Rooftop star trails
Cities are not the best places to capture star trails because they always have a lot of artificial light. To capture long star trails from my rooftop, I take a large number of 15-second shots and stitch them digitally. I also capture short star trails (with exposure times less than 10 minutes) without any digital manipulation.

Rooftop star trails with two aeroplanes (#1)
The discontinuity of the aeroplane lights reveals that this is a digitally stitched image.

Rooftop star trails with two aeroplanes (#2)
The discontinuity of the aeroplane lights reveals that this is a digitally stitched image.

Retirement
ISO: 100
F-stop: f/11
Exposure time: 577 seconds
Focal length: 23 mm
No photoshop

Rooftop star trails (Indore)
(Stitched image)

Raining stars
ISO: 100
F-stop: f/4.5
Exposure time: 300 seconds
Focal length: 35 mm
No photoshop

Starry rain
(Stitched image)