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 2025-01-07.

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%	104847
	Night	14% 6% 2 6% 4 4 4 4 6% 7% 42%	104142
Transparency	Day	39% 6% 12% 24% 16% 3	108488
	Night	39% 5% 12% 24% 17% 3	108640
Seeing	Day	19% 13% 26% 23% 14% 5%	15089
	Night	18% 11% 29% 29% 12% 1	24736

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	17% 5% 2 5% 3 4 4 4 5% 6% 45%	2698
	11th to 20th	Day	14% 11% 3 6% 6% 4 4 4 5% 5% 38%	2840
	21st to end	Day	17% 9% 3 8% 5% 4 4 4 5% 6% 36%	3124
February	1st to 10th	Day	13% 9% 3 6% 5% 5% 6% 4 5% 7% 38%	1710
	11th to 20th	Day	17% 7% 3 6% 5% 4 4 3 5% 7% 40%	1679
	21st to end	Day	17% 10% 2 6% 5% 4 5% 3 4 6% 40%	1570
March	1st to 10th	Day	21% 9% 2 6% 4 5% 5% 3 5% 6% 35%	3435
	11th to 20th	Day	10% 5% 1 5% 5% 5% 5% 4 6% 7% 48%	3480
	21st to end	Day	19% 6% 2 6% 5% 3 4 3 5% 6% 39%	3836
April	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 6% 7% 40%	2280
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 45%	2254
	21st to end	Day	18% 6% 3 6% 5% 3 4 3 6% 6% 41%	2287
May	1st to 10th	Day	22% 7% 3 6% 5% 5% 5% 4 6% 7% 30%	4082
	11th to 20th	Day	24% 7% 2 6% 4 4 4 4 5% 8% 32%	4225
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 7% 9% 44%	4823
June	1st to 10th	Day	12% 5% 2 5% 5% 4 4 4 8% 9% 43%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 5% 7% 8% 41%	2660
	21st to end	Day	10% 3 2 5% 4 5% 5% 4 7% 11% 44%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 42%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 7% 11% 41%	4226
	21st to end	Day	10% 6% 3 7% 6% 5% 5% 4 6% 8% 38%	4466
August	1st to 10th	Day	15% 5% 2 7% 5% 5% 6% 5% 7% 9% 34%	4104
	11th to 20th	Day	9% 4 2 7% 5% 5% 5% 5% 7% 9% 42%	3929
	21st to end	Day	11% 5% 2 5% 4 4 4 4 6% 8% 48%	4180
September	1st to 10th	Day	16% 5% 1 6% 4 4 4 4 5% 6% 46%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 6% 7% 47%	2271
	21st to end	Day	21% 6% 2 6% 4 4 4 3 5% 7% 38%	1986
October	1st to 10th	Day	17% 5% 2 5% 3 4 3 3 4 8% 46%	1900
	11th to 20th	Day	16% 4 2 5% 4 4 4 3 4 6% 49%	1900
	21st to end	Day	14% 5% 2 5% 3 3 4 3 4 6% 51%	2090
November	1st to 10th	Day	12% 6% 2 4 4 3 3 3 5% 7% 51%	1892
	11th to 20th	Day	14% 6% 2 5% 3 3 4 3 5% 6% 48%	1730
	21st to end	Day	14% 6% 2 5% 4 4 5% 3 5% 6% 46%	1600
December	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 5% 7% 48%	2600
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 4 7% 40%	2990
	21st to end	Day	17% 8% 2 7% 5% 4 5% 3 6% 8% 35%	3960
January	1st to 10th	Night	12% 8% 3 6% 4 5% 4 3 6% 6% 44%	4379
	11th to 20th	Night	19% 7% 2 5% 4 3 3 3 5% 7% 44%	4120
	21st to end	Night	18% 10% 3 6% 4 3 4 3 5% 6% 38%	4532
February	1st to 10th	Night	14% 8% 2 7% 4 4 4 4 5% 7% 41%	2470
	11th to 20th	Night	17% 8% 2 6% 4 4 5% 4 5% 5% 41%	2385
	21st to end	Night	18% 8% 3 5% 4 4 4 4 4 6% 40%	1881
March	1st to 10th	Night	20% 8% 2 6% 4 4 4 4 5% 6% 37%	3418
	11th to 20th	Night	11% 5% 2 4 4 5% 4 3 5% 7% 49%	3480
	21st to end	Night	14% 9% 2 6% 3 4 3 3 4 5% 47%	3796
April	1st to 10th	Night	14% 8% 2 7% 4 5% 4 4 7% 6% 39%	1900
	11th to 20th	Night	12% 5% 2 7% 4 4 4 4 6% 8% 44%	1875
	21st to end	Night	16% 5% 2 5% 4 4 4 4 6% 8% 43%	1900
May	1st to 10th	Night	22% 8% 3 7% 5% 4 4 3 5% 8% 30%	2822
	11th to 20th	Night	24% 9% 3 7% 4 3 4 3 5% 7% 31%	2668
	21st to end	Night	11% 5% 2 6% 4 4 5% 5% 8% 10% 41%	2732
June	1st to 10th	Night	11% 5% 2 5% 4 4 5% 5% 7% 8% 44%	1520
	11th to 20th	Night	11% 6% 2 5% 4 5% 5% 5% 8% 8% 42%	1520
	21st to end	Night	8% 5% 2 5% 4 4 6% 3 8% 11% 44%	1520
July	1st to 10th	Night	6% 5% 2 6% 6% 5% 7% 6% 8% 11% 39%	2520
	11th to 20th	Night	6% 6% 2 7% 5% 5% 6% 6% 7% 11% 38%	2730
	21st to end	Night	10% 6% 3 6% 4 5% 6% 5% 7% 9% 38%	3087
August	1st to 10th	Night	15% 5% 2 7% 5% 6% 6% 5% 6% 9% 33%	2825
	11th to 20th	Night	9% 7% 2 8% 5% 5% 5% 4 7% 9% 40%	2867
	21st to end	Night	13% 4 2 5% 3 4 5% 3 5% 8% 48%	3476
September	1st to 10th	Night	15% 5% 2 6% 4 3 4 4 6% 7% 44%	1900
	11th to 20th	Night	11% 6% 2 6% 4 3 3 3 3 6% 53%	1905
	21st to end	Night	21% 7% 2 6% 4 3 3 3 4 6% 41%	2194
October	1st to 10th	Night	20% 5% 2 5% 3 3 3 3 4 6% 46%	2280
	11th to 20th	Night	14% 4 2 5% 3 3 3 3 4 6% 52%	2280
	21st to end	Night	14% 5% 2 5% 3 3 3 3 5% 7% 51%	2508
November	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 5% 6% 54%	2406
	11th to 20th	Night	14% 7% 2 5% 3 3 4 4 5% 6% 48%	2665
	21st to end	Night	14% 4 2 6% 4 3 5% 4 5% 8% 46%	2800
December	1st to 10th	Night	10% 4 2 5% 3 4 5% 3 5% 7% 51%	4580
	11th to 20th	Night	19% 7% 2 5% 4 4 4 4 5% 7% 39%	5205
	21st to end	Night	16% 7% 2 7% 4 5% 6% 4 7% 8% 34%	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	39% 4 8% 30% 14% 4	2699
	11th to 20th	Day	47% 4 9% 20% 16% 5%	2840
	21st to end	Day	49% 4 11% 23% 12% 2	3124
February	1st to 10th	Day	44% 5% 13% 23% 12% 2	1710
	11th to 20th	Day	45% 5% 9% 24% 16% 3	1688
	21st to end	Day	46% 4 11% 20% 15% 4	1570
March	1st to 10th	Day	49% 5% 9% 21% 13% 3	3435
	11th to 20th	Day	33% 5% 8% 28% 21% 4	3480
	21st to end	Day	46% 4 11% 21% 16% 3	3836
April	1st to 10th	Day	40% 6% 12% 19% 19% 4	2280
	11th to 20th	Day	37% 5% 11% 23% 19% 5%	2254
	21st to end	Day	44% 5% 9% 23% 16% 4	2287
May	1st to 10th	Day	50% 7% 10% 21% 10% 1	4120
	11th to 20th	Day	49% 7% 12% 23% 8% 1	4229
	21st to end	Day	33% 8% 15% 25% 17% 2	4837
June	1st to 10th	Day	35% 7% 14% 26% 16% 1	2660
	11th to 20th	Day	38% 8% 15% 24% 14% 2	2660
	21st to end	Day	32% 8% 16% 26% 16% 2	2660
July	1st to 10th	Day	34% 9% 17% 24% 12% 4	4370
	11th to 20th	Day	36% 7% 14% 30% 11% 1	4153
	21st to end	Day	43% 6% 10% 22% 18% 1	4324
August	1st to 10th	Day	44% 7% 15% 25% 8% 1	4091
	11th to 20th	Day	36% 8% 12% 28% 15% 1	3968
	21st to end	Day	34% 6% 14% 27% 17% 2	4180
September	1st to 10th	Day	39% 6% 11% 19% 21% 4	2280
	11th to 20th	Day	35% 5% 8% 27% 21% 3	2271
	21st to end	Day	46% 5% 9% 19% 18% 2	1986
October	1st to 10th	Day	37% 3 7% 21% 27% 5%	3160
	11th to 20th	Day	27% 3 8% 29% 24% 9%	3140
	21st to end	Day	23% 3 10% 30% 27% 6%	3428
November	1st to 10th	Day	33% 4 12% 26% 22% 4	1892
	11th to 20th	Day	37% 2 12% 23% 22% 4	1730
	21st to end	Day	38% 4 11% 28% 16% 2	1600
December	1st to 10th	Day	36% 5% 12% 30% 13% 4	2600
	11th to 20th	Day	45% 3 13% 26% 10% 2	2986
	21st to end	Day	46% 5% 16% 19% 14% 1	3960
January	1st to 10th	Night	38% 4 10% 28% 17% 3	4379
	11th to 20th	Night	41% 3 10% 25% 17% 3	4120
	21st to end	Night	46% 3 9% 27% 13% 1	4532
February	1st to 10th	Night	42% 5% 12% 25% 14% 2	2470
	11th to 20th	Night	44% 4 9% 23% 16% 4	2387
	21st to end	Night	45% 3 11% 22% 14% 5%	1881
March	1st to 10th	Night	47% 4 9% 27% 11% 2	3418
	11th to 20th	Night	33% 5% 9% 30% 21% 3	3480
	21st to end	Night	40% 4 9% 24% 19% 5%	3796
April	1st to 10th	Night	42% 5% 10% 20% 19% 4	1900
	11th to 20th	Night	38% 5% 12% 21% 19% 6%	1875
	21st to end	Night	39% 5% 12% 26% 13% 4	1900
May	1st to 10th	Night	53% 6% 10% 19% 10% 3	2849
	11th to 20th	Night	51% 7% 11% 20% 9% 1	2669
	21st to end	Night	34% 8% 17% 26% 12% 3	2739
June	1st to 10th	Night	35% 8% 11% 26% 17% 2	1520
	11th to 20th	Night	36% 8% 14% 26% 14% 2	1520
	21st to end	Night	33% 6% 16% 25% 18% 3	1520
July	1st to 10th	Night	36% 8% 20% 18% 12% 5%	2480
	11th to 20th	Night	37% 9% 18% 22% 13% 1	2680
	21st to end	Night	40% 8% 15% 19% 17% 1	2988
August	1st to 10th	Night	45% 8% 15% 23% 8% 1	2814
	11th to 20th	Night	39% 7% 11% 27% 15% 1	2894
	21st to end	Night	35% 5% 13% 29% 16% 2	3476
September	1st to 10th	Night	38% 6% 11% 21% 19% 5%	1900
	11th to 20th	Night	35% 4 9% 28% 23% 3	1905
	21st to end	Night	45% 5% 9% 20% 17% 3	2194
October	1st to 10th	Night	40% 4 9% 22% 21% 3	3800
	11th to 20th	Night	24% 3 11% 23% 31% 7%	3779
	21st to end	Night	23% 3 9% 32% 27% 6%	4120
November	1st to 10th	Night	32% 4 10% 26% 23% 5%	2406
	11th to 20th	Night	36% 4 7% 26% 22% 6%	2665
	21st to end	Night	36% 4 12% 25% 19% 3	2800
December	1st to 10th	Night	33% 4 13% 31% 18% 1	4580
	11th to 20th	Night	45% 4 13% 20% 16% 3	5208
	21st to end	Night	45% 6% 15% 19% 14% 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	30% 26% 28% 13% 3	231
	11th to 20th	Day	31% 25% 30% 13% 2	270
	21st to end	Day	25% 32% 29% 11% 2 1	297
February	1st to 10th	Day	22% 26% 36% 13% 3	270
	11th to 20th	Day	33% 29% 30% 6% 2	286
	21st to end	Day	30% 19% 33% 16% 2	382
March	1st to 10th	Day	24% 23% 27% 22% 3	460
	11th to 20th	Day	25% 23% 30% 16% 4 2	460
	21st to end	Day	22% 20% 34% 17% 5% 1	506
April	1st to 10th	Day	22% 25% 27% 18% 7% 1	460
	11th to 20th	Day	17% 19% 29% 19% 13% 3	452
	21st to end	Day	24% 16% 29% 19% 9% 2	460
May	1st to 10th	Day	24% 16% 27% 19% 10% 3	463
	11th to 20th	Day	22% 11% 28% 21% 14% 4	487
	21st to end	Day	20% 7% 22% 25% 21% 6%	529
June	1st to 10th	Day	13% 8% 27% 26% 19% 6%	490
	11th to 20th	Day	14% 8% 26% 29% 17% 6%	490
	21st to end	Day	9% 7% 29% 31% 17% 7%	490
July	1st to 10th	Day	11% 6% 16% 31% 26% 12%	485
	11th to 20th	Day	6% 2 21% 31% 31% 8%	484
	21st to end	Day	12% 5% 20% 32% 22% 8%	532
August	1st to 10th	Day	13% 5% 18% 28% 22% 14%	486
	11th to 20th	Day	12% 4 21% 30% 22% 11%	479
	21st to end	Day	9% 4 20% 30% 24% 14%	539
September	1st to 10th	Day	17% 8% 18% 26% 21% 10%	490
	11th to 20th	Day	15% 5% 18% 32% 19% 11%	490
	21st to end	Day	26% 10% 22% 25% 13% 4	490
October	1st to 10th	Day	20% 7% 21% 26% 20% 6%	490
	11th to 20th	Day	17% 14% 24% 29% 13% 3	490
	21st to end	Day	16% 12% 34% 25% 11% 3	539
November	1st to 10th	Day	18% 11% 31% 27% 9% 4	462
	11th to 20th	Day	21% 16% 33% 19% 10% 1	330
	21st to end	Day	24% 20% 32% 18% 6% 1	200
December	1st to 10th	Day	20% 24% 37% 14% 4 1	200
	11th to 20th	Day	23% 26% 27% 20% 5%	200
	21st to end	Day	22% 20% 32% 19% 6% 1	220
January	1st to 10th	Night	20% 20% 39% 18% 3	785
	11th to 20th	Night	24% 15% 32% 25% 4	760
	21st to end	Night	19% 17% 40% 21% 2	836
February	1st to 10th	Night	17% 18% 36% 27% 2	760
	11th to 20th	Night	24% 21% 36% 17% 2	743
	21st to end	Night	26% 17% 37% 18% 3	628
March	1st to 10th	Night	20% 17% 37% 22% 3	760
	11th to 20th	Night	24% 17% 33% 21% 5% 1	760
	21st to end	Night	21% 16% 38% 21% 4 1	836
April	1st to 10th	Night	19% 19% 36% 22% 4	760
	11th to 20th	Night	16% 12% 36% 27% 8% 1	751
	21st to end	Night	20% 12% 32% 29% 8%	760
May	1st to 10th	Night	23% 7% 25% 34% 11%	579
	11th to 20th	Night	21% 5% 26% 36% 11% 1	482
	21st to end	Night	15% 4 24% 39% 18% 1	411
June	1st to 10th	Night	12% 2 26% 39% 20% 1	380
	11th to 20th	Night	13% 4 19% 40% 23% 1	380
	21st to end	Night	9% 3 23% 46% 18% 1	380
July	1st to 10th	Night	10% 3 15% 41% 27% 4	370
	11th to 20th	Night	7% 2 12% 41% 36% 3	485
	21st to end	Night	8% 2 17% 42% 28% 3	624
August	1st to 10th	Night	11% 3 11% 43% 29% 3	567
	11th to 20th	Night	9% 4 13% 40% 30% 3	607
	21st to end	Night	13% 2 15% 39% 26% 4	836
September	1st to 10th	Night	17% 3 17% 33% 27% 4	760
	11th to 20th	Night	14% 3 17% 35% 28% 4	760
	21st to end	Night	23% 5% 22% 28% 21% 1	760
October	1st to 10th	Night	21% 6% 21% 28% 21% 3	760
	11th to 20th	Night	16% 11% 25% 33% 14% 1	760
	21st to end	Night	18% 11% 30% 30% 11% 1	836
November	1st to 10th	Night	14% 9% 34% 31% 11% 1	780
	11th to 20th	Night	19% 13% 33% 27% 8% 1	800
	21st to end	Night	16% 15% 34% 27% 7%	800
December	1st to 10th	Night	21% 15% 35% 23% 6%	800
	11th to 20th	Night	20% 12% 38% 27% 4	800
	21st to end	Night	20% 13% 34% 31% 2	880

Page generated at 2025-01-04 03:23:58. Version ac07

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