North Raymer
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Raymer clear sky chart from 2005-11-06 to 2026-02-16.

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	6% 5% 2 5% 4 4 4 4 6% 8% 54%	139580
	Night	6% 6% 2 6% 4 4 4 3 5% 7% 53%	138751
Transparency	Day	28% 5% 10% 26% 23% 8%	134500
	Night	30% 5% 11% 25% 22% 7%	134841
Seeing	Day	8% 8% 27% 32% 20% 6%	17379
	Night	8% 7% 32% 40% 12% 1	27502

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	3 8% 3 7% 4 4 4 2 4 5% 56%	4720
	11th to 20th	Day	2 6% 2 7% 4 4 4 3 5% 7% 55%	4740
	21st to end	Day	2 6% 3 6% 4 3 3 3 5% 6% 59%	5623
February	1st to 10th	Day	3 8% 4 8% 5% 4 4 4 5% 6% 47%	1923
	11th to 20th	Day	3 8% 3 7% 4 4 5% 4 6% 7% 49%	1999
	21st to end	Day	3 8% 3 8% 4 3 3 3 6% 6% 53%	1650
March	1st to 10th	Day	4 9% 2 5% 3 3 4 2 5% 7% 55%	4500
	11th to 20th	Day	7% 6% 2 5% 4 4 4 3 5% 7% 55%	4714
	21st to end	Day	6% 8% 3 7% 4 4 5% 4 6% 8% 45%	5959
April	1st to 10th	Day	8% 8% 2 5% 4 3 3 4 6% 7% 50%	2400
	11th to 20th	Day	12% 9% 2 5% 4 3 4 4 5% 6% 45%	2371
	21st to end	Day	11% 7% 2 6% 4 4 4 4 6% 9% 44%	2435
May	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 4 5% 6% 49%	5900
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 9% 50%	6159
	21st to end	Day	13% 5% 2 4 4 4 4 4 6% 7% 47%	6925
June	1st to 10th	Day	6% 3 1 3 3 4 4 4 7% 10% 55%	2800
	11th to 20th	Day	6% 3 1 4 3 4 5% 4 6% 7% 56%	2800
	21st to end	Day	4 3 1 4 3 4 4 4 6% 9% 58%	2800
July	1st to 10th	Day	5% 3 1 4 3 3 4 4 5% 8% 57%	6339
	11th to 20th	Day	4 3 1 4 4 4 5% 5% 7% 10% 53%	6340
	21st to end	Day	5% 3 1 5% 4 4 6% 5% 7% 9% 51%	6903
August	1st to 10th	Day	8% 3 1 4 3 3 5% 4 7% 10% 51%	5890
	11th to 20th	Day	3 3 1 3 3 4 4 4 7% 8% 61%	5366
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 50%	5984
September	1st to 10th	Day	5% 3 1 3 2 3 3 4 4 7% 63%	2400
	11th to 20th	Day	7% 2 1 3 3 3 3 3 5% 7% 62%	2320
	21st to end	Day	8% 3 1 4 2 2 3 2 4 6% 65%	2200
October	1st to 10th	Day	6% 3 1 2 1 2 2 2 3 5% 74%	3436
	11th to 20th	Day	4 5% 2 4 3 3 3 3 4 6% 64%	3250
	21st to end	Day	7% 6% 2 3 2 3 3 2 5% 7% 60%	3265
November	1st to 10th	Day	3 6% 2 4 3 3 3 3 5% 8% 61%	1853
	11th to 20th	Day	3 6% 2 4 3 3 4 3 5% 6% 61%	1890
	21st to end	Day	4 7% 3 5% 3 3 3 3 5% 6% 60%	1828
December	1st to 10th	Day	2 4 2 5% 3 3 3 2 4 6% 66%	2700
	11th to 20th	Day	3 6% 2 5% 3 3 3 4 5% 7% 60%	3106
	21st to end	Day	4 8% 3 7% 4 3 4 4 6% 8% 49%	4092
January	1st to 10th	Night	3 8% 3 7% 4 4 4 3 4 7% 53%	8201
	11th to 20th	Night	2 7% 2 6% 4 4 4 4 5% 7% 54%	8250
	21st to end	Night	2 6% 3 6% 4 4 3 3 5% 6% 57%	8636
February	1st to 10th	Night	4 9% 4 8% 4 4 5% 4 5% 7% 48%	2695
	11th to 20th	Night	4 8% 3 7% 6% 5% 5% 4 6% 6% 47%	2398
	21st to end	Night	4 7% 3 6% 4 4 4 3 4 5% 56%	1980
March	1st to 10th	Night	5% 9% 3 6% 3 3 3 3 4 5% 55%	5374
	11th to 20th	Night	8% 8% 2 5% 4 3 3 3 4 6% 53%	5269
	21st to end	Night	10% 10% 2 7% 4 4 4 4 6% 7% 42%	4992
April	1st to 10th	Night	9% 7% 2 6% 5% 3 5% 3 4 6% 49%	2000
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 5% 6% 46%	1977
	21st to end	Night	15% 8% 2 5% 4 4 4 3 5% 6% 42%	1965
May	1st to 10th	Night	11% 7% 2 6% 4 5% 4 3 5% 7% 45%	4080
	11th to 20th	Night	10% 4 2 5% 4 5% 5% 4 7% 8% 47%	3752
	21st to end	Night	16% 7% 2 6% 5% 3 4 4 5% 7% 41%	3972
June	1st to 10th	Night	6% 4 2 4 4 3 4 4 8% 12% 50%	1600
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 8% 53%	1600
	21st to end	Night	6% 4 2 5% 4 5% 5% 4 7% 9% 49%	1600
July	1st to 10th	Night	4 3 2 5% 4 4 5% 4 6% 8% 55%	3640
	11th to 20th	Night	6% 3 1 4 4 5% 5% 5% 7% 10% 49%	3640
	21st to end	Night	6% 4 2 7% 5% 4 6% 4 8% 9% 46%	3970
August	1st to 10th	Night	10% 4 2 6% 5% 5% 6% 4 7% 9% 42%	3916
	11th to 20th	Night	4 5% 2 6% 4 5% 6% 5% 6% 9% 49%	4483
	21st to end	Night	8% 5% 2 6% 5% 4 5% 5% 8% 9% 44%	4993
September	1st to 10th	Night	6% 4 1 4 4 3 3 4 6% 7% 57%	2000
	11th to 20th	Night	7% 4 1 4 3 3 4 3 5% 8% 58%	2080
	21st to end	Night	6% 4 1 4 3 3 3 3 4 6% 63%	2200
October	1st to 10th	Night	6% 3 1 2 1 2 3 2 3 5% 71%	3745
	11th to 20th	Night	7% 3 1 4 4 3 3 3 5% 7% 60%	3898
	21st to end	Night	6% 5% 2 4 3 3 3 3 4 5% 61%	4503
November	1st to 10th	Night	5% 4 2 4 4 2 3 3 5% 7% 60%	2665
	11th to 20th	Night	5% 6% 1 4 3 3 4 3 5% 6% 59%	2730
	21st to end	Night	5% 7% 2 5% 4 3 3 2 5% 6% 57%	2788
December	1st to 10th	Night	2 4 1 5% 3 3 3 3 5% 5% 66%	4710
	11th to 20th	Night	3 5% 2 5% 3 3 3 3 5% 7% 60%	5321
	21st to end	Night	7% 9% 2 7% 4 4 4 4 6% 7% 47%	7128

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	32% 3 8% 32% 21% 5%	4723
	11th to 20th	Day	29% 4 11% 27% 23% 6%	4740
	21st to end	Day	26% 4 11% 28% 25% 7%	5623
February	1st to 10th	Day	36% 4 12% 25% 17% 5%	1923
	11th to 20th	Day	33% 4 11% 27% 20% 4	2009
	21st to end	Day	30% 4 9% 26% 22% 8%	1650
March	1st to 10th	Day	29% 3 6% 20% 34% 8%	4500
	11th to 20th	Day	29% 4 9% 25% 29% 4	4714
	21st to end	Day	34% 7% 14% 31% 12% 2	5959
April	1st to 10th	Day	32% 6% 12% 26% 17% 8%	2400
	11th to 20th	Day	38% 6% 11% 21% 17% 7%	2374
	21st to end	Day	36% 6% 9% 28% 18% 2	2435
May	1st to 10th	Day	34% 6% 11% 30% 16% 4	5900
	11th to 20th	Day	29% 7% 11% 24% 24% 5%	6163
	21st to end	Day	34% 6% 13% 26% 18% 3	6926
June	1st to 10th	Day	23% 8% 19% 27% 17% 6%	2800
	11th to 20th	Day	25% 7% 10% 25% 23% 11%	2800
	21st to end	Day	21% 6% 10% 26% 26% 11%	2800
July	1st to 10th	Day	24% 4 8% 19% 32% 12%	6271
	11th to 20th	Day	24% 4 13% 28% 20% 11%	6265
	21st to end	Day	28% 5% 12% 20% 18% 17%	6705
August	1st to 10th	Day	29% 5% 15% 27% 17% 7%	4289
	11th to 20th	Day	24% 5% 12% 22% 24% 12%	3882
	21st to end	Day	23% 4 11% 20% 27% 15%	4311
September	1st to 10th	Day	20% 4 8% 23% 28% 17%	2400
	11th to 20th	Day	22% 5% 8% 22% 28% 15%	2320
	21st to end	Day	22% 3 7% 23% 35% 11%	2200
October	1st to 10th	Day	16% 3 6% 18% 31% 26%	3436
	11th to 20th	Day	23% 3 8% 30% 26% 9%	3250
	21st to end	Day	25% 3 8% 27% 29% 9%	3265
November	1st to 10th	Day	22% 3 12% 27% 26% 10%	1853
	11th to 20th	Day	22% 5% 8% 29% 29% 7%	1890
	21st to end	Day	25% 4 10% 27% 26% 8%	1828
December	1st to 10th	Day	21% 3 7% 34% 29% 6%	2700
	11th to 20th	Day	24% 3 7% 36% 24% 4	3104
	21st to end	Day	32% 5% 10% 30% 18% 5%	4092
January	1st to 10th	Night	33% 3 10% 29% 19% 6%	8202
	11th to 20th	Night	29% 5% 9% 27% 22% 8%	8250
	21st to end	Night	28% 4 10% 28% 24% 6%	8636
February	1st to 10th	Night	35% 6% 11% 24% 20% 5%	2695
	11th to 20th	Night	35% 5% 13% 25% 18% 4	2398
	21st to end	Night	30% 4 9% 24% 25% 9%	1980
March	1st to 10th	Night	31% 4 6% 19% 31% 10%	5374
	11th to 20th	Night	33% 4 10% 17% 29% 7%	5269
	21st to end	Night	39% 7% 15% 26% 12% 2	4992
April	1st to 10th	Night	36% 6% 10% 23% 18% 7%	2000
	11th to 20th	Night	38% 6% 12% 22% 17% 5%	1977
	21st to end	Night	40% 7% 10% 23% 17% 2	1965
May	1st to 10th	Night	36% 7% 15% 28% 10% 4	4080
	11th to 20th	Night	32% 7% 13% 26% 16% 5%	3753
	21st to end	Night	41% 9% 15% 21% 11% 3	3972
June	1st to 10th	Night	25% 10% 23% 24% 14% 4	1600
	11th to 20th	Night	28% 8% 13% 24% 17% 10%	1600
	21st to end	Night	30% 6% 13% 25% 21% 6%	1600
July	1st to 10th	Night	27% 5% 11% 24% 28% 5%	3600
	11th to 20th	Night	30% 4 19% 24% 19% 5%	3592
	21st to end	Night	33% 5% 15% 21% 18% 9%	3856
August	1st to 10th	Night	40% 7% 17% 20% 13% 3	2841
	11th to 20th	Night	34% 8% 13% 21% 16% 7%	3243
	21st to end	Night	27% 4 17% 22% 21% 9%	3597
September	1st to 10th	Night	25% 5% 9% 23% 25% 13%	2000
	11th to 20th	Night	25% 5% 9% 25% 24% 12%	2080
	21st to end	Night	23% 4 7% 26% 26% 13%	2200
October	1st to 10th	Night	17% 4 6% 19% 28% 26%	3745
	11th to 20th	Night	24% 4 9% 29% 26% 8%	3898
	21st to end	Night	26% 3 8% 27% 25% 11%	4503
November	1st to 10th	Night	22% 5% 10% 26% 26% 11%	2665
	11th to 20th	Night	25% 4 9% 26% 26% 9%	2730
	21st to end	Night	29% 4 9% 25% 26% 7%	2788
December	1st to 10th	Night	21% 3 9% 34% 27% 6%	4710
	11th to 20th	Night	24% 3 6% 39% 23% 5%	5322
	21st to end	Night	36% 5% 8% 27% 21% 3	7128

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	6% 10% 30% 39% 13% 3	330
	11th to 20th	Day	9% 12% 38% 35% 6% 1	330
	21st to end	Day	5% 11% 44% 31% 7% 2	363
February	1st to 10th	Day	6% 11% 44% 33% 5% 1	330
	11th to 20th	Day	5% 12% 39% 35% 9% 1	315
	21st to end	Day	5% 18% 40% 31% 6%	249
March	1st to 10th	Day	9% 10% 31% 29% 19% 2	300
	11th to 20th	Day	11% 12% 31% 30% 14% 2	370
	21st to end	Day	13% 13% 36% 27% 10% 1	550
April	1st to 10th	Day	15% 14% 34% 26% 10% 2	500
	11th to 20th	Day	16% 16% 32% 23% 11% 2	492
	21st to end	Day	14% 17% 27% 26% 13% 3	535
May	1st to 10th	Day	15% 11% 28% 28% 15% 4	703
	11th to 20th	Day	14% 7% 26% 29% 19% 4	725
	21st to end	Day	11% 9% 25% 28% 22% 5%	789
June	1st to 10th	Day	6% 5% 21% 32% 25% 11%	730
	11th to 20th	Day	6% 5% 28% 35% 21% 4	730
	21st to end	Day	5% 3 24% 38% 23% 6%	730
July	1st to 10th	Day	7% 3 15% 33% 34% 8%	721
	11th to 20th	Day	5% 2 15% 33% 33% 12%	718
	21st to end	Day	4 1 15% 33% 37% 10%	794
August	1st to 10th	Day	7% 2 14% 36% 32% 8%	629
	11th to 20th	Day	3 4 19% 36% 26% 13%	517
	21st to end	Day	5% 2 19% 36% 28% 11%	583
September	1st to 10th	Day	6% 3 19% 31% 30% 11%	530
	11th to 20th	Day	5% 3 19% 32% 29% 12%	450
	21st to end	Day	11% 3 19% 27% 25% 14%	330
October	1st to 10th	Day	11% 5% 22% 24% 25% 13%	330
	11th to 20th	Day	5% 9% 35% 30% 14% 7%	330
	21st to end	Day	10% 10% 30% 30% 15% 4	363
November	1st to 10th	Day	5% 10% 31% 36% 12% 5%	330
	11th to 20th	Day	5% 10% 34% 34% 15% 2	330
	21st to end	Day	8% 10% 25% 41% 12% 3	330
December	1st to 10th	Day	5% 15% 33% 34% 12% 2	330
	11th to 20th	Day	8% 10% 43% 33% 7%	330
	21st to end	Day	10% 12% 40% 29% 9% 1	363
January	1st to 10th	Night	6% 10% 34% 39% 10% 1	1050
	11th to 20th	Night	6% 11% 41% 33% 8% 1	1050
	21st to end	Night	5% 8% 45% 35% 7% 1	1021
February	1st to 10th	Night	8% 9% 44% 33% 6%	840
	11th to 20th	Night	6% 9% 44% 35% 6%	804
	21st to end	Night	7% 12% 46% 32% 3	660
March	1st to 10th	Night	8% 11% 35% 40% 7%	800
	11th to 20th	Night	10% 9% 33% 37% 10% 1	800
	21st to end	Night	11% 10% 41% 32% 6% 1	668
April	1st to 10th	Night	12% 13% 38% 32% 5%	600
	11th to 20th	Night	17% 10% 35% 33% 6% 1	593
	21st to end	Night	18% 12% 28% 34% 8% 1	600
May	1st to 10th	Night	13% 12% 30% 34% 12%	600
	11th to 20th	Night	16% 6% 28% 36% 12% 1	591
	21st to end	Night	13% 7% 33% 33% 14%	650
June	1st to 10th	Night	7% 5% 24% 44% 20% 1	600
	11th to 20th	Night	6% 6% 30% 47% 10% 1	600
	21st to end	Night	6% 3 28% 47% 17%	600
July	1st to 10th	Night	8% 2 16% 49% 24% 1	585
	11th to 20th	Night	5% 2 16% 51% 24% 2	582
	21st to end	Night	5% 2 14% 51% 27% 1	657
August	1st to 10th	Night	6% 2 15% 49% 25% 1	597
	11th to 20th	Night	5% 2 18% 51% 23%	594
	21st to end	Night	6% 1 18% 49% 24% 1	660
September	1st to 10th	Night	7% 3 17% 51% 21% 1	600
	11th to 20th	Night	8% 5% 22% 43% 21% 2	600
	21st to end	Night	8% 3 26% 45% 18% 1	600
October	1st to 10th	Night	13% 6% 23% 37% 19% 1	690
	11th to 20th	Night	8% 7% 34% 35% 16% 1	800
	21st to end	Night	8% 9% 30% 40% 12% 1	1030
November	1st to 10th	Night	6% 5% 36% 40% 11% 1	1025
	11th to 20th	Night	7% 9% 35% 40% 8%	1050
	21st to end	Night	8% 7% 33% 41% 10% 1	1050
December	1st to 10th	Night	5% 10% 40% 38% 6%	1050
	11th to 20th	Night	7% 9% 40% 37% 6%	1050
	21st to end	Night	10% 11% 35% 38% 6% 1	1155

Page generated at 2026-02-12 23:42:16. Version ac07

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