I bought a Celestron 6" Schmidt Cassegrain for lunar and planetary work. I added a x0.8 reducer/corrector for small bright deep space work at f/6.3. I then added a Starzona Hyperstar 6 v4 for large dim deep space targets at f/2. I chose a 6" SVT (instead of an 8") because that with a SvBony 405cc (asi294) plus the reducer/corrector or Hyperstar plus a Celestron aluminum dew shield is the heaviest my Sky-Watcher Star Adventurer GTi can handle. Quite nice and versatile rig. I have and really like a couple Newtonians, but the wind keeps blowing dust down the tube onto the primary mirror and I have to keep disassembling them to clean it. They are also rather large sails and when the wind gets up I can do 12 knots on the lake. I have an SvBony 80mm ED refractor and it really easy to use, but is a wide field and not of much use for planetary and lunar work. I also have a wide field (70mm and 80mm) achromats and a Celestron 102mm achromat with a 1000mm focal length. I like it a lot. Good for lunar and planetary work and small bright deep space objects and only suffers limited chromatic aberration.

Excellent report! I would just like to comment that in reality the degree of obstruction of the secondary of the Cassegrain designs (classical or SCT), along with that of the Ritchey-Chrétien, is among the highest, in this sense the loss of contrast in a Newton design will always be somewhat minor, especially in Newtonians with high focal ratios. In astrophotography, SCT has the "advantage" (if I can say that, since many of us don't dislike how they look in photos) that it avoids the diffraction spikes typical of Newtonians. Finally, I think it is important to also note the "image-shift" effect typical of designs whose focusing is carried out by moving the primary mirror, and which, especially at high magnification, can be a bit annoying until the image is stabilized. It can be solved by incorporating an R&P focuser in the optical train. It is also worth mentioning that they are collimable (only the secondary mirror) and, in fact, their collimation status should be monitored, especially if they are transported. In this sense, the refractor is the world champion of "maintenance-free"... The comparison between the 4" ED refractor and the 5" SCT will be very interesting...

I have always wanted to own a SCT but could never afford it; maybe one day. Until then, I have owned a 10" Newtonian reflector on a German equatorial mount that has provided years of enjoyment. Thank you for a very informative video.

well presented, well thought out ! Look forward to more watching more of your content !

Thanks for an excellent and informative video, as always. I acquired a 6-inch SCT as the largest practical size that I could bring on a commercial airliner as carry on. I was also able to transport it quite easily by car from Toronto to Dallas for the recent total solar eclipse and the view were absolutely outstanding.

Great video!! Most appreciated!

Excellent video. I wonder how the 125mm SCT would compare on the Moon, planets and DSO to the 102mm Svbony ED :)

I am new to telescopes but old at looking at the sky. I understood most of what you said here. Thank you.

For wide view the Starizona Hyperstar is available for 6” SCT and larger. Gives you F/2 for wide field and less time needed for taking images. F/6.3 and F/10 for galaxies and planets. A very versatile scope. I just got into this hobby last year and I got an Celestron 8” SCT with AFX mount. My experience over the last 6 months tells me I would advise spending a little more on a mount vs getting something like the Celestron AVX, a Skywatcher HEQ5 would’ve been a better choice for an affordable equatorial mount. Higher focal lengths need better guiding. You will also need to use an OAG for guiding vs a guide scope. Higher focal lengths can cause issues with plate solving so choosing the correct camera for astrophotography is important. I had my C8 corrector plate adjusted and the secondary mirror collimated with the primary mirror as they were slightly off from the factory. My C8 with Starizona F7 corrector, Celestron OAG, ASI174mm guide camera and ASI071MC weighs in at about 19lbs.

A video with the 5 inch SCT vs 4 inch Svbony ED please :)

Unfortunately SCTs are so expensive, the one with 150mm aperture is over 1000 euro and the 200mm over 2000 euro.

Comparing SCT's with their cousins Maksutov-Cassegrains would be interesting too. I have heard the following points: 1) Maks have thicker and more complex corrector, and because of that, due to economic considerations, they're limited to about 6 inches of aperture (bigger corrector lenses for Maks are simply to expensive to manufacture); 2) Since Maksutovs have thicker correctors, they need more time to reach ambient temperature than Schmidt-Cassegrains; 3) On the bright side, Maksutovs have smaller secondary mirrors, which means less obstruction for the light, and bigger effective aperture, compared to SCTs of the same size. I have also noticed that Maksutovs have greater focal lengths and slower F-stops, but i'm not sure this is a hard rule. Are these points correct? Have I missed anything?

Bogdan, I just love your videos ❤. I am about to buy a 6" SCT and pair it with skywatcher AZ gtix, so I can add a Lunt solar telescope at the same time for sun observations in continuum and H alfa.

I would be interested in a side by side comparison between the SCT and your 4 inch APO.

Thanks Bogdan.

Outstanding video! Thank you so much for putting you together. I love my SCT. Would you please consider doing a similar video for the RASA design for Astro photography? Thanks again!

Well a 5 inch SCT is 450-500 euro, for that money I would rather buy a 4 inch ED FPL51 Svbony doublet like yours.

Hello Bogdan, an off topic question. What magnification do you use with your Svbony 102 refractor to see galaxies and nebulas ? I also have the Svbony 102 and weirdly I can see galaxies better with a 20mm 68 degree eyepiece at 35x magnification than with a 32mm Super Plossl at 22x magnification. I thought the lower the magnification, the higher the brightness for galaxies. Now I’m confused. Did you experience something similar? Thank you!

Excellent review of the Schmidt-Cassegrain telescope Bogdan, thank you. A question; are there SCTs with parabolic as oppose to spherical mirror?

I am having a very hard time plate solving with my C14 and a full frame camera😢 For example, impossible to plate solve when pointing at M 51 .

👌👌👌

@Bogdan you tested 120mm triplet and this c8, cost is about the same around 1700eu, which one you think does a better job doing the jack of all trades for visual?

Would the larger focal length of an SCT benefit someone who just does visual astronomy? Higher focal length= higher magnification resolution which would mean planetary viewing would be better than a traditional Dobsonian? Let's say the dob/SCT have the same aperture for argument sake

Where is your 122mm apochromat?

A deep dive into SCT that stopped at Celestron. LOL