Hannibal
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hannibal clear sky chart from 2005-11-05 to 2024-10-14.

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	12% 8% 3 7% 4 4 4 4 6% 8% 41%	101132
	Night	13% 9% 3 7% 4 4 4 3 5% 7% 42%	97515
Transparency	Day	23% 47% 7% 14% 8% 1	100928
	Night	24% 48% 6% 13% 8% 1	97395
Seeing	Day	14% 10% 27% 28% 16% 5%	15647
	Night	16% 9% 30% 31% 13% 1	25438

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	11% 11% 5% 13% 6% 5% 4 4 5% 6% 29%	2527
	11th to 20th	Day	12% 11% 4 10% 7% 7% 6% 4 6% 5% 30%	2757
	21st to end	Day	17% 18% 9% 9% 5% 3 3 3 3 5% 24%	3135
February	1st to 10th	Day	15% 11% 5% 9% 5% 5% 5% 3 4 7% 32%	1710
	11th to 20th	Day	13% 11% 3 7% 5% 5% 6% 4 5% 7% 36%	1752
	21st to end	Day	14% 10% 4 8% 5% 4 4 3 4 6% 38%	1570
March	1st to 10th	Day	17% 11% 4 6% 3 3 3 3 4 4 41%	3268
	11th to 20th	Day	10% 7% 2 5% 4 3 5% 3 5% 7% 48%	3480
	21st to end	Day	17% 12% 4 8% 5% 4 4 3 5% 6% 32%	3959
April	1st to 10th	Day	14% 8% 3 8% 4 4 4 4 6% 7% 39%	2280
	11th to 20th	Day	16% 7% 2 8% 5% 4 3 3 5% 7% 40%	2254
	21st to end	Day	19% 6% 3 7% 5% 4 4 3 6% 7% 36%	2280
May	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 4 7% 10% 34%	3974
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 8% 38%	4399
	21st to end	Day	10% 6% 2 6% 4 4 4 4 5% 7% 46%	4824
June	1st to 10th	Day	5% 4 2 6% 4 5% 5% 5% 7% 10% 46%	2660
	11th to 20th	Day	7% 5% 2 6% 4 4 5% 5% 7% 9% 47%	2660
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 4 6% 10% 44%	2660
July	1st to 10th	Day	11% 6% 2 7% 4 4 5% 5% 7% 10% 38%	4440
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 7% 10% 49%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 9% 11% 39%	4537
August	1st to 10th	Day	4 4 2 5% 4 4 5% 5% 8% 11% 48%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	3850
	21st to end	Day	5% 4 2 5% 3 4 5% 4 7% 10% 51%	4180
September	1st to 10th	Day	10% 6% 2 4 3 4 4 3 5% 7% 52%	2280
	11th to 20th	Day	10% 4 2 5% 4 4 3 4 6% 8% 52%	2280
	21st to end	Day	8% 5% 1 5% 4 5% 4 4 6% 8% 51%	2024
October	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 5% 6% 53%	1900
	11th to 20th	Day	15% 7% 3 6% 3 3 3 3 4 6% 47%	1830
	21st to end	Day	18% 8% 3 6% 4 4 3 3 4 6% 43%	1980
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 5% 6% 52%	1682
	11th to 20th	Day	15% 7% 3 7% 4 3 3 3 5% 7% 44%	1710
	21st to end	Day	17% 11% 3 7% 4 4 3 4 4 5% 38%	1525
December	1st to 10th	Day	12% 11% 4 7% 6% 4 4 3 4 6% 39%	1520
	11th to 20th	Day	14% 9% 4 7% 4 5% 4 3 6% 6% 38%	1918
	21st to end	Day	19% 16% 5% 10% 5% 4 5% 3 4 5% 22%	2783
January	1st to 10th	Night	13% 12% 6% 12% 5% 5% 4 3 4 5% 32%	4428
	11th to 20th	Night	13% 16% 6% 9% 4 5% 6% 5% 6% 4 26%	4212
	21st to end	Night	21% 17% 5% 10% 5% 3 3 3 4 6% 23%	4532
February	1st to 10th	Night	14% 13% 5% 7% 5% 5% 4 4 4 6% 34%	2470
	11th to 20th	Night	13% 9% 3 7% 5% 5% 4 4 4 7% 39%	2314
	21st to end	Night	16% 9% 3 7% 4 4 3 3 4 6% 41%	1884
March	1st to 10th	Night	19% 11% 3 5% 3 3 4 3 4 4 41%	3615
	11th to 20th	Night	13% 7% 2 6% 4 3 4 3 3 6% 50%	3480
	21st to end	Night	20% 10% 4 8% 6% 4 5% 4 5% 6% 29%	3672
April	1st to 10th	Night	12% 7% 3 7% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	14% 7% 2 6% 4 5% 3 4 5% 6% 45%	1875
	21st to end	Night	17% 8% 3 7% 4 3 4 3 4 5% 41%	1900
May	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 4 6% 7% 36%	2922
	11th to 20th	Night	12% 7% 3 7% 5% 4 4 4 5% 8% 41%	2506
	21st to end	Night	7% 6% 2 6% 4 4 4 4 6% 9% 49%	2743
June	1st to 10th	Night	7% 5% 2 5% 3 4 4 4 6% 9% 53%	1520
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 7% 8% 49%	1520
	21st to end	Night	6% 4 2 4 4 5% 5% 5% 5% 10% 50%	1520
July	1st to 10th	Night	11% 7% 2 7% 4 4 4 4 6% 9% 42%	2530
	11th to 20th	Night	4 3 2 4 4 4 4 3 6% 8% 58%	2530
	21st to end	Night	7% 5% 2 6% 5% 4 5% 5% 8% 10% 43%	3022
August	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 10% 59%	2836
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 5% 7% 52%	2980
	21st to end	Night	4 3 1 5% 3 4 5% 4 7% 11% 54%	3476
September	1st to 10th	Night	10% 5% 1 4 2 4 3 4 5% 6% 56%	1900
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 5% 7% 52%	1900
	21st to end	Night	7% 4 2 5% 4 4 4 3 4 7% 54%	2133
October	1st to 10th	Night	9% 4 2 4 3 3 3 4 5% 7% 57%	2280
	11th to 20th	Night	14% 5% 1 5% 3 3 4 3 3 6% 52%	2203
	21st to end	Night	18% 8% 2 5% 4 3 3 3 5% 5% 43%	2376
November	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 4 6% 55%	2393
	11th to 20th	Night	12% 7% 3 6% 5% 4 3 3 5% 6% 47%	2470
	21st to end	Night	17% 9% 3 6% 3 3 3 3 5% 6% 42%	2650
December	1st to 10th	Night	14% 10% 4 7% 5% 4 4 4 6% 6% 35%	2660
	11th to 20th	Night	15% 9% 3 7% 4 4 3 3 4 5% 42%	3279
	21st to end	Night	20% 18% 6% 11% 6% 5% 3 3 3 4 21%	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	40% 36% 5% 15% 4	2528
	11th to 20th	Day	37% 36% 10% 11% 6%	2757
	21st to end	Day	44% 38% 5% 7% 6%	3135
February	1st to 10th	Day	19% 65% 4 7% 5% 1	1710
	11th to 20th	Day	19% 64% 3 9% 5%	1761
	21st to end	Day	18% 64% 3 8% 6% 1	1570
March	1st to 10th	Day	30% 39% 4 13% 12% 1	3268
	11th to 20th	Day	18% 39% 7% 19% 15% 2	3480
	21st to end	Day	33% 39% 12% 13% 3	3959
April	1st to 10th	Day	20% 64% 4 8% 4	2280
	11th to 20th	Day	16% 65% 3 9% 6%	2254
	21st to end	Day	17% 65% 3 8% 7% 1	2280
May	1st to 10th	Day	27% 39% 9% 17% 8%	4009
	11th to 20th	Day	29% 39% 7% 20% 5%	4403
	21st to end	Day	21% 39% 4 18% 18%	4837
June	1st to 10th	Day	10% 65% 6% 11% 6% 2	2660
	11th to 20th	Day	13% 66% 3 10% 6% 1	2660
	21st to end	Day	14% 64% 7% 9% 5% 1	2660
July	1st to 10th	Day	29% 36% 7% 18% 8% 1	4371
	11th to 20th	Day	20% 36% 9% 22% 12%	4365
	21st to end	Day	24% 36% 16% 17% 7%	4394
August	1st to 10th	Day	18% 37% 10% 27% 7%	4090
	11th to 20th	Day	27% 37% 8% 18% 10%	3889
	21st to end	Day	20% 38% 13% 22% 6% 2	4179
September	1st to 10th	Day	11% 60% 5% 12% 9% 3	2280
	11th to 20th	Day	12% 59% 5% 13% 9% 3	2280
	21st to end	Day	14% 60% 4 12% 9% 1	2024
October	1st to 10th	Day	18% 60% 3 8% 11% 1	1900
	11th to 20th	Day	13% 62% 2 11% 10% 2	1830
	21st to end	Day	19% 61% 4 8% 7% 1	1980
November	1st to 10th	Day	15% 58% 6% 10% 9% 2	1682
	11th to 20th	Day	16% 59% 3 10% 10% 1	1710
	21st to end	Day	22% 59% 3 12% 4	1525
December	1st to 10th	Day	20% 59% 5% 9% 7%	1520
	11th to 20th	Day	22% 47% 7% 15% 8% 1	1915
	21st to end	Day	48% 36% 4 8% 3 1	2783
January	1st to 10th	Night	40% 35% 6% 14% 5%	4428
	11th to 20th	Night	43% 35% 5% 10% 6%	4212
	21st to end	Night	44% 38% 4 11% 3	4532
February	1st to 10th	Night	19% 65% 4 7% 5% 1	2470
	11th to 20th	Night	16% 63% 4 10% 6%	2315
	21st to end	Night	16% 64% 3 7% 8% 2	1884
March	1st to 10th	Night	32% 39% 4 14% 10% 1	3615
	11th to 20th	Night	19% 39% 4 18% 15% 4	3480
	21st to end	Night	34% 39% 6% 18% 3	3672
April	1st to 10th	Night	17% 65% 5% 8% 4 1	1900
	11th to 20th	Night	13% 66% 4 10% 7% 1	1875
	21st to end	Night	17% 65% 2 7% 7% 1	1900
May	1st to 10th	Night	31% 39% 8% 14% 7%	2952
	11th to 20th	Night	27% 39% 9% 20% 4	2507
	21st to end	Night	20% 38% 7% 14% 19% 1	2751
June	1st to 10th	Night	9% 65% 6% 10% 8% 2	1520
	11th to 20th	Night	13% 65% 3 10% 8% 1	1520
	21st to end	Night	10% 65% 7% 13% 6% 1	1520
July	1st to 10th	Night	29% 36% 8% 18% 7% 2	2490
	11th to 20th	Night	15% 35% 8% 24% 17% 1	2482
	21st to end	Night	25% 35% 14% 16% 10%	2926
August	1st to 10th	Night	13% 37% 13% 25% 12%	2826
	11th to 20th	Night	23% 37% 7% 18% 15%	3007
	21st to end	Night	18% 37% 15% 22% 7% 1	3476
September	1st to 10th	Night	10% 60% 5% 12% 12% 3	1900
	11th to 20th	Night	12% 60% 4 11% 11% 2	1900
	21st to end	Night	15% 59% 4 11% 10% 1	2133
October	1st to 10th	Night	15% 60% 4 9% 9% 2	2280
	11th to 20th	Night	11% 61% 4 12% 11% 2	2208
	21st to end	Night	16% 62% 4 8% 9% 1	2376
November	1st to 10th	Night	15% 59% 5% 11% 8% 3	2393
	11th to 20th	Night	15% 59% 3 10% 11% 2	2470
	21st to end	Night	20% 59% 3 11% 6%	2650
December	1st to 10th	Night	20% 60% 5% 9% 7% 1	2660
	11th to 20th	Night	20% 48% 5% 16% 9% 1	3281
	21st to end	Night	50% 36% 4 6% 4 1	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	17% 19% 35% 23% 6%	270
	11th to 20th	Day	27% 18% 40% 14% 1	270
	21st to end	Day	17% 20% 40% 20% 3	297
February	1st to 10th	Day	25% 16% 39% 16% 4	270
	11th to 20th	Day	21% 19% 34% 19% 6%	270
	21st to end	Day	23% 16% 42% 16% 4	225
March	1st to 10th	Day	18% 21% 43% 17% 1	270
	11th to 20th	Day	24% 17% 34% 20% 4 1	270
	21st to end	Day	30% 19% 33% 15% 3	378
April	1st to 10th	Day	20% 17% 34% 21% 7% 1	460
	11th to 20th	Day	19% 16% 31% 24% 9% 1	452
	21st to end	Day	21% 12% 37% 22% 7% 1	460
May	1st to 10th	Day	17% 11% 38% 22% 10% 2	553
	11th to 20th	Day	20% 11% 25% 28% 13% 3	675
	21st to end	Day	13% 9% 29% 27% 15% 6%	734
June	1st to 10th	Day	6% 5% 23% 34% 24% 9%	680
	11th to 20th	Day	8% 3 25% 36% 24% 5%	680
	21st to end	Day	9% 7% 30% 34% 18% 3	680
July	1st to 10th	Day	9% 3 16% 34% 25% 13%	671
	11th to 20th	Day	7% 4 19% 38% 25% 7%	668
	21st to end	Day	10% 2 18% 32% 31% 7%	739
August	1st to 10th	Day	7% 2 16% 40% 26% 8%	676
	11th to 20th	Day	9% 2 18% 33% 28% 10%	552
	21st to end	Day	9% 2 14% 32% 32% 12%	539
September	1st to 10th	Day	12% 4 16% 30% 28% 10%	490
	11th to 20th	Day	8% 3 16% 33% 28% 12%	490
	21st to end	Day	9% 7% 23% 31% 20% 10%	405
October	1st to 10th	Day	15% 8% 29% 27% 13% 8%	300
	11th to 20th	Day	14% 22% 32% 23% 8% 1	279
	21st to end	Day	26% 16% 31% 22% 4 1	297
November	1st to 10th	Day	11% 9% 41% 24% 10% 4	270
	11th to 20th	Day	20% 17% 29% 24% 8% 2	270
	21st to end	Day	23% 16% 31% 24% 6%	270
December	1st to 10th	Day	13% 13% 45% 19% 6% 4	270
	11th to 20th	Day	18% 17% 37% 24% 4	270
	21st to end	Day	25% 23% 35% 14% 3	297
January	1st to 10th	Night	16% 16% 40% 23% 6%	950
	11th to 20th	Night	20% 16% 37% 22% 5%	950
	21st to end	Night	19% 13% 39% 26% 2	1045
February	1st to 10th	Night	21% 12% 39% 25% 3	950
	11th to 20th	Night	18% 16% 36% 26% 4	840
	21st to end	Night	20% 18% 38% 22% 2	628
March	1st to 10th	Night	19% 14% 42% 21% 4	694
	11th to 20th	Night	21% 11% 34% 29% 5% 1	570
	21st to end	Night	25% 13% 33% 25% 4	627
April	1st to 10th	Night	14% 16% 36% 28% 4	570
	11th to 20th	Night	18% 12% 35% 27% 8%	563
	21st to end	Night	20% 7% 36% 31% 6%	570
May	1st to 10th	Night	15% 8% 34% 34% 8% 1	570
	11th to 20th	Night	16% 6% 28% 36% 13% 1	561
	21st to end	Night	12% 4 27% 34% 21% 2	617
June	1st to 10th	Night	9% 3 21% 42% 25% 2	570
	11th to 20th	Night	10% 2 21% 43% 22% 2	570
	21st to end	Night	6% 2 28% 43% 20% 1	570
July	1st to 10th	Night	10% 3 11% 38% 34% 4	555
	11th to 20th	Night	7% 1 17% 43% 28% 3	552
	21st to end	Night	8% 1 13% 42% 35%	624
August	1st to 10th	Night	5% 2 11% 49% 30% 3	567
	11th to 20th	Night	8% 2 12% 41% 32% 5%	564
	21st to end	Night	6% 1 11% 38% 41% 2	627
September	1st to 10th	Night	12% 2 17% 38% 26% 5%	570
	11th to 20th	Night	8% 3 21% 36% 27% 5%	570
	21st to end	Night	9% 6% 24% 34% 22% 4	722
October	1st to 10th	Night	10% 4 28% 33% 22% 3	760
	11th to 20th	Night	18% 9% 33% 29% 10% 1	735
	21st to end	Night	22% 11% 34% 26% 7%	792
November	1st to 10th	Night	14% 9% 36% 31% 9% 1	740
	11th to 20th	Night	16% 14% 38% 27% 5%	760
	21st to end	Night	23% 11% 36% 24% 6%	940
December	1st to 10th	Night	18% 12% 38% 26% 5% 1	950
	11th to 20th	Night	24% 9% 33% 27% 6%	950
	21st to end	Night	24% 17% 34% 23% 3	1045

Page generated at 2024-10-11 09:50:03. Version ac07

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