Little Ranch Observatory
Clear Sky Chart
History

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

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 3 4 4 6% 8% 55%	105199
	Night	6% 6% 2 6% 4 4 4 3 5% 7% 52%	102670
Transparency	Day	27% 5% 13% 27% 21% 7%	104940
	Night	30% 5% 13% 26% 19% 6%	102519
Seeing	Day	9% 7% 30% 30% 18% 5%	15775
	Night	9% 8% 38% 36% 9%	25732

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 5% 2 8% 5% 4 4 3 5% 6% 56%	2538
	11th to 20th	Day	4 7% 3 9% 6% 4 5% 5% 7% 7% 45%	2540
	21st to end	Day	3 5% 2 4 3 3 3 3 4 7% 63%	2893
February	1st to 10th	Day	4 8% 4 9% 5% 4 6% 5% 6% 7% 43%	1773
	11th to 20th	Day	5% 7% 2 7% 5% 5% 4 3 5% 7% 49%	1849
	21st to end	Day	3 10% 3 5% 4 4 4 4 4 6% 52%	1570
March	1st to 10th	Day	7% 9% 3 4 3 4 4 2 6% 7% 52%	3130
	11th to 20th	Day	7% 7% 2 4 3 3 3 3 4 5% 59%	3244
	21st to end	Day	7% 8% 2 7% 5% 5% 4 4 6% 8% 44%	4165
April	1st to 10th	Day	9% 7% 2 5% 4 3 4 3 5% 7% 50%	2280
	11th to 20th	Day	13% 7% 2 7% 4 4 4 3 6% 8% 43%	2251
	21st to end	Day	11% 6% 2 7% 4 4 4 4 5% 8% 44%	2378
May	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 8% 45%	4120
	11th to 20th	Day	10% 5% 2 5% 3 4 5% 4 6% 9% 48%	4233
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	4825
June	1st to 10th	Day	6% 3 1 3 3 4 4 5% 7% 8% 55%	2660
	11th to 20th	Day	7% 4 2 4 4 4 4 4 7% 7% 54%	2660
	21st to end	Day	3 3 1 4 2 4 4 3 6% 10% 60%	2660
July	1st to 10th	Day	7% 4 1 4 3 3 4 4 5% 7% 58%	4430
	11th to 20th	Day	2 2 1 3 3 4 4 5% 8% 11% 58%	4430
	21st to end	Day	2 2 1 3 3 3 4 4 7% 11% 60%	4802
August	1st to 10th	Day	11% 4 1 4 3 3 4 4 7% 10% 50%	4288
	11th to 20th	Day	5% 4 2 5% 3 3 4 4 6% 8% 56%	3726
	21st to end	Day	4 3 1 4 3 3 4 4 6% 8% 61%	4180
September	1st to 10th	Day	6% 4 2 4 3 3 3 3 5% 5% 63%	2280
	11th to 20th	Day	7% 3 1 3 3 3 3 3 4 6% 64%	2170
	21st to end	Day	8% 3 1 3 2 2 2 3 4 7% 64%	2090
October	1st to 10th	Day	6% 3 1 2 1 2 2 1 3 4 74%	3419
	11th to 20th	Day	5% 4 1 5% 4 3 3 2 4 7% 62%	3129
	21st to end	Day	7% 7% 2 5% 3 3 3 3 4 6% 56%	3091
November	1st to 10th	Day	5% 5% 1 4 3 2 4 3 6% 8% 59%	1763
	11th to 20th	Day	4 5% 2 4 3 3 3 3 5% 7% 62%	1710
	21st to end	Day	5% 7% 2 5% 4 3 3 3 4 6% 58%	1682
December	1st to 10th	Day	5% 7% 2 6% 3 3 4 4 6% 8% 52%	1520
	11th to 20th	Day	3 6% 2 4 4 4 3 4 5% 8% 58%	1926
	21st to end	Day	5% 8% 3 7% 5% 5% 5% 4 5% 6% 47%	2794
January	1st to 10th	Night	3 7% 3 8% 5% 3 4 3 5% 7% 53%	4417
	11th to 20th	Night	2 7% 3 7% 4 4 4 3 6% 7% 52%	4430
	21st to end	Night	3 5% 2 7% 4 4 5% 3 6% 7% 55%	4805
February	1st to 10th	Night	4 10% 4 8% 5% 5% 4 3 6% 7% 45%	2405
	11th to 20th	Night	4 8% 3 6% 5% 4 5% 4 6% 7% 47%	2218
	21st to end	Night	4 9% 3 7% 3 4 4 3 5% 6% 52%	1884
March	1st to 10th	Night	7% 11% 3 6% 3 3 3 3 5% 5% 51%	3734
	11th to 20th	Night	8% 9% 2 6% 4 3 3 3 4 6% 54%	3722
	21st to end	Night	7% 8% 3 7% 4 4 5% 4 6% 9% 43%	3477
April	1st to 10th	Night	11% 8% 3 6% 5% 3 3 4 6% 7% 45%	1900
	11th to 20th	Night	11% 7% 3 6% 4 4 3 3 5% 6% 48%	1877
	21st to end	Night	14% 8% 3 6% 4 4 5% 3 5% 6% 42%	1800
May	1st to 10th	Night	12% 6% 2 8% 4 4 5% 4 7% 9% 39%	2850
	11th to 20th	Night	10% 4 1 5% 3 4 4 4 8% 9% 47%	2657
	21st to end	Night	14% 6% 2 6% 4 4 5% 4 5% 7% 43%	2762
June	1st to 10th	Night	8% 4 2 4 4 3 5% 5% 6% 10% 49%	1520
	11th to 20th	Night	8% 4 2 4 3 5% 4 4 7% 9% 50%	1520
	21st to end	Night	6% 3 2 5% 6% 5% 4 5% 8% 9% 48%	1520
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 4 6% 7% 51%	2540
	11th to 20th	Night	3 2 1 3 4 4 5% 5% 8% 11% 54%	2540
	21st to end	Night	4 3 2 4 5% 5% 4 4 6% 9% 54%	2761
August	1st to 10th	Night	12% 6% 2 6% 5% 6% 5% 5% 6% 9% 40%	2651
	11th to 20th	Night	6% 6% 2 7% 4 4 5% 5% 7% 8% 46%	3108
	21st to end	Night	3 3 2 5% 4 5% 5% 4 7% 9% 52%	3487
September	1st to 10th	Night	8% 4 1 4 3 4 3 3 5% 8% 58%	1900
	11th to 20th	Night	6% 4 2 4 3 3 4 2 5% 7% 60%	2009
	21st to end	Night	7% 5% 1 4 3 3 4 3 4 6% 61%	2090
October	1st to 10th	Night	7% 3 1 3 2 1 2 2 3 4 74%	3539
	11th to 20th	Night	8% 4 1 3 2 2 3 2 5% 6% 63%	3778
	21st to end	Night	6% 5% 2 5% 3 3 3 3 5% 6% 58%	4457
November	1st to 10th	Night	5% 5% 2 5% 3 4 3 3 6% 7% 57%	2535
	11th to 20th	Night	5% 5% 2 5% 3 4 3 3 5% 7% 57%	2477
	21st to end	Night	5% 7% 2 4 4 3 4 3 5% 6% 57%	2496
December	1st to 10th	Night	5% 7% 2 7% 4 3 4 3 5% 6% 55%	2660
	11th to 20th	Night	4 5% 2 4 3 3 4 4 6% 9% 56%	3271
	21st to end	Night	6% 8% 4 8% 5% 4 4 3 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	29% 4 12% 30% 23% 2	2539
	11th to 20th	Day	36% 5% 18% 20% 18% 2	2540
	21st to end	Day	21% 5% 20% 34% 16% 3	2893
February	1st to 10th	Day	38% 6% 15% 24% 15% 3	1773
	11th to 20th	Day	34% 4 11% 27% 19% 5%	1859
	21st to end	Day	32% 5% 12% 26% 18% 6%	1570
March	1st to 10th	Day	31% 3 9% 24% 28% 5%	3130
	11th to 20th	Day	28% 4 16% 30% 20% 3	3244
	21st to end	Day	35% 8% 16% 31% 9% 1	4165
April	1st to 10th	Day	34% 5% 14% 26% 16% 5%	2280
	11th to 20th	Day	38% 6% 14% 21% 17% 4	2254
	21st to end	Day	37% 5% 11% 27% 18% 2	2378
May	1st to 10th	Day	34% 7% 16% 23% 14% 6%	4120
	11th to 20th	Day	30% 8% 15% 31% 15% 1	4237
	21st to end	Day	31% 8% 18% 28% 14% 2	4825
June	1st to 10th	Day	23% 8% 19% 32% 14% 4	2660
	11th to 20th	Day	26% 7% 11% 27% 22% 7%	2660
	21st to end	Day	19% 5% 12% 29% 26% 8%	2660
July	1st to 10th	Day	26% 4 8% 22% 29% 11%	4361
	11th to 20th	Day	19% 4 12% 29% 25% 11%	4355
	21st to end	Day	18% 5% 11% 25% 24% 17%	4651
August	1st to 10th	Day	30% 5% 14% 28% 19% 5%	4273
	11th to 20th	Day	26% 6% 13% 23% 25% 8%	3762
	21st to end	Day	22% 3 12% 23% 24% 16%	4179
September	1st to 10th	Day	23% 4 8% 24% 27% 14%	2280
	11th to 20th	Day	21% 5% 8% 24% 30% 13%	2170
	21st to end	Day	22% 4 7% 25% 33% 9%	2090
October	1st to 10th	Day	17% 2 6% 20% 33% 22%	3419
	11th to 20th	Day	25% 2 9% 35% 22% 7%	3129
	21st to end	Day	30% 2 11% 27% 24% 6%	3091
November	1st to 10th	Day	22% 5% 14% 28% 23% 8%	1763
	11th to 20th	Day	23% 3 11% 31% 28% 5%	1710
	21st to end	Day	26% 4 10% 30% 24% 6%	1682
December	1st to 10th	Day	29% 5% 14% 27% 21% 4	1520
	11th to 20th	Day	24% 5% 13% 34% 22% 2	1924
	21st to end	Day	36% 7% 9% 31% 15% 3	2794
January	1st to 10th	Night	30% 5% 12% 33% 18% 2	4417
	11th to 20th	Night	31% 4 17% 24% 19% 4	4430
	21st to end	Night	27% 7% 16% 33% 15% 2	4805
February	1st to 10th	Night	38% 5% 14% 24% 16% 3	2405
	11th to 20th	Night	35% 5% 14% 28% 16% 4	2218
	21st to end	Night	31% 4 11% 25% 22% 7%	1884
March	1st to 10th	Night	33% 5% 8% 20% 27% 6%	3734
	11th to 20th	Night	33% 4 12% 27% 22% 3	3722
	21st to end	Night	34% 9% 22% 25% 8% 1	3477
April	1st to 10th	Night	36% 8% 13% 20% 17% 6%	1900
	11th to 20th	Night	37% 5% 14% 25% 15% 4	1877
	21st to end	Night	40% 8% 9% 26% 16% 1	1800
May	1st to 10th	Night	38% 8% 19% 20% 12% 4	2850
	11th to 20th	Night	30% 10% 17% 31% 8% 3	2658
	21st to end	Night	38% 9% 16% 26% 10% 3	2762
June	1st to 10th	Night	29% 9% 24% 25% 11% 2	1520
	11th to 20th	Night	28% 9% 16% 25% 15% 7%	1520
	21st to end	Night	29% 8% 13% 24% 21% 4	1520
July	1st to 10th	Night	31% 5% 12% 22% 26% 4	2500
	11th to 20th	Night	23% 5% 18% 25% 22% 8%	2492
	21st to end	Night	26% 5% 16% 22% 18% 13%	2674
August	1st to 10th	Night	40% 5% 17% 21% 15% 2	2643
	11th to 20th	Night	35% 6% 14% 23% 18% 5%	3138
	21st to end	Night	28% 4 16% 20% 21% 11%	3487
September	1st to 10th	Night	26% 5% 9% 23% 26% 12%	1900
	11th to 20th	Night	24% 5% 9% 26% 23% 13%	2009
	21st to end	Night	25% 4 7% 27% 26% 11%	2090
October	1st to 10th	Night	17% 2 6% 19% 30% 25%	3539
	11th to 20th	Night	23% 3 9% 31% 25% 7%	3778
	21st to end	Night	28% 3 10% 29% 23% 8%	4457
November	1st to 10th	Night	25% 4 14% 26% 23% 7%	2535
	11th to 20th	Night	26% 4 12% 28% 23% 8%	2477
	21st to end	Night	27% 5% 10% 28% 24% 7%	2496
December	1st to 10th	Night	29% 4 14% 29% 19% 5%	2660
	11th to 20th	Night	24% 4 14% 35% 20% 3	3272
	21st to end	Night	36% 5% 11% 31% 15% 2	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	7% 10% 38% 29% 15% 2	270
	11th to 20th	Day	9% 13% 39% 32% 8%	270
	21st to end	Day	8% 11% 52% 19% 7% 3	297
February	1st to 10th	Day	8% 11% 55% 23% 3	270
	11th to 20th	Day	10% 11% 49% 22% 7% 1	270
	21st to end	Day	10% 18% 45% 22% 4	225
March	1st to 10th	Day	8% 14% 37% 27% 12% 2	270
	11th to 20th	Day	11% 8% 32% 31% 15% 3	278
	21st to end	Day	13% 11% 41% 25% 8% 2	506
April	1st to 10th	Day	13% 17% 37% 25% 7% 1	460
	11th to 20th	Day	18% 14% 34% 23% 8% 2	452
	21st to end	Day	13% 13% 32% 27% 14% 2	558
May	1st to 10th	Day	16% 10% 31% 25% 14% 4	653
	11th to 20th	Day	18% 6% 25% 31% 15% 4	675
	21st to end	Day	12% 9% 28% 29% 18% 4	734
June	1st to 10th	Day	8% 5% 23% 31% 26% 8%	680
	11th to 20th	Day	7% 6% 33% 30% 19% 4	680
	21st to end	Day	4 4 29% 35% 23% 6%	680
July	1st to 10th	Day	8% 2 19% 36% 28% 7%	671
	11th to 20th	Day	4 2 16% 39% 32% 7%	668
	21st to end	Day	5% 2 16% 36% 33% 9%	739
August	1st to 10th	Day	7% 1 16% 37% 33% 6%	676
	11th to 20th	Day	4 3 23% 36% 25% 9%	477
	21st to end	Day	5% 2 21% 35% 27% 10%	539
September	1st to 10th	Day	7% 2 21% 36% 24% 10%	490
	11th to 20th	Day	5% 2 20% 32% 30% 11%	380
	21st to end	Day	10% 3 26% 27% 23% 11%	300
October	1st to 10th	Day	12% 6% 26% 24% 21% 11%	300
	11th to 20th	Day	8% 10% 34% 30% 13% 6%	300
	21st to end	Day	11% 12% 38% 25% 12% 2	330
November	1st to 10th	Day	7% 8% 44% 26% 11% 4	300
	11th to 20th	Day	7% 12% 40% 27% 13% 1	270
	21st to end	Day	10% 7% 39% 31% 11% 1	270
December	1st to 10th	Day	7% 11% 45% 26% 11%	270
	11th to 20th	Day	8% 11% 47% 27% 7%	270
	21st to end	Day	11% 15% 48% 19% 6% 1	297
January	1st to 10th	Night	5% 12% 42% 31% 8% 1	950
	11th to 20th	Night	6% 15% 43% 30% 5%	950
	21st to end	Night	7% 11% 48% 29% 5%	1003
February	1st to 10th	Night	9% 11% 51% 26% 4	760
	11th to 20th	Night	7% 11% 51% 25% 6%	744
	21st to end	Night	8% 9% 53% 27% 3	628
March	1st to 10th	Night	10% 10% 44% 31% 5%	760
	11th to 20th	Night	11% 7% 42% 32% 8%	729
	21st to end	Night	12% 10% 40% 33% 5%	627
April	1st to 10th	Night	12% 13% 40% 31% 4	570
	11th to 20th	Night	15% 11% 40% 31% 3	563
	21st to end	Night	17% 13% 29% 35% 6%	570
May	1st to 10th	Night	15% 10% 33% 34% 8% 1	570
	11th to 20th	Night	18% 5% 29% 37% 11%	561
	21st to end	Night	15% 10% 34% 30% 11%	617
June	1st to 10th	Night	9% 5% 32% 38% 15% 1	570
	11th to 20th	Night	9% 5% 39% 40% 6%	570
	21st to end	Night	5% 5% 28% 49% 11% 1	570
July	1st to 10th	Night	8% 3 26% 45% 17% 1	555
	11th to 20th	Night	5% 1 23% 55% 15%	552
	21st to end	Night	4 1 23% 50% 20%	624
August	1st to 10th	Night	8% 2 18% 54% 17% 1	567
	11th to 20th	Night	7% 2 27% 51% 13%	564
	21st to end	Night	5% 1 24% 55% 15%	627
September	1st to 10th	Night	9% 3 28% 44% 14% 1	570
	11th to 20th	Night	9% 3 28% 42% 16% 2	570
	21st to end	Night	11% 4 29% 44% 13%	570
October	1st to 10th	Night	14% 6% 29% 35% 15% 1	603
	11th to 20th	Night	9% 8% 36% 36% 11%	760
	21st to end	Night	11% 8% 37% 35% 9% 1	1035
November	1st to 10th	Night	8% 5% 42% 37% 7% 1	975
	11th to 20th	Night	8% 12% 42% 32% 6% 1	953
	21st to end	Night	8% 10% 38% 35% 8% 1	950
December	1st to 10th	Night	8% 11% 48% 27% 5% 1	950
	11th to 20th	Night	7% 8% 48% 30% 6%	950
	21st to end	Night	10% 13% 43% 30% 4	1045

Page generated at 2024-11-08 04:44:49. Version ac07

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