Radomski Observatory
Clear Sky Chart
History

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

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	16% 11% 4 8% 5% 5% 4 4 5% 7% 31%	101146
	Night	17% 12% 4 8% 5% 4 4 3 5% 6% 32%	97823
Transparency	Day	51% 4 11% 22% 11% 1	104793
	Night	52% 3 10% 22% 11% 2	102315
Seeing	Day	25% 12% 25% 21% 12% 5%	14748
	Night	24% 10% 24% 28% 12% 1	24393

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	19% 22% 8% 13% 5% 4 3 2 3 5% 18%	2781
	11th to 20th	Day	12% 22% 10% 17% 9% 4 3 2 3 3 16%	2840
	21st to end	Day	25% 21% 7% 13% 5% 4 3 2 3 4 13%	3124
February	1st to 10th	Day	20% 17% 5% 10% 8% 5% 4 3 3 5% 20%	1710
	11th to 20th	Day	17% 17% 7% 11% 5% 5% 3 3 5% 6% 20%	1663
	21st to end	Day	22% 15% 5% 12% 5% 3 3 3 5% 5% 23%	1572
March	1st to 10th	Day	20% 12% 4 8% 4 4 4 3 5% 6% 29%	3435
	11th to 20th	Day	15% 11% 5% 10% 5% 5% 5% 4 4 5% 31%	3480
	21st to end	Day	19% 11% 3 9% 5% 5% 4 3 5% 6% 31%	3815
April	1st to 10th	Day	16% 14% 3 7% 5% 5% 4 5% 5% 7% 30%	2209
	11th to 20th	Day	16% 12% 4 6% 5% 4 4 3 5% 7% 33%	2254
	21st to end	Day	21% 9% 3 8% 5% 5% 4 4 4 6% 33%	2465
May	1st to 10th	Day	25% 9% 2 8% 5% 4 4 4 5% 6% 27%	4082
	11th to 20th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 6% 30%	4081
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 5% 7% 9% 36%	4787
June	1st to 10th	Day	15% 6% 3 7% 6% 5% 5% 5% 7% 8% 34%	2660
	11th to 20th	Day	13% 7% 3 6% 5% 6% 5% 5% 7% 9% 35%	2660
	21st to end	Day	14% 6% 2 6% 6% 4 6% 4 7% 9% 36%	2660
July	1st to 10th	Day	10% 7% 2 7% 5% 5% 5% 5% 6% 8% 40%	4358
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 10% 38%	4120
	21st to end	Day	13% 7% 3 7% 5% 6% 5% 4 6% 8% 36%	4466
August	1st to 10th	Day	14% 8% 4 8% 6% 6% 5% 5% 7% 8% 29%	4104
	11th to 20th	Day	12% 7% 3 7% 5% 5% 6% 4 7% 8% 35%	4044
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	4276
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 3 5% 6% 45%	2280
	11th to 20th	Day	12% 6% 2 5% 5% 4 4 4 6% 7% 45%	2128
	21st to end	Day	21% 8% 3 6% 4 4 4 3 5% 7% 35%	2068
October	1st to 10th	Day	18% 6% 2 6% 5% 4 5% 4 5% 7% 40%	1900
	11th to 20th	Day	19% 9% 3 7% 5% 4 4 3 5% 6% 35%	1900
	21st to end	Day	23% 11% 2 6% 4 3 3 3 4 6% 34%	2090
November	1st to 10th	Day	11% 10% 4 6% 6% 4 3 3 5% 7% 41%	1856
	11th to 20th	Day	16% 16% 3 8% 4 4 4 4 4 7% 30%	1556
	21st to end	Day	19% 17% 5% 7% 5% 3 4 3 5% 6% 26%	1520
December	1st to 10th	Day	21% 19% 6% 12% 6% 4 4 2 4 5% 17%	1520
	11th to 20th	Day	20% 20% 8% 10% 4 3 3 3 3 6% 21%	1910
	21st to end	Day	23% 23% 7% 10% 5% 4 3 2 4 4 15%	2772
January	1st to 10th	Night	17% 21% 7% 13% 5% 4 4 3 4 4 18%	4159
	11th to 20th	Night	16% 21% 8% 13% 7% 5% 4 3 3 4 16%	4120
	21st to end	Night	27% 19% 6% 12% 6% 3 3 2 2 3 17%	4532
February	1st to 10th	Night	19% 16% 6% 11% 5% 4 3 3 4 4 24%	2470
	11th to 20th	Night	18% 15% 5% 10% 6% 5% 3 3 3 6% 24%	2403
	21st to end	Night	20% 14% 5% 11% 5% 4 4 3 5% 4 25%	1875
March	1st to 10th	Night	22% 12% 3 7% 4 3 3 2 4 6% 33%	3418
	11th to 20th	Night	18% 14% 5% 7% 4 4 3 2 4 6% 33%	3480
	21st to end	Night	17% 10% 3 7% 4 4 4 3 4 5% 38%	3817
April	1st to 10th	Night	18% 14% 4 7% 4 3 4 3 5% 5% 35%	1970
	11th to 20th	Night	17% 8% 2 6% 4 4 5% 3 5% 8% 37%	1875
	21st to end	Night	16% 9% 3 7% 5% 3 4 4 5% 7% 37%	1730
May	1st to 10th	Night	27% 11% 4 7% 4 4 4 3 5% 6% 26%	2813
	11th to 20th	Night	19% 9% 3 8% 5% 4 4 3 5% 7% 33%	2812
	21st to end	Night	13% 7% 3 7% 4 4 4 4 7% 9% 37%	2767
June	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 3 6% 8% 42%	1520
	11th to 20th	Night	11% 6% 2 6% 4 5% 4 5% 7% 9% 39%	1520
	21st to end	Night	12% 6% 2 5% 4 5% 4 4 7% 11% 41%	1520
July	1st to 10th	Night	11% 8% 2 8% 4 4 5% 4 6% 8% 39%	2584
	11th to 20th	Night	10% 6% 2 7% 5% 5% 5% 5% 6% 9% 39%	2840
	21st to end	Night	12% 9% 3 7% 6% 5% 5% 4 6% 7% 37%	3087
August	1st to 10th	Night	14% 9% 3 7% 5% 5% 5% 4 7% 8% 32%	2825
	11th to 20th	Night	14% 8% 3 6% 5% 4 4 4 5% 6% 41%	2785
	21st to end	Night	7% 5% 3 6% 5% 4 6% 4 7% 9% 43%	3347
September	1st to 10th	Night	13% 5% 2 5% 3 4 3 5% 5% 8% 47%	1900
	11th to 20th	Night	11% 4 2 4 3 4 4 3 5% 7% 52%	2047
	21st to end	Night	18% 8% 3 6% 4 4 4 3 5% 6% 40%	2110
October	1st to 10th	Night	16% 7% 2 5% 4 4 4 3 5% 6% 44%	2280
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 4 5% 6% 38%	2280
	21st to end	Night	25% 8% 2 5% 3 4 3 3 4 6% 36%	2508
November	1st to 10th	Night	14% 10% 3 6% 4 4 3 3 4 6% 44%	2318
	11th to 20th	Night	19% 14% 3 7% 5% 4 4 3 5% 5% 32%	2622
	21st to end	Night	20% 15% 4 7% 5% 3 4 3 5% 6% 30%	2660
December	1st to 10th	Night	22% 19% 7% 10% 5% 4 4 3 5% 5% 19%	2660
	11th to 20th	Night	19% 19% 5% 11% 4 4 3 2 3 5% 23%	3285
	21st to end	Night	24% 20% 6% 10% 6% 4 4 3 4 5% 15%	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	72% 2 9% 13% 4	2782
	11th to 20th	Day	76% 1 6% 12% 4 1	2840
	21st to end	Day	79% 1 7% 11% 2	3124
February	1st to 10th	Day	68% 3 8% 14% 6%	1710
	11th to 20th	Day	64% 3 9% 16% 7%	1672
	21st to end	Day	63% 3 10% 14% 7% 2	1572
March	1st to 10th	Day	57% 2 9% 24% 7%	3435
	11th to 20th	Day	56% 3 10% 24% 7% 1	3480
	21st to end	Day	55% 2 9% 22% 10% 1	3815
April	1st to 10th	Day	54% 3 10% 20% 11% 2	2209
	11th to 20th	Day	51% 3 11% 17% 16% 2	2254
	21st to end	Day	53% 3 9% 23% 10% 2	2465
May	1st to 10th	Day	58% 2 10% 21% 8% 1	4120
	11th to 20th	Day	54% 3 11% 23% 8% 1	4085
	21st to end	Day	42% 4 15% 24% 11% 2	4801
June	1st to 10th	Day	46% 5% 14% 24% 11% 1	2660
	11th to 20th	Day	45% 5% 14% 24% 12% 1	2660
	21st to end	Day	43% 5% 13% 27% 12% 1	2660
July	1st to 10th	Day	40% 6% 12% 25% 15% 3	4290
	11th to 20th	Day	40% 5% 13% 27% 14% 1	4051
	21st to end	Day	46% 5% 10% 22% 16% 1	4324
August	1st to 10th	Day	49% 7% 13% 23% 8%	4091
	11th to 20th	Day	43% 5% 12% 28% 12%	4083
	21st to end	Day	36% 7% 13% 28% 14% 2	4276
September	1st to 10th	Day	40% 4 10% 23% 20% 3	2280
	11th to 20th	Day	38% 4 12% 29% 16% 1	2128
	21st to end	Day	49% 3 10% 24% 14%	2068
October	1st to 10th	Day	35% 3 9% 33% 19% 1	3160
	11th to 20th	Day	44% 4 11% 23% 13% 5%	3140
	21st to end	Day	37% 3 10% 29% 20% 1	3428
November	1st to 10th	Day	44% 3 12% 22% 16% 3	1856
	11th to 20th	Day	54% 4 9% 20% 12% 2	1556
	21st to end	Day	60% 3 11% 19% 6% 1	1520
December	1st to 10th	Day	71% 2 10% 13% 4	1520
	11th to 20th	Day	67% 2 11% 17% 4	1906
	21st to end	Day	74% 2 9% 12% 3	2772
January	1st to 10th	Night	71% 1 9% 14% 4	4159
	11th to 20th	Night	74% 1 10% 11% 3	4120
	21st to end	Night	76% 1 5% 14% 3	4532
February	1st to 10th	Night	63% 2 9% 18% 6%	2470
	11th to 20th	Night	64% 2 9% 17% 8%	2405
	21st to end	Night	63% 2 9% 16% 9% 1	1875
March	1st to 10th	Night	55% 1 9% 26% 8%	3418
	11th to 20th	Night	55% 2 11% 26% 6% 1	3480
	21st to end	Night	49% 2 8% 25% 14% 2	3817
April	1st to 10th	Night	53% 3 9% 20% 13% 2	1970
	11th to 20th	Night	45% 3 12% 21% 15% 4	1875
	21st to end	Night	48% 4 8% 26% 11% 4	1730
May	1st to 10th	Night	60% 3 8% 17% 10% 2	2840
	11th to 20th	Night	52% 3 11% 24% 9% 1	2813
	21st to end	Night	42% 4 14% 24% 11% 4	2774
June	1st to 10th	Night	39% 5% 12% 27% 15% 2	1520
	11th to 20th	Night	40% 6% 14% 27% 12% 2	1520
	21st to end	Night	37% 6% 14% 25% 16% 2	1520
July	1st to 10th	Night	42% 5% 10% 24% 16% 4	2542
	11th to 20th	Night	39% 6% 15% 24% 15% 1	2786
	21st to end	Night	44% 5% 10% 18% 20% 2	2988
August	1st to 10th	Night	47% 7% 14% 23% 9%	2814
	11th to 20th	Night	42% 5% 10% 27% 15% 1	2812
	21st to end	Night	35% 6% 14% 31% 13% 2	3347
September	1st to 10th	Night	36% 4 11% 25% 20% 4	1900
	11th to 20th	Night	31% 4 12% 29% 23% 1	2047
	21st to end	Night	45% 3 9% 24% 17% 1	2110
October	1st to 10th	Night	37% 3 8% 29% 22% 2	3800
	11th to 20th	Night	38% 4 10% 26% 15% 8%	3779
	21st to end	Night	37% 2 8% 29% 22% 2	4120
November	1st to 10th	Night	42% 3 10% 23% 18% 4	2318
	11th to 20th	Night	54% 3 8% 21% 12% 2	2622
	21st to end	Night	57% 2 10% 22% 8% 1	2660
December	1st to 10th	Night	68% 2 11% 14% 5%	2660
	11th to 20th	Night	66% 2 10% 18% 4	3288
	21st to end	Night	73% 2 10% 12% 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	34% 23% 25% 11% 5% 2	256
	11th to 20th	Day	40% 22% 29% 6% 3 1	270
	21st to end	Day	37% 21% 31% 7% 2 2	297
February	1st to 10th	Day	36% 20% 33% 10% 1	270
	11th to 20th	Day	40% 25% 28% 6% 1	270
	21st to end	Day	37% 23% 30% 10%	280
March	1st to 10th	Day	31% 19% 27% 18% 5%	460
	11th to 20th	Day	36% 19% 28% 12% 4 1	460
	21st to end	Day	32% 15% 30% 17% 5% 1	506
April	1st to 10th	Day	32% 17% 27% 15% 8% 1	460
	11th to 20th	Day	25% 19% 28% 15% 9% 4	452
	21st to end	Day	29% 13% 32% 17% 8% 2	460
May	1st to 10th	Day	32% 11% 28% 18% 9% 3	463
	11th to 20th	Day	24% 12% 26% 23% 9% 6%	487
	21st to end	Day	19% 7% 25% 24% 16% 8%	529
June	1st to 10th	Day	18% 9% 27% 27% 15% 4	490
	11th to 20th	Day	19% 8% 25% 26% 18% 4	490
	21st to end	Day	16% 9% 28% 28% 16% 3	490
July	1st to 10th	Day	16% 4 17% 30% 21% 12%	485
	11th to 20th	Day	15% 5% 22% 32% 17% 8%	484
	21st to end	Day	16% 4 23% 32% 18% 8%	532
August	1st to 10th	Day	17% 4 18% 30% 22% 9%	486
	11th to 20th	Day	19% 3 16% 28% 22% 12%	479
	21st to end	Day	16% 3 20% 27% 22% 13%	539
September	1st to 10th	Day	20% 5% 18% 27% 21% 9%	490
	11th to 20th	Day	14% 4 15% 30% 25% 12%	490
	21st to end	Day	28% 9% 21% 21% 16% 5%	490
October	1st to 10th	Day	20% 8% 26% 22% 18% 6%	490
	11th to 20th	Day	23% 14% 28% 22% 10% 3	490
	21st to end	Day	31% 12% 29% 17% 10% 1	539
November	1st to 10th	Day	21% 12% 30% 23% 11% 3	430
	11th to 20th	Day	32% 17% 30% 15% 6% 1	196
	21st to end	Day	30% 18% 37% 11% 3 1	180
December	1st to 10th	Day	32% 23% 29% 11% 3 1	180
	11th to 20th	Day	34% 22% 29% 12% 2	180
	21st to end	Day	39% 20% 23% 14% 4 1	198
January	1st to 10th	Night	33% 18% 28% 16% 4	760
	11th to 20th	Night	35% 15% 31% 17% 3	760
	21st to end	Night	33% 18% 26% 20% 2	836
February	1st to 10th	Night	32% 16% 25% 24% 3	760
	11th to 20th	Night	31% 20% 32% 16% 1	743
	21st to end	Night	31% 16% 33% 18% 2	628
March	1st to 10th	Night	25% 18% 29% 23% 5%	760
	11th to 20th	Night	30% 15% 27% 21% 7% 1	760
	21st to end	Night	27% 13% 31% 23% 6% 1	836
April	1st to 10th	Night	29% 12% 30% 21% 6%	760
	11th to 20th	Night	23% 11% 30% 26% 10% 1	751
	21st to end	Night	20% 10% 30% 33% 7%	590
May	1st to 10th	Night	26% 7% 21% 34% 11% 1	570
	11th to 20th	Night	24% 7% 22% 35% 11%	561
	21st to end	Night	12% 3 22% 34% 26% 3	434
June	1st to 10th	Night	13% 4 22% 43% 18% 1	380
	11th to 20th	Night	14% 3 20% 42% 19% 1	380
	21st to end	Night	13% 3 25% 39% 19% 1	380
July	1st to 10th	Night	10% 3 17% 43% 23% 4	406
	11th to 20th	Night	11% 3 16% 37% 29% 4	552
	21st to end	Night	15% 2 12% 41% 28% 2	624
August	1st to 10th	Night	12% 2 12% 42% 30% 2	567
	11th to 20th	Night	15% 2 10% 39% 30% 4	564
	21st to end	Night	12% 2 14% 38% 29% 4	759
September	1st to 10th	Night	16% 3 16% 35% 27% 4	760
	11th to 20th	Night	13% 3 13% 40% 28% 4	760
	21st to end	Night	22% 6% 21% 29% 20% 3	760
October	1st to 10th	Night	19% 6% 21% 31% 20% 2	760
	11th to 20th	Night	20% 9% 28% 31% 11% 1	760
	21st to end	Night	29% 10% 23% 29% 8% 1	836
November	1st to 10th	Night	20% 9% 25% 34% 11% 1	760
	11th to 20th	Night	29% 12% 26% 24% 8% 1	760
	21st to end	Night	31% 12% 28% 23% 6%	760
December	1st to 10th	Night	34% 14% 28% 18% 6%	760
	11th to 20th	Night	30% 18% 27% 21% 4	760
	21st to end	Night	33% 15% 26% 24% 2	836

Page generated at 2024-11-03 02:11:16. Version ac07

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