Televue Paracorr 2 vs Baader MPCC MkIII on a 10" f/4

[furgle (Adam)]

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.

[Slawomir (Suavi)]

Thank you for sharing your findings Adam. It looks like both correctors significantly decrease the FWHM across the field

I have found that in order to get reliable measurements with CCD Inspector, I must take a minimum of 15, ideally dithered images, and also calibrate them with a master bias, and then upload the images to CCD Inspector for analysis.

I know it usually is a pain, but it might also be worthwhile in a long term, if only for the peace of mind, to move the correctors 1mm closer and also 1mm further away to see if that improves stars shapes.

I have been contemplating a fast 10" Newtonian myself, so I will be looking forward to reading about the results of your investigations

[Atmos (Colin)]

This is pretty close to what I've seen done on another astro forum

The Paracorr also has tighter FWHM than the MPCC.

[gb44 (Glenn)]

I would like to know how the original Baader MPCC (which I have) would compare to the Parrcor... have they improved it towards the later versions?


GlennB


Newts 18in f4.5
Dk 16in f6.9