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 2024-12-02.

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	13% 8% 3 6% 4 4 4 3 5% 7% 44%	101354
	Night	13% 8% 3 6% 4 3 3 3 5% 6% 46%	98339
Transparency	Day	38% 5% 12% 25% 17% 3	105003
	Night	37% 5% 11% 25% 18% 3	102831
Seeing	Day	17% 12% 29% 26% 13% 2	15704
	Night	16% 12% 31% 28% 12% 1	25555

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	14% 12% 3 8% 4 4 4 3 4 5% 39%	2816
	11th to 20th	Day	12% 12% 3 10% 4 6% 4 3 4 5% 37%	2850
	21st to end	Day	18% 13% 4 8% 3 3 3 2 4 5% 35%	3135
February	1st to 10th	Day	16% 11% 4 9% 6% 4 3 3 3 6% 35%	1710
	11th to 20th	Day	15% 10% 3 6% 4 4 4 4 4 4 41%	1673
	21st to end	Day	17% 11% 3 5% 4 3 4 3 5% 5% 39%	1615
March	1st to 10th	Day	17% 10% 3 6% 3 3 3 2 4 5% 46%	3436
	11th to 20th	Day	14% 8% 3 5% 3 3 3 3 4 6% 50%	3480
	21st to end	Day	18% 12% 3 7% 5% 4 4 3 5% 6% 33%	3814
April	1st to 10th	Day	14% 8% 2 6% 5% 4 4 4 4 6% 43%	2263
	11th to 20th	Day	17% 8% 2 6% 3 4 4 4 5% 6% 41%	2254
	21st to end	Day	23% 7% 2 6% 5% 3 4 3 5% 6% 35%	2280
May	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 4 6% 7% 34%	4072
	11th to 20th	Day	16% 7% 2 6% 4 5% 5% 3 5% 6% 40%	4082
	21st to end	Day	13% 6% 2 7% 5% 4 5% 3 5% 7% 43%	4793
June	1st to 10th	Day	7% 5% 2 5% 5% 5% 4 4 7% 9% 47%	2660
	11th to 20th	Day	8% 4 2 5% 5% 5% 5% 4 7% 9% 45%	2660
	21st to end	Day	5% 3 1 5% 4 4 5% 4 6% 9% 53%	2660
July	1st to 10th	Day	13% 7% 2 6% 5% 4 5% 4 6% 8% 42%	4330
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 7% 9% 49%	4120
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 9% 12% 39%	4465
August	1st to 10th	Day	5% 3 2 4 4 4 5% 5% 6% 10% 52%	4104
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 6% 8% 46%	3959
	21st to end	Day	6% 4 2 4 3 4 3 4 5% 9% 56%	4180
September	1st to 10th	Day	11% 6% 2 5% 4 4 3 3 5% 7% 51%	2280
	11th to 20th	Day	11% 6% 2 5% 3 3 3 3 5% 6% 52%	2233
	21st to end	Day	8% 5% 2 5% 4 4 4 3 6% 6% 53%	2006
October	1st to 10th	Day	11% 5% 2 5% 3 3 3 2 4 5% 56%	1900
	11th to 20th	Day	15% 6% 2 5% 2 2 3 2 3 4 55%	1900
	21st to end	Day	19% 8% 3 5% 3 3 3 3 3 5% 46%	2090
November	1st to 10th	Day	12% 7% 2 4 3 3 3 3 4 5% 54%	1958
	11th to 20th	Day	17% 7% 2 4 2 3 4 3 4 6% 49%	1747
	21st to end	Day	17% 10% 3 4 3 2 3 3 5% 6% 45%	1600
December	1st to 10th	Day	13% 10% 4 7% 4 3 3 3 4 6% 43%	1528
	11th to 20th	Day	14% 12% 3 7% 4 3 3 3 3 5% 43%	1918
	21st to end	Day	19% 17% 5% 9% 4 4 4 3 4 5% 26%	2783
January	1st to 10th	Night	11% 11% 5% 13% 5% 3 3 3 3 4 38%	4136
	11th to 20th	Night	12% 8% 4 11% 7% 7% 6% 4 4 4 33%	4120
	21st to end	Night	20% 14% 5% 7% 3 3 3 2 3 5% 34%	4532
February	1st to 10th	Night	14% 12% 4 7% 4 3 4 4 5% 6% 37%	2470
	11th to 20th	Night	14% 8% 3 7% 4 4 3 3 4 6% 43%	2393
	21st to end	Night	16% 9% 3 7% 4 4 3 3 3 5% 43%	1856
March	1st to 10th	Night	17% 10% 2 5% 4 3 3 3 4 4 45%	3419
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 5% 6% 50%	3480
	21st to end	Night	19% 11% 4 7% 4 4 4 3 5% 5% 33%	3817
April	1st to 10th	Night	11% 8% 2 5% 3 3 3 3 4 7% 51%	1915
	11th to 20th	Night	14% 8% 3 5% 3 3 3 3 4 8% 45%	1875
	21st to end	Night	18% 7% 2 6% 5% 5% 4 3 5% 5% 41%	1900
May	1st to 10th	Night	17% 8% 2 7% 4 4 3 4 6% 7% 40%	2830
	11th to 20th	Night	14% 7% 3 6% 4 4 3 4 5% 8% 42%	2823
	21st to end	Night	12% 5% 2 6% 3 4 3 3 5% 9% 48%	2756
June	1st to 10th	Night	7% 4 2 4 3 3 4 5% 7% 9% 52%	1520
	11th to 20th	Night	5% 4 1 4 3 3 5% 5% 9% 9% 51%	1520
	21st to end	Night	3 3 1 3 2 3 4 3 7% 9% 61%	1520
July	1st to 10th	Night	12% 6% 3 6% 3 4 4 3 5% 9% 46%	2621
	11th to 20th	Night	4 3 2 4 3 3 4 3 6% 11% 57%	2850
	21st to end	Night	5% 5% 1 5% 3 4 4 3 6% 12% 51%	3098
August	1st to 10th	Night	3 2 1 3 3 3 3 3 5% 9% 64%	2836
	11th to 20th	Night	9% 6% 2 6% 4 4 3 3 5% 6% 52%	2875
	21st to end	Night	4 3 1 3 3 3 4 4 7% 8% 60%	3476
September	1st to 10th	Night	11% 4 1 3 3 3 3 3 4 7% 58%	1900
	11th to 20th	Night	10% 5% 1 5% 3 3 4 4 6% 7% 53%	1944
	21st to end	Night	8% 5% 1 4 4 3 3 3 5% 6% 58%	2153
October	1st to 10th	Night	7% 4 2 4 3 2 3 3 5% 5% 61%	2280
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 4 5% 54%	2280
	21st to end	Night	17% 6% 1 5% 3 4 3 3 4 5% 51%	2508
November	1st to 10th	Night	12% 6% 1 3 2 2 3 2 4 6% 57%	2340
	11th to 20th	Night	13% 7% 2 6% 4 3 3 2 3 6% 51%	2646
	21st to end	Night	16% 10% 2 5% 3 3 3 3 4 4 48%	2800
December	1st to 10th	Night	13% 12% 3 6% 4 4 4 3 5% 5% 42%	2687
	11th to 20th	Night	15% 11% 4 7% 3 3 3 3 5% 5% 41%	3279
	21st to end	Night	21% 18% 5% 9% 3 3 3 3 3 4 27%	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	47% 4 9% 26% 13%	2817
	11th to 20th	Day	49% 4 12% 24% 11%	2850
	21st to end	Day	52% 3 10% 17% 15% 3	3135
February	1st to 10th	Day	53% 5% 10% 20% 11% 1	1710
	11th to 20th	Day	46% 4 12% 19% 15% 3	1682
	21st to end	Day	47% 4 8% 23% 13% 5%	1615
March	1st to 10th	Day	43% 3 8% 22% 19% 4	3436
	11th to 20th	Day	36% 4 11% 28% 16% 5%	3480
	21st to end	Day	51% 6% 16% 20% 7% 1	3814
April	1st to 10th	Day	41% 5% 10% 23% 17% 2	2263
	11th to 20th	Day	42% 5% 13% 22% 15% 2	2254
	21st to end	Day	50% 5% 11% 21% 12% 1	2280
May	1st to 10th	Day	47% 8% 11% 20% 13% 1	4110
	11th to 20th	Day	43% 7% 13% 22% 14%	4086
	21st to end	Day	39% 8% 10% 27% 16% 1	4806
June	1st to 10th	Day	32% 8% 16% 26% 16% 2	2660
	11th to 20th	Day	33% 7% 15% 27% 16% 3	2660
	21st to end	Day	27% 6% 17% 30% 15% 4	2660
July	1st to 10th	Day	40% 6% 13% 24% 15% 3	4264
	11th to 20th	Day	30% 7% 13% 30% 18% 2	4051
	21st to end	Day	34% 7% 21% 27% 10% 1	4325
August	1st to 10th	Day	27% 7% 18% 27% 22%	4090
	11th to 20th	Day	37% 6% 14% 28% 15% 1	3998
	21st to end	Day	26% 5% 14% 37% 15% 4	4179
September	1st to 10th	Day	33% 6% 11% 25% 19% 6%	2280
	11th to 20th	Day	33% 5% 9% 25% 26% 2	2233
	21st to end	Day	30% 6% 10% 26% 23% 4	2006
October	1st to 10th	Day	19% 3 6% 19% 40% 14%	3160
	11th to 20th	Day	22% 2 5% 23% 39% 9%	3140
	21st to end	Day	36% 3 7% 26% 26% 3	3428
November	1st to 10th	Day	33% 3 12% 25% 22% 4	1958
	11th to 20th	Day	38% 3 9% 22% 23% 5%	1747
	21st to end	Day	42% 4 8% 28% 16% 2	1600
December	1st to 10th	Day	43% 4 10% 29% 13% 1	1528
	11th to 20th	Day	44% 4 8% 27% 15% 2	1915
	21st to end	Day	60% 4 10% 16% 8% 1	2783
January	1st to 10th	Night	51% 3 12% 21% 12% 1	4136
	11th to 20th	Night	54% 4 10% 21% 9% 1	4120
	21st to end	Night	54% 4 10% 20% 11% 1	4532
February	1st to 10th	Night	47% 5% 11% 22% 13% 2	2470
	11th to 20th	Night	43% 4 11% 22% 16% 3	2394
	21st to end	Night	45% 4 8% 22% 16% 5%	1856
March	1st to 10th	Night	44% 4 9% 20% 20% 5%	3419
	11th to 20th	Night	35% 5% 10% 24% 23% 3	3480
	21st to end	Night	51% 6% 12% 21% 8% 1	3817
April	1st to 10th	Night	34% 5% 11% 25% 21% 4	1915
	11th to 20th	Night	39% 5% 9% 24% 18% 5%	1875
	21st to end	Night	45% 5% 11% 24% 14% 1	1900
May	1st to 10th	Night	43% 7% 13% 20% 15% 2	2857
	11th to 20th	Night	41% 6% 12% 28% 12% 1	2824
	21st to end	Night	33% 8% 13% 27% 17% 1	2764
June	1st to 10th	Night	27% 7% 16% 29% 17% 4	1520
	11th to 20th	Night	24% 9% 13% 27% 22% 4	1520
	21st to end	Night	17% 6% 19% 31% 22% 6%	1520
July	1st to 10th	Night	37% 5% 13% 25% 16% 3	2579
	11th to 20th	Night	21% 5% 12% 38% 21% 2	2796
	21st to end	Night	26% 5% 21% 35% 12% 1	2999
August	1st to 10th	Night	18% 5% 19% 31% 23% 2	2826
	11th to 20th	Night	34% 4 12% 30% 18% 2	2902
	21st to end	Night	21% 5% 14% 39% 17% 4	3476
September	1st to 10th	Night	28% 5% 11% 26% 24% 7%	1900
	11th to 20th	Night	28% 6% 11% 24% 26% 5%	1944
	21st to end	Night	27% 4 9% 28% 29% 3	2153
October	1st to 10th	Night	15% 3 6% 21% 43% 12%	3800
	11th to 20th	Night	23% 3 7% 21% 30% 17%	3779
	21st to end	Night	33% 2 7% 30% 25% 3	4120
November	1st to 10th	Night	30% 3 12% 27% 21% 6%	2340
	11th to 20th	Night	36% 4 7% 25% 24% 5%	2646
	21st to end	Night	41% 4 9% 27% 18% 2	2800
December	1st to 10th	Night	44% 5% 11% 24% 15% 1	2687
	11th to 20th	Night	45% 4 9% 26% 14% 1	3281
	21st to end	Night	62% 4 9% 15% 9% 2	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	21% 24% 37% 16% 3	270
	11th to 20th	Day	31% 22% 38% 8% 1	270
	21st to end	Day	18% 25% 43% 12% 2	297
February	1st to 10th	Day	28% 23% 37% 11%	270
	11th to 20th	Day	23% 28% 36% 11% 2	270
	21st to end	Day	33% 24% 33% 8% 2	225
March	1st to 10th	Day	20% 30% 36% 13% 1	270
	11th to 20th	Day	34% 16% 32% 15% 2	270
	21st to end	Day	36% 24% 29% 9% 2	297
April	1st to 10th	Day	26% 17% 34% 17% 5% 1	443
	11th to 20th	Day	23% 21% 34% 18% 4	452
	21st to end	Day	27% 15% 33% 19% 5%	460
May	1st to 10th	Day	20% 19% 37% 19% 5%	643
	11th to 20th	Day	19% 15% 30% 25% 10% 1	675
	21st to end	Day	16% 10% 35% 24% 12% 3	734
June	1st to 10th	Day	8% 6% 27% 33% 22% 4	680
	11th to 20th	Day	8% 5% 30% 37% 18% 1	680
	21st to end	Day	6% 8% 35% 36% 13% 3	680
July	1st to 10th	Day	12% 4 18% 30% 29% 7%	671
	11th to 20th	Day	4 3 25% 38% 26% 4	668
	21st to end	Day	9% 3 20% 36% 27% 5%	739
August	1st to 10th	Day	9% 3 20% 41% 23% 4	676
	11th to 20th	Day	10% 4 22% 36% 24% 4	622
	21st to end	Day	11% 1 14% 37% 31% 7%	539
September	1st to 10th	Day	12% 4 16% 36% 27% 5%	490
	11th to 20th	Day	9% 6% 22% 35% 20% 8%	443
	21st to end	Day	12% 8% 30% 33% 13% 4	300
October	1st to 10th	Day	13% 10% 30% 29% 14% 4	300
	11th to 20th	Day	19% 18% 35% 22% 6%	300
	21st to end	Day	29% 21% 31% 18% 1 1	330
November	1st to 10th	Day	18% 13% 44% 18% 6% 1	300
	11th to 20th	Day	25% 18% 33% 18% 5% 1	300
	21st to end	Day	33% 14% 29% 22% 2	300
December	1st to 10th	Day	18% 21% 36% 19% 6% 2	273
	11th to 20th	Day	23% 23% 35% 16% 3 1	270
	21st to end	Day	25% 27% 36% 11% 1	297
January	1st to 10th	Night	18% 21% 37% 20% 5%	950
	11th to 20th	Night	20% 22% 37% 17% 4	950
	21st to end	Night	18% 20% 39% 20% 2	1045
February	1st to 10th	Night	21% 19% 39% 18% 3	950
	11th to 20th	Night	21% 20% 38% 19% 2	919
	21st to end	Night	24% 21% 37% 16% 3	600
March	1st to 10th	Night	18% 18% 40% 21% 2	570
	11th to 20th	Night	25% 14% 32% 26% 4	570
	21st to end	Night	29% 15% 33% 19% 4	627
April	1st to 10th	Night	17% 18% 36% 25% 5%	570
	11th to 20th	Night	20% 15% 34% 25% 7%	563
	21st to end	Night	21% 12% 39% 21% 7%	570
May	1st to 10th	Night	16% 10% 36% 30% 7%	570
	11th to 20th	Night	16% 9% 28% 33% 13% 1	561
	21st to end	Night	15% 7% 30% 29% 17% 2	617
June	1st to 10th	Night	8% 2 22% 39% 26% 2	570
	11th to 20th	Night	7% 2 28% 43% 19% 2	570
	21st to end	Night	4 2 32% 42% 18% 2	570
July	1st to 10th	Night	12% 2 13% 41% 27% 5%	555
	11th to 20th	Night	5% 1 19% 43% 29% 3	552
	21st to end	Night	8% 3 15% 39% 34% 2	624
August	1st to 10th	Night	6% 2 15% 45% 31% 2	567
	11th to 20th	Night	6% 3 15% 45% 27% 3	564
	21st to end	Night	5% 1 16% 38% 35% 4	627
September	1st to 10th	Night	13% 3 16% 39% 26% 3	570
	11th to 20th	Night	12% 3 18% 36% 27% 5%	570
	21st to end	Night	10% 5% 25% 36% 21% 3	633
October	1st to 10th	Night	9% 7% 29% 31% 21% 3	760
	11th to 20th	Night	17% 12% 36% 27% 8%	760
	21st to end	Night	22% 13% 33% 24% 7%	836
November	1st to 10th	Night	14% 13% 37% 26% 9%	780
	11th to 20th	Night	17% 18% 33% 23% 7%	860
	21st to end	Night	24% 14% 35% 21% 6%	1000
December	1st to 10th	Night	19% 17% 37% 22% 5%	960
	11th to 20th	Night	24% 14% 35% 24% 3	950
	21st to end	Night	23% 20% 35% 19% 2	1045

Page generated at 2024-11-29 09:43:06. Version ac07

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