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1998 C8 SCT Starbright vs new C9.25 XLT SCT Visual only

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#1 GGK

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Posted 14 May 2021 - 03:36 PM

Has anyone done a visual observing comparison between a C8 SCT with Starbright coatings and a C9.25 SCT with XLT coatings?  Visual only, please.

 

I have read all I can find on CN and see many opinions and theories and quoted numbers, but haven't found anyone who said that they actually looked through both enough to know if the C9.25 XLT enables someone to see any more detail or any more faint objects visually when compared to an older C8 with only Starbright coatings.

 

I read that moving from Starbright coatings to XLT coatings in the same OTA size is barely noticeable.  I also read that moving from an 8 inch SCT to a 9.25 inch SCT is barely noticeable. (that you really need to step to an 11 inch to get any significant impact)

 

I have a 1998 C8 Starbright SCT and might have the opportunity to replace that with a new C9.25 XLT SCT.  Although the OTA price is good, I would need the larger dew shield, heater strip and case, so there is still a lot of money involved.

 

I am a visual observer only.  What difference, if any, good or bad, will I see in my eyepiece if I make the change?

 

I use an EQ6-R mount so have no issue with the weight. I know I will lose some field of view. With my C8, I use 1-1/4 and 2 inch eye pieces with and without a focal reducer, and use both a 2" Baader BBHS Mirror diagonal and a BBHS T2 prism diagonal.

 

Thanks, Gary



#2 BlueTrane2028

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Posted 14 May 2021 - 03:45 PM

I have two Celestron SCTs.  An 8" Celestar, unsure of production date, starbright coatings, and an Evolution labeled C6, XLT coatings.

The 8 pulls more light than the 6, "worse" coatings or not.  Seems likely that the extra what, 2% in reflectivity, isn't able to make up for the much larger than 2% aperture increase (8" is nearly double a 6" using area of circle math).

Now, to the 8" vs 9.25" question.

9.25" is a third larger than the 8" using area of circle math.  It will be a difference, but perhaps not enough to truly wow you.

I once owned Dobsonians in 6", 8", 10" and 12" all at the same time.

10" was like a brighter 8", the 12" was the "wow this is better."  Kept the 8" and the 12", although I'm likely to sell my 8".

If this is making sense to you, great.

I presently own SCTs in 6", 8" and 12" sizes.  Haven't gotten the 12" out the door just yet, but I am looking forward to planet season with it.


Edited by BlueTrane2028, 14 May 2021 - 03:47 PM.

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#3 Supernova74

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Posted 14 May 2021 - 03:51 PM

Well without a side by side comparison it would be a close call I used to own the C8 with starbright coatings back in the earlier part of the 90,s mind you this would be comparing to the more modern XLT coatings which are more advanced however not leaps and bounds but should be noticeable!?.the 9.25 on the other hand is a different kettle of fish altogether not so much it’s slight more light grasp it’s shear optical performance is second to none and in my opinion is celestrons gem in there line up it’s just a great performer for visual moon,planetary observing and no slouch either on deep sky objects.


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#4 junomike

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Posted 14 May 2021 - 04:32 PM

I've compared a C11 StarBright against a C11 XLT.  The difference was noticeable If you looked for it, otherwise they seemed more similar than different.

The larger aperture IME will be more of a factor than anything.


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#5 GGK

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Posted 14 May 2021 - 05:48 PM

Thanks for all of the comments so far. Everyone is seeing the challenge to the question. Will the combination of the improved coatings AND the next step in aperture make an easily noticeable visual improvement in the eyepiece even though either change by itself is not of major significance? As said, I truly appreciate everyone’s comments and experience because I surely don’t know the answer to this one.


Edited by GGK, 14 May 2021 - 05:51 PM.


#6 ewave

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Posted 14 May 2021 - 06:25 PM

I compared my former C8 edge to my slightly older C9.25 Edge and found quite a difference between those 2 scopes.

The C9.25 edge outperformed it on planets and DSOs.  It went deeper and resolved better.  My c9.25 behaves more like a C11

than a C8.  Even the color saturation of Jupiter, Mars and Saturn and some contrasting double stars were very apparent. Planetary

detail also outstanding.

 

My recommendation is for a new C9.25 (fastar ready on the secondary) to ensure you get one with the latest coatings.  You will notice a difference.

Besides, just how long before those older coatings begin to wear on your C8?  Go for a C9.25.  You'll be glad you did.

 

Clear skies


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#7 Bean614

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Posted 14 May 2021 - 07:02 PM

I've had all the scopes mentioned, and I'm of the opinion that the 9.25 scope is just better, period. The XLT coatings are one factor, the larger aperture another.  But, there's also the 'slower' mirror of the 9.25 (f/2.3 vs f/2), that adds to the equation. 

Now, in 2018 I  had 2 Nexstar-11 GPS scopes, both Carbon Fiber, both made in the US, both with Fastar capabilities. 

  One had Starbright coatings, the other XLT. 

    On Planets,  they were, to me and to my friends, identical!

However....... On EVERYTHING else, the one with XLT coatings was clearly better, in many different ways--- Color, Brightness,  Contast, Depth, and more.

      And this was, for the others observing, a true 'blind test', since both tubes were wrapped in Reflectix,  and exposed parts, and mounts, were identical.


Edited by Bean614, 14 May 2021 - 07:26 PM.

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#8 sevenofnine

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Posted 14 May 2021 - 09:05 PM

You have some great answers from the forum's most experienced observers. I will just add that Ed Ting has a recent video on these SCT's that may (or not) help you with the decision. He mentions the only con to the 9.25 is the weight. Everything else is just better. Good luck with your decision! waytogo.gif


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#9 GGK

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Posted 15 May 2021 - 01:53 PM

Thanks to all of you for your great information and comments. Very valuable to me. I committed to buying the new C9.25 XLT. As said, I bought my C8 Starbright about 23 years ago and have used nothing else since then. It will be both fun and interesting to try the new C9.25.

I had thought about piggybacking a small light refractor on my C8 once or twice over the years. I guess that will be even more applicable with the longer focal length of the C9.25.

Thanks again for taking the time to reply.

Gary

#10 alphatripleplus

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Posted 16 May 2021 - 07:18 AM

It is not just the XLT coatings and extra aperture that may make a difference. In addition, the reflectivity of the 23 year old mirrors may have deteriorated in your old C8. If you could have made a hypothetical comparison of your C8 wth Starbright coatings 23 years ago, with your C8 as it is today, you may find that the scope 23 years ago outperforms your C8 today because of a deterioration in the mirrors' reflectivity over time.


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#11 GGK

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Posted 16 May 2021 - 07:47 AM

It is not just the XLT coatings and extra aperture that may make a difference. In addition, the reflectivity of the 23 year old mirrors may have deteriorated in your old C8. If you could have made a hypothetical comparison of your C8 wth Starbright coatings 23 years ago, with your C8 as it is today, you may find that the scope 23 years ago outperforms your C8 today because of a deterioration in the mirrors' reflectivity over time.

That's a good point, and one more thing that might favor the change to the new OTA.  I have no way of knowing the condition of the coatings on my C8.  The mirrors still look clean and highly reflective, of course, but that really means nothing since they would need to be very bad not to look that way.



#12 Tangent

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Posted 16 May 2021 - 08:01 AM

Another thing to consider is that every telescope is unique when it comes off of the production line; some are dialed in perfectly, some just "meet specs".  To truly know which one you prefer, you would need to actually use them, preferably set up at the same time which isn't really practical unless you have two mounts (or can borrow one).


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#13 Supernova74

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Posted 16 May 2021 - 12:43 PM

Just to add to my initial post the 9.25 optically is most probably the best sct cassagrain I’ve ever owned I’m no way and means an expert in telescope ownership and I can just comment from my experience and obviously what I’ve seen with my own eyes!?i beleive the 9.25 is even manufactured in a different facility altogether is this just hearsay or perhaps a rumour I do not know unfortunately however I’ve not known a sct cassagrain to perform so well on lunar and planetary observation I will even go a far of saying it’s apo refractor like in contrast and sharpness.there was hardly any coma or false colour when tested at near full phase observing the moon and planetary observation can be a litte soft at times to say the least in many sct cassagrains regarding the brand name either from celestron or Meade,there something special about that 9.25 primary mirror is it possible it’s a different design altogether form other sct,s in there lineup maybe so.and lastly the only reason why I sold it was the same old aperture fever which I was craving more light grasp for deep sky objects.


Edited by Supernova74, 16 May 2021 - 12:44 PM.

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#14 Old Speckled Hen

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Posted 16 May 2021 - 02:13 PM

And then there the smoking gunn colimation ...


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#15 KTAZ

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Posted 16 May 2021 - 02:35 PM

It is not just the XLT coatings and extra aperture that may make a difference. In addition, the reflectivity of the 23 year old mirrors may have deteriorated in your old C8. If you could have made a hypothetical comparison of your C8 wth Starbright coatings 23 years ago, with your C8 as it is today, you may find that the scope 23 years ago outperforms your C8 today because of a deterioration in the mirrors' reflectivity over time.

You beat me to it, Errol.

 

I am a very happy owner of the 9.25XLT. I owned an 8" SCT years ago and can tell you that the 9.25 definitely performs better.

 

If you are visual and really want to see more resolution in those faint fuzzies and galaxies, you will appreciate the difference. Being able to see detail on a target, whereas you previously only saw fuzz, will make you appreciate your decision instantly.


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#16 topomountain

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Posted 16 May 2021 - 08:03 PM

i have a c90, a c5, and two c8's.  i have not seen a c9.25 but mine always surprise me how much larger, heavier etc they are given the small increase in aperture.  the c5 definitely has the sweet spot of size and views in my collection.  both of my c8 scopes are older black starbright and one is vastly different than the other and they are both colimated the same as far as i can determine.

 

the op has not stated any concerns of the extra size and weight of the c9, but i wonder just how much harder it is to handle than the c8, for that matter can anyone tell me how the c6 would fit in between the c5 and c8.... i find the c5 very portable, the c8 not really a portable scope but i can move it around, thinking the c6 might really be my next scope.

 

i may even sell both c8's and get a c9.25 depending on how this thread goes, hah, the never ending quest and dilemma.... i mostly enjoy my scope after a car ride, where smaller is better, but every time i get a bigger scope my smaller ones just seem so inferior.... my beloved and well used c90 looks like a miniature scope, though it is very sharp btw, optically i think it my best celestron, reminds me of my old iphone 3gs, still works great for music but can hardly read the screen!

 

as we age we all need to factor in the size hassle factor as well as the views...

 

love all the combined knowledge in this universe of nerds....


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#17 Nippon

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Posted 16 May 2021 - 09:54 PM

Modern Celestron SCTs use water white glass for the corrector while older models used soda lime glass and I believe the transmission of the water white is better. Many people believe the current Celestron SCT's have better figure and polish than older models also. 


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#18 whizbang

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Posted 16 May 2021 - 11:29 PM

I owned a late 70's orange tube at the same time as my  seven year old Evo C8.  The newer Evo tube out performed the orange tube.

 

I still own the Evo 8 and I got a C9.25 last year.  The 9.25 out performs the Evo 8.

 

Therefore, the 9.25 would vastly out perform my old orange tube.

 

Good luck with you 9.25.  Good choice!!


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#19 Supernova74

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Posted 17 May 2021 - 03:49 AM

i have a c90, a c5, and two c8's.  i have not seen a c9.25 but mine always surprise me how much larger, heavier etc they are given the small increase in aperture.  the c5 definitely has the sweet spot of size and views in my collection.  both of my c8 scopes are older black starbright and one is vastly different than the other and they are both colimated the same as far as i can determine.

 

the op has not stated any concerns of the extra size and weight of the c9, but i wonder just how much harder it is to handle than the c8, for that matter can anyone tell me how the c6 would fit in between the c5 and c8.... i find the c5 very portable, the c8 not really a portable scope but i can move it around, thinking the c6 might really be my next scope.

 

i may even sell both c8's and get a c9.25 depending on how this thread goes, hah, the never ending quest and dilemma.... i mostly enjoy my scope after a car ride, where smaller is better, but every time i get a bigger scope my smaller ones just seem so inferior.... my beloved and well used c90 looks like a miniature scope, though it is very sharp btw, optically i think it my best celestron, reminds me of my old iphone 3gs, still works great for music but can hardly read the screen!

 

as we age we all need to factor in the size hassle factor as well as the views...

 

love all the combined knowledge in this universe of nerds....

Well even tho there is minimal aperture increase and light gathering power it is noticeable however what you do notice is the optical performance over the C8 is dramatically improved!?.the other important factor you need to consider is what kind of format you would consider when puchasing the C 9.25 as yes it’s quite weighty if you considered the CPC.9.25 but managble tho.the C8 weighs in at a shade over 12lbs and the 9.25 is 20lbs so still comes in at under 10kg


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#20 Old Speckled Hen

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Posted 17 May 2021 - 02:55 PM

I seem to remember there is quite a step up between XLT and starbright XLT coatings..

 

https://www.celestro...ptical-coatings

 

https://www.celestro...ptical-coatings

 

And from the horse's mouth as it were..

 

https://www.cloudyni...re-they-really/


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#21 GGK

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Posted 17 May 2021 - 07:11 PM

Thank you all for the great comments and information.  I reread everything and also read through the links.

 

To summarize the details above, changing from my 23 year old C8 Starbright to a new C9.25 XLT will have the following benefits, which is a pretty decent list.  Each individual benefit is small, but the cumulative impact might be very noticeable.

 

- Increased light transmission from the newer XLT coatings

- Improved corrector throughput from the better corrector glass

- Increased aperture

- Eliminating any light transmission loss from age-related coating deterioration in my current C8

- Flatter field due to the slower primary of the C9.25

- Larger exit pupil at the same magnification -- this might be specific to me, but my eyes will notice

 

The comment that the C9.25 might show me details with direct vision that required averted vision in the C8 was interesting.  That would be nice.

 

The performance / use negatives are

- Weight increases 8 pounds

- Field of view decreases with the longer focal length

 

My mount is a Skywatcher EQ6-R Pro with a payload capacity of 44 pounds.  Since I set up in various locations around the yard and greater neighborhood, I always remove the OTA from the Mount and break everything down into transport cases.  I am organized very nicely for this, so it takes little time or effort.

 

The extra 8 pounds for the OTA will not be a problem for me to lift, but I did order a Vixen top dovetail bar and will put on a handle for safe lifting.

 

My C8 uses a Vixen dovetail to mount, but I will be much happier with the larger D style dovetail for mounting the C9.25.

 

I live in SW Florida at 26.5 degrees latitude.  We're moving into the wet season soon, so how much the skies cooperate will be anyone's guess, but I will try to get a reasonable comparison between the two OTAs before selling the C8.  Unfortunately I only have one mount so I will need to do the comparing across multiple nights rather than side-by-side.

 

If anyone has a specific target in mind that might be good for a comparison, please let me know.  I was thinking M3 because it minimizes the atmosphere by passing close to the zenith for me after the night air is usually settled.  Plus, I can see enough detail in my C8 to know if I see more with the C9.25.  

 

I should get the new OTA and needed accessories over the next week.

 

Thanks.  Gary



#22 gjanke

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Posted 18 May 2021 - 12:56 AM

The gain will be minimal and the cool down will increase significantly. The size of the scope changes and you’ll need a much better mount to handle the scope. Think on the order of a CGEM or the likes of it. All of the thread has just been a rationalization to of getting something bigger. If you’re really gonna go that route get a C11. The 9.25 will having you thinking the views might be better but the C11 will leave no doubt.

 

When it’s all over and done don’t be surprised if you end up back with the C8. Its truly is the best size for a SCT. Not too big not too small, the cool down is reasonable and the weight is very manageable.

 

Last thing, if a comparison of the two can’t be done side by side all of the evidence is suspect. Viewing changes from night to some much it just wouldn’t be a fair comparison and therefore a poor means to make any decisions by.

 

ive had all of these scopes multiple times,  HD, XLT and starbright and have ended up with a C8 XLT after having purchasing the Celestron SCT in all the varying sizes from 6” to 11”. There is a reason the 8” is referred to as the workhorse of the hobby.

 

Good luck in your quest. You’re gonna buy the 9.25 but in the end you’ll end up with a 8” when it’s all said and done. 


Edited by gjanke, 18 May 2021 - 07:04 AM.

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#23 Visit-the-Moon

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Posted 18 May 2021 - 06:30 AM

I have a 1996 C8 (Ultima2000, StarBright) and two CPC9.25s (XTL), from ~2008 and ~2016 (permanent Hyperstar set-up for imaging). Side-by-side the 2008 C9.25 outperforms the C8 on planets (resolution and color), moon (resolution) and deep sky (more stars, more nebulosity). Both have had a lot of visual use over the years, though I now mainly do imaging/EAA. Due to the larger aperture and better coatings, the C9.25 collects almost 50% more light than the old C8. The C9.25 also has a noticeably flatter field. Interestingly I found their equilibration times to be similar. However the C9.25 is much larger and heavier. If portability is an important consideration you'll get more use out of the C8. My C9.25s are permanently mounted.


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#24 Old Speckled Hen

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Posted 18 May 2021 - 07:18 AM

I have a 1996 C8 (Ultima2000, StarBright) and two CPC9.25s (XTL), from ~2008 and ~2016 (permanent Hyperstar set-up for imaging). Side-by-side the 2008 C9.25 outperforms the C8 on planets (resolution and color), moon (resolution) and deep sky (more stars, more nebulosity). Both have had a lot of visual use over the years, though I now mainly do imaging/EAA. Due to the larger aperture and better coatings, the C9.25 collects almost 50% more light than the old C8. The C9.25 also has a noticeably flatter field. Interestingly I found their equilibration times to be similar. However the C9.25 is much larger and heavier. If portability is an important consideration you'll get more use out of the C8. My C9.25s are permanently mounted.

I was about to say you can add 10lbs onto a scope, ext focuser, dew shield,  2"  diagonal/eyepieces heaters, they all quickly add up.

 

Saying that, as a 8" owner, a decent, properly collimated 9.25 would be a NICE scope, as long as it fits on my astro trolley along with rest of my "essentials" for movement..


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#25 GGK

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Posted 18 May 2021 - 07:34 AM

And then there the smoking gunn colimation ...

I ordered some Bob's Knobs.  Time will tell if the C9.25 stays collimated as well as my C8.




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