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Nexstar 8" - Questions diagonal and low power EP.

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#1 N3p

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Posted 22 July 2021 - 11:42 AM

My boss bought a Nexstar 8" and asked me infos about it, I have the following questions:

 

#1. The 90d diagonal coming with the telescope, is it good enough to start with or it should be upgraded directly from the start?

 

#2. I want to propose a low power 1.25" eyepiece for it (along with a medium and higher power), my question is about the low power one. Telescope is 2032 mm of focal length, a 24mm would give 84x.

 

For me it's a bit too high, I would prefer a choice aound 40 ~ 50x. But I don't want vignetted views, it needs to be a low power eyepiece 100% compatible with a reducer, the telescope and it's visual back, the diagonal.

 

--> Which reducer, which eyepiece focal length and which eyepiece AFOV would be the best bet?

 

Thanks


Edited by N3p, 22 July 2021 - 11:43 AM.


#2 Notdarkenough

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Posted 22 July 2021 - 12:09 PM

Hello. My NexStar 8in EdgeHD came with a 2" diagonal. I am happy I got started on that path. Now every ep, filter, whatever costs a bit more than 1.25, but the product at low power is much better. I upgraded to the Baader Maxbright 2" ClickLock with SCT threads after a few months. The optical upgrade was nice, but the functionality and increased security allowed me to buy really nice eps.  My first post-clicklock ep buy was the Nagler Type 5 31mm; amazing views and securely held by a better mechanism than a few tiny thumb screws! A 2" diagonal offers choices, a 1.25" comes with restrictions. 

 

My recommendation? A solid 2" diagonal and then the best wide-field eps are all available. My Nagler preference has more to do with Dioptrx than any specific brand loyalty. The Nagler line is great, as is ADM ultra-wide-angle offerings. There are other excellent models, these are just the 2 I have firsthand experience with. Good luck-

 

Mike



#3 wrvond

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Posted 22 July 2021 - 12:22 PM

The scope already comes with a 25mm Plössl, this is plenty low enough for now. At this point a decent 2x Barlow would be a good investment. The diagonal that came with the scope will work just fine.

Experience is much more valuable than accessories yet costs so much less. 


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#4 N3p

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Posted 22 July 2021 - 12:37 PM

Ahh the knowledge is coming back to me now, slowly but it's coming back. 


Edited by N3p, 22 July 2021 - 12:37 PM.


#5 Supernova74

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Posted 22 July 2021 - 12:45 PM

Well to be honest you already at the limit,which is considered lowest useful magnification and even with a 2”40mm eyepiece 

your looking at 51.2x that’s the problem with sct cassagrains thay really not designed optically for lower power wide feild views due to the long focal length.the only other eyepiece i can think of is the Meade series 4000 56mm plossel eyepiece

which will give you 36x then funny things start happening in tunnel vision type of effect,well at least when I used it in my Meade 12”ACF 3045mm it did,in a scope almost 1000mm less in focal length unfortunately i do not know.


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#6 treadmarks

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Posted 22 July 2021 - 12:55 PM

I like the low power view in a 1.25" 32mm Plossl, they're inexpensive and will give you about 40X with the reducer/corrector.


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#7 N3p

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Posted 22 July 2021 - 01:12 PM

Ok, it's possible to reduce a plossl without problem, they usually have a 50d AFOV. I am pushing my luck by asking, what about a 24mm Panpotic 68d AFOV?

 

Could it be reduced and still be in the range of good?  It's really a yes or no question. (with which reducer)

 

Just for discussion.


Edited by N3p, 22 July 2021 - 01:13 PM.


#8 treadmarks

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Posted 22 July 2021 - 01:29 PM

If you're referring to vignetting, I think the field stop is a more reliable guide than AFOV. And the 24 Pan has the same field stop as a 32mm Plossl. So yes, it can be R/C'd with minimal issues. I know there are some other good R/C's out there but I don't think you can go wrong with the Celestron one (which I have).


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#9 wrvond

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Posted 22 July 2021 - 01:31 PM

Ok, it's possible to reduce a plossl without problem, they usually have a 50d AFOV. I am pushing my luck by asking, what about a 24mm Panpotic 68d AFOV?

 

Could it be reduced and still be in the range of good?  It's really a yes or no question. (with which reducer)

 

Just for discussion.

Yes.

Reducer/Corrector f/6.3

https://www.celestro...ducer-corrector


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#10 Supernova74

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Posted 22 July 2021 - 01:33 PM

Ok, it's possible to reduce a plossl without problem, they usually have a 50d AFOV. I am pushing my luck by asking, what about a 24mm Panpotic 68d AFOV?

 

Could it be reduced and still be in the range of good?  It's really a yes or no question. (with which reducer)

 

Just for discussion.

Well the genral rule i go by the less glass in the optical chain the better,in meaning natural image as possible I’m mixed about focal reducers especially in a sct cassagrains as strange things can happen to the image in becoming unnatural looking you may be absolutely fine,however I’ve never really understood why some folks go down this path as it might of been more worth while in purchasing a refractor instead to achieve lower power views.

horses for courses in some ways



#11 wrvond

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Posted 22 July 2021 - 01:48 PM

Here's what Saturn would look like in a C8 using a 24 Pan without a reducer/corrector:

c8 no rc.jpg

 

And here's what Saturn would look like in a C8 using a 24 Pan with a .63 reducer/corrector.

c8 with rc.jpg



#12 N3p

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Posted 22 July 2021 - 01:49 PM

Well the genral rule i go by the less glass in the optical chain the better,in meaning natural image as possible I’m mixed about focal reducers especially in a sct cassagrains as strange things can happen to the image in becoming unnatural looking you may be absolutely fine,however I’ve never really understood why some folks go down this path as it might of been more worth while in purchasing a refractor instead to achieve lower power views.

horses for courses in some ways

Ahh smile.gif  I don't dislike that path so much because It's just 1 reduced eyepiece. That EP would be an awesome eyepiece at 24mm, it can be barlowed and even reduced as a bonus. The same good eyepiece used in 3 different scenarios.

 

It looks like a very good deal to me if it works without any vignetting in reduction. Still remembering that the reduced result might suffer a bit.

 

If it's so bad with the reducer.. its still a useful 24mm.



#13 N3p

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Posted 22 July 2021 - 01:56 PM

Here's what Saturn would look like in a C8 using a 24 Pan without a reducer/corrector:

attachicon.gifc8 no rc.jpg

 

And here's what Saturn would look like in a C8 using a 24 Pan with a .63 reducer/corrector.

attachicon.gifc8 with rc.jpg

Using it with the reducer would be more for the observation of large star clouds and large clusters in an attempt to gain a bit of TFOV and with a wider AFOV EP.

 

For me, 53.3d TFOV is much nicer for star observation and large nebulae especially with 8" of aperture. Your image is showing it well.

 

Most of the time 85x will get a resolution penalty from sky conditions compared to 53.3, that's also a major thing.


Edited by N3p, 22 July 2021 - 01:58 PM.


#14 wrvond

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Posted 22 July 2021 - 02:08 PM

Ahh smile.gif  I don't dislike that path so much because It's just 1 reduced eyepiece. That EP would be an awesome eyepiece at 24mm, it can be barlowed and even reduced as a bonus. The same good eyepiece used in 3 different scenarios.

 

It looks like a very good deal to me if it works without any vignetting in reduction. Still remembering that the reduced result might suffer a bit.

 

If it's so bad with the reducer.. its still a useful 24mm.

The Celestron .63 reducer/corrector works well with 1.25" eyepieces equal to or shorter than 32mm. 


Edited by wrvond, 22 July 2021 - 02:12 PM.


#15 Supernova74

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Posted 22 July 2021 - 02:10 PM

Ahh smile.gif  I don't dislike that path so much because It's just 1 reduced eyepiece. That EP would be an awesome eyepiece at 24mm, it can be barlowed and even reduced as a bonus. The same good eyepiece used in 3 different scenarios.

 

It looks like a very good deal to me if it works without any vignetting in reduction. Still remembering that the reduced result might suffer a bit.

 

If it's so bad with the reducer.. its still a useful 24mm.

Well no harm in trying it out i suppose it can only go 50/50 yes or no.im guessing how much of a critical observer you are also!?



#16 ShaulaB

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Posted 22 July 2021 - 02:31 PM

Did your boss know much about astronomy or telescopes before buying the gear? Before making big plans for upgrades, I would suggest getting to know the scope first. Skills like aligning the finder and learning how best to use the mount will take some time.

As others have said, a 30-ish mm Plossl will be a good way to get lower magnification at low cost. Of course, spending a lot of money is an attraction for some folks. 😊

The stock diagonal is just fine, worry about other aspects of telescope use. Learning constellations and bright star names, how to differentiate bright planets from stars, and how celestial motion works will occupy some time.
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#17 Nippon

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Posted 22 July 2021 - 03:49 PM

The much maligned Celestron 1.25" prism diagonal is actually quite good optically and fine mechanically for standard field of view Plossls and orthos. The stock 25mm that it comes with it is a decent eyepiece. Adding a 15mm and a 9 or 10mm should cover most observing needs. For a wider true field perhaps a 32mm Plossl or better yet the f/6.3 reducer/corrector



#18 N3p

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Posted 22 July 2021 - 08:21 PM

Did your boss know much about astronomy or telescopes before buying the gear? Before making big plans for upgrades, I would suggest getting to know the scope first. Skills like aligning the finder and learning how best to use the mount will take some time.

As others have said, a 30-ish mm Plossl will be a good way to get lower magnification at low cost. Of course, spending a lot of money is an attraction for some folks.

The stock diagonal is just fine, worry about other aspects of telescope use. Learning constellations and bright star names, how to differentiate bright planets from stars, and how celestial motion works will occupy some time.

He don't know much right now, he bought the telescope before talking to me.. perhaps by reading the reviews on Amazon, the ratings are very high.

 

I will go there with my eyepieces and we will start from scratch including checking the collimation and using the finder. I'll bring my own eyepieces there so we can test them, this will give him an idea. Like suggested there won't be any buying for the moment.. the telescope comes with a 25mm.. I have a 10mm Svbonny that I can lend him and maybe a 12mm Xcel LX.

 

I need to learn about Schmidt-Cassgrain collimation myself, at least just to validate if the telescope is OK or if it needs collimation.

 

 

 

 



#19 Echolight

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Posted 22 July 2021 - 10:12 PM

First thing I’d buy is a TalentCell battery. Unless is is an Evolution.

 

When I first read Nexstar 8, I assumed it was the one made back around 2000 without any other designation.


Edited by Echolight, 22 July 2021 - 10:15 PM.

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#20 N3p

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Posted 23 July 2021 - 10:55 AM

First thing I’d buy is a TalentCell battery. Unless is is an Evolution.

 

When I first read Nexstar 8, I assumed it was the one made back around 2000 without any other designation.

I'll add that to the list, I guess if that telescope has no more batteries.. it must be pretty useless.

 

This is it: Nexstar 11069 8SE

 

https://www.amazon.c...27055545&sr=8-2
 

I found the PDF Manuel, I am going to RTFM now.


Edited by N3p, 23 July 2021 - 11:00 AM.

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#21 Supernova74

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Posted 23 July 2021 - 10:59 AM

Lol think what i be worried about regarding your boss,will you have a job if you get it wrong lol so you better to a good job.



#22 Mike G.

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Posted 23 July 2021 - 11:40 AM

what he has is workable, and he should probably get used to what he has before upgrading.  having a C8 myself (and a few other sct's), my recommendation for excellent low power views that will blow him away would be to convert to a 2" VB (clicklock preferred), a 2" decent quality diagonal and a 35mm TV Panoptic or, if he has the wallet, 31mm T5.  this will provide some of the best low power views that the 8" can deliver.  35mm Pans can be picked up regularly (but not frequently) used for just a bit more than half what the T5 goes for.  but he needs to make the jump to 2" EP's to get the most out of the scope.  wallet permitting of course.


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#23 N3p

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Posted 23 July 2021 - 11:54 AM

Lol think what i be worried about regarding your boss,will you have a job if you get it wrong lol so you better to a good job.

I have no worries, in fact I am sure it's going to be a very interesting experience.



#24 N3p

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Posted 23 July 2021 - 12:01 PM

what he has is workable, and he should probably get used to what he has before upgrading.  having a C8 myself (and a few other sct's), my recommendation for excellent low power views that will blow him away would be to convert to a 2" VB (clicklock preferred), a 2" decent quality diagonal and a 35mm TV Panoptic or, if he has the wallet, 31mm T5.  this will provide some of the best low power views that the 8" can deliver.  35mm Pans can be picked up regularly (but not frequently) used for just a bit more than half what the T5 goes for.  but he needs to make the jump to 2" EP's to get the most out of the scope.  wallet permitting of course.

Ok I keep that in mind for the 2" eyepieces, Notdarkenough suggested it also.

 

I didn't had the time to search google yet, In the manual, the telescope comes with 1.25" diagonal, can it take a 2" diagonal directly?


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#25 Supernova74

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Posted 23 July 2021 - 12:11 PM

I have no worries, in fact I am sure it's going to be a very interesting experience.

Do a good job then pop the question for a well deserved pay rise!?




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