Yes those are the two setups I am comparing.
I am using the astro physics photo visual 0.75 reducer with the c11. I bought adapters so that this reducer plugs in before the diagonal. I’m pretty sure this was the setup I was using in February when I was doing my galaxy observing with the c11 (there’s a thread with images here but I don’t specifically mention the reducer).
Since getting my Tak Epsilon in September I’ve been much more focused on getting nice edge stars because I think the Epsilon produced such horrible stars at the edge with the 55mm plossl.
So I recall that I do get round stars at the edge with the c11 and 55mm plossl, both with and without the photo visual reducer. To be honest I’m not seeing any flattening affect from any reducer I am using (eg the gso reducer with the Baader earlier this week didn’t have any noticeable impact on the edge stars but I’m happy with that since they look fine to me). Certainly the images I took in February with the c11 show decent edge stars imo. But I will check this next time I’m out with the c11.
Over the past 6 months I’ve gradually become more negative about using the 55mm plossl afocally. It gives noticeable edge distortions even with f6.6 refractors. This is something that has been noticed by all the U.K. NV users. I’m guessing that operating the plossl at such large exit pupils of 10mm plus is pushing it too hard. I think the 41mm pan will be my main NV eyepiece now using it in the Epsilon and most of my refractors (in conjunction with the gso or ap reducer).
However, the exception may be the c11 where I really need to reducer and 55mm plossl to get the speed down to an acceptable for me visually of f3.5.
I tried a field flattener with the Baader and 55mm plossl but this just bloated the edge stars significantly so didn’t work.
A big issue I have found with the reducers and 41mm panoptic is the need for lots of in focus. Hence i need to put the reducer in the diagonal rather than before the diagonal which reduces the reduction a bit to say 0.8x but enables me to reach focus.
With the c11 this hasn’t been an issue. So another experiment I’m going to try is the ap reducer before the diagonal and the gso reducer after the diagonal. May well cause vignetting but would get the c11 down to f 2.8 which for visual would be nice.
For phonetography I can take exposures up to 30 seconds so f3.5 to f5 works fine but for visual I’d like to get nearer f2. The Epsilon with the 41mm pan giving f2 is a very nice visual setup.
Edited by Gavster, 02 April 2019 - 02:39 AM.