Lozwott Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lozwott Observatory clear sky chart from 2005-11-06 to 2026-03-03.

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 6% 4 4 4 3 5% 7% 44%	131096
	Night	12% 8% 3 6% 4 4 3 3 5% 6% 46%	130329
Transparency	Day	39% 5% 11% 25% 17% 3	134706
	Night	39% 4 11% 25% 18% 4	134797
Seeing	Day	17% 13% 30% 25% 13% 2	17351
	Night	17% 12% 31% 27% 12% 1	27333

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	15% 11% 4 8% 4 4 4 3 4 5% 41%	5245
	11th to 20th	Day	7% 10% 3 9% 5% 6% 5% 3 4 6% 44%	5310
	21st to end	Day	15% 11% 3 8% 3 4 3 3 5% 5% 41%	5812
February	1st to 10th	Day	16% 10% 3 9% 5% 4 3 3 4 6% 36%	1890
	11th to 20th	Day	15% 10% 3 6% 4 4 4 4 4 4 41%	1855
	21st to end	Day	15% 10% 3 5% 4 3 4 3 5% 5% 41%	1780
March	1st to 10th	Day	15% 10% 3 5% 3 3 3 2 4 4 49%	4958
	11th to 20th	Day	11% 6% 2 5% 3 3 4 3 5% 6% 53%	4980
	21st to end	Day	15% 10% 3 8% 5% 4 5% 4 5% 7% 34%	5462
April	1st to 10th	Day	15% 8% 2 6% 5% 4 4 3 4 5% 42%	2382
	11th to 20th	Day	17% 8% 2 6% 3 4 4 4 5% 6% 41%	2374
	21st to end	Day	23% 8% 3 6% 6% 3 4 3 4 7% 34%	2400
May	1st to 10th	Day	17% 8% 2 7% 4 4 5% 4 6% 8% 35%	5852
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 6% 7% 40%	5862
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 6% 40%	6890
June	1st to 10th	Day	8% 5% 2 5% 4 5% 4 4 7% 9% 47%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 5% 5% 4 7% 9% 45%	2800
	21st to end	Day	6% 3 1 5% 5% 4 5% 4 6% 9% 52%	2800
July	1st to 10th	Day	10% 6% 2 6% 4 4 4 4 5% 8% 46%	6208
	11th to 20th	Day	6% 5% 2 7% 4 5% 5% 4 7% 10% 42%	5900
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 8% 12% 41%	6422
August	1st to 10th	Day	4 3 2 5% 4 4 5% 5% 6% 10% 52%	4234
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 6% 8% 47%	4087
	21st to end	Day	6% 4 2 4 3 4 4 4 5% 9% 55%	4312
September	1st to 10th	Day	10% 6% 2 5% 4 4 4 3 5% 7% 50%	2400
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 5% 7% 51%	2350
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 6% 53%	2111
October	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 4 5% 56%	2000
	11th to 20th	Day	15% 6% 2 5% 2 3 3 2 3 4 55%	2000
	21st to end	Day	19% 8% 3 5% 2 3 3 3 3 5% 46%	2200
November	1st to 10th	Day	12% 7% 2 5% 3 3 3 3 4 5% 55%	2058
	11th to 20th	Day	16% 6% 2 4 3 3 4 3 4 6% 49%	1834
	21st to end	Day	18% 11% 3 4 3 2 3 3 5% 6% 44%	1680
December	1st to 10th	Day	9% 9% 3 7% 3 3 3 2 4 5% 51%	2690
	11th to 20th	Day	12% 9% 3 6% 3 3 3 3 4 5% 48%	3088
	21st to end	Day	20% 22% 5% 10% 4 3 3 2 3 4 24%	4070
January	1st to 10th	Night	13% 12% 5% 12% 5% 4 3 2 3 4 37%	7662
	11th to 20th	Night	9% 7% 3 11% 6% 5% 4 3 3 4 45%	7680
	21st to end	Night	15% 11% 4 7% 5% 4 4 3 4 5% 39%	8402
February	1st to 10th	Night	14% 11% 4 7% 4 3 4 4 5% 6% 38%	2730
	11th to 20th	Night	15% 9% 3 7% 4 4 3 3 4 6% 42%	2651
	21st to end	Night	14% 9% 3 7% 4 4 3 4 3 6% 45%	2045
March	1st to 10th	Night	17% 11% 2 5% 3 3 3 3 4 4 44%	4941
	11th to 20th	Night	12% 7% 2 4 3 3 3 3 5% 6% 52%	4980
	21st to end	Night	16% 10% 4 7% 4 4 4 3 5% 6% 36%	5467
April	1st to 10th	Night	11% 8% 2 5% 3 3 3 3 4 7% 51%	2016
	11th to 20th	Night	15% 8% 3 5% 3 3 3 3 5% 7% 46%	1975
	21st to end	Night	19% 7% 2 6% 5% 5% 4 3 5% 5% 40%	2000
May	1st to 10th	Night	17% 9% 3 6% 3 3 3 3 5% 7% 40%	4060
	11th to 20th	Night	13% 7% 3 5% 4 3 3 4 6% 9% 44%	4053
	21st to end	Night	17% 7% 2 6% 3 3 3 3 4 7% 45%	3969
June	1st to 10th	Night	7% 4 2 4 4 4 4 5% 7% 9% 51%	1600
	11th to 20th	Night	6% 4 1 4 3 3 5% 4 9% 10% 50%	1600
	21st to end	Night	3 3 1 3 2 3 4 3 7% 10% 61%	1600
July	1st to 10th	Night	9% 6% 2 6% 4 4 4 3 5% 10% 47%	3751
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 7% 10% 50%	4077
	21st to end	Night	5% 4 1 5% 3 4 4 4 8% 12% 49%	4449
August	1st to 10th	Night	3 2 1 3 4 3 3 3 5% 9% 63%	2926
	11th to 20th	Night	9% 6% 2 6% 4 4 3 3 5% 6% 52%	2967
	21st to end	Night	4 3 1 3 3 3 4 4 6% 8% 60%	3586
September	1st to 10th	Night	11% 4 1 4 3 3 3 3 4 7% 56%	2000
	11th to 20th	Night	9% 5% 1 5% 3 4 4 4 6% 7% 53%	2047
	21st to end	Night	8% 4 1 4 4 3 3 3 5% 6% 58%	2267
October	1st to 10th	Night	7% 4 2 4 3 3 4 3 5% 6% 61%	2400
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 4 5% 53%	2400
	21st to end	Night	18% 7% 1 5% 3 3 3 3 3 4 50%	2640
November	1st to 10th	Night	12% 6% 1 3 2 2 3 3 4 6% 57%	2460
	11th to 20th	Night	12% 7% 2 5% 4 3 3 2 3 6% 52%	2779
	21st to end	Night	17% 11% 2 5% 3 3 3 3 4 4 47%	2940
December	1st to 10th	Night	10% 9% 2 6% 4 4 3 3 4 5% 50%	4720
	11th to 20th	Night	15% 10% 3 6% 3 3 3 2 4 5% 43%	5339
	21st to end	Night	24% 18% 5% 8% 3 3 3 2 3 4 27%	7150

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	47% 3 10% 26% 12% 1	5246
	11th to 20th	Day	42% 3 9% 28% 14% 5%	5310
	21st to end	Day	47% 2 9% 18% 17% 6%	5812
February	1st to 10th	Day	52% 4 10% 22% 11% 1	1890
	11th to 20th	Day	47% 4 11% 20% 15% 3	1864
	21st to end	Day	45% 4 8% 23% 16% 5%	1780
March	1st to 10th	Day	40% 2 7% 22% 22% 6%	4958
	11th to 20th	Day	33% 4 8% 23% 24% 8%	4980
	21st to end	Day	49% 5% 15% 25% 6%	5464
April	1st to 10th	Day	43% 5% 10% 23% 17% 3	2382
	11th to 20th	Day	43% 5% 13% 22% 15% 2	2374
	21st to end	Day	51% 5% 11% 21% 12% 1	2400
May	1st to 10th	Day	46% 6% 12% 21% 14% 1	5890
	11th to 20th	Day	41% 6% 13% 23% 14% 2	5866
	21st to end	Day	44% 6% 9% 26% 14% 1	6904
June	1st to 10th	Day	33% 8% 15% 26% 16% 2	2800
	11th to 20th	Day	33% 7% 14% 27% 15% 3	2800
	21st to end	Day	27% 6% 17% 30% 15% 4	2800
July	1st to 10th	Day	36% 5% 12% 24% 21% 2	6142
	11th to 20th	Day	36% 6% 14% 30% 13% 1	5831
	21st to end	Day	33% 6% 19% 32% 9% 1	6240
August	1st to 10th	Day	26% 7% 18% 27% 21%	4220
	11th to 20th	Day	36% 6% 14% 29% 15% 1	4126
	21st to end	Day	27% 5% 13% 37% 15% 4	4311
September	1st to 10th	Day	33% 6% 11% 25% 19% 6%	2400
	11th to 20th	Day	34% 5% 9% 26% 24% 2	2350
	21st to end	Day	30% 6% 10% 26% 24% 4	2111
October	1st to 10th	Day	19% 3 6% 19% 40% 13%	3260
	11th to 20th	Day	23% 2 5% 24% 38% 9%	3240
	21st to end	Day	36% 3 7% 26% 25% 3	3538
November	1st to 10th	Day	32% 3 12% 26% 22% 4	2058
	11th to 20th	Day	38% 3 9% 23% 23% 4	1834
	21st to end	Day	43% 4 8% 28% 15% 2	1680
December	1st to 10th	Day	37% 3 10% 35% 15% 1	2690
	11th to 20th	Day	40% 3 9% 30% 17% 1	3085
	21st to end	Day	65% 3 10% 15% 6% 1	4070
January	1st to 10th	Night	53% 2 11% 24% 10%	7663
	11th to 20th	Night	45% 3 6% 26% 17% 4	7680
	21st to end	Night	49% 2 10% 20% 15% 3	8402
February	1st to 10th	Night	47% 4 12% 22% 13% 2	2730
	11th to 20th	Night	44% 4 11% 22% 16% 3	2652
	21st to end	Night	43% 4 8% 23% 18% 5%	2045
March	1st to 10th	Night	44% 3 6% 19% 23% 4	4941
	11th to 20th	Night	33% 4 8% 22% 26% 7%	4980
	21st to end	Night	47% 5% 13% 22% 11% 1	5467
April	1st to 10th	Night	35% 5% 12% 25% 21% 4	2016
	11th to 20th	Night	38% 5% 9% 25% 18% 5%	1975
	21st to end	Night	46% 5% 11% 24% 14% 1	2000
May	1st to 10th	Night	44% 6% 14% 21% 14% 2	4087
	11th to 20th	Night	38% 6% 11% 24% 16% 5%	4054
	21st to end	Night	39% 6% 11% 26% 16% 2	3977
June	1st to 10th	Night	28% 7% 16% 30% 17% 4	1600
	11th to 20th	Night	25% 9% 13% 26% 22% 4	1600
	21st to end	Night	18% 6% 19% 30% 22% 6%	1600
July	1st to 10th	Night	34% 4 14% 25% 21% 2	3711
	11th to 20th	Night	28% 5% 13% 36% 16% 2	4026
	21st to end	Night	27% 5% 19% 38% 11% 1	4320
August	1st to 10th	Night	18% 5% 19% 32% 23% 2	2916
	11th to 20th	Night	34% 4 12% 30% 18% 2	2994
	21st to end	Night	21% 5% 14% 39% 17% 4	3586
September	1st to 10th	Night	29% 4 10% 26% 23% 7%	2000
	11th to 20th	Night	29% 6% 11% 25% 24% 5%	2047
	21st to end	Night	27% 4 9% 28% 28% 4	2267
October	1st to 10th	Night	15% 3 6% 21% 43% 12%	3920
	11th to 20th	Night	24% 2 7% 21% 29% 16%	3899
	21st to end	Night	33% 2 7% 30% 24% 3	4252
November	1st to 10th	Night	30% 3 12% 28% 21% 6%	2460
	11th to 20th	Night	35% 4 8% 25% 23% 5%	2779
	21st to end	Night	42% 4 9% 27% 17% 2	2940
December	1st to 10th	Night	38% 3 10% 34% 14% 1	4720
	11th to 20th	Night	44% 3 10% 25% 17% 1	5341
	21st to end	Night	63% 3 11% 16% 6% 1	7150

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	22% 22% 39% 15% 2	330
	11th to 20th	Day	28% 24% 39% 8% 1	330
	21st to end	Day	19% 24% 45% 11% 1	363
February	1st to 10th	Day	27% 24% 38% 11% 1	330
	11th to 20th	Day	25% 27% 37% 10% 2	330
	21st to end	Day	30% 25% 33% 9% 3	273
March	1st to 10th	Day	22% 29% 35% 12% 1	306
	11th to 20th	Day	34% 17% 32% 15% 2	300
	21st to end	Day	34% 24% 31% 9% 2	330
April	1st to 10th	Day	29% 17% 33% 16% 4 1	482
	11th to 20th	Day	24% 21% 33% 17% 4	492
	21st to end	Day	27% 15% 32% 20% 5%	500
May	1st to 10th	Day	20% 19% 36% 19% 5%	693
	11th to 20th	Day	18% 16% 29% 25% 10% 1	725
	21st to end	Day	18% 10% 34% 23% 12% 2	789
June	1st to 10th	Day	9% 7% 27% 32% 22% 4	730
	11th to 20th	Day	10% 5% 30% 36% 18% 2	730
	21st to end	Day	6% 7% 35% 36% 13% 2	730
July	1st to 10th	Day	11% 4 18% 31% 29% 7%	721
	11th to 20th	Day	5% 3 26% 37% 25% 4	718
	21st to end	Day	8% 3 20% 36% 27% 5%	794
August	1st to 10th	Day	8% 3 21% 42% 22% 4	726
	11th to 20th	Day	10% 3 21% 36% 25% 5%	670
	21st to end	Day	10% 2 15% 36% 30% 7%	583
September	1st to 10th	Day	12% 4 17% 37% 25% 5%	530
	11th to 20th	Day	9% 6% 22% 34% 20% 8%	480
	21st to end	Day	12% 8% 28% 32% 15% 5%	330
October	1st to 10th	Day	13% 9% 30% 30% 13% 4	330
	11th to 20th	Day	19% 17% 34% 22% 6% 1	330
	21st to end	Day	31% 20% 31% 16% 1 1	363
November	1st to 10th	Day	17% 14% 45% 16% 6% 1	330
	11th to 20th	Day	24% 19% 33% 18% 5% 1	330
	21st to end	Day	33% 15% 30% 21% 2	330
December	1st to 10th	Day	18% 22% 36% 17% 5% 2	330
	11th to 20th	Day	21% 23% 37% 14% 4 1	330
	21st to end	Day	27% 25% 36% 11% 1	363
January	1st to 10th	Night	19% 20% 37% 20% 4	1050
	11th to 20th	Night	20% 23% 37% 16% 4	1050
	21st to end	Night	18% 20% 40% 20% 2	1155
February	1st to 10th	Night	21% 19% 39% 19% 3	1050
	11th to 20th	Night	22% 20% 37% 19% 2	1017
	21st to end	Night	22% 20% 38% 17% 3	661
March	1st to 10th	Night	19% 18% 39% 21% 2	606
	11th to 20th	Night	25% 14% 32% 25% 4	600
	21st to end	Night	28% 15% 35% 19% 4	660
April	1st to 10th	Night	17% 18% 36% 25% 4	600
	11th to 20th	Night	20% 15% 34% 24% 6%	593
	21st to end	Night	21% 12% 38% 22% 7%	600
May	1st to 10th	Night	17% 10% 36% 31% 7%	600
	11th to 20th	Night	15% 9% 29% 33% 13% 1	591
	21st to end	Night	15% 7% 30% 29% 16% 2	650
June	1st to 10th	Night	8% 3 22% 39% 26% 2	600
	11th to 20th	Night	7% 3 26% 42% 19% 2	600
	21st to end	Night	4 2 32% 42% 18% 2	600
July	1st to 10th	Night	11% 2 13% 42% 28% 5%	585
	11th to 20th	Night	5% 1 19% 43% 29% 3	582
	21st to end	Night	7% 2 15% 40% 34% 2	657
August	1st to 10th	Night	5% 2 16% 45% 30% 2	597
	11th to 20th	Night	6% 3 15% 44% 29% 3	594
	21st to end	Night	5% 1 16% 39% 34% 4	660
September	1st to 10th	Night	13% 4 16% 40% 25% 3	600
	11th to 20th	Night	12% 3 17% 35% 28% 5%	600
	21st to end	Night	10% 5% 24% 37% 21% 3	667
October	1st to 10th	Night	9% 7% 29% 32% 21% 3	800
	11th to 20th	Night	17% 12% 35% 27% 9%	800
	21st to end	Night	23% 13% 33% 23% 7%	880
November	1st to 10th	Night	14% 13% 37% 27% 9%	820
	11th to 20th	Night	17% 18% 34% 24% 7%	903
	21st to end	Night	25% 14% 35% 21% 6%	1050
December	1st to 10th	Night	19% 18% 36% 22% 5%	1050
	11th to 20th	Night	24% 14% 36% 23% 3	1050
	21st to end	Night	24% 20% 35% 19% 2	1155

Page generated at 2026-02-28 00:40:23. Version ac07

Copyright © 2026 Attilla Danko.