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Zhumell Z8 vs Celestron Nexstar 8SE - opinions please - time sensitive!

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#1 kiltedcelt

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Posted 30 June 2020 - 10:49 AM

Okay - a little background to the question in the title -

I currently live in Chicago so my dark sky/viewing is SERIOUSLY bad! Most places I could go with a telescope I literally can't even see enough stars to be able to sky hop. I bought a Zhumell a few years ago, but then I sold my car right afterwards. I get around everywhere by bike and was planning to build a trailer that I could use to haul the Z8 out of the city - maybe do some camping and be somewhere with slightly darker skies. I also have an e-bike with a LOT  of range, mileage-wise so hauling a 'scope by bike is no big deal. However, I was concerned about collimation issues and safely cushioning the OTA for transport. Some folks on here a few years ago had suggested stripping all the parts off the Dob and making into one of those ultra-portable Dobs. That's more complexity than I want to deal with and there are some other issues as well. 

 

I want to do a mix of visual observation but also maybe dabble a little bit in astrophotography. That pretty much rules out the Dob without undertaking some serious modifications, building a tracking base, etc. I'm not always going to live in Chicago, and my wife and I have been planning to move to the southwestern US for a few years now - probably Fort Collins, CO area or maybe Santa Fe/Albuquerque, NM area. So, better skies in the future and a house with a yard vs. crappy Chicago skies and apartment living. The plan is still to live car-free wherever we move so portability is again an issue. Given wanting to do some astrophotography, but even more, my current inability to really see a whole lot effectively where I live kind of gives the edge to the Celestron mentioned in the title. The automatic functions would allow me to view *some* variety of objects without trying to star hop in excessively light-polluted skies. Also, I can build a case for the Nexstar to transport it easier than I can transport a full-size Dob. 

 

Basically, the time-sensitive part of this query is that Celestron is offering the Nexstar 8SE at $200 off, but just through today. I know they do these sales quite frequently though. Around $1000 is the limit of my budget. I'm seriously considering just buying the Nexstar and then trying to sell my Z8. The Z8 is in pristine, practically brand-new condition and I think I might even still have the box and all the foam packing materials in a closet. If I could sell that for close to new price shelling out for the Celestron might not sting so bad. Just thinking about the kind of observing I'd want to do and the fact that astronomy is not a major hobby for me, I'm leaning towards the Celestron over keeping the Z8 because I feel like I might get more use out of a guided scope rather than the cumbersome Dob. Anyone got any opinions or suggestions?

 



#2 SeattleScott

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Posted 30 June 2020 - 11:24 AM

The SCT is definitely more portable and GoTo is good in light pollution. You probably won’t get more than $200-250 for the Dob. You might find after biking two hours to get somewhat out of the city, you don’t have a lot of energy for spending ten minutes doing a GoTo alignment. And occasionally there will be issues, dead battery, lost cord, enter the wrong date/time, you center the wrong alignment star, or even just a weird, unexplained system glitch now and then. This could feel especially frustrating after you just biked two hours, and knowing you have another two hours to get home.

Scott

#3 barbarosa

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Posted 30 June 2020 - 11:30 AM

Buy the C-8 or a C-6. A go to mount just makes good sense in the city, The SE mount is not suitable for standard long exposure imaging. But when you are ready for that you can buy a  better mount.

 

But before that move you can buy a CMOS camera and start with EAA (aka video or live imaging).There is software that will align and stack (to reduce noise and build detail) successive short images (<<60s and often <30s). The process corrects for drift and field rotation.

 

There are guys (and gals) using EAA to get acceptable images from urban areas and from darker sites. Many of use are in light pollution "red zones" that make an eyepiece almost useless. Visit the EAA forum.

 

But be aware that an SCT has a narrow field of view, and is slow (f/10) you will want to buy the f/6.3 reducer corrector after you buy the camera.



#4 Jon Isaacs

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Posted 30 June 2020 - 11:32 AM

A few thoughts:

 

- Transporting either the Dob or the 8 inch Nexstar SE via bicycle will be quite a challenge.  The Z-8 is large and bulky but robust, it's pretty hard to do any damage that can't be easily repaired.  The SCT is more compact but more delicate.  The vibration of the ride and bounce of the ride is likely to take a toll on the internals of the mount and scope itself.  And the ever present fragile nature of the corrector plate is always present.. 

 

- An SCT on an alt-az mount is not well suited for astrophotography. The Nexstar 8SE is particularly a poor choice.  It's barely adequate for visual and for AP with the 2032mm focal length, it's going to be very difficult.

 

In your shoes, I would be looking at a smaller refractor that I could carry in a backpack and mount on a simple tripod.  It's a quick setup and it could be an apo, 80mm and suitable for astrophotography.

 

Jon



#5 mfoose

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Posted 30 June 2020 - 11:33 AM

I have not owned these specific models, but I have owned numerous 8" f/6 Dobs and 8" SCTs over the years. I am also not into astrophotography. That being said I would not consider either of these scopes a starter scope for astrophotography. For starting astrophotography many recommend a Go-To GEM (German Equatorial Mount) and a small APO refractor. Dobs don't have tracking mounts and SCTs, unmodified, have a native focal ratio of f/10 which is not recommended for astrophotography. So I would not consider either of these for starting in astrophotography. Certainly you can take some good pictures through them, but you would be largely limited to bright solar system objects.

 

Now, 8" f/6 Dob vs 8" SCT. Having owned multiple adaptions of both of these scopes I much prefer the 8" f/6 Dob. Yes, the tube is bigger than the 8" SCT but you are not just going to have to travel with the 8" SCT tube you will need to bring the mount, tripod, and a power source as well. I have used the Nexstar Go-To system on a 8" CPC when I was in college and you need to be able to identify stars to align it before using it. I would be much more concerned about collimation and safety of an 8" SCT than an 8" Dob. Newtonian type telescopes are much easier to collimate then SCTs and the front corrector glass on an SCT is much more fragile then the primary of a Newtonian. Just look up some of the instances of people who have received SCTs in the mail with a broken corrector or an SCT that slipped out of their hands when hoisting on the mount. SCTs are much more fragile then Dobs. A broken corrector is a death sentence for an SCT. I also much prefer the view of an 8" Dob over an 8" SCT. More often then not the optics are better on a Dob then an SCT and the Dob will give you a wider field of view, f/6 vs f/10. SCTs need more accessories too like some form of dew shield or heater to keep the corrector free of moisture and a diagonal. Those are more things to travel with on a bike.

 

Given your circumstances I would not recommend an 8" SCT. You have a great instrument already in the 8" Dob. Light pollution is obviously going to hamper any view you have regardless of SCT or Dob, but putting more money in an SCT given what you describe does not sound like a good idea. I think you would end up observing even less with and less pleasing views through it. I would recommend keeping the Zhumell 8" Dob and focus on brighter objects like the moon, planets (which are great right now), double stars, and bright star clusters. Since you're having trouble star hopping, I'd using a planetarium software on your phone and a pair of binoculars. Something like 7x35, 8x42, 7x50, or 10x50. These are easy to use by hand and have a much wider FoV then your Dob and can be had for a reasonable price. I bring a pair of 8x42s with me each time I observe with my 10" Dob. Use the binoculars to find the object in the sky and then find it with the Dob. You could even mount your phone on your Dob and use the planetarium software to on your phone like a finder scope. If the tube is too big, here is a collapsible tube 8" f/6 Dob: https://www.adorama.com/skws11700.html selling your current Dob will help off set the cost. But I would not swap the Zhumell 8" Dob for a Nexstar 8" SCT. YMMV


Edited by mfoose, 30 June 2020 - 11:36 AM.


#6 Sam M

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Posted 30 June 2020 - 12:16 PM

I can't imagine transporting a Z8 on a bike, and the 8SE seems like a stretch too.  The other question is, 'What are you really gaining by traveling by bike?"  Going 10 or 15 miles is unlikely to make a big difference in light pollution.  Can you walk to a spot without a lot of street lights?  That might be a better benchmark for portability. 



#7 kiltedcelt

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Posted 30 June 2020 - 12:58 PM

Just to clarify - re: travelling by bike - We're not talking about carrying in a backpack or something like that. I have trailers and cargo bikes so I can carry pretty big things. I've hauled remodeling contractor tools around. Also, I'm a fabricator and I can build boxes, cushioning systems etc. Additionally, my bikes all use fairly large, high-volume tires that have inherent suspension to them. Basically, me transporting a scope of any kind by bike and the inherent moving it around and setting it up is probably only marginally less cushioned than doing so by car. However, given that information about hauling - a case that would hold a Nexstar and carrying the tripod is going to be much easier and take up FAR less space than hauling the Z8. Luckily I live within a five-minute ride of Lake Michigan where I have the ability to get to a handful of spots that don't have streetlights right over them - however, with current restrictions on access to the parks and such you're not allowed to be out on the lakefront trail park areas past 7:00 PM anyway.

 

Anyway, I certainly won't gain much riding anywhere in the city as most places you're simply trying to find a spot where you don't have a streetlight right on top of you. Most of my observing would be a short trip over to the lake if restrictions get lifted enough to allow me to be out later in the evening. However, even without that, I can see a lot of the planets and some objects just from my street or the green space a block south of me, depending on time of evening/time of year. I'm mostly thinking a longer game about a scope that is easier for me to use mostly as a very casual amateur astronomer. Frankly I don't even know that I'm going to do any astrophotography because a lot of the post-processing seems to be so time-consuming. I might dabble a bit with planets and the Moon but that's probably about it. I have too many other hobbies and interests to delve too far into the photography end of things. I'm honestly more interested in something that is more portable than the Z8 and which will allow me to see more in light-polluted locations. Where I see the Nexstar potentially being better besides the Go-To aspect is the portability. It could easily fit into a bike trailer with some camping gear for a trip somewhere like one of the parks that is more than 20-30 miles away from the city. I can get to Indiana Dunes or Illinois Beach State Park, both places that are much darker than urban Chicago, albeit still tainted by way too much skyglow nearby. 


Edited by kiltedcelt, 30 June 2020 - 04:44 PM.


#8 Sam M

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Posted 30 June 2020 - 03:15 PM

Got it.  The bike is a wagon.  Not knowing your design, I can't really say how practical it is to tow around an 8SE.  Jon's point about the fragile glass on the front of the 8" SCT is an important one to consider.  I've dragged my C6 around in a backpack quite a bit, but the 8 would likely be more fragile, and bike rides have sharp bumps.  Break that glass, and you're hosed.  Assuming you could fabricate something that could protect it in transit, the 8SE seems like it would suit your needs.  The scope is more suited for narrow field, so you won't be able to see all of M31 or larger nebulae, etc.

 

The other consideration is collimation.  An SCT should hold collimation better than a newtonian, but it's harder to adjust.  So, again, you want to keep the vibrations to a minimum on the OTA.


Edited by Sam M, 30 June 2020 - 03:20 PM.


#9 kiltedcelt

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Posted 30 June 2020 - 04:42 PM

I went ahead and pulled the trigger on getting the 8SE. I know they've got their limitations, but I'm really pretty "amateur" when it comes to astronomy and I'm probably not going to have marathon viewing sessions or anything, at least until we move somewhere with a lot less light pollution. Thanks for the additional input on transport issues. I plan on building a custom foam-lined case for it, and I'm pretty sure I could even devise some shock-absorbing suspension system - as long as it doesn't end up taking up as much space as hauling the Z8 would! One of my major issues with trying to figure out how to carry the Z8 was that the OTA would have to be carried horizontally, and I don't know how well a mirror would tolerate shocks when being held on-edge like that. That being said, I wonder if there's any real difference as to whether a scope like the 8SE is transported horizontally or vertically. 




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