Murphicus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Murphicus Observatory clear sky chart from 2005-11-06 to 2026-05-02.

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	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	131824
	Night	14% 6% 2 6% 4 4 4 4 6% 7% 43%	130663
Transparency	Day	39% 6% 11% 24% 16% 3	135421
	Night	39% 5% 11% 24% 18% 3	135136
Seeing	Day	19% 14% 26% 23% 13% 5%	16810
	Night	18% 11% 29% 29% 12% 1	26486

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% 4 2 6% 4 4 5% 4 5% 7% 45%	4919
	11th to 20th	Day	13% 9% 3 5% 4 3 3 3 4 5% 48%	5280
	21st to end	Day	13% 6% 2 7% 4 4 5% 5% 6% 7% 40%	5780
February	1st to 10th	Day	12% 9% 3 6% 5% 4 6% 4 5% 7% 40%	1890
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 3 5% 6% 39%	1861
	21st to end	Day	16% 10% 2 6% 5% 3 4 3 4 6% 41%	1730
March	1st to 10th	Day	17% 7% 2 5% 4 5% 5% 3 5% 6% 41%	5045
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 5% 7% 48%	5090
	21st to end	Day	15% 6% 2 6% 5% 5% 5% 4 5% 7% 39%	5621
April	1st to 10th	Day	13% 7% 3 6% 5% 5% 4 4 6% 7% 40%	2520
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2494
	21st to end	Day	17% 6% 3 6% 5% 3 4 3 6% 6% 41%	2528
May	1st to 10th	Day	19% 7% 3 6% 4 5% 5% 5% 7% 9% 31%	5875
	11th to 20th	Day	23% 7% 2 6% 4 4 4 4 6% 10% 31%	6061
	21st to end	Day	16% 5% 2 6% 4 4 5% 4 7% 9% 38%	6934
June	1st to 10th	Day	12% 5% 2 5% 5% 4 4 4 7% 9% 43%	2800
	11th to 20th	Day	11% 5% 2 6% 5% 5% 6% 4 7% 8% 41%	2800
	21st to end	Day	10% 3 2 5% 4 5% 5% 4 7% 11% 45%	2800
July	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 5% 8% 10% 44%	6360
	11th to 20th	Day	8% 6% 2 7% 6% 6% 7% 5% 8% 12% 32%	6048
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 10% 40%	6424
August	1st to 10th	Day	15% 6% 2 7% 5% 5% 6% 4 7% 9% 35%	4234
	11th to 20th	Day	10% 4 2 7% 5% 5% 5% 5% 7% 9% 41%	4055
	21st to end	Day	11% 5% 2 5% 4 4 4 4 6% 7% 49%	4312
September	1st to 10th	Day	15% 5% 1 6% 4 4 4 3 5% 6% 47%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 6% 7% 47%	2390
	21st to end	Day	22% 6% 2 6% 4 4 4 3 5% 7% 37%	2090
October	1st to 10th	Day	16% 5% 2 5% 3 4 3 3 4 8% 47%	2000
	11th to 20th	Day	16% 4 2 5% 3 4 4 3 4 6% 49%	2000
	21st to end	Day	14% 5% 2 5% 3 3 4 3 4 6% 51%	2200
November	1st to 10th	Day	11% 5% 2 4 4 3 3 3 5% 7% 51%	1989
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 5% 6% 49%	1816
	21st to end	Day	14% 6% 2 5% 4 4 5% 3 5% 6% 46%	1680
December	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 5% 7% 47%	2680
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 4 7% 40%	3070
	21st to end	Day	17% 8% 2 7% 5% 4 5% 3 6% 8% 35%	4048
January	1st to 10th	Night	9% 7% 2 6% 5% 5% 5% 4 6% 7% 43%	7959
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 6% 49%	7680
	21st to end	Night	12% 7% 2 5% 3 3 4 4 5% 6% 47%	8401
February	1st to 10th	Night	13% 8% 2 7% 4 4 5% 4 5% 7% 41%	2730
	11th to 20th	Night	17% 8% 2 6% 4 3 5% 4 5% 5% 40%	2643
	21st to end	Night	16% 8% 3 5% 4 4 4 4 5% 6% 41%	2073
March	1st to 10th	Night	16% 7% 2 6% 4 3 3 3 4 6% 46%	5028
	11th to 20th	Night	10% 5% 2 5% 4 5% 4 3 5% 6% 49%	5090
	21st to end	Night	12% 7% 2 6% 4 5% 4 4 6% 6% 44%	5553
April	1st to 10th	Night	15% 7% 2 7% 4 5% 4 4 6% 6% 39%	2100
	11th to 20th	Night	12% 5% 3 7% 4 4 4 4 6% 8% 43%	2075
	21st to end	Night	15% 5% 2 5% 4 4 4 4 6% 8% 44%	2100
May	1st to 10th	Night	21% 8% 3 7% 5% 5% 5% 4 5% 8% 29%	4051
	11th to 20th	Night	25% 8% 3 6% 4 4 4 4 6% 8% 30%	3832
	21st to end	Night	17% 7% 2 6% 4 4 5% 5% 7% 8% 35%	3920
June	1st to 10th	Night	11% 5% 2 5% 4 4 5% 5% 7% 8% 44%	1600
	11th to 20th	Night	12% 6% 2 5% 4 5% 5% 5% 7% 8% 42%	1600
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 8% 10% 44%	1600
July	1st to 10th	Night	7% 6% 3 7% 5% 5% 7% 5% 8% 10% 39%	3598
	11th to 20th	Night	8% 7% 3 9% 6% 6% 6% 6% 8% 10% 30%	3905
	21st to end	Night	8% 5% 2 6% 4 5% 6% 5% 7% 10% 42%	4427
August	1st to 10th	Night	15% 5% 2 7% 5% 6% 6% 5% 6% 9% 33%	2915
	11th to 20th	Night	9% 7% 2 7% 5% 5% 5% 4 7% 9% 40%	2959
	21st to end	Night	13% 4 2 5% 3 4 4 3 6% 8% 47%	3586
September	1st to 10th	Night	15% 4 2 6% 4 3 4 4 6% 7% 45%	2000
	11th to 20th	Night	12% 6% 2 6% 3 3 3 3 3 6% 52%	2005
	21st to end	Night	21% 7% 2 7% 4 4 3 3 5% 6% 39%	2310
October	1st to 10th	Night	19% 5% 2 5% 3 3 3 3 4 6% 48%	2400
	11th to 20th	Night	15% 4 2 5% 3 3 3 2 4 6% 53%	2400
	21st to end	Night	14% 5% 2 5% 3 3 3 3 5% 7% 51%	2640
November	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 5% 6% 54%	2529
	11th to 20th	Night	14% 7% 2 5% 3 3 4 4 5% 7% 48%	2799
	21st to end	Night	13% 4 2 6% 4 3 5% 4 5% 8% 46%	2940
December	1st to 10th	Night	10% 4 2 5% 3 4 5% 3 5% 7% 51%	4720
	11th to 20th	Night	19% 7% 2 5% 4 4 4 4 5% 7% 39%	5345
	21st to end	Night	15% 7% 2 7% 4 5% 5% 4 7% 8% 34%	7150

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	39% 4 9% 26% 17% 5%	4920
	11th to 20th	Day	39% 3 7% 21% 20% 10%	5280
	21st to end	Day	41% 3 10% 29% 13% 3	5780
February	1st to 10th	Day	43% 5% 12% 24% 13% 3	1890
	11th to 20th	Day	46% 5% 9% 22% 16% 2	1870
	21st to end	Day	45% 4 10% 22% 14% 4	1730
March	1st to 10th	Day	43% 4 8% 21% 16% 8%	5045
	11th to 20th	Day	34% 5% 9% 26% 20% 6%	5090
	21st to end	Day	43% 4 10% 18% 18% 5%	5621
April	1st to 10th	Day	41% 5% 12% 20% 18% 4	2520
	11th to 20th	Day	37% 5% 11% 23% 19% 5%	2494
	21st to end	Day	43% 5% 9% 24% 15% 3	2528
May	1st to 10th	Day	47% 8% 13% 20% 10% 2	5910
	11th to 20th	Day	48% 6% 11% 25% 9% 1	6065
	21st to end	Day	40% 7% 13% 22% 16% 2	6949
June	1st to 10th	Day	35% 7% 14% 26% 17% 1	2800
	11th to 20th	Day	38% 7% 15% 23% 14% 2	2800
	21st to end	Day	32% 8% 15% 26% 17% 2	2800
July	1st to 10th	Day	34% 9% 15% 23% 15% 4	6290
	11th to 20th	Day	41% 10% 16% 24% 8% 1	5975
	21st to end	Day	37% 7% 10% 23% 22% 1	6240
August	1st to 10th	Day	44% 7% 14% 25% 9%	4221
	11th to 20th	Day	36% 8% 12% 28% 15% 1	4094
	21st to end	Day	34% 6% 14% 27% 17% 2	4312
September	1st to 10th	Day	38% 6% 11% 20% 21% 4	2400
	11th to 20th	Day	35% 5% 8% 28% 21% 3	2390
	21st to end	Day	47% 5% 9% 18% 18% 2	2090
October	1st to 10th	Day	36% 3 7% 21% 28% 5%	3260
	11th to 20th	Day	27% 3 8% 29% 24% 9%	3240
	21st to end	Day	23% 3 10% 30% 28% 5%	3538
November	1st to 10th	Day	32% 4 12% 26% 22% 4	1989
	11th to 20th	Day	37% 2 11% 23% 22% 4	1816
	21st to end	Day	38% 4 12% 28% 16% 2	1680
December	1st to 10th	Day	36% 5% 12% 29% 13% 4	2680
	11th to 20th	Day	45% 4 13% 26% 10% 2	3066
	21st to end	Day	45% 5% 16% 20% 14% 1	4048
January	1st to 10th	Night	39% 4 9% 26% 20% 3	7960
	11th to 20th	Night	37% 3 7% 23% 24% 7%	7680
	21st to end	Night	37% 3 8% 32% 18% 3	8401
February	1st to 10th	Night	42% 4 12% 24% 15% 2	2730
	11th to 20th	Night	45% 4 10% 23% 15% 4	2645
	21st to end	Night	44% 3 11% 22% 15% 5%	2073
March	1st to 10th	Night	40% 3 9% 26% 14% 8%	5028
	11th to 20th	Night	34% 4 10% 27% 19% 6%	5090
	21st to end	Night	40% 4 10% 22% 20% 5%	5553
April	1st to 10th	Night	43% 5% 10% 21% 18% 4	2100
	11th to 20th	Night	38% 5% 12% 21% 18% 5%	2075
	21st to end	Night	38% 5% 13% 27% 14% 4	2100
May	1st to 10th	Night	53% 6% 12% 17% 9% 4	4078
	11th to 20th	Night	50% 6% 10% 22% 10% 1	3833
	21st to end	Night	44% 7% 14% 24% 9% 2	3927
June	1st to 10th	Night	36% 8% 11% 26% 18% 3	1600
	11th to 20th	Night	37% 7% 14% 25% 14% 2	1600
	21st to end	Night	33% 7% 15% 25% 18% 2	1600
July	1st to 10th	Night	38% 9% 16% 18% 15% 3	3560
	11th to 20th	Night	46% 11% 18% 16% 9% 1	3858
	21st to end	Night	35% 7% 14% 23% 20% 1	4297
August	1st to 10th	Night	45% 8% 15% 23% 9% 1	2904
	11th to 20th	Night	39% 7% 11% 27% 15% 1	2986
	21st to end	Night	35% 5% 13% 30% 16% 2	3586
September	1st to 10th	Night	37% 6% 11% 22% 19% 5%	2000
	11th to 20th	Night	35% 4 9% 27% 23% 2	2005
	21st to end	Night	47% 5% 9% 19% 17% 2	2310
October	1st to 10th	Night	40% 4 9% 23% 22% 3	3920
	11th to 20th	Night	25% 3 11% 23% 31% 7%	3899
	21st to end	Night	24% 3 9% 32% 27% 6%	4252
November	1st to 10th	Night	32% 4 10% 26% 23% 5%	2529
	11th to 20th	Night	36% 4 7% 25% 22% 5%	2799
	21st to end	Night	36% 4 12% 26% 19% 3	2940
December	1st to 10th	Night	33% 4 13% 30% 18% 1	4720
	11th to 20th	Night	44% 4 12% 20% 16% 3	5348
	21st to end	Night	45% 6% 15% 19% 14% 1	7150

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	32% 24% 27% 14% 2	267
	11th to 20th	Day	31% 28% 29% 11% 2	330
	21st to end	Day	25% 31% 31% 10% 2 1	363
February	1st to 10th	Day	23% 27% 34% 13% 3	330
	11th to 20th	Day	38% 26% 28% 5% 2	348
	21st to end	Day	28% 18% 35% 16% 2	446
March	1st to 10th	Day	25% 23% 28% 21% 3	540
	11th to 20th	Day	27% 21% 30% 17% 4 2	540
	21st to end	Day	22% 21% 34% 17% 5% 1	594
April	1st to 10th	Day	23% 26% 25% 18% 7% 1	540
	11th to 20th	Day	18% 20% 30% 18% 12% 3	532
	21st to end	Day	24% 16% 29% 19% 10% 2	540
May	1st to 10th	Day	24% 16% 28% 19% 9% 3	507
	11th to 20th	Day	22% 12% 28% 20% 14% 4	527
	21st to end	Day	21% 8% 23% 24% 19% 5%	573
June	1st to 10th	Day	13% 8% 28% 25% 19% 6%	530
	11th to 20th	Day	15% 8% 25% 29% 17% 6%	530
	21st to end	Day	9% 7% 27% 30% 19% 7%	530
July	1st to 10th	Day	10% 5% 16% 31% 26% 11%	525
	11th to 20th	Day	7% 2 20% 31% 30% 10%	524
	21st to end	Day	12% 4 20% 32% 24% 9%	576
August	1st to 10th	Day	14% 4 18% 29% 22% 13%	526
	11th to 20th	Day	14% 4 20% 30% 22% 10%	519
	21st to end	Day	9% 4 21% 29% 23% 13%	583
September	1st to 10th	Day	16% 8% 18% 27% 20% 10%	530
	11th to 20th	Day	15% 4 18% 32% 20% 11%	530
	21st to end	Day	28% 9% 22% 25% 13% 4	530
October	1st to 10th	Day	18% 6% 21% 27% 19% 8%	530
	11th to 20th	Day	18% 15% 24% 28% 12% 3	530
	21st to end	Day	17% 13% 33% 24% 10% 2	583
November	1st to 10th	Day	17% 13% 32% 26% 8% 4	499
	11th to 20th	Day	22% 16% 33% 19% 9% 1	356
	21st to end	Day	25% 20% 32% 17% 6% 1	220
December	1st to 10th	Day	20% 24% 38% 13% 4 1	220
	11th to 20th	Day	23% 24% 29% 20% 5%	220
	21st to end	Day	24% 20% 32% 17% 6% 1	242
January	1st to 10th	Night	20% 19% 39% 19% 3	840
	11th to 20th	Night	23% 17% 33% 23% 4	840
	21st to end	Night	19% 17% 42% 20% 2	924
February	1st to 10th	Night	18% 17% 38% 26% 2	840
	11th to 20th	Night	25% 21% 35% 17% 2	823
	21st to end	Night	25% 16% 38% 18% 2	692
March	1st to 10th	Night	22% 17% 37% 22% 3	840
	11th to 20th	Night	23% 17% 33% 21% 5%	840
	21st to end	Night	20% 17% 39% 20% 4 1	924
April	1st to 10th	Night	20% 18% 36% 22% 4	840
	11th to 20th	Night	17% 12% 36% 27% 7% 1	831
	21st to end	Night	19% 12% 31% 30% 8%	840
May	1st to 10th	Night	22% 7% 25% 34% 11%	612
	11th to 20th	Night	22% 5% 25% 36% 11% 1	508
	21st to end	Night	15% 4 24% 38% 17% 1	433
June	1st to 10th	Night	13% 3 25% 39% 20% 1	400
	11th to 20th	Night	14% 4 19% 39% 23% 1	400
	21st to end	Night	9% 3 23% 45% 20% 2	400
July	1st to 10th	Night	11% 3 15% 40% 28% 3	390
	11th to 20th	Night	7% 2 12% 40% 36% 3	512
	21st to end	Night	8% 2 16% 43% 29% 3	657
August	1st to 10th	Night	11% 3 10% 44% 29% 3	597
	11th to 20th	Night	10% 4 12% 41% 30% 4	639
	21st to end	Night	13% 2 16% 39% 26% 4	880
September	1st to 10th	Night	17% 2 17% 33% 27% 4	800
	11th to 20th	Night	14% 3 16% 36% 28% 3	800
	21st to end	Night	23% 5% 22% 29% 20% 1	800
October	1st to 10th	Night	20% 6% 21% 28% 22% 3	800
	11th to 20th	Night	17% 11% 25% 33% 13% 1	800
	21st to end	Night	18% 10% 30% 31% 11% 1	880
November	1st to 10th	Night	14% 10% 34% 31% 10% 1	820
	11th to 20th	Night	19% 13% 33% 27% 7% 1	840
	21st to end	Night	16% 15% 34% 26% 7%	840
December	1st to 10th	Night	21% 15% 35% 23% 6%	840
	11th to 20th	Night	21% 12% 37% 26% 4	840
	21st to end	Night	20% 14% 35% 29% 2	924

Page generated at 2026-04-29 02:21:43. Version ac07

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