Nameless Valley Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nameless Valley Ranch clear sky chart from 2005-11-06 to 2026-06-01.

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	12% 6% 2 5% 4 4 4 4 5% 7% 48%	132491
	Night	14% 6% 2 4 3 3 3 3 5% 6% 51%	131001
Transparency	Day	35% 4 10% 21% 20% 10%	136259
	Night	34% 3 10% 20% 21% 12%	135297
Seeing	Day	13% 10% 24% 30% 19% 4	16926
	Night	15% 8% 28% 34% 13% 1	26893

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	13% 8% 2 5% 3 4 3 3 4 5% 51%	5289
	11th to 20th	Day	13% 5% 2 4 3 2 3 3 5% 5% 56%	5310
	21st to end	Day	24% 8% 2 7% 4 3 3 2 3 5% 40%	6127
February	1st to 10th	Day	19% 6% 3 5% 3 4 3 2 3 5% 46%	2100
	11th to 20th	Day	17% 7% 2 5% 3 4 4 3 5% 6% 45%	2049
	21st to end	Day	19% 5% 2 4 3 2 3 3 3 4 52%	1730
March	1st to 10th	Day	14% 7% 2 5% 3 3 3 3 4 6% 50%	5014
	11th to 20th	Day	14% 7% 2 6% 3 3 3 3 4 5% 51%	5090
	21st to end	Day	13% 7% 3 5% 3 3 4 3 5% 6% 47%	5583
April	1st to 10th	Day	15% 8% 2 7% 4 3 4 3 5% 6% 42%	2310
	11th to 20th	Day	17% 8% 3 6% 4 4 4 3 4 5% 42%	2286
	21st to end	Day	15% 6% 2 5% 4 4 4 3 5% 6% 44%	2693
May	1st to 10th	Day	20% 7% 3 6% 4 4 5% 4 7% 7% 33%	5992
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 9% 45%	5992
	21st to end	Day	14% 7% 2 7% 5% 5% 6% 5% 7% 9% 35%	6577
June	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 6% 8% 51%	2601
	11th to 20th	Day	8% 4 2 4 4 4 5% 5% 8% 9% 49%	2600
	21st to end	Day	6% 5% 2 5% 5% 5% 5% 6% 8% 10% 43%	2600
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 6% 10% 39%	5900
	11th to 20th	Day	5% 4 2 5% 4 4 5% 5% 7% 12% 48%	5900
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 7% 11% 44%	6422
August	1st to 10th	Day	1 1 2 3 3 3 3 4 8% 72%	4234
	11th to 20th	Day	3 2 1 3 2 3 4 4 7% 10% 59%	3917
	21st to end	Day	4 3 1 5% 5% 5% 6% 5% 7% 11% 49%	4119
September	1st to 10th	Day	9% 5% 2 6% 5% 4 4 4 6% 7% 47%	2200
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 6% 7% 45%	2200
	21st to end	Day	6% 4 2 5% 4 4 5% 4 5% 8% 53%	2200
October	1st to 10th	Day	6% 4 1 4 3 4 3 3 5% 7% 60%	2200
	11th to 20th	Day	11% 4 2 4 3 3 3 3 4 5% 56%	2045
	21st to end	Day	11% 4 2 4 4 3 3 2 4 4 60%	2200
November	1st to 10th	Day	15% 7% 2 4 3 3 3 2 4 6% 50%	2058
	11th to 20th	Day	10% 5% 2 5% 4 3 3 3 4 5% 54%	1965
	21st to end	Day	17% 6% 3 6% 4 3 4 3 4 5% 47%	1890
December	1st to 10th	Day	21% 7% 2 6% 4 3 3 2 4 4 43%	3030
	11th to 20th	Day	17% 8% 2 6% 4 3 4 3 5% 5% 45%	3481
	21st to end	Day	15% 5% 1 4 2 2 2 2 3 4 58%	4587
January	1st to 10th	Night	15% 6% 2 4 3 2 3 2 3 5% 55%	7634
	11th to 20th	Night	10% 3 1 3 2 2 2 3 5% 5% 64%	7680
	21st to end	Night	27% 6% 2 6% 3 3 3 3 3 5% 39%	8132
February	1st to 10th	Night	18% 8% 2 4 2 3 3 2 3 5% 51%	2520
	11th to 20th	Night	19% 7% 2 4 3 3 3 2 4 5% 49%	2458
	21st to end	Night	19% 6% 2 4 3 3 3 2 3 4 50%	2076
March	1st to 10th	Night	16% 7% 2 5% 3 4 3 3 5% 7% 46%	5059
	11th to 20th	Night	14% 7% 2 5% 3 3 4 3 4 5% 51%	5090
	21st to end	Night	17% 9% 2 6% 3 3 3 2 4 6% 45%	5588
April	1st to 10th	Night	15% 6% 2 5% 3 4 3 3 5% 6% 47%	2310
	11th to 20th	Night	19% 6% 3 5% 4 3 3 4 4 6% 44%	2283
	21st to end	Night	18% 8% 2 5% 3 3 3 3 3 7% 45%	1919
May	1st to 10th	Night	23% 8% 2 6% 3 4 4 3 5% 7% 36%	4143
	11th to 20th	Night	9% 6% 3 5% 4 4 4 4 6% 7% 48%	4143
	21st to end	Night	14% 7% 2 7% 4 4 5% 4 6% 8% 38%	4542
June	1st to 10th	Night	4 4 1 3 3 3 3 4 6% 9% 59%	1800
	11th to 20th	Night	6% 3 1 3 3 3 4 3 7% 10% 57%	1800
	21st to end	Night	6% 5% 2 4 4 3 3 4 6% 9% 55%	1800
July	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 7% 9% 44%	4078
	11th to 20th	Night	3 3 1 4 3 3 4 4 7% 11% 56%	4077
	21st to end	Night	7% 5% 2 5% 3 4 5% 4 7% 10% 49%	4449
August	1st to 10th	Night	1 1 1 1 1 2 2 2 5% 8% 77%	2926
	11th to 20th	Night	3 2 1 3 2 3 3 3 6% 11% 62%	3137
	21st to end	Night	4 3 1 4 3 4 4 4 6% 11% 56%	3783
September	1st to 10th	Night	8% 5% 2 5% 4 4 4 4 6% 7% 51%	2200
	11th to 20th	Night	9% 6% 2 5% 4 4 5% 4 5% 8% 48%	2200
	21st to end	Night	8% 4 1 4 3 3 4 3 6% 8% 56%	2200
October	1st to 10th	Night	6% 3 1 3 4 3 2 3 4 6% 65%	2200
	11th to 20th	Night	12% 4 1 4 3 2 3 2 5% 6% 58%	2334
	21st to end	Night	14% 5% 1 3 2 3 2 3 3 4 60%	2640
November	1st to 10th	Night	15% 5% 2 5% 3 2 3 3 4 5% 55%	2460
	11th to 20th	Night	10% 4 2 4 3 3 3 3 5% 6% 58%	2651
	21st to end	Night	18% 6% 2 5% 3 3 4 3 4 5% 48%	2730
December	1st to 10th	Night	21% 7% 2 5% 3 3 4 3 4 5% 43%	4380
	11th to 20th	Night	21% 9% 2 4 3 2 3 2 3 4 47%	4946
	21st to end	Night	18% 6% 1 4 2 2 2 2 3 4 57%	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	37% 2 4 25% 23% 9%	5290
	11th to 20th	Day	32% 1 4 16% 28% 19%	5310
	21st to end	Day	49% 2 4 12% 22% 11%	6127
February	1st to 10th	Day	42% 3 5% 13% 22% 16%	2100
	11th to 20th	Day	41% 3 7% 18% 20% 12%	2059
	21st to end	Day	37% 3 5% 18% 22% 15%	1730
March	1st to 10th	Day	37% 2 4 18% 18% 20%	5014
	11th to 20th	Day	38% 2 6% 9% 16% 29%	5090
	21st to end	Day	39% 3 8% 20% 21% 8%	5585
April	1st to 10th	Day	43% 4 8% 18% 15% 13%	2310
	11th to 20th	Day	45% 3 7% 16% 18% 11%	2286
	21st to end	Day	41% 4 7% 21% 19% 8%	2693
May	1st to 10th	Day	48% 4 11% 19% 15% 4	6030
	11th to 20th	Day	38% 4 12% 17% 23% 7%	5996
	21st to end	Day	44% 5% 11% 24% 13% 3	6590
June	1st to 10th	Day	30% 5% 14% 29% 19% 3	2601
	11th to 20th	Day	29% 6% 13% 29% 19% 6%	2600
	21st to end	Day	34% 8% 12% 25% 19% 3	2600
July	1st to 10th	Day	40% 6% 19% 28% 6% 1	5836
	11th to 20th	Day	26% 7% 17% 32% 16% 2	5831
	21st to end	Day	31% 7% 17% 27% 15% 3	6240
August	1st to 10th	Day	13% 4 10% 40% 32% 1	4220
	11th to 20th	Day	19% 4 21% 40% 13% 3	3955
	21st to end	Day	26% 9% 18% 26% 19% 2	4118
September	1st to 10th	Day	36% 5% 10% 22% 17% 10%	2200
	11th to 20th	Day	37% 5% 12% 22% 18% 6%	2200
	21st to end	Day	29% 5% 9% 22% 21% 15%	2200
October	1st to 10th	Day	16% 3 6% 14% 25% 37%	3590
	11th to 20th	Day	20% 2 7% 20% 30% 21%	3311
	21st to end	Day	25% 2 5% 20% 34% 14%	3538
November	1st to 10th	Day	37% 3 7% 18% 23% 11%	2058
	11th to 20th	Day	33% 3 7% 19% 21% 16%	1965
	21st to end	Day	41% 3 5% 17% 20% 13%	1890
December	1st to 10th	Day	47% 1 7% 16% 21% 9%	3030
	11th to 20th	Day	42% 3 7% 13% 23% 13%	3479
	21st to end	Day	32% 2 5% 17% 28% 16%	4587
January	1st to 10th	Night	35% 2 4 20% 26% 13%	7635
	11th to 20th	Night	24% 1 3 18% 31% 23%	7680
	21st to end	Night	50% 2 3 11% 22% 13%	8132
February	1st to 10th	Night	38% 3 5% 14% 22% 18%	2520
	11th to 20th	Night	40% 3 6% 18% 19% 14%	2458
	21st to end	Night	40% 2 5% 14% 21% 17%	2076
March	1st to 10th	Night	40% 3 5% 17% 21% 14%	5059
	11th to 20th	Night	38% 2 8% 12% 14% 26%	5090
	21st to end	Night	43% 3 7% 17% 20% 10%	5588
April	1st to 10th	Night	38% 4 9% 18% 16% 15%	2310
	11th to 20th	Night	42% 4 9% 14% 17% 14%	2283
	21st to end	Night	41% 3 10% 19% 18% 9%	1919
May	1st to 10th	Night	48% 4 8% 20% 14% 6%	4170
	11th to 20th	Night	36% 3 11% 22% 18% 10%	4144
	21st to end	Night	43% 4 14% 26% 10% 4	4551
June	1st to 10th	Night	22% 5% 17% 30% 23% 3	1800
	11th to 20th	Night	23% 4 16% 30% 21% 6%	1800
	21st to end	Night	26% 6% 17% 29% 19% 4	1800
July	1st to 10th	Night	36% 8% 24% 27% 5% 1	4035
	11th to 20th	Night	21% 6% 22% 36% 13% 1	4026
	21st to end	Night	29% 7% 21% 26% 13% 4	4320
August	1st to 10th	Night	8% 3 13% 43% 31% 1	2916
	11th to 20th	Night	17% 5% 30% 34% 13% 2	3165
	21st to end	Night	22% 9% 21% 28% 18% 2	3783
September	1st to 10th	Night	30% 7% 13% 24% 18% 8%	2200
	11th to 20th	Night	34% 5% 15% 25% 15% 7%	2200
	21st to end	Night	26% 4 13% 25% 18% 13%	2200
October	1st to 10th	Night	15% 2 7% 16% 21% 40%	3590
	11th to 20th	Night	19% 3 8% 17% 32% 20%	3794
	21st to end	Night	25% 2 5% 19% 32% 17%	4252
November	1st to 10th	Night	33% 3 7% 18% 24% 14%	2460
	11th to 20th	Night	29% 3 8% 21% 22% 17%	2651
	21st to end	Night	39% 2 7% 17% 19% 15%	2730
December	1st to 10th	Night	45% 2 6% 17% 19% 10%	4380
	11th to 20th	Night	44% 2 5% 10% 23% 17%	4947
	21st to end	Night	34% 2 4 16% 28% 16%	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	21% 18% 34% 22% 4 1	330
	11th to 20th	Day	22% 17% 32% 22% 5% 1	330
	21st to end	Day	21% 22% 34% 18% 4	363
February	1st to 10th	Day	28% 13% 35% 20% 4	330
	11th to 20th	Day	25% 22% 36% 15% 3	330
	21st to end	Day	26% 23% 36% 14% 1	273
March	1st to 10th	Day	24% 21% 36% 16% 2	330
	11th to 20th	Day	18% 25% 37% 15% 5%	330
	21st to end	Day	14% 22% 40% 18% 5% 1	363
April	1st to 10th	Day	23% 20% 39% 14% 4	330
	11th to 20th	Day	20% 23% 34% 17% 5%	324
	21st to end	Day	21% 17% 38% 19% 6%	713
May	1st to 10th	Day	17% 14% 39% 24% 6%	753
	11th to 20th	Day	18% 10% 30% 30% 10% 2	775
	21st to end	Day	15% 9% 29% 33% 12% 2	844
June	1st to 10th	Day	6% 5% 20% 40% 24% 5%	731
	11th to 20th	Day	9% 2 21% 46% 18% 4	730
	21st to end	Day	6% 3 17% 37% 29% 8%	730
July	1st to 10th	Day	8% 3 11% 40% 29% 8%	721
	11th to 20th	Day	4 2 9% 40% 40% 5%	718
	21st to end	Day	5% 1 7% 38% 41% 8%	794
August	1st to 10th	Day	2 1 6% 40% 40% 10%	726
	11th to 20th	Day	5% 7% 43% 37% 9%	564
	21st to end	Day	6% 1 8% 31% 39% 15%	468
September	1st to 10th	Day	9% 2 9% 28% 39% 12%	330
	11th to 20th	Day	7% 1 11% 30% 42% 9%	330
	21st to end	Day	9% 2 9% 37% 33% 10%	330
October	1st to 10th	Day	3 3 17% 38% 32% 6%	330
	11th to 20th	Day	10% 7% 27% 34% 19% 4	330
	21st to end	Day	18% 13% 25% 27% 14% 2	363
November	1st to 10th	Day	21% 10% 28% 28% 9% 4	330
	11th to 20th	Day	14% 12% 33% 28% 9% 3	330
	21st to end	Day	22% 19% 34% 15% 9% 1	330
December	1st to 10th	Day	19% 12% 37% 21% 8% 3	330
	11th to 20th	Day	19% 16% 36% 21% 8%	330
	21st to end	Day	18% 13% 38% 23% 7% 1	363
January	1st to 10th	Night	19% 11% 33% 30% 6%	1050
	11th to 20th	Night	19% 14% 30% 30% 6%	1050
	21st to end	Night	22% 13% 32% 27% 6%	1065
February	1st to 10th	Night	24% 13% 31% 29% 4	840
	11th to 20th	Night	25% 15% 34% 23% 2	824
	21st to end	Night	24% 15% 40% 20% 1	692
March	1st to 10th	Night	24% 14% 36% 22% 3	647
	11th to 20th	Night	20% 13% 34% 28% 4	630
	21st to end	Night	18% 13% 44% 22% 3	693
April	1st to 10th	Night	17% 13% 41% 26% 2	630
	11th to 20th	Night	22% 14% 38% 22% 4	623
	21st to end	Night	20% 11% 41% 21% 7%	630
May	1st to 10th	Night	16% 12% 40% 27% 4	630
	11th to 20th	Night	13% 10% 35% 31% 10% 1	621
	21st to end	Night	14% 6% 36% 31% 12%	683
June	1st to 10th	Night	5% 3 26% 45% 19% 2	600
	11th to 20th	Night	7% 2 35% 44% 11% 1	600
	21st to end	Night	7% 3 20% 47% 22% 3	600
July	1st to 10th	Night	7% 2 16% 46% 25% 4	585
	11th to 20th	Night	4 1 13% 54% 25% 2	582
	21st to end	Night	4 1 15% 51% 26% 3	657
August	1st to 10th	Night	1 11% 57% 27% 4	597
	11th to 20th	Night	6% 1 11% 52% 28% 3	594
	21st to end	Night	5% 1 7% 49% 32% 5%	660
September	1st to 10th	Night	10% 1 11% 43% 31% 5%	600
	11th to 20th	Night	12% 1 10% 43% 31% 3	600
	21st to end	Night	10% 1 17% 35% 34% 2	600
October	1st to 10th	Night	7% 1 15% 46% 27% 4	600
	11th to 20th	Night	13% 4 24% 39% 18% 2	734
	21st to end	Night	15% 11% 27% 28% 18% 1	880
November	1st to 10th	Night	15% 5% 25% 38% 15% 1	820
	11th to 20th	Night	12% 10% 30% 35% 12% 1	971
	21st to end	Night	21% 11% 28% 29% 11% 1	1050
December	1st to 10th	Night	18% 11% 32% 31% 9%	1050
	11th to 20th	Night	22% 12% 30% 30% 6%	1050
	21st to end	Night	20% 11% 31% 31% 7%	1155

Page generated at 2026-05-29 00:53:27. Version ac07

Copyright © 2026 Attilla Danko.