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Beginner seeking Advice on Refractor

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#1 ivanvan21

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Posted 27 February 2020 - 09:59 PM

Hello everyone my name is Ivan and I’m kinda new to Astronomy, I have a Celestron Nexstar 102 GT and I'm fascinated with it but I feel like I need to take it to the next level.

I was thinking of getting a Sky-watcher EvoStar 100ED, but I found this place and found out that there's many more options out there.

I mainly want to look at the moon, nebulas, planets etc, not many photography but could be a plus.

Any help would be really appreciated it, I'm thinking 500-1000.

Thanks in Advanced.


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#2 vtornado

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Posted 27 February 2020 - 10:24 PM

Hello Ivan and welcome to CN

 

I have the 102GT and a Orion 100 f/9 ED.

 

For planetary the ED puts up a cleaner, crisper image at the same mag on Jupiter, the colors are better.

 

Although the purple on the moon in noticable in the Achro, it does not detract much from the detail I can see.

I feel confident the ED would put up a better image of Mars when it returns, but I did not own the ED when Mars was up last time.

Saturn in not much difference.

 

I would say overall the ED puts up a 10-20% better image at medium to high power.  That is a very hard thing to quantify, and

I don't know how too.  I'm sure the experience is very personal too.

 

Is the ED worth 3-4x the price of an Acho?  Only you can decide that.

 

A 6 inch mirrored scope is a step above the 100 ED, and an 8 inch mirror is a leap.

Both of them can be had for less than a 100mm ED.  That is why I stopped buying refractors at 100mm.

Used 100ED can be had for $400, but  the 120 ED is a lot more even used.

(Well except for a cheap 120 f/5 I used for a sweeper).


Edited by vtornado, 27 February 2020 - 10:34 PM.

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#3 clearwaterdave

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Posted 27 February 2020 - 10:55 PM

A bigger scope may need a bigger mount as well.,price and weight both go up.,Food for thought.,


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#4 ivanvan21

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Posted 27 February 2020 - 11:08 PM

Hello Ivan and welcome to CN

 

I have the 102GT and a Orion 100 f/9 ED.

 

For planetary the ED puts up a cleaner, crisper image at the same mag on Jupiter, the colors are better.

 

Although the purple on the moon in noticable in the Achro, it does not detract much from the detail I can see.

I feel confident the ED would put up a better image of Mars when it returns, but I did not own the ED when Mars was up last time.

Saturn in not much difference.

 

I would say overall the ED puts up a 10-20% better image at medium to high power.  That is a very hard thing to quantify, and

I don't know how too.  I'm sure the experience is very personal too.

 

Is the ED worth 3-4x the price of an Acho?  Only you can decide that.

 

A 6 inch mirrored scope is a step above the 100 ED, and an 8 inch mirror is a leap.

Both of them can be had for less than a 100mm ED.  That is why I stopped buying refractors at 100mm.

Used 100ED can be had for $400, but  the 120 ED is a lot more even used.

(Well except for a cheap 120 f/5 I used for a sweeper).

 

Thanks for the reply, I like the refractor cuz they are super sexy, but if a mirror scope is more suitable for my idea,  I wouldn't mind getting a 6 or even better a 8 inch one, any suggestions?


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#5 MalVeauX

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Posted 27 February 2020 - 11:14 PM

Heya,

 

Going from a 4" achromat to an ED doublet of the same size aperture may help with CA, but if you want more resolution, more deep field, etc, it comes aperture. I would look into a larger 127mm~150mm~200mm mirror based scope (Newtonian or SCT or Mak).

 

Very best,


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#6 Stellar1

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Posted 27 February 2020 - 11:15 PM

If you got yourself an 8 inch dobsonian you'll be leaps and bounds ahead of your 100mm refractor, you cannot beat dobsonians for cost vs performance factor. Aside from this, the much larger mirror 

will show nebula a lot brighter and, clusters will reveal a lot more density of stars. Having said that, if you want something smaller, i have a 150mm skywatcher Maksutov, it is small, easily portable grab and go scope and, it is an absolute planet/lunar killer. If you wanted something easily portable then i would really suggest you take a look at the 150 skywatcher mak, i have taken some awesome planetary and lunar images with it also. Ignore the solar image, that is an eyepiece image taken with my solar scope and, they are low resolution for this site.

Attached Thumbnails

  • IMG_4185134.JPG

Edited by Stellar1, 27 February 2020 - 11:33 PM.

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#7 vtornado

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Posted 27 February 2020 - 11:16 PM

I like refractors because they are little fuss and cool down fast, but they get expensive once they go over 100 - 120mm

 

6 inch scopes would include a 6 inch SCT, or a 6 inch newt. 

A 6 inch f/5 newt could be on an alt az mount  f/5 or table top.

A  6 inch f/8 newt is best dob mounted.

 

An 8 inch scope could be an 8 inch SCT or 8 inch dob. 

 

The form of the scope is a personal decisicion.  SCT will get you a small package and tracking.

A newt will be cheaper and larger.


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#8 PNW

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Posted 28 February 2020 - 01:39 AM

I think a wide field refractor and an 8" SCT really compliment each other. I use the refractor for large open clusters in the winter and the SCT for higher powers on the Globs and Planets in the summer.


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#9 sg6

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Posted 28 February 2020 - 04:14 AM

You will not gain any real light gather by the change but you will get a better quality image.

Planetary detail will be better - although the planets are not exactly close so keep expectations realistic. Many claims are unrealistic in astronomy.

 

I was talking to a person with a 9.25 SCT, they still use a 3" refractor for planets most of the time. So be carefule of claims that aperture cures everything. The catch is that besides aperture you need quality aperture and quality costs, and usually costs a lot more then the simply bigger aperture bit.

 

A 100ED will do lots and should do it well.

Yes an 8" will collect more light, pi*r2 forces that. What it does not force is a quality result.

 

Another aspect is that magnifications over around 150x are maybe of little real use. Most people use 60x to 80x. I was using 140x a couple of nights back and for the target a lot of the impact of the target was lost. 60x would have been better, just impossible. I now keep a short list of targets less then 0.3 degrees for ideas.

 

Since a 100ED will do 150x I would have said easily, then no concerns.

 

If future AP is in mind then it should do that although 100mm may be a bit on the large side with regards focal length. In AP small and high quality is often better. Still with care/thought possible.

 

One thing I have noticed is that rarely does someone buy a nice refractor and regret it.


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#10 SeaBee1

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Posted 28 February 2020 - 08:46 AM

I upgraded from a Celestron Omni 102mm XLT to a SW120ED because the CA was beginning to bother me (it really was minimal, but noticeable), and I felt like my 61 year old eyes need a 'frac with a wee bit more aperture. The CA in the SW120 is simply unnoticeable but now I have come to find out my 61 year old eyes have cataracts and probably the reason they were craving more aperture...

 

At any rate, the 102mm achro is a great scope, it has shown me a LOT of stuff, and if the CA had not bothered me and the cataracts had not been present, I would likely not have purchased the SW120ED. BUT... I do love my SW120ED and I am happy I got it...

 

I would not upgrade to an ED scope without upgrading aperture as well... and to me, the SW120ED hits a sweet spot... but it will be over your budget...

 

Yeah, OK... maybe that wasn't much help...

 

Good hunting!

 

CB


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#11 JoshUrban

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Posted 28 February 2020 - 10:33 AM

Hey Ivan, and congrats on getting drawn into this wonderful "black hole" of telescopes and the heavens!  :)  

 

  I just got an AstroTech 102mmED, and love it.  However, it often takes a backseat to my 12.5" dob.  I'd definitely buy it again, and a nice refractor is awesome!  However, as it's been suggested here, you  might get more bang for your buck by getting an 8-10" dob and one or two 2" widefield eyepieces.  The scopes could then compliment each other nicely.  After you have fun with that, THEN you might want to add a premium refractor.  

 

  Just my two cents, but as someone who went from an 80mm short tube to a 10" dob, well, THAT was a jump.  Globular clusters became incredible!  


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#12 brentknight

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Posted 28 February 2020 - 12:10 PM

Ivan...

 

Don't make the mistake of putting too much of your budget into the scope itself and treating the mount as an afterthought.  A great telescope that is under mounted will be a crappy scope to use.  Especially if you are considering anything over 100mm and about F/7, figure at least $300 - $500 for the mount.  Your SkyWatcher 100ED would then be closer to $1200.

 

I hate to say this, but if your $1000 is a hard number, you will get more value from the 6" to 8" dobsonian.  And then you will likely want to spend on some nicer eyepieces and such.  But don't sell the refractor...


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#13 aeajr

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Posted 02 March 2020 - 11:14 AM

Thanks for the reply, I like the refractor cuz they are super sexy, but if a mirror scope is more suitable for my idea,  I wouldn't mind getting a 6 or even better a 8 inch one, any suggestions?


Every type of scope has its compromises. None are perfect.

Refractor vs. Reflector – Which is better?
https://telescopicwa...tor-telescopes/

Your current scope is a GoTo scope. Are you looking for another GoTo scope?  You don't mention this in your first post.

 

I have my eye on the Astro-Tech 102 ED  F7 sold by Astronomics.  

https://www.astronom...ractor-ota.html

 

Add a 2" Diagonal and you have a real powerhouse of a scope.  I have friends with this scope and they all LOVE it.

If you get the recommended 2" diagonal and AltAz mount you are talking $920.  Not cheap but a great value , especially when compare to APOs.  It is within your budget


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#14 ivanvan21

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Posted 02 March 2020 - 03:14 PM

Every type of scope has its compromises. None are perfect.

Refractor vs. Reflector – Which is better?
https://telescopicwa...tor-telescopes/

Your current scope is a GoTo scope. Are you looking for another GoTo scope?  You don't mention this in your first post.

 

I have my eye on the Astro-Tech 102 ED  F7 sold by Astronomics.  

https://www.astronom...ractor-ota.html

 

Add a 2" Diagonal and you have a real powerhouse of a scope.  I have friends with this scope and they all LOVE it.

If you get the recommended 2" diagonal and AltAz mount you are talking $920.  Not cheap but a great value , especially when compare to APOs.  It is within your budget

 

Does't have to be a goto, I haven't even use the goto in my current Telescope, mostly hand point, currently trying to get a Celestron C9.25 SCT OTA telescope with XLT coating, but now I need to find a proper mount.



#15 aeajr

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Posted 02 March 2020 - 03:41 PM

 

Every type of scope has its compromises. None are perfect.

Refractor vs. Reflector – Which is better?
https://telescopicwa...tor-telescopes/

Your current scope is a GoTo scope. Are you looking for another GoTo scope?  You don't mention this in your first post.
 
I have my eye on the Astro-Tech 102 ED  F7 sold by Astronomics.  
https://www.astronom...ractor-ota.html
 
Add a 2" Diagonal and you have a real powerhouse of a scope.  I have friends with this scope and they all LOVE it.
If you get the recommended 2" diagonal and AltAz mount you are talking $920.  Not cheap but a great value , especially when compare to APOs.  It is within your budget
 
Does't have to be a goto, I haven't even use the goto in my current Telescope, mostly hand point, currently trying to get a Celestron C9.25 SCT OTA telescope with XLT coating, but now I need to find a proper mount.

 

When you quote someone, your typing should be in the white area, not in with the quoted text.  We have to try and pick out what was written by aeajr and what was written by ivanvan21.

 

See how my response is outside the box? 

 

Why have you not used the GoTo?  That is a terrific feature of that mount.  Once it finds the target it tracks it.   


Edited by aeajr, 02 March 2020 - 03:45 PM.

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#16 Chesterguy1

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Posted 07 March 2020 - 01:38 PM

The OP never states whether they have a preferred type of targets. Lots of good suggestions from the CN responders. 

 

I started with a 90mm refractor, which I still have. It is an excellent performer on the planets, moon, double stars and brighter DSOs--given it's small aperture. It is a breeze to set up  and is basically ready to go in an instant. I have a 120mm, which is definitely more work to hoist and requires a bit more substantial mount to make me comfortable. At 8" everything is brighter and more detailed, but my reflector requires acclimation, regular collimation and it is substantially larger and heavier than the refractors. It is not hard to move on two-wheel dolly. 

 

A 90mm-100mm refractor can keep someone happy for a very long time. If the OP gets the DSO bug they can replace (or preferably supplement) the 100mm with a 6"-8" and depending on their stated interest in some photography, they could opt for an SCT, which, with the right mount could support both the refractor or SCT--even at the same time like my AZMP.

 

There are often excellent deals on used equipment through CN classifieds or AM. That's how I picked up my SkyWatcher 120 ED, which has impressed me. Real bang for the buck.

 

Chesterguy


Edited by Chesterguy1, 07 March 2020 - 01:40 PM.


#17 klausW

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Posted 24 March 2020 - 05:59 PM

hi all together, I just arrived in CLOUDY NIGHTS. I am a hobby astronomer since a few years, read a lot but had a hard time with my equatorial mount (my scope is a ORION 90mm refractor) once I started observing. The scope does not go where I want it to. After a few nights I resigned. I would like a easy alt-azimuth mount for simple star-hopping and a little more "inch". Has anybody experiences with the 127mm achromat refractor from Explore Scientific?

thanks for your help

klausW



#18 phillip

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Posted 25 March 2020 - 04:09 AM

I still keep looking at refractors. Did have a 120mm size achro and indeed had fun with its performance. 

 

Years back a Mars close encounter coming and decided moving up on aperature so sold the achro and purchased the 8 inch dob. Wow huge difference, brighter image, detail on those rare near steady sky highly rewarding. 

 

Not saying against refractor, just larger size quickly gets cumbersome. They are Terrific! 

 

A clever description on just aperture increase regardless of scope used, go into a dark basement, do you want to use a match or a bigger flashlight referring to increased aperature! Obvious!

 

8 inch dob used extensively...

Setup near instant, always in trunk thermal Ready! 



#19 Tony Flanders

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Posted 25 March 2020 - 06:09 AM

I have not used or seen the Nexstar 102GT. But it is a 102-mm f/9.8, and at that long focal ratio, false color is pretty small. So assuming that your scope's optics are good, I think that you would perceive little difference between the images that your scope produces and the images from a 102-mm ED refractor. As everyone else here has said, to get significantly better images, you need a bigger aperture.

 

My answer to that question would be quite different if your were starting from, say, a 102-mm f/6 refractor, which does indeed show tons of false color.

 

Looking at the stock photo of your scope, it looks as though its biggest liability is the mount. That tripod looks mighty flimsy! Do you find it waving around in the breeze, or have trouble focusing it because it wiggles when you touch the focuser? If I were in your position, I would be thinking about replacing the mount before replacing the optical tube.

 

Or you could get an 8-inch Dob, with vastly superior images and a vastly stabler mount.

 

Or perhaps best yet, just stick with the existing scope until you have explored its capabilities a little more thoroughly. Precisely why do you feel that you need to take your scope "to the next level?" Is it because of some specific deficiency in your current scope, or just a vague desire to spend more money?


Edited by Tony Flanders, 25 March 2020 - 06:13 AM.

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#20 Jon Isaacs

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Posted 25 March 2020 - 06:36 AM

Or perhaps best yet, just stick with the existing scope until you have explored its capabilities a little more thoroughly. Precisely why do you feel that you need to take your scope "to the next level?" Is it because of some specific deficiency in your current scope, or just a vague desire to spend more money?

 

 

:waytogo:

 

Tony:  

 

I will say this:  I have had a brief encounter with the  NexStar 102GT.   As you point out, the mount is a way undersized, balance is difficult because of the dovetail being mounted directly to the OTA.  It's not a scope I would choose to use, not because of the optics but because of the mount. 

 

An undersized mount makes observing difficult, focusing is a challenge because the scope vibrates with every touch, blurring the image.  Operation of the mount is compromised,.  

 

Jon



#21 aeajr

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Posted 25 March 2020 - 07:58 AM

Hello everyone my name is Ivan and I’m kinda new to Astronomy, I have a Celestron Nexstar 102 GT and I'm fascinated with it but I feel like I need to take it to the next level.

I was thinking of getting a Sky-watcher EvoStar 100ED, but I found this place and found out that there's many more options out there.

I mainly want to look at the moon, nebulas, planets etc, not many photography but could be a plus.

Any help would be really appreciated it, I'm thinking 500-1000.

Thanks in Advanced.

Ivanvan21,

 

What is the reason for going from the 102GT to the EvoStar 100ED?  What are you trying to achieve?

 

The key benefit of one optical tube over the other is that the 100ED will show less CA, chromatic aberration which is the color fringing you will see on very bright objects, like the Moon.  You get a false edge of violet.   The 100 ED will reduce this some.  Other than that, what you see will be quite similar.

 

If you want to see more detail, or you wish to apply more magnification while still getting a good image, you need more aperture.

 

That 9.5" SCT will do that.   It gathers about 5 times as much light as the 102 mm refractor.  You can find typical configurations with that OTA at the Celestron website.

https://www.celestro...ions/telescopes

 

Why have you picked this one?

 

Are you prepared to deal with the size and weight of that OTA and the mount it requires?

 

  • Where will you store it?
  • Where will  you use it?
  • Are there stairs involved in the set-up process?
  • How much weight can you handle?

Edited by aeajr, 25 March 2020 - 08:21 AM.


#22 Jon Isaacs

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Posted 25 March 2020 - 09:29 AM

The key benefit of one optical tube over the other is that the 100ED will show less CA, chromatic aberration which is the color fringing you will see on very bright objects, like the Moon.  You get a false edge of violet.   The 100 ED will reduce this some.  Other than that, what you see will be quite similar.

 

 

The ED-100 will not just reduce the chromatic aberration "some", it will essentially eliminate it.  

 

And it's important to understand that the purple fringes one sees are only part of the issue with chromatic aberration.  Chromatic aberrations in an achromat means that only two colors come to focus and the remainder are out of focus to some extent.  So what chromatic aberration does to a planet like Jupiter is reduce the contrast significantly.  

 

Some numbers:

 

The color blur of an 4 inch F/10 achromat is about 4 times the diameter of the Airy disk, this means that the blur affects surrounding regions significantly. 

 

The color blur of a 100mm F/9 FPL-53 doublet is about 0.8 times the diameter of the Airy disk, this means there is little effect on surrounding regions.  

 

At the eyepiece, the difference is very apparent.

 

Jon


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#23 Tank

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Posted 25 March 2020 - 09:46 AM

OP

100 ED will be nicer

however all depends on what you looking for

to me a 8" DOB would be miles a head as far as ultimately what you see at the EP

also much cheap!

as far as the 100 ED thou its probably the best Value for a refactor that you can get



#24 LDW47

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Posted 25 March 2020 - 09:48 AM

Hello everyone my name is Ivan and I’m kinda new to Astronomy, I have a Celestron Nexstar 102 GT and I'm fascinated with it but I feel like I need to take it to the next level.

I was thinking of getting a Sky-watcher EvoStar 100ED, but I found this place and found out that there's many more options out there.

I mainly want to look at the moon, nebulas, planets etc, not many photography but could be a plus.

Any help would be really appreciated it, I'm thinking 500-1000.

Thanks in Advanced.

Don’t be afraid to peruse the used scope market for less $, many do and not just by newcomers !  Clear new skiys ! 



#25 chemist

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Posted 25 March 2020 - 06:48 PM

The Nexstar 102GT has very good optics, but it needs help with mount and focuser.  I use an Orion Astroview GEM which supports the 102GT scope very well (and provides tracking) and I upgraded the focuser to a GSO two speed Crayford.  These mods would cost around $400 and make a significant improvement in the usability of the 102GT.

 

Chemist


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