scope and camera

Meade LX200 and Nikon D70

A simple test showing how well a collimated SCT can serve as a telephoto lens for a Digital SLR. The story and pictures are below.


Sunday, 25-June-2006

In one of my telescope groups earlier today a person was complaining he couldn't focus on the fastening bolts of a satellite dish across the street and he asked "Why?".

I answered "your collimation is off", but some people (mistakenly) thought otherwise. [Collimation is the alignment of all the optical parts of a scope; with an SCT that means two mirrors and a large corrector lens.]

Just for fun, I went outside to take some pictures with one of my LX200 to prove the point a well-collimated scope can be a fantastic camera lens.

The rains since last October/November have caused things to grow and I couldn't see any of my neighbors' dishes, so I decided to focus (no pun :-) on mine.

As you'll note in this series of pictures taken late-afternoon today, there's a microwave transceiver on my tower. These pictures are all "Saved for Web" so they're relatively small (40-70kB) and NO post-processing was performed — the pictures are solely cropped to highlight the area of attention. Click on any thumbnail for a larger picture in a new window.

thb_tower+antenna.jpg The diamond-shaped microwave transceiver about 10 feet from the top of the tower is my 6Mbits/S Sprint Broadband link to the 'Net. Other devices on the tower include a VHF/UHF array, an NIST WWV antenna pointing to Fort Collins, Colorado, and the wind speed (anemometer) and direction sensors for my Oregon Scientific weather station.
thb_antenna_w_200mm.jpg Here's a shot from the same location of the label on the transceiver taken handheld with a Nikon ED-IF AF-S VR-Nikkor 70-200mm f/2.8G at 200mm on a D70s. Whew, the VR (Vibration Reduction) really works! Can't quite read the printing on the label, though.
thb_antenna_w_400mm.jpg Transceiver label taken handheld using a Nikon ED AF VR-Nikkor 80-400mm f/4.5-5.6D at 400mm on a D70s. The label still isn't fully readable.
thb_LX200+Nikon_1.jpg Now for the fun part and the point of the exercise. I brought out my 8" Meade LX200 SCT (Schmidt-Cassegrain Telescope, 200mm aperture, 2000mm focal length, f/10) and set it up as shown here at the same location of the handheld shots using the telephoto lenses.
thb_LX200+Nikon_2.jpg Detail side view showing the rear cell of the telescope, the JMI NGF-S Crayford microfocuser, a portion of the 2" Orion (USA) prime focus camera adapter (part# 05269), a T-mount adapter for the Nikon F mount, and one of my D70s cameras with a DR-6 right angle viewing attachment and a Nikon MC-DC1 remote shutter release.
thb_LX200+Nikon_3.jpg Rear-view closeup showing the camera attached to the scope. The DR-6 right angle adapter is worth its weight in gold — no crouching and peering upwards. Focusing is two-staged: coarse by moving the scope's primary mirror, and fine using the motorized JMI NGF-S Crayford focuser. The camera is in Manual mode and the only feasible settings are white balance and exposure time.
thb_antenna_w_2000mm_LX200.jpg The transceiver label, shot using the LX200 and D70s, is now clearly readable. A depth-of-field issue is apparent with a slight fuzziness near the right portion of the label. No chromatic aberration or other distortions are evident; all in all, a fine imaging setup except for the weight: 57 pounds (25.9 kg) so this isn't something one would casually backpack into the wilderness.
thb_mocker_w_2000mm_LX200.jpg Coincidentally, my favorite mockingbird (who has my whistle in his repertoire :-) flew in, landed on the TV antenna, and decided to check out what I was doing, so I took his portrait with the LX200+D70s. I suspect he realized he was the center of attention for he began serenading the neighborhood while flitting from antenna rod to rod. :-)


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