[Slawomir (Suavi)]

Ahoy Comrades!

Happy days and cloudy nights have arrived to SE Queensland!

A few months ago I decided to upgrade my 4” ED doublet from TS. It served me very well over the past three years, and I have learnt a fair bit about the never-ending journey to perfection in taking pretty astronomical pictures.

After upgrading my mount last year I started wondering whether I would be able to get even better data with premium optics. So after a lot of thinking, reading, thinking, reading…I decided that for the time being I want to stick with a 4” refracting telescope. Then it came down to picking the dream telescope that will be most suitable for my mount and camera and being portable at the same time. Cutting long story short, I contacted CFF telescopes and rather quickly ordered their 105mm f/6 oil spaced refractor.

Catalin from CFF has been extremely helpful, quick in responding and he made everything possible that I was getting what I wanted, including customised carry case, which in itself is a piece of art. He even designed and made custom adaptors needed for my specific camera, so it matches perfectly with CFF’s humongous (to me anyway) field flattener and also with the Riccardi reducer. The flattener offers 44 mm corrected imaging circle at f/6, while the Riccardi speeds the telescope to f/4.5 and the imaging circle is about 40 mm (I need to double check that number). FT true 3” focuser ensures that pretty much all light gathered by the lens is passed onto the field flattener. In one of the photos I placed a 1.25” diffraction grating next to the field flattener. It is a real shame that my current camera’s sensor is so tiny!

As expected, clouds have intensified after the delivery so I am yet to take the telescope out. I will certainly peek through it with my TeleVue eyepiece (yes, I have one eyepiece!) before I attach the camera to the telescope.

The telescope came with optical test report signed by CFF’s optician Pal Gyulai who hand figured the lens. There are a lot of numbers in the optical report that I am yet to understand, but a few numbers caught my eye - RMS wavefront error of 1/62.2 waves, Strehl ratio of 0.990 (both at 550nm) and also RMS surface error of 4.422nm. I think these are outstanding for an f/6 refracting telescope, so I am expecting nice tight stars even with RGB filters.

I will write an update once I have an opportunity to test the telescope visually, at least.

Thank you for reading.

Suavi

P.S. I knew I had to take unpacking photos, otherwise “it did not happen”…


P.P.S. Just confirming the fully corrected circle with the Riccardi 0.75 reducer is indeed 40mm