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 2024-01-14.

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	15% 11% 5% 8% 6% 3 4 4 5% 7% 31%	74570
	Night	15% 13% 6% 10% 7% 3 4 4 4 5% 28%	75164
Transparency	Day	53% 6% 11% 18% 10% 1	74276
	Night	59% 6% 11% 16% 8% 1	74993
Seeing	Day	20% 13% 30% 23% 11% 4	14490
	Night	20% 11% 30% 28% 10% 1	24326

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	12% 20% 10% 15% 11% 6% 4 4 3 4 11%	1517
	11th to 20th	Day	16% 20% 9% 16% 10% 5% 4 3 3 4 9%	1464
	21st to end	Day	13% 18% 11% 17% 11% 5% 6% 4 3 3 10%	1584
February	1st to 10th	Day	9% 17% 8% 14% 19% 4 5% 3 4 4 12%	1557
	11th to 20th	Day	13% 16% 8% 13% 13% 4 5% 4 3 4 18%	1726
	21st to end	Day	13% 18% 8% 14% 9% 3 4 4 4 6% 17%	1480
March	1st to 10th	Day	14% 11% 6% 11% 9% 4 5% 4 5% 5% 27%	1798
	11th to 20th	Day	12% 11% 6% 10% 7% 3 5% 4 4 6% 32%	1939
	21st to end	Day	17% 13% 4 7% 6% 3 4 3 5% 7% 29%	2236
April	1st to 10th	Day	19% 13% 6% 8% 5% 3 5% 4 4 6% 26%	2160
	11th to 20th	Day	21% 14% 4 5% 3 2 3 4 4 6% 33%	2240
	21st to end	Day	17% 12% 4 7% 5% 3 4 5% 5% 7% 31%	2340
May	1st to 10th	Day	17% 9% 3 6% 4 3 4 4 6% 7% 36%	2340
	11th to 20th	Day	15% 8% 3 5% 5% 2 5% 4 5% 6% 41%	2359
	21st to end	Day	13% 6% 2 5% 5% 3 5% 5% 6% 8% 43%	2725
June	1st to 10th	Day	14% 6% 2 4 5% 3 5% 5% 6% 8% 41%	2650
	11th to 20th	Day	14% 5% 2 5% 5% 3 5% 5% 6% 9% 40%	2700
	21st to end	Day	15% 5% 3 5% 5% 3 5% 6% 6% 8% 40%	2641
July	1st to 10th	Day	11% 3 1 3 4 3 4 5% 7% 10% 48%	2520
	11th to 20th	Day	14% 5% 2 4 5% 3 4 5% 6% 9% 43%	2520
	21st to end	Day	10% 4 3 4 5% 3 5% 5% 7% 10% 45%	2743
August	1st to 10th	Day	10% 5% 2 6% 6% 4 6% 6% 7% 8% 40%	2394
	11th to 20th	Day	12% 5% 2 5% 6% 3 6% 4 6% 8% 43%	2303
	21st to end	Day	15% 6% 3 6% 4 2 4 4 5% 7% 43%	2494
September	1st to 10th	Day	17% 5% 2 5% 4 2 4 4 6% 7% 41%	2123
	11th to 20th	Day	15% 5% 2 5% 4 3 4 4 6% 7% 45%	1980
	21st to end	Day	18% 8% 3 5% 5% 3 4 6% 6% 8% 35%	1980
October	1st to 10th	Day	20% 9% 4 7% 6% 2 3 4 4 8% 33%	1979
	11th to 20th	Day	27% 17% 4 7% 7% 3 3 5% 5% 5% 18%	1710
	21st to end	Day	24% 19% 5% 8% 6% 3 4 4 5% 5% 17%	1782
November	1st to 10th	Day	18% 18% 5% 6% 6% 3 4 3 5% 6% 26%	1672
	11th to 20th	Day	13% 22% 10% 11% 7% 3 5% 4 5% 5% 15%	1710
	21st to end	Day	17% 22% 12% 12% 6% 2 5% 3 4 4 14%	1569
December	1st to 10th	Day	14% 20% 15% 16% 7% 4 5% 3 3 3 10%	1330
	11th to 20th	Day	14% 22% 11% 16% 10% 3 4 4 4 4 10%	1671
	21st to end	Day	19% 19% 10% 17% 9% 4 4 3 3 4 8%	2634
January	1st to 10th	Night	14% 17% 9% 19% 11% 4 5% 3 4 3 11%	2648
	11th to 20th	Night	15% 18% 9% 16% 12% 5% 4 4 3 3 13%	2575
	21st to end	Night	12% 17% 10% 16% 14% 5% 5% 3 3 3 10%	2772
February	1st to 10th	Night	10% 17% 10% 13% 17% 6% 5% 4 4 3 13%	2401
	11th to 20th	Night	12% 14% 8% 15% 12% 5% 6% 3 3 4 18%	2117
	21st to end	Night	15% 18% 7% 12% 9% 4 3 3 4 5% 21%	1776
March	1st to 10th	Night	11% 12% 5% 9% 6% 4 4 4 4 6% 34%	2149
	11th to 20th	Night	12% 12% 5% 9% 7% 3 5% 4 4 5% 34%	2020
	21st to end	Night	16% 10% 4 7% 5% 3 5% 5% 5% 5% 35%	2136
April	1st to 10th	Night	19% 13% 4 8% 5% 3 4 4 5% 6% 27%	1800
	11th to 20th	Night	20% 12% 3 5% 5% 3 4 5% 4 5% 34%	1668
	21st to end	Night	17% 11% 3 7% 5% 3 4 3 5% 6% 36%	1620
May	1st to 10th	Night	16% 9% 3 5% 6% 3 6% 5% 5% 7% 34%	1620
	11th to 20th	Night	14% 11% 3 7% 6% 3 4 5% 5% 6% 35%	1532
	21st to end	Night	13% 6% 2 5% 5% 3 4 4 5% 9% 44%	1551
June	1st to 10th	Night	13% 6% 2 6% 5% 4 5% 4 4 8% 43%	1303
	11th to 20th	Night	11% 6% 2 5% 5% 4 5% 4 6% 9% 43%	1260
	21st to end	Night	12% 6% 2 5% 4 3 5% 4 6% 7% 46%	1312
July	1st to 10th	Night	9% 4 1 4 4 3 4 4 6% 10% 51%	1440
	11th to 20th	Night	9% 5% 2 4 5% 3 5% 4 5% 7% 49%	1440
	21st to end	Night	9% 5% 3 6% 5% 3 5% 4 6% 7% 49%	1575
August	1st to 10th	Night	9% 3 3 5% 6% 3 4 4 7% 9% 48%	1543
	11th to 20th	Night	11% 5% 2 4 4 3 4 4 6% 7% 50%	1598
	21st to end	Night	14% 6% 2 5% 5% 3 4 4 4 7% 45%	1859
September	1st to 10th	Night	13% 5% 2 5% 3 2 4 4 5% 7% 49%	1818
	11th to 20th	Night	16% 5% 3 4 4 2 3 4 5% 7% 47%	1980
	21st to end	Night	20% 7% 3 5% 5% 3 4 4 5% 7% 36%	1980
October	1st to 10th	Night	19% 9% 3 6% 5% 3 4 4 4 5% 39%	1980
	11th to 20th	Night	25% 13% 4 6% 6% 3 4 5% 4 6% 24%	2248
	21st to end	Night	27% 16% 4 7% 5% 3 5% 4 4 5% 21%	2574
November	1st to 10th	Night	17% 17% 6% 7% 5% 3 5% 3 5% 6% 27%	2406
	11th to 20th	Night	15% 21% 8% 11% 7% 3 4 4 4 5% 18%	2470
	21st to end	Night	18% 21% 11% 11% 6% 3 4 3 3 5% 14%	2603
December	1st to 10th	Night	14% 22% 14% 17% 8% 2 4 3 3 3 10%	2850
	11th to 20th	Night	14% 20% 9% 19% 10% 3 4 4 3 4 11%	3526
	21st to end	Night	21% 21% 9% 14% 6% 3 4 4 4 4 9%	5014

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	80% 5% 6% 7% 3	1518
	11th to 20th	Day	80% 5% 6% 5% 2	1464
	21st to end	Day	81% 4 6% 7% 2	1584
February	1st to 10th	Day	78% 6% 6% 9% 2	1557
	11th to 20th	Day	71% 6% 8% 10% 5%	1736
	21st to end	Day	68% 6% 9% 13% 3 1	1480
March	1st to 10th	Day	61% 6% 10% 16% 7% 1	1800
	11th to 20th	Day	54% 5% 11% 20% 7% 2	1939
	21st to end	Day	55% 6% 11% 18% 9% 1	2236
April	1st to 10th	Day	59% 6% 10% 16% 9%	2160
	11th to 20th	Day	53% 5% 10% 18% 13% 1	2240
	21st to end	Day	51% 7% 11% 13% 14% 3	2340
May	1st to 10th	Day	47% 6% 10% 22% 12% 3	2340
	11th to 20th	Day	44% 6% 10% 22% 15% 3	2363
	21st to end	Day	39% 8% 13% 25% 15% 1	2725
June	1st to 10th	Day	39% 7% 13% 25% 14% 2	2650
	11th to 20th	Day	38% 9% 13% 21% 18% 1	2700
	21st to end	Day	41% 8% 14% 23% 14% 1	2641
July	1st to 10th	Day	30% 8% 14% 28% 19% 2	2451
	11th to 20th	Day	36% 8% 13% 26% 15% 1	2445
	21st to end	Day	34% 8% 14% 26% 17% 1	2591
August	1st to 10th	Day	39% 9% 16% 25% 11% 1	2379
	11th to 20th	Day	38% 8% 14% 26% 13% 1	2303
	21st to end	Day	40% 7% 14% 24% 14% 2	2494
September	1st to 10th	Day	41% 7% 12% 24% 15% 1	2123
	11th to 20th	Day	38% 7% 15% 29% 10% 1	1980
	21st to end	Day	46% 7% 16% 23% 8%	1980
October	1st to 10th	Day	51% 7% 9% 24% 9% 1	1979
	11th to 20th	Day	68% 6% 9% 14% 3	1710
	21st to end	Day	70% 6% 11% 10% 3	1782
November	1st to 10th	Day	60% 6% 10% 18% 7%	1672
	11th to 20th	Day	71% 7% 10% 8% 4	1710
	21st to end	Day	75% 5% 10% 8% 1	1569
December	1st to 10th	Day	81% 5% 6% 7% 1	1330
	11th to 20th	Day	80% 6% 8% 5% 1	1671
	21st to end	Day	84% 4 7% 3 2	2634
January	1st to 10th	Night	80% 5% 6% 7% 2	2648
	11th to 20th	Night	79% 5% 7% 6% 3	2575
	21st to end	Night	80% 5% 7% 6% 2	2772
February	1st to 10th	Night	78% 5% 6% 8% 3	2401
	11th to 20th	Night	71% 4 8% 13% 4	2118
	21st to end	Night	67% 5% 10% 13% 5%	1776
March	1st to 10th	Night	52% 5% 12% 21% 9% 1	2160
	11th to 20th	Night	53% 6% 10% 18% 12% 2	2021
	21st to end	Night	50% 6% 11% 20% 12% 1	2136
April	1st to 10th	Night	58% 5% 9% 18% 11% 1	1800
	11th to 20th	Night	52% 6% 8% 19% 13% 2	1668
	21st to end	Night	50% 4 11% 19% 14% 2	1620
May	1st to 10th	Night	48% 7% 11% 19% 11% 4	1620
	11th to 20th	Night	50% 5% 8% 21% 14% 2	1533
	21st to end	Night	38% 6% 14% 25% 15% 3	1552
June	1st to 10th	Night	40% 6% 11% 26% 16% 1	1303
	11th to 20th	Night	38% 7% 13% 25% 15% 3	1260
	21st to end	Night	37% 7% 14% 25% 16% 2	1312
July	1st to 10th	Night	28% 6% 15% 28% 19% 3	1400
	11th to 20th	Night	33% 6% 16% 26% 18% 1	1392
	21st to end	Night	34% 7% 15% 28% 16% 1	1487
August	1st to 10th	Night	32% 8% 18% 29% 11% 1	1534
	11th to 20th	Night	32% 8% 16% 28% 15% 1	1598
	21st to end	Night	40% 7% 14% 23% 15% 1	1859
September	1st to 10th	Night	34% 7% 14% 25% 18% 1	1818
	11th to 20th	Night	37% 6% 17% 29% 11% 1	1980
	21st to end	Night	47% 7% 15% 23% 8%	1980
October	1st to 10th	Night	47% 6% 11% 23% 12% 1	1980
	11th to 20th	Night	60% 6% 13% 16% 5%	2248
	21st to end	Night	65% 5% 10% 14% 5%	2574
November	1st to 10th	Night	58% 6% 11% 17% 6% 1	2406
	11th to 20th	Night	69% 6% 10% 10% 5% 1	2470
	21st to end	Night	73% 6% 11% 8% 1	2603
December	1st to 10th	Night	81% 5% 6% 7% 1	2850
	11th to 20th	Night	78% 7% 9% 5% 2	3525
	21st to end	Night	80% 7% 8% 3 1	5014

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	20% 17% 38% 17% 6%	270
	11th to 20th	Day	28% 13% 35% 19% 4	249
	21st to end	Day	23% 15% 36% 20% 5%	264
February	1st to 10th	Day	19% 29% 40% 8% 3	240
	11th to 20th	Day	21% 25% 37% 14% 3	240
	21st to end	Day	25% 27% 39% 8% 2	198
March	1st to 10th	Day	21% 27% 35% 14% 3	240
	11th to 20th	Day	21% 13% 37% 20% 7% 1	379
	21st to end	Day	28% 13% 28% 23% 8% 1	462
April	1st to 10th	Day	26% 13% 34% 18% 7% 2	420
	11th to 20th	Day	31% 15% 28% 13% 11% 2	412
	21st to end	Day	22% 15% 30% 21% 10% 2	420
May	1st to 10th	Day	23% 18% 28% 17% 11% 3	423
	11th to 20th	Day	17% 13% 32% 25% 9% 4	505
	21st to end	Day	14% 11% 30% 29% 12% 4	679
June	1st to 10th	Day	15% 12% 32% 28% 11% 3	630
	11th to 20th	Day	17% 10% 29% 29% 12% 3	630
	21st to end	Day	18% 6% 29% 32% 12% 3	630
July	1st to 10th	Day	11% 5% 27% 32% 17% 8%	621
	11th to 20th	Day	13% 9% 26% 29% 17% 6%	618
	21st to end	Day	9% 6% 32% 31% 17% 5%	684
August	1st to 10th	Day	12% 5% 24% 27% 23% 10%	513
	11th to 20th	Day	14% 4 19% 30% 20% 13%	439
	21st to end	Day	19% 7% 21% 28% 17% 8%	495
September	1st to 10th	Day	20% 8% 24% 24% 16% 8%	450
	11th to 20th	Day	14% 8% 20% 30% 19% 8%	450
	21st to end	Day	21% 11% 19% 27% 16% 5%	450
October	1st to 10th	Day	24% 15% 25% 21% 12% 3	450
	11th to 20th	Day	34% 14% 30% 17% 4 1	360
	21st to end	Day	32% 19% 32% 11% 5% 1	297
November	1st to 10th	Day	27% 14% 33% 19% 6% 1	270
	11th to 20th	Day	20% 26% 37% 14% 3	270
	21st to end	Day	24% 27% 31% 15% 3	214
December	1st to 10th	Day	29% 14% 39% 11% 4 2	180
	11th to 20th	Day	25% 22% 40% 11% 1 1	180
	21st to end	Day	27% 28% 34% 9% 1 1	258
January	1st to 10th	Night	19% 17% 36% 21% 6% 1	950
	11th to 20th	Night	24% 14% 34% 22% 6%	920
	21st to end	Night	20% 12% 35% 27% 6% 1	990
February	1st to 10th	Night	17% 17% 35% 27% 4 1	781
	11th to 20th	Night	19% 18% 33% 24% 5%	703
	21st to end	Night	24% 15% 34% 23% 4	592
March	1st to 10th	Night	17% 12% 36% 25% 10% 1	720
	11th to 20th	Night	18% 14% 37% 25% 5%	720
	21st to end	Night	21% 10% 30% 30% 8% 1	750
April	1st to 10th	Night	26% 11% 31% 25% 6% 1	540
	11th to 20th	Night	26% 10% 30% 26% 8%	533
	21st to end	Night	21% 9% 29% 31% 9% 1	540
May	1st to 10th	Night	18% 9% 32% 32% 9% 1	540
	11th to 20th	Night	18% 7% 32% 32% 10% 1	531
	21st to end	Night	16% 5% 26% 37% 15% 1	584
June	1st to 10th	Night	16% 6% 27% 41% 9% 1	403
	11th to 20th	Night	9% 6% 26% 45% 14%	360
	21st to end	Night	15% 3 27% 37% 16% 1	412
July	1st to 10th	Night	11% 2 18% 46% 21% 2	525
	11th to 20th	Night	11% 4 21% 38% 25% 2	522
	21st to end	Night	10% 4 24% 37% 24% 2	591
August	1st to 10th	Night	10% 3 17% 45% 24% 1	537
	11th to 20th	Night	13% 4 16% 37% 27% 4	534
	21st to end	Night	16% 5% 19% 40% 19% 2	594
September	1st to 10th	Night	15% 3 24% 35% 20% 3	558
	11th to 20th	Night	18% 4 20% 35% 19% 3	720
	21st to end	Night	23% 7% 22% 31% 15% 3	720
October	1st to 10th	Night	23% 9% 23% 31% 13% 1	720
	11th to 20th	Night	32% 11% 27% 23% 6% 1	720
	21st to end	Night	35% 12% 28% 20% 5% 1	792
November	1st to 10th	Night	25% 13% 31% 25% 6%	740
	11th to 20th	Night	24% 17% 36% 19% 4	760
	21st to end	Night	27% 15% 35% 20% 2	779
December	1st to 10th	Night	23% 17% 38% 19% 3	950
	11th to 20th	Night	23% 16% 38% 18% 4 1	950
	21st to end	Night	27% 17% 36% 18% 2	1045

Page generated at 2024-01-11 13:31:59. Version ac07

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