Deposit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deposit clear sky chart from 2005-11-06 to 2026-07-16.

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	17% 11% 4 9% 5% 5% 5% 4 5% 7% 29%	138400
	Night	17% 12% 4 10% 6% 4 4 3 5% 6% 29%	134287
Transparency	Day	36% 37% 7% 13% 7% 1	141906
	Night	38% 36% 7% 12% 7% 1	138870
Seeing	Day	29% 17% 27% 17% 8% 3	16920
	Night	26% 16% 26% 22% 9% 1	26092

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	12% 17% 11% 24% 8% 3 3 2 3 4 14%	4661
	11th to 20th	Day	12% 16% 8% 19% 7% 6% 5% 3 4 4 15%	4650
	21st to end	Day	14% 13% 7% 10% 8% 7% 5% 3 5% 5% 21%	5696
February	1st to 10th	Day	15% 15% 5% 14% 8% 6% 4 3 5% 5% 20%	1890
	11th to 20th	Day	13% 15% 8% 13% 7% 5% 4 3 5% 6% 22%	1942
	21st to end	Day	19% 14% 4 12% 7% 4 4 3 5% 6% 24%	1730
March	1st to 10th	Day	20% 15% 6% 10% 6% 3 3 3 3 4 27%	4576
	11th to 20th	Day	14% 14% 5% 8% 5% 4 3 3 4 6% 34%	5086
	21st to end	Day	17% 11% 4 11% 5% 5% 4 3 5% 5% 29%	5910
April	1st to 10th	Day	18% 16% 4 8% 5% 4 4 3 4 5% 30%	2520
	11th to 20th	Day	16% 11% 3 8% 5% 5% 5% 3 5% 6% 32%	2494
	21st to end	Day	19% 12% 3 7% 4 4 4 3 4 7% 32%	2520
May	1st to 10th	Day	26% 10% 3 7% 4 4 5% 3 5% 7% 25%	7993
	11th to 20th	Day	18% 10% 3 7% 5% 5% 5% 4 5% 6% 32%	8221
	21st to end	Day	22% 9% 2 7% 5% 5% 5% 4 7% 7% 27%	9060
June	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 4 6% 8% 33%	2940
	11th to 20th	Day	17% 7% 3 7% 5% 5% 5% 4 7% 8% 31%	2940
	21st to end	Day	17% 7% 2 8% 5% 4 5% 5% 6% 9% 33%	2940
July	1st to 10th	Day	10% 7% 3 8% 6% 5% 5% 5% 7% 9% 34%	6500
	11th to 20th	Day	10% 7% 3 7% 6% 7% 6% 5% 8% 11% 32%	6430
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 7% 8% 37%	6926
August	1st to 10th	Day	20% 8% 4 7% 4 5% 5% 3 6% 7% 30%	4286
	11th to 20th	Day	15% 8% 2 8% 6% 6% 5% 4 7% 9% 30%	3954
	21st to end	Day	18% 6% 2 6% 4 4 5% 4 7% 9% 35%	4312
September	1st to 10th	Day	17% 8% 3 7% 3 4 4 3 5% 7% 39%	2400
	11th to 20th	Day	13% 7% 3 6% 3 4 4 3 6% 7% 43%	2380
	21st to end	Day	20% 8% 2 7% 4 4 5% 4 6% 7% 33%	2175
October	1st to 10th	Day	18% 8% 4 7% 5% 4 5% 4 5% 6% 35%	2000
	11th to 20th	Day	18% 12% 2 7% 4 4 5% 4 5% 6% 33%	2000
	21st to end	Day	23% 14% 3 7% 5% 4 4 3 4 6% 27%	2090
November	1st to 10th	Day	14% 12% 4 7% 4 4 4 3 5% 6% 36%	1851
	11th to 20th	Day	15% 18% 5% 9% 4 4 4 3 4 5% 29%	1853
	21st to end	Day	19% 17% 5% 11% 5% 3 4 3 5% 5% 23%	1680
December	1st to 10th	Day	16% 19% 8% 18% 5% 5% 4 3 4 4 14%	2680
	11th to 20th	Day	19% 16% 9% 10% 4 4 3 2 3 4 25%	3066
	21st to end	Day	19% 18% 7% 11% 5% 4 4 3 4 5% 19%	4048
January	1st to 10th	Night	14% 16% 7% 25% 7% 4 4 2 3 4 14%	8234
	11th to 20th	Night	11% 17% 7% 20% 9% 5% 4 3 4 5% 15%	8235
	21st to end	Night	13% 12% 4 11% 10% 10% 7% 4 4 4 21%	8484
February	1st to 10th	Night	15% 14% 5% 12% 7% 6% 5% 3 5% 5% 23%	2730
	11th to 20th	Night	14% 14% 6% 13% 9% 5% 6% 4 4 5% 20%	2564
	21st to end	Night	19% 13% 4 13% 5% 4 4 3 5% 5% 25%	2076
March	1st to 10th	Night	19% 12% 5% 11% 7% 4 4 3 4 5% 26%	5484
	11th to 20th	Night	15% 15% 5% 8% 5% 4 3 2 4 5% 33%	5089
	21st to end	Night	17% 14% 4 11% 5% 4 4 3 5% 5% 28%	5263
April	1st to 10th	Night	20% 14% 4 9% 5% 3 4 4 4 6% 27%	2100
	11th to 20th	Night	20% 11% 2 8% 5% 3 3 3 5% 6% 35%	2075
	21st to end	Night	19% 9% 3 7% 4 4 4 3 5% 6% 35%	2100
May	1st to 10th	Night	29% 11% 3 6% 4 4 3 3 4 6% 27%	4945
	11th to 20th	Night	19% 9% 3 6% 5% 4 4 4 6% 7% 34%	4639
	21st to end	Night	22% 10% 3 7% 4 4 4 3 5% 6% 31%	5114
June	1st to 10th	Night	15% 8% 2 6% 4 4 4 3 6% 8% 39%	1680
	11th to 20th	Night	16% 8% 2 5% 4 4 5% 4 6% 9% 38%	1680
	21st to end	Night	14% 4 2 5% 5% 5% 5% 5% 6% 8% 42%	1680
July	1st to 10th	Night	11% 8% 3 7% 6% 5% 5% 4 5% 8% 38%	3680
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 4 6% 9% 36%	3640
	21st to end	Night	13% 6% 2 6% 3 4 4 4 5% 7% 46%	3926
August	1st to 10th	Night	21% 8% 2 7% 4 4 5% 4 6% 6% 32%	2846
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 5% 6% 39%	3061
	21st to end	Night	15% 7% 2 5% 4 4 4 4 5% 7% 43%	3586
September	1st to 10th	Night	15% 7% 2 5% 4 3 4 3 4 7% 44%	2000
	11th to 20th	Night	14% 6% 1 5% 4 4 4 3 4 6% 50%	2020
	21st to end	Night	18% 8% 3 6% 4 4 4 3 5% 6% 38%	2221
October	1st to 10th	Night	18% 9% 2 7% 4 4 4 3 5% 6% 37%	2400
	11th to 20th	Night	21% 9% 2 7% 5% 3 3 3 5% 5% 38%	2400
	21st to end	Night	23% 14% 3 7% 4 4 4 3 4 6% 28%	2748
November	1st to 10th	Night	12% 14% 3 7% 4 3 3 4 5% 7% 37%	2667
	11th to 20th	Night	19% 12% 4 8% 4 4 4 4 5% 5% 31%	2762
	21st to end	Night	15% 14% 4 9% 6% 5% 5% 4 6% 6% 26%	2940
December	1st to 10th	Night	16% 17% 7% 13% 6% 5% 4 4 5% 6% 19%	4720
	11th to 20th	Night	23% 15% 5% 10% 4 3 3 2 3 4 27%	5348
	21st to end	Night	22% 15% 8% 11% 6% 4 4 3 4 5% 19%	7150

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% 22% 6% 7% 2	4662
	11th to 20th	Day	58% 23% 5% 8% 5%	4680
	21st to end	Day	49% 25% 7% 14% 5%	5696
February	1st to 10th	Day	27% 60% 3 7% 2	1890
	11th to 20th	Day	27% 59% 2 8% 4	1951
	21st to end	Day	24% 59% 4 9% 3	1730
March	1st to 10th	Day	46% 30% 6% 9% 8% 1	4579
	11th to 20th	Day	36% 29% 13% 15% 4 3	5086
	21st to end	Day	40% 31% 6% 8% 13% 2	5910
April	1st to 10th	Day	27% 59% 3 8% 3 1	2520
	11th to 20th	Day	21% 61% 5% 7% 7%	2494
	21st to end	Day	23% 59% 4 8% 5% 1	2520
May	1st to 10th	Day	47% 25% 9% 12% 6% 1	8005
	11th to 20th	Day	42% 25% 8% 18% 7%	8225
	21st to end	Day	44% 26% 9% 13% 7%	9061
June	1st to 10th	Day	19% 60% 4 9% 7%	2940
	11th to 20th	Day	20% 61% 5% 8% 5%	2940
	21st to end	Day	19% 60% 4 11% 6%	2940
July	1st to 10th	Day	33% 30% 11% 17% 9%	6430
	11th to 20th	Day	33% 31% 11% 18% 7%	6355
	21st to end	Day	32% 28% 8% 21% 11%	6728
August	1st to 10th	Day	36% 38% 8% 12% 5%	4272
	11th to 20th	Day	31% 41% 10% 15% 3	3993
	21st to end	Day	25% 39% 9% 23% 4	4312
September	1st to 10th	Day	16% 58% 6% 14% 6%	2400
	11th to 20th	Day	17% 57% 5% 10% 11% 1	2380
	21st to end	Day	21% 58% 5% 9% 5% 1	2175
October	1st to 10th	Day	30% 39% 5% 16% 9% 1	3260
	11th to 20th	Day	25% 38% 6% 15% 12% 4	3240
	21st to end	Day	21% 38% 11% 21% 8% 1	3354
November	1st to 10th	Day	25% 54% 6% 9% 4	1851
	11th to 20th	Day	24% 54% 4 10% 7% 1	1853
	21st to end	Day	29% 56% 6% 6% 2 1	1680
December	1st to 10th	Day	50% 37% 5% 6% 2	2680
	11th to 20th	Day	46% 32% 6% 9% 7%	3066
	21st to end	Day	50% 27% 5% 10% 7% 1	4048
January	1st to 10th	Night	61% 22% 6% 8% 3	8234
	11th to 20th	Night	57% 24% 7% 7% 4 1	8280
	21st to end	Night	52% 24% 5% 9% 9%	8484
February	1st to 10th	Night	25% 60% 5% 6% 3	2730
	11th to 20th	Night	29% 59% 3 7% 3	2566
	21st to end	Night	23% 59% 5% 8% 4 1	2076
March	1st to 10th	Night	44% 30% 9% 10% 7%	5494
	11th to 20th	Night	38% 29% 15% 11% 4 3	5090
	21st to end	Night	42% 32% 4 12% 10% 1	5263
April	1st to 10th	Night	26% 59% 4 7% 4	2100
	11th to 20th	Night	20% 60% 5% 7% 8%	2075
	21st to end	Night	22% 59% 3 8% 7% 1	2100
May	1st to 10th	Night	47% 25% 8% 12% 7% 1	4951
	11th to 20th	Night	39% 27% 12% 16% 6%	4640
	21st to end	Night	46% 24% 8% 14% 8%	5115
June	1st to 10th	Night	17% 60% 3 11% 8%	1680
	11th to 20th	Night	19% 60% 5% 10% 6%	1680
	21st to end	Night	17% 59% 6% 10% 7% 1	1680
July	1st to 10th	Night	34% 28% 11% 15% 11% 1	3640
	11th to 20th	Night	35% 30% 9% 16% 9% 1	3592
	21st to end	Night	27% 28% 9% 24% 12%	3809
August	1st to 10th	Night	37% 39% 8% 11% 4	2836
	11th to 20th	Night	30% 38% 10% 18% 4	3088
	21st to end	Night	24% 37% 8% 26% 5%	3586
September	1st to 10th	Night	15% 58% 6% 13% 8% 1	2000
	11th to 20th	Night	15% 57% 5% 12% 10% 1	2020
	21st to end	Night	21% 58% 5% 10% 5% 1	2221
October	1st to 10th	Night	32% 38% 6% 16% 7% 1	3920
	11th to 20th	Night	25% 38% 8% 12% 13% 4	3899
	21st to end	Night	23% 37% 12% 20% 7%	4434
November	1st to 10th	Night	23% 55% 5% 10% 7%	2667
	11th to 20th	Night	24% 56% 4 9% 6% 1	2762
	21st to end	Night	28% 56% 6% 8% 2	2940
December	1st to 10th	Night	44% 37% 6% 12% 1	4720
	11th to 20th	Night	43% 32% 6% 10% 8%	5348
	21st to end	Night	51% 27% 5% 8% 7% 1	7150

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	35% 26% 25% 11% 1	220
	11th to 20th	Day	50% 21% 23% 5% 2	220
	21st to end	Day	37% 28% 26% 5% 4	347
February	1st to 10th	Day	35% 30% 29% 6%	330
	11th to 20th	Day	42% 27% 26% 5%	429
	21st to end	Day	39% 24% 28% 8% 1	446
March	1st to 10th	Day	37% 23% 26% 11% 3	540
	11th to 20th	Day	39% 24% 23% 11% 3 1	540
	21st to end	Day	38% 25% 23% 9% 4 1	594
April	1st to 10th	Day	42% 18% 25% 11% 3	540
	11th to 20th	Day	34% 24% 24% 11% 6% 2	532
	21st to end	Day	34% 18% 30% 11% 5% 1	540
May	1st to 10th	Day	39% 17% 26% 10% 5% 3	543
	11th to 20th	Day	24% 18% 29% 19% 6% 3	567
	21st to end	Day	24% 12% 30% 20% 11% 3	617
June	1st to 10th	Day	25% 14% 28% 21% 10% 2	570
	11th to 20th	Day	23% 13% 29% 22% 11% 1	570
	21st to end	Day	20% 16% 31% 21% 9% 2	570
July	1st to 10th	Day	14% 9% 31% 28% 14% 4	565
	11th to 20th	Day	14% 7% 30% 32% 14% 4	544
	21st to end	Day	18% 9% 33% 25% 11% 4	576
August	1st to 10th	Day	17% 9% 23% 25% 19% 7%	526
	11th to 20th	Day	17% 7% 26% 30% 15% 6%	519
	21st to end	Day	18% 11% 28% 22% 14% 8%	583
September	1st to 10th	Day	21% 12% 23% 22% 15% 7%	530
	11th to 20th	Day	16% 8% 26% 21% 16% 13%	530
	21st to end	Day	25% 11% 29% 20% 11% 5%	530
October	1st to 10th	Day	28% 11% 22% 20% 13% 6%	530
	11th to 20th	Day	29% 17% 28% 17% 8% 2	530
	21st to end	Day	34% 16% 28% 16% 6%	522
November	1st to 10th	Day	29% 21% 22% 19% 8% 1	425
	11th to 20th	Day	32% 25% 22% 15% 6% 1	393
	21st to end	Day	40% 23% 29% 7% 1	220
December	1st to 10th	Day	40% 22% 28% 5% 4 1	220
	11th to 20th	Day	39% 25% 26% 8% 2	220
	21st to end	Day	38% 24% 27% 9% 2 1	242
January	1st to 10th	Night	30% 26% 30% 13% 2	840
	11th to 20th	Night	32% 22% 26% 16% 3	840
	21st to end	Night	26% 25% 32% 15% 2	924
February	1st to 10th	Night	29% 23% 30% 17% 2	840
	11th to 20th	Night	30% 26% 31% 12% 1	823
	21st to end	Night	36% 22% 28% 12% 2	692
March	1st to 10th	Night	31% 23% 28% 16% 2	840
	11th to 20th	Night	32% 23% 27% 15% 3	840
	21st to end	Night	29% 23% 27% 15% 6%	924
April	1st to 10th	Night	30% 20% 29% 18% 3	840
	11th to 20th	Night	28% 19% 29% 17% 6%	831
	21st to end	Night	26% 18% 29% 22% 5%	840
May	1st to 10th	Night	32% 12% 25% 24% 7%	523
	11th to 20th	Night	19% 13% 29% 30% 7% 1	414
	21st to end	Night	19% 7% 29% 31% 14% 1	455
June	1st to 10th	Night	21% 8% 21% 39% 11%	420
	11th to 20th	Night	20% 7% 23% 35% 14%	420
	21st to end	Night	15% 7% 24% 42% 12%	420
July	1st to 10th	Night	15% 4 18% 43% 17% 2	410
	11th to 20th	Night	15% 3 21% 40% 19% 1	398
	21st to end	Night	16% 4 18% 45% 17% 1	438
August	1st to 10th	Night	16% 2 21% 35% 23% 2	554
	11th to 20th	Night	18% 5% 12% 36% 26% 3	702
	21st to end	Night	19% 6% 16% 35% 24% 1	880
September	1st to 10th	Night	20% 6% 21% 33% 18% 2	800
	11th to 20th	Night	17% 6% 20% 28% 24% 6%	800
	21st to end	Night	23% 8% 24% 26% 17% 2	800
October	1st to 10th	Night	27% 11% 20% 24% 17% 2	800
	11th to 20th	Night	26% 13% 28% 26% 6% 1	800
	21st to end	Night	33% 15% 28% 20% 4	880
November	1st to 10th	Night	23% 17% 31% 21% 8%	820
	11th to 20th	Night	29% 21% 26% 17% 5% 1	840
	21st to end	Night	26% 23% 27% 19% 4 1	840
December	1st to 10th	Night	33% 24% 28% 13% 4	840
	11th to 20th	Night	32% 23% 27% 17% 1	840
	21st to end	Night	33% 24% 28% 13% 3	924

Page generated at 2026-07-13 03:14:47. Version ac07

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