Batavia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Batavia 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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	149831
	Night	14% 10% 3 8% 5% 4 4 3 5% 7% 36%	141642
Transparency	Day	45% 6% 11% 23% 14% 2	153473
	Night	46% 6% 10% 22% 14% 2	146060
Seeing	Day	20% 13% 27% 22% 13% 5%	17818
	Night	19% 11% 26% 27% 14% 2	27228

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	16% 15% 7% 12% 5% 4 3 2 4 5% 25%	5258
	11th to 20th	Day	12% 13% 5% 17% 6% 5% 4 3 3 5% 28%	5280
	21st to end	Day	19% 12% 6% 10% 7% 6% 5% 4 5% 5% 22%	5780
February	1st to 10th	Day	19% 13% 5% 8% 5% 4 3 3 5% 5% 30%	1986
	11th to 20th	Day	17% 11% 5% 11% 5% 4 4 3 4 5% 30%	2048
	21st to end	Day	18% 13% 6% 9% 4 4 3 3 4 6% 31%	1730
March	1st to 10th	Day	17% 14% 6% 9% 4 4 3 3 4 5% 31%	4662
	11th to 20th	Day	13% 8% 3 7% 5% 5% 5% 3 5% 8% 39%	5090
	21st to end	Day	16% 10% 3 8% 4 4 4 3 5% 7% 35%	5586
April	1st to 10th	Day	15% 10% 3 7% 5% 4 5% 3 6% 7% 36%	2452
	11th to 20th	Day	16% 8% 3 8% 5% 3 4 3 5% 7% 38%	2565
	21st to end	Day	16% 8% 3 8% 5% 5% 4 3 5% 7% 36%	2730
May	1st to 10th	Day	17% 9% 3 8% 5% 5% 6% 4 7% 8% 30%	7616
	11th to 20th	Day	17% 8% 3 7% 5% 4 5% 3 6% 8% 36%	7626
	21st to end	Day	17% 8% 3 8% 6% 5% 6% 5% 7% 8% 28%	8391
June	1st to 10th	Day	11% 6% 2 7% 5% 4 6% 5% 6% 8% 40%	2730
	11th to 20th	Day	9% 5% 2 7% 5% 4 5% 4 7% 10% 41%	2862
	21st to end	Day	9% 6% 2 6% 6% 5% 5% 5% 6% 9% 40%	2940
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 7% 9% 40%	8280
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 10% 38%	7800
	21st to end	Day	8% 7% 3 9% 6% 6% 6% 5% 8% 9% 33%	8340
August	1st to 10th	Day	10% 5% 2 7% 4 5% 5% 5% 7% 10% 39%	6014
	11th to 20th	Day	10% 8% 3 8% 6% 5% 6% 5% 8% 10% 33%	5951
	21st to end	Day	4 4 2 5% 3 4 4 4 6% 9% 57%	6172
September	1st to 10th	Day	12% 5% 2 5% 4 3 4 4 5% 6% 51%	2373
	11th to 20th	Day	9% 4 1 5% 4 4 5% 4 6% 9% 49%	2310
	21st to end	Day	17% 7% 2 5% 4 3 3 3 4 6% 46%	2288
October	1st to 10th	Day	11% 5% 1 5% 4 4 5% 4 4 5% 51%	2200
	11th to 20th	Day	13% 6% 2 6% 4 3 4 3 5% 7% 47%	2019
	21st to end	Day	19% 9% 2 6% 3 4 3 3 5% 6% 40%	2072
November	1st to 10th	Day	10% 7% 2 5% 4 3 3 3 4 7% 51%	1852
	11th to 20th	Day	14% 12% 3 8% 5% 4 4 3 4 6% 36%	1890
	21st to end	Day	17% 12% 4 8% 4 4 4 2 4 5% 36%	1890
December	1st to 10th	Day	18% 10% 4 7% 4 4 4 3 4 4 37%	3020
	11th to 20th	Day	18% 15% 5% 10% 5% 5% 4 4 4 4 26%	3463
	21st to end	Day	21% 20% 4 10% 5% 4 4 3 4 5% 19%	4565
January	1st to 10th	Night	13% 15% 6% 14% 7% 5% 5% 4 5% 5% 21%	7635
	11th to 20th	Night	12% 15% 6% 15% 7% 5% 5% 3 4 4 24%	7680
	21st to end	Night	18% 12% 4 9% 6% 5% 4 3 4 5% 31%	8401
February	1st to 10th	Night	20% 12% 5% 8% 5% 4 4 4 4 6% 29%	2630
	11th to 20th	Night	19% 12% 4 9% 5% 4 5% 3 4 6% 30%	2458
	21st to end	Night	18% 15% 4 8% 4 4 3 2 4 6% 31%	2076
March	1st to 10th	Night	18% 14% 3 6% 4 4 3 2 4 5% 37%	5411
	11th to 20th	Night	12% 7% 3 7% 4 4 4 4 5% 7% 42%	5090
	21st to end	Night	16% 11% 4 8% 5% 5% 4 3 5% 6% 33%	5588
April	1st to 10th	Night	14% 10% 3 6% 6% 4 4 4 6% 7% 36%	2185
	11th to 20th	Night	14% 7% 2 5% 5% 4 5% 5% 6% 7% 40%	2004
	21st to end	Night	16% 8% 3 7% 5% 3 3 3 6% 9% 37%	1890
May	1st to 10th	Night	19% 9% 3 7% 5% 4 5% 4 6% 8% 31%	5237
	11th to 20th	Night	14% 7% 2 7% 5% 5% 5% 4 7% 8% 36%	5234
	21st to end	Night	16% 8% 3 8% 5% 4 5% 4 6% 8% 32%	5761
June	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 7% 9% 48%	1890
	11th to 20th	Night	9% 5% 2 5% 4 4 4 3 7% 11% 47%	1750
	21st to end	Night	7% 5% 1 4 5% 5% 5% 5% 8% 10% 45%	1680
July	1st to 10th	Night	8% 6% 2 7% 5% 4 4 3 6% 9% 46%	4708
	11th to 20th	Night	9% 6% 3 7% 5% 5% 5% 4 7% 9% 41%	5158
	21st to end	Night	9% 6% 3 7% 6% 5% 5% 5% 7% 9% 39%	5736
August	1st to 10th	Night	10% 8% 3 8% 5% 4 5% 4 7% 7% 40%	4135
	11th to 20th	Night	11% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	4095
	21st to end	Night	3 2 1 4 3 3 4 3 6% 11% 59%	4950
September	1st to 10th	Night	10% 5% 2 4 3 4 2 4 5% 7% 53%	2225
	11th to 20th	Night	8% 4 2 6% 3 4 5% 4 5% 7% 53%	2310
	21st to end	Night	15% 6% 2 6% 4 3 4 3 5% 6% 47%	2289
October	1st to 10th	Night	8% 5% 2 5% 4 3 4 3 5% 7% 55%	2200
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 5% 7% 46%	2380
	21st to end	Night	18% 9% 2 5% 4 4 4 3 5% 5% 42%	2765
November	1st to 10th	Night	13% 7% 3 5% 4 3 4 3 5% 7% 46%	2666
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 5% 6% 40%	2730
	21st to end	Night	18% 14% 3 7% 5% 4 4 3 4 6% 32%	2730
December	1st to 10th	Night	17% 12% 4 8% 4 4 3 2 4 5% 37%	4380
	11th to 20th	Night	18% 15% 6% 9% 5% 4 4 3 4 5% 26%	4952
	21st to end	Night	21% 19% 6% 11% 6% 4 4 3 4 5% 17%	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	62% 3 12% 16% 6%	5259
	11th to 20th	Day	59% 3 9% 14% 13% 2	5280
	21st to end	Day	64% 3 8% 16% 6% 2	5780
February	1st to 10th	Day	56% 4 10% 20% 9% 1	1986
	11th to 20th	Day	56% 4 10% 18% 11% 1	2058
	21st to end	Day	55% 4 10% 20% 10% 2	1730
March	1st to 10th	Day	54% 6% 7% 19% 12% 3	4662
	11th to 20th	Day	43% 6% 9% 27% 14% 1	5090
	21st to end	Day	48% 5% 12% 21% 12% 2	5586
April	1st to 10th	Day	46% 6% 12% 23% 12% 1	2452
	11th to 20th	Day	45% 6% 10% 22% 14% 3	2565
	21st to end	Day	46% 7% 12% 22% 11% 2	2730
May	1st to 10th	Day	49% 7% 12% 20% 10% 1	7651
	11th to 20th	Day	46% 7% 11% 24% 13%	7630
	21st to end	Day	49% 8% 11% 19% 11% 2	8405
June	1st to 10th	Day	39% 9% 11% 23% 17% 2	2730
	11th to 20th	Day	35% 9% 14% 23% 17% 1	2862
	21st to end	Day	39% 9% 13% 22% 14% 4	2940
July	1st to 10th	Day	38% 7% 12% 25% 17% 1	8211
	11th to 20th	Day	38% 8% 12% 29% 12% 1	7729
	21st to end	Day	43% 8% 11% 22% 14% 2	8156
August	1st to 10th	Day	38% 9% 14% 27% 11% 2	6001
	11th to 20th	Day	43% 7% 12% 27% 11%	5990
	21st to end	Day	24% 6% 17% 33% 19% 2	6171
September	1st to 10th	Day	33% 6% 12% 25% 20% 5%	2373
	11th to 20th	Day	31% 6% 12% 24% 23% 3	2310
	21st to end	Day	40% 5% 9% 22% 22% 2	2288
October	1st to 10th	Day	22% 5% 7% 32% 32% 2	3590
	11th to 20th	Day	29% 3 10% 29% 28% 2	3259
	21st to end	Day	35% 4 10% 25% 23% 3	3322
November	1st to 10th	Day	35% 4 10% 28% 20% 3	1852
	11th to 20th	Day	48% 5% 7% 22% 16% 3	1890
	21st to end	Day	51% 4 9% 22% 13% 1	1890
December	1st to 10th	Day	51% 4 9% 26% 10%	3020
	11th to 20th	Day	60% 6% 8% 19% 7%	3460
	21st to end	Day	67% 5% 9% 13% 6% 1	4565
January	1st to 10th	Night	62% 6% 9% 15% 7%	7636
	11th to 20th	Night	63% 4 7% 13% 10% 3	7680
	21st to end	Night	55% 4 10% 21% 10% 1	8401
February	1st to 10th	Night	56% 4 11% 20% 8% 1	2630
	11th to 20th	Night	55% 4 10% 19% 11% 1	2459
	21st to end	Night	56% 4 10% 17% 10% 2	2076
March	1st to 10th	Night	51% 4 6% 26% 11% 2	5411
	11th to 20th	Night	39% 6% 10% 28% 16% 1	5090
	21st to end	Night	51% 5% 7% 24% 11% 1	5588
April	1st to 10th	Night	45% 7% 11% 23% 13% 2	2185
	11th to 20th	Night	41% 7% 11% 20% 17% 5%	2004
	21st to end	Night	45% 5% 11% 22% 14% 3	1890
May	1st to 10th	Night	50% 7% 10% 21% 9% 2	5264
	11th to 20th	Night	43% 8% 14% 22% 12% 1	5235
	21st to end	Night	46% 7% 14% 18% 11% 4	5771
June	1st to 10th	Night	31% 7% 13% 25% 21% 2	1890
	11th to 20th	Night	32% 7% 16% 22% 20% 4	1750
	21st to end	Night	30% 10% 17% 22% 17% 4	1680
July	1st to 10th	Night	35% 7% 12% 25% 18% 3	4670
	11th to 20th	Night	38% 8% 12% 27% 15% 1	5110
	21st to end	Night	39% 7% 12% 24% 15% 3	5606
August	1st to 10th	Night	41% 7% 13% 25% 13% 2	4124
	11th to 20th	Night	42% 8% 13% 24% 13%	4122
	21st to end	Night	19% 6% 17% 35% 21% 2	4950
September	1st to 10th	Night	29% 6% 12% 25% 22% 6%	2225
	11th to 20th	Night	30% 6% 11% 23% 27% 3	2310
	21st to end	Night	38% 5% 9% 20% 26% 2	2289
October	1st to 10th	Night	22% 4 7% 25% 39% 2	3590
	11th to 20th	Night	27% 4 9% 26% 31% 3	3866
	21st to end	Night	33% 3 8% 22% 27% 6%	4465
November	1st to 10th	Night	37% 5% 10% 22% 22% 4	2666
	11th to 20th	Night	45% 4 9% 21% 18% 3	2730
	21st to end	Night	54% 4 10% 20% 12% 2	2730
December	1st to 10th	Night	51% 4 10% 24% 11%	4380
	11th to 20th	Night	58% 5% 11% 18% 7% 1	4954
	21st to end	Night	69% 5% 8% 13% 4	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	28% 24% 32% 13% 3	330
	11th to 20th	Day	34% 26% 32% 6% 1	330
	21st to end	Day	34% 25% 29% 11% 1	363
February	1st to 10th	Day	29% 24% 34% 11% 2	330
	11th to 20th	Day	35% 28% 30% 6% 1	330
	21st to end	Day	34% 21% 40% 5%	273
March	1st to 10th	Day	29% 30% 29% 12% 1	360
	11th to 20th	Day	27% 23% 32% 14% 4	540
	21st to end	Day	33% 19% 31% 13% 4	594
April	1st to 10th	Day	25% 19% 32% 16% 7% 1	540
	11th to 20th	Day	25% 21% 29% 15% 8% 2	532
	21st to end	Day	24% 19% 33% 14% 8% 2	540
May	1st to 10th	Day	27% 20% 29% 15% 6% 3	543
	11th to 20th	Day	24% 10% 29% 23% 10% 4	567
	21st to end	Day	19% 8% 26% 26% 14% 7%	617
June	1st to 10th	Day	15% 7% 25% 29% 15% 7%	570
	11th to 20th	Day	13% 8% 26% 31% 16% 7%	702
	21st to end	Day	10% 7% 28% 31% 18% 6%	780
July	1st to 10th	Day	14% 3 18% 26% 23% 16%	771
	11th to 20th	Day	10% 4 22% 31% 23% 10%	604
	21st to end	Day	11% 4 21% 31% 21% 11%	620
August	1st to 10th	Day	12% 5% 16% 31% 24% 13%	566
	11th to 20th	Day	11% 5% 21% 32% 22% 9%	559
	21st to end	Day	8% 4 17% 33% 26% 12%	627
September	1st to 10th	Day	14% 4 18% 30% 25% 9%	570
	11th to 20th	Day	10% 2 18% 27% 31% 12%	570
	21st to end	Day	22% 9% 20% 22% 20% 6%	562
October	1st to 10th	Day	11% 6% 26% 31% 20% 7%	530
	11th to 20th	Day	17% 13% 32% 23% 12% 3	530
	21st to end	Day	24% 12% 40% 18% 6%	455
November	1st to 10th	Day	17% 18% 35% 19% 8% 2	330
	11th to 20th	Day	24% 24% 31% 15% 5% 2	330
	21st to end	Day	29% 20% 35% 13% 2	330
December	1st to 10th	Day	26% 22% 35% 13% 4	330
	11th to 20th	Day	23% 26% 38% 10% 4	330
	21st to end	Day	33% 18% 36% 10% 1 1	363
January	1st to 10th	Night	23% 22% 32% 19% 4	840
	11th to 20th	Night	28% 21% 32% 16% 3	840
	21st to end	Night	25% 18% 35% 19% 3	924
February	1st to 10th	Night	27% 14% 36% 21% 2	840
	11th to 20th	Night	26% 21% 31% 20% 1	823
	21st to end	Night	28% 17% 36% 18% 1	692
March	1st to 10th	Night	25% 19% 30% 21% 5%	840
	11th to 20th	Night	25% 16% 32% 20% 6% 1	840
	21st to end	Night	23% 14% 33% 23% 6%	924
April	1st to 10th	Night	21% 13% 34% 24% 7%	715
	11th to 20th	Night	20% 12% 34% 24% 10% 1	623
	21st to end	Night	18% 11% 38% 24% 9% 1	630
May	1st to 10th	Night	22% 9% 31% 27% 10% 1	630
	11th to 20th	Night	18% 7% 25% 31% 17% 2	621
	21st to end	Night	11% 4 24% 35% 21% 5%	683
June	1st to 10th	Night	11% 3 23% 38% 23% 1	630
	11th to 20th	Night	11% 4 17% 42% 24% 3	630
	21st to end	Night	7% 3 23% 39% 24% 3	630
July	1st to 10th	Night	14% 1 11% 32% 35% 8%	615
	11th to 20th	Night	8% 1 17% 34% 37% 3	612
	21st to end	Night	12% 2 11% 39% 31% 4	690
August	1st to 10th	Night	9% 2 11% 40% 34% 4	627
	11th to 20th	Night	11% 2 11% 40% 31% 5%	624
	21st to end	Night	6% 1 14% 36% 37% 6%	693
September	1st to 10th	Night	14% 3 13% 35% 31% 4	755
	11th to 20th	Night	10% 3 14% 33% 34% 6%	840
	21st to end	Night	17% 6% 21% 31% 21% 3	833
October	1st to 10th	Night	11% 5% 23% 35% 23% 4	800
	11th to 20th	Night	18% 9% 27% 31% 14% 1	800
	21st to end	Night	23% 10% 34% 23% 10%	880
November	1st to 10th	Night	17% 11% 29% 27% 14% 2	820
	11th to 20th	Night	21% 17% 30% 23% 9% 1	840
	21st to end	Night	26% 13% 27% 26% 7% 1	840
December	1st to 10th	Night	27% 14% 33% 21% 4	840
	11th to 20th	Night	26% 14% 33% 22% 5% 1	840
	21st to end	Night	31% 16% 30% 20% 3	924

Page generated at 2026-09-26 04:18:41. Version ac07

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