furgle
19-08-2017, 08:26 AM
I've been working on preparing a new GSO 10" f/4 Newtonian for imaging, and last night I finally had all the spacers and adapters needed to make everything fit together.
I originally bought a Baader MPCC MkIII when I visited OPT in California a few months ago, but completely forgot about it when I ordered a Televue Paracorr 2 from B&H.
Since I had both, I thought I would compare the flattening abilities of both.
Both units require 55mm of backfocus, which I could easily make with spacers, but I'm a big fan of on-axis guiding. Unfortunately the optical path for the ONAG unit was way too long to work with either. I'll have to go back to off-axis guiding, yuck!
With the recommended APS sensor size on my QSI683-ws8, it turns out, the Paracorr is amazingly flat from edge to edge. The MPCC is quite flat in the middle, but quickly curves out at the edges.
The attached pictures show a 3D plot of the field curvature.
The first image shows the curvature without any corrector.
The second image shows the curvature with a Baader MPCC MkIII
The third image shows the curvature with a Televue Paracorr Type 2.
The Paracorr is very long and heavy, but that's the one I'll be using. Maybe I should try the MPCC on some longer focal length scopes as another experiment.
I originally bought a Baader MPCC MkIII when I visited OPT in California a few months ago, but completely forgot about it when I ordered a Televue Paracorr 2 from B&H.
Since I had both, I thought I would compare the flattening abilities of both.
Both units require 55mm of backfocus, which I could easily make with spacers, but I'm a big fan of on-axis guiding. Unfortunately the optical path for the ONAG unit was way too long to work with either. I'll have to go back to off-axis guiding, yuck!
With the recommended APS sensor size on my QSI683-ws8, it turns out, the Paracorr is amazingly flat from edge to edge. The MPCC is quite flat in the middle, but quickly curves out at the edges.
The attached pictures show a 3D plot of the field curvature.
The first image shows the curvature without any corrector.
The second image shows the curvature with a Baader MPCC MkIII
The third image shows the curvature with a Televue Paracorr Type 2.
The Paracorr is very long and heavy, but that's the one I'll be using. Maybe I should try the MPCC on some longer focal length scopes as another experiment.