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5" Celestron NexStar is better than 8" ?

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#26 Peter Besenbruch

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Posted 01 July 2019 - 01:26 PM

Funny, basicly we are speaking here about mounts and not about the telescopes although the threadtitle suggests otherwise,...just saying.

 

There is no way a 5" SCT performs better than a 8" SCT as Eddgie explains as well.

You clearly didn't watch the movie. Even the Youtube poster acknowledges that the 8" will outperform the 5" optically. The valid part of the poster's video lies with the mount. Not only is the 5" lighter, and likely to be used more, the 8" is a bit too large for the mount. People will get a more satisfactory experience with the 8" on a higher capacity mount. Don't underestimate the mount when it comes to telescope performance and satisfaction.

 

The beefier mount also contributes to overall portability and ease of set-up issues. It's not just SCTs that have this issue, all designs do. People love 6" ED refractors and gush about them, but a year later they either don't use them as much, or they are thinking of selling them. Dob owners decide that maybe they bit off more than they could chew, or advancing age will allow, and downsize in aperture and f-ratio.

 

The advantage of the Nexstar 5 is that it is still a "one arm carry out the door" scope that performs pretty well. The Nexstar 8 isn't, and the Evo 8 certainly isn't.



#27 ShaulaB

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Posted 01 July 2019 - 01:30 PM

It's the Internet. Anybody can post a video stating just about anything. Factual accuracy is not needed when uploading.

Many SCT owners are ignorant of the fact that their optical tubes need collimation. A badly collimated C8, especially one not at temperature equilibrium, would probably put up a poorer planet view than a perfectly acclimated and collimated 5 inch.

#28 Stargazer3236

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Posted 01 July 2019 - 01:40 PM

You clearly didn't watch the movie. Even the Youtube poster acknowledges that the 8" will outperform the 5" optically. The valid part of the poster's video lies with the mount. Not only is the 5" lighter, and likely to be used more, the 8" is a bit too large for the mount. People will get a more satisfactory experience with the 8" on a higher capacity mount. Don't underestimate the mount when it comes to telescope performance and satisfaction.

 

The beefier mount also contributes to overall portability and ease of set-up issues. It's not just SCTs that have this issue, all designs do. People love 6" ED refractors and gush about them, but a year later they either don't use them as much, or they are thinking of selling them. Dob owners decide that maybe they bit off more than they could chew, or advancing age will allow, and downsize in aperture and f-ratio.

 

The advantage of the Nexstar 5 is that it is still a "one arm carry out the door" scope that performs pretty well. The Nexstar 8 isn't, and the Evo 8 certainly isn't.

The Nexstar 6se is also another "one arm carry out the door" type of scope. It is a very good performer for planets, given optimum seeing conditions. I have my second Nexstar 6se after having sold an older one 3 years back in order to upgrade to my current Nexstar 8se. I should also mention the 6se performs very well on deep sky objects. I take pics with my 6se and the images come out very nicely. I hardly ever use my 8se on its one arm mount anymore, gets to be very fidgety due to the weight and payload of the one arm. It mostly rides atop my iOptron ZEQ25 mount 100% of the time.

 

But the most popular adage comes to mind: "The best telescope to have is the one you will use the most often."


Edited by Stargazer3236, 01 July 2019 - 01:40 PM.


#29 Jon Isaacs

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Posted 01 July 2019 - 01:55 PM

You clearly didn't watch the movie. Even the Youtube poster acknowledges that the 8" will outperform the 5" optically. The valid part of the poster's video lies with the mount. Not only is the 5" lighter, and likely to be used more, the 8" is a bit too large for the mount. People will get a more satisfactory experience with the 8" on a higher capacity mount. Don't underestimate the mount when it comes to telescope performance and satisfaction.

 

 

Still. While the 8 inch mount is not optimal, it's workable and results in a package that can be carried out the door in one trip. No real difference in setup.

 

And it ultimately does come down the optical prowess. 

 

However: These are really two very different scopes and should not be considered in the same breath. A Nexstar 5 is small telescope and portable. The OTA is about 12 inches long.

 

A Nexstar 8 is a medium aperture telescope, larger but still easily managed, at least by my standards, a 71 year old guy used to wrestling with some pretty big scopes.

 

These scopes are not competitors, they're plenty different enough that owning both makes good sense, they make reasonable companions.  It's like comparing a 5 inch mini-Dob with an 8 inch or 10 inch Dob, they fill different roles. 

 

The choice depends on what you want to do with the scope, how you want to use it.

 

Jon



#30 Stargazer3236

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Posted 01 July 2019 - 02:16 PM

Although I already have the 6se and the 8se, I might buy the 5se due to its included wedge, which would make imaging a lot nicer and contained all-in-one system, without the need to buy a separate wedge.

 

I refurbished a Meade standard wedge on a tripod, along with a used Meade 2080 telescope ota I had gotten for free. I set it up one night, using my Nexstar 6SE on the Meade wedge and tweaking the PA, I managed to get it relatively spot on in polar alignment. While I did not have the basics of EQ PA with the Nexstar telescope (I have often used just Alt-Az), I was unable to secure a stable PA using two stars. So, I just used PA on Jupiter and it was a remarkable success, keeping Jupiter perfectly centered in the FOV. I hastened to start imaging Jupiter because of seeing issues in my neck of the woods. The images came out pretty good, I must say.

 

So having a wedge on the Nexstar 5SE would certainly be a bonus. All you need is the Nexstar 5SE, battery pack, camera, focal reducer or barlow or both, a laptop computer, some free imaging software and you are good to go!



#31 Peter Besenbruch

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Posted 03 July 2019 - 07:48 PM

But the most popular adage comes to mind: "The best telescope to have is the one you will use the most often."

I agree, and it's nice that the 6 is still fairly portable.



#32 Peter Besenbruch

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Posted 03 July 2019 - 07:54 PM

Still. While the 8 inch mount is not optimal, it's workable and results in a package that can be carried out the door in one trip. No real difference in setup.

 

And it ultimately does come down the optical prowess. 

 

However: These are really two very different scopes...

Yes, and the Nexstar5 is a nice package, while my experiences with the 8" version were not good. Jiggling when focusing gets old in a hurry. So does jiggling when touching the side of the eyepiece with my eyebrow, and jiggling when the wind blows, not good. The C8 needs a beefier mount.


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#33 CharlesC

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Posted 03 July 2019 - 08:13 PM

Although I already have the 6se and the 8se, I might buy the 5se due to its included wedge, which would make imaging a lot nicer and contained all-in-one system, without the need to buy a separate wedge.

 

I refurbished a Meade standard wedge on a tripod, along with a used Meade 2080 telescope ota I had gotten for free. I set it up one night, using my Nexstar 6SE on the Meade wedge and tweaking the PA, I managed to get it relatively spot on in polar alignment. While I did not have the basics of EQ PA with the Nexstar telescope (I have often used just Alt-Az), I was unable to secure a stable PA using two stars. So, I just used PA on Jupiter and it was a remarkable success, keeping Jupiter perfectly centered in the FOV. I hastened to start imaging Jupiter because of seeing issues in my neck of the woods. The images came out pretty good, I must say.

 

So having a wedge on the Nexstar 5SE would certainly be a bonus. All you need is the Nexstar 5SE, battery pack, camera, focal reducer or barlow or both, a laptop computer, some free imaging software and you are good to go!

An interesting solution to mount a C5 is to use Meade ETX-125 tripod (#884) with a Celestron GT mount.   It has an integrated wedge but don't know if that is very useful.  Just have to drill out the center hole.

https://www.cloudyni...ny-suggestions/


Edited by CharlesC, 03 July 2019 - 08:14 PM.


#34 CeleNoptic

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Posted 04 July 2019 - 07:31 PM

BTW, C6 has Central Obstruction of 37% vs 31% in C8 which also works in favor of C8, IMO.


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#35 Poconut

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Posted 04 July 2019 - 10:29 PM

The advantage of the Nexstar 5 is that it is still a "one arm carry out the door" scope that performs pretty well. The Nexstar 8 isn't, and the Evo 8 certainly isn't.

I have to strongly disagree with this statement.  My 8se is indeed a one arm carry down the deck steps and out the door kind of scope.  I am not a very strong person, desk job jockey, zero exercise and 55yo.  To not be able to lift the tripod, mount and scope intact of the 8se would indeed be a very weak person.  I've used the 6se in the same set up and while it might be just a wee bit lighter, I would never compromise the aperture gain given the choice.  If it's bad seeing, as was mentioned a few times above, I don't bother with anything to begin with.

Pffft! vibration while focusing?  It's out of focus anyhow, who cares - wait a second to see the results!  Again, talking about the mount and not the OTA capability!  I put the 8" SCT on my CGX-L and it's not budging, however, the CGX-L is two trips for the tripod and mount alone!  A 3rd trip for the tube.  Perhaps a 4th for the counter weights, but again, we are now talking mount portability and not scope capability!


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#36 Peter Besenbruch

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Posted 11 July 2019 - 08:01 PM

I have to strongly disagree with this statement.  My 8se is indeed a one arm carry down the deck steps and out the door kind of scope.  I am not a very strong person, desk job jockey, zero exercise and 55yo.

Continue your lifestyle another ten years, and it won't be. 4.gif Best to start lifting weights NOW!

 

 

Pffft! vibration while focusing?  It's out of focus anyhow, who cares - wait a second to see the results!

I have higher standards. I have found Nexstar 8s something of a pain to work with.



#37 Boom

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Posted 11 July 2019 - 11:02 PM

What is a Selestron anyway?

#38 Stargazer3236

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Posted 11 July 2019 - 11:31 PM

Selestron = Celestron


Edited by Stargazer3236, 11 July 2019 - 11:31 PM.

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#39 JP-Astro

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Posted 12 July 2019 - 02:02 PM

Of course it's 'Celestron' although it sounds the same.

One interesting note to add is that I've read through quite a few of '8" vs 9.25" SCT' threads and they all conclude that the 9.25" is more desirable. 5" version isn't even mentioned. Of course 11" is by far the best choice (not touching on the 14" yet) but 9.25" is still more manageable according to the common advice.


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#40 gezak22

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Posted 12 July 2019 - 02:57 PM

Of course it's 'Celestron' although it sounds the same.

One interesting note to add is that I've read through quite a few of '8" vs 9.25" SCT' threads and they all conclude that the 9.25" is more desirable. 5" version isn't even mentioned. Of course 11" is by far the best choice (not touching on the 14" yet) but 9.25" is still more manageable according to the common advice.

In part because the 9.25" has an f/2.5 primary while the others are f/2. This makes the 9.25" easier to collimate (though still tough).


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#41 Boom

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Posted 12 July 2019 - 06:16 PM

Of course it's 'Celestron' although it sounds the same.
One interesting note to add is that I've read through quite a few of '8" vs 9.25" SCT' threads and they all conclude that the 9.25" is more desirable. 5" version isn't even mentioned. Of course 11" is by far the best choice (not touching on the 14" yet) but 9.25" is still more manageable according to the common advice.


Thanks for correcting the topic title. TBH the typo was rather bothersome.
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#42 JP-Astro

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Posted 13 July 2019 - 06:59 AM

Thanks for correcting the topic title. TBH the typo was rather bothersome.

I actually felt embarrassed when I realized (after your comment) that 'Selestron' wasn't exactly how I intended to identify the trademark.

For a non-native English speaker such spellings can often be confusing.


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#43 JP-Astro

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Posted 13 July 2019 - 07:20 AM

BTW, C6 has Central Obstruction of 37% vs 31% in C8 which also works in favor of C8, IMO.

Here is the whole Celestron OTA line-up according to the official specs in respect to the CO:

 

5":      CO = 51mm, 40% by diameter, 16.6% by area

6":      CO = 56mm, 37% by diameter, 14% by area

8":      CO = 64mm, 31% by diameter, 9.77% by area

9.25": CO = 85mm, 36% by diameter, 13% by area

11":    CO = 95mm, 34% by diameter, 12% by area

14":    CO = 114mm, 32% by diameter, 10% by area

 

It's interesting to note that 8" has the smallest CO of the whole family. I doubt it has any noticeable effect on its performance though.


Edited by JP-Astro, 13 July 2019 - 07:22 AM.


#44 Jon Isaacs

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Posted 13 July 2019 - 11:34 PM

Orion lists the C-8 Edge as having a 34% CO, 69mm.  

 

https://www.telescop...c/14/p/9553.uts

 

Manufacturers are always trying to understate the CO, often ignoring the secondary baffle and such things.

 

Jon


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#45 Bill Barlow

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Posted 14 July 2019 - 09:57 AM

Jon is right, the CO is closer to 34-35% after I measured it.  The secondary mirror may be 31% but the secondary mirror housing is a tad wider.

 

Bill


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#46 JP-Astro

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Posted 14 July 2019 - 03:35 PM

Jon is right, the CO is closer to 34-35% after I measured it.  The secondary mirror may be 31% but the secondary mirror housing is a tad wider.

 

Bill

... which most probably means that for all other versions below and above 8" the CO will be larger proportionally?

Poor 5" cutie with its 40% in the specs!



#47 Bill Barlow

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Posted 16 July 2019 - 09:37 AM

No the other specs for the CO in Celestron 5”, 6”, 9.25”, 11” and 14” models are correct.  

 

Bill



#48 JP-Astro

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Posted 16 July 2019 - 09:59 AM

No the other specs for the CO in Celestron 5”, 6”, 9.25”, 11” and 14” models are correct.  

 

Bill

Bill - do you have the whole line at hand or what makes you believe that 11" for instance has a 95 mm mirror housing and not the mirror itself. Why would Celestron keep publishing wrong data for the 8" and not the others?



#49 Bill Barlow

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Posted 17 July 2019 - 11:40 AM

Probably to boost sales.  I have owned all of the Celestron scopes at one time or another and have measured the CO’s on all of them.  But they are smaller than the Meade 6”-8”-14” SCT’s.

 

Bill


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#50 Megiddo

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Posted 17 July 2019 - 02:06 PM

He mentioned at the end, you would have to buy a case for the telescope at $300???


The box it came in is free. wink.gif   Ok, yeah a fancy case would be more expensive.




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