Marra's Frustration Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marra's Frustration Center clear sky chart from 2005-11-06 to 2025-08-05.

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% 9% 3 8% 5% 4 4 4 5% 7% 36%	125754
	Night	15% 10% 3 8% 5% 4 4 3 5% 7% 36%	122297
Transparency	Day	47% 3 10% 24% 14% 2	129392
	Night	47% 3 10% 23% 15% 2	126728
Seeing	Day	19% 11% 27% 23% 14% 6%	16351
	Night	20% 8% 26% 30% 15% 2	26033

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% 18% 8% 12% 4 4 3 3 4 5% 25%	3617
	11th to 20th	Day	13% 14% 6% 14% 6% 5% 4 3 3 4 27%	3910
	21st to end	Day	22% 13% 6% 9% 5% 5% 4 3 4 5% 24%	4466
February	1st to 10th	Day	19% 14% 4 9% 5% 4 4 4 4 6% 28%	1909
	11th to 20th	Day	17% 12% 4 10% 6% 5% 4 3 4 5% 30%	1948
	21st to end	Day	18% 12% 5% 9% 6% 3 4 3 4 5% 30%	1650
March	1st to 10th	Day	17% 14% 6% 10% 4 4 3 2 4 4 31%	4515
	11th to 20th	Day	13% 9% 3 7% 4 4 4 4 5% 7% 40%	4980
	21st to end	Day	17% 10% 3 8% 5% 4 4 3 5% 7% 34%	5465
April	1st to 10th	Day	15% 11% 3 7% 5% 4 4 4 5% 7% 35%	2365
	11th to 20th	Day	15% 9% 3 7% 4 4 3 4 5% 6% 38%	2425
	21st to end	Day	18% 8% 3 6% 5% 4 4 4 5% 7% 36%	2600
May	1st to 10th	Day	20% 9% 4 8% 6% 5% 5% 4 6% 7% 28%	5862
	11th to 20th	Day	20% 9% 3 7% 4 4 4 3 5% 7% 34%	5861
	21st to end	Day	13% 6% 3 7% 6% 5% 6% 5% 7% 9% 32%	6433
June	1st to 10th	Day	12% 5% 3 7% 5% 4 5% 4 7% 8% 40%	2610
	11th to 20th	Day	9% 5% 2 6% 6% 5% 5% 4 7% 8% 43%	2800
	21st to end	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 9% 40%	2800
July	1st to 10th	Day	10% 6% 3 7% 4 4 5% 5% 7% 10% 40%	6360
	11th to 20th	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 11% 38%	6158
	21st to end	Day	11% 6% 3 9% 6% 6% 6% 5% 7% 9% 31%	6424
August	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 43%	4156
	11th to 20th	Day	8% 6% 2 6% 4 5% 5% 4 7% 10% 43%	4044
	21st to end	Day	6% 4 2 5% 3 4 4 4 6% 8% 54%	4194
September	1st to 10th	Day	12% 5% 2 4 4 5% 3 4 5% 7% 48%	2166
	11th to 20th	Day	8% 6% 2 6% 4 4 4 3 7% 8% 49%	2090
	21st to end	Day	15% 6% 2 5% 4 4 3 3 4 6% 46%	2090
October	1st to 10th	Day	11% 5% 2 6% 4 5% 4 3 5% 7% 48%	2090
	11th to 20th	Day	12% 7% 2 6% 5% 4 3 3 5% 7% 46%	1933
	21st to end	Day	20% 8% 2 6% 4 4 4 3 4 7% 38%	1939
November	1st to 10th	Day	9% 6% 3 5% 4 4 4 3 4 6% 52%	1762
	11th to 20th	Day	15% 10% 4 8% 5% 3 4 3 6% 7% 36%	1800
	21st to end	Day	18% 10% 4 7% 6% 4 3 3 5% 6% 35%	1800
December	1st to 10th	Day	18% 10% 3 7% 5% 4 3 3 3 5% 38%	2930
	11th to 20th	Day	17% 15% 5% 10% 5% 4 4 4 5% 5% 26%	3373
	21st to end	Day	22% 19% 5% 11% 5% 4 4 3 4 5% 18%	4229
January	1st to 10th	Night	15% 17% 6% 14% 7% 5% 4 3 5% 5% 19%	6348
	11th to 20th	Night	14% 17% 7% 13% 7% 5% 5% 3 4 4 20%	6022
	21st to end	Night	21% 13% 4 8% 4 4 4 3 4 4 30%	6490
February	1st to 10th	Night	21% 12% 4 10% 5% 4 4 4 4 5% 28%	2490
	11th to 20th	Night	17% 11% 4 10% 5% 5% 4 4 5% 6% 29%	2338
	21st to end	Night	21% 13% 3 7% 4 4 4 3 5% 6% 31%	1980
March	1st to 10th	Night	19% 13% 3 6% 4 3 3 2 4 5% 37%	5337
	11th to 20th	Night	12% 7% 3 6% 5% 4 4 4 5% 7% 43%	4980
	21st to end	Night	17% 9% 4 9% 4 4 4 4 5% 6% 34%	5467
April	1st to 10th	Night	16% 9% 3 6% 4 5% 4 4 5% 6% 37%	2050
	11th to 20th	Night	14% 8% 2 6% 5% 4 3 4 6% 8% 40%	1922
	21st to end	Night	16% 8% 2 6% 5% 4 4 4 7% 8% 37%	1800
May	1st to 10th	Night	21% 10% 3 8% 5% 5% 5% 4 5% 7% 28%	4033
	11th to 20th	Night	16% 7% 3 7% 5% 5% 5% 4 7% 9% 34%	4032
	21st to end	Night	14% 5% 3 7% 4 5% 5% 4 6% 9% 38%	4421
June	1st to 10th	Night	9% 6% 2 5% 5% 4 4 4 4 9% 49%	1783
	11th to 20th	Night	9% 5% 2 5% 3 4 5% 3 7% 11% 45%	1600
	21st to end	Night	6% 4 2 6% 4 4 5% 4 7% 10% 47%	1600
July	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 6% 8% 47%	3618
	11th to 20th	Night	7% 6% 3 6% 4 5% 5% 5% 7% 10% 43%	3793
	21st to end	Night	9% 6% 3 7% 5% 5% 5% 5% 7% 10% 39%	4427
August	1st to 10th	Night	8% 7% 3 7% 4 4 5% 4 6% 9% 44%	2861
	11th to 20th	Night	8% 6% 2 7% 4 5% 5% 4 5% 9% 45%	2785
	21st to end	Night	3 3 1 5% 3 4 4 4 6% 9% 58%	3444
September	1st to 10th	Night	12% 5% 2 4 4 3 3 4 5% 7% 51%	1994
	11th to 20th	Night	8% 5% 1 6% 3 3 4 3 5% 6% 56%	2090
	21st to end	Night	14% 6% 2 6% 4 3 4 3 3 5% 49%	2090
October	1st to 10th	Night	8% 4 2 6% 3 4 3 3 4 7% 55%	2090
	11th to 20th	Night	14% 6% 2 6% 5% 4 4 3 4 7% 45%	2247
	21st to end	Night	17% 9% 3 6% 4 3 4 3 5% 6% 41%	2655
November	1st to 10th	Night	13% 8% 2 5% 3 4 4 3 5% 6% 47%	2536
	11th to 20th	Night	16% 8% 3 7% 4 4 4 3 5% 6% 40%	2600
	21st to end	Night	19% 13% 4 7% 5% 4 4 3 4 7% 31%	2600
December	1st to 10th	Night	17% 11% 4 8% 4 4 3 3 4 5% 38%	4250
	11th to 20th	Night	18% 14% 5% 10% 5% 4 4 3 5% 5% 26%	4822
	21st to end	Night	23% 18% 6% 11% 6% 4 4 3 4 5% 17%	6702

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	63% 2 9% 19% 7%	3618
	11th to 20th	Day	63% 2 8% 14% 12% 1	3910
	21st to end	Day	65% 2 9% 16% 7% 2	4466
February	1st to 10th	Day	59% 2 9% 19% 10% 1	1909
	11th to 20th	Day	57% 3 9% 21% 10% 1	1958
	21st to end	Day	57% 2 9% 22% 9% 2	1650
March	1st to 10th	Day	59% 2 5% 20% 12% 3	4515
	11th to 20th	Day	44% 2 8% 28% 16% 1	4980
	21st to end	Day	51% 2 11% 22% 12% 2	5465
April	1st to 10th	Day	50% 2 11% 22% 14% 1	2365
	11th to 20th	Day	47% 2 9% 24% 14% 3	2425
	21st to end	Day	49% 3 9% 25% 12% 2	2600
May	1st to 10th	Day	55% 4 11% 19% 10% 1	5897
	11th to 20th	Day	51% 3 11% 24% 11%	5865
	21st to end	Day	46% 4 11% 24% 13% 1	6447
June	1st to 10th	Day	42% 4 10% 25% 17% 2	2610
	11th to 20th	Day	38% 4 14% 24% 18% 2	2800
	21st to end	Day	39% 5% 14% 22% 16% 4	2800
July	1st to 10th	Day	38% 5% 11% 27% 18% 1	6291
	11th to 20th	Day	39% 7% 13% 27% 14% 1	6083
	21st to end	Day	46% 6% 13% 19% 13% 2	6240
August	1st to 10th	Day	33% 6% 15% 32% 13% 1	4143
	11th to 20th	Day	35% 5% 11% 33% 16% 1	4083
	21st to end	Day	28% 4 13% 31% 20% 3	4193
September	1st to 10th	Day	36% 3 10% 25% 20% 6%	2166
	11th to 20th	Day	34% 3 9% 28% 22% 3	2090
	21st to end	Day	40% 3 9% 25% 22% 2	2090
October	1st to 10th	Day	24% 3 7% 33% 30% 2	3480
	11th to 20th	Day	31% 3 8% 31% 26% 2	3186
	21st to end	Day	37% 2 9% 26% 24% 2	3176
November	1st to 10th	Day	35% 3 8% 30% 21% 3	1762
	11th to 20th	Day	49% 2 8% 23% 15% 3	1800
	21st to end	Day	52% 2 8% 24% 13% 1	1800
December	1st to 10th	Day	51% 2 8% 28% 11%	2930
	11th to 20th	Day	62% 3 7% 19% 8%	3370
	21st to end	Day	69% 3 9% 13% 5%	4229
January	1st to 10th	Night	68% 2 7% 14% 8%	6348
	11th to 20th	Night	69% 2 8% 12% 8% 2	6022
	21st to end	Night	59% 2 8% 21% 9% 1	6490
February	1st to 10th	Night	60% 2 9% 20% 8% 1	2490
	11th to 20th	Night	56% 2 9% 20% 12% 1	2339
	21st to end	Night	56% 3 10% 19% 10% 2	1980
March	1st to 10th	Night	52% 2 5% 28% 12% 2	5337
	11th to 20th	Night	41% 2 10% 29% 17% 1	4980
	21st to end	Night	52% 2 7% 26% 12% 2	5467
April	1st to 10th	Night	48% 3 9% 25% 13% 2	2050
	11th to 20th	Night	42% 2 10% 21% 19% 5%	1922
	21st to end	Night	45% 3 12% 23% 14% 3	1800
May	1st to 10th	Night	57% 4 9% 19% 8% 3	4060
	11th to 20th	Night	47% 4 13% 25% 10% 1	4033
	21st to end	Night	43% 4 14% 25% 11% 3	4429
June	1st to 10th	Night	35% 4 10% 27% 22% 3	1783
	11th to 20th	Night	33% 5% 14% 23% 21% 4	1600
	21st to end	Night	31% 5% 17% 23% 19% 5%	1600
July	1st to 10th	Night	35% 6% 11% 24% 19% 5%	3580
	11th to 20th	Night	35% 8% 14% 27% 15% 1	3748
	21st to end	Night	38% 6% 12% 26% 15% 3	4297
August	1st to 10th	Night	36% 5% 13% 32% 12% 2	2850
	11th to 20th	Night	35% 6% 10% 31% 18% 1	2812
	21st to end	Night	23% 5% 15% 33% 22% 3	3444
September	1st to 10th	Night	33% 3 12% 26% 20% 7%	1994
	11th to 20th	Night	29% 3 8% 27% 28% 3	2090
	21st to end	Night	40% 2 7% 23% 26% 2	2090
October	1st to 10th	Night	23% 2 6% 29% 37% 3	3480
	11th to 20th	Night	29% 1 8% 27% 33% 2	3733
	21st to end	Night	35% 3 7% 24% 28% 5%	4368
November	1st to 10th	Night	39% 3 10% 22% 23% 4	2536
	11th to 20th	Night	46% 2 7% 23% 18% 3	2600
	21st to end	Night	54% 2 10% 21% 11% 1	2600
December	1st to 10th	Night	50% 3 11% 26% 10%	4250
	11th to 20th	Night	61% 2 10% 19% 8% 1	4824
	21st to end	Night	72% 2 8% 14% 4	6702

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	26% 20% 34% 15% 4	300
	11th to 20th	Day	28% 24% 33% 12% 3	300
	21st to end	Day	30% 21% 31% 14% 4	330
February	1st to 10th	Day	30% 22% 32% 14% 2	300
	11th to 20th	Day	29% 27% 31% 10% 2 1	300
	21st to end	Day	30% 15% 44% 9% 1	249
March	1st to 10th	Day	28% 25% 31% 15% 2	309
	11th to 20th	Day	28% 18% 31% 17% 5%	500
	21st to end	Day	32% 15% 31% 16% 5% 1	550
April	1st to 10th	Day	24% 16% 31% 20% 9% 1	500
	11th to 20th	Day	24% 19% 26% 19% 9% 3	492
	21st to end	Day	23% 16% 33% 16% 9% 2	500
May	1st to 10th	Day	28% 10% 31% 18% 9% 3	503
	11th to 20th	Day	23% 12% 28% 21% 11% 5%	527
	21st to end	Day	16% 8% 27% 26% 16% 8%	573
June	1st to 10th	Day	14% 8% 24% 29% 19% 6%	540
	11th to 20th	Day	11% 7% 25% 30% 20% 6%	730
	21st to end	Day	10% 6% 27% 30% 19% 9%	730
July	1st to 10th	Day	13% 3 18% 27% 24% 14%	721
	11th to 20th	Day	10% 5% 23% 28% 22% 12%	633
	21st to end	Day	13% 3 15% 31% 24% 14%	576
August	1st to 10th	Day	9% 6% 16% 28% 26% 15%	502
	11th to 20th	Day	12% 4 20% 31% 20% 13%	479
	21st to end	Day	10% 4 15% 28% 29% 15%	539
September	1st to 10th	Day	12% 4 16% 28% 30% 11%	490
	11th to 20th	Day	11% 3 14% 27% 32% 14%	490
	21st to end	Day	18% 8% 21% 24% 21% 7%	490
October	1st to 10th	Day	11% 7% 23% 30% 22% 7%	490
	11th to 20th	Day	16% 13% 31% 23% 12% 4	490
	21st to end	Day	24% 11% 36% 22% 5% 1	388
November	1st to 10th	Day	12% 16% 37% 22% 10% 3	300
	11th to 20th	Day	25% 19% 28% 19% 7% 1	300
	21st to end	Day	26% 16% 39% 15% 5%	300
December	1st to 10th	Day	21% 22% 36% 15% 6% 1	300
	11th to 20th	Day	23% 18% 37% 16% 6%	300
	21st to end	Day	33% 15% 33% 15% 3 1	330
January	1st to 10th	Night	23% 16% 30% 25% 5%	1000
	11th to 20th	Night	29% 14% 31% 22% 3	857
	21st to end	Night	25% 13% 32% 26% 3	880
February	1st to 10th	Night	30% 11% 32% 25% 3	800
	11th to 20th	Night	25% 15% 33% 23% 3	783
	21st to end	Night	29% 13% 32% 25% 2	660
March	1st to 10th	Night	23% 12% 33% 27% 5%	800
	11th to 20th	Night	24% 12% 33% 24% 6% 1	800
	21st to end	Night	25% 12% 29% 27% 7%	880
April	1st to 10th	Night	21% 12% 34% 24% 9%	650
	11th to 20th	Night	20% 8% 33% 28% 10% 1	593
	21st to end	Night	19% 7% 38% 26% 10% 1	600
May	1st to 10th	Night	22% 9% 29% 28% 12% 1	600
	11th to 20th	Night	19% 5% 25% 31% 17% 2	591
	21st to end	Night	11% 4 23% 35% 24% 3	650
June	1st to 10th	Night	10% 4 19% 43% 22% 2	600
	11th to 20th	Night	12% 3 17% 43% 22% 4	600
	21st to end	Night	6% 2 23% 39% 27% 3	600
July	1st to 10th	Night	13% 2 11% 34% 33% 8%	585
	11th to 20th	Night	8% 3 16% 35% 34% 4	582
	21st to end	Night	10% 2 13% 40% 31% 4	657
August	1st to 10th	Night	9% 3 12% 37% 35% 3	579
	11th to 20th	Night	9% 1 11% 45% 28% 5%	564
	21st to end	Night	6% 1 13% 34% 40% 6%	627
September	1st to 10th	Night	15% 2 14% 31% 34% 4	664
	11th to 20th	Night	9% 3 14% 33% 35% 6%	760
	21st to end	Night	17% 6% 19% 31% 24% 3	760
October	1st to 10th	Night	12% 3 22% 36% 23% 4	760
	11th to 20th	Night	19% 9% 25% 30% 16% 1	760
	21st to end	Night	23% 9% 31% 25% 11% 1	836
November	1st to 10th	Night	18% 8% 28% 28% 16% 1	780
	11th to 20th	Night	22% 12% 29% 27% 10% 1	800
	21st to end	Night	26% 9% 26% 30% 7% 1	800
December	1st to 10th	Night	28% 10% 30% 26% 6%	800
	11th to 20th	Night	25% 10% 32% 27% 6% 1	800
	21st to end	Night	32% 13% 28% 23% 4	975

Page generated at 2025-08-02 01:32:27. Version ac07

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