Is the William Optics RedCat 51 worth buying?

Started 4 months ago | Questions
starman1969
starman1969 Veteran Member • Posts: 4,414
Is the William Optics RedCat 51 worth buying?

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?

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Steve

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Rodger in Edmonton
Rodger in Edmonton Senior Member • Posts: 3,313
Re: Is the William Optics RedCat 51 worth buying?

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?

I would go for a DSLR lens at that FL , my shortest refractor is a Televue Pronto  at 480 mm

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mikeyL
mikeyL Contributing Member • Posts: 977
Re: Is the William Optics RedCat 51 worth buying?

So firstly, I am a Canon shooter, so my advice on Nikon is based on reading and one Nikon friend who owns the 180mm prime I refer to below:

I have heard and seen some good things from the Redcat scopes. They seemingly fill a niche for a small refractor with decent performance. If you are not familiar with Astrobin, you can head over there (www.astrobin.com ) and type "Redcat Nikon" in the search window, and bring up a number of images captured using that scope on a Nikon DSLR. Some good stuff there.

Conversely, if you then type in "Nikon 180mm" you will get some very nice images shot using that lens on Nikon DSLRs too.

I would guess that the Redcat is likely maybe a little bit better in the corners for star aberrations (coma, etc.) than the camera lens, as the telescope is optimized for infinity focus, and has a simpler lens design than the camera lens. On the other hand the lens is ~3x faster optically, meaning you will get the same signal with the lens and a 1 minute subframe as you would get taking 3 minutes on the Redcat. That is not a small delta, and depending on how well your mount tracks, that could be the difference between a good final image and one with trailed stars. The 180mm is available refurbished for about the same money as the telescope it seems:

https://www.bhphotovideo.com/c/product/731050-REG/Nikon_1940B_Refurbished_Telephoto_AF_Nikkor.html

The lens of course is additionally useful for terrestrial photography and has autofocus. If you add a 1.4x teleconverter to the 180mm, you are at 252mm (identical focal length) and still faster by ~1.5x too.

So from my perspective, while I think the Redcat would give you great results, I think you could get basically as good results optically with easier tracking requirements using the lens. Eventually if you added the teleconverter you would have the best of everything.

Good luck, hope that helps.

ML

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little jim Regular Member • Posts: 149
Re: Is the William Optics RedCat 51 worth buying?

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).

Jim

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little jim

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mikeyL
mikeyL Contributing Member • Posts: 977
Re: Is the William Optics RedCat 51 worth buying?
1

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).

Jim

Jim's advice is spot on - for any deep sky style astroimaging, the mount is absolutely critical for your results. You can have a $20,000 telescope, but if it cannot track the sky accurately, your results will be unusable. So only once you have that figured out should you then see what your remaining budget is for some sort of a telescope or camera lens to use for imaging. Of course, as I stated earlier, for lower magnification and/or faster optics, the tracking requirements are lower than with high magnification or optically slower scopes or lenses. But it is always best to buy more mount than you think you need, as if you stay in the hobby you will likely grow into it with larger scopes or optics in the future that will benefit from its higher weight capacity and better tracking ability

ML

ML

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starman1969
OP starman1969 Veteran Member • Posts: 4,414
Re: Is the William Optics RedCat 51 worth buying?

mikeyL wrote:

So firstly, I am a Canon shooter, so my advice on Nikon is based on reading and one Nikon friend who owns the 180mm prime I refer to below:

I have heard and seen some good things from the Redcat scopes. They seemingly fill a niche for a small refractor with decent performance. If you are not familiar with Astrobin, you can head over there (www.astrobin.com ) and type "Redcat Nikon" in the search window, and bring up a number of images captured using that scope on a Nikon DSLR. Some good stuff there.

Conversely, if you then type in "Nikon 180mm" you will get some very nice images shot using that lens on Nikon DSLRs too.

I would guess that the Redcat is likely maybe a little bit better in the corners for star aberrations (coma, etc.) than the camera lens, as the telescope is optimized for infinity focus, and has a simpler lens design than the camera lens. On the other hand the lens is ~3x faster optically, meaning you will get the same signal with the lens and a 1 minute subframe as you would get taking 3 minutes on the Redcat. That is not a small delta, and depending on how well your mount tracks, that could be the difference between a good final image and one with trailed stars. The 180mm is available refurbished for about the same money as the telescope it seems:

https://www.bhphotovideo.com/c/product/731050-REG/Nikon_1940B_Refurbished_Telephoto_AF_Nikkor.html

The lens of course is additionally useful for terrestrial photography and has autofocus. If you add a 1.4x teleconverter to the 180mm, you are at 252mm (identical focal length) and still faster by ~1.5x too.

So from my perspective, while I think the Redcat would give you great results, I think you could get basically as good results optically with easier tracking requirements using the lens. Eventually if you added the teleconverter you would have the best of everything.

Good luck, hope that helps.

ML

Thank you Mikey. Some good info there. I'm sure the RedCat will have a better quality, but as you say, the 180 here will be faster and it can also be used as an everyday tele lens. Some things to weigh up yet.

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Steve

 starman1969's gear list:starman1969's gear list
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starman1969
OP starman1969 Veteran Member • Posts: 4,414
Re: Is the William Optics RedCat 51 worth buying?

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).

Jim

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.

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Steve

 starman1969's gear list:starman1969's gear list
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elgol20
elgol20 Contributing Member • Posts: 819
Re: Is the William Optics RedCat 51 worth buying?
1

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).

Jim

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
_____
Stefan

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Astrophotographer 10 Forum Pro • Posts: 13,875
Re: Is the William Optics RedCat 51 worth buying?
1

I have had 2 Nikon 180 F2.8 ED lenses and a Redcat 51.

The Nikon 180 was a good lens a long time ago but by today's standards I think it lacks a fair bit. It has chromatic aberration wide open. Its not as sharp as a Redcat.

The Redcat 51's main issue is tilt. It comes with a tilt adjuster now and be prepared to have to use it as my copy was quite off in tilt so corners were quite bad on a full frame.

If you correct the tilt its a good performer.

It is sharp though. F5 is fine for widefield deep sky.

I think though that you would get better bang for your buck by getting a similar costing telescope from William Optics. They have a few around 60-81mm in aperture. The Redcat 51 objective is about 50mm in aperture.

Greg.

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Astrophotographer 10 Forum Pro • Posts: 13,875
Re: Is the William Optics RedCat 51 worth buying?

I have LT 11 mount as well. I would regard using it to run a DSLR FF plus a Redcat 51 as adventurous and you will find your results will only be as good as your Polar alignment is accurate and even then I suspect rather variable.

That probably would also require a balancing arm to get best results. Its pushing it.

Northern Hemisphere users have an easier time of getting a decent polar alignment but I suspect its still close to the absolute limit of a Fornax LT 11.

Greg.

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starman1969
OP starman1969 Veteran Member • Posts: 4,414
Re: Is the William Optics RedCat 51 worth buying?

Astrophotographer 10 wrote:

I have had 2 Nikon 180 F2.8 ED lenses and a Redcat 51.

The Nikon 180 was a good lens a long time ago but by today's standards I think it lacks a fair bit. It has chromatic aberration wide open. Its not as sharp as a Redcat.

The Redcat 51's main issue is tilt. It comes with a tilt adjuster now and be prepared to have to use it as my copy was quite off in tilt so corners were quite bad on a full frame.

If you correct the tilt its a good performer.

It is sharp though. F5 is fine for widefield deep sky.

I think though that you would get better bang for your buck by getting a similar costing telescope from William Optics. They have a few around 60-81mm in aperture. The Redcat 51 objective is about 50mm in aperture.

Greg.

Thanks Greg. I have a bit to ponder. TBH I really wish I never sold my Altair Starwave 72 doublet refractor years ago. I've never been pleased with any scope since.

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Steve

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JeffSlade
JeffSlade Regular Member • Posts: 496
Re: Is the William Optics RedCat 51 worth buying?

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?

It seems to have been designed with the iOptron Skyguider Pro and Sky-Watcher Star Adventurer mounts payload limitations in mind.

I think if you go to astrobin.com you may be able to search for images collected with the RC51 to decide for yourself. Of course post processing skills of the people posting images should be taken into consideration when viewing the image.

The above are my opinions. I'm just another dude on the Internet.

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I believe in wabi-sabi : a world view centered on the acceptance of transience and imperfection. I appreciate beauty that is "imperfect, impermanent, and incomplete" in nature.

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Astrophotographer 10 Forum Pro • Posts: 13,875
Re: Is the William Optics RedCat 51 worth buying?

Check out the Sharpstar 61mm triplet APO at optcorp.com.

With the flattener it handles a full frame sensor and is quite cheap plus a nice focuser.

I'd say that would give the Redcat 51 a serious run for its money.

There are rumours of a Redcat 91 in production.

Greg.

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Saabster Regular Member • Posts: 281
Re: Is the William Optics RedCat 51 worth buying?
3

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?

As an owner of the Whitecat 51 (Redcat was out of stock and Spacecat hadn't been released yet) I have to say yes, it's worth it over a camera lens.

My main camera is a Pentax K-1 and I mount the whitecat on either a Losmandy G-11 or Explore Scientific IEXOS-100.

I absolutely love the FF/Whitecat combo. I also have the following lenses (amongst others), 300mm f/4, 70-200 f/2.8, 150-450 f4.5-5.6. None have them have the flat field, pinpoint stars, and lack of CA that the WC has. Not to mention that I can use 2" Astronomical filters with it.

Here's a few samples of the combination:

M31 45x60sec

51x120sec

M42 60x120sec Optolong L-Enhance filter used.

JeffSlade
JeffSlade Regular Member • Posts: 496
Re: Is the William Optics RedCat 51 worth buying?

Saabster 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?

As an owner of the Whitecat 51 (Redcat was out of stock and Spacecat hadn't been released yet) I have to say yes, it's worth it over a camera lens.

My main camera is a Pentax K-1 and I mount the whitecat on either a Losmandy G-11 or Explore Scientific IEXOS-100.

I absolutely love the FF/Whitecat combo. I also have the following lenses (amongst others), 300mm f/4, 70-200 f/2.8, 150-450 f4.5-5.6. None have them have the flat field, pinpoint stars, and lack of CA that the WC has. Not to mention that I can use 2" Astronomical filters with it.

Here's a few samples of the combination:

M31 45x60sec

51x120sec

M42 60x120sec Optolong L-Enhance filter used.

Beautiful images! What Bortle area were those taken from if I may ask?

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I believe in wabi-sabi : a world view centered on the acceptance of transience and imperfection. I appreciate beauty that is "imperfect, impermanent, and incomplete" in nature.

https://www.flickr.com/photos/billpoplawski/albums/with/72157716942456506
https://www.youtube.com/c/twelfthavenuecuisine

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starman1969
OP starman1969 Veteran Member • Posts: 4,414
Re: Is the William Optics RedCat 51 worth buying?

Saabster 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?

As an owner of the Whitecat 51 (Redcat was out of stock and Spacecat hadn't been released yet) I have to say yes, it's worth it over a camera lens.

My main camera is a Pentax K-1 and I mount the whitecat on either a Losmandy G-11 or Explore Scientific IEXOS-100.

I absolutely love the FF/Whitecat combo. I also have the following lenses (amongst others), 300mm f/4, 70-200 f/2.8, 150-450 f4.5-5.6. None have them have the flat field, pinpoint stars, and lack of CA that the WC has. Not to mention that I can use 2" Astronomical filters with it.

Here's a few samples of the combination:

M31 45x60sec

51x120sec

M42 60x120sec Optolong L-Enhance filter used.

Beautiful images there.

-- hide signature --

Steve

 starman1969's gear list:starman1969's gear list
Nikon AF-S Nikkor 50mm F1.8G Nikon D850 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II Nikon AF-S Nikkor 24-70mm f/2.8G ED Epson Stylus Pro 3880 +1 more
Saabster Regular Member • Posts: 281
Re: Is the William Optics RedCat 51 worth buying?
1

JeffSlade wrote:

Saabster 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?

As an owner of the Whitecat 51 (Redcat was out of stock and Spacecat hadn't been released yet) I have to say yes, it's worth it over a camera lens.

My main camera is a Pentax K-1 and I mount the whitecat on either a Losmandy G-11 or Explore Scientific IEXOS-100.

I absolutely love the FF/Whitecat combo. I also have the following lenses (amongst others), 300mm f/4, 70-200 f/2.8, 150-450 f4.5-5.6. None have them have the flat field, pinpoint stars, and lack of CA that the WC has. Not to mention that I can use 2" Astronomical filters with it.

Here's a few samples of the combination:

M31 45x60sec

51x120sec

M42 60x120sec Optolong L-Enhance filter used.

Beautiful images! What Bortle area were those taken from if I may ask?

Thank you.

M31 was shot in Bortle 7/8 skies

M8/M20 were shot in Bortle 6/7 skies

The Orion Complex was shot in Bortle 5 skies with the Optolong l-Enhance filter. All unguided.

AstroDan Regular Member • Posts: 275
Re: Is the William Optics RedCat 51 worth buying?

There are a lot of excellent results out there for the RedCat. The RedCat (and most telescopes designed with a full frame image circle and matched corrector) will typically outperform a competing lens in terms of resolution/star quality. Where lenses have the advantage is that they are often faster.

I seriously considered a RedCat, but went with the Sigma 105mm instead. My Canon 100-400 overlaps quite closely with the RedCat51 and forthcoming RedCat71, and is one of the few lenses (and a zoom at that) has a flat field, and *reasonably* good stars. It isn't quite as good, but is more flexible, and the overlap left me unable to justify the purchase. The Sigma offered a new tool, so I went that route.

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