CN FORUMS ARCHIVE Telescope Reviews: Reasons I choose a Baader Mk.V

I've owned both and used them extensively in the short Stowaway, the long Stowaway, the Traveler, the AP 130 f6, the AP 155 f7, and the AP 10" f14.6 Mak-Cass. They work in all, but certain scope/eyepiece combinations need the Barcon to come to focus. The Mk IV is a very nice binoviewer. Both have excellent optics/prisms and take high power eyepieces without showing prism aberrations. The MkV has better light throughput due to better coatings but the difference is at the limit of perception and is barely noticeable, hence Roland's decision not to upgrade (AFAIK, he didn't say he preferred the Mk IV, he said he just didn't feel the need to upgrade). The most notable difference is the MkV's adjustable self-centering eyepiece holders. Nice. The Mk IV doesn't have them, just a single setscrew, so diopter adjustment involves pulling one eyepiece out a bit.

There were a few issues with the initial production run of the Mk IV's that were addressed in subsequent runs, so if you are looking for one be sure to find out when it was produced.

First, there was no stop that would prevent a very long eyepiece barrel from hitting the prism. Not a problem with normal length eyepieces but some of the Radians have a long barrel and can ding the prism on one side (can't remember which side, right or left, but I think it was the right side). There was a user-installable stop issued and it solved the problem; installation involved opening the housing of the binoviewer and installing the stop over the prism, but it is an easy fix as long as you are very careful.

Second, the eyepiece opening of the initial run units was exactly 1.25" and an eyepiece that has a barrel of exactly 1.25" will get stuck in the holder, depending on temperature (differential expansion between the aluminum eyepiece holder and the brass barrel of the eyepiece, would fit if the temperature was low but would bind when the temp was above about 85 degrees F). My Zeiss Abbe orthos, whose barrels measure exactly 1.25" (gotta love that German precision!), would get stuck during solar observing and I'd have to cool them down to extract them. I sent the binoviewers to Roland and he machined out the eyepiece opening 0.001" and they worked just fine thereafter. Of course, the anodizing was gone on the inside of the eyepiece holder but that was a cosmetic issue that could only be seen by looking into the opening. He reported the problem to Baader and they adjusted the opening size a little on subsequent runs so it would not be an issue.

Third, the Baader prism diagonal originally had a plastic housing. Worked just fine but seemed a little cheap to put even one piece of plastic on a fine instrument like that. They later went to a metal housing for the prism diagonal, not sure if there was a change in optics to go with it, but the one that comes with the MkV is superb.

If you get the Mk IV look for the Lapides adjustable eyepiece holders. Expensive (about $500 IIRC) but they work very well, adding both a diopter adjustment on one eye and brass compression rings on both. Keep in mind you will have to recollimate the eyepiece holders once you change them out, not difficult but something to keep in mind.

Overall, I'm glad I upgraded to the MkV and you'll love them if you get one, but if you can get a deal on the Mk IV's and don't mind not having a diopter adjustment they will give you excellent images at a much lower price.

Paul Gustafson