Reidland
Clear Sky Chart
History

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

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% 7% 2 6% 4 4 4 4 5% 8% 43%	101003
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 45%	98096
Transparency	Day	39% 5% 10% 25% 18% 3	104676
	Night	37% 5% 9% 24% 20% 4	102564
Seeing	Day	15% 6% 21% 26% 21% 11%	15446
	Night	17% 6% 23% 32% 19% 3	25222

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% 10% 3 9% 5% 3 3 3 5% 5% 37%	2527
	11th to 20th	Day	19% 9% 3 6% 4 4 4 3 5% 5% 40%	2626
	21st to end	Day	24% 12% 4 8% 5% 4 3 3 3 5% 30%	3135
February	1st to 10th	Day	18% 11% 2 6% 5% 4 3 3 5% 7% 36%	1894
	11th to 20th	Day	18% 10% 3 7% 3 4 4 3 4 5% 39%	1848
	21st to end	Day	18% 9% 4 8% 6% 4 3 3 4 6% 35%	1570
March	1st to 10th	Day	20% 14% 3 7% 4 3 3 3 4 6% 34%	3120
	11th to 20th	Day	15% 8% 2 5% 3 3 3 2 4 6% 50%	3301
	21st to end	Day	12% 8% 2 7% 5% 4 5% 3 5% 7% 41%	4165
April	1st to 10th	Day	12% 6% 3 6% 4 4 4 4 5% 7% 45%	2280
	11th to 20th	Day	14% 8% 2 7% 5% 4 4 3 5% 6% 41%	2254
	21st to end	Day	16% 8% 3 6% 4 4 4 4 5% 7% 40%	2280
May	1st to 10th	Day	16% 7% 2 7% 5% 4 6% 5% 7% 10% 31%	3988
	11th to 20th	Day	18% 7% 2 7% 4 4 4 4 6% 8% 37%	4081
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 4 6% 8% 40%	4657
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 45%	2660
	11th to 20th	Day	5% 3 1 5% 5% 4 5% 5% 6% 10% 50%	2660
	21st to end	Day	5% 5% 2 5% 5% 5% 6% 5% 7% 10% 45%	2660
July	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 10% 40%	4440
	11th to 20th	Day	6% 4 1 6% 4 4 5% 4 7% 11% 49%	4440
	21st to end	Day	9% 9% 3 10% 6% 6% 6% 4 7% 8% 31%	4695
August	1st to 10th	Day	5% 4 2 4 3 4 5% 4 5% 10% 55%	3785
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 43%	3729
	21st to end	Day	5% 3 1 5% 4 3 4 4 6% 8% 57%	4180
September	1st to 10th	Day	12% 5% 2 5% 5% 4 4 5% 5% 7% 47%	2280
	11th to 20th	Day	10% 6% 2 5% 4 4 5% 4 5% 8% 48%	2157
	21st to end	Day	12% 6% 2 5% 4 3 3 3 5% 7% 51%	2090
October	1st to 10th	Day	9% 4 2 4 3 3 3 3 4 7% 59%	2074
	11th to 20th	Day	14% 5% 2 6% 4 4 3 2 4 6% 52%	1900
	21st to end	Day	19% 5% 2 4 3 3 3 3 4 5% 47%	1988
November	1st to 10th	Day	10% 6% 2 5% 3 3 4 3 5% 6% 53%	1717
	11th to 20th	Day	14% 8% 2 5% 4 3 3 3 4 5% 49%	1710
	21st to end	Day	18% 10% 2 4 3 3 3 3 4 5% 43%	1710
December	1st to 10th	Day	17% 10% 2 6% 4 3 4 4 4 6% 40%	1701
	11th to 20th	Day	15% 9% 3 7% 6% 4 5% 4 4 6% 36%	1918
	21st to end	Day	20% 13% 4 8% 4 4 4 3 4 5% 31%	2783
January	1st to 10th	Night	19% 8% 2 6% 3 3 4 4 5% 7% 39%	4428
	11th to 20th	Night	16% 10% 4 7% 4 4 4 3 5% 6% 37%	4340
	21st to end	Night	25% 11% 4 6% 3 3 3 3 5% 6% 31%	4532
February	1st to 10th	Night	20% 11% 3 8% 4 3 3 3 3 5% 35%	2284
	11th to 20th	Night	18% 8% 3 8% 4 3 3 3 4 5% 41%	2218
	21st to end	Night	19% 9% 3 8% 5% 4 4 4 4 4 37%	1884
March	1st to 10th	Night	24% 10% 3 7% 4 3 4 2 4 4 36%	3733
	11th to 20th	Night	13% 7% 2 6% 3 4 4 3 4 6% 48%	3686
	21st to end	Night	15% 8% 2 7% 4 4 4 3 5% 6% 42%	3466
April	1st to 10th	Night	12% 5% 2 5% 4 4 3 4 6% 7% 49%	1900
	11th to 20th	Night	15% 6% 2 6% 3 3 3 3 5% 8% 46%	1875
	21st to end	Night	17% 8% 2 5% 4 4 4 4 5% 6% 41%	1900
May	1st to 10th	Night	18% 8% 2 5% 4 3 3 3 5% 9% 39%	2894
	11th to 20th	Night	14% 7% 2 7% 4 4 4 3 5% 7% 44%	2812
	21st to end	Night	9% 5% 2 6% 4 4 5% 5% 7% 10% 43%	2900
June	1st to 10th	Night	10% 5% 3 5% 3 4 5% 4 7% 8% 46%	1520
	11th to 20th	Night	4 3 1 5% 3 4 5% 5% 8% 9% 54%	1520
	21st to end	Night	3 3 1 4 4 4 6% 5% 9% 13% 49%	1520
July	1st to 10th	Night	9% 5% 2 4 4 5% 6% 4 7% 8% 47%	2530
	11th to 20th	Night	6% 3 2 4 4 3 3 3 5% 10% 56%	2530
	21st to end	Night	8% 7% 3 9% 6% 5% 5% 5% 7% 9% 37%	2860
August	1st to 10th	Night	4 3 1 5% 3 4 3 4 6% 8% 60%	3144
	11th to 20th	Night	5% 4 2 5% 4 4 4 4 7% 9% 53%	3100
	21st to end	Night	5% 3 1 3 3 3 3 3 6% 8% 61%	3476
September	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 4 5% 57%	1900
	11th to 20th	Night	9% 5% 2 6% 3 3 4 3 4 7% 54%	2003
	21st to end	Night	11% 4 2 5% 3 3 4 3 5% 6% 55%	2090
October	1st to 10th	Night	7% 5% 2 4 3 3 3 3 4 6% 60%	2103
	11th to 20th	Night	13% 4 1 4 4 4 3 2 4 6% 55%	2280
	21st to end	Night	19% 6% 2 5% 4 3 3 3 4 6% 47%	2608
November	1st to 10th	Night	13% 5% 2 4 3 3 2 3 5% 6% 55%	2483
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 4 7% 51%	2470
	21st to end	Night	17% 7% 3 5% 4 3 3 2 4 5% 48%	2470
December	1st to 10th	Night	19% 9% 3 6% 4 3 4 3 4 5% 39%	2474
	11th to 20th	Night	17% 8% 2 5% 4 4 4 3 4 5% 43%	3279
	21st to end	Night	18% 11% 4 8% 5% 5% 5% 3 4 6% 31%	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	48% 4 8% 26% 12% 2	2528
	11th to 20th	Day	46% 4 8% 24% 16% 2	2626
	21st to end	Day	57% 3 9% 19% 10% 2	3135
February	1st to 10th	Day	49% 3 9% 25% 13% 2	1894
	11th to 20th	Day	49% 3 9% 22% 13% 5%	1858
	21st to end	Day	51% 3 9% 18% 13% 6%	1570
March	1st to 10th	Day	53% 4 5% 19% 13% 7%	3120
	11th to 20th	Day	38% 4 9% 28% 17% 5%	3301
	21st to end	Day	41% 5% 11% 22% 19% 1	4165
April	1st to 10th	Day	39% 5% 10% 26% 19% 2	2280
	11th to 20th	Day	43% 3 9% 22% 19% 4	2254
	21st to end	Day	44% 5% 9% 26% 14% 2	2280
May	1st to 10th	Day	45% 9% 13% 20% 12% 1	4024
	11th to 20th	Day	44% 8% 10% 24% 13% 1	4085
	21st to end	Day	39% 7% 12% 19% 22% 1	4670
June	1st to 10th	Day	33% 7% 13% 22% 21% 2	2660
	11th to 20th	Day	28% 7% 13% 28% 22% 3	2660
	21st to end	Day	32% 8% 15% 23% 16% 5%	2660
July	1st to 10th	Day	37% 7% 14% 28% 12% 3	4371
	11th to 20th	Day	29% 6% 12% 37% 13% 2	4365
	21st to end	Day	49% 7% 12% 22% 9% 1	4547
August	1st to 10th	Day	25% 6% 15% 30% 24% 1	3773
	11th to 20th	Day	35% 7% 11% 26% 19% 1	3765
	21st to end	Day	24% 5% 12% 35% 21% 3	4179
September	1st to 10th	Day	36% 6% 9% 25% 20% 4	2280
	11th to 20th	Day	35% 5% 9% 24% 24% 3	2157
	21st to end	Day	34% 4 7% 25% 25% 5%	2090
October	1st to 10th	Day	18% 2 6% 19% 46% 9%	3451
	11th to 20th	Day	24% 2 5% 24% 31% 13%	3140
	21st to end	Day	30% 3 4 28% 29% 6%	3252
November	1st to 10th	Day	32% 4 8% 25% 25% 6%	1717
	11th to 20th	Day	39% 3 6% 23% 23% 6%	1710
	21st to end	Day	44% 3 6% 26% 17% 4	1710
December	1st to 10th	Day	46% 4 10% 23% 14% 2	1701
	11th to 20th	Day	47% 5% 8% 24% 13% 2	1915
	21st to end	Day	55% 4 11% 18% 11% 1	2783
January	1st to 10th	Night	45% 4 8% 29% 13% 1	4428
	11th to 20th	Night	48% 5% 8% 23% 14% 2	4340
	21st to end	Night	52% 4 9% 22% 12% 1	4532
February	1st to 10th	Night	54% 3 8% 20% 14% 1	2284
	11th to 20th	Night	47% 3 7% 22% 17% 3	2219
	21st to end	Night	50% 5% 9% 17% 16% 4	1884
March	1st to 10th	Night	52% 4 6% 14% 18% 6%	3733
	11th to 20th	Night	37% 5% 11% 21% 17% 8%	3686
	21st to end	Night	43% 5% 9% 27% 15% 1	3466
April	1st to 10th	Night	34% 4 11% 26% 20% 4	1900
	11th to 20th	Night	37% 4 9% 22% 21% 7%	1875
	21st to end	Night	42% 5% 9% 24% 18% 2	1900
May	1st to 10th	Night	41% 8% 14% 24% 12% 1	2922
	11th to 20th	Night	40% 7% 12% 24% 16% 1	2813
	21st to end	Night	34% 8% 13% 27% 16% 2	2908
June	1st to 10th	Night	33% 7% 12% 22% 23% 3	1520
	11th to 20th	Night	23% 7% 14% 27% 23% 6%	1520
	21st to end	Night	23% 8% 16% 27% 18% 7%	1520
July	1st to 10th	Night	34% 6% 13% 28% 15% 3	2490
	11th to 20th	Night	24% 5% 12% 37% 18% 3	2482
	21st to end	Night	43% 8% 12% 25% 11% 1	2770
August	1st to 10th	Night	22% 5% 14% 37% 21% 1	3132
	11th to 20th	Night	27% 6% 16% 29% 19% 3	3130
	21st to end	Night	20% 5% 10% 36% 25% 3	3476
September	1st to 10th	Night	30% 5% 8% 28% 24% 5%	1900
	11th to 20th	Night	31% 5% 7% 28% 24% 5%	2003
	21st to end	Night	31% 4 9% 26% 23% 7%	2090
October	1st to 10th	Night	18% 3 4 15% 46% 14%	3506
	11th to 20th	Night	21% 2 4 20% 40% 12%	3779
	21st to end	Night	29% 2 5% 24% 28% 11%	4294
November	1st to 10th	Night	32% 3 7% 26% 26% 6%	2483
	11th to 20th	Night	35% 3 6% 24% 23% 8%	2470
	21st to end	Night	40% 3 7% 24% 23% 3	2470
December	1st to 10th	Night	48% 4 10% 21% 15% 2	2474
	11th to 20th	Night	44% 4 9% 22% 19% 3	3281
	21st to end	Night	54% 5% 9% 17% 12% 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	27% 11% 33% 22% 7% 1	270
	11th to 20th	Day	29% 13% 33% 21% 3 1	270
	21st to end	Day	24% 10% 43% 17% 6%	297
February	1st to 10th	Day	26% 12% 35% 21% 5% 1	270
	11th to 20th	Day	27% 16% 38% 16% 3 1	270
	21st to end	Day	29% 14% 32% 19% 6%	225
March	1st to 10th	Day	21% 11% 41% 20% 6% 1	270
	11th to 20th	Day	23% 13% 37% 21% 5% 1	275
	21st to end	Day	23% 14% 32% 22% 8% 1	506
April	1st to 10th	Day	19% 12% 30% 26% 12% 1	460
	11th to 20th	Day	20% 11% 27% 26% 13% 2	452
	21st to end	Day	20% 7% 32% 26% 11% 4	460
May	1st to 10th	Day	17% 10% 27% 28% 13% 5%	463
	11th to 20th	Day	21% 4 19% 27% 21% 9%	487
	21st to end	Day	11% 2 20% 29% 23% 14%	632
June	1st to 10th	Day	13% 3 14% 28% 27% 16%	680
	11th to 20th	Day	6% 1 15% 32% 34% 13%	680
	21st to end	Day	7% 2 14% 36% 26% 15%	680
July	1st to 10th	Day	11% 2 9% 25% 27% 26%	671
	11th to 20th	Day	6% 1 10% 27% 37% 19%	668
	21st to end	Day	8% 2 11% 27% 33% 20%	720
August	1st to 10th	Day	9% 1 7% 28% 34% 20%	486
	11th to 20th	Day	12% 3 10% 26% 33% 16%	479
	21st to end	Day	9% 1 6% 21% 37% 26%	539
September	1st to 10th	Day	10% 3 9% 23% 35% 20%	490
	11th to 20th	Day	11% 2 6% 25% 33% 22%	490
	21st to end	Day	15% 6% 16% 23% 26% 14%	490
October	1st to 10th	Day	9% 3 16% 34% 30% 9%	474
	11th to 20th	Day	15% 7% 31% 26% 15% 6%	300
	21st to end	Day	25% 11% 27% 24% 11% 3	330
November	1st to 10th	Day	17% 6% 27% 29% 13% 7%	285
	11th to 20th	Day	14% 9% 33% 28% 14% 2	270
	21st to end	Day	28% 7% 25% 27% 11% 2	270
December	1st to 10th	Day	21% 11% 33% 20% 12% 3	270
	11th to 20th	Day	23% 12% 29% 25% 11%	270
	21st to end	Day	27% 12% 35% 22% 3 1	297
January	1st to 10th	Night	24% 11% 30% 29% 6%	950
	11th to 20th	Night	25% 12% 34% 23% 5%	950
	21st to end	Night	22% 7% 38% 29% 3	1045
February	1st to 10th	Night	26% 9% 33% 29% 3	764
	11th to 20th	Night	23% 11% 36% 27% 3	743
	21st to end	Night	25% 11% 36% 25% 2	628
March	1st to 10th	Night	23% 10% 28% 33% 6%	760
	11th to 20th	Night	23% 6% 35% 29% 7%	703
	21st to end	Night	21% 9% 27% 35% 7%	627
April	1st to 10th	Night	14% 9% 34% 34% 9% 1	570
	11th to 20th	Night	18% 8% 28% 32% 13% 1	563
	21st to end	Night	19% 5% 29% 34% 12% 1	570
May	1st to 10th	Night	18% 3 26% 35% 16% 1	570
	11th to 20th	Night	14% 5% 16% 39% 24% 2	561
	21st to end	Night	7% 2 14% 41% 31% 4	617
June	1st to 10th	Night	12% 2 12% 37% 32% 4	570
	11th to 20th	Night	5% 2 8% 44% 39% 2	570
	21st to end	Night	5% 1 12% 41% 36% 5%	570
July	1st to 10th	Night	9% 1 6% 28% 45% 11%	555
	11th to 20th	Night	8% 2 7% 29% 47% 9%	552
	21st to end	Night	7% 2 9% 32% 42% 9%	624
August	1st to 10th	Night	6% 2 6% 32% 46% 8%	567
	11th to 20th	Night	9% 1 9% 34% 41% 6%	564
	21st to end	Night	9% 1 4 29% 48% 10%	627
September	1st to 10th	Night	11% 1 8% 33% 41% 6%	570
	11th to 20th	Night	10% 1 7% 31% 43% 7%	673
	21st to end	Night	12% 3 14% 34% 30% 6%	760
October	1st to 10th	Night	9% 3 16% 35% 31% 6%	760
	11th to 20th	Night	15% 4 24% 34% 20% 2	760
	21st to end	Night	22% 6% 24% 33% 13% 1	836
November	1st to 10th	Night	15% 5% 24% 38% 17% 1	764
	11th to 20th	Night	17% 6% 31% 32% 13%	760
	21st to end	Night	21% 7% 27% 31% 12% 1	760
December	1st to 10th	Night	24% 8% 29% 31% 8% 1	764
	11th to 20th	Night	23% 5% 29% 34% 8%	950
	21st to end	Night	28% 9% 29% 30% 5%	1045

Page generated at 2024-11-03 12:19:03. Version ac07

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