Quilchena Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quilchena Ranch clear sky chart from 2005-11-06 to 2024-09-29.

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	8% 9% 3 8% 6% 5% 5% 4 6% 7% 37%	101251
	Night	7% 11% 4 9% 6% 6% 6% 5% 6% 7% 34%	97028
Transparency	Day	43% 9% 15% 20% 11% 3	101007
	Night	45% 10% 16% 19% 8% 2	96918
Seeing	Day	16% 14% 24% 25% 16% 6%	15362
	Night	14% 9% 23% 33% 18% 3	23685

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	11% 18% 6% 15% 7% 5% 7% 4 6% 7% 14%	2219
	11th to 20th	Day	8% 15% 4 11% 8% 7% 6% 4 6% 8% 23%	2391
	21st to end	Day	10% 15% 6% 14% 8% 7% 6% 5% 7% 7% 15%	2794
February	1st to 10th	Day	9% 16% 5% 12% 8% 6% 6% 4 6% 7% 22%	1591
	11th to 20th	Day	5% 14% 5% 10% 7% 7% 6% 5% 8% 7% 26%	1665
	21st to end	Day	6% 14% 5% 13% 9% 6% 7% 6% 6% 6% 21%	1511
March	1st to 10th	Day	6% 15% 5% 13% 7% 6% 6% 5% 6% 7% 25%	3138
	11th to 20th	Day	3 9% 3 8% 7% 6% 7% 5% 8% 7% 37%	3391
	21st to end	Day	8% 13% 5% 11% 7% 6% 6% 5% 7% 8% 26%	4070
April	1st to 10th	Day	8% 12% 4 11% 7% 7% 7% 6% 8% 7% 24%	2280
	11th to 20th	Day	9% 12% 4 10% 6% 5% 5% 5% 7% 8% 29%	2252
	21st to end	Day	9% 12% 4 9% 6% 5% 6% 6% 7% 8% 28%	2644
May	1st to 10th	Day	7% 9% 3 7% 6% 5% 5% 5% 6% 8% 39%	4420
	11th to 20th	Day	6% 7% 3 9% 6% 6% 5% 5% 8% 12% 32%	4377
	21st to end	Day	13% 12% 4 10% 6% 6% 6% 4 7% 7% 25%	4813
June	1st to 10th	Day	14% 8% 3 8% 5% 5% 6% 4 6% 6% 33%	2932
	11th to 20th	Day	14% 9% 3 7% 7% 5% 5% 5% 6% 7% 32%	3040
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 4 6% 7% 43%	3015
July	1st to 10th	Day	4 4 1 5% 3 4 3 3 5% 6% 63%	4740
	11th to 20th	Day	3 2 1 3 2 3 3 3 4 5% 72%	4648
	21st to end	Day	5% 3 1 4 3 3 4 3 5% 7% 63%	4790
August	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 9% 61%	4401
	11th to 20th	Day	3 4 1 5% 5% 6% 5% 5% 7% 8% 51%	4247
	21st to end	Day	8% 4 2 5% 4 5% 6% 4 7% 9% 47%	4287
September	1st to 10th	Day	8% 5% 2 7% 4 4 4 3 5% 7% 51%	2280
	11th to 20th	Day	11% 6% 2 7% 5% 5% 4 4 5% 7% 42%	2280
	21st to end	Day	12% 7% 3 8% 5% 4 5% 5% 7% 8% 36%	2017
October	1st to 10th	Day	12% 10% 4 9% 5% 5% 4 4 5% 6% 37%	1800
	11th to 20th	Day	12% 10% 3 10% 6% 6% 5% 4 7% 7% 31%	1776
	21st to end	Day	13% 11% 4 9% 5% 5% 6% 5% 7% 8% 27%	1782
November	1st to 10th	Day	16% 14% 4 9% 6% 6% 7% 4 5% 6% 24%	1536
	11th to 20th	Day	10% 13% 4 10% 6% 6% 6% 5% 6% 8% 26%	1520
	21st to end	Day	10% 16% 4 9% 8% 6% 7% 4 6% 8% 22%	1463
December	1st to 10th	Day	7% 13% 5% 12% 11% 8% 8% 5% 6% 6% 19%	1330
	11th to 20th	Day	8% 12% 6% 13% 10% 8% 7% 5% 7% 7% 18%	1547
	21st to end	Day	8% 12% 5% 13% 9% 9% 8% 6% 7% 7% 16%	2264
January	1st to 10th	Night	11% 20% 6% 14% 8% 7% 6% 4 5% 7% 12%	4726
	11th to 20th	Night	9% 16% 5% 12% 8% 5% 6% 4 8% 8% 19%	4505
	21st to end	Night	9% 15% 6% 14% 9% 8% 7% 5% 6% 6% 16%	4862
February	1st to 10th	Night	9% 19% 6% 12% 7% 5% 5% 4 5% 6% 22%	2587
	11th to 20th	Night	4 13% 5% 10% 7% 6% 5% 4 7% 7% 30%	2402
	21st to end	Night	5% 12% 5% 14% 8% 6% 7% 4 7% 7% 25%	1942
March	1st to 10th	Night	4 12% 4 10% 7% 6% 7% 6% 7% 9% 27%	3736
	11th to 20th	Night	4 9% 2 6% 4 5% 5% 5% 7% 10% 43%	3587
	21st to end	Night	7% 12% 4 9% 6% 6% 6% 6% 7% 7% 31%	3583
April	1st to 10th	Night	6% 12% 3 7% 7% 7% 5% 6% 6% 7% 34%	1900
	11th to 20th	Night	7% 10% 3 8% 6% 5% 6% 6% 8% 7% 35%	1879
	21st to end	Night	5% 10% 3 7% 5% 6% 5% 5% 7% 9% 39%	1533
May	1st to 10th	Night	6% 9% 3 8% 6% 5% 4 3 5% 7% 43%	2540
	11th to 20th	Night	5% 7% 3 7% 5% 5% 6% 4 8% 10% 39%	2516
	21st to end	Night	7% 8% 4 10% 6% 6% 7% 5% 7% 7% 33%	2762
June	1st to 10th	Night	10% 8% 2 6% 6% 5% 7% 4 8% 9% 35%	1244
	11th to 20th	Night	8% 6% 3 7% 5% 6% 6% 6% 8% 10% 35%	1140
	21st to end	Night	5% 5% 2 6% 5% 4 4 4 7% 8% 50%	1160
July	1st to 10th	Night	3 3 2 5% 3 3 4 4 5% 7% 61%	2220
	11th to 20th	Night	3 2 1 2 2 2 2 3 4 6% 73%	2311
	21st to end	Night	3 2 1 3 2 3 4 4 5% 6% 67%	2762
August	1st to 10th	Night	2 2 1 3 3 4 5% 4 7% 8% 61%	2529
	11th to 20th	Night	3 2 1 5% 4 5% 5% 4 6% 9% 55%	2581
	21st to end	Night	7% 5% 2 5% 4 4 5% 5% 7% 10% 47%	3388
September	1st to 10th	Night	6% 3 1 4 4 4 4 3 5% 7% 58%	1900
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 7% 8% 49%	1900
	21st to end	Night	9% 7% 3 7% 5% 5% 4 4 6% 8% 43%	2126
October	1st to 10th	Night	9% 8% 3 7% 5% 5% 6% 4 5% 6% 43%	2160
	11th to 20th	Night	13% 9% 3 8% 6% 4 5% 4 5% 5% 37%	2183
	21st to end	Night	11% 11% 3 9% 5% 5% 5% 5% 6% 6% 33%	2574
November	1st to 10th	Night	15% 15% 4 9% 6% 5% 6% 4 6% 6% 24%	2540
	11th to 20th	Night	12% 12% 4 9% 7% 6% 6% 5% 7% 6% 25%	2660
	21st to end	Night	11% 17% 4 10% 6% 6% 6% 5% 6% 8% 22%	2694
December	1st to 10th	Night	8% 14% 5% 11% 8% 7% 6% 4 6% 7% 24%	2850
	11th to 20th	Night	10% 19% 7% 14% 9% 6% 5% 5% 5% 6% 15%	3640
	21st to end	Night	7% 13% 5% 14% 9% 8% 8% 7% 8% 6% 16%	5406

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	65% 11% 12% 10% 2	2219
	11th to 20th	Day	55% 10% 18% 11% 2 5%	2415
	21st to end	Day	61% 13% 14% 10% 2	2794
February	1st to 10th	Day	60% 10% 11% 13% 5% 1	1591
	11th to 20th	Day	52% 12% 16% 13% 7%	1674
	21st to end	Day	58% 9% 15% 14% 5%	1511
March	1st to 10th	Day	55% 10% 11% 17% 7%	3138
	11th to 20th	Day	39% 10% 20% 24% 6%	3391
	21st to end	Day	54% 10% 16% 11% 8%	4070
April	1st to 10th	Day	55% 10% 15% 17% 4	2280
	11th to 20th	Day	50% 9% 13% 16% 10% 1	2252
	21st to end	Day	52% 7% 16% 16% 9% 1	2644
May	1st to 10th	Day	42% 6% 15% 25% 11% 1	4420
	11th to 20th	Day	41% 11% 20% 21% 7%	4380
	21st to end	Day	56% 9% 16% 15% 4 1	4814
June	1st to 10th	Day	49% 8% 14% 17% 9% 4	2932
	11th to 20th	Day	50% 8% 13% 20% 7% 1	3040
	21st to end	Day	39% 7% 17% 22% 13% 2	3015
July	1st to 10th	Day	22% 6% 10% 20% 26% 16%	4666
	11th to 20th	Day	15% 4 10% 25% 30% 15%	4567
	21st to end	Day	20% 5% 15% 30% 21% 9%	4639
August	1st to 10th	Day	17% 7% 13% 30% 28% 5%	4384
	11th to 20th	Day	27% 9% 24% 26% 11% 2	4289
	21st to end	Day	31% 8% 20% 28% 11% 1	4286
September	1st to 10th	Day	32% 7% 16% 26% 16% 4	2280
	11th to 20th	Day	40% 7% 13% 23% 14% 3	2280
	21st to end	Day	42% 10% 19% 19% 9% 2	2017
October	1st to 10th	Day	46% 7% 16% 24% 6%	1800
	11th to 20th	Day	49% 9% 16% 21% 5%	1776
	21st to end	Day	52% 10% 17% 17% 4	1782
November	1st to 10th	Day	59% 9% 15% 14% 3	1536
	11th to 20th	Day	54% 10% 17% 14% 5%	1520
	21st to end	Day	57% 12% 13% 14% 4	1463
December	1st to 10th	Day	60% 11% 13% 14% 2	1330
	11th to 20th	Day	56% 18% 13% 9% 4	1548
	21st to end	Day	59% 15% 14% 11% 1	2264
January	1st to 10th	Night	66% 11% 13% 8% 2	4726
	11th to 20th	Night	58% 9% 15% 11% 3 5%	4543
	21st to end	Night	60% 16% 13% 8% 2	4862
February	1st to 10th	Night	61% 8% 13% 12% 6%	2587
	11th to 20th	Night	49% 9% 18% 16% 8%	2404
	21st to end	Night	55% 10% 13% 16% 6%	1942
March	1st to 10th	Night	47% 11% 15% 20% 8%	3736
	11th to 20th	Night	31% 10% 22% 29% 8%	3588
	21st to end	Night	49% 11% 16% 16% 9%	3583
April	1st to 10th	Night	46% 10% 22% 18% 5%	1900
	11th to 20th	Night	43% 10% 18% 20% 10%	1879
	21st to end	Night	39% 11% 20% 21% 9%	1533
May	1st to 10th	Night	40% 8% 14% 26% 12% 1	2540
	11th to 20th	Night	34% 13% 21% 26% 6%	2516
	21st to end	Night	45% 12% 21% 16% 5%	2762
June	1st to 10th	Night	41% 10% 17% 21% 8% 3	1244
	11th to 20th	Night	41% 9% 21% 21% 9%	1140
	21st to end	Night	31% 7% 23% 24% 13% 2	1160
July	1st to 10th	Night	21% 7% 12% 26% 19% 15%	2185
	11th to 20th	Night	13% 5% 11% 30% 34% 7%	2269
	21st to end	Night	17% 6% 16% 30% 17% 14%	2674
August	1st to 10th	Night	17% 8% 14% 27% 30% 4	2521
	11th to 20th	Night	22% 9% 28% 26% 11% 3	2605
	21st to end	Night	29% 9% 23% 26% 12% 1	3388
September	1st to 10th	Night	25% 7% 17% 31% 16% 3	1900
	11th to 20th	Night	33% 7% 17% 22% 16% 4	1900
	21st to end	Night	39% 8% 21% 20% 11% 2	2126
October	1st to 10th	Night	39% 8% 18% 25% 9%	2160
	11th to 20th	Night	46% 7% 17% 22% 8%	2183
	21st to end	Night	48% 8% 16% 22% 6%	2574
November	1st to 10th	Night	57% 9% 14% 14% 5%	2540
	11th to 20th	Night	54% 13% 15% 12% 5% 1	2660
	21st to end	Night	57% 11% 15% 12% 4	2694
December	1st to 10th	Night	56% 9% 15% 16% 4	2850
	11th to 20th	Night	66% 12% 11% 8% 3	3638
	21st to end	Night	57% 13% 14% 13% 3	5406

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	19% 13% 14% 29% 15% 9%	180
	11th to 20th	Day	14% 8% 16% 35% 22% 4	180
	21st to end	Day	15% 9% 21% 35% 16% 4	198
February	1st to 10th	Day	22% 16% 26% 26% 9% 2	251
	11th to 20th	Day	16% 16% 26% 24% 14% 4	365
	21st to end	Day	18% 19% 23% 25% 12% 4	355
March	1st to 10th	Day	22% 18% 22% 22% 13% 2	460
	11th to 20th	Day	18% 19% 25% 16% 15% 7%	460
	21st to end	Day	19% 23% 25% 16% 13% 4	506
April	1st to 10th	Day	21% 22% 25% 20% 9% 3	460
	11th to 20th	Day	19% 23% 21% 21% 11% 6%	452
	21st to end	Day	23% 16% 28% 17% 11% 4	460
May	1st to 10th	Day	16% 16% 26% 25% 13% 4	463
	11th to 20th	Day	16% 12% 22% 26% 18% 6%	488
	21st to end	Day	17% 13% 26% 24% 14% 6%	529
June	1st to 10th	Day	18% 17% 29% 21% 13% 2	762
	11th to 20th	Day	20% 16% 24% 23% 14% 3	870
	21st to end	Day	13% 13% 23% 27% 18% 7%	845
July	1st to 10th	Day	10% 14% 27% 28% 16% 5%	671
	11th to 20th	Day	8% 15% 27% 28% 17% 6%	615
	21st to end	Day	6% 8% 26% 29% 22% 8%	531
August	1st to 10th	Day	7% 6% 24% 28% 25% 11%	487
	11th to 20th	Day	8% 8% 23% 29% 22% 11%	477
	21st to end	Day	12% 11% 26% 25% 17% 9%	539
September	1st to 10th	Day	12% 12% 22% 24% 21% 10%	490
	11th to 20th	Day	15% 12% 22% 25% 19% 7%	490
	21st to end	Day	19% 13% 24% 23% 15% 6%	483
October	1st to 10th	Day	22% 11% 23% 20% 13% 13%	450
	11th to 20th	Day	23% 16% 15% 21% 18% 7%	426
	21st to end	Day	25% 12% 21% 27% 10% 5%	297
November	1st to 10th	Day	24% 11% 20% 29% 13% 3	204
	11th to 20th	Day	21% 14% 19% 23% 14% 8%	180
	21st to end	Day	19% 9% 23% 24% 17% 8%	180
December	1st to 10th	Day	16% 6% 15% 32% 21% 11%	180
	11th to 20th	Day	18% 9% 21% 30% 14% 7%	180
	21st to end	Day	12% 6% 23% 41% 15% 3	198
January	1st to 10th	Night	24% 10% 23% 29% 12% 2	850
	11th to 20th	Night	16% 9% 23% 36% 14% 2	793
	21st to end	Night	13% 9% 25% 36% 14% 3	836
February	1st to 10th	Night	19% 10% 24% 34% 11% 3	760
	11th to 20th	Night	11% 7% 26% 39% 16% 2	744
	21st to end	Night	11% 11% 22% 33% 21% 2	628
March	1st to 10th	Night	14% 11% 25% 29% 18% 2	760
	11th to 20th	Night	13% 16% 25% 28% 16% 2	760
	21st to end	Night	14% 13% 25% 29% 16% 3	836
April	1st to 10th	Night	13% 12% 20% 35% 18% 2	760
	11th to 20th	Night	11% 13% 26% 30% 18% 2	751
	21st to end	Night	11% 13% 23% 38% 13% 3	393
May	1st to 10th	Night	12% 12% 22% 37% 15% 3	380
	11th to 20th	Night	7% 8% 22% 34% 26% 2	374
	21st to end	Night	12% 7% 25% 33% 21% 2	411
June	1st to 10th	Night	13% 10% 28% 35% 12% 2	380
	11th to 20th	Night	12% 9% 30% 32% 16% 2	380
	21st to end	Night	7% 8% 27% 36% 19% 3	380
July	1st to 10th	Night	7% 6% 23% 41% 22% 1	370
	11th to 20th	Night	5% 7% 25% 40% 22% 1	368
	21st to end	Night	3 3 25% 39% 26% 4	416
August	1st to 10th	Night	3 3 14% 38% 37% 4	378
	11th to 20th	Night	5% 3 17% 37% 35% 4	421
	21st to end	Night	8% 6% 20% 35% 28% 3	765
September	1st to 10th	Night	8% 7% 18% 35% 26% 6%	760
	11th to 20th	Night	10% 6% 17% 28% 31% 8%	760
	21st to end	Night	13% 11% 21% 31% 20% 4	756
October	1st to 10th	Night	14% 7% 17% 36% 22% 4	720
	11th to 20th	Night	19% 10% 19% 29% 20% 3	720
	21st to end	Night	19% 11% 23% 31% 14% 3	792
November	1st to 10th	Night	23% 10% 20% 36% 9% 1	740
	11th to 20th	Night	19% 12% 28% 26% 13% 1	760
	21st to end	Night	18% 11% 24% 32% 12% 3	794
December	1st to 10th	Night	13% 8% 24% 35% 16% 3	950
	11th to 20th	Night	18% 11% 26% 33% 11% 1	990
	21st to end	Night	16% 10% 24% 37% 11% 1	1049

Page generated at 2024-09-26 06:52:19. Version ac07

Copyright © 2024 Attilla Danko.