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 2026-02-16.

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 4 2 6% 4 4 5% 4 6% 7% 57%	139051
	Night	3 4 2 5% 4 4 4 4 6% 7% 59%	139317
Transparency	Day	26% 4 7% 17% 27% 19%	133990
	Night	23% 4 8% 17% 29% 19%	135382
Seeing	Day	9% 16% 27% 26% 17% 5%	16055
	Night	5% 13% 27% 32% 20% 3	26710

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 9% 5% 5% 5% 3 6% 6% 54%	5318
	11th to 20th	Day	1 2 1 3 2 2 3 3 4 4 75%	5340
	21st to end	Day	2 8% 3 6% 3 3 3 3 5% 6% 57%	5844
February	1st to 10th	Day	1 6% 2 5% 4 3 3 3 5% 8% 60%	1890
	11th to 20th	Day	2 5% 2 6% 4 5% 5% 3 6% 8% 54%	1883
	21st to end	Day	2 6% 2 5% 4 5% 5% 3 5% 6% 57%	1739
March	1st to 10th	Day	1 5% 2 4 4 3 5% 4 6% 8% 59%	4954
	11th to 20th	Day	3 10% 4 7% 5% 4 5% 4 7% 8% 45%	5000
	21st to end	Day	2 4 2 6% 4 4 4 4 6% 9% 55%	5486
April	1st to 10th	Day	1 4 2 4 4 3 4 4 5% 6% 63%	2360
	11th to 20th	Day	2 4 2 4 4 4 5% 3 5% 6% 62%	2371
	21st to end	Day	2 4 2 4 3 3 3 4 4 7% 65%	2400
May	1st to 10th	Day	2 4 2 5% 4 4 5% 4 6% 5% 60%	5545
	11th to 20th	Day	2 3 1 4 4 4 4 4 5% 5% 63%	5841
	21st to end	Day	2 2 1 4 3 3 3 3 4 6% 69%	6423
June	1st to 10th	Day	3 3 1 3 3 4 4 4 5% 8% 62%	2600
	11th to 20th	Day	2 2 1 4 3 3 3 2 4 4 70%	2600
	21st to end	Day	4 5% 2 6% 4 6% 6% 4 6% 6% 52%	2600
July	1st to 10th	Day	4 3 2 6% 5% 5% 5% 4 5% 6% 56%	5879
	11th to 20th	Day	3 4 3 8% 7% 8% 8% 6% 8% 9% 35%	5880
	21st to end	Day	5% 6% 3 9% 7% 6% 7% 6% 7% 8% 35%	6401
August	1st to 10th	Day	4 4 2 7% 6% 6% 6% 5% 7% 8% 46%	5779
	11th to 20th	Day	4 4 2 6% 6% 6% 7% 5% 7% 8% 44%	5501
	21st to end	Day	5% 5% 2 8% 6% 6% 7% 6% 8% 10% 38%	5984
September	1st to 10th	Day	7% 6% 2 8% 5% 6% 5% 4 7% 7% 44%	2400
	11th to 20th	Day	6% 5% 2 6% 4 3 4 3 6% 6% 55%	2335
	21st to end	Day	4 3 2 5% 3 4 4 3 5% 6% 61%	2135
October	1st to 10th	Day	5% 4 2 5% 4 3 3 3 3 4 64%	3270
	11th to 20th	Day	6% 5% 2 4 3 3 3 3 4 5% 64%	3250
	21st to end	Day	1 1 1 3 1 2 2 2 3 5% 78%	3548
November	1st to 10th	Day	1 2 1 3 3 3 3 3 4 6% 70%	2059
	11th to 20th	Day	1 2 1 3 3 3 4 3 6% 6% 68%	2100
	21st to end	Day	2 5% 1 5% 3 4 4 2 5% 6% 62%	1803
December	1st to 10th	Day	1 3 1 3 2 2 3 2 4 5% 75%	2700
	11th to 20th	Day	2 4 2 5% 4 3 3 2 4 7% 62%	3224
	21st to end	Day	1 4 2 4 3 4 4 3 5% 6% 64%	4609
January	1st to 10th	Night	1 6% 2 8% 5% 5% 5% 4 6% 7% 51%	7605
	11th to 20th	Night	1 1 1 2 2 2 2 2 4 4 79%	7650
	21st to end	Night	2 5% 2 6% 4 4 4 4 6% 7% 55%	8370
February	1st to 10th	Night	1 4 2 5% 3 3 3 3 4 7% 65%	2730
	11th to 20th	Night	2 5% 2 5% 4 3 5% 4 6% 8% 57%	2512
	21st to end	Night	1 4 1 4 3 3 4 4 5% 8% 64%	1889
March	1st to 10th	Night	1 3 2 6% 3 3 3 3 5% 7% 65%	4940
	11th to 20th	Night	5% 9% 4 6% 3 3 3 3 5% 6% 52%	5000
	21st to end	Night	1 2 1 4 3 3 3 4 5% 7% 66%	5489
April	1st to 10th	Night	2 3 1 4 3 3 3 3 6% 7% 66%	2038
	11th to 20th	Night	2 3 1 3 3 3 3 4 6% 6% 65%	1977
	21st to end	Night	1 3 1 3 3 3 3 3 4 7% 69%	2000
May	1st to 10th	Night	4 4 2 4 3 4 4 3 5% 6% 61%	4418
	11th to 20th	Night	2 3 1 4 3 3 3 3 4 6% 68%	4074
	21st to end	Night	1 3 1 4 3 3 3 2 4 6% 71%	4474
June	1st to 10th	Night	3 3 2 4 3 3 5% 4 4 6% 62%	1800
	11th to 20th	Night	3 2 1 2 3 3 3 3 4 5% 72%	1800
	21st to end	Night	5% 5% 2 5% 4 5% 6% 4 6% 6% 52%	1800
July	1st to 10th	Night	3 4 2 6% 4 4 4 4 6% 7% 56%	4100
	11th to 20th	Night	4 4 2 8% 6% 6% 7% 6% 10% 11% 36%	4100
	21st to end	Night	4 5% 3 9% 6% 7% 8% 7% 9% 10% 34%	4472
August	1st to 10th	Night	2 3 2 7% 6% 7% 7% 6% 9% 11% 39%	4033
	11th to 20th	Night	4 4 2 7% 6% 7% 8% 6% 8% 10% 37%	4347
	21st to end	Night	5% 4 2 8% 6% 6% 8% 7% 11% 10% 33%	4993
September	1st to 10th	Night	7% 5% 2 7% 4 5% 5% 5% 8% 8% 44%	2000
	11th to 20th	Night	4 4 1 5% 3 5% 4 3 4 6% 59%	2060
	21st to end	Night	4 4 2 4 2 3 3 3 4 6% 66%	2264
October	1st to 10th	Night	4 3 1 4 3 3 3 2 4 5% 69%	3920
	11th to 20th	Night	7% 5% 2 5% 3 3 3 3 5% 6% 59%	3898
	21st to end	Night	2 1 1 2 2 2 3 3 4 5% 75%	4252
November	1st to 10th	Night	2 2 1 2 2 2 3 3 5% 6% 72%	2460
	11th to 20th	Night	1 2 1 3 2 2 3 3 5% 7% 72%	2520
	21st to end	Night	3 5% 2 4 3 3 3 3 5% 6% 62%	2783
December	1st to 10th	Night	1 2 1 2 2 2 2 3 4 6% 74%	4710
	11th to 20th	Night	1 4 1 4 3 3 3 3 6% 9% 63%	5228
	21st to end	Night	2 3 1 4 3 3 3 4 5% 7% 65%	6611

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	31% 2 6% 23% 31% 6%	5321
	11th to 20th	Day	13% 2 6% 20% 32% 26%	5340
	21st to end	Day	28% 3 4 12% 27% 26%	5844
February	1st to 10th	Day	23% 3 10% 19% 28% 17%	1890
	11th to 20th	Day	26% 4 7% 23% 26% 14%	1892
	21st to end	Day	25% 4 5% 17% 26% 22%	1739
March	1st to 10th	Day	21% 3 6% 11% 36% 22%	4954
	11th to 20th	Day	33% 5% 5% 14% 30% 13%	5000
	21st to end	Day	24% 4 7% 25% 33% 7%	5486
April	1st to 10th	Day	21% 4 6% 18% 35% 17%	2360
	11th to 20th	Day	23% 3 5% 15% 33% 21%	2374
	21st to end	Day	19% 4 6% 18% 36% 16%	2400
May	1st to 10th	Day	24% 3 5% 18% 32% 17%	5545
	11th to 20th	Day	19% 4 8% 10% 34% 26%	5844
	21st to end	Day	17% 2 3 9% 26% 42%	6424
June	1st to 10th	Day	19% 5% 7% 13% 28% 28%	2600
	11th to 20th	Day	17% 3 4 8% 23% 45%	2600
	21st to end	Day	29% 5% 8% 12% 23% 24%	2600
July	1st to 10th	Day	27% 5% 6% 10% 16% 36%	5816
	11th to 20th	Day	42% 4 13% 20% 11% 8%	5811
	21st to end	Day	44% 5% 14% 17% 15% 4	6217
August	1st to 10th	Day	42% 5% 19% 15% 12% 7%	4208
	11th to 20th	Day	35% 5% 10% 23% 17% 9%	3983
	21st to end	Day	42% 6% 13% 19% 17% 4	4311
September	1st to 10th	Day	37% 7% 9% 14% 20% 14%	2400
	11th to 20th	Day	28% 5% 7% 15% 26% 19%	2335
	21st to end	Day	23% 4 7% 16% 28% 21%	2135
October	1st to 10th	Day	25% 3 4 13% 23% 32%	3270
	11th to 20th	Day	26% 1 3 14% 36% 20%	3250
	21st to end	Day	11% 2 4 16% 37% 30%	3548
November	1st to 10th	Day	14% 3 6% 22% 36% 19%	2059
	11th to 20th	Day	15% 4 6% 19% 38% 17%	2100
	21st to end	Day	24% 3 6% 16% 33% 18%	1803
December	1st to 10th	Day	13% 4 4 26% 37% 17%	2700
	11th to 20th	Day	23% 4 5% 19% 39% 10%	3222
	21st to end	Day	20% 4 7% 26% 29% 15%	4609
January	1st to 10th	Night	31% 3 7% 21% 31% 8%	7605
	11th to 20th	Night	11% 2 5% 20% 38% 24%	7650
	21st to end	Night	27% 3 5% 11% 26% 27%	8370
February	1st to 10th	Night	19% 4 9% 20% 29% 18%	2730
	11th to 20th	Night	24% 4 8% 23% 24% 17%	2513
	21st to end	Night	17% 5% 7% 17% 34% 20%	1889
March	1st to 10th	Night	19% 3 4 16% 38% 21%	4940
	11th to 20th	Night	32% 4 5% 18% 29% 13%	5000
	21st to end	Night	16% 4 6% 27% 40% 6%	5489
April	1st to 10th	Night	17% 3 5% 23% 34% 17%	2038
	11th to 20th	Night	17% 4 5% 17% 34% 23%	1977
	21st to end	Night	15% 5% 7% 18% 38% 17%	2000
May	1st to 10th	Night	23% 3 9% 17% 35% 15%	4415
	11th to 20th	Night	16% 4 7% 13% 38% 22%	4075
	21st to end	Night	17% 2 3 8% 27% 43%	4474
June	1st to 10th	Night	21% 5% 5% 14% 27% 28%	1800
	11th to 20th	Night	15% 3 4 11% 22% 46%	1800
	21st to end	Night	30% 5% 11% 13% 15% 26%	1800
July	1st to 10th	Night	28% 5% 11% 10% 14% 33%	4055
	11th to 20th	Night	38% 6% 17% 20% 10% 10%	4046
	21st to end	Night	43% 6% 20% 18% 10% 3	4344
August	1st to 10th	Night	42% 7% 21% 14% 10% 7%	2928
	11th to 20th	Night	40% 6% 15% 16% 13% 10%	3141
	21st to end	Night	39% 9% 18% 17% 11% 6%	3597
September	1st to 10th	Night	33% 7% 12% 17% 18% 14%	2000
	11th to 20th	Night	25% 6% 9% 16% 25% 20%	2060
	21st to end	Night	20% 4 8% 16% 29% 23%	2264
October	1st to 10th	Night	19% 3 4 13% 30% 31%	3920
	11th to 20th	Night	28% 2 3 16% 31% 21%	3898
	21st to end	Night	13% 2 3 15% 40% 27%	4252
November	1st to 10th	Night	13% 3 5% 24% 38% 18%	2460
	11th to 20th	Night	12% 5% 5% 21% 37% 20%	2520
	21st to end	Night	22% 4 6% 16% 34% 18%	2783
December	1st to 10th	Night	12% 3 5% 28% 30% 22%	4710
	11th to 20th	Night	18% 4 6% 17% 37% 17%	5228
	21st to end	Night	18% 4 8% 21% 32% 16%	6611

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	8% 30% 31% 22% 9% 1	330
	11th to 20th	Day	10% 24% 27% 23% 14% 2	330
	21st to end	Day	5% 20% 36% 25% 10% 4	363
February	1st to 10th	Day	6% 28% 30% 25% 10% 2	330
	11th to 20th	Day	9% 28% 38% 19% 6%	315
	21st to end	Day	13% 37% 24% 18% 6% 1	338
March	1st to 10th	Day	13% 29% 31% 21% 6% 2	500
	11th to 20th	Day	17% 26% 32% 15% 9% 1	500
	21st to end	Day	14% 33% 33% 14% 5% 1	550
April	1st to 10th	Day	11% 24% 36% 19% 7% 2	500
	11th to 20th	Day	14% 29% 33% 18% 5% 1	492
	21st to end	Day	11% 24% 36% 22% 5% 1	500
May	1st to 10th	Day	8% 21% 42% 21% 7% 1	503
	11th to 20th	Day	8% 18% 35% 25% 12% 3	528
	21st to end	Day	6% 20% 35% 25% 12% 2	573
June	1st to 10th	Day	5% 11% 32% 33% 17% 2	530
	11th to 20th	Day	5% 12% 30% 31% 17% 4	530
	21st to end	Day	8% 9% 26% 33% 18% 5%	530
July	1st to 10th	Day	5% 3 17% 40% 26% 8%	526
	11th to 20th	Day	7% 7% 32% 38% 16%	524
	21st to end	Day	8% 2 7% 29% 40% 15%	575
August	1st to 10th	Day	8% 3 12% 32% 34% 11%	527
	11th to 20th	Day	7% 4 12% 35% 29% 13%	517
	21st to end	Day	10% 3 13% 31% 30% 13%	583
September	1st to 10th	Day	10% 4 16% 35% 28% 8%	530
	11th to 20th	Day	8% 5% 25% 35% 21% 6%	530
	21st to end	Day	7% 9% 25% 32% 21% 6%	465
October	1st to 10th	Day	8% 12% 27% 24% 21% 8%	330
	11th to 20th	Day	12% 12% 28% 26% 15% 7%	330
	21st to end	Day	9% 12% 26% 28% 18% 6%	363
November	1st to 10th	Day	5% 18% 36% 22% 15% 3	330
	11th to 20th	Day	5% 13% 28% 32% 16% 6%	330
	21st to end	Day	6% 23% 31% 23% 14% 3	330
December	1st to 10th	Day	8% 19% 25% 30% 15% 2	330
	11th to 20th	Day	6% 27% 26% 25% 14% 2	330
	21st to end	Day	14% 24% 35% 17% 9% 2	363
January	1st to 10th	Night	5% 19% 27% 32% 15% 3	840
	11th to 20th	Night	7% 16% 31% 30% 14% 3	840
	21st to end	Night	4 17% 31% 29% 16% 2	924
February	1st to 10th	Night	4 21% 34% 27% 12% 2	840
	11th to 20th	Night	5% 20% 39% 26% 8% 1	804
	21st to end	Night	6% 24% 37% 27% 5%	660
March	1st to 10th	Night	3 24% 34% 26% 12% 1	800
	11th to 20th	Night	7% 18% 30% 28% 16% 1	800
	21st to end	Night	5% 21% 36% 28% 10%	880
April	1st to 10th	Night	5% 23% 35% 27% 9%	638
	11th to 20th	Night	6% 24% 36% 25% 8%	593
	21st to end	Night	3 24% 38% 26% 9% 1	600
May	1st to 10th	Night	6% 14% 40% 32% 8% 1	600
	11th to 20th	Night	3 14% 35% 33% 13% 2	591
	21st to end	Night	3 12% 39% 32% 14%	650
June	1st to 10th	Night	5% 7% 35% 37% 15% 2	600
	11th to 20th	Night	4 8% 34% 38% 14% 1	600
	21st to end	Night	7% 4 26% 36% 25% 3	600
July	1st to 10th	Night	6% 2 15% 43% 32% 3	585
	11th to 20th	Night	5% 8% 35% 42% 9%	582
	21st to end	Night	9% 2 7% 24% 46% 12%	657
August	1st to 10th	Night	5% 2 8% 29% 44% 12%	597
	11th to 20th	Night	8% 2 9% 32% 43% 7%	594
	21st to end	Night	6% 1 8% 33% 46% 6%	660
September	1st to 10th	Night	9% 2 10% 38% 37% 4	600
	11th to 20th	Night	5% 3 15% 42% 32% 3	660
	21st to end	Night	5% 4 21% 37% 29% 5%	800
October	1st to 10th	Night	6% 7% 25% 37% 22% 3	800
	11th to 20th	Night	5% 7% 25% 40% 20% 3	800
	21st to end	Night	5% 10% 25% 34% 22% 4	880
November	1st to 10th	Night	4 9% 29% 33% 21% 4	820
	11th to 20th	Night	2 12% 29% 32% 22% 4	840
	21st to end	Night	7% 18% 26% 26% 20% 3	993
December	1st to 10th	Night	6% 17% 26% 34% 15% 2	1050
	11th to 20th	Night	4 21% 31% 27% 16% 1	1008
	21st to end	Night	6% 21% 32% 29% 10% 2	924

Page generated at 2026-02-12 23:42:17. Version ac07

Copyright © 2026 Attilla Danko.