Twin Dogs Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Twin Dogs Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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	18% 10% 3 9% 6% 5% 5% 4 5% 6% 29%	101740
	Night	17% 10% 4 8% 5% 5% 5% 4 5% 6% 31%	97881
Transparency	Day	53% 7% 13% 18% 9% 1	105214
	Night	52% 7% 14% 18% 8% 1	102497
Seeing	Day	25% 19% 31% 17% 7% 1	15953
	Night	23% 16% 31% 22% 7%	24034

By Month

Percentage Cloud Cover NE (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	14% 14% 5% 11% 8% 6% 4 3 4 7% 23%	2252
	11th to 20th	Day	13% 12% 5% 16% 8% 6% 4 4 4 5% 24%	2520
	21st to end	Day	9% 10% 5% 13% 6% 6% 5% 5% 6% 6% 29%	2772
February	1st to 10th	Day	10% 14% 5% 11% 9% 6% 5% 4 5% 6% 24%	1653
	11th to 20th	Day	13% 16% 5% 11% 8% 5% 5% 4 6% 6% 22%	1703
	21st to end	Day	12% 12% 4 10% 8% 7% 4 4 5% 6% 28%	1570
March	1st to 10th	Day	20% 16% 4 9% 5% 4 3 4 5% 5% 25%	3134
	11th to 20th	Day	18% 22% 6% 11% 6% 4 4 3 3 4 18%	3480
	21st to end	Day	21% 15% 5% 10% 5% 3 4 2 4 5% 27%	3816
April	1st to 10th	Day	22% 15% 3 9% 6% 4 4 3 4 5% 25%	2288
	11th to 20th	Day	19% 12% 2 8% 6% 4 4 3 4 6% 32%	2442
	21st to end	Day	25% 12% 3 7% 4 3 3 3 4 5% 32%	2470
May	1st to 10th	Day	17% 10% 4 9% 7% 5% 5% 4 5% 6% 28%	4106
	11th to 20th	Day	21% 10% 3 7% 5% 4 5% 4 5% 7% 30%	4331
	21st to end	Day	17% 8% 3 8% 6% 6% 6% 5% 7% 7% 28%	5185
June	1st to 10th	Day	22% 8% 3 8% 5% 4 5% 3 6% 7% 27%	2850
	11th to 20th	Day	20% 6% 3 8% 6% 5% 5% 4 6% 7% 31%	2850
	21st to end	Day	24% 10% 3 8% 7% 5% 4 4 5% 6% 24%	2850
July	1st to 10th	Day	15% 7% 3 8% 6% 6% 6% 5% 7% 8% 30%	4760
	11th to 20th	Day	16% 6% 2 7% 5% 6% 5% 5% 7% 9% 34%	4615
	21st to end	Day	13% 6% 3 7% 4 5% 5% 4 8% 8% 38%	4814
August	1st to 10th	Day	16% 6% 3 8% 6% 7% 6% 5% 7% 8% 30%	4180
	11th to 20th	Day	16% 8% 3 9% 6% 6% 6% 4 6% 8% 26%	4045
	21st to end	Day	17% 6% 2 7% 5% 4 5% 4 6% 8% 37%	4532
September	1st to 10th	Day	14% 7% 3 7% 4 4 5% 3 5% 7% 41%	2247
	11th to 20th	Day	16% 6% 2 6% 4 4 3 2 4 6% 46%	2090
	21st to end	Day	17% 7% 3 7% 4 4 4 3 4 7% 40%	2090
October	1st to 10th	Day	18% 9% 3 7% 4 4 5% 3 4 7% 36%	2009
	11th to 20th	Day	21% 9% 4 8% 5% 5% 4 4 5% 5% 30%	1848
	21st to end	Day	25% 11% 3 8% 5% 4 4 3 4 6% 28%	1881
November	1st to 10th	Day	17% 12% 4 8% 6% 5% 4 4 5% 5% 30%	1761
	11th to 20th	Day	19% 11% 3 9% 6% 5% 6% 4 5% 6% 25%	1616
	21st to end	Day	20% 15% 4 9% 5% 5% 4 3 3 5% 26%	1551
December	1st to 10th	Day	21% 15% 4 10% 7% 5% 4 3 5% 5% 22%	1330
	11th to 20th	Day	18% 15% 5% 9% 5% 4 5% 4 5% 5% 26%	1668
	21st to end	Day	21% 12% 5% 12% 6% 5% 4 3 4 4 24%	2431
January	1st to 10th	Night	11% 12% 6% 13% 8% 7% 6% 5% 6% 7% 19%	4686
	11th to 20th	Night	12% 13% 5% 12% 9% 6% 5% 4 6% 6% 23%	4440
	21st to end	Night	8% 13% 6% 10% 6% 5% 4 5% 7% 7% 29%	4884
February	1st to 10th	Night	10% 14% 5% 11% 6% 6% 5% 4 6% 6% 28%	2527
	11th to 20th	Night	11% 16% 5% 11% 7% 6% 5% 4 5% 6% 24%	2361
	21st to end	Night	13% 14% 3 7% 7% 6% 4 4 4 6% 33%	1884
March	1st to 10th	Night	17% 14% 5% 10% 5% 5% 7% 3 4 4 28%	3705
	11th to 20th	Night	15% 15% 6% 10% 7% 6% 5% 3 4 5% 23%	3479
	21st to end	Night	23% 14% 4 8% 5% 3 3 3 4 5% 29%	3816
April	1st to 10th	Night	21% 13% 4 7% 5% 4 4 3 4 4 32%	1889
	11th to 20th	Night	20% 11% 3 7% 4 4 3 3 5% 7% 33%	1688
	21st to end	Night	26% 10% 3 7% 4 4 3 3 4 5% 32%	1710
May	1st to 10th	Night	20% 10% 3 6% 4 4 4 4 6% 6% 33%	2834
	11th to 20th	Night	22% 9% 4 9% 5% 4 5% 3 5% 5% 28%	2580
	21st to end	Night	15% 5% 2 5% 4 4 4 4 7% 9% 39%	2401
June	1st to 10th	Night	23% 9% 3 5% 4 5% 5% 4 6% 6% 29%	1330
	11th to 20th	Night	16% 5% 2 5% 4 4 5% 4 7% 8% 41%	1330
	21st to end	Night	22% 10% 2 8% 5% 4 4 4 5% 6% 30%	1330
July	1st to 10th	Night	12% 7% 2 6% 5% 5% 5% 4 7% 8% 40%	2210
	11th to 20th	Night	18% 6% 2 5% 4 4 5% 4 6% 7% 38%	2334
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 6% 7% 43%	2739
August	1st to 10th	Night	18% 6% 2 8% 5% 5% 5% 4 6% 6% 34%	2717
	11th to 20th	Night	14% 7% 3 8% 5% 5% 5% 5% 7% 8% 33%	2782
	21st to end	Night	17% 5% 2 5% 4 4 4 3 4 5% 45%	3124
September	1st to 10th	Night	14% 6% 2 5% 4 4 4 4 5% 8% 44%	1928
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 6% 6% 47%	2090
	21st to end	Night	16% 6% 2 5% 4 3 3 3 5% 6% 46%	2090
October	1st to 10th	Night	19% 7% 2 6% 4 3 3 3 4 7% 41%	2170
	11th to 20th	Night	20% 7% 2 7% 4 5% 4 3 5% 6% 36%	2328
	21st to end	Night	21% 10% 3 7% 4 5% 3 3 4 7% 33%	2717
November	1st to 10th	Night	18% 10% 3 7% 5% 4 4 4 6% 7% 31%	2537
	11th to 20th	Night	18% 11% 3 9% 5% 4 4 4 5% 7% 30%	2782
	21st to end	Night	20% 11% 4 10% 6% 5% 4 4 5% 6% 25%	2842
December	1st to 10th	Night	21% 13% 5% 9% 6% 5% 4 3 5% 5% 24%	2850
	11th to 20th	Night	22% 11% 4 8% 6% 5% 5% 4 6% 6% 24%	3531
	21st to end	Night	20% 15% 4 10% 6% 4 4 3 5% 5% 24%	5236

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	59% 8% 14% 14% 5%	2253
	11th to 20th	Day	59% 10% 8% 16% 6% 1	2520
	21st to end	Day	50% 10% 12% 15% 13%	2772
February	1st to 10th	Day	59% 6% 10% 13% 10% 2	1653
	11th to 20th	Day	61% 7% 11% 13% 7% 1	1711
	21st to end	Day	54% 7% 9% 19% 8% 2	1570
March	1st to 10th	Day	59% 7% 10% 12% 10% 3	3137
	11th to 20th	Day	68% 8% 9% 9% 5% 1	3480
	21st to end	Day	59% 5% 7% 16% 10% 3	3816
April	1st to 10th	Day	62% 6% 8% 14% 7% 3	2288
	11th to 20th	Day	53% 6% 10% 18% 12% 2	2442
	21st to end	Day	55% 5% 8% 17% 12% 3	2470
May	1st to 10th	Day	52% 9% 10% 17% 9% 1	4120
	11th to 20th	Day	50% 10% 14% 15% 9% 1	4335
	21st to end	Day	48% 11% 12% 17% 12% 1	5185
June	1st to 10th	Day	54% 9% 12% 14% 10% 1	2850
	11th to 20th	Day	50% 7% 13% 17% 10% 2	2850
	21st to end	Day	59% 8% 10% 15% 7% 1	2850
July	1st to 10th	Day	51% 6% 16% 19% 9%	4685
	11th to 20th	Day	47% 6% 17% 26% 5%	4534
	21st to end	Day	43% 7% 17% 24% 8%	4661
August	1st to 10th	Day	50% 7% 17% 19% 7%	4166
	11th to 20th	Day	54% 6% 16% 18% 4	4084
	21st to end	Day	45% 6% 16% 22% 11%	4532
September	1st to 10th	Day	42% 7% 14% 24% 13%	2247
	11th to 20th	Day	40% 6% 12% 27% 15%	2090
	21st to end	Day	43% 7% 13% 25% 12%	2090
October	1st to 10th	Day	54% 3 13% 24% 6%	3334
	11th to 20th	Day	54% 4 11% 24% 6%	3051
	21st to end	Day	50% 4 16% 17% 13%	3081
November	1st to 10th	Day	56% 6% 13% 18% 7%	1761
	11th to 20th	Day	58% 8% 12% 14% 8%	1616
	21st to end	Day	61% 7% 15% 15% 3	1551
December	1st to 10th	Day	65% 6% 11% 12% 5%	1330
	11th to 20th	Day	60% 7% 9% 13% 12%	1668
	21st to end	Day	60% 9% 12% 13% 5% 1	2431
January	1st to 10th	Night	59% 13% 13% 11% 4	4686
	11th to 20th	Night	57% 10% 14% 14% 5%	4440
	21st to end	Night	50% 8% 12% 18% 11% 1	4884
February	1st to 10th	Night	55% 7% 12% 15% 10% 1	2527
	11th to 20th	Night	61% 7% 10% 15% 7% 1	2364
	21st to end	Night	53% 5% 11% 18% 11% 2	1884
March	1st to 10th	Night	59% 6% 9% 17% 7% 1	3715
	11th to 20th	Night	61% 8% 11% 12% 7% 1	3480
	21st to end	Night	58% 4 7% 18% 10% 2	3816
April	1st to 10th	Night	56% 6% 8% 15% 13% 3	1889
	11th to 20th	Night	51% 5% 10% 18% 14% 1	1688
	21st to end	Night	55% 5% 8% 17% 13% 2	1710
May	1st to 10th	Night	47% 10% 14% 18% 10% 1	2840
	11th to 20th	Night	51% 11% 14% 16% 6% 1	2581
	21st to end	Night	37% 12% 17% 21% 13%	2402
June	1st to 10th	Night	52% 7% 13% 18% 8% 1	1330
	11th to 20th	Night	40% 9% 16% 22% 12% 2	1330
	21st to end	Night	55% 7% 13% 16% 8% 1	1330
July	1st to 10th	Night	43% 4 23% 24% 6%	2175
	11th to 20th	Night	45% 6% 20% 23% 6%	2292
	21st to end	Night	40% 7% 23% 22% 8%	2651
August	1st to 10th	Night	50% 6% 15% 24% 5%	2707
	11th to 20th	Night	47% 8% 21% 16% 7%	2809
	21st to end	Night	41% 6% 15% 23% 13% 1	3124
September	1st to 10th	Night	38% 7% 17% 25% 12% 1	1928
	11th to 20th	Night	37% 8% 16% 26% 13%	2090
	21st to end	Night	39% 7% 14% 26% 13% 1	2090
October	1st to 10th	Night	49% 3 12% 28% 7% 1	3625
	11th to 20th	Night	48% 4 12% 28% 7%	3864
	21st to end	Night	44% 4 20% 19% 13%	4467
November	1st to 10th	Night	51% 8% 14% 20% 6%	2537
	11th to 20th	Night	53% 8% 14% 15% 10% 1	2782
	21st to end	Night	60% 8% 15% 12% 6%	2842
December	1st to 10th	Night	63% 7% 12% 15% 4	2850
	11th to 20th	Night	58% 8% 12% 14% 7%	3532
	21st to end	Night	59% 8% 12% 13% 6% 1	5236

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	27% 27% 33% 9% 3	180
	11th to 20th	Day	35% 20% 31% 10% 4	180
	21st to end	Day	21% 23% 36% 12% 8% 1	198
February	1st to 10th	Day	24% 24% 32% 14% 5% 1	313
	11th to 20th	Day	25% 25% 34% 13% 3	386
	21st to end	Day	23% 25% 33% 15% 4 1	382
March	1st to 10th	Day	27% 21% 34% 15% 3	460
	11th to 20th	Day	28% 23% 28% 12% 8% 1	460
	21st to end	Day	29% 23% 25% 17% 4 1	506
April	1st to 10th	Day	32% 26% 25% 12% 3 2	460
	11th to 20th	Day	31% 21% 27% 15% 5%	452
	21st to end	Day	32% 22% 31% 10% 3 1	460
May	1st to 10th	Day	34% 16% 32% 14% 4	463
	11th to 20th	Day	29% 18% 29% 17% 6%	543
	21st to end	Day	26% 22% 29% 17% 6%	735
June	1st to 10th	Day	26% 18% 31% 17% 6% 1	680
	11th to 20th	Day	23% 19% 26% 23% 8% 1	680
	21st to end	Day	25% 15% 33% 20% 7%	680
July	1st to 10th	Day	18% 16% 34% 22% 10%	670
	11th to 20th	Day	18% 12% 34% 26% 9% 1	588
	21st to end	Day	15% 11% 40% 23% 9% 1	532
August	1st to 10th	Day	17% 12% 34% 25% 9% 2	486
	11th to 20th	Day	18% 11% 31% 27% 11% 2	479
	21st to end	Day	22% 14% 26% 22% 12% 3	539
September	1st to 10th	Day	17% 16% 34% 20% 10% 3	490
	11th to 20th	Day	21% 12% 29% 24% 11% 4	490
	21st to end	Day	20% 18% 30% 16% 11% 5%	490
October	1st to 10th	Day	19% 18% 29% 18% 11% 4	447
	11th to 20th	Day	31% 18% 27% 14% 9% 2	390
	21st to end	Day	31% 21% 29% 14% 4	429
November	1st to 10th	Day	31% 21% 27% 16% 5% 1	395
	11th to 20th	Day	29% 20% 30% 14% 6% 1	400
	21st to end	Day	38% 17% 31% 11% 3 1	352
December	1st to 10th	Day	28% 24% 26% 14% 7% 1	180
	11th to 20th	Day	33% 23% 32% 9% 3 1	180
	21st to end	Day	33% 25% 25% 13% 3 1	198
January	1st to 10th	Night	21% 23% 37% 16% 2	832
	11th to 20th	Night	25% 23% 31% 18% 4	760
	21st to end	Night	15% 20% 38% 22% 4	836
February	1st to 10th	Night	19% 25% 34% 17% 4	760
	11th to 20th	Night	24% 26% 30% 16% 4	743
	21st to end	Night	22% 18% 39% 17% 4	628
March	1st to 10th	Night	21% 19% 39% 19% 3	760
	11th to 20th	Night	25% 18% 32% 18% 7% 1	760
	21st to end	Night	23% 17% 34% 20% 5%	836
April	1st to 10th	Night	30% 18% 30% 19% 4 1	745
	11th to 20th	Night	25% 18% 31% 19% 6%	564
	21st to end	Night	33% 16% 25% 20% 6%	570
May	1st to 10th	Night	25% 14% 33% 23% 4	570
	11th to 20th	Night	26% 13% 30% 22% 8% 1	488
	21st to end	Night	22% 14% 35% 24% 6%	411
June	1st to 10th	Night	27% 8% 29% 29% 7% 1	380
	11th to 20th	Night	18% 9% 26% 37% 10%	380
	21st to end	Night	26% 7% 30% 28% 8%	380
July	1st to 10th	Night	16% 9% 36% 28% 11%	370
	11th to 20th	Night	15% 6% 32% 36% 11%	368
	21st to end	Night	17% 6% 28% 36% 12% 1	416
August	1st to 10th	Night	18% 5% 29% 37% 11%	498
	11th to 20th	Night	14% 6% 31% 35% 14%	562
	21st to end	Night	13% 9% 30% 33% 13% 1	627
September	1st to 10th	Night	17% 10% 31% 31% 11%	708
	11th to 20th	Night	19% 10% 26% 29% 13% 2	760
	21st to end	Night	20% 12% 28% 26% 13%	760
October	1st to 10th	Night	22% 13% 30% 26% 9% 1	760
	11th to 20th	Night	24% 14% 33% 19% 9%	760
	21st to end	Night	28% 20% 29% 18% 5%	836
November	1st to 10th	Night	25% 18% 33% 19% 5%	780
	11th to 20th	Night	28% 18% 29% 19% 5% 1	892
	21st to end	Night	28% 20% 29% 19% 4	899
December	1st to 10th	Night	29% 17% 34% 15% 3 1	850
	11th to 20th	Night	28% 20% 31% 17% 3	850
	21st to end	Night	30% 22% 28% 15% 4 1	935

Page generated at 2024-11-27 17:30:48. Version ac07

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