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Questions about the Zhumell Z100

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#1 Autumn

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Posted 22 October 2021 - 01:37 PM

Hello everyone,

 

I am a university student who wishes to upgrade my telescope from a 70mm refractor to a reflector with a larger aperture. I hope to get one that is portable, as I will often be carrying this telescope in my hands from my dorm room to dark areas on campus for stargazing. When I'm not in school, I of course wish to be able to take the reflector telescope by car to dark sky locations such as Killarney Provincial Park, North Frontenac Dark Sky Preserve, provincial parks as well as attend some dark sky star parties once the pandemic is over and it is safe to do so.

 

One telescope I am considering is the Zhumell Z100. I like the fact that it has a parabolic mirror. It is within my budget (not exactly flush with cash as most of my money is going towards tuition and school related expenses). Being an F/4 telescope, I have read that any reflector telescope above f/6 could suffer from coma issues. Is there a noticeable coma issue with this telescope or do the eye pieces it comes with, avert that problem?

 

I do have a Celestron Omni 2x barlow lens, will that help reduce the coma, if any?

 

https://zhumell.com/...ector-telescope

 

 

I have read that F/4 fast reflectors require precision collimation in order to get clear sharp views. This telescope's parabolic mirror is tightly mounted into the back end of the tube and barring major modification to the telescope, this telescope is one where the user cannot collimate the primary mirror. For others who have had this telescope, do you know if, barring any shock accidents, the telescope will be able to hold collimation for many many years so that it has good longevity?


Edited by Autumn, 22 October 2021 - 01:54 PM.


#2 Anony

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Posted 22 October 2021 - 02:16 PM

I'm not quite sure a 100mm reflector is that big an upgrade over a 70mm refractor due to obstruction. If I had to guess, a 100m reflector is about equivalent to an 80mm refractor, as far as light-grasp goes? And going from 70mm to 80mm, while an upgrade, might be a shrug your shoulders, meh, sort of upgrade.

 

Maybe look at the 114mm models at least? Or ideally 130mm... something like an AWB (although then it's much more expensive).

 

 

I suggest also taking a look at used scopes locally, see if you can find any bargains.


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#3 Mitrovarr

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Posted 22 October 2021 - 02:36 PM

Coma tends to be more of an issue with larger telescopes than smaller telescopes, and also tends to be more of an issue with experienced observers. I wouldn't worry about it.

 

On the other hand, the inability to collimate is a problem. Nobody has ever made an amateur reflector I would ever consider to never need collimation, and collimating the secondary doesn't fix bad collimation of the primary in a newtonian. Generally, reports have been pretty positive, but I wouldn't expect it to keep collimation for many years. You might conceivably be able to tear it apart and fix the collimation yourself, but it would be more of an invasive process and more difficult.



#4 rgk901

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Posted 22 October 2021 - 04:22 PM

z100, you can't rotate it, can't collimate it, shorter focal length, making it best as a low power sweeper.

 

I would spring the extra $50 and get the Z114. Collimating the scope will allow maximum performance and it will have more aperture. Rotation will allow a comfortable view no matter your position.

 

Best is to save extra $100 and get the z130 (or AWB / heritage or similar 130mm) it is enough aperture that you may never need to upgrade it as far as it being a travel grab n' go. It rotates, it collimates and has an F/5 mirror which is easier on eyepieces. But it's a bit heavier and bigger.

 

I have the z130 and this little thing is a great performer, specially at dark sites, and SHOULD be $200 new. Cheaper used. But that extra $100 gets you a larger aperture, longer focal length and the ability to collimate it for the best performance. And has rings/dovetail so can throw it on any mount in the future!

 

Only down side to these smaller table tops from Zhumell (Orion) is the plastic focuser, it's sloppy but can be DIY'd to remove most of the slop with simple UHMW/ tape (even scotch tape if funds are low). The heritage / AWB have a helical focuser, something different but usable and can also improve the slop with some cheap teflon tape. But these fold down for easier transport, but will need a shroud (from cheap crafting foam)

 

I understand the budget, but buying twice sucks more. Since you already bought the 70mm now you will buy the 100mm and next year want the 130 or bigger.... Just save up now, or get used, and try for that 130mm for that extra $100 and done (at least till you graduate, get a job and get yourself that 16" smile.gif

 

Good luck! Hope it works out!


Edited by rgk901, 22 October 2021 - 04:27 PM.


#5 rgk901

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Posted 22 October 2021 - 04:38 PM

To save $$ drill yourself a 2mm hole in the scopes dust cap, paint the underside of cap white and you have a free cheshire that will do a good job of aligning the primary mirror. Make sure to drill the hole dead center of cap!!

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#6 SteveG

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Posted 22 October 2021 - 05:37 PM

To save $$ drill yourself a 2mm hole in the scopes dust cap, paint the underside of cap white and you have a free cheshire that will do a good job of aligning the primary mirror. Make sure to drill the hole dead center of cap!!

The scope he is looking at does not have a collimating primary. It’s fixed, so a collimating cap would do no good.



#7 SteveG

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Posted 22 October 2021 - 05:39 PM

Hello everyone,

 

I am a university student who wishes to upgrade my telescope from a 70mm refractor to a reflector with a larger aperture. I hope to get one that is portable, as I will often be carrying this telescope in my hands from my dorm room to dark areas on campus for stargazing. When I'm not in school, I of course wish to be able to take the reflector telescope by car to dark sky locations such as Killarney Provincial Park, North Frontenac Dark Sky Preserve, provincial parks as well as attend some dark sky star parties once the pandemic is over and it is safe to do so.

 

One telescope I am considering is the Zhumell Z100. I like the fact that it has a parabolic mirror. It is within my budget (not exactly flush with cash as most of my money is going towards tuition and school related expenses). Being an F/4 telescope, I have read that any reflector telescope above f/6 could suffer from coma issues. Is there a noticeable coma issue with this telescope or do the eye pieces it comes with, avert that problem?

 

I do have a Celestron Omni 2x barlow lens, will that help reduce the coma, if any?

 

https://zhumell.com/...ector-telescope

 

 

I have read that F/4 fast reflectors require precision collimation in order to get clear sharp views. This telescope's parabolic mirror is tightly mounted into the back end of the tube and barring major modification to the telescope, this telescope is one where the user cannot collimate the primary mirror. For others who have had this telescope, do you know if, barring any shock accidents, the telescope will be able to hold collimation for many many years so that it has good longevity?

Don’t waste your money on a 100 mm scope that cannot be collimated. Your 70 mm refractor will provide better views. 

 

I too highly recommend the 114 or 130 mm table-top scopes. The 130 versions can rival a $1000 4” Ed refractor.



#8 rgk901

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Posted 22 October 2021 - 06:03 PM

The scope he is looking at does not have a collimating primary. It’s fixed, so a collimating cap would do no good.

I know, but since we are all advising against the 100mm I'm figuring OP will buy the 114 or 130 hopefully.


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#9 stnagy

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Posted 23 October 2021 - 06:15 AM

You might also consider the Skywatcher 150p flex tube table top dobsonian. It is basically a slightly larger version of the AWB Onesky 130 / Skywatcher 130p flex tube that has already been mentioned in this thread, and would give you just a little bit extra light grasp. If you are going to buy something in the tabletop category, this is the one I would suggest. 

 

Nobody else has answered this yet … you will probably notice coma at the edge of the visual field in an F4 telescope without some kind of corrector. The eyepieces won’t have a corrector built in. A barlow will eliminate the coma, but it will also obviously change the view you get, so not ideal. These smaller, faster scopes excel with wide-field views, and the barlow kind of kills that. Better to go with an F5 system if you don’t want to deal with a corrector, in my opinion. 


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#10 Autumn

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Posted 24 October 2021 - 04:44 PM

I would like to thank everyone for their informative replies. It's really great to hear from the astronomy community and see what others who have taken up this interest, say.

 

As I live in the dorms of a university campus, I was planning to walk to the dark places on campus and carry my telescope with me. That is why I was targeting a lighter one, such as the Zhumell Z100 which I read is 6.2 pounds / 2.8 kilograms with the tube and the tabletop dobsonian style base. I had considered taking the telescope in my arms and having a friend help me take the Amazon Basics tripod with me. That tripod is said to be able to support 6.6 pounds, so I can mount the Zhumell Z100 telescope on it for observing. The dark areas on campus are about a 15 to 20 minute walk from my dorm. I thought, the lighter it is, the more I will probably use it, thus I was considering this telescope. I do see that everyone here is suggesting I get a telescope with more aperture though .....

 

I do like the Zhumell Z130 as well, if I do get that, at F/5, does mirror collimation need to be very exact for there to be good views?

 

The Zhumell Z130 doesn't have a tripod so I would need to invest money in a tripod or table. Plus be able to carry that across campus as well for 15 to 20 minutes while walking. Would an alternative telescope like the Celestron Cometron 114az be a good alternative as it comes with a tripod? ..... My concerns about that scope is that it is F/4 which might require precision collimation? F/4 might have serious coma issues? Tripod doesn't have slow motion controls?

 

@rgk901, thank you for the tip about using the dust cap as a cheshire

 

 

@stnagy, thank you very much for answering my question about coma!



#11 SteveG

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Posted 25 October 2021 - 04:47 PM

I would like to thank everyone for their informative replies. It's really great to hear from the astronomy community and see what others who have taken up this interest, say.

 

As I live in the dorms of a university campus, I was planning to walk to the dark places on campus and carry my telescope with me. That is why I was targeting a lighter one, such as the Zhumell Z100 which I read is 6.2 pounds / 2.8 kilograms with the tube and the tabletop dobsonian style base. I had considered taking the telescope in my arms and having a friend help me take the Amazon Basics tripod with me. That tripod is said to be able to support 6.6 pounds, so I can mount the Zhumell Z100 telescope on it for observing. The dark areas on campus are about a 15 to 20 minute walk from my dorm. I thought, the lighter it is, the more I will probably use it, thus I was considering this telescope. I do see that everyone here is suggesting I get a telescope with more aperture though .....

 

I do like the Zhumell Z130 as well, if I do get that, at F/5, does mirror collimation need to be very exact for there to be good views?

 

The Zhumell Z130 doesn't have a tripod so I would need to invest money in a tripod or table. Plus be able to carry that across campus as well for 15 to 20 minutes while walking. Would an alternative telescope like the Celestron Cometron 114az be a good alternative as it comes with a tripod? ..... My concerns about that scope is that it is F/4 which might require precision collimation? F/4 might have serious coma issues? Tripod doesn't have slow motion controls?

 

@rgk901, thank you for the tip about using the dust cap as a cheshire

 

 

@stnagy, thank you very much for answering my question about coma!

Perhaps you should consider something like this:

https://www.telescop...7BoCSVwQAvD_BwE



#12 Anony

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Posted 25 October 2021 - 11:39 PM

Perhaps you should consider something like this:

https://www.telescop...7BoCSVwQAvD_BwE

I think the OP already owns a 70mm scope... hence why a 100mm reflector may not be much of an upgrade (unless the 70mm totally stinks).



#13 Don H

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Posted 26 October 2021 - 02:54 AM

I would like to thank everyone for their informative replies. It's really great to hear from the astronomy community and see what others who have taken up this interest, say.

 

As I live in the dorms of a university campus, I was planning to walk to the dark places on campus and carry my telescope with me. That is why I was targeting a lighter one, such as the Zhumell Z100 which I read is 6.2 pounds / 2.8 kilograms with the tube and the tabletop dobsonian style base. I had considered taking the telescope in my arms and having a friend help me take the Amazon Basics tripod with me. That tripod is said to be able to support 6.6 pounds, so I can mount the Zhumell Z100 telescope on it for observing. The dark areas on campus are about a 15 to 20 minute walk from my dorm. I thought, the lighter it is, the more I will probably use it, thus I was considering this telescope. I do see that everyone here is suggesting I get a telescope with more aperture though .....

 

I do like the Zhumell Z130 as well, if I do get that, at F/5, does mirror collimation need to be very exact for there to be good views?

 

The Zhumell Z130 doesn't have a tripod so I would need to invest money in a tripod or table. Plus be able to carry that across campus as well for 15 to 20 minutes while walking. Would an alternative telescope like the Celestron Cometron 114az be a good alternative as it comes with a tripod? ..... My concerns about that scope is that it is F/4 which might require precision collimation? F/4 might have serious coma issues? Tripod doesn't have slow motion controls?

 

 

 

I think you would be disappointed trying to put the whole Z130 on the AB tripod. A 6.6 lb rating would mean that the scope would be at capacity, so when you magnify the view at all, you will greatly magnify the shakes and vibration in the ep. I think the Cometron 114 may be a nice choice for what you want to do. Even though its tripod looks a bit less sturdy than it should be, having the scope on a tripod will give you the ability to hike and carry it, then set up and/or move the scope quite easily. And you will not need to carry a table or chairs with you. I have an Orion 114 f/4 and it is really not that much harder to collimate than my 6" f/5. You can easily reach around and make adjustments while looking in the tube, which makes it handy to see if what you are doing is making things better or not. The eyepieces it comes with may work ok to start, but at f/4, if you upgrade to premium eps in the future, the view improves a lot. I would not worry about slow motion controls. My 114 is on a Versago II mount which does not have them. The tubes are light enough that it is not too hard to track. And since they are so nice at low powers, tracking is easier. 

 

Here is my set up. I had to buy the rings, dovetail, and mount, besides the initial scope purchase. But it made the scope my favorite grab and go I ever had. Under dark skies, it amazes me, and I have had many larger, and smaller scopes. You could get the Z130, and since it has rings, you could put it on a Versago or similar mount. But it will cost three times as much and weigh twice as much. It looks like the Cometron is In Stock and On Sale, too.

 

https://www.amazon.c...e/dp/B00DV6TJMK

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Edited by Don H, 26 October 2021 - 03:36 PM.


#14 Binojunky

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Posted 26 October 2021 - 11:12 AM

To the OP, forget the Z100, go with the Z114 orZ130, Dave.



#15 Anony

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Posted 28 October 2021 - 01:55 AM

Someone locally was selling a Z100 at a cheap price, and even though I don't really need it, I picked it up, somewhat out of curiosity as to how such a small scope would work. It was cheap enough that it's something to play with when I want something super light, or I figure I can loan it to friends/family, or worst case resell down the road.

 

I need to check collimation on it (not that it necessarily matters, since these can't really be collimated so easily)... but I can't say I'm exactly thrilled with the views with my first outing.

 

It's... okay-ish... but that's sort of it. It may be coma, but a lot of the stars looked somewhat mushy to me -- hard to focus outside of the center stars.

 

Jupiter was... bleh. The moon was fine, but nothing special either. I'll try it again when seeing is better, but my C5 destroyed it (expected, but it means seeing wasn't super bad)... and based on memory, my 80mm refractor was much better than the Z100 (didn't bother taking the 80mm out tonight). I even preferred my tiny 70mm scope when viewing the Pleiades.

 

So... OP is probably better off with the 70mm refractor they already own than go with the Z100, as has been stated several times in this thread. Just wanted to mention how the Z100 came across to my eyeballs. I don't think it's worth bothering with.


Edited by Anony, 28 October 2021 - 01:56 AM.

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