Moran
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moran clear sky chart from 2005-11-06 to 2024-11-08.

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% 10% 4 8% 5% 5% 5% 4 5% 7% 33%	101410
	Night	15% 12% 4 9% 5% 5% 4 4 5% 6% 31%	97797
Transparency	Day	27% 48% 7% 13% 6%	104892
	Night	28% 48% 7% 11% 5%	102402
Seeing	Day	19% 14% 33% 23% 9% 2	15633
	Night	20% 12% 31% 26% 10% 1	25114

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	14% 16% 9% 17% 10% 6% 6% 3 5% 5% 10%	2527
	11th to 20th	Day	12% 17% 5% 18% 13% 9% 5% 3 3 4 10%	2530
	21st to end	Day	14% 22% 11% 15% 6% 6% 4 3 5% 4 10%	2783
February	1st to 10th	Day	9% 15% 6% 12% 7% 7% 5% 4 6% 7% 22%	1619
	11th to 20th	Day	13% 13% 5% 12% 7% 5% 6% 4 6% 7% 22%	1786
	21st to end	Day	11% 14% 5% 14% 9% 5% 5% 4 5% 6% 24%	1570
March	1st to 10th	Day	12% 13% 4 7% 5% 5% 4 3 5% 7% 35%	3118
	11th to 20th	Day	9% 14% 4 12% 8% 5% 5% 3 5% 5% 30%	3416
	21st to end	Day	15% 13% 8% 13% 6% 5% 5% 3 4 5% 23%	3906
April	1st to 10th	Day	18% 13% 4 8% 4 5% 5% 4 5% 6% 29%	2280
	11th to 20th	Day	19% 11% 4 7% 4 4 4 3 5% 7% 33%	2394
	21st to end	Day	16% 10% 3 9% 5% 5% 4 4 5% 6% 34%	2470
May	1st to 10th	Day	16% 8% 3 6% 4 4 4 4 6% 7% 38%	4108
	11th to 20th	Day	11% 8% 2 7% 4 4 4 3 6% 8% 41%	4257
	21st to end	Day	14% 6% 2 5% 4 4 4 4 6% 9% 43%	5015
June	1st to 10th	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 41%	2850
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 6% 9% 39%	2850
	21st to end	Day	15% 8% 2 5% 4 4 4 3 6% 8% 41%	2850
July	1st to 10th	Day	16% 8% 2 6% 4 4 4 3 5% 8% 40%	4612
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 6% 8% 47%	4440
	21st to end	Day	10% 5% 2 4 3 4 4 4 6% 9% 49%	4814
August	1st to 10th	Day	8% 6% 2 6% 5% 5% 6% 5% 6% 9% 41%	4263
	11th to 20th	Day	14% 5% 2 5% 3 3 5% 4 6% 7% 47%	4044
	21st to end	Day	15% 6% 2 6% 4 4 4 3 4 7% 46%	4447
September	1st to 10th	Day	16% 6% 2 5% 3 4 4 4 6% 7% 43%	2238
	11th to 20th	Day	13% 7% 2 6% 5% 4 5% 4 7% 8% 41%	2090
	21st to end	Day	14% 8% 3 6% 4 5% 5% 3 6% 8% 37%	2090
October	1st to 10th	Day	18% 8% 3 7% 5% 4 4 3 5% 8% 34%	2066
	11th to 20th	Day	21% 13% 4 9% 6% 5% 5% 5% 5% 6% 21%	1800
	21st to end	Day	22% 14% 4 9% 7% 6% 4 3 6% 6% 20%	1881
November	1st to 10th	Day	20% 12% 3 9% 5% 4 5% 4 6% 6% 24%	1735
	11th to 20th	Day	16% 15% 6% 12% 7% 6% 6% 3 6% 6% 18%	1675
	21st to end	Day	20% 20% 5% 12% 6% 6% 5% 4 5% 5% 13%	1454
December	1st to 10th	Day	14% 20% 6% 13% 8% 5% 5% 4 4 5% 16%	1330
	11th to 20th	Day	19% 20% 6% 13% 5% 4 5% 3 4 6% 14%	1671
	21st to end	Day	23% 21% 7% 15% 6% 4 3 2 3 4 11%	2431
January	1st to 10th	Night	14% 17% 7% 15% 8% 5% 5% 4 4 6% 14%	4428
	11th to 20th	Night	11% 15% 5% 16% 11% 8% 5% 4 4 5% 14%	4440
	21st to end	Night	16% 21% 9% 13% 7% 5% 4 4 5% 5% 12%	4884
February	1st to 10th	Night	9% 16% 5% 10% 9% 7% 6% 4 5% 6% 23%	2559
	11th to 20th	Night	11% 14% 5% 14% 7% 6% 5% 3 6% 6% 25%	2279
	21st to end	Night	12% 14% 5% 12% 7% 5% 5% 4 4 6% 25%	1884
March	1st to 10th	Night	16% 10% 3 6% 4 3 3 3 4 7% 40%	3722
	11th to 20th	Night	10% 12% 4 8% 5% 4 3 3 5% 8% 38%	3529
	21st to end	Night	15% 10% 5% 10% 5% 5% 4 3 5% 6% 31%	3754
April	1st to 10th	Night	18% 12% 4 6% 6% 5% 5% 4 6% 6% 29%	1900
	11th to 20th	Night	19% 10% 3 7% 4 3 3 4 5% 5% 36%	1735
	21st to end	Night	17% 9% 4 6% 6% 4 4 3 4 6% 37%	1710
May	1st to 10th	Night	18% 8% 3 7% 4 4 4 4 5% 6% 36%	2833
	11th to 20th	Night	13% 8% 3 8% 6% 5% 4 4 5% 7% 38%	2640
	21st to end	Night	17% 7% 2 6% 3 3 4 4 6% 8% 39%	2568
June	1st to 10th	Night	12% 5% 3 7% 5% 4 5% 4 7% 8% 40%	1330
	11th to 20th	Night	12% 6% 2 7% 4 5% 6% 4 7% 7% 42%	1330
	21st to end	Night	14% 8% 3 6% 4 3 4 3 6% 8% 42%	1330
July	1st to 10th	Night	13% 7% 2 5% 4 5% 4 4 6% 8% 41%	2354
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 6% 7% 52%	2530
	21st to end	Night	10% 5% 2 5% 3 4 3 3 5% 8% 50%	2750
August	1st to 10th	Night	10% 6% 3 6% 4 5% 4 4 7% 7% 43%	2670
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 4 8% 52%	2785
	21st to end	Night	10% 5% 2 5% 4 4 4 3 4 7% 50%	3206
September	1st to 10th	Night	12% 6% 2 6% 4 4 5% 3 5% 7% 47%	1922
	11th to 20th	Night	15% 5% 2 4 4 3 4 3 6% 8% 46%	2090
	21st to end	Night	16% 7% 2 7% 4 5% 4 3 6% 6% 39%	2090
October	1st to 10th	Night	17% 8% 2 6% 4 4 4 4 6% 7% 38%	2113
	11th to 20th	Night	22% 10% 3 8% 5% 4 4 4 5% 6% 28%	2379
	21st to end	Night	25% 12% 3 9% 5% 4 5% 3 5% 7% 23%	2717
November	1st to 10th	Night	17% 11% 3 8% 5% 4 4 4 5% 7% 30%	2504
	11th to 20th	Night	17% 14% 4 10% 6% 6% 6% 3 6% 6% 21%	2503
	21st to end	Night	18% 18% 5% 9% 5% 5% 5% 4 5% 6% 18%	2721
December	1st to 10th	Night	13% 19% 6% 12% 7% 5% 5% 4 5% 5% 18%	2850
	11th to 20th	Night	17% 17% 6% 13% 6% 4 4 3 5% 6% 19%	3526
	21st to end	Night	25% 21% 7% 12% 5% 4 5% 3 3 4 10%	5232

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	47% 44% 4 3 1	2528
	11th to 20th	Day	47% 42% 5% 4 1	2530
	21st to end	Day	51% 41% 5% 2 1	2783
February	1st to 10th	Day	21% 66% 6% 6% 2	1619
	11th to 20th	Day	22% 64% 4 5% 5%	1795
	21st to end	Day	22% 65% 4 5% 4	1570
March	1st to 10th	Day	28% 43% 9% 11% 9% 1	3120
	11th to 20th	Day	36% 41% 9% 10% 3 1	3416
	21st to end	Day	39% 44% 6% 6% 4 1	3906
April	1st to 10th	Day	21% 65% 4 7% 3	2280
	11th to 20th	Day	18% 66% 2 8% 5% 1	2394
	21st to end	Day	17% 65% 3 8% 6% 1	2470
May	1st to 10th	Day	24% 43% 7% 15% 8% 2	4120
	11th to 20th	Day	22% 45% 6% 18% 9%	4261
	21st to end	Day	23% 42% 8% 13% 11% 2	5015
June	1st to 10th	Day	14% 66% 4 8% 6% 1	2850
	11th to 20th	Day	17% 65% 5% 9% 4 1	2850
	21st to end	Day	15% 64% 6% 10% 5% 1	2850
July	1st to 10th	Day	33% 36% 10% 14% 7% 1	4542
	11th to 20th	Day	21% 37% 10% 26% 5%	4365
	21st to end	Day	19% 36% 7% 24% 14%	4662
August	1st to 10th	Day	24% 38% 9% 22% 8%	4248
	11th to 20th	Day	27% 37% 8% 22% 5%	4083
	21st to end	Day	26% 37% 11% 20% 5%	4446
September	1st to 10th	Day	17% 61% 6% 11% 4	2238
	11th to 20th	Day	15% 61% 6% 13% 5%	2090
	21st to end	Day	16% 62% 7% 11% 4	2090
October	1st to 10th	Day	21% 38% 8% 21% 12%	3430
	11th to 20th	Day	31% 38% 8% 22% 2	2964
	21st to end	Day	40% 38% 7% 12% 2	3081
November	1st to 10th	Day	26% 58% 6% 9% 2	1735
	11th to 20th	Day	27% 61% 5% 5% 2	1675
	21st to end	Day	31% 61% 4 3 2	1454
December	1st to 10th	Day	28% 62% 4 4 2	1330
	11th to 20th	Day	37% 52% 3 6% 1	1671
	21st to end	Day	50% 40% 3 4 4	2431
January	1st to 10th	Night	42% 42% 8% 6% 2	4428
	11th to 20th	Night	44% 42% 8% 5% 1	4440
	21st to end	Night	48% 42% 6% 3 1	4884
February	1st to 10th	Night	21% 65% 3 7% 3	2559
	11th to 20th	Night	20% 65% 4 9% 2	2280
	21st to end	Night	18% 66% 4 5% 6%	1884
March	1st to 10th	Night	25% 42% 11% 15% 5%	3733
	11th to 20th	Night	26% 41% 11% 15% 5% 1	3530
	21st to end	Night	32% 44% 7% 11% 5% 1	3754
April	1st to 10th	Night	21% 66% 2 6% 4 1	1900
	11th to 20th	Night	18% 66% 3 8% 3 2	1735
	21st to end	Night	19% 65% 3 7% 6% 1	1710
May	1st to 10th	Night	27% 43% 6% 15% 8% 1	2840
	11th to 20th	Night	25% 44% 4 20% 7%	2641
	21st to end	Night	28% 44% 8% 10% 8% 4	2569
June	1st to 10th	Night	13% 66% 5% 9% 7%	1330
	11th to 20th	Night	17% 66% 4 7% 5% 2	1330
	21st to end	Night	15% 64% 3 12% 5% 1	1330
July	1st to 10th	Night	31% 36% 10% 13% 9% 1	2315
	11th to 20th	Night	19% 36% 12% 23% 11%	2482
	21st to end	Night	19% 36% 9% 17% 16% 2	2662
August	1st to 10th	Night	26% 37% 7% 20% 10%	2661
	11th to 20th	Night	24% 38% 9% 21% 8% 1	2812
	21st to end	Night	22% 38% 8% 24% 8%	3206
September	1st to 10th	Night	16% 61% 5% 12% 6%	1922
	11th to 20th	Night	15% 60% 6% 13% 5% 1	2090
	21st to end	Night	17% 62% 6% 11% 5%	2090
October	1st to 10th	Night	25% 37% 6% 24% 7%	3529
	11th to 20th	Night	27% 38% 10% 19% 6%	3954
	21st to end	Night	34% 38% 11% 15% 2	4467
November	1st to 10th	Night	26% 57% 6% 7% 4	2504
	11th to 20th	Night	23% 62% 6% 6% 2	2503
	21st to end	Night	27% 62% 5% 4 2	2721
December	1st to 10th	Night	27% 60% 5% 7% 1	2850
	11th to 20th	Night	34% 52% 7% 5% 2	3525
	21st to end	Night	51% 40% 4 4 2	5232

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% 16% 34% 21% 4 1	270
	11th to 20th	Day	22% 14% 41% 17% 4 1	270
	21st to end	Day	24% 13% 34% 24% 5%	297
February	1st to 10th	Day	16% 27% 38% 15% 4 1	270
	11th to 20th	Day	19% 28% 34% 14% 4 1	270
	21st to end	Day	20% 31% 35% 13%	225
March	1st to 10th	Day	18% 20% 40% 17% 4	270
	11th to 20th	Day	19% 17% 38% 17% 8% 1	422
	21st to end	Day	26% 17% 28% 20% 8% 1	506
April	1st to 10th	Day	25% 15% 37% 17% 5% 1	460
	11th to 20th	Day	27% 22% 25% 17% 7% 2	452
	21st to end	Day	21% 17% 34% 18% 8% 2	460
May	1st to 10th	Day	24% 16% 31% 19% 9% 2	463
	11th to 20th	Day	18% 12% 37% 23% 7% 3	585
	21st to end	Day	15% 12% 33% 28% 9% 2	734
June	1st to 10th	Day	15% 13% 36% 27% 8% 2	680
	11th to 20th	Day	16% 13% 37% 25% 7% 2	680
	21st to end	Day	21% 9% 33% 28% 9% 1	680
July	1st to 10th	Day	9% 6% 38% 32% 12% 3	671
	11th to 20th	Day	12% 9% 31% 32% 11% 5%	668
	21st to end	Day	12% 5% 32% 33% 12% 5%	739
August	1st to 10th	Day	13% 7% 28% 34% 13% 5%	581
	11th to 20th	Day	13% 6% 24% 32% 18% 8%	479
	21st to end	Day	17% 9% 27% 28% 16% 3	539
September	1st to 10th	Day	20% 10% 28% 22% 15% 5%	490
	11th to 20th	Day	14% 9% 28% 31% 13% 5%	490
	21st to end	Day	17% 11% 28% 30% 12% 3	490
October	1st to 10th	Day	22% 17% 30% 18% 11% 2	490
	11th to 20th	Day	27% 17% 35% 17% 3 1	390
	21st to end	Day	31% 18% 36% 12% 3 1	330
November	1st to 10th	Day	24% 22% 31% 18% 4	291
	11th to 20th	Day	21% 26% 35% 12% 5%	253
	21st to end	Day	22% 26% 38% 12% 2	180
December	1st to 10th	Day	23% 19% 33% 18% 6% 1	180
	11th to 20th	Day	28% 25% 33% 8% 6% 1	180
	21st to end	Day	32% 26% 28% 10% 3 2	198
January	1st to 10th	Night	22% 19% 33% 22% 4	950
	11th to 20th	Night	22% 15% 35% 22% 6%	950
	21st to end	Night	21% 14% 35% 24% 6% 1	1045
February	1st to 10th	Night	17% 17% 35% 25% 5%	849
	11th to 20th	Night	19% 17% 32% 24% 8%	743
	21st to end	Night	18% 16% 37% 24% 5%	628
March	1st to 10th	Night	18% 11% 38% 24% 9%	760
	11th to 20th	Night	18% 14% 35% 25% 7% 1	760
	21st to end	Night	18% 12% 32% 30% 8%	798
April	1st to 10th	Night	22% 11% 33% 28% 5% 1	570
	11th to 20th	Night	26% 10% 28% 26% 10% 1	563
	21st to end	Night	21% 10% 31% 28% 9% 1	570
May	1st to 10th	Night	18% 9% 31% 31% 12%	570
	11th to 20th	Night	17% 6% 33% 30% 12% 1	561
	21st to end	Night	13% 7% 30% 33% 16%	513
June	1st to 10th	Night	12% 7% 32% 39% 11%	380
	11th to 20th	Night	13% 7% 29% 33% 17% 1	380
	21st to end	Night	15% 8% 23% 38% 14% 1	380
July	1st to 10th	Night	12% 4 23% 43% 16% 2	445
	11th to 20th	Night	11% 4 24% 31% 25% 4	552
	21st to end	Night	12% 4 21% 39% 21% 2	624
August	1st to 10th	Night	9% 4 25% 39% 22% 1	567
	11th to 20th	Night	11% 4 20% 33% 28% 4	564
	21st to end	Night	12% 7% 23% 39% 18% 1	627
September	1st to 10th	Night	17% 4 25% 31% 20% 4	592
	11th to 20th	Night	16% 7% 26% 28% 20% 3	760
	21st to end	Night	19% 9% 23% 29% 17% 3	760
October	1st to 10th	Night	20% 12% 28% 26% 12% 1	760
	11th to 20th	Night	25% 15% 30% 23% 7%	760
	21st to end	Night	29% 15% 29% 22% 5%	836
November	1st to 10th	Night	25% 16% 33% 20% 6% 1	771
	11th to 20th	Night	23% 19% 33% 19% 5%	760
	21st to end	Night	27% 20% 33% 17% 3	821
December	1st to 10th	Night	23% 19% 35% 17% 5%	950
	11th to 20th	Night	27% 18% 35% 15% 4 1	950
	21st to end	Night	32% 14% 33% 18% 4	1045

Page generated at 2024-11-05 08:15:53. Version ac07

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