AllSky Camera - Tatla Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AllSky Camera - Tatla Lake clear sky chart from 2005-11-06 to 2024-11-01.

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	5% 8% 3 8% 6% 6% 6% 5% 7% 9% 37%	101845
	Night	4 8% 4 9% 6% 6% 6% 5% 8% 9% 36%	97185
Transparency	Day	40% 11% 16% 21% 11% 2	101585
	Night	40% 12% 17% 20% 9% 1	97091
Seeing	Day	12% 18% 31% 23% 12% 3	15712
	Night	8% 11% 37% 31% 13% 1	23504

By Month

Percentage Cloud Cover NW (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	3 13% 5% 10% 10% 8% 9% 7% 9% 8% 20%	2219
	11th to 20th	Day	2 9% 5% 9% 7% 6% 7% 6% 9% 11% 29%	2199
	21st to end	Day	2 9% 3 11% 8% 7% 9% 6% 9% 11% 24%	2442
February	1st to 10th	Day	3 9% 3 11% 7% 7% 7% 6% 9% 11% 27%	1671
	11th to 20th	Day	1 10% 5% 9% 6% 6% 5% 6% 8% 9% 35%	1665
	21st to end	Day	1 7% 5% 11% 7% 7% 8% 6% 9% 9% 30%	1413
March	1st to 10th	Day	1 5% 3 11% 8% 6% 6% 6% 9% 13% 32%	3211
	11th to 20th	Day	2 7% 3 8% 6% 6% 7% 7% 9% 11% 34%	3490
	21st to end	Day	1 10% 4 11% 7% 6% 7% 5% 7% 9% 33%	3854
April	1st to 10th	Day	3 11% 5% 11% 8% 7% 7% 5% 7% 9% 27%	2314
	11th to 20th	Day	3 10% 3 12% 7% 7% 7% 6% 7% 8% 30%	2438
	21st to end	Day	3 13% 5% 10% 6% 6% 7% 5% 8% 8% 29%	2532
May	1st to 10th	Day	4 10% 3 9% 7% 6% 6% 5% 7% 8% 35%	4420
	11th to 20th	Day	5% 10% 4 11% 7% 7% 7% 5% 8% 8% 28%	4557
	21st to end	Day	11% 11% 4 11% 7% 7% 7% 5% 6% 7% 23%	5161
June	1st to 10th	Day	11% 9% 3 9% 6% 6% 6% 5% 7% 7% 31%	2850
	11th to 20th	Day	10% 11% 3 9% 7% 6% 7% 5% 7% 8% 27%	2850
	21st to end	Day	9% 7% 3 9% 7% 7% 6% 5% 8% 8% 33%	2850
July	1st to 10th	Day	5% 4 2 4 3 3 4 3 4 6% 62%	4740
	11th to 20th	Day	4 4 2 4 4 3 3 3 5% 7% 62%	4740
	21st to end	Day	4 5% 3 7% 5% 5% 5% 5% 7% 8% 47%	5138
August	1st to 10th	Day	4 3 1 4 3 3 4 3 5% 8% 61%	4486
	11th to 20th	Day	5% 6% 2 6% 5% 6% 6% 5% 6% 9% 44%	4026
	21st to end	Day	6% 7% 2 7% 5% 4 5% 5% 7% 9% 42%	4521
September	1st to 10th	Day	6% 5% 2 7% 5% 5% 5% 4 6% 8% 47%	2317
	11th to 20th	Day	8% 8% 3 6% 6% 6% 5% 4 5% 7% 41%	2207
	21st to end	Day	7% 7% 3 7% 5% 4 5% 4 7% 10% 41%	2049
October	1st to 10th	Day	7% 10% 3 9% 6% 6% 6% 5% 7% 7% 35%	1900
	11th to 20th	Day	6% 7% 3 7% 6% 6% 6% 4 9% 11% 35%	1900
	21st to end	Day	4 8% 3 9% 6% 5% 6% 4 6% 10% 39%	1800
November	1st to 10th	Day	4 9% 5% 8% 5% 7% 7% 6% 9% 10% 32%	1488
	11th to 20th	Day	2 6% 3 9% 7% 6% 8% 7% 10% 10% 33%	1520
	21st to end	Day	2 9% 4 9% 5% 5% 7% 5% 8% 10% 35%	1420
December	1st to 10th	Day	1 6% 3 8% 7% 6% 7% 7% 10% 11% 33%	1330
	11th to 20th	Day	4 11% 5% 12% 6% 6% 8% 6% 10% 9% 24%	1685
	21st to end	Day	1 6% 3 9% 5% 6% 7% 6% 11% 12% 33%	2442
January	1st to 10th	Night	2 13% 7% 14% 9% 8% 8% 6% 8% 8% 17%	4726
	11th to 20th	Night	4 9% 3 8% 8% 8% 9% 6% 12% 9% 24%	4699
	21st to end	Night	2 9% 5% 11% 7% 7% 8% 6% 9% 11% 26%	5214
February	1st to 10th	Night	3 10% 4 10% 7% 7% 7% 6% 7% 9% 31%	2505
	11th to 20th	Night	2 9% 4 11% 7% 6% 5% 4 7% 8% 37%	2402
	21st to end	Night	2 10% 4 11% 8% 8% 6% 6% 7% 8% 31%	2041
March	1st to 10th	Night	1 5% 4 14% 6% 4 5% 5% 10% 13% 32%	3658
	11th to 20th	Night	1 6% 3 7% 6% 5% 6% 5% 9% 10% 42%	3489
	21st to end	Night	3 12% 4 9% 5% 5% 5% 5% 7% 9% 36%	3798
April	1st to 10th	Night	2 10% 4 10% 7% 5% 6% 6% 8% 10% 32%	1862
	11th to 20th	Night	3 10% 3 9% 5% 5% 6% 5% 7% 9% 36%	1691
	21st to end	Night	3 9% 4 10% 7% 6% 5% 4 7% 8% 36%	1648
May	1st to 10th	Night	3 8% 3 9% 6% 4 5% 4 6% 8% 42%	2540
	11th to 20th	Night	6% 8% 2 7% 5% 6% 7% 6% 9% 10% 34%	2337
	21st to end	Night	13% 10% 3 11% 7% 6% 6% 6% 6% 6% 26%	2414
June	1st to 10th	Night	10% 7% 3 8% 7% 5% 6% 5% 8% 8% 33%	1330
	11th to 20th	Night	10% 8% 3 7% 5% 5% 5% 5% 8% 10% 34%	1330
	21st to end	Night	11% 5% 3 8% 5% 5% 5% 5% 6% 6% 41%	1330
July	1st to 10th	Night	5% 4 1 3 3 4 4 3 6% 6% 61%	2220
	11th to 20th	Night	5% 2 1 4 3 3 4 3 4 7% 65%	2220
	21st to end	Night	5% 6% 2 5% 3 3 6% 4 6% 9% 52%	2414
August	1st to 10th	Night	5% 5% 3 5% 4 4 4 4 4 6% 56%	2440
	11th to 20th	Night	8% 5% 2 7% 5% 5% 5% 4 6% 9% 44%	2812
	21st to end	Night	8% 7% 3 6% 5% 4 4 4 6% 8% 45%	3146
September	1st to 10th	Night	7% 6% 3 6% 4 3 4 3 7% 8% 49%	1863
	11th to 20th	Night	9% 7% 3 6% 5% 5% 5% 3 6% 6% 46%	1971
	21st to end	Night	7% 7% 3 9% 5% 4 5% 4 7% 8% 40%	2131
October	1st to 10th	Night	9% 10% 4 7% 5% 5% 5% 4 5% 8% 39%	2280
	11th to 20th	Night	5% 9% 2 8% 5% 5% 6% 5% 7% 10% 38%	2280
	21st to end	Night	4 10% 4 7% 5% 6% 5% 4 7% 9% 38%	2795
November	1st to 10th	Night	3 10% 4 10% 7% 6% 6% 7% 7% 10% 30%	2596
	11th to 20th	Night	2 8% 3 9% 6% 6% 6% 6% 10% 9% 34%	2660
	21st to end	Night	2 9% 3 9% 7% 7% 6% 6% 9% 10% 32%	2759
December	1st to 10th	Night	2 8% 4 8% 7% 7% 8% 7% 9% 10% 29%	2850
	11th to 20th	Night	3 13% 6% 14% 7% 7% 7% 5% 8% 8% 23%	3520
	21st to end	Night	1 7% 4 10% 7% 7% 7% 7% 10% 10% 29%	5214

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	49% 16% 15% 14% 5% 1	2219
	11th to 20th	Day	45% 9% 18% 16% 5% 8%	2220
	21st to end	Day	41% 20% 17% 16% 6% 1	2442
February	1st to 10th	Day	48% 13% 15% 14% 8% 1	1671
	11th to 20th	Day	43% 11% 15% 19% 11% 1	1674
	21st to end	Day	44% 11% 15% 21% 8% 1	1413
March	1st to 10th	Day	37% 11% 17% 20% 15% 1	3211
	11th to 20th	Day	37% 12% 18% 23% 8% 1	3490
	21st to end	Day	44% 12% 18% 16% 10% 1	3854
April	1st to 10th	Day	49% 12% 16% 13% 9% 1	2314
	11th to 20th	Day	48% 12% 11% 17% 12%	2438
	21st to end	Day	49% 12% 14% 16% 8% 1	2532
May	1st to 10th	Day	41% 11% 16% 23% 9%	4420
	11th to 20th	Day	48% 14% 14% 18% 6% 1	4560
	21st to end	Day	53% 13% 13% 16% 5%	5162
June	1st to 10th	Day	48% 10% 14% 16% 10% 3	2850
	11th to 20th	Day	51% 10% 15% 17% 7%	2850
	21st to end	Day	45% 12% 14% 19% 8% 2	2850
July	1st to 10th	Day	24% 6% 9% 22% 27% 12%	4666
	11th to 20th	Day	23% 6% 14% 31% 24% 2	4659
	21st to end	Day	32% 8% 19% 23% 15% 3	4976
August	1st to 10th	Day	21% 7% 14% 40% 17% 1	4468
	11th to 20th	Day	32% 11% 19% 27% 9% 1	4065
	21st to end	Day	37% 9% 25% 21% 7% 1	4520
September	1st to 10th	Day	33% 9% 20% 26% 10% 2	2317
	11th to 20th	Day	40% 8% 16% 24% 9% 2	2207
	21st to end	Day	37% 11% 17% 23% 10% 1	2049
October	1st to 10th	Day	46% 9% 18% 20% 7%	1900
	11th to 20th	Day	40% 12% 17% 23% 7%	1900
	21st to end	Day	40% 11% 17% 21% 11% 1	1800
November	1st to 10th	Day	42% 13% 18% 21% 6%	1488
	11th to 20th	Day	42% 13% 19% 15% 11%	1520
	21st to end	Day	42% 11% 18% 20% 7% 2	1420
December	1st to 10th	Day	41% 14% 17% 20% 7% 2	1330
	11th to 20th	Day	48% 12% 20% 13% 6%	1688
	21st to end	Day	33% 17% 19% 23% 7% 2	2442
January	1st to 10th	Night	53% 13% 15% 14% 4	4726
	11th to 20th	Night	46% 12% 16% 13% 6% 6%	4740
	21st to end	Night	41% 17% 22% 13% 7% 1	5214
February	1st to 10th	Night	47% 11% 17% 14% 10% 1	2505
	11th to 20th	Night	44% 9% 15% 20% 11% 1	2404
	21st to end	Night	48% 9% 14% 21% 8% 1	2041
March	1st to 10th	Night	36% 11% 19% 17% 17%	3658
	11th to 20th	Night	31% 10% 18% 28% 12% 1	3490
	21st to end	Night	40% 12% 17% 19% 11% 1	3798
April	1st to 10th	Night	40% 14% 21% 17% 7%	1862
	11th to 20th	Night	40% 12% 16% 22% 9%	1691
	21st to end	Night	44% 10% 14% 22% 9%	1648
May	1st to 10th	Night	33% 12% 20% 25% 8%	2540
	11th to 20th	Night	38% 13% 21% 23% 4	2337
	21st to end	Night	52% 13% 13% 18% 4	2414
June	1st to 10th	Night	43% 12% 16% 17% 8% 3	1330
	11th to 20th	Night	44% 12% 13% 23% 7%	1330
	21st to end	Night	41% 11% 15% 21% 9% 2	1330
July	1st to 10th	Night	23% 7% 11% 19% 30% 9%	2185
	11th to 20th	Night	20% 7% 14% 41% 18%	2178
	21st to end	Night	28% 7% 20% 23% 19% 3	2337
August	1st to 10th	Night	26% 8% 12% 40% 13% 1	2433
	11th to 20th	Night	34% 11% 21% 26% 6% 2	2839
	21st to end	Night	37% 9% 27% 22% 4	3146
September	1st to 10th	Night	30% 9% 19% 29% 11% 2	1863
	11th to 20th	Night	38% 9% 16% 24% 11% 3	1971
	21st to end	Night	39% 11% 18% 23% 7% 1	2131
October	1st to 10th	Night	43% 11% 17% 23% 7%	2280
	11th to 20th	Night	39% 12% 17% 22% 9%	2280
	21st to end	Night	39% 12% 17% 23% 8%	2795
November	1st to 10th	Night	47% 13% 16% 17% 6% 1	2596
	11th to 20th	Night	43% 11% 19% 18% 9%	2660
	21st to end	Night	43% 12% 19% 17% 7% 3	2759
December	1st to 10th	Night	46% 12% 17% 17% 7% 1	2850
	11th to 20th	Night	51% 15% 15% 14% 5%	3516
	21st to end	Night	37% 16% 16% 18% 12% 1	5214

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	4 13% 42% 28% 7% 6%	180
	11th to 20th	Day	2 16% 36% 30% 13% 3	180
	21st to end	Day	5% 11% 43% 25% 14% 3	198
February	1st to 10th	Day	9% 23% 40% 22% 6%	367
	11th to 20th	Day	8% 17% 40% 25% 9% 1	365
	21st to end	Day	11% 21% 42% 16% 8% 1	307
March	1st to 10th	Day	6% 25% 30% 22% 15% 2	427
	11th to 20th	Day	8% 24% 34% 22% 11% 2	460
	21st to end	Day	13% 23% 31% 20% 11% 2	506
April	1st to 10th	Day	15% 26% 32% 20% 7% 1	460
	11th to 20th	Day	10% 25% 30% 20% 11% 3	452
	21st to end	Day	17% 23% 26% 22% 10% 3	460
May	1st to 10th	Day	10% 21% 27% 30% 11% 1	463
	11th to 20th	Day	15% 17% 29% 24% 12% 3	588
	21st to end	Day	18% 20% 30% 18% 11% 2	735
June	1st to 10th	Day	16% 22% 35% 19% 7% 1	680
	11th to 20th	Day	17% 21% 30% 20% 10% 2	680
	21st to end	Day	12% 16% 34% 24% 12% 3	680
July	1st to 10th	Day	12% 15% 30% 24% 15% 4	671
	11th to 20th	Day	10% 15% 29% 26% 15% 4	668
	21st to end	Day	7% 15% 31% 25% 17% 5%	739
August	1st to 10th	Day	9% 9% 23% 31% 20% 7%	550
	11th to 20th	Day	6% 12% 23% 31% 21% 7%	477
	21st to end	Day	9% 16% 32% 26% 14% 3	539
September	1st to 10th	Day	10% 14% 30% 26% 15% 4	490
	11th to 20th	Day	15% 12% 27% 27% 15% 5%	490
	21st to end	Day	16% 22% 30% 21% 10% 1	490
October	1st to 10th	Day	18% 17% 27% 22% 13% 4	490
	11th to 20th	Day	13% 20% 34% 22% 9% 2	490
	21st to end	Day	15% 18% 39% 15% 11% 2	332
November	1st to 10th	Day	13% 21% 35% 22% 8% 1	180
	11th to 20th	Day	4 16% 32% 32% 12% 3	180
	21st to end	Day	9% 21% 31% 21% 9% 8%	180
December	1st to 10th	Day	4 11% 36% 29% 13% 6%	180
	11th to 20th	Day	5% 17% 38% 24% 11% 6%	180
	21st to end	Day	7% 15% 38% 29% 11% 1	198
January	1st to 10th	Night	6% 13% 45% 25% 8% 2	850
	11th to 20th	Night	6% 11% 41% 34% 6% 2	850
	21st to end	Night	4 13% 43% 26% 11% 2	935
February	1st to 10th	Night	8% 14% 41% 26% 10% 1	776
	11th to 20th	Night	6% 9% 42% 30% 13% 1	744
	21st to end	Night	7% 12% 38% 32% 9% 2	628
March	1st to 10th	Night	3 14% 43% 27% 12% 1	760
	11th to 20th	Night	2 13% 43% 30% 11%	760
	21st to end	Night	7% 13% 36% 29% 14% 1	836
April	1st to 10th	Night	7% 12% 34% 35% 12% 1	722
	11th to 20th	Night	7% 9% 41% 32% 11%	563
	21st to end	Night	7% 11% 38% 32% 11% 1	508
May	1st to 10th	Night	3 9% 37% 38% 13%	380
	11th to 20th	Night	10% 9% 29% 43% 8% 1	374
	21st to end	Night	17% 9% 31% 34% 9%	411
June	1st to 10th	Night	11% 10% 37% 34% 7%	380
	11th to 20th	Night	13% 8% 34% 32% 11% 1	380
	21st to end	Night	13% 5% 29% 40% 13%	380
July	1st to 10th	Night	10% 5% 29% 39% 16%	370
	11th to 20th	Night	10% 6% 29% 39% 17%	368
	21st to end	Night	6% 3 27% 40% 22% 2	416
August	1st to 10th	Night	10% 2 17% 38% 31% 2	379
	11th to 20th	Night	5% 4 21% 37% 31% 2	564
	21st to end	Night	9% 7% 29% 37% 18% 1	627
September	1st to 10th	Night	12% 6% 24% 36% 21% 1	723
	11th to 20th	Night	13% 7% 25% 28% 24% 4	760
	21st to end	Night	11% 14% 34% 28% 12% 1	760
October	1st to 10th	Night	14% 11% 31% 29% 13% 2	760
	11th to 20th	Night	9% 11% 40% 25% 14% 1	760
	21st to end	Night	12% 12% 39% 27% 9% 2	836
November	1st to 10th	Night	5% 17% 43% 26% 7% 1	742
	11th to 20th	Night	5% 15% 47% 25% 7% 1	760
	21st to end	Night	5% 13% 47% 25% 7% 2	807
December	1st to 10th	Night	5% 11% 40% 29% 14% 2	850
	11th to 20th	Night	6% 11% 43% 29% 9% 2	850
	21st to end	Night	6% 10% 48% 28% 8% 1	935

Page generated at 2024-10-29 08:20:50. Version ac07

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