Dobie North Observing Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dobie North Observing Field clear sky chart from 2005-11-06 to 2026-02-01.

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	14% 12% 4 10% 5% 4 4 3 5% 6% 31%	126855
	Night	14% 14% 6% 12% 6% 4 4 3 4 5% 27%	125344
Transparency	Day	53% 6% 10% 20% 10% 1	130348
	Night	58% 6% 11% 16% 9% 1	129925
Seeing	Day	20% 14% 30% 23% 11% 3	17268
	Night	20% 12% 30% 28% 10% 1	27090

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	8% 21% 11% 31% 6% 4 3 2 3 3 8%	3697
	11th to 20th	Day	10% 18% 8% 25% 14% 10% 5% 2 2 2 4	3669
	21st to end	Day	12% 18% 9% 21% 10% 5% 6% 3 3 3 11%	4070
February	1st to 10th	Day	9% 19% 7% 15% 17% 5% 4 3 4 4 13%	1730
	11th to 20th	Day	12% 17% 7% 16% 11% 6% 4 3 3 4 16%	1923
	21st to end	Day	12% 19% 7% 15% 8% 4 5% 3 5% 5% 18%	1650
March	1st to 10th	Day	12% 11% 4 14% 6% 5% 4 4 5% 5% 30%	4478
	11th to 20th	Day	11% 13% 5% 15% 5% 4 5% 4 6% 7% 25%	4883
	21st to end	Day	20% 13% 7% 17% 6% 4 3 2 4 4 20%	5619
April	1st to 10th	Day	17% 16% 5% 10% 4 4 4 4 4 6% 27%	2400
	11th to 20th	Day	20% 15% 4 6% 3 3 3 3 4 6% 33%	2493
	21st to end	Day	16% 12% 4 8% 4 4 4 4 6% 7% 31%	2600
May	1st to 10th	Day	17% 10% 3 6% 3 3 4 3 5% 7% 40%	5888
	11th to 20th	Day	12% 10% 2 6% 4 4 4 3 5% 6% 43%	6031
	21st to end	Day	14% 9% 3 7% 4 4 4 3 5% 7% 39%	6949
June	1st to 10th	Day	14% 7% 2 5% 4 4 5% 4 6% 8% 40%	2945
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 5% 6% 9% 39%	3000
	21st to end	Day	16% 5% 2 6% 4 5% 5% 4 6% 8% 39%	2933
July	1st to 10th	Day	18% 6% 2 5% 3 3 4 3 6% 10% 41%	6359
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 8% 48%	6360
	21st to end	Day	10% 5% 2 5% 4 3 4 4 6% 11% 46%	6926
August	1st to 10th	Day	9% 6% 3 7% 5% 6% 5% 5% 7% 8% 39%	4345
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 45%	4174
	21st to end	Day	14% 7% 3 7% 4 4 4 3 5% 6% 43%	4520
September	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 6% 7% 41%	2358
	11th to 20th	Day	13% 6% 2 5% 4 4 3 3 6% 7% 46%	2200
	21st to end	Day	17% 8% 3 6% 4 4 4 5% 5% 8% 36%	2200
October	1st to 10th	Day	18% 9% 3 8% 5% 3 3 3 5% 8% 35%	2198
	11th to 20th	Day	25% 17% 3 9% 5% 4 3 4 5% 5% 20%	1900
	21st to end	Day	22% 19% 4 9% 5% 5% 4 4 5% 5% 19%	1980
November	1st to 10th	Day	18% 19% 5% 7% 5% 4 3 2 5% 6% 25%	1852
	11th to 20th	Day	14% 24% 8% 12% 5% 4 4 3 5% 5% 16%	1890
	21st to end	Day	16% 25% 11% 13% 5% 3 4 2 4 4 13%	1733
December	1st to 10th	Day	12% 29% 11% 21% 5% 4 4 2 2 2 7%	2350
	11th to 20th	Day	11% 24% 11% 20% 9% 5% 4 3 3 3 6%	2691
	21st to end	Day	19% 22% 8% 18% 7% 4 4 2 3 4 9%	3861
January	1st to 10th	Night	10% 18% 10% 29% 7% 5% 3 2 3 3 11%	6488
	11th to 20th	Night	10% 16% 8% 21% 16% 10% 5% 2 3 2 6%	6456
	21st to end	Night	10% 20% 10% 22% 9% 6% 6% 3 3 3 9%	7150
February	1st to 10th	Night	9% 19% 7% 16% 14% 7% 4 3 4 3 14%	2669
	11th to 20th	Night	11% 16% 8% 17% 11% 6% 5% 2 3 4 17%	2359
	21st to end	Night	13% 19% 6% 14% 7% 4 3 3 4 5% 22%	1980
March	1st to 10th	Night	14% 12% 4 9% 7% 4 3 2 4 7% 34%	5362
	11th to 20th	Night	11% 14% 5% 10% 5% 4 4 4 5% 7% 32%	5076
	21st to end	Night	19% 13% 6% 11% 4 3 4 3 4 5% 28%	5342
April	1st to 10th	Night	19% 14% 4 9% 5% 4 3 3 5% 5% 28%	2000
	11th to 20th	Night	21% 13% 3 6% 4 3 4 3 4 5% 33%	1855
	21st to end	Night	17% 13% 3 7% 5% 4 4 2 5% 5% 35%	1800
May	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 7% 41%	4053
	11th to 20th	Night	13% 10% 2 6% 4 4 4 4 6% 6% 39%	3868
	21st to end	Night	18% 10% 2 6% 4 3 3 2 4 6% 42%	3949
June	1st to 10th	Night	14% 6% 2 6% 5% 5% 4 3 5% 7% 43%	1447
	11th to 20th	Night	11% 6% 2 7% 5% 5% 4 4 6% 8% 42%	1400
	21st to end	Night	14% 8% 2 6% 3 4 4 3 6% 7% 43%	1458
July	1st to 10th	Night	13% 8% 2 6% 4 4 4 4 6% 8% 41%	3620
	11th to 20th	Night	10% 7% 2 5% 4 4 4 3 5% 6% 50%	3620
	21st to end	Night	8% 7% 2 6% 4 4 4 3 5% 7% 50%	3948
August	1st to 10th	Night	13% 6% 3 7% 5% 4 4 3 6% 8% 42%	2805
	11th to 20th	Night	17% 7% 2 4 2 3 3 3 5% 6% 48%	2875
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 5% 7% 47%	3375
September	1st to 10th	Night	13% 5% 2 5% 3 3 4 3 5% 7% 49%	2021
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 6% 7% 48%	2200
	21st to end	Night	19% 8% 2 6% 4 4 4 3 5% 6% 38%	2200
October	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 5% 5% 41%	2200
	11th to 20th	Night	23% 14% 4 7% 5% 4 4 4 4 6% 25%	2498
	21st to end	Night	25% 16% 3 7% 4 5% 4 3 4 5% 23%	2860
November	1st to 10th	Night	17% 18% 6% 7% 4 4 4 3 5% 6% 27%	2666
	11th to 20th	Night	14% 23% 7% 12% 5% 4 5% 3 4 5% 18%	2730
	21st to end	Night	17% 24% 11% 12% 5% 4 4 2 3 4 13%	2878
December	1st to 10th	Night	11% 24% 15% 19% 6% 4 4 3 3 3 9%	5060
	11th to 20th	Night	11% 23% 8% 21% 9% 4 3 3 3 4 10%	5736
	21st to end	Night	20% 20% 9% 16% 5% 5% 4 3 4 4 11%	7340

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	83% 4 5% 6% 2	3698
	11th to 20th	Day	89% 4 4 3 1	3700
	21st to end	Day	79% 4 9% 6% 2	4070
February	1st to 10th	Day	76% 6% 6% 9% 2	1730
	11th to 20th	Day	71% 6% 8% 9% 5%	1933
	21st to end	Day	67% 7% 9% 14% 3	1650
March	1st to 10th	Day	54% 5% 15% 15% 9% 2	4480
	11th to 20th	Day	57% 6% 13% 17% 7% 1	4883
	21st to end	Day	67% 5% 8% 13% 7%	5619
April	1st to 10th	Day	59% 6% 9% 17% 9% 1	2400
	11th to 20th	Day	52% 5% 10% 20% 13% 1	2493
	21st to end	Day	51% 7% 11% 15% 14% 3	2600
May	1st to 10th	Day	43% 6% 9% 21% 18% 3	5897
	11th to 20th	Day	41% 6% 9% 24% 17% 3	6035
	21st to end	Day	43% 7% 9% 20% 19% 3	6949
June	1st to 10th	Day	39% 6% 12% 26% 14% 2	2945
	11th to 20th	Day	40% 9% 13% 21% 17% 1	3000
	21st to end	Day	41% 7% 13% 23% 13% 1	2933
July	1st to 10th	Day	39% 6% 13% 26% 14% 1	6291
	11th to 20th	Day	32% 7% 13% 35% 13% 1	6285
	21st to end	Day	32% 7% 13% 32% 15% 1	6728
August	1st to 10th	Day	39% 8% 13% 27% 13% 1	4330
	11th to 20th	Day	39% 6% 11% 30% 13% 1	4213
	21st to end	Day	41% 7% 12% 29% 10% 1	4519
September	1st to 10th	Day	41% 7% 13% 24% 15% 1	2358
	11th to 20th	Day	36% 7% 14% 30% 12% 1	2200
	21st to end	Day	44% 7% 15% 23% 11%	2200
October	1st to 10th	Day	36% 5% 8% 34% 17%	3575
	11th to 20th	Day	56% 5% 9% 19% 11%	3077
	21st to end	Day	63% 6% 12% 15% 4	3180
November	1st to 10th	Day	59% 5% 10% 18% 7%	1852
	11th to 20th	Day	70% 7% 10% 9% 4	1890
	21st to end	Day	76% 5% 9% 8% 2	1733
December	1st to 10th	Day	85% 5% 5% 4 1	2350
	11th to 20th	Day	84% 5% 6% 4 1	2691
	21st to end	Day	81% 5% 6% 5% 3	3861
January	1st to 10th	Night	80% 4 6% 7% 3	6488
	11th to 20th	Night	85% 5% 6% 3 1	6500
	21st to end	Night	80% 5% 7% 7% 1	7150
February	1st to 10th	Night	76% 5% 6% 9% 4	2669
	11th to 20th	Night	71% 4 9% 12% 3	2360
	21st to end	Night	65% 5% 10% 14% 5%	1980
March	1st to 10th	Night	51% 5% 17% 18% 9%	5373
	11th to 20th	Night	52% 6% 17% 19% 7% 1	5077
	21st to end	Night	58% 5% 10% 16% 9% 1	5342
April	1st to 10th	Night	57% 5% 8% 19% 10% 1	2000
	11th to 20th	Night	53% 5% 8% 19% 13% 2	1855
	21st to end	Night	51% 5% 10% 18% 14% 2	1800
May	1st to 10th	Night	42% 6% 11% 18% 19% 4	4060
	11th to 20th	Night	44% 6% 7% 24% 18% 1	3869
	21st to end	Night	43% 5% 12% 22% 14% 5%	3950
June	1st to 10th	Night	40% 6% 11% 27% 16% 1	1447
	11th to 20th	Night	39% 7% 13% 24% 15% 2	1400
	21st to end	Night	40% 7% 13% 24% 15% 2	1458
July	1st to 10th	Night	39% 5% 14% 24% 15% 3	3580
	11th to 20th	Night	33% 6% 13% 30% 18% 1	3572
	21st to end	Night	32% 6% 15% 29% 16% 1	3832
August	1st to 10th	Night	39% 7% 15% 25% 12% 1	2796
	11th to 20th	Night	36% 5% 15% 30% 14%	2902
	21st to end	Night	35% 7% 15% 26% 16% 1	3375
September	1st to 10th	Night	34% 7% 15% 26% 17% 1	2021
	11th to 20th	Night	35% 6% 16% 29% 13% 1	2200
	21st to end	Night	46% 7% 14% 22% 10% 1	2200
October	1st to 10th	Night	41% 5% 11% 29% 13%	3590
	11th to 20th	Night	50% 5% 10% 20% 14%	4060
	21st to end	Night	58% 5% 13% 19% 5%	4610
November	1st to 10th	Night	58% 6% 11% 17% 7%	2666
	11th to 20th	Night	68% 6% 10% 10% 5% 1	2730
	21st to end	Night	75% 6% 10% 8% 1	2878
December	1st to 10th	Night	80% 6% 7% 6% 1	5060
	11th to 20th	Night	79% 5% 7% 7% 1	5735
	21st to end	Night	78% 6% 7% 5% 4	7340

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% 21% 38% 16% 5%	330
	11th to 20th	Day	24% 20% 36% 17% 3	330
	21st to end	Day	22% 17% 37% 20% 4	363
February	1st to 10th	Day	18% 30% 36% 11% 4 1	300
	11th to 20th	Day	22% 24% 37% 14% 2	300
	21st to end	Day	24% 25% 39% 10% 2	249
March	1st to 10th	Day	20% 27% 37% 14% 2	300
	11th to 20th	Day	23% 16% 35% 18% 6% 1	455
	21st to end	Day	28% 16% 28% 21% 7% 1	550
April	1st to 10th	Day	26% 15% 34% 17% 6% 2	500
	11th to 20th	Day	30% 18% 28% 12% 10% 2	492
	21st to end	Day	22% 15% 31% 20% 9% 2	500
May	1st to 10th	Day	23% 17% 30% 17% 10% 3	503
	11th to 20th	Day	18% 12% 32% 26% 9% 4	593
	21st to end	Day	16% 12% 29% 28% 12% 3	789
June	1st to 10th	Day	15% 13% 33% 26% 10% 3	730
	11th to 20th	Day	18% 11% 31% 26% 11% 3	730
	21st to end	Day	20% 8% 29% 30% 10% 2	730
July	1st to 10th	Day	12% 6% 29% 32% 15% 7%	721
	11th to 20th	Day	13% 9% 27% 29% 17% 5%	718
	21st to end	Day	9% 6% 31% 32% 18% 4	794
August	1st to 10th	Day	10% 5% 24% 28% 23% 10%	599
	11th to 20th	Day	15% 4 19% 30% 19% 12%	519
	21st to end	Day	19% 8% 21% 28% 17% 8%	583
September	1st to 10th	Day	19% 10% 22% 23% 17% 8%	530
	11th to 20th	Day	12% 7% 18% 29% 22% 11%	530
	21st to end	Day	19% 11% 20% 28% 17% 5%	530
October	1st to 10th	Day	22% 16% 26% 22% 12% 3	530
	11th to 20th	Day	32% 14% 32% 19% 3	430
	21st to end	Day	31% 18% 31% 13% 6% 1	363
November	1st to 10th	Day	29% 16% 33% 16% 5% 1	330
	11th to 20th	Day	23% 25% 35% 14% 3	330
	21st to end	Day	26% 27% 30% 15% 2	261
December	1st to 10th	Day	27% 18% 37% 12% 4 1	220
	11th to 20th	Day	26% 21% 40% 11% 1	220
	21st to end	Day	28% 27% 34% 8% 2 1	316
January	1st to 10th	Night	19% 18% 36% 21% 6% 1	1050
	11th to 20th	Night	23% 16% 36% 20% 5%	1050
	21st to end	Night	19% 13% 35% 27% 5% 1	1155
February	1st to 10th	Night	17% 17% 35% 27% 4 1	869
	11th to 20th	Night	18% 19% 33% 24% 5%	783
	21st to end	Night	22% 15% 35% 23% 4	660
March	1st to 10th	Night	18% 13% 36% 25% 9% 1	800
	11th to 20th	Night	17% 15% 37% 25% 5%	800
	21st to end	Night	22% 11% 30% 30% 7% 1	832
April	1st to 10th	Night	26% 12% 31% 25% 5% 1	600
	11th to 20th	Night	27% 11% 29% 24% 8%	593
	21st to end	Night	22% 12% 29% 30% 8% 1	600
May	1st to 10th	Night	17% 9% 31% 34% 8% 1	600
	11th to 20th	Night	18% 8% 31% 33% 9% 1	591
	21st to end	Night	17% 6% 26% 36% 15% 1	650
June	1st to 10th	Night	16% 6% 29% 40% 9% 1	447
	11th to 20th	Night	9% 8% 27% 44% 13%	400
	21st to end	Night	17% 4 28% 36% 15% 1	458
July	1st to 10th	Night	12% 3 18% 45% 21% 2	585
	11th to 20th	Night	11% 4 20% 39% 24% 2	582
	21st to end	Night	10% 3 23% 39% 23% 2	657
August	1st to 10th	Night	11% 3 16% 44% 25% 1	597
	11th to 20th	Night	14% 3 16% 36% 27% 3	594
	21st to end	Night	15% 5% 18% 40% 20% 2	660
September	1st to 10th	Night	14% 4 24% 34% 21% 3	621
	11th to 20th	Night	16% 4 18% 37% 21% 3	800
	21st to end	Night	22% 7% 22% 32% 15% 3	800
October	1st to 10th	Night	22% 9% 25% 31% 12% 1	800
	11th to 20th	Night	31% 12% 28% 24% 6% 1	800
	21st to end	Night	33% 13% 28% 21% 5% 1	880
November	1st to 10th	Night	26% 13% 30% 24% 6%	820
	11th to 20th	Night	25% 17% 35% 19% 4	840
	21st to end	Night	28% 15% 35% 19% 2	861
December	1st to 10th	Night	22% 17% 37% 20% 3	1050
	11th to 20th	Night	22% 18% 38% 17% 4 1	1050
	21st to end	Night	27% 17% 35% 18% 3	1155

Page generated at 2026-01-29 01:21:41. Version ac07

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