Amazing Spot Diagrams

The William Optics Cat 91 WIFD telescope has an amazingly flat field, as shown in the attached spot diagrams. Its spots are smaller than the Cat 71 and the Tak 106, and are just barely larger than the Airy disc, meaning that the Cat 91 has effectively diffraction-limited optics. See our video short and unboxing video for details:
https://youtube.com/shorts/U5-3OE1IOag
https://youtu.be/6CY6tjgaBWM

We're excited for the clouds to disappear so we can get this scope under the stars! I see in this forum that a few have already taken images with it.

By the way, the William Optics website is listing this telescope as the "Cat 91 WIFD," not the "RedCat 91 WIFD." The same applies to the other cats, they're now called the Cat 51, Cat 61, and Cat 71.

spots.png

Mine is getting delivered today, very excited to test it out

Glad it’s starting to arrive!

Preordered from a German store but no news on delivery date yet.

following.

Using the ASTAP Aberration Inspector, Ren and I tested star shapes and sizes on the Cat 91 in this video, using actual images that we took of the night sky using our Cat 91 telescope and ASI6200 MM Pro camera:
https://youtu.be/45oKJdrK0JQ
The stars are tiny and round all the way to the corners of a full-frame sensor. This scope's a winner!
Boyd

Spot diagrams are cool - but I would never buy a scope based on marketing 'data' the manufacturer provides to sell the scope…

Lots of people are saying "oh but its spot diagrams are better than a Tak FSQ106EDX4…." and sure. That's what William Optics is saying… But William Optics want you to buy the scope… They will say anything they can get away with saying in order to make that happen.

Until I see a side by side comparison of the Cat 91 vs FSQ106N (N, not EDX4, the N is the better scope) that clearly shows the WO scope is better, I'm going to believe that this is marketing hype, not factual data.

Its definitely a known thing that people with Tak refractors will believe until the end of time that their ridiculously expensive telescope is the be all and end all of optical perfection - and I honestly feel that they are generally over priced and only a few select models are really stand out, incredible telescopes. The FSQ106N, is one such model, along with the TOA130 and TOA150. The newer FSQ106's (EDX models) are not as nice as the N. Almost all Tak scopes come with garbage rings (clamshells), the focusers are generally rubbish and require replacement…

Do I think the WO Cat 91 could be, dollar for dollar, an all round 'better buy' than the FSQ106? yep… I think so… Will it outperform an FSQ106 optically in the real world… I doubt it.

Alex Nicholas:
Spot diagrams are cool - but I would never buy a scope based on marketing 'data' the manufacturer provides to sell the scope...

Lots of people are saying "oh but its spot diagrams are better than a Tak FSQ106EDX4...." and sure. That's what William Optics is saying... But William Optics want you to buy the scope... They will say anything they can get away with saying in order to make that happen.

Until I see a side by side comparison of the Cat 91 vs FSQ106N (N, not EDX4, the N is the better scope) that clearly shows the WO scope is better, I'm going to believe that this is marketing hype, not factual data.

Its definitely a known thing that people with Tak refractors will believe until the end of time that their ridiculously expensive telescope is the be all and end all of optical perfection - and I honestly feel that they are generally over priced and only a few select models are really stand out, incredible telescopes. The FSQ106N, is one such model, along with the TOA130 and TOA150. The newer FSQ106's (EDX models) are not as nice as the N. Almost all Tak scopes come with garbage rings (clamshells), the focusers are generally rubbish and require replacement...

Do I think the WO Cat 91 could be, dollar for dollar, an all round 'better buy' than the FSQ106? yep... I think so... Will it outperform an FSQ106 optically in the real world... I doubt it.

Alex, our new video compares actual star shapes in images that we took of the night sky by the Cat 91, not spot diagrams, with the Cat 71. It would certainly be interesting for someone to compare star shapes of the Cat 91 with a Tak, but I don't own one. If you do, please contact me so we can arrange for an image comparison.
Boyd

There will be a RedCat 108 and WO planning to make a comparison among the RC108, SQA106, and FSQ106.

Shun-Chia yang:
There will be a RedCat 108 and WO planning to make a comparison among the RC108, SQA106, and FSQ106.

That's interesting!
Boyd

Ren and I posted our Cat 91 First Light video on our Sensor Sensibility YouTube channel: https://youtu.be/Ly60EQ8eBfM
And we posted our first Cat 91 images to our Sensor Sensibility Astrobin gallery: https://www.astrobin.com/users/SensorSensibility/
Boyd

Would really appreciate some raw stacks and subs on a full frame sensor if you are willing to share. Thanks.

Shun-Chia yang:
There will be a RedCat 108 and WO planning to make a comparison among the RC108, SQA106, and FSQ106.

That is indeed interesting. I have a RedCat 71 WIFD and it is nice but a bit short FL. I also have a 106N - close 20 years old. As another post said, this is a great scope and better than the current FSQ - but only after equipped with a decent focuser (Nightcrawler in my case) and a decent mount (AP 1600 in my case - it is only one of two scopes on that). The QC on my 106 was also not what it should have been and originally had to go back to Japan to be fixed. Once that was all done it has been wonderful (which it should have been out of the box).

It would be great if WO can come up with a true competitor to the FSQ and with a better focuser and better QC (and hopefully a lower price). That would all but kill off Takahashi's FSQ which, as is stands, is less than ideal in many respects and needs a lot of band-aiding to bring it up to what it should have been to begin with.

Bill McLaughlin:
Shun-Chia yang:
There will be a RedCat 108 and WO planning to make a comparison among the RC108, SQA106, and FSQ106.

That is indeed interesting. I have a RedCat 71 WIFD and it is nice but a bit short FL. I also have a 106N - close 20 years old. As another post said, this is a great scope and better than the current FSQ - but only after equipped with a decent focuser (Nightcrawler in my case) and a decent mount (AP 1600 in my case - it is only one of two scopes on that). The QC on my 106 was also not what it should have been and originally had to go back to Japan to be fixed. Once that was all done it has been wonderful (which it should have been out of the box).

It would be great if WO can come up with a true competitor to the FSQ and with a better focuser and better QC (and hopefully a lower price). That would all but kill off Takahashi's FSQ which, as is stands, is less than ideal in many respects and needs a lot of band-aiding to bring it up to what it should have been to begin with.

It looks like their current focuser is pretty good with its resistance to sag. The only question is how to outfit it with a premium autofocuser. Has anyone outfitted it with an Optec? If these scopes are really good optically I’d seriously consider one if I could use something better than an EAF or clone.

Dan:
It looks like their current focuser is pretty good with its resistance to sag.

I can't imagine why anyone would want to put an aftermarket focuser on any WIFD scope. The whole idea is to focus internally and eliminate camera sag. I am quite impressed with my 71 WIFD although since it is mounted next to my CDK 14, it has only had one image so faras the CDK tends to get used more.

Ashraf AbuSara:
Would really appreciate some raw stacks and subs on a full frame sensor if you are willing to share. Thanks.

Happy to help. For what purpose would you like the data? We could supply raw stacks of our Andromeda or Rosette image. Supplying individual subs would take a huge amount of space, but we could supply a few if needed.

Bill McLaughlin:
Dan:
It looks like their current focuser is pretty good with its resistance to sag.

I can't imagine why anyone would want to put an aftermarket focuser on any WIFD scope. The whole idea is to focus internally and eliminate camera sag. I am quite impressed with my 71 WIFD although since it is mounted next to my CDK 14, it has only had one image so faras the CDK tends to get used more.

Right - I don’t think replacing the focuser would be desirable or even possible. It would just be good if a premium autofocus could be put on it. Right now I think only the EAF and maybe the QHY Q are compatible.

Dan:
Right now I think only the EAF and maybe the QHY Q are compatible.
QUOTE

Agreed. The EAF and QHY are OK but the step size could be smaller, especially for that f ratio. Maybe WO will come out with something better......

Dan H. M.:
Bill McLaughlin:
Dan:
It looks like their current focuser is pretty good with its resistance to sag.

I can't imagine why anyone would want to put an aftermarket focuser on any WIFD scope. The whole idea is to focus internally and eliminate camera sag. I am quite impressed with my 71 WIFD although since it is mounted next to my CDK 14, it has only had one image so faras the CDK tends to get used more.

Right - I don’t think replacing the focuser would be desirable or even possible. It would just be good if a premium autofocus could be put on it. Right now I think only the EAF and maybe the QHY Q are compatible.

The Astroasis Rose is also compatible with the 33mm clamp (at least on the currently released WIFD scopes).

Bill McLaughlin:
The EAF and QHY are OK but the step size could be smaller, especially for that f ratio.

There's a high-precision version of the QHY that would probably do the trick.

Those of you who have bought one, do the actual pictures live up to the spot diagrams? I would like to get one of these this summer but I want know if the hype is real.

Jim Bishop:
Those of you who have bought one, do the actual pictures live up to the spot diagrams? I would like to get one of these this summer but I want know if the hype is real.

I was thinking that if it is really that good as the spotdiagrams I would very likely buy it.

However, from what I have seen on CN, it looks IMO horrible.

The posts of December 13th by w7ay. Might be a day more or less depending your timezone.

https://www.cloudynights.com/topic/941228-william-optics-redcat-91-wifd-f49-petzval-refractor-telescope/page-7

Habib Sekha:
Jim Bishop:
Those of you who have bought one, do the actual pictures live up to the spot diagrams? I would like to get one of these this summer but I want know if the hype is real.

I was thinking that if it is really that good as the spotdiagrams I would very likely buy it.

However, from what I have seen on CN, it looks IMO horrible.

The posts of December 13th by w7ay. Might be a day more or less depending your timezone.

https://www.cloudynights.com/topic/941228-william-optics-redcat-91-wifd-f49-petzval-refractor-telescope/page-7

What looks horrible about it? A spot diagram just shows what in-focus stars should look like across the frame. Someone’s raw results right out of the box will never be perfect. Especially with a FF chip tilt correction will need to be done. In the photo there it looks like that is the case.

Jim Bishop:
Those of you who have bought one, do the actual pictures live up to the spot diagrams? I would like to get one of these this summer but I want know if the hype is real.

Yes. The pictures live up to the spot diagrams. See https://www.youtube.com/playlist?list=PLbjxJx_E7x9DHPj-LW6lxDFzRPa5e8bmN
and
https://www.astrobin.com/users/SensorSensibility/

Boyd Edwards:
Jim Bishop:
Those of you who have bought one, do the actual pictures live up to the spot diagrams? I would like to get one of these this summer but I want know if the hype is real.

Yes. The pictures live up to the spot diagrams. See https://www.youtube.com/playlist?list=PLbjxJx_E7x9DHPj-LW6lxDFzRPa5e8bmN
and
https://www.astrobin.com/users/SensorSensibility/

I saw that review and thank you for that. One is point, two is a line, three is the beginning of a trend. ;)

Dan H. M.:
Bill McLaughlin:
Dan:
It looks like their current focuser is pretty good with its resistance to sag.

I can't imagine why anyone would want to put an aftermarket focuser on any WIFD scope. The whole idea is to focus internally and eliminate camera sag. I am quite impressed with my 71 WIFD although since it is mounted next to my CDK 14, it has only had one image so faras the CDK tends to get used more.

Right - I don’t think replacing the focuser would be desirable or even possible. It would just be good if a premium autofocus could be put on it. Right now I think only the EAF and maybe the QHY Q are compatible.

Turns out the Optec ThirdLynx DirectSync APX25 is compatible with the WIFD focusers. If I ever do get one of these scopes it will be nice not to have to deal with a crappy autofocuser.

My scope has arrived as well the Optec ThirdLynx DirectSync APX25. Once assembled and placed on top of my C11" in my observatory, I will send a few images to share and report on its utility. I am hopeful that the 91 WIFD design prevents sagging with a 7- position filter wheel, rotator and ASI6200mm as such sagging did occur with my Tak FSQ 85-EDX.
Just as a FYI, I own 2 other Optec ThirdLynx DirectSync autofocusers and these are fantastic, albeit expensive, autofocusers.

I have the mentioned Takahashi FSQ106N. so thought I would comment.

Some people say the focuser is not good, but I would dispute that. I have no issues with the Tak Focuser and I also run mine with a ZWO EAF. it works great.

as for spots, I believe they are just theoretical things, which might not have a real value. experts will know more.

its nice to compare images from different telescopes, and draw conclusions, but seeing on the night makes an incredible impact on FWHM values.

FWHM values can fluctuate to the extent that no relevant data comparison can be obtained, unless of coarse dual imaging trains were running simultaneously.

I also very much doubt that any mass produced optics can reliably compete with hand configured optics like Stellarvue, Takahashi and Astro Physics.

Time will proves how good this new scope is. are they hand configured ?

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