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D7200 DSLR Piggyback Imaging: M31 Andromeda Galaxy

Posted: 2 December 2015

Monday, 30 November 2015, dawned clear but clouds began appearing mid-morning. Tuesday, 1 December, dawned clear. This night's session was short as I would be a judge at a local school Science Fair early on Wednesday. This is the second year I have been a judge at the school.

Open: Tuesday, 1 December 2015, 1807 MST
Temperature: 54°F
Session: 891
Conditions: Clear

1817 MST: Viewed M31 (Andromeda Galaxy), 83X. Then began setting up to image M31 with the D7200 DSLR piggyback on the 8" LX200-ACF. Used my 70-300mm lens set for a focal length of 300mm (35mm equivalent FL 450mm). I slewed the telescope to the star Aldebaran and attached the Gerd Neumann Bahtinov Mask for Camera Lens to focus. Used Live View on the Nikon DSLR to initially set the focus; confirmed by taking a f/5.6, 1 second, ISO 102,400 exposure. The Mask in-focus diffraction pattern is easy to see:


Then did a GOTO M31 and slewed to visually center the Andromeda Galaxy in the camera viewfinder. The piggyback adapter I use does not precisely align the camera optics to the telescope optical axis, so some slewing is always required when I do piggyback astrophotography. And the position of M31 this night near the Zenith made looking through the viewfinder difficult. Once I got M31 sort of centered I did some framing test exposures (1 minute, ISO 6400) and slewing until I was happy with the framing. I then looked for a good guide star. I found a faint star that provided reasonable framing. I did 2, 5, and 10 minute exposures at ISO 6400 and 2 and 5 minute exposures at ISO 12800. All exposures were f/5.6 at FL 300mm. As it turned out, the star was a little too faint for the 5 and 10 minute exposures; I had difficulty keeping the star centered in the illuminated reticle eyepiece on the telescope. However, the guided 2 minute exposures turned out very nice. And even at ISO 12800, the image was very good, as seen in this slightly cropped photo:

Click or tap on image for larger version

The companion galaxies of M110 and M32 are also visible in the image above. M110 is above M31 and M32 is below the nucleus of M31 and just at the edge of the spiral arms.

1933 MST: completed imaging. Checked out NGC1499 (California Nebula), which will be my piggyback imaging target on the next session.

Close: Tuesday, 1 December 2015, 2004 MST
Temperature: 43°F
Session Length: 1h 57m
Conditions: Clear

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