Point MacKenzie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point MacKenzie clear sky chart from 2005-11-06 to 2024-12-02.

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	20% 13% 4 9% 5% 5% 5% 4 5% 6% 25%	106692
	Night	18% 15% 4 9% 5% 5% 4 4 5% 5% 26%	101559
Transparency	Day	33% 48% 8% 8% 3	106382
	Night	32% 48% 7% 8% 4 1	101518
Seeing	Day	22% 7% 18% 25% 20% 7%	18159
	Night	25% 7% 21% 26% 18% 3	22515

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	9% 16% 5% 11% 5% 7% 6% 5% 6% 7% 22%	1275
	11th to 20th	Day	13% 13% 4 8% 6% 5% 4 4 6% 4 33%	1641
	21st to end	Day	12% 15% 5% 9% 7% 5% 4 2 4 4 33%	2090
February	1st to 10th	Day	13% 18% 3 8% 5% 3 4 2 4 5% 34%	1309
	11th to 20th	Day	18% 22% 5% 9% 6% 5% 4 2 4 4 21%	1468
	21st to end	Day	11% 17% 4 8% 6% 4 4 3 3 6% 33%	1372
March	1st to 10th	Day	9% 20% 6% 12% 5% 4 4 3 3 4 31%	3048
	11th to 20th	Day	12% 11% 4 10% 6% 6% 5% 4 5% 7% 28%	3283
	21st to end	Day	21% 22% 5% 8% 5% 4 4 3 5% 4 21%	4128
April	1st to 10th	Day	10% 16% 6% 10% 6% 5% 5% 4 5% 6% 27%	2326
	11th to 20th	Day	9% 12% 4 8% 6% 6% 5% 5% 5% 6% 34%	2626
	21st to end	Day	11% 12% 4 9% 6% 6% 5% 4 6% 6% 29%	2679
May	1st to 10th	Day	21% 20% 6% 12% 6% 5% 4 3 4 4 15%	5034
	11th to 20th	Day	11% 12% 4 10% 6% 6% 6% 4 5% 7% 29%	5023
	21st to end	Day	21% 12% 4 10% 6% 5% 5% 4 5% 6% 23%	5981
June	1st to 10th	Day	15% 12% 4 9% 6% 5% 6% 4 6% 8% 24%	3420
	11th to 20th	Day	16% 9% 3 9% 6% 6% 5% 4 7% 7% 28%	3420
	21st to end	Day	18% 9% 3 8% 6% 5% 5% 5% 6% 7% 27%	3420
July	1st to 10th	Day	24% 11% 4 10% 6% 5% 6% 4 5% 6% 19%	5700
	11th to 20th	Day	28% 11% 4 9% 5% 5% 4 3 5% 6% 19%	5546
	21st to end	Day	26% 10% 3 8% 5% 4 4 3 5% 6% 26%	5541
August	1st to 10th	Day	31% 9% 3 8% 6% 4 4 4 5% 6% 19%	5001
	11th to 20th	Day	31% 9% 4 7% 5% 4 4 3 4 6% 24%	4446
	21st to end	Day	27% 10% 4 8% 5% 5% 5% 3 5% 7% 22%	4884
September	1st to 10th	Day	31% 12% 5% 9% 6% 4 4 4 4 4 16%	2346
	11th to 20th	Day	33% 13% 5% 8% 4 4 5% 3 4 4 18%	2280
	21st to end	Day	25% 11% 4 9% 4 5% 4 3 5% 4 26%	2019
October	1st to 10th	Day	20% 9% 4 10% 6% 7% 7% 6% 6% 6% 19%	3143
	11th to 20th	Day	14% 10% 3 7% 4 5% 3 3 5% 6% 40%	2782
	21st to end	Day	20% 13% 3 6% 3 2 3 2 4 5% 39%	2693
November	1st to 10th	Day	17% 17% 5% 12% 5% 5% 3 2 4 4 25%	1355
	11th to 20th	Day	13% 13% 3 7% 5% 4 4 2 5% 4 39%	1200
	21st to end	Day	15% 15% 6% 9% 8% 5% 5% 3 4 4 26%	1040
December	1st to 10th	Day	21% 20% 6% 9% 5% 4 3 2 4 4 22%	809
	11th to 20th	Day	11% 22% 9% 11% 6% 4 5% 3 4 6% 20%	967
	21st to end	Day	9% 16% 6% 11% 7% 6% 6% 4 6% 9% 20%	1397
January	1st to 10th	Night	13% 16% 5% 10% 6% 5% 6% 4 5% 6% 24%	5677
	11th to 20th	Night	14% 14% 4 10% 5% 4 3 3 4 5% 33%	5273
	21st to end	Night	13% 13% 4 9% 5% 4 3 3 4 5% 37%	5577
February	1st to 10th	Night	13% 18% 4 9% 5% 3 3 3 5% 5% 32%	2869
	11th to 20th	Night	19% 23% 5% 10% 5% 4 4 3 4 4 19%	2599
	21st to end	Night	12% 16% 4 10% 5% 5% 4 3 4 5% 32%	2079
March	1st to 10th	Night	9% 20% 5% 10% 4 4 4 3 4 5% 32%	3806
	11th to 20th	Night	12% 13% 5% 11% 5% 5% 5% 4 5% 6% 28%	3672
	21st to end	Night	17% 24% 5% 9% 4 4 4 3 4 4 22%	3503
April	1st to 10th	Night	11% 21% 6% 10% 7% 5% 4 3 4 4 26%	1853
	11th to 20th	Night	13% 14% 3 8% 5% 5% 5% 4 5% 6% 32%	1503
	21st to end	Night	11% 11% 5% 10% 7% 5% 5% 4 6% 6% 29%	1501
May	1st to 10th	Night	19% 19% 4 12% 7% 7% 5% 4 5% 5% 14%	1933
	11th to 20th	Night	13% 15% 5% 10% 6% 5% 5% 4 5% 7% 26%	1882
	21st to end	Night	22% 12% 3 8% 6% 5% 5% 5% 7% 7% 21%	1600
June	1st to 10th	Night	20% 13% 3 10% 5% 7% 6% 6% 6% 4 20%	760
	11th to 20th	Night	17% 11% 4 8% 6% 6% 6% 4 5% 8% 25%	760
	21st to end	Night	17% 11% 4 10% 8% 7% 7% 3 6% 7% 21%	760
July	1st to 10th	Night	31% 11% 4 9% 6% 5% 5% 4 5% 6% 15%	1270
	11th to 20th	Night	31% 12% 3 7% 5% 4 4 4 5% 7% 18%	1426
	21st to end	Night	27% 8% 3 8% 6% 4 4 3 5% 7% 25%	2025
August	1st to 10th	Night	31% 10% 4 9% 4 4 3 3 5% 6% 22%	1924
	11th to 20th	Night	34% 6% 2 5% 4 4 3 3 5% 6% 28%	2392
	21st to end	Night	32% 9% 3 9% 6% 5% 5% 4 4 4 19%	2783
September	1st to 10th	Night	36% 12% 4 8% 6% 4 3 3 4 4 16%	1833
	11th to 20th	Night	35% 11% 4 8% 5% 4 4 3 4 4 19%	1900
	21st to end	Night	28% 10% 3 8% 5% 4 4 3 4 5% 25%	2160
October	1st to 10th	Night	23% 12% 4 11% 7% 6% 6% 4 5% 5% 17%	3818
	11th to 20th	Night	15% 10% 3 8% 4 5% 4 4 5% 7% 34%	4142
	21st to end	Night	18% 14% 4 8% 5% 4 4 3 5% 5% 31%	4866
November	1st to 10th	Night	19% 17% 5% 9% 4 5% 4 3 4 5% 25%	2942
	11th to 20th	Night	12% 13% 4 9% 5% 4 4 3 4 5% 37%	3200
	21st to end	Night	16% 18% 5% 10% 4 4 4 3 4 5% 28%	3360
December	1st to 10th	Night	24% 18% 4 8% 6% 5% 4 3 4 5% 19%	3401
	11th to 20th	Night	13% 21% 7% 14% 7% 5% 4 3 4 4 19%	4240
	21st to end	Night	10% 17% 5% 12% 7% 5% 6% 6% 6% 6% 19%	6270

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	36% 44% 6% 7% 5% 1	1275
	11th to 20th	Day	27% 40% 7% 15% 9% 2	1656
	21st to end	Day	30% 39% 6% 12% 9% 4	2090
February	1st to 10th	Day	14% 66% 3 7% 6% 4	1309
	11th to 20th	Day	23% 64% 5% 4 3 1	1475
	21st to end	Day	18% 65% 5% 8% 4	1372
March	1st to 10th	Day	36% 41% 5% 5% 8% 4	3048
	11th to 20th	Day	35% 43% 9% 5% 6% 1	3283
	21st to end	Day	43% 42% 5% 4 5% 1	4128
April	1st to 10th	Day	19% 66% 4 8% 3 1	2326
	11th to 20th	Day	16% 67% 4 9% 3	2626
	21st to end	Day	20% 66% 4 7% 2	2679
May	1st to 10th	Day	48% 41% 4 6% 1	5034
	11th to 20th	Day	30% 43% 8% 16% 3	5026
	21st to end	Day	40% 45% 7% 7% 1	5982
June	1st to 10th	Day	18% 69% 6% 6% 1	3420
	11th to 20th	Day	18% 67% 6% 6% 2	3420
	21st to end	Day	20% 66% 9% 6%	3420
July	1st to 10th	Day	44% 40% 12% 3	5611
	11th to 20th	Day	46% 38% 13% 3	5447
	21st to end	Day	37% 39% 14% 10%	5366
August	1st to 10th	Day	42% 41% 12% 5%	4982
	11th to 20th	Day	37% 40% 11% 10%	4490
	21st to end	Day	39% 39% 11% 9% 2	4883
September	1st to 10th	Day	27% 61% 5% 6% 2	2346
	11th to 20th	Day	31% 61% 5% 3	2280
	21st to end	Day	23% 61% 6% 9% 1	2019
October	1st to 10th	Day	39% 39% 10% 10% 2	3143
	11th to 20th	Day	23% 38% 14% 14% 10%	2782
	21st to end	Day	30% 37% 8% 23% 3	2693
November	1st to 10th	Day	30% 57% 5% 5% 3	1355
	11th to 20th	Day	22% 58% 5% 11% 4	1200
	21st to end	Day	30% 57% 3 5% 5% 1	1040
December	1st to 10th	Day	27% 61% 6% 5% 1	809
	11th to 20th	Day	39% 49% 4 6% 2	970
	21st to end	Day	35% 41% 9% 6% 9% 1	1397
January	1st to 10th	Night	39% 41% 7% 6% 6% 1	5677
	11th to 20th	Night	30% 40% 8% 14% 7% 1	5321
	21st to end	Night	25% 40% 5% 12% 12% 6%	5577
February	1st to 10th	Night	15% 65% 2 8% 6% 4	2869
	11th to 20th	Night	23% 64% 4 5% 4 1	2603
	21st to end	Night	20% 65% 3 6% 6%	2079
March	1st to 10th	Night	33% 41% 5% 9% 6% 6%	3806
	11th to 20th	Night	36% 43% 9% 4 6% 1	3674
	21st to end	Night	41% 43% 5% 5% 4 1	3503
April	1st to 10th	Night	22% 66% 3 6% 3	1853
	11th to 20th	Night	18% 67% 4 8% 3	1503
	21st to end	Night	20% 66% 4 6% 2	1501
May	1st to 10th	Night	44% 43% 5% 6% 1	1933
	11th to 20th	Night	34% 42% 9% 13% 2	1883
	21st to end	Night	39% 46% 7% 6% 1	1600
June	1st to 10th	Night	24% 68% 3 5%	760
	11th to 20th	Night	18% 67% 6% 6% 2	760
	21st to end	Night	22% 68% 6% 4	760
July	1st to 10th	Night	45% 40% 11% 4	1250
	11th to 20th	Night	45% 38% 13% 4	1402
	21st to end	Night	38% 37% 17% 7%	1961
August	1st to 10th	Night	41% 39% 12% 7%	1918
	11th to 20th	Night	34% 41% 12% 9% 4	2414
	21st to end	Night	45% 39% 8% 5% 3	2783
September	1st to 10th	Night	28% 62% 4 4 3	1833
	11th to 20th	Night	30% 61% 4 3 1	1900
	21st to end	Night	22% 61% 8% 8% 1	2160
October	1st to 10th	Night	44% 38% 6% 10% 2	3818
	11th to 20th	Night	27% 39% 12% 11% 11%	4142
	21st to end	Night	35% 38% 8% 16% 4	4866
November	1st to 10th	Night	29% 57% 5% 6% 2	2942
	11th to 20th	Night	22% 58% 4 11% 5%	3200
	21st to end	Night	27% 57% 4 6% 5% 1	3360
December	1st to 10th	Night	30% 60% 3 4 2	3401
	11th to 20th	Night	38% 50% 4 5% 2	4236
	21st to end	Night	38% 39% 11% 6% 5% 1	6270

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	13% 10% 16% 31% 24% 6%	96
	11th to 20th	Day	24% 8% 21% 25% 18% 5%	280
	21st to end	Day	26% 9% 19% 24% 15% 6%	308
February	1st to 10th	Day	20% 5% 21% 30% 12% 11%	280
	11th to 20th	Day	27% 10% 24% 24% 11% 4	360
	21st to end	Day	21% 7% 27% 28% 12% 6%	307
March	1st to 10th	Day	18% 9% 25% 21% 22% 5%	370
	11th to 20th	Day	12% 8% 20% 32% 19% 10%	441
	21st to end	Day	17% 6% 20% 26% 22% 9%	616
April	1st to 10th	Day	15% 8% 26% 25% 20% 5%	567
	11th to 20th	Day	13% 7% 17% 27% 26% 10%	640
	21st to end	Day	16% 5% 16% 30% 26% 7%	650
May	1st to 10th	Day	23% 9% 20% 25% 19% 5%	653
	11th to 20th	Day	18% 8% 20% 27% 20% 7%	675
	21st to end	Day	22% 7% 19% 30% 17% 5%	846
June	1st to 10th	Day	17% 9% 16% 25% 24% 9%	870
	11th to 20th	Day	16% 6% 17% 31% 24% 6%	870
	21st to end	Day	16% 6% 16% 25% 27% 9%	870
July	1st to 10th	Day	20% 6% 14% 30% 25% 5%	856
	11th to 20th	Day	24% 3 14% 30% 24% 5%	852
	21st to end	Day	27% 4 14% 24% 23% 8%	768
August	1st to 10th	Day	29% 4 16% 25% 20% 6%	676
	11th to 20th	Day	30% 6% 17% 21% 19% 7%	665
	21st to end	Day	32% 6% 13% 21% 20% 8%	748
September	1st to 10th	Day	31% 7% 18% 17% 20% 7%	595
	11th to 20th	Day	36% 7% 12% 17% 19% 8%	580
	21st to end	Day	26% 6% 16% 24% 19% 9%	404
October	1st to 10th	Day	32% 7% 19% 19% 17% 6%	390
	11th to 20th	Day	25% 9% 18% 26% 14% 8%	390
	21st to end	Day	24% 7% 22% 24% 15% 8%	429
November	1st to 10th	Day	24% 8% 28% 20% 15% 5%	387
	11th to 20th	Day	18% 8% 24% 28% 19% 3	300
	21st to end	Day	22% 6% 27% 24% 16% 5%	140
December	1st to 10th	Day	27% 9% 20% 22% 20% 2	91
	11th to 20th	Day	22% 9% 29% 21% 16% 3	90
	21st to end	Day	22% 11% 26% 27% 10% 3	99
January	1st to 10th	Night	16% 6% 21% 36% 18% 3	940
	11th to 20th	Night	24% 6% 25% 28% 14% 3	919
	21st to end	Night	26% 6% 23% 30% 12% 2	935
February	1st to 10th	Night	20% 6% 25% 30% 14% 4	850
	11th to 20th	Night	28% 10% 24% 26% 11% 1	834
	21st to end	Night	21% 8% 24% 31% 12% 3	584
March	1st to 10th	Night	18% 11% 25% 27% 17% 3	660
	11th to 20th	Night	13% 5% 29% 29% 19% 5%	660
	21st to end	Night	17% 7% 20% 26% 24% 6%	638
April	1st to 10th	Night	20% 8% 20% 25% 19% 7%	570
	11th to 20th	Night	20% 5% 14% 27% 28% 7%	563
	21st to end	Night	14% 5% 16% 30% 31% 5%	570
May	1st to 10th	Night	18% 9% 17% 28% 26% 3	400
	11th to 20th	Night	20% 6% 16% 30% 26% 2	374
	21st to end	Night	19% 6% 19% 33% 22% 1	247
June	1st to 10th	Night	22% 7% 11% 30% 29% 1	190
	11th to 20th	Night	19% 2 19% 35% 25%	190
	21st to end	Night	18% 5% 15% 35% 24% 2	190
July	1st to 10th	Night	28% 5% 13% 32% 21% 1	185
	11th to 20th	Night	32% 3 10% 29% 23% 3	275
	21st to end	Night	32% 4 13% 21% 25% 5%	416
August	1st to 10th	Night	34% 5% 14% 24% 21% 3	378
	11th to 20th	Night	39% 4 14% 21% 19% 4	504
	21st to end	Night	37% 6% 13% 17% 21% 6%	627
September	1st to 10th	Night	39% 4 16% 21% 16% 4	570
	11th to 20th	Night	40% 7% 8% 16% 22% 6%	570
	21st to end	Night	32% 6% 17% 18% 22% 6%	615
October	1st to 10th	Night	37% 6% 16% 21% 17% 3	675
	11th to 20th	Night	27% 5% 19% 25% 20% 4	860
	21st to end	Night	27% 6% 22% 25% 18% 2	946
November	1st to 10th	Night	27% 8% 25% 26% 13% 2	880
	11th to 20th	Night	19% 9% 25% 31% 14% 2	900
	21st to end	Night	26% 8% 24% 24% 16% 2	900
December	1st to 10th	Night	31% 9% 20% 26% 12% 3	926
	11th to 20th	Night	21% 7% 28% 29% 13% 3	940
	21st to end	Night	24% 8% 25% 24% 14% 3	1034

Page generated at 2024-11-29 06:43:06. Version ac07

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