Help with focal reducers

[Thefatkitty]

Hi all,

I have a question about focal reducers... Not even sure if one will help me so I thought to ask.

So here's the deal. For six years now I have been using my C80-HD at f/11.4 and a Canon camera to take W/L pics of the Sun. The whole Sun fits easily into the FOV, and I align the images with PIPP and stack the results of that with AS3.

At the end of May I acquired the new Baader Ca-K filter. I tried with the DSLR to take pics with it, but the result was really not all that good, as you can probably imagine.

Yikes:

And the same scope/camera setup with a Solar Continuum and UV/IR cut filter (these are from May 29th). Much better:

Alright, I need a mono camera for the Ca-K, and the W/L might even be better. I got myself a ZWO ASI174mm USB 3.0 camera, from what I gather it's pretty much the best for ol' Sol in W/L, Ca-K and H/A, at least in my budget. Since I now have all three wavelengths, I figured this would be a good investment.

So far so good with the camera. I can't speak for the H/A part recently as I'm waiting for a new motherboard for my EQ5, but I know from using my new H/A scope and ZWO camera at Mikes (Solsearcher's) place it does work very well.

This is from that day with my H/A scope and camera; still one of my best days ever:

Now here is where I'm running into a bit of a problem. If I use the ZWO with my C80 I get vignetting. Not a lot, but the whole disc won't fit into the FOV. I have the stock focuser racked out pretty far too, thankfully it's actually very well made.

This is from June 22nd, with my C80 and the ZWO. No processing with this, and the detail is great to me (especially in false colour), but it's not a full disc.

And this is the same day with my William Optics 61mm at f/5.9 and the ZWO. A full disc, but at that F/L I find it a bit "choppy" for detail. The scope is fine, but it's better for wide field deep sky than our star, at least for imaging.

So I'm thinking to make it work with the C80 I need a focal reducer. Agena Astro has a good article on that topic which led me to think this is what I need. They have a GSO 0.5X, but from what I gather that would reduce the focal length of my C80 to a bit over f/6. Not far off from my WO 61mm. Would that degrade the image (my 80mm is an achro, though a very good one)?

And if a focal reducer is what I need, is there one that is 0.8X or about that?

Thanks in advance for any and all help

Clear skies,

[Solsearcher]

A focal reducer will squeeze a full disk image on to the sensor of your 174 using your C80 but will also compress the detail that it captures . Your WO 61 likely has better optics and is better suited for full disk at F 5.9 . The short answer is yes it would work but you might not be happy with the results .
Your F/10 Ha scope is more suited for getting closer higher resolution views and images , for full disk shorter F/L is required , that is what my SM 60 (F6.6) is for . My 60 will contain the full disk but could never bring me the resolution my 90 can .
You will be able to make nice high resolution full disk images with your 90mm Ha scope but it will require a 4 image mosaic . This is more time consuming than a single capture but the results will be much better .

[Lady Fraktor]

I agree with Mike on this, if you do feel the need to experiment with a FR then make sure to purchase from somewhere that you can do a return.
Antares make/ made a 0.7x and 0.8x which a friend uses and really likes them.
He uses a TMB 105 mm f/6.2 for Ha/ Ca-K