Deep Sky West Remote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deep Sky West Remote Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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	3 3 1 4 3 4 4 4 6% 8% 60%	100880
	Night	3 4 2 5% 4 4 4 4 6% 7% 59%	98318
Transparency	Day	20% 5% 11% 21% 26% 17%	100637
	Night	22% 6% 10% 21% 26% 15%	98150
Seeing	Day	7% 15% 28% 29% 17% 4	15111
	Night	5% 11% 31% 35% 16% 2	25190

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	1 6% 3 6% 4 3 3 2 5% 7% 60%	2762
	11th to 20th	Day	2 3 2 3 2 2 3 2 4 5% 71%	2860
	21st to end	Day	3 7% 3 5% 4 4 4 4 5% 8% 54%	3146
February	1st to 10th	Day	2 6% 1 4 3 3 3 3 6% 7% 61%	1771
	11th to 20th	Day	2 5% 2 5% 2 4 3 3 5% 7% 63%	1849
	21st to end	Day	2 4 2 3 3 3 3 2 5% 7% 66%	1570
March	1st to 10th	Day	1 4 1 3 2 2 3 3 5% 7% 68%	3246
	11th to 20th	Day	3 6% 3 7% 5% 4 4 3 6% 7% 52%	3490
	21st to end	Day	2 4 2 4 4 3 4 3 6% 7% 62%	3979
April	1st to 10th	Day	3 3 1 3 2 3 4 3 7% 7% 65%	2280
	11th to 20th	Day	3 4 2 4 3 3 3 2 4 7% 65%	2251
	21st to end	Day	3 4 1 3 3 3 3 3 5% 8% 66%	2280
May	1st to 10th	Day	2 2 1 2 2 3 3 3 5% 5% 72%	3800
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 7% 60%	3904
	21st to end	Day	2 1 1 2 2 2 3 2 4 5% 76%	4825
June	1st to 10th	Day	2 2 1 4 3 3 5% 4 6% 9% 61%	2660
	11th to 20th	Day	2 2 1 3 2 3 3 4 6% 6% 69%	2660
	21st to end	Day	5% 4 1 5% 5% 4 5% 4 7% 8% 55%	2660
July	1st to 10th	Day	3 3 1 5% 5% 5% 6% 5% 7% 9% 52%	4430
	11th to 20th	Day	2 2 1 5% 4 6% 8% 7% 10% 12% 44%	4111
	21st to end	Day	5% 4 2 6% 6% 6% 7% 7% 9% 10% 38%	4454
August	1st to 10th	Day	3 2 1 5% 5% 6% 7% 6% 8% 10% 46%	3921
	11th to 20th	Day	3 2 1 4 4 4 5% 5% 6% 9% 58%	3726
	21st to end	Day	3 3 1 7% 5% 6% 7% 5% 8% 10% 44%	4180
September	1st to 10th	Day	6% 4 2 5% 4 5% 4 4 6% 8% 52%	2280
	11th to 20th	Day	6% 3 1 4 3 4 4 4 6% 7% 58%	2280
	21st to end	Day	4 2 1 3 3 3 3 3 4 6% 71%	2084
October	1st to 10th	Day	7% 3 2 4 4 3 3 3 5% 6% 61%	1900
	11th to 20th	Day	3 3 1 3 2 2 2 2 3 4 76%	1900
	21st to end	Day	4 3 1 3 2 2 2 2 3 4 74%	2090
November	1st to 10th	Day	1 2 1 2 2 2 3 3 5% 8% 71%	1789
	11th to 20th	Day	2 3 1 3 2 2 3 3 4 8% 70%	1710
	21st to end	Day	4 5% 1 4 3 3 3 3 5% 6% 65%	1710
December	1st to 10th	Day	2 4 1 4 3 3 3 3 5% 8% 65%	1602
	11th to 20th	Day	3 3 2 6% 4 4 4 3 4 8% 58%	1926
	21st to end	Day	2 5% 1 3 2 2 3 3 6% 6% 66%	2794
January	1st to 10th	Night	1 5% 2 8% 5% 4 4 2 4 5% 58%	4221
	11th to 20th	Night	2 3 1 3 3 4 3 3 4 5% 68%	4110
	21st to end	Night	2 6% 3 5% 3 4 4 4 6% 8% 54%	4521
February	1st to 10th	Night	2 6% 2 5% 2 3 3 3 5% 7% 63%	2408
	11th to 20th	Night	3 5% 1 4 4 3 3 3 4 6% 63%	2218
	21st to end	Night	3 4 1 4 3 2 3 3 4 7% 66%	1884
March	1st to 10th	Night	1 3 1 4 2 3 3 3 5% 6% 69%	3619
	11th to 20th	Night	4 7% 3 7% 5% 4 4 4 5% 6% 52%	3490
	21st to end	Night	2 3 1 4 3 4 4 3 5% 7% 64%	3655
April	1st to 10th	Night	3 3 1 3 3 3 3 2 4 7% 67%	1900
	11th to 20th	Night	3 4 2 4 3 3 3 3 5% 6% 65%	1877
	21st to end	Night	3 3 1 4 3 3 2 3 4 6% 67%	1900
May	1st to 10th	Night	2 3 1 3 3 3 4 3 5% 6% 67%	3170
	11th to 20th	Night	5% 5% 3 5% 4 5% 5% 4 6% 7% 52%	2993
	21st to end	Night	3 2 1 3 2 2 2 2 4 5% 73%	2762
June	1st to 10th	Night	3 3 2 4 4 3 4 4 8% 9% 54%	1520
	11th to 20th	Night	3 2 1 3 3 3 3 3 4 7% 67%	1520
	21st to end	Night	5% 4 2 5% 4 4 7% 4 7% 9% 49%	1520
July	1st to 10th	Night	4 5% 2 6% 6% 7% 6% 4 7% 7% 46%	2540
	11th to 20th	Night	4 3 1 6% 5% 4 6% 6% 10% 13% 42%	2853
	21st to end	Night	7% 5% 2 6% 4 5% 6% 5% 8% 11% 42%	3109
August	1st to 10th	Night	2 4 2 8% 7% 8% 9% 7% 9% 11% 33%	3018
	11th to 20th	Night	3 3 2 5% 5% 5% 7% 6% 8% 11% 46%	3113
	21st to end	Night	4 4 2 8% 7% 6% 7% 7% 10% 11% 34%	3487
September	1st to 10th	Night	5% 4 2 5% 4 5% 5% 5% 7% 9% 51%	1900
	11th to 20th	Night	5% 4 2 5% 2 4 5% 4 7% 8% 56%	1900
	21st to end	Night	4 4 1 3 2 3 4 3 4 6% 65%	2091
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 5% 5% 62%	2280
	11th to 20th	Night	3 2 1 3 2 2 2 2 4 4 75%	2280
	21st to end	Night	4 2 1 3 3 2 3 2 4 6% 72%	2508
November	1st to 10th	Night	2 2 1 2 2 2 3 2 4 6% 74%	2293
	11th to 20th	Night	1 2 1 3 2 3 2 3 4 6% 73%	2470
	21st to end	Night	4 5% 1 4 3 3 3 3 4 6% 64%	2470
December	1st to 10th	Night	3 3 2 4 2 3 4 2 4 7% 66%	2574
	11th to 20th	Night	2 3 2 4 4 4 4 3 5% 7% 60%	3271
	21st to end	Night	3 5% 2 5% 3 3 3 2 4 6% 63%	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	21% 4 10% 29% 31% 5%	2763
	11th to 20th	Day	13% 6% 11% 36% 29% 5%	2860
	21st to end	Day	25% 7% 10% 21% 30% 8%	3146
February	1st to 10th	Day	21% 4 10% 23% 29% 13%	1771
	11th to 20th	Day	21% 4 7% 24% 28% 16%	1859
	21st to end	Day	18% 3 6% 18% 34% 22%	1570
March	1st to 10th	Day	16% 3 6% 15% 38% 22%	3246
	11th to 20th	Day	23% 7% 11% 22% 27% 10%	3490
	21st to end	Day	18% 4 9% 20% 37% 12%	3979
April	1st to 10th	Day	16% 4 7% 18% 34% 20%	2280
	11th to 20th	Day	20% 3 6% 18% 30% 23%	2254
	21st to end	Day	16% 3 8% 20% 37% 16%	2280
May	1st to 10th	Day	13% 4 8% 15% 33% 28%	3800
	11th to 20th	Day	20% 6% 11% 16% 30% 17%	3907
	21st to end	Day	10% 4 7% 12% 21% 47%	4825
June	1st to 10th	Day	16% 6% 12% 20% 24% 22%	2660
	11th to 20th	Day	14% 3 7% 13% 22% 40%	2660
	21st to end	Day	25% 4 12% 18% 20% 21%	2660
July	1st to 10th	Day	23% 9% 16% 15% 15% 22%	4361
	11th to 20th	Day	25% 8% 19% 29% 13% 5%	4041
	21st to end	Day	32% 10% 17% 28% 11% 2	4314
August	1st to 10th	Day	26% 11% 20% 22% 14% 7%	3907
	11th to 20th	Day	20% 7% 11% 26% 23% 13%	3762
	21st to end	Day	31% 9% 17% 23% 17% 3	4179
September	1st to 10th	Day	29% 6% 11% 20% 24% 10%	2280
	11th to 20th	Day	24% 5% 10% 19% 23% 18%	2280
	21st to end	Day	17% 4 6% 22% 32% 19%	2084
October	1st to 10th	Day	25% 4 7% 18% 25% 21%	1900
	11th to 20th	Day	15% 3 4 13% 33% 31%	1900
	21st to end	Day	15% 2 6% 20% 36% 20%	2090
November	1st to 10th	Day	12% 3 7% 19% 40% 18%	1789
	11th to 20th	Day	14% 2 8% 23% 39% 14%	1710
	21st to end	Day	20% 2 7% 19% 34% 18%	1710
December	1st to 10th	Day	18% 4 10% 30% 26% 12%	1602
	11th to 20th	Day	23% 6% 10% 22% 29% 11%	1924
	21st to end	Day	16% 3 10% 21% 33% 16%	2794
January	1st to 10th	Night	23% 6% 10% 25% 26% 9%	4221
	11th to 20th	Night	15% 6% 10% 34% 27% 8%	4110
	21st to end	Night	21% 9% 10% 24% 29% 7%	4521
February	1st to 10th	Night	20% 4 9% 24% 30% 13%	2408
	11th to 20th	Night	21% 4 7% 23% 29% 15%	2218
	21st to end	Night	18% 2 5% 18% 35% 22%	1884
March	1st to 10th	Night	15% 2 7% 15% 41% 20%	3619
	11th to 20th	Night	27% 8% 8% 22% 25% 9%	3490
	21st to end	Night	17% 3 10% 23% 34% 12%	3655
April	1st to 10th	Night	17% 3 7% 18% 31% 23%	1900
	11th to 20th	Night	18% 4 7% 18% 28% 25%	1877
	21st to end	Night	17% 5% 8% 20% 34% 16%	1900
May	1st to 10th	Night	14% 5% 12% 12% 28% 29%	3170
	11th to 20th	Night	23% 8% 14% 21% 19% 14%	2994
	21st to end	Night	13% 3 9% 9% 16% 49%	2762
June	1st to 10th	Night	22% 9% 15% 16% 17% 21%	1520
	11th to 20th	Night	17% 4 7% 14% 20% 39%	1520
	21st to end	Night	29% 6% 13% 16% 15% 21%	1520
July	1st to 10th	Night	30% 7% 15% 17% 11% 19%	2500
	11th to 20th	Night	27% 9% 21% 30% 9% 4	2800
	21st to end	Night	33% 9% 17% 29% 10% 1	3011
August	1st to 10th	Night	38% 10% 17% 16% 13% 6%	3009
	11th to 20th	Night	27% 9% 16% 21% 19% 8%	3143
	21st to end	Night	36% 11% 17% 23% 9% 4	3487
September	1st to 10th	Night	27% 7% 14% 22% 22% 9%	1900
	11th to 20th	Night	25% 6% 11% 17% 23% 18%	1900
	21st to end	Night	19% 4 8% 18% 31% 19%	2091
October	1st to 10th	Night	23% 5% 8% 19% 20% 24%	2280
	11th to 20th	Night	14% 3 5% 13% 33% 31%	2280
	21st to end	Night	15% 3 6% 18% 37% 20%	2508
November	1st to 10th	Night	12% 2 6% 20% 40% 20%	2293
	11th to 20th	Night	13% 3 6% 22% 40% 16%	2470
	21st to end	Night	22% 3 6% 19% 31% 19%	2470
December	1st to 10th	Night	18% 4 9% 29% 29% 10%	2574
	11th to 20th	Night	22% 4 9% 23% 32% 10%	3272
	21st to end	Night	20% 6% 8% 21% 33% 13%	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	9% 24% 34% 26% 7% 1	270
	11th to 20th	Day	12% 24% 34% 21% 8% 1	270
	21st to end	Day	2 18% 43% 26% 9% 2	297
February	1st to 10th	Day	6% 31% 34% 24% 6%	270
	11th to 20th	Day	7% 31% 40% 17% 5%	270
	21st to end	Day	14% 33% 36% 15% 2	225
March	1st to 10th	Day	9% 29% 32% 24% 6%	334
	11th to 20th	Day	15% 27% 30% 19% 7% 1	460
	21st to end	Day	14% 33% 34% 15% 4 1	506
April	1st to 10th	Day	10% 28% 37% 17% 6% 1	460
	11th to 20th	Day	11% 31% 37% 16% 5%	452
	21st to end	Day	9% 27% 38% 23% 2 1	460
May	1st to 10th	Day	7% 24% 43% 21% 5% 1	463
	11th to 20th	Day	8% 13% 36% 28% 13% 2	549
	21st to end	Day	6% 12% 38% 32% 12% 1	734
June	1st to 10th	Day	3 7% 24% 40% 23% 4	680
	11th to 20th	Day	4 8% 28% 36% 23% 2	680
	21st to end	Day	5% 6% 24% 34% 24% 6%	680
July	1st to 10th	Day	5% 2 14% 36% 36% 7%	671
	11th to 20th	Day	5% 1 7% 34% 37% 16%	484
	21st to end	Day	4 1 9% 30% 41% 15%	531
August	1st to 10th	Day	5% 2 11% 36% 36% 10%	487
	11th to 20th	Day	3 2 15% 39% 31% 9%	477
	21st to end	Day	5% 1 14% 41% 30% 9%	539
September	1st to 10th	Day	6% 2 15% 42% 27% 7%	490
	11th to 20th	Day	4 3 27% 41% 19% 5%	490
	21st to end	Day	7% 6% 29% 31% 20% 7%	302
October	1st to 10th	Day	7% 13% 28% 27% 18% 6%	300
	11th to 20th	Day	9% 14% 28% 30% 15% 3	300
	21st to end	Day	11% 15% 31% 26% 14% 3	330
November	1st to 10th	Day	5% 25% 37% 23% 8% 1	273
	11th to 20th	Day	5% 14% 36% 31% 13% 1	270
	21st to end	Day	11% 24% 31% 24% 9% 1	270
December	1st to 10th	Day	7% 23% 37% 25% 7% 1	270
	11th to 20th	Day	8% 22% 42% 24% 4	270
	21st to end	Day	13% 32% 32% 19% 3 1	297
January	1st to 10th	Night	3 14% 39% 31% 12%	832
	11th to 20th	Night	6% 14% 41% 29% 9% 1	760
	21st to end	Night	5% 14% 39% 31% 11% 1	836
February	1st to 10th	Night	5% 15% 42% 31% 7%	760
	11th to 20th	Night	6% 17% 42% 28% 7%	744
	21st to end	Night	8% 17% 51% 22% 2	628
March	1st to 10th	Night	4 17% 41% 30% 7% 1	760
	11th to 20th	Night	7% 16% 34% 34% 10%	760
	21st to end	Night	5% 16% 42% 31% 6%	740
April	1st to 10th	Night	5% 20% 43% 27% 5%	570
	11th to 20th	Night	5% 18% 39% 31% 7%	563
	21st to end	Night	5% 17% 40% 32% 5% 1	570
May	1st to 10th	Night	3 12% 40% 37% 9%	570
	11th to 20th	Night	6% 9% 30% 39% 14% 1	561
	21st to end	Night	5% 8% 38% 37% 12%	617
June	1st to 10th	Night	2 5% 26% 45% 21%	570
	11th to 20th	Night	3 4 29% 49% 15% 1	570
	21st to end	Night	5% 4 19% 44% 27% 2	570
July	1st to 10th	Night	6% 1 11% 45% 35% 2	555
	11th to 20th	Night	3 1 7% 37% 47% 5%	552
	21st to end	Night	5% 2 7% 33% 47% 6%	624
August	1st to 10th	Night	4 1 8% 33% 45% 8%	567
	11th to 20th	Night	3 2 9% 40% 41% 4	564
	21st to end	Night	3 1 7% 43% 40% 5%	627
September	1st to 10th	Night	4 2 13% 44% 33% 3	570
	11th to 20th	Night	5% 3 14% 48% 27% 2	570
	21st to end	Night	5% 4 23% 44% 22% 2	574
October	1st to 10th	Night	8% 5% 22% 46% 18% 2	760
	11th to 20th	Night	4 8% 31% 41% 14% 2	760
	21st to end	Night	5% 9% 31% 35% 18% 3	836
November	1st to 10th	Night	3 8% 32% 40% 14% 2	805
	11th to 20th	Night	2 10% 36% 38% 12% 2	950
	21st to end	Night	6% 14% 33% 34% 12% 2	950
December	1st to 10th	Night	6% 15% 39% 32% 8% 1	950
	11th to 20th	Night	5% 18% 38% 30% 8%	950
	21st to end	Night	8% 16% 44% 27% 4	1045

Page generated at 2024-10-29 23:22:54. Version ac07

Copyright © 2024 Attilla Danko.