Quote:I am not aware that a binoviewer increases magnification in Newts unless you use a GPC or Barlow.In SCTs and MCTs with moving mirrors, they do increase magnification, but not in Newts without the use of a GPC or Barlow.
Hardin DSH-10 f5,DSH-6 f8, dobs Tasco Luminova 4.5in newt ota f8 Coulter e-scopes primary SkyWatcher Pro 100 ED f9 refractor Generic ST80 Omni cg4 eq, Vixen Porta II alt/az, mounts 2in 53mm pl & barlows; 1.25in 26mm pl, 19mm w70, Speers-Waler 13.4mm,4.9mm; Orion 6mm planetary, Vixen nlv 4mm, Antares 2x 3-element barlow. Burgess Model 24 binoviewer. 10x50,15x70 binocs Other eps,barlows,stuff
Quote:Ebbisham has nailed it, but I will add a little.Because the binoviwer uses prisms, a fast light cone can start to seperate and show chromatic aberration because of these prisms.The Glass Path Corrector is designed to cancel this error out and to shorten the light path.A Balow that doubles the focal ratio will do much the same thing but only at 2X or greater.If one desires to get the least magnification possible and can reach focus without the GPC, then it is not really required for general observing, but the binoviewer will induce CA in fast telescopes.For example, I tried Solar White Light with my SV110ED. Even though I could reach focus without the GPC, I was shocked to see how bad the CA was.I put in the 1.25 GPC and the improvement was pretty dramatic. There was still a tiny amount of CA, but that was coming from the scope itself.So, I use the GPC for planets and solar, but I remove it for DSO and wide field observing.Again, if you use a 2X Barlow or a slow scope like an SCT, you may not see the result, but with a fast scope, expect the see CA without a properly designed GPC.
Quote:I do not know if the Denkmeier GPC was specifically designed to ofset CA or not, but since the Denk front element is bascially a 2x Barlow, the light cone from it is not all that steep.The most important element would be the low power reducer arm becasuse this will make the light cone fastser.But this is also the low power element, so at low powers, CA will not be as noticable or as important.And straight though, the front OCS is working and that is somehthing like 2.3x, so even an f/5 telescope light cone will hit the BV body at f/10, yes?I have useed two Denkmeier powerswitch systems and have not noticed CA.Now if you used an a la carte bino head in a fast refractor, my guess is that you would have CA without a GPC.But these are all just guesses. I don't know what steps Denk has taken to deal with the issue, but for the low power arm, it probably does not make any difference, and straigh though and high powers are running behind the 2X GPC with a very shallow light cone.