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6" f/4 Astrograph

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This unique "telescope" is probably best described as an astrograph as it features a wide field of view that is fully corrected across a full frame DSLR's sensor size (36mm x 24mm) and displays minimal vignetting or optical aberrations across that entire field. It is made from what was originally a Nikon 600mm f/4 ED IF lens, but now has an Astro-Physics 2.7" focuser on the back of the lens, yielding about 95mm of back focus (roughly 50mm more than a standard Nikon lens). Because it now has a standard focuser, any camera (DSLR, CCD, CMOS) can be attached with conventional telescope adapters and accessories. It can also be used for visual observations with everyday visual accessories such as eyepieces, star diagonals, etc.

The story behind it is that the original owner dropped his Nikon camera and lens in a lake. They sent the lens to a lens repair shop in Colorado, and it was going to be cost prohibitive to replace the motors, electronics, etc. The owner told the shop to keep it. The lens shop then mounted the lens on a 14" Losmandy D style dovetail, removed the back end of the lens and connected it all to a 2.7" Astro Physics focuser. They sold it to a Colorado local astrophotographer. I bought the telescope from this second owner about 3 years ago.

Since then, it's been quite a performer. To see a complete portfolio I've captured with this OTA, go to my website at astronomersdoitinthedark. On the left side, scroll near the bottom and click on "Nikon 600mm f/4 ED IF". I have about 40 images there that I've captured with this lens.

The lens is very sharp when used wide open at f/4. However, like most camera lenses, it is that much sharper when stopped down. I have aperture masks that stop it down to 5" (f/4.8), and 4" (f/6). Because I have lots of dark nights available to me, I've mostly imaged at f/6. When capturing narrowband, I've typically used it at f/4. I suspect for most astrophotographers, they'd be quite happy with the performance even when it's wide open.

The lens does have a small blemish in the coatings on the front element. It's been there since I bought it and does not appear to affect the performance in any way. I tried to show it in the pictures, but it's difficult to see. The lens is designed for a full frame camera (36mm x 24mm), and I've used it extensively with a Canon 6D. I've also used it with my QSI 690wsg-8 cCD camera as well. I can supply sample subexposures and flat frames if requested.

Included in the price of $2,600 is Paypal Fee, shipping in Continental US and:

Nikon 600mm f/4 ED IF lens
Astro-Physics 2.7" focuser
Losmandy D style Dovetail
3/8" Piggyback camera mount
AP 2.7" to 2" eyepiece adapter
6" lens cap
5" black anodized aluminum aperture mask (f/4.8)
4" black anodized aluminum aperture mask (f/6)
Aluminum carrying case (has some dings and scratches, but closes, locks, and protects lens fine)

For additional price, I also have for sale with the lens:
Astro-Physics Canon EOS Wide Mount Camera adapter (67RLEOS) - $135 new, sell for $70

2.7" to 6x7 Outer Bayonet Adapter (ADA2767) (required to use the EOS adapter) - $85 new, sell for $45
(the above 2 items allow you to connect a Canon EOS camera and will not vignette even on a full frame camera)

Robofocus motor and AP adapter for Robocus (does not include Robofocus controller) - $175 new, sell for $115

1mm thick Precise Parts AP 2.7" to 48mm male thread adapter - only adds 1mm to backfocus. Has scratch on anodized surface, but works fine otherwise. If you buy this, be sure to put plumber's tape on threads - don't make the same mistake I did! - $127 new, sell for $60

NOT included (and shown in the pictures) are:
QSI camera
Lodestar autoguider
Starlight Xpress Adaptive Optics
Telescope mount
Dew heater straps
Anything else you see not listed above!

Thanks for looking!