Observatoire Maucar de La Motte
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Maucar de La Motte clear sky chart from 2005-11-06 to 2024-11-04.

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	17% 12% 4 9% 6% 5% 5% 4 5% 6% 27%	101769
	Night	17% 14% 5% 11% 6% 5% 5% 4 4 5% 24%	97292
Transparency	Day	57% 6% 11% 18% 7% 1	105269
	Night	61% 6% 10% 16% 7% 1	101882
Seeing	Day	24% 16% 33% 19% 7% 2	15092
	Night	25% 13% 31% 23% 8% 1	23932

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	15% 22% 9% 14% 5% 8% 7% 4 5% 5% 8%	2208
	11th to 20th	Day	9% 15% 8% 20% 9% 4 7% 5% 5% 5% 13%	2253
	21st to end	Day	12% 20% 9% 17% 6% 5% 4 3 4 5% 15%	2904
February	1st to 10th	Day	9% 16% 6% 13% 8% 10% 6% 3 5% 7% 16%	1710
	11th to 20th	Day	11% 20% 5% 13% 7% 6% 7% 4 5% 5% 18%	1663
	21st to end	Day	13% 16% 6% 13% 7% 5% 4 4 5% 5% 22%	1429
March	1st to 10th	Day	20% 15% 4 9% 5% 4 5% 3 4 5% 26%	3293
	11th to 20th	Day	11% 18% 6% 17% 5% 4 3 3 3 4 26%	3480
	21st to end	Day	11% 13% 5% 14% 7% 7% 4 3 3 5% 27%	3897
April	1st to 10th	Day	20% 16% 5% 9% 5% 3 4 4 4 5% 24%	2280
	11th to 20th	Day	20% 12% 4 9% 5% 4 3 4 4 5% 30%	2356
	21st to end	Day	21% 12% 4 7% 5% 4 4 3 5% 5% 31%	2489
May	1st to 10th	Day	18% 12% 3 7% 5% 4 5% 4 5% 7% 29%	4426
	11th to 20th	Day	16% 9% 3 7% 5% 6% 5% 5% 7% 8% 30%	4398
	21st to end	Day	18% 9% 3 7% 5% 4 4 4 5% 7% 35%	4837
June	1st to 10th	Day	22% 8% 3 7% 5% 5% 5% 4 6% 7% 28%	2845
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 5% 7% 35%	2850
	21st to end	Day	19% 8% 3 7% 5% 5% 6% 5% 5% 7% 31%	2850
July	1st to 10th	Day	18% 7% 3 7% 6% 5% 6% 5% 7% 9% 29%	4760
	11th to 20th	Day	16% 8% 3 6% 5% 5% 4 5% 6% 8% 35%	4760
	21st to end	Day	16% 7% 2 7% 5% 4 5% 4 6% 8% 35%	4825
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 6% 5% 6% 8% 31%	4307
	11th to 20th	Day	19% 7% 3 7% 4 5% 5% 4 6% 8% 32%	4044
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 3 6% 8% 38%	4384
September	1st to 10th	Day	20% 7% 3 6% 4 5% 5% 4 6% 7% 32%	2280
	11th to 20th	Day	21% 9% 2 6% 5% 4 4 4 6% 7% 32%	2269
	21st to end	Day	24% 11% 3 6% 5% 4 4 4 4 5% 31%	1990
October	1st to 10th	Day	22% 13% 2 8% 4 4 4 4 4 5% 30%	1900
	11th to 20th	Day	30% 21% 4 8% 3 3 3 3 4 4 18%	1900
	21st to end	Day	28% 19% 4 8% 5% 5% 4 3 4 5% 15%	1962
November	1st to 10th	Day	21% 21% 6% 11% 5% 5% 4 2 3 5% 18%	1510
	11th to 20th	Day	21% 19% 7% 14% 7% 6% 4 3 4 4 12%	1520
	21st to end	Day	24% 23% 8% 13% 7% 4 4 3 2 3 8%	1520
December	1st to 10th	Day	18% 24% 8% 14% 6% 5% 3 2 4 4 11%	1520
	11th to 20th	Day	17% 19% 7% 11% 9% 5% 5% 4 4 4 14%	1719
	21st to end	Day	17% 21% 7% 18% 10% 5% 3 3 3 3 10%	2431
January	1st to 10th	Night	14% 18% 8% 17% 9% 6% 6% 4 4 3 11%	4748
	11th to 20th	Night	11% 16% 6% 17% 9% 7% 7% 5% 4 5% 14%	4714
	21st to end	Night	9% 18% 10% 16% 9% 8% 7% 3 5% 4 11%	4748
February	1st to 10th	Night	10% 17% 6% 11% 9% 6% 6% 5% 6% 6% 19%	2470
	11th to 20th	Night	12% 18% 6% 13% 8% 6% 5% 3 3 6% 20%	2403
	21st to end	Night	10% 17% 6% 13% 8% 7% 7% 4 4 6% 19%	2023
March	1st to 10th	Night	15% 15% 4 9% 5% 4 5% 4 5% 6% 28%	3546
	11th to 20th	Night	14% 22% 6% 13% 6% 5% 5% 3 4 4 19%	3479
	21st to end	Night	13% 12% 4 12% 6% 5% 5% 4 4 5% 29%	3734
April	1st to 10th	Night	19% 16% 4 9% 5% 4 3 3 4 4 28%	1900
	11th to 20th	Night	18% 10% 3 8% 4 5% 5% 4 6% 6% 31%	1791
	21st to end	Night	19% 11% 4 7% 4 4 3 3 4 6% 34%	1690
May	1st to 10th	Night	19% 11% 4 7% 5% 5% 5% 3 5% 7% 30%	2514
	11th to 20th	Night	16% 9% 3 8% 4 3 4 4 5% 7% 35%	2495
	21st to end	Night	19% 7% 2 7% 5% 5% 4 5% 7% 8% 31%	2738
June	1st to 10th	Night	20% 7% 4 7% 6% 5% 5% 4 5% 6% 30%	1330
	11th to 20th	Night	17% 7% 2 7% 5% 4 4 4 5% 6% 38%	1330
	21st to end	Night	15% 6% 2 7% 5% 5% 5% 4 7% 7% 37%	1330
July	1st to 10th	Night	19% 8% 2 6% 4 4 4 5% 5% 9% 35%	2210
	11th to 20th	Night	17% 9% 3 7% 5% 5% 5% 4 6% 7% 33%	2210
	21st to end	Night	17% 6% 2 5% 4 4 4 4 5% 7% 41%	2725
August	1st to 10th	Night	12% 5% 3 7% 6% 5% 6% 4 6% 9% 38%	2619
	11th to 20th	Night	16% 8% 3 7% 5% 4 5% 3 5% 6% 36%	2785
	21st to end	Night	15% 7% 3 8% 4 4 4 4 5% 6% 39%	3239
September	1st to 10th	Night	19% 7% 3 7% 5% 4 4 3 5% 6% 38%	1900
	11th to 20th	Night	20% 8% 3 6% 4 3 4 2 5% 6% 39%	1909
	21st to end	Night	22% 9% 3 5% 4 3 3 3 5% 6% 36%	2190
October	1st to 10th	Night	22% 9% 3 8% 5% 5% 4 4 5% 6% 31%	2280
	11th to 20th	Night	28% 17% 4 9% 4 4 3 3 4 4 20%	2280
	21st to end	Night	25% 19% 4 8% 4 4 4 3 4 5% 19%	2632
November	1st to 10th	Night	19% 18% 6% 11% 5% 4 4 3 4 5% 21%	2641
	11th to 20th	Night	20% 18% 5% 14% 7% 4 4 3 4 4 16%	2660
	21st to end	Night	24% 20% 7% 14% 7% 4 4 3 4 4 10%	2660
December	1st to 10th	Night	17% 24% 7% 15% 7% 6% 3 3 3 3 11%	2660
	11th to 20th	Night	18% 20% 6% 14% 8% 6% 5% 3 4 3 13%	3473
	21st to end	Night	18% 20% 10% 17% 8% 4 3 2 2 3 12%	5236

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	78% 6% 9% 6% 1	2209
	11th to 20th	Day	72% 5% 6% 13% 3	2253
	21st to end	Day	73% 3 7% 12% 5%	2904
February	1st to 10th	Day	68% 5% 6% 14% 7%	1710
	11th to 20th	Day	68% 5% 7% 13% 6%	1672
	21st to end	Day	64% 4 8% 16% 7% 1	1429
March	1st to 10th	Day	61% 5% 7% 18% 8% 1	3296
	11th to 20th	Day	63% 4 7% 17% 8% 1	3480
	21st to end	Day	59% 5% 8% 18% 9% 2	3897
April	1st to 10th	Day	62% 5% 9% 12% 10% 1	2280
	11th to 20th	Day	56% 5% 9% 18% 11% 1	2356
	21st to end	Day	55% 4 8% 16% 14% 2	2489
May	1st to 10th	Day	51% 9% 11% 19% 9% 1	4440
	11th to 20th	Day	48% 9% 13% 20% 8% 1	4402
	21st to end	Day	48% 7% 10% 20% 15% 1	4837
June	1st to 10th	Day	52% 7% 10% 20% 9% 1	2845
	11th to 20th	Day	47% 7% 9% 23% 12% 2	2850
	21st to end	Day	51% 7% 12% 21% 9% 1	2850
July	1st to 10th	Day	49% 7% 15% 23% 5%	4686
	11th to 20th	Day	44% 8% 16% 22% 9% 1	4679
	21st to end	Day	46% 7% 12% 28% 6%	4672
August	1st to 10th	Day	48% 8% 16% 24% 4	4293
	11th to 20th	Day	47% 8% 15% 22% 8%	4083
	21st to end	Day	43% 7% 12% 28% 10%	4384
September	1st to 10th	Day	49% 8% 13% 20% 8% 1	2280
	11th to 20th	Day	50% 8% 16% 21% 5%	2269
	21st to end	Day	55% 7% 11% 20% 7%	1990
October	1st to 10th	Day	59% 4 10% 20% 6% 1	3160
	11th to 20th	Day	64% 5% 12% 14% 5%	3140
	21st to end	Day	70% 6% 13% 6% 5%	3214
November	1st to 10th	Day	71% 5% 11% 8% 4	1510
	11th to 20th	Day	77% 5% 8% 8% 2	1520
	21st to end	Day	84% 5% 5% 5% 2	1520
December	1st to 10th	Day	77% 5% 8% 8% 2	1520
	11th to 20th	Day	74% 5% 5% 13% 3	1719
	21st to end	Day	80% 4 6% 9% 1	2431
January	1st to 10th	Night	77% 5% 10% 6% 1	4748
	11th to 20th	Night	72% 6% 6% 11% 5%	4714
	21st to end	Night	75% 5% 6% 9% 5% 1	4748
February	1st to 10th	Night	64% 7% 8% 13% 8%	2470
	11th to 20th	Night	67% 5% 8% 14% 6%	2405
	21st to end	Night	66% 4 8% 14% 7% 1	2023
March	1st to 10th	Night	57% 6% 10% 14% 12% 2	3556
	11th to 20th	Night	69% 4 8% 12% 6% 1	3480
	21st to end	Night	54% 5% 10% 16% 12% 3	3734
April	1st to 10th	Night	59% 4 8% 14% 13% 1	1900
	11th to 20th	Night	52% 6% 10% 20% 11% 1	1791
	21st to end	Night	51% 5% 7% 19% 16% 2	1690
May	1st to 10th	Night	51% 8% 13% 16% 11% 1	2520
	11th to 20th	Night	45% 7% 14% 21% 11% 1	2496
	21st to end	Night	46% 9% 11% 19% 13% 1	2739
June	1st to 10th	Night	53% 7% 9% 19% 10% 1	1330
	11th to 20th	Night	46% 6% 10% 22% 14% 3	1330
	21st to end	Night	44% 8% 13% 24% 11% 1	1330
July	1st to 10th	Night	45% 7% 14% 26% 8%	2175
	11th to 20th	Night	48% 7% 16% 20% 8%	2168
	21st to end	Night	44% 7% 14% 29% 7%	2638
August	1st to 10th	Night	42% 7% 18% 29% 5%	2609
	11th to 20th	Night	46% 7% 16% 24% 6%	2812
	21st to end	Night	45% 7% 14% 25% 8% 2	3239
September	1st to 10th	Night	46% 7% 16% 21% 9% 1	1900
	11th to 20th	Night	46% 8% 17% 22% 7%	1909
	21st to end	Night	50% 7% 14% 23% 6%	2190
October	1st to 10th	Night	54% 6% 12% 20% 8% 1	3800
	11th to 20th	Night	63% 5% 10% 20% 2	3779
	21st to end	Night	63% 6% 14% 10% 6% 1	4330
November	1st to 10th	Night	66% 7% 13% 12% 2	2641
	11th to 20th	Night	72% 6% 9% 9% 4	2660
	21st to end	Night	79% 5% 7% 7% 1	2660
December	1st to 10th	Night	79% 5% 8% 7% 2	2660
	11th to 20th	Night	76% 4 6% 10% 3	3472
	21st to end	Night	80% 4 4 9% 3	5236

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	20% 24% 42% 9% 4 1	180
	11th to 20th	Day	17% 18% 39% 20% 5% 1	180
	21st to end	Day	19% 12% 38% 24% 7% 1	236
February	1st to 10th	Day	21% 26% 35% 14% 3	270
	11th to 20th	Day	19% 25% 39% 14% 3	270
	21st to end	Day	24% 24% 38% 12% 2	241
March	1st to 10th	Day	21% 19% 40% 15% 5%	460
	11th to 20th	Day	23% 19% 35% 17% 5%	460
	21st to end	Day	24% 21% 35% 15% 5% 1	506
April	1st to 10th	Day	27% 19% 30% 16% 7% 2	460
	11th to 20th	Day	29% 17% 30% 16% 6% 1	452
	21st to end	Day	29% 19% 29% 15% 5% 1	460
May	1st to 10th	Day	25% 16% 32% 19% 6% 1	463
	11th to 20th	Day	27% 17% 31% 17% 6% 2	487
	21st to end	Day	23% 18% 31% 23% 5% 1	529
June	1st to 10th	Day	24% 15% 34% 20% 6%	675
	11th to 20th	Day	21% 16% 34% 20% 6% 2	680
	21st to end	Day	21% 12% 31% 26% 8% 1	680
July	1st to 10th	Day	17% 14% 35% 24% 9% 1	671
	11th to 20th	Day	17% 12% 37% 24% 9% 1	668
	21st to end	Day	19% 10% 31% 26% 11% 2	543
August	1st to 10th	Day	21% 9% 31% 26% 10% 3	486
	11th to 20th	Day	20% 7% 26% 26% 14% 6%	479
	21st to end	Day	21% 12% 29% 20% 12% 6%	539
September	1st to 10th	Day	22% 13% 35% 18% 9% 3	490
	11th to 20th	Day	22% 9% 32% 24% 10% 3	490
	21st to end	Day	28% 13% 27% 19% 10% 2	490
October	1st to 10th	Day	28% 16% 27% 19% 8% 2	490
	11th to 20th	Day	38% 19% 28% 11% 3 1	490
	21st to end	Day	35% 17% 31% 14% 3	463
November	1st to 10th	Day	33% 25% 32% 9% 1	186
	11th to 20th	Day	28% 22% 33% 16% 2 1	180
	21st to end	Day	41% 23% 28% 5% 2 1	180
December	1st to 10th	Day	26% 17% 33% 16% 7% 1	180
	11th to 20th	Day	23% 17% 46% 10% 2 2	180
	21st to end	Day	32% 15% 33% 13% 5% 2	198
January	1st to 10th	Night	27% 12% 36% 19% 5%	950
	11th to 20th	Night	25% 15% 34% 21% 5%	917
	21st to end	Night	17% 12% 33% 27% 11% 1	836
February	1st to 10th	Night	17% 18% 36% 23% 6%	760
	11th to 20th	Night	22% 13% 34% 25% 5%	743
	21st to end	Night	20% 20% 36% 19% 5%	628
March	1st to 10th	Night	21% 20% 31% 23% 5% 1	760
	11th to 20th	Night	27% 19% 29% 21% 4 1	760
	21st to end	Night	22% 14% 38% 21% 5% 1	836
April	1st to 10th	Night	28% 16% 30% 21% 6%	760
	11th to 20th	Night	24% 17% 28% 23% 7%	667
	21st to end	Night	24% 12% 33% 25% 6% 1	550
May	1st to 10th	Night	23% 12% 31% 25% 9%	380
	11th to 20th	Night	24% 9% 29% 29% 8% 2	374
	21st to end	Night	23% 11% 33% 27% 7%	411
June	1st to 10th	Night	23% 9% 34% 25% 9%	380
	11th to 20th	Night	21% 10% 32% 30% 8%	380
	21st to end	Night	17% 9% 28% 34% 12%	380
July	1st to 10th	Night	17% 10% 30% 34% 8% 1	370
	11th to 20th	Night	16% 8% 26% 37% 12%	368
	21st to end	Night	16% 6% 27% 37% 13% 1	416
August	1st to 10th	Night	20% 5% 26% 31% 16% 2	439
	11th to 20th	Night	16% 6% 26% 30% 20% 1	564
	21st to end	Night	23% 9% 25% 27% 14% 3	690
September	1st to 10th	Night	23% 9% 30% 25% 12% 1	760
	11th to 20th	Night	24% 10% 26% 26% 13% 1	760
	21st to end	Night	28% 9% 25% 26% 11% 1	760
October	1st to 10th	Night	27% 12% 29% 23% 8% 1	760
	11th to 20th	Night	38% 13% 27% 17% 5% 1	760
	21st to end	Night	37% 11% 31% 16% 4 1	836
November	1st to 10th	Night	30% 14% 35% 15% 5% 1	755
	11th to 20th	Night	31% 18% 30% 16% 5%	760
	21st to end	Night	35% 16% 31% 15% 3	760
December	1st to 10th	Night	31% 16% 30% 18% 5% 1	760
	11th to 20th	Night	27% 17% 31% 18% 6% 2	897
	21st to end	Night	30% 18% 26% 19% 6% 1	1045

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