Stockton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stockton clear sky chart from 2005-11-06 to 2025-02-25.

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	6% 4 1 4 3 3 3 2 4 5% 66%	112646
	Night	8% 4 1 4 3 3 3 3 4 5% 63%	114839
Transparency	Day	22% 4 7% 18% 25% 24%	112399
	Night	24% 5% 9% 19% 23% 21%	114675
Seeing	Day	7% 5% 17% 29% 29% 14%	15605
	Night	8% 3 15% 40% 29% 4	25088

By Month

Percentage Cloud Cover SW (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% 9% 3 8% 5% 4 5% 3 6% 7% 35%	3667
	11th to 20th	Day	12% 8% 3 7% 4 4 3 2 3 4 49%	4100
	21st to end	Day	15% 8% 3 8% 4 4 4 3 4 6% 40%	4510
February	1st to 10th	Day	17% 6% 4 6% 4 4 4 4 4 5% 42%	1800
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 5% 7% 46%	1893
	21st to end	Day	13% 4 2 6% 4 3 3 3 5% 6% 51%	1611
March	1st to 10th	Day	11% 8% 3 8% 6% 6% 6% 5% 6% 7% 33%	3279
	11th to 20th	Day	9% 5% 1 4 3 3 3 3 5% 6% 59%	3490
	21st to end	Day	10% 7% 2 7% 5% 4 5% 4 7% 9% 40%	3961
April	1st to 10th	Day	10% 7% 2 4 3 3 3 4 6% 6% 51%	2280
	11th to 20th	Day	8% 4 1 5% 3 3 3 3 5% 6% 60%	2249
	21st to end	Day	5% 3 1 2 2 2 3 3 4 7% 67%	2280
May	1st to 10th	Day	4 2 1 2 2 1 2 2 2 4 77%	3822
	11th to 20th	Day	1 1 1 1 1 1 1 1 3 3 84%	4310
	21st to end	Day	2 1 2 1 1 2 2 3 5% 81%	4813
June	1st to 10th	Day	2 3 1 2 3 2 2 2 4 6% 72%	2660
	11th to 20th	Day	1 1 1 1 1 2 3 5% 85%	2660
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	2660
July	1st to 10th	Day	1 1 2 95%	4420
	11th to 20th	Day	1 1 1 1 1 1 1 1 2 3 86%	4313
	21st to end	Day	1 1 1 1 1 2 3 91%	4455
August	1st to 10th	Day	1 1 1 2 1 1 2 2 3 4 82%	4091
	11th to 20th	Day	1 1 1 1 1 2 3 91%	3758
	21st to end	Day	1 1 1 1 1 1 1 1 3 89%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 2 2 90%	2280
	11th to 20th	Day	1 1 1 2 2 2 2 2 3 5% 79%	2280
	21st to end	Day	2 2 2 1 1 2 1 3 3 81%	2048
October	1st to 10th	Day	1 1 1 2 1 2 2 2 3 6% 79%	3180
	11th to 20th	Day	2 2 1 2 2 2 2 2 4 4 77%	3161
	21st to end	Day	3 2 1 3 3 3 4 3 5% 7% 66%	3448
November	1st to 10th	Day	6% 5% 2 4 4 4 3 4 5% 7% 58%	1841
	11th to 20th	Day	9% 6% 3 5% 4 4 4 4 5% 8% 49%	1800
	21st to end	Day	11% 7% 2 5% 4 4 3 3 5% 8% 49%	1694
December	1st to 10th	Day	7% 5% 2 6% 4 4 5% 5% 7% 9% 46%	2620
	11th to 20th	Day	20% 11% 5% 13% 7% 5% 4 3 4 5% 22%	3028
	21st to end	Day	18% 9% 3 9% 5% 6% 6% 4 7% 8% 25%	4004
January	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 9% 45%	6264
	11th to 20th	Night	14% 6% 2 6% 4 3 4 3 4 5% 50%	5880
	21st to end	Night	14% 6% 2 6% 4 4 4 3 4 6% 47%	6468
February	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 4 6% 50%	2600
	11th to 20th	Night	12% 4 2 5% 4 3 3 3 6% 7% 52%	2393
	21st to end	Night	12% 4 2 3 3 3 3 3 5% 6% 55%	1937
March	1st to 10th	Night	14% 8% 3 8% 4 4 5% 4 5% 6% 39%	3591
	11th to 20th	Night	10% 5% 2 4 3 3 3 2 3 4 62%	3490
	21st to end	Night	14% 7% 3 5% 4 4 4 4 5% 6% 44%	3690
April	1st to 10th	Night	9% 4 2 5% 3 4 3 3 5% 7% 55%	1900
	11th to 20th	Night	7% 4 1 3 3 3 3 3 5% 6% 61%	1879
	21st to end	Night	4 2 1 3 2 2 3 3 5% 7% 68%	1900
May	1st to 10th	Night	1 1 2 1 2 2 2 3 5% 80%	3153
	11th to 20th	Night	2 1 1 1 1 1 1 1 2 3 86%	2580
	21st to end	Night	1 1 1 1 1 1 2 2 4 85%	2762
June	1st to 10th	Night	2 2 1 3 1 2 2 2 4 5% 75%	1520
	11th to 20th	Night	1 1 1 1 1 2 1 2 4 87%	1520
	21st to end	Night	1 1 1 1 1 2 1 2 2 87%	1520
July	1st to 10th	Night	1 1 1 1 1 95%	2540
	11th to 20th	Night	1 2 2 1 1 1 1 2 3 85%	2633
	21st to end	Night	1 1 1 1 1 1 1 2 3 88%	3109
August	1st to 10th	Night	2 1 1 2 1 1 2 2 4 4 81%	2848
	11th to 20th	Night	1 1 1 1 1 2 3 91%	3089
	21st to end	Night	2 1 1 1 1 1 1 1 2 90%	3498
September	1st to 10th	Night	1 1 1 1 1 2 3 91%	1900
	11th to 20th	Night	2 1 1 2 1 1 1 2 3 3 83%	1900
	21st to end	Night	1 1 1 1 2 1 1 3 4 85%	2128
October	1st to 10th	Night	2 1 1 1 1 2 2 2 3 4 81%	3800
	11th to 20th	Night	2 1 1 2 1 2 2 2 3 5% 80%	3777
	21st to end	Night	4 2 1 3 2 3 3 3 4 5% 70%	4121
November	1st to 10th	Night	8% 4 1 3 3 2 2 2 5% 8% 63%	2456
	11th to 20th	Night	8% 4 2 4 3 3 3 3 4 8% 58%	2600
	21st to end	Night	10% 4 1 4 3 2 4 3 5% 6% 57%	2705
December	1st to 10th	Night	8% 3 1 4 3 3 4 4 6% 7% 56%	4560
	11th to 20th	Night	17% 9% 3 9% 5% 5% 5% 4 7% 9% 26%	5176
	21st to end	Night	18% 8% 3 9% 6% 5% 5% 4 6% 7% 29%	6952

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	45% 9% 14% 19% 10% 3	3667
	11th to 20th	Day	40% 6% 6% 17% 21% 11%	4100
	21st to end	Day	44% 7% 8% 12% 24% 5%	4510
February	1st to 10th	Day	44% 5% 9% 21% 16% 6%	1800
	11th to 20th	Day	37% 4 13% 22% 19% 5%	1903
	21st to end	Day	36% 5% 9% 25% 20% 5%	1611
March	1st to 10th	Day	45% 11% 11% 17% 15% 2	3279
	11th to 20th	Day	26% 6% 11% 30% 17% 11%	3490
	21st to end	Day	37% 10% 14% 24% 12% 3	3961
April	1st to 10th	Day	32% 5% 12% 25% 18% 7%	2280
	11th to 20th	Day	24% 6% 12% 27% 25% 6%	2252
	21st to end	Day	18% 4 11% 30% 29% 7%	2280
May	1st to 10th	Day	13% 2 7% 29% 28% 20%	3822
	11th to 20th	Day	8% 2 4 27% 43% 16%	4313
	21st to end	Day	8% 2 9% 31% 36% 13%	4814
June	1st to 10th	Day	14% 4 10% 26% 30% 16%	2660
	11th to 20th	Day	5% 2 6% 21% 37% 29%	2660
	21st to end	Day	6% 2 2 11% 33% 46%	2660
July	1st to 10th	Day	2 1 5% 13% 78%	4351
	11th to 20th	Day	7% 1 2 6% 15% 68%	4238
	21st to end	Day	3 1 1 4 27% 63%	4315
August	1st to 10th	Day	8% 1 2 6% 28% 55%	4076
	11th to 20th	Day	3 1 1 6% 39% 49%	3794
	21st to end	Day	5% 1 3 9% 35% 47%	4179
September	1st to 10th	Day	4 1 2 9% 29% 54%	2280
	11th to 20th	Day	9% 2 5% 21% 40% 23%	2280
	21st to end	Day	10% 2 4 18% 39% 28%	2048
October	1st to 10th	Day	9% 3 5% 11% 27% 45%	3180
	11th to 20th	Day	12% 3 6% 26% 35% 19%	3161
	21st to end	Day	18% 3 8% 20% 37% 14%	3448
November	1st to 10th	Day	26% 6% 8% 27% 26% 8%	1841
	11th to 20th	Day	33% 6% 12% 26% 20% 3	1800
	21st to end	Day	35% 4 12% 23% 20% 6%	1694
December	1st to 10th	Day	32% 6% 11% 29% 17% 4	2620
	11th to 20th	Day	63% 6% 7% 13% 9% 2	3028
	21st to end	Day	53% 11% 13% 15% 7% 1	4004
January	1st to 10th	Night	31% 11% 18% 26% 10% 4	6264
	11th to 20th	Night	37% 5% 9% 17% 23% 9%	5880
	21st to end	Night	38% 7% 10% 13% 24% 9%	6468
February	1st to 10th	Night	37% 4 9% 21% 21% 8%	2600
	11th to 20th	Night	31% 5% 12% 23% 23% 6%	2394
	21st to end	Night	30% 5% 10% 28% 21% 6%	1937
March	1st to 10th	Night	41% 12% 14% 15% 15% 4	3591
	11th to 20th	Night	27% 4 9% 26% 19% 13%	3490
	21st to end	Night	37% 9% 13% 24% 12% 5%	3690
April	1st to 10th	Night	29% 5% 14% 23% 21% 8%	1900
	11th to 20th	Night	23% 5% 12% 29% 20% 11%	1879
	21st to end	Night	16% 4 14% 29% 30% 7%	1900
May	1st to 10th	Night	9% 4 11% 26% 31% 19%	3153
	11th to 20th	Night	7% 1 5% 26% 41% 20%	2580
	21st to end	Night	7% 3 8% 35% 35% 12%	2762
June	1st to 10th	Night	13% 3 10% 25% 33% 16%	1520
	11th to 20th	Night	5% 2 6% 20% 35% 33%	1520
	21st to end	Night	6% 2 1 13% 30% 48%	1520
July	1st to 10th	Night	2 1 5% 13% 78%	2500
	11th to 20th	Night	7% 1 2 7% 16% 67%	2585
	21st to end	Night	5% 1 2 5% 24% 63%	3011
August	1st to 10th	Night	8% 1 2 8% 25% 55%	2839
	11th to 20th	Night	4 1 1 6% 34% 54%	3119
	21st to end	Night	6% 1 2 9% 32% 51%	3498
September	1st to 10th	Night	3 1 3 8% 29% 56%	1900
	11th to 20th	Night	8% 2 5% 21% 38% 27%	1900
	21st to end	Night	7% 2 4 18% 36% 33%	2128
October	1st to 10th	Night	10% 2 4 10% 20% 53%	3800
	11th to 20th	Night	10% 2 6% 28% 30% 24%	3777
	21st to end	Night	17% 3 5% 21% 33% 21%	4121
November	1st to 10th	Night	21% 5% 9% 25% 25% 15%	2456
	11th to 20th	Night	25% 5% 10% 25% 27% 7%	2600
	21st to end	Night	28% 4 9% 24% 26% 9%	2705
December	1st to 10th	Night	26% 5% 11% 27% 23% 8%	4560
	11th to 20th	Night	52% 8% 11% 17% 11% 2	5176
	21st to end	Night	51% 10% 13% 17% 7% 2	6952

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% 6% 17% 24% 17% 7%	215
	11th to 20th	Day	17% 7% 16% 25% 21% 15%	400
	21st to end	Day	15% 5% 16% 26% 21% 16%	440
February	1st to 10th	Day	19% 9% 18% 20% 20% 16%	400
	11th to 20th	Day	13% 10% 25% 25% 17% 11%	467
	21st to end	Day	13% 9% 21% 25% 25% 8%	399
March	1st to 10th	Day	17% 9% 19% 28% 20% 7%	460
	11th to 20th	Day	16% 9% 18% 26% 18% 13%	460
	21st to end	Day	14% 9% 23% 28% 19% 8%	506
April	1st to 10th	Day	13% 9% 22% 27% 18% 11%	460
	11th to 20th	Day	9% 7% 25% 28% 19% 12%	452
	21st to end	Day	5% 8% 24% 29% 22% 12%	460
May	1st to 10th	Day	5% 7% 26% 31% 21% 10%	463
	11th to 20th	Day	4 5% 24% 27% 26% 13%	488
	21st to end	Day	4 5% 18% 27% 31% 16%	529
June	1st to 10th	Day	4 5% 19% 32% 28% 12%	490
	11th to 20th	Day	1 6% 20% 37% 30% 7%	490
	21st to end	Day	1 2 16% 33% 36% 12%	490
July	1st to 10th	Day	1 1 12% 34% 43% 9%	486
	11th to 20th	Day	1 1 8% 33% 44% 13%	484
	21st to end	Day	1 7% 36% 40% 16%	531
August	1st to 10th	Day	2 2 10% 35% 39% 12%	487
	11th to 20th	Day	1 2 13% 36% 33% 14%	477
	21st to end	Day	1 1 8% 34% 41% 15%	539
September	1st to 10th	Day	1 2 9% 32% 43% 13%	490
	11th to 20th	Day	3 3 17% 30% 30% 17%	490
	21st to end	Day	2 2 11% 31% 34% 19%	490
October	1st to 10th	Day	1 3 17% 26% 29% 23%	490
	11th to 20th	Day	5% 5% 11% 22% 31% 27%	490
	21st to end	Day	7% 4 14% 24% 30% 21%	539
November	1st to 10th	Day	6% 6% 18% 20% 26% 24%	377
	11th to 20th	Day	9% 3 19% 22% 31% 16%	300
	21st to end	Day	11% 3 13% 30% 32% 12%	246
December	1st to 10th	Day	15% 6% 15% 24% 24% 18%	200
	11th to 20th	Day	18% 5% 19% 22% 25% 13%	200
	21st to end	Day	18% 8% 20% 25% 21% 6%	220
January	1st to 10th	Night	17% 4 15% 35% 24% 5%	800
	11th to 20th	Night	15% 4 13% 37% 27% 5%	800
	21st to end	Night	14% 4 14% 37% 27% 5%	880
February	1st to 10th	Night	19% 5% 15% 34% 25% 3	800
	11th to 20th	Night	14% 5% 18% 34% 25% 4	784
	21st to end	Night	13% 5% 20% 42% 18% 3	646
March	1st to 10th	Night	17% 7% 17% 34% 22% 2	760
	11th to 20th	Night	13% 6% 18% 36% 24% 3	760
	21st to end	Night	13% 6% 22% 38% 20% 1	836
April	1st to 10th	Night	11% 4 22% 39% 22% 1	760
	11th to 20th	Night	7% 7% 26% 37% 20% 4	751
	21st to end	Night	4 4 25% 39% 25% 3	760
May	1st to 10th	Night	3 3 25% 44% 21% 4	746
	11th to 20th	Night	3 2 18% 44% 31% 1	412
	21st to end	Night	3 3 23% 42% 29%	411
June	1st to 10th	Night	4 1 22% 48% 23% 1	380
	11th to 20th	Night	1 2 22% 51% 24% 1	380
	21st to end	Night	1 15% 53% 29% 2	380
July	1st to 10th	Night	1 7% 55% 37% 1	370
	11th to 20th	Night	1 6% 55% 37% 2	422
	21st to end	Night	1 1 6% 45% 44% 3	624
August	1st to 10th	Night	2 1 7% 44% 44% 3	567
	11th to 20th	Night	1 1 13% 47% 35% 3	727
	21st to end	Night	1 8% 47% 42% 2	836
September	1st to 10th	Night	1 9% 47% 40% 3	760
	11th to 20th	Night	2 2 14% 43% 34% 5%	760
	21st to end	Night	2 1 13% 40% 37% 7%	760
October	1st to 10th	Night	4 3 13% 40% 32% 8%	760
	11th to 20th	Night	4 3 13% 35% 39% 6%	760
	21st to end	Night	5% 3 11% 35% 35% 11%	836
November	1st to 10th	Night	8% 3 12% 36% 33% 7%	780
	11th to 20th	Night	9% 2 13% 42% 30% 5%	800
	21st to end	Night	11% 3 14% 37% 31% 5%	800
December	1st to 10th	Night	13% 4 13% 37% 27% 7%	800
	11th to 20th	Night	20% 4 14% 35% 24% 4	800
	21st to end	Night	17% 8% 19% 35% 20% 2	880

Page generated at 2025-02-22 03:51:39. Version ac07

Copyright © 2025 Attilla Danko.