Redcat vrs Nikkor Orion

A comparison of images taken with the 250mm RedCat f/5 telescope and the 300 mm Nikkor ED f/4.5 SIS manual lens prompts more questions than it answers. This is not an apples-to-apples comparison, but I'm eager to learn more about the effects of the differences in these two images.

RecCat image:

  • Taken under a bright, Bortle 6+, suburban sky.
  • f/5 telescope has no iris
  • Sony a7 iii sensor has lower noise (about one stop) and lower resolution (6k x 4k in a full frame vrs. an APS-C sensor)
  • Total exposure time of 114 minutes, 228 30 second exposures stacked
  • ISO 640
  • Vixen Polarie Star Tracker with hall head

Nikor image:

  • Taken under a dark, Bortle 1, rural sky.
  • Lens stopped down to f/5.6
  • Sony a6300 sensor has higher resolution (1.5x) and about one stop more noise than the a7 iii
  • Total exposure time 14 minutes, best 7 of 14 two minute exposures stacked
  • ISO 400
  • Vixen Polarie Star Tracker with more stable counterweighted azimuth bracket

The Nikkor and Williams Optics RedCat are similar aperture and focal length lenses. I'm very pleased with the RedCat image, but need to look more closely at the effects of processing, camera sensor, exposure time, and ISO.

Content created: 2020-01-01

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