Finally we began installation of the long awaited 16″ telescope. It took 6 months for the manufacturing! Every telescope is built to order. I spent years researching which design and configuration to go with. 10 years ago the “RCOS” Ritchey Chretien was all the rage. They have since gone out of business, but they are still wonderful telescopes. After all the Hubble utilizes the same optics. However they require additional external field flatteners to get a flat uniform image. They are also notoriously difficult to collimate. Much more difficult to manufacture so this is reflected in the cost. Another option was an imaging newtonian. My first telescope was a Cave Astrola newtonian reflector for those of you old enough to remember those. When I got into imaging in the early 2000’s I converted the old telescope into an astrograph and it worked pretty well but there are limitations. The main one is the lack of backfocus restricting your imaging train options. Can’t have too much stuff back there. Accurate collimation is also difficult. However I honestly believe the newtonian is a very close second. You can’t beat the beautiful razor sharp diffraction spikes seen in their images! I may decide to try a medium sized version one day. The design I ultimately decided on was a CDK or corrected Dall Kirkham. The CDK employs 2 mirrors like the Ritchey but the secondary is spherical. The primary is aspherical. There is a corrector lens group placed before the focal plane. This arrangement provides the widest, flattest, error free field with the added bonuses of relative ease of collimation and very generous backfocus. Naturally I have looked at tons of images taken with these by the top imagers in the world. I don’t know that there is a discernible difference between, say an RC , a CDK or newtonian in the hands of skilled individuals. So I could not base my decision on that. The final choice was between a CDK manufactured here in the US vs one that was made by a company in Italy known as Officina Stellare (workshop of the stars). Their version is actually called “RiDK” or “Riccardi Dall Kirkham” named after the optical designer Riccardi Massimo. Their optical design is slightly different with respect to where the corrective lens is positioned and the shape of the primary (“aspherical”) as opposed to ellipsoidal. The result is a somewhat wider field based on the numbers I have read. I also felt the Italian version produced better images than the US version. Additionally I just got the sense that the OS scopes were produced with a little more attention to detail. Each one is custom made, not mass produced. They build them for aerospace and the optical designer is better known (Riccardi Honders fame). So that was my choice!
The journey to first light begins again! This time way more challenging. Not being an electrical or mechanical engineer, it does seem daunting to install and operate a high end professional instrument, especially a foreign one! For this reason I have created a separate blog page entitled “Installing and operating a high end professional telescope…for the rest of us!” This basically will chronicle the installation from the arrival to first light.
Thanks for reading!