Just want to share with you all my experience on building my own APO Triplet refractor. I always wanted to build my own refractor, I did it recently by purchasing a skywatcher esprit 80ED lens and build the tube around it, but then I wanted a bigger scope with longer focal length.
My aim is to build myself a refractor with APO Triplet lens. It is hard to get the manufacturer that sell the lens cells alone so when iStar Optical released their first batch of 140mm APO Triplet lens, I did not put any hesitation and take a bold jump to be the first adapter of this lens.
It took me 2 months to get the lens from ordering to delivery and meanwhile, I communicated with iStar optical to get the detailed lens drawing as well as the focal length data I need to determine the tube size.
Since I am currently stuck to a tiny island with Bortle 9 sky called Singapore, if I want to use this telescope on a dark skies, means I will have to travel abroad. Thus I will need to design the tube to be in sections so I can take it apart easily and put it into a luggage. Then I went into several design iteration before finally decided to make the tube into 3 sections where each sections is held by a support ring, which also doubles as the ring to hold the lens cells. The next step is to find a factory to fabricate the tube and the support ring and after several email exchange, all went well and produced as per my designed.
As for the rest of the accessories, I bought it from various other brands such as Lens Cover+Bahtinov mask from William Optics, Tube Ring and Dovetail from Primaluce Lab and 3.7" focuser from Teleskop Express. I am also using Flat 68III 1.0x Field Flattener from William Optics and QHY600M for the camera. The full assembled setup can be seen as below. The tube itself is baffled with my very limited understanding on how to do a good baffle, but it works for now.
There is bit of optical tilt on the initial test result thus i have to get a image tilt adapter from Teleskop Express to be installed on the focuser side to counter it. I did consider making a lens cells holder with adjustable tilt screw but that will be too complex for my design.
As I enjoyed the process on making the ATM itself, I have less concern about how the quality of the lens will be, as I already have Skywatcher Esprit 80ED and William Optics GT102 which performs well for imaging. To my surprise, the initial test and subsequent test using iStar Optical lens, shows a very promising result and the more I use it, the more I like it.
This is the test latest test result that I have, NGC 3372 Eta Carinae Nebula with total integration time of 8 hours (Ha: 28x600s & Oiii: 20x600s) using Chroma 3nm narrowband for the filters and QHY600M for the camera. Unfortunately the sky has been less forgiving for the last few weeks and I got problem with my camera but I am excited to get more data with this scope. Full version of the image can be found here: https://www.astrobin.../full/axh2c5/0/
Do let me know what you think or if you have any questions or suggestions.