160 replies to this topic

[Stopforths]

http://scopeviews.co.uk/TMB_C8.htm

 

came across the review above. 

Surprised me how apparently superior the 4 inch apo is and how relatively poorly the c8 performed.

 

I've been using a 4 inch f-8 FC classic Tak and a meade 8 inch classic sct lx200GPS for a couple of years now often side by side:)

 

The Tak is superb identical star pattern either side of focus very sharp appears to perform to its potential.  A florite doublet no CA visible at any power on any object in focus.  On Jupiter and Saturn there is plenty to see and I often use 200 x plus to advantage.

 

5th and 6th star in trapezium easy most nights in the refractor and Sirius is easy to split most nights.  It is high here in NZ.  Deep sky is excellent razor sharp stars amazing detail on emission nebula.  Globular clusters  like Omega Centaurus and 47 Tukana nicely resolved. Cooldown is fast no question and in general this scope inch for inch would be superior to the Meade 8 inch sct

 

 

The Meade is a good example very nice all round views.  It takes longer to cooldown than 4 inch apo  but in under 1 hour its usually no longer showing the plume in out of focus diffraction rings.  The in and out diffraction rings show very little spherical aberration and a generally smooth figure.  The 2003 model has the uhtc coatings.

 

To sum this up the refractor is sharper and in poor seeing before the meade 8 is properly cooled seems indeed to outperform the SCT.  However on Jupiter the 4 just can't keep up the meade shows more detail and better colour etc.  Its still very sharp in the apo and like an etching but it's not able to beat the laws of physics.  The meade shows amazing detail at 230-250 times on Jupiter the refarctor runs out of steam at 200 X.

 

Saturn same again refractor goes well up to 250 x but sct handles 300 plus more to see more colour more detail.

 

Re deep sky refractor is sharper but the sct outperforms it on most objects brighter and still very nice images.   Very obvious on 47 Tuk and Omega centaurus its so much brighter and still sharp.  Eta carina is also much better in the 8 a lot more nebula visible.  On close doubles well the refractor has an edge on close double stars in poor seeing but not when things get going.

 

I spend hours looking through the Meade 8 and really enjoy it.  It can't go as low or as wide as the refractor but its gulping a lot more light.  I compared it to an 8 inch sw newt recently and there was little to separate them.

 

So my impression is slightly different than the review above but there you have it.

 

 

 

[alnitak22]

I’ve had my 6” f/8 Newt side by side on Jupiter with a friend’s Tak FS102 three times over the years. The 6” Newt edged out the 4” apo on all 3 occasions. And not just in my eyes..also in my friend’s opinion. My 6” f/12 Mak is even a bit better than my Newt on Jupiter. So there you go! My Mak is insulated and needs zero acclimation time for high power use even in dead of winter.

[jgraham]

I was shocked at the super sharp image produced by my 1950s vintage 4” f/15 Unitron refractor. It sets the high mark for a sharp image.

 

However…

 

If I critically compare the true resolution of the Unitron with an 8” SCT the 8” actually delivers a smidge higher true resolution as measured by the ability to split close doubles. The image through the Unitron _looks_ sharper as it shows a sharp, textbook Airy disk surrounded by beautifully sharp, tight, concentric diffraction rings. In contrast the Airy disk and diffraction rings produced by the SCT are not as clean.

 

Soooo, my conclusion is that my 4” f/15 refractor produces a higher quality image, but the SCT delivers a smidge higher resolution.

 

How about that, physics works.

 

P.S.

 

I also noticed that as I compare larger SCTs up to 12” the true resolution continues to improve as it should, but the larger aperture pumps more light into the image, making little flaws and foibles easier to see. The refractor also acclimates so darned fast it settles down _much_ faster than any Cat. Thank goodness for Lymax!

 

Edited by jgraham, 03 May 2023 - 04:59 PM.

[RichA]

http://scopeviews.co.uk/TMB_C8.htm

 

came across the review above. 

Surprised me how apparently superior the 4 inch apo is and how relatively poorly the c8 performed.

 

I've been using a 4 inch f-8 FC classic Tak and a meade 8 inch classic sct lx200GPS for a couple of years now often side by side:)

 

The Tak is superb identical star pattern either side of focus very sharp appears to perform to its potential.  A florite doublet no CA visible at any power on any object in focus.  On Jupiter and Saturn there is plenty to see and I often use 200 x plus to advantage.

 

5th and 6th star in trapezium easy most nights in the refractor and Sirius is easy to split most nights.  It is high here in NZ.  Deep sky is excellent razor sharp stars amazing detail on emission nebula.  Globular clusters  like Omega Centaurus and 47 Tukana nicely resolved. Cooldown is fast no question and in general this scope inch for inch would be superior to the Meade 8 inch sct

 

 

The Meade is a good example very nice all round views.  It takes longer to cooldown than 4 inch apo  but in under 1 hour its usually no longer showing the plume in out of focus diffraction rings.  The in and out diffraction rings show very little spherical aberration and a generally smooth figure.  The 2003 model has the uhtc coatings.

 

To sum this up the refractor is sharper and in poor seeing before the meade 8 is properly cooled seems indeed to outperform the SCT.  However on Jupiter the 4 just can't keep up the meade shows more detail and better colour etc.  Its still very sharp in the apo and like an etching but it's not able to beat the laws of physics.  The meade shows amazing detail at 230-250 times on Jupiter the refarctor runs out of steam at 200 X.

 

Saturn same again refractor goes well up to 250 x but sct handles 300 plus more to see more colour more detail.

 

Re deep sky refractor is sharper but the sct outperforms it on most objects brighter and still very nice images.   Very obvious on 47 Tuk and Omega centaurus its so much brighter and still sharp.  Eta carina is also much better in the 8 a lot more nebula visible.  On close doubles well the refractor has an edge on close double stars in poor seeing but not when things get going.

 

I spend hours looking through the Meade 8 and really enjoy it.  It can't go as low or as wide as the refractor but its gulping a lot more light.  I compared it to an 8 inch sw newt recently and there was little to separate them.

 

So my impression is slightly different than the review above but there you have it.

Under good seeing conditions, with good optics, the 4 inch should beat the 8 inch SCT on everything except:  the Moon, sun, planets, asteroids, comets, globular clusters, open clusters, galaxies, reflection and emission nebula, planetary nebula.

[Oldfracguy]

This thread could not have appeared at a better time!

 

I've had a few 4" ED Doublets over the past couple years.  Some have been the "regular" ED type with FCD-1, FPL-51 or FK-61 glass elements;, while others have had the better SD glass FPL-53 or FCD-100.  I recently sold a used  AT115EDT to fund the purchase of a Celestron Evolution C8 SCT--my first foray in the SCT world--after trying a number of Maks ranging from 90 mm to 150 mm in aperture.  I only do visual observation, so I thought gaining some aperture would be of some benefit.

 

I was pretty impressed when, on the very first clear night with the C8, I could see both the E and F stars in the Trapezium from my Bortle 6-7 backyard.  I had only previously seen the E and F stars using an AT125EDL, and the F star appeared intermittently when I was able to see it.  However, as time went on, I could tell that the images with the C8 were not as sharp and detailed as with a refractor.  In fact, I was looking at Albireo the other night, or should I say early morning, and it looked better with a 90mm achromat!  The colors of the component stars were more pleasing in the little refractor than in the SCT.  So now the C8 is gone, and as its replacement, arriving in a fews days, is a new AT102EDL.

[Bomber Bob]

Considering these 3 Classic Scopes (all from the 1980s):  Tak FC-100, Meade 826, and C8... at my age, it boils down to:  What do I want to see? and/or Do I want to see color?  How much time do I have?  Is also a factor; as is each scope's hassle-factor.  My 4" APO rig is easiest, followed by my C8, then my 8" EQ Newt.  On a clear, moon-less, non-work night, ease-of-use doesn't matter.  Does the night favor faint fuzzies?  My Newt wins.  Is the seeing iffy / does it limit observing to doubles?  My Tak wins.  I'm still learning what my C8 can do, but generally, I see it as the multi-object scope when seeing is less than 8, but good enough to do some looking.  Up to now, my FC-100 got the most use, but I think it my C8 may move into that role:

 

- Pretty Good at most objects.  (As the OP posted, Planetary Colors!)

- Easy 2-step setup / take down.

- Comfortable (refractor like) observing posture.

 

BUT... The Swamp doesn't put thermal stress on scopes.  Most nights, air temps drop gradually, and CATs adapt about as well as Newts.  In fact, my TV eyepieces are more likely to fog-up than my scopes!

 

 

Another small detail that I like about my C8:  It uses 2" accessories, and I have an uncommon set of 1980s spectros Kellners (50/40/30mm) with 35mm barrels & a 2" adapter for them.  They perform so well in this old CAT:  pin-point stars in FLAT fields in their natural colors.  It's possible that these eyepieces have Zeiss glass.  Either way, M35 - M38 are stunning views.

Edited by Bomber Bob, 03 May 2023 - 06:49 PM.

[Echolight]

I love my 8 inch SCT for being able to go way high on the Moon and seeing details that would be unavailable in a four inch anything. I swear the seas look like the sands of the Sahara. And every wrinkle rille and dimple reveals itself.

It sucks up nebulosity like a vacuum.

 

I use a reducer corrector. And I believe it makes the view flatter, better, wider, more precise way out.

 

Edited by Echolight, 03 May 2023 - 07:03 PM.

[gstrumol]

You may not believe this, but a few months ago I submitted an article to CN entitled "Can a 4" APO beat an 8" SCT? Yes and no". 

 

Hoping to see it appear soon ...

[carolinaskies]

It's an apples to oranges comparison, and always has been with the refractor camp insisting it's 'better'. 

The reality is a well aclimated and collimated SCT of 8" performs as an F/10 while the compared refractors perform at F/8 and often include extreme internal baffling and happen to cost 2-3x as much.  It's going to therefore exhibit the attributes of having the more compact native FOV and any extraneous light scatter removed entirely.  It's simple.  

What isn't discussed often in these comparisons is the body gymnastics of observing with the refractor vs the SCT.  They eyepiece placement varies considerably while using a refractor while the SCT on it's native fork mount is ergonomically much more reasonable over a long night's observing. 

As SCT aperture increases the ability of the scope to immediately pop out fainter targets increases dramatically, it's the nature of having 200% more light hitting the retina and actually firing off more color receptors.  If you observe long enough with larger SCTs the eye becomes accustomed to being more relaxed with the longer FL eyepieces even as power climbs above 200x, meanwhile smaller apertures have to pull out shorter FL eyepieces and often require having about every minor difference in FL to try to push the little aperture to it's extremes.  

The SCT doesn't have to push to extremes when it's got aperture to spare, the eye stays relaxed, the iris opens, and the target becomes mesmerizing as the eye soaks in the photons over a long period.  Aperture simply trumps the game.  

These days, those in the know use reflectix or some other thermal blanket to even the playing ground on cool down BTW.  

 

[luxo II]

You may not believe this, but a few months ago I submitted an article to CN entitled "Can a 4" APO beat an 8" SCT? Yes and no". 

You donned a flame-proof suit, right ?

Edited by luxo II, 03 May 2023 - 09:03 PM.

[gstrumol]

You donned a flame-proof suit, right ?

Like stuntmen use in the movies! 

 

Although with the answer being 'yes and no' it's clear everyone will be both satisfied and disappointed!

[Stopforths]

You are all lucky I didn't throw the Mewlon 180c in the mix now thats a fine scope a wee bit dimmer (no surprises there) than the Meade but clearly has a slight edge on planets.  I love the dilemma which one will I use.  

 

lx200 8 great for starparties public groups and just enjoying whats up there on any night generally gets more use.  

[Spikey131]

I have a halfway decent 4” refractor which I hang a few inches to the left of a pretty nice recent 8” SCT.  So I get to make comparisons quite a bit.

 

They make a great pair.  And they both have their strengths and weaknesses.  But there have been so many times that I am straining to see some planetary detail in the 4”, and then pop over to the 8” and then, well, there it is, plain as day.  Or a tight double, or one with a dim secondary, the 8” just plain shows you stuff that a 4” won’t.

 

Of course the Beehive or the Pleiades or the double cluster just fit better in the great FOV of the NP101.  And the star images are just beautiful.  So it is a great complement to the C8.

 

But anyone calling a 4” refractor “superior” to an 8” SCT is just not paying attention.  Mr. Vine’s “review” is stacked in favor of the objects selected.  For double stars, he picked 3 wide bright examples.  I would like to see how the TMB performs on a dim sub-arc second pair like Omega Leonis.

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[alnitak22]

I have a halfway decent 4” refractor which I hang a few inches to the left of a pretty nice recent 8” SCT.  So I get to make comparisons quite a bit.

 

They make a great pair.  And they both have their strengths and weaknesses.  But there have been so many times that I am straining to see some planetary detail in the 4”, and then pop over to the 8” and then, well, there it is, plain as day.  Or a tight double, or one with a dim secondary, the 8” just plain shows you stuff that a 4” won’t.

 

Of course the Beehive or the Pleiades or the double cluster just fit better in the great FOV of the NP101.  And the star images are just beautiful.  So it is a great complement to the C8.

 

But anyone calling a 4” refractor “superior” to an 8” SCT is just not paying attention.  Mr. Vine’s “review” is stacked in favor of the objects selected.  For double stars, he picked 3 wide bright examples.  I would like to see how the TMB performs on a dim sub-arc second pair like Omega Leonis.

A great combo! 

[Brent Campbell]

I directly compared my 102 mm Stellarvue access to my ultima c8 on Jupiter. The c8 that night topped out at 303x with an explore scientific 6.7 mm eyepiece.  The Stellarvue topped out at 238 x using a 3 mm eyepiece but the best combination of detail was with a 5 mm eyepiece at 143x.  The c8 showed more detail but the refractor was close.  I would say for functionality the refractor was 75 percent of the c8 in terms of detail,  If the seeing was better that night I believe that the c8 would show its aperture advantage more.  
 

Npthing wrong with either scope.  I am really enomoured with the Stellarvue right now.  I believe it has a bit more magnification in it and I recently purchased a couple of barlows to see if I can used the equivalent of a 2.5 mm eyepiece.  But there is no way the Stellarvue will beat the c8 there is just too much aperture advantage.  However the Stellarvue is a really sweet scope where the ergonomics are much better.

[RichA]

I have a halfway decent 4” refractor which I hang a few inches to the left of a pretty nice recent 8” SCT.  So I get to make comparisons quite a bit.

 

They make a great pair.  And they both have their strengths and weaknesses.  But there have been so many times that I am straining to see some planetary detail in the 4”, and then pop over to the 8” and then, well, there it is, plain as day.  Or a tight double, or one with a dim secondary, the 8” just plain shows you stuff that a 4” won’t.

 

Of course the Beehive or the Pleiades or the double cluster just fit better in the great FOV of the NP101.  And the star images are just beautiful.  So it is a great complement to the C8.

 

But anyone calling a 4” refractor “superior” to an 8” SCT is just not paying attention.  Mr. Vine’s “review” is stacked in favor of the objects selected.  For double stars, he picked 3 wide bright examples.  I would like to see how the TMB performs on a dim sub-arc second pair like Omega Leonis.

It's great.  I've done the same comparison.  Then it starts to change around 200x when the refractor begins running out of light. Colours of planets begin shifting to the green as the other  colours become too dim to trigger the color response of the cones in the eye.

[quilty]

I'd very much have the TMB side by side with my venerable 2080. Pretty sure, my conclusions were quite different from those in the quoted review.

[bobhen]

I don't think that your findings are a surprise. The 8" SCT is twice the size! The fact that the much smaller 4" refractor even keeps up with the SCT on Jupiter is surprising. Would that 4" refractor come as close if compared to an 8" refractor? Would anyone even think of comparing a 4" SCT to an 8" refractor? Why don't people ever do that? What would the differences between a 4" SCT and an 8" refractor be on Jupiter? Would there only be a 30-50x difference?

 

Here is a section of Mr. Yoshida’s List of telescopes ranked for "planetary observing". Notice that a Takahashi TSA 120mm (only 20mm larger) than the 4" refractor bests the C8. Every refractor on the list larger than 120mm bests the C8 when it comes to planetary observing.

 

(73）TAKAHASHI TSA-120
(73）Takahashi FS-128
(73）INTES-MICRO ALTER-7
(72）William Optics FLT132
(72）Takahashi CN212
(70) TMB 115mm/F7 LW
(70）PENTAX 125SDP
(70）Takahashi FS-102 TWIN+EMS
(70）CELESTRON C8

 

As refractors get close to or over 5" and when compared to a C8 on deep sky, it starts to become object dependent. Objects that are already high in contrast like globular clusters (bright points on a black background) are best seen with raw aperture, even if that aperture is of lesser quality. Objects that are low in contrast like say M1 can be better seen with optics (mirrors or lenses) that are of high optical quality and are inherently high in contrast, even if "slightly" smaller. This is true of deep sky objects as well as with the planets.

 

Here is what Mr. Zambuto has to say about contrast: HERE is a link.

 

I currently own a C8 and a TSA 120 refractor. I have also compared the TSA 120 to 4 other 8" SCTs. And for the planets, I totally agree with the placement of the two scopes on the list above.

 

Bob

Edited by bobhen, 04 May 2023 - 06:53 AM.

[quilty]

I wouldn't state a 4" SC equals a 4" frac, but many SCs perform below their potential. Due to unnoticed missalignment or mirror shift/flop whereas such thing is most unlikely to occur to a frac.
I just assume in comparison with my 2080 the above test wouldn't have been that clear. Even more, I think at most disciplines the SC would have bested the frac. And indeed, all comparisons at the same powers.
No doubt that pleiades is better in a short frac (like my Bresser 102/460) for you can't get them properly into the f/10 SC.
But that wasn't a fair comparison.

I guess we all know the SC is a compromise and no one aiming for optical perfection would consider it.
But a good 8" SC is at price and hassle level similar to a small frac and at performance not inferior.

Just read, pretty much the same as KevH is writing.

Edited by quilty, 04 May 2023 - 07:42 AM.

[KevH]

I don't think that your findings are a surprise. The 8" SCT is twice the size! The fact that the much smaller 4" refractor even keeps up with the SCT on Jupiter is surprising. Would that 4" refractor come as close if compared to an 8" refractor? Would anyone even think of comparing a 4" SCT to an 8" refractor? Why don't people ever do that? What would the differences between a 4" SCT and an 8" refractor be on Jupiter? Would there only be a 30-50x difference?

 

 

 

Bob

I think the answer is pretty obvious why one might compare a 4" refractor to an 8" SCT as opposed to the other way around.  In general, the typical  4" refractor and the 8" SCT share price points and mounting requirements. You can get a nice 4" ED doublet for $1,000 - $1,200 and a basic C8 for $1,200ish.  If you go triplet vs EDGE or ACF, the prices are again similar. Couple this with the fact that an 8" SCT and 4" refractor can both ride on a GP class mount and it is obvious to me why they might be compared often.  

 

When given time to acclimate and with good seeing, the 8" SCT will pretty handily beat a 4" refractor.  Although having spent time with both, I currently have the refractor and not the SCT.  Glad I took the time to compare them to see what worked best for me.

Edited by KevH, 04 May 2023 - 08:53 AM.

[Oldfracguy]

Putting a layer of that double-sided reflective radiant barrier "reflectix-like" stuff on that C8 I had was the first thing I did when it arrived.  I also used it to cover a dew shield I fashioned out of think flat black poster board:

 

 

Using this reflective stuff on SCTs and Maks is pretty much par for the course nowadays, because it works. 

 

I won't dispute the fact that 8" of aperture will trump a 4" anything.  It was quite pleasing to be able to use a 10mm UFF eyepiece with ample Eye Relief and hit 200x without shifting out of second gear as they say.  I routinely had this Evolution C8 past 400x when seeing permitted.

 

I just prefer the pristine views through a good ED refractor.  It's simply a personal preference thing.

 

 

[Echolight]

I think the answer is pretty obvious why one might compare a 4" refractor to an 8" SCT as opposed to the other way around.  In general, the typical  4" refractor and the 8" SCT share price points and mounting requirements. You can get a nice 4" ED doublet for $1,000 - $1,200 and a basic C8 for $1,200ish.  If you go triplet vs EDGE or ACF, the prices are again similar. Couple this with the fact that an 8" SCT and 4" refractor can both ride on a a GP class mount and it is obvious to me why they might be compared often.  

 

When given time to acclimate and with good seeing, the 8" SCT will pretty handily beat a 4" refractor.  Although having spent time with both, I currently have the refractor and not the SCT.  Glad I took the time to compare them to see what worked best for me.

My C8 was way cheaper than any 4 inch apo new or used. 

 

Comparing it to something like a TMB 115 mentioned in the post above is ludicrous from a financial standpoint. Plus that 115 is like a boat anchor in comparison weight wise.

Nice scope, sure. But who wants a 20 pound 115.

[Douglas Matulis]

Aside from the fact that many SCT owners don't collimate their telescopes well, if at all, I wonder if the fact that he compared a modern APO against a 40 year old Celestron SCT....?  Just wondering...

[KevH]

My C8 was way cheaper than any 4 inch apo new or used. 

 

Comparing it to something like a TMB 115 mentioned in the post above is ludicrous from a financial standpoint. Plus that 115 is like a boat anchor in comparison weight wise.

Nice scope, sure. But who wants a 20 pound 115.

SCTs can be had cheaper on the used market for sure which is another reason someone may compare one to a 4" refractor.  More aperture, less money, same mount.  Buy the cheaper SCT and maybe sell the refractor and pocket some cash.  If you are buying new, they are comparable to entry level APOs though. I bought my 4" doublet for $1,100 brand new.  New C8s are listed everywhere I looked for $1,200 - $1,300.  Close enough and my point on why people may compare the two stands.

Edited by KevH, 04 May 2023 - 09:04 AM.

[Jeff Lee]

My avatar says it all for me.