Murphy
Clear Sky Chart
History

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

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	12% 7% 3 6% 4 4 4 4 6% 8% 42%	101262
	Night	13% 8% 3 6% 4 4 4 3 5% 7% 43%	97949
Transparency	Day	37% 6% 12% 25% 17% 3	104882
	Night	39% 6% 11% 24% 18% 3	102471
Seeing	Day	15% 9% 25% 27% 18% 6%	15637
	Night	16% 8% 28% 32% 14% 1	25439

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	9% 12% 5% 11% 6% 4 5% 4 6% 7% 31%	2527
	11th to 20th	Day	12% 8% 4 8% 5% 5% 5% 4 5% 7% 36%	2754
	21st to end	Day	21% 15% 5% 7% 4 4 3 3 3 5% 29%	3135
February	1st to 10th	Day	15% 10% 4 9% 4 3 5% 4 6% 6% 34%	1710
	11th to 20th	Day	15% 10% 3 7% 5% 4 4 3 6% 5% 38%	1829
	21st to end	Day	14% 10% 2 7% 4 4 3 4 5% 7% 39%	1570
March	1st to 10th	Day	18% 12% 3 6% 4 3 3 2 3 5% 41%	3176
	11th to 20th	Day	12% 8% 2 5% 4 3 3 3 5% 6% 49%	3480
	21st to end	Day	15% 8% 3 7% 5% 4 5% 4 6% 7% 36%	4022
April	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 7% 7% 42%	2280
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 4 6% 41%	2254
	21st to end	Day	18% 7% 2 6% 6% 5% 5% 4 5% 7% 37%	2280
May	1st to 10th	Day	13% 7% 3 7% 5% 5% 6% 5% 7% 9% 32%	3847
	11th to 20th	Day	17% 8% 3 6% 4 4 4 3 6% 8% 37%	4353
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	4824
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 45%	2660
	11th to 20th	Day	7% 5% 1 5% 4 4 4 4 6% 10% 50%	2660
	21st to end	Day	4 4 2 5% 5% 5% 4 5% 7% 11% 47%	2660
July	1st to 10th	Day	12% 5% 3 6% 4 5% 5% 4 7% 9% 41%	4440
	11th to 20th	Day	4 4 2 5% 4 5% 5% 4 7% 11% 49%	4440
	21st to end	Day	7% 5% 2 8% 5% 5% 6% 5% 7% 10% 40%	4545
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 4 7% 9% 51%	4082
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 6% 9% 43%	3729
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 10% 52%	4180
September	1st to 10th	Day	13% 5% 1 5% 3 4 4 3 5% 7% 50%	2280
	11th to 20th	Day	9% 5% 2 6% 4 4 3 3 6% 9% 48%	2256
	21st to end	Day	7% 5% 2 6% 4 3 4 3 5% 7% 53%	2082
October	1st to 10th	Day	9% 5% 2 5% 4 3 3 3 5% 6% 56%	1900
	11th to 20th	Day	13% 6% 1 5% 3 3 3 3 4 6% 53%	1900
	21st to end	Day	16% 8% 2 4 4 3 3 2 4 5% 47%	2079
November	1st to 10th	Day	11% 5% 2 5% 4 4 3 2 6% 6% 53%	1753
	11th to 20th	Day	13% 6% 2 6% 4 3 3 3 5% 7% 47%	1710
	21st to end	Day	15% 10% 3 6% 5% 4 3 4 3 6% 41%	1644
December	1st to 10th	Day	13% 11% 3 7% 3 3 5% 3 5% 8% 39%	1520
	11th to 20th	Day	13% 10% 5% 7% 5% 3 4 3 5% 7% 38%	1918
	21st to end	Day	19% 14% 5% 9% 5% 5% 4 3 4 6% 27%	2783
January	1st to 10th	Night	14% 9% 5% 10% 6% 5% 4 3 4 5% 35%	4428
	11th to 20th	Night	13% 10% 4 11% 7% 7% 7% 4 4 4 30%	4213
	21st to end	Night	23% 15% 5% 8% 4 3 3 3 4 6% 28%	4532
February	1st to 10th	Night	16% 11% 4 9% 5% 4 4 3 5% 5% 34%	2470
	11th to 20th	Night	14% 8% 3 8% 5% 4 4 3 4 6% 42%	2234
	21st to end	Night	16% 9% 3 9% 5% 4 3 3 4 5% 40%	1884
March	1st to 10th	Night	21% 10% 2 6% 3 3 3 2 3 4 42%	3705
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 6% 51%	3480
	21st to end	Night	16% 10% 3 9% 5% 5% 5% 3 5% 5% 34%	3608
April	1st to 10th	Night	11% 6% 3 6% 4 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	13% 6% 2 7% 4 3 4 3 5% 7% 44%	1875
	21st to end	Night	20% 8% 3 6% 4 3 3 3 4 7% 41%	1900
May	1st to 10th	Night	17% 8% 3 6% 3 4 4 3 6% 8% 38%	3046
	11th to 20th	Night	15% 7% 2 6% 4 3 4 4 5% 8% 43%	2548
	21st to end	Night	8% 6% 2 7% 5% 5% 6% 4 6% 9% 41%	2743
June	1st to 10th	Night	8% 4 2 6% 4 4 4 4 7% 10% 48%	1520
	11th to 20th	Night	6% 4 2 4 4 4 3 4 5% 9% 56%	1520
	21st to end	Night	4 4 1 4 4 4 5% 3 7% 9% 55%	1520
July	1st to 10th	Night	13% 4 2 5% 3 4 4 4 6% 9% 47%	2530
	11th to 20th	Night	5% 4 2 5% 3 4 4 3 5% 9% 56%	2530
	21st to end	Night	7% 6% 2 8% 5% 4 5% 5% 8% 9% 41%	3000
August	1st to 10th	Night	4 3 2 4 4 3 4 4 6% 8% 58%	2857
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 3 6% 8% 46%	3100
	21st to end	Night	5% 3 1 4 3 4 4 4 6% 9% 58%	3476
September	1st to 10th	Night	12% 5% 1 5% 4 3 4 3 4 6% 54%	1900
	11th to 20th	Night	9% 5% 2 5% 5% 3 5% 4 5% 7% 52%	1904
	21st to end	Night	10% 5% 2 4 3 3 5% 3 5% 7% 53%	2095
October	1st to 10th	Night	7% 4 2 4 3 3 3 3 4 7% 59%	2280
	11th to 20th	Night	13% 6% 2 4 3 3 3 3 4 6% 54%	2280
	21st to end	Night	17% 7% 2 5% 2 3 4 3 5% 5% 48%	2517
November	1st to 10th	Night	11% 6% 1 5% 3 3 3 2 5% 5% 56%	2530
	11th to 20th	Night	15% 5% 2 5% 4 3 4 3 4 6% 49%	2470
	21st to end	Night	18% 9% 3 5% 3 2 3 3 5% 6% 44%	2531
December	1st to 10th	Night	15% 12% 3 6% 4 3 4 4 5% 7% 37%	2660
	11th to 20th	Night	16% 9% 3 6% 4 5% 4 3 4 5% 41%	3279
	21st to end	Night	17% 18% 4 10% 6% 5% 4 4 5% 5% 23%	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	49% 7% 12% 23% 8% 1	2528
	11th to 20th	Day	45% 6% 14% 21% 14%	2754
	21st to end	Day	56% 4 10% 16% 11% 2	3135
February	1st to 10th	Day	49% 6% 11% 23% 11% 1	1710
	11th to 20th	Day	47% 5% 10% 20% 14% 4	1839
	21st to end	Day	45% 5% 10% 22% 14% 4	1570
March	1st to 10th	Day	47% 4 7% 20% 16% 5%	3176
	11th to 20th	Day	36% 5% 10% 26% 17% 6%	3480
	21st to end	Day	43% 8% 17% 21% 10% 1	4022
April	1st to 10th	Day	38% 6% 12% 26% 18% 1	2280
	11th to 20th	Day	43% 5% 10% 23% 15% 4	2254
	21st to end	Day	46% 7% 11% 22% 13% 1	2280
May	1st to 10th	Day	43% 11% 13% 23% 11% 1	3882
	11th to 20th	Day	44% 7% 11% 25% 12% 1	4357
	21st to end	Day	36% 8% 12% 22% 21% 1	4837
June	1st to 10th	Day	34% 8% 13% 26% 17% 2	2660
	11th to 20th	Day	28% 7% 13% 26% 23% 3	2660
	21st to end	Day	28% 9% 18% 25% 15% 5%	2660
July	1st to 10th	Day	37% 7% 12% 29% 12% 2	4371
	11th to 20th	Day	26% 8% 15% 32% 17% 2	4365
	21st to end	Day	36% 9% 17% 26% 11% 1	4402
August	1st to 10th	Day	25% 8% 16% 35% 15%	4068
	11th to 20th	Day	37% 6% 13% 25% 17% 1	3765
	21st to end	Day	27% 7% 14% 34% 15% 3	4179
September	1st to 10th	Day	33% 6% 10% 25% 20% 5%	2280
	11th to 20th	Day	33% 6% 10% 25% 24% 2	2256
	21st to end	Day	30% 6% 10% 27% 24% 3	2082
October	1st to 10th	Day	18% 3 6% 19% 46% 8%	3160
	11th to 20th	Day	23% 3 8% 21% 36% 10%	3140
	21st to end	Day	32% 3 7% 28% 27% 3	3405
November	1st to 10th	Day	33% 4 13% 26% 19% 6%	1753
	11th to 20th	Day	37% 5% 9% 23% 21% 5%	1710
	21st to end	Day	44% 4 9% 26% 15%	1644
December	1st to 10th	Day	44% 5% 12% 26% 12% 1	1520
	11th to 20th	Day	47% 5% 10% 22% 15% 2	1915
	21st to end	Day	58% 6% 10% 15% 9% 1	2783
January	1st to 10th	Night	50% 5% 10% 24% 10% 1	4428
	11th to 20th	Night	55% 5% 9% 20% 9% 1	4213
	21st to end	Night	58% 4 9% 20% 7% 1	4532
February	1st to 10th	Night	51% 5% 10% 20% 13% 1	2470
	11th to 20th	Night	44% 5% 10% 21% 18% 3	2235
	21st to end	Night	47% 4 11% 19% 14% 4	1884
March	1st to 10th	Night	47% 5% 7% 24% 15% 3	3705
	11th to 20th	Night	35% 5% 11% 24% 20% 4	3480
	21st to end	Night	49% 8% 11% 24% 7%	3608
April	1st to 10th	Night	36% 6% 11% 27% 18% 4	1900
	11th to 20th	Night	39% 5% 10% 24% 18% 4	1875
	21st to end	Night	44% 5% 9% 24% 16% 2	1900
May	1st to 10th	Night	42% 8% 16% 20% 13% 1	3076
	11th to 20th	Night	38% 7% 14% 26% 13% 1	2549
	21st to end	Night	35% 9% 14% 23% 17% 2	2751
June	1st to 10th	Night	30% 7% 15% 26% 17% 4	1520
	11th to 20th	Night	24% 6% 12% 28% 26% 4	1520
	21st to end	Night	24% 7% 16% 28% 19% 7%	1520
July	1st to 10th	Night	34% 5% 13% 28% 15% 4	2490
	11th to 20th	Night	24% 6% 11% 36% 19% 3	2482
	21st to end	Night	34% 9% 19% 24% 13% 2	2905
August	1st to 10th	Night	21% 8% 18% 33% 19% 1	2847
	11th to 20th	Night	35% 6% 13% 24% 19% 2	3130
	21st to end	Night	23% 6% 15% 35% 19% 3	3476
September	1st to 10th	Night	32% 5% 9% 25% 23% 6%	1900
	11th to 20th	Night	31% 5% 9% 24% 26% 4	1904
	21st to end	Night	30% 7% 9% 23% 27% 4	2095
October	1st to 10th	Night	15% 3 6% 17% 50% 9%	3800
	11th to 20th	Night	22% 3 7% 22% 37% 10%	3779
	21st to end	Night	30% 4 9% 24% 27% 5%	4141
November	1st to 10th	Night	30% 4 12% 25% 23% 6%	2530
	11th to 20th	Night	37% 4 8% 24% 23% 4	2470
	21st to end	Night	42% 4 10% 24% 18% 2	2531
December	1st to 10th	Night	46% 6% 10% 24% 12% 1	2660
	11th to 20th	Night	46% 4 10% 23% 16% 1	3281
	21st to end	Night	60% 6% 10% 15% 8% 1	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	23% 17% 33% 19% 7% 1	270
	11th to 20th	Day	27% 14% 41% 16% 2	270
	21st to end	Day	21% 18% 40% 17% 5%	297
February	1st to 10th	Day	23% 17% 39% 17% 4	270
	11th to 20th	Day	23% 21% 33% 16% 6% 1	270
	21st to end	Day	26% 18% 38% 16% 2	225
March	1st to 10th	Day	18% 17% 47% 14% 4	270
	11th to 20th	Day	29% 15% 36% 14% 5% 1	270
	21st to end	Day	28% 16% 32% 19% 6%	415
April	1st to 10th	Day	18% 13% 38% 20% 9%	460
	11th to 20th	Day	21% 13% 33% 20% 12%	452
	21st to end	Day	23% 12% 36% 20% 8%	460
May	1st to 10th	Day	18% 13% 29% 29% 10% 2	463
	11th to 20th	Day	19% 8% 29% 25% 16% 4	642
	21st to end	Day	12% 5% 30% 31% 15% 7%	734
June	1st to 10th	Day	12% 5% 20% 30% 26% 7%	680
	11th to 20th	Day	8% 3 20% 39% 22% 8%	680
	21st to end	Day	5% 5% 27% 36% 21% 7%	680
July	1st to 10th	Day	12% 2 13% 27% 31% 16%	671
	11th to 20th	Day	6% 3 16% 37% 29% 8%	668
	21st to end	Day	9% 1 15% 36% 31% 8%	739
August	1st to 10th	Day	9% 2 14% 35% 30% 10%	667
	11th to 20th	Day	12% 3 15% 28% 32% 10%	479
	21st to end	Day	10% 2 11% 28% 37% 12%	539
September	1st to 10th	Day	14% 3 13% 27% 32% 11%	490
	11th to 20th	Day	9% 2 11% 30% 32% 15%	490
	21st to end	Day	10% 9% 18% 31% 22% 10%	482
October	1st to 10th	Day	13% 7% 22% 36% 15% 7%	300
	11th to 20th	Day	15% 13% 33% 25% 12% 2	300
	21st to end	Day	28% 18% 24% 22% 7%	330
November	1st to 10th	Day	15% 9% 32% 29% 11% 4	297
	11th to 20th	Day	18% 18% 30% 20% 12% 2	270
	21st to end	Day	25% 14% 29% 21% 10% 1	270
December	1st to 10th	Day	16% 17% 38% 18% 7% 4	270
	11th to 20th	Day	23% 13% 35% 23% 4 1	270
	21st to end	Day	28% 18% 36% 14% 3 1	297
January	1st to 10th	Night	19% 13% 39% 24% 5%	950
	11th to 20th	Night	22% 16% 35% 23% 5%	950
	21st to end	Night	19% 13% 39% 27% 2	1045
February	1st to 10th	Night	22% 13% 36% 26% 3	950
	11th to 20th	Night	19% 13% 41% 25% 1	759
	21st to end	Night	21% 14% 40% 23% 2	628
March	1st to 10th	Night	21% 12% 37% 25% 4	745
	11th to 20th	Night	21% 11% 36% 26% 5%	570
	21st to end	Night	26% 10% 32% 28% 5%	627
April	1st to 10th	Night	16% 11% 38% 28% 6%	570
	11th to 20th	Night	17% 10% 34% 28% 11%	563
	21st to end	Night	22% 6% 38% 26% 7%	570
May	1st to 10th	Night	18% 6% 30% 35% 10% 1	570
	11th to 20th	Night	18% 4 24% 36% 16% 1	561
	21st to end	Night	11% 4 22% 40% 20% 3	617
June	1st to 10th	Night	9% 3 18% 43% 26% 1	570
	11th to 20th	Night	7% 3 18% 49% 22% 1	570
	21st to end	Night	5% 2 23% 44% 24% 2	570
July	1st to 10th	Night	10% 1 9% 38% 34% 8%	555
	11th to 20th	Night	6% 2 12% 45% 33% 3	552
	21st to end	Night	7% 2 12% 42% 33% 3	624
August	1st to 10th	Night	7% 1 10% 43% 36% 3	567
	11th to 20th	Night	7% 2 11% 40% 36% 4	564
	21st to end	Night	6% 2 9% 38% 40% 5%	627
September	1st to 10th	Night	13% 2 11% 37% 31% 6%	570
	11th to 20th	Night	9% 3 13% 34% 36% 5%	574
	21st to end	Night	11% 4 21% 32% 28% 4	760
October	1st to 10th	Night	8% 4 25% 34% 25% 4	760
	11th to 20th	Night	17% 8% 31% 31% 13% 1	760
	21st to end	Night	23% 9% 32% 29% 7%	836
November	1st to 10th	Night	13% 7% 35% 34% 11% 1	779
	11th to 20th	Night	17% 13% 31% 30% 9%	760
	21st to end	Night	23% 9% 34% 28% 6% 1	821
December	1st to 10th	Night	22% 10% 34% 29% 5% 1	950
	11th to 20th	Night	23% 9% 29% 33% 6%	950
	21st to end	Night	25% 13% 34% 25% 3	1045

Page generated at 2024-11-07 05:55:46. Version ac07

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