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 2024-11-30.

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% 55%	105387
	Night	6% 6% 2 5% 4 4 4 4 6% 7% 52%	102925
Transparency	Day	27% 6% 11% 26% 22% 9%	105128
	Night	30% 6% 12% 25% 20% 7%	102774
Seeing	Day	8% 7% 26% 32% 20% 6%	15769
	Night	8% 7% 32% 40% 13% 1	25785

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	2 7% 2 7% 4 4 3 2 4 5% 58%	2538
	11th to 20th	Day	2 7% 3 10% 5% 5% 5% 4 6% 7% 46%	2540
	21st to end	Day	3 5% 2 5% 3 3 3 3 6% 7% 60%	3022
February	1st to 10th	Day	4 9% 4 9% 5% 4 4 3 5% 6% 45%	1739
	11th to 20th	Day	3 8% 3 6% 4 3 5% 4 6% 7% 50%	1849
	21st to end	Day	3 8% 3 8% 4 3 3 3 6% 6% 52%	1570
March	1st to 10th	Day	5% 9% 2 5% 4 3 4 3 5% 7% 52%	3130
	11th to 20th	Day	7% 6% 2 4 4 4 4 3 4 6% 55%	3288
	21st to end	Day	5% 7% 3 7% 5% 4 5% 4 6% 8% 46%	4155
April	1st to 10th	Day	8% 8% 2 5% 3 3 3 4 6% 7% 50%	2280
	11th to 20th	Day	13% 9% 2 5% 4 4 4 4 5% 6% 44%	2251
	21st to end	Day	11% 7% 2 6% 4 4 4 4 6% 9% 44%	2313
May	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 7% 43%	4120
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 7% 9% 48%	4288
	21st to end	Day	8% 4 2 4 4 4 4 4 6% 8% 51%	4825
June	1st to 10th	Day	6% 3 1 3 3 4 4 4 7% 10% 55%	2660
	11th to 20th	Day	6% 3 2 4 3 4 5% 4 7% 7% 55%	2660
	21st to end	Day	3 3 1 4 3 4 5% 4 7% 9% 58%	2660
July	1st to 10th	Day	7% 4 2 5% 3 4 4 4 5% 8% 56%	4430
	11th to 20th	Day	3 2 1 3 3 4 5% 5% 8% 10% 56%	4430
	21st to end	Day	3 2 1 4 4 4 5% 4 7% 9% 57%	4802
August	1st to 10th	Day	11% 3 1 4 3 4 5% 4 7% 10% 48%	4172
	11th to 20th	Day	4 4 1 4 4 4 4 4 7% 8% 57%	3726
	21st to end	Day	4 3 1 4 3 3 4 4 6% 9% 59%	4180
September	1st to 10th	Day	5% 4 1 3 2 3 4 4 4 7% 63%	2280
	11th to 20th	Day	7% 2 1 3 3 3 3 3 5% 6% 63%	2204
	21st to end	Day	8% 3 1 4 2 2 2 2 4 6% 65%	2090
October	1st to 10th	Day	6% 3 1 2 1 2 2 2 3 5% 75%	3331
	11th to 20th	Day	4 5% 2 4 3 3 3 3 4 6% 64%	3150
	21st to end	Day	8% 6% 2 3 2 2 3 2 5% 7% 60%	3164
November	1st to 10th	Day	3 6% 2 4 3 3 3 3 5% 7% 61%	1763
	11th to 20th	Day	3 6% 2 4 3 3 4 3 5% 6% 61%	1800
	21st to end	Day	3 7% 3 5% 2 3 3 3 5% 6% 60%	1737
December	1st to 10th	Day	3 7% 3 8% 4 4 4 3 6% 7% 52%	1520
	11th to 20th	Day	4 8% 2 6% 4 3 4 4 5% 7% 52%	1926
	21st to end	Day	5% 10% 3 7% 4 4 5% 4 5% 6% 48%	2794
January	1st to 10th	Night	3 7% 3 7% 3 3 3 3 5% 8% 54%	4417
	11th to 20th	Night	2 6% 3 7% 4 5% 4 4 6% 8% 50%	4430
	21st to end	Night	3 6% 2 7% 5% 4 4 3 5% 5% 55%	4675
February	1st to 10th	Night	4 9% 4 8% 4 4 5% 4 5% 7% 48%	2439
	11th to 20th	Night	4 8% 2 7% 5% 4 5% 4 6% 6% 49%	2218
	21st to end	Night	4 7% 3 7% 5% 4 4 3 4 5% 55%	1884
March	1st to 10th	Night	4 10% 3 6% 3 3 4 3 5% 5% 54%	3734
	11th to 20th	Night	10% 9% 2 5% 3 3 3 3 4 5% 52%	3681
	21st to end	Night	7% 8% 2 7% 4 4 4 4 6% 8% 45%	3485
April	1st to 10th	Night	9% 7% 2 6% 5% 3 5% 4 5% 6% 49%	1900
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 5% 6% 45%	1877
	21st to end	Night	14% 8% 2 6% 5% 4 4 3 5% 7% 42%	1867
May	1st to 10th	Night	11% 7% 3 7% 4 6% 5% 4 6% 8% 39%	2850
	11th to 20th	Night	11% 4 2 5% 5% 5% 5% 4 7% 9% 45%	2613
	21st to end	Night	12% 6% 2 6% 6% 4 5% 4 6% 8% 41%	2762
June	1st to 10th	Night	6% 3 2 4 3 3 4 4 8% 13% 50%	1520
	11th to 20th	Night	7% 4 2 4 4 4 4 4 6% 8% 53%	1520
	21st to end	Night	6% 4 1 5% 4 5% 5% 5% 7% 8% 49%	1520
July	1st to 10th	Night	5% 4 2 5% 5% 4 5% 4 5% 8% 53%	2540
	11th to 20th	Night	4 3 1 4 4 5% 5% 4 7% 11% 53%	2540
	21st to end	Night	5% 3 1 5% 4 3 4 4 8% 9% 52%	2761
August	1st to 10th	Night	13% 4 2 6% 5% 5% 6% 4 8% 9% 37%	2761
	11th to 20th	Night	5% 6% 2 6% 4 5% 6% 5% 6% 9% 45%	3113
	21st to end	Night	3 3 1 4 4 4 5% 5% 9% 10% 50%	3487
September	1st to 10th	Night	6% 4 1 4 4 3 3 4 6% 7% 57%	1900
	11th to 20th	Night	7% 3 1 4 3 3 4 3 5% 8% 59%	1976
	21st to end	Night	6% 4 1 4 3 2 3 3 4 6% 64%	2090
October	1st to 10th	Night	6% 2 1 2 2 2 3 2 3 5% 71%	3630
	11th to 20th	Night	7% 3 1 4 4 3 3 3 5% 7% 60%	3778
	21st to end	Night	6% 5% 2 4 3 3 3 3 4 5% 61%	4363
November	1st to 10th	Night	5% 4 2 4 4 3 3 3 6% 7% 59%	2535
	11th to 20th	Night	5% 6% 1 5% 4 3 4 3 4 6% 60%	2600
	21st to end	Night	5% 7% 2 5% 4 3 3 3 5% 6% 57%	2655
December	1st to 10th	Night	3 6% 2 7% 3 4 4 3 6% 7% 55%	2660
	11th to 20th	Night	4 6% 2 5% 3 4 4 4 6% 7% 56%	3271
	21st to end	Night	7% 9% 2 6% 4 4 4 4 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	28% 4 12% 31% 20% 6%	2539
	11th to 20th	Day	35% 7% 16% 23% 15% 4	2540
	21st to end	Day	23% 6% 17% 32% 19% 4	3022
February	1st to 10th	Day	37% 4 13% 25% 16% 5%	1739
	11th to 20th	Day	31% 5% 10% 28% 21% 5%	1859
	21st to end	Day	31% 5% 9% 26% 21% 8%	1570
March	1st to 10th	Day	30% 4 8% 21% 30% 7%	3130
	11th to 20th	Day	29% 5% 13% 33% 17% 3	3288
	21st to end	Day	32% 9% 14% 33% 10% 2	4155
April	1st to 10th	Day	32% 6% 13% 25% 17% 8%	2280
	11th to 20th	Day	38% 7% 11% 21% 16% 7%	2254
	21st to end	Day	35% 6% 9% 28% 18% 2	2313
May	1st to 10th	Day	37% 8% 11% 26% 14% 5%	4120
	11th to 20th	Day	29% 9% 13% 29% 17% 3	4292
	21st to end	Day	28% 8% 15% 27% 19% 3	4825
June	1st to 10th	Day	22% 8% 19% 28% 16% 7%	2660
	11th to 20th	Day	26% 7% 10% 24% 23% 10%	2660
	21st to end	Day	21% 6% 10% 27% 26% 11%	2660
July	1st to 10th	Day	26% 5% 8% 18% 31% 12%	4361
	11th to 20th	Day	21% 5% 12% 25% 22% 15%	4355
	21st to end	Day	21% 6% 11% 22% 19% 21%	4651
August	1st to 10th	Day	29% 5% 15% 27% 16% 7%	4157
	11th to 20th	Day	25% 5% 12% 22% 24% 12%	3762
	21st to end	Day	22% 4 11% 21% 27% 16%	4179
September	1st to 10th	Day	20% 5% 8% 22% 27% 18%	2280
	11th to 20th	Day	21% 5% 7% 22% 29% 16%	2204
	21st to end	Day	21% 3 7% 23% 35% 11%	2090
October	1st to 10th	Day	15% 3 6% 18% 31% 27%	3331
	11th to 20th	Day	23% 3 8% 30% 26% 9%	3150
	21st to end	Day	25% 3 8% 27% 29% 9%	3164
November	1st to 10th	Day	23% 3 13% 27% 25% 10%	1763
	11th to 20th	Day	23% 5% 8% 28% 28% 8%	1800
	21st to end	Day	25% 4 10% 26% 27% 9%	1737
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	29% 5% 11% 31% 21% 3	4417
	11th to 20th	Night	30% 7% 12% 23% 20% 7%	4430
	21st to end	Night	29% 6% 14% 33% 16% 3	4675
February	1st to 10th	Night	36% 6% 12% 23% 18% 5%	2439
	11th to 20th	Night	33% 5% 13% 26% 19% 4	2218
	21st to end	Night	31% 4 9% 23% 24% 9%	1884
March	1st to 10th	Night	31% 5% 8% 20% 27% 9%	3734
	11th to 20th	Night	34% 5% 14% 22% 22% 3	3681
	21st to end	Night	33% 9% 16% 29% 11% 2	3485
April	1st to 10th	Night	35% 7% 10% 23% 18% 7%	1900
	11th to 20th	Night	38% 6% 12% 22% 16% 5%	1877
	21st to end	Night	40% 7% 10% 23% 18% 2	1867
May	1st to 10th	Night	38% 10% 17% 21% 9% 5%	2850
	11th to 20th	Night	33% 9% 17% 28% 10% 3	2614
	21st to end	Night	37% 12% 17% 18% 11% 4	2762
June	1st to 10th	Night	24% 10% 24% 24% 14% 4	1520
	11th to 20th	Night	28% 8% 13% 24% 17% 10%	1520
	21st to end	Night	29% 6% 13% 25% 22% 5%	1520
July	1st to 10th	Night	29% 5% 13% 22% 27% 5%	2500
	11th to 20th	Night	24% 5% 17% 22% 25% 7%	2492
	21st to end	Night	25% 5% 15% 24% 18% 12%	2674
August	1st to 10th	Night	41% 7% 17% 20% 12% 3	2753
	11th to 20th	Night	35% 8% 14% 21% 16% 7%	3143
	21st to end	Night	26% 4 17% 23% 21% 9%	3487
September	1st to 10th	Night	25% 5% 9% 22% 25% 14%	1900
	11th to 20th	Night	23% 5% 9% 25% 25% 13%	1976
	21st to end	Night	22% 4 8% 27% 27% 12%	2090
October	1st to 10th	Night	17% 4 6% 18% 28% 27%	3630
	11th to 20th	Night	24% 4 9% 29% 26% 8%	3778
	21st to end	Night	27% 3 9% 27% 24% 11%	4363
November	1st to 10th	Night	23% 5% 11% 25% 26% 11%	2535
	11th to 20th	Night	25% 4 10% 25% 26% 9%	2600
	21st to end	Night	28% 4 9% 25% 27% 7%	2655
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% 35% 7% 1	270
	21st to end	Day	5% 10% 44% 30% 8% 2	297
February	1st to 10th	Day	7% 11% 44% 32% 5% 1	270
	11th to 20th	Day	5% 13% 40% 33% 9% 1	270
	21st to end	Day	6% 17% 40% 30% 6%	225
March	1st to 10th	Day	9% 10% 31% 29% 19% 1	270
	11th to 20th	Day	10% 12% 31% 31% 14% 2	336
	21st to end	Day	14% 12% 36% 28% 9% 1	506
April	1st to 10th	Day	15% 13% 34% 26% 10% 2	460
	11th to 20th	Day	16% 17% 32% 22% 11% 2	452
	21st to end	Day	14% 17% 26% 26% 14% 3	493
May	1st to 10th	Day	15% 11% 28% 28% 14% 3	653
	11th to 20th	Day	15% 6% 25% 30% 19% 4	675
	21st to end	Day	10% 9% 25% 28% 22% 6%	734
June	1st to 10th	Day	6% 5% 21% 32% 26% 11%	680
	11th to 20th	Day	7% 6% 28% 35% 20% 4	680
	21st to end	Day	4 3 24% 39% 24% 6%	680
July	1st to 10th	Day	7% 3 14% 33% 35% 8%	671
	11th to 20th	Day	5% 1 14% 34% 34% 12%	668
	21st to end	Day	4 1 14% 34% 37% 10%	739
August	1st to 10th	Day	7% 1 13% 36% 34% 9%	584
	11th to 20th	Day	3 4 20% 35% 25% 13%	477
	21st to end	Day	4 2 19% 35% 28% 11%	539
September	1st to 10th	Day	7% 3 18% 31% 31% 10%	490
	11th to 20th	Day	5% 2 19% 31% 30% 13%	414
	21st to end	Day	11% 4 20% 28% 24% 14%	300
October	1st to 10th	Day	12% 5% 21% 24% 24% 14%	300
	11th to 20th	Day	5% 8% 35% 31% 14% 8%	300
	21st to end	Day	11% 11% 31% 29% 14% 4	330
November	1st to 10th	Day	5% 11% 30% 35% 13% 6%	300
	11th to 20th	Day	5% 10% 35% 33% 14% 3	300
	21st to end	Day	8% 8% 27% 41% 13% 3	299
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% 41% 33% 9% 1	950
	21st to end	Night	6% 7% 43% 35% 7% 1	925
February	1st to 10th	Night	9% 9% 44% 33% 6%	760
	11th to 20th	Night	7% 9% 43% 35% 6%	744
	21st to end	Night	7% 11% 46% 32% 3	628
March	1st to 10th	Night	8% 11% 35% 39% 7%	760
	11th to 20th	Night	10% 9% 33% 36% 11% 1	760
	21st to end	Night	10% 10% 42% 32% 6% 1	635
April	1st to 10th	Night	13% 12% 38% 32% 6%	570
	11th to 20th	Night	17% 10% 35% 32% 6% 1	563
	21st to end	Night	18% 12% 28% 34% 9% 1	570
May	1st to 10th	Night	13% 12% 30% 34% 11%	570
	11th to 20th	Night	17% 6% 26% 37% 13% 1	561
	21st to end	Night	12% 7% 33% 33% 14%	617
June	1st to 10th	Night	6% 4 24% 44% 21% 1	570
	11th to 20th	Night	6% 6% 30% 47% 10% 1	570
	21st to end	Night	5% 2 27% 47% 17%	570
July	1st to 10th	Night	8% 2 15% 49% 24% 1	555
	11th to 20th	Night	4 1 16% 52% 24% 2	552
	21st to end	Night	5% 2 14% 50% 28% 1	624
August	1st to 10th	Night	6% 2 14% 49% 27% 1	567
	11th to 20th	Night	5% 2 19% 51% 22%	564
	21st to end	Night	6% 1 18% 49% 25% 1	627
September	1st to 10th	Night	7% 2 17% 50% 21% 1	570
	11th to 20th	Night	7% 5% 21% 44% 21% 2	570
	21st to end	Night	7% 3 27% 44% 18% 1	570
October	1st to 10th	Night	13% 6% 24% 36% 20% 2	655
	11th to 20th	Night	8% 6% 33% 35% 17% 1	760
	21st to end	Night	8% 9% 30% 40% 12% 1	978
November	1st to 10th	Night	7% 4 35% 41% 11% 1	975
	11th to 20th	Night	7% 9% 35% 40% 8% 1	1000
	21st to end	Night	7% 7% 33% 41% 10% 1	1000
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

Page generated at 2024-11-27 15:30:54. Version ac07

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