LX90 10" versus LX200 GPS 8"

norm · #1 21-10-2005, 10:49 PM

Hi All,
Just interested in any comments on either of the 2 scopes and which one would you choose? Both scopes are similar in price with the LX90 around $100 dearer atm.
Even though I may dabble and experiment in a bit of astrophotography/ccd imaging, it will never be something of serious concern.

How does a 10" premium dob compare with either of the above?

If money wasn't a factor would you go for the dob or SCT ? Is collimation as much of an issue with a SCT? Also will I be equally impressed with seeing DSO's with a SCT as I have when viewing thru some dobs? Optics ???

PS: portability has become a factor for me now and hence maybe an SCT.
Price wise I know the dob wins hands down.

Looking forward to the responses!

[1ponders] (Paul) · #2 21-10-2005, 11:04 PM

Hi Norm.

I've never had a dob but I have had an LX200 8" and I loved it. It does have a larger central obstruction compared to a similar sized newt "as does the 10"" but it was a dream to use. Heavy though for a small scope. If you decide to get one I would highly recommend you build a "springy thingy" to help mounting the scope on the tripod. Same thing for the LX90.

For visual, a quick star check used to be all I needed to do (get a set of bobs knobs for ease of collimating) . IME I found the collimation quite forgiving for visual work. Bit different for imaging. More tweaking required.

Money no object

and I was looking for a similar thing again. No brainer for me, LX200.

RAJAH235 · #3 21-10-2005, 11:30 PM

The LX90's apparently are built cheaper. ie; instead of bronze gears they use Aluminium, & smaller bearings etc etc. Optics are the same.
HTH.

L.

acropolite (Phil) · #4 22-10-2005, 01:25 AM

If photography isn't a big issue the 10 inch LX90 would be my choice. The LX90 is a very nice piece of equipment, the OTA is identical to the equivalent LX200 size with the exception that there is no mirror lock. The gears may not be as sturdy, but you don't see reports of stripped or worn gears from LX90 owners. I would however be watching closely for favourable reports on the 8 inch Mak that Saxon and other manufacturers are offering on an HEQ5 eq mount...

Starkler (Geoff) · #5 22-10-2005, 01:41 AM

Quote:

Originally Posted by norm

How does a 10" premium dob compare with either of the above?

If money wasn't a factor would you go for the dob or SCT ?

A dob with good optics will beat an sct optically.
Pay 7x as much for an sct and you get tracking.

There seems to be a misconception that a dob is somehow a poor mans scope

Ambermile · #6 22-10-2005, 02:05 AM

Well, it's not that simple but you do have a point Starkler - but he did say imaging/ccd stuff so tracking is really a requirement. I have to say that myself and a friend put an Autostar system onto a 20" dob last year (that was fun

) and it was awesome to use - at f/3.8 it was awesome to look through as well!

But it most definitely was *not* portable. My 12" LX200 wasn't either. I wouldn't consider the 10" as totally portable either but it's getting there. I'd prolly suggest a decent EQ mount and one of the 8 or 10 inch SCT OTA's in this case. Gives one more options for the future as you are not nailed down to one OTA.

Arthur

RAJAH235 · #7 22-10-2005, 02:06 AM

It all gets back to the basic Q. What do you really want to do?
First rule 'Aperture Wins'. A good 10" Dob will fit in the 'normal' sized car & is cheap, easy to move, collimate etc etc..... + the don't suffer from the dreaded dew problem...
To answer your question re; SCT collimation... shouldn't be nec., unless your into pics in a big way, like RR & a few others.....
The Dob can be fitted with digital setting circles/tracking platform etc., to assist in finding/photographing things. See Mike's Dob set-up.
HTH a bit.

L.
ps. check out the 'Show us your equipment' in here >
http://www.iceinspace.com.au/forum/forumdisplay.php?f=6

rumples riot · #8 22-10-2005, 12:13 PM

Thanks Rajah guess I will have to comment.

First, we need to clear something up, I grow tired of this falicious argument that Dobs are better than SCT's, quite frankly this is bull dust, each scope has its benefits and flaws and I will give some of them. All the LX range scopes are f10 meaning that they are slower photographically and visually. The sky will not be as bright visually. The images will still be good and sharp though. There are many good astrophotographers who are using LX series scopes, you just have to take longer and deeper images to get the same results as say a SN10 on a good mount. Besides the LX scope is setup for astrophotography, a dob is not.

Second, these scopes are made for people who don't want to go searching for objects in the sky. I did this for 20 years and I grew really tired of it. A dob on the other hand means that you will have to know the sky quite well to see many objects that are faint. It can be rewarding to do this, but also frustrating.

Third, LX scopes are relatively small and are easier to transport. They can fit easily in a good size boot and the 8" is very easy to lift. A dob can be hard to fit into a boot and is at times cumberesome.

Fourth, the optics on a LX series scopes are very good. Good bang for buck and you dont get coma. Nor do you get aberation. These are symptomatic of Newtonians. Paracors are needed on Newtonians to correct this issue. They are very costly.

Fifth, the longer focal length of the LX series scopes means that you can do serious planetary observation and photography given the right seeing conditions. A dob is not designed for this and many mods have to be made to attempt this. Look at the work Mike has done on his scope. Even with a 5x on his scope his image scale is only just the bigger than a 2.5x on mine.

Sixth, the LX series scopes are really a moderate all rounder. They can do lots of things but they are only a master of planetary stuff and high mag work. They have their limitations. A dob can only be a master of visual work on DSO's if it is setup correctly. They don't have tracking, the focal length or the computer system. I think that by and large most owners of the LX series scopes will say they are happy with their scopes.

Seven and more to your question. Aperture, aperture rules. LX 90 10 will show more than the 8", not only on really hard objects. Also the 10 is a lot heavier than the 8". I am a pretty fit guy and quite strong. If you not this way inclined go and have a look at a 10 and ask if you can lift it. You don't want to be a wirey person trying to lift this. However GPs does come in handy, you should consider this option.

Finally, you must decide what is in your budget, what you want out of a scope, how much you are going to use it and what are your future goals. This hobby can be really infectious and astrophotography is certainly on most peoples minds. If you buy wisely then you will have little need to sell one scope and then buy another. For myself, if given the chance again, I would have bought the C9.25 purely for planetary work.
In addition to the above collimation is not really an issue for the average SCT user. I have gone collimation mad because I do planetary imaging at very high magnifications. Collimation under such demands needs to be excellent, not just good. Most people would not know the difference between good collimation and excellent collimation, but it can mean the difference in an imaging session. Besides collimating a SCT is actually easier than a Newt.

Anyway that is my take. Feel free to ask questions if you like.

Mick (Michael) · #9 22-10-2005, 01:11 PM

I had the same requirements, a visual scope and some astrophotography. I picked the LX 90 8" sct and I'm very happy with it's light gathering power and ease of use, if I could pick only one scope it would be the 8" sct. Size and weight wise the 8" sct is very easy to set up and use for visual work. Planetary and Lunar photos are relatively easy to take with the scope in Alt/Az, Dso's are more difficult but not impossible. I do own a 12" dob f/5 and it is a good Dso scope but it's Focal ratio is a problem for me, I hate coma, for this reason I will never own another scope under f/6 for visual observation.
This is just my thoughts and I respect that other people will not have the same opinion.

Good luck Norm.

About Coma

Starkler (Geoff) · #10 22-10-2005, 01:25 PM

Just a few comments about Pauls points above.

First: While im sure there are some good sct's and bad dob mirrors around, the complexity of the sct optics means there are more optical surfaces to get right and theres more room for error. Modern dobs like the gso have very good mirrors and I have heard comments from a number of people that these dobs beat sct's in sharpness of focus.

Second: For object finding its much cheaper to retrofit a dob with dsc like an argonavis than to think one must spend the extra for a fork mounted sct just to find objects. Object tracking is another matter.

Third: The sct may break down into smaller pieces for transport, but is much more time consuming to set up and pack away. My 10 inch dob ota lays across my back seat, and the base goes into the boot. On arriving at a site i can be viewing within 5 minutes and pack up just as quickly.

Fourth: Coma is only an issue with short f-ratio newts and at wide fields of view that the sct wont allow anyway due to its slow f-ratio. Very few find a paracorr wanting at f5. Eyepiece abberrations are often incorrectly labelled as coma . It is true that faster scopes are more demanding on eyepieces and in general wide field eyepieces that work well at fast f ratios are more expensive.

Fifth: planetary viewing in a dob is not a problem with the right focal length eyepieces. Planetary imaging is another ball game.

THe point of my earlier post is just to point out that its not necessary to spend thousands of dollars to get good views, and that your not going to get superior views by spending that much more money to buy an sct.
Im not interested in astrophotography myself, but for somebody who is, an sct with tracking makes life easy.

Horses for courses.

matt · #11 22-10-2005, 01:28 PM

rumples and mick

Very good and fair comments on what is a tricky subject for most of us who are new to this wonderful pursuit.

I've only been a member of this website's forum for about a month but I would like to convey my highest recommendation to anyone else who may be new and travelling through its various subjects and associated threads looking for advic and information.

You will find whatever you're looking for here. Don't be afraid to ask. Everyone here is keen and only too happy to share their knowledge and expertise.

It's a great little community and beginners won't find it anywhere near as intimidating as other sites.

Enjoy

Mick (Michael) · #12 22-10-2005, 01:45 PM

Things change the price of dobs have come down alright, I paid $1700 two years ago for my 12" dob landed at my door.

acropolite (Phil) · #13 22-10-2005, 04:47 PM

Geoff Said

Quote:

The sct may break down into smaller pieces for transport, but is much more time consuming to set up and pack away

Not true. My LX breaks into 2 pieces, the OTA and tripod after loosening one knob. The OTA lays on the back seat( just like yours) and the tripod on the floor. No more complicated to dissemble and pack away than a dob. For assembly the same is true, however as someone pointed out in another thread one has to wait while the LX does the chicken dance, probably an extra minute or so. For a newbie attempting to find a faint object this time difference would be insignificant compared to the savings in time afforded by the goto facilities. The electronics in the LX can be left switched off and the OTA pointed in exactly the same manner as the dob if required.
One thing that is always apparent in these threads is that there don't seem to be any go-toers that wish their equipment was push to, but there are a large amount of dobbers out there who wish they had tracking and goto.

Starkler (Geoff) · #14 22-10-2005, 04:55 PM

Push to does me fine

ballaratdragons (Ken) · #15 22-10-2005, 05:13 PM

Quote:

Originally Posted by acropolite

One thing that is always apparent in these threads is that there don't seem to be any go-toers that wish their equipment was push to, but there are a large amount of dobbers out there who wish they had tracking and goto.

Ow! That stung!

But oh so true in my case

I love using my dob, but I am at a point where I would like to press a few buttons and view. Plus getting into Astropics now I want to do DSO photography.

I don't know what do do really, coz I may get an SCT and hate it

xstream (John) · #16 22-10-2005, 05:22 PM

But Ken you'll be able to try out the old SCT at Star Camp.

You'll love coming over to the Dark Side.

ballaratdragons (Ken) · #17 22-10-2005, 05:33 PM

John, the Darker the Better (astronomically speaking LOL!).

I will be trying to learn as much as possible about all styles of scopes at camp. Dobs do have lots of advantages, but never having anything to do with other scopes I am eager to learn.

xstream (John) · #18 22-10-2005, 05:43 PM

Ken I don't really consider any one scope better than the other they all have their strengths and weaknesses.
As Geoff said earlier it's Horses for Courses.

ballaratdragons (Ken) · #19 22-10-2005, 05:47 PM

True John and Geoff. I just have to discover which horse I prefer. I have always been a Newt man (not by choice, but by dollars). I have never ever seen through anything else!!!! (except the 100 year old refractor at our society)

xstream (John) · #20 22-10-2005, 05:56 PM

Well you'll be in for something completely different.