Erwin W. Fick Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Erwin W. Fick Observatory 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% 5% 4 4 4 6% 7% 39%	101168
	Night	12% 8% 3 8% 4 4 4 3 5% 7% 42%	97463
Transparency	Day	43% 6% 13% 23% 13% 1	100970
	Night	41% 6% 13% 24% 14% 2	97337
Seeing	Day	15% 10% 30% 28% 14% 3	15797
	Night	15% 9% 33% 32% 11% 1	25615

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	7% 13% 5% 21% 9% 6% 4 3 5% 5% 21%	2536
	11th to 20th	Day	8% 14% 5% 12% 6% 7% 8% 4 7% 7% 23%	2850
	21st to end	Day	13% 16% 8% 16% 6% 5% 5% 3 5% 5% 19%	3135
February	1st to 10th	Day	10% 15% 5% 9% 6% 6% 5% 3 5% 7% 29%	1710
	11th to 20th	Day	11% 10% 4 8% 5% 5% 5% 4 5% 6% 37%	1664
	21st to end	Day	14% 11% 3 10% 5% 5% 4 3 4 6% 35%	1512
March	1st to 10th	Day	15% 9% 3 7% 4 4 4 3 3 5% 43%	3436
	11th to 20th	Day	11% 7% 3 8% 4 3 4 4 5% 6% 45%	3480
	21st to end	Day	23% 14% 6% 9% 5% 4 5% 3 4 5% 22%	3814
April	1st to 10th	Day	17% 11% 3 6% 4 4 4 4 6% 6% 35%	2254
	11th to 20th	Day	18% 9% 3 7% 4 4 3 4 5% 6% 36%	2254
	21st to end	Day	22% 8% 3 6% 4 4 3 4 5% 6% 35%	2446
May	1st to 10th	Day	19% 8% 3 7% 4 4 5% 4 6% 8% 31%	4082
	11th to 20th	Day	14% 7% 2 7% 5% 4 4 4 6% 7% 40%	4298
	21st to end	Day	14% 7% 2 6% 5% 4 4 4 5% 7% 42%	4824
June	1st to 10th	Day	10% 5% 2 6% 4 5% 4 4 6% 8% 45%	2660
	11th to 20th	Day	10% 4 2 5% 5% 5% 4 5% 7% 10% 44%	2660
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 4 6% 9% 42%	2660
July	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 5% 8% 11% 37%	4440
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 7% 58%	4360
	21st to end	Day	5% 4 1 5% 5% 5% 6% 5% 8% 11% 46%	4465
August	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 7% 10% 46%	4104
	11th to 20th	Day	14% 7% 2 6% 4 4 5% 4 7% 8% 39%	4041
	21st to end	Day	7% 4 2 7% 5% 5% 4 4 6% 8% 48%	4290
September	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 53%	2280
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 6% 7% 49%	2192
	21st to end	Day	12% 5% 2 4 3 4 4 3 5% 6% 51%	2033
October	1st to 10th	Day	15% 6% 2 5% 4 3 2 3 4 7% 48%	1900
	11th to 20th	Day	16% 7% 2 6% 4 3 4 3 5% 6% 45%	1830
	21st to end	Day	15% 9% 3 6% 4 3 4 4 5% 6% 41%	1980
November	1st to 10th	Day	10% 7% 3 5% 4 3 5% 4 6% 7% 46%	1717
	11th to 20th	Day	13% 9% 3 6% 6% 4 3 4 5% 7% 40%	1520
	21st to end	Day	14% 10% 3 6% 4 4 4 3 5% 6% 40%	1520
December	1st to 10th	Day	12% 10% 4 10% 4 4 4 4 5% 7% 35%	1520
	11th to 20th	Day	11% 10% 4 9% 6% 5% 5% 3 6% 8% 32%	1918
	21st to end	Day	20% 15% 6% 14% 6% 4 4 2 4 5% 19%	2783
January	1st to 10th	Night	9% 11% 5% 22% 7% 5% 4 3 5% 4 24%	4414
	11th to 20th	Night	9% 14% 5% 10% 6% 5% 7% 4 9% 6% 25%	4120
	21st to end	Night	14% 15% 6% 14% 5% 4 4 3 4 6% 24%	4532
February	1st to 10th	Night	11% 12% 4 11% 7% 4 4 3 6% 6% 32%	2470
	11th to 20th	Night	11% 10% 3 7% 4 5% 4 4 5% 6% 40%	2403
	21st to end	Night	12% 9% 3 9% 6% 4 4 3 4 5% 42%	1956
March	1st to 10th	Night	14% 8% 2 6% 3 3 3 2 5% 6% 48%	3419
	11th to 20th	Night	11% 7% 2 5% 4 3 3 3 4 7% 50%	3480
	21st to end	Night	22% 12% 4 12% 6% 4 4 3 4 6% 23%	3817
April	1st to 10th	Night	14% 9% 2 6% 5% 5% 4 3 5% 7% 42%	1925
	11th to 20th	Night	15% 9% 3 7% 5% 4 3 3 5% 5% 41%	1875
	21st to end	Night	16% 7% 3 7% 4 3 4 3 4 7% 41%	1730
May	1st to 10th	Night	19% 6% 3 6% 3 4 4 4 5% 6% 40%	2823
	11th to 20th	Night	12% 7% 2 6% 4 3 3 3 5% 7% 48%	2603
	21st to end	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2743
June	1st to 10th	Night	6% 4 2 6% 4 4 5% 4 5% 7% 52%	1520
	11th to 20th	Night	7% 6% 2 6% 3 4 4 4 6% 9% 49%	1520
	21st to end	Night	8% 5% 2 4 4 4 4 4 6% 8% 51%	1520
July	1st to 10th	Night	8% 5% 2 5% 4 5% 4 4 6% 9% 48%	2530
	11th to 20th	Night	4 3 1 4 3 3 4 3 6% 8% 62%	2593
	21st to end	Night	5% 3 1 5% 4 5% 5% 5% 8% 11% 49%	3098
August	1st to 10th	Night	5% 4 2 5% 4 4 4 3 6% 8% 54%	2836
	11th to 20th	Night	9% 5% 2 5% 3 3 4 3 4 6% 55%	2798
	21st to end	Night	9% 5% 1 5% 3 3 3 3 5% 8% 56%	3368
September	1st to 10th	Night	10% 3 2 6% 3 3 3 2 4 6% 58%	1900
	11th to 20th	Night	10% 5% 2 5% 2 3 3 3 5% 6% 56%	1985
	21st to end	Night	9% 4 1 4 3 3 3 3 5% 7% 58%	2128
October	1st to 10th	Night	12% 6% 2 4 3 3 3 3 5% 5% 54%	2280
	11th to 20th	Night	16% 6% 2 6% 4 3 3 3 4 6% 49%	2203
	21st to end	Night	15% 9% 3 5% 3 3 3 3 4 6% 45%	2376
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 4 7% 53%	2355
	11th to 20th	Night	12% 8% 3 7% 4 3 4 4 5% 6% 44%	2660
	21st to end	Night	14% 8% 3 7% 4 3 4 3 4 7% 44%	2660
December	1st to 10th	Night	10% 10% 4 8% 6% 5% 5% 4 6% 6% 36%	2660
	11th to 20th	Night	11% 11% 3 9% 4 4 4 4 5% 6% 38%	3279
	21st to end	Night	19% 15% 7% 15% 5% 3 3 3 3 4 23%	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	63% 8% 11% 12% 7%	2537
	11th to 20th	Day	59% 4 10% 21% 5%	2850
	21st to end	Day	66% 6% 10% 14% 4	3135
February	1st to 10th	Day	55% 5% 13% 18% 9% 1	1710
	11th to 20th	Day	48% 6% 12% 21% 11% 2	1673
	21st to end	Day	51% 4 14% 18% 11% 3	1512
March	1st to 10th	Day	44% 5% 10% 24% 14% 2	3436
	11th to 20th	Day	38% 7% 12% 26% 14% 3	3480
	21st to end	Day	63% 7% 11% 14% 4 1	3814
April	1st to 10th	Day	47% 6% 11% 24% 10% 1	2254
	11th to 20th	Day	48% 6% 11% 20% 13% 1	2254
	21st to end	Day	48% 6% 12% 22% 12% 1	2446
May	1st to 10th	Day	47% 10% 13% 17% 12% 1	4120
	11th to 20th	Day	41% 8% 11% 27% 12% 1	4302
	21st to end	Day	39% 8% 13% 23% 17% 1	4837
June	1st to 10th	Day	35% 9% 16% 23% 16% 2	2660
	11th to 20th	Day	33% 7% 15% 24% 19% 2	2660
	21st to end	Day	37% 9% 14% 24% 14% 2	2660
July	1st to 10th	Day	40% 6% 17% 28% 8% 2	4371
	11th to 20th	Day	25% 5% 15% 32% 20% 2	4285
	21st to end	Day	30% 7% 20% 26% 16% 2	4325
August	1st to 10th	Day	33% 6% 16% 28% 16% 1	4090
	11th to 20th	Day	43% 5% 13% 26% 13% 1	4080
	21st to end	Day	34% 5% 17% 26% 16% 3	4289
September	1st to 10th	Day	31% 5% 13% 27% 20% 4	2280
	11th to 20th	Day	33% 6% 14% 30% 17% 1	2192
	21st to end	Day	33% 5% 11% 30% 20% 1	2033
October	1st to 10th	Day	36% 5% 11% 27% 20% 1	1900
	11th to 20th	Day	40% 6% 9% 25% 19% 2	1830
	21st to end	Day	44% 5% 12% 22% 16% 2	1980
November	1st to 10th	Day	35% 6% 16% 22% 18% 2	1717
	11th to 20th	Day	43% 5% 14% 22% 16% 1	1520
	21st to end	Day	45% 5% 14% 24% 11% 1	1520
December	1st to 10th	Day	48% 6% 18% 18% 9% 2	1520
	11th to 20th	Day	49% 6% 18% 21% 6%	1915
	21st to end	Day	68% 5% 10% 13% 4 1	2783
January	1st to 10th	Night	62% 6% 10% 13% 9%	4414
	11th to 20th	Night	55% 5% 14% 15% 10% 1	4120
	21st to end	Night	61% 6% 12% 14% 7% 1	4532
February	1st to 10th	Night	52% 5% 12% 20% 9% 2	2470
	11th to 20th	Night	44% 6% 12% 24% 12% 2	2404
	21st to end	Night	45% 5% 11% 21% 16% 3	1956
March	1st to 10th	Night	37% 5% 11% 28% 17% 2	3419
	11th to 20th	Night	33% 5% 11% 32% 15% 4	3480
	21st to end	Night	61% 9% 14% 10% 4 1	3817
April	1st to 10th	Night	42% 5% 12% 25% 14% 2	1925
	11th to 20th	Night	44% 6% 10% 21% 17% 3	1875
	21st to end	Night	42% 6% 13% 23% 14% 2	1730
May	1st to 10th	Night	42% 7% 12% 21% 17% 1	2850
	11th to 20th	Night	36% 6% 11% 27% 15% 5%	2604
	21st to end	Night	37% 8% 13% 22% 18% 3	2751
June	1st to 10th	Night	30% 7% 15% 28% 15% 4	1520
	11th to 20th	Night	30% 7% 13% 22% 22% 5%	1520
	21st to end	Night	30% 7% 15% 27% 18% 3	1520
July	1st to 10th	Night	32% 6% 16% 32% 13% 2	2490
	11th to 20th	Night	21% 4 19% 34% 21% 2	2545
	21st to end	Night	26% 9% 20% 26% 18% 2	2999
August	1st to 10th	Night	28% 5% 16% 33% 15% 2	2826
	11th to 20th	Night	32% 5% 16% 31% 16% 2	2825
	21st to end	Night	28% 5% 17% 29% 17% 5%	3368
September	1st to 10th	Night	28% 4 12% 27% 25% 5%	1900
	11th to 20th	Night	29% 5% 11% 34% 20% 1	1985
	21st to end	Night	27% 5% 10% 31% 24% 3	2128
October	1st to 10th	Night	33% 5% 10% 27% 22% 3	2280
	11th to 20th	Night	37% 5% 11% 24% 19% 4	2208
	21st to end	Night	40% 5% 12% 22% 20% 2	2376
November	1st to 10th	Night	31% 5% 16% 25% 20% 4	2355
	11th to 20th	Night	40% 5% 14% 26% 14% 1	2660
	21st to end	Night	42% 4 12% 26% 14% 2	2660
December	1st to 10th	Night	48% 5% 14% 23% 10% 1	2660
	11th to 20th	Night	44% 6% 14% 28% 7%	3281
	21st to end	Night	65% 6% 8% 15% 6%	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	19% 12% 34% 24% 9% 2	270
	11th to 20th	Day	18% 12% 43% 22% 4	270
	21st to end	Day	19% 12% 35% 27% 6% 1	297
February	1st to 10th	Day	16% 18% 41% 21% 3 1	270
	11th to 20th	Day	16% 17% 36% 24% 6% 1	270
	21st to end	Day	20% 17% 44% 17% 3	225
March	1st to 10th	Day	18% 16% 39% 20% 7%	270
	11th to 20th	Day	26% 12% 35% 19% 8%	270
	21st to end	Day	32% 16% 32% 15% 4	297
April	1st to 10th	Day	25% 15% 34% 20% 6%	434
	11th to 20th	Day	25% 16% 29% 21% 9%	452
	21st to end	Day	24% 14% 30% 22% 8% 2	626
May	1st to 10th	Day	22% 14% 33% 22% 8% 1	653
	11th to 20th	Day	21% 12% 29% 24% 10% 3	675
	21st to end	Day	16% 10% 26% 30% 14% 3	734
June	1st to 10th	Day	8% 7% 28% 29% 24% 4	680
	11th to 20th	Day	11% 6% 29% 36% 14% 4	680
	21st to end	Day	8% 7% 36% 33% 14% 3	680
July	1st to 10th	Day	7% 5% 18% 33% 25% 12%	671
	11th to 20th	Day	6% 4 25% 35% 22% 8%	668
	21st to end	Day	6% 1 21% 41% 26% 5%	739
August	1st to 10th	Day	9% 4 21% 35% 26% 5%	676
	11th to 20th	Day	14% 3 18% 35% 23% 6%	665
	21st to end	Day	10% 4 21% 37% 22% 6%	610
September	1st to 10th	Day	12% 5% 24% 30% 22% 7%	490
	11th to 20th	Day	7% 4 25% 38% 21% 5%	402
	21st to end	Day	13% 8% 26% 34% 16% 3	300
October	1st to 10th	Day	17% 6% 30% 29% 14% 4	300
	11th to 20th	Day	18% 22% 32% 19% 8% 1	279
	21st to end	Day	20% 15% 34% 21% 7% 2	297
November	1st to 10th	Day	14% 13% 41% 20% 8% 3	270
	11th to 20th	Day	17% 21% 33% 20% 8% 1	270
	21st to end	Day	23% 13% 37% 20% 5% 1	270
December	1st to 10th	Day	10% 13% 45% 22% 8% 1	270
	11th to 20th	Day	13% 16% 36% 26% 9% 1	270
	21st to end	Day	24% 16% 40% 17% 3	297
January	1st to 10th	Night	12% 14% 37% 30% 7%	950
	11th to 20th	Night	16% 13% 35% 27% 8% 1	950
	21st to end	Night	19% 11% 34% 29% 6%	1045
February	1st to 10th	Night	16% 11% 38% 30% 4	950
	11th to 20th	Night	16% 13% 39% 28% 5%	929
	21st to end	Night	16% 12% 42% 23% 5% 2	700
March	1st to 10th	Night	19% 10% 37% 25% 8% 1	570
	11th to 20th	Night	18% 9% 38% 27% 8%	570
	21st to end	Night	22% 12% 39% 20% 6% 1	627
April	1st to 10th	Night	17% 15% 40% 25% 4	570
	11th to 20th	Night	18% 13% 35% 28% 5% 1	563
	21st to end	Night	19% 9% 37% 27% 7% 1	570
May	1st to 10th	Night	19% 8% 34% 31% 8%	570
	11th to 20th	Night	16% 10% 31% 32% 11% 1	561
	21st to end	Night	16% 7% 28% 35% 14%	617
June	1st to 10th	Night	8% 5% 28% 41% 19%	570
	11th to 20th	Night	9% 4 29% 46% 11%	570
	21st to end	Night	8% 5% 31% 42% 12% 1	570
July	1st to 10th	Night	6% 2 16% 44% 30% 2	555
	11th to 20th	Night	4 1 21% 45% 26% 2	552
	21st to end	Night	4 3 17% 50% 25% 1	624
August	1st to 10th	Night	8% 2 17% 49% 23% 1	567
	11th to 20th	Night	8% 2 16% 45% 26% 3	564
	21st to end	Night	9% 3 20% 43% 22% 3	627
September	1st to 10th	Night	9% 4 24% 40% 21% 2	570
	11th to 20th	Night	13% 1 24% 40% 20% 2	570
	21st to end	Night	10% 6% 29% 38% 16% 1	608
October	1st to 10th	Night	14% 7% 33% 32% 13% 1	760
	11th to 20th	Night	17% 13% 34% 29% 7%	735
	21st to end	Night	23% 9% 32% 28% 8%	792
November	1st to 10th	Night	14% 9% 39% 30% 9%	794
	11th to 20th	Night	16% 14% 42% 22% 6%	950
	21st to end	Night	17% 13% 34% 30% 7%	950
December	1st to 10th	Night	15% 11% 39% 28% 7%	950
	11th to 20th	Night	19% 9% 34% 32% 5% 1	950
	21st to end	Night	21% 13% 38% 24% 4	1045

Page generated at 2024-10-11 09:49:59. Version ac07

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