Mountain City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain City clear sky chart from 2005-11-06 to 2024-01-15.

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% 9% 4 7% 6% 4 5% 5% 6% 7% 33%	74924
	Night	13% 10% 4 7% 5% 3 5% 5% 6% 7% 36%	74857
Transparency	Day	49% 8% 11% 18% 13% 3	74647
	Night	46% 8% 12% 18% 13% 3	74653
Seeing	Day	23% 16% 23% 19% 13% 6%	13980
	Night	21% 15% 20% 25% 17% 3	24120

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	16% 13% 5% 9% 8% 3 4 4 4 6% 30%	1706
	11th to 20th	Day	17% 14% 7% 10% 6% 3 4 4 4 5% 27%	1656
	21st to end	Day	13% 12% 9% 7% 5% 3 5% 4 5% 5% 32%	1782
February	1st to 10th	Day	16% 13% 6% 8% 7% 4 4 5% 4 6% 28%	1620
	11th to 20th	Day	20% 12% 6% 8% 5% 3 4 3 3 6% 29%	1748
	21st to end	Day	21% 12% 5% 8% 4 2 3 3 4 6% 33%	1480
March	1st to 10th	Day	13% 11% 5% 6% 4 3 4 3 4 5% 41%	1964
	11th to 20th	Day	19% 11% 4 7% 6% 3 5% 3 6% 6% 30%	1980
	21st to end	Day	18% 11% 4 7% 5% 3 4 4 5% 6% 32%	2178
April	1st to 10th	Day	13% 10% 4 5% 5% 3 4 4 6% 7% 38%	1980
	11th to 20th	Day	16% 9% 3 5% 4 3 5% 5% 5% 6% 38%	2160
	21st to end	Day	16% 9% 4 6% 5% 3 5% 4 5% 6% 36%	2340
May	1st to 10th	Day	16% 8% 3 7% 6% 4 6% 5% 5% 7% 31%	2340
	11th to 20th	Day	20% 8% 4 7% 6% 4 6% 5% 5% 7% 29%	2301
	21st to end	Day	12% 7% 3 6% 7% 4 6% 7% 8% 10% 30%	2531
June	1st to 10th	Day	12% 7% 3 6% 7% 4 6% 6% 7% 8% 32%	2340
	11th to 20th	Day	10% 7% 3 8% 9% 4 7% 6% 7% 9% 31%	2340
	21st to end	Day	11% 6% 3 6% 7% 5% 8% 7% 8% 8% 30%	2340
July	1st to 10th	Day	12% 7% 5% 6% 8% 4 7% 7% 8% 9% 27%	2340
	11th to 20th	Day	13% 7% 4 9% 6% 5% 7% 6% 6% 9% 28%	2340
	21st to end	Day	14% 7% 4 9% 8% 5% 7% 7% 7% 8% 24%	2547
August	1st to 10th	Day	11% 7% 3 8% 8% 5% 7% 8% 8% 9% 24%	2327
	11th to 20th	Day	14% 7% 4 7% 8% 5% 8% 8% 7% 8% 25%	2303
	21st to end	Day	10% 7% 4 7% 7% 4 7% 7% 6% 9% 33%	2454
September	1st to 10th	Day	12% 6% 3 6% 6% 5% 6% 7% 7% 9% 34%	1980
	11th to 20th	Day	14% 7% 4 7% 6% 3 6% 6% 5% 7% 34%	1980
	21st to end	Day	15% 6% 3 6% 6% 3 6% 4 7% 8% 35%	1980
October	1st to 10th	Day	15% 6% 2 6% 5% 3 4 4 4 8% 43%	1904
	11th to 20th	Day	16% 7% 3 5% 4 2 4 4 4 6% 46%	1800
	21st to end	Day	15% 10% 2 5% 3 2 3 3 5% 6% 43%	1980
November	1st to 10th	Day	11% 8% 2 5% 3 2 4 4 4 7% 50%	1796
	11th to 20th	Day	11% 11% 3 5% 5% 3 4 4 6% 7% 42%	1710
	21st to end	Day	13% 10% 3 6% 5% 3 4 4 6% 5% 42%	1710
December	1st to 10th	Day	18% 13% 6% 9% 5% 3 4 3 5% 6% 28%	1710
	11th to 20th	Day	15% 13% 6% 5% 5% 2 4 4 5% 8% 33%	2153
	21st to end	Day	12% 13% 7% 9% 6% 3 6% 5% 5% 5% 27%	3124
January	1st to 10th	Night	15% 12% 6% 10% 8% 3 4 4 5% 5% 29%	2459
	11th to 20th	Night	17% 14% 6% 10% 6% 4 4 4 5% 4 26%	2393
	21st to end	Night	13% 12% 7% 11% 5% 3 4 3 4 4 32%	2574
February	1st to 10th	Night	15% 11% 5% 8% 5% 3 4 4 6% 6% 32%	2336
	11th to 20th	Night	18% 13% 5% 10% 7% 3 4 4 4 5% 28%	2098
	21st to end	Night	19% 14% 5% 9% 5% 2 3 4 4 5% 31%	1776
March	1st to 10th	Night	14% 12% 6% 7% 5% 2 4 4 4 5% 38%	1994
	11th to 20th	Night	17% 12% 4 7% 5% 3 5% 5% 6% 7% 30%	1980
	21st to end	Night	14% 11% 5% 7% 5% 3 4 4 5% 7% 34%	2178
April	1st to 10th	Night	14% 11% 3 6% 5% 2 3 5% 6% 7% 38%	1980
	11th to 20th	Night	12% 9% 4 5% 4 2 5% 5% 6% 8% 40%	1761
	21st to end	Night	14% 8% 3 5% 6% 3 5% 4 6% 6% 40%	1620
May	1st to 10th	Night	16% 9% 3 6% 5% 2 4 5% 7% 8% 34%	1620
	11th to 20th	Night	14% 7% 3 6% 6% 4 6% 6% 9% 9% 31%	1592
	21st to end	Night	8% 7% 3 7% 6% 4 6% 6% 8% 11% 34%	1744
June	1st to 10th	Night	9% 5% 3 6% 6% 4 6% 6% 7% 11% 37%	1620
	11th to 20th	Night	7% 6% 2 6% 5% 3 6% 6% 7% 10% 40%	1620
	21st to end	Night	10% 6% 3 5% 6% 4 5% 6% 8% 10% 37%	1620
July	1st to 10th	Night	11% 5% 3 7% 6% 3 6% 6% 7% 9% 37%	1620
	11th to 20th	Night	9% 6% 2 6% 6% 3 5% 7% 8% 12% 37%	1620
	21st to end	Night	8% 5% 3 7% 7% 4 6% 8% 10% 10% 33%	1771
August	1st to 10th	Night	11% 6% 2 6% 6% 4 6% 7% 7% 11% 35%	1611
	11th to 20th	Night	12% 6% 2 7% 6% 4 7% 7% 9% 9% 32%	1598
	21st to end	Night	9% 6% 3 6% 5% 4 7% 6% 7% 10% 39%	1878
September	1st to 10th	Night	11% 7% 2 5% 6% 4 4 5% 6% 8% 42%	1980
	11th to 20th	Night	14% 7% 3 5% 5% 3 4 5% 5% 7% 42%	1980
	21st to end	Night	13% 7% 2 5% 4 3 5% 6% 6% 6% 43%	1980
October	1st to 10th	Night	15% 6% 2 5% 3 2 4 4 5% 7% 46%	2056
	11th to 20th	Night	15% 8% 2 4 5% 2 4 4 5% 6% 45%	2160
	21st to end	Night	13% 11% 3 4 3 3 3 3 4 7% 45%	2376
November	1st to 10th	Night	12% 9% 3 4 4 3 4 4 4 6% 48%	2278
	11th to 20th	Night	13% 9% 4 6% 3 3 4 4 5% 8% 42%	2470
	21st to end	Night	13% 10% 4 6% 3 2 5% 4 5% 5% 43%	2470
December	1st to 10th	Night	17% 12% 5% 10% 7% 3 4 4 4 6% 28%	2470
	11th to 20th	Night	15% 13% 6% 11% 5% 3 4 3 4 5% 31%	3042
	21st to end	Night	13% 14% 10% 11% 7% 3 5% 5% 6% 7% 21%	4532

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	55% 6% 7% 16% 12% 4	1707
	11th to 20th	Day	59% 5% 6% 16% 11% 3	1656
	21st to end	Day	53% 4 8% 18% 14% 2	1782
February	1st to 10th	Day	56% 6% 8% 15% 13% 2	1620
	11th to 20th	Day	58% 3 8% 15% 14% 2	1758
	21st to end	Day	53% 5% 9% 14% 14% 5%	1480
March	1st to 10th	Day	46% 3 8% 20% 18% 5%	1964
	11th to 20th	Day	54% 5% 9% 16% 11% 4	1980
	21st to end	Day	52% 6% 11% 20% 9% 2	2178
April	1st to 10th	Day	43% 6% 11% 23% 14% 3	1980
	11th to 20th	Day	44% 7% 9% 19% 17% 4	2160
	21st to end	Day	48% 8% 11% 21% 10% 2	2340
May	1st to 10th	Day	50% 8% 12% 19% 10% 1	2340
	11th to 20th	Day	54% 8% 13% 17% 6% 1	2305
	21st to end	Day	45% 12% 15% 21% 7%	2531
June	1st to 10th	Day	47% 10% 15% 17% 10% 1	2340
	11th to 20th	Day	48% 12% 13% 15% 11% 2	2340
	21st to end	Day	46% 11% 13% 18% 11% 1	2340
July	1st to 10th	Day	48% 12% 16% 14% 9% 1	2275
	11th to 20th	Day	50% 12% 15% 12% 9% 2	2271
	21st to end	Day	51% 13% 13% 15% 7% 1	2405
August	1st to 10th	Day	53% 13% 14% 15% 6%	2314
	11th to 20th	Day	53% 12% 13% 14% 8%	2303
	21st to end	Day	45% 12% 15% 16% 10% 2	2454
September	1st to 10th	Day	43% 11% 12% 18% 12% 4	1980
	11th to 20th	Day	47% 8% 9% 19% 15% 2	1980
	21st to end	Day	46% 8% 12% 17% 13% 4	1980
October	1st to 10th	Day	40% 7% 10% 21% 18% 5%	1904
	11th to 20th	Day	39% 6% 8% 23% 19% 5%	1800
	21st to end	Day	41% 5% 7% 23% 18% 6%	1980
November	1st to 10th	Day	36% 5% 8% 18% 27% 6%	1796
	11th to 20th	Day	40% 5% 9% 17% 23% 6%	1710
	21st to end	Day	43% 4 7% 21% 20% 5%	1710
December	1st to 10th	Day	57% 5% 8% 15% 12% 3	1710
	11th to 20th	Day	48% 4 10% 15% 20% 3	2150
	21st to end	Day	54% 5% 8% 21% 11% 1	3124
January	1st to 10th	Night	56% 5% 7% 14% 12% 5%	2459
	11th to 20th	Night	59% 5% 7% 13% 12% 3	2393
	21st to end	Night	55% 4 8% 15% 15% 3	2574
February	1st to 10th	Night	52% 5% 9% 19% 13% 2	2336
	11th to 20th	Night	59% 5% 7% 15% 11% 4	2099
	21st to end	Night	56% 5% 8% 17% 10% 4	1776
March	1st to 10th	Night	49% 5% 7% 17% 18% 4	1994
	11th to 20th	Night	52% 7% 11% 20% 9% 1	1980
	21st to end	Night	50% 7% 11% 19% 11% 2	2178
April	1st to 10th	Night	43% 8% 13% 21% 13% 3	1980
	11th to 20th	Night	40% 8% 12% 19% 17% 4	1761
	21st to end	Night	43% 6% 12% 26% 12% 1	1620
May	1st to 10th	Night	46% 9% 15% 21% 8% 1	1620
	11th to 20th	Night	45% 12% 17% 19% 6% 1	1593
	21st to end	Night	41% 13% 18% 20% 7% 1	1745
June	1st to 10th	Night	39% 13% 18% 19% 11%	1620
	11th to 20th	Night	36% 12% 21% 22% 9% 1	1620
	21st to end	Night	39% 12% 17% 19% 11% 2	1620
July	1st to 10th	Night	40% 11% 18% 18% 11% 1	1575
	11th to 20th	Night	36% 13% 23% 17% 9% 2	1566
	21st to end	Night	38% 15% 19% 21% 7%	1672
August	1st to 10th	Night	42% 14% 18% 19% 8%	1600
	11th to 20th	Night	43% 14% 16% 16% 10% 1	1598
	21st to end	Night	38% 10% 19% 22% 10% 1	1878
September	1st to 10th	Night	38% 11% 16% 19% 13% 3	1980
	11th to 20th	Night	40% 8% 15% 20% 16% 1	1980
	21st to end	Night	40% 9% 11% 22% 16% 2	1980
October	1st to 10th	Night	37% 8% 10% 21% 20% 4	2056
	11th to 20th	Night	39% 6% 9% 24% 17% 4	2160
	21st to end	Night	41% 5% 6% 22% 20% 7%	2376
November	1st to 10th	Night	37% 6% 9% 19% 23% 6%	2278
	11th to 20th	Night	41% 5% 7% 19% 21% 7%	2470
	21st to end	Night	42% 5% 7% 21% 20% 5%	2470
December	1st to 10th	Night	57% 5% 7% 15% 12% 3	2470
	11th to 20th	Night	56% 4 6% 13% 17% 4	3044
	21st to end	Night	59% 6% 8% 13% 11% 1	4532

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	35% 32% 24% 7% 1 1	270
	11th to 20th	Day	39% 27% 26% 6% 1	252
	21st to end	Day	39% 34% 19% 7% 1	264
February	1st to 10th	Day	37% 32% 24% 6% 2	240
	11th to 20th	Day	50% 26% 21% 2	240
	21st to end	Day	48% 25% 22% 4 1	198
March	1st to 10th	Day	26% 30% 26% 13% 4	404
	11th to 20th	Day	35% 29% 20% 12% 3 1	420
	21st to end	Day	33% 23% 24% 15% 4	462
April	1st to 10th	Day	29% 22% 27% 14% 7% 1	420
	11th to 20th	Day	27% 21% 24% 16% 10% 2	412
	21st to end	Day	29% 19% 25% 15% 9% 5%	420
May	1st to 10th	Day	26% 21% 30% 11% 9% 4	423
	11th to 20th	Day	24% 13% 23% 23% 10% 6%	447
	21st to end	Day	16% 10% 24% 21% 17% 13%	485
June	1st to 10th	Day	15% 9% 27% 24% 18% 7%	450
	11th to 20th	Day	14% 10% 24% 24% 19% 9%	450
	21st to end	Day	16% 12% 26% 25% 14% 8%	450
July	1st to 10th	Day	15% 6% 19% 25% 20% 15%	445
	11th to 20th	Day	11% 5% 19% 30% 23% 11%	444
	21st to end	Day	12% 5% 22% 26% 22% 13%	488
August	1st to 10th	Day	15% 7% 19% 26% 18% 15%	446
	11th to 20th	Day	15% 5% 19% 23% 25% 13%	439
	21st to end	Day	13% 4 18% 27% 20% 18%	495
September	1st to 10th	Day	14% 4 16% 26% 27% 13%	450
	11th to 20th	Day	17% 4 17% 25% 25% 11%	450
	21st to end	Day	18% 10% 24% 24% 18% 6%	450
October	1st to 10th	Day	21% 10% 21% 23% 19% 6%	450
	11th to 20th	Day	21% 18% 20% 23% 15% 2	450
	21st to end	Day	24% 16% 26% 20% 9% 4	495
November	1st to 10th	Day	19% 17% 28% 22% 11% 3	394
	11th to 20th	Day	27% 25% 24% 18% 5% 1	270
	21st to end	Day	25% 24% 30% 14% 6% 1	270
December	1st to 10th	Day	36% 23% 29% 10% 2	270
	11th to 20th	Day	31% 24% 29% 13% 3	270
	21st to end	Day	31% 28% 28% 9% 4	297
January	1st to 10th	Night	28% 29% 21% 18% 4	760
	11th to 20th	Night	31% 22% 23% 20% 4	737
	21st to end	Night	24% 32% 24% 17% 3	792
February	1st to 10th	Night	26% 25% 24% 22% 3	720
	11th to 20th	Night	33% 30% 23% 13% 1	703
	21st to end	Night	33% 27% 25% 13% 2	592
March	1st to 10th	Night	23% 25% 29% 19% 4	720
	11th to 20th	Night	28% 21% 25% 18% 7% 1	720
	21st to end	Night	23% 19% 31% 22% 6%	792
April	1st to 10th	Night	25% 19% 25% 23% 8% 1	720
	11th to 20th	Night	20% 19% 25% 23% 12% 1	664
	21st to end	Night	18% 17% 20% 34% 9% 1	540
May	1st to 10th	Night	22% 11% 27% 25% 14% 1	540
	11th to 20th	Night	17% 9% 20% 31% 19% 3	531
	21st to end	Night	12% 5% 16% 30% 29% 7%	584
June	1st to 10th	Night	11% 4 16% 34% 30% 5%	540
	11th to 20th	Night	9% 5% 15% 30% 33% 7%	540
	21st to end	Night	12% 4 14% 35% 31% 4	540
July	1st to 10th	Night	14% 3 10% 27% 40% 5%	525
	11th to 20th	Night	12% 3 7% 29% 43% 7%	522
	21st to end	Night	9% 3 9% 29% 41% 9%	591
August	1st to 10th	Night	13% 1 10% 31% 40% 6%	537
	11th to 20th	Night	14% 2 8% 32% 35% 9%	534
	21st to end	Night	11% 1 11% 30% 37% 9%	668
September	1st to 10th	Night	14% 4 12% 29% 34% 7%	720
	11th to 20th	Night	16% 5% 12% 28% 33% 6%	720
	21st to end	Night	17% 6% 18% 29% 27% 3	720
October	1st to 10th	Night	19% 10% 18% 23% 24% 6%	720
	11th to 20th	Night	20% 12% 23% 26% 16% 3	720
	21st to end	Night	21% 14% 24% 27% 12% 2	792
November	1st to 10th	Night	18% 13% 22% 28% 16% 3	740
	11th to 20th	Night	23% 18% 19% 29% 10% 1	760
	21st to end	Night	21% 18% 23% 26% 11% 1	760
December	1st to 10th	Night	30% 20% 24% 20% 6%	760
	11th to 20th	Night	26% 24% 19% 24% 6% 1	760
	21st to end	Night	31% 19% 22% 23% 4	836

Page generated at 2024-01-11 22:33:48. Version ac07

Copyright 2024 Attilla Danko