Geraldton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Geraldton clear sky chart from 2005-11-06 to 2024-11-10.

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	15% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	101880
	Night	14% 13% 4 10% 6% 6% 5% 4 5% 6% 27%	97424
Transparency	Day	53% 6% 11% 20% 9% 1	105292
	Night	56% 6% 12% 18% 7% 1	102099
Seeing	Day	22% 15% 33% 20% 8% 2	15779
	Night	20% 12% 33% 25% 9% 1	25128

By Month

Percentage Cloud Cover NE (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% 12% 12% 14% 7% 4 7% 4 9%	2316
	11th to 20th	Day	6% 9% 6% 16% 10% 10% 8% 5% 7% 6% 16%	2530
	21st to end	Day	13% 18% 11% 14% 7% 6% 6% 5% 6% 6% 9%	2783
February	1st to 10th	Day	6% 14% 5% 10% 8% 8% 9% 6% 7% 7% 21%	1520
	11th to 20th	Day	6% 12% 6% 13% 10% 7% 6% 5% 7% 7% 23%	1696
	21st to end	Day	6% 13% 5% 14% 8% 6% 6% 5% 5% 7% 25%	1570
March	1st to 10th	Day	12% 13% 4 11% 7% 5% 5% 3 4 4 33%	3118
	11th to 20th	Day	9% 18% 6% 11% 7% 7% 4 3 4 5% 26%	3274
	21st to end	Day	15% 17% 4 11% 5% 5% 4 3 3 4 29%	4128
April	1st to 10th	Day	13% 14% 5% 9% 6% 5% 4 4 5% 6% 29%	2280
	11th to 20th	Day	18% 15% 4 8% 5% 4 3 3 5% 5% 29%	2366
	21st to end	Day	16% 13% 4 7% 4 4 3 3 5% 6% 35%	2470
May	1st to 10th	Day	18% 13% 4 8% 5% 4 4 3 4 6% 31%	4423
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 4 5% 7% 34%	4399
	21st to end	Day	21% 9% 2 5% 4 4 4 4 5% 8% 34%	5184
June	1st to 10th	Day	22% 9% 2 7% 6% 5% 4 4 5% 5% 31%	2850
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 4 6% 7% 37%	2850
	21st to end	Day	18% 7% 2 7% 5% 4 4 4 6% 8% 35%	2850
July	1st to 10th	Day	14% 6% 2 7% 4 5% 5% 4 7% 8% 38%	4760
	11th to 20th	Day	11% 5% 2 7% 4 4 5% 4 6% 9% 44%	4542
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 8% 9% 37%	4814
August	1st to 10th	Day	18% 6% 2 6% 4 5% 5% 4 6% 8% 34%	4423
	11th to 20th	Day	13% 4 1 6% 3 4 5% 3 6% 9% 46%	4231
	21st to end	Day	14% 7% 2 6% 4 5% 5% 4 5% 8% 40%	4382
September	1st to 10th	Day	17% 6% 2 8% 5% 5% 4 3 4 7% 38%	2280
	11th to 20th	Day	24% 10% 3 5% 3 4 5% 3 5% 7% 30%	2152
	21st to end	Day	20% 12% 3 7% 5% 3 4 3 4 7% 31%	2090
October	1st to 10th	Day	19% 16% 4 7% 5% 3 4 4 4 7% 27%	2014
	11th to 20th	Day	22% 20% 4 9% 5% 5% 3 4 6% 6% 18%	1730
	21st to end	Day	20% 22% 6% 9% 5% 5% 5% 3 4 5% 15%	1881
November	1st to 10th	Day	17% 16% 7% 13% 6% 5% 5% 4 4 5% 17%	1753
	11th to 20th	Day	16% 21% 7% 15% 10% 6% 4 2 4 4 12%	1459
	21st to end	Day	17% 20% 8% 16% 8% 6% 4 2 4 4 11%	1330
December	1st to 10th	Day	10% 16% 7% 16% 12% 8% 7% 4 5% 4 12%	1330
	11th to 20th	Day	10% 15% 5% 13% 10% 9% 7% 5% 6% 6% 14%	1671
	21st to end	Day	18% 23% 6% 13% 9% 7% 5% 3 4 3 10%	2431
January	1st to 10th	Night	10% 16% 5% 13% 8% 11% 8% 6% 7% 6% 12%	4638
	11th to 20th	Night	5% 11% 6% 16% 13% 10% 9% 6% 6% 5% 12%	4440
	21st to end	Night	9% 17% 8% 14% 8% 7% 8% 6% 6% 5% 13%	4884
February	1st to 10th	Night	7% 13% 5% 10% 7% 6% 8% 6% 8% 6% 23%	2660
	11th to 20th	Night	8% 12% 5% 10% 9% 9% 7% 5% 6% 7% 22%	2368
	21st to end	Night	6% 13% 6% 12% 7% 6% 8% 6% 7% 5% 25%	1884
March	1st to 10th	Night	12% 10% 4 13% 7% 6% 6% 4 6% 7% 27%	3722
	11th to 20th	Night	9% 15% 6% 12% 7% 5% 4 3 4 6% 29%	3685
	21st to end	Night	14% 13% 5% 10% 6% 6% 5% 3 4 5% 30%	3532
April	1st to 10th	Night	14% 14% 4 9% 6% 5% 5% 4 6% 5% 29%	1900
	11th to 20th	Night	18% 12% 4 9% 5% 4 4 4 5% 7% 29%	1763
	21st to end	Night	17% 12% 3 6% 5% 3 4 4 5% 6% 36%	1710
May	1st to 10th	Night	18% 12% 3 6% 4 4 4 3 5% 7% 34%	2525
	11th to 20th	Night	15% 8% 3 8% 4 5% 5% 3 6% 7% 36%	2506
	21st to end	Night	19% 10% 2 6% 4 3 3 3 5% 6% 39%	2402
June	1st to 10th	Night	17% 6% 2 7% 4 4 5% 4 6% 8% 37%	1330
	11th to 20th	Night	16% 5% 2 5% 4 5% 5% 4 6% 7% 39%	1330
	21st to end	Night	16% 8% 3 6% 5% 4 4 4 6% 6% 37%	1330
July	1st to 10th	Night	12% 5% 2 6% 4 5% 5% 4 6% 9% 41%	2210
	11th to 20th	Night	11% 7% 2 6% 4 3 4 4 6% 9% 44%	2424
	21st to end	Night	11% 6% 2 6% 4 4 4 4 6% 8% 44%	2750
August	1st to 10th	Night	15% 6% 2 6% 4 4 3 4 5% 8% 42%	2517
	11th to 20th	Night	11% 6% 2 5% 3 3 3 3 4 7% 53%	2604
	21st to end	Night	12% 6% 2 6% 4 3 4 4 5% 7% 48%	3270
September	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 6% 6% 44%	1900
	11th to 20th	Night	19% 9% 3 5% 4 3 4 3 5% 6% 39%	2009
	21st to end	Night	24% 9% 3 6% 3 3 4 3 6% 6% 33%	2090
October	1st to 10th	Night	20% 15% 2 6% 4 4 3 3 4 6% 32%	2163
	11th to 20th	Night	20% 19% 5% 9% 4 4 4 2 5% 6% 21%	2449
	21st to end	Night	20% 17% 6% 11% 5% 5% 5% 4 5% 5% 17%	2717
November	1st to 10th	Night	17% 19% 6% 12% 7% 4 5% 3 5% 5% 18%	2530
	11th to 20th	Night	17% 17% 6% 14% 9% 5% 6% 3 4 5% 14%	2720
	21st to end	Night	16% 19% 5% 16% 8% 7% 4 3 4 4 13%	2850
December	1st to 10th	Night	9% 19% 6% 18% 10% 8% 6% 4 4 5% 12%	2850
	11th to 20th	Night	12% 17% 5% 13% 7% 7% 7% 6% 5% 5% 17%	3526
	21st to end	Night	18% 22% 5% 13% 9% 5% 4 3 4 4 12%	5236

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	75% 5% 9% 8% 3	2317
	11th to 20th	Day	65% 6% 10% 16% 3	2530
	21st to end	Day	73% 5% 8% 8% 5%	2783
February	1st to 10th	Day	59% 6% 10% 17% 7% 2	1520
	11th to 20th	Day	59% 5% 10% 19% 7%	1705
	21st to end	Day	58% 4 9% 16% 11% 2	1570
March	1st to 10th	Day	55% 5% 7% 17% 15% 1	3120
	11th to 20th	Day	62% 4 7% 19% 7% 1	3274
	21st to end	Day	60% 4 7% 16% 13% 1	4128
April	1st to 10th	Day	56% 5% 8% 19% 10% 1	2280
	11th to 20th	Day	56% 5% 8% 20% 10% 1	2366
	21st to end	Day	50% 5% 10% 17% 16% 2	2470
May	1st to 10th	Day	53% 5% 8% 20% 13% 1	4435
	11th to 20th	Day	48% 7% 9% 20% 14% 2	4403
	21st to end	Day	47% 8% 12% 19% 14% 1	5184
June	1st to 10th	Day	53% 6% 10% 18% 11% 1	2850
	11th to 20th	Day	45% 7% 11% 24% 14% 1	2850
	21st to end	Day	46% 7% 13% 25% 9%	2850
July	1st to 10th	Day	41% 8% 15% 27% 9% 1	4686
	11th to 20th	Day	35% 9% 18% 28% 10% 1	4463
	21st to end	Day	40% 8% 14% 30% 8%	4662
August	1st to 10th	Day	44% 8% 14% 25% 8%	4408
	11th to 20th	Day	34% 7% 18% 33% 8%	4273
	21st to end	Day	41% 8% 12% 28% 11%	4381
September	1st to 10th	Day	46% 7% 13% 25% 10%	2280
	11th to 20th	Day	52% 8% 18% 18% 4	2152
	21st to end	Day	54% 6% 13% 20% 7%	2090
October	1st to 10th	Day	52% 7% 15% 16% 11%	3352
	11th to 20th	Day	57% 6% 13% 23% 2	2855
	21st to end	Day	64% 6% 15% 13% 1	3081
November	1st to 10th	Day	68% 6% 11% 12% 2	1753
	11th to 20th	Day	78% 5% 8% 7% 3	1459
	21st to end	Day	78% 5% 8% 6% 3	1330
December	1st to 10th	Day	74% 6% 9% 8% 3	1330
	11th to 20th	Day	69% 6% 8% 14% 4	1671
	21st to end	Day	80% 4 5% 8% 3	2431
January	1st to 10th	Night	70% 6% 11% 10% 2	4638
	11th to 20th	Night	71% 5% 10% 12% 3	4440
	21st to end	Night	69% 7% 10% 10% 4	4884
February	1st to 10th	Night	56% 6% 11% 18% 9%	2660
	11th to 20th	Night	59% 5% 10% 18% 7%	2369
	21st to end	Night	57% 5% 12% 16% 9% 1	1884
March	1st to 10th	Night	56% 5% 10% 18% 10% 1	3733
	11th to 20th	Night	57% 5% 8% 23% 6% 1	3686
	21st to end	Night	57% 4 8% 14% 14% 2	3532
April	1st to 10th	Night	55% 6% 8% 17% 12% 2	1900
	11th to 20th	Night	53% 5% 9% 19% 12% 2	1763
	21st to end	Night	47% 6% 10% 19% 14% 3	1710
May	1st to 10th	Night	48% 6% 9% 27% 9% 1	2532
	11th to 20th	Night	46% 7% 11% 22% 12% 1	2507
	21st to end	Night	46% 7% 11% 20% 14% 1	2403
June	1st to 10th	Night	43% 8% 11% 27% 10%	1330
	11th to 20th	Night	41% 7% 12% 24% 15% 1	1330
	21st to end	Night	45% 8% 14% 23% 10% 1	1330
July	1st to 10th	Night	38% 10% 19% 23% 10%	2175
	11th to 20th	Night	35% 8% 19% 28% 9% 1	2380
	21st to end	Night	36% 8% 15% 31% 10%	2662
August	1st to 10th	Night	38% 8% 16% 31% 7%	2508
	11th to 20th	Night	32% 6% 18% 35% 9%	2628
	21st to end	Night	35% 7% 17% 27% 13%	3270
September	1st to 10th	Night	40% 7% 14% 29% 9% 1	1900
	11th to 20th	Night	46% 7% 21% 22% 5%	2009
	21st to end	Night	51% 7% 14% 19% 9%	2090
October	1st to 10th	Night	42% 5% 16% 24% 13%	3605
	11th to 20th	Night	56% 6% 12% 21% 5%	4063
	21st to end	Night	64% 7% 16% 11% 2	4467
November	1st to 10th	Night	68% 7% 10% 12% 3	2530
	11th to 20th	Night	72% 6% 9% 11% 3	2720
	21st to end	Night	75% 6% 9% 7% 3	2850
December	1st to 10th	Night	76% 5% 7% 9% 4	2850
	11th to 20th	Night	66% 6% 8% 14% 6%	3525
	21st to end	Night	77% 4 6% 10% 3	5236

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% 14% 40% 19% 7%	213
	11th to 20th	Day	12% 14% 35% 26% 11% 2	270
	21st to end	Day	16% 18% 38% 20% 7% 1	297
February	1st to 10th	Day	16% 18% 40% 20% 6% 1	270
	11th to 20th	Day	11% 24% 44% 16% 3 3	270
	21st to end	Day	16% 27% 44% 11% 1	225
March	1st to 10th	Day	19% 17% 38% 20% 6%	270
	11th to 20th	Day	22% 18% 40% 14% 4 2	332
	21st to end	Day	20% 16% 37% 18% 6% 3	506
April	1st to 10th	Day	22% 17% 33% 22% 6% 1	460
	11th to 20th	Day	28% 20% 23% 19% 8% 1	452
	21st to end	Day	24% 15% 31% 20% 8% 2	460
May	1st to 10th	Day	26% 15% 33% 18% 6% 2	648
	11th to 20th	Day	25% 14% 34% 17% 9% 1	675
	21st to end	Day	26% 17% 31% 19% 6% 1	734
June	1st to 10th	Day	27% 12% 34% 19% 6% 2	680
	11th to 20th	Day	19% 16% 35% 20% 8% 2	680
	21st to end	Day	20% 14% 34% 21% 9% 3	680
July	1st to 10th	Day	16% 13% 34% 23% 11% 3	671
	11th to 20th	Day	13% 15% 32% 26% 12% 2	668
	21st to end	Day	14% 10% 34% 26% 13% 4	739
August	1st to 10th	Day	17% 14% 32% 25% 10% 3	676
	11th to 20th	Day	16% 11% 27% 27% 13% 7%	592
	21st to end	Day	22% 13% 30% 21% 12% 3	539
September	1st to 10th	Day	22% 13% 30% 21% 11% 3	490
	11th to 20th	Day	29% 13% 28% 17% 12% 1	490
	21st to end	Day	28% 12% 26% 22% 10% 1	490
October	1st to 10th	Day	29% 16% 30% 15% 7% 2	414
	11th to 20th	Day	30% 18% 34% 13% 4	300
	21st to end	Day	31% 20% 35% 11% 2 1	330
November	1st to 10th	Day	27% 19% 32% 18% 5%	297
	11th to 20th	Day	26% 19% 35% 15% 4 2	223
	21st to end	Day	27% 22% 33% 16% 2 1	180
December	1st to 10th	Day	20% 18% 31% 19% 7% 5%	180
	11th to 20th	Day	25% 12% 38% 18% 6% 1	180
	21st to end	Day	20% 19% 32% 20% 6% 4	198
January	1st to 10th	Night	19% 15% 39% 21% 6%	950
	11th to 20th	Night	17% 14% 34% 26% 7% 1	950
	21st to end	Night	16% 12% 36% 26% 8% 1	1045
February	1st to 10th	Night	13% 13% 38% 28% 7% 1	950
	11th to 20th	Night	14% 14% 37% 24% 10% 2	842
	21st to end	Night	12% 13% 40% 25% 9% 1	628
March	1st to 10th	Night	12% 15% 35% 27% 10% 1	760
	11th to 20th	Night	18% 16% 36% 21% 7% 1	760
	21st to end	Night	18% 13% 32% 25% 10% 2	667
April	1st to 10th	Night	22% 11% 33% 25% 7% 2	570
	11th to 20th	Night	23% 13% 30% 26% 8% 1	563
	21st to end	Night	20% 11% 32% 27% 9% 1	570
May	1st to 10th	Night	26% 9% 29% 27% 8%	570
	11th to 20th	Night	23% 11% 30% 29% 6% 1	561
	21st to end	Night	25% 10% 33% 29% 4	411
June	1st to 10th	Night	19% 7% 37% 27% 10%	380
	11th to 20th	Night	20% 10% 32% 31% 7% 1	380
	21st to end	Night	19% 9% 33% 29% 10% 1	380
July	1st to 10th	Night	14% 10% 32% 32% 11%	370
	11th to 20th	Night	14% 7% 35% 33% 10% 1	489
	21st to end	Night	16% 6% 29% 32% 16% 1	624
August	1st to 10th	Night	14% 7% 29% 38% 11% 1	567
	11th to 20th	Night	13% 6% 28% 30% 21% 1	564
	21st to end	Night	15% 7% 37% 26% 14% 1	627
September	1st to 10th	Night	18% 8% 31% 31% 11% 1	570
	11th to 20th	Night	24% 8% 35% 25% 7%	679
	21st to end	Night	30% 11% 23% 24% 11% 1	760
October	1st to 10th	Night	28% 16% 26% 22% 7% 1	760
	11th to 20th	Night	30% 13% 29% 22% 5% 1	760
	21st to end	Night	27% 12% 31% 20% 9%	836
November	1st to 10th	Night	27% 15% 30% 21% 6% 1	779
	11th to 20th	Night	27% 16% 31% 19% 5% 1	911
	21st to end	Night	27% 15% 32% 20% 5%	950
December	1st to 10th	Night	18% 18% 34% 19% 10% 1	950
	11th to 20th	Night	20% 14% 34% 23% 8% 2	950
	21st to end	Night	25% 13% 31% 20% 10% 2	1045

Page generated at 2024-11-07 06:55:44. Version ac07

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