High Springs Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Springs Observatory clear sky chart from 2005-11-06 to 2026-09-29.

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	8% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	148690
	Night	9% 6% 2 6% 4 4 5% 4 7% 9% 43%	142719
Transparency	Day	36% 8% 17% 19% 14% 6%	152439
	Night	36% 7% 16% 19% 15% 7%	147042
Seeing	Day	10% 6% 19% 25% 23% 17%	17889
	Night	11% 5% 20% 34% 25% 6%	27875

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	8% 7% 2 5% 3 3 4 3 5% 7% 53%	5258
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 5% 7% 37%	5280
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 6% 9% 49%	6110
February	1st to 10th	Day	14% 7% 2 6% 5% 3 3 3 5% 7% 46%	2100
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 6% 48%	2048
	21st to end	Day	12% 7% 2 4 3 4 3 3 5% 6% 50%	1740
March	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 6% 9% 41%	5045
	11th to 20th	Day	8% 3 1 4 3 3 4 4 6% 8% 56%	5090
	21st to end	Day	11% 4 2 5% 4 4 4 4 6% 8% 50%	5586
April	1st to 10th	Day	7% 5% 2 5% 4 4 5% 3 6% 10% 48%	2310
	11th to 20th	Day	9% 5% 2 6% 5% 4 4 4 5% 7% 49%	2286
	21st to end	Day	4 3 2 5% 4 5% 5% 4 6% 8% 54%	2652
May	1st to 10th	Day	7% 5% 2 7% 5% 4 6% 4 7% 10% 43%	7616
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 7% 9% 45%	7626
	21st to end	Day	4 4 2 5% 5% 5% 6% 5% 9% 13% 41%	8391
June	1st to 10th	Day	8% 7% 3 9% 8% 6% 7% 6% 9% 10% 28%	2730
	11th to 20th	Day	6% 4 2 8% 7% 8% 8% 7% 10% 11% 28%	2730
	21st to end	Day	7% 5% 2 9% 7% 7% 7% 7% 8% 10% 31%	2730
July	1st to 10th	Day	6% 5% 2 7% 6% 7% 8% 7% 11% 15% 26%	7680
	11th to 20th	Day	4 3 2 7% 6% 7% 7% 7% 10% 16% 31%	7680
	21st to end	Day	5% 4 2 6% 6% 6% 7% 6% 10% 15% 32%	8340
August	1st to 10th	Day	11% 6% 3 9% 7% 6% 7% 6% 9% 13% 23%	6014
	11th to 20th	Day	4 4 2 6% 5% 6% 6% 5% 8% 13% 39%	5601
	21st to end	Day	8% 5% 2 8% 6% 6% 7% 6% 9% 14% 29%	5683
September	1st to 10th	Day	9% 7% 3 10% 8% 8% 7% 6% 8% 10% 23%	2310
	11th to 20th	Day	10% 6% 3 9% 7% 8% 6% 7% 8% 8% 27%	2310
	21st to end	Day	9% 6% 3 8% 5% 5% 6% 5% 6% 9% 37%	2288
October	1st to 10th	Day	12% 6% 3 8% 5% 5% 5% 5% 6% 8% 39%	2200
	11th to 20th	Day	6% 4 2 4 4 4 4 2 5% 7% 58%	2035
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 5% 7% 52%	2200
November	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 7% 51%	2057
	11th to 20th	Day	9% 5% 2 5% 3 4 4 4 6% 6% 51%	2026
	21st to end	Day	10% 5% 2 6% 3 5% 4 3 5% 7% 48%	1890
December	1st to 10th	Day	6% 4 2 5% 4 3 4 4 5% 6% 56%	3020
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	3463
	21st to end	Day	15% 9% 3 7% 4 3 4 3 4 6% 43%	4565
January	1st to 10th	Night	9% 7% 2 4 2 2 3 3 4 8% 56%	7635
	11th to 20th	Night	16% 7% 2 7% 5% 5% 4 4 6% 7% 37%	7680
	21st to end	Night	14% 7% 2 6% 4 3 4 4 5% 8% 42%	8066
February	1st to 10th	Night	12% 6% 2 6% 4 4 3 3 5% 6% 48%	2520
	11th to 20th	Night	12% 7% 2 6% 4 4 3 3 4 6% 48%	2458
	21st to end	Night	11% 7% 2 5% 4 4 3 3 4 7% 50%	2064
March	1st to 10th	Night	14% 8% 3 8% 4 4 4 3 5% 6% 42%	5028
	11th to 20th	Night	6% 5% 1 4 3 3 4 3 6% 9% 55%	5090
	21st to end	Night	10% 5% 2 5% 4 4 4 4 6% 7% 50%	5588
April	1st to 10th	Night	8% 6% 3 4 4 3 4 4 5% 8% 49%	2310
	11th to 20th	Night	6% 5% 3 5% 4 4 4 4 6% 7% 53%	2283
	21st to end	Night	5% 4 1 4 3 4 5% 4 7% 8% 56%	1981
May	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 4 6% 9% 44%	5237
	11th to 20th	Night	9% 7% 2 6% 4 4 4 4 5% 9% 47%	5234
	21st to end	Night	5% 4 2 5% 4 5% 4 4 6% 12% 49%	5761
June	1st to 10th	Night	10% 5% 3 8% 5% 5% 6% 5% 9% 12% 33%	1890
	11th to 20th	Night	5% 5% 2 7% 5% 6% 5% 6% 10% 15% 34%	1890
	21st to end	Night	5% 5% 2 6% 6% 4 6% 6% 8% 14% 37%	1890
July	1st to 10th	Night	7% 5% 3 8% 6% 6% 7% 7% 9% 15% 27%	5278
	11th to 20th	Night	3 4 2 6% 5% 6% 7% 6% 10% 15% 36%	5277
	21st to end	Night	6% 6% 3 8% 6% 6% 7% 7% 10% 13% 30%	5736
August	1st to 10th	Night	10% 6% 3 9% 6% 6% 7% 6% 9% 13% 24%	4135
	11th to 20th	Night	3 3 2 5% 4 5% 6% 6% 10% 15% 43%	4439
	21st to end	Night	7% 5% 3 8% 6% 6% 7% 6% 9% 13% 31%	5393
September	1st to 10th	Night	8% 7% 4 9% 6% 6% 7% 5% 8% 10% 29%	2310
	11th to 20th	Night	10% 8% 2 8% 5% 6% 5% 5% 8% 10% 33%	2310
	21st to end	Night	8% 6% 2 8% 5% 4 5% 4 6% 9% 42%	2289
October	1st to 10th	Night	9% 6% 2 9% 5% 5% 4 4 5% 7% 43%	2200
	11th to 20th	Night	6% 5% 2 4 3 3 4 3 6% 7% 56%	2363
	21st to end	Night	7% 5% 2 6% 4 4 4 3 6% 7% 52%	2640
November	1st to 10th	Night	6% 4 2 5% 4 4 4 3 6% 8% 53%	2461
	11th to 20th	Night	9% 6% 2 5% 4 4 3 4 6% 7% 52%	2588
	21st to end	Night	10% 6% 3 6% 4 4 4 3 6% 7% 48%	2730
December	1st to 10th	Night	10% 5% 2 6% 3 3 3 3 4 7% 54%	4380
	11th to 20th	Night	11% 7% 2 6% 4 3 4 3 5% 7% 48%	4952
	21st to end	Night	14% 8% 2 6% 4 5% 4 3 5% 6% 42%	6633

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	31% 3 10% 16% 26% 13%	5259
	11th to 20th	Day	49% 2 5% 13% 17% 15%	5280
	21st to end	Day	31% 4 11% 23% 17% 13%	6110
February	1st to 10th	Day	39% 3 9% 14% 22% 13%	2100
	11th to 20th	Day	36% 4 9% 17% 23% 11%	2058
	21st to end	Day	35% 4 9% 17% 21% 14%	1740
March	1st to 10th	Day	39% 5% 10% 16% 19% 11%	5045
	11th to 20th	Day	26% 4 11% 17% 24% 18%	5090
	21st to end	Day	31% 4 9% 25% 20% 11%	5586
April	1st to 10th	Day	31% 5% 13% 20% 19% 12%	2310
	11th to 20th	Day	34% 4 8% 19% 25% 10%	2286
	21st to end	Day	26% 5% 12% 25% 23% 9%	2652
May	1st to 10th	Day	34% 8% 15% 25% 14% 4	7651
	11th to 20th	Day	34% 6% 15% 29% 13% 2	7630
	21st to end	Day	31% 10% 21% 24% 13% 2	8405
June	1st to 10th	Day	46% 8% 18% 18% 9% 1	2730
	11th to 20th	Day	43% 11% 22% 18% 5%	2730
	21st to end	Day	43% 11% 23% 16% 6%	2730
July	1st to 10th	Day	42% 15% 33% 10% 1	7615
	11th to 20th	Day	36% 14% 38% 11% 1	7611
	21st to end	Day	35% 13% 31% 20% 1	8156
August	1st to 10th	Day	49% 12% 27% 11% 2	6001
	11th to 20th	Day	32% 12% 34% 17% 6%	5639
	21st to end	Day	41% 13% 26% 17% 3	5683
September	1st to 10th	Day	51% 11% 19% 12% 7% 1	2310
	11th to 20th	Day	48% 10% 16% 16% 8% 1	2310
	21st to end	Day	42% 6% 13% 20% 15% 4	2288
October	1st to 10th	Day	51% 7% 8% 13% 14% 7%	3590
	11th to 20th	Day	19% 3 5% 18% 40% 15%	3288
	21st to end	Day	20% 4 7% 24% 36% 9%	3538
November	1st to 10th	Day	31% 4 10% 21% 19% 15%	2057
	11th to 20th	Day	33% 4 8% 19% 24% 12%	2026
	21st to end	Day	35% 4 7% 22% 24% 8%	1890
December	1st to 10th	Day	28% 4 11% 22% 23% 12%	3020
	11th to 20th	Day	35% 5% 9% 22% 20% 8%	3460
	21st to end	Day	42% 4 8% 18% 22% 6%	4565
January	1st to 10th	Night	29% 3 10% 18% 28% 12%	7636
	11th to 20th	Night	47% 3 6% 15% 17% 12%	7680
	21st to end	Night	41% 5% 10% 18% 16% 10%	8066
February	1st to 10th	Night	37% 4 9% 15% 21% 14%	2520
	11th to 20th	Night	37% 5% 8% 20% 18% 12%	2459
	21st to end	Night	36% 4 9% 18% 22% 12%	2064
March	1st to 10th	Night	44% 5% 8% 16% 17% 10%	5028
	11th to 20th	Night	27% 4 13% 17% 20% 19%	5090
	21st to end	Night	32% 5% 10% 22% 20% 11%	5588
April	1st to 10th	Night	33% 5% 15% 20% 18% 10%	2310
	11th to 20th	Night	30% 5% 8% 23% 24% 10%	2283
	21st to end	Night	24% 6% 14% 29% 20% 8%	1981
May	1st to 10th	Night	34% 8% 17% 25% 12% 4	5264
	11th to 20th	Night	34% 6% 17% 27% 13% 3	5235
	21st to end	Night	28% 9% 21% 26% 15% 1	5771
June	1st to 10th	Night	40% 9% 21% 22% 7%	1890
	11th to 20th	Night	35% 12% 28% 21% 4	1890
	21st to end	Night	34% 13% 26% 21% 5% 1	1890
July	1st to 10th	Night	43% 14% 32% 9% 1	5235
	11th to 20th	Night	35% 15% 39% 10% 1	5226
	21st to end	Night	41% 13% 28% 17% 1	5606
August	1st to 10th	Night	48% 13% 28% 8% 2	4124
	11th to 20th	Night	25% 14% 37% 18% 5%	4467
	21st to end	Night	40% 15% 27% 14% 3	5393
September	1st to 10th	Night	44% 13% 23% 14% 5% 1	2310
	11th to 20th	Night	45% 10% 20% 17% 7% 1	2310
	21st to end	Night	37% 7% 19% 20% 13% 4	2289
October	1st to 10th	Night	51% 8% 11% 13% 11% 7%	3590
	11th to 20th	Night	21% 4 7% 21% 34% 13%	3849
	21st to end	Night	22% 4 6% 23% 35% 10%	4252
November	1st to 10th	Night	29% 4 11% 23% 19% 14%	2461
	11th to 20th	Night	32% 3 9% 20% 23% 13%	2588
	21st to end	Night	35% 4 10% 20% 21% 10%	2730
December	1st to 10th	Night	31% 3 10% 21% 18% 16%	4380
	11th to 20th	Night	37% 5% 10% 21% 18% 10%	4954
	21st to end	Night	42% 4 9% 19% 20% 6%	6633

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	9% 14% 46% 22% 8% 1	330
	11th to 20th	Day	12% 14% 37% 26% 8% 2	330
	21st to end	Day	13% 21% 43% 18% 5%	363
February	1st to 10th	Day	11% 15% 34% 28% 11% 2	330
	11th to 20th	Day	16% 16% 34% 27% 6% 1	330
	21st to end	Day	11% 13% 40% 24% 10% 1	283
March	1st to 10th	Day	11% 12% 31% 29% 14% 2	540
	11th to 20th	Day	14% 9% 32% 27% 14% 3	540
	21st to end	Day	11% 9% 31% 31% 16% 2	594
April	1st to 10th	Day	11% 12% 27% 25% 20% 4	540
	11th to 20th	Day	10% 8% 28% 28% 20% 6%	532
	21st to end	Day	4 6% 21% 34% 25% 10%	540
May	1st to 10th	Day	7% 6% 22% 29% 24% 12%	543
	11th to 20th	Day	7% 6% 15% 30% 25% 17%	567
	21st to end	Day	7% 2 12% 22% 32% 24%	617
June	1st to 10th	Day	10% 3 11% 25% 27% 24%	570
	11th to 20th	Day	8% 3 9% 20% 29% 31%	570
	21st to end	Day	5% 2 4 19% 32% 37%	570
July	1st to 10th	Day	6% 1 4 13% 29% 46%	565
	11th to 20th	Day	6% 1 2 11% 33% 46%	564
	21st to end	Day	8% 1 5% 13% 33% 40%	620
August	1st to 10th	Day	12% 1 6% 17% 28% 36%	566
	11th to 20th	Day	6% 2 4 13% 28% 47%	559
	21st to end	Day	11% 1 5% 18% 32% 32%	627
September	1st to 10th	Day	11% 3 8% 20% 30% 29%	570
	11th to 20th	Day	12% 2 7% 27% 31% 21%	570
	21st to end	Day	8% 3 9% 25% 34% 21%	562
October	1st to 10th	Day	15% 3 20% 32% 21% 9%	530
	11th to 20th	Day	6% 6% 16% 32% 32% 9%	530
	21st to end	Day	9% 5% 20% 39% 22% 4	583
November	1st to 10th	Day	10% 5% 22% 33% 24% 6%	535
	11th to 20th	Day	12% 8% 26% 33% 16% 4	466
	21st to end	Day	11% 8% 35% 31% 14% 2	330
December	1st to 10th	Day	10% 13% 34% 25% 13% 5%	330
	11th to 20th	Day	15% 12% 30% 28% 13% 1	330
	21st to end	Day	13% 9% 32% 30% 13% 3	363
January	1st to 10th	Night	14% 10% 31% 36% 9%	840
	11th to 20th	Night	12% 10% 27% 38% 13% 1	840
	21st to end	Night	18% 10% 33% 33% 6%	924
February	1st to 10th	Night	15% 6% 31% 38% 10%	840
	11th to 20th	Night	15% 9% 30% 36% 8% 1	823
	21st to end	Night	14% 7% 34% 39% 6%	692
March	1st to 10th	Night	9% 9% 32% 39% 11%	840
	11th to 20th	Night	10% 9% 30% 37% 14% 1	840
	21st to end	Night	10% 7% 31% 37% 15% 1	924
April	1st to 10th	Night	10% 9% 28% 37% 15%	840
	11th to 20th	Night	8% 7% 29% 40% 15% 1	831
	21st to end	Night	6% 4 23% 43% 24% 1	707
May	1st to 10th	Night	7% 4 19% 45% 23% 3	630
	11th to 20th	Night	8% 2 17% 40% 30% 2	621
	21st to end	Night	6% 2 10% 37% 40% 6%	683
June	1st to 10th	Night	12% 2 10% 37% 32% 7%	630
	11th to 20th	Night	6% 2 7% 24% 42% 19%	630
	21st to end	Night	7% 1 4 21% 48% 18%	630
July	1st to 10th	Night	7% 2 3 17% 48% 24%	615
	11th to 20th	Night	6% 1 2 13% 51% 27%	612
	21st to end	Night	5% 2 4 16% 54% 20%	690
August	1st to 10th	Night	9% 1 3 15% 52% 20%	627
	11th to 20th	Night	5% 2 3 13% 50% 27%	624
	21st to end	Night	11% 4 6% 22% 40% 18%	845
September	1st to 10th	Night	12% 2 8% 23% 39% 16%	840
	11th to 20th	Night	13% 3 8% 33% 34% 10%	840
	21st to end	Night	11% 1 12% 31% 39% 6%	833
October	1st to 10th	Night	12% 2 18% 37% 27% 4	800
	11th to 20th	Night	7% 4 18% 39% 30% 3	800
	21st to end	Night	10% 4 19% 42% 24% 2	880
November	1st to 10th	Night	8% 4 23% 41% 22% 2	820
	11th to 20th	Night	12% 5% 21% 42% 18% 2	840
	21st to end	Night	12% 6% 26% 40% 15% 1	840
December	1st to 10th	Night	14% 6% 23% 37% 19% 1	840
	11th to 20th	Night	13% 8% 25% 38% 16% 1	840
	21st to end	Night	14% 7% 26% 37% 15%	924

Page generated at 2026-09-26 04:18:40. Version ac07

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