Gold Ridge observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold Ridge observatory 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	12% 7% 2 6% 5% 5% 5% 4 6% 8% 41%	104955
	Night	12% 7% 2 6% 4 4 4 4 5% 7% 44%	104041
Transparency	Day	39% 6% 11% 20% 19% 6%	108787
	Night	37% 5% 10% 20% 20% 7%	108347
Seeing	Day	16% 10% 23% 24% 18% 9%	14930
	Night	15% 9% 23% 28% 21% 4	24975

By Month

Percentage Cloud Cover SE (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	17% 11% 4 5% 3 4 4 3 6% 6% 37%	2890
	11th to 20th	Day	13% 6% 2 4 4 3 3 3 5% 5% 51%	2840
	21st to end	Day	23% 11% 2 5% 3 2 2 2 4 5% 40%	3421
February	1st to 10th	Day	16% 10% 3 6% 5% 4 4 3 4 6% 38%	1900
	11th to 20th	Day	20% 10% 3 6% 3 4 3 3 3 5% 42%	1848
	21st to end	Day	19% 8% 2 6% 5% 4 4 4 4 6% 38%	1570
March	1st to 10th	Day	22% 11% 3 7% 3 3 3 3 6% 5% 34%	3120
	11th to 20th	Day	14% 6% 3 6% 5% 4 4 3 5% 7% 44%	3471
	21st to end	Day	17% 6% 2 7% 4 4 4 4 6% 7% 38%	3815
April	1st to 10th	Day	13% 6% 3 5% 5% 4 4 4 5% 6% 45%	2248
	11th to 20th	Day	12% 7% 2 6% 5% 4 5% 3 5% 7% 46%	2254
	21st to end	Day	8% 5% 2 5% 4 5% 5% 3 6% 7% 50%	2342
May	1st to 10th	Day	9% 5% 2 7% 5% 5% 5% 4 6% 9% 43%	4082
	11th to 20th	Day	16% 8% 3 6% 4 5% 5% 5% 5% 7% 37%	4081
	21st to end	Day	8% 5% 2 6% 5% 5% 4 5% 6% 10% 44%	4476
June	1st to 10th	Day	10% 8% 3 9% 6% 7% 6% 5% 7% 10% 31%	2470
	11th to 20th	Day	6% 4 1 5% 6% 6% 7% 5% 8% 11% 41%	2470
	21st to end	Day	6% 4 2 7% 7% 8% 6% 5% 9% 9% 36%	2470
July	1st to 10th	Day	8% 7% 3 9% 7% 7% 8% 7% 9% 11% 24%	4120
	11th to 20th	Day	7% 5% 2 8% 6% 6% 7% 6% 8% 12% 32%	4120
	21st to end	Day	9% 9% 4 11% 8% 8% 9% 7% 8% 9% 19%	4466
August	1st to 10th	Day	4 4 2 5% 4 6% 6% 6% 8% 13% 42%	3926
	11th to 20th	Day	7% 4 2 5% 5% 5% 5% 4 6% 10% 46%	3729
	21st to end	Day	7% 4 2 5% 4 5% 6% 4 6% 9% 49%	4180
September	1st to 10th	Day	10% 6% 3 7% 6% 6% 5% 4 7% 7% 38%	2155
	11th to 20th	Day	15% 6% 2 5% 4 5% 5% 4 6% 7% 41%	2090
	21st to end	Day	12% 6% 3 6% 4 4 3 4 4 6% 47%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 4 6% 53%	2090
	11th to 20th	Day	11% 5% 1 4 3 3 3 2 4 6% 56%	2062
	21st to end	Day	12% 5% 1 5% 4 4 3 3 4 5% 55%	2028
November	1st to 10th	Day	11% 7% 2 5% 4 4 3 3 4 5% 52%	1762
	11th to 20th	Day	14% 5% 2 4 4 3 3 3 5% 6% 53%	1800
	21st to end	Day	13% 8% 1 5% 4 3 4 2 6% 7% 47%	1800
December	1st to 10th	Day	18% 6% 2 4 4 3 4 3 5% 6% 45%	2930
	11th to 20th	Day	14% 9% 3 8% 5% 5% 4 3 5% 4 42%	3373
	21st to end	Day	19% 8% 3 6% 4 3 4 3 4 6% 40%	4466
January	1st to 10th	Night	17% 12% 2 5% 3 3 4 3 4 6% 39%	4188
	11th to 20th	Night	14% 9% 3 5% 4 4 4 3 4 6% 44%	4120
	21st to end	Night	22% 14% 2 5% 3 3 3 3 3 3 39%	4230
February	1st to 10th	Night	15% 8% 3 6% 5% 4 3 4 5% 6% 42%	2280
	11th to 20th	Night	19% 8% 3 6% 4 3 3 3 4 5% 42%	2218
	21st to end	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	1884
March	1st to 10th	Night	23% 11% 3 7% 4 3 3 3 5% 5% 33%	3733
	11th to 20th	Night	11% 7% 2 4 3 4 4 4 6% 8% 47%	3485
	21st to end	Night	15% 6% 2 7% 5% 4 5% 3 5% 6% 42%	3817
April	1st to 10th	Night	11% 6% 2 5% 4 5% 4 4 6% 7% 45%	1947
	11th to 20th	Night	13% 6% 2 5% 4 3 2 4 5% 7% 49%	1875
	21st to end	Night	8% 5% 2 4 4 4 5% 3 5% 6% 54%	1835
May	1st to 10th	Night	8% 5% 3 6% 5% 5% 5% 5% 7% 9% 43%	2813
	11th to 20th	Night	15% 8% 2 6% 4 5% 5% 4 5% 7% 39%	2812
	21st to end	Night	6% 3 1 5% 3 4 4 5% 8% 11% 49%	3079
June	1st to 10th	Night	5% 6% 2 7% 5% 6% 7% 6% 9% 11% 37%	1710
	11th to 20th	Night	3 3 2 5% 4 5% 4 6% 8% 12% 48%	1710
	21st to end	Night	5% 5% 2 6% 5% 5% 5% 4 8% 10% 45%	1710
July	1st to 10th	Night	8% 7% 3 9% 6% 6% 7% 6% 8% 11% 29%	2840
	11th to 20th	Night	6% 4 2 7% 6% 6% 7% 5% 10% 13% 33%	2840
	21st to end	Night	8% 10% 4 10% 7% 6% 7% 6% 9% 11% 23%	3087
August	1st to 10th	Night	4 4 2 5% 4 5% 6% 5% 8% 12% 46%	2999
	11th to 20th	Night	5% 3 2 6% 5% 4 5% 4 6% 9% 51%	3100
	21st to end	Night	7% 5% 2 5% 4 4 4 3 6% 8% 51%	3476
September	1st to 10th	Night	8% 5% 2 6% 4 5% 5% 5% 7% 10% 44%	2004
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 6% 7% 45%	2090
	21st to end	Night	10% 5% 2 6% 3 4 4 3 5% 8% 51%	2090
October	1st to 10th	Night	9% 4 2 4 3 3 3 3 4 6% 60%	2090
	11th to 20th	Night	9% 6% 2 5% 3 3 3 3 4 5% 57%	2115
	21st to end	Night	12% 6% 2 5% 3 3 3 3 4 4 57%	2566
November	1st to 10th	Night	11% 6% 2 4 4 3 2 3 4 5% 56%	2536
	11th to 20th	Night	12% 7% 2 4 3 3 3 3 3 6% 54%	2600
	21st to end	Night	12% 7% 2 6% 4 4 4 4 4 6% 48%	2600
December	1st to 10th	Night	15% 8% 3 6% 3 3 3 2 4 5% 49%	4250
	11th to 20th	Night	15% 7% 2 6% 4 3 4 3 4 6% 46%	4822
	21st to end	Night	18% 9% 3 6% 3 4 3 3 4 6% 40%	6490

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	46% 5% 5% 16% 22% 6%	2891
	11th to 20th	Day	34% 4 6% 26% 23% 7%	2840
	21st to end	Day	49% 2 5% 15% 20% 8%	3421
February	1st to 10th	Day	47% 4 7% 17% 21% 5%	1900
	11th to 20th	Day	46% 3 4 18% 22% 7%	1858
	21st to end	Day	48% 4 6% 13% 21% 8%	1570
March	1st to 10th	Day	50% 4 9% 13% 16% 8%	3120
	11th to 20th	Day	40% 5% 8% 18% 22% 8%	3471
	21st to end	Day	43% 4 11% 16% 20% 5%	3815
April	1st to 10th	Day	39% 4 9% 20% 19% 8%	2248
	11th to 20th	Day	38% 3 7% 19% 25% 9%	2254
	21st to end	Day	31% 6% 10% 23% 25% 4	2342
May	1st to 10th	Day	35% 6% 13% 24% 19% 3	4120
	11th to 20th	Day	44% 6% 13% 26% 11% 1	4085
	21st to end	Day	34% 6% 14% 27% 17% 2	4489
June	1st to 10th	Day	45% 9% 13% 20% 12% 1	2470
	11th to 20th	Day	32% 9% 19% 24% 15% 2	2470
	21st to end	Day	39% 11% 17% 21% 11% 3	2470
July	1st to 10th	Day	46% 10% 23% 15% 4 1	4055
	11th to 20th	Day	41% 11% 20% 22% 6% 1	4051
	21st to end	Day	56% 12% 14% 14% 4	4324
August	1st to 10th	Day	30% 9% 14% 34% 13%	3913
	11th to 20th	Day	32% 7% 17% 28% 15% 2	3765
	21st to end	Day	31% 7% 16% 23% 21% 3	4179
September	1st to 10th	Day	43% 7% 13% 16% 15% 5%	2155
	11th to 20th	Day	41% 7% 11% 18% 21% 2	2090
	21st to end	Day	39% 5% 9% 19% 22% 6%	2090
October	1st to 10th	Day	25% 4 5% 12% 35% 19%	3480
	11th to 20th	Day	19% 2 4 17% 29% 29%	3406
	21st to end	Day	23% 3 5% 20% 37% 11%	3317
November	1st to 10th	Day	35% 3 7% 16% 27% 12%	1762
	11th to 20th	Day	33% 3 7% 17% 28% 13%	1800
	21st to end	Day	37% 4 8% 18% 26% 8%	1800
December	1st to 10th	Day	41% 3 6% 18% 26% 7%	2930
	11th to 20th	Day	45% 4 6% 18% 21% 6%	3370
	21st to end	Day	45% 4 6% 23% 20% 2	4466
January	1st to 10th	Night	46% 3 5% 16% 24% 5%	4188
	11th to 20th	Night	40% 4 5% 23% 20% 8%	4120
	21st to end	Night	50% 3 3 13% 24% 7%	4230
February	1st to 10th	Night	44% 3 6% 19% 19% 9%	2280
	11th to 20th	Night	46% 3 4 17% 20% 9%	2219
	21st to end	Night	45% 4 9% 14% 19% 10%	1884
March	1st to 10th	Night	52% 4 8% 15% 14% 7%	3733
	11th to 20th	Night	34% 4 9% 17% 24% 11%	3485
	21st to end	Night	42% 5% 6% 19% 21% 7%	3817
April	1st to 10th	Night	37% 5% 10% 18% 21% 9%	1947
	11th to 20th	Night	35% 4 6% 22% 23% 10%	1875
	21st to end	Night	30% 5% 11% 26% 22% 6%	1835
May	1st to 10th	Night	34% 8% 14% 22% 19% 3	2840
	11th to 20th	Night	42% 7% 13% 26% 11% 1	2813
	21st to end	Night	25% 7% 16% 32% 18% 2	3087
June	1st to 10th	Night	36% 11% 17% 20% 14% 1	1710
	11th to 20th	Night	25% 9% 24% 25% 14% 2	1710
	21st to end	Night	31% 8% 20% 21% 15% 4	1710
July	1st to 10th	Night	44% 11% 22% 16% 6% 1	2795
	11th to 20th	Night	37% 14% 22% 19% 7% 1	2786
	21st to end	Night	50% 12% 18% 14% 5% 1	2988
August	1st to 10th	Night	28% 8% 14% 37% 12% 1	2988
	11th to 20th	Night	28% 7% 17% 31% 14% 2	3130
	21st to end	Night	29% 7% 16% 19% 25% 3	3476
September	1st to 10th	Night	34% 9% 17% 19% 15% 7%	2004
	11th to 20th	Night	37% 8% 10% 22% 19% 3	2090
	21st to end	Night	32% 6% 9% 22% 22% 8%	2090
October	1st to 10th	Night	25% 3 7% 16% 33% 17%	3480
	11th to 20th	Night	18% 3 3 17% 30% 30%	3510
	21st to end	Night	22% 2 4 23% 33% 16%	4227
November	1st to 10th	Night	31% 3 10% 17% 25% 14%	2536
	11th to 20th	Night	33% 3 5% 18% 27% 14%	2600
	21st to end	Night	38% 3 7% 17% 25% 9%	2600
December	1st to 10th	Night	39% 2 6% 20% 27% 6%	4250
	11th to 20th	Night	40% 3 11% 15% 25% 6%	4824
	21st to end	Night	45% 3 6% 24% 20% 2	6490

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	29% 24% 35% 10% 2	288
	11th to 20th	Day	24% 24% 31% 13% 6% 1	270
	21st to end	Day	25% 27% 33% 13% 2 1	297
February	1st to 10th	Day	24% 24% 36% 13% 3	270
	11th to 20th	Day	36% 21% 31% 10% 2	270
	21st to end	Day	30% 20% 41% 8%	225
March	1st to 10th	Day	28% 19% 33% 17% 1 2	270
	11th to 20th	Day	22% 18% 35% 17% 8% 1	451
	21st to end	Day	24% 18% 30% 22% 6% 1	506
April	1st to 10th	Day	21% 17% 32% 19% 10% 2	460
	11th to 20th	Day	17% 15% 31% 23% 11% 2	452
	21st to end	Day	15% 10% 31% 30% 11% 2	460
May	1st to 10th	Day	13% 13% 28% 25% 15% 5%	463
	11th to 20th	Day	12% 6% 23% 33% 16% 10%	487
	21st to end	Day	13% 5% 17% 33% 19% 14%	529
June	1st to 10th	Day	12% 4 17% 33% 22% 12%	490
	11th to 20th	Day	7% 4 15% 27% 26% 22%	490
	21st to end	Day	8% 3 16% 26% 30% 17%	490
July	1st to 10th	Day	8% 2 9% 28% 32% 22%	485
	11th to 20th	Day	6% 2 9% 24% 31% 28%	484
	21st to end	Day	7% 2 10% 24% 36% 22%	532
August	1st to 10th	Day	9% 2 12% 25% 32% 20%	486
	11th to 20th	Day	9% 1 10% 30% 31% 17%	479
	21st to end	Day	13% 3 9% 27% 31% 18%	539
September	1st to 10th	Day	9% 5% 11% 29% 31% 15%	490
	11th to 20th	Day	17% 4 13% 28% 30% 9%	490
	21st to end	Day	14% 4 20% 25% 28% 10%	490
October	1st to 10th	Day	14% 3 27% 32% 18% 7%	490
	11th to 20th	Day	13% 7% 25% 31% 19% 4	490
	21st to end	Day	16% 9% 26% 27% 19% 3	477
November	1st to 10th	Day	20% 9% 28% 33% 8% 2	300
	11th to 20th	Day	16% 19% 37% 21% 7% 1	300
	21st to end	Day	14% 17% 42% 18% 7% 1	300
December	1st to 10th	Day	26% 20% 34% 17% 2 1	300
	11th to 20th	Day	22% 21% 34% 18% 5% 1	300
	21st to end	Day	29% 15% 33% 18% 5%	330
January	1st to 10th	Night	24% 18% 31% 23% 4	785
	11th to 20th	Night	22% 17% 30% 24% 7%	760
	21st to end	Night	22% 17% 35% 22% 4	836
February	1st to 10th	Night	22% 12% 33% 28% 5%	760
	11th to 20th	Night	25% 17% 31% 25% 2	743
	21st to end	Night	22% 18% 36% 21% 3	628
March	1st to 10th	Night	18% 16% 33% 27% 6%	760
	11th to 20th	Night	18% 13% 36% 23% 10% 1	760
	21st to end	Night	16% 15% 30% 29% 9%	836
April	1st to 10th	Night	15% 12% 34% 27% 11% 1	617
	11th to 20th	Night	17% 11% 29% 28% 13% 2	563
	21st to end	Night	9% 10% 24% 41% 16% 1	570
May	1st to 10th	Night	10% 7% 27% 31% 23% 2	570
	11th to 20th	Night	11% 5% 20% 34% 25% 5%	561
	21st to end	Night	11% 1 13% 35% 35% 5%	617
June	1st to 10th	Night	8% 2 11% 39% 34% 6%	570
	11th to 20th	Night	3 1 12% 29% 38% 17%	570
	21st to end	Night	6% 1 8% 33% 42% 9%	570
July	1st to 10th	Night	8% 1 8% 21% 46% 14%	555
	11th to 20th	Night	5% 1 4 20% 49% 20%	552
	21st to end	Night	8% 1 7% 25% 44% 15%	624
August	1st to 10th	Night	5% 1 6% 26% 44% 18%	567
	11th to 20th	Night	10% 1 6% 27% 47% 9%	564
	21st to end	Night	13% 2 7% 27% 38% 12%	627
September	1st to 10th	Night	9% 2 13% 27% 40% 9%	674
	11th to 20th	Night	15% 3 12% 28% 36% 6%	760
	21st to end	Night	13% 3 14% 32% 34% 5%	760
October	1st to 10th	Night	11% 3 20% 35% 24% 6%	760
	11th to 20th	Night	11% 8% 24% 32% 21% 4	760
	21st to end	Night	14% 8% 22% 33% 19% 3	836
November	1st to 10th	Night	15% 7% 23% 33% 21% 2	780
	11th to 20th	Night	17% 11% 31% 28% 13% 2	800
	21st to end	Night	17% 14% 27% 30% 12%	800
December	1st to 10th	Night	22% 13% 28% 27% 9% 1	800
	11th to 20th	Night	24% 9% 31% 27% 8% 1	800
	21st to end	Night	26% 13% 26% 27% 6%	880

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