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 2024-11-01.

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% 6% 2 6% 4 4 4 4 6% 8% 42%	100955
	Night	15% 6% 2 6% 4 4 4 3 5% 7% 43%	97946
Transparency	Day	38% 8% 13% 22% 16% 3	100762
	Night	39% 7% 11% 21% 18% 4	97809
Seeing	Day	18% 12% 27% 24% 15% 5%	15165
	Night	17% 10% 28% 30% 13% 1	24844

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 4 2 2 3 3 4 5% 52%	2808
	11th to 20th	Day	14% 7% 2 5% 3 3 4 3 5% 6% 47%	2840
	21st to end	Day	18% 8% 3 7% 4 4 3 3 4 6% 39%	3124
February	1st to 10th	Day	12% 7% 2 6% 5% 4 6% 4 6% 7% 41%	1710
	11th to 20th	Day	21% 6% 2 4 4 3 3 3 5% 5% 44%	1736
	21st to end	Day	18% 7% 3 6% 4 4 5% 4 5% 6% 37%	1579
March	1st to 10th	Day	21% 10% 3 6% 3 3 3 3 4 6% 37%	3435
	11th to 20th	Day	10% 4 2 5% 3 3 4 4 6% 6% 53%	3480
	21st to end	Day	20% 6% 2 5% 4 4 4 3 5% 7% 40%	3837
April	1st to 10th	Day	12% 5% 1 5% 4 4 3 3 6% 7% 51%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 4 7% 49%	2254
	21st to end	Day	16% 6% 2 6% 3 3 4 3 5% 7% 44%	2280
May	1st to 10th	Day	15% 7% 2 7% 5% 5% 6% 5% 7% 9% 32%	3940
	11th to 20th	Day	19% 6% 2 6% 5% 4 4 4 6% 8% 33%	4081
	21st to end	Day	9% 5% 1 5% 4 4 5% 4 6% 10% 48%	4810
June	1st to 10th	Day	10% 5% 2 5% 5% 3 5% 5% 7% 10% 43%	2660
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 5% 7% 10% 42%	2660
	21st to end	Day	8% 4 2 5% 5% 4 6% 5% 8% 11% 41%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 7% 6% 9% 13% 38%	4325
	11th to 20th	Day	11% 6% 2 6% 6% 6% 5% 6% 7% 11% 34%	4120
	21st to end	Day	9% 7% 3 8% 7% 5% 7% 5% 8% 9% 32%	4466
August	1st to 10th	Day	16% 7% 3 8% 6% 5% 6% 5% 7% 11% 27%	4104
	11th to 20th	Day	11% 5% 2 8% 5% 6% 6% 5% 8% 8% 36%	3826
	21st to end	Day	8% 4 2 5% 4 4 4 4 7% 10% 48%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 5% 5% 4 6% 8% 43%	2280
	11th to 20th	Day	13% 6% 2 6% 5% 5% 4 4 5% 7% 42%	2280
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 5% 6% 37%	1987
October	1st to 10th	Day	16% 6% 2 6% 4 4 3 3 4 6% 47%	1900
	11th to 20th	Day	16% 4 2 4 4 3 3 2 3 6% 53%	1900
	21st to end	Day	12% 5% 1 5% 3 3 3 3 4 6% 54%	2090
November	1st to 10th	Day	13% 5% 2 5% 3 3 3 3 4 5% 54%	1853
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 4 6% 50%	1710
	21st to end	Day	15% 4 2 5% 3 3 3 3 5% 6% 52%	1558
December	1st to 10th	Day	15% 7% 3 6% 3 4 4 3 6% 7% 41%	1520
	11th to 20th	Day	15% 6% 2 5% 3 2 2 2 4 5% 53%	1910
	21st to end	Day	15% 7% 3 5% 4 4 3 3 5% 7% 43%	2772
January	1st to 10th	Night	14% 8% 2 6% 4 3 4 3 4 5% 47%	4132
	11th to 20th	Night	17% 8% 2 6% 4 3 4 3 4 5% 45%	4120
	21st to end	Night	21% 7% 3 6% 3 3 3 3 4 4 44%	4532
February	1st to 10th	Night	16% 7% 2 5% 4 3 4 3 6% 6% 44%	2470
	11th to 20th	Night	19% 8% 2 5% 4 4 3 3 4 6% 41%	2328
	21st to end	Night	17% 7% 3 5% 3 3 3 3 5% 6% 46%	1871
March	1st to 10th	Night	23% 7% 2 6% 4 4 4 3 5% 6% 37%	3418
	11th to 20th	Night	15% 4 2 5% 3 3 3 3 5% 6% 52%	3480
	21st to end	Night	16% 6% 3 6% 3 3 3 2 3 5% 49%	3794
April	1st to 10th	Night	13% 6% 3 6% 4 5% 4 3 5% 6% 45%	1900
	11th to 20th	Night	12% 5% 2 5% 4 4 3 3 5% 7% 49%	1875
	21st to end	Night	14% 6% 2 5% 4 4 5% 3 5% 7% 46%	1900
May	1st to 10th	Night	16% 7% 3 7% 5% 5% 4 3 5% 8% 36%	2984
	11th to 20th	Night	23% 7% 3 7% 4 3 4 3 5% 6% 35%	2812
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 9% 45%	2741
June	1st to 10th	Night	11% 5% 2 5% 5% 5% 5% 6% 7% 9% 40%	1520
	11th to 20th	Night	9% 6% 3 6% 5% 4 6% 4 7% 10% 40%	1520
	21st to end	Night	7% 5% 2 5% 6% 4 6% 4 6% 12% 42%	1520
July	1st to 10th	Night	7% 4 2 6% 5% 6% 6% 6% 10% 10% 39%	2630
	11th to 20th	Night	10% 5% 3 6% 6% 5% 6% 6% 8% 9% 35%	2840
	21st to end	Night	12% 8% 3 10% 7% 6% 5% 4 6% 8% 29%	3087
August	1st to 10th	Night	17% 7% 3 7% 5% 4 5% 4 7% 10% 29%	2825
	11th to 20th	Night	9% 6% 3 7% 5% 4 5% 4 7% 9% 40%	2969
	21st to end	Night	9% 4 2 5% 4 4 4 4 7% 10% 47%	3476
September	1st to 10th	Night	12% 5% 2 7% 5% 4 4 4 5% 8% 44%	1900
	11th to 20th	Night	13% 5% 2 6% 4 5% 6% 3 6% 7% 44%	1900
	21st to end	Night	22% 7% 3 7% 4 3 4 3 5% 6% 35%	2188
October	1st to 10th	Night	16% 5% 2 6% 4 4 4 3 4 6% 47%	2280
	11th to 20th	Night	15% 6% 2 6% 3 3 3 2 4 6% 50%	2280
	21st to end	Night	14% 4 2 5% 3 3 3 3 3 7% 53%	2508
November	1st to 10th	Night	13% 6% 2 6% 4 3 3 3 4 5% 52%	2228
	11th to 20th	Night	15% 6% 2 4 3 3 4 3 4 6% 50%	2470
	21st to end	Night	13% 5% 2 5% 4 3 4 3 5% 6% 51%	2619
December	1st to 10th	Night	17% 8% 3 5% 5% 4 4 3 4 5% 42%	2660
	11th to 20th	Night	16% 7% 2 5% 4 3 3 3 4 6% 47%	3285
	21st to end	Night	15% 7% 2 6% 4 3 4 3 5% 7% 43%	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	47% 5% 9% 18% 14% 6%	3435
	11th to 20th	Day	29% 7% 9% 23% 23% 9%	3480
	21st to end	Day	43% 7% 11% 19% 17% 3	3837
April	1st to 10th	Day	32% 7% 12% 22% 20% 8%	2280
	11th to 20th	Day	35% 5% 11% 22% 21% 6%	2254
	21st to end	Day	39% 6% 13% 21% 16% 5%	2280
May	1st to 10th	Day	44% 11% 15% 18% 10% 2	3975
	11th to 20th	Day	45% 9% 15% 21% 9% 1	4085
	21st to end	Day	29% 9% 17% 24% 18% 2	4824
June	1st to 10th	Day	34% 10% 16% 25% 14% 1	2660
	11th to 20th	Day	35% 11% 15% 22% 16% 1	2660
	21st to end	Day	33% 11% 17% 23% 14% 2	2660
July	1st to 10th	Day	33% 12% 23% 17% 10% 4	4258
	11th to 20th	Day	41% 10% 24% 18% 6% 1	4051
	21st to end	Day	44% 11% 14% 16% 14%	4324
August	1st to 10th	Day	49% 9% 18% 19% 5%	4091
	11th to 20th	Day	40% 10% 15% 23% 11% 1	3865
	21st to end	Day	29% 8% 15% 29% 18% 1	4180
September	1st to 10th	Day	38% 9% 14% 15% 20% 4	2280
	11th to 20th	Day	39% 7% 11% 21% 18% 3	2280
	21st to end	Day	48% 6% 9% 20% 14% 3	1987
October	1st to 10th	Day	40% 5% 9% 21% 20% 4	1900
	11th to 20th	Day	35% 4 7% 24% 24% 6%	1900
	21st to end	Day	32% 4 7% 24% 25% 8%	2090
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	47% 6% 9% 18% 17% 3	3418
	11th to 20th	Night	32% 6% 7% 19% 26% 10%	3480
	21st to end	Night	39% 5% 8% 24% 20% 5%	3794
April	1st to 10th	Night	38% 7% 10% 17% 22% 7%	1900
	11th to 20th	Night	33% 6% 11% 22% 21% 7%	1875
	21st to end	Night	37% 7% 13% 23% 16% 5%	1900
May	1st to 10th	Night	44% 9% 15% 19% 11% 2	3014
	11th to 20th	Night	47% 10% 11% 22% 8% 1	2813
	21st to end	Night	31% 11% 17% 24% 16% 1	2748
June	1st to 10th	Night	36% 10% 17% 23% 13% 2	1520
	11th to 20th	Night	37% 11% 16% 21% 14% 1	1520
	21st to end	Night	34% 10% 13% 22% 18% 3	1520
July	1st to 10th	Night	35% 15% 18% 18% 11% 3	2587
	11th to 20th	Night	41% 12% 22% 19% 5% 1	2786
	21st to end	Night	52% 9% 12% 17% 11%	2988
August	1st to 10th	Night	48% 9% 19% 18% 6%	2814
	11th to 20th	Night	39% 8% 18% 22% 12%	2996
	21st to end	Night	31% 8% 13% 27% 20% 1	3476
September	1st to 10th	Night	37% 9% 14% 18% 17% 5%	1900
	11th to 20th	Night	37% 8% 10% 21% 21% 2	1900
	21st to end	Night	48% 7% 10% 17% 14% 4	2188
October	1st to 10th	Night	40% 5% 10% 21% 21% 4	2280
	11th to 20th	Night	36% 5% 8% 22% 23% 6%	2280
	21st to end	Night	32% 5% 8% 24% 24% 8%	2508
November	1st to 10th	Night	35% 5% 10% 21% 24% 5%	2228
	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	25% 21% 31% 18% 5%	460
	11th to 20th	Day	23% 23% 34% 15% 4 2	460
	21st to end	Day	23% 20% 37% 15% 5% 1	506
April	1st to 10th	Day	24% 19% 33% 17% 7%	460
	11th to 20th	Day	18% 15% 33% 22% 10% 3	452
	21st to end	Day	21% 13% 33% 24% 7% 1	460
May	1st to 10th	Day	18% 16% 33% 23% 9% 2	463
	11th to 20th	Day	21% 9% 28% 28% 11% 3	487
	21st to end	Day	19% 4 25% 28% 17% 6%	529
June	1st to 10th	Day	13% 4 28% 29% 21% 4	490
	11th to 20th	Day	10% 7% 23% 33% 20% 7%	490
	21st to end	Day	9% 5% 26% 35% 20% 4	490
July	1st to 10th	Day	9% 3 18% 33% 29% 8%	485
	11th to 20th	Day	7% 2 16% 36% 30% 10%	484
	21st to end	Day	10% 2 21% 35% 23% 8%	532
August	1st to 10th	Day	14% 3 19% 30% 27% 7%	486
	11th to 20th	Day	12% 4 16% 30% 28% 9%	479
	21st to end	Day	8% 2 19% 31% 25% 14%	539
September	1st to 10th	Day	15% 4 18% 26% 22% 15%	490
	11th to 20th	Day	16% 4 17% 30% 22% 12%	490
	21st to end	Day	26% 9% 25% 23% 13% 3	490
October	1st to 10th	Day	21% 6% 20% 26% 19% 8%	490
	11th to 20th	Day	17% 12% 23% 28% 17% 2	490
	21st to end	Day	15% 11% 33% 26% 11% 4	539
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% 35% 25% 3	760
	11th to 20th	Night	21% 18% 35% 20% 5%	760
	21st to end	Night	19% 15% 41% 21% 4	836
April	1st to 10th	Night	18% 18% 38% 22% 4	760
	11th to 20th	Night	14% 15% 37% 25% 9%	751
	21st to end	Night	16% 11% 35% 30% 7%	760
May	1st to 10th	Night	18% 10% 34% 29% 8%	679
	11th to 20th	Night	17% 7% 29% 37% 10% 1	561
	21st to end	Night	16% 3 19% 40% 21% 1	421
June	1st to 10th	Night	11% 4 21% 44% 20%	380
	11th to 20th	Night	8% 5% 19% 46% 19% 3	380
	21st to end	Night	7% 2 22% 48% 19% 1	380
July	1st to 10th	Night	11% 2 17% 42% 27% 2	425
	11th to 20th	Night	6% 14% 41% 36% 3	552
	21st to end	Night	8% 2 18% 43% 24% 5%	624
August	1st to 10th	Night	11% 2 16% 41% 27% 3	567
	11th to 20th	Night	12% 3 13% 42% 26% 4	670
	21st to end	Night	11% 3 14% 34% 33% 5%	836
September	1st to 10th	Night	13% 3 13% 39% 27% 5%	760
	11th to 20th	Night	15% 3 17% 31% 30% 4	760
	21st to end	Night	25% 6% 20% 31% 17% 1	760
October	1st to 10th	Night	17% 6% 21% 29% 23% 4	760
	11th to 20th	Night	18% 8% 26% 31% 16% 1	760
	21st to end	Night	17% 9% 28% 29% 15% 2	836
November	1st to 10th	Night	16% 9% 30% 29% 14% 2	743
	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 2024-10-29 11:20:47. Version ac07

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