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 2024-11-28.

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% 32%	101376
	Night	15% 14% 5% 11% 6% 4 4 3 4 5% 29%	98247
Transparency	Day	52% 6% 11% 20% 11% 1	104886
	Night	57% 6% 11% 17% 9% 1	102812
Seeing	Day	20% 13% 30% 23% 11% 4	15739
	Night	20% 11% 30% 28% 10% 1	25431

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	11% 25% 13% 24% 7% 5% 2 2 2 2 7%	2527
	11th to 20th	Day	12% 20% 7% 21% 12% 11% 5% 2 2 2 5%	2530
	21st to end	Day	16% 23% 10% 16% 8% 5% 5% 3 3 3 8%	2783
February	1st to 10th	Day	9% 20% 7% 15% 16% 5% 4 3 4 4 13%	1643
	11th to 20th	Day	12% 17% 8% 16% 10% 5% 5% 3 3 4 17%	1824
	21st to end	Day	12% 19% 7% 15% 8% 4 5% 3 5% 5% 18%	1570
March	1st to 10th	Day	13% 14% 5% 10% 5% 4 3 4 5% 5% 31%	3118
	11th to 20th	Day	9% 13% 7% 18% 5% 4 4 3 5% 7% 26%	3411
	21st to end	Day	16% 13% 7% 17% 6% 5% 4 3 4 5% 21%	3927
April	1st to 10th	Day	18% 15% 5% 9% 4 4 4 4 4 6% 27%	2280
	11th to 20th	Day	21% 15% 4 6% 3 3 3 3 4 6% 33%	2367
	21st to end	Day	16% 12% 4 8% 4 4 4 4 6% 6% 31%	2470
May	1st to 10th	Day	16% 9% 3 6% 4 4 4 3 5% 7% 40%	4108
	11th to 20th	Day	11% 7% 2 6% 4 3 5% 3 5% 6% 47%	4195
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 8% 43%	4837
June	1st to 10th	Day	14% 7% 2 5% 4 4 5% 4 6% 8% 40%	2798
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 5% 6% 9% 40%	2850
	21st to end	Day	16% 5% 2 5% 4 5% 5% 4 6% 8% 39%	2787
July	1st to 10th	Day	20% 7% 2 5% 4 3 4 4 6% 9% 37%	4440
	11th to 20th	Day	11% 5% 1 4 4 4 4 4 6% 9% 49%	4440
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 6% 10% 45%	4814
August	1st to 10th	Day	9% 6% 3 7% 5% 6% 5% 5% 7% 8% 38%	4212
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 45%	4044
	21st to end	Day	14% 7% 3 7% 4 4 4 3 5% 6% 43%	4382
September	1st to 10th	Day	16% 5% 2 6% 4 3 4 3 6% 7% 42%	2240
	11th to 20th	Day	14% 6% 2 5% 4 4 3 3 6% 7% 46%	2090
	21st to end	Day	18% 8% 3 6% 4 4 4 5% 6% 8% 36%	2090
October	1st to 10th	Day	19% 9% 3 8% 5% 3 3 3 5% 8% 34%	2088
	11th to 20th	Day	25% 17% 4 9% 5% 4 3 4 5% 5% 20%	1805
	21st to end	Day	23% 19% 4 9% 5% 4 4 4 5% 5% 17%	1881
November	1st to 10th	Day	18% 19% 5% 7% 5% 4 3 3 5% 6% 26%	1762
	11th to 20th	Day	13% 24% 8% 13% 6% 5% 4 3 5% 5% 16%	1800
	21st to end	Day	17% 24% 10% 13% 5% 3 4 2 4 4 13%	1628
December	1st to 10th	Day	14% 24% 11% 17% 6% 5% 4 2 3 3 10%	1330
	11th to 20th	Day	14% 24% 9% 18% 8% 4 4 3 4 4 9%	1671
	21st to end	Day	18% 21% 9% 19% 8% 4 4 2 3 4 8%	2634
January	1st to 10th	Night	13% 21% 11% 21% 7% 5% 3 2 3 3 11%	4428
	11th to 20th	Night	11% 17% 7% 20% 13% 11% 5% 3 3 2 8%	4440
	21st to end	Night	14% 22% 11% 19% 9% 5% 4 3 3 3 8%	4884
February	1st to 10th	Night	9% 19% 8% 15% 14% 7% 4 3 4 3 14%	2535
	11th to 20th	Night	11% 16% 7% 17% 11% 6% 5% 2 3 4 18%	2238
	21st to end	Night	14% 19% 6% 13% 7% 4 3 2 4 5% 22%	1884
March	1st to 10th	Night	14% 11% 4 8% 4 4 3 3 4 7% 39%	3722
	11th to 20th	Night	9% 15% 6% 11% 5% 4 4 3 4 5% 34%	3548
	21st to end	Night	14% 14% 7% 12% 5% 4 4 3 5% 5% 27%	3734
April	1st to 10th	Night	19% 14% 4 9% 5% 4 3 3 5% 5% 28%	1900
	11th to 20th	Night	21% 12% 3 6% 4 3 4 4 4 5% 33%	1761
	21st to end	Night	17% 12% 3 7% 5% 4 4 2 5% 5% 36%	1710
May	1st to 10th	Night	15% 9% 3 5% 5% 4 4 4 5% 6% 40%	2833
	11th to 20th	Night	13% 9% 3 7% 5% 4 4 4 5% 6% 42%	2700
	21st to end	Night	18% 7% 2 6% 4 3 3 3 5% 7% 42%	2750
June	1st to 10th	Night	14% 6% 2 6% 6% 5% 4 3 5% 7% 42%	1375
	11th to 20th	Night	11% 6% 2 6% 5% 5% 4 4 7% 8% 43%	1330
	21st to end	Night	13% 7% 2 6% 3 4 4 3 6% 7% 45%	1385
July	1st to 10th	Night	13% 8% 2 6% 4 4 4 3 6% 8% 41%	2530
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 5% 6% 51%	2530
	21st to end	Night	8% 6% 2 6% 4 4 5% 3 6% 7% 49%	2750
August	1st to 10th	Night	13% 6% 3 7% 5% 4 4 3 6% 8% 42%	2719
	11th to 20th	Night	17% 7% 2 4 2 3 3 3 5% 6% 49%	2785
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 5% 7% 46%	3271
September	1st to 10th	Night	13% 6% 2 5% 3 2 4 3 5% 7% 50%	1920
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 5% 7% 48%	2090
	21st to end	Night	19% 8% 2 6% 4 4 4 3 5% 6% 38%	2090
October	1st to 10th	Night	19% 9% 3 7% 4 3 3 3 4 5% 40%	2090
	11th to 20th	Night	23% 14% 4 7% 5% 4 4 4 4 6% 25%	2373
	21st to end	Night	26% 16% 3 7% 4 5% 4 3 4 5% 22%	2717
November	1st to 10th	Night	17% 18% 6% 7% 4 4 4 3 4 6% 27%	2536
	11th to 20th	Night	15% 23% 7% 12% 5% 4 4 3 4 5% 18%	2600
	21st to end	Night	18% 23% 10% 12% 5% 4 4 3 3 4 14%	2699
December	1st to 10th	Night	13% 26% 11% 18% 6% 3 3 3 3 3 10%	2850
	11th to 20th	Night	13% 21% 8% 21% 8% 4 4 3 3 4 11%	3526
	21st to end	Night	21% 22% 9% 16% 5% 4 4 3 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	86% 4 4 4 2	2528
	11th to 20th	Day	87% 4 4 3 1	2530
	21st to end	Day	82% 5% 8% 4 1	2783
February	1st to 10th	Day	76% 6% 6% 9% 2	1643
	11th to 20th	Day	70% 6% 8% 10% 5%	1834
	21st to end	Day	66% 7% 9% 14% 3 1	1570
March	1st to 10th	Day	54% 6% 12% 19% 9%	3120
	11th to 20th	Day	57% 6% 12% 18% 5% 1	3411
	21st to end	Day	64% 6% 8% 13% 7% 1	3927
April	1st to 10th	Day	58% 6% 9% 17% 9%	2280
	11th to 20th	Day	52% 5% 10% 19% 13% 1	2367
	21st to end	Day	51% 7% 11% 14% 14% 3	2470
May	1st to 10th	Day	42% 6% 10% 21% 18% 2	4120
	11th to 20th	Day	36% 7% 11% 28% 16% 2	4199
	21st to end	Day	37% 7% 11% 22% 20% 2	4837
June	1st to 10th	Day	40% 7% 13% 25% 14% 2	2798
	11th to 20th	Day	39% 9% 13% 21% 18% 1	2850
	21st to end	Day	41% 7% 13% 24% 13% 1	2787
July	1st to 10th	Day	44% 6% 14% 21% 14% 1	4371
	11th to 20th	Day	30% 7% 14% 34% 13% 1	4365
	21st to end	Day	32% 8% 13% 28% 18% 1	4662
August	1st to 10th	Day	40% 8% 13% 26% 13% 1	4197
	11th to 20th	Day	39% 6% 11% 30% 13% 1	4083
	21st to end	Day	41% 7% 12% 29% 10% 1	4381
September	1st to 10th	Day	40% 7% 12% 25% 16% 1	2240
	11th to 20th	Day	37% 7% 14% 29% 12% 1	2090
	21st to end	Day	44% 7% 15% 24% 10%	2090
October	1st to 10th	Day	36% 5% 8% 34% 17%	3465
	11th to 20th	Day	56% 5% 9% 19% 11%	2982
	21st to end	Day	65% 6% 12% 15% 3	3081
November	1st to 10th	Day	60% 5% 10% 18% 7%	1762
	11th to 20th	Day	71% 7% 10% 8% 4	1800
	21st to end	Day	76% 5% 10% 8% 2	1628
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	79% 5% 7% 8% 1	4428
	11th to 20th	Night	83% 6% 6% 4 2	4440
	21st to end	Night	82% 6% 7% 4 1	4884
February	1st to 10th	Night	76% 5% 6% 9% 4	2535
	11th to 20th	Night	70% 4 9% 13% 3	2239
	21st to end	Night	65% 5% 10% 14% 5%	1884
March	1st to 10th	Night	47% 5% 16% 22% 10%	3733
	11th to 20th	Night	52% 6% 11% 22% 8% 1	3549
	21st to end	Night	57% 6% 10% 18% 7% 1	3734
April	1st to 10th	Night	57% 5% 8% 18% 10% 1	1900
	11th to 20th	Night	52% 6% 8% 19% 13% 2	1761
	21st to end	Night	50% 5% 10% 18% 14% 2	1710
May	1st to 10th	Night	43% 7% 12% 19% 17% 3	2840
	11th to 20th	Night	42% 6% 8% 26% 17% 1	2701
	21st to end	Night	40% 7% 14% 19% 15% 5%	2751
June	1st to 10th	Night	41% 6% 11% 26% 16% 1	1375
	11th to 20th	Night	37% 7% 13% 25% 15% 2	1330
	21st to end	Night	38% 7% 14% 24% 15% 2	1385
July	1st to 10th	Night	40% 5% 14% 23% 14% 4	2490
	11th to 20th	Night	31% 6% 15% 30% 17% 1	2482
	21st to end	Night	34% 7% 15% 26% 18% 1	2662
August	1st to 10th	Night	39% 7% 15% 25% 12% 1	2710
	11th to 20th	Night	36% 5% 14% 30% 14%	2812
	21st to end	Night	35% 7% 15% 26% 17% 1	3271
September	1st to 10th	Night	33% 7% 14% 27% 18% 1	1920
	11th to 20th	Night	36% 6% 16% 29% 13% 1	2090
	21st to end	Night	46% 7% 15% 23% 9% 1	2090
October	1st to 10th	Night	42% 5% 11% 28% 13%	3480
	11th to 20th	Night	50% 5% 11% 21% 13%	3935
	21st to end	Night	59% 5% 13% 19% 4	4467
November	1st to 10th	Night	58% 6% 12% 17% 6% 1	2536
	11th to 20th	Night	69% 6% 9% 10% 5% 1	2600
	21st to end	Night	74% 6% 10% 8% 1	2699
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	26% 16% 36% 19% 3	270
	21st to end	Day	24% 14% 37% 20% 5%	297
February	1st to 10th	Day	17% 28% 39% 10% 5% 1	270
	11th to 20th	Day	21% 25% 36% 15% 2	270
	21st to end	Day	23% 26% 40% 9% 1	225
March	1st to 10th	Day	19% 27% 37% 14% 2	270
	11th to 20th	Day	22% 15% 36% 19% 7% 1	417
	21st to end	Day	27% 14% 29% 22% 8% 1	506
April	1st to 10th	Day	26% 15% 35% 17% 6% 2	460
	11th to 20th	Day	31% 17% 28% 12% 10% 2	452
	21st to end	Day	23% 15% 30% 21% 10% 2	460
May	1st to 10th	Day	23% 17% 29% 17% 10% 3	463
	11th to 20th	Day	17% 12% 32% 27% 9% 4	549
	21st to end	Day	15% 11% 29% 29% 12% 4	734
June	1st to 10th	Day	15% 13% 32% 28% 10% 3	680
	11th to 20th	Day	17% 11% 31% 27% 11% 3	680
	21st to end	Day	20% 8% 29% 31% 11% 3	680
July	1st to 10th	Day	12% 6% 28% 31% 16% 7%	671
	11th to 20th	Day	12% 9% 27% 29% 18% 6%	668
	21st to end	Day	9% 6% 30% 32% 19% 4	739
August	1st to 10th	Day	11% 5% 24% 27% 23% 10%	556
	11th to 20th	Day	14% 4 19% 30% 19% 13%	479
	21st to end	Day	20% 7% 21% 28% 17% 7%	539
September	1st to 10th	Day	19% 9% 23% 24% 17% 8%	490
	11th to 20th	Day	13% 8% 20% 30% 21% 9%	490
	21st to end	Day	20% 11% 20% 28% 16% 5%	490
October	1st to 10th	Day	23% 17% 26% 21% 11% 2	490
	11th to 20th	Day	33% 14% 30% 18% 4 1	395
	21st to end	Day	32% 19% 31% 12% 5% 1	330
November	1st to 10th	Day	29% 16% 32% 17% 5% 1	300
	11th to 20th	Day	22% 25% 37% 14% 3	300
	21st to end	Day	25% 27% 30% 15% 3	231
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	23% 15% 35% 21% 6%	950
	21st to end	Night	20% 12% 34% 28% 6% 1	1045
February	1st to 10th	Night	16% 17% 35% 27% 4 1	825
	11th to 20th	Night	18% 18% 34% 24% 5%	743
	21st to end	Night	23% 15% 36% 23% 3	628
March	1st to 10th	Night	17% 12% 36% 25% 9% 1	760
	11th to 20th	Night	17% 14% 37% 26% 5%	760
	21st to end	Night	21% 11% 30% 30% 7% 1	791
April	1st to 10th	Night	25% 12% 31% 25% 5% 1	570
	11th to 20th	Night	27% 11% 30% 25% 7%	563
	21st to end	Night	21% 10% 29% 30% 8% 1	570
May	1st to 10th	Night	18% 9% 31% 34% 8% 1	570
	11th to 20th	Night	18% 7% 31% 33% 10% 1	561
	21st to end	Night	16% 6% 26% 36% 15% 1	617
June	1st to 10th	Night	16% 6% 28% 40% 9% 1	425
	11th to 20th	Night	8% 7% 26% 44% 14%	380
	21st to end	Night	17% 3 27% 36% 15% 1	435
July	1st to 10th	Night	12% 3 18% 45% 21% 2	555
	11th to 20th	Night	11% 4 20% 39% 24% 2	552
	21st to end	Night	10% 4 22% 38% 24% 2	624
August	1st to 10th	Night	11% 3 17% 43% 24% 1	567
	11th to 20th	Night	14% 4 15% 36% 27% 3	564
	21st to end	Night	16% 5% 19% 40% 19% 2	627
September	1st to 10th	Night	14% 4 24% 35% 20% 3	590
	11th to 20th	Night	17% 4 19% 36% 20% 3	760
	21st to end	Night	22% 7% 21% 32% 15% 3	760
October	1st to 10th	Night	23% 10% 24% 31% 12% 1	760
	11th to 20th	Night	31% 11% 27% 24% 6% 1	760
	21st to end	Night	34% 13% 28% 20% 5% 1	836
November	1st to 10th	Night	26% 13% 31% 24% 6%	780
	11th to 20th	Night	24% 17% 36% 19% 4	800
	21st to end	Night	28% 15% 35% 20% 2	808
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 2024-11-25 00:22:19. Version ac07

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