My-Spot West Observatory
Clear Sky Chart
History

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

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	4 6% 2 6% 4 4 5% 4 7% 8% 49%	105839
	Night	3 6% 2 6% 4 4 4 4 6% 9% 52%	102045
Transparency	Day	30% 8% 14% 24% 18% 7%	105589
	Night	27% 7% 16% 26% 18% 6%	101886
Seeing	Day	9% 13% 36% 30% 11% 2	15834
	Night	7% 7% 37% 37% 11% 1	25598

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	1 5% 3 7% 4 5% 6% 4 7% 10% 47%	2538
	11th to 20th	Day	3 2 8% 6% 6% 6% 6% 8% 11% 44%	2682
	21st to end	Day	1 4 3 5% 4 4 4 4 6% 8% 57%	3146
February	1st to 10th	Day	1 6% 3 9% 5% 4 6% 5% 8% 9% 43%	1710
	11th to 20th	Day	1 6% 3 10% 6% 5% 4 4 5% 8% 45%	1665
	21st to end	Day	1 6% 4 6% 7% 5% 5% 5% 8% 10% 44%	1437
March	1st to 10th	Day	1 4 3 7% 4 4 5% 4 8% 12% 49%	3434
	11th to 20th	Day	1 9% 3 7% 6% 4 4 4 6% 8% 48%	3490
	21st to end	Day	6% 12% 4 10% 7% 5% 7% 5% 7% 9% 28%	3825
April	1st to 10th	Day	5% 11% 3 8% 4 4 5% 5% 7% 11% 37%	2264
	11th to 20th	Day	6% 11% 4 8% 6% 5% 5% 5% 6% 7% 36%	2300
	21st to end	Day	10% 11% 4 7% 6% 5% 5% 5% 6% 8% 33%	2470
May	1st to 10th	Day	10% 15% 4 10% 6% 6% 5% 5% 5% 7% 28%	4169
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 5% 8% 9% 44%	4388
	21st to end	Day	9% 10% 3 7% 5% 5% 6% 5% 7% 8% 33%	4825
June	1st to 10th	Day	7% 5% 2 6% 5% 5% 6% 5% 9% 9% 40%	2660
	11th to 20th	Day	6% 5% 2 5% 5% 5% 6% 5% 8% 9% 45%	2688
	21st to end	Day	2 3 1 4 4 4 5% 5% 7% 8% 58%	2850
July	1st to 10th	Day	3 2 1 4 4 5% 6% 5% 8% 9% 53%	4568
	11th to 20th	Day	2 2 1 3 4 4 6% 5% 8% 9% 57%	4430
	21st to end	Day	3 3 1 5% 4 5% 6% 5% 8% 8% 53%	4593
August	1st to 10th	Day	6% 5% 2 6% 4 5% 5% 5% 7% 8% 47%	4092
	11th to 20th	Day	3 2 1 4 4 5% 6% 5% 8% 8% 54%	4028
	21st to end	Day	3 3 1 4 3 3 4 4 5% 6% 64%	4376
September	1st to 10th	Day	5% 3 1 4 4 3 3 4 5% 7% 60%	2280
	11th to 20th	Day	7% 4 2 4 3 3 4 4 5% 7% 59%	2192
	21st to end	Day	7% 4 2 5% 3 3 4 3 4 7% 58%	2052
October	1st to 10th	Day	6% 5% 2 5% 2 3 3 2 3 4 65%	3170
	11th to 20th	Day	5% 6% 2 3 3 3 3 3 4 6% 62%	3150
	21st to end	Day	3 9% 2 6% 4 4 4 3 6% 8% 51%	3438
November	1st to 10th	Day	3 7% 2 7% 5% 5% 6% 5% 7% 6% 48%	1649
	11th to 20th	Day	1 6% 3 6% 4 5% 5% 4 7% 9% 50%	1520
	21st to end	Day	2 7% 3 7% 4 4 3 3 6% 9% 52%	1520
December	1st to 10th	Day	1 5% 3 8% 4 4 4 5% 7% 9% 52%	1520
	11th to 20th	Day	1 4 2 6% 4 3 5% 5% 8% 10% 50%	1926
	21st to end	Day	2 7% 2 6% 4 4 4 4 6% 8% 54%	2794
January	1st to 10th	Night	3 3 7% 5% 5% 6% 4 8% 11% 48%	4417
	11th to 20th	Night	3 2 9% 8% 6% 5% 5% 7% 9% 47%	4304
	21st to end	Night	1 7% 3 7% 4 5% 4 3 6% 9% 51%	4521
February	1st to 10th	Night	1 5% 3 10% 5% 5% 6% 5% 6% 7% 46%	2470
	11th to 20th	Night	1 6% 4 8% 6% 5% 5% 4 7% 8% 46%	2402
	21st to end	Night	5% 4 10% 4 4 5% 5% 7% 8% 49%	2015
March	1st to 10th	Night	1 7% 2 6% 4 4 4 4 6% 10% 53%	3436
	11th to 20th	Night	2 7% 2 6% 4 4 4 4 7% 11% 50%	3490
	21st to end	Night	5% 9% 4 8% 5% 5% 5% 5% 7% 11% 36%	3828
April	1st to 10th	Night	4 11% 3 6% 4 5% 5% 4 8% 7% 44%	1915
	11th to 20th	Night	6% 11% 3 8% 6% 4 4 4 6% 8% 39%	1823
	21st to end	Night	7% 12% 3 7% 5% 4 4 4 6% 8% 41%	1710
May	1st to 10th	Night	11% 13% 4 7% 4 4 3 4 6% 7% 38%	2801
	11th to 20th	Night	7% 6% 2 5% 3 3 5% 4 5% 7% 53%	2517
	21st to end	Night	12% 7% 2 6% 4 5% 6% 4 7% 9% 38%	2762
June	1st to 10th	Night	7% 5% 2 5% 4 5% 6% 5% 7% 9% 46%	1520
	11th to 20th	Night	6% 4 1 4 4 5% 5% 4 5% 9% 53%	1481
	21st to end	Night	2 3 2 4 4 3 4 3 6% 6% 64%	1330
July	1st to 10th	Night	2 2 1 3 3 3 3 4 6% 9% 64%	2379
	11th to 20th	Night	1 1 1 2 3 4 4 4 9% 10% 60%	2540
	21st to end	Night	2 2 1 3 2 3 4 4 7% 8% 63%	2967
August	1st to 10th	Night	5% 4 2 4 3 4 4 4 7% 8% 54%	2847
	11th to 20th	Night	3 2 1 4 3 4 5% 5% 7% 9% 56%	2811
	21st to end	Night	3 3 1 3 2 2 3 3 5% 5% 70%	3291
September	1st to 10th	Night	5% 3 1 3 3 3 3 3 4 7% 64%	1900
	11th to 20th	Night	6% 4 2 4 3 2 3 4 5% 8% 61%	1985
	21st to end	Night	8% 5% 2 4 3 3 3 2 4 6% 61%	2126
October	1st to 10th	Night	6% 4 1 4 2 2 2 2 4 6% 67%	3800
	11th to 20th	Night	6% 6% 2 5% 4 4 3 3 4 6% 57%	3778
	21st to end	Night	5% 7% 3 5% 4 3 4 3 5% 7% 54%	4120
November	1st to 10th	Night	3 5% 2 6% 4 4 4 4 7% 10% 51%	2628
	11th to 20th	Night	2 6% 2 6% 4 4 4 4 7% 9% 51%	2667
	21st to end	Night	3 8% 3 5% 4 4 4 4 6% 9% 50%	2660
December	1st to 10th	Night	1 6% 3 6% 5% 4 4 4 8% 10% 50%	2660
	11th to 20th	Night	1 5% 2 6% 4 4 4 4 7% 12% 52%	3271
	21st to end	Night	1 6% 2 7% 5% 3 4 4 7% 8% 53%	4873

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	28% 9% 16% 29% 16% 2	2539
	11th to 20th	Day	24% 13% 22% 23% 16% 2	2682
	21st to end	Day	22% 9% 23% 29% 16% 2	3146
February	1st to 10th	Day	33% 10% 20% 25% 11% 1	1710
	11th to 20th	Day	36% 8% 19% 21% 12% 3	1674
	21st to end	Day	32% 9% 18% 23% 14% 4	1437
March	1st to 10th	Day	23% 9% 18% 29% 16% 5%	3434
	11th to 20th	Day	29% 10% 20% 31% 9% 1	3490
	21st to end	Day	43% 15% 18% 20% 3	3825
April	1st to 10th	Day	39% 9% 17% 24% 10% 1	2264
	11th to 20th	Day	43% 8% 18% 23% 7%	2303
	21st to end	Day	46% 9% 15% 22% 8%	2470
May	1st to 10th	Day	50% 9% 12% 18% 8% 3	4169
	11th to 20th	Day	31% 11% 15% 27% 12% 4	4392
	21st to end	Day	41% 11% 16% 21% 10% 1	4825
June	1st to 10th	Day	34% 11% 20% 21% 12% 2	2660
	11th to 20th	Day	31% 10% 15% 19% 19% 5%	2688
	21st to end	Day	21% 8% 13% 25% 21% 13%	2850
July	1st to 10th	Day	24% 5% 8% 24% 31% 8%	4499
	11th to 20th	Day	21% 4 6% 19% 29% 21%	4355
	21st to end	Day	26% 4 6% 17% 33% 14%	4448
August	1st to 10th	Day	33% 4 10% 21% 18% 14%	4078
	11th to 20th	Day	26% 4 9% 27% 24% 11%	4067
	21st to end	Day	20% 4 7% 22% 33% 15%	4375
September	1st to 10th	Day	23% 5% 8% 20% 31% 13%	2280
	11th to 20th	Day	25% 5% 10% 26% 27% 7%	2192
	21st to end	Day	26% 4 11% 27% 25% 6%	2052
October	1st to 10th	Day	25% 4 7% 16% 31% 17%	3170
	11th to 20th	Day	25% 4 10% 33% 21% 7%	3150
	21st to end	Day	30% 4 11% 34% 19% 3	3438
November	1st to 10th	Day	32% 8% 15% 22% 19% 3	1649
	11th to 20th	Day	28% 9% 19% 25% 17% 3	1520
	21st to end	Day	29% 7% 17% 26% 18% 2	1520
December	1st to 10th	Day	26% 9% 20% 25% 15% 4	1520
	11th to 20th	Day	22% 10% 26% 30% 11% 1	1924
	21st to end	Day	26% 6% 13% 26% 20% 9%	2794
January	1st to 10th	Night	26% 10% 19% 26% 18% 1	4417
	11th to 20th	Night	30% 9% 23% 21% 13% 4	4304
	21st to end	Night	26% 8% 21% 30% 13% 2	4521
February	1st to 10th	Night	32% 9% 21% 27% 9% 2	2470
	11th to 20th	Night	32% 9% 19% 23% 13% 3	2403
	21st to end	Night	30% 8% 18% 23% 18% 3	2015
March	1st to 10th	Night	23% 7% 16% 27% 20% 7%	3436
	11th to 20th	Night	23% 9% 22% 32% 12% 2	3490
	21st to end	Night	36% 11% 23% 24% 6% 1	3828
April	1st to 10th	Night	35% 9% 20% 23% 11% 2	1915
	11th to 20th	Night	40% 8% 19% 23% 9% 1	1823
	21st to end	Night	40% 7% 15% 29% 9%	1710
May	1st to 10th	Night	43% 7% 12% 22% 13% 4	2801
	11th to 20th	Night	26% 9% 17% 36% 10% 2	2518
	21st to end	Night	33% 11% 20% 25% 11%	2762
June	1st to 10th	Night	31% 10% 20% 22% 15% 1	1520
	11th to 20th	Night	25% 8% 19% 24% 17% 7%	1481
	21st to end	Night	19% 6% 12% 30% 22% 11%	1330
July	1st to 10th	Night	16% 4 11% 33% 30% 6%	2340
	11th to 20th	Night	15% 3 6% 26% 36% 14%	2492
	21st to end	Night	17% 3 6% 21% 36% 17%	2874
August	1st to 10th	Night	26% 4 12% 23% 24% 11%	2838
	11th to 20th	Night	22% 3 8% 32% 20% 13%	2838
	21st to end	Night	16% 3 7% 24% 32% 18%	3291
September	1st to 10th	Night	19% 4 9% 22% 32% 14%	1900
	11th to 20th	Night	22% 5% 12% 26% 26% 9%	1985
	21st to end	Night	25% 4 10% 28% 27% 6%	2126
October	1st to 10th	Night	21% 4 8% 23% 31% 14%	3800
	11th to 20th	Night	29% 4 9% 31% 23% 4	3778
	21st to end	Night	31% 5% 9% 27% 20% 8%	4120
November	1st to 10th	Night	27% 9% 16% 27% 17% 3	2628
	11th to 20th	Night	26% 8% 21% 28% 15% 2	2667
	21st to end	Night	29% 6% 18% 27% 17% 3	2660
December	1st to 10th	Night	26% 8% 23% 25% 15% 4	2660
	11th to 20th	Night	23% 10% 23% 31% 13% 1	3272
	21st to end	Night	26% 8% 14% 26% 16% 10%	4873

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	7% 12% 37% 29% 13% 2	270
	11th to 20th	Day	3 11% 48% 23% 11% 4	270
	21st to end	Day	6% 15% 44% 27% 7% 1	297
February	1st to 10th	Day	6% 21% 51% 20% 1	270
	11th to 20th	Day	5% 24% 43% 21% 7%	270
	21st to end	Day	8% 21% 42% 22% 8%	225
March	1st to 10th	Day	6% 22% 46% 23% 2	450
	11th to 20th	Day	7% 20% 42% 24% 5% 1	460
	21st to end	Day	13% 19% 37% 25% 6%	506
April	1st to 10th	Day	13% 23% 38% 23% 3	460
	11th to 20th	Day	14% 22% 39% 22% 3	452
	21st to end	Day	18% 17% 31% 25% 7% 1	460
May	1st to 10th	Day	14% 16% 33% 24% 11% 2	496
	11th to 20th	Day	17% 10% 27% 31% 13% 2	675
	21st to end	Day	16% 11% 28% 27% 15% 3	734
June	1st to 10th	Day	7% 13% 30% 32% 15% 3	680
	11th to 20th	Day	10% 15% 34% 30% 9% 1	680
	21st to end	Day	4 10% 34% 36% 15% 2	680
July	1st to 10th	Day	4 7% 29% 35% 22% 4	671
	11th to 20th	Day	3 5% 32% 43% 15% 1	668
	21st to end	Day	4 5% 36% 35% 17% 2	618
August	1st to 10th	Day	8% 6% 37% 36% 11% 2	487
	11th to 20th	Day	4 7% 31% 39% 15% 3	477
	21st to end	Day	5% 9% 35% 36% 13% 3	539
September	1st to 10th	Day	7% 8% 37% 34% 11% 3	490
	11th to 20th	Day	10% 11% 33% 31% 11% 4	490
	21st to end	Day	9% 13% 35% 30% 11% 2	452
October	1st to 10th	Day	9% 13% 28% 33% 14% 3	300
	11th to 20th	Day	13% 13% 30% 29% 11% 4	300
	21st to end	Day	10% 18% 39% 26% 6% 2	330
November	1st to 10th	Day	8% 17% 40% 24% 7% 4	300
	11th to 20th	Day	11% 13% 40% 28% 6% 1	270
	21st to end	Day	10% 13% 40% 31% 4	270
December	1st to 10th	Day	4 15% 46% 24% 9% 1	270
	11th to 20th	Day	7% 14% 48% 27% 4	270
	21st to end	Day	5% 12% 48% 24% 10% 1	297
January	1st to 10th	Night	3 11% 42% 35% 8% 1	950
	11th to 20th	Night	4 10% 52% 23% 9% 3	876
	21st to end	Night	4 8% 51% 29% 6% 1	836
February	1st to 10th	Night	5% 8% 52% 28% 6%	760
	11th to 20th	Night	5% 9% 47% 29% 8% 1	744
	21st to end	Night	2 12% 47% 30% 8% 1	628
March	1st to 10th	Night	4 11% 43% 33% 8%	760
	11th to 20th	Night	5% 8% 44% 35% 8%	760
	21st to end	Night	7% 8% 37% 40% 6% 1	836
April	1st to 10th	Night	9% 8% 44% 31% 8%	585
	11th to 20th	Night	12% 9% 41% 32% 6% 1	563
	21st to end	Night	13% 8% 34% 32% 12% 1	570
May	1st to 10th	Night	16% 8% 25% 36% 15%	570
	11th to 20th	Night	14% 6% 21% 41% 17% 1	561
	21st to end	Night	17% 6% 22% 38% 16% 1	617
June	1st to 10th	Night	8% 6% 25% 39% 19% 2	570
	11th to 20th	Night	7% 8% 34% 41% 10%	531
	21st to end	Night	4 2 21% 52% 21% 1	380
July	1st to 10th	Night	3 1 15% 53% 27% 1	460
	11th to 20th	Night	1 3 24% 55% 17%	552
	21st to end	Night	2 2 21% 53% 22% 1	624
August	1st to 10th	Night	4 2 16% 57% 20%	567
	11th to 20th	Night	4 3 15% 55% 21% 1	564
	21st to end	Night	5% 2 25% 44% 22% 2	627
September	1st to 10th	Night	6% 2 25% 48% 17% 2	570
	11th to 20th	Night	7% 4 23% 47% 16% 4	655
	21st to end	Night	11% 3 27% 39% 17% 2	760
October	1st to 10th	Night	14% 4 28% 38% 14% 2	760
	11th to 20th	Night	8% 6% 38% 32% 14% 2	760
	21st to end	Night	7% 6% 46% 32% 8% 1	836
November	1st to 10th	Night	6% 8% 45% 33% 8% 1	918
	11th to 20th	Night	6% 11% 49% 30% 4 1	953
	21st to end	Night	7% 8% 42% 36% 6%	950
December	1st to 10th	Night	4 11% 47% 30% 7% 1	950
	11th to 20th	Night	3 9% 50% 31% 7% 1	950
	21st to end	Night	4 8% 50% 30% 7% 1	1045

Page generated at 2024-11-08 04:44:52. Version ac07

Copyright © 2024 Attilla Danko.