Astrophotography on the (very, very) cheap.

So, in an effort to get some better wide-field shots, I recently acquired a trio of old Vivitar (or clone) prime lenses, for the princely total sum of just under $120, including having them shipped to my door.  After doing some evaluation for astro-work, I’ll keep the best and list the other two for sale on eBay.

From left to right we have an “Expert” branded 200mm f/3.5:

A Vemar-branded 300mm f/5.5:

… and a Tokina-built, Vivitar-branded 400mm f/5.6:

The 300mm came with a UV filter (which also fits the 200mm):

And the 400mm came with an old Vivitar Skylight (1A) filter:

As a means of evaluating them, I set up the scope, then ran each one piggyback in turn.   I brought out the dew heater, but didn’t need it until I switched targets and fired off a 200-shot salvo at the Pleiades.

The goal was to shoot a bunch of shots of Andromeda, but with the galaxy threatening to slip behind the trees, I only managed ten 10-second shots with each lens.  This was plenty for an initial eval, as I was able to stack them up in Deep Sky Stacker and get a reasonable baseline for comparison. 10x 10-second shots, ISO 12,800.

200mm f/3.5:

300mm, f/5.5:

400mm, f/5.6:

And here’s a zoomed-in comparison where each image shows approximately the same field of view (200mm, 300mm, and 400mm, left to right):
wpid4039-Autosave032.jpg  wpid4043-Autosave034.jpg  wpid4047-Autosave035.jpg


At first glance, it is obvious that the 200mm lens has some serious coma issues wide-open, as all the bright stars above Andromeda are bloomed and badly misshaped.   Of course this is the best lens for terrestrial work, so hopefully it should be relatively easy to resell.  Looking back and forth between the 300mm and 400mm images, the 300mm appears to have slightly less chromatic aberration, and slightly better color renditioning, while the 400mm has slightly better contrast, and the stars don’t bloom quite as much.  However, the ones that do bloom on the 400mm, tend to do so with a good bit of coma, which is more difficult to deal with in post-processing.  The 300mm also has less fall-off in the corners, although this is readily fixable with a proper set of flats.

So, after the 1st round, the 200mm is right out, and I need to pick another target to try and differentiate between the 300mm and 400mm lenses.  The extra contrast and slight edge in reach for the 400mm may win out, but we’ll see.  I think I might have to figure out when / where Orion might be observable once the moon swings out of the way for the month for round 2… More to follow.

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