Is the William Optics RedCat 51 worth buying?

Started 4 months ago | Questions thread
elgol20 Contributing Member • Posts: 820
Re: Is the William Optics RedCat 51 worth buying?

starman1969 wrote:

little jim wrote:

starman1969 wrote:

I've been after a short focal length refractor for wide field deep space imaging and I have been looking at so many scopes. For a while I have been using standard camera telephoto lenses due to being without a scope for a while.

The RedCat would suit my style of astrophotography more than any other, but I'd like to know if it is worth buying over a similar focal length standard camera lens?

There's no doubt the Redcat51 (250mm/F4.9) would yield fantastic images, even with your full-frame Nikons (most refractors perform best with APSC cameras, FF image circles are hard).

But, given your heavy investment in premium Nikon FF cameras and lenses, I'd recommend seriously considering a premium quality new or used 300mm/F2.8 prime lens, which would complement your 70-200/F2.8 and 500mm/F4. This class of telephoto would give you >4 stops more light and (arguably) better resolution than the Redcat51 with its ~100mm aperture.

But you also don't mention what mount you're using. The saying "put your money where your mount is" applies here.

Committing to the 300/2.8 could put you on the following roadmap (in no particular order):

1) purchase FF mirrorless camera and adapters for best in class Nikkor lenses

2) modify your 800E to astro

3) invest in premium quality equatorial mount

4) think about the manual focus Samyang/Rokinon 135mm/F2 prime to fill out your astro lens collection

5) start saving for a premium quality 600mm/F4!

I've followed the above roadmap (purchased the Sony A7R3 for all-purpose photography, adapted my Sony A7 (Kolari) for AP, adapters for FD and EF Canon lenses, purchased the EF 300/F2.8L UXM (no IS) and FDn 500mm/F4.5L legacy lenses (30 and 40 yrs old respectively) while upgrading my mount from SkyWatcher HEQ5 to iOptron CEM40.

I went through the GAS of considering purchase of a premium quality 5" refractor--purchasing the FD500 and CEM40 cured me temporarily LOL. I'm having a blast with the adapted lens strategy.

Good luck with your choice, you can't go wrong with the Redcat (or its larger aperture siblings).


Thanks for that Jim. Much to ponder here although I used to own a 300mm AF-S f2.8 and it was an absolute beast. Shame I had to sell it as I wasn't using it as much. I'm really after something small & light, otherwise I would have to upgrade my tracking mount. I am using a Fornax LighTrack II tracker.

Hi Steve,

not sure if any here used a Redcat... The quality is better than my Nikon 400 f/2.8, which is really good at f/4, comparing star shapes on fullframe. Given the rather small aperture, it is a joy to use. Easy to focus, superb bahtinov mask, rotator and full frame coverage. The tilting unit might be crucial, but mine was spot on fullframe. So if you get a centered copy and can live with 51mm...

I dare say the telephoto primes will not match it in term of image quality, except maybe a view. From what I know and have seen only the Sigma Art 135mm comes close in the corners. not sure if this is the best it can get. look at mine:

This is done with a D750 and LT II, 2 min exposure and yet far from a perfect alignment.

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Best regards

 elgol20's gear list:elgol20's gear list
Nikon D800E Nikon D750 Nikon D810A Nikon AF-S Nikkor 400mm f/2.8G ED VR II Carl Zeiss Apo Sonnar T* 2/135 +8 more
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