Gold
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold clear sky chart from 2005-11-06 to 2025-01-07.

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	15% 12% 4 10% 6% 5% 5% 4 5% 6% 29%	105055
	Night	14% 13% 5% 11% 6% 5% 4 3 5% 6% 28%	103982
Transparency	Day	53% 6% 10% 20% 10% 1	108658
	Night	54% 7% 10% 18% 9% 1	108467
Seeing	Day	25% 19% 29% 17% 7% 3	14810
	Night	23% 20% 29% 20% 8% 1	24291

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	13% 20% 10% 17% 6% 3 4 2 2 4 20%	2565
	11th to 20th	Day	9% 18% 9% 22% 8% 4 4 2 3 4 18%	2741
	21st to end	Day	20% 16% 8% 16% 7% 4 3 3 3 4 15%	3124
February	1st to 10th	Day	13% 18% 7% 14% 8% 5% 4 3 5% 5% 19%	1710
	11th to 20th	Day	11% 14% 6% 16% 8% 5% 6% 3 4 7% 21%	1663
	21st to end	Day	17% 15% 4 12% 7% 3 3 3 4 6% 27%	1536
March	1st to 10th	Day	18% 15% 7% 9% 4 3 3 3 4 6% 27%	3388
	11th to 20th	Day	9% 18% 7% 12% 6% 4 3 3 4 5% 30%	3480
	21st to end	Day	15% 12% 4 11% 7% 5% 4 4 5% 5% 29%	3863
April	1st to 10th	Day	14% 17% 5% 8% 5% 4 4 3 5% 6% 29%	2280
	11th to 20th	Day	16% 13% 4 8% 5% 5% 5% 3 5% 5% 30%	2254
	21st to end	Day	19% 12% 3 8% 5% 4 5% 3 5% 4 33%	2384
May	1st to 10th	Day	24% 11% 3 7% 5% 4 3 3 4 6% 30%	4131
	11th to 20th	Day	22% 11% 4 8% 6% 5% 5% 4 5% 7% 24%	4398
	21st to end	Day	12% 8% 3 7% 5% 5% 5% 4 6% 8% 39%	4837
June	1st to 10th	Day	16% 9% 3 8% 5% 5% 5% 3 6% 8% 33%	2660
	11th to 20th	Day	15% 7% 3 7% 5% 5% 6% 5% 7% 7% 33%	2660
	21st to end	Day	13% 8% 3 7% 5% 6% 5% 4 6% 8% 35%	2660
July	1st to 10th	Day	10% 7% 3 7% 6% 6% 6% 5% 8% 10% 35%	4440
	11th to 20th	Day	9% 7% 2 7% 5% 6% 6% 6% 8% 9% 34%	4440
	21st to end	Day	10% 7% 3 8% 6% 6% 6% 5% 7% 8% 35%	4538
August	1st to 10th	Day	19% 8% 3 6% 5% 5% 5% 4 7% 8% 29%	4104
	11th to 20th	Day	16% 8% 3 8% 6% 6% 7% 5% 8% 9% 25%	4028
	21st to end	Day	13% 8% 3 6% 4 5% 5% 4 7% 8% 37%	4180
September	1st to 10th	Day	18% 8% 2 7% 4 4 5% 3 5% 7% 37%	2280
	11th to 20th	Day	14% 7% 3 7% 4 3 4 3 5% 6% 43%	2273
	21st to end	Day	22% 8% 3 8% 5% 4 4 3 5% 7% 31%	1986
October	1st to 10th	Day	17% 10% 3 7% 4 5% 5% 3 7% 6% 32%	1900
	11th to 20th	Day	19% 11% 3 8% 6% 4 4 3 5% 6% 30%	1900
	21st to end	Day	21% 15% 3 7% 5% 4 4 4 6% 5% 26%	2090
November	1st to 10th	Day	12% 14% 4 7% 5% 4 4 3 5% 7% 36%	1801
	11th to 20th	Day	14% 19% 5% 10% 5% 4 4 4 6% 7% 23%	1615
	21st to end	Day	16% 20% 7% 10% 6% 4 4 3 5% 6% 20%	1600
December	1st to 10th	Day	15% 20% 10% 22% 6% 3 3 3 3 4 11%	2600
	11th to 20th	Day	17% 18% 8% 12% 7% 4 4 3 3 5% 19%	2986
	21st to end	Day	16% 22% 8% 13% 6% 4 3 3 4 4 16%	3960
January	1st to 10th	Night	13% 17% 11% 15% 6% 5% 4 3 4 6% 16%	4514
	11th to 20th	Night	11% 18% 9% 18% 8% 5% 5% 3 4 5% 14%	4216
	21st to end	Night	18% 18% 7% 16% 10% 5% 4 2 3 3 14%	4532
February	1st to 10th	Night	12% 16% 6% 13% 10% 6% 5% 3 5% 4 21%	2470
	11th to 20th	Night	12% 13% 6% 14% 9% 7% 6% 3 6% 5% 20%	2403
	21st to end	Night	15% 13% 5% 15% 7% 5% 4 3 5% 4 24%	1918
March	1st to 10th	Night	16% 17% 5% 11% 6% 4 4 3 4 5% 26%	3451
	11th to 20th	Night	12% 17% 8% 12% 6% 4 4 4 4 6% 24%	3479
	21st to end	Night	11% 13% 4 10% 5% 4 3 3 5% 5% 36%	3768
April	1st to 10th	Night	16% 13% 5% 11% 5% 4 5% 4 4 6% 27%	1900
	11th to 20th	Night	17% 13% 3 8% 5% 4 3 3 4 6% 35%	1875
	21st to end	Night	16% 12% 3 8% 4 5% 4 3 5% 6% 35%	1812
May	1st to 10th	Night	25% 13% 3 6% 4 3 3 2 4 6% 31%	2806
	11th to 20th	Night	21% 13% 3 6% 4 4 5% 3 5% 6% 29%	2495
	21st to end	Night	12% 8% 2 8% 5% 5% 5% 3 6% 7% 39%	2738
June	1st to 10th	Night	14% 8% 2 7% 5% 4 4 4 6% 9% 37%	1520
	11th to 20th	Night	12% 7% 2 6% 5% 4 5% 5% 7% 9% 38%	1520
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 3 5% 8% 41%	1520
July	1st to 10th	Night	10% 10% 3 8% 6% 5% 4 4 5% 8% 38%	2520
	11th to 20th	Night	9% 6% 2 7% 4 5% 4 4 7% 10% 42%	2520
	21st to end	Night	13% 7% 2 7% 5% 5% 4 4 5% 6% 42%	3012
August	1st to 10th	Night	18% 9% 3 7% 4 4 4 4 5% 7% 35%	2825
	11th to 20th	Night	18% 9% 2 5% 4 4 4 4 6% 7% 37%	2785
	21st to end	Night	11% 9% 2 6% 4 4 5% 5% 6% 8% 42%	3459
September	1st to 10th	Night	15% 8% 2 6% 5% 3 4 3 4 6% 45%	1900
	11th to 20th	Night	11% 8% 2 6% 4 3 4 3 5% 7% 46%	1904
	21st to end	Night	18% 9% 3 7% 4 5% 4 3 5% 6% 35%	2194
October	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 4 7% 38%	2280
	11th to 20th	Night	17% 13% 3 8% 4 4 3 3 6% 7% 33%	2280
	21st to end	Night	22% 14% 3 8% 5% 3 4 4 4 6% 28%	2508
November	1st to 10th	Night	10% 13% 3 8% 5% 5% 4 3 5% 6% 38%	2494
	11th to 20th	Night	15% 16% 5% 10% 6% 5% 4 3 5% 6% 26%	2780
	21st to end	Night	14% 17% 6% 12% 6% 5% 4 3 5% 6% 21%	2800
December	1st to 10th	Night	11% 17% 8% 21% 8% 6% 5% 3 4 5% 12%	4580
	11th to 20th	Night	17% 16% 8% 15% 6% 4 4 3 4 4 20%	5208
	21st to end	Night	16% 19% 9% 14% 7% 5% 4 3 5% 4 15%	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	69% 5% 7% 13% 4 2	2566
	11th to 20th	Day	71% 5% 6% 12% 5%	2741
	21st to end	Day	74% 5% 6% 11% 4 1	3124
February	1st to 10th	Day	67% 6% 9% 11% 6% 1	1710
	11th to 20th	Day	63% 6% 6% 16% 8%	1672
	21st to end	Day	59% 5% 8% 18% 7% 2	1536
March	1st to 10th	Day	57% 5% 9% 22% 6% 1	3391
	11th to 20th	Day	56% 5% 12% 17% 8% 2	3480
	21st to end	Day	55% 6% 6% 21% 10% 2	3863
April	1st to 10th	Day	56% 5% 10% 17% 11% 1	2280
	11th to 20th	Day	53% 7% 9% 17% 13% 1	2254
	21st to end	Day	53% 6% 6% 19% 13% 2	2384
May	1st to 10th	Day	56% 4 8% 22% 8% 1	4143
	11th to 20th	Day	57% 8% 10% 17% 7%	4402
	21st to end	Day	42% 7% 12% 24% 14% 1	4837
June	1st to 10th	Day	48% 7% 12% 20% 13% 1	2660
	11th to 20th	Day	47% 7% 14% 19% 12% 1	2660
	21st to end	Day	45% 7% 13% 24% 11%	2660
July	1st to 10th	Day	42% 8% 14% 24% 11% 1	4370
	11th to 20th	Day	40% 9% 15% 24% 13%	4365
	21st to end	Day	43% 8% 13% 24% 11% 1	4393
August	1st to 10th	Day	51% 7% 13% 20% 9%	4091
	11th to 20th	Day	50% 9% 14% 21% 5%	4067
	21st to end	Day	42% 7% 11% 30% 9% 1	4180
September	1st to 10th	Day	45% 6% 10% 24% 14% 2	2280
	11th to 20th	Day	41% 6% 10% 25% 17% 1	2273
	21st to end	Day	52% 5% 10% 19% 13% 1	1986
October	1st to 10th	Day	44% 5% 11% 21% 17% 1	3160
	11th to 20th	Day	47% 4 11% 19% 15% 4	3140
	21st to end	Day	43% 5% 15% 25% 11% 1	3428
November	1st to 10th	Day	48% 6% 10% 20% 13% 3	1801
	11th to 20th	Day	58% 6% 9% 18% 6% 2	1615
	21st to end	Day	65% 6% 10% 14% 5% 1	1600
December	1st to 10th	Day	77% 4 7% 9% 3	2600
	11th to 20th	Day	67% 5% 10% 13% 5%	2986
	21st to end	Day	71% 4 9% 9% 6%	3960
January	1st to 10th	Night	67% 8% 7% 13% 4	4514
	11th to 20th	Night	70% 8% 8% 11% 3 1	4216
	21st to end	Night	75% 5% 4 10% 4 1	4532
February	1st to 10th	Night	63% 7% 9% 13% 7%	2470
	11th to 20th	Night	62% 8% 9% 14% 6% 1	2405
	21st to end	Night	62% 6% 9% 14% 8% 2	1918
March	1st to 10th	Night	61% 5% 10% 16% 7% 1	3461
	11th to 20th	Night	58% 8% 11% 16% 6% 1	3480
	21st to end	Night	48% 6% 7% 21% 15% 2	3768
April	1st to 10th	Night	57% 6% 9% 16% 12%	1900
	11th to 20th	Night	51% 5% 11% 19% 12% 2	1875
	21st to end	Night	49% 6% 9% 21% 13% 2	1812
May	1st to 10th	Night	56% 5% 9% 21% 8% 1	2813
	11th to 20th	Night	54% 8% 14% 17% 7% 1	2496
	21st to end	Night	42% 9% 11% 20% 14% 4	2739
June	1st to 10th	Night	42% 7% 13% 23% 13% 1	1520
	11th to 20th	Night	40% 8% 15% 25% 11% 2	1520
	21st to end	Night	40% 8% 12% 26% 13% 1	1520
July	1st to 10th	Night	43% 6% 14% 20% 16% 1	2480
	11th to 20th	Night	34% 8% 17% 26% 14% 1	2472
	21st to end	Night	41% 7% 11% 24% 17% 1	2916
August	1st to 10th	Night	47% 8% 14% 23% 7% 1	2814
	11th to 20th	Night	43% 8% 14% 27% 8%	2812
	21st to end	Night	38% 6% 15% 31% 10% 1	3459
September	1st to 10th	Night	40% 5% 13% 25% 14% 2	1900
	11th to 20th	Night	36% 6% 13% 25% 18% 2	1904
	21st to end	Night	49% 6% 12% 21% 12% 1	2194
October	1st to 10th	Night	46% 6% 9% 22% 16% 1	3800
	11th to 20th	Night	43% 5% 12% 20% 13% 7%	3779
	21st to end	Night	43% 5% 16% 24% 11% 1	4120
November	1st to 10th	Night	45% 8% 11% 20% 14% 2	2494
	11th to 20th	Night	57% 6% 10% 17% 8% 3	2780
	21st to end	Night	61% 7% 10% 17% 4 1	2800
December	1st to 10th	Night	71% 7% 9% 10% 2	4580
	11th to 20th	Night	67% 5% 9% 14% 6%	5208
	21st to end	Night	70% 6% 7% 10% 6%	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	36% 30% 22% 8% 4	192
	11th to 20th	Day	33% 33% 26% 6% 1	242
	21st to end	Day	30% 30% 31% 7% 2	297
February	1st to 10th	Day	38% 32% 25% 5%	270
	11th to 20th	Day	37% 32% 29% 2	270
	21st to end	Day	42% 25% 28% 5% 1	348
March	1st to 10th	Day	34% 26% 28% 9% 2 1	460
	11th to 20th	Day	33% 27% 27% 10% 2 1	460
	21st to end	Day	31% 27% 27% 10% 3 1	506
April	1st to 10th	Day	33% 23% 28% 11% 3 1	460
	11th to 20th	Day	29% 26% 25% 12% 5% 2	452
	21st to end	Day	29% 22% 31% 14% 3 1	460
May	1st to 10th	Day	30% 22% 26% 13% 6% 2	463
	11th to 20th	Day	27% 18% 30% 16% 7% 2	487
	21st to end	Day	19% 13% 32% 20% 11% 4	529
June	1st to 10th	Day	20% 17% 33% 21% 8% 2	490
	11th to 20th	Day	19% 15% 29% 25% 10% 2	490
	21st to end	Day	18% 15% 36% 22% 6% 3	490
July	1st to 10th	Day	13% 10% 34% 24% 13% 5%	485
	11th to 20th	Day	11% 12% 32% 27% 14% 4	484
	21st to end	Day	14% 11% 34% 27% 10% 4	532
August	1st to 10th	Day	15% 11% 25% 29% 15% 6%	486
	11th to 20th	Day	16% 9% 30% 26% 11% 7%	479
	21st to end	Day	15% 12% 31% 22% 13% 7%	539
September	1st to 10th	Day	22% 13% 21% 24% 13% 6%	490
	11th to 20th	Day	15% 8% 26% 26% 18% 8%	490
	21st to end	Day	26% 16% 24% 19% 11% 3	490
October	1st to 10th	Day	23% 15% 27% 19% 13% 3	490
	11th to 20th	Day	27% 21% 30% 15% 6% 1	490
	21st to end	Day	32% 23% 28% 14% 3	539
November	1st to 10th	Day	27% 20% 31% 14% 7% 2	415
	11th to 20th	Day	35% 24% 29% 10% 2	215
	21st to end	Day	36% 29% 30% 5% 1 1	200
December	1st to 10th	Day	40% 30% 22% 4 3 1	200
	11th to 20th	Day	36% 32% 26% 6% 1	200
	21st to end	Day	34% 30% 31% 5% 1	220
January	1st to 10th	Night	25% 33% 31% 9% 2	785
	11th to 20th	Night	27% 29% 29% 13% 2	760
	21st to end	Night	24% 33% 30% 12% 1	836
February	1st to 10th	Night	26% 30% 32% 12%	760
	11th to 20th	Night	28% 33% 29% 9% 1	743
	21st to end	Night	33% 28% 29% 10% 1	628
March	1st to 10th	Night	24% 32% 33% 10% 2	760
	11th to 20th	Night	30% 25% 27% 14% 3	760
	21st to end	Night	23% 28% 32% 13% 4 1	836
April	1st to 10th	Night	26% 24% 32% 16% 2	760
	11th to 20th	Night	26% 20% 32% 16% 6% 1	751
	21st to end	Night	23% 16% 34% 23% 4	672
May	1st to 10th	Night	26% 13% 27% 26% 8%	556
	11th to 20th	Night	18% 14% 35% 24% 9% 1	374
	21st to end	Night	14% 10% 29% 32% 14% 1	411
June	1st to 10th	Night	16% 11% 29% 33% 11% 1	380
	11th to 20th	Night	14% 10% 28% 39% 8%	380
	21st to end	Night	11% 11% 34% 33% 11%	380
July	1st to 10th	Night	11% 5% 26% 38% 18% 2	370
	11th to 20th	Night	9% 6% 28% 35% 20% 1	368
	21st to end	Night	14% 6% 22% 38% 18% 2	575
August	1st to 10th	Night	12% 5% 22% 38% 22% 2	567
	11th to 20th	Night	16% 7% 19% 33% 22% 2	564
	21st to end	Night	13% 8% 23% 31% 22% 3	819
September	1st to 10th	Night	19% 8% 26% 29% 16% 3	760
	11th to 20th	Night	13% 9% 23% 27% 24% 4	760
	21st to end	Night	22% 13% 26% 22% 15% 3	760
October	1st to 10th	Night	22% 14% 27% 20% 16% 2	760
	11th to 20th	Night	24% 19% 30% 19% 6% 1	760
	21st to end	Night	29% 21% 31% 16% 3	836
November	1st to 10th	Night	19% 22% 33% 20% 6%	780
	11th to 20th	Night	28% 23% 30% 14% 4 1	800
	21st to end	Night	27% 25% 32% 13% 3 1	800
December	1st to 10th	Night	29% 30% 29% 9% 3	800
	11th to 20th	Night	29% 29% 28% 12% 2	800
	21st to end	Night	30% 27% 31% 10% 1	880

Page generated at 2025-01-04 03:23:57. Version ac07

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