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 2025-03-12.

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% 4 4 4 5% 7% 29%	108844
	Night	17% 12% 4 10% 5% 4 4 3 5% 6% 29%	110135
Transparency	Day	32% 45% 6% 12% 6%	112396
	Night	34% 43% 6% 11% 6% 1	114747
Seeing	Day	28% 16% 27% 17% 8% 3	15133
	Night	26% 16% 26% 22% 9% 1	24473

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	11% 16% 13% 24% 7% 3 2 2 3 4 15%	3597
	11th to 20th	Day	13% 17% 9% 21% 7% 5% 4 3 4 3 13%	3570
	21st to end	Day	17% 15% 8% 10% 7% 5% 4 3 4 5% 23%	4396
February	1st to 10th	Day	16% 15% 6% 14% 8% 5% 4 3 5% 5% 19%	1800
	11th to 20th	Day	13% 14% 7% 13% 8% 5% 4 3 4 7% 22%	1847
	21st to end	Day	19% 13% 4 13% 7% 4 4 3 5% 6% 23%	1650
March	1st to 10th	Day	23% 16% 5% 10% 5% 3 3 2 3 4 26%	3216
	11th to 20th	Day	11% 18% 6% 10% 6% 4 3 3 4 6% 28%	3487
	21st to end	Day	20% 13% 3 10% 5% 4 3 3 4 5% 31%	4034
April	1st to 10th	Day	18% 16% 4 8% 5% 4 4 3 4 5% 30%	2280
	11th to 20th	Day	17% 11% 3 8% 5% 5% 4 3 4 6% 33%	2254
	21st to end	Day	19% 12% 4 7% 4 4 4 3 4 7% 31%	2280
May	1st to 10th	Day	27% 9% 2 6% 4 3 4 3 5% 6% 30%	4294
	11th to 20th	Day	20% 9% 3 8% 6% 6% 5% 4 6% 7% 27%	4398
	21st to end	Day	14% 6% 2 6% 5% 5% 5% 4 6% 8% 39%	4837
June	1st to 10th	Day	18% 8% 3 6% 6% 4 5% 4 6% 8% 31%	2660
	11th to 20th	Day	17% 7% 3 7% 5% 5% 4 4 7% 9% 32%	2660
	21st to end	Day	17% 7% 2 8% 5% 4 5% 5% 6% 8% 33%	2660
July	1st to 10th	Day	10% 7% 3 7% 6% 5% 6% 6% 8% 10% 33%	4440
	11th to 20th	Day	9% 6% 2 7% 5% 7% 6% 5% 8% 11% 34%	4440
	21st to end	Day	13% 7% 3 8% 6% 6% 5% 5% 7% 8% 32%	4814
August	1st to 10th	Day	20% 8% 4 7% 4 5% 5% 4 6% 7% 29%	4154
	11th to 20th	Day	16% 8% 2 8% 6% 6% 5% 4 7% 9% 29%	3831
	21st to end	Day	18% 6% 2 6% 4 4 5% 4 6% 9% 35%	4180
September	1st to 10th	Day	17% 8% 3 7% 3 4 4 3 5% 7% 38%	2280
	11th to 20th	Day	14% 7% 3 6% 3 4 4 3 5% 7% 43%	2261
	21st to end	Day	20% 8% 2 7% 4 4 5% 4 5% 6% 34%	2066
October	1st to 10th	Day	18% 9% 4 8% 5% 4 5% 4 5% 6% 33%	1900
	11th to 20th	Day	18% 11% 2 7% 4 4 5% 4 6% 6% 34%	1900
	21st to end	Day	24% 14% 3 7% 4 4 4 3 4 6% 27%	1986
November	1st to 10th	Day	14% 12% 4 6% 4 4 4 3 5% 6% 37%	1761
	11th to 20th	Day	16% 17% 5% 9% 4 4 4 3 4 5% 30%	1765
	21st to end	Day	19% 16% 5% 10% 5% 3 5% 3 5% 6% 23%	1600
December	1st to 10th	Day	16% 19% 9% 18% 5% 5% 4 3 3 4 14%	2600
	11th to 20th	Day	19% 16% 9% 10% 4 4 3 2 3 4 25%	2986
	21st to end	Day	19% 18% 7% 11% 5% 4 4 3 4 5% 19%	3960
January	1st to 10th	Night	13% 13% 8% 26% 7% 4 4 2 3 4 15%	6349
	11th to 20th	Night	10% 16% 7% 20% 8% 5% 4 3 4 5% 17%	6315
	21st to end	Night	16% 14% 5% 12% 9% 7% 5% 4 4 5% 21%	6559
February	1st to 10th	Night	16% 14% 6% 12% 7% 5% 5% 3 5% 5% 23%	2600
	11th to 20th	Night	14% 14% 6% 13% 9% 5% 6% 4 4 6% 20%	2439
	21st to end	Night	19% 13% 4 12% 5% 4 4 3 5% 5% 25%	1980
March	1st to 10th	Night	22% 15% 5% 10% 5% 3 4 3 3 5% 27%	3844
	11th to 20th	Night	12% 19% 7% 9% 5% 4 4 3 4 5% 27%	3497
	21st to end	Night	15% 16% 3 10% 5% 4 4 3 4 4 31%	3597
April	1st to 10th	Night	19% 14% 4 8% 5% 3 4 4 4 6% 29%	1900
	11th to 20th	Night	20% 10% 2 8% 5% 3 3 3 5% 6% 35%	1875
	21st to end	Night	19% 9% 3 7% 4 4 4 3 5% 6% 36%	1900
May	1st to 10th	Night	29% 9% 3 5% 4 4 3 3 3 6% 32%	2659
	11th to 20th	Night	20% 9% 3 7% 5% 4 4 4 6% 6% 32%	2495
	21st to end	Night	13% 9% 3 7% 4 4 5% 4 6% 7% 37%	2738
June	1st to 10th	Night	16% 9% 2 6% 5% 3 3 3 6% 8% 39%	1520
	11th to 20th	Night	14% 8% 2 5% 4 4 5% 4 6% 8% 40%	1520
	21st to end	Night	13% 4 2 5% 5% 5% 5% 5% 6% 8% 41%	1520
July	1st to 10th	Night	11% 7% 3 7% 6% 5% 5% 3 6% 8% 38%	2520
	11th to 20th	Night	12% 7% 2 6% 5% 4 5% 4 7% 10% 39%	2520
	21st to end	Night	16% 6% 3 6% 4 4 4 4 5% 7% 40%	2739
August	1st to 10th	Night	22% 8% 2 7% 4 4 5% 4 6% 6% 32%	2758
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 5% 6% 39%	2965
	21st to end	Night	14% 7% 2 5% 4 4 4 4 5% 7% 43%	3476
September	1st to 10th	Night	15% 8% 3 5% 4 3 4 3 4 7% 43%	1900
	11th to 20th	Night	14% 6% 1 5% 4 4 4 3 4 6% 49%	1919
	21st to end	Night	19% 7% 3 6% 4 4 4 4 5% 6% 38%	2110
October	1st to 10th	Night	19% 9% 2 8% 5% 4 4 4 5% 6% 35%	2280
	11th to 20th	Night	20% 9% 2 7% 5% 3 3 3 4 5% 38%	2280
	21st to end	Night	23% 14% 3 7% 4 4 4 3 5% 6% 28%	2610
November	1st to 10th	Night	12% 14% 3 7% 4 4 3 4 5% 7% 38%	2537
	11th to 20th	Night	19% 12% 3 7% 4 4 4 4 5% 6% 32%	2630
	21st to end	Night	15% 14% 4 9% 5% 5% 4 4 6% 6% 27%	2800
December	1st to 10th	Night	16% 17% 7% 13% 6% 5% 4 3 5% 6% 19%	4580
	11th to 20th	Night	23% 15% 5% 9% 4 3 3 2 3 4 27%	5208
	21st to end	Night	22% 15% 8% 11% 6% 4 4 3 4 5% 19%	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	58% 27% 4 8% 2	3598
	11th to 20th	Day	57% 28% 4 7% 3	3600
	21st to end	Day	46% 29% 6% 13% 5%	4396
February	1st to 10th	Day	26% 63% 3 6% 2	1800
	11th to 20th	Day	24% 62% 2 8% 5%	1856
	21st to end	Day	22% 62% 4 9% 3	1650
March	1st to 10th	Day	42% 40% 5% 8% 5%	3219
	11th to 20th	Day	34% 41% 8% 12% 4 1	3487
	21st to end	Day	34% 41% 4 9% 11% 1	4034
April	1st to 10th	Day	23% 65% 2 7% 2 1	2280
	11th to 20th	Day	18% 66% 4 6% 6%	2254
	21st to end	Day	21% 64% 3 6% 4 1	2280
May	1st to 10th	Day	35% 41% 7% 11% 5% 1	4308
	11th to 20th	Day	38% 41% 8% 11% 2	4402
	21st to end	Day	25% 42% 6% 17% 10%	4837
June	1st to 10th	Day	18% 66% 4 7% 5%	2660
	11th to 20th	Day	17% 66% 4 8% 4	2660
	21st to end	Day	17% 65% 3 10% 5%	2660
July	1st to 10th	Day	26% 40% 11% 15% 7%	4370
	11th to 20th	Day	27% 40% 11% 16% 6%	4365
	21st to end	Day	32% 39% 9% 13% 7%	4661
August	1st to 10th	Day	36% 39% 8% 11% 4	4140
	11th to 20th	Day	31% 42% 10% 15% 2	3870
	21st to end	Day	25% 40% 9% 23% 3	4180
September	1st to 10th	Day	15% 61% 5% 12% 6%	2280
	11th to 20th	Day	16% 59% 4 9% 10% 1	2261
	21st to end	Day	19% 61% 5% 9% 5% 1	2066
October	1st to 10th	Day	30% 40% 5% 16% 9% 1	3160
	11th to 20th	Day	24% 39% 6% 15% 13% 4	3140
	21st to end	Day	20% 39% 11% 21% 8% 1	3250
November	1st to 10th	Day	24% 57% 6% 9% 4	1761
	11th to 20th	Day	21% 57% 4 10% 7% 1	1765
	21st to end	Day	26% 58% 6% 6% 2 1	1600
December	1st to 10th	Day	50% 38% 4 6% 1	2600
	11th to 20th	Day	46% 32% 6% 9% 7%	2986
	21st to end	Day	49% 27% 5% 10% 7% 1	3960
January	1st to 10th	Night	56% 27% 6% 7% 2	6349
	11th to 20th	Night	52% 29% 8% 7% 3 1	6360
	21st to end	Night	49% 29% 5% 7% 9% 1	6559
February	1st to 10th	Night	24% 63% 5% 6% 3	2600
	11th to 20th	Night	26% 62% 2 6% 3	2441
	21st to end	Night	21% 62% 5% 8% 4 1	1980
March	1st to 10th	Night	39% 40% 6% 9% 6% 1	3854
	11th to 20th	Night	36% 42% 8% 11% 3	3498
	21st to end	Night	33% 44% 3 10% 9% 1	3597
April	1st to 10th	Night	21% 65% 3 7% 4	1900
	11th to 20th	Night	16% 65% 4 6% 8%	1875
	21st to end	Night	19% 65% 3 7% 6%	1900
May	1st to 10th	Night	34% 41% 6% 14% 4 1	2665
	11th to 20th	Night	34% 43% 12% 10% 2	2496
	21st to end	Night	29% 42% 7% 12% 10%	2739
June	1st to 10th	Night	15% 66% 3 10% 7%	1520
	11th to 20th	Night	15% 66% 5% 8% 5%	1520
	21st to end	Night	15% 64% 4 9% 6% 1	1520
July	1st to 10th	Night	30% 39% 9% 11% 11%	2480
	11th to 20th	Night	26% 39% 9% 17% 8%	2472
	21st to end	Night	30% 37% 8% 16% 9%	2651
August	1st to 10th	Night	37% 41% 8% 11% 3	2748
	11th to 20th	Night	30% 39% 10% 17% 4	2992
	21st to end	Night	23% 38% 8% 25% 5%	3476
September	1st to 10th	Night	14% 61% 6% 12% 7% 1	1900
	11th to 20th	Night	15% 60% 4 9% 10% 1	1919
	21st to end	Night	19% 61% 5% 10% 5% 1	2110
October	1st to 10th	Night	33% 39% 6% 15% 6%	3800
	11th to 20th	Night	24% 39% 8% 11% 13% 5%	3779
	21st to end	Night	22% 38% 12% 21% 6%	4296
November	1st to 10th	Night	21% 58% 5% 9% 7%	2537
	11th to 20th	Night	22% 58% 4 9% 6% 1	2630
	21st to end	Night	25% 58% 6% 8% 2	2800
December	1st to 10th	Night	43% 38% 6% 12% 1	4580
	11th to 20th	Night	43% 33% 6% 10% 8%	5208
	21st to end	Night	51% 28% 5% 8% 8% 1	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	35% 25% 26% 13% 2 1	200
	11th to 20th	Day	48% 20% 25% 6% 2	200
	21st to end	Day	33% 29% 29% 5% 4	315
February	1st to 10th	Day	36% 31% 28% 5%	300
	11th to 20th	Day	43% 27% 24% 6%	394
	21st to end	Day	40% 22% 28% 9% 1	414
March	1st to 10th	Day	36% 24% 26% 10% 3	500
	11th to 20th	Day	36% 25% 23% 12% 3 1	464
	21st to end	Day	37% 24% 22% 10% 5% 1	506
April	1st to 10th	Day	39% 18% 27% 12% 4	460
	11th to 20th	Day	33% 22% 24% 11% 7% 2	452
	21st to end	Day	35% 17% 30% 12% 5% 1	460
May	1st to 10th	Day	38% 15% 26% 11% 6% 3	463
	11th to 20th	Day	23% 17% 30% 20% 7% 3	487
	21st to end	Day	20% 11% 30% 23% 12% 4	529
June	1st to 10th	Day	25% 14% 29% 20% 10% 2	490
	11th to 20th	Day	21% 12% 29% 24% 13% 1	490
	21st to end	Day	20% 17% 32% 21% 9% 2	490
July	1st to 10th	Day	15% 8% 30% 27% 16% 4	485
	11th to 20th	Day	13% 7% 30% 32% 14% 4	484
	21st to end	Day	19% 9% 33% 25% 11% 4	532
August	1st to 10th	Day	18% 9% 24% 25% 18% 6%	486
	11th to 20th	Day	17% 7% 26% 29% 14% 6%	479
	21st to end	Day	18% 11% 27% 21% 14% 8%	539
September	1st to 10th	Day	22% 11% 23% 21% 16% 7%	490
	11th to 20th	Day	17% 8% 25% 22% 16% 12%	490
	21st to end	Day	25% 10% 29% 20% 11% 5%	490
October	1st to 10th	Day	29% 12% 22% 20% 12% 6%	490
	11th to 20th	Day	28% 16% 28% 18% 8% 2	490
	21st to end	Day	33% 16% 28% 16% 6%	484
November	1st to 10th	Day	28% 21% 22% 20% 9% 1	395
	11th to 20th	Day	32% 24% 22% 15% 5% 1	365
	21st to end	Day	38% 23% 31% 8% 2	200
December	1st to 10th	Day	40% 22% 28% 6% 4 1	200
	11th to 20th	Day	39% 24% 28% 9% 2	200
	21st to end	Day	36% 23% 29% 9% 2 1	220
January	1st to 10th	Night	30% 26% 29% 13% 2	800
	11th to 20th	Night	31% 22% 27% 17% 3	800
	21st to end	Night	25% 25% 33% 16% 2	880
February	1st to 10th	Night	29% 23% 31% 16% 2	800
	11th to 20th	Night	30% 26% 30% 12% 1	783
	21st to end	Night	36% 22% 28% 12% 3	660
March	1st to 10th	Night	31% 23% 29% 16% 2	800
	11th to 20th	Night	30% 24% 27% 15% 4	767
	21st to end	Night	28% 23% 27% 16% 6%	836
April	1st to 10th	Night	28% 21% 29% 19% 3	760
	11th to 20th	Night	28% 18% 30% 17% 7%	751
	21st to end	Night	25% 18% 29% 22% 6%	760
May	1st to 10th	Night	33% 10% 24% 25% 8%	473
	11th to 20th	Night	18% 13% 30% 30% 7% 1	374
	21st to end	Night	16% 7% 29% 32% 15% 1	411
June	1st to 10th	Night	21% 8% 22% 38% 11%	380
	11th to 20th	Night	19% 6% 23% 37% 16% 1	380
	21st to end	Night	15% 7% 24% 42% 12%	380
July	1st to 10th	Night	15% 4 18% 42% 18% 2	370
	11th to 20th	Night	14% 4 21% 40% 20% 1	368
	21st to end	Night	17% 4 17% 44% 18% 1	416
August	1st to 10th	Night	17% 2 22% 34% 22% 2	526
	11th to 20th	Night	18% 5% 12% 36% 26% 3	666
	21st to end	Night	19% 6% 15% 35% 24% 1	836
September	1st to 10th	Night	20% 6% 22% 32% 18% 3	760
	11th to 20th	Night	18% 6% 20% 26% 23% 6%	760
	21st to end	Night	23% 8% 24% 26% 17% 2	760
October	1st to 10th	Night	27% 11% 20% 24% 16% 2	760
	11th to 20th	Night	26% 12% 28% 27% 7% 1	760
	21st to end	Night	33% 15% 27% 20% 4	836
November	1st to 10th	Night	23% 17% 31% 21% 8% 1	780
	11th to 20th	Night	28% 21% 27% 17% 5% 1	800
	21st to end	Night	25% 24% 28% 18% 4 1	800
December	1st to 10th	Night	33% 23% 27% 13% 4	800
	11th to 20th	Night	31% 23% 27% 18% 2	800
	21st to end	Night	31% 25% 28% 13% 3	880

Page generated at 2025-03-09 08:08:48. Version ac07

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