Marmora
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marmora 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	16% 10% 3 7% 5% 4 4 4 5% 7% 34%	105180
	Night	17% 11% 3 8% 5% 4 4 4 5% 6% 33%	103846
Transparency	Day	48% 7% 12% 21% 11% 1	108740
	Night	49% 6% 12% 21% 11% 1	108374
Seeing	Day	23% 16% 31% 19% 8% 3	14587
	Night	22% 14% 31% 24% 9% 1	23926

By Month

Percentage Cloud Cover NE (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% 17% 5% 9% 4 4 4 3 4 6% 28%	2565
	11th to 20th	Day	13% 18% 6% 13% 6% 6% 5% 3 4 4 22%	2520
	21st to end	Day	20% 20% 6% 11% 6% 4 4 3 3 3 20%	3124
February	1st to 10th	Day	14% 16% 4 12% 7% 5% 5% 4 5% 4 23%	1710
	11th to 20th	Day	13% 16% 5% 12% 7% 5% 3 3 4 5% 28%	1663
	21st to end	Day	17% 16% 4 9% 8% 4 4 3 4 4 26%	1503
March	1st to 10th	Day	21% 13% 4 8% 4 4 4 3 4 6% 29%	3308
	11th to 20th	Day	12% 16% 5% 9% 5% 5% 4 3 5% 6% 30%	3480
	21st to end	Day	14% 9% 2 6% 4 3 3 3 4 6% 45%	3896
April	1st to 10th	Day	20% 14% 4 7% 4 4 4 3 4 6% 32%	2280
	11th to 20th	Day	23% 8% 2 5% 4 3 3 3 5% 6% 37%	2254
	21st to end	Day	22% 10% 2 8% 5% 4 4 3 4 5% 32%	2451
May	1st to 10th	Day	20% 8% 2 7% 5% 5% 4 3 5% 6% 34%	4316
	11th to 20th	Day	16% 10% 3 8% 5% 4 4 4 5% 9% 32%	4398
	21st to end	Day	14% 6% 2 6% 5% 4 5% 3 5% 8% 42%	4837
June	1st to 10th	Day	18% 8% 2 7% 5% 5% 5% 5% 6% 7% 32%	2660
	11th to 20th	Day	15% 6% 2 5% 5% 5% 5% 5% 7% 9% 37%	2660
	21st to end	Day	17% 7% 3 6% 5% 4 5% 4 6% 7% 36%	2660
July	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 10% 38%	4440
	11th to 20th	Day	13% 4 2 5% 4 5% 4 3 7% 9% 45%	4440
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 43%	4790
August	1st to 10th	Day	17% 8% 2 7% 4 4 5% 4 6% 7% 37%	4104
	11th to 20th	Day	16% 6% 2 7% 5% 5% 4 4 6% 9% 36%	4044
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 4 6% 9% 41%	4246
September	1st to 10th	Day	14% 5% 3 6% 4 5% 4 4 5% 7% 42%	2280
	11th to 20th	Day	10% 6% 2 5% 4 3 4 4 5% 6% 50%	2280
	21st to end	Day	18% 6% 3 6% 4 4 4 4 5% 7% 39%	1986
October	1st to 10th	Day	20% 8% 3 7% 6% 4 4 3 5% 7% 34%	1900
	11th to 20th	Day	22% 9% 3 8% 5% 4 5% 3 6% 7% 29%	1900
	21st to end	Day	26% 11% 3 7% 4 5% 4 4 4 5% 26%	2048
November	1st to 10th	Day	16% 8% 3 8% 4 5% 5% 5% 5% 7% 34%	1691
	11th to 20th	Day	16% 13% 4 8% 6% 4 4 5% 5% 6% 30%	1600
	21st to end	Day	21% 16% 4 7% 6% 4 4 4 5% 6% 23%	1600
December	1st to 10th	Day	19% 21% 4 10% 5% 5% 4 3 4 5% 19%	2600
	11th to 20th	Day	16% 20% 6% 11% 5% 4 3 3 3 4 25%	2986
	21st to end	Day	24% 16% 4 10% 5% 4 3 3 4 4 24%	3960
January	1st to 10th	Night	18% 16% 7% 12% 6% 4 4 3 4 5% 20%	4514
	11th to 20th	Night	14% 13% 5% 13% 8% 6% 5% 4 5% 5% 21%	4436
	21st to end	Night	19% 16% 7% 10% 6% 5% 5% 3 4 5% 20%	4532
February	1st to 10th	Night	13% 16% 5% 10% 7% 6% 4 4 4 6% 25%	2470
	11th to 20th	Night	13% 14% 6% 9% 6% 4 4 4 5% 5% 29%	2403
	21st to end	Night	16% 11% 3 10% 6% 4 5% 3 5% 6% 31%	1951
March	1st to 10th	Night	20% 11% 4 8% 5% 4 4 3 4 6% 30%	3516
	11th to 20th	Night	16% 14% 4 9% 5% 5% 4 3 5% 6% 28%	3479
	21st to end	Night	16% 8% 3 6% 4 3 4 3 5% 7% 41%	3736
April	1st to 10th	Night	20% 10% 3 7% 4 4 4 3 5% 5% 35%	1900
	11th to 20th	Night	19% 8% 2 7% 4 4 4 3 5% 6% 37%	1875
	21st to end	Night	19% 7% 3 6% 5% 5% 5% 3 6% 7% 34%	1745
May	1st to 10th	Night	20% 9% 3 6% 5% 3 4 3 5% 6% 35%	2624
	11th to 20th	Night	17% 9% 2 6% 4 4 5% 5% 5% 6% 37%	2495
	21st to end	Night	12% 6% 2 6% 4 4 4 3 5% 7% 46%	2738
June	1st to 10th	Night	15% 6% 2 7% 5% 5% 4 4 6% 8% 38%	1520
	11th to 20th	Night	11% 6% 3 5% 5% 5% 4 5% 5% 8% 44%	1520
	21st to end	Night	14% 6% 3 8% 4 4 4 4 6% 8% 40%	1520
July	1st to 10th	Night	9% 4 2 8% 5% 4 6% 4 6% 7% 45%	2520
	11th to 20th	Night	13% 5% 2 6% 3 4 3 3 5% 7% 48%	2520
	21st to end	Night	11% 4 2 5% 4 4 4 3 6% 8% 50%	2760
August	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 6% 7% 47%	2825
	11th to 20th	Night	15% 6% 2 5% 3 3 4 3 6% 7% 45%	2785
	21st to end	Night	10% 5% 2 5% 4 4 4 4 6% 9% 48%	3377
September	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 6% 8% 46%	1900
	11th to 20th	Night	12% 4 1 3 4 4 4 4 5% 6% 53%	1900
	21st to end	Night	18% 6% 2 6% 3 4 4 3 5% 7% 42%	2191
October	1st to 10th	Night	18% 7% 2 6% 4 5% 4 4 4 6% 40%	2280
	11th to 20th	Night	21% 9% 3 8% 5% 5% 4 3 4 6% 32%	2280
	21st to end	Night	23% 11% 3 6% 4 4 5% 4 5% 6% 29%	2548
November	1st to 10th	Night	19% 9% 2 6% 4 4 4 3 5% 6% 37%	2602
	11th to 20th	Night	18% 11% 3 7% 5% 5% 4 4 5% 7% 31%	2800
	21st to end	Night	21% 12% 3 7% 5% 5% 5% 5% 6% 6% 25%	2800
December	1st to 10th	Night	20% 17% 4 8% 6% 5% 5% 5% 6% 7% 19%	4580
	11th to 20th	Night	19% 16% 5% 10% 5% 4 4 4 5% 5% 22%	5208
	21st to end	Night	26% 17% 3 10% 5% 4 3 3 4 4 20%	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	56% 7% 14% 15% 7% 2	2566
	11th to 20th	Day	67% 5% 11% 11% 7%	2520
	21st to end	Day	70% 5% 8% 11% 5% 1	3124
February	1st to 10th	Day	62% 6% 10% 17% 5% 1	1710
	11th to 20th	Day	60% 4 9% 15% 11% 1	1672
	21st to end	Day	61% 6% 9% 13% 10% 1	1503
March	1st to 10th	Day	55% 5% 13% 16% 10% 1	3311
	11th to 20th	Day	53% 5% 15% 15% 10% 2	3480
	21st to end	Day	40% 5% 7% 27% 17% 3	3896
April	1st to 10th	Day	54% 4 8% 20% 11% 3	2280
	11th to 20th	Day	48% 4 9% 21% 17% 1	2254
	21st to end	Day	54% 4 8% 18% 14% 2	2451
May	1st to 10th	Day	49% 7% 9% 22% 12% 2	4329
	11th to 20th	Day	48% 8% 12% 21% 10% 1	4402
	21st to end	Day	38% 7% 12% 24% 16% 3	4837
June	1st to 10th	Day	49% 8% 11% 18% 14% 1	2660
	11th to 20th	Day	41% 7% 12% 24% 14% 2	2660
	21st to end	Day	45% 7% 12% 21% 13% 1	2660
July	1st to 10th	Day	38% 8% 15% 25% 14% 1	4370
	11th to 20th	Day	33% 8% 15% 34% 10%	4365
	21st to end	Day	35% 9% 14% 29% 12%	4637
August	1st to 10th	Day	44% 7% 15% 22% 12% 1	4091
	11th to 20th	Day	42% 8% 14% 27% 9%	4083
	21st to end	Day	37% 8% 13% 31% 10% 1	4246
September	1st to 10th	Day	38% 8% 13% 28% 12% 1	2280
	11th to 20th	Day	33% 6% 13% 32% 15% 1	2280
	21st to end	Day	43% 7% 13% 27% 10%	1986
October	1st to 10th	Day	41% 7% 13% 28% 11% 1	3160
	11th to 20th	Day	44% 7% 15% 23% 11% 1	3140
	21st to end	Day	52% 7% 13% 20% 8%	3350
November	1st to 10th	Day	48% 7% 15% 21% 9% 1	1691
	11th to 20th	Day	53% 7% 13% 16% 11% 1	1600
	21st to end	Day	60% 7% 12% 13% 7%	1600
December	1st to 10th	Day	66% 5% 15% 10% 4	2600
	11th to 20th	Day	63% 5% 10% 14% 8%	2986
	21st to end	Day	63% 5% 9% 15% 8%	3960
January	1st to 10th	Night	64% 7% 12% 13% 5%	4514
	11th to 20th	Night	63% 7% 12% 13% 5% 1	4436
	21st to end	Night	65% 6% 10% 12% 6%	4532
February	1st to 10th	Night	59% 6% 11% 17% 6% 1	2470
	11th to 20th	Night	57% 5% 9% 20% 9% 1	2405
	21st to end	Night	52% 6% 12% 20% 10% 1	1951
March	1st to 10th	Night	55% 5% 9% 21% 10% 1	3526
	11th to 20th	Night	55% 5% 13% 18% 9% 1	3480
	21st to end	Night	41% 4 9% 24% 19% 2	3736
April	1st to 10th	Night	51% 4 8% 21% 14% 2	1900
	11th to 20th	Night	48% 5% 9% 19% 17% 1	1875
	21st to end	Night	47% 7% 10% 17% 16% 3	1745
May	1st to 10th	Night	49% 6% 11% 18% 14% 2	2630
	11th to 20th	Night	43% 9% 12% 24% 10% 2	2496
	21st to end	Night	37% 7% 12% 22% 21% 2	2739
June	1st to 10th	Night	43% 6% 12% 23% 15% 1	1520
	11th to 20th	Night	37% 7% 11% 22% 21% 3	1520
	21st to end	Night	42% 6% 14% 22% 14% 2	1520
July	1st to 10th	Night	36% 8% 13% 24% 17% 2	2480
	11th to 20th	Night	34% 7% 13% 32% 14%	2472
	21st to end	Night	31% 8% 16% 32% 12% 1	2672
August	1st to 10th	Night	36% 6% 14% 28% 15% 1	2814
	11th to 20th	Night	36% 7% 18% 27% 12% 1	2812
	21st to end	Night	30% 8% 14% 35% 12% 1	3377
September	1st to 10th	Night	36% 7% 15% 27% 14% 1	1900
	11th to 20th	Night	31% 7% 13% 32% 17% 1	1900
	21st to end	Night	42% 7% 11% 27% 12% 1	2191
October	1st to 10th	Night	35% 6% 11% 29% 19%	3800
	11th to 20th	Night	44% 5% 15% 28% 9%	3779
	21st to end	Night	46% 7% 14% 25% 8%	4196
November	1st to 10th	Night	47% 5% 13% 23% 11% 1	2602
	11th to 20th	Night	52% 5% 13% 19% 10% 2	2800
	21st to end	Night	57% 7% 15% 16% 5%	2800
December	1st to 10th	Night	61% 7% 14% 15% 3	4580
	11th to 20th	Night	61% 6% 12% 13% 7%	5208
	21st to end	Night	67% 5% 8% 11% 8%	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	24% 22% 34% 16% 2 1	192
	11th to 20th	Day	27% 25% 31% 14% 3	180
	21st to end	Day	29% 20% 33% 13% 4	297
February	1st to 10th	Day	31% 26% 31% 10% 2	270
	11th to 20th	Day	30% 26% 39% 4 1	270
	21st to end	Day	36% 22% 32% 10% 1	315
March	1st to 10th	Day	26% 19% 35% 16% 3	460
	11th to 20th	Day	27% 20% 33% 15% 3 1	460
	21st to end	Day	33% 19% 29% 13% 6% 1	506
April	1st to 10th	Day	29% 21% 34% 10% 6%	460
	11th to 20th	Day	33% 22% 20% 15% 7% 3	452
	21st to end	Day	31% 18% 33% 10% 6% 2	460
May	1st to 10th	Day	25% 16% 30% 19% 7% 4	463
	11th to 20th	Day	19% 14% 34% 21% 8% 3	487
	21st to end	Day	18% 14% 36% 17% 11% 4	529
June	1st to 10th	Day	21% 14% 33% 23% 7% 2	490
	11th to 20th	Day	15% 15% 33% 24% 11% 2	490
	21st to end	Day	22% 14% 32% 19% 10% 3	490
July	1st to 10th	Day	12% 9% 33% 30% 14% 3	485
	11th to 20th	Day	15% 11% 29% 26% 16% 4	484
	21st to end	Day	11% 10% 37% 27% 11% 4	532
August	1st to 10th	Day	12% 10% 31% 29% 13% 6%	486
	11th to 20th	Day	13% 8% 30% 27% 16% 6%	479
	21st to end	Day	14% 10% 31% 25% 12% 7%	539
September	1st to 10th	Day	13% 13% 33% 22% 12% 8%	490
	11th to 20th	Day	11% 9% 27% 22% 19% 12%	490
	21st to end	Day	19% 14% 26% 25% 11% 6%	490
October	1st to 10th	Day	25% 17% 25% 16% 11% 5%	490
	11th to 20th	Day	26% 19% 31% 16% 7% 2	490
	21st to end	Day	31% 18% 29% 18% 4	516
November	1st to 10th	Day	28% 19% 27% 17% 9% 1	325
	11th to 20th	Day	31% 23% 31% 12% 4 1	200
	21st to end	Day	31% 23% 30% 14% 3 1	200
December	1st to 10th	Day	32% 17% 34% 15% 3	200
	11th to 20th	Day	35% 23% 30% 10% 2 1	200
	21st to end	Day	35% 15% 35% 11% 3	220
January	1st to 10th	Night	27% 21% 29% 19% 4 1	785
	11th to 20th	Night	28% 17% 31% 19% 4	760
	21st to end	Night	22% 15% 35% 23% 5% 1	836
February	1st to 10th	Night	23% 21% 35% 19% 1	760
	11th to 20th	Night	22% 20% 37% 17% 4	743
	21st to end	Night	25% 20% 34% 18% 3	628
March	1st to 10th	Night	24% 16% 36% 21% 3	760
	11th to 20th	Night	26% 19% 31% 19% 4 1	760
	21st to end	Night	22% 17% 31% 23% 7%	836
April	1st to 10th	Night	24% 18% 33% 21% 4	760
	11th to 20th	Night	24% 20% 29% 19% 8%	751
	21st to end	Night	21% 14% 31% 24% 10%	605
May	1st to 10th	Night	22% 10% 29% 26% 11% 2	451
	11th to 20th	Night	15% 11% 33% 32% 9%	374
	21st to end	Night	12% 8% 37% 30% 14%	411
June	1st to 10th	Night	16% 7% 36% 29% 11%	380
	11th to 20th	Night	14% 10% 31% 33% 12% 1	380
	21st to end	Night	16% 9% 28% 33% 13% 1	380
July	1st to 10th	Night	6% 8% 27% 44% 14% 1	370
	11th to 20th	Night	11% 3 29% 35% 21%	368
	21st to end	Night	10% 4 30% 40% 15% 1	425
August	1st to 10th	Night	12% 4 24% 34% 24% 2	567
	11th to 20th	Night	10% 6% 22% 38% 23% 2	564
	21st to end	Night	11% 6% 31% 32% 19% 2	776
September	1st to 10th	Night	13% 7% 31% 30% 17% 3	760
	11th to 20th	Night	13% 5% 24% 28% 26% 5%	760
	21st to end	Night	19% 9% 24% 26% 19% 3	760
October	1st to 10th	Night	20% 12% 26% 24% 15% 2	760
	11th to 20th	Night	26% 13% 31% 21% 9% 1	760
	21st to end	Night	29% 15% 30% 21% 5%	836
November	1st to 10th	Night	25% 13% 26% 26% 9% 1	780
	11th to 20th	Night	25% 16% 33% 18% 7% 1	800
	21st to end	Night	28% 18% 28% 21% 5%	800
December	1st to 10th	Night	30% 18% 30% 18% 3	800
	11th to 20th	Night	27% 18% 36% 17% 3	800
	21st to end	Night	35% 14% 32% 16% 3	880

Page generated at 2025-01-04 03:24:01. Version ac07

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