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
Last edited by Slawomir; 04-03-2017 at 09:32 AM.
Reason: Clarity and corrected some details
Yes, I think I am good with my astro gear for a while. Now just need to be patient and wait till we move to a new place that will be more conducive for astro-imaging. In the meantime will try to take a few quick snapshots of the night sky and try taking low resolution star spectra. Has anyone got a cloud repellent?
I do wonder what the polychromatic strehl is! It'll certainly be good but I do wonder how good The number itself won't
See any different except to satisfy my morbid curiosity hehe
I have no idea Colin, but to my knowledge my new telescope is diffraction limited within the visible spectrum. Refracting telescope at f/6 will certainly have lower than 0.990 Strehl ratio for blue and red light.
On the report I also got multiple Zernike coefficients and all are near zero. For example Z8 is 0.01 and as I understand this coefficient is a measure of spherical aberration. Several other coefficients are in the order of ten thousandths (4 places after decimal place).
I guess we will need to wait for my first image taken with my new babe :-)
As a side note, if my memory serves me well, I remember reading on CloudyNights that CFF makes also planetary series with longer focal lengths, and their f/10 105mm telescope had/has Strehl ratio equal or greater than 0.995 from red to blue. Now, peeking through such telescope on a clear night would be a very special treat :-)
While I am waiting for some time off work to test the telescope...images of a beautiful 3.2" FT focuser and dedicated corrector that came with the telescope. It is a rock solid beast of a flattener! I do not expect any vignetting on my ICX814
Yes Wavytone, I also hope that the lens will delver, and my expectations are very high since I have been looking for a perfect system.
I'm not worried about reflections in this photo form the inside part of the corrector, as I took the images from the camera's side, with a flash and at an angle that light will not/should not hit it. Similar brighter parts are also present in the Massimo Riccardi reducer that I have, when I take photos in the same way. Anyway everything will be revealed in first test images.
BTW, I would never ever use a pen on a lens, brand new one in particular, as it would void warranty...
EDIT: Weather permitting will have a peek through the new telescope tonight.
Last edited by Slawomir; 07-03-2017 at 04:35 PM.
Reason: Clarity
Being an imaging guy I currently only have hardly used one TeleVue low magnification eyepiece and one even less used TV barlow...nonetheless I was curious how this telescope compares visually with my previous mass produced ones, so taking advantage of clear skies, I had a peek through the new telescope.
First of all, it was not very easy navigating the mount with my laptop while looking through the eyepiece. A hand controller or at least a game pad would make life easier.
But apart from that, it was a true joy just slewing across the sky. Stars were pinpoint and some had natural delicate colour - red, blue, orange points of light. Open star clusters were simply stunning. My low magnification eyepiece hardly challenged the telescope, but these were the sharpest stars I have ever seen. Inside focus and outside focus diffraction patterns looked identical with perfectly centred diffraction rings.
In spite of being purely imaging guy, I am now tempted to look into getting a few nice eyepieces that will complement this beautiful telescope, and I think I may start having an occasional peek through the telescope in between imaging sessions. I think that says something about this telescope.
I should get out doing visual more often... maybe when the mosquito plague buggers off!
Not wanting to get Ross River Fever :/ I went out before to make sure that my stars were coming out round and I could wave my hand around and feel myself hitting them mid flight :/
Really glad you're enjoying your new scope! I'd LOVE one of the 160/180mm super planetaries
may I ask did you import the CFF yourself or go through the local distributor. And how long did you wait for delivery?
I'm thinking of a 140mm CFF as my "final one scope for rest of life"
Edit - my questions are a bit dumb, Suavi, careful reading of your posts indicate you ordered direct and probably waited less than 6 months. (That's what Astro-Physics offered in their early days.)
Colin- we have similar problem with mossies, I do not come outside the house at night without a repellent on. I figured it is better to have some chemicals on my skin than pathogens/parasites in my body
160/180 mm refractor would be nice for sure...but that means a larger mount would be needed too!
Rob - yes, my partner agrees- no more spendings on astro gear!
Dunk - I will need to wait for school holidays before I will take the first image with the new telescope - have too much work at this time!
John - I waited just over 3 months. Delivery from Europe took 4 days. I recommend writing directly to Catalin - you will find him very helpful and he will happily answer any questions you might have. Thus you will be able to clarify any points in regards to your dream telescope and with your planning. I nearly went for their 132mm telescope, but decided that 105mm will be more suitable for me at this stage for imaging with my camera.
I first came across Catalin Fus way back in 2009. He helped me with some very critical objective prisms....
Lost touch when I moved to Belgium/ Australia but I'm glad to see he is following his dream.