Dogstar Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dogstar Observatory clear sky chart from 2005-11-06 to 2026-08-30.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	143544
	Night	14% 9% 3 7% 4 4 4 4 5% 7% 39%	138684
Transparency	Day	43% 8% 11% 17% 14% 6%	147281
	Night	41% 8% 13% 17% 15% 6%	143019
Seeing	Day	21% 14% 23% 21% 14% 7%	17400
	Night	20% 10% 21% 28% 18% 4	27392

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	16% 9% 4 6% 3 3 3 3 4 5% 46%	5258
	11th to 20th	Day	9% 9% 4 6% 3 3 3 2 2 3 56%	5280
	21st to end	Day	18% 9% 4 6% 4 3 3 2 4 5% 40%	5780
February	1st to 10th	Day	15% 10% 4 7% 5% 5% 4 3 4 5% 39%	2032
	11th to 20th	Day	18% 12% 3 6% 5% 4 3 3 4 6% 37%	2048
	21st to end	Day	19% 10% 2 7% 5% 4 4 3 4 6% 37%	1730
March	1st to 10th	Day	20% 8% 3 6% 4 4 4 3 4 6% 38%	4858
	11th to 20th	Day	13% 8% 2 5% 3 3 3 3 4 6% 50%	5090
	21st to end	Day	17% 8% 3 6% 4 4 4 3 5% 5% 42%	5586
April	1st to 10th	Day	12% 9% 3 6% 5% 4 5% 5% 6% 7% 40%	2310
	11th to 20th	Day	13% 9% 3 7% 4 4 5% 4 5% 6% 41%	2527
	21st to end	Day	14% 8% 2 6% 5% 5% 4 3 5% 7% 41%	2730
May	1st to 10th	Day	16% 10% 3 7% 5% 5% 5% 3 6% 8% 33%	7616
	11th to 20th	Day	14% 9% 4 9% 5% 5% 6% 5% 6% 7% 31%	7626
	21st to end	Day	17% 10% 4 10% 6% 5% 6% 5% 6% 7% 25%	8391
June	1st to 10th	Day	12% 10% 3 9% 7% 7% 6% 5% 7% 7% 27%	2730
	11th to 20th	Day	8% 7% 3 10% 6% 7% 8% 6% 9% 9% 28%	2730
	21st to end	Day	9% 7% 3 7% 7% 6% 7% 6% 8% 9% 30%	2730
July	1st to 10th	Day	7% 5% 2 9% 7% 7% 7% 6% 9% 10% 31%	7680
	11th to 20th	Day	10% 7% 4 10% 8% 8% 8% 6% 8% 9% 21%	7680
	21st to end	Day	12% 8% 4 11% 8% 8% 8% 6% 7% 9% 20%	8340
August	1st to 10th	Day	9% 8% 4 9% 7% 7% 7% 6% 8% 9% 25%	4364
	11th to 20th	Day	10% 6% 3 8% 6% 7% 7% 5% 8% 11% 30%	4304
	21st to end	Day	8% 7% 3 9% 7% 6% 6% 5% 7% 7% 36%	4374
September	1st to 10th	Day	11% 9% 4 9% 6% 6% 7% 5% 6% 7% 31%	2200
	11th to 20th	Day	14% 9% 4 9% 6% 6% 5% 4 6% 9% 29%	2200
	21st to end	Day	14% 8% 3 7% 5% 6% 6% 4 5% 6% 35%	2200
October	1st to 10th	Day	11% 6% 2 6% 4 5% 4 3 5% 7% 46%	2200
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 4 6% 54%	2000
	21st to end	Day	13% 8% 1 4 3 3 3 2 4 6% 52%	2200
November	1st to 10th	Day	10% 6% 2 5% 3 4 3 4 5% 5% 54%	1922
	11th to 20th	Day	12% 7% 2 4 3 3 4 3 5% 7% 50%	1890
	21st to end	Day	13% 9% 2 6% 3 3 4 3 5% 6% 45%	1890
December	1st to 10th	Day	19% 7% 2 4 3 3 3 3 4 5% 46%	3020
	11th to 20th	Day	21% 10% 3 5% 4 4 3 3 5% 4 38%	3463
	21st to end	Day	17% 8% 4 6% 4 3 4 3 4 6% 41%	4565
January	1st to 10th	Night	15% 10% 3 5% 3 3 3 2 4 5% 48%	7635
	11th to 20th	Night	14% 9% 2 5% 3 3 3 2 3 4 51%	7680
	21st to end	Night	16% 13% 3 6% 3 3 3 3 3 4 42%	8401
February	1st to 10th	Night	13% 11% 3 6% 4 5% 4 3 5% 6% 40%	2583
	11th to 20th	Night	20% 11% 3 7% 4 3 4 3 4 5% 37%	2458
	21st to end	Night	19% 9% 4 8% 5% 4 4 4 5% 6% 33%	2076
March	1st to 10th	Night	19% 13% 4 6% 4 4 4 3 5% 5% 33%	5213
	11th to 20th	Night	13% 7% 2 5% 3 3 4 3 5% 7% 47%	5090
	21st to end	Night	15% 8% 3 6% 5% 4 4 3 5% 6% 41%	5588
April	1st to 10th	Night	14% 8% 3 6% 4 4 5% 4 5% 6% 41%	2310
	11th to 20th	Night	11% 9% 3 5% 4 3 4 3 6% 7% 46%	2057
	21st to end	Night	12% 7% 3 7% 5% 4 4 3 5% 7% 44%	1890
May	1st to 10th	Night	17% 10% 3 7% 5% 5% 6% 4 6% 7% 30%	5237
	11th to 20th	Night	16% 10% 3 8% 5% 5% 4 3 5% 7% 33%	5234
	21st to end	Night	19% 11% 4 8% 5% 5% 5% 4 6% 7% 26%	5761
June	1st to 10th	Night	10% 8% 3 7% 5% 5% 5% 5% 8% 11% 33%	1890
	11th to 20th	Night	7% 7% 2 7% 4 4 7% 5% 8% 11% 38%	1890
	21st to end	Night	9% 6% 2 5% 4 5% 6% 6% 8% 11% 37%	1890
July	1st to 10th	Night	8% 6% 2 7% 6% 6% 6% 5% 7% 12% 34%	5278
	11th to 20th	Night	13% 7% 3 7% 6% 6% 6% 5% 8% 11% 30%	5277
	21st to end	Night	15% 9% 4 8% 6% 6% 6% 4 7% 9% 25%	5736
August	1st to 10th	Night	9% 6% 3 8% 6% 6% 7% 5% 7% 12% 31%	3005
	11th to 20th	Night	15% 7% 2 8% 5% 5% 5% 4 6% 9% 33%	2965
	21st to end	Night	8% 6% 2 5% 4 5% 5% 4 7% 10% 45%	3682
September	1st to 10th	Night	10% 7% 4 8% 5% 6% 5% 5% 8% 8% 34%	2200
	11th to 20th	Night	12% 7% 3 9% 5% 5% 6% 5% 6% 9% 34%	2200
	21st to end	Night	13% 8% 2 6% 4 5% 4 4 5% 7% 42%	2200
October	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 5% 7% 48%	2200
	11th to 20th	Night	11% 7% 2 7% 4 4 4 3 4 6% 49%	2400
	21st to end	Night	12% 8% 2 5% 3 4 4 3 4 5% 51%	2640
November	1st to 10th	Night	11% 7% 2 5% 4 4 3 3 5% 6% 48%	2593
	11th to 20th	Night	12% 9% 2 6% 4 3 3 3 4 6% 48%	2730
	21st to end	Night	15% 9% 2 5% 3 3 4 4 4 6% 45%	2730
December	1st to 10th	Night	18% 10% 3 5% 3 3 3 3 3 5% 45%	4380
	11th to 20th	Night	20% 10% 4 8% 3 3 4 3 3 4 38%	4952
	21st to end	Night	15% 11% 5% 7% 4 4 4 3 4 7% 36%	6633

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	37% 5% 9% 17% 25% 7%	5259
	11th to 20th	Day	31% 5% 5% 10% 30% 19%	5280
	21st to end	Day	44% 4 8% 14% 18% 13%	5780
February	1st to 10th	Day	45% 5% 8% 19% 17% 6%	2032
	11th to 20th	Day	49% 5% 5% 16% 19% 6%	2058
	21st to end	Day	47% 5% 8% 12% 20% 8%	1730
March	1st to 10th	Day	46% 4 6% 13% 18% 12%	4858
	11th to 20th	Day	35% 4 6% 15% 21% 20%	5090
	21st to end	Day	44% 4 9% 25% 14% 5%	5586
April	1st to 10th	Day	41% 6% 11% 20% 18% 4	2310
	11th to 20th	Day	41% 6% 10% 18% 21% 5%	2527
	21st to end	Day	42% 6% 10% 25% 15% 2	2730
May	1st to 10th	Day	47% 9% 11% 21% 12% 1	7651
	11th to 20th	Day	48% 10% 13% 19% 8% 2	7630
	21st to end	Day	55% 9% 10% 14% 11% 1	8405
June	1st to 10th	Day	50% 10% 15% 17% 7% 1	2730
	11th to 20th	Day	45% 12% 17% 16% 10% 1	2730
	21st to end	Day	45% 12% 16% 16% 9% 2	2730
July	1st to 10th	Day	41% 16% 19% 17% 6%	7615
	11th to 20th	Day	51% 18% 19% 9% 2	7611
	21st to end	Day	55% 13% 13% 12% 6% 1	8156
August	1st to 10th	Day	48% 13% 16% 19% 3	4351
	11th to 20th	Day	42% 12% 21% 14% 8% 3	4343
	21st to end	Day	42% 12% 12% 22% 11% 1	4374
September	1st to 10th	Day	48% 9% 11% 16% 14% 3	2200
	11th to 20th	Day	51% 7% 11% 17% 13% 2	2200
	21st to end	Day	46% 8% 12% 15% 14% 5%	2200
October	1st to 10th	Day	28% 6% 7% 18% 29% 12%	3590
	11th to 20th	Day	22% 3 6% 18% 22% 29%	3240
	21st to end	Day	27% 4 7% 23% 22% 16%	3538
November	1st to 10th	Day	31% 4 9% 17% 27% 11%	1922
	11th to 20th	Day	33% 4 7% 21% 25% 10%	1890
	21st to end	Day	39% 4 7% 19% 25% 6%	1890
December	1st to 10th	Day	39% 5% 6% 16% 23% 11%	3020
	11th to 20th	Day	47% 4 7% 14% 19% 9%	3460
	21st to end	Day	41% 4 13% 24% 16% 3	4565
January	1st to 10th	Night	36% 5% 13% 16% 20% 9%	7636
	11th to 20th	Night	35% 6% 4 12% 27% 16%	7680
	21st to end	Night	42% 6% 7% 12% 21% 11%	8401
February	1st to 10th	Night	43% 4 10% 18% 19% 6%	2583
	11th to 20th	Night	48% 7% 6% 16% 18% 5%	2459
	21st to end	Night	49% 6% 8% 15% 17% 5%	2076
March	1st to 10th	Night	48% 6% 11% 12% 17% 7%	5213
	11th to 20th	Night	34% 6% 8% 19% 17% 16%	5090
	21st to end	Night	43% 6% 12% 21% 13% 5%	5588
April	1st to 10th	Night	40% 6% 12% 20% 19% 3	2310
	11th to 20th	Night	35% 6% 11% 23% 20% 4	2057
	21st to end	Night	37% 8% 13% 26% 14% 1	1890
May	1st to 10th	Night	47% 13% 11% 20% 8% 1	5264
	11th to 20th	Night	47% 9% 18% 17% 8% 1	5235
	21st to end	Night	51% 12% 13% 17% 7%	5771
June	1st to 10th	Night	41% 13% 18% 19% 8% 1	1890
	11th to 20th	Night	35% 12% 24% 22% 7% 1	1890
	21st to end	Night	35% 13% 19% 20% 10% 2	1890
July	1st to 10th	Night	37% 15% 24% 19% 4	5235
	11th to 20th	Night	44% 18% 25% 11% 2 1	5226
	21st to end	Night	50% 13% 20% 11% 5% 2	5606
August	1st to 10th	Night	40% 15% 25% 16% 4	2994
	11th to 20th	Night	43% 12% 22% 13% 9% 1	2992
	21st to end	Night	31% 11% 21% 27% 9% 1	3682
September	1st to 10th	Night	42% 12% 15% 17% 12% 2	2200
	11th to 20th	Night	45% 10% 14% 18% 14% 1	2200
	21st to end	Night	40% 9% 13% 19% 15% 4	2200
October	1st to 10th	Night	29% 8% 10% 18% 28% 9%	3590
	11th to 20th	Night	25% 4 8% 16% 20% 27%	3899
	21st to end	Night	29% 5% 7% 21% 21% 17%	4252
November	1st to 10th	Night	34% 5% 10% 20% 23% 9%	2593
	11th to 20th	Night	36% 5% 7% 16% 25% 11%	2730
	21st to end	Night	39% 4 7% 21% 22% 7%	2730
December	1st to 10th	Night	41% 4 7% 15% 22% 11%	4380
	11th to 20th	Night	46% 5% 9% 14% 20% 7%	4954
	21st to end	Night	45% 4 13% 18% 17% 3	6633

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	37% 22% 29% 11% 1	330
	11th to 20th	Day	41% 23% 20% 14% 2	330
	21st to end	Day	35% 29% 26% 8% 2	363
February	1st to 10th	Day	32% 25% 32% 8% 2	330
	11th to 20th	Day	48% 24% 22% 6%	330
	21st to end	Day	44% 27% 22% 6% 1	273
March	1st to 10th	Day	35% 17% 29% 12% 6%	452
	11th to 20th	Day	31% 23% 28% 13% 3 1	540
	21st to end	Day	28% 24% 28% 14% 5% 1	594
April	1st to 10th	Day	26% 20% 25% 20% 8% 1	540
	11th to 20th	Day	22% 23% 22% 21% 10% 2	532
	21st to end	Day	23% 14% 29% 20% 11% 4	540
May	1st to 10th	Day	23% 22% 26% 15% 9% 4	543
	11th to 20th	Day	23% 14% 24% 21% 12% 6%	567
	21st to end	Day	18% 13% 21% 24% 14% 10%	617
June	1st to 10th	Day	16% 9% 22% 26% 16% 10%	570
	11th to 20th	Day	10% 9% 23% 24% 23% 12%	570
	21st to end	Day	13% 8% 26% 23% 19% 12%	570
July	1st to 10th	Day	10% 5% 15% 31% 23% 16%	565
	11th to 20th	Day	12% 4 15% 28% 23% 18%	564
	21st to end	Day	11% 6% 15% 25% 25% 17%	620
August	1st to 10th	Day	17% 7% 18% 23% 20% 15%	566
	11th to 20th	Day	12% 6% 18% 25% 28% 12%	559
	21st to end	Day	13% 5% 15% 25% 24% 17%	619
September	1st to 10th	Day	11% 6% 16% 28% 26% 12%	530
	11th to 20th	Day	14% 6% 18% 27% 24% 10%	530
	21st to end	Day	17% 9% 19% 29% 21% 5%	530
October	1st to 10th	Day	16% 9% 21% 28% 18% 8%	530
	11th to 20th	Day	14% 14% 28% 26% 15% 3	530
	21st to end	Day	21% 14% 23% 27% 12% 3	583
November	1st to 10th	Day	19% 16% 28% 24% 11% 2	400
	11th to 20th	Day	23% 22% 30% 20% 5%	330
	21st to end	Day	24% 20% 33% 17% 5% 1	330
December	1st to 10th	Day	35% 22% 28% 12% 3	330
	11th to 20th	Day	31% 17% 30% 17% 3 1	330
	21st to end	Day	31% 20% 33% 13% 4	363
January	1st to 10th	Night	29% 14% 30% 23% 5%	840
	11th to 20th	Night	27% 17% 31% 20% 5%	840
	21st to end	Night	23% 16% 36% 22% 3	924
February	1st to 10th	Night	22% 13% 31% 29% 4	840
	11th to 20th	Night	31% 16% 32% 19% 1	823
	21st to end	Night	31% 19% 28% 19% 3	692
March	1st to 10th	Night	25% 15% 30% 26% 5%	840
	11th to 20th	Night	27% 15% 26% 24% 7% 1	840
	21st to end	Night	23% 14% 30% 23% 8%	924
April	1st to 10th	Night	24% 17% 25% 24% 9% 1	840
	11th to 20th	Night	19% 12% 26% 29% 12% 2	673
	21st to end	Night	16% 10% 22% 35% 16% 1	630
May	1st to 10th	Night	17% 10% 25% 30% 16% 2	630
	11th to 20th	Night	15% 10% 19% 32% 20% 4	621
	21st to end	Night	17% 5% 13% 29% 29% 6%	683
June	1st to 10th	Night	13% 4 14% 34% 29% 6%	630
	11th to 20th	Night	11% 2 15% 30% 32% 11%	630
	21st to end	Night	11% 3 9% 32% 39% 7%	630
July	1st to 10th	Night	12% 2 9% 24% 44% 8%	615
	11th to 20th	Night	11% 2 7% 25% 43% 13%	612
	21st to end	Night	10% 4 7% 24% 44% 11%	690
August	1st to 10th	Night	14% 3 8% 28% 37% 10%	627
	11th to 20th	Night	13% 4 8% 29% 38% 9%	624
	21st to end	Night	12% 3 9% 27% 37% 12%	710
September	1st to 10th	Night	13% 4 10% 30% 35% 8%	800
	11th to 20th	Night	15% 4 13% 29% 30% 9%	800
	21st to end	Night	16% 6% 14% 35% 26% 4	800
October	1st to 10th	Night	16% 7% 19% 27% 25% 7%	800
	11th to 20th	Night	16% 9% 25% 31% 17% 3	800
	21st to end	Night	18% 11% 18% 36% 15% 3	880
November	1st to 10th	Night	16% 7% 22% 34% 17% 4	820
	11th to 20th	Night	20% 11% 24% 32% 10% 3	840
	21st to end	Night	22% 13% 20% 30% 13% 1	840
December	1st to 10th	Night	28% 11% 26% 27% 7%	840
	11th to 20th	Night	24% 12% 26% 29% 7% 1	840
	21st to end	Night	28% 13% 25% 30% 4	924

Page generated at 2026-08-27 04:07:14. Version ac07

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