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Considering buying an older lx90, anything to be aware of?

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#1 GFisher2001

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Posted 21 October 2021 - 08:43 PM

In the market for a new scope. I'm coming from a Celestron 127 SLT, with Goto. 

 

How does the LX90 mount work in the 8, 10, 12" sizes, is it undersized? 

 

What would a good price be, used for a 12"?

 

Is a 10 or 12" absurd to set-up?

 

Do they need frequent collimating before every session? 

 

I enjoy being able to take my 127 SLT in and out of the house for short sessions ( in addition to longer sessions ). 

 

I've gotten some pictures I've really been proud of, of Orion's Nebula and Jupiter/Saturn with the 127 SLT, would a 12" be a massive step up for DSO in light polluted skies?

 

TL:DR:  I haven't had much luck seeing DSO besides Orion's Nebula (which looks pretty good at about 15 seconds, single exposure, dslr) in my fairly light polluted area. I feel I have sort of maxed out the abilities of my current scope. I've learned how to use it well, but beyond the planets and Orion I don't see much else interesting and I'm wondering if it partly has to do with my aperture size. With GoTo working perfectly, I see nothing of Bodie's Nebula, California Nebula, Hercules Cluster. Uranus is basically a single pin **** of blue. Jupiter looks decent, with usually about 3 moons visible, but very hard to discern clouds/red spot. Saturn you can tell has rings, but no variation in color. Mars is very hard to make out either of the ice caps. Moon looks great. All of the aforementioned items were in clear, chilly skies with cleardarksky making as great seeing (so about as ideal as I'll get here on the eastern seaboard of U.S.) I was fortunate to travel to very very dark skies Bortle 2 this summer (Milky Way easily visible to the naked eye) and I was able to see the Hercules Cluster with my 127mm Mak-Cas. At home in Bortle5-6 skies I couldn't see any of the cluster. Wondering if aperture would help resolve some DSO better in light pollution. 

 

Any responses to any of the above would be greatly appreciated.  



#2 Piet Le Roux

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Posted 22 October 2021 - 01:34 AM

Good day,

I have been using a 8" LX90ACF for more than 3 years and is very happy with it. I am in my 60's and have gotten rid of my bigger scopes, a 10" SCT and 15" Dobson, and have kept the 8" because it's has the best effort to performance ratio for me. There is a difference between the SC and ACF (advanced coma free) models and the ACF produces better views with wide angle eyepieces and gives near pin sharp stars edge to edge. There are also a GPS and none GPS model, I think all the ACF models have GPS, the only advantage with GPS is that you dont have to enter the time, date and coordinates every time. The goto performance with the Autostar/Audiostar controller for me is excellent, some would disagree, but my experience is that you have to do maintenance on the drives once a year and do drive training now and then, I check my training values after drive training to decide if the drive needs ajustment. When setting up take care to get the scope OTA  level in all directions before you do a two star alignment, true North is not critical so don't waste time to get it perfect, remember this is not a "plug and play" scope! I have found the collimation do not need frequent ajustment but if possible star check the collimation of the scope you intend to buy, the patten does not need to be perfect but its preferable that its identical both sides of focus. 

Good luck.....


Edited by Piet Le Roux, 22 October 2021 - 01:59 AM.


#3 Daveatvt01

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Posted 22 October 2021 - 02:33 AM

At one point I went from a 5” sct to a 10” sct in a city setting, and can say it was a big step up. However, many nebulae are going to be pretty dim from light polluted areas. 

 

I wouldn’t consider a 10” sct to be absurd to set up a few nights a week, but that varies depending on the person/situation. The scope/fork mount of my 10” LX200 classic weighs about 60lbs, and it’s closer to 70 with accessories. It takes minimum 3 trips outside to get it set up. If I had to take it down 3 flights of stairs I’d feel differently.

 

An sct shouldn’t need constant collimation. It should be checked regularly though.

 

Planets will look better in a bigger scope if seeing allows/they are high above the horizon/scope is cooled. A big sct will take a long time to cool too, but you can insulate them if it’s a problem. Also mars is only really impressive every couple of years when it is closest to us. But a 5” mak should do quite well on planets, so if you can’t see more detail on saturn or jupiter it’s likely your seeing and/or scope not being cooled are affecting your view.

You might consider going through a list designed for light polluted locations and seeing if there are other things besides nebulae you might enjoy too.

Here’s one with a good article that explains a lot to go with it: https://skyandtelesc...yDeepSky111.pdf

All DSO’s are not the same brightness too, the California Nebula is considerably dimmer visually than M13 or M81/82. 



#4 carolinaskies

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Posted 22 October 2021 - 01:08 PM

Lets be clear first.

The LX90 is lighter than the LX200. Due to this it is more portable than it's bigger cousin. 
What size does this portability drop off? After 10" the width of the fork arms makes the 12" far less manageable than the 10" even though the weight isn't much more.  This is very true especially if you plan to mount on a wedge. If you're only mounting Alt-Az the 12" is 'possible' for a strong person solo if you use a landing plate on the tripod(I use one on my 10").  

Weight wise lets take a look... 

LX90 8" is 33lbs (LX200 - 45lbs)
LX90 10" is 50lbs (LX200 - 62lbs)
LX90 12" is 60lbs (LX200 - 83lbs) 

I personally have a 10" LX200gps.  I'm 6'1" and it's a heafty lift from prone in it's carrying case.  I also have an older LX200 8" classic, and it's doable without much issue.  I have a couple of C8's which are much closer to the LX90 and by comparison they are light.  

SCTs don't particularly need regular collimation.  Check them when you receive it, then a yearly check is fine unless you notice issues. 

If you want a good tradeoff between short observing sessions and longer ones consider the 8".  If you spend a lot more time observing go with the 10".  

 



#5 nitegeezer

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Posted 22 October 2021 - 01:21 PM

The big difference between the LX90 and LX200 is the strength when used on a wedge for AP. The LX200 is the better choice but as been stated it is heavier to work with. I originally planned to get a 12", and a friend mentioned a bigger scope is no good if it reduces the frequency of use due to it's weight. He talked me down to an 8" and I am really glad he did. It allows me to use my scope at outreach events, if I had gone heavier it would stay in the observatory.

#6 Levant

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Posted 22 October 2021 - 04:13 PM

Celestron 127SLT is a good grab & go scope and you better not sell it but keep it because the best scope is the one that you use most.

I have an 8 inch Meade ACF that is an excellent scope for what I can see. I can see 5 or more bands of Jupiter, 3-4 color tones and two rings of Saturn and the polar cap of Mars (once) but I cannot see many DSOs under my Bortle 9 skies. I am worried that you may not be fully satisfied after paying thousand of dollars for an 8 inch and cannot see a huge difference with your 127SLT.

I did not have any chance to try 10 inch or larger scopes but they say that there is a significant difference between 8 and 10 inch about what that number of DSOs you can see.

Many people recommend 10 inch Dobsonians for a satisfactory result. I think that Celestron Edge HD or Meade ACF will be also very good although they are costlier and have narrower FOV. 

Many discoverers use 12 inch however they say you need an observatory for it because it is almost not portable. If you prefer an 12 inch or larger Dobsonian, you need to be a tall guy.



#7 GFisher2001

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Posted 22 October 2021 - 07:54 PM

Thanks for all of the info. The scope I was going to look at tomorrow sold, my search continues, thank you everyone. 



#8 Daveatvt01

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Posted 22 October 2021 - 10:44 PM

Ah, too bad. In the meantime, you can keep trying with your scope. I’d be really surprised if m13 was undetectable from your location. It was resolvable in a 4” scope from tucson tonight (bortle 7 at best, though low humidity) with a two-day-past full moon above the horizon. It helps to keep one eye dark adapted. Also if it’s invisible at low power, upping the magnification can really help. 




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