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9.25 SCT, it ain't no planet scope

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#101 Asbytec

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Posted 26 October 2018 - 12:39 AM

I've owned two 10" and one 11" SCT and one MCT. None of which I'd consider bad. It's been my experience seeing and thermal stability trump obstruction and modest aberration. My new 8" Dob may shed some light on the topic.
 

#102 astro744

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Posted 26 October 2018 - 01:50 AM

You’re being very kind to the SCT folks .... In 45 years I’ve never seen an SCT that compared side by side on the same targets to a good f/6 or f/7 Newtonian or Intes/TEC maks of similar aperture... sure there are a lot of rather ordinary newtonians, too.

Perhaps I too have been too kind toward the SCT for it has never equaled and certainly not out performed my Newtonian but it nonetheless provides me with pleasing views with the obvious noticeable difference being lower contrast and I put this down the the central obstruction.  However given excellent seeing my Newtonian is in a different league and I would think this is more to do with the quality of the mirror than anything else.

 

The benefits of a premium mirror have been debated on this forum many times and I don't want to start this again here in this thread but for me it was money well spent for it showed me what a Newtonian is capable of.


 

#103 Fatcat

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Posted 26 October 2018 - 02:36 AM

Excellent pic in a typical, SCTs suck thread.  I wonder how long it will be until this one gets locked.  Now we just need CHASXL200 to come along and say how all SCTs suck compared to a good Newt..  Oh wait.  He just did.  And of course Eddgie to say how refractors, even an achromat are so much better.

 

Thanks for speaking up about the Troll issue that seems to be on this forum. I always assumed that the majority of the people here like Cats but there are some haters here that in my opinion shouldnt be allowed to post there repetitive negative inflammatory comments. Myself I find it to be a big turnoff and dont understand why they are not moderated.


 

#104 Magnetic Field

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Posted 26 October 2018 - 02:49 AM

Thanks for speaking up about the Troll issue that seems to be on this forum. I always assumed that the majority of the people here like Cats but there are some haters here that in my opinion shouldnt be allowed to post there repetitive negative inflammatory comments. Myself I find it to be a big turnoff and dont understand why they are not moderated.

 

But if  it is/were true that SCTs are worse than Maks, Newtonians or Refractors I want to hear it**.

 

**I don't even own a refractor.


Edited by Magnetic Field, 26 October 2018 - 02:49 AM.

 

#105 Axunator

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Posted 26 October 2018 - 04:21 AM

But if it is/were true that SCTs are worse than Maks, Newtonians or Refractors I want to hear it**.

**I don't even own a refractor.

Define ”worse”. As an amateur with a limited budget (the budget limit may be small or large, depending on the point of view, but ”unlimited” it isn’t for the vast majority of us), I try to find the best tools for my own purposes, at prices I can afford. ”Worse” or ”better” can therefore mean a lot of things...

Mass-produced SCTs do not represent optical perfection, but I guess you and others reading this thread knew that already. I don’t need to look through 10” Matthias Wirth APM Mak-Cass (that can be bought for measly 11990€) to know that my C9.25 XLT (800€ used) is most probably worse optically. A 9-10” APO? Probably over 50000€ plus another 50K for the mount and permanent observatory (IF you had the property to build the obsy on already). A 9-10” f/6 Newton, even with premium mirrors, would be much cheaper than a 10” Mak (but probably not cheaper than C9.25), but I would never use it because it would be too large and cumbersome for transportation, especially if it were a solid tube OTA on a GEM. Even as a solid tube dob it would be a bit too large for car transportation, and I would miss the tracking and goto, which are quite easy and cheap to arrange for an SCT.

So yes, aperture for aperture, if optical perfection is the only aspect we are interested in, well-built Newtonians, Maks and APOs are all likely to be better than similar-aperture, mass-produced, run-of-the-mill SCTs. However, if, instead, the stratifying variable is ”performance/portability ratio” or ”performance/price ratio” (allowing even aperture to vary), the order may quickly change. SCTs pack so much aperture into such a small, portable and affordable container, that for some of us they are the most desirable option easily available.

In real life plagued with budget and portability constraints, humble SCTs, with fair to moderate (but still diffraction-limited) optical quality and rather large central obstructions, have the brute force provided by the aperture that help them to go a long way on the highway of MTF curve in the competition against smaller but optically superior designs.

It’s a cheap workhorse, and good at that. Just my opinion.

Edited by Axunator, 26 October 2018 - 04:25 AM.

 

#106 CHASLX200

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Posted 26 October 2018 - 05:16 AM

You’re being very kind to the SCT folks .... In 45 years I’ve never seen an SCT that compared side by side on the same targets to a good f/6 or f/7 Newtonian or Intes/TEC maks of similar aperture... sure there are a lot of rather ordinary newtonians, too.

I agree.


 

#107 CHASLX200

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Posted 26 October 2018 - 05:20 AM

Thanks for speaking up about the Troll issue that seems to be on this forum. I always assumed that the majority of the people here like Cats but there are some haters here that in my opinion shouldnt be allowed to post there repetitive negative inflammatory comments. Myself I find it to be a big turnoff and dont understand why they are not moderated.

I never used the word suck buck.  But it is fact they don't compare.  People need to face the simple facts that some scopes are better for some objects over other kinds of scopes. And the SCT is better at doing some things better than other scopes.


 

#108 K4PDM

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Posted 26 October 2018 - 06:34 AM

 I'd recommend trying to collimate a newt before buying before buying one. I've got a Zambuto 11" F5 that never would have been bought if I'd done so. As to my C9.25 it's easy to collimate and I've seen shadings on Ganymede and Uranus with it. David 

A little off topic, but I'd have to agree with this statement. I have had two dobs for many years and the views through them don't come close to my 8 inch SCT. Makes me think I never correctly collimated the dobs.


 

#109 Asbytec

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Posted 26 October 2018 - 06:35 AM

It's likely most folks can agree they do not compare with some minimally obstructed or premium scopes or whatever. The OP said it ain't no planetary scope cuz images dont measure up to two other scopes.

The implication seems to be they cannot deliver pleasing planetary images and, by extension, lunar and double stars. In other words, they suck. Many of us argued they actually do suck when suffering thermals, poor collimation, poor seeing, or lack of skill.

Bottom line is, they deliver a good and rewarding level of planetary detail. Maybe not to the liking of everyone, but to the liking of more than a few.

Obstructions and abberations combined can soften images Compared to some other scopes, and so can induced aberrations like seeing and thermals. But they do not completely destroy the image unless it's severe enough to destroy an image in any scope.

Unless that's the case, you're gonna see planetary detail through a C9, an SCT, or a CAT generally. It matters how much one appreciates what they can see. It does not matter what others do not or cannot see or don't appreciate.

 

Edit: One might just as well ask if a 6" is a good planetary scope because a 10" shows more. It cannot compare. 


Edited by Asbytec, 26 October 2018 - 07:05 AM.

 

#110 wargrafix

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Posted 26 October 2018 - 07:24 AM

*cracks knuckles*

 

 

gallery_218407_320_11982.jpg

 

gallery_218407_320_7163.jpg

 

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C9.25 for the win


 

#111 wargrafix

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Posted 26 October 2018 - 07:26 AM

La Luna says hello

 

med_gallery_218407_322_691506.jpg


 

#112 Magnetic Field

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Posted 26 October 2018 - 08:18 AM

*cracks knuckles*

 

 

gallery_218407_320_11982.jpg

 

gallery_218407_320_7163.jpg

 

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C9.25 for the win

 

Very good.

 

But how much is thanks due to image post processing?


 

#113 SandyHouTex

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Posted 26 October 2018 - 08:36 AM

Luxo II did not respond but I supect from the "Lambda/6" in his comment he was referring to the image of the test report I posted. If he did indeed say what he did in response to my post, he's throwing my integrity into doubt as I did the test myself. It's been a while but the test was done using a green interference filter and the results were not surprising given how the scope performed. This scope has given me the lifelong best view of Mars, the other being a TSC 225, and I could see no difference in the images produced by the two. This was during a surprisingly good night in Feb (I think) when seeing was excellent and Mars was near opposition and high in the sky. During the same night, I could see Castor with each component showing one diffraction ring. Something I've never seen since in a large aperture.

 

I also did Roddier tests when my secondary rotated and I was trying to determine which of the three possible positions it was originally at: at the two other positions, the Roddier test showed L/3 Strehl 0.8-something. One position was clearly better than the other two. 

 

Here are some of the images I've taken with this scope (I know, I know digital processing yada yada). One thing that is common among them is that they were all taken on nights of excellent seeing with a Philips ToUCam, before the ASI CMOS cameras became all the rage, and minimally processed. (The Jupiter one was taken with a DMK but that's practically identical to the ToUCam). I especially remember seeing almost the same amount of detail on the Moon in the eyepiece as was visible in the images. I wish I had preserved the AVIs but hard drive space was precious back then.

 

FXqM0DYh.jpg

 

i1m3gaih.jpg

2NOapTnh.jpg

jrQI51gh.jpg

 

Two of Jupiter, one with the R channel as luminance to bring out different detail, just for fun.

 

EzpBQwoh.jpg

Nice pics.  Lot's of detail.


 

#114 earlyriser

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Posted 26 October 2018 - 08:43 AM

 I'd recommend trying to collimate a newt before buying before buying one. I've got a Zambuto 11" F5 that never would have been bought if I'd done so. As to my C9.25 it's easy to collimate and I've seen shadings on Ganymede and Uranus with it. David 

What tools are you using to collimate the Zambuto? Collimating a Newtonian shouldn't be too difficult once you get the hang of it, but everyone has a different tolerance level for that sort of thing.


 

#115 GOLGO13

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Posted 26 October 2018 - 09:00 AM

I've always heard that the C 9.25 has been a special scope. Especially back in the early 2000s.

 

I do think collimation and thermal cooling plagues a lot of telescopes in use. Sure there are probably ones which are not as good optically as they could be.

 

I did have really nice planetary views with C5 and C6's in the past. And i just got a C8 collimated recently and look forward to comparing it to my 5 inch APO and 10 inch dob. It's an Ultima 2000 and appears to be a really nice sample.

 

When people were comparing these 5 inch apos to 9.25 SCTs, they should also (if possible) compare it to a 5-6 inch SCT to see if it's more of a condition/cooling situation.


 

#116 DMach

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Posted 26 October 2018 - 10:02 AM

A little off topic 

This whole thread has strayed waaaay off topic if you ask me ... so go for it! Lol


 

#117 Glass Eye

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Posted 26 October 2018 - 10:03 AM

Very good.

 

But how much is thanks due to image post processing?

The Jupiter image is close to what my last visual observation.


 

#118 Axunator

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Posted 26 October 2018 - 10:10 AM

This whole thread has strayed waaaay off topic if you ask me ... so go for it! Lol


The thread started with a blanket statement in the title, followed by the OP comparing the planetary views of his C9.25 to his 5” frac and 8” dob. I think it has stayed on topic remarkably well for 5 pages! Plus it has been the most entertaining thread on CN for a while 😜 All IMO, of course.
 

#119 PETER DREW

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Posted 26 October 2018 - 10:37 AM

In the UK I have Meade 8", 12" and 16" SCT's, each is a decent optical standard within the SCT range. I also have a Celestron 8se which matches the Meades for planetary performance. The main difference is that the Celestron is based in Tenerife.
 

#120 Axunator

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Posted 26 October 2018 - 11:10 AM

In the UK I have Meade 8", 12" and 16" SCT's, each is a decent optical standard within the SCT range. I also have a Celestron 8se which matches the Meades for planetary performance. The main difference is that the Celestron is based in Tenerife.

If your Meade 8 under UK skies matches your C8 in Tenerife, I’d say your Meade is definitely a keeper! grin.gif


 

#121 TG

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Posted 26 October 2018 - 01:47 PM

But how much is thanks due to image post processing?


Please. This has already been discredited multiple times. Let's give it a rest.
 

#122 Peter Besenbruch

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Posted 26 October 2018 - 03:51 PM

I've owned two 10" and one 11" SCT and one MCT. None of which I'd consider bad. It's been my experience seeing and thermal stability trump obstruction and modest aberration. My new 8" Dob may shed some light on the topic.

I had a nice experience with an older member of our club. She gave up on a German made, 12" ultra-light Dob., and bought an 8" Orion (US). She has been a member of the club since forever, and I wasn't surprised to see the scope in good collimation. It gave nice images. The mirrors were obviously decent.

 

We did some view trading on planets, me with a 7" Mak. There wasn't much difference at 250x. Maybe mine was just the tiniest hair sharper, but that may have been the result of the insulation I was using. Frankly, I would have been very happy with the Dob's optics.

 

Mine is the only scope that I'm aware of that is insulated in our club. It still attracts, "I wouldn't be caught dead with that stuff" looks. Last night I was out showing the sky in seeing that probably supported 30x at our massively floodlit museum. Looking at the scope, even the general public thought I was weird. About a dozen folks worked up the courage to ask about it, at least.

 

To the OP: When you get the collimation down, consider insulating your C9.25.


 

#123 barbie

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Posted 26 October 2018 - 04:43 PM

I think that how well the design is implemented is the most important factor in SCT's or any of the other CATS, or really in any telescope for that matter.  I've seen SCT's and Maks that give refractor like images as well as Newtonians that do the same(I own one!!).  I know that my 3.5" Mak does so when it is properly cooled.  It puts up images that rival my old 90mm refractors of similar focal length and I'm sure a C9.25 would do the same, when properly cooled and collimated.  I'm not surprised that the insulation idea works so well and may try the same thing for my C90 for winter time observing.


 

#124 George Methvin

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Posted 26 October 2018 - 04:52 PM

I have owed and still own and use SCT scope plus reflectors and refractors and I think they all good performer IF the optics are good and IF the seeing is good and steady. For me on most good nights side by side I really don't see that big of a difference in most of the objects I am viewing. Now I guess if you are the type person that is very picky about every little thing and spend more time worrying about which scope is better then the others then you may never be happy. There are always going to be trade offs in anything but its really very simple just try to view through as many difference scopes as you can and just pick the scope that makes you happy if you don't like Sct then don't buy one.  I have seen good planetary detail in my 8 inch sct and also in my 6 inch dob and through my 14 inch dob and my 120mm Ed refractor but they are all nice scopes. I just hate so see treads like this running down a type of scope to my mind there is not one bad or perfect scope type and it took me 40 years to realize the strength and weakness of each type of scope lol I am a slow learner. I think a Celestron 9.25 could very well be a good planetary scope IF well made but that can be said of all scopes. Like I have heard before difference tools for difference jobs its the same with scopes. If planetary viewing is you passion you should try the following scopes  I have hear through the years that the best scope of planetary viewing is a 6 to 8 inch apo refractor or a well made custom 8 inch to 10 inch f/6 to f/8 reflector if so and you can afford it get one of these types of scope and be happy lol there's always a trade off.    Clear skies 


Edited by George Methvin, 26 October 2018 - 04:56 PM.

 

#125 CHASLX200

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Posted 26 October 2018 - 05:43 PM

A little off topic, but I'd have to agree with this statement. I have had two dobs for many years and the views through them don't come close to my 8 inch SCT. Makes me think I never correctly collimated the dobs.

Fast Newts really get soft without dead on collimation and they need a Paracorr. So the SCT wins out there, but they need to be collimated. 


 


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