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Best choice for a used sct ?

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#1 rugby

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Posted 04 April 2019 - 08:53 PM

I am starting a search to buy a used sct to complement my large dobsonians. Apparenty some models are better than others. I am strictly a visual observer but need tracking for sketching. T he old orange c8 seemed perfect but there are references to bad optics in the mid 80's. I like the 9.25 or 10 inch models but dont want the goto optons..I am a star hopper needing good optics with a mount I can move quickly.  What should I avoid or consider buying?



#2 otocycle

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Posted 04 April 2019 - 09:15 PM

Hi -  newer optics with more modern light transmission coatings favor buying more recently manufactured "used" SCTs compared to more vintage instruments, all else being equal.   You can find some very good older equipment, but it is riskier unless you can test it before buying/owning.  

 

You don't need ACF/flatter field optics just for visual, so no need to pay for that premium unless it's still a great deal.

 

Like you, I have larger Dobs that I wanted to complement with an SCT on a driven or alt-az mount, so I settled for the C9.25 (big enough) and newer C6 (small enough).

 

I would avoid any of the Criterion/ B& L SCTs that went out of production many years ago.

 

A Takahashi TSC-225 would be worth considering, but they are rare and command a premium price.



#3 Spikey131

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Posted 04 April 2019 - 09:19 PM

I don’t know what your budget is, but I would advise getting the most recent SCT you can afford. New technology with optics and coatings have really improved these scopes.
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#4 MrRoberts

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Posted 04 April 2019 - 09:28 PM

I don't know much about this one but how about Celestron's Nexstar Evolution 6 or 8. I have the C-8/E on an Ioptron AZ Mount Pro (much more than you need or are thinking of). I'm on this site daily but don't recall seeing any Evo's for sale. Hopefully someone can chime in with thoughts/suggestions.


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#5 Gary Z

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Posted 04 April 2019 - 09:55 PM

One thing about the EVO mount is its versatility.  guess what, turn off the power, loosen the clutches and move the scope around as you see fit.  But I believe at some point, you'll enjoy the goto as well.The movement after loosening the clutches is quite smooth.

 

Gary



#6 photomagica

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Posted 04 April 2019 - 09:56 PM

If you want or need a used one, buy the one that gives images you like when well collimated and used with a known star diagonal and eyepiece. If at all possible buy one conditional on satisfactory performance when tested or arrange to look through it first.

 

Why collimation and a known good star diagonal and eyepiece? I got a used older C-8 at one point. It was terrible. Collimation brought it up to fair. Then I got a new Celestron 2" dielectric diagonal and used it with Nagler eyepieces. That made a marked difference and brought it up to good. The diagonal was just pain awful so I threw it out! So you need collimation and good downstream optics for a fair test. Also let the 'scope come to temperature. There is sample variation among SCT's of any vintage so it is worth the effort to visually test if you possibly can.

 

BTW I have an Evolution 8 and it gives excellent images. I've heard good things about the Evo 8 from other users.

Bill



#7 rugby

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Posted 05 April 2019 - 06:34 AM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?



#8 otocycle

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Posted 05 April 2019 - 07:25 AM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?

 

De-forked Meade 8" SCT would be fine (LX90 or LX200GPS), but larger than that is 10" and the Meades tend to be heavier OTAs than the Celestrons.  Anecdotally, there also seems to be more used Celestron product offered for sale/auction.

 

Meade also had UHTC and non-UHTC coatings for a while, and UHTC is preferred for higher light transmission.



#9 MrRoberts

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Posted 05 April 2019 - 09:08 AM

How big is your DOB?

Just a reminder, but once one starts getting into SCT's larger than 8", weight and mount requirements start to be a more important concern. 



#10 photomagica

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Posted 05 April 2019 - 10:16 AM

When I bought my Evo 8 I debated getting the 9.25. I'm glad I got the 8 for portability reasons. If I had a permanent location or semi-permanent, then I'd go for the bigger aperture.

 

I haven't enough experience with Meade's to offer advice. I have seen samples of Celestron SCTs that do perform impressively well on the planets.  It was this experience that led me to get the Evo 8 and I was not disappointed.

Bill



#11 Nippon

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Posted 05 April 2019 - 02:18 PM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?

I have an Edge 8 I use on a Losmandy GM8. I'm picky about optics and own two high end 4" apo refractors and the Edge 8 optics still impress me. As far as used buy either pre Haley comet era scopes or models produced in the 90s and beyond. Celestron scopes got pretty bad during the mad rush of production for the anticipated demand as the great comet approached



#12 JohnnyBGood

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Posted 19 April 2019 - 08:04 AM

It's hard to find SCTs without GOTO or even the ability to use them manually if the battery/computer/drive motor goes out. I'm 98% visual and wanted a non-GOTO SCT that could be used manually. For me the 8" LX-10 ended up being the ideal scope. Good optics (same OTA as the LX-200), no frills, low price. It's pretty much the last of the manually operable SCTs.


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#13 gnowellsct

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Posted 20 April 2019 - 06:33 AM

It's hard to find SCTs without GOTO or even the ability to use them manually if the battery/computer/drive motor goes out. I'm 98% visual and wanted a non-GOTO SCT that could be used manually. For me the 8" LX-10 ended up being the ideal scope. Good optics (same OTA as the LX-200), no frills, low price. It's pretty much the last of the manually operable SCTs.


That's not really true. You just buy an OTA and put it on a non go to mount.

It is true that COMPLETE SYSTEMS are sold mostly go to. I'll grant that.

But I haven't used a complete system in 17 years. Why bother with Meade or celestron mounts when the G11 is available or the Mach 1s.

I'm on the board of an outreach organization and three directors of local observatories noted they get a lot of offers of donated scopes and they're always Meades and always don't work. In fact I have one of those in my basement right now. The goal is to fix it up for sale and put the funds for outreach. Often the first step in rehabbing these older systems is to take them off the fork. The ten inch lx200 is a monster. I don't know how people solo observe with those.

A c8 or 9.25 are both good choices. The requirement above for tracking for sketching makes sense. But tracking and moving the rig around the yard are contrary requirements. There's the power supply, the wires, alignment protocol for alt az, and power supply and wires for a GEM. I guess if approximate tracking is ok you can just use a compass for polar alignment. It's what I do for solar.

The need to move around the yard gives the nod to the c8. Less weight and a larger field of view for reacquiring objects.

#14 Jon Isaacs

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Posted 20 April 2019 - 07:15 AM

I don’t know what your budget is, but I would advise getting the most recent SCT you can afford. New technology with optics and coatings have really improved these scopes.

:waytogo:

 

The Celestron White Paper on the Starbright XLT coatings is a good read.

 

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

 

According to the white paper, Starbright XLT coatings have an average transmission of 84% across the visual band.  That was an increase of 16% over older Starbright coatings, that's about 71% transmission.  And many older scopes do not even have Starbright coatings.  This does not include the loss due to the secondary shadow but all SCTs have that.  It also does not include any degradation the older mirror coating might have suffered. 

 

Jon


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#15 wrnchhead

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Posted 20 April 2019 - 08:32 AM

If I needed a scope, I would jump on Agustus' listed C8 Ultima OTA in the classefieds. I have an identical one and it's great. Wish I'd have went with sct over my dob originally! Only weighs 11 lbs. It would need a mount so that's a consideration. 

 

Plus if someone buys it, I will quit feeling so tempted to get it myself!! 


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#16 MalVeauX

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Posted 20 April 2019 - 05:20 PM

I am starting a search to buy a used sct to complement my large dobsonians. Apparenty some models are better than others. I am strictly a visual observer but need tracking for sketching. T he old orange c8 seemed perfect but there are references to bad optics in the mid 80's. I like the 9.25 or 10 inch models but dont want the goto optons..I am a star hopper needing good optics with a mount I can move quickly.  What should I avoid or consider buying?

There's generally nothing wrong with 30~40 year old SCT mirrors. The older 70's Celestrons are actually quite good and still sought after. I would avoid older Meades (they're heavier and cost a lot less for a reason... those optics seems to be variable and the coatings are not great after 30+ years, especially those old `silvered' ones).

 

Unless you're on an extreme budget, I would recommend you look at used SCT's that are recent with modern coatings.

 

OPT cycles through used gear often and have great deals. I got my used C8 Edge HD + feather touch focuser for $1k there.

 

Very best,


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