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New to SCTs & I Have Questions

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#1 fdanowski

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Posted 22 September 2021 - 10:43 AM

- On the threaded rod that mounts the scope to the tripod, WD40 or silicon? It squeaks like hell
- Does focusing normally shift the objects position in the eyepiece?
- What’s the best way to display it when it isn’t in use, vertical or horizontal on its tripod?
- Compared to my 8” Dob, focus seems a bit soft… not focus necessarily but ghosting, smearing, or blooming
- Are special Barlows required for SCTs / prisms? Looks sharp without but blurry with
- Do some eyepieces require special prisms to fit into the diagonal?
- Lastly what’s the best way to bring this thing’s electronics into the 21st century (LX200 EMC) Audiostar upgrade? WiFi/ app upgrade? How does that work with WiFi in the middle of nowhere?

Thanks!

Edited by fdanowski, 22 September 2021 - 10:45 AM.


#2 Stellar1

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Posted 22 September 2021 - 12:11 PM

A small shot of WD on the threaded rod is fine to stopethe squeak.

 

Yes almost all SCTs have some degree of mirror shift as it is the mirror which is moved when focusing an SCT.

 

There really is no “best way” to display it, what’s more important is that the scope is balanced so as not to strain the mount in whatever position it is in.

 

”soft focus” may be your collimation, of the main mirror is not correctly aligned to the secondary it can cause less than sharp images which never seem to come to focus, look up collimating SCT and checking alignment.

 

I have never heard of any eyepiece which requires an additional piece of hardware in order to use with a diagonal, the closest thing I can think of is a reducer from 2” to 1.25” when using a 2” diagonal with a 1.25” eyepiece.

 

As for the electronics, sorry but I cannot help with that but someone may chime in on that.


Edited by Stellar1, 22 September 2021 - 12:14 PM.


#3 Mike G.

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Posted 22 September 2021 - 12:37 PM

Welcome to CloudyNights!

 

I'm not an expert (and there are many more knowledgeable people here than me), but I will give you what I can to answer your questions.  more will chime in soon, no doubt.

 

personally, I am unfamiliar with the LX200 so I can't help you with the threaded rod thingy.

 

for image shift, this is something of a bane on SCT telescopes.  in the SCT, focus is achieved by moving the primary up and down on the baffle tube.  in order to do this, there has to be some mechanical clearance between the O.D. of the baffle and the I.D. of the mirror carrier. ideally, the clearance would be so small that the mirror wouldn't shift slightly as it moves back and forth in response to the pressure exerted by focusing.  but these are commercial scopes and manufacturing tolerances are a fact of life in Mass Production so it's quite typical for there to be enough tolerance between the O.D. and the I.D. that the mirror 'wobbles' enough to make a noticeable shift in the position of the object being viewed.

 

that said, there are some solutions, some more effective than others.  first, I would suggest running the primary through the full range of the focuser a few times.  this has the effect of spreading the grease used to make the movement smooth over the entire length of the baffle.  sometimes this is all that is needed to fix the image shift.  other remedies include taking the scope apart, cleaning the old grease off and replacing it with new grease.  still others involve more complicated modifications to the focusing mechanism.

 

most SCT owners just live with it.

 

I don't know if there is a 'best way' to store the scope; as in vertical or horizontal, mine live on the floor of my office in horizontal position because that's most convenient for me.

 

soft focus?  well, there are some people who think that is characteristic of SCT's but I don't.  I have looked through plenty of SCT's that are 'soft', but none of mine are.  I attribute that to a couple things:  first, you ALWAYS need to use a dew shield to prevent incident light from entering the tube and bouncing around.  the corrector amplifies this problem, an the inside of the OTA is (typically) pretty poorly controlled for eliminating stray light.  my SCT's all have been flocked on the inside of the tube and the inside of the baffle.  another cause of 'soft' images are tube currents inside the OTA.  there are lots of metal surfaces that tend to cool the air they are in contact with and cause turbulence in the double pass light path.  making sure you acclimate the scope AND insulate it will sharpen your images up quite a bit.

 

SCT's can use the same barlows as anything else, in fact, because of the long-ish focal length (f10), even inexpensive eyepieces and barlows will provide good images.  nothing special required, unless you have money burning a hole in your wallet

 

as I said previously, I am not familiar with this scope/mount, so can't offer any advice on upgrading the mount.

 

run the focuser back and forth a few time for the entire length of travel, get a dewshield and use it religiously and insulate the tube.  you will see improvement with these simple mods.

 

and report back!!


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#4 rkinnett

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Posted 22 September 2021 - 12:43 PM

Yeah, most of those observations are indeed common characteristics of SCTs.

 

Your Dob has much shorter focal length, so if you're comparing views with the same EP, you're operating at very different magnifications, and the lower magnification will always appear sharper, assuming good collimation in both.

 

Rather than upgrading electronics (assuming all is at least functional), you could get a $15 cable on amazon and control this scope from a laptop, if you're open to that.  That effectively brings this old platform up to the same level as modern platforms.  Driving a scope from Stellarium is very enjoyable.  A similar but more compact and lower-power option would be to setup a raspberry pi to control your scope through Kstars, and drive over wifi from a phone or tablet.  If you're not comfortable with linux, you can do the same with windows and Stellarium (et al) on a mini-pc, at substantially higher cost.

 

Be sure to check out http://www.lx200classic.com/ if you haven't already.  I miss my old LX200 EMC!



#5 Daveatvt01

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Posted 22 September 2021 - 12:53 PM

Congrats on the new scope.

 

There is also an AutofiLX200 device that ships from Ukraine, I have one and it works well. It plugs into one of the ports on the scope and generates its own wifi signal and you connect your phone to its "network". I can run my lx200 classic from skysafari on an iphone. At about $50 it's more affordable than the audiostar upgrade.

 

Also these scopes have old tantalum capacitors that can go poof and wreck electronics, you should look up "lx200 classic capacitor replacement" and consider replacing the troublesome ones, especially the one in the hand* controller. Even with the wifi dongle you'll need the hand controller to start up the scope and do the initial alignment.

 

*edited for spelling


Edited by Daveatvt01, 23 September 2021 - 11:50 AM.

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#6 Piet Le Roux

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Posted 22 September 2021 - 12:54 PM

I use white marine grease on the threaded rod and the focuser needs adjustment, I will include the the instructions, if this is still not satisfactory you should do the bearing mod.

Attached Files


Edited by Piet Le Roux, 22 September 2021 - 12:56 PM.

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#7 KTAZ

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Posted 22 September 2021 - 01:10 PM

- What’s the best way to display it when it isn’t in use, vertical or horizontal on its tripod?

 

I always store mine in a horizontal position. Why?

 

Well, gravity exists and anything that exists in your OTA tube including dust, grease, loose screws, small insects grin.gif (okay, I'm reaching here) will eventually migrate downward onto your corrector plate if you store your scope on its nice flat face.


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#8 Cliff Hipsher

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Posted 23 September 2021 - 06:26 AM

If you decide to open the tube and re-grease the baffle you need to use Dow-Corning High Vacuum Grease

 

This stuff is "stiff" and it does not out gas.


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#9 fdanowski

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Posted 23 September 2021 - 12:51 PM

Thank you everyone for commenting here. I figured that the movement of the object while focusing is a Cassegrain thing. Thanks also for the capacitor replacement idea. I understand that they just go POOF in these models. Currently, mine is is great working condition. It was a donation to my astronomy club and I won it in a raffle. The thing is in brand new condition (10" LX200 EMC f/6.3)! It also sounds like I can display it however, as long as I go easy on the mechanics of it. Originally I had the thing vertical, corrector plate face down. Then I thought, I don't know if that's good for the primary mirror to be suspended like that, so I began displaying it in the Zero position... Lastly, I think that the blooming/smearing issue might be stray light reflecting off the corrector plate. I have two dew shields and I'll start using them even for shorter sessions. Thanks again!



#10 MikeBY

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Posted 07 October 2021 - 11:49 AM

Don't use WD40 as a lubricant. It's not designed for that purpose.  WD40 get's it's name from it's function (Water Displacement). 
It dries out and leaves an awful coating.  I suggest a simple light bearing grease on the threads, then after you've attached the scope once wipe off all excess when the scope

is removed.

 

Regards,

 

M

 

 


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#11 MikeBY

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Posted 07 October 2021 - 03:39 PM

Thank you everyone for commenting here. I figured that the movement of the object while focusing is a Cassegrain thing. Thanks also for the capacitor replacement idea. I understand that they just go POOF in these models. Currently, mine is is great working condition. It was a donation to my astronomy club and I won it in a raffle. The thing is in brand new condition (10" LX200 EMC f/6.3)! It also sounds like I can display it however, as long as I go easy on the mechanics of it. Originally I had the thing vertical, corrector plate face down. Then I thought, I don't know if that's good for the primary mirror to be suspended like that, so I began displaying it in the Zero position... Lastly, I think that the blooming/smearing issue might be stray light reflecting off the corrector plate. I have two dew shields and I'll start using them even for shorter sessions. Thanks again!

The capacitor issue is VERY real and should NOT be ignored even if the scope is working normally.  You risk considerable damage to the telescope electronics.
There are a few issues with the electronics that are 30+ years old.
I most STRONGLY suggest that you DO NOT USE the original AC power supply adapter supplied by Meade (Sceptre brand) under any circumstances.  Buy a 15 volt DC 5 amp regulated power supply to use with this telescope.  
ALWAYS follow this sequence when connecting and powering on the telescope

1. Be SURE the power switch for the telescope is OFF.

2. Physically connect ALL cables (handset, DEC motor cable and power cable from your battery or AC adapter.

3. Turn on the power source (if switched) or connect the power cable to the battery or plug in the AC power cord 

4. Turn on the Telescope.

 

Power down in reverse order. Always turn off the telescope then disconnect the power source.

 

Do not connect power to the telescope with the power switch ON.
There is a significant power demand when power is first connected to the telescope even when the power switch is off.
The combined demand of the initial draw plus the demand from the electronics will cause power supply issues and voltage fluctuations that can damage both the power supply and the telescope.

 

The LX200 EMC has wonderful optics, and works well, but there are a few quirks and issues that must be addressed for reliable operation.



#12 fdanowski

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Posted 09 October 2021 - 06:27 PM

Hi: Enough has been made of the capacitor issue that I definitely take it seriously. The AC transformer that came with it outputs 15v DC. I bought a Jackery power station to run it via its 12v DC output. I’ll use that most of the time. Thank you for your reply with the power up/down sequences.


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