I’ve already tried this refractor Field Flattener on a SkyWatcher Evostar 80ED in a previous post. To sum it up, it did perform well on the Evostar and the best value was the Starguider 2″ Field Flattener sold by Sky’s the Limit on ebay.co.uk, which is identical to the TSFlat2 from TS (but the TSFlat2 is more expensive and does not include any adapters/extensions). So, without any delay here is my first test with the flattener at 119mm from the Canon 600D sensor:
It is a 1:1 crop of the left side of the image (click to see full size). As you can see the correction is pretty good. There is a SkyWatcher corrector/flattener for the Equinox, but it is good to see there is a generic like the Starguider / TSFlat2 which works well in multiple refractors, so you could get it without worrying whether it will work when you switch/upgrade to another refractor.
The 119mm distance was achieved by using the 15mm extension and the 38mm T-adapter included with the Starguider, as well as a couple of 2″ filter rings:
Inexpensive extensions to achieve perfect distance
As you can see above, I have a few 2″/48mm filter rings that I can use as extensions to achieve the perfect distance between the flattener and the sensor. Most filter rings add about 5mm to the optical distance and you can find them either in surplus places like astroboot, or salvage them from broken etc filters, or find some cheap 48mm photographic filters on ebay and remove the filter.
There is another clever thing you can do if you want a small (usually about 7mm) extension ring like this one for under $5:
Yep, that’s a 48-52mm step up ring and a 52-48mm step down ring which together form a 48mm extension, you can find them very cheaply on ebay (esp. if you get them from China). You can also look for 48-49 stepping rings etc, but the 48-52mm are the most common right now on ebay.