% 14% 2	1800
	11th to 20th	Night	47% 2 8% 22% 17% 4	1775
	21st to end	Night	48% 4 10% 22% 13% 3	1728
May	1st to 10th	Night	47% 3 13% 26% 12%	1620
	11th to 20th	Night	41% 5% 12% 26% 15% 1	1463
	21st to end	Night	40% 5% 14% 21% 18% 3	1552
June	1st to 10th	Night	32% 3 13% 27% 20% 4	1440
	11th to 20th	Night	34% 3 11% 26% 23% 3	1440
	21st to end	Night	38% 5% 14% 23% 16% 3	1440
July	1st to 10th	Night	32% 4 14% 27% 18% 5%	1400
	11th to 20th	Night	29% 3 13% 29% 22% 4	1392
	21st to end	Night	25% 4 17% 28% 20% 5%	1487
August	1st to 10th	Night	30% 5% 17% 30% 17% 2	1479
	11th to 20th	Night	27% 4 16% 30% 21% 2	1776
	21st to end	Night	28% 4 11% 31% 21% 5%	1980
September	1st to 10th	Night	32% 3 11% 27% 23% 4	1800
	11th to 20th	Night	30% 2 7% 33% 25% 3	1881
	21st to end	Night	35% 4 11% 29% 18% 3	1980
October	1st to 10th	Night	34% 3 10% 28% 22% 3	2044
	11th to 20th	Night	41% 1 8% 27% 21% 2	2160
	21st to end	Night	48% 2 9% 25% 14% 1	2560
November	1st to 10th	Night	37% 3 9% 28% 19% 4	2406
	11th to 20th	Night	47% 2 11% 24% 14% 2	2470
	21st to end	Night	49% 2 11% 25% 12% 1	2540
December	1st to 10th	Night	54% 2 11% 23% 8% 1	2660
	11th to 20th	Night	55% 2 12% 20% 10% 1	3281
	21st to end	Night	73% 2 8% 12% 4	4884

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	22% 7% 34% 27% 9% 1	270
	11th to 20th	Day	23% 13% 33% 23% 7% 1	255
	21st to end	Day	23% 14% 27% 28% 7% 1	264
February	1st to 10th	Day	24% 17% 35% 21% 3	240
	11th to 20th	Day	25% 14% 34% 21% 6%	240
	21st to end	Day	26% 12% 41% 17% 4	198
March	1st to 10th	Day	25% 18% 33% 20% 4	240
	11th to 20th	Day	25% 13% 34% 19% 9% 1	247
	21st to end	Day	30% 10% 30% 20% 8% 2	462
April	1st to 10th	Day	23% 11% 31% 26% 8% 1	420
	11th to 20th	Day	21% 15% 29% 20% 12% 3	412
	21st to end	Day	24% 10% 29% 25% 9% 2	420
May	1st to 10th	Day	22% 10% 28% 28% 10% 3	423
	11th to 20th	Day	22% 7% 27% 27% 13% 4	576
	21st to end	Day	14% 5% 30% 22% 19% 9%	679
June	1st to 10th	Day	11% 6% 26% 29% 22% 7%	630
	11th to 20th	Day	12% 4 27% 31% 20% 6%	630
	21st to end	Day	14% 5% 30% 29% 17% 5%	630
July	1st to 10th	Day	11% 1 14% 29% 25% 19%	621
	11th to 20th	Day	13% 3 20% 31% 22% 11%	618
	21st to end	Day	7% 2 20% 35% 26% 8%	684
August	1st to 10th	Day	7% 2 13% 35% 29% 14%	590
	11th to 20th	Day	13% 3 13% 26% 29% 15%	439
	21st to end	Day	8% 1 17% 32% 27% 15%	495
September	1st to 10th	Day	14% 4 18% 29% 28% 8%	450
	11th to 20th	Day	12% 1 15% 31% 28% 13%	450
	21st to end	Day	14% 6% 24% 26% 22% 8%	450
October	1st to 10th	Day	15% 4 25% 31% 18% 6%	383
	11th to 20th	Day	19% 17% 33% 22% 8% 1	270
	21st to end	Day	31% 9% 32% 20% 7% 1	297
November	1st to 10th	Day	15% 11% 36% 24% 10% 5%	270
	11th to 20th	Day	23% 13% 35% 19% 7% 3	270
	21st to end	Day	28% 7% 31% 26% 9%	270
December	1st to 10th	Day	19% 12% 39% 20% 9% 1	270
	11th to 20th	Day	19% 11% 38% 24% 8%	270
	21st to end	Day	29% 15% 35% 17% 3	297
January	1st to 10th	Night	22% 12% 35% 25% 6%	950
	11th to 20th	Night	24% 11% 34% 25% 6% 1	926
	21st to end	Night	21% 11% 32% 31% 5%	990
February	1st to 10th	Night	25% 9% 36% 25% 4 1	873
	11th to 20th	Night	22% 11% 34% 28% 5%	703
	21st to end	Night	24% 10% 38% 24% 4 1	592
March	1st to 10th	Night	21% 13% 35% 26% 6%	720
	11th to 20th	Night	18% 9% 33% 32% 7% 1	680
	21st to end	Night	26% 9% 32% 25% 7% 1	594
April	1st to 10th	Night	19% 10% 36% 27% 7%	540
	11th to 20th	Night	22% 10% 32% 29% 7%	533
	21st to end	Night	23% 7% 32% 29% 9%	540
May	1st to 10th	Night	21% 4 35% 31% 9%	540
	11th to 20th	Night	21% 4 27% 35% 12% 1	531
	21st to end	Night	13% 4 24% 40% 18% 1	584
June	1st to 10th	Night	12% 2 24% 45% 16%	540
	11th to 20th	Night	12% 3 23% 47% 14% 1	540
	21st to end	Night	11% 3 25% 40% 20% 1	540
July	1st to 10th	Night	10% 2 11% 43% 30% 5%	525
	11th to 20th	Night	8% 2 17% 41% 28% 3	522
	21st to end	Night	6% 2 13% 48% 29% 3	591
August	1st to 10th	Night	6% 1 9% 46% 33% 5%	537
	11th to 20th	Night	8% 2 10% 41% 35% 4	534
	21st to end	Night	9% 1 15% 39% 33% 3	594
September	1st to 10th	Night	12% 2 15% 39% 29% 3	540
	11th to 20th	Night	11% 2 16% 37% 30% 4	621
	21st to end	Night	12% 5% 23% 35% 23% 2	720
October	1st to 10th	Night	14% 5% 24% 37% 20% 1	720
	11th to 20th	Night	22% 10% 28% 30% 11%	720
	21st to end	Night	26% 9% 30% 27% 8%	792
November	1st to 10th	Night	15% 10% 36% 26% 11% 1	740
	11th to 20th	Night	21% 12% 32% 27% 7% 1	760
	21st to end	Night	21% 10% 34% 29% 7%	830
December	1st to 10th	Night	22% 9% 34% 27% 6%	950
	11th to 20th	Night	22% 10% 32% 29% 7%	950
	21st to end	Night	29% 12% 31% 25% 4	1045

Page generated at 2024-01-13 00:38:09. Version ac07

Copyright 2024 Attilla Danko