Pier 2, the wide field platform, at Orion’s Belt Remote Observatory currently has two available options for imaging scopes. For the last year I have been using the Takahashi 180mm hyperbolic reflector. I decided to retire that for now and install the FSQ106N, just to change things up for the new year 😊
The FSQ is a 4” refractor, employing lenses as opposed to mirrors for the optical elements. The story of the Takahashi FSQ refractors is very interesting. In the early 2000’s the Takahashi company, Japan based, produced a new brand of refractors specially designed for imaging. The inherent problem with lenses is that different colors will focus to different points because of their differing refractive indices. This causes what is known in the industry as “chromatic aberration” so when you are looking in a refractor with lenses that do not correct for this you will see fringes of different colors around whatever you are looking at. Not good obviously.
Manufacturers of refractors therefore produced telescopes with “ED glass” or “Extra low dispersion” glass which is actually a lens doublet providing good correction of the color error. The FSQ line of refractors takes this a step further and actually employs a “quadruplet” lens system based on the design originally invented by Joseph Petzval, a German-Hungarian mathematician, in 1840. This design which employs two doublet lenses not only corrects the color distortion but also creates a much “faster” optical system meaning you are able to register much more signal with your camera in a much shorter period of time.
A few years back I purchased my first Takahashi refractor for visual use. This was an FS102. I had heard for years about the reputation of Tak refractors being amongst the best in the world. The FS series was produced with fluorite glass. Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration than even ED glass. The first time I looked through this FS102 I was blown away! The crispness of the colors and detail were so much better than anything else I had ever seen. It almost had a 3 dimensional look to it where you felt as though you were right there in front of the star cluster or whatever else you were looking at! What does all this have to do with the FSQ? Well up until 2005 Takahashi manufactured the FSQ106N. The “N” version employs one of the two doublets made from fluorite glass as opposed to ED glass. That was the key. Of the 3 models produced since 2000, the FSQ106N, FSQ106ED and FSQ106EDX, the FSQ106N in my opinion yields significantly better contrast than the FSQ-106ED, markedly superior color in images (due to less scatter with the fluorite) and noticeably better flare control on bright objects in imaging. So despite the fact that the N version is the oldest and no longer produced, that was the one I chose. I have produced a couple of images with it already if you look at the Andromeda Galaxy and the most recent one, the IC 410 nebula. For those images I actually had the FSQ mounted on the other Tak scope which was a little cumbersome. This set up with the FSQ by itself should be much more efficient. We will see!
Thanks for reading, and Happy New Year everyone!
DrDave