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 2025-12-03.

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	11% 7% 3 7% 4 4 4 4 6% 8% 42%	126957
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 43%	123945
Transparency	Day	38% 6% 12% 25% 17% 3	130538
	Night	40% 5% 11% 23% 18% 3	128442
Seeing	Day	16% 9% 25% 27% 18% 6%	17078
	Night	17% 8% 28% 32% 14% 1	26875

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	12% 12% 5% 13% 5% 4 4 4 5% 6% 29%	3617
	11th to 20th	Day	9% 8% 4 8% 5% 5% 5% 4 5% 7% 41%	3942
	21st to end	Day	17% 12% 4 9% 4 4 3 3 4 5% 35%	4488
February	1st to 10th	Day	16% 10% 4 9% 5% 3 5% 4 6% 6% 34%	1800
	11th to 20th	Day	15% 10% 3 8% 5% 4 4 3 6% 5% 37%	1929
	21st to end	Day	14% 10% 2 7% 4 4 3 4 5% 7% 40%	1650
March	1st to 10th	Day	15% 11% 3 5% 3 3 3 2 3 4 49%	4564
	11th to 20th	Day	9% 7% 2 5% 4 3 4 3 5% 6% 52%	4980
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 6% 8% 37%	5754
April	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 4 6% 7% 42%	2400
	11th to 20th	Day	16% 8% 3 6% 4 4 4 4 4 6% 41%	2374
	21st to end	Day	17% 7% 2 6% 6% 5% 5% 4 5% 7% 36%	2400
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 5% 5% 7% 9% 31%	5515
	11th to 20th	Day	16% 8% 3 6% 4 5% 5% 4 6% 8% 35%	6245
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 4 6% 7% 40%	6935
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 46%	2800
	11th to 20th	Day	7% 5% 1 5% 4 4 5% 5% 6% 10% 49%	2800
	21st to end	Day	4 4 2 5% 5% 5% 4 5% 7% 11% 47%	2800
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 47%	6360
	11th to 20th	Day	6% 4 2 7% 5% 5% 6% 5% 8% 12% 41%	6360
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 11% 41%	6544
August	1st to 10th	Day	5% 4 2 4 4 4 5% 4 7% 9% 52%	4211
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 6% 9% 43%	3849
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 10% 52%	4312
September	1st to 10th	Day	13% 5% 2 5% 3 4 4 3 5% 7% 50%	2400
	11th to 20th	Day	9% 5% 2 6% 4 4 3 3 6% 9% 49%	2375
	21st to end	Day	8% 5% 2 5% 4 3 4 3 5% 7% 53%	2191
October	1st to 10th	Day	9% 5% 2 4 4 3 3 3 5% 6% 56%	2000
	11th to 20th	Day	13% 6% 1 5% 3 3 3 3 4 5% 53%	2000
	21st to end	Day	17% 8% 2 4 4 3 3 2 4 5% 47%	2188
November	1st to 10th	Day	11% 5% 2 5% 4 4 3 2 6% 6% 53%	1852
	11th to 20th	Day	13% 6% 2 7% 4 4 3 3 4 7% 47%	1890
	21st to end	Day	15% 11% 4 6% 5% 4 3 4 3 6% 41%	1816
December	1st to 10th	Day	9% 10% 2 6% 3 3 4 3 4 7% 50%	2626
	11th to 20th	Day	13% 8% 6% 8% 5% 4 4 3 5% 7% 38%	3008
	21st to end	Day	22% 17% 5% 9% 5% 4 4 2 3 4 24%	3982
January	1st to 10th	Night	15% 10% 5% 12% 6% 5% 4 3 4 5% 32%	6348
	11th to 20th	Night	11% 9% 4 11% 6% 6% 5% 3 4 5% 35%	6021
	21st to end	Night	18% 12% 4 9% 5% 3 3 3 4 5% 35%	6490
February	1st to 10th	Night	16% 11% 4 9% 6% 4 4 3 5% 5% 34%	2600
	11th to 20th	Night	15% 9% 3 8% 4 4 4 3 4 6% 40%	2354
	21st to end	Night	15% 9% 3 8% 5% 4 3 3 4 5% 41%	1980
March	1st to 10th	Night	18% 11% 3 5% 3 3 3 3 3 4 42%	5331
	11th to 20th	Night	11% 8% 2 5% 3 4 3 3 5% 6% 50%	4980
	21st to end	Night	16% 9% 3 8% 5% 5% 5% 3 5% 6% 35%	5174
April	1st to 10th	Night	12% 6% 3 6% 5% 4 4 3 5% 7% 46%	2000
	11th to 20th	Night	13% 6% 2 7% 4 3 4 3 5% 7% 45%	1975
	21st to end	Night	19% 8% 3 6% 4 3 3 3 4 7% 41%	2000
May	1st to 10th	Night	17% 8% 3 7% 4 4 5% 3 6% 9% 34%	4364
	11th to 20th	Night	13% 7% 2 6% 4 4 4 5% 6% 8% 42%	3651
	21st to end	Night	13% 7% 3 7% 5% 4 5% 4 6% 8% 39%	3942
June	1st to 10th	Night	8% 4 2 6% 4 4 4 4 7% 10% 48%	1600
	11th to 20th	Night	6% 4 2 4 4 4 3 4 5% 9% 55%	1600
	21st to end	Night	4 4 1 4 4 4 5% 4 7% 9% 55%	1600
July	1st to 10th	Night	11% 5% 2 5% 3 4 4 3 5% 9% 49%	3618
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 4 6% 10% 48%	3617
	21st to end	Night	6% 5% 2 7% 5% 5% 6% 5% 8% 10% 42%	4309
August	1st to 10th	Night	4 3 2 4 4 3 4 4 6% 8% 58%	2948
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 3 6% 8% 47%	3200
	21st to end	Night	5% 3 2 4 3 4 4 4 6% 9% 58%	3586
September	1st to 10th	Night	11% 5% 1 6% 4 3 4 3 4 6% 53%	2000
	11th to 20th	Night	8% 4 2 5% 4 3 5% 4 5% 7% 52%	2004
	21st to end	Night	10% 5% 2 5% 3 3 5% 3 5% 7% 53%	2205
October	1st to 10th	Night	7% 4 2 5% 3 3 3 3 4 7% 59%	2400
	11th to 20th	Night	13% 6% 2 4 3 3 3 3 4 6% 54%	2400
	21st to end	Night	18% 8% 2 5% 2 2 3 3 4 5% 47%	2650
November	1st to 10th	Night	11% 6% 1 5% 3 3 3 2 5% 5% 55%	2666
	11th to 20th	Night	14% 5% 2 5% 4 4 4 3 4 6% 50%	2730
	21st to end	Night	18% 9% 3 5% 3 3 3 3 4 6% 42%	2798
December	1st to 10th	Night	12% 9% 3 7% 4 3 4 3 4 6% 46%	4609
	11th to 20th	Night	14% 8% 3 6% 4 5% 4 3 4 6% 42%	5199
	21st to end	Night	23% 16% 4 9% 5% 4 4 3 4 5% 22%	6996

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	53% 5% 11% 19% 10% 2	3618
	11th to 20th	Day	40% 5% 12% 22% 17% 4	3942
	21st to end	Day	50% 4 10% 15% 15% 5%	4488
February	1st to 10th	Day	49% 6% 11% 22% 10% 1	1800
	11th to 20th	Day	49% 5% 10% 19% 14% 4	1939
	21st to end	Day	44% 5% 10% 22% 15% 4	1650
March	1st to 10th	Day	41% 3 5% 22% 23% 6%	4564
	11th to 20th	Day	32% 4 8% 25% 24% 6%	4980
	21st to end	Day	42% 7% 15% 26% 9% 1	5756
April	1st to 10th	Day	39% 6% 12% 25% 18% 1	2400
	11th to 20th	Day	43% 5% 10% 23% 15% 4	2374
	21st to end	Day	46% 6% 11% 23% 13% 1	2400
May	1st to 10th	Day	46% 9% 11% 22% 11%	5550
	11th to 20th	Day	45% 7% 11% 23% 13% 1	6249
	21st to end	Day	41% 7% 11% 22% 19% 1	6949
June	1st to 10th	Day	34% 8% 13% 26% 17% 2	2800
	11th to 20th	Day	29% 7% 13% 26% 22% 3	2800
	21st to end	Day	27% 9% 18% 25% 15% 5%	2800
July	1st to 10th	Day	33% 6% 11% 30% 18% 2	6291
	11th to 20th	Day	33% 9% 17% 27% 13% 2	6285
	21st to end	Day	34% 8% 18% 29% 10% 1	6359
August	1st to 10th	Day	25% 8% 16% 36% 15%	4197
	11th to 20th	Day	36% 7% 13% 25% 17% 1	3885
	21st to end	Day	27% 7% 14% 34% 15% 3	4311
September	1st to 10th	Day	33% 6% 11% 25% 20% 5%	2400
	11th to 20th	Day	32% 6% 10% 26% 24% 2	2375
	21st to end	Day	30% 5% 9% 26% 26% 3	2191
October	1st to 10th	Day	18% 3 6% 19% 46% 8%	3260
	11th to 20th	Day	23% 3 8% 21% 36% 10%	3240
	21st to end	Day	33% 3 7% 27% 27% 3	3514
November	1st to 10th	Day	32% 4 12% 27% 20% 5%	1852
	11th to 20th	Day	37% 5% 9% 24% 20% 5%	1890
	21st to end	Day	45% 4 9% 25% 15%	1816
December	1st to 10th	Day	36% 4 12% 32% 16%	2626
	11th to 20th	Day	46% 4 12% 22% 15% 1	3005
	21st to end	Day	64% 5% 11% 13% 7% 1	3982
January	1st to 10th	Night	55% 5% 10% 22% 9%	6348
	11th to 20th	Night	51% 5% 7% 23% 13% 2	6021
	21st to end	Night	51% 3 8% 20% 16% 2	6490
February	1st to 10th	Night	51% 5% 10% 20% 12% 1	2600
	11th to 20th	Night	46% 5% 9% 20% 17% 3	2355
	21st to end	Night	45% 4 10% 21% 15% 4	1980
March	1st to 10th	Night	46% 4 6% 22% 20% 2	5331
	11th to 20th	Night	35% 5% 9% 23% 21% 6%	4980
	21st to end	Night	48% 7% 10% 23% 10% 1	5174
April	1st to 10th	Night	36% 5% 11% 26% 17% 3	2000
	11th to 20th	Night	39% 5% 10% 25% 18% 4	1975
	21st to end	Night	44% 5% 9% 24% 16% 2	2000
May	1st to 10th	Night	46% 9% 14% 18% 12% 1	4394
	11th to 20th	Night	39% 7% 13% 24% 15% 2	3652
	21st to end	Night	40% 7% 13% 22% 15% 2	3950
June	1st to 10th	Night	31% 7% 15% 26% 17% 4	1600
	11th to 20th	Night	26% 6% 12% 27% 25% 4	1600
	21st to end	Night	24% 7% 16% 28% 19% 7%	1600
July	1st to 10th	Night	33% 6% 11% 27% 20% 3	3580
	11th to 20th	Night	30% 8% 16% 30% 14% 2	3572
	21st to end	Night	32% 8% 21% 26% 12% 1	4184
August	1st to 10th	Night	21% 8% 18% 33% 18% 1	2938
	11th to 20th	Night	34% 6% 14% 25% 18% 2	3230
	21st to end	Night	23% 6% 15% 34% 19% 3	3586
September	1st to 10th	Night	33% 5% 10% 25% 22% 6%	2000
	11th to 20th	Night	30% 5% 9% 24% 27% 3	2004
	21st to end	Night	30% 6% 9% 22% 27% 5%	2205
October	1st to 10th	Night	15% 3 6% 17% 50% 9%	3920
	11th to 20th	Night	22% 3 7% 22% 36% 10%	3899
	21st to end	Night	31% 4 9% 24% 27% 5%	4274
November	1st to 10th	Night	31% 4 12% 25% 23% 6%	2666
	11th to 20th	Night	37% 4 8% 24% 23% 4	2730
	21st to end	Night	43% 4 10% 24% 17% 2	2798
December	1st to 10th	Night	39% 5% 10% 31% 15% 1	4609
	11th to 20th	Night	43% 4 13% 21% 18% 1	5201
	21st to end	Night	63% 6% 12% 13% 5% 1	6996

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% 18% 34% 18% 6% 1	300
	11th to 20th	Day	25% 15% 42% 15% 2	300
	21st to end	Day	20% 18% 42% 16% 4	330
February	1st to 10th	Day	24% 16% 41% 16% 3	300
	11th to 20th	Day	25% 22% 32% 14% 6% 1	300
	21st to end	Day	24% 18% 39% 17% 2	249
March	1st to 10th	Day	18% 18% 45% 15% 4	300
	11th to 20th	Day	30% 17% 34% 14% 5% 1	300
	21st to end	Day	28% 17% 32% 17% 5%	454
April	1st to 10th	Day	21% 13% 37% 20% 9%	500
	11th to 20th	Day	23% 14% 32% 19% 11%	492
	21st to end	Day	23% 11% 36% 21% 9% 1	500
May	1st to 10th	Day	19% 13% 29% 29% 10% 1	503
	11th to 20th	Day	19% 9% 29% 24% 15% 4	690
	21st to end	Day	13% 5% 30% 31% 14% 7%	789
June	1st to 10th	Day	13% 5% 20% 29% 25% 7%	730
	11th to 20th	Day	9% 3 19% 40% 21% 8%	730
	21st to end	Day	5% 5% 25% 37% 21% 7%	730
July	1st to 10th	Day	11% 2 13% 26% 32% 16%	721
	11th to 20th	Day	6% 3 16% 37% 30% 8%	718
	21st to end	Day	9% 2 14% 36% 31% 9%	794
August	1st to 10th	Day	9% 2 14% 36% 30% 9%	716
	11th to 20th	Day	11% 3 14% 28% 33% 11%	519
	21st to end	Day	9% 2 11% 29% 36% 12%	583
September	1st to 10th	Day	13% 2 14% 29% 32% 10%	530
	11th to 20th	Day	8% 2 11% 29% 33% 16%	530
	21st to end	Day	10% 8% 18% 30% 23% 11%	521
October	1st to 10th	Day	12% 6% 22% 37% 16% 7%	330
	11th to 20th	Day	16% 13% 32% 25% 12% 2	330
	21st to end	Day	31% 18% 25% 21% 6%	363
November	1st to 10th	Day	16% 11% 32% 27% 10% 4	330
	11th to 20th	Day	18% 17% 33% 20% 10% 2	330
	21st to end	Day	27% 15% 28% 21% 9% 1	330
December	1st to 10th	Day	16% 18% 37% 19% 6% 3	306
	11th to 20th	Day	23% 14% 35% 22% 4 1	300
	21st to end	Day	31% 16% 35% 14% 4 1	330
January	1st to 10th	Night	20% 13% 39% 24% 5%	1000
	11th to 20th	Night	21% 16% 36% 22% 4	1000
	21st to end	Night	18% 13% 40% 27% 2	1100
February	1st to 10th	Night	22% 13% 36% 26% 3	1000
	11th to 20th	Night	21% 14% 39% 25% 1	799
	21st to end	Night	20% 14% 40% 25% 2	660
March	1st to 10th	Night	22% 13% 36% 25% 4	784
	11th to 20th	Night	21% 11% 36% 26% 5%	600
	21st to end	Night	26% 10% 31% 28% 5%	660
April	1st to 10th	Night	17% 11% 38% 28% 6%	600
	11th to 20th	Night	17% 10% 35% 28% 10%	593
	21st to end	Night	22% 6% 38% 27% 7%	600
May	1st to 10th	Night	19% 6% 30% 36% 10% 1	600
	11th to 20th	Night	18% 5% 24% 36% 16% 1	591
	21st to end	Night	11% 4 22% 40% 20% 3	650
June	1st to 10th	Night	9% 3 19% 43% 25% 1	600
	11th to 20th	Night	8% 3 18% 49% 22% 1	600
	21st to end	Night	5% 2 22% 44% 25% 2	600
July	1st to 10th	Night	11% 1 9% 37% 35% 7%	585
	11th to 20th	Night	6% 2 12% 45% 33% 3	582
	21st to end	Night	7% 2 12% 42% 34% 3	657
August	1st to 10th	Night	7% 1 10% 44% 35% 3	597
	11th to 20th	Night	7% 2 10% 41% 37% 4	594
	21st to end	Night	6% 2 9% 39% 40% 5%	660
September	1st to 10th	Night	13% 2 12% 37% 31% 6%	600
	11th to 20th	Night	9% 3 12% 34% 37% 5%	604
	21st to end	Night	12% 4 20% 32% 28% 4	800
October	1st to 10th	Night	8% 4 24% 35% 25% 4	800
	11th to 20th	Night	16% 8% 30% 31% 14% 1	800
	21st to end	Night	23% 10% 32% 29% 6%	880
November	1st to 10th	Night	13% 8% 35% 33% 10% 1	820
	11th to 20th	Night	17% 12% 32% 30% 8%	840
	21st to end	Night	24% 9% 33% 27% 6% 1	908
December	1st to 10th	Night	22% 10% 34% 29% 5% 1	1011
	11th to 20th	Night	23% 9% 30% 32% 6%	1000
	21st to end	Night	26% 12% 34% 25% 3	1100

Page generated at 2025-11-30 00:00:51. Version ac07

Copyright © 2025 Attilla Danko.