Chechaquo Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chechaquo Ranch 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	6% 10% 3 7% 5% 5% 5% 4 6% 7% 43%	102160
	Night	6% 11% 3 7% 5% 4 5% 4 6% 8% 42%	96894
Transparency	Day	37% 11% 15% 19% 14% 5%	101925
	Night	38% 11% 16% 21% 12% 3	96775
Seeing	Day	14% 23% 34% 20% 7% 1	14734
	Night	12% 14% 38% 26% 9% 1	23183

By Month

Percentage Cloud Cover NW (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% 18% 8% 13% 6% 5% 5% 4 6% 6% 22%	2539
	11th to 20th	Day	7% 15% 5% 12% 4 4 4 3 5% 7% 34%	2516
	21st to end	Day	13% 25% 5% 10% 4 4 4 3 5% 6% 20%	2794
February	1st to 10th	Day	5% 13% 5% 9% 6% 6% 6% 5% 8% 9% 28%	1634
	11th to 20th	Day	4 12% 5% 10% 5% 4 6% 5% 6% 10% 34%	1665
	21st to end	Day	3 13% 5% 13% 8% 6% 7% 4 8% 9% 25%	1538
March	1st to 10th	Day	4 14% 7% 10% 5% 5% 6% 5% 6% 6% 32%	3138
	11th to 20th	Day	3 11% 4 6% 4 4 5% 4 6% 7% 45%	3393
	21st to end	Day	9% 16% 5% 8% 5% 5% 6% 4 7% 8% 28%	4069
April	1st to 10th	Day	8% 13% 3 9% 8% 7% 6% 5% 6% 9% 25%	2280
	11th to 20th	Day	5% 11% 4 9% 6% 6% 6% 5% 7% 9% 30%	2252
	21st to end	Day	5% 11% 3 7% 6% 7% 6% 6% 7% 9% 32%	2566
May	1st to 10th	Day	6% 8% 2 6% 5% 5% 5% 5% 7% 8% 44%	4420
	11th to 20th	Day	6% 8% 2 6% 4 4 5% 4 6% 9% 46%	4377
	21st to end	Day	12% 12% 3 9% 6% 6% 5% 4 6% 7% 30%	4813
June	1st to 10th	Day	11% 8% 2 8% 6% 6% 6% 5% 6% 7% 35%	2660
	11th to 20th	Day	8% 8% 3 8% 6% 6% 6% 5% 8% 8% 34%	2792
	21st to end	Day	6% 5% 2 6% 5% 5% 5% 4 7% 7% 47%	2850
July	1st to 10th	Day	2 3 1 3 3 2 3 3 4 5% 71%	4677
	11th to 20th	Day	3 2 1 3 3 2 3 3 4 5% 72%	4420
	21st to end	Day	2 3 1 3 3 3 3 3 5% 6% 68%	4790
August	1st to 10th	Day	2 2 1 4 3 4 4 3 6% 7% 64%	4401
	11th to 20th	Day	3 3 2 5% 5% 5% 5% 4 7% 7% 55%	4179
	21st to end	Day	6% 5% 2 6% 4 4 4 4 6% 6% 53%	4242
September	1st to 10th	Day	5% 4 2 4 3 3 3 3 5% 8% 60%	2280
	11th to 20th	Day	6% 6% 2 6% 5% 5% 5% 4 5% 7% 48%	2280
	21st to end	Day	9% 8% 1 5% 4 4 4 3 6% 6% 49%	2042
October	1st to 10th	Day	10% 7% 2 6% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Day	10% 7% 3 7% 5% 4 4 4 7% 8% 40%	1895
	21st to end	Day	11% 12% 3 7% 5% 4 5% 5% 5% 7% 37%	1881
November	1st to 10th	Day	11% 16% 3 7% 5% 4 5% 5% 7% 9% 28%	1598
	11th to 20th	Day	8% 16% 4 8% 6% 6% 4 4 6% 7% 31%	1520
	21st to end	Day	5% 14% 4 11% 7% 7% 5% 4 5% 8% 30%	1520
December	1st to 10th	Day	5% 13% 4 8% 6% 5% 4 5% 6% 7% 35%	1520
	11th to 20th	Day	6% 17% 5% 9% 5% 4 4 4 6% 7% 33%	1925
	21st to end	Day	7% 19% 8% 12% 5% 5% 5% 4 5% 6% 25%	2794
January	1st to 10th	Night	7% 18% 7% 13% 6% 5% 5% 4 5% 7% 22%	4406
	11th to 20th	Night	6% 17% 6% 10% 5% 4 4 4 6% 8% 30%	4382
	21st to end	Night	11% 26% 6% 9% 5% 5% 4 3 5% 6% 21%	4862
February	1st to 10th	Night	7% 14% 4 8% 6% 6% 5% 5% 7% 8% 29%	2542
	11th to 20th	Night	4 11% 3 7% 5% 4 5% 5% 8% 9% 39%	2402
	21st to end	Night	3 14% 4 10% 5% 6% 6% 6% 9% 9% 27%	1915
March	1st to 10th	Night	3 13% 6% 10% 5% 6% 5% 4 6% 9% 32%	3736
	11th to 20th	Night	3 10% 3 6% 4 4 4 4 5% 7% 51%	3582
	21st to end	Night	6% 14% 4 10% 6% 6% 6% 5% 6% 7% 30%	3583
April	1st to 10th	Night	5% 10% 3 7% 6% 5% 6% 6% 8% 10% 35%	1900
	11th to 20th	Night	4 8% 4 6% 6% 4 5% 5% 7% 7% 42%	1879
	21st to end	Night	5% 7% 2 6% 5% 5% 6% 4 6% 9% 44%	1609
May	1st to 10th	Night	6% 6% 2 6% 4 4 5% 3 6% 7% 51%	2540
	11th to 20th	Night	5% 4 1 4 4 4 4 3 5% 9% 57%	2516
	21st to end	Night	6% 6% 2 5% 4 5% 6% 4 8% 10% 43%	2762
June	1st to 10th	Night	8% 7% 2 5% 5% 6% 5% 5% 8% 9% 41%	1520
	11th to 20th	Night	5% 4 2 4 5% 5% 6% 5% 8% 10% 47%	1382
	21st to end	Night	4 3 1 3 4 4 5% 4 6% 9% 57%	1330
July	1st to 10th	Night	2 2 2 1 2 3 2 4 6% 77%	2279
	11th to 20th	Night	2 1 2 2 2 3 2 3 5% 78%	2540
	21st to end	Night	2 1 2 2 2 2 3 4 6% 75%	2762
August	1st to 10th	Night	1 2 1 3 4 3 4 3 4 6% 69%	2529
	11th to 20th	Night	2 2 1 3 2 3 3 3 5% 9% 67%	2650
	21st to end	Night	5% 3 1 3 3 4 5% 3 6% 7% 61%	3434
September	1st to 10th	Night	3 2 1 4 3 3 4 3 5% 6% 65%	1900
	11th to 20th	Night	6% 4 1 4 3 4 4 4 6% 7% 56%	1900
	21st to end	Night	7% 5% 2 5% 4 3 4 4 7% 10% 49%	2134
October	1st to 10th	Night	8% 6% 2 5% 5% 3 4 4 6% 8% 49%	2280
	11th to 20th	Night	9% 7% 3 6% 5% 4 5% 4 6% 8% 43%	2285
	21st to end	Night	11% 10% 2 6% 4 5% 4 4 7% 8% 39%	2717
November	1st to 10th	Night	12% 17% 4 6% 4 4 5% 4 7% 7% 30%	2514
	11th to 20th	Night	8% 14% 3 8% 5% 5% 6% 5% 6% 8% 32%	2660
	21st to end	Night	6% 16% 5% 10% 6% 5% 5% 5% 7% 8% 30%	2660
December	1st to 10th	Night	7% 14% 4 8% 5% 5% 5% 4 6% 9% 33%	2660
	11th to 20th	Night	8% 18% 6% 10% 6% 5% 5% 5% 6% 7% 24%	3280
	21st to end	Night	9% 21% 6% 11% 5% 4 4 4 5% 6% 25%	4862

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	59% 12% 12% 11% 5% 1	2539
	11th to 20th	Day	52% 8% 14% 17% 6% 3	2540
	21st to end	Day	64% 9% 11% 10% 5%	2794
February	1st to 10th	Day	49% 15% 18% 13% 4 1	1634
	11th to 20th	Day	43% 15% 18% 15% 8% 1	1674
	21st to end	Day	50% 15% 14% 14% 7%	1538
March	1st to 10th	Day	47% 14% 11% 12% 12% 4	3138
	11th to 20th	Day	34% 11% 17% 33% 4	3393
	21st to end	Day	50% 16% 14% 13% 7% 1	4069
April	1st to 10th	Day	50% 14% 18% 14% 4	2280
	11th to 20th	Day	47% 14% 15% 14% 8% 2	2252
	21st to end	Day	42% 14% 17% 17% 8% 1	2566
May	1st to 10th	Day	33% 12% 15% 20% 18% 1	4420
	11th to 20th	Day	31% 11% 23% 25% 10%	4380
	21st to end	Day	50% 14% 15% 19% 3	4814
June	1st to 10th	Day	45% 10% 14% 17% 11% 3	2660
	11th to 20th	Day	41% 13% 19% 17% 9% 1	2792
	21st to end	Day	31% 11% 17% 24% 15% 2	2850
July	1st to 10th	Day	16% 6% 9% 16% 29% 24%	4604
	11th to 20th	Day	15% 4 7% 14% 27% 32%	4345
	21st to end	Day	15% 4 11% 26% 29% 14%	4639
August	1st to 10th	Day	16% 7% 10% 25% 32% 10%	4384
	11th to 20th	Day	20% 9% 19% 31% 16% 3	4221
	21st to end	Day	28% 8% 16% 24% 20% 4	4241
September	1st to 10th	Day	22% 7% 14% 29% 22% 5%	2280
	11th to 20th	Day	32% 9% 12% 21% 21% 5%	2280
	21st to end	Day	33% 8% 18% 21% 16% 3	2042
October	1st to 10th	Day	37% 8% 15% 27% 12% 1	1900
	11th to 20th	Day	38% 13% 14% 21% 13% 1	1895
	21st to end	Day	43% 12% 13% 21% 11%	1881
November	1st to 10th	Day	49% 13% 15% 15% 8% 1	1598
	11th to 20th	Day	51% 12% 15% 13% 7% 1	1520
	21st to end	Day	50% 12% 15% 13% 7% 3	1520
December	1st to 10th	Day	46% 13% 14% 16% 10%	1520
	11th to 20th	Day	50% 11% 19% 14% 6%	1928
	21st to end	Day	59% 11% 11% 12% 7%	2794
January	1st to 10th	Night	59% 11% 12% 12% 5% 1	4406
	11th to 20th	Night	49% 12% 13% 15% 9% 3	4420
	21st to end	Night	65% 8% 11% 10% 5% 1	4862
February	1st to 10th	Night	49% 13% 16% 14% 6% 1	2542
	11th to 20th	Night	40% 14% 18% 19% 9% 1	2404
	21st to end	Night	47% 15% 14% 15% 8%	1915
March	1st to 10th	Night	43% 13% 15% 12% 13% 4	3736
	11th to 20th	Night	30% 11% 21% 33% 6%	3583
	21st to end	Night	48% 15% 18% 15% 3	3583
April	1st to 10th	Night	39% 15% 21% 19% 6%	1900
	11th to 20th	Night	36% 12% 19% 20% 11% 1	1879
	21st to end	Night	33% 12% 20% 24% 10%	1609
May	1st to 10th	Night	28% 10% 16% 28% 18%	2540
	11th to 20th	Night	21% 12% 25% 32% 9% 1	2516
	21st to end	Night	28% 19% 26% 23% 4	2762
June	1st to 10th	Night	35% 11% 19% 20% 13% 2	1520
	11th to 20th	Night	28% 12% 22% 24% 12% 1	1382
	21st to end	Night	21% 11% 22% 30% 15% 2	1330
July	1st to 10th	Night	11% 5% 9% 24% 29% 21%	2243
	11th to 20th	Night	10% 4 9% 20% 32% 25%	2492
	21st to end	Night	10% 5% 13% 27% 29% 16%	2674
August	1st to 10th	Night	14% 7% 12% 27% 31% 9%	2521
	11th to 20th	Night	13% 7% 24% 38% 15% 3	2674
	21st to end	Night	19% 8% 18% 32% 20% 2	3434
September	1st to 10th	Night	18% 7% 15% 33% 23% 4	1900
	11th to 20th	Night	25% 8% 13% 29% 22% 3	1900
	21st to end	Night	29% 9% 19% 27% 14% 4	2134
October	1st to 10th	Night	33% 9% 14% 29% 13% 1	2280
	11th to 20th	Night	38% 11% 15% 24% 12%	2285
	21st to end	Night	41% 10% 15% 22% 12%	2717
November	1st to 10th	Night	48% 13% 16% 14% 8% 1	2514
	11th to 20th	Night	47% 14% 15% 16% 6% 2	2660
	21st to end	Night	49% 13% 14% 13% 7% 2	2660
December	1st to 10th	Night	48% 11% 16% 17% 8%	2660
	11th to 20th	Night	57% 12% 14% 11% 5% 1	3276
	21st to end	Night	58% 10% 11% 13% 7% 1	4862

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	22% 23% 26% 18% 9% 3	180
	11th to 20th	Day	17% 18% 32% 21% 9% 3	180
	21st to end	Day	21% 19% 35% 16% 9%	198
February	1st to 10th	Day	18% 31% 37% 10% 4	294
	11th to 20th	Day	21% 24% 37% 14% 4 1	365
	21st to end	Day	13% 28% 38% 18% 3	368
March	1st to 10th	Day	18% 30% 32% 15% 4 1	460
	11th to 20th	Day	17% 28% 29% 18% 8% 1	460
	21st to end	Day	21% 28% 32% 15% 2	506
April	1st to 10th	Day	22% 29% 32% 12% 4	460
	11th to 20th	Day	18% 33% 27% 17% 4 1	452
	21st to end	Day	15% 31% 32% 14% 6% 2	460
May	1st to 10th	Day	12% 25% 37% 21% 5% 1	463
	11th to 20th	Day	20% 19% 29% 22% 8% 2	488
	21st to end	Day	18% 23% 31% 20% 6% 2	529
June	1st to 10th	Day	17% 23% 36% 18% 6%	490
	11th to 20th	Day	17% 27% 35% 16% 4 1	622
	21st to end	Day	10% 24% 37% 21% 7% 1	680
July	1st to 10th	Day	7% 23% 36% 27% 6%	635
	11th to 20th	Day	8% 17% 36% 29% 8% 2	484
	21st to end	Day	5% 17% 37% 30% 10% 2	531
August	1st to 10th	Day	7% 14% 38% 28% 11% 2	487
	11th to 20th	Day	4 14% 34% 34% 13% 2	477
	21st to end	Day	7% 22% 36% 25% 7% 1	539
September	1st to 10th	Day	9% 21% 39% 22% 9% 2	490
	11th to 20th	Day	12% 21% 34% 23% 9% 1	490
	21st to end	Day	16% 24% 33% 20% 6% 1	490
October	1st to 10th	Day	13% 23% 34% 21% 9% 1	490
	11th to 20th	Day	16% 27% 27% 20% 8% 2	485
	21st to end	Day	20% 22% 35% 16% 6% 2	330
November	1st to 10th	Day	17% 28% 33% 16% 5%	233
	11th to 20th	Day	18% 23% 31% 16% 9% 3	180
	21st to end	Day	21% 12% 38% 17% 9% 4	180
December	1st to 10th	Day	18% 16% 28% 19% 15% 4	180
	11th to 20th	Day	11% 22% 38% 23% 6% 1	180
	21st to end	Day	9% 21% 40% 22% 9% 1	198
January	1st to 10th	Night	17% 18% 36% 20% 8% 1	760
	11th to 20th	Night	16% 15% 41% 19% 8% 1	760
	21st to end	Night	15% 13% 38% 26% 8%	836
February	1st to 10th	Night	15% 19% 42% 19% 5% 1	760
	11th to 20th	Night	11% 16% 41% 25% 7%	744
	21st to end	Night	15% 15% 38% 22% 10%	628
March	1st to 10th	Night	11% 17% 38% 27% 8% 1	760
	11th to 20th	Night	12% 16% 39% 23% 10%	760
	21st to end	Night	13% 14% 43% 25% 5% 1	836
April	1st to 10th	Night	9% 16% 41% 25% 8% 1	760
	11th to 20th	Night	8% 20% 40% 24% 7% 2	751
	21st to end	Night	10% 18% 42% 22% 7% 1	469
May	1st to 10th	Night	9% 14% 39% 31% 6%	380
	11th to 20th	Night	11% 12% 32% 33% 11%	374
	21st to end	Night	12% 12% 36% 30% 9%	411
June	1st to 10th	Night	12% 14% 39% 27% 8%	380
	11th to 20th	Night	8% 18% 40% 29% 5%	380
	21st to end	Night	6% 10% 39% 34% 11%	380
July	1st to 10th	Night	4 10% 40% 36% 10%	370
	11th to 20th	Night	3 11% 42% 36% 8%	368
	21st to end	Night	1 10% 34% 42% 13%	416
August	1st to 10th	Night	4 7% 30% 41% 17%	378
	11th to 20th	Night	2 7% 33% 38% 18% 2	464
	21st to end	Night	5% 13% 33% 34% 14% 1	798
September	1st to 10th	Night	5% 11% 37% 29% 16% 2	760
	11th to 20th	Night	7% 12% 27% 30% 20% 5%	760
	21st to end	Night	11% 11% 32% 29% 14% 3	760
October	1st to 10th	Night	12% 12% 33% 31% 12% 1	760
	11th to 20th	Night	14% 14% 37% 23% 12% 1	760
	21st to end	Night	18% 17% 34% 22% 7% 2	836
November	1st to 10th	Night	20% 17% 39% 20% 4	748
	11th to 20th	Night	20% 15% 38% 18% 8% 1	760
	21st to end	Night	16% 13% 39% 20% 9% 3	760
December	1st to 10th	Night	15% 12% 40% 24% 8% 2	760
	11th to 20th	Night	16% 15% 43% 23% 2 1	760
	21st to end	Night	15% 16% 43% 21% 4	836

Page generated at 2024-10-30 10:19:22. Version ac07

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