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 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	6% 5% 2 4 4 3 4 4 6% 8% 54%	74819
	Night	7% 5% 2 5% 4 3 4 4 5% 7% 53%	74972
Transparency	Day	28% 6% 11% 26% 21% 8%	74523
	Night	30% 6% 12% 25% 21% 7%	74790
Seeing	Day	9% 7% 26% 32% 21% 6%	14524
	Night	8% 7% 32% 39% 13% 1	24652

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 6% 2 5% 4 3 4 3 4 6% 58%	1518
	11th to 20th	Day	4 7% 3 6% 5% 3 4 5% 5% 7% 52%	1472
	21st to end	Day	3 6% 3 6% 5% 2 3 4 6% 8% 52%	1714
February	1st to 10th	Day	3 8% 5% 8% 5% 3 5% 4 5% 7% 47%	1648
	11th to 20th	Day	4 8% 3 5% 5% 2 5% 5% 7% 7% 50%	1749
	21st to end	Day	3 8% 3 8% 5% 2 3 4 6% 7% 51%	1480
March	1st to 10th	Day	5% 7% 2 5% 5% 3 5% 4 5% 8% 53%	1800
	11th to 20th	Day	8% 6% 3 4 5% 3 5% 3 4 7% 52%	1862
	21st to end	Day	7% 8% 3 6% 5% 3 4 5% 5% 7% 46%	2366
April	1st to 10th	Day	9% 7% 3 5% 4 2 3 5% 6% 7% 50%	2160
	11th to 20th	Day	12% 8% 3 4 5% 3 4 5% 5% 7% 45%	2131
	21st to end	Day	10% 6% 2 5% 5% 3 4 5% 5% 9% 45%	2191
May	1st to 10th	Day	12% 5% 2 5% 6% 3 5% 6% 6% 7% 43%	2340
	11th to 20th	Day	13% 5% 2 4 5% 3 5% 5% 6% 9% 43%	2417
	21st to end	Day	9% 4 2 4 5% 3 4 5% 6% 10% 47%	2724
June	1st to 10th	Day	6% 3 1 3 3 3 4 5% 7% 10% 55%	2520
	11th to 20th	Day	6% 3 2 3 3 2 6% 5% 6% 8% 55%	2520
	21st to end	Day	3 3 1 3 4 3 5% 5% 6% 9% 58%	2520
July	1st to 10th	Day	6% 3 2 4 4 2 5% 5% 6% 10% 54%	2520
	11th to 20th	Day	4 3 1 2 3 3 4 5% 7% 9% 58%	2520
	21st to end	Day	4 3 2 4 5% 3 6% 6% 8% 10% 49%	2742
August	1st to 10th	Day	4 3 2 4 4 4 6% 6% 8% 12% 49%	2377
	11th to 20th	Day	4 3 2 3 4 2 4 4 6% 8% 61%	2123
	21st to end	Day	4 3 1 3 3 2 4 4 6% 9% 60%	2376
September	1st to 10th	Day	5% 3 1 3 3 3 3 4 4 7% 63%	2160
	11th to 20th	Day	7% 2 1 3 3 2 3 4 4 7% 63%	2088
	21st to end	Day	8% 3 1 3 3 2 2 2 4 6% 65%	1980
October	1st to 10th	Day	11% 4 1 3 2 2 3 3 4 8% 58%	1896
	11th to 20th	Day	6% 4 2 3 2 2 2 4 4 6% 65%	1800
	21st to end	Day	8% 6% 2 3 3 2 3 4 4 6% 60%	1828
November	1st to 10th	Day	2 5% 2 4 3 2 3 4 5% 8% 62%	1673
	11th to 20th	Day	3 5% 2 4 3 2 3 4 5% 6% 61%	1710
	21st to end	Day	4 6% 3 4 3 2 3 4 4 6% 60%	1654
December	1st to 10th	Day	3 7% 3 6% 5% 3 4 4 6% 7% 53%	1520
	11th to 20th	Day	5% 7% 3 5% 5% 2 4 5% 5% 8% 53%	1926
	21st to end	Day	5% 9% 4 6% 5% 3 5% 5% 5% 6% 48%	2794
January	1st to 10th	Night	3 6% 3 5% 4 2 3 3 4 8% 58%	2647
	11th to 20th	Night	4 6% 4 5% 4 3 4 5% 5% 7% 54%	2577
	21st to end	Night	4 7% 3 6% 5% 3 4 4 5% 6% 54%	2658
February	1st to 10th	Night	4 8% 4 7% 4 3 6% 5% 5% 7% 49%	2310
	11th to 20th	Night	4 7% 2 6% 5% 4 5% 5% 6% 7% 49%	2098
	21st to end	Night	4 8% 4 6% 6% 3 4 4 4 6% 54%	1776
March	1st to 10th	Night	5% 7% 3 5% 4 2 4 4 5% 6% 54%	2160
	11th to 20th	Night	8% 6% 2 4 4 2 3 4 4 6% 54%	2093
	21st to end	Night	8% 8% 3 6% 6% 3 4 5% 6% 8% 45%	1988
April	1st to 10th	Night	10% 6% 3 5% 5% 2 4 5% 4 6% 49%	1800
	11th to 20th	Night	12% 7% 4 5% 5% 3 4 4 4 6% 46%	1777
	21st to end	Night	14% 7% 3 5% 5% 3 4 4 5% 7% 43%	1769
May	1st to 10th	Night	13% 6% 2 5% 4 4 5% 5% 5% 8% 41%	1620
	11th to 20th	Night	16% 5% 2 5% 5% 3 3 4 5% 8% 43%	1474
	21st to end	Night	11% 6% 2 5% 7% 3 5% 6% 7% 9% 39%	1552
June	1st to 10th	Night	6% 3 2 4 4 2 5% 4 8% 13% 49%	1440
	11th to 20th	Night	7% 3 2 4 4 3 5% 5% 5% 8% 54%	1440
	21st to end	Night	6% 4 1 4 5% 4 6% 5% 6% 9% 50%	1440
July	1st to 10th	Night	7% 3 2 5% 6% 4 5% 5% 6% 8% 47%	1440
	11th to 20th	Night	4 2 1 4 4 3 5% 6% 7% 9% 53%	1440
	21st to end	Night	5% 4 2 4 5% 2 5% 6% 8% 11% 47%	1576
August	1st to 10th	Night	5% 4 3 5% 6% 4 7% 6% 7% 10% 43%	1556
	11th to 20th	Night	4 4 2 3 4 3 5% 5% 5% 9% 55%	1778
	21st to end	Night	5% 3 1 4 4 2 4 6% 7% 8% 56%	1980
September	1st to 10th	Night	6% 4 2 4 4 2 3 5% 6% 8% 56%	1800
	11th to 20th	Night	7% 3 1 3 4 2 4 3 5% 8% 59%	1872
	21st to end	Night	6% 4 2 3 3 2 3 3 4 6% 64%	1980
October	1st to 10th	Night	11% 4 2 3 3 2 3 4 5% 7% 56%	2060
	11th to 20th	Night	7% 3 2 3 3 1 3 3 4 5% 65%	2160
	21st to end	Night	7% 5% 3 4 4 3 2 4 4 6% 59%	2510
November	1st to 10th	Night	4 3 2 3 4 2 3 4 5% 7% 60%	2405
	11th to 20th	Night	5% 5% 2 4 4 2 5% 4 4 6% 59%	2470
	21st to end	Night	5% 6% 2 5% 5% 3 3 3 5% 6% 57%	2522
December	1st to 10th	Night	3 5% 3 6% 4 3 4 4 6% 7% 55%	2660
	11th to 20th	Night	4 5% 3 5% 4 2 4 5% 5% 8% 56%	3271
	21st to end	Night	7% 9% 2 5% 5% 3 4 5% 5% 7% 47%	4873

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	27% 4 13% 33% 19% 4	1519
	11th to 20th	Day	32% 4 12% 29% 18% 5%	1472
	21st to end	Day	29% 5% 15% 29% 18% 4	1714
February	1st to 10th	Day	37% 4 13% 25% 15% 5%	1648
	11th to 20th	Day	32% 5% 10% 28% 20% 5%	1759
	21st to end	Day	32% 5% 9% 27% 20% 7%	1480
March	1st to 10th	Day	31% 4 10% 26% 24% 6%	1800
	11th to 20th	Day	33% 4 13% 22% 23% 5%	1862
	21st to end	Day	37% 6% 14% 25% 14% 4	2366
April	1st to 10th	Day	33% 6% 13% 24% 16% 8%	2160
	11th to 20th	Day	38% 7% 12% 21% 16% 7%	2134
	21st to end	Day	36% 6% 9% 28% 19% 3	2191
May	1st to 10th	Day	38% 8% 12% 27% 13% 2	2340
	11th to 20th	Day	37% 8% 14% 27% 13% 1	2421
	21st to end	Day	32% 8% 16% 25% 14% 5%	2724
June	1st to 10th	Day	23% 8% 18% 27% 16% 7%	2520
	11th to 20th	Day	25% 7% 10% 23% 23% 11%	2520
	21st to end	Day	21% 6% 10% 26% 26% 11%	2520
July	1st to 10th	Day	25% 7% 11% 23% 25% 9%	2451
	11th to 20th	Day	20% 7% 11% 25% 25% 12%	2445
	21st to end	Day	26% 9% 14% 27% 18% 7%	2590
August	1st to 10th	Day	26% 8% 17% 27% 14% 8%	2361
	11th to 20th	Day	20% 6% 10% 28% 25% 12%	2123
	21st to end	Day	21% 5% 9% 23% 29% 14%	2376
September	1st to 10th	Day	21% 5% 8% 22% 26% 18%	2160
	11th to 20th	Day	21% 5% 8% 21% 29% 16%	2088
	21st to end	Day	22% 3 7% 24% 35% 9%	1980
October	1st to 10th	Day	27% 5% 10% 22% 27% 10%	1896
	11th to 20th	Day	22% 4 8% 27% 26% 13%	1800
	21st to end	Day	25% 4 10% 28% 21% 12%	1828
November	1st to 10th	Day	21% 3 13% 27% 25% 10%	1673
	11th to 20th	Day	23% 5% 9% 29% 27% 6%	1710
	21st to end	Day	25% 4 10% 25% 27% 9%	1654
December	1st to 10th	Day	30% 5% 11% 30% 19% 5%	1520
	11th to 20th	Day	30% 5% 9% 27% 26% 3	1924
	21st to end	Day	35% 7% 9% 28% 17% 4	2794
January	1st to 10th	Night	27% 4 13% 29% 23% 4	2647
	11th to 20th	Night	29% 5% 10% 25% 26% 5%	2577
	21st to end	Night	31% 4 11% 31% 18% 4	2658
February	1st to 10th	Night	35% 6% 12% 24% 18% 5%	2310
	11th to 20th	Night	33% 5% 13% 26% 19% 4	2098
	21st to end	Night	33% 4 9% 24% 23% 7%	1776
March	1st to 10th	Night	30% 4 10% 24% 25% 7%	2160
	11th to 20th	Night	31% 5% 10% 22% 27% 5%	2093
	21st to end	Night	36% 7% 15% 24% 16% 3	1988
April	1st to 10th	Night	36% 7% 9% 23% 18% 7%	1800
	11th to 20th	Night	39% 6% 12% 22% 16% 5%	1777
	21st to end	Night	40% 7% 9% 23% 18% 2	1769
May	1st to 10th	Night	40% 9% 13% 24% 13% 1	1620
	11th to 20th	Night	39% 7% 17% 25% 9% 2	1475
	21st to end	Night	39% 12% 18% 18% 8% 6%	1552
June	1st to 10th	Night	25% 10% 24% 24% 13% 4	1440
	11th to 20th	Night	27% 8% 13% 24% 16% 10%	1440
	21st to end	Night	29% 6% 13% 26% 21% 5%	1440
July	1st to 10th	Night	33% 8% 13% 23% 18% 5%	1400
	11th to 20th	Night	25% 7% 12% 26% 21% 9%	1392
	21st to end	Night	27% 9% 17% 27% 15% 5%	1488
August	1st to 10th	Night	33% 10% 19% 21% 13% 4	1548
	11th to 20th	Night	25% 7% 12% 27% 20% 9%	1778
	21st to end	Night	22% 5% 13% 27% 23% 10%	1980
September	1st to 10th	Night	25% 5% 9% 21% 24% 14%	1800
	11th to 20th	Night	24% 5% 9% 25% 25% 13%	1872
	21st to end	Night	22% 4 8% 28% 27% 11%	1980
October	1st to 10th	Night	27% 6% 11% 21% 25% 10%	2060
	11th to 20th	Night	22% 4 11% 26% 24% 13%	2160
	21st to end	Night	27% 4 11% 23% 23% 12%	2510
November	1st to 10th	Night	22% 5% 11% 25% 26% 11%	2405
	11th to 20th	Night	26% 4 10% 26% 25% 8%	2470
	21st to end	Night	29% 4 9% 24% 27% 8%	2522
December	1st to 10th	Night	28% 5% 13% 29% 18% 7%	2660
	11th to 20th	Night	27% 4 8% 32% 25% 4	3272
	21st to end	Night	35% 6% 10% 27% 18% 4	4873

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% 9% 29% 39% 14% 3	270
	11th to 20th	Day	9% 10% 38% 36% 7% 1	252
	21st to end	Day	6% 11% 48% 30% 5%	264
February	1st to 10th	Day	7% 11% 48% 30% 5%	240
	11th to 20th	Day	6% 13% 42% 31% 7% 1	240
	21st to end	Day	6% 17% 39% 32% 6%	198
March	1st to 10th	Day	9% 10% 33% 28% 18% 2	240
	11th to 20th	Day	11% 12% 31% 31% 13% 2	302
	21st to end	Day	14% 11% 37% 28% 9% 1	462
April	1st to 10th	Day	15% 13% 34% 26% 10% 2	420
	11th to 20th	Day	17% 16% 33% 23% 10% 1	412
	21st to end	Day	14% 16% 26% 25% 15% 4	451
May	1st to 10th	Day	16% 9% 28% 29% 15% 3	603
	11th to 20th	Day	16% 6% 25% 30% 19% 4	625
	21st to end	Day	10% 9% 25% 27% 23% 6%	679
June	1st to 10th	Day	6% 4 20% 32% 27% 12%	630
	11th to 20th	Day	6% 5% 27% 36% 21% 4	630
	21st to end	Day	4 3 23% 38% 25% 7%	630
July	1st to 10th	Day	7% 3 13% 33% 37% 7%	621
	11th to 20th	Day	5% 1 14% 34% 34% 12%	618
	21st to end	Day	5% 1 14% 33% 37% 10%	684
August	1st to 10th	Day	6% 1 13% 35% 35% 9%	539
	11th to 20th	Day	3 4 19% 35% 25% 14%	437
	21st to end	Day	4 2 19% 36% 29% 10%	495
September	1st to 10th	Day	7% 3 18% 32% 30% 9%	450
	11th to 20th	Day	5% 2 19% 30% 30% 14%	378
	21st to end	Day	11% 3 20% 27% 24% 14%	270
October	1st to 10th	Day	13% 5% 21% 23% 23% 15%	270
	11th to 20th	Day	5% 8% 34% 31% 13% 8%	270
	21st to end	Day	11% 10% 31% 28% 15% 4	297
November	1st to 10th	Day	4 10% 30% 36% 14% 7%	270
	11th to 20th	Day	5% 10% 35% 32% 15% 3	270
	21st to end	Day	9% 8% 26% 41% 12% 4	270
December	1st to 10th	Day	6% 12% 34% 35% 13%	270
	11th to 20th	Day	9% 9% 43% 33% 8%	270
	21st to end	Day	11% 12% 37% 30% 8% 1	297
January	1st to 10th	Night	6% 10% 33% 39% 11% 1	950
	11th to 20th	Night	6% 10% 40% 33% 9% 1	921
	21st to end	Night	6% 8% 45% 34% 6% 1	876
February	1st to 10th	Night	8% 8% 45% 32% 6%	720
	11th to 20th	Night	7% 9% 43% 35% 6%	704
	21st to end	Night	7% 11% 45% 33% 4	592
March	1st to 10th	Night	7% 10% 36% 39% 8%	720
	11th to 20th	Night	10% 9% 33% 36% 11% 1	720
	21st to end	Night	10% 9% 41% 33% 6% 1	602
April	1st to 10th	Night	13% 12% 37% 32% 6%	540
	11th to 20th	Night	17% 10% 35% 32% 6% 1	533
	21st to end	Night	17% 12% 27% 34% 9% 1	540
May	1st to 10th	Night	13% 11% 29% 35% 12%	540
	11th to 20th	Night	18% 6% 27% 36% 13% 2	531
	21st to end	Night	11% 7% 33% 32% 15% 1	584
June	1st to 10th	Night	6% 4 24% 43% 22% 1	540
	11th to 20th	Night	6% 5% 30% 48% 11% 1	540
	21st to end	Night	5% 2 27% 47% 18%	540
July	1st to 10th	Night	9% 2 14% 49% 25% 1	525
	11th to 20th	Night	4 2 16% 52% 25% 2	522
	21st to end	Night	5% 2 13% 50% 29% 1	591
August	1st to 10th	Night	6% 2 15% 49% 28% 1	537
	11th to 20th	Night	5% 2 18% 51% 23%	534
	21st to end	Night	6% 1 17% 49% 25% 1	594
September	1st to 10th	Night	8% 3 18% 49% 21% 1	540
	11th to 20th	Night	8% 4 21% 43% 22% 2	540
	21st to end	Night	7% 3 27% 44% 18% 1	540
October	1st to 10th	Night	14% 6% 24% 35% 19% 2	620
	11th to 20th	Night	8% 7% 34% 34% 17% 1	720
	21st to end	Night	9% 9% 29% 40% 12% 1	926
November	1st to 10th	Night	6% 4 35% 42% 12% 2	925
	11th to 20th	Night	7% 8% 35% 40% 9% 1	950
	21st to end	Night	7% 8% 33% 40% 11% 1	950
December	1st to 10th	Night	5% 9% 41% 38% 6%	950
	11th to 20th	Night	8% 9% 38% 39% 7% 1	950
	21st to end	Night	10% 11% 34% 38% 6% 1	1045

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