Reisterstown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reisterstown clear sky chart from 2005-11-05 to 2018-08-29.

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 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
33%
16373
20%
50619
10%
16332
45%
16332
23%
31844

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
18%
778
21%
2654
6%
776
36%
776
16%
1653
January16th to endNight
14%
832
23%
2704
5%
832
35%
832
18%
1676
February1st to 15thNight
15%
764
17%
2482
3%
761
32%
761
17%
1568
February16th to endNight
13%
683
22%
2067
4%
683
35%
683
17%
1342
March1st to 15thNight
21%
780
21%
2191
7%
780
35%
780
21%
1426
March16th to endNight
18%
832
21%
2249
6%
832
31%
832
22%
1490
April1st to 15thNight
19%
778
19%
1946
4%
778
28%
778
24%
1303
April16th to endNight
31%
771
18%
1927
5%
771
38%
771
27%
1295
May1st to 15thNight
35%
578
17%
1748
10%
578
42%
578
22%
1174
May16th to endNight
45%
406
16%
1625
12%
406
52%
406
19%
1000
June1st to 15thNight
46%
390
19%
1560
17%
390
57%
390
23%
912
June16th to endNight
57%
390
17%
1560
18%
390
63%
390
26%
883
July1st to 15thNight
55%
370
14%
1480
14%
370
59%
370
19%
915
July16th to endNight
65%
552
16%
1679
13%
519
70%
519
32%
966
August1st to 15thNight
60%
575
17%
1715
12%
572
62%
572
30%
1075
August16th to endNight
61%
817
19%
2047
11%
817
62%
817
34%
1333
September1st to 15thNight
53%
720
25%
1800
13%
720
58%
720
34%
1155
September16th to endNight
52%
717
25%
1968
20%
717
57%
717
31%
1268
October1st to 15thNight
41%
720
21%
2160
17%
720
50%
720
25%
1391
October16th to endNight
32%
768
29%
2304
15%
768
51%
768
29%
1334
November1st to 15thNight
31%
760
23%
2439
12%
760
47%
760
24%
1478
November16th to endNight
25%
780
23%
2672
11%
780
42%
780
20%
1579
December1st to 15thNight
20%
780
16%
2730
5%
780
35%
780
15%
1779
December16th to endNight
16%
832
20%
2912
5%
832
34%
832
16%
1849

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
14%5%245%3445%7%40%
51621
Night
14%5%2442445%7%43%
50801
Cloud CoverDay
14%5%25%5%345%5%7%40%
51631
Night
14%5%2442445%7%43%
50805
TransparencyDay
41%6%11%22%15%2
51321
Night
39%5%12%23%16%2
50619
SeeingDay
18%13%26%23%13%4
6873
Night
17%14%30%25%11%1
16376

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
15%7%245%245%47%39%
1611
16th to endDay
13%8%25%5%43446%41%
1872
February1st to 15thDay
14%6%35%5%3445%6%37%
1710
16th to endDay
16%8%25%5%34336%39%
1690
March1st to 15thDay
14%7%34424347%42%
2085
16th to endDay
16%7%35%5%33445%40%
2327
April1st to 15thDay
14%6%3443436%7%40%
2332
16th to endDay
17%5%25%42335%6%43%
2308
May1st to 15thDay
17%5%345%3445%8%36%
2541
16th to endDay
17%5%246%35%45%8%36%
2842
June1st to 15thDay
12%5%24436%46%10%38%
2730
16th to endDay
11%4245%35%46%9%42%
2730
July1st to 15thDay
8%425%5%35%6%7%9%40%
2730
16th to endDay
8%425%5%46%7%7%10%36%
2731
August1st to 15thDay
11%5%247%36%6%6%8%37%
2477
16th to endDay
11%4245%346%6%8%40%
2449
September1st to 15thDay
14%424424447%44%
2160
16th to endDay
14%6%245%34447%41%
1990
October1st to 15thDay
19%5%14423346%43%
1800
16th to endDay
14%5%2442345%5%47%
1920
November1st to 15thDay
14%6%2332445%6%45%
1747
16th to endDay
16%5%24424445%45%
1615
December1st to 15thDay
16%5%25%5%25%45%7%39%
1560
16th to endDay
16%6%25%5%2435%8%38%
1664
January1st to 15thNight
16%5%25%42345%7%41%
2654
16th to endNight
16%6%24423446%43%
2704
February1st to 15thNight
14%7%25%42345%6%42%
2480
16th to endNight
14%6%26%5%33447%41%
2067
March1st to 15thNight
15%5%2333445%5%44%
2179
16th to endNight
14%6%25%6%24436%43%
2249
April1st to 15thNight
12%5%344245%5%7%41%
1946
16th to endNight
16%5%2433236%7%43%
1927
May1st to 15thNight
18%7%24424446%40%
1748
16th to endNight
13%7%245%34447%41%
1623
June1st to 15thNight
11%425%425%5%5%8%44%
1560
16th to endNight
9%324435%5%5%11%43%
1560
July1st to 15thNight
8%5%26%6%37%6%6%8%38%
1560
16th to endNight
6%323426%5%6%12%44%
1786
August1st to 15thNight
10%5%2443447%8%43%
1726
16th to endNight
11%4244245%6%9%45%
2047
September1st to 15thNight
12%5%25%413448%47%
1800
16th to endNight
13%5%245%24346%46%
1968
October1st to 15thNight
19%5%2443435%5%44%
2160
16th to endNight
14%412323346%51%
2304
November1st to 15thNight
13%6%25%42334449%
2439
16th to endNight
15%5%2442445%7%44%
2672
December1st to 15thNight
16%5%25%5%35%5%5%6%37%
2730
16th to endNight
16%6%25%5%2445%7%40%
2912

Percentage Cloud Cover SE (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
15%6%34435%447%39%
1611
16th to endDay
13%7%35%5%245%45%41%
1872
February1st to 15thDay
14%7%35%5%3446%6%38%
1710
16th to endDay
16%7%25%434346%39%
1690
March1st to 15thDay
14%7%345%23437%43%
2096
16th to endDay
16%6%36%5%33445%40%
2326
April1st to 15thDay
14%6%25%5%3336%7%40%
2332
16th to endDay
17%5%24424345%43%
2308
May1st to 15thDay
17%5%2443446%8%36%
2541
16th to endDay
17%4346%3446%8%36%
2842
June1st to 15thDay
12%5%25%5%35%5%6%10%38%
2730
16th to endDay
10%42444446%8%42%
2730
July1st to 15thDay
8%4246%36%6%7%8%40%
2730
16th to endDay
8%415%5%46%7%8%9%37%
2731
August1st to 15thDay
11%426%6%45%7%6%7%36%
2477
16th to endDay
11%4245%446%6%8%41%
2449
September1st to 15thDay
13%425%5%2445%7%43%
2160
16th to endDay
15%5%25%5%23448%41%
1990
October1st to 15thDay
18%5%14423446%43%
1800
16th to endDay
14%5%244235%45%47%
1920
November1st to 15thDay
14%5%3432345%6%45%
1747
16th to endDay
15%6%24423346%45%
1615
December1st to 15thDay
16%426%4345%47%40%
1560
16th to endDay
16%7%25%5%24348%38%
1664
January1st to 15thNight
16%5%25%42445%7%41%
2654
16th to endNight
16%6%2342445%6%43%
2704
February1st to 15thNight
14%7%245%2445%6%42%
2473
16th to endNight
14%6%25%5%23446%42%
2067
March1st to 15thNight
14%6%243345%5%6%44%
2191
16th to endNight
14%6%25%5%24446%43%
2249
April1st to 15thNight
12%6%345%3445%7%42%
1946
16th to endNight
17%5%2442435%7%43%
1927
May1st to 15thNight
18%7%25%424346%40%
1747
16th to endNight
14%6%245%34447%41%
1623
June1st to 15thNight
11%424425%5%6%8%43%
1560
16th to endNight
9%324335%5%6%11%42%
1560
July1st to 15thNight
8%5%26%6%47%6%6%9%37%
1560
16th to endNight
6%223426%5%6%13%45%
1786
August1st to 15thNight
10%5%25%4345%7%8%43%
1726
16th to endNight
10%4244245%5%9%44%
2047
September1st to 15thNight
12%5%25%323448%47%
1800
16th to endNight
12%6%25%42435%6%45%
1968
October1st to 15thNight
19%5%2333335%5%44%
2160
16th to endNight
14%313312446%52%
2304
November1st to 15thNight
13%6%25%423345%49%
2439
16th to endNight
15%42442445%6%45%
2672
December1st to 15thNight
16%6%25%6%26%45%5%37%
2730
16th to endNight
16%6%24433447%40%
2912

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
43%5%12%20%13%3
1612
16th to endDay
43%412%24%11%3
1872
February1st to 15thDay
44%5%11%24%10%2
1712
16th to endDay
45%411%24%11%1
1690
March1st to 15thDay
42%5%11%23%16%2
2096
16th to endDay
46%5%9%18%17%2
2327
April1st to 15thDay
42%5%10%21%16%3
2332
16th to endDay
41%48%19%21%5%
2308
May1st to 15thDay
44%6%13%20%14%1
2541
16th to endDay
45%6%13%20%12%1
2846
June1st to 15thDay
40%8%12%23%14%
2730
16th to endDay
36%8%14%22%17%1
2730
July1st to 15thDay
37%8%13%21%15%3
2581
16th to endDay
38%9%13%23%12%2
2575
August1st to 15thDay
41%9%12%20%15%1
2464
16th to endDay
37%7%12%23%15%2
2449
September1st to 15thDay
38%5%11%20%21%2
2160
16th to endDay
41%48%22%20%2
1990
October1st to 15thDay
40%5%11%22%17%2
1800
16th to endDay
37%410%26%19%
1920
November1st to 15thDay
38%5%12%21%16%4
1747
16th to endDay
40%410%26%15%2
1615
December1st to 15thDay
42%6%13%23%11%2
1560
16th to endDay
45%5%13%22%12%
1664
January1st to 15thNight
42%411%20%16%4
2654
16th to endNight
41%411%27%14%1
2704
February1st to 15thNight
42%413%22%13%2
2482
16th to endNight
42%49%23%16%2
2067
March1st to 15thNight
39%5%11%26%14%1
2191
16th to endNight
42%412%21%16%3
2249
April1st to 15thNight
39%5%13%20%18%2
1946
16th to endNight
39%5%10%19%18%6%
1927
May1st to 15thNight
43%6%10%22%13%2
1748
16th to endNight
40%7%15%18%14%3
1625
June1st to 15thNight
35%8%11%26%16%
1560
16th to endNight
33%8%14%24%17%2
1560
July1st to 15thNight
41%8%15%18%12%4
1480
16th to endNight
29%9%17%24%16%2
1679
August1st to 15thNight
35%8%15%22%16%2
1715
16th to endNight
34%6%11%24%18%3
2047
September1st to 15thNight
35%5%11%21%22%3
1800
16th to endNight
38%48%22%22%3
1968
October1st to 15thNight
41%410%22%17%2
2160
16th to endNight
32%310%30%20%2
2304
November1st to 15thNight
38%48%24%18%6%
2439
16th to endNight
38%410%25%18%2
2672
December1st to 15thNight
46%5%11%23%12%1
2730
16th to endNight
42%5%14%22%12%1
2912

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
21%38%25%10%3
104
16th to endDay
21%33%31%12%
144
February1st to 15thDay
26%34%34%3
135
16th to endDay
23%26%37%10%1
271
March1st to 15thDay
18%27%32%18%3
330
16th to endDay
20%20%34%18%31
352
April1st to 15thDay
20%21%33%16%6%1
330
16th to endDay
18%15%33%15%14%2
319
May1st to 15thDay
27%16%25%18%9%3
348
16th to endDay
22%6%22%26%18%3
395
June1st to 15thDay
16%10%27%24%17%4
375
16th to endDay
14%8%29%30%14%3
375
July1st to 15thDay
10%423%32%20%7%
365
16th to endDay
12%419%31%25%6%
390
August1st to 15thDay
13%5%20%30%20%10%
358
16th to endDay
12%115%32%22%14%
384
September1st to 15thDay
14%9%19%22%22%10%
315
16th to endDay
18%6%14%31%17%11%
314
October1st to 15thDay
24%7%17%25%18%6%
315
16th to endDay
14%17%30%23%12%2
336
November1st to 15thDay
17%14%28%21%16%1
287
16th to endDay
17%22%35%14%8%
145
December1st to 15thDay
20%28%26%15%7%1
90
16th to endDay
20%28%35%11%4
96
January1st to 15thNight
20%23%32%20%3
780
16th to endNight
20%22%39%15%1
832
February1st to 15thNight
20%20%38%18%1
764
16th to endNight
20%25%37%15%1
683
March1st to 15thNight
20%20%35%20%3
780
16th to endNight
18%18%41%16%4
832
April1st to 15thNight
16%22%38%18%3
778
16th to endNight
19%15%29%26%8%1
771
May1st to 15thNight
21%9%30%27%10%1
578
16th to endNight
19%7%21%33%17%
407
June1st to 15thNight
12%232%31%21%
390
16th to endNight
11%222%46%17%
390
July1st to 15thNight
9%220%40%25%1
370
16th to endNight
7%118%39%28%4
552
August1st to 15thNight
13%115%42%23%2
575
16th to endNight
13%216%34%28%4
817
September1st to 15thNight
13%420%32%26%2
720
16th to endNight
15%419%30%24%4
717
October1st to 15thNight
21%9%20%26%17%4
720
16th to endNight
17%14%33%23%11%
768
November1st to 15thNight
16%15%30%25%10%1
760
16th to endNight
18%20%31%21%7%
780
December1st to 15thNight
22%16%35%16%8%
780
16th to endNight
20%20%37%19%2
832
Page generated at 2018-08-30 05:34:22. Version ac04

Copyright 2018 A. Danko


Reisterstown Clear Sky Chart |Charts Home