NGC 4565 (Caldwell 38) and NGC 4562 in continuum light

NGC 4565 (also known as Caldwell 38) and the smaller NGC 4562 are spiral galaxies in constellation Coma Berenices which both belong to the Coma I group.

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NGC 4565 (Caldwell 38) and NGC 4562 in continuum light
The edge-on galaxy is NGC 4565. NGC 4562 is the smaller galaxy in bottom right quarter. The faint bluish object next to NGC 4565 is the irregular galaxy IC 3571. (In the Javascript viewer annotations can be enabled via the menu or by pressing the key '3'.)

None of these galaxies show details in H-alpha. For that reason only a continuum image is presented which maps NIR (near infrared) to red, yellow to green and blue to blue.

Image data

FOV: 0.48° × 0.4°
Date: 2019-2022
Location: Pulsnitz, Germany
Instrument: 400mm Newton at f=1520mm
Camera Sensor: Panasonic MN34230
Orientation: North is up (approximately)
Scale: 0.8 arcsec/pixel (at full resolution)
Total exposure times:
NIR: 4.0 h
Yellow (540nm to 650nm): 6.4 h
Blue: 4.0 h
(H-alpha (3nm): 9.5h, not used for the image because no details visible)

Image processing

All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.

Image processing steps where:

  1. Bias correction, dark current subtraction, flatfield correction
  2. Alignment and brightness calibration using stars from reference image
  3. Stacking with masking unlikely values and background correction
  4. Denoising and deconvolution
  5. Color composition
  6. Dynamic range compression using non-linear high-pass filter
  7. Tonal curve correction

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