Lorenz Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lorenz Observatory clear sky chart from 2005-11-06 to 2024-05-10.

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	15% 10% 4 7% 6% 3 5% 5% 5% 7% 35%	83466
	Night	16% 9% 4 7% 6% 3 5% 5% 5% 7% 35%	85951
Transparency	Day	48% 7% 13% 20% 11% 1	83174
	Night	49% 7% 13% 19% 11% 1	85777
Seeing	Day	19% 14% 31% 22% 10% 4	13763
	Night	19% 12% 30% 27% 11% 1	23197

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	15% 16% 5% 8% 5% 3 4 4 4 5% 32%	2517
	11th to 20th	Day	11% 17% 7% 11% 8% 4 6% 5% 4 4 21%	2566
	21st to end	Day	20% 19% 6% 10% 7% 3 4 3 4 4 20%	3124
February	1st to 10th	Day	12% 15% 5% 10% 8% 3 6% 5% 5% 5% 25%	1710
	11th to 20th	Day	11% 13% 6% 11% 10% 4 4 4 4 7% 28%	1663
	21st to end	Day	18% 12% 5% 8% 8% 3 4 4 4 5% 27%	1494
March	1st to 10th	Day	19% 13% 4 6% 6% 3 4 4 5% 6% 31%	3354
	11th to 20th	Day	10% 14% 4 8% 7% 4 5% 5% 5% 6% 32%	3480
	21st to end	Day	14% 9% 2 5% 4 3 4 4 4 6% 45%	3868
April	1st to 10th	Day	18% 11% 4 8% 6% 3 4 4 4 6% 32%	2280
	11th to 20th	Day	21% 7% 4 6% 4 3 3 3 4 6% 39%	2254
	21st to end	Day	20% 8% 3 6% 6% 4 4 5% 3 6% 34%	2460
May	1st to 10th	Day	17% 7% 3 7% 6% 3 6% 4 6% 7% 35%	2545
	11th to 20th	Day	14% 6% 2 6% 5% 2 4 6% 5% 7% 41%	2478
	21st to end	Day	12% 5% 3 5% 6% 3 6% 5% 6% 8% 42%	2725
June	1st to 10th	Day	17% 6% 3 5% 6% 3 5% 5% 7% 8% 36%	2520
	11th to 20th	Day	13% 6% 2 5% 5% 4 4 5% 6% 10% 41%	2520
	21st to end	Day	14% 6% 3 5% 5% 3 5% 6% 6% 9% 38%	2520
July	1st to 10th	Day	9% 4 2 4 5% 3 6% 6% 7% 8% 46%	2520
	11th to 20th	Day	10% 5% 3 5% 5% 4 6% 6% 7% 9% 39%	2520
	21st to end	Day	9% 5% 2 5% 6% 4 7% 7% 8% 10% 38%	2697
August	1st to 10th	Day	9% 5% 2 5% 6% 4 5% 6% 7% 9% 42%	2327
	11th to 20th	Day	9% 5% 2 5% 6% 4 6% 6% 7% 9% 40%	2303
	21st to end	Day	11% 6% 2 5% 5% 3 5% 6% 8% 9% 40%	2422
September	1st to 10th	Day	12% 6% 3 5% 6% 4 5% 5% 5% 8% 43%	2160
	11th to 20th	Day	11% 4 2 4 4 3 4 5% 5% 7% 49%	2151
	21st to end	Day	14% 6% 3 5% 5% 3 5% 5% 5% 7% 41%	1885
October	1st to 10th	Day	18% 9% 3 6% 6% 3 5% 5% 5% 7% 34%	1800
	11th to 20th	Day	18% 9% 3 7% 7% 4 4 6% 4 7% 29%	1800
	21st to end	Day	25% 12% 3 6% 5% 4 5% 5% 4 5% 26%	1965
November	1st to 10th	Day	14% 9% 4 7% 6% 4 4 4 5% 6% 36%	1600
	11th to 20th	Day	15% 10% 4 7% 6% 3 6% 6% 6% 7% 30%	1520
	21st to end	Day	19% 14% 4 7% 7% 3 5% 5% 4 7% 25%	1520
December	1st to 10th	Day	17% 15% 6% 9% 8% 4 5% 4 5% 5% 23%	1520
	11th to 20th	Day	17% 14% 5% 7% 6% 3 4 4 5% 5% 29%	1906
	21st to end	Day	27% 15% 5% 8% 5% 3 4 3 4 5% 20%	2772
January	1st to 10th	Night	18% 13% 5% 8% 6% 3 5% 5% 5% 6% 25%	4429
	11th to 20th	Night	14% 12% 5% 10% 9% 5% 6% 4 5% 5% 24%	4377
	21st to end	Night	20% 14% 6% 8% 6% 3 5% 4 4 5% 25%	4532
February	1st to 10th	Night	13% 15% 5% 8% 8% 4 5% 5% 5% 6% 26%	2470
	11th to 20th	Night	12% 12% 5% 8% 7% 3 5% 6% 6% 5% 30%	2403
	21st to end	Night	14% 11% 4 8% 6% 4 4 5% 5% 7% 32%	1960
March	1st to 10th	Night	17% 10% 4 8% 6% 3 5% 4 4 6% 33%	3483
	11th to 20th	Night	14% 11% 4 7% 6% 3 5% 5% 6% 6% 33%	3479
	21st to end	Night	16% 7% 2 5% 4 2 3 3 4 6% 48%	3764
April	1st to 10th	Night	18% 9% 4 6% 5% 3 4 5% 4 6% 36%	1900
	11th to 20th	Night	18% 7% 3 6% 6% 3 4 4 4 6% 39%	1875
	21st to end	Night	17% 7% 2 7% 5% 4 4 6% 6% 7% 36%	1737
May	1st to 10th	Night	18% 7% 2 6% 5% 3 5% 5% 6% 7% 35%	1618
	11th to 20th	Night	12% 5% 3 4 5% 3 4 5% 7% 7% 45%	1415
	21st to end	Night	10% 5% 3 5% 4 3 4 5% 5% 8% 49%	1550
June	1st to 10th	Night	14% 5% 3 6% 5% 3 6% 4 7% 8% 39%	1440
	11th to 20th	Night	10% 5% 2 6% 5% 3 3 5% 6% 8% 45%	1440
	21st to end	Night	11% 6% 3 5% 6% 4 5% 4 6% 8% 42%	1440
July	1st to 10th	Night	6% 4 2 5% 5% 4 5% 4 5% 9% 53%	1440
	11th to 20th	Night	10% 5% 3 4 4 3 5% 4 6% 9% 48%	1440
	21st to end	Night	8% 5% 2 4 5% 3 5% 5% 6% 7% 50%	1618
August	1st to 10th	Night	8% 5% 3 5% 5% 2 4 4 7% 8% 49%	1611
	11th to 20th	Night	8% 5% 2 6% 5% 3 3 6% 6% 8% 48%	1598
	21st to end	Night	9% 5% 2 5% 4 3 6% 5% 6% 8% 48%	1916
September	1st to 10th	Night	11% 5% 3 5% 5% 3 5% 5% 6% 8% 45%	1800
	11th to 20th	Night	12% 4 2 3 4 2 4 4 6% 7% 52%	1807
	21st to end	Night	15% 6% 3 5% 4 3 4 4 3 6% 46%	2074
October	1st to 10th	Night	17% 6% 3 6% 5% 3 5% 4 5% 7% 39%	2160
	11th to 20th	Night	18% 8% 3 7% 8% 3 5% 4 5% 6% 33%	2160
	21st to end	Night	21% 9% 4 8% 6% 3 4 4 5% 7% 29%	2389
November	1st to 10th	Night	17% 7% 3 5% 5% 3 4 4 6% 7% 39%	2474
	11th to 20th	Night	17% 9% 3 6% 6% 4 6% 5% 6% 7% 32%	2660
	21st to end	Night	19% 10% 4 6% 6% 3 5% 5% 6% 7% 27%	2660
December	1st to 10th	Night	18% 13% 5% 8% 7% 4 5% 6% 5% 6% 23%	2660
	11th to 20th	Night	17% 14% 4 8% 6% 4 4 5% 5% 6% 27%	3288
	21st to end	Night	28% 16% 5% 8% 5% 3 4 5% 4 6% 17%	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	54% 7% 16% 15% 7% 1	2518
	11th to 20th	Day	66% 7% 10% 10% 6%	2566
	21st to end	Day	68% 6% 10% 10% 5% 1	3124
February	1st to 10th	Day	60% 7% 11% 16% 5% 1	1710
	11th to 20th	Day	57% 5% 11% 15% 10% 2	1672
	21st to end	Day	59% 5% 10% 15% 9% 1	1494
March	1st to 10th	Day	53% 6% 13% 18% 9% 1	3357
	11th to 20th	Day	50% 6% 17% 15% 10% 2	3480
	21st to end	Day	40% 6% 9% 26% 17% 3	3868
April	1st to 10th	Day	53% 5% 10% 19% 11% 2	2280
	11th to 20th	Day	48% 4 10% 21% 16% 1	2254
	21st to end	Day	51% 5% 10% 18% 13% 2	2460
May	1st to 10th	Day	48% 7% 9% 19% 14% 3	2545
	11th to 20th	Day	40% 8% 11% 24% 16% 2	2482
	21st to end	Day	38% 7% 15% 23% 14% 2	2725
June	1st to 10th	Day	44% 7% 14% 20% 14% 1	2520
	11th to 20th	Day	37% 8% 14% 25% 14% 2	2520
	21st to end	Day	40% 8% 15% 22% 14% 1	2520
July	1st to 10th	Day	31% 9% 14% 28% 17% 2	2450
	11th to 20th	Day	36% 9% 16% 28% 10% 1	2445
	21st to end	Day	37% 11% 16% 25% 11% 1	2546
August	1st to 10th	Day	35% 10% 17% 24% 12% 2	2314
	11th to 20th	Day	36% 9% 17% 26% 12%	2303
	21st to end	Day	35% 9% 15% 28% 11% 2	2422
September	1st to 10th	Day	37% 8% 14% 28% 11% 1	2160
	11th to 20th	Day	32% 7% 15% 30% 15% 1	2151
	21st to end	Day	41% 7% 15% 27% 9%	1885
October	1st to 10th	Day	49% 7% 13% 20% 11% 1	1800
	11th to 20th	Day	53% 7% 15% 18% 6% 1	1800
	21st to end	Day	59% 5% 12% 15% 8% 1	1965
November	1st to 10th	Day	46% 7% 16% 20% 11% 1	1600
	11th to 20th	Day	50% 7% 17% 15% 10% 1	1520
	21st to end	Day	58% 8% 13% 14% 7%	1520
December	1st to 10th	Day	62% 6% 13% 13% 5%	1520
	11th to 20th	Day	57% 7% 14% 13% 8%	1906
	21st to end	Day	67% 6% 11% 12% 4	2772
January	1st to 10th	Night	59% 8% 16% 12% 5%	4429
	11th to 20th	Night	60% 8% 14% 13% 4 1	4377
	21st to end	Night	62% 7% 12% 12% 6%	4532
February	1st to 10th	Night	58% 7% 13% 16% 5%	2470
	11th to 20th	Night	54% 6% 12% 19% 9%	2405
	21st to end	Night	50% 6% 14% 20% 9% 1	1960
March	1st to 10th	Night	53% 6% 9% 21% 10% 1	3493
	11th to 20th	Night	49% 7% 14% 18% 10% 1	3480
	21st to end	Night	37% 4 10% 24% 21% 3	3764
April	1st to 10th	Night	48% 6% 10% 20% 14% 2	1900
	11th to 20th	Night	46% 6% 10% 18% 18% 2	1875
	21st to end	Night	45% 7% 12% 16% 16% 2	1737
May	1st to 10th	Night	46% 6% 11% 18% 15% 3	1618
	11th to 20th	Night	36% 7% 11% 25% 18% 4	1416
	21st to end	Night	33% 7% 15% 23% 19% 4	1551
June	1st to 10th	Night	40% 8% 12% 23% 14% 2	1440
	11th to 20th	Night	35% 7% 13% 20% 22% 3	1440
	21st to end	Night	40% 7% 12% 24% 15% 2	1440
July	1st to 10th	Night	28% 9% 11% 27% 24% 2	1400
	11th to 20th	Night	33% 7% 13% 28% 18% 1	1392
	21st to end	Night	32% 7% 13% 33% 13% 2	1528
August	1st to 10th	Night	32% 7% 16% 30% 13% 1	1600
	11th to 20th	Night	32% 8% 17% 28% 14% 2	1598
	21st to end	Night	32% 9% 13% 30% 15% 1	1916
September	1st to 10th	Night	36% 8% 15% 26% 14% 1	1800
	11th to 20th	Night	31% 7% 12% 32% 18% 1	1807
	21st to end	Night	41% 6% 11% 29% 13% 1	2074
October	1st to 10th	Night	45% 7% 12% 21% 14% 1	2160
	11th to 20th	Night	52% 7% 14% 20% 8%	2160
	21st to end	Night	54% 7% 13% 15% 11% 1	2389
November	1st to 10th	Night	43% 7% 14% 22% 13% 1	2474
	11th to 20th	Night	48% 8% 14% 18% 10% 2	2660
	21st to end	Night	53% 9% 17% 15% 5%	2660
December	1st to 10th	Night	59% 9% 13% 14% 5%	2660
	11th to 20th	Night	57% 7% 13% 15% 7% 1	3288
	21st to end	Night	68% 7% 11% 10% 3	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	24% 21% 32% 16% 6% 1	180
	11th to 20th	Day	23% 27% 32% 14% 4 1	195
	21st to end	Day	23% 24% 32% 16% 4 1	297
February	1st to 10th	Day	25% 29% 31% 12% 3	270
	11th to 20th	Day	21% 28% 40% 10% 1	270
	21st to end	Day	30% 23% 35% 11% 1	306
March	1st to 10th	Day	22% 20% 36% 17% 5%	460
	11th to 20th	Day	25% 19% 33% 19% 3	460
	21st to end	Day	30% 16% 33% 14% 7% 1	506
April	1st to 10th	Day	24% 20% 34% 14% 6% 1	460
	11th to 20th	Day	28% 16% 28% 17% 7% 4	452
	21st to end	Day	26% 15% 35% 17% 6% 1	460
May	1st to 10th	Day	24% 13% 31% 19% 8% 5%	459
	11th to 20th	Day	18% 11% 32% 25% 10% 4	447
	21st to end	Day	14% 10% 29% 29% 13% 5%	485
June	1st to 10th	Day	17% 12% 33% 26% 11% 2	450
	11th to 20th	Day	13% 12% 31% 26% 14% 4	450
	21st to end	Day	17% 10% 29% 27% 13% 4	450
July	1st to 10th	Day	9% 7% 25% 35% 20% 5%	445
	11th to 20th	Day	14% 6% 28% 29% 16% 8%	444
	21st to end	Day	9% 8% 32% 34% 11% 6%	488
August	1st to 10th	Day	9% 6% 27% 31% 18% 8%	446
	11th to 20th	Day	11% 4 24% 33% 20% 8%	439
	21st to end	Day	12% 8% 27% 31% 14% 8%	495
September	1st to 10th	Day	11% 8% 32% 24% 17% 9%	450
	11th to 20th	Day	12% 6% 26% 26% 19% 11%	450
	21st to end	Day	13% 12% 30% 24% 16% 6%	450
October	1st to 10th	Day	20% 13% 29% 18% 14% 6%	450
	11th to 20th	Day	23% 18% 29% 22% 7% 1	450
	21st to end	Day	29% 19% 26% 20% 6%	487
November	1st to 10th	Day	24% 18% 26% 23% 9% 1	294
	11th to 20th	Day	22% 21% 38% 16% 3 1	180
	21st to end	Day	23% 23% 31% 17% 7%	180
December	1st to 10th	Day	26% 19% 34% 14% 6%	180
	11th to 20th	Day	27% 28% 32% 10% 2 1	180
	21st to end	Day	33% 23% 32% 11% 2	198
January	1st to 10th	Night	25% 18% 31% 19% 6%	760
	11th to 20th	Night	26% 16% 30% 22% 6%	760
	21st to end	Night	21% 15% 33% 25% 6%	836
February	1st to 10th	Night	22% 19% 38% 19% 2	760
	11th to 20th	Night	20% 18% 38% 20% 4	743
	21st to end	Night	22% 20% 35% 19% 4	628
March	1st to 10th	Night	19% 16% 35% 25% 4	760
	11th to 20th	Night	21% 18% 33% 23% 4 1	760
	21st to end	Night	20% 12% 35% 25% 7% 1	836
April	1st to 10th	Night	21% 13% 36% 25% 5%	760
	11th to 20th	Night	20% 15% 32% 22% 9% 1	751
	21st to end	Night	20% 10% 31% 27% 11%	597
May	1st to 10th	Night	21% 6% 28% 30% 13% 2	480
	11th to 20th	Night	13% 6% 33% 35% 13%	354
	21st to end	Night	11% 5% 30% 36% 17% 1	389
June	1st to 10th	Night	13% 3 36% 33% 14% 1	360
	11th to 20th	Night	11% 6% 26% 39% 17% 1	360
	21st to end	Night	13% 6% 26% 38% 17% 1	360
July	1st to 10th	Night	6% 4 26% 44% 19% 1	350
	11th to 20th	Night	10% 4 22% 39% 24% 1	348
	21st to end	Night	8% 3 24% 45% 18% 2	438
August	1st to 10th	Night	10% 3 16% 40% 28% 2	537
	11th to 20th	Night	8% 4 19% 36% 28% 4	534
	21st to end	Night	11% 4 26% 34% 23% 2	728
September	1st to 10th	Night	13% 5% 24% 34% 22% 3	720
	11th to 20th	Night	13% 5% 20% 32% 25% 6%	720
	21st to end	Night	16% 8% 21% 30% 20% 5%	720
October	1st to 10th	Night	20% 8% 29% 24% 18% 2	720
	11th to 20th	Night	21% 13% 30% 26% 8% 1	720
	21st to end	Night	26% 12% 31% 24% 6%	792
November	1st to 10th	Night	23% 13% 24% 28% 10% 1	740
	11th to 20th	Night	21% 16% 33% 22% 6% 2	760
	21st to end	Night	24% 15% 31% 23% 7%	760
December	1st to 10th	Night	27% 18% 33% 18% 4	760
	11th to 20th	Night	24% 17% 36% 19% 4	760
	21st to end	Night	30% 16% 33% 17% 3	836

Page generated at 2024-05-07 07:25:02. Version ac07

Copyright © 2024 Attilla Danko.