Melita
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Melita clear sky chart from 2005-11-06 to 2026-06-16.

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	10% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	146914
	Night	8% 9% 3 9% 6% 5% 6% 4 6% 7% 36%	142548
Transparency	Day	44% 5% 16% 25% 10% 1	141460
	Night	46% 5% 15% 24% 10% 1	139025
Seeing	Day	13% 8% 29% 31% 15% 4	18430
	Night	14% 6% 31% 36% 12% 1	28422

By Month

Percentage Cloud Cover SW (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	5% 11% 6% 15% 9% 8% 6% 6% 8% 7% 20%	4259
	11th to 20th	Day	3 9% 5% 13% 11% 10% 12% 7% 8% 7% 16%	4740
	21st to end	Day	5% 11% 5% 11% 7% 6% 4 4 6% 8% 34%	5188
February	1st to 10th	Day	8% 14% 5% 14% 8% 6% 5% 3 6% 6% 25%	1680
	11th to 20th	Day	6% 13% 5% 9% 9% 8% 7% 5% 7% 8% 24%	1904
	21st to end	Day	6% 10% 4 12% 9% 6% 7% 5% 7% 8% 25%	1730
March	1st to 10th	Day	7% 13% 5% 14% 8% 5% 5% 5% 7% 7% 24%	4600
	11th to 20th	Day	7% 12% 6% 13% 8% 7% 6% 4 6% 7% 24%	4882
	21st to end	Day	10% 12% 5% 14% 7% 6% 5% 4 6% 7% 23%	5884
April	1st to 10th	Day	8% 10% 3 8% 5% 4 4 4 6% 8% 39%	2520
	11th to 20th	Day	14% 12% 4 9% 4 4 5% 4 7% 7% 30%	2649
	21st to end	Day	13% 9% 3 8% 6% 5% 4 4 5% 8% 35%	2730
May	1st to 10th	Day	11% 6% 2 6% 5% 5% 4 4 6% 7% 43%	8026
	11th to 20th	Day	21% 9% 3 6% 4 4 4 4 5% 7% 33%	8305
	21st to end	Day	13% 6% 2 6% 4 4 4 3 5% 6% 48%	9682
June	1st to 10th	Day	13% 5% 3 6% 4 4 5% 4 6% 8% 42%	3150
	11th to 20th	Day	15% 6% 3 7% 5% 4 4 5% 7% 8% 36%	3076
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 6% 9% 41%	3000
July	1st to 10th	Day	7% 5% 2 5% 4 5% 5% 5% 7% 10% 45%	6799
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 9% 47%	6573
	21st to end	Day	6% 4 2 5% 4 4 5% 4 7% 10% 48%	6903
August	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 4 6% 9% 43%	6232
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 6% 9% 49%	5953
	21st to end	Day	7% 4 2 5% 3 4 4 3 5% 8% 56%	6366
September	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 5% 7% 52%	2400
	11th to 20th	Day	14% 6% 2 7% 4 4 3 3 5% 5% 46%	2245
	21st to end	Day	14% 5% 2 4 3 3 3 4 4 6% 50%	2200
October	1st to 10th	Day	10% 7% 2 6% 4 4 4 3 5% 7% 49%	3517
	11th to 20th	Day	7% 8% 2 6% 4 3 4 3 6% 8% 49%	2922
	21st to end	Day	11% 10% 4 9% 3 4 4 3 5% 7% 39%	3190
November	1st to 10th	Day	15% 12% 4 10% 5% 4 4 4 5% 6% 32%	1853
	11th to 20th	Day	10% 15% 5% 12% 7% 4 4 3 5% 6% 29%	1638
	21st to end	Day	8% 15% 4 11% 7% 5% 6% 5% 6% 5% 29%	1470
December	1st to 10th	Day	5% 15% 6% 15% 10% 9% 7% 4 5% 5% 19%	2360
	11th to 20th	Day	10% 13% 5% 12% 8% 6% 7% 4 6% 10% 20%	2713
	21st to end	Day	5% 9% 5% 15% 6% 6% 7% 5% 5% 6% 30%	3575
January	1st to 10th	Night	5% 11% 5% 17% 9% 9% 7% 5% 6% 6% 20%	8661
	11th to 20th	Night	5% 9% 4 12% 10% 9% 10% 6% 7% 8% 20%	8250
	21st to end	Night	4 10% 5% 13% 7% 6% 6% 5% 7% 8% 27%	9026
February	1st to 10th	Night	9% 14% 5% 11% 7% 6% 6% 5% 6% 6% 26%	2940
	11th to 20th	Night	7% 10% 4 9% 9% 6% 5% 5% 6% 7% 32%	2621
	21st to end	Night	6% 11% 5% 9% 6% 5% 6% 4 6% 7% 35%	2076
March	1st to 10th	Night	8% 11% 4 12% 6% 5% 5% 5% 7% 8% 30%	5494
	11th to 20th	Night	7% 10% 4 10% 7% 5% 6% 4 6% 8% 33%	5307
	21st to end	Night	8% 14% 6% 13% 6% 5% 6% 4 6% 7% 26%	5289
April	1st to 10th	Night	6% 9% 3 8% 5% 4 5% 5% 6% 8% 42%	2100
	11th to 20th	Night	14% 11% 3 8% 5% 5% 5% 3 6% 6% 34%	1918
	21st to end	Night	14% 8% 2 8% 5% 4 5% 3 5% 7% 38%	1890
May	1st to 10th	Night	11% 6% 2 6% 4 5% 5% 4 6% 7% 45%	4917
	11th to 20th	Night	17% 6% 2 6% 5% 4 4 4 6% 8% 36%	4585
	21st to end	Night	11% 7% 2 6% 4 4 4 3 5% 6% 47%	4526
June	1st to 10th	Night	14% 4 1 5% 5% 4 5% 4 7% 8% 43%	1470
	11th to 20th	Night	12% 5% 2 7% 5% 4 5% 4 6% 7% 41%	1435
	21st to end	Night	10% 4 1 5% 4 4 5% 5% 6% 9% 45%	1400
July	1st to 10th	Night	6% 3 1 4 4 4 5% 5% 8% 11% 49%	3180
	11th to 20th	Night	10% 3 2 5% 4 3 4 3 6% 8% 53%	3404
	21st to end	Night	5% 4 1 6% 4 4 4 4 6% 10% 51%	3970
August	1st to 10th	Night	8% 4 2 6% 4 3 4 3 7% 8% 51%	3580
	11th to 20th	Night	6% 3 2 6% 4 4 5% 4 7% 9% 51%	3895
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 8% 60%	4595
September	1st to 10th	Night	7% 4 2 5% 4 3 4 3 5% 7% 56%	2000
	11th to 20th	Night	13% 5% 2 5% 3 3 3 4 6% 8% 47%	2155
	21st to end	Night	14% 7% 2 5% 4 4 3 3 4 7% 47%	2200
October	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 4 6% 52%	3637
	11th to 20th	Night	10% 7% 2 6% 4 4 5% 4 6% 7% 44%	4217
	21st to end	Night	9% 8% 2 7% 5% 4 5% 3 6% 6% 44%	4610
November	1st to 10th	Night	12% 11% 4 8% 5% 4 5% 5% 5% 7% 35%	2665
	11th to 20th	Night	9% 12% 5% 12% 7% 5% 4 3 5% 6% 32%	2976
	21st to end	Night	8% 12% 4 11% 8% 5% 4 3 6% 6% 33%	3150
December	1st to 10th	Night	6% 13% 5% 13% 9% 7% 8% 6% 6% 7% 21%	5050
	11th to 20th	Night	9% 14% 4 10% 8% 6% 6% 4 5% 9% 23%	5714
	21st to end	Night	5% 9% 3 13% 8% 7% 8% 5% 6% 6% 29%	7645

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	61% 4 13% 15% 7%	4261
	11th to 20th	Day	64% 3 12% 14% 6%	4740
	21st to end	Day	49% 3 18% 23% 7%	5188
February	1st to 10th	Day	60% 3 13% 16% 7% 1	1680
	11th to 20th	Day	55% 5% 12% 19% 8%	1913
	21st to end	Day	55% 4 16% 19% 5%	1730
March	1st to 10th	Day	56% 5% 17% 16% 6%	4600
	11th to 20th	Day	58% 4 17% 18% 4	4882
	21st to end	Day	59% 6% 12% 18% 6%	5884
April	1st to 10th	Day	41% 3 17% 27% 11% 1	2520
	11th to 20th	Day	51% 4 13% 20% 11% 1	2652
	21st to end	Day	47% 5% 16% 24% 8%	2730
May	1st to 10th	Day	38% 4 13% 30% 13% 2	8026
	11th to 20th	Day	50% 4 11% 21% 12% 2	8309
	21st to end	Day	37% 4 9% 28% 22% 1	9683
June	1st to 10th	Day	39% 4 20% 27% 9% 1	3150
	11th to 20th	Day	43% 6% 18% 23% 8% 1	3076
	21st to end	Day	39% 6% 20% 27% 7% 1	3000
July	1st to 10th	Day	32% 7% 25% 30% 6%	6726
	11th to 20th	Day	33% 6% 19% 35% 7%	6492
	21st to end	Day	30% 6% 22% 31% 10% 1	6705
August	1st to 10th	Day	33% 5% 17% 32% 13% 1	4536
	11th to 20th	Day	31% 5% 21% 36% 7%	4308
	21st to end	Day	31% 4 17% 37% 9%	4589
September	1st to 10th	Day	31% 4 16% 34% 14% 1	2400
	11th to 20th	Day	40% 4 19% 24% 12% 1	2245
	21st to end	Day	35% 3 14% 32% 15%	2200
October	1st to 10th	Day	37% 3 13% 34% 12% 1	3517
	11th to 20th	Day	33% 3 15% 38% 11%	2922
	21st to end	Day	45% 3 12% 30% 10%	3190
November	1st to 10th	Day	52% 4 16% 20% 7% 1	1853
	11th to 20th	Day	56% 3 16% 16% 7% 1	1638
	21st to end	Day	55% 7% 16% 17% 5%	1470
December	1st to 10th	Day	67% 4 14% 11% 4	2360
	11th to 20th	Day	60% 4 17% 16% 3	2710
	21st to end	Day	53% 4 10% 23% 9% 1	3575
January	1st to 10th	Night	63% 4 11% 16% 6%	8662
	11th to 20th	Night	59% 3 14% 18% 6%	8250
	21st to end	Night	52% 5% 17% 19% 7%	9026
February	1st to 10th	Night	57% 4 14% 17% 7%	2940
	11th to 20th	Night	48% 5% 14% 21% 12%	2622
	21st to end	Night	47% 3 15% 24% 10%	2076
March	1st to 10th	Night	50% 4 20% 21% 5%	5494
	11th to 20th	Night	48% 4 17% 24% 7%	5307
	21st to end	Night	57% 5% 11% 22% 5%	5289
April	1st to 10th	Night	39% 5% 12% 26% 15% 2	2100
	11th to 20th	Night	51% 4 9% 23% 12% 1	1918
	21st to end	Night	46% 4 11% 25% 12% 2	1890
May	1st to 10th	Night	37% 4 10% 31% 18% 1	4918
	11th to 20th	Night	44% 4 11% 27% 12% 1	4586
	21st to end	Night	38% 4 9% 25% 23% 1	4526
June	1st to 10th	Night	37% 6% 16% 26% 13% 3	1470
	11th to 20th	Night	39% 5% 17% 25% 12% 2	1435
	21st to end	Night	33% 7% 20% 32% 8% 1	1400
July	1st to 10th	Night	27% 8% 25% 30% 8% 1	3145
	11th to 20th	Night	30% 5% 17% 39% 9% 1	3362
	21st to end	Night	29% 5% 22% 29% 12% 2	3856
August	1st to 10th	Night	26% 5% 19% 34% 14% 2	2600
	11th to 20th	Night	28% 5% 20% 37% 9% 1	2816
	21st to end	Night	27% 4 18% 36% 14% 1	3316
September	1st to 10th	Night	28% 4 13% 34% 19% 2	2000
	11th to 20th	Night	35% 4 18% 27% 14% 1	2155
	21st to end	Night	38% 4 12% 31% 14% 2	2200
October	1st to 10th	Night	35% 3 11% 34% 14% 4	3637
	11th to 20th	Night	39% 3 11% 34% 13% 1	4217
	21st to end	Night	40% 3 13% 34% 10%	4610
November	1st to 10th	Night	48% 5% 14% 22% 8% 2	2665
	11th to 20th	Night	52% 5% 16% 20% 6%	2976
	21st to end	Night	52% 5% 19% 18% 5%	3150
December	1st to 10th	Night	62% 6% 17% 11% 4	5050
	11th to 20th	Night	58% 4 18% 16% 3	5716
	21st to end	Night	53% 6% 11% 20% 10% 1	7645

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	10% 5% 34% 32% 14% 5%	330
	11th to 20th	Day	10% 9% 38% 32% 9% 2	330
	21st to end	Day	13% 9% 32% 34% 11% 2	363
February	1st to 10th	Day	13% 8% 37% 33% 8%	330
	11th to 20th	Day	10% 7% 35% 30% 14% 4	330
	21st to end	Day	5% 6% 32% 41% 14% 3	273
March	1st to 10th	Day	11% 9% 37% 29% 10% 3	330
	11th to 20th	Day	12% 10% 30% 30% 15% 3	330
	21st to end	Day	16% 7% 32% 26% 16% 3	494
April	1st to 10th	Day	11% 11% 33% 34% 9% 2	540
	11th to 20th	Day	19% 9% 32% 27% 12% 1	690
	21st to end	Day	16% 9% 27% 32% 14% 2	750
May	1st to 10th	Day	13% 8% 30% 31% 14% 3	753
	11th to 20th	Day	21% 8% 27% 26% 14% 4	775
	21st to end	Day	17% 9% 22% 31% 17% 4	844
June	1st to 10th	Day	13% 10% 29% 28% 16% 4	780
	11th to 20th	Day	15% 10% 30% 28% 13% 4	756
	21st to end	Day	11% 9% 25% 33% 18% 3	730
July	1st to 10th	Day	9% 4 22% 35% 22% 7%	721
	11th to 20th	Day	9% 6% 31% 31% 17% 6%	718
	21st to end	Day	5% 3 27% 36% 22% 7%	794
August	1st to 10th	Day	10% 5% 21% 36% 20% 7%	726
	11th to 20th	Day	10% 6% 22% 29% 26% 7%	715
	21st to end	Day	11% 6% 24% 33% 20% 6%	757
September	1st to 10th	Day	9% 9% 32% 29% 15% 5%	530
	11th to 20th	Day	19% 10% 26% 30% 14% 1	375
	21st to end	Day	21% 10% 28% 25% 15% 1	330
October	1st to 10th	Day	20% 8% 30% 26% 13% 3	330
	11th to 20th	Day	19% 13% 29% 26% 9% 3	330
	21st to end	Day	24% 6% 36% 25% 7% 3	363
November	1st to 10th	Day	24% 9% 25% 30% 9% 2	330
	11th to 20th	Day	16% 11% 39% 24% 10% 1	330
	21st to end	Day	14% 8% 37% 31% 8% 2	330
December	1st to 10th	Day	11% 8% 37% 29% 13% 2	330
	11th to 20th	Day	17% 10% 40% 25% 6% 2	330
	21st to end	Day	10% 6% 36% 31% 13% 4	363
January	1st to 10th	Night	11% 6% 36% 34% 13% 1	1050
	11th to 20th	Night	14% 8% 35% 34% 8% 1	1050
	21st to end	Night	12% 9% 35% 35% 9%	1155
February	1st to 10th	Night	15% 9% 30% 33% 11% 2	1050
	11th to 20th	Night	12% 6% 31% 37% 13% 2	934
	21st to end	Night	11% 7% 28% 38% 14% 2	692
March	1st to 10th	Night	14% 7% 34% 31% 12% 2	840
	11th to 20th	Night	10% 8% 34% 35% 12% 1	730
	21st to end	Night	12% 7% 32% 35% 11% 3	693
April	1st to 10th	Night	10% 7% 36% 36% 10% 1	630
	11th to 20th	Night	20% 6% 29% 37% 7%	623
	21st to end	Night	17% 6% 29% 35% 13% 1	630
May	1st to 10th	Night	15% 6% 29% 36% 14%	630
	11th to 20th	Night	17% 4 31% 36% 11%	621
	21st to end	Night	19% 6% 25% 38% 12% 1	683
June	1st to 10th	Night	15% 6% 31% 32% 16% 1	630
	11th to 20th	Night	15% 4 31% 36% 13% 1	615
	21st to end	Night	12% 4 27% 41% 16% 1	600
July	1st to 10th	Night	7% 3 19% 46% 25% 1	585
	11th to 20th	Night	8% 4 26% 46% 15% 1	582
	21st to end	Night	5% 3 23% 51% 15% 2	657
August	1st to 10th	Night	8% 4 21% 46% 18% 1	597
	11th to 20th	Night	7% 4 22% 43% 22% 3	594
	21st to end	Night	10% 3 29% 41% 16% 1	660
September	1st to 10th	Night	8% 5% 28% 39% 17% 3	600
	11th to 20th	Night	15% 5% 33% 35% 11% 1	600
	21st to end	Night	17% 6% 31% 34% 13% 1	600
October	1st to 10th	Night	17% 6% 32% 34% 11%	621
	11th to 20th	Night	19% 8% 30% 32% 10% 1	990
	21st to end	Night	18% 8% 32% 32% 9% 1	1100
November	1st to 10th	Night	18% 8% 34% 31% 7% 1	1025
	11th to 20th	Night	14% 9% 36% 30% 9% 2	1050
	21st to end	Night	13% 9% 38% 33% 8%	1050
December	1st to 10th	Night	12% 7% 36% 32% 12% 2	1050
	11th to 20th	Night	16% 9% 33% 31% 10% 1	1050
	21st to end	Night	17% 5% 32% 33% 12% 2	1155

Page generated at 2026-06-13 01:31:41. Version ac07

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