That's an awesome instrument, but you don't have to spend anywhere near that to get a conventional 'manual' refractometer that will give you accurate readings. I have had
this one for about a year and have been very pleased with it. There are a lot of inexpensive ones for sale on ebay or Amazon. I can definitely recommend this seller, nis_sales (National Industrial Supply) on ebay or magnum_media on Amazon. Pay the little extra to get the aluminum instead of plastic housing, and I'd also recommend the hard plastic case.
I use mine pre boil, pre fermentation before pitching, during fermentation and post fermentation without issues. I've checked them against my hydrometer and it's pretty darn close. As for adjustment, there are programs online that will adjust post fermentation numbers. I'd recommend getting one with both Brix and SG. Mine only has Brix so I have to convert it everytime.
If you use the post-fermentation corrections from
Sean Terrill's website or
spreadsheet, your results will accurately match your hydrometer readings. Most of the other calculators, such as at Morebeer or Brewer's Friend, have pretty big errors, predicting a FG much too low.
I've read that at least some of the refractometers that list both brix and SG aren't that good because the SG scale is not very accurate. It's very easy to print out a chart that converts from brix to SG and just consult the chart whenever you take a reading, so I'd buy one that lists only brix.
Many of them are incorrect, just using a linear factor of 4X, which is valid up to ~1.040/10 Brix, but in error at 1.084/20 Brix. The one I referenced above says it is in error for the SG reading, but it is actually corrected. However, the SG reading is only valid pre-fermentation; once there's alcohol present, you always need the Sean Terrill correction from the Brix reading. Thus, the corrected dual scale is nice to have, but not a necessity.