I have come across a Tamron SP 70 to 210 mm zoom lens which I plan to use for taking wide-field images. I used a DIY adapter to attach the lens to an astronomy camera. I took images at various focal lengths (70 mm, 135 mm, 160 mm, and 210 mm) and found out that I could get acceptable results at 160 mm f/4.

I am currently building an electronic microfocuser for this lens, for a more precise focusing.
Related link:
Specifications of Tamron SP 70-210 mm lens
For a complete list of astrophoto images, click here.
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