StellaLyra Classic Cassegrain Review | Planetary & Lunar Scopes

The StellaLyra range of telescopes are f/12 Classic-Cassegrain scopes available from First Light Optics. I received the 6" and 8" models through to play with and in this video I share my feelings and thoughts on these long focal length instruments.
StellaLyra 6" CC f12: bit.ly/37UWKRc
StellaLyra 8" CC f12: bit.ly/2GkGr4M
StellaLyra 6" RC f9: bit.ly/3mIiuDX
StellaLyra 8" RC f8: bit.ly/2HT4msx
StellaLyra RC Reducer: bit.ly/2Jj3y0A
==== My Equipment ====
ZWO ASI 071mc Pro: bit.ly/2RISH0V
Sky-Watcher EQ6-R Pro: bit.ly/2RCrcY9
Sky-Watcher HEQ5 Pro: bit.ly/2L1hyKn
Sky-Watcher Evostar 80ED Pro: bit.ly/2qTd55L
Evostar 80ED Field Flattener: bit.ly/2Uuv7qV
Astro Essentials Mini Guide Scope: bit.ly/2S8Y2yn
ZWO ASI 120mm Guide Camera: bit.ly/31j7kfl
Baader Narrowband Filters: bit.ly/2Us7xvA
iOptron SkyGuider Pro: bit.ly/3g7955D
Rowan Belt Mod Kit: bit.ly/2DMW6EZ
IDAS NGS1 Filter: bit.ly/3ccajvD
Disclaimer: Affiliate links are in use. If you buy through these links then (at no extra cost to you) I get a few pennies :)
==== Contact ====
[e-mail]
www.astrofarsography.com
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===== Music =====
Stellaris OST
Sparks by Chaël:
chael-music.com/
/ chaelmusic
/ chael_music
/ chaelmusicofficial
/ @chaelofficial

[@StargazerFS128]

Nice job giving a rundown of these scopes.

[@derekbaker3279]

I'm a bit late to the party, but here are a number of very important points regarding the importance & impact of the size of the secondary obstruction in an optical system: (This is, by social media standards, a very long message, but worth reading if you're planning on purchasing a telescope...) 1. Yes, a larger secondary will block more light than a smaller secondary, but it is not a significant issue for making visual observations or imaging of the Moon or planets. That's because, as said in the video, all but the outer planets are quite bright, as is the Moon. However, there is another reason... it also has to do with the fact that the light gathering ability of an optical system has to do with the *surface area* of the primary & the *surface area(s)* of any obstruction (s), not just their diameters. Since the *surface area* of a telescope mirror or lens is the *area* of a circle, then the *surface area* of a miirror or lens increases by the *square* of the circle's *radius* (A = pi times r-squared). So, the surface area of the primary in a mirror system is much larger than the surface area of the system's secondary mirror, even if the diameter of the secondary is a third of the primary's diameter. 2. While the increasing the diameter of the secondary's obstruction has only a small effect on the light gathering ability of an optical system, a large secondary still plays havoc with our ability to observe detail on the planets & even on the Moon. That's because seeing planetary details is not just a matter of resolving closely spaced details on a object of small apparent size (i.e. "resolving power"), it's also a matter of discerning features that have low contrast. (In fact, contrast is a more important issue than resolving power when observing the planets) Why is contrast affected? Well, the larger the central obstruction, the greater the level of diffraction of light, which means that point sources become blurry discs & this reduces the contrast in the image. Now, since the resolving power of the objective & the amount of diffraction caused by the secondary/central obstruction both depend on just their diameters (not the square of their diameters), the primary doesn't have as much of an advantage over the secondary. That means even a small increase in the size of the secondary will cause a noticable change in the contrast in the image. Generally, for visual observations, a central obstruction less than 20% of the diameter of the primary causes a detectable but subtle reduction in contrast. A central obstruction that has a diameter that's 25% of the diameter of the primary causes a noticeable reduction in contrast, and central obstructions of 30% to 40% (e.g. Cassegrains, Schmidt-Cassegrains, and Maksutov Cassegrains) cause a significant reduction in contrast. This is why apo refractors provide such enjoyable views & have been the favourites of planetary observers...contrast in planetary, lunar, and even deep sky objects is maximized, because there is no central obstruction. So, for example, the views of planets, the Moon, and bright deep sky objects in a 5-inch apo refractor are significantly better than in a 5-inch Newtonian, Cassegrain, Schmidt-Cassegrain, or Maksutov-Cassegrain. If you ever get a chance to do a side-by-side comparison one evening, you'll see that the difference is not subtle. 3. But how can we compare the contrast of a large reflecting telescope to a smaller apo refractor? Well, it turns out that it's a simple process. If you subtract the diameter of the central obstruction from the diameter of the primary, you will get the diameter of the refrractor objective that gives the same contrast. So, for example, an 8-inch Cassegrain that has a 3-inch diameter central obstruction with will (theoretically) produce the same contrast as a 8"-3"=5" apo refractor. An 10-inch Schmidt-Cassegrain with a 4-inch diameter central obstruction will (theoretically) provide the same contrast as a 6-inch refractor. If you want the best of both worlds, the best option is a F/6 or F/7 Newtonian relector with a moderate to large primary, a small secondary that's less than 25% of the diameter of the primary mirror, as well as accurate, smooth, well-collimated optics. The bad news is that an 8-inch Cassegrain or 8-inch Schmidt-Cassegrain will be less heavy, more easily mounted, more portable, and easier to pack in the car than an 8-inch F/6 or F/7 Newtonian reflector. 4. BTW, why did I say "theoretically" when comparing contrast in a mirror system to an apo refractor? Well, telescopes with mirrors have other sources of diffraction & other image degrading effects that impact refactors less, so the math & comparisons are, in practice, a best-case scenario. 5. Finally, what about imaging the Moon & planets using a camera? Well, to some degree, we can improve the contrast of a single image with processing on the computer & we can noticeably increase contrast by stacking multiple images using computer programs. So, imaging the Moon & planets with a camera is less affected by having a telescope with a large central obstruction than is making visual observations. Furthermore, while larger telescopes are more sensitive to atmospheric turbulence (which degrades the sharpness & contrast in images), they also gather more light, which enables the camera to use shorter exposures & catch brief moments when the atmosphere is not degrading the images as much. The bottom line? Don't expect these Cassegrain telescopes to provide naked-eye views of the planets that blow away the views you get through a 4 to 6-inch apo refractor. However, on nights when the atmosphere is not terribly turbulent, 8-inch Cassegrains, Schmidt-Cassegrains, Maksutovs & Newtonians have the potential to yield better camera images, especially if you can stack hundreds of very short exposures using software (assuming high qualty optics, plus very good/excellent collimation)

[@johnpiettro4644]

Larry Carlino posted a good qualitative review of the 8" GSO CC on CN. He compared its performance to a good 6" APO. While he admitted he had been a long term refractor fan nevertheless he highly praised the 8" CC performance in comparison to his 6" APO. From his review it follows that according to his observing experience side by side 8" GSO CC provided all the visual details on Jupiter he could see in his 6" APO. In his other clarification post he explained that he didn't mean "equal contrast" - however the 8" GSO CC provided just enough contrast not to lag much behind the APO. Some other forum members when sharing their thoughts on using their 8" GSO CC said that they'd never seen so clear Jupiter festoons with any other equipment of equal potential in the similar price niche. Larry emphasized high perceived contrast in the 8" GSO CC. The "theoretical factor" vs practical implementation can probably have great effect on the final image.

[@derekbaker3279]

@@johnpiettro4644 Very interesting! Thank you for sharing this information John. 👍👍

[@jgricourt]

​@@johnpiettro4644 Yep this is what I read too from CN members who did side by side comparisons, this CC beats any classical Celestron 8 for contrast and thus fine resolution on the moon. This is a quite new instrument on the market (not the formula though) and it'll take times before the CC will take Celestron territories in the planetary observing and imaging departments. Now how would it compare to the best planetary reflector of all time, I want to say the Takahashi Mewlon 180 ou 210 ?

[@DanielBoychuk]

@@johnpiettro4644 would a contrast boosting filter offset that contrast loss for visual use? Without dimming the image too much?

[@genefoster8936]

Good review. Clear, concise and useful as I'm looking for an 8" telescope.

[@AstroPixUK]

Another fair and useful review. Keep it up mate.

[@AstroFarsography]

Thank you James, appreciate the kind words. More to come! :)

[@RaysAstrophotography]

Very comprehensive review Ruz!

[@AstroFarsography]

Thank you Ray 😊

[@ohwell2790]

Have one coming the 6 inch should arrive first day of Feb 2021 I am strictly visual and may get a planetary camera for the clear skys of Arizona USA and I am at 3,700 ft altitude -114 longitude and 35.2 Latitude. Thanks for the review very timely

[@mgastronomy]

Hi Ruz. Greetings from Toronto. Ruz, the RC6 is the one I am interested. I want to start learning using this OTA for medium size nebulae and galaxies. I have an 80Mm Apo refractor, but the RC brings the power needed for medium size targets. Your video is focused mostly for planetary imaging. Can you expand about the use of the RC6 for DSO. Very much appreciated. Clear Skies!!

[@MM0IMC]

"Pluto is a planet", well said!

[@MrSpike2450]

Nice one m8, keep the videos coming :)

[@AstroFarsography]

Cheers mate, yep still got a few more to come!

[@williamshaw9950]

Thanks for this video which is very helpful. Clearly this model is targeted at planetary work. However, I’m curious to know for DSO possibility what the diameter is of the decently lit imaging circle and what the increase in spot size is at the edge of that. Also a 0.67 reducer would take this to f/8 which is in DSO Zone. Are there any and if so what is the size of the region of decent correction and illumination?

[@charlessands6933]

Are you saying that the rings are necessary to reach focus visually or photographocally?

[@chrisstrobel3439]

Bit off topic. What size pixels would you recommend for an 8” RC8 using it at f/8? Last time I did deep sky astrophotography was 30 years ago on hypered medium format (6x7) film. Thanks!

[@richiebricker]

Thank you for making this and saving me $500. I was about to part with my money thinking these would be good for deep sky stuff. So I might owe you several hundred dollars

[@MrProulx]

lol nope. They're great for DSO. F12 isnt even slow. I have done DSO at F4-F30. Unless you're observing... Cameras have been around for 100 years though.

[@edenorion]

I Have one of These, a 8" GSO CC. It is fantastic for Moon and Planets. I can operate it Box to visual Moon in about 8 minutes As I'm into Smartphone photography, I've tried it also for Deep sky imaging with Smartphone!!! Some of the results are Quite good for such combination

[@vivek-pc7ld]

Great work

[@AstroFarsography]

Thank you 😌

[@Neil-clare]

Is this scope any good for astrophotography with a ccd ? If so any problems with back focus ? Thx

[@ronstewtsaw]

So what would be a good beginner planetary photography scope? Hopefully one that remains useful after you're no longer a beginner.

[@TheUrbanAstronomer]

Great review.. I have the GSO 8 inch classical cassegrain which I guess is the same thing. Great for planetary, all the points you covered are spot on. Since you asked, do check out my Mars captures with the 8 inch CC and let me know your thoughts 🙂

[@AstroFarsography]

Thanks Nate. I'll be sure to look you up and have a see at these photos ☺️

[@KYREKING]

Good job!

[@AstroFarsography]

Thanks mate ☺️

[@Seafox0011]

Ah the dust caps ... actually they do fit very well ... but nobody tells you how they work. Basically you have to twist them in after finding the loose insertion position, as they are intentionally not perfectly circular. It takes a bit of trying out, but when you get it you realise 'Oh that's how its supposed to work'. The same for taking them off - a slight twist is needed before pulling away. Like a screw top without the screw - effectively a friction collar.

[@AstroFarsography]

Oooooooh I see. Thats handy to know for sure! Thanks for clarifying that most certainly 😊

[@ohwell2790]

I do have one a CC6 and the dust cap just pops in, maybe in your case it is different. Most of the time they just fall out on there own. This telescopes mirrors need a long cool down time, so when I observe it is left outside to cool down. The mirrors are just so so but for the price guess they are a good choice. And people who say they are excellent have never looked thru a really good scope. They are made to a price and that is wheat you get. It is a planetary and lunar scope, for any thing else not so much.

[@Dryfee]

Music is from the game Stellaris.

[@AstroLaVista]

Cool review Ruz :) Look at you juggling them OTA's like they weight nothing, If I tried that I would be making all sorts of straining noises. You do indeed move the primary mirror to focus with both Mak's and SCT's so off axis guiding is needed for mirror flop. I think you'd be ok to guide with a separate scope on the rail because of the fixed mirror, although the thought of trying DSO's with a CC at f/12 is petrifying lol Kudos for giving that a go and talking about it. Cheers. EDIT: You can swap the rails over so you don't need a Losmandy adaptor, this is what I did with my Stella Lyra 8" RC to fit the Vixen saddle of my EXOS2 PMC Eight. I agree the dust caps are annoying to get on and off, they don't match the fit and finish of the rest of the scope.

[@AstroFarsography]

Thanks buddy, yeah it looks a lot easier in the video 😂😂 I see then, so OAG would be better for SCT/Mak and a regular guider should be fine for these. That's good to know I'll remember to add that to my written review! Glad I'm not the only one about the dust covers then ☺️

[@AstroLaVista]

@@AstroFarsography The only things I'll add Ruz is it's probably best to have a reasonably long focal length guide scope so there isn't too much of a discrepancy between arc second per pixels. E.g. if your guide scope is at 4 "/pixel and your main scope is at 1 "/pixel then your main scope could smear the stars quite a bit before your guider notices any change. An OAG may still be a good idea if you're struggling with load capacity or think you may have too much flexure where your guide scope attaches to your main scope. ps I only know all this from years of reading forum posts, I mainly used to image at shorter focal lengths unguided, but that will need to change with the 8RC!

[@Mistr_A]

Great video

[@AstroFarsography]

Thanks Nick!

[@southbronxny5727]

Imo-Pluto is the only true planet. Pluto is the only one that orbits on the Sun's true ecliptic plane. The Sun is tilted 7 degrees and none of the current classified planets are on it.

[@AstroFarsography]

Ooh that's a scientific way to make a claim about Pluto. Love it! Didn't know that either so that's my thing learnt for today 😏 thanks

[@edjones3390]

Great review -would love to hear your opinion on the StellaLyra RCs if you should get a chance

[@AstroFarsography]

Thank you Ed. I would love to sometime with the RC model but I don't think that's what the plan is next. I know Chris at DIY Astro has just got himself the 8" StellaLyra RC I believe if you want to go check him out.

[@GarnettLeary]

You’re correct in Maks. The mirror is moved inside the system.

[@AstroFarsography]

Thanks for confirming that. I really dislike that system. What do you think about it?

[@GarnettLeary]

@@AstroFarsography I absolutely love Maksutovs. I prefer the optical design being perfectly corrected right out of the box. I like that it holds collimation so well. I like the high focal lengths. I like the closed system. I don’t mind that it’s typically F10 or higher because I prefer depth to speed. That’s my overall thoughts on Maks.

[@lornaz1975]

The focuser and the tube cap makes me think it is manufactured by GSO.

[@DavesAstrophotography]

Long focal length is a nightmare to align. I went from the 1000mm 8" Newtonian to the 2800mm 11" SCT Edge and the first time I looked through the eyepiece I hadn't a clue where I was looking at. You try to point to what you think is the alignment star and you are miles off and so many more stars appear its near on impossible to work out what's what. In this instance, the likes of the Star Sense Auto Align is essential.

[@AstroFarsography]

Yeah I know what a pain to align huh. I thought I was at Vega for example bust couldn't see anything at all. A while to set up intially but at least it's semi easy to keep your focus marks and such

[@Astronurd]

Just use a 30mm 82 degree eyepiece to find and centering your target. Piece of cake

[@runematthijssens2304]

0:01 What a badass.😎

[@AstroFarsography]

😎

[@TheAngryAstronomer]

The cost of mirrors seems to go up by the square of it's diameter. I swear this is just a slightly modified GSO Ritchey Chretien though.

[@stew_redman]

Exactly what I was thinking. Focuser looks like the standard GSO (Bintel) model.

[@Seafox0011]

Partly correct, RC's have a differently configured primary mirror and secondary mirrors (hyperbolic). Whereas the Classic Cassegrains (these here) have a parabolic primary and hyperbolic secondary mirror. In all the other aspects these are GSO form factor branded tubes. One thing to note, is that there are 2 different types of glass used ... and the more expensive ones offer less thermal expansion ... which is critical for holding the very fine focus required with these. (Buyer beware as ever! In other words really research what is on offer.)

[@TheAngryAstronomer]

@@Seafox0011 This is the kind of nuanced reply I was hoping for. :)

[@stew_redman]

@@TheAngryAstronomer Your original comment, which I read properly, did say "modified" :)

[@AstroFarsography]

That makes a bit more sense now then and explains the price for an extra 2" 😊 thanks

[@Sislajo]

For the 6 inch. CO = (58/154) x 100% = 38%. 33% CO is for the 8 inch and the reason is it has a undersized secondary, making it lose light.

[@charlessands6933]

Using both metric and imperial measures is common.

[@charlessands6933]

Yes, in Maks and SCs, the mirror DOES move.

[@vivek-pc7ld]

How many price in indian money

[@AstroFarsography]

About 76,500 rupees, but converting money isn't always exact

[@ShevillMathers]

I thought RC scopes were around the f/8 ratio, unlike those under review. RC’s tend to be more expensive.

[@AstroFarsography]

They are, these are classical Cassegrain versions but StellaLyra do have F8 and F9 RC variants available also. But they are actually s out the same price

[@ShevillMathers]

@@AstroFarsography I have a real mix of scopes from Newtonian's, SN-10, SN-10 modified (rare).Tak Mewlon 210, Tak 180 /2.8 Astrograph, Tak. FS 102 an a range of lower priced scopes. I have far more scopes and cameras than is decent, obscene really but as one ages and does not smoke, drink or play golf, I indulge now and again apart from all the scopes I have built.Southern Cross Observatory-Tasmania 42 South. Ex Pom living down under with dark skies where so many or the 'goodies' are located. Did my 32 years in Leeds and smog and clouds and rain and snow----

[@BrianFraser]

Wow 6 months and these have gone up by 25%

[@backgammonbacon]

F number is meaningless without knowing aperture and focal length. F12 at 1836mm focal length is amazing. Increasing the focal length i.e. the zoom on a fancy ED 80 to 1800mm changes it's F number from 7.5 to 22.5! And you have no detail in your images because you have a tiny aperture of 80mm instead of 153mm of the StellaLyra. Stop being obsessed about F numbers, they are useless on their own. The StellaLyra is blindingly fast for the focal length it uses.

[@rickpaul9858]

Pluto IS a planet.

[@AstroFarsography]

Yes! 👊

[@1966wasp]

Tuned out at £800.

[@AstroFarsography]

Yeah, it's s few pennies isn't it

[@PerEinarL]

1:40 Pluto IS a planet, but a minor one🤪

[@AstroFarsography]

I can never keep track of its designation these days haha

[@PerEinarL]

@@AstroFarsography lol! I’ve hunted asteroids this fall and have been a contributor to the team of OSIRIS-REX😎 a couple of days ago my scope was assigned with a observatory code and is now called G13😁 it’s an very interesting part of astronomy😉

[@AstroFarsography]

@@PerEinarL oh wow what an awesome experience, congratulations! 🤯 Hope you and your G13 go on to achieve great things! Astroid hunting does seem an interesting part but I don't think I'd be able to contribute much from bortle 6 skies unfortunately 😂

[@PerEinarL]

It’s actuallu not that hard, but it’s some work because you have to know where the asteroids are, and some of they change place very fast🙈 the asteroids shows up like stars do, so bortle 6 is no obstacle😉

[@I_Spaced_Out]

Did you just say Pluto is a planet? I'm unsubbing... :p

[@AstroFarsography]

:O Wow, rude! :p

[@I_Spaced_Out]

@@AstroFarsography ;)