Syzygy Observatory, Alberta
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Syzygy Observatory, Alberta clear sky chart from 2005-11-06 to 2024-12-06.

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	9% 9% 3 8% 6% 5% 5% 4 7% 8% 35%	106587
	Night	8% 9% 4 10% 6% 5% 5% 4 6% 8% 33%	101686
Transparency	Day	44% 8% 18% 22% 7%	106327
	Night	46% 8% 16% 21% 8% 1	101592
Seeing	Day	13% 6% 23% 31% 20% 7%	16035
	Night	13% 6% 27% 36% 17% 2	24541

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	4 13% 6% 12% 11% 6% 6% 5% 8% 7% 21%	2219
	11th to 20th	Day	4 10% 4 9% 7% 6% 5% 6% 8% 9% 32%	2199
	21st to end	Day	7% 12% 4 9% 5% 4 5% 5% 6% 7% 34%	2601
February	1st to 10th	Day	8% 14% 6% 11% 7% 6% 6% 4 8% 8% 22%	1520
	11th to 20th	Day	5% 13% 5% 12% 6% 5% 8% 5% 8% 6% 27%	1598
	21st to end	Day	4 12% 4 10% 8% 7% 6% 4 7% 7% 29%	1460
March	1st to 10th	Day	4 11% 6% 13% 8% 6% 5% 4 6% 10% 27%	3138
	11th to 20th	Day	4 11% 4 10% 6% 4 4 4 6% 10% 37%	3449
	21st to end	Day	8% 13% 5% 16% 7% 5% 5% 4 6% 8% 24%	3886
April	1st to 10th	Day	7% 13% 3 9% 7% 5% 6% 5% 7% 8% 31%	2377
	11th to 20th	Day	9% 12% 3 8% 6% 5% 5% 4 7% 8% 33%	2440
	21st to end	Day	10% 9% 3 8% 6% 4 7% 5% 6% 8% 32%	2470
May	1st to 10th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	4688
	11th to 20th	Day	12% 10% 3 8% 5% 6% 5% 5% 7% 9% 31%	4694
	21st to end	Day	12% 8% 3 9% 7% 6% 6% 5% 7% 9% 29%	5161
June	1st to 10th	Day	15% 8% 3 9% 6% 5% 5% 5% 6% 7% 31%	2850
	11th to 20th	Day	18% 9% 3 8% 7% 6% 5% 5% 6% 7% 25%	3015
	21st to end	Day	10% 6% 2 7% 5% 6% 5% 5% 8% 9% 39%	3040
July	1st to 10th	Day	9% 5% 2 5% 4 5% 5% 5% 7% 8% 45%	4975
	11th to 20th	Day	9% 5% 2 5% 4 4 4 5% 6% 9% 47%	4740
	21st to end	Day	13% 5% 2 5% 5% 4 4 4 6% 8% 43%	5138
August	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 7% 9% 41%	4541
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 7% 10% 43%	4178
	21st to end	Day	11% 5% 2 7% 5% 4 5% 4 6% 9% 42%	4521
September	1st to 10th	Day	11% 6% 3 7% 5% 4 5% 4 6% 8% 42%	2422
	11th to 20th	Day	14% 7% 1 6% 5% 4 5% 4 6% 9% 39%	2090
	21st to end	Day	9% 7% 2 6% 5% 5% 5% 4 6% 8% 42%	2090
October	1st to 10th	Day	10% 9% 3 8% 5% 5% 5% 4 6% 8% 37%	3298
	11th to 20th	Day	11% 10% 3 8% 5% 5% 4 3 6% 8% 36%	2873
	21st to end	Day	7% 10% 6% 9% 5% 6% 5% 4 5% 7% 35%	3044
November	1st to 10th	Day	10% 14% 4 11% 7% 6% 6% 4 5% 7% 27%	1568
	11th to 20th	Day	7% 12% 5% 12% 6% 6% 5% 4 6% 8% 29%	1415
	21st to end	Day	4 13% 6% 12% 8% 7% 5% 5% 6% 7% 29%	1400
December	1st to 10th	Day	5% 14% 4 11% 7% 7% 6% 4 7% 8% 27%	1365
	11th to 20th	Day	7% 10% 4 12% 7% 7% 7% 5% 8% 9% 26%	1682
	21st to end	Day	3 7% 3 9% 6% 6% 5% 5% 7% 8% 40%	2442
January	1st to 10th	Night	4 11% 5% 16% 10% 7% 7% 5% 6% 6% 24%	4726
	11th to 20th	Night	4 9% 3 10% 8% 7% 7% 6% 7% 7% 34%	4699
	21st to end	Night	7% 13% 4 10% 7% 5% 6% 4 6% 8% 30%	5086
February	1st to 10th	Night	6% 11% 5% 13% 8% 7% 6% 5% 7% 7% 26%	2660
	11th to 20th	Night	5% 12% 4 11% 6% 7% 7% 5% 8% 8% 28%	2469
	21st to end	Night	4 10% 5% 10% 7% 6% 7% 6% 7% 8% 30%	1994
March	1st to 10th	Night	3 10% 5% 12% 7% 7% 5% 5% 7% 10% 29%	3736
	11th to 20th	Night	5% 9% 4 10% 5% 5% 6% 4 7% 10% 36%	3530
	21st to end	Night	7% 11% 6% 16% 9% 6% 5% 4 5% 6% 24%	3753
April	1st to 10th	Night	7% 10% 4 9% 7% 7% 6% 6% 7% 6% 31%	1802
	11th to 20th	Night	10% 11% 4 10% 7% 5% 5% 4 7% 7% 30%	1691
	21st to end	Night	11% 10% 3 8% 5% 5% 4 5% 6% 9% 35%	1710
May	1st to 10th	Night	21% 9% 3 8% 5% 4 6% 3 6% 5% 30%	2271
	11th to 20th	Night	12% 10% 3 10% 6% 6% 5% 5% 7% 7% 30%	2199
	21st to end	Night	12% 9% 4 8% 6% 6% 5% 5% 8% 9% 28%	2414
June	1st to 10th	Night	15% 9% 3 8% 5% 5% 5% 5% 7% 8% 30%	1330
	11th to 20th	Night	15% 10% 3 8% 6% 5% 7% 7% 8% 8% 22%	1160
	21st to end	Night	8% 7% 2 6% 6% 5% 6% 6% 7% 8% 38%	1140
July	1st to 10th	Night	9% 4 2 7% 5% 4 5% 4 6% 8% 46%	1982
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 11% 41%	2220
	21st to end	Night	13% 7% 2 5% 4 4 5% 4 7% 8% 42%	2414
August	1st to 10th	Night	11% 6% 2 8% 5% 4 5% 4 6% 7% 42%	2387
	11th to 20th	Night	11% 7% 3 8% 4 5% 5% 4 6% 9% 38%	2654
	21st to end	Night	12% 6% 2 5% 4 4 4 4 6% 8% 45%	3146
September	1st to 10th	Night	12% 5% 3 6% 4 4 4 4 6% 8% 44%	1755
	11th to 20th	Night	12% 7% 2 5% 4 4 4 3 6% 8% 44%	2090
	21st to end	Night	9% 8% 2 7% 3 5% 4 4 5% 7% 45%	2090
October	1st to 10th	Night	7% 7% 3 9% 5% 6% 6% 4 7% 8% 38%	3676
	11th to 20th	Night	10% 8% 3 6% 5% 4 5% 4 7% 9% 39%	4053
	21st to end	Night	7% 9% 3 8% 5% 5% 6% 5% 7% 9% 36%	4483
November	1st to 10th	Night	13% 15% 5% 10% 6% 5% 5% 3 6% 6% 27%	2730
	11th to 20th	Night	7% 14% 5% 11% 8% 5% 6% 4 6% 7% 27%	2980
	21st to end	Night	6% 12% 6% 13% 8% 5% 6% 5% 6% 7% 27%	3000
December	1st to 10th	Night	7% 14% 4 11% 7% 6% 5% 4 6% 7% 30%	2932
	11th to 20th	Night	7% 13% 5% 12% 6% 6% 5% 5% 7% 7% 25%	3510
	21st to end	Night	3 7% 3 9% 6% 5% 6% 4 7% 9% 41%	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	57% 8% 13% 17% 5% 1	2219
	11th to 20th	Day	46% 6% 13% 15% 17% 2	2220
	21st to end	Day	46% 8% 21% 19% 6%	2601
February	1st to 10th	Day	56% 6% 15% 14% 8%	1520
	11th to 20th	Day	51% 9% 17% 15% 7%	1606
	21st to end	Day	50% 8% 13% 22% 7%	1460
March	1st to 10th	Day	52% 6% 15% 21% 6%	3138
	11th to 20th	Day	41% 8% 21% 21% 9%	3450
	21st to end	Day	56% 8% 14% 19% 3	3886
April	1st to 10th	Day	46% 10% 17% 18% 7%	2377
	11th to 20th	Day	46% 7% 15% 23% 8%	2440
	21st to end	Day	46% 8% 17% 21% 6% 2	2470
May	1st to 10th	Day	49% 6% 11% 25% 8%	4688
	11th to 20th	Day	45% 9% 13% 25% 8%	4698
	21st to end	Day	46% 12% 18% 16% 8%	5162
June	1st to 10th	Day	48% 8% 15% 20% 7% 1	2850
	11th to 20th	Day	54% 9% 16% 15% 5%	3015
	21st to end	Day	39% 9% 23% 22% 6% 1	3040
July	1st to 10th	Day	34% 8% 17% 28% 12% 1	4898
	11th to 20th	Day	33% 7% 18% 28% 13%	4659
	21st to end	Day	37% 8% 22% 24% 9%	4976
August	1st to 10th	Day	37% 9% 22% 30% 2	4523
	11th to 20th	Day	33% 9% 24% 25% 9%	4220
	21st to end	Day	37% 7% 28% 25% 4	4520
September	1st to 10th	Day	38% 9% 20% 25% 7% 2	2422
	11th to 20th	Day	40% 7% 20% 26% 7%	2090
	21st to end	Day	37% 9% 18% 27% 8% 2	2090
October	1st to 10th	Day	44% 5% 23% 22% 5%	3298
	11th to 20th	Day	46% 5% 15% 26% 8%	2873
	21st to end	Day	47% 6% 17% 26% 3	3044
November	1st to 10th	Day	55% 7% 16% 15% 6% 1	1568
	11th to 20th	Day	52% 7% 17% 19% 5%	1415
	21st to end	Day	53% 8% 15% 17% 5% 1	1400
December	1st to 10th	Day	54% 6% 15% 17% 7% 1	1365
	11th to 20th	Day	51% 9% 18% 16% 6%	1684
	21st to end	Day	38% 7% 12% 27% 14% 2	2442
January	1st to 10th	Night	57% 8% 13% 15% 6% 1	4726
	11th to 20th	Night	46% 7% 14% 17% 15% 1	4740
	21st to end	Night	51% 7% 20% 16% 6%	5086
February	1st to 10th	Night	55% 7% 13% 16% 7% 1	2660
	11th to 20th	Night	50% 9% 15% 16% 9% 1	2471
	21st to end	Night	48% 8% 14% 21% 9% 1	1994
March	1st to 10th	Night	47% 7% 17% 21% 7%	3736
	11th to 20th	Night	40% 8% 21% 19% 11% 1	3530
	21st to end	Night	56% 9% 12% 16% 6%	3753
April	1st to 10th	Night	47% 10% 14% 18% 11% 1	1802
	11th to 20th	Night	50% 6% 11% 19% 11% 2	1691
	21st to end	Night	45% 7% 11% 23% 13% 1	1710
May	1st to 10th	Night	53% 6% 10% 20% 10% 1	2271
	11th to 20th	Night	46% 12% 11% 21% 10% 1	2199
	21st to end	Night	46% 11% 18% 16% 8% 1	2414
June	1st to 10th	Night	49% 8% 13% 19% 9% 1	1330
	11th to 20th	Night	53% 11% 15% 16% 5%	1160
	21st to end	Night	39% 11% 21% 23% 5% 1	1140
July	1st to 10th	Night	35% 7% 17% 24% 16% 1	1950
	11th to 20th	Night	35% 9% 17% 30% 10%	2178
	21st to end	Night	38% 7% 21% 28% 7%	2337
August	1st to 10th	Night	39% 8% 20% 31% 1	2380
	11th to 20th	Night	42% 8% 19% 22% 9%	2678
	21st to end	Night	35% 6% 25% 28% 5%	3146
September	1st to 10th	Night	37% 7% 18% 27% 9% 2	1755
	11th to 20th	Night	37% 6% 17% 30% 9% 1	2090
	21st to end	Night	37% 7% 15% 27% 12% 2	2090
October	1st to 10th	Night	41% 7% 21% 24% 7%	3676
	11th to 20th	Night	40% 5% 14% 33% 7%	4053
	21st to end	Night	42% 8% 22% 23% 5%	4483
November	1st to 10th	Night	57% 6% 12% 20% 6%	2730
	11th to 20th	Night	55% 8% 13% 17% 6%	2980
	21st to end	Night	54% 9% 15% 17% 4 1	3000
December	1st to 10th	Night	53% 6% 13% 18% 9% 1	2932
	11th to 20th	Night	56% 7% 16% 15% 6%	3507
	21st to end	Night	38% 6% 17% 22% 15% 2	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	9% 9% 22% 36% 19% 5%	180
	11th to 20th	Day	8% 8% 26% 36% 16% 7%	180
	21st to end	Day	11% 9% 29% 31% 14% 7%	198
February	1st to 10th	Day	12% 9% 29% 32% 12% 7%	180
	11th to 20th	Day	13% 4 31% 29% 17% 7%	238
	21st to end	Day	6% 5% 30% 32% 19% 8%	272
March	1st to 10th	Day	12% 5% 24% 38% 18% 4	460
	11th to 20th	Day	10% 4 22% 37% 20% 7%	460
	21st to end	Day	15% 4 22% 31% 24% 5%	506
April	1st to 10th	Day	8% 7% 28% 35% 18% 4	460
	11th to 20th	Day	13% 6% 21% 33% 19% 8%	452
	21st to end	Day	13% 8% 24% 29% 18% 7%	460
May	1st to 10th	Day	13% 8% 23% 31% 21% 5%	624
	11th to 20th	Day	11% 5% 24% 33% 20% 7%	675
	21st to end	Day	15% 6% 17% 31% 20% 11%	734
June	1st to 10th	Day	17% 7% 26% 29% 19% 4	680
	11th to 20th	Day	19% 4 21% 27% 20% 8%	845
	21st to end	Day	12% 4 17% 29% 26% 11%	870
July	1st to 10th	Day	12% 4 16% 32% 26% 10%	812
	11th to 20th	Day	12% 5% 19% 28% 27% 9%	668
	21st to end	Day	11% 5% 18% 30% 27% 10%	739
August	1st to 10th	Day	12% 5% 18% 27% 23% 14%	575
	11th to 20th	Day	9% 5% 22% 35% 22% 8%	477
	21st to end	Day	10% 8% 22% 28% 22% 10%	539
September	1st to 10th	Day	14% 8% 26% 27% 17% 8%	490
	11th to 20th	Day	17% 8% 22% 30% 19% 4	490
	21st to end	Day	10% 13% 29% 29% 14% 4	490
October	1st to 10th	Day	14% 9% 27% 27% 18% 4	376
	11th to 20th	Day	13% 7% 29% 31% 17% 3	300
	21st to end	Day	15% 12% 33% 25% 12% 3	330
November	1st to 10th	Day	18% 5% 29% 29% 16% 2	300
	11th to 20th	Day	11% 6% 33% 34% 13% 3	207
	21st to end	Day	8% 9% 34% 31% 13% 7%	200
December	1st to 10th	Day	8% 7% 31% 38% 10% 6%	190
	11th to 20th	Day	9% 7% 24% 42% 15% 3	180
	21st to end	Day	8% 4 23% 35% 23% 8%	198
January	1st to 10th	Night	11% 5% 32% 35% 15% 3	950
	11th to 20th	Night	11% 8% 29% 37% 14% 1	950
	21st to end	Night	14% 10% 32% 30% 13% 2	969
February	1st to 10th	Night	10% 8% 25% 36% 17% 4	760
	11th to 20th	Night	11% 4 32% 35% 17% 1	744
	21st to end	Night	7% 4 27% 35% 20% 6%	628
March	1st to 10th	Night	9% 6% 26% 40% 16% 4	760
	11th to 20th	Night	11% 5% 30% 34% 16% 3	760
	21st to end	Night	13% 6% 23% 38% 18% 2	836
April	1st to 10th	Night	11% 6% 25% 37% 18% 3	662
	11th to 20th	Night	14% 5% 25% 38% 15% 2	563
	21st to end	Night	15% 6% 24% 36% 17% 1	570
May	1st to 10th	Night	15% 5% 24% 34% 20% 2	389
	11th to 20th	Night	12% 5% 22% 39% 19% 2	374
	21st to end	Night	19% 6% 20% 33% 20% 2	411
June	1st to 10th	Night	18% 8% 17% 41% 14% 2	380
	11th to 20th	Night	20% 5% 19% 30% 23% 2	380
	21st to end	Night	10% 4 19% 36% 27% 4	380
July	1st to 10th	Night	12% 4 14% 42% 27% 1	370
	11th to 20th	Night	13% 3 19% 39% 23% 3	368
	21st to end	Night	11% 4 13% 41% 27% 4	416
August	1st to 10th	Night	9% 4 16% 34% 31% 5%	378
	11th to 20th	Night	12% 4 18% 37% 27% 3	468
	21st to end	Night	13% 3 20% 39% 23% 2	627
September	1st to 10th	Night	15% 4 20% 38% 22% 2	610
	11th to 20th	Night	15% 5% 19% 41% 18% 2	760
	21st to end	Night	14% 6% 28% 39% 13% 2	760
October	1st to 10th	Night	15% 5% 26% 39% 14% 1	760
	11th to 20th	Night	12% 6% 29% 38% 12% 2	760
	21st to end	Night	13% 8% 32% 33% 13%	850
November	1st to 10th	Night	20% 5% 30% 32% 11% 2	975
	11th to 20th	Night	13% 7% 34% 32% 12% 3	1000
	21st to end	Night	10% 6% 36% 35% 12% 2	1000
December	1st to 10th	Night	13% 8% 32% 30% 14% 4	978
	11th to 20th	Night	11% 6% 32% 35% 14% 2	950
	21st to end	Night	11% 4 27% 37% 18% 4	1045

Page generated at 2024-12-03 04:45:13. Version ac07

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