SPARQ Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SPARQ Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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% 5% 2 4 3 3 3 2 4 6% 60%	105138
	Night	11% 6% 2 6% 3 3 3 3 4 6% 53%	102722
Transparency	Day	27% 3 8% 20% 23% 19%	104898
	Night	32% 4 9% 18% 21% 17%	102552
Seeing	Day	11% 11% 23% 30% 19% 6%	15390
	Night	12% 5% 15% 32% 29% 6%	24632

By Month

Percentage Cloud Cover SW (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	17% 7% 3 7% 5% 3 3 3 5% 5% 41%	2708
	11th to 20th	Day	23% 9% 3 8% 4 4 4 3 4 5% 32%	2860
	21st to end	Day	23% 9% 3 8% 4 4 4 3 5% 6% 32%	3146
February	1st to 10th	Day	17% 6% 2 7% 4 4 3 3 4 4 47%	1710
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 5% 7% 43%	1697
	21st to end	Day	16% 7% 2 4 5% 3 3 3 4 7% 47%	1570
March	1st to 10th	Day	21% 12% 4 8% 5% 3 4 3 4 5% 30%	3436
	11th to 20th	Day	12% 5% 2 4 3 3 4 3 5% 6% 54%	3490
	21st to end	Day	18% 8% 3 6% 4 4 5% 3 6% 7% 36%	3842
April	1st to 10th	Day	14% 8% 2 6% 4 4 4 3 6% 7% 42%	2280
	11th to 20th	Day	9% 5% 3 5% 4 4 4 3 5% 6% 52%	2249
	21st to end	Day	7% 4 1 4 3 3 3 3 6% 9% 57%	2280
May	1st to 10th	Day	6% 3 1 3 1 2 2 2 3 5% 72%	4063
	11th to 20th	Day	4 3 1 3 2 2 2 2 4 5% 71%	4146
	21st to end	Day	3 3 1 3 2 2 2 2 3 5% 73%	4813
June	1st to 10th	Day	7% 6% 2 4 2 2 3 3 5% 8% 59%	2660
	11th to 20th	Day	2 3 1 2 2 2 2 3 4 6% 74%	2660
	21st to end	Day	3 3 1 3 2 2 2 2 3 4 76%	2660
July	1st to 10th	Day	1 2 1 3 1 1 2 1 2 4 81%	4420
	11th to 20th	Day	1 3 2 3 2 2 2 2 4 6% 75%	4119
	21st to end	Day	1 3 2 3 2 2 2 2 3 4 77%	4455
August	1st to 10th	Day	1 3 2 5% 2 3 3 3 6% 7% 64%	4091
	11th to 20th	Day	1 2 1 3 2 1 2 2 3 5% 79%	3916
	21st to end	Day	1 4 2 5% 2 2 2 2 4 6% 70%	4180
September	1st to 10th	Day	1 3 1 3 2 2 2 2 4 5% 75%	2280
	11th to 20th	Day	4 4 2 5% 2 3 3 3 4 7% 63%	2267
	21st to end	Day	4 2 1 3 2 1 2 2 3 6% 73%	2005
October	1st to 10th	Day	4 2 1 2 2 2 3 2 4 6% 71%	3180
	11th to 20th	Day	8% 4 2 4 2 2 3 2 4 4 65%	3161
	21st to end	Day	7% 4 1 5% 3 3 4 3 5% 8% 57%	3448
November	1st to 10th	Day	10% 4 1 4 3 4 3 3 5% 7% 55%	1913
	11th to 20th	Day	12% 6% 3 5% 5% 3 3 3 4 7% 49%	1671
	21st to end	Day	11% 5% 1 5% 3 3 5% 3 5% 6% 54%	1520
December	1st to 10th	Day	18% 7% 3 5% 4 3 3 3 5% 6% 44%	1520
	11th to 20th	Day	32% 9% 2 6% 3 2 3 2 5% 5% 30%	1928
	21st to end	Day	22% 9% 3 6% 4 3 3 3 4 7% 35%	2794
January	1st to 10th	Night	16% 8% 2 6% 4 3 4 3 6% 7% 41%	4237
	11th to 20th	Night	23% 8% 3 8% 5% 4 5% 4 5% 5% 32%	4110
	21st to end	Night	25% 10% 3 7% 4 4 4 3 4 5% 32%	4521
February	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 6% 48%	2470
	11th to 20th	Night	14% 8% 3 6% 4 4 3 3 5% 8% 43%	2369
	21st to end	Night	14% 6% 2 3 2 3 4 2 4 6% 53%	1884
March	1st to 10th	Night	20% 12% 3 6% 4 4 4 3 4 5% 34%	3435
	11th to 20th	Night	13% 5% 2 5% 3 3 3 2 4 5% 54%	3490
	21st to end	Night	16% 11% 3 7% 4 3 4 3 5% 5% 39%	3809
April	1st to 10th	Night	11% 7% 3 6% 5% 2 4 3 4 6% 51%	1900
	11th to 20th	Night	8% 7% 2 5% 4 3 3 3 4 6% 55%	1879
	21st to end	Night	6% 5% 2 3 3 3 3 3 4 6% 61%	1900
May	1st to 10th	Night	5% 4 1 4 2 2 2 1 3 5% 70%	2905
	11th to 20th	Night	3 5% 3 9% 5% 3 3 3 4 5% 59%	2752
	21st to end	Night	3 3 2 3 2 1 2 2 3 4 75%	2762
June	1st to 10th	Night	5% 7% 2 4 3 3 3 3 5% 8% 58%	1520
	11th to 20th	Night	2 3 1 3 3 2 3 3 3 5% 72%	1520
	21st to end	Night	3 4 2 3 2 2 2 2 3 4 70%	1520
July	1st to 10th	Night	1 2 2 3 2 2 2 2 4 5% 76%	2540
	11th to 20th	Night	1 3 3 6% 4 3 2 2 3 5% 68%	2847
	21st to end	Night	1 6% 4 6% 4 2 4 4 6% 8% 56%	3109
August	1st to 10th	Night	2 5% 3 12% 5% 4 4 6% 5% 8% 45%	2848
	11th to 20th	Night	2 2 4 2 2 2 2 3 6% 73%	2926
	21st to end	Night	2 5% 3 8% 3 2 2 2 6% 6% 61%	3498
September	1st to 10th	Night	3 1 3 3 2 3 2 5% 7% 70%	1900
	11th to 20th	Night	5% 6% 2 6% 3 3 3 2 5% 7% 59%	1909
	21st to end	Night	3 5% 1 5% 2 2 2 2 5% 5% 68%	2175
October	1st to 10th	Night	3 4 1 3 3 2 2 2 4 6% 70%	3800
	11th to 20th	Night	6% 7% 3 7% 3 2 3 2 4 5% 58%	3777
	21st to end	Night	9% 4 2 4 3 3 4 3 5% 7% 58%	4121
November	1st to 10th	Night	10% 5% 2 4 3 3 3 3 5% 8% 54%	2323
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 7% 50%	2508
	21st to end	Night	10% 4 1 5% 3 3 3 2 5% 6% 56%	2660
December	1st to 10th	Night	20% 6% 3 5% 3 3 3 3 4 6% 44%	2660
	11th to 20th	Night	32% 7% 2 5% 3 3 4 3 5% 6% 32%	3276
	21st to end	Night	22% 8% 2 6% 4 4 4 3 4 5% 37%	4862

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	45% 5% 12% 27% 8% 3	2708
	11th to 20th	Day	55% 5% 10% 13% 10% 8%	2860
	21st to end	Day	53% 4 9% 18% 11% 5%	3146
February	1st to 10th	Day	42% 4 7% 19% 20% 8%	1710
	11th to 20th	Day	41% 5% 8% 20% 18% 7%	1706
	21st to end	Day	39% 5% 9% 25% 15% 7%	1570
March	1st to 10th	Day	57% 6% 8% 16% 12% 2	3436
	11th to 20th	Day	31% 5% 10% 30% 13% 11%	3490
	21st to end	Day	46% 8% 13% 21% 11% 2	3842
April	1st to 10th	Day	41% 5% 13% 21% 16% 4	2280
	11th to 20th	Day	33% 5% 14% 23% 19% 5%	2252
	21st to end	Day	24% 5% 14% 30% 23% 4	2280
May	1st to 10th	Day	17% 3 12% 31% 21% 16%	4063
	11th to 20th	Day	16% 3 7% 31% 31% 13%	4149
	21st to end	Day	15% 4 12% 38% 29% 3	4814
June	1st to 10th	Day	24% 5% 11% 29% 25% 6%	2660
	11th to 20th	Day	13% 3 10% 20% 38% 14%	2660
	21st to end	Day	14% 2 4 16% 36% 28%	2660
July	1st to 10th	Day	10% 1 3 7% 15% 63%	4351
	11th to 20th	Day	12% 2 5% 8% 20% 54%	4049
	21st to end	Day	12% 1 3 8% 29% 47%	4315
August	1st to 10th	Day	18% 2 5% 11% 27% 38%	4076
	11th to 20th	Day	9% 1 4 13% 42% 31%	3955
	21st to end	Day	17% 2 5% 14% 37% 27%	4179
September	1st to 10th	Day	11% 1 5% 11% 31% 41%	2280
	11th to 20th	Day	21% 3 6% 25% 34% 11%	2267
	21st to end	Day	14% 3 5% 22% 32% 24%	2005
October	1st to 10th	Day	16% 2 3 12% 25% 41%	3180
	11th to 20th	Day	23% 3 6% 22% 26% 20%	3161
	21st to end	Day	26% 4 8% 24% 26% 12%	3448
November	1st to 10th	Day	29% 5% 8% 28% 18% 11%	1913
	11th to 20th	Day	36% 5% 11% 23% 17% 9%	1671
	21st to end	Day	32% 4 11% 20% 19% 13%	1520
December	1st to 10th	Day	41% 6% 8% 18% 19% 9%	1520
	11th to 20th	Day	58% 3 7% 12% 15% 5%	1928
	21st to end	Day	49% 5% 13% 20% 9% 4	2794
January	1st to 10th	Night	41% 6% 19% 22% 8% 3	4237
	11th to 20th	Night	53% 7% 11% 12% 9% 8%	4110
	21st to end	Night	55% 5% 10% 12% 13% 6%	4521
February	1st to 10th	Night	38% 4 8% 20% 18% 11%	2470
	11th to 20th	Night	40% 5% 10% 19% 20% 7%	2371
	21st to end	Night	33% 4 11% 27% 20% 5%	1884
March	1st to 10th	Night	51% 8% 10% 14% 14% 2	3435
	11th to 20th	Night	32% 3 11% 22% 23% 10%	3490
	21st to end	Night	46% 6% 12% 23% 10% 3	3809
April	1st to 10th	Night	35% 6% 14% 21% 20% 5%	1900
	11th to 20th	Night	31% 4 13% 27% 17% 9%	1879
	21st to end	Night	24% 4 11% 31% 25% 6%	1900
May	1st to 10th	Night	19% 2 6% 27% 28% 17%	2905
	11th to 20th	Night	25% 3 8% 19% 27% 19%	2753
	21st to end	Night	15% 3 8% 40% 30% 5%	2762
June	1st to 10th	Night	24% 4 10% 23% 30% 8%	1520
	11th to 20th	Night	14% 2 8% 21% 36% 19%	1520
	21st to end	Night	19% 2 5% 12% 32% 31%	1520
July	1st to 10th	Night	12% 1 2 6% 17% 62%	2500
	11th to 20th	Night	21% 1 4 8% 15% 51%	2794
	21st to end	Night	25% 1 3 7% 21% 42%	3011
August	1st to 10th	Night	33% 1 3 12% 24% 27%	2839
	11th to 20th	Night	13% 1 4 10% 38% 33%	2953
	21st to end	Night	23% 1 5% 13% 32% 26%	3498
September	1st to 10th	Night	13% 2 5% 9% 31% 40%	1900
	11th to 20th	Night	25% 2 7% 18% 33% 15%	1909
	21st to end	Night	18% 2 4 21% 28% 27%	2175
October	1st to 10th	Night	17% 2 5% 10% 23% 44%	3800
	11th to 20th	Night	29% 2 6% 22% 20% 21%	3777
	21st to end	Night	26% 4 6% 22% 26% 17%	4121
November	1st to 10th	Night	30% 4 11% 26% 18% 11%	2323
	11th to 20th	Night	33% 4 12% 25% 17% 9%	2508
	21st to end	Night	30% 3 10% 20% 23% 14%	2660
December	1st to 10th	Night	42% 4 9% 16% 19% 10%	2660
	11th to 20th	Night	54% 4 9% 13% 15% 4	3276
	21st to end	Night	50% 6% 11% 18% 11% 4	4862

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	30% 13% 25% 18% 11% 4	284
	11th to 20th	Day	23% 12% 24% 24% 15% 2	370
	21st to end	Day	17% 12% 24% 28% 17% 2	407
February	1st to 10th	Day	19% 14% 20% 24% 19% 4	370
	11th to 20th	Day	19% 18% 27% 23% 12% 1	380
	21st to end	Day	17% 15% 26% 27% 14% 1	382
March	1st to 10th	Day	26% 18% 27% 20% 7% 2	460
	11th to 20th	Day	23% 15% 27% 20% 11% 4	460
	21st to end	Day	17% 19% 31% 23% 8% 1	506
April	1st to 10th	Day	16% 20% 27% 24% 9% 3	460
	11th to 20th	Day	14% 20% 28% 22% 11% 4	452
	21st to end	Day	8% 18% 30% 26% 12% 6%	460
May	1st to 10th	Day	11% 17% 30% 27% 12% 3	463
	11th to 20th	Day	10% 14% 29% 27% 15% 4	488
	21st to end	Day	10% 12% 25% 29% 18% 5%	529
June	1st to 10th	Day	9% 12% 25% 31% 16% 7%	490
	11th to 20th	Day	5% 12% 30% 37% 13% 4	490
	21st to end	Day	3 4 28% 35% 24% 6%	490
July	1st to 10th	Day	5% 4 20% 43% 22% 5%	486
	11th to 20th	Day	2 1 18% 43% 28% 8%	484
	21st to end	Day	1 2 12% 48% 29% 8%	531
August	1st to 10th	Day	3 4 21% 42% 23% 7%	487
	11th to 20th	Day	3 4 21% 36% 26% 9%	477
	21st to end	Day	4 2 20% 38% 28% 8%	539
September	1st to 10th	Day	2 4 20% 40% 26% 9%	490
	11th to 20th	Day	6% 8% 22% 34% 21% 8%	490
	21st to end	Day	5% 8% 21% 34% 25% 8%	490
October	1st to 10th	Day	6% 9% 23% 26% 24% 11%	490
	11th to 20th	Day	8% 8% 19% 29% 25% 11%	490
	21st to end	Day	13% 9% 18% 30% 24% 7%	539
November	1st to 10th	Day	11% 10% 18% 27% 27% 6%	467
	11th to 20th	Day	10% 9% 15% 27% 25% 14%	251
	21st to end	Day	10% 9% 24% 26% 20% 10%	180
December	1st to 10th	Day	18% 18% 14% 21% 18% 10%	180
	11th to 20th	Day	24% 12% 21% 18% 16% 8%	180
	21st to end	Day	20% 14% 23% 23% 16% 4	198
January	1st to 10th	Night	21% 6% 16% 29% 23% 4	760
	11th to 20th	Night	21% 6% 15% 33% 21% 4	760
	21st to end	Night	20% 6% 15% 33% 23% 4	836
February	1st to 10th	Night	20% 6% 14% 35% 23% 2	760
	11th to 20th	Night	17% 8% 19% 31% 22% 4	744
	21st to end	Night	16% 10% 20% 34% 18% 2	628
March	1st to 10th	Night	22% 10% 19% 27% 19% 3	760
	11th to 20th	Night	19% 7% 17% 32% 22% 3	760
	21st to end	Night	18% 8% 27% 29% 16% 3	836
April	1st to 10th	Night	13% 9% 25% 30% 20% 3	760
	11th to 20th	Night	11% 13% 22% 28% 21% 5%	751
	21st to end	Night	9% 11% 27% 25% 23% 5%	760
May	1st to 10th	Night	9% 7% 21% 32% 26% 4	602
	11th to 20th	Night	6% 4 20% 31% 35% 4	519
	21st to end	Night	7% 8% 21% 31% 29% 5%	411
June	1st to 10th	Night	8% 6% 21% 33% 29% 2	380
	11th to 20th	Night	4 5% 18% 43% 27% 2	380
	21st to end	Night	4 1 15% 39% 37% 3	380
July	1st to 10th	Night	3 1 9% 36% 45% 5%	370
	11th to 20th	Night	3 1 4 31% 47% 13%	540
	21st to end	Night	4 4 33% 49% 10%	624
August	1st to 10th	Night	5% 1 9% 31% 43% 11%	567
	11th to 20th	Night	2 1 8% 35% 45% 9%	626
	21st to end	Night	4 1 7% 33% 47% 8%	836
September	1st to 10th	Night	2 1 8% 31% 48% 10%	760
	11th to 20th	Night	6% 3 10% 35% 37% 9%	760
	21st to end	Night	5% 3 13% 32% 36% 11%	760
October	1st to 10th	Night	7% 4 14% 31% 34% 9%	760
	11th to 20th	Night	9% 3 13% 29% 38% 8%	760
	21st to end	Night	10% 4 11% 29% 33% 11%	836
November	1st to 10th	Night	11% 4 15% 29% 32% 8%	770
	11th to 20th	Night	14% 3 13% 35% 30% 6%	760
	21st to end	Night	11% 6% 16% 35% 27% 6%	760
December	1st to 10th	Night	22% 6% 13% 31% 22% 6%	760
	11th to 20th	Night	27% 6% 14% 29% 20% 3	760
	21st to end	Night	23% 7% 19% 32% 17% 2	836

Page generated at 2024-11-05 05:15:52. Version ac07

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