Dwarf/Seestar Comparison
Since we finally had some decent weather March 11-13 I decided to use some of my observing
time to do a comparison of the Dwarf II and the Seestar S50 on the same targets. I imaged
M51 (Whirlpool Galaxy) and M81 (Bode’s Galaxy) with both scopes. For context, here is a
comparison of the scope specifications.
Parameter Dwarf II Seestar S50
Aperture (mm) 24 50
Focal Length (mm) 100 250
Focal Ratio 4.17 5.00
Diffraction Limit @ 500 nm (arcsec) 4.30 2.06
Pixel Scale (arcsec) 2.99 2.39
Imaging Chip IMX415 IMX462
Pixel Size (µm) 1.45 2.90
X-Pixels 2176 1080
Y-Pixels 3864 1920
FOV-X (deg) 1.81 0.72
FOV-Y (deg) 3.21 1.28
The diffraction limit is the limiting resolution for a given aperture. Ideally, based on
Nyquist sampling theory, there should at least two pixels per resolution element. This is
roughly the case for the Dwarf, but the Seestar is significantly under sampled. Drizzling
may provide some benefit for the Seestar. I will experiment with this next.
All of the images are cropped to 800x800 pixels. Due to the difference in pixel scale, the
galaxy images for the Seestar are 2.99/2.39 = 1.25 times larger.
The M81 images were taken on March 11, the M51 Seestar image was taken on March 12, and
the M51 Dwarf image was taken on March 13.
M81-Dwarf-709 of 999 (15 sec subs, 177.25 min)
M81-Seestar-1105 of 1300 (10 sec subs, 184.17 min)
M51-Dwarf-316 of 437 (15 sec subs, 79 min)
M51-Seestar-608 of 719 (10 sec subs, 101.33 min)
M51-Dwarf-316 of 437 (15 sec subs, 79 min)
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