Spring Gulch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spring Gulch clear sky chart from 2005-11-06 to 2024-04-03.

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	3 6% 3 6% 6% 3 5% 6% 6% 8% 48%	78972
	Night	3 6% 3 6% 5% 3 5% 5% 6% 7% 52%	81210
Transparency	Day	35% 8% 13% 20% 17% 6%	78687
	Night	32% 9% 14% 22% 18% 6%	81017
Seeing	Day	10% 14% 29% 29% 15% 2	14573
	Night	6% 6% 25% 40% 21% 2	24846

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	1 5% 3 13% 10% 5% 6% 7% 7% 8% 36%	2584
	11th to 20th	Day	1 9% 7% 11% 9% 4 5% 5% 7% 7% 37%	2860
	21st to end	Day	1 8% 4 7% 7% 3 5% 5% 5% 6% 49%	3146
February	1st to 10th	Day	2 9% 5% 10% 8% 4 6% 5% 5% 6% 40%	1710
	11th to 20th	Day	1 10% 6% 8% 7% 4 5% 6% 5% 7% 41%	1707
	21st to end	Day	1 8% 6% 9% 7% 4 6% 6% 7% 6% 40%	1570
March	1st to 10th	Day	3 9% 5% 8% 6% 3 5% 5% 5% 6% 46%	2036
	11th to 20th	Day	2 7% 3 7% 6% 4 5% 6% 7% 7% 46%	2090
	21st to end	Day	2 10% 4 7% 6% 5% 6% 7% 6% 8% 37%	2332
April	1st to 10th	Day	4 8% 4 6% 6% 4 5% 6% 6% 8% 45%	2185
	11th to 20th	Day	4 9% 3 7% 7% 3 6% 7% 6% 8% 39%	2131
	21st to end	Day	4 7% 3 7% 7% 4 6% 7% 7% 8% 43%	2160
May	1st to 10th	Day	5% 7% 3 7% 6% 3 6% 6% 6% 9% 40%	2302
	11th to 20th	Day	6% 6% 2 6% 5% 4 6% 6% 7% 9% 43%	2423
	21st to end	Day	5% 4 2 5% 6% 4 7% 7% 7% 8% 46%	2724
June	1st to 10th	Day	3 3 1 3 3 3 5% 5% 7% 9% 58%	2520
	11th to 20th	Day	3 2 1 3 4 3 4 5% 6% 7% 62%	2520
	21st to end	Day	2 2 1 2 3 3 5% 5% 7% 8% 62%	2520
July	1st to 10th	Day	4 2 2 3 5% 3 7% 7% 7% 9% 51%	2520
	11th to 20th	Day	3 3 2 5% 6% 4 7% 6% 8% 10% 47%	2460
	21st to end	Day	5% 4 3 6% 7% 5% 6% 7% 7% 10% 40%	2545
August	1st to 10th	Day	6% 5% 2 5% 7% 5% 7% 7% 7% 9% 39%	2328
	11th to 20th	Day	4 3 2 4 5% 4 5% 6% 7% 8% 53%	2235
	21st to end	Day	3 3 2 5% 6% 3 5% 7% 8% 10% 48%	2376
September	1st to 10th	Day	5% 2 1 5% 4 3 4 5% 5% 7% 58%	2160
	11th to 20th	Day	5% 2 1 3 5% 4 4 5% 6% 8% 57%	2160
	21st to end	Day	6% 3 2 4 3 2 4 4 5% 6% 62%	1905
October	1st to 10th	Day	6% 4 2 5% 4 3 5% 5% 5% 6% 55%	1800
	11th to 20th	Day	5% 5% 2 4 2 2 3 4 4 7% 64%	1800
	21st to end	Day	5% 7% 3 4 3 2 3 5% 4 5% 58%	1980
November	1st to 10th	Day	2 5% 2 4 3 2 3 4 6% 7% 63%	1755
	11th to 20th	Day	3 7% 3 5% 4 2 3 4 5% 5% 59%	1668
	21st to end	Day	2 6% 4 8% 5% 3 3 4 4 5% 56%	1520
December	1st to 10th	Day	2 8% 4 9% 9% 4 6% 4 4 5% 46%	1520
	11th to 20th	Day	2 7% 4 8% 6% 3 4 5% 5% 7% 47%	1926
	21st to end	Day	1 7% 4 9% 7% 4 6% 6% 5% 6% 44%	2794
January	1st to 10th	Night	1 8% 6% 12% 8% 4 5% 5% 5% 6% 40%	4385
	11th to 20th	Night	1 10% 5% 9% 11% 5% 5% 5% 5% 6% 39%	4110
	21st to end	Night	2 10% 5% 8% 6% 4 4 5% 5% 6% 45%	4521
February	1st to 10th	Night	1 7% 4 8% 6% 4 5% 6% 6% 7% 47%	2470
	11th to 20th	Night	1 7% 5% 7% 6% 3 6% 6% 6% 8% 44%	2360
	21st to end	Night	2 9% 5% 8% 5% 4 5% 5% 5% 7% 45%	1884
March	1st to 10th	Night	1 7% 4 7% 5% 3 5% 6% 6% 8% 48%	2142
	11th to 20th	Night	2 7% 3 5% 4 3 5% 4 6% 7% 55%	2090
	21st to end	Night	3 9% 3 5% 5% 4 6% 6% 6% 9% 44%	2264
April	1st to 10th	Night	4 6% 3 5% 6% 4 6% 6% 6% 7% 48%	1820
	11th to 20th	Night	4 9% 3 6% 5% 3 5% 6% 5% 9% 46%	1777
	21st to end	Night	5% 6% 3 5% 5% 3 4 4 6% 7% 51%	1800
May	1st to 10th	Night	5% 5% 3 5% 4 3 5% 5% 7% 9% 48%	1656
	11th to 20th	Night	5% 4 2 5% 4 3 4 5% 7% 9% 52%	1471
	21st to end	Night	4 3 2 3 4 3 5% 5% 6% 8% 58%	1552
June	1st to 10th	Night	2 2 1 2 3 2 4 4 7% 8% 65%	1440
	11th to 20th	Night	4 2 1 3 3 3 3 4 5% 7% 64%	1440
	21st to end	Night	1 1 2 2 2 3 5% 6% 9% 69%	1440
July	1st to 10th	Night	4 2 2 2 5% 3 5% 5% 7% 10% 57%	1440
	11th to 20th	Night	2 2 1 3 4 3 5% 5% 8% 10% 57%	1496
	21st to end	Night	4 3 1 3 6% 3 6% 7% 9% 11% 47%	1773
August	1st to 10th	Night	4 3 1 4 5% 3 4 7% 8% 10% 51%	1611
	11th to 20th	Night	3 3 2 3 4 3 4 4 6% 8% 59%	1664
	21st to end	Night	3 2 2 4 4 3 4 5% 6% 9% 58%	1980
September	1st to 10th	Night	4 3 2 4 4 3 4 4 5% 6% 62%	1800
	11th to 20th	Night	3 2 1 3 4 2 4 5% 6% 9% 61%	1800
	21st to end	Night	4 2 1 3 3 2 3 4 4 6% 68%	2051
October	1st to 10th	Night	4 4 1 3 4 3 3 4 5% 8% 60%	2160
	11th to 20th	Night	4 3 1 3 3 2 3 4 5% 6% 66%	2160
	21st to end	Night	5% 7% 2 4 3 2 3 3 4 5% 61%	2376
November	1st to 10th	Night	2 5% 2 3 3 1 4 4 6% 7% 64%	2304
	11th to 20th	Night	3 7% 2 4 4 2 4 5% 4 6% 59%	2509
	21st to end	Night	2 6% 3 5% 4 3 4 5% 5% 6% 57%	2660
December	1st to 10th	Night	1 8% 4 7% 7% 4 5% 5% 4 5% 50%	2660
	11th to 20th	Night	3 7% 3 6% 6% 3 5% 5% 6% 9% 45%	3271
	21st to end	Night	1 7% 4 8% 8% 4 6% 5% 5% 6% 46%	4873

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	41% 13% 16% 20% 10% 1	2585
	11th to 20th	Day	46% 12% 19% 15% 8%	2860
	21st to end	Day	35% 10% 19% 25% 10% 1	3146
February	1st to 10th	Day	47% 8% 16% 17% 10% 2	1710
	11th to 20th	Day	48% 6% 10% 21% 13% 2	1716
	21st to end	Day	46% 8% 13% 18% 13% 3	1570
March	1st to 10th	Day	41% 7% 13% 23% 16% 1	2036
	11th to 20th	Day	35% 11% 15% 25% 11% 3	2090
	21st to end	Day	46% 10% 14% 20% 9% 2	2332
April	1st to 10th	Day	39% 8% 14% 17% 16% 6%	2185
	11th to 20th	Day	44% 9% 12% 18% 16% 2	2134
	21st to end	Day	39% 8% 14% 23% 14% 2	2160
May	1st to 10th	Day	41% 9% 11% 20% 16% 2	2302
	11th to 20th	Day	37% 10% 13% 24% 13% 3	2427
	21st to end	Day	34% 9% 11% 21% 20% 5%	2724
June	1st to 10th	Day	23% 7% 12% 22% 26% 11%	2520
	11th to 20th	Day	22% 7% 8% 15% 26% 22%	2520
	21st to end	Day	20% 6% 8% 19% 26% 21%	2520
July	1st to 10th	Day	30% 6% 11% 15% 20% 18%	2451
	11th to 20th	Day	30% 9% 16% 18% 16% 11%	2385
	21st to end	Day	37% 11% 18% 17% 12% 6%	2404
August	1st to 10th	Day	39% 9% 14% 15% 15% 8%	2313
	11th to 20th	Day	30% 8% 14% 16% 21% 11%	2235
	21st to end	Day	31% 9% 14% 18% 20% 8%	2376
September	1st to 10th	Day	27% 7% 9% 16% 22% 19%	2160
	11th to 20th	Day	27% 7% 12% 18% 25% 11%	2160
	21st to end	Day	26% 5% 7% 23% 31% 9%	1905
October	1st to 10th	Day	32% 7% 11% 22% 21% 6%	1800
	11th to 20th	Day	26% 4 8% 29% 27% 7%	1800
	21st to end	Day	28% 7% 14% 28% 19% 4	1980
November	1st to 10th	Day	24% 7% 14% 25% 27% 3	1755
	11th to 20th	Day	28% 6% 16% 28% 19% 3	1668
	21st to end	Day	34% 5% 12% 30% 15% 4	1520
December	1st to 10th	Day	43% 8% 16% 20% 10% 3	1520
	11th to 20th	Day	39% 8% 12% 27% 13%	1924
	21st to end	Day	39% 11% 11% 18% 18% 3	2794
January	1st to 10th	Night	38% 17% 14% 20% 10% 1	4385
	11th to 20th	Night	47% 9% 17% 17% 9% 1	4110
	21st to end	Night	40% 10% 20% 19% 9% 2	4521
February	1st to 10th	Night	40% 10% 16% 22% 11% 1	2470
	11th to 20th	Night	39% 8% 14% 24% 12% 2	2361
	21st to end	Night	42% 7% 13% 22% 14% 3	1884
March	1st to 10th	Night	36% 8% 13% 26% 16%	2142
	11th to 20th	Night	29% 9% 16% 29% 13% 4	2090
	21st to end	Night	38% 11% 15% 24% 11% 2	2264
April	1st to 10th	Night	37% 7% 13% 20% 19% 4	1820
	11th to 20th	Night	36% 10% 13% 22% 16% 3	1777
	21st to end	Night	34% 8% 13% 24% 19% 2	1800
May	1st to 10th	Night	35% 8% 13% 25% 17% 2	1656
	11th to 20th	Night	28% 11% 16% 28% 14% 3	1472
	21st to end	Night	25% 9% 15% 22% 23% 7%	1552
June	1st to 10th	Night	18% 7% 12% 24% 28% 12%	1440
	11th to 20th	Night	21% 7% 7% 15% 24% 26%	1440
	21st to end	Night	13% 5% 12% 17% 27% 25%	1440
July	1st to 10th	Night	23% 10% 12% 15% 19% 21%	1400
	11th to 20th	Night	19% 10% 17% 22% 17% 15%	1448
	21st to end	Night	26% 11% 24% 19% 13% 7%	1674
August	1st to 10th	Night	26% 10% 19% 20% 15% 10%	1602
	11th to 20th	Night	21% 8% 15% 19% 23% 14%	1664
	21st to end	Night	24% 8% 13% 20% 21% 15%	1980
September	1st to 10th	Night	24% 6% 11% 15% 23% 22%	1800
	11th to 20th	Night	22% 7% 13% 18% 25% 15%	1800
	21st to end	Night	19% 6% 8% 23% 35% 10%	2051
October	1st to 10th	Night	25% 8% 11% 25% 21% 11%	2160
	11th to 20th	Night	21% 5% 11% 28% 29% 7%	2160
	21st to end	Night	27% 6% 13% 29% 21% 5%	2376
November	1st to 10th	Night	22% 7% 14% 26% 27% 4	2304
	11th to 20th	Night	28% 7% 13% 29% 20% 3	2509
	21st to end	Night	31% 6% 11% 29% 19% 4	2660
December	1st to 10th	Night	39% 6% 17% 21% 15% 2	2660
	11th to 20th	Night	37% 9% 15% 25% 15% 1	3272
	21st to end	Night	39% 9% 13% 17% 21% 1	4873

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	11% 13% 24% 35% 16% 1	270
	11th to 20th	Day	13% 12% 34% 30% 11%	270
	21st to end	Day	7% 11% 33% 34% 15% 1	297
February	1st to 10th	Day	14% 16% 37% 26% 5% 1	270
	11th to 20th	Day	15% 19% 31% 29% 6% 1	270
	21st to end	Day	20% 19% 35% 20% 6%	225
March	1st to 10th	Day	20% 23% 29% 22% 6%	406
	11th to 20th	Day	12% 22% 33% 26% 7%	460
	21st to end	Day	16% 30% 35% 15% 4	506
April	1st to 10th	Day	17% 28% 31% 16% 7% 1	429
	11th to 20th	Day	20% 29% 27% 17% 5% 1	412
	21st to end	Day	14% 28% 32% 20% 6% 1	420
May	1st to 10th	Day	14% 24% 38% 17% 6% 1	423
	11th to 20th	Day	11% 14% 28% 30% 14% 2	570
	21st to end	Day	8% 15% 28% 30% 17% 2	679
June	1st to 10th	Day	5% 13% 28% 30% 22% 2	630
	11th to 20th	Day	5% 14% 32% 32% 16% 1	630
	21st to end	Day	3 11% 31% 31% 22% 2	630
July	1st to 10th	Day	5% 4 22% 35% 30% 4	621
	11th to 20th	Day	2 3 24% 38% 28% 4	558
	21st to end	Day	5% 5% 23% 39% 23% 6%	487
August	1st to 10th	Day	7% 7% 27% 35% 19% 5%	447
	11th to 20th	Day	3 5% 29% 38% 22% 5%	437
	21st to end	Day	3 6% 23% 39% 23% 5%	495
September	1st to 10th	Day	6% 9% 26% 31% 22% 5%	450
	11th to 20th	Day	6% 11% 33% 32% 15% 4	450
	21st to end	Day	12% 12% 24% 29% 16% 6%	347
October	1st to 10th	Day	11% 13% 21% 30% 17% 8%	270
	11th to 20th	Day	10% 17% 25% 29% 17% 4	270
	21st to end	Day	12% 12% 33% 28% 13% 2	297
November	1st to 10th	Day	14% 18% 29% 25% 14% 1	270
	11th to 20th	Day	8% 14% 28% 34% 14% 2	270
	21st to end	Day	9% 13% 30% 30% 15% 2	270
December	1st to 10th	Day	10% 13% 34% 28% 13% 2	270
	11th to 20th	Day	10% 10% 30% 35% 14%	270
	21st to end	Day	12% 14% 36% 28% 9%	297
January	1st to 10th	Night	5% 9% 29% 39% 16% 2	931
	11th to 20th	Night	7% 7% 32% 38% 15% 1	760
	21st to end	Night	7% 5% 28% 44% 14% 2	836
February	1st to 10th	Night	6% 8% 36% 43% 8%	760
	11th to 20th	Night	6% 8% 35% 40% 11%	744
	21st to end	Night	9% 8% 40% 38% 5%	628
March	1st to 10th	Night	6% 10% 35% 38% 10% 1	760
	11th to 20th	Night	5% 8% 26% 45% 16%	760
	21st to end	Night	8% 9% 32% 40% 11%	801
April	1st to 10th	Night	8% 12% 35% 36% 8%	546
	11th to 20th	Night	9% 11% 33% 35% 12% 1	533
	21st to end	Night	10% 9% 27% 36% 16% 2	540
May	1st to 10th	Night	9% 7% 31% 40% 13% 1	540
	11th to 20th	Night	8% 4 22% 40% 24% 2	531
	21st to end	Night	8% 7% 21% 37% 24% 3	584
June	1st to 10th	Night	4 4 17% 44% 30% 1	540
	11th to 20th	Night	6% 6% 23% 44% 20% 1	540
	21st to end	Night	1 1 19% 44% 33% 1	540
July	1st to 10th	Night	4 1 12% 39% 42% 3	525
	11th to 20th	Night	2 1 7% 44% 43% 4	522
	21st to end	Night	3 1 5% 34% 55% 3	591
August	1st to 10th	Night	7% 1 8% 39% 43% 2	537
	11th to 20th	Night	4 1 11% 42% 39% 3	534
	21st to end	Night	2 1 11% 39% 44% 4	594
September	1st to 10th	Night	4 2 13% 47% 34% 1	540
	11th to 20th	Night	4 3 14% 45% 33% 2	540
	21st to end	Night	4 3 18% 38% 33% 4	688
October	1st to 10th	Night	6% 4 23% 42% 23% 2	720
	11th to 20th	Night	5% 4 27% 39% 22% 3	720
	21st to end	Night	9% 7% 23% 39% 20% 3	792
November	1st to 10th	Night	5% 7% 31% 37% 20% 1	824
	11th to 20th	Night	8% 9% 28% 38% 15% 2	950
	21st to end	Night	7% 9% 26% 39% 18% 1	950
December	1st to 10th	Night	7% 7% 33% 40% 12% 1	950
	11th to 20th	Night	9% 10% 31% 35% 14% 1	950
	21st to end	Night	9% 9% 33% 37% 10% 1	1045

Page generated at 2024-03-31 04:08:51. Version ac07

Copyright © 2024 Attilla Danko.