Grundmeier Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grundmeier Farm clear sky chart from 2005-11-06 to 2024-04-25.

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% 6% 3 5% 5% 5% 7% 40%	83433
	Night	11% 8% 3 7% 6% 3 4 4 5% 7% 43%	85719
Transparency	Day	45% 4 12% 25% 13% 2	83148
	Night	42% 3 12% 25% 15% 2	85524
Seeing	Day	16% 10% 31% 27% 13% 3	15019
	Night	14% 10% 35% 30% 10% 1	25090

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% 12% 6% 16% 14% 5% 4 4 5% 5% 22%	2669
	11th to 20th	Day	8% 12% 5% 11% 8% 4 8% 4 5% 6% 26%	2850
	21st to end	Day	10% 13% 7% 16% 9% 4 4 5% 4 7% 21%	3135
February	1st to 10th	Day	10% 11% 6% 9% 9% 5% 5% 4 5% 6% 29%	1710
	11th to 20th	Day	10% 10% 5% 9% 6% 4 5% 4 5% 5% 38%	1664
	21st to end	Day	13% 10% 5% 8% 7% 3 4 4 5% 6% 35%	1527
March	1st to 10th	Day	14% 8% 4 7% 4 3 2 3 4 5% 45%	3436
	11th to 20th	Day	12% 7% 3 6% 5% 3 4 4 5% 6% 45%	3480
	21st to end	Day	23% 12% 7% 10% 6% 3 5% 4 5% 5% 20%	3814
April	1st to 10th	Day	16% 10% 3 6% 5% 3 4 4 5% 7% 38%	2204
	11th to 20th	Day	17% 10% 3 6% 6% 3 4 3 4 6% 37%	2307
	21st to end	Day	22% 8% 3 5% 4 3 5% 4 5% 6% 36%	2394
May	1st to 10th	Day	19% 8% 3 5% 4 4 5% 6% 5% 7% 34%	2340
	11th to 20th	Day	16% 8% 3 6% 5% 4 4 6% 5% 7% 37%	2341
	21st to end	Day	17% 7% 3 6% 6% 3 6% 5% 5% 8% 35%	2725
June	1st to 10th	Day	11% 5% 2 5% 5% 3 5% 5% 5% 9% 44%	2520
	11th to 20th	Day	9% 4 2 5% 5% 3 5% 5% 7% 8% 46%	2520
	21st to end	Day	8% 4 2 5% 6% 4 6% 6% 6% 7% 46%	2520
July	1st to 10th	Day	7% 4 2 4 4 3 4 6% 6% 10% 51%	2520
	11th to 20th	Day	6% 4 1 4 4 3 4 4 5% 8% 55%	2386
	21st to end	Day	6% 4 2 4 5% 3 5% 5% 7% 10% 49%	2546
August	1st to 10th	Day	9% 6% 2 6% 6% 4 6% 6% 7% 10% 39%	2328
	11th to 20th	Day	11% 6% 2 4 5% 3 4 5% 5% 8% 48%	2301
	21st to end	Day	9% 5% 2 4 4 2 4 5% 6% 8% 51%	2497
September	1st to 10th	Day	13% 4 2 4 4 2 4 4 5% 7% 51%	2160
	11th to 20th	Day	10% 5% 2 4 4 2 4 4 4 8% 53%	1998
	21st to end	Day	12% 3 1 4 4 3 3 4 5% 7% 53%	1973
October	1st to 10th	Day	14% 6% 2 5% 4 3 4 4 4 7% 48%	1800
	11th to 20th	Day	14% 7% 3 4 4 2 3 4 4 6% 50%	1800
	21st to end	Day	15% 8% 3 6% 5% 3 4 4 4 6% 42%	1980
November	1st to 10th	Day	10% 6% 2 5% 4 2 4 5% 4 7% 50%	1727
	11th to 20th	Day	11% 8% 3 9% 6% 3 4 4 5% 7% 41%	1520
	21st to end	Day	13% 9% 4 5% 5% 2 3 3 5% 6% 43%	1520
December	1st to 10th	Day	10% 8% 4 8% 7% 3 5% 5% 4 6% 38%	1520
	11th to 20th	Day	9% 10% 4 9% 8% 4 5% 6% 6% 7% 32%	1918
	21st to end	Day	17% 10% 5% 18% 7% 3 4 4 4 5% 21%	2783
January	1st to 10th	Night	9% 10% 5% 17% 14% 4 4 4 4 5% 25%	4268
	11th to 20th	Night	7% 12% 5% 8% 8% 4 7% 6% 9% 7% 27%	4120
	21st to end	Night	10% 15% 7% 13% 8% 3 4 5% 4 5% 27%	4532
February	1st to 10th	Night	11% 10% 5% 10% 8% 4 4 4 4 5% 35%	2470
	11th to 20th	Night	10% 9% 4 7% 5% 3 5% 4 6% 7% 39%	2403
	21st to end	Night	10% 8% 3 8% 6% 3 5% 3 4 5% 44%	1943
March	1st to 10th	Night	12% 7% 3 6% 4 2 3 3 4 5% 50%	3419
	11th to 20th	Night	11% 7% 2 5% 4 2 3 3 4 7% 52%	3480
	21st to end	Night	21% 11% 5% 10% 8% 3 4 4 5% 6% 24%	3817
April	1st to 10th	Night	13% 9% 2 5% 6% 2 4 5% 5% 7% 43%	1976
	11th to 20th	Night	14% 8% 3 6% 5% 3 4 4 4 7% 43%	1820
	21st to end	Night	17% 8% 3 5% 4 3 4 4 5% 6% 40%	1665
May	1st to 10th	Night	16% 6% 3 5% 5% 3 4 5% 6% 8% 39%	1620
	11th to 20th	Night	15% 6% 3 5% 4 3 4 3 5% 7% 45%	1554
	21st to end	Night	13% 6% 3 6% 6% 3 4 6% 6% 9% 38%	1551
June	1st to 10th	Night	7% 4 2 5% 4 3 4 5% 6% 8% 51%	1440
	11th to 20th	Night	6% 4 2 4 4 3 4 5% 6% 10% 52%	1440
	21st to end	Night	5% 4 1 4 4 3 4 4 6% 9% 55%	1440
July	1st to 10th	Night	4 4 2 3 3 3 4 5% 5% 10% 58%	1440
	11th to 20th	Night	4 2 1 3 2 3 4 3 4 9% 65%	1570
	21st to end	Night	3 2 1 3 4 3 5% 4 6% 10% 58%	1772
August	1st to 10th	Night	6% 5% 3 5% 5% 3 5% 4 6% 9% 49%	1611
	11th to 20th	Night	8% 3 2 4 5% 2 3 3 5% 7% 58%	1600
	21st to end	Night	7% 4 2 4 4 3 3 5% 6% 8% 56%	1858
September	1st to 10th	Night	9% 4 1 4 4 2 3 4 4 7% 58%	1800
	11th to 20th	Night	10% 4 2 4 4 2 4 4 6% 6% 55%	1958
	21st to end	Night	10% 5% 2 4 4 2 3 3 4 6% 57%	1980
October	1st to 10th	Night	14% 6% 2 4 4 3 3 3 4 7% 51%	2148
	11th to 20th	Night	16% 6% 3 5% 3 2 2 3 4 6% 50%	2160
	21st to end	Night	15% 7% 3 6% 3 2 3 3 3 6% 48%	2376
November	1st to 10th	Night	7% 5% 2 4 5% 2 4 4 5% 7% 55%	2345
	11th to 20th	Night	11% 6% 3 7% 6% 3 4 4 5% 6% 46%	2660
	21st to end	Night	12% 8% 3 6% 4 2 4 3 4 6% 46%	2660
December	1st to 10th	Night	8% 10% 3 9% 7% 3 5% 5% 4 7% 39%	2660
	11th to 20th	Night	9% 9% 4 8% 7% 4 4 5% 5% 7% 39%	3279
	21st to end	Night	16% 13% 6% 15% 7% 3 4 3 4 4 26%	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	65% 3 11% 14% 7% 1	2670
	11th to 20th	Day	59% 2 8% 24% 6%	2850
	21st to end	Day	63% 3 13% 14% 6%	3135
February	1st to 10th	Day	55% 4 11% 19% 10% 1	1710
	11th to 20th	Day	49% 3 11% 22% 13% 2	1673
	21st to end	Day	51% 4 10% 21% 11% 4	1527
March	1st to 10th	Day	44% 2 8% 29% 14% 2	3436
	11th to 20th	Day	41% 3 10% 28% 14% 3	3480
	21st to end	Day	66% 4 11% 14% 4 1	3814
April	1st to 10th	Day	47% 4 11% 27% 10% 1	2204
	11th to 20th	Day	50% 3 12% 21% 13% 2	2307
	21st to end	Day	50% 4 10% 24% 12% 1	2394
May	1st to 10th	Day	49% 4 13% 22% 11%	2340
	11th to 20th	Day	47% 5% 12% 25% 10% 1	2345
	21st to end	Day	47% 5% 14% 21% 12% 1	2725
June	1st to 10th	Day	37% 6% 15% 26% 14% 2	2520
	11th to 20th	Day	34% 6% 14% 28% 17% 2	2520
	21st to end	Day	36% 5% 16% 27% 13% 3	2520
July	1st to 10th	Day	29% 6% 15% 34% 13% 3	2451
	11th to 20th	Day	27% 5% 16% 28% 19% 5%	2314
	21st to end	Day	30% 5% 16% 30% 17% 2	2405
August	1st to 10th	Day	38% 6% 17% 27% 11% 1	2314
	11th to 20th	Day	34% 5% 13% 33% 14% 1	2301
	21st to end	Day	31% 5% 12% 28% 19% 4	2497
September	1st to 10th	Day	33% 4 12% 29% 19% 3	2160
	11th to 20th	Day	31% 4 13% 33% 18% 1	1998
	21st to end	Day	31% 4 12% 31% 22% 1	1973
October	1st to 10th	Day	37% 3 10% 31% 18% 1	1800
	11th to 20th	Day	37% 2 9% 30% 19% 4	1800
	21st to end	Day	44% 3 11% 21% 18% 3	1980
November	1st to 10th	Day	34% 4 15% 26% 19% 3	1727
	11th to 20th	Day	44% 3 12% 25% 16% 1	1520
	21st to end	Day	43% 3 14% 25% 14% 1	1520
December	1st to 10th	Day	46% 3 15% 22% 10% 2	1520
	11th to 20th	Day	51% 3 18% 23% 5%	1915
	21st to end	Day	66% 3 9% 15% 6% 1	2783
January	1st to 10th	Night	63% 2 10% 15% 10% 1	4268
	11th to 20th	Night	53% 3 12% 19% 10% 2	4120
	21st to end	Night	59% 3 12% 16% 9% 1	4532
February	1st to 10th	Night	52% 3 10% 21% 11% 2	2470
	11th to 20th	Night	45% 4 10% 23% 14% 3	2404
	21st to end	Night	44% 3 10% 22% 18% 3	1943
March	1st to 10th	Night	38% 3 8% 31% 18% 2	3419
	11th to 20th	Night	34% 3 9% 33% 15% 4	3480
	21st to end	Night	63% 5% 15% 12% 4 1	3817
April	1st to 10th	Night	41% 4 11% 26% 17% 1	1976
	11th to 20th	Night	43% 4 11% 23% 17% 2	1820
	21st to end	Night	44% 4 12% 23% 16% 1	1665
May	1st to 10th	Night	42% 5% 13% 23% 14% 2	1620
	11th to 20th	Night	41% 5% 14% 25% 15% 1	1555
	21st to end	Night	42% 6% 17% 20% 12% 3	1552
June	1st to 10th	Night	29% 6% 15% 31% 16% 2	1440
	11th to 20th	Night	27% 5% 14% 27% 21% 5%	1440
	21st to end	Night	26% 5% 16% 32% 18% 4	1440
July	1st to 10th	Night	24% 4 17% 34% 19% 3	1400
	11th to 20th	Night	19% 4 18% 34% 21% 5%	1519
	21st to end	Night	21% 4 16% 35% 21% 3	1673
August	1st to 10th	Night	32% 4 18% 29% 15% 3	1601
	11th to 20th	Night	27% 4 14% 33% 19% 4	1600
	21st to end	Night	26% 5% 13% 27% 21% 8%	1858
September	1st to 10th	Night	28% 4 12% 29% 23% 5%	1800
	11th to 20th	Night	29% 3 12% 33% 22% 2	1958
	21st to end	Night	29% 3 10% 33% 23% 3	1980
October	1st to 10th	Night	35% 3 11% 27% 21% 2	2148
	11th to 20th	Night	37% 3 9% 25% 22% 4	2160
	21st to end	Night	39% 3 12% 23% 21% 1	2376
November	1st to 10th	Night	29% 4 16% 26% 21% 4	2345
	11th to 20th	Night	40% 2 14% 26% 16% 2	2660
	21st to end	Night	40% 3 11% 28% 15% 2	2660
December	1st to 10th	Night	45% 4 13% 27% 11% 1	2660
	11th to 20th	Night	45% 4 14% 30% 7% 1	3281
	21st to end	Night	64% 3 8% 19% 7% 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	16% 17% 36% 23% 7% 1	270
	11th to 20th	Day	19% 16% 38% 22% 4 1	270
	21st to end	Day	19% 13% 39% 22% 6% 1	297
February	1st to 10th	Day	17% 17% 40% 24% 2	270
	11th to 20th	Day	16% 17% 38% 23% 5% 1	270
	21st to end	Day	20% 20% 41% 17% 3	225
March	1st to 10th	Day	19% 19% 39% 17% 6%	270
	11th to 20th	Day	24% 14% 35% 20% 6%	270
	21st to end	Day	33% 16% 34% 13% 3	297
April	1st to 10th	Day	25% 15% 37% 20% 3	384
	11th to 20th	Day	25% 15% 33% 20% 6% 1	505
	21st to end	Day	25% 14% 30% 23% 7% 1	622
May	1st to 10th	Day	24% 14% 30% 22% 8% 1	603
	11th to 20th	Day	22% 11% 30% 23% 12% 3	625
	21st to end	Day	16% 8% 30% 30% 14% 2	679
June	1st to 10th	Day	10% 7% 25% 32% 24% 3	630
	11th to 20th	Day	9% 6% 35% 31% 16% 3	630
	21st to end	Day	9% 8% 34% 30% 15% 3	630
July	1st to 10th	Day	7% 3 20% 36% 24% 9%	621
	11th to 20th	Day	7% 4 29% 35% 17% 7%	618
	21st to end	Day	6% 2 24% 41% 24% 3	684
August	1st to 10th	Day	9% 4 19% 38% 25% 5%	626
	11th to 20th	Day	11% 5% 20% 37% 23% 5%	615
	21st to end	Day	10% 4 21% 40% 19% 5%	616
September	1st to 10th	Day	14% 5% 27% 35% 14% 5%	450
	11th to 20th	Day	8% 6% 35% 29% 18% 4	288
	21st to end	Day	15% 10% 33% 31% 11%	270
October	1st to 10th	Day	21% 9% 29% 23% 16% 2	270
	11th to 20th	Day	17% 19% 37% 20% 6% 1	270
	21st to end	Day	21% 19% 35% 18% 6% 1	297
November	1st to 10th	Day	15% 16% 40% 20% 6% 3	270
	11th to 20th	Day	18% 20% 40% 17% 5%	270
	21st to end	Day	22% 14% 37% 20% 6%	270
December	1st to 10th	Day	12% 13% 45% 23% 7%	270
	11th to 20th	Day	14% 19% 35% 24% 7% 1	270
	21st to end	Day	27% 15% 43% 12% 2	297
January	1st to 10th	Night	12% 16% 40% 26% 5% 1	950
	11th to 20th	Night	14% 15% 41% 23% 6% 1	950
	21st to end	Night	18% 13% 39% 25% 4	1045
February	1st to 10th	Night	15% 13% 43% 24% 5%	950
	11th to 20th	Night	16% 11% 43% 24% 4 1	929
	21st to end	Night	14% 15% 43% 22% 5% 1	687
March	1st to 10th	Night	19% 10% 38% 24% 7% 1	570
	11th to 20th	Night	18% 12% 37% 25% 9%	570
	21st to end	Night	24% 13% 33% 23% 6% 1	627
April	1st to 10th	Night	19% 16% 39% 23% 4	570
	11th to 20th	Night	18% 13% 38% 24% 6%	563
	21st to end	Night	20% 12% 34% 25% 8% 1	555
May	1st to 10th	Night	19% 8% 36% 29% 7% 1	540
	11th to 20th	Night	17% 10% 28% 34% 10% 1	531
	21st to end	Night	15% 6% 33% 33% 14%	584
June	1st to 10th	Night	8% 3 26% 45% 17%	540
	11th to 20th	Night	7% 4 34% 41% 13%	540
	21st to end	Night	6% 6% 33% 39% 16%	540
July	1st to 10th	Night	6% 3 18% 43% 30% 1	525
	11th to 20th	Night	4 2 24% 46% 23% 2	522
	21st to end	Night	3 2 17% 53% 25% 1	591
August	1st to 10th	Night	7% 4 20% 44% 24% 2	537
	11th to 20th	Night	9% 3 21% 41% 23% 3	534
	21st to end	Night	8% 3 23% 43% 20% 3	594
September	1st to 10th	Night	10% 5% 23% 39% 20% 3	540
	11th to 20th	Night	11% 4 30% 38% 14% 3	540
	21st to end	Night	12% 7% 32% 36% 12% 1	540
October	1st to 10th	Night	15% 9% 31% 31% 12% 2	708
	11th to 20th	Night	19% 12% 37% 26% 6%	720
	21st to end	Night	20% 13% 31% 26% 9%	792
November	1st to 10th	Night	11% 13% 40% 28% 8%	861
	11th to 20th	Night	13% 16% 44% 22% 5%	950
	21st to end	Night	16% 13% 40% 24% 7%	950
December	1st to 10th	Night	14% 14% 40% 25% 6%	950
	11th to 20th	Night	15% 12% 40% 27% 5% 1	950
	21st to end	Night	19% 15% 39% 23% 4	1045

Page generated at 2024-04-22 08:25:46. Version ac07

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