Red Rock Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Rock Farm clear sky chart from 2005-11-06 to 2026-08-15.

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	9% 5% 2 5% 4 3 4 3 5% 7% 52%	143628
	Night	9% 5% 2 4 3 3 3 3 5% 7% 57%	138642
Transparency	Day	32% 3 10% 26% 23% 7%	147332
	Night	28% 3 9% 25% 26% 9%	143005
Seeing	Day	12% 9% 27% 29% 18% 5%	17815
	Night	12% 10% 32% 33% 13% 1	27596

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	10% 6% 3 6% 3 4 4 3 4 6% 51%	5289
	11th to 20th	Day	5% 5% 2 5% 2 2 3 2 3 4 67%	5310
	21st to end	Day	15% 8% 3 5% 3 2 2 2 3 5% 52%	5812
February	1st to 10th	Day	13% 9% 3 6% 4 4 3 2 4 6% 48%	1967
	11th to 20th	Day	13% 7% 2 5% 3 4 4 3 4 6% 49%	2049
	21st to end	Day	13% 7% 2 6% 3 3 3 2 4 5% 52%	1730
March	1st to 10th	Day	10% 7% 3 5% 3 3 3 2 4 6% 55%	4996
	11th to 20th	Day	7% 5% 2 6% 3 3 3 3 4 7% 55%	5090
	21st to end	Day	13% 10% 2 6% 4 4 3 3 5% 7% 43%	5583
April	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 4 6% 52%	2310
	11th to 20th	Day	12% 5% 2 6% 4 4 4 2 5% 6% 48%	2466
	21st to end	Day	16% 7% 3 5% 5% 3 3 3 4 5% 45%	2730
May	1st to 10th	Day	15% 8% 3 6% 4 3 4 3 5% 6% 43%	7617
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 7% 49%	7627
	21st to end	Day	14% 7% 3 8% 5% 5% 5% 4 6% 7% 37%	8392
June	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 6% 9% 48%	2730
	11th to 20th	Day	6% 5% 2 5% 4 4 5% 4 5% 7% 53%	2730
	21st to end	Day	4 4 1 4 4 3 4 4 6% 8% 58%	2730
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 7% 10% 46%	7680
	11th to 20th	Day	4 3 2 5% 4 4 4 4 6% 10% 53%	7680
	21st to end	Day	3 2 1 4 3 3 4 3 6% 9% 62%	8337
August	1st to 10th	Day	4 3 1 5% 4 4 4 3 5% 9% 59%	4364
	11th to 20th	Day	6% 3 1 4 3 4 4 4 6% 10% 56%	4224
	21st to end	Day	4 3 1 4 4 3 4 3 5% 8% 61%	4356
September	1st to 10th	Day	10% 4 2 4 3 4 3 3 6% 6% 55%	2200
	11th to 20th	Day	11% 4 2 6% 3 3 4 4 5% 7% 50%	2200
	21st to end	Day	8% 4 2 4 2 3 4 3 5% 7% 59%	2200
October	1st to 10th	Day	8% 4 1 5% 3 3 3 2 4 6% 62%	2149
	11th to 20th	Day	9% 4 1 4 2 2 3 2 3 5% 66%	2000
	21st to end	Day	13% 5% 2 4 3 3 2 2 4 5% 58%	2200
November	1st to 10th	Day	10% 4 2 4 3 2 2 3 5% 6% 60%	2002
	11th to 20th	Day	8% 4 2 2 4 3 3 3 3 5% 64%	1890
	21st to end	Day	12% 5% 2 4 3 2 2 2 4 5% 58%	1890
December	1st to 10th	Day	6% 7% 2 5% 3 2 3 3 5% 7% 55%	3030
	11th to 20th	Day	11% 5% 2 5% 3 3 3 2 5% 6% 56%	3481
	21st to end	Day	17% 9% 2 6% 3 3 3 3 4 5% 45%	4587
January	1st to 10th	Night	12% 6% 2 6% 3 3 3 3 5% 6% 50%	7634
	11th to 20th	Night	4 3 1 3 2 2 3 3 3 6% 71%	7680
	21st to end	Night	16% 8% 2 5% 3 3 3 2 4 5% 48%	8402
February	1st to 10th	Night	12% 7% 2 5% 4 3 3 3 3 4 53%	2671
	11th to 20th	Night	12% 9% 2 5% 3 3 3 3 4 6% 52%	2458
	21st to end	Night	11% 7% 2 5% 3 3 3 2 4 5% 54%	2076
March	1st to 10th	Night	12% 6% 2 6% 3 3 3 2 4 6% 54%	5079
	11th to 20th	Night	7% 4 1 3 3 2 3 3 4 6% 64%	5090
	21st to end	Night	11% 7% 2 4 4 3 4 4 5% 8% 48%	5588
April	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 5% 6% 55%	2310
	11th to 20th	Night	13% 5% 2 4 3 3 4 3 4 7% 54%	2099
	21st to end	Night	13% 5% 2 5% 3 4 4 4 4 6% 52%	1890
May	1st to 10th	Night	14% 7% 2 5% 4 4 4 3 5% 7% 46%	5266
	11th to 20th	Night	9% 4 2 4 3 3 4 3 6% 9% 53%	5265
	21st to end	Night	12% 6% 2 5% 4 4 4 4 6% 8% 45%	5793
June	1st to 10th	Night	6% 3 1 4 3 3 4 2 6% 12% 56%	1890
	11th to 20th	Night	5% 4 2 4 4 2 3 4 5% 9% 58%	1890
	21st to end	Night	3 2 1 3 2 3 3 3 6% 10% 66%	1890
July	1st to 10th	Night	4 3 1 5% 4 4 5% 4 7% 11% 51%	5308
	11th to 20th	Night	2 2 1 4 3 4 4 4 6% 10% 61%	5307
	21st to end	Night	2 2 1 2 2 2 2 2 5% 10% 70%	5770
August	1st to 10th	Night	2 1 1 3 2 3 3 3 5% 9% 67%	3016
	11th to 20th	Night	4 2 1 3 4 4 5% 4 6% 9% 59%	2924
	21st to end	Night	3 2 1 3 2 3 3 3 5% 9% 65%	3544
September	1st to 10th	Night	8% 5% 2 5% 3 3 4 3 4 5% 60%	2200
	11th to 20th	Night	9% 5% 2 6% 4 3 4 3 4 7% 53%	2200
	21st to end	Night	7% 4 2 5% 2 3 3 3 5% 6% 62%	2200
October	1st to 10th	Night	6% 3 1 4 3 3 4 3 4 7% 63%	2230
	11th to 20th	Night	9% 4 1 4 3 3 3 2 3 4 65%	2400
	21st to end	Night	13% 5% 2 3 2 2 2 2 3 4 61%	2640
November	1st to 10th	Night	8% 4 1 4 2 3 2 2 3 5% 65%	2513
	11th to 20th	Night	7% 5% 2 5% 4 2 3 2 3 5% 63%	2730
	21st to end	Night	12% 6% 1 3 3 2 3 2 4 6% 57%	2730
December	1st to 10th	Night	7% 5% 2 4 3 2 2 2 4 6% 62%	4380
	11th to 20th	Night	11% 5% 2 5% 4 3 3 2 3 4 58%	4946
	21st to end	Night	16% 8% 2 4 3 3 3 2 4 4 51%	6633

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	36% 1 7% 29% 24% 4	5290
	11th to 20th	Day	24% 1 7% 20% 40% 7%	5310
	21st to end	Day	38% 1 4 22% 28% 7%	5812
February	1st to 10th	Day	40% 2 8% 23% 23% 5%	1967
	11th to 20th	Day	37% 3 7% 28% 20% 6%	2059
	21st to end	Day	37% 2 5% 17% 28% 11%	1730
March	1st to 10th	Day	33% 2 5% 17% 21% 22%	4996
	11th to 20th	Day	32% 2 7% 20% 22% 18%	5090
	21st to end	Day	42% 2 9% 27% 17% 3	5585
April	1st to 10th	Day	34% 4 10% 24% 22% 7%	2310
	11th to 20th	Day	38% 3 8% 23% 21% 7%	2466
	21st to end	Day	42% 3 9% 25% 18% 4	2730
May	1st to 10th	Day	43% 3 11% 20% 19% 5%	7655
	11th to 20th	Day	35% 3 11% 25% 20% 6%	7631
	21st to end	Day	46% 4 12% 19% 13% 5%	8405
June	1st to 10th	Day	33% 5% 17% 27% 16% 3	2730
	11th to 20th	Day	30% 5% 13% 29% 21% 3	2730
	21st to end	Day	23% 5% 17% 28% 23% 5%	2730
July	1st to 10th	Day	33% 6% 13% 29% 17% 2	7616
	11th to 20th	Day	26% 6% 17% 28% 21% 3	7611
	21st to end	Day	18% 4 13% 41% 23% 1	8155
August	1st to 10th	Day	24% 4 10% 27% 25% 10%	4350
	11th to 20th	Day	25% 4 16% 34% 18% 3	4263
	21st to end	Day	21% 5% 12% 44% 15% 3	4355
September	1st to 10th	Day	29% 3 9% 25% 24% 10%	2200
	11th to 20th	Day	32% 5% 9% 25% 23% 6%	2200
	21st to end	Day	26% 3 8% 26% 30% 7%	2200
October	1st to 10th	Day	17% 2 6% 13% 45% 17%	3500
	11th to 20th	Day	18% 2 5% 25% 34% 16%	3240
	21st to end	Day	24% 2 7% 29% 30% 9%	3538
November	1st to 10th	Day	26% 2 7% 24% 31% 10%	2002
	11th to 20th	Day	25% 2 7% 26% 29% 11%	1890
	21st to end	Day	30% 2 6% 27% 27% 9%	1890
December	1st to 10th	Day	29% 2 8% 35% 23% 2	3030
	11th to 20th	Day	31% 2 4 24% 30% 9%	3479
	21st to end	Day	43% 2 5% 25% 20% 5%	4587
January	1st to 10th	Night	36% 2 6% 28% 24% 4	7635
	11th to 20th	Night	18% 2 10% 20% 37% 13%	7680
	21st to end	Night	41% 1 6% 16% 28% 8%	8402
February	1st to 10th	Night	37% 2 8% 22% 24% 7%	2671
	11th to 20th	Night	36% 3 6% 25% 23% 7%	2458
	21st to end	Night	34% 2 5% 19% 27% 13%	2076
March	1st to 10th	Night	34% 2 4 17% 25% 18%	5079
	11th to 20th	Night	23% 1 5% 25% 21% 25%	5090
	21st to end	Night	35% 3 11% 25% 23% 3	5588
April	1st to 10th	Night	31% 3 9% 23% 22% 13%	2310
	11th to 20th	Night	31% 4 11% 23% 20% 11%	2099
	21st to end	Night	34% 4 11% 25% 22% 4	1890
May	1st to 10th	Night	39% 3 12% 21% 19% 6%	5293
	11th to 20th	Night	29% 3 13% 27% 20% 8%	5266
	21st to end	Night	37% 5% 15% 20% 17% 6%	5805
June	1st to 10th	Night	23% 4 18% 31% 20% 3	1890
	11th to 20th	Night	23% 4 17% 29% 22% 5%	1890
	21st to end	Night	16% 4 15% 29% 29% 7%	1890
July	1st to 10th	Night	26% 5% 16% 32% 18% 3	5265
	11th to 20th	Night	19% 5% 16% 33% 23% 4	5256
	21st to end	Night	13% 2 13% 41% 29% 2	5641
August	1st to 10th	Night	15% 3 12% 27% 34% 9%	3006
	11th to 20th	Night	22% 4 11% 35% 24% 4	2951
	21st to end	Night	17% 4 13% 42% 20% 5%	3544
September	1st to 10th	Night	27% 3 8% 25% 25% 12%	2200
	11th to 20th	Night	32% 4 8% 22% 26% 9%	2200
	21st to end	Night	24% 3 6% 26% 31% 10%	2200
October	1st to 10th	Night	15% 2 7% 14% 39% 23%	3646
	11th to 20th	Night	17% 2 4 19% 39% 19%	3899
	21st to end	Night	23% 2 5% 28% 32% 10%	4252
November	1st to 10th	Night	24% 2 7% 23% 32% 12%	2513
	11th to 20th	Night	26% 2 6% 25% 29% 11%	2730
	21st to end	Night	31% 2 7% 22% 28% 10%	2730
December	1st to 10th	Night	25% 2 6% 36% 26% 5%	4380
	11th to 20th	Night	32% 2 4 22% 31% 10%	4947
	21st to end	Night	38% 2 5% 26% 22% 7%	6633

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	18% 15% 39% 23% 5%	330
	11th to 20th	Day	17% 21% 37% 22% 2 1	330
	21st to end	Day	14% 15% 42% 21% 7% 1	363
February	1st to 10th	Day	18% 17% 43% 18% 3 1	330
	11th to 20th	Day	18% 23% 42% 16% 1	330
	21st to end	Day	20% 18% 42% 16% 4	273
March	1st to 10th	Day	17% 22% 37% 19% 4 1	330
	11th to 20th	Day	20% 19% 40% 16% 4 1	330
	21st to end	Day	20% 19% 40% 15% 6%	363
April	1st to 10th	Day	17% 22% 31% 25% 5% 1	330
	11th to 20th	Day	16% 23% 40% 18% 3	504
	21st to end	Day	20% 15% 35% 21% 7% 2	750
May	1st to 10th	Day	13% 14% 38% 29% 6%	753
	11th to 20th	Day	16% 11% 32% 25% 13% 2	775
	21st to end	Day	14% 7% 32% 27% 16% 4	844
June	1st to 10th	Day	10% 6% 20% 34% 24% 6%	780
	11th to 20th	Day	7% 3 26% 40% 19% 4	780
	21st to end	Day	4 2 22% 42% 23% 6%	780
July	1st to 10th	Day	6% 2 12% 34% 34% 12%	771
	11th to 20th	Day	3 1 12% 41% 34% 9%	768
	21st to end	Day	5% 7% 35% 40% 13%	849
August	1st to 10th	Day	5% 2 10% 40% 35% 7%	776
	11th to 20th	Day	7% 2 11% 39% 33% 8%	736
	21st to end	Day	5% 1 8% 35% 36% 14%	614
September	1st to 10th	Day	9% 1 10% 33% 31% 16%	330
	11th to 20th	Day	7% 2 13% 35% 33% 11%	330
	21st to end	Day	13% 4 17% 33% 26% 7%	330
October	1st to 10th	Day	7% 5% 27% 35% 19% 6%	330
	11th to 20th	Day	9% 12% 33% 34% 11% 2	330
	21st to end	Day	24% 11% 29% 22% 11% 2	363
November	1st to 10th	Day	15% 10% 39% 25% 9% 2	330
	11th to 20th	Day	12% 14% 35% 27% 9% 2	330
	21st to end	Day	18% 15% 37% 21% 8% 1	330
December	1st to 10th	Day	12% 16% 40% 23% 7% 1	330
	11th to 20th	Day	17% 15% 37% 23% 8%	330
	21st to end	Day	18% 17% 38% 22% 4	363
January	1st to 10th	Night	13% 14% 39% 27% 6%	1050
	11th to 20th	Night	13% 16% 38% 29% 5%	1050
	21st to end	Night	13% 13% 39% 29% 5% 1	1155
February	1st to 10th	Night	16% 14% 43% 24% 3	991
	11th to 20th	Night	17% 20% 37% 23% 4	824
	21st to end	Night	16% 16% 41% 23% 3	692
March	1st to 10th	Night	15% 16% 34% 32% 3	656
	11th to 20th	Night	18% 15% 38% 25% 4	630
	21st to end	Night	16% 14% 43% 22% 5%	693
April	1st to 10th	Night	15% 14% 43% 23% 5%	630
	11th to 20th	Night	15% 15% 41% 25% 4	623
	21st to end	Night	15% 13% 40% 26% 7%	630
May	1st to 10th	Night	11% 12% 39% 30% 7%	630
	11th to 20th	Night	12% 9% 35% 30% 13% 1	621
	21st to end	Night	10% 5% 33% 33% 16% 2	683
June	1st to 10th	Night	7% 5% 24% 40% 22% 2	630
	11th to 20th	Night	7% 3 28% 49% 13% 1	630
	21st to end	Night	3 1 26% 48% 19% 3	630
July	1st to 10th	Night	5% 1 14% 45% 32% 3	615
	11th to 20th	Night	3 1 12% 52% 31% 2	612
	21st to end	Night	3 1 8% 50% 35% 2	690
August	1st to 10th	Night	3 13% 53% 29% 2	627
	11th to 20th	Night	4 1 14% 46% 33% 2	606
	21st to end	Night	4 1 9% 44% 37% 5%	660
September	1st to 10th	Night	9% 2 12% 45% 29% 3	600
	11th to 20th	Night	11% 2 19% 37% 27% 4	600
	21st to end	Night	9% 3 20% 44% 21% 5%	600
October	1st to 10th	Night	7% 4 28% 37% 20% 3	630
	11th to 20th	Night	11% 8% 34% 35% 12% 1	800
	21st to end	Night	16% 10% 31% 31% 11% 1	880
November	1st to 10th	Night	10% 7% 37% 34% 11% 1	873
	11th to 20th	Night	10% 12% 36% 33% 9% 1	1050
	21st to end	Night	16% 13% 36% 27% 8% 1	1050
December	1st to 10th	Night	12% 14% 38% 30% 6%	1050
	11th to 20th	Night	18% 11% 37% 28% 6%	1050
	21st to end	Night	15% 13% 37% 30% 5%	1155

Page generated at 2026-08-12 02:37:14. Version ac07

Copyright © 2026 Attilla Danko.