Crossfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crossfield clear sky chart from 2005-11-05 to 2017-09-21.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
41%
15189
12%
46835
8%
15159
45%
15159
21%
32199

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
30%
897
11%
2685
6%
895
35%
895
15%
2018
January16th to endNight
33%
831
18%
2751
11%
831
42%
831
19%
1851
February1st to 15thNight
41%
699
12%
2422
11%
696
46%
696
17%
1647
February16th to endNight
39%
632
13%
1981
11%
632
44%
632
19%
1406
March1st to 15thNight
37%
720
12%
2118
7%
720
42%
720
20%
1511
March16th to endNight
36%
768
11%
2083
5%
767
41%
767
19%
1567
April1st to 15thNight
34%
624
11%
1704
4%
624
38%
624
17%
1285
April16th to endNight
37%
540
11%
1620
7%
540
40%
540
19%
1164
May1st to 15thNight
43%
410
10%
1398
9%
410
47%
410
21%
912
May16th to endNight
45%
374
4%
1309
2%
374
46%
374
16%
936
June1st to 15thNight
40%
360
0%
1260
0%
360
40%
360
14%
916
June16th to endNight
49%
360
0%
1260
0%
360
49%
360
19%
839
July1st to 15thNight
59%
340
0%
1190
0%
340
59%
340
22%
758
July16th to endNight
61%
376
8%
1269
7%
354
64%
354
28%
725
August1st to 15thNight
63%
393
8%
1465
11%
391
64%
391
22%
901
August16th to endNight
62%
573
18%
1719
16%
573
64%
573
37%
1003
September1st to 15thNight
55%
660
17%
1806
12%
660
56%
660
34%
1123
September16th to endNight
50%
680
20%
1881
13%
680
56%
680
36%
1164
October1st to 15thNight
43%
660
16%
1949
9%
660
49%
660
22%
1343
October16th to endNight
43%
704
17%
2288
12%
704
50%
704
22%
1506
November1st to 15thNight
34%
828
17%
2403
9%
828
42%
828
24%
1619
November16th to endNight
31%
900
13%
2694
7%
900
37%
900
19%
1908
December1st to 15thNight
34%
900
11%
2700
8%
900
37%
900
16%
2013
December16th to endNight
34%
960
15%
2880
9%
960
40%
960
18%
2084

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 ForecastData
Points
Cloud CoverDay
11%8%36%6%35%5%6%7%33%
48061
Night
8%9%47%6%35%5%6%8%34%
46987
TransparencyDay
47%8%16%19%7%1
47714
Night
45%7%15%20%8%1
46838
SeeingDay
15%6%26%30%16%3
6045
Night
12%5%29%34%15%2
15199

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
7%11%5%8%7%26%45%8%33%
1253
16th to endDay
6%10%6%9%6%45%5%6%8%30%
1485
February1st to 15thDay
7%10%5%7%6%45%47%7%30%
1440
16th to endDay
411%7%9%7%45%7%6%8%26%
1491
March1st to 15thDay
411%5%9%8%46%6%5%6%30%
1842
16th to endDay
9%14%6%7%6%36%5%7%7%23%
2135
April1st to 15thDay
12%14%6%8%7%35%5%6%6%23%
2243
16th to endDay
16%11%46%6%345%5%7%28%
2340
May1st to 15thDay
12%8%37%5%46%5%6%7%32%
2550
16th to endDay
21%8%36%6%35%5%6%7%24%
2802
June1st to 15thDay
19%8%36%6%36%5%6%6%25%
2700
16th to endDay
14%6%36%7%36%6%6%8%29%
2700
July1st to 15thDay
13%5%15%6%35%6%6%7%38%
2700
16th to endDay
9%413435%6%7%9%44%
2813
August1st to 15thDay
14%4245%35%5%6%7%40%
2487
16th to endDay
10%3145%345%6%8%46%
2483
September1st to 15thDay
14%6%24423445%46%
2153
16th to endDay
10%6%245%345%5%8%43%
1871
October1st to 15thDay
14%8%38%6%245%5%8%32%
1680
16th to endDay
8%8%37%6%35%5%5%7%37%
1584
November1st to 15thDay
7%12%47%6%3446%7%33%
1442
16th to endDay
6%12%5%6%6%4445%9%34%
1263
December1st to 15thDay
5%11%6%12%7%5%5%5%7%6%25%
1260
16th to endDay
39%5%9%8%36%7%7%9%28%
1344
January1st to 15thNight
5%12%5%9%8%46%6%7%8%25%
2685
16th to endNight
5%12%48%6%36%47%8%32%
2751
February1st to 15thNight
6%10%48%7%5%5%45%7%33%
2411
16th to endNight
411%6%8%8%36%5%6%7%30%
1981
March1st to 15thNight
5%11%5%7%7%37%5%7%9%28%
2118
16th to endNight
7%13%6%8%6%36%6%6%8%26%
2083
April1st to 15thNight
12%12%47%6%46%5%6%8%26%
1704
16th to endNight
12%11%46%6%35%5%6%6%30%
1620
May1st to 15thNight
12%9%35%6%345%5%6%37%
1397
16th to endNight
20%6%25%5%36%5%6%7%30%
1309
June1st to 15thNight
18%6%46%6%37%6%5%7%26%
1260
16th to endNight
14%6%36%5%35%6%6%7%34%
1260
July1st to 15thNight
9%3246%46%6%8%10%37%
1260
16th to endNight
7%225%425%45%9%49%
1355
August1st to 15thNight
12%325%5%35%5%5%8%41%
1473
16th to endNight
7%4243136%5%8%50%
1719
September1st to 15thNight
13%5%24322348%48%
1806
16th to endNight
9%5%14325%46%8%47%
1881
October1st to 15thNight
12%8%36%6%345%5%7%36%
1949
16th to endNight
9%9%26%5%345%7%8%37%
2288
November1st to 15thNight
7%11%45%5%35%5%6%7%37%
2403
16th to endNight
5%12%6%8%6%45%46%8%32%
2694
December1st to 15thNight
5%10%6%11%7%47%5%6%7%27%
2700
16th to endNight
312%5%9%8%45%46%8%29%
2880

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
49%5%14%23%5%2
1253
16th to endDay
49%6%14%14%10%3
1485
February1st to 15thDay
49%7%15%17%7%2
1440
16th to endDay
52%8%14%16%6%
1491
March1st to 15thDay
50%8%17%16%6%
1842
16th to endDay
57%7%14%16%4
2136
April1st to 15thDay
58%7%13%13%6%
2243
16th to endDay
53%7%14%16%7%1
2340
May1st to 15thDay
47%7%15%19%9%
2550
16th to endDay
55%8%14%15%4
2807
June1st to 15thDay
55%8%14%15%41
2700
16th to endDay
49%9%16%20%4
2700
July1st to 15thDay
42%9%20%21%5%
2541
16th to endDay
34%10%21%25%7%
2636
August1st to 15thDay
39%10%22%22%5%
2470
16th to endDay
32%7%20%28%9%1
2483
September1st to 15thDay
38%5%15%22%14%3
2153
16th to endDay
37%6%13%27%11%2
1871
October1st to 15thDay
47%9%15%20%6%
1680
16th to endDay
43%7%14%25%8%
1584
November1st to 15thDay
48%8%14%19%7%1
1442
16th to endDay
46%6%16%19%8%1
1263
December1st to 15thDay
56%6%14%14%7%
1260
16th to endDay
47%9%14%17%9%1
1344
January1st to 15thNight
53%9%13%15%6%2
2685
16th to endNight
46%6%13%19%9%3
2751
February1st to 15thNight
48%7%13%20%9%1
2422
16th to endNight
50%6%12%17%12%1
1981
March1st to 15thNight
48%7%19%18%5%
2118
16th to endNight
52%7%14%18%6%
2086
April1st to 15thNight
53%7%13%15%8%
1704
16th to endNight
50%6%14%20%5%1
1620
May1st to 15thNight
44%6%16%20%10%
1398
16th to endNight
50%9%16%17%5%1
1309
June1st to 15thNight
54%7%15%15%6%
1260
16th to endNight
44%8%19%20%5%
1260
July1st to 15thNight
38%11%20%23%6%
1190
16th to endNight
29%11%20%28%9%
1269
August1st to 15thNight
37%10%20%24%6%
1465
16th to endNight
27%8%19%28%12%2
1719
September1st to 15thNight
34%5%16%23%15%4
1806
16th to endNight
32%6%17%25%12%4
1881
October1st to 15thNight
45%8%13%22%8%1
1949
16th to endNight
41%9%16%23%8%
2288
November1st to 15thNight
42%7%15%21%11%1
2403
16th to endNight
48%7%16%16%7%3
2694
December1st to 15thNight
53%8%13%18%4
2700
16th to endNight
50%7%12%21%7%
2880

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
13%328%23%18%13%
60
16th to endDay
7%329%21%28%9%
64
February1st to 15thDay
14%8%20%32%17%4
67
16th to endDay
14%6%24%40%13%1
150
March1st to 15thDay
10%9%42%30%41
270
16th to endDay
12%9%42%25%7%2
288
April1st to 15thDay
21%11%29%28%9%
269
16th to endDay
24%10%26%25%11%1
270
May1st to 15thDay
14%7%28%26%19%3
381
16th to endDay
23%418%32%17%4
517
June1st to 15thDay
19%9%24%28%15%2
495
16th to endDay
15%427%31%16%4
495
July1st to 15thDay
15%319%32%26%3
475
16th to endDay
8%427%36%18%4
482
August1st to 15thDay
14%420%32%20%6%
315
16th to endDay
9%5%26%36%15%6%
332
September1st to 15thDay
19%5%28%25%13%6%
315
16th to endDay
13%9%29%30%11%5%
276
October1st to 15thDay
19%8%25%32%12%1
153
16th to endDay
14%323%36%19%2
96
November1st to 15thDay
15%7%35%30%7%3
90
16th to endDay
9%14%19%27%14%13%
61
December1st to 15thDay
6%333%30%25%1
60
16th to endDay
6%7%20%35%25%4
64
January1st to 15thNight
12%8%35%31%11%1
900
16th to endNight
9%9%35%32%10%1
831
February1st to 15thNight
10%7%28%33%16%3
704
16th to endNight
8%5%32%32%17%3
632
March1st to 15thNight
9%5%36%35%12%1
720
16th to endNight
13%5%29%38%11%1
768
April1st to 15thNight
16%7%29%31%14%1
624
16th to endNight
18%6%25%36%12%
540
May1st to 15thNight
13%7%28%33%17%
411
16th to endNight
21%221%36%17%
375
June1st to 15thNight
21%426%30%15%1
360
16th to endNight
16%321%35%21%1
360
July1st to 15thNight
11%215%43%25%1
340
16th to endNight
6%221%45%21%1
376
August1st to 15thNight
15%112%37%31%3
393
16th to endNight
8%220%42%26%1
573
September1st to 15thNight
16%119%36%22%3
660
16th to endNight
11%228%36%17%2
680
October1st to 15thNight
16%426%33%16%2
660
16th to endNight
12%231%39%11%1
704
November1st to 15thNight
11%7%37%31%9%2
828
16th to endNight
9%7%41%30%9%2
900
December1st to 15thNight
10%8%33%32%13%2
900
16th to endNight
8%5%35%35%11%3
960
Page generated at 2017-09-22 05:35:37. Version ac04

Copyright 2017 A. Danko


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