Pine Bluff Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine Bluff Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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	13% 9% 3 8% 5% 4 4 4 6% 7% 37%	101482
	Night	13% 10% 4 8% 5% 4 4 4 5% 6% 38%	97615
Transparency	Day	44% 5% 11% 25% 13% 1	105009
	Night	44% 5% 11% 24% 15% 2	102228
Seeing	Day	17% 11% 29% 25% 14% 4	15906
	Night	17% 10% 31% 30% 11% 1	25745

By Month

Percentage Cloud Cover SE (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	10% 14% 8% 16% 6% 4 3 3 4 5% 26%	2527
	11th to 20th	Day	9% 12% 5% 15% 6% 5% 5% 7% 8% 7% 20%	2530
	21st to end	Day	16% 17% 10% 12% 5% 3 3 2 4 5% 21%	2943
February	1st to 10th	Day	12% 13% 6% 10% 5% 3 5% 4 5% 7% 31%	1710
	11th to 20th	Day	13% 11% 4 8% 5% 5% 4 4 6% 6% 35%	1770
	21st to end	Day	12% 13% 5% 11% 6% 5% 4 3 5% 5% 31%	1570
March	1st to 10th	Day	14% 8% 3 6% 4 3 4 3 5% 6% 44%	3120
	11th to 20th	Day	11% 6% 3 9% 5% 4 5% 4 5% 7% 43%	3384
	21st to end	Day	21% 13% 4 10% 5% 4 4 3 4 6% 27%	4096
April	1st to 10th	Day	18% 13% 3 8% 4 5% 4 3 5% 6% 30%	2280
	11th to 20th	Day	17% 11% 3 8% 5% 4 4 4 5% 6% 34%	2254
	21st to end	Day	18% 10% 3 8% 5% 5% 4 3 5% 6% 33%	2328
May	1st to 10th	Day	16% 7% 3 7% 5% 5% 4 4 6% 6% 37%	4260
	11th to 20th	Day	13% 7% 3 7% 5% 4 4 3 5% 7% 43%	4399
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 6% 8% 38%	4824
June	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 6% 9% 44%	2660
	11th to 20th	Day	11% 6% 2 5% 5% 4 5% 4 6% 9% 41%	2660
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 9% 39%	2660
July	1st to 10th	Day	10% 7% 3 7% 6% 5% 6% 5% 7% 10% 35%	4440
	11th to 20th	Day	5% 4 2 6% 4 4 5% 4 7% 9% 50%	4440
	21st to end	Day	9% 7% 3 7% 5% 4 6% 4 6% 9% 41%	4813
August	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 7% 10% 40%	4331
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 3 5% 8% 47%	3833
	21st to end	Day	9% 6% 2 6% 4 4 4 4 6% 10% 44%	4180
September	1st to 10th	Day	13% 6% 2 6% 4 5% 5% 3 5% 7% 44%	2280
	11th to 20th	Day	12% 6% 2 4 3 3 3 3 6% 8% 49%	2231
	21st to end	Day	13% 7% 2 7% 4 5% 4 3 5% 6% 45%	2090
October	1st to 10th	Day	12% 7% 3 6% 4 3 3 4 4 7% 47%	1921
	11th to 20th	Day	18% 10% 3 7% 4 4 4 3 5% 7% 36%	1900
	21st to end	Day	18% 10% 3 6% 4 4 3 3 4 5% 40%	1926
November	1st to 10th	Day	11% 8% 3 7% 5% 4 5% 3 5% 7% 44%	1699
	11th to 20th	Day	14% 11% 5% 9% 5% 5% 4 3 5% 6% 33%	1682
	21st to end	Day	13% 12% 4 9% 5% 3 3 3 4 6% 37%	1520
December	1st to 10th	Day	13% 14% 5% 9% 6% 4 4 3 6% 7% 30%	1520
	11th to 20th	Day	13% 14% 5% 10% 6% 4 4 4 7% 6% 28%	1918
	21st to end	Day	17% 21% 9% 12% 5% 4 3 4 5% 4 16%	2783
January	1st to 10th	Night	11% 12% 7% 12% 6% 4 4 3 4 5% 30%	4428
	11th to 20th	Night	11% 14% 7% 14% 7% 4 5% 5% 7% 6% 21%	4440
	21st to end	Night	15% 18% 9% 11% 5% 5% 4 2 4 4 23%	4720
February	1st to 10th	Night	10% 14% 4 9% 6% 5% 5% 3 5% 6% 33%	2470
	11th to 20th	Night	11% 10% 3 8% 6% 4 5% 3 5% 6% 39%	2297
	21st to end	Night	16% 12% 4 8% 5% 3 3 3 5% 5% 36%	1884
March	1st to 10th	Night	16% 10% 3 6% 4 4 4 3 5% 4 41%	3733
	11th to 20th	Night	9% 6% 2 6% 5% 4 4 4 6% 8% 45%	3590
	21st to end	Night	23% 12% 4 10% 6% 4 4 3 4 5% 28%	3535
April	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 36%	1900
	11th to 20th	Night	18% 9% 2 7% 4 4 4 4 5% 6% 38%	1875
	21st to end	Night	17% 8% 2 6% 4 4 5% 4 6% 7% 38%	1850
May	1st to 10th	Night	16% 7% 3 7% 4 4 4 4 7% 7% 36%	2637
	11th to 20th	Night	12% 7% 3 7% 4 5% 5% 4 5% 7% 42%	2506
	21st to end	Night	10% 8% 2 6% 6% 4 4 4 6% 7% 43%	2743
June	1st to 10th	Night	8% 5% 2 6% 4 5% 4 4 9% 9% 44%	1520
	11th to 20th	Night	12% 6% 1 4 4 4 4 3 7% 10% 46%	1520
	21st to end	Night	8% 6% 2 6% 4 3 4 4 6% 7% 51%	1520
July	1st to 10th	Night	14% 7% 2 5% 4 3 4 4 6% 8% 42%	2530
	11th to 20th	Night	4 3 2 5% 4 4 5% 4 6% 8% 56%	2530
	21st to end	Night	6% 5% 2 5% 4 5% 5% 4 6% 9% 49%	2750
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 5% 8% 49%	2606
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	2998
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 6% 7% 50%	3476
September	1st to 10th	Night	9% 5% 2 5% 3 3 4 2 5% 7% 55%	1900
	11th to 20th	Night	11% 4 2 5% 4 4 3 3 5% 7% 51%	1929
	21st to end	Night	10% 6% 2 5% 4 3 4 4 5% 7% 50%	2090
October	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 4 6% 50%	2256
	11th to 20th	Night	16% 7% 2 6% 4 4 3 3 5% 6% 43%	2280
	21st to end	Night	17% 8% 3 6% 4 4 4 4 6% 7% 36%	2670
November	1st to 10th	Night	12% 8% 3 6% 4 4 5% 4 4 6% 46%	2452
	11th to 20th	Night	13% 10% 4 9% 6% 5% 5% 4 5% 5% 34%	2497
	21st to end	Night	16% 11% 3 7% 4 3 4 3 4 6% 38%	2660
December	1st to 10th	Night	13% 14% 4 10% 5% 5% 5% 5% 5% 6% 30%	2660
	11th to 20th	Night	14% 15% 6% 11% 5% 5% 4 3 5% 5% 28%	3279
	21st to end	Night	19% 17% 6% 11% 5% 5% 4 4 4 4 19%	4884

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	62% 3 12% 16% 6%	2528
	11th to 20th	Day	59% 6% 10% 18% 8%	2530
	21st to end	Day	66% 3 10% 15% 5%	2943
February	1st to 10th	Day	54% 4 12% 19% 12% 1	1710
	11th to 20th	Day	49% 5% 11% 23% 11% 2	1779
	21st to end	Day	54% 4 8% 20% 11% 3	1570
March	1st to 10th	Day	41% 5% 10% 29% 13% 3	3120
	11th to 20th	Day	39% 6% 10% 31% 13% 1	3384
	21st to end	Day	59% 5% 11% 16% 8% 2	4096
April	1st to 10th	Day	54% 5% 9% 21% 12%	2280
	11th to 20th	Day	51% 4 8% 21% 13% 2	2254
	21st to end	Day	52% 5% 10% 19% 12% 2	2328
May	1st to 10th	Day	45% 6% 9% 22% 16% 1	4298
	11th to 20th	Day	40% 6% 9% 31% 14%	4403
	21st to end	Day	42% 7% 11% 23% 15% 3	4837
June	1st to 10th	Day	37% 5% 14% 27% 16% 2	2660
	11th to 20th	Day	37% 6% 13% 25% 17% 1	2660
	21st to end	Day	41% 6% 14% 24% 14% 2	2660
July	1st to 10th	Day	43% 6% 14% 27% 9% 1	4371
	11th to 20th	Day	29% 6% 17% 31% 17% 1	4365
	21st to end	Day	38% 7% 14% 21% 18% 2	4662
August	1st to 10th	Day	38% 6% 14% 28% 13% 1	4316
	11th to 20th	Day	35% 5% 13% 33% 13% 1	3871
	21st to end	Day	35% 5% 13% 29% 16% 1	4179
September	1st to 10th	Day	39% 6% 10% 25% 18% 2	2280
	11th to 20th	Day	32% 5% 11% 33% 17% 2	2231
	21st to end	Day	40% 5% 9% 29% 16% 1	2090
October	1st to 10th	Day	24% 3 6% 41% 26% 1	3194
	11th to 20th	Day	36% 3 9% 27% 23% 2	3140
	21st to end	Day	43% 2 10% 28% 14% 3	3151
November	1st to 10th	Day	40% 4 13% 26% 14% 2	1699
	11th to 20th	Day	51% 4 12% 21% 11% 1	1682
	21st to end	Day	49% 4 16% 23% 8% 1	1520
December	1st to 10th	Day	55% 3 14% 18% 8% 1	1520
	11th to 20th	Day	55% 3 15% 16% 8% 3	1915
	21st to end	Day	72% 4 8% 10% 6%	2783
January	1st to 10th	Night	56% 5% 9% 21% 9%	4428
	11th to 20th	Night	62% 4 9% 16% 9%	4440
	21st to end	Night	66% 3 8% 16% 6% 1	4720
February	1st to 10th	Night	53% 3 10% 20% 13% 2	2470
	11th to 20th	Night	46% 4 10% 24% 14% 1	2298
	21st to end	Night	51% 3 10% 21% 12% 3	1884
March	1st to 10th	Night	46% 4 11% 25% 10% 5%	3733
	11th to 20th	Night	35% 6% 9% 29% 18% 3	3590
	21st to end	Night	61% 4 6% 18% 10% 1	3535
April	1st to 10th	Night	48% 5% 10% 22% 14% 2	1900
	11th to 20th	Night	48% 4 7% 20% 18% 3	1875
	21st to end	Night	44% 6% 11% 24% 13% 2	1850
May	1st to 10th	Night	44% 7% 12% 17% 20% 1	2664
	11th to 20th	Night	40% 7% 9% 26% 17% 1	2507
	21st to end	Night	36% 9% 10% 21% 20% 4	2751
June	1st to 10th	Night	32% 7% 13% 28% 19% 1	1520
	11th to 20th	Night	34% 5% 10% 26% 23% 2	1520
	21st to end	Night	33% 5% 17% 23% 18% 3	1520
July	1st to 10th	Night	40% 5% 15% 24% 13% 3	2490
	11th to 20th	Night	26% 5% 14% 35% 18% 2	2482
	21st to end	Night	31% 8% 15% 22% 20% 5%	2662
August	1st to 10th	Night	33% 5% 14% 26% 20% 2	2597
	11th to 20th	Night	32% 5% 13% 32% 17% 1	3026
	21st to end	Night	34% 5% 12% 27% 19% 3	3476
September	1st to 10th	Night	30% 5% 11% 28% 23% 3	1900
	11th to 20th	Night	31% 5% 11% 33% 19% 2	1929
	21st to end	Night	32% 5% 10% 31% 22% 1	2090
October	1st to 10th	Night	25% 3 5% 37% 28% 2	3763
	11th to 20th	Night	33% 3 11% 28% 24% 2	3779
	21st to end	Night	43% 4 9% 27% 15% 2	4395
November	1st to 10th	Night	39% 5% 10% 27% 17% 3	2452
	11th to 20th	Night	50% 4 12% 20% 12% 1	2497
	21st to end	Night	47% 4 13% 24% 10% 1	2660
December	1st to 10th	Night	54% 5% 12% 20% 8% 1	2660
	11th to 20th	Night	57% 5% 11% 18% 8% 1	3281
	21st to end	Night	67% 5% 8% 15% 5%	4884

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% 15% 33% 23% 10% 1	270
	11th to 20th	Day	17% 19% 39% 19% 6% 1	270
	21st to end	Day	24% 14% 34% 22% 5%	297
February	1st to 10th	Day	16% 20% 40% 18% 5%	270
	11th to 20th	Day	21% 21% 37% 16% 5%	270
	21st to end	Day	21% 17% 45% 15% 1	225
March	1st to 10th	Day	19% 19% 43% 14% 5%	270
	11th to 20th	Day	19% 19% 37% 17% 5% 3	270
	21st to end	Day	29% 11% 32% 20% 7% 2	463
April	1st to 10th	Day	25% 16% 34% 20% 5%	460
	11th to 20th	Day	26% 18% 25% 19% 11% 2	452
	21st to end	Day	23% 14% 28% 23% 9% 2	460
May	1st to 10th	Day	21% 12% 33% 25% 9% 1	563
	11th to 20th	Day	19% 12% 30% 25% 12% 3	675
	21st to end	Day	19% 8% 26% 25% 16% 5%	734
June	1st to 10th	Day	11% 8% 29% 30% 18% 5%	680
	11th to 20th	Day	14% 6% 32% 28% 16% 4	680
	21st to end	Day	13% 8% 30% 29% 15% 5%	680
July	1st to 10th	Day	8% 5% 18% 31% 25% 12%	671
	11th to 20th	Day	10% 5% 25% 31% 20% 10%	668
	21st to end	Day	9% 3 26% 33% 22% 7%	739
August	1st to 10th	Day	8% 4 19% 35% 24% 10%	676
	11th to 20th	Day	12% 5% 19% 27% 23% 13%	547
	21st to end	Day	11% 6% 21% 31% 23% 9%	539
September	1st to 10th	Day	14% 8% 23% 27% 20% 7%	490
	11th to 20th	Day	12% 3 21% 31% 24% 8%	490
	21st to end	Day	15% 11% 27% 25% 18% 4	490
October	1st to 10th	Day	17% 10% 28% 26% 16% 3	321
	11th to 20th	Day	25% 16% 34% 17% 7%	300
	21st to end	Day	26% 17% 31% 20% 5% 2	330
November	1st to 10th	Day	15% 15% 37% 25% 6% 1	279
	11th to 20th	Day	20% 18% 37% 16% 9%	270
	21st to end	Day	23% 14% 40% 19% 5%	270
December	1st to 10th	Day	18% 18% 40% 16% 6% 1	270
	11th to 20th	Day	20% 12% 39% 20% 9% 1	270
	21st to end	Day	27% 18% 36% 17% 2	297
January	1st to 10th	Night	16% 17% 36% 23% 7% 1	950
	11th to 20th	Night	20% 13% 38% 24% 5% 1	950
	21st to end	Night	20% 12% 37% 26% 5% 1	1045
February	1st to 10th	Night	18% 13% 37% 26% 6%	950
	11th to 20th	Night	16% 14% 39% 26% 4	822
	21st to end	Night	23% 14% 39% 20% 3	628
March	1st to 10th	Night	22% 12% 36% 23% 6% 1	760
	11th to 20th	Night	16% 11% 37% 28% 7%	641
	21st to end	Night	22% 10% 34% 27% 6% 1	627
April	1st to 10th	Night	20% 12% 39% 24% 4	570
	11th to 20th	Night	22% 13% 29% 29% 7%	563
	21st to end	Night	20% 9% 32% 29% 9% 1	570
May	1st to 10th	Night	20% 9% 34% 29% 7% 1	570
	11th to 20th	Night	18% 7% 31% 34% 9%	561
	21st to end	Night	14% 5% 27% 36% 16% 1	617
June	1st to 10th	Night	10% 4 29% 41% 15%	570
	11th to 20th	Night	15% 6% 28% 38% 13%	570
	21st to end	Night	10% 4 27% 42% 16%	570
July	1st to 10th	Night	9% 3 12% 41% 31% 4	555
	11th to 20th	Night	7% 3 23% 41% 23% 2	552
	21st to end	Night	7% 1 17% 49% 22% 3	624
August	1st to 10th	Night	7% 2 15% 49% 24% 4	567
	11th to 20th	Night	10% 2 13% 44% 26% 5%	564
	21st to end	Night	11% 2 18% 43% 23% 3	627
September	1st to 10th	Night	9% 5% 24% 35% 22% 6%	570
	11th to 20th	Night	13% 3 22% 36% 23% 3	599
	21st to end	Night	13% 8% 24% 36% 18% 2	760
October	1st to 10th	Night	15% 5% 29% 32% 18% 1	760
	11th to 20th	Night	19% 12% 31% 29% 8%	760
	21st to end	Night	22% 11% 33% 27% 6% 1	836
November	1st to 10th	Night	14% 11% 39% 25% 10% 1	755
	11th to 20th	Night	19% 15% 39% 21% 6%	787
	21st to end	Night	21% 14% 35% 24% 6%	950
December	1st to 10th	Night	20% 14% 39% 21% 5%	950
	11th to 20th	Night	23% 12% 35% 23% 6% 1	950
	21st to end	Night	27% 13% 34% 22% 3	1045

Page generated at 2024-11-01 21:47:48. Version ac07

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