SkyWatcher Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SkyWatcher Ranch clear sky chart from 2005-11-06 to 2024-12-09.

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	9% 6% 2 5% 4 4 4 4 5% 7% 51%	101270
	Night	8% 6% 2 5% 3 3 3 3 5% 7% 54%	98608
Transparency	Day	32% 6% 10% 21% 21% 11%	105140
	Night	30% 5% 10% 21% 21% 13%	102852
Seeing	Day	12% 9% 25% 31% 19% 4	14926
	Night	12% 8% 31% 35% 13% 1	24910

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	9% 7% 3 6% 3 2 2 3 3 5% 57%	2847
	11th to 20th	Day	9% 8% 2 3 2 2 2 2 5% 5% 58%	2891
	21st to end	Day	11% 7% 3 5% 4 3 4 3 4 7% 50%	3487
February	1st to 10th	Day	12% 6% 2 5% 4 2 3 3 4 6% 52%	1900
	11th to 20th	Day	12% 8% 2 5% 3 3 3 3 5% 6% 49%	1849
	21st to end	Day	12% 6% 2 4 3 3 3 3 4 6% 54%	1570
March	1st to 10th	Day	12% 8% 3 5% 4 4 4 2 4 6% 48%	3254
	11th to 20th	Day	15% 9% 3 8% 5% 4 4 3 4 6% 38%	3480
	21st to end	Day	8% 7% 2 5% 4 4 4 4 5% 7% 50%	3814
April	1st to 10th	Day	10% 7% 2 6% 3 3 5% 4 5% 7% 48%	2090
	11th to 20th	Day	12% 6% 2 7% 4 4 4 3 4 6% 48%	2219
	21st to end	Day	10% 8% 2 6% 5% 3 4 3 3 5% 51%	2329
May	1st to 10th	Day	14% 7% 3 8% 4 5% 4 4 5% 6% 39%	4082
	11th to 20th	Day	12% 7% 2 6% 4 4 5% 4 5% 6% 46%	4082
	21st to end	Day	8% 7% 2 6% 4 5% 5% 5% 7% 8% 43%	4477
June	1st to 10th	Day	4 4 1 5% 5% 5% 4 4 6% 9% 53%	2470
	11th to 20th	Day	4 4 1 5% 5% 4 4 4 7% 9% 52%	2470
	21st to end	Day	5% 5% 1 6% 5% 5% 6% 5% 7% 10% 44%	2470
July	1st to 10th	Day	5% 5% 2 6% 4 5% 6% 4 7% 8% 48%	4120
	11th to 20th	Day	3 3 1 4 4 4 5% 5% 6% 9% 56%	4120
	21st to end	Day	7% 5% 2 6% 5% 4 5% 5% 7% 10% 44%	4465
August	1st to 10th	Day	1 1 1 3 3 3 4 3 5% 9% 68%	3831
	11th to 20th	Day	4 2 1 4 3 3 4 3 5% 8% 62%	3726
	21st to end	Day	4 3 2 6% 5% 4 5% 4 7% 10% 49%	4151
September	1st to 10th	Day	9% 5% 3 7% 5% 4 6% 4 5% 7% 44%	2090
	11th to 20th	Day	9% 5% 3 7% 5% 6% 5% 4 6% 7% 43%	2090
	21st to end	Day	9% 4 2 6% 4 5% 4 5% 6% 6% 50%	2090
October	1st to 10th	Day	5% 4 2 5% 3 4 4 4 5% 7% 57%	2090
	11th to 20th	Day	11% 5% 1 5% 4 3 4 2 4 6% 55%	2049
	21st to end	Day	10% 5% 2 4 2 3 3 2 4 5% 60%	2090
November	1st to 10th	Day	12% 7% 2 6% 3 3 3 3 5% 7% 50%	1899
	11th to 20th	Day	8% 5% 1 5% 4 4 5% 3 5% 6% 56%	1800
	21st to end	Day	12% 7% 2 6% 3 4 2 3 4 6% 51%	1800
December	1st to 10th	Day	13% 8% 2 4 3 2 3 2 6% 7% 49%	1782
	11th to 20th	Day	10% 8% 2 6% 4 4 4 3 5% 6% 50%	2161
	21st to end	Day	11% 6% 2 5% 2 3 2 3 3 5% 59%	3135
January	1st to 10th	Night	11% 6% 2 6% 3 3 2 2 3 6% 56%	4108
	11th to 20th	Night	10% 5% 1 3 2 2 2 2 2 4 67%	4106
	21st to end	Night	14% 8% 2 6% 3 3 3 2 4 7% 48%	4180
February	1st to 10th	Night	11% 7% 2 6% 4 3 2 3 5% 6% 52%	2280
	11th to 20th	Night	12% 6% 3 5% 3 4 3 3 5% 6% 52%	2218
	21st to end	Night	12% 6% 3 6% 3 3 3 4 5% 5% 51%	1884
March	1st to 10th	Night	8% 7% 3 6% 4 3 4 4 6% 7% 48%	3591
	11th to 20th	Night	14% 10% 3 7% 5% 4 5% 3 5% 5% 39%	3480
	21st to end	Night	8% 8% 2 6% 4 3 4 3 4 6% 50%	3817
April	1st to 10th	Night	6% 6% 2 6% 4 4 3 4 6% 6% 53%	2090
	11th to 20th	Night	10% 7% 3 7% 5% 4 3 3 4 5% 49%	1906
	21st to end	Night	11% 6% 2 5% 4 2 3 4 5% 6% 52%	1848
May	1st to 10th	Night	15% 10% 3 6% 4 3 4 3 4 7% 41%	2823
	11th to 20th	Night	7% 7% 3 6% 4 4 4 3 5% 6% 52%	2823
	21st to end	Night	9% 6% 2 6% 3 3 4 4 6% 9% 49%	3090
June	1st to 10th	Night	2 3 1 3 3 3 4 3 7% 11% 60%	1710
	11th to 20th	Night	3 3 1 3 3 3 3 5% 6% 8% 62%	1710
	21st to end	Night	4 5% 1 5% 4 3 5% 4 5% 10% 55%	1710
July	1st to 10th	Night	3 4 1 5% 4 3 4 3 6% 9% 57%	2850
	11th to 20th	Night	2 3 1 4 2 3 4 3 6% 8% 64%	2850
	21st to end	Night	4 7% 3 6% 4 4 3 3 7% 9% 48%	3098
August	1st to 10th	Night	1 1 1 2 2 2 2 2 4 7% 74%	3090
	11th to 20th	Night	3 2 1 4 2 3 3 4 7% 10% 62%	3113
	21st to end	Night	3 4 2 5% 4 4 5% 4 6% 10% 54%	3513
September	1st to 10th	Night	7% 5% 3 5% 4 4 3 3 5% 8% 53%	2090
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 7% 8% 48%	2090
	21st to end	Night	7% 4 2 4 4 3 4 4 6% 8% 53%	2090
October	1st to 10th	Night	5% 3 1 4 3 3 3 3 4 7% 64%	2090
	11th to 20th	Night	9% 4 2 5% 3 3 3 3 4 6% 58%	2109
	21st to end	Night	11% 5% 2 4 3 2 3 2 3 4 62%	2508
November	1st to 10th	Night	10% 7% 2 5% 3 2 3 2 5% 6% 56%	2394
	11th to 20th	Night	7% 6% 1 4 3 3 4 3 5% 6% 59%	2600
	21st to end	Night	13% 5% 2 6% 4 3 3 3 4 6% 51%	2600
December	1st to 10th	Night	11% 6% 2 5% 3 4 3 3 4 6% 53%	2581
	11th to 20th	Night	11% 8% 2 7% 4 4 3 4 4 5% 49%	3036
	21st to end	Night	12% 8% 2 4 2 2 2 2 3 5% 58%	4532

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	30% 4 3 16% 25% 22%	2848
	11th to 20th	Day	29% 3 6% 14% 31% 17%	2891
	21st to end	Day	35% 4 6% 14% 29% 12%	3487
February	1st to 10th	Day	35% 4 7% 13% 22% 19%	1900
	11th to 20th	Day	37% 4 6% 18% 19% 17%	1859
	21st to end	Day	32% 3 7% 16% 23% 19%	1570
March	1st to 10th	Day	38% 5% 6% 13% 20% 17%	3254
	11th to 20th	Day	47% 6% 8% 11% 17% 10%	3480
	21st to end	Day	32% 6% 9% 17% 20% 17%	3814
April	1st to 10th	Day	36% 5% 9% 17% 18% 15%	2090
	11th to 20th	Day	38% 5% 7% 16% 21% 13%	2219
	21st to end	Day	36% 5% 7% 20% 20% 12%	2329
May	1st to 10th	Day	44% 7% 10% 14% 17% 8%	4120
	11th to 20th	Day	38% 6% 8% 17% 21% 9%	4086
	21st to end	Day	35% 9% 11% 27% 13% 4	4489
June	1st to 10th	Day	28% 7% 12% 28% 22% 3	2470
	11th to 20th	Day	28% 8% 12% 26% 20% 6%	2470
	21st to end	Day	35% 9% 11% 22% 18% 5%	2470
July	1st to 10th	Day	31% 8% 15% 38% 7%	4056
	11th to 20th	Day	23% 7% 14% 35% 18% 3	4051
	21st to end	Day	30% 8% 17% 30% 13% 1	4325
August	1st to 10th	Day	14% 5% 10% 39% 30% 1	3817
	11th to 20th	Day	21% 5% 20% 39% 13% 2	3762
	21st to end	Day	28% 10% 16% 25% 19% 2	4150
September	1st to 10th	Day	39% 7% 9% 19% 18% 9%	2090
	11th to 20th	Day	39% 8% 10% 19% 18% 6%	2090
	21st to end	Day	33% 6% 10% 20% 19% 12%	2090
October	1st to 10th	Day	16% 5% 7% 13% 26% 34%	3480
	11th to 20th	Day	27% 3 6% 18% 22% 23%	3380
	21st to end	Day	24% 3 6% 16% 38% 13%	3428
November	1st to 10th	Day	35% 4 9% 19% 21% 12%	1899
	11th to 20th	Day	30% 5% 7% 18% 22% 19%	1800
	21st to end	Day	37% 3 5% 18% 23% 15%	1800
December	1st to 10th	Day	36% 4 7% 19% 25% 10%	1782
	11th to 20th	Day	36% 5% 8% 11% 23% 17%	2159
	21st to end	Day	30% 3 4 15% 28% 19%	3135
January	1st to 10th	Night	31% 3 4 13% 26% 22%	4108
	11th to 20th	Night	24% 2 4 18% 26% 26%	4106
	21st to end	Night	38% 4 5% 12% 27% 14%	4180
February	1st to 10th	Night	34% 5% 7% 13% 22% 20%	2280
	11th to 20th	Night	34% 4 7% 16% 21% 18%	2218
	21st to end	Night	35% 5% 7% 12% 23% 19%	1884
March	1st to 10th	Night	33% 8% 8% 14% 22% 14%	3591
	11th to 20th	Night	45% 7% 8% 12% 15% 12%	3480
	21st to end	Night	35% 6% 9% 17% 17% 17%	3817
April	1st to 10th	Night	32% 6% 9% 19% 16% 18%	2090
	11th to 20th	Night	36% 6% 9% 14% 18% 17%	1906
	21st to end	Night	34% 5% 9% 20% 20% 12%	1848
May	1st to 10th	Night	43% 8% 8% 18% 13% 10%	2850
	11th to 20th	Night	31% 8% 11% 22% 18% 10%	2824
	21st to end	Night	32% 9% 14% 28% 11% 6%	3099
June	1st to 10th	Night	17% 8% 18% 33% 21% 2	1710
	11th to 20th	Night	21% 6% 16% 28% 23% 6%	1710
	21st to end	Night	26% 7% 15% 28% 19% 4	1710
July	1st to 10th	Night	24% 8% 22% 39% 6% 1	2805
	11th to 20th	Night	19% 7% 17% 36% 19% 2	2796
	21st to end	Night	32% 7% 19% 30% 11%	2999
August	1st to 10th	Night	12% 4 14% 43% 26% 1	3080
	11th to 20th	Night	18% 6% 26% 38% 11% 2	3143
	21st to end	Night	26% 10% 20% 25% 18% 2	3513
September	1st to 10th	Night	31% 6% 13% 23% 19% 9%	2090
	11th to 20th	Night	33% 8% 15% 22% 16% 6%	2090
	21st to end	Night	29% 6% 11% 21% 19% 13%	2090
October	1st to 10th	Night	14% 3 8% 15% 22% 37%	3480
	11th to 20th	Night	23% 3 8% 16% 30% 20%	3491
	21st to end	Night	25% 2 5% 19% 34% 16%	4120
November	1st to 10th	Night	31% 4 8% 19% 23% 15%	2394
	11th to 20th	Night	27% 5% 7% 22% 21% 18%	2600
	21st to end	Night	36% 3 7% 16% 21% 16%	2600
December	1st to 10th	Night	33% 4 8% 18% 23% 13%	2581
	11th to 20th	Night	38% 4 5% 13% 19% 21%	3037
	21st to end	Night	32% 3 5% 15% 29% 18%	4532

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	17% 19% 41% 19% 5% 1	270
	11th to 20th	Day	22% 15% 34% 21% 7%	270
	21st to end	Day	14% 18% 41% 22% 5%	297
February	1st to 10th	Day	25% 14% 34% 20% 7%	270
	11th to 20th	Day	23% 16% 40% 17% 3 1	270
	21st to end	Day	21% 20% 40% 18% 2	225
March	1st to 10th	Day	18% 21% 43% 16% 2	270
	11th to 20th	Day	17% 23% 37% 17% 6%	270
	21st to end	Day	16% 20% 44% 16% 3 1	297
April	1st to 10th	Day	19% 22% 39% 18% 3	270
	11th to 20th	Day	16% 21% 41% 16% 5%	417
	21st to end	Day	16% 17% 44% 18% 5%	509
May	1st to 10th	Day	14% 13% 42% 25% 5%	653
	11th to 20th	Day	18% 9% 33% 30% 8% 1	675
	21st to end	Day	15% 9% 31% 34% 9% 1	734
June	1st to 10th	Day	6% 4 23% 43% 21% 4	680
	11th to 20th	Day	7% 3 23% 47% 18% 2	680
	21st to end	Day	6% 2 18% 40% 29% 5%	680
July	1st to 10th	Day	8% 2 12% 39% 31% 8%	671
	11th to 20th	Day	3 8% 43% 39% 7%	668
	21st to end	Day	4 1 8% 40% 37% 11%	739
August	1st to 10th	Day	2 1 4 41% 43% 10%	520
	11th to 20th	Day	8% 7% 35% 39% 12%	477
	21st to end	Day	5% 1 7% 35% 38% 14%	523
September	1st to 10th	Day	10% 1 9% 33% 33% 14%	300
	11th to 20th	Day	6% 7% 32% 42% 12%	300
	21st to end	Day	12% 1 7% 34% 36% 9%	300
October	1st to 10th	Day	6% 3 16% 38% 30% 7%	300
	11th to 20th	Day	9% 5% 25% 42% 16% 3	300
	21st to end	Day	16% 13% 28% 28% 12% 2	330
November	1st to 10th	Day	20% 7% 33% 28% 10% 3	300
	11th to 20th	Day	18% 11% 34% 22% 10% 5%	300
	21st to end	Day	21% 21% 30% 18% 6% 3	300
December	1st to 10th	Day	17% 13% 30% 30% 7% 2	294
	11th to 20th	Day	18% 17% 36% 21% 8%	270
	21st to end	Day	18% 15% 34% 26% 8%	297
January	1st to 10th	Night	15% 11% 36% 30% 8%	950
	11th to 20th	Night	17% 11% 37% 30% 5%	936
	21st to end	Night	17% 12% 35% 30% 6%	836
February	1st to 10th	Night	18% 16% 34% 27% 6%	760
	11th to 20th	Night	18% 15% 38% 27% 3	744
	21st to end	Night	17% 15% 47% 19% 1	628
March	1st to 10th	Night	15% 15% 41% 26% 3	682
	11th to 20th	Night	17% 11% 40% 29% 3	570
	21st to end	Night	13% 13% 50% 21% 3	627
April	1st to 10th	Night	10% 14% 50% 23% 3	570
	11th to 20th	Night	13% 20% 45% 20% 2	563
	21st to end	Night	15% 12% 47% 21% 4 1	570
May	1st to 10th	Night	12% 15% 46% 24% 3	570
	11th to 20th	Night	12% 9% 39% 32% 7%	561
	21st to end	Night	12% 8% 41% 29% 8% 1	617
June	1st to 10th	Night	3 2 29% 48% 16% 1	570
	11th to 20th	Night	4 3 39% 45% 9%	570
	21st to end	Night	6% 3 22% 46% 20% 2	570
July	1st to 10th	Night	7% 2 15% 48% 27% 2	555
	11th to 20th	Night	3 1 12% 56% 27% 2	552
	21st to end	Night	4 1 10% 56% 26% 3	624
August	1st to 10th	Night	1 1 10% 56% 31% 2	567
	11th to 20th	Night	5% 1 10% 50% 31% 3	564
	21st to end	Night	4 2 9% 43% 37% 4	627
September	1st to 10th	Night	9% 1 12% 42% 32% 3	570
	11th to 20th	Night	11% 1 9% 41% 35% 3	570
	21st to end	Night	9% 2 13% 44% 30% 2	570
October	1st to 10th	Night	6% 1 16% 47% 28% 2	570
	11th to 20th	Night	11% 5% 26% 41% 15% 2	589
	21st to end	Night	13% 10% 29% 29% 17% 2	836
November	1st to 10th	Night	14% 6% 27% 37% 14% 1	834
	11th to 20th	Night	10% 9% 33% 34% 13% 2	1000
	21st to end	Night	17% 10% 31% 30% 11% 1	1000
December	1st to 10th	Night	16% 8% 32% 36% 8% 1	993
	11th to 20th	Night	17% 12% 34% 31% 7%	950
	21st to end	Night	14% 12% 34% 33% 7%	1045

Page generated at 2024-12-06 02:54:53. Version ac07

Copyright © 2024 Attilla Danko.