Stargate Observatory
Clear Sky Chart
History

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

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	13% 10% 3 8% 5% 5% 5% 4 6% 7% 34%	101053
	Night	14% 10% 3 8% 5% 4 4 4 5% 7% 36%	97940
Transparency	Day	46% 6% 12% 22% 12% 1	104681
	Night	46% 5% 12% 22% 12% 1	102452
Seeing	Day	16% 10% 28% 25% 15% 6%	15343
	Night	18% 8% 29% 30% 13% 1	24925

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	15% 18% 6% 11% 6% 4 4 4 4 5% 23%	2527
	11th to 20th	Day	15% 18% 6% 12% 9% 7% 5% 4 5% 5% 14%	2533
	21st to end	Day	26% 19% 6% 10% 6% 4 4 3 3 3 16%	3124
February	1st to 10th	Day	15% 15% 4 13% 8% 5% 5% 3 4 5% 22%	1710
	11th to 20th	Day	13% 14% 4 12% 8% 4 5% 3 5% 6% 26%	1761
	21st to end	Day	13% 16% 5% 11% 6% 4 4 4 6% 5% 26%	1570
March	1st to 10th	Day	17% 16% 5% 10% 5% 4 3 3 4 6% 27%	3234
	11th to 20th	Day	13% 12% 5% 9% 5% 6% 4 4 5% 6% 32%	3480
	21st to end	Day	18% 13% 4 9% 5% 5% 4 3 4 5% 30%	3815
April	1st to 10th	Day	15% 12% 4 8% 5% 4 4 4 6% 6% 32%	2180
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 5% 7% 34%	2432
	21st to end	Day	17% 9% 3 8% 5% 4 5% 4 4 6% 34%	2470
May	1st to 10th	Day	16% 8% 3 8% 4 4 5% 4 5% 8% 35%	4082
	11th to 20th	Day	16% 8% 3 7% 5% 5% 4 4 6% 7% 35%	4081
	21st to end	Day	9% 6% 2 7% 5% 4 4 4 5% 8% 46%	4476
June	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 8% 41%	2811
	11th to 20th	Day	9% 5% 2 7% 4 5% 5% 4 7% 9% 42%	2850
	21st to end	Day	9% 6% 2 6% 5% 6% 6% 5% 7% 10% 37%	2819
July	1st to 10th	Day	10% 6% 2 7% 6% 5% 6% 5% 7% 9% 37%	4440
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 5% 8% 11% 45%	4440
	21st to end	Day	6% 5% 3 7% 6% 5% 6% 6% 8% 9% 39%	4498
August	1st to 10th	Day	12% 5% 2 5% 5% 5% 6% 4 7% 8% 40%	4104
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 5% 8% 10% 39%	4044
	21st to end	Day	9% 5% 3 7% 5% 5% 6% 5% 7% 10% 38%	4532
September	1st to 10th	Day	10% 6% 3 6% 5% 5% 5% 4 6% 9% 41%	2142
	11th to 20th	Day	9% 5% 1 6% 4 4 5% 5% 6% 9% 46%	2090
	21st to end	Day	14% 8% 3 6% 5% 5% 6% 4 6% 8% 35%	2090
October	1st to 10th	Day	11% 7% 3 6% 5% 4 4 4 6% 7% 43%	2014
	11th to 20th	Day	17% 8% 3 7% 5% 6% 5% 4 4 7% 34%	1900
	21st to end	Day	19% 10% 4 9% 4 4 5% 4 4 6% 31%	1959
November	1st to 10th	Day	11% 10% 3 8% 5% 4 4 4 6% 8% 37%	1699
	11th to 20th	Day	13% 10% 4 9% 6% 5% 4 5% 6% 6% 33%	1710
	21st to end	Day	18% 12% 4 9% 5% 4 4 4 4 6% 29%	1533
December	1st to 10th	Day	13% 14% 6% 12% 7% 6% 4 3 5% 6% 22%	1520
	11th to 20th	Day	15% 16% 4 10% 5% 4 3 5% 7% 6% 25%	1788
	21st to end	Day	26% 20% 6% 10% 5% 4 4 3 4 5% 13%	2595
January	1st to 10th	Night	16% 15% 5% 10% 6% 5% 4 3 5% 6% 25%	4428
	11th to 20th	Night	14% 17% 6% 14% 7% 6% 5% 4 4 5% 18%	4435
	21st to end	Night	23% 18% 7% 10% 5% 4 4 3 3 4 19%	4532
February	1st to 10th	Night	14% 15% 5% 12% 8% 5% 5% 3 5% 4 23%	2470
	11th to 20th	Night	13% 13% 5% 10% 6% 6% 5% 4 6% 5% 28%	2300
	21st to end	Night	18% 12% 4 9% 5% 5% 4 3 5% 5% 29%	1884
March	1st to 10th	Night	15% 13% 4 9% 5% 4 3 3 4 6% 34%	3619
	11th to 20th	Night	9% 8% 3 6% 5% 5% 5% 4 6% 8% 40%	3480
	21st to end	Night	16% 9% 3 8% 5% 4 4 4 4 5% 38%	3817
April	1st to 10th	Night	17% 10% 3 6% 5% 4 4 4 6% 6% 35%	2015
	11th to 20th	Night	18% 8% 3 6% 4 4 4 4 5% 7% 37%	1696
	21st to end	Night	16% 9% 2 6% 4 4 5% 3 6% 8% 39%	1710
May	1st to 10th	Night	16% 9% 2 8% 5% 4 3 4 6% 8% 37%	2813
	11th to 20th	Night	14% 7% 3 8% 5% 5% 4 4 5% 7% 40%	2812
	21st to end	Night	9% 5% 2 6% 4 4 4 4 6% 8% 49%	3062
June	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 9% 46%	1364
	11th to 20th	Night	9% 5% 3 6% 4 4 5% 5% 6% 8% 45%	1330
	21st to end	Night	8% 5% 2 6% 5% 4 4 3 6% 8% 49%	1355
July	1st to 10th	Night	8% 4 2 4 4 4 5% 3 6% 11% 49%	2530
	11th to 20th	Night	9% 3 1 5% 3 4 3 3 7% 9% 53%	2530
	21st to end	Night	4 4 2 6% 4 5% 6% 5% 9% 10% 46%	3051
August	1st to 10th	Night	11% 6% 3 6% 3 4 5% 3 6% 8% 46%	2825
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 4 6% 8% 47%	2785
	21st to end	Night	7% 5% 2 7% 5% 5% 5% 4 6% 7% 48%	3124
September	1st to 10th	Night	8% 6% 2 7% 5% 4 4 3 5% 7% 48%	2013
	11th to 20th	Night	9% 5% 2 5% 3 3 4 3 5% 8% 54%	2090
	21st to end	Night	15% 6% 2 6% 4 3 5% 4 5% 7% 44%	2090
October	1st to 10th	Night	13% 6% 2 6% 3 3 4 3 6% 7% 46%	2166
	11th to 20th	Night	17% 9% 3 7% 5% 5% 4 4 5% 5% 36%	2280
	21st to end	Night	20% 9% 3 6% 5% 5% 4 4 5% 7% 32%	2636
November	1st to 10th	Night	13% 9% 2 6% 4 4 4 3 5% 7% 43%	2452
	11th to 20th	Night	15% 10% 3 7% 5% 6% 5% 4 7% 7% 31%	2470
	21st to end	Night	18% 13% 4 8% 4 5% 4 4 5% 6% 29%	2645
December	1st to 10th	Night	17% 14% 5% 11% 6% 4 5% 4 6% 6% 23%	2660
	11th to 20th	Night	14% 14% 5% 10% 6% 5% 5% 3 6% 6% 26%	3404
	21st to end	Night	27% 21% 6% 10% 5% 4 3 3 4 4 14%	5067

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	63% 4 14% 13% 5% 1	2528
	11th to 20th	Day	71% 6% 11% 9% 3	2533
	21st to end	Day	73% 4 12% 7% 3 1	3124
February	1st to 10th	Day	64% 5% 9% 15% 7%	1710
	11th to 20th	Day	58% 4 10% 18% 8% 2	1770
	21st to end	Day	59% 3 12% 18% 6% 2	1570
March	1st to 10th	Day	58% 5% 11% 20% 5% 1	3234
	11th to 20th	Day	52% 5% 12% 21% 8% 2	3480
	21st to end	Day	55% 6% 12% 15% 10% 2	3815
April	1st to 10th	Day	51% 5% 11% 20% 12% 1	2180
	11th to 20th	Day	49% 5% 11% 20% 13% 2	2432
	21st to end	Day	49% 6% 13% 18% 13% 2	2470
May	1st to 10th	Day	44% 7% 11% 23% 12% 2	4120
	11th to 20th	Day	46% 6% 15% 23% 9% 1	4085
	21st to end	Day	37% 5% 12% 18% 23% 5%	4489
June	1st to 10th	Day	39% 6% 13% 26% 14% 2	2811
	11th to 20th	Day	36% 7% 14% 24% 16% 3	2850
	21st to end	Day	38% 8% 12% 24% 15% 2	2819
July	1st to 10th	Day	40% 8% 13% 21% 15% 2	4371
	11th to 20th	Day	29% 8% 15% 33% 15% 1	4365
	21st to end	Day	35% 10% 14% 17% 22% 2	4356
August	1st to 10th	Day	37% 8% 13% 24% 16% 1	4091
	11th to 20th	Day	36% 8% 12% 32% 10% 1	4083
	21st to end	Day	38% 8% 12% 27% 14% 1	4531
September	1st to 10th	Day	39% 6% 15% 25% 13% 2	2142
	11th to 20th	Day	32% 6% 12% 33% 15% 1	2090
	21st to end	Day	44% 6% 13% 25% 12% 1	2090
October	1st to 10th	Day	31% 5% 11% 32% 19% 2	3352
	11th to 20th	Day	40% 5% 11% 26% 18%	3140
	21st to end	Day	45% 6% 13% 23% 13% 1	3209
November	1st to 10th	Day	43% 7% 13% 25% 11% 1	1699
	11th to 20th	Day	50% 6% 14% 19% 10% 1	1710
	21st to end	Day	57% 5% 13% 19% 6% 1	1533
December	1st to 10th	Day	62% 5% 12% 17% 4	1520
	11th to 20th	Day	58% 5% 15% 16% 6%	1784
	21st to end	Day	75% 4 10% 8% 3	2595
January	1st to 10th	Night	60% 5% 13% 16% 5% 1	4428
	11th to 20th	Night	66% 6% 13% 11% 3	4435
	21st to end	Night	69% 3 10% 15% 3	4532
February	1st to 10th	Night	62% 6% 9% 15% 7% 1	2470
	11th to 20th	Night	56% 5% 10% 19% 9% 1	2302
	21st to end	Night	56% 3 12% 19% 8% 1	1884
March	1st to 10th	Night	53% 3 13% 24% 6% 1	3619
	11th to 20th	Night	40% 5% 14% 22% 17% 1	3480
	21st to end	Night	48% 4 10% 24% 13% 1	3817
April	1st to 10th	Night	48% 5% 11% 21% 13% 2	2015
	11th to 20th	Night	45% 5% 11% 19% 17% 2	1696
	21st to end	Night	43% 5% 11% 20% 16% 4	1710
May	1st to 10th	Night	46% 4 12% 21% 14% 4	2840
	11th to 20th	Night	42% 5% 12% 26% 13% 2	2813
	21st to end	Night	32% 6% 12% 22% 21% 7%	3069
June	1st to 10th	Night	34% 6% 11% 30% 17% 2	1364
	11th to 20th	Night	35% 6% 13% 24% 19% 2	1330
	21st to end	Night	33% 6% 12% 27% 21% 1	1355
July	1st to 10th	Night	28% 5% 14% 32% 15% 6%	2490
	11th to 20th	Night	27% 6% 14% 34% 17% 1	2482
	21st to end	Night	28% 10% 17% 21% 21% 2	2954
August	1st to 10th	Night	34% 6% 15% 27% 17% 1	2814
	11th to 20th	Night	33% 8% 13% 32% 12% 2	2812
	21st to end	Night	33% 8% 12% 32% 15% 1	3124
September	1st to 10th	Night	35% 6% 14% 28% 16% 2	2013
	11th to 20th	Night	29% 5% 14% 31% 21% 1	2090
	21st to end	Night	40% 4 13% 29% 12% 1	2090
October	1st to 10th	Night	26% 4 10% 32% 27% 1	3608
	11th to 20th	Night	43% 4 11% 24% 17% 1	3779
	21st to end	Night	41% 5% 13% 28% 13% 1	4336
November	1st to 10th	Night	41% 5% 13% 26% 14% 1	2452
	11th to 20th	Night	50% 5% 15% 21% 9% 1	2470
	21st to end	Night	56% 4 15% 19% 6%	2645
December	1st to 10th	Night	61% 5% 13% 15% 5%	2660
	11th to 20th	Night	57% 5% 14% 16% 7% 1	3407
	21st to end	Night	74% 5% 11% 7% 3	5067

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	20% 18% 37% 17% 7% 1	270
	11th to 20th	Day	21% 14% 43% 17% 4 1	270
	21st to end	Day	25% 11% 38% 19% 5% 1	297
February	1st to 10th	Day	21% 17% 41% 15% 4 1	270
	11th to 20th	Day	21% 17% 40% 19% 3	270
	21st to end	Day	20% 20% 45% 12% 3	225
March	1st to 10th	Day	22% 17% 38% 18% 4 1	332
	11th to 20th	Day	20% 15% 32% 26% 7% 1	460
	21st to end	Day	27% 12% 31% 23% 6% 1	506
April	1st to 10th	Day	14% 16% 38% 23% 8% 1	460
	11th to 20th	Day	25% 14% 28% 18% 10% 5%	452
	21st to end	Day	22% 12% 29% 23% 12% 2	460
May	1st to 10th	Day	21% 10% 29% 25% 12% 3	463
	11th to 20th	Day	18% 9% 25% 26% 15% 7%	487
	21st to end	Day	14% 5% 21% 30% 21% 9%	529
June	1st to 10th	Day	11% 7% 31% 32% 16% 4	641
	11th to 20th	Day	11% 5% 30% 32% 18% 4	680
	21st to end	Day	12% 7% 26% 31% 19% 5%	680
July	1st to 10th	Day	8% 5% 20% 30% 23% 14%	671
	11th to 20th	Day	9% 5% 23% 34% 20% 9%	668
	21st to end	Day	7% 4 22% 30% 26% 11%	551
August	1st to 10th	Day	9% 5% 18% 27% 27% 15%	486
	11th to 20th	Day	12% 3 14% 32% 24% 15%	479
	21st to end	Day	11% 4 18% 31% 23% 13%	539
September	1st to 10th	Day	11% 5% 23% 24% 24% 12%	490
	11th to 20th	Day	9% 3 18% 22% 31% 16%	490
	21st to end	Day	16% 9% 23% 23% 20% 8%	490
October	1st to 10th	Day	13% 11% 26% 23% 18% 9%	490
	11th to 20th	Day	19% 14% 32% 24% 8% 3	490
	21st to end	Day	23% 13% 38% 18% 7% 1	408
November	1st to 10th	Day	17% 15% 36% 21% 9% 2	279
	11th to 20th	Day	19% 19% 35% 17% 8% 1	270
	21st to end	Day	24% 15% 37% 20% 4	185
December	1st to 10th	Day	20% 17% 42% 13% 8% 1	180
	11th to 20th	Day	29% 14% 38% 13% 4 1	180
	21st to end	Day	26% 18% 34% 18% 4	245
January	1st to 10th	Night	23% 12% 37% 22% 5% 1	950
	11th to 20th	Night	25% 12% 34% 25% 4 1	945
	21st to end	Night	20% 9% 35% 28% 7%	836
February	1st to 10th	Night	20% 11% 42% 24% 3	760
	11th to 20th	Night	20% 13% 36% 26% 5%	743
	21st to end	Night	23% 14% 39% 21% 2	628
March	1st to 10th	Night	20% 10% 36% 28% 6%	760
	11th to 20th	Night	16% 13% 38% 26% 6% 1	760
	21st to end	Night	22% 8% 33% 28% 8%	836
April	1st to 10th	Night	22% 11% 34% 28% 4	685
	11th to 20th	Night	22% 9% 33% 26% 8% 2	563
	21st to end	Night	19% 7% 31% 33% 9%	570
May	1st to 10th	Night	17% 6% 29% 36% 11% 1	570
	11th to 20th	Night	20% 5% 26% 33% 16% 1	561
	21st to end	Night	9% 3 23% 41% 22% 2	612
June	1st to 10th	Night	11% 4 26% 45% 14%	380
	11th to 20th	Night	11% 4 24% 46% 16% 1	380
	21st to end	Night	11% 3 20% 45% 20%	405
July	1st to 10th	Night	8% 2 16% 41% 28% 5%	555
	11th to 20th	Night	9% 3 16% 41% 26% 3	552
	21st to end	Night	6% 3 17% 46% 26% 2	624
August	1st to 10th	Night	9% 2 14% 39% 33% 3	567
	11th to 20th	Night	7% 2 17% 38% 32% 4	564
	21st to end	Night	10% 2 17% 35% 32% 3	627
September	1st to 10th	Night	10% 6% 19% 34% 26% 5%	701
	11th to 20th	Night	10% 3 17% 34% 29% 5%	760
	21st to end	Night	16% 5% 20% 34% 20% 5%	760
October	1st to 10th	Night	16% 8% 25% 31% 18% 2	760
	11th to 20th	Night	22% 10% 29% 27% 10% 2	760
	21st to end	Night	25% 9% 33% 29% 5%	836
November	1st to 10th	Night	18% 10% 30% 29% 13% 1	755
	11th to 20th	Night	20% 14% 33% 24% 8% 1	760
	21st to end	Night	26% 11% 34% 23% 6%	760
December	1st to 10th	Night	26% 11% 38% 20% 6%	760
	11th to 20th	Night	23% 11% 38% 24% 4	835
	21st to end	Night	29% 11% 33% 24% 3	1045

Page generated at 2024-11-01 22:47:47. Version ac07

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