New Moon Telescopes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Moon Telescopes Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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% 5% 2 5% 5% 3 4 5% 5% 8% 44%	78618
	Night	15% 6% 3 5% 5% 3 4 4 5% 7% 44%	80894
Transparency	Day	38% 7% 12% 22% 17% 4	78337
	Night	39% 7% 11% 21% 18% 4	80694
Seeing	Day	18% 12% 27% 24% 15% 5%	14205
	Night	17% 10% 28% 30% 13% 1	24032

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	17% 5% 2 3 3 2 3 4 4 5% 52%	2808
	11th to 20th	Day	15% 7% 2 5% 4 2 4 4 5% 6% 48%	2840
	21st to end	Day	18% 8% 3 6% 5% 3 3 4 4 6% 39%	3124
February	1st to 10th	Day	12% 7% 2 6% 5% 3 6% 5% 6% 7% 41%	1710
	11th to 20th	Day	21% 5% 2 4 4 2 4 4 5% 6% 44%	1736
	21st to end	Day	18% 6% 3 6% 5% 3 6% 5% 5% 7% 37%	1579
March	1st to 10th	Day	14% 6% 2 4 3 2 3 4 4 7% 50%	2035
	11th to 20th	Day	17% 6% 3 6% 4 3 4 5% 5% 7% 42%	1980
	21st to end	Day	17% 7% 3 6% 6% 4 4 4 5% 7% 40%	2187
April	1st to 10th	Day	12% 4 2 3 4 2 4 4 6% 7% 52%	2160
	11th to 20th	Day	12% 4 3 4 5% 3 4 4 4 7% 49%	2134
	21st to end	Day	16% 6% 3 5% 4 2 5% 4 5% 7% 44%	2160
May	1st to 10th	Day	15% 5% 2 4 5% 3 4 6% 6% 9% 41%	2251
	11th to 20th	Day	17% 5% 3 5% 5% 3 5% 4 5% 7% 40%	2301
	21st to end	Day	14% 6% 2 5% 5% 3 5% 5% 5% 9% 41%	2712
June	1st to 10th	Day	11% 4 2 4 5% 2 6% 6% 7% 10% 44%	2520
	11th to 20th	Day	11% 5% 3 4 5% 3 5% 6% 7% 10% 41%	2520
	21st to end	Day	8% 4 2 5% 5% 3 6% 7% 7% 12% 40%	2520
July	1st to 10th	Day	8% 5% 2 6% 6% 4 7% 6% 7% 11% 39%	2461
	11th to 20th	Day	6% 4 2 5% 7% 5% 6% 7% 8% 12% 39%	2340
	21st to end	Day	7% 4 3 6% 7% 4 7% 8% 8% 10% 37%	2547
August	1st to 10th	Day	10% 5% 3 6% 6% 3 6% 7% 8% 10% 35%	2327
	11th to 20th	Day	13% 5% 2 7% 7% 4 6% 6% 6% 8% 36%	2183
	21st to end	Day	10% 5% 2 6% 6% 3 6% 6% 7% 9% 40%	2376
September	1st to 10th	Day	14% 5% 2 5% 5% 4 4 5% 6% 8% 43%	2160
	11th to 20th	Day	12% 5% 3 6% 6% 4 4 5% 5% 7% 43%	2160
	21st to end	Day	19% 7% 3 6% 5% 3 4 3 5% 6% 39%	1884
October	1st to 10th	Day	17% 5% 2 5% 5% 3 3 4 4 6% 47%	1800
	11th to 20th	Day	17% 4 2 4 5% 2 4 3 3 6% 51%	1800
	21st to end	Day	13% 5% 2 5% 5% 3 3 4 4 5% 52%	1980
November	1st to 10th	Day	13% 5% 2 4 3 2 3 4 3 6% 54%	1853
	11th to 20th	Day	15% 5% 2 5% 3 2 3 4 4 6% 50%	1710
	21st to end	Day	15% 4 2 4 4 2 3 3 5% 6% 52%	1558
December	1st to 10th	Day	16% 7% 3 5% 4 3 4 4 6% 7% 41%	1520
	11th to 20th	Day	15% 6% 2 5% 3 2 3 3 4 5% 54%	1910
	21st to end	Day	16% 7% 3 5% 4 3 4 4 5% 7% 43%	2772
January	1st to 10th	Night	14% 7% 3 5% 4 3 4 4 4 5% 47%	4132
	11th to 20th	Night	17% 7% 3 5% 5% 2 4 4 4 5% 45%	4120
	21st to end	Night	21% 7% 3 5% 4 2 3 3 4 4 44%	4532
February	1st to 10th	Night	16% 7% 2 5% 5% 2 4 4 6% 6% 44%	2470
	11th to 20th	Night	20% 7% 2 5% 4 3 4 4 4 6% 41%	2328
	21st to end	Night	17% 7% 3 5% 3 2 3 3 4 6% 46%	1871
March	1st to 10th	Night	14% 5% 2 4 4 3 4 3 5% 6% 50%	2042
	11th to 20th	Night	18% 4 3 5% 5% 3 4 5% 6% 7% 41%	1980
	21st to end	Night	15% 6% 3 6% 5% 3 4 3 4 7% 42%	2168
April	1st to 10th	Night	13% 5% 3 5% 4 4 5% 4 5% 7% 45%	1800
	11th to 20th	Night	12% 5% 3 5% 3 2 4 4 4 8% 49%	1775
	21st to end	Night	15% 5% 2 5% 4 3 4 4 5% 7% 46%	1800
May	1st to 10th	Night	14% 6% 2 4 4 3 4 4 6% 10% 41%	1724
	11th to 20th	Night	15% 5% 3 5% 5% 3 5% 4 5% 8% 40%	1592
	21st to end	Night	15% 6% 2 5% 5% 3 4 5% 5% 9% 42%	1559
June	1st to 10th	Night	12% 4 3 4 5% 4 4 7% 7% 9% 41%	1440
	11th to 20th	Night	9% 5% 3 6% 6% 3 6% 5% 7% 10% 40%	1440
	21st to end	Night	8% 5% 3 5% 6% 3 6% 6% 6% 12% 41%	1440
July	1st to 10th	Night	9% 4 3 5% 6% 4 6% 6% 7% 10% 41%	1494
	11th to 20th	Night	4 4 3 5% 6% 3 7% 7% 8% 9% 43%	1620
	21st to end	Night	6% 4 2 6% 7% 5% 6% 5% 7% 12% 39%	1771
August	1st to 10th	Night	9% 4 3 6% 7% 4 7% 6% 8% 11% 37%	1611
	11th to 20th	Night	11% 5% 3 7% 6% 4 5% 5% 7% 10% 36%	1698
	21st to end	Night	10% 5% 2 5% 6% 3 6% 6% 8% 9% 39%	1980
September	1st to 10th	Night	12% 5% 3 6% 5% 4 4 5% 5% 8% 43%	1800
	11th to 20th	Night	12% 5% 3 5% 5% 3 6% 4 6% 7% 45%	1800
	21st to end	Night	22% 7% 3 6% 5% 3 4 4 5% 6% 36%	2072
October	1st to 10th	Night	16% 5% 2 5% 5% 3 3 4 4 6% 47%	2160
	11th to 20th	Night	16% 6% 3 5% 4 2 3 4 4 6% 48%	2160
	21st to end	Night	15% 4 2 4 4 2 4 3 3 7% 51%	2376
November	1st to 10th	Night	13% 5% 2 5% 5% 2 4 3 4 5% 52%	2221
	11th to 20th	Night	15% 5% 3 4 4 2 4 4 4 6% 50%	2470
	21st to end	Night	13% 4 2 4 5% 2 4 4 5% 6% 51%	2619
December	1st to 10th	Night	17% 8% 3 5% 5% 3 4 4 4 5% 42%	2660
	11th to 20th	Night	17% 6% 2 4 4 2 3 4 4 6% 47%	3285
	21st to end	Night	15% 7% 3 5% 5% 2 4 4 5% 7% 44%	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	34% 4 8% 30% 20% 4	2809
	11th to 20th	Day	36% 5% 8% 20% 25% 5%	2840
	21st to end	Day	46% 5% 10% 20% 16% 4	3124
February	1st to 10th	Day	41% 6% 11% 24% 15% 3	1710
	11th to 20th	Day	41% 5% 7% 21% 21% 5%	1745
	21st to end	Day	46% 6% 12% 14% 17% 5%	1579
March	1st to 10th	Day	35% 5% 10% 25% 21% 5%	2035
	11th to 20th	Day	41% 6% 9% 20% 16% 7%	1980
	21st to end	Day	45% 6% 10% 18% 17% 4	2187
April	1st to 10th	Day	31% 6% 12% 23% 20% 8%	2160
	11th to 20th	Day	35% 5% 11% 21% 21% 6%	2134
	21st to end	Day	39% 6% 13% 20% 16% 6%	2160
May	1st to 10th	Day	39% 8% 17% 19% 15% 3	2251
	11th to 20th	Day	42% 9% 13% 23% 10% 2	2305
	21st to end	Day	39% 8% 15% 25% 12%	2712
June	1st to 10th	Day	34% 10% 16% 26% 14% 1	2520
	11th to 20th	Day	36% 11% 15% 21% 15% 1	2520
	21st to end	Day	34% 12% 17% 22% 13% 2	2520
July	1st to 10th	Day	37% 11% 16% 20% 13% 3	2394
	11th to 20th	Day	33% 12% 22% 21% 10% 1	2271
	21st to end	Day	37% 13% 17% 20% 14% 1	2405
August	1st to 10th	Day	40% 11% 17% 22% 9% 1	2314
	11th to 20th	Day	42% 11% 15% 20% 11% 1	2183
	21st to end	Day	37% 10% 18% 20% 13% 2	2376
September	1st to 10th	Day	38% 9% 14% 16% 19% 4	2160
	11th to 20th	Day	38% 7% 12% 21% 19% 3	2160
	21st to end	Day	47% 6% 9% 20% 15% 3	1884
October	1st to 10th	Day	41% 5% 10% 21% 20% 4	1800
	11th to 20th	Day	36% 4 8% 25% 23% 5%	1800
	21st to end	Day	34% 4 7% 23% 25% 7%	1980
November	1st to 10th	Day	33% 5% 9% 23% 26% 4	1853
	11th to 20th	Day	35% 5% 9% 21% 22% 8%	1710
	21st to end	Day	34% 4 8% 25% 24% 5%	1558
December	1st to 10th	Day	41% 5% 12% 22% 16% 4	1520
	11th to 20th	Day	35% 3 7% 29% 18% 8%	1906
	21st to end	Day	39% 6% 10% 27% 16% 2	2772
January	1st to 10th	Night	39% 5% 8% 22% 21% 5%	4132
	11th to 20th	Night	42% 5% 7% 20% 22% 4	4120
	21st to end	Night	45% 4 6% 21% 17% 6%	4532
February	1st to 10th	Night	40% 5% 11% 23% 17% 4	2470
	11th to 20th	Night	44% 4 7% 19% 19% 7%	2330
	21st to end	Night	39% 5% 9% 21% 18% 7%	1871
March	1st to 10th	Night	36% 5% 9% 23% 23% 5%	2042
	11th to 20th	Night	41% 7% 8% 21% 18% 5%	1980
	21st to end	Night	43% 5% 9% 20% 17% 4	2168
April	1st to 10th	Night	39% 6% 10% 17% 21% 7%	1800
	11th to 20th	Night	34% 5% 10% 22% 22% 7%	1775
	21st to end	Night	38% 7% 12% 22% 16% 5%	1800
May	1st to 10th	Night	37% 9% 15% 21% 15% 3	1724
	11th to 20th	Night	42% 9% 14% 20% 14% 2	1593
	21st to end	Night	38% 10% 14% 24% 13% 1	1560
June	1st to 10th	Night	36% 9% 17% 23% 13% 2	1440
	11th to 20th	Night	38% 11% 16% 20% 14% 1	1440
	21st to end	Night	35% 10% 13% 21% 18% 3	1440
July	1st to 10th	Night	35% 13% 15% 19% 14% 4	1451
	11th to 20th	Night	30% 14% 21% 24% 8% 2	1566
	21st to end	Night	36% 10% 17% 25% 11% 1	1672
August	1st to 10th	Night	39% 12% 20% 20% 10%	1600
	11th to 20th	Night	41% 10% 19% 17% 12% 1	1698
	21st to end	Night	36% 11% 18% 22% 11% 3	1980
September	1st to 10th	Night	38% 9% 14% 18% 17% 4	1800
	11th to 20th	Night	36% 8% 10% 22% 21% 2	1800
	21st to end	Night	47% 7% 10% 18% 15% 4	2072
October	1st to 10th	Night	39% 5% 10% 22% 20% 4	2160
	11th to 20th	Night	37% 5% 8% 22% 22% 5%	2160
	21st to end	Night	34% 5% 8% 22% 24% 7%	2376
November	1st to 10th	Night	35% 5% 10% 21% 24% 5%	2221
	11th to 20th	Night	36% 5% 9% 18% 22% 10%	2470
	21st to end	Night	34% 5% 9% 23% 23% 6%	2619
December	1st to 10th	Night	44% 5% 8% 21% 17% 4	2660
	11th to 20th	Night	38% 5% 9% 20% 21% 6%	3288
	21st to end	Night	39% 6% 11% 24% 18% 2	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	27% 24% 30% 14% 5%	263
	11th to 20th	Day	30% 30% 29% 10% 2	270
	21st to end	Day	26% 24% 38% 12% 1	297
February	1st to 10th	Day	21% 27% 37% 12% 3	270
	11th to 20th	Day	35% 25% 29% 10% 1	343
	21st to end	Day	29% 19% 32% 17% 3	382
March	1st to 10th	Day	23% 21% 32% 19% 5%	440
	11th to 20th	Day	24% 23% 34% 14% 4 2	420
	21st to end	Day	22% 20% 37% 15% 6% 1	462
April	1st to 10th	Day	24% 18% 31% 18% 8%	420
	11th to 20th	Day	18% 14% 32% 22% 11% 3	412
	21st to end	Day	22% 13% 33% 23% 8% 1	420
May	1st to 10th	Day	19% 15% 33% 23% 8% 2	423
	11th to 20th	Day	21% 9% 28% 27% 11% 4	447
	21st to end	Day	21% 4 23% 29% 18% 6%	485
June	1st to 10th	Day	14% 4 27% 30% 21% 4	450
	11th to 20th	Day	11% 8% 24% 31% 20% 7%	450
	21st to end	Day	10% 5% 27% 34% 20% 4	450
July	1st to 10th	Day	10% 3 18% 32% 28% 8%	445
	11th to 20th	Day	6% 2 16% 36% 31% 10%	444
	21st to end	Day	9% 2 21% 35% 24% 9%	488
August	1st to 10th	Day	12% 4 18% 30% 28% 8%	446
	11th to 20th	Day	13% 4 15% 29% 30% 10%	439
	21st to end	Day	8% 3 20% 30% 25% 14%	495
September	1st to 10th	Day	16% 4 17% 25% 22% 16%	450
	11th to 20th	Day	14% 4 17% 31% 22% 13%	450
	21st to end	Day	25% 8% 25% 24% 14% 4	450
October	1st to 10th	Day	22% 7% 20% 25% 19% 7%	450
	11th to 20th	Day	18% 10% 24% 28% 17% 2	450
	21st to end	Day	16% 12% 33% 26% 10% 3	495
November	1st to 10th	Day	17% 12% 31% 21% 15% 4	453
	11th to 20th	Day	20% 15% 30% 22% 12% 1	370
	21st to end	Day	21% 17% 26% 24% 10% 2	218
December	1st to 10th	Day	22% 21% 36% 15% 7%	180
	11th to 20th	Day	23% 15% 37% 18% 6% 1	180
	21st to end	Day	25% 16% 30% 20% 8% 2	198
January	1st to 10th	Night	20% 18% 37% 21% 3	760
	11th to 20th	Night	20% 19% 31% 26% 4	760
	21st to end	Night	21% 17% 37% 24% 2	836
February	1st to 10th	Night	19% 14% 39% 25% 3	760
	11th to 20th	Night	25% 20% 36% 18% 1	743
	21st to end	Night	22% 16% 37% 21% 3	628
March	1st to 10th	Night	19% 17% 36% 25% 4	743
	11th to 20th	Night	22% 17% 35% 21% 6%	720
	21st to end	Night	19% 15% 41% 21% 4	792
April	1st to 10th	Night	18% 17% 38% 23% 4	720
	11th to 20th	Night	14% 15% 36% 25% 9%	711
	21st to end	Night	17% 11% 34% 30% 7%	720
May	1st to 10th	Night	18% 10% 34% 28% 9%	644
	11th to 20th	Night	16% 6% 29% 37% 10% 1	531
	21st to end	Night	17% 4 18% 40% 21% 1	399
June	1st to 10th	Night	11% 3 20% 44% 21%	360
	11th to 20th	Night	8% 5% 19% 45% 20% 3	360
	21st to end	Night	8% 3 22% 48% 19% 1	360
July	1st to 10th	Night	10% 1 17% 41% 27% 2	401
	11th to 20th	Night	5% 14% 40% 37% 3	522
	21st to end	Night	7% 2 18% 43% 24% 5%	591
August	1st to 10th	Night	10% 1 16% 42% 28% 4	537
	11th to 20th	Night	12% 3 14% 41% 26% 4	634
	21st to end	Night	12% 3 14% 33% 33% 6%	792
September	1st to 10th	Night	13% 3 12% 38% 28% 5%	720
	11th to 20th	Night	13% 3 17% 32% 31% 4	720
	21st to end	Night	25% 6% 20% 31% 17% 1	720
October	1st to 10th	Night	17% 6% 22% 28% 23% 4	720
	11th to 20th	Night	18% 8% 26% 30% 16% 1	720
	21st to end	Night	18% 9% 29% 29% 13% 2	792
November	1st to 10th	Night	16% 9% 30% 29% 14% 2	740
	11th to 20th	Night	18% 13% 30% 29% 10%	760
	21st to end	Night	15% 14% 29% 31% 11% 1	760
December	1st to 10th	Night	23% 13% 34% 22% 8%	760
	11th to 20th	Night	18% 11% 36% 28% 6%	760
	21st to end	Night	20% 17% 27% 32% 4	836

Page generated at 2024-03-03 06:29:01. Version ac07

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