Fleischmanns Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fleischmanns Observatory clear sky chart from 2005-11-06 to 2024-12-09.

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% 6% 5% 5% 4 6% 6% 29%	101692
	Night	14% 13% 5% 10% 6% 5% 4 3 5% 6% 30%	98090
Transparency	Day	53% 4 11% 20% 11% 1	105199
	Night	53% 4 11% 20% 11% 1	102659
Seeing	Day	26% 21% 28% 15% 7% 2	14918
	Night	25% 22% 24% 20% 8% 1	24079

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% 15% 9% 18% 6% 4 4 2 4 3 22%	2517
	11th to 20th	Day	10% 17% 8% 15% 7% 7% 5% 3 4 4 20%	2520
	21st to end	Day	17% 17% 9% 12% 6% 5% 4 4 3 3 20%	2968
February	1st to 10th	Day	12% 14% 6% 14% 9% 6% 5% 4 4 5% 21%	1710
	11th to 20th	Day	8% 12% 6% 14% 8% 5% 5% 5% 5% 7% 26%	1796
	21st to end	Day	14% 15% 3 12% 8% 5% 5% 3 5% 5% 26%	1570
March	1st to 10th	Day	20% 18% 5% 10% 5% 3 3 2 3 5% 26%	3116
	11th to 20th	Day	10% 17% 8% 12% 6% 4 4 3 4 5% 27%	3377
	21st to end	Day	19% 11% 4 11% 5% 4 3 2 4 6% 31%	4102
April	1st to 10th	Day	14% 18% 4 9% 5% 4 4 3 4 5% 29%	2280
	11th to 20th	Day	13% 13% 4 8% 5% 4 5% 4 5% 5% 33%	2254
	21st to end	Day	17% 15% 5% 8% 5% 4 4 2 4 6% 31%	2313
May	1st to 10th	Day	24% 12% 4 7% 5% 4 4 3 5% 6% 28%	4229
	11th to 20th	Day	19% 10% 3 8% 5% 5% 6% 4 6% 7% 27%	4398
	21st to end	Day	12% 7% 2 7% 5% 5% 5% 5% 6% 8% 36%	4837
June	1st to 10th	Day	16% 9% 4 8% 6% 5% 6% 4 7% 8% 28%	2660
	11th to 20th	Day	15% 9% 3 8% 5% 5% 6% 6% 6% 10% 29%	2660
	21st to end	Day	16% 9% 3 8% 6% 5% 5% 5% 7% 8% 29%	2660
July	1st to 10th	Day	10% 7% 3 8% 6% 6% 6% 5% 8% 9% 32%	4440
	11th to 20th	Day	9% 6% 3 9% 6% 7% 6% 6% 9% 10% 31%	4440
	21st to end	Day	13% 9% 3 8% 7% 6% 5% 6% 7% 7% 30%	4814
August	1st to 10th	Day	17% 8% 4 10% 6% 5% 5% 4 6% 8% 27%	4279
	11th to 20th	Day	12% 8% 3 9% 5% 7% 7% 6% 8% 8% 27%	3762
	21st to end	Day	12% 8% 3 8% 4 5% 5% 5% 7% 8% 34%	4180
September	1st to 10th	Day	15% 7% 2 8% 5% 4 4 4 6% 7% 38%	2280
	11th to 20th	Day	12% 8% 3 7% 4 4 4 4 4 7% 43%	2222
	21st to end	Day	15% 8% 3 7% 5% 4 5% 4 5% 7% 36%	2090
October	1st to 10th	Day	16% 12% 4 9% 6% 5% 4 3 5% 6% 31%	1939
	11th to 20th	Day	13% 14% 3 7% 4 4 5% 3 6% 5% 36%	1900
	21st to end	Day	18% 17% 3 9% 4 4 4 3 5% 5% 27%	1936
November	1st to 10th	Day	12% 13% 4 7% 4 4 3 3 6% 5% 38%	1761
	11th to 20th	Day	13% 16% 4 11% 7% 5% 4 3 4 4 30%	1800
	21st to end	Day	14% 17% 6% 10% 6% 3 5% 3 4 6% 26%	1620
December	1st to 10th	Day	12% 18% 7% 16% 7% 5% 4 4 4 4 19%	1584
	11th to 20th	Day	15% 15% 8% 13% 6% 3 3 3 4 4 25%	1906
	21st to end	Day	14% 18% 7% 15% 7% 5% 4 3 6% 5% 16%	2772
January	1st to 10th	Night	12% 15% 7% 14% 6% 5% 4 3 5% 6% 24%	4429
	11th to 20th	Night	8% 18% 10% 17% 8% 6% 4 3 4 4 18%	4440
	21st to end	Night	17% 17% 6% 14% 8% 6% 4 3 4 4 19%	4683
February	1st to 10th	Night	11% 14% 5% 13% 8% 6% 6% 4 5% 6% 22%	2470
	11th to 20th	Night	8% 13% 7% 15% 8% 7% 5% 5% 5% 5% 22%	2270
	21st to end	Night	15% 12% 5% 11% 7% 4 5% 4 5% 6% 26%	1884
March	1st to 10th	Night	17% 14% 5% 11% 6% 4 4 3 5% 5% 26%	3724
	11th to 20th	Night	9% 16% 10% 12% 7% 5% 4 3 4 5% 26%	3579
	21st to end	Night	13% 14% 7% 11% 5% 4 4 3 3 5% 32%	3530
April	1st to 10th	Night	13% 16% 5% 10% 6% 5% 5% 4 5% 6% 26%	1900
	11th to 20th	Night	16% 13% 4 6% 5% 4 4 3 5% 6% 34%	1875
	21st to end	Night	18% 13% 5% 6% 4 4 5% 3 4 4 34%	1867
May	1st to 10th	Night	24% 12% 3 6% 4 4 3 3 5% 6% 30%	2738
	11th to 20th	Night	16% 13% 4 8% 5% 5% 4 3 5% 6% 31%	2495
	21st to end	Night	13% 10% 3 7% 5% 5% 5% 4 6% 8% 36%	2738
June	1st to 10th	Night	15% 9% 3 7% 5% 4 5% 3 7% 6% 38%	1520
	11th to 20th	Night	16% 9% 2 6% 4 4 3 3 7% 9% 37%	1520
	21st to end	Night	12% 7% 2 6% 5% 4 5% 5% 5% 8% 40%	1520
July	1st to 10th	Night	11% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	2520
	11th to 20th	Night	12% 7% 4 7% 4 4 4 4 6% 9% 39%	2520
	21st to end	Night	14% 9% 3 6% 6% 5% 5% 4 5% 7% 37%	2739
August	1st to 10th	Night	21% 10% 3 8% 4 4 5% 3 5% 6% 31%	2633
	11th to 20th	Night	15% 9% 3 9% 5% 4 4 4 5% 6% 38%	3033
	21st to end	Night	11% 11% 3 7% 4 4 3 3 5% 7% 43%	3476
September	1st to 10th	Night	14% 8% 2 7% 4 4 4 4 5% 7% 42%	1900
	11th to 20th	Night	14% 7% 2 5% 3 3 4 3 4 7% 49%	1957
	21st to end	Night	15% 9% 3 7% 4 5% 5% 3 5% 5% 39%	2090
October	1st to 10th	Night	17% 11% 3 8% 5% 4 4 3 5% 5% 34%	2237
	11th to 20th	Night	15% 11% 3 8% 4 4 4 3 4 7% 37%	2280
	21st to end	Night	19% 14% 4 7% 5% 4 5% 3 5% 6% 27%	2660
November	1st to 10th	Night	10% 14% 4 9% 5% 3 5% 3 5% 5% 38%	2537
	11th to 20th	Night	14% 16% 5% 9% 5% 4 4 4 5% 5% 29%	2600
	21st to end	Night	11% 15% 5% 9% 6% 5% 5% 3 5% 6% 28%	2775
December	1st to 10th	Night	13% 16% 7% 14% 7% 5% 5% 4 5% 6% 19%	2779
	11th to 20th	Night	15% 16% 6% 13% 6% 4 4 3 5% 4 23%	3288
	21st to end	Night	17% 17% 7% 15% 6% 5% 4 3 4 5% 18%	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	60% 2 7% 22% 7% 1	2518
	11th to 20th	Day	67% 2 7% 16% 6% 2	2520
	21st to end	Day	67% 2 7% 17% 7% 1	2968
February	1st to 10th	Day	61% 3 9% 17% 9% 1	1710
	11th to 20th	Day	53% 3 8% 21% 13% 2	1805
	21st to end	Day	57% 2 9% 19% 10% 1	1570
March	1st to 10th	Day	62% 2 9% 16% 10% 2	3119
	11th to 20th	Day	59% 2 9% 21% 8% 1	3377
	21st to end	Day	57% 2 5% 15% 18% 4	4102
April	1st to 10th	Day	58% 3 7% 19% 11% 2	2280
	11th to 20th	Day	53% 3 10% 20% 12% 2	2254
	21st to end	Day	57% 2 8% 18% 12% 3	2313
May	1st to 10th	Day	59% 2 9% 19% 10% 2	4243
	11th to 20th	Day	58% 2 11% 21% 7% 1	4402
	21st to end	Day	45% 3 12% 26% 13% 1	4837
June	1st to 10th	Day	53% 4 12% 19% 11%	2660
	11th to 20th	Day	52% 5% 13% 20% 9% 1	2660
	21st to end	Day	51% 6% 12% 22% 9%	2660
July	1st to 10th	Day	46% 7% 14% 22% 10% 1	4370
	11th to 20th	Day	43% 8% 16% 23% 10%	4365
	21st to end	Day	50% 5% 13% 19% 11% 1	4661
August	1st to 10th	Day	54% 5% 13% 19% 9%	4265
	11th to 20th	Day	48% 7% 15% 24% 5%	3799
	21st to end	Day	44% 5% 13% 28% 9% 1	4180
September	1st to 10th	Day	45% 4 10% 25% 13% 1	2280
	11th to 20th	Day	41% 4 9% 23% 21% 1	2222
	21st to end	Day	48% 4 10% 20% 16% 2	2090
October	1st to 10th	Day	50% 3 9% 20% 16% 2	3225
	11th to 20th	Day	42% 3 9% 22% 17% 6%	3140
	21st to end	Day	41% 4 14% 24% 13% 3	3161
November	1st to 10th	Day	45% 3 12% 22% 15% 3	1761
	11th to 20th	Day	55% 2 8% 17% 14% 3	1800
	21st to end	Day	58% 3 12% 19% 7% 1	1620
December	1st to 10th	Day	64% 4 9% 14% 7% 1	1584
	11th to 20th	Day	59% 3 12% 18% 7% 1	1906
	21st to end	Day	67% 3 7% 13% 9%	2772
January	1st to 10th	Night	57% 2 8% 23% 9% 2	4429
	11th to 20th	Night	67% 3 8% 14% 6% 2	4440
	21st to end	Night	67% 2 7% 15% 8% 1	4683
February	1st to 10th	Night	57% 4 12% 17% 10% 1	2470
	11th to 20th	Night	57% 4 10% 16% 12% 1	2272
	21st to end	Night	55% 3 10% 21% 9% 3	1884
March	1st to 10th	Night	61% 2 9% 17% 9% 3	3734
	11th to 20th	Night	59% 1 12% 19% 8% 1	3580
	21st to end	Night	56% 2 5% 16% 18% 3	3530
April	1st to 10th	Night	58% 4 9% 17% 10% 2	1900
	11th to 20th	Night	51% 4 11% 20% 14%	1875
	21st to end	Night	52% 3 8% 21% 13% 2	1867
May	1st to 10th	Night	57% 2 9% 20% 9% 2	2744
	11th to 20th	Night	56% 4 10% 22% 7% 1	2496
	21st to end	Night	46% 4 14% 22% 13%	2739
June	1st to 10th	Night	46% 4 11% 26% 12%	1520
	11th to 20th	Night	45% 5% 16% 24% 9%	1520
	21st to end	Night	39% 7% 17% 26% 11% 1	1520
July	1st to 10th	Night	43% 7% 17% 20% 12% 1	2480
	11th to 20th	Night	40% 7% 16% 27% 10%	2472
	21st to end	Night	47% 4 13% 23% 12% 1	2651
August	1st to 10th	Night	54% 4 14% 21% 6%	2623
	11th to 20th	Night	45% 6% 16% 25% 9%	3062
	21st to end	Night	41% 5% 12% 32% 9% 1	3476
September	1st to 10th	Night	42% 5% 12% 26% 14% 1	1900
	11th to 20th	Night	37% 3 10% 25% 23% 1	1957
	21st to end	Night	48% 3 9% 23% 16% 1	2090
October	1st to 10th	Night	52% 5% 10% 21% 11% 1	3731
	11th to 20th	Night	42% 4 12% 18% 18% 6%	3779
	21st to end	Night	43% 5% 15% 24% 11% 2	4372
November	1st to 10th	Night	47% 4 9% 20% 17% 3	2537
	11th to 20th	Night	53% 3 9% 18% 13% 3	2600
	21st to end	Night	54% 3 13% 22% 7% 1	2775
December	1st to 10th	Night	61% 4 11% 18% 6%	2779
	11th to 20th	Night	61% 3 10% 14% 11% 1	3288
	21st to end	Night	66% 2 8% 16% 8%	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	36% 25% 28% 8% 2 1	180
	11th to 20th	Day	38% 28% 24% 8% 1 1	180
	21st to end	Day	30% 34% 24% 9% 2	254
February	1st to 10th	Day	41% 34% 20% 4	270
	11th to 20th	Day	39% 34% 19% 7% 1	404
	21st to end	Day	39% 28% 24% 7% 2	382
March	1st to 10th	Day	33% 27% 29% 9% 2	460
	11th to 20th	Day	36% 28% 24% 9% 3 1	460
	21st to end	Day	37% 28% 21% 8% 4 2	506
April	1st to 10th	Day	37% 28% 19% 12% 5% 1	460
	11th to 20th	Day	34% 25% 24% 10% 5% 2	452
	21st to end	Day	32% 26% 28% 8% 4 2	460
May	1st to 10th	Day	36% 22% 27% 7% 5% 3	463
	11th to 20th	Day	23% 21% 34% 15% 5% 2	487
	21st to end	Day	18% 14% 36% 19% 10% 3	529
June	1st to 10th	Day	22% 19% 31% 19% 7% 1	490
	11th to 20th	Day	17% 20% 31% 21% 9% 2	490
	21st to end	Day	22% 19% 33% 17% 7% 1	490
July	1st to 10th	Day	15% 11% 37% 22% 12% 3	485
	11th to 20th	Day	11% 11% 39% 28% 9% 2	484
	21st to end	Day	16% 15% 39% 19% 8% 3	532
August	1st to 10th	Day	10% 17% 32% 24% 13% 5%	486
	11th to 20th	Day	16% 13% 32% 22% 10% 6%	479
	21st to end	Day	16% 14% 30% 22% 12% 6%	539
September	1st to 10th	Day	22% 13% 24% 22% 13% 6%	490
	11th to 20th	Day	14% 15% 27% 20% 12% 11%	490
	21st to end	Day	23% 16% 28% 20% 8% 6%	490
October	1st to 10th	Day	25% 17% 26% 19% 10% 3	490
	11th to 20th	Day	28% 19% 28% 17% 7% 1	490
	21st to end	Day	28% 25% 29% 13% 4 1	457
November	1st to 10th	Day	27% 22% 27% 15% 8% 1	395
	11th to 20th	Day	36% 23% 25% 11% 4 1	400
	21st to end	Day	38% 26% 25% 10%	220
December	1st to 10th	Day	37% 31% 21% 8% 3 1	196
	11th to 20th	Day	41% 29% 22% 6% 2	180
	21st to end	Day	36% 30% 25% 7% 2 1	198
January	1st to 10th	Night	29% 31% 27% 10% 2	760
	11th to 20th	Night	30% 27% 25% 16% 2	760
	21st to end	Night	25% 31% 27% 14% 2	836
February	1st to 10th	Night	29% 30% 29% 12% 1	760
	11th to 20th	Night	29% 33% 25% 12% 1	743
	21st to end	Night	35% 25% 25% 13% 2	628
March	1st to 10th	Night	32% 27% 25% 13% 3	760
	11th to 20th	Night	31% 28% 23% 15% 3	760
	21st to end	Night	28% 27% 24% 16% 5% 1	836
April	1st to 10th	Night	27% 27% 26% 16% 4	760
	11th to 20th	Night	28% 24% 25% 17% 6% 1	751
	21st to end	Night	28% 22% 24% 18% 8%	727
May	1st to 10th	Night	31% 18% 23% 20% 8% 1	513
	11th to 20th	Night	20% 21% 25% 29% 5% 1	374
	21st to end	Night	17% 12% 27% 27% 15% 1	411
June	1st to 10th	Night	18% 14% 26% 28% 13%	380
	11th to 20th	Night	20% 11% 22% 33% 14% 1	380
	21st to end	Night	16% 10% 26% 35% 12% 1	380
July	1st to 10th	Night	14% 9% 23% 36% 15% 2	370
	11th to 20th	Night	14% 8% 25% 35% 17% 1	368
	21st to end	Night	14% 9% 25% 36% 16% 1	416
August	1st to 10th	Night	12% 6% 28% 31% 21% 2	453
	11th to 20th	Night	18% 7% 20% 32% 20% 3	710
	21st to end	Night	17% 10% 20% 30% 21% 2	836
September	1st to 10th	Night	17% 11% 27% 26% 17% 3	760
	11th to 20th	Night	18% 12% 22% 22% 19% 7%	760
	21st to end	Night	20% 13% 24% 24% 16% 3	760
October	1st to 10th	Night	26% 17% 19% 22% 14% 2	760
	11th to 20th	Night	25% 18% 25% 22% 9% 1	760
	21st to end	Night	30% 26% 23% 17% 4	836
November	1st to 10th	Night	23% 24% 26% 19% 8% 1	780
	11th to 20th	Night	30% 25% 22% 14% 7% 2	800
	21st to end	Night	27% 28% 25% 16% 4 1	800
December	1st to 10th	Night	32% 29% 23% 12% 4	795
	11th to 20th	Night	32% 26% 26% 14% 3	760
	21st to end	Night	32% 32% 21% 12% 2	836

Page generated at 2024-12-06 03:54:52. Version ac07

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