Imaged at Perth Observatory semi-dark site This image was captured with a 1970's Pentax SMC 135mm f/2.5 K-mount lens with Canon EOS adapter. The lens is stopped to f/3.6 using a 37mm step down ring. This ensures circular stars compared to internal stop down blades that cause diffraction spikes . The chosen f/ratio gives acceptable flatness to the corners (non-flared star images). There are no bright stars in this field so internal reflections as noted on Crux images this same date. This relatively cheap lens does a pretty good job! DeepSkyStacker 4.2.2 Stacked 85% (21) of 25 Images ISO 1600 @45 Sec, 72 DARK @ 120 Sec, 17 BIAS, 19 FLATS, Post-processed with Adobe Photoshop CC 2019 Pentax SMC 135mm f/2.5, 37mm stop ring to f/3.6, PK/EOS adapter, Hoya UV filter, Baader BCF modified Canon 70D DSLR field 564' x 377' , Ambient ~24C. Skywatcher Star Adenturer in sidereal tracking mode, no guiding.
Imaged at Perth Observatory semi-dark site This image was captured with a 1970's Pentax SMC 135mm f/2.5 K-mount lens with Canon EOS adapter. The lens is stopped to f/3.6 using a 37mm step down ring. This ensures circular stars compared to internal stop down blades that cause diffraction spikes . The chosen f/ratio gives acceptable flatness to the corners (non-flared star images). There are no bright stars in this field so internal reflections as noted on Crux images this same date. This relatively cheap lens does a pretty good job! DeepSkyStacker 4.2.2 Stacked 85% (30) of 36 Images ISO 1600 @45 Sec, 72 DARK @ 120 Sec, 17 BIAS, 19 FLATS, Post-processed with Adobe Photoshop CC 2019 Pentax SMC 135mm f/2.5, 37mm stop ring to f/3.6, PK/EOS adapter, Hoya UV filter, Baader BCF modified Canon 70D DSLR field 564' x 377' , Ambient ~24C. Skywatcher Star Adenturer in sidereal tracking mode, no guiding.
Orion setting over Perth Observatory and Perth's sky glow
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