Carranza Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carranza Field clear sky chart from 2005-11-06 to 2025-11-03.

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	16% 7% 2 6% 4 4 4 4 5% 7% 41%	126738
	Night	16% 7% 2 6% 4 4 4 3 5% 6% 43%	123292
Transparency	Day	41% 5% 11% 23% 17% 3	130266
	Night	40% 4 11% 23% 18% 4	127838
Seeing	Day	19% 14% 29% 23% 11% 3	16365
	Night	19% 11% 31% 29% 10% 1	25570

By Month

Percentage Cloud Cover NE (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% 7% 2 4 3 3 3 3 4 5% 51%	3597
	11th to 20th	Day	14% 7% 2 8% 5% 4 3 3 4 5% 45%	3598
	21st to end	Day	19% 9% 2 6% 3 3 4 2 4 5% 42%	4466
February	1st to 10th	Day	14% 9% 3 6% 4 4 4 3 6% 7% 40%	1803
	11th to 20th	Day	18% 7% 3 5% 3 4 4 4 5% 6% 41%	1948
	21st to end	Day	17% 9% 3 7% 4 4 3 3 4 6% 41%	1650
March	1st to 10th	Day	21% 6% 1 4 3 3 3 3 4 5% 47%	4476
	11th to 20th	Day	12% 7% 2 6% 4 4 4 3 5% 6% 46%	4883
	21st to end	Day	18% 6% 2 6% 4 3 4 3 5% 5% 44%	5868
April	1st to 10th	Day	18% 7% 2 6% 5% 4 4 3 5% 7% 40%	2400
	11th to 20th	Day	15% 5% 3 5% 4 4 4 3 6% 8% 42%	2374
	21st to end	Day	16% 6% 3 6% 4 3 4 4 6% 8% 41%	2400
May	1st to 10th	Day	25% 8% 2 6% 4 5% 4 4 6% 8% 29%	5789
	11th to 20th	Day	26% 8% 3 6% 4 4 3 2 4 6% 34%	6265
	21st to end	Day	20% 6% 2 6% 4 4 4 3 6% 8% 36%	6949
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 5% 6% 9% 40%	2800
	11th to 20th	Day	14% 5% 2 6% 4 5% 5% 4 6% 8% 40%	2800
	21st to end	Day	10% 5% 2 7% 4 5% 5% 5% 7% 8% 41%	2800
July	1st to 10th	Day	9% 6% 2 6% 5% 6% 6% 5% 7% 10% 36%	6360
	11th to 20th	Day	12% 7% 3 7% 6% 6% 7% 5% 8% 10% 30%	6360
	21st to end	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 9% 38%	6893
August	1st to 10th	Day	18% 7% 3 7% 5% 5% 5% 4 7% 8% 31%	4152
	11th to 20th	Day	13% 6% 2 6% 5% 5% 6% 4 7% 10% 37%	3850
	21st to end	Day	10% 5% 2 5% 4 4 5% 5% 8% 9% 44%	4312
September	1st to 10th	Day	14% 6% 2 5% 4 5% 4 4 5% 6% 44%	2400
	11th to 20th	Day	13% 6% 1 6% 4 3 4 4 4 8% 48%	2337
	21st to end	Day	19% 7% 3 7% 5% 4 5% 3 5% 6% 38%	2200
October	1st to 10th	Day	18% 6% 2 6% 4 3 3 3 5% 6% 45%	2055
	11th to 20th	Day	17% 6% 1 4 3 2 3 3 4 7% 50%	2000
	21st to end	Day	17% 6% 2 5% 3 3 4 3 4 7% 47%	2098
November	1st to 10th	Day	14% 5% 1 4 4 3 3 2 4 7% 53%	1779
	11th to 20th	Day	15% 6% 2 5% 4 3 3 3 5% 6% 48%	1800
	21st to end	Day	15% 5% 2 5% 3 5% 4 4 4 6% 47%	1730
December	1st to 10th	Day	13% 6% 2 5% 3 3 4 4 5% 7% 47%	2600
	11th to 20th	Day	21% 9% 2 5% 3 2 3 2 3 4 46%	2986
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 6% 8% 42%	3960
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 4 5% 52%	6349
	11th to 20th	Night	16% 7% 2 5% 3 3 3 2 4 5% 49%	6270
	21st to end	Night	17% 8% 2 6% 4 4 4 3 4 6% 43%	6490
February	1st to 10th	Night	17% 8% 3 5% 3 3 4 3 5% 6% 41%	2595
	11th to 20th	Night	19% 8% 2 5% 4 4 3 3 5% 5% 42%	2338
	21st to end	Night	18% 7% 2 6% 4 3 4 3 4 6% 43%	1980
March	1st to 10th	Night	19% 9% 2 5% 3 3 2 2 4 5% 46%	5364
	11th to 20th	Night	13% 10% 3 5% 4 3 4 2 4 5% 48%	5073
	21st to end	Night	16% 8% 2 6% 4 4 3 3 4 5% 44%	5064
April	1st to 10th	Night	18% 7% 2 7% 4 4 4 3 5% 5% 41%	2000
	11th to 20th	Night	15% 8% 3 7% 4 3 4 2 5% 6% 43%	1975
	21st to end	Night	17% 6% 2 5% 3 4 4 3 6% 7% 43%	2000
May	1st to 10th	Night	21% 9% 3 8% 4 4 4 4 5% 9% 29%	4151
	11th to 20th	Night	23% 9% 2 6% 4 4 4 3 6% 6% 33%	3670
	21st to end	Night	21% 7% 2 6% 4 4 3 3 4 8% 37%	3926
June	1st to 10th	Night	14% 6% 2 6% 4 4 5% 4 6% 9% 41%	1600
	11th to 20th	Night	11% 7% 2 7% 5% 5% 5% 4 6% 8% 41%	1600
	21st to end	Night	9% 5% 3 4 5% 5% 5% 5% 7% 11% 41%	1600
July	1st to 10th	Night	9% 7% 3 9% 6% 6% 5% 5% 7% 9% 35%	3600
	11th to 20th	Night	12% 9% 3 8% 5% 5% 5% 5% 7% 10% 32%	3600
	21st to end	Night	12% 6% 3 7% 5% 4 5% 3 6% 9% 41%	3942
August	1st to 10th	Night	21% 7% 3 6% 4 4 5% 4 6% 8% 32%	2966
	11th to 20th	Night	12% 7% 2 6% 4 4 4 4 5% 7% 44%	3197
	21st to end	Night	9% 5% 2 5% 4 4 4 3 5% 7% 52%	3586
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 4 7% 46%	2000
	11th to 20th	Night	11% 5% 2 4 4 3 3 3 4 8% 52%	2062
	21st to end	Night	20% 7% 2 6% 3 3 3 4 5% 7% 40%	2200
October	1st to 10th	Night	18% 6% 2 5% 3 4 4 3 4 6% 46%	2341
	11th to 20th	Night	17% 5% 2 4 3 3 3 2 4 6% 51%	2400
	21st to end	Night	16% 6% 2 5% 3 3 3 3 4 6% 48%	2740
November	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 5% 7% 52%	2564
	11th to 20th	Night	16% 7% 2 6% 3 3 3 3 4 6% 48%	2600
	21st to end	Night	13% 6% 2 5% 5% 3 4 4 6% 6% 46%	2665
December	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 49%	4580
	11th to 20th	Night	22% 6% 2 5% 3 3 3 3 4 6% 42%	5208
	21st to end	Night	18% 7% 3 6% 4 4 4 3 5% 5% 42%	6996

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	35% 3 8% 26% 26% 3	3598
	11th to 20th	Day	42% 3 7% 24% 17% 6%	3628
	21st to end	Day	47% 2 9% 26% 13% 3	4466
February	1st to 10th	Day	43% 4 13% 26% 14% 2	1803
	11th to 20th	Day	45% 4 8% 24% 16% 3	1957
	21st to end	Day	46% 3 8% 23% 15% 5%	1650
March	1st to 10th	Day	40% 3 8% 24% 17% 7%	4479
	11th to 20th	Day	37% 4 8% 28% 17% 5%	4883
	21st to end	Day	42% 4 8% 17% 23% 7%	5868
April	1st to 10th	Day	44% 4 10% 20% 16% 6%	2400
	11th to 20th	Day	40% 4 13% 23% 17% 4	2374
	21st to end	Day	41% 4 10% 21% 19% 5%	2400
May	1st to 10th	Day	52% 5% 15% 18% 9% 1	5800
	11th to 20th	Day	52% 4 10% 22% 12% 1	6269
	21st to end	Day	44% 6% 10% 23% 15% 1	6949
June	1st to 10th	Day	41% 7% 13% 22% 16% 2	2800
	11th to 20th	Day	40% 7% 13% 25% 12% 3	2800
	21st to end	Day	38% 7% 13% 22% 17% 2	2800
July	1st to 10th	Day	39% 10% 16% 21% 13% 1	6290
	11th to 20th	Day	45% 9% 18% 19% 8% 1	6285
	21st to end	Day	39% 8% 11% 22% 19% 1	6695
August	1st to 10th	Day	47% 8% 15% 21% 9% 1	4139
	11th to 20th	Day	40% 7% 13% 26% 12% 1	3886
	21st to end	Day	31% 7% 13% 29% 18% 2	4312
September	1st to 10th	Day	38% 5% 14% 19% 21% 3	2400
	11th to 20th	Day	35% 4 9% 26% 23% 4	2337
	21st to end	Day	48% 4 9% 18% 19% 3	2200
October	1st to 10th	Day	35% 4 9% 19% 28% 5%	3341
	11th to 20th	Day	25% 3 8% 25% 30% 9%	3240
	21st to end	Day	26% 3 12% 27% 26% 6%	3362
November	1st to 10th	Day	34% 3 12% 28% 20% 4	1779
	11th to 20th	Day	37% 3 10% 23% 24% 3	1800
	21st to end	Day	38% 3 11% 31% 14% 3	1730
December	1st to 10th	Day	35% 5% 16% 26% 16% 2	2600
	11th to 20th	Day	44% 2 10% 29% 11% 3	2986
	21st to end	Day	40% 4 13% 23% 18% 2	3960
January	1st to 10th	Night	36% 2 7% 25% 22% 7%	6349
	11th to 20th	Night	39% 3 8% 24% 18% 7%	6315
	21st to end	Night	43% 3 9% 24% 19% 3	6490
February	1st to 10th	Night	44% 3 14% 24% 14% 2	2595
	11th to 20th	Night	44% 4 8% 21% 18% 6%	2340
	21st to end	Night	43% 2 8% 23% 17% 6%	1980
March	1st to 10th	Night	42% 3 8% 24% 13% 10%	5374
	11th to 20th	Night	40% 4 12% 24% 15% 5%	5074
	21st to end	Night	43% 4 7% 17% 24% 5%	5064
April	1st to 10th	Night	46% 3 8% 19% 18% 5%	2000
	11th to 20th	Night	44% 3 9% 21% 20% 4	1975
	21st to end	Night	40% 5% 9% 20% 21% 5%	2000
May	1st to 10th	Night	53% 5% 12% 17% 10% 2	4157
	11th to 20th	Night	51% 4 11% 19% 13% 1	3671
	21st to end	Night	47% 5% 11% 20% 15% 2	3927
June	1st to 10th	Night	40% 7% 11% 22% 19% 2	1600
	11th to 20th	Night	41% 6% 13% 26% 13% 2	1600
	21st to end	Night	35% 7% 17% 24% 16% 2	1600
July	1st to 10th	Night	44% 9% 14% 20% 11% 1	3560
	11th to 20th	Night	45% 9% 18% 20% 7% 1	3552
	21st to end	Night	38% 7% 14% 22% 17% 1	3825
August	1st to 10th	Night	49% 6% 17% 18% 9% 1	2955
	11th to 20th	Night	38% 5% 13% 31% 11% 1	3227
	21st to end	Night	31% 5% 12% 29% 21% 2	3586
September	1st to 10th	Night	39% 4 13% 20% 20% 3	2000
	11th to 20th	Night	32% 4 11% 26% 24% 3	2062
	21st to end	Night	44% 5% 8% 22% 18% 2	2200
October	1st to 10th	Night	37% 4 10% 24% 22% 3	3835
	11th to 20th	Night	25% 3 10% 25% 30% 7%	3899
	21st to end	Night	26% 3 11% 31% 25% 4	4413
November	1st to 10th	Night	32% 4 12% 25% 21% 6%	2564
	11th to 20th	Night	40% 3 8% 22% 22% 5%	2600
	21st to end	Night	37% 3 12% 26% 19% 2	2665
December	1st to 10th	Night	36% 3 12% 29% 16% 3	4580
	11th to 20th	Night	44% 3 11% 24% 15% 4	5208
	21st to end	Night	44% 4 11% 20% 18% 3	6996

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	25% 22% 36% 13% 4 1	200
	11th to 20th	Day	27% 30% 29% 13% 2	207
	21st to end	Day	25% 25% 30% 14% 4 1	330
February	1st to 10th	Day	25% 25% 35% 11% 3	303
	11th to 20th	Day	30% 24% 32% 12% 2	496
	21st to end	Day	26% 23% 33% 14% 3	414
March	1st to 10th	Day	24% 25% 29% 19% 3	500
	11th to 20th	Day	19% 28% 33% 13% 4 2	500
	21st to end	Day	24% 21% 33% 16% 5%	550
April	1st to 10th	Day	26% 23% 31% 15% 5% 1	500
	11th to 20th	Day	20% 20% 35% 17% 7% 1	492
	21st to end	Day	24% 16% 35% 17% 6% 2	500
May	1st to 10th	Day	28% 17% 31% 16% 6% 2	503
	11th to 20th	Day	23% 15% 32% 21% 7% 2	527
	21st to end	Day	21% 9% 22% 29% 16% 3	573
June	1st to 10th	Day	15% 12% 29% 28% 14% 2	530
	11th to 20th	Day	16% 10% 32% 27% 12% 3	530
	21st to end	Day	11% 7% 30% 31% 17% 4	530
July	1st to 10th	Day	13% 5% 24% 30% 22% 7%	525
	11th to 20th	Day	8% 3 25% 35% 23% 6%	524
	21st to end	Day	11% 5% 27% 34% 17% 6%	576
August	1st to 10th	Day	12% 4 29% 30% 19% 6%	526
	11th to 20th	Day	14% 2 22% 33% 21% 7%	519
	21st to end	Day	12% 6% 25% 30% 19% 9%	583
September	1st to 10th	Day	17% 8% 26% 24% 16% 9%	530
	11th to 20th	Day	14% 5% 24% 31% 16% 9%	530
	21st to end	Day	23% 10% 27% 25% 11% 5%	530
October	1st to 10th	Day	22% 8% 25% 24% 12% 8%	530
	11th to 20th	Day	19% 15% 27% 23% 13% 3	530
	21st to end	Day	19% 14% 33% 20% 13% 2	526
November	1st to 10th	Day	16% 11% 36% 24% 11% 2	401
	11th to 20th	Day	18% 20% 32% 23% 7%	400
	21st to end	Day	19% 18% 32% 21% 8% 2	330
December	1st to 10th	Day	24% 21% 39% 11% 5% 1	200
	11th to 20th	Day	30% 17% 36% 14% 4 1	200
	21st to end	Day	25% 16% 32% 18% 8% 1	220
January	1st to 10th	Night	21% 19% 37% 20% 3 1	800
	11th to 20th	Night	23% 18% 33% 22% 4	800
	21st to end	Night	19% 16% 40% 23% 2	880
February	1st to 10th	Night	21% 16% 39% 23% 2	800
	11th to 20th	Night	25% 21% 37% 15% 1	783
	21st to end	Night	23% 20% 34% 19% 3	660
March	1st to 10th	Night	21% 17% 36% 22% 4	800
	11th to 20th	Night	22% 18% 34% 20% 6% 1	800
	21st to end	Night	22% 11% 42% 19% 5%	880
April	1st to 10th	Night	22% 19% 37% 17% 5%	800
	11th to 20th	Night	19% 14% 38% 25% 5%	791
	21st to end	Night	19% 11% 36% 28% 5%	800
May	1st to 10th	Night	21% 11% 36% 25% 7%	645
	11th to 20th	Night	22% 11% 34% 27% 5%	437
	21st to end	Night	21% 3 22% 40% 13% 1	433
June	1st to 10th	Night	18% 5% 27% 40% 11% 1	400
	11th to 20th	Night	13% 3 28% 42% 14%	400
	21st to end	Night	9% 3 28% 46% 14%	400
July	1st to 10th	Night	12% 2 20% 47% 17% 2	390
	11th to 20th	Night	10% 3 18% 47% 20% 2	388
	21st to end	Night	9% 3 22% 48% 17% 1	442
August	1st to 10th	Night	13% 2 16% 45% 23% 2	622
	11th to 20th	Night	12% 4 18% 40% 24% 2	790
	21st to end	Night	13% 1 20% 40% 23% 3	880
September	1st to 10th	Night	17% 3 23% 37% 17% 3	800
	11th to 20th	Night	14% 4 19% 37% 23% 4	800
	21st to end	Night	24% 4 22% 32% 16% 1	800
October	1st to 10th	Night	20% 6% 25% 28% 17% 3	800
	11th to 20th	Night	19% 10% 26% 32% 13% 1	800
	21st to end	Night	19% 10% 35% 27% 9%	880
November	1st to 10th	Night	16% 9% 34% 29% 11% 1	789
	11th to 20th	Night	19% 13% 33% 28% 7% 1	800
	21st to end	Night	16% 15% 35% 25% 8% 1	800
December	1st to 10th	Night	23% 15% 34% 21% 7% 1	800
	11th to 20th	Night	20% 14% 37% 24% 6%	800
	21st to end	Night	21% 12% 36% 28% 3	880

Page generated at 2025-10-31 02:02:42. Version ac07

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