Fix mirror shift in ETX Maks and a cool mod

[@MiguelGarcia-ut3fn]

Managed to eliminate most of image shift following your video!. Mirror is a solid piece of glass, not as delicate as what most people think. I put a “cover” on the mirror with soft material so I could work freely when doing the adjustment w/o any risk of damaging the mirror. My only mistake was not to properly clean the protective surface and I had to clean the mirror afterwards…not a big deal with alcohol and cotton.

[@kenn7915]

Thank you Sir for posting this. This will give me the courage to take apart my 180mm Maksutov when the time comes. I never seen image shift before. I read about it, pictured it in my mind, but never seen it live. Thank you for going where most do not.

[@GarnettLeary]

Absolutely. In the information age there’s zero excuse for no visual reference. Anything I undertake, investigate, or get stumped by is something I consider sharing. Imagine a world where nobody had to repeat mistakes or struggle to get an answer. Anything else is illogical and unproductive. I’m willing to bet that 180 you have is very similar internally. Thanks for watching and clear skies.

[@kenn7915]

@@GarnettLeary I always check collimation and its pretty good. I will setup a control environment and test/ determine shift. Thank you again Sir.

[@GarnettLeary]

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[@kamon242]

Excellent video. It's always nice to have resources like this when researching to tweak, repair or preserve this beautiful instruments. You should get the camera on a tripod tho, no need to force yourself onto doing everything one handed. Also, I hadn't cringed so hard in a long time, please don't do that near a mirror ever again.

[@GarnettLeary]

True on both points. Ha ha. Living on the edge.

[@shanehowell9149]

Thank you for your time making this video. Saved me from a ton of r and d

[@GarnettLeary]

Glad it was helpful. Thanks for watching

[@ErrorTH]

Thanks for the video! My ETX-90 is older and don't have anything to grab onto on the mirror side. should re-check the back. As for those wrenches, to everyone using them, warning: tighten the interchangeable metal tips! Chance of them falling from the wrench right on the piece of glass you are working with is surprisingly high. Luckily i learned this NOT the hard way.

[@GarnettLeary]

Good advice. Thanks for adding

[@vascoribeiro69]

That is similar to the Konus 130/2000. I bought one in bad condition and removed that back plate. I printed a new back which took the metallic visual back, although I don't like it. Good corrector plate coating. I got here since I noticed a big backlash in the focuser knob.

[@JenhamsAstro]

Superb video Garnett. I won't try it for fun as a scratch would no doubt follow! My Synta Maks don't seem to suffer too much shift so I guess the equivalent of the collar is more secure, but if I ever pick up a 125 I'll know how to fix it. Enjoy the holiday season.

[@GarnettLeary]

Thanks for watching. I truly value your opinion. I look forward to your next as always. Clear skies friend.

[@AstroBananna]

How to tell if i have this problem? Couldnt quite understand the demo of it at the start of the video

[@AstroBananna]

I might have got it, so image moves laterally instead of just between focus levels

[@Booruvcheek]

Thank you for the video. I have just bought a ETX-90, hopefully I'm not going to need to to this, but if I do, now I know how. And knowing if half the battle. BTW, about that spanner wrench - you'd have to "wrap" it around the central baffle tube, right? Which also means it has to have long enough prongs, right?

[@GarnettLeary]

Awesome. Hope you enjoy it. Yes, that’s correct. Clear skies

[@Manuel_Rdz]

Great video! I fixed my etx125 with your help. Thank you!

[@GarnettLeary]

Awesome and thank you. Happy new year

[@RyanParle81]

I've been considering the Wega backplate for my ETX125 which I have recently de-forked from a mount with dead electronics. My only reservation is that there is no access to the collimation screws with this backplate so I'm thinking of designing my own, I'll probably 3d print it first to check the concept if it works I'll get one made from aluminium by a friendly local cnc shop

[@GarnettLeary]

That would be awesome. It’s the only downside to the plate. As you know they do hold collimation well tho

[@GalaxyArtMedia]

Great video Garnett! Is good to have more tutorials for situations like this! Clear sky!

[@GarnettLeary]

Looking at the mechanics of this it can be surmised that one could lower the mirror to the mounting platform and then use spacers, instead of the focuser, to achieve focus.... mitigating any possibility of mirror tilt. An SCT draw tube focuser addition would greatly improve a Maksutov. Of all the scopes that move the primary mirror to focus I’d have to say the Maksutov is superior in this respect. It’s easy to see why collimation is hardly necessary in this design.

[@GalaxyArtMedia]

@@GarnettLeary I bought a Ritchey- chretien and does not have problems with mirror shift, but does require collimation and seems it is more sensitive at dew than my refractor

[@SonOfSpock]

Great video! Can’t wait to fix my old ETX!!!

[@Astrolavista]

I was a nervous for you when you were 'flirting with disaster' lol Glad it went well, and it was interesting to see an ETX disassembled. A trusty ETX90 was my companion throughout Uni :) I think this will be a handy resource, as you know, there are tons of ETX's on the second hand market!

[@GarnettLeary]

So true. I only had to search “ETX mirror shift” to see how much lack of info was available. I love resurrecting seemingly dead equipment. I appreciate you watching. I love your work. That Wegat Optical adapter has an interesting story attached to it. I’d love to get my hands on one of the white tubes. If you’re bored go to Wegat Optical and check out the history of how ETX’s were used. Happy holidays.

[@Astrolavista]

@@GarnettLeary I was intrigued so I've been happily reading the Wegat Optical site. I didn't even know that kind of telecom technology ever existed! Very interesting! It's such a shame we won't see new products from Meade any more, so it's great that you're adding to the resources to keep the old ones going! Hope you get clear skies to test out the improvement soon :)

[@girolamodiceglie7312]

Hi, the video is very interesting. I tried but I can't unscrew the back. It looks glued.

[@3_Gold_Coins]

My Meade LX85 focuser moves in and out. It also moves side to side. Maybe I have a loose collar? Your video is the only one showing how to open it up.

[@GarnettLeary]

I can try to help. The Meade LX85 is actually the name of the mount, not the telescope. That platform is available with a variety of different scope types. Which scope do you have?

[@jimmymullins4997]

Awesome video great detail. Do you have a video on the de-forking? Thanks

[@GarnettLeary]

Thank you. Unfortunately no. It’s pretty simple if you take it on yourself tho. I can refer you to the ETX expert tho: www.weasner.com/etx/techtips/2006/removal-ota-lnt.html

[@lylestephens8828]

There is no need to defork the tube. Just remove the knob and three screws and pull the tube forward. You also don't have to completely remove the grub screw from the knob. Just a slight turn will loosen it.

[@ajdaly5634]

Very helpful. Thank you. (Any tips on how to collimate the primary? I recently bought a beat up 125 and was able to put back together. But collimatiom is off. Thanks)

[@GarnettLeary]

Thank you. I need to make a video. I use an LED flashlight. Aluminum foil over the light then poke a very small pin hole in it. You need it a good distance away mounted on something. You can simulate a star this way. The ETX’s, because of the lack of conventional visual backs, have to be collimated prior to reinstalling it. The trick is finding something square that will allow a 1.25” ep to fit. Very careful use of gaffers tape, cardboard, etc. Alternatively I considered drilling holes in the back plate as access points. Once you get it spot on, like any Maksutov, you won’t need to fiddle with collimation for a good long while.

[@ajdaly5634]

Great tips. I will work on them and let you know. Thank you

[@GarnettLeary]

You’re welcome. Good luck

[@superkg2]

Fantastic video! Question - With the Wegat backplate and 2" eyepieces what could you expect to see with such a long focal point on the ETX-125 if using with a wide FOV eyepiece? Say a 40mm or higher; 2".

[@GarnettLeary]

Unfortunately the small light path hole of the back of the scope still limits the use of 2” eyepieces. There’s vignette around the outer edge or clipping rather. Typically the optics are better in larger eyepieces so it’s mostly just a gain in quality.

[@avt_astro206]

Excellent Tutorial

[@GarnettLeary]

Thank you. I hope you have a safe and wonderful holiday.

[@christopherleveck6835]

Soooooo what IS that "useless" thread at the camera port on the back of the tube? If you know could you please share it with us?

[@GarnettLeary]

I believe it’s a specialty thread that works with the Orion 5122 Long 2-Inch Adapter for Crayford-Type Telescope Focuser. I may be wrong. I’m out of state but will try to confirm asap. It’s basically useless tho.

[@donturner4271]

My etx125 is of the Observer series and is built a bit different but I believe the collor on my primary mirror is also loose (by the way the focus knob sometimes moves without me touchin it!); I was able to get the back off my scope but couldnt unthread it t pull out the primary mirror assembly; any suggestions?

[@GarnettLeary]

There should be a set screw ( grub screw ) under in the knob shaft. Look closely. If it’s like the 80 and is vertical you’ll find a lock nut inside. When you take the nut off the whole assembly lifts out. Be careful to put the washers back in the correct orientation

[@brucei8767]

Thank you Thank you for this video!

[@GarnettLeary]

Thank you for watching. Clear skies.

[@dumpydalekobservatory]

I've only just found this interesting & helpful video Garnett, I've got a RASA 11 V1 which suffers with mirror flop & I'm wondering by doing the same as you would help? If that possible of course I will be getting the proper tools to tighten it as I were kinda thinking don't slip with that screwdriver lol. I've already stripped the thing down once to fix the focuser as I fitted a retrofit focuser from Celestron which when it screwed down so far jammed due bad machining of the threads & my unwillingness to stop when things didn't seem right, but at least I know how it all comes apart & goes back together again. As the scope was originally water damaged the paint on the inside isn't in great shape so I were going to flock it at some point so thought I'd just fix the whole thing up while it's stripped down. (Apologies for the long thread)

[@GarnettLeary]

I don’t know honestly. There’s so many variations of these things mechanically across the years. On the C8 I opened the collar was just threaded down onto the mirror. Making a gasket to go under it was the solution. Something to compress down and apply equal amounts of outward pressure. I don’t know anything about the RASA’s other than they include an internal lens and mirror locks that the C series don’t have. Practically every 80’s scope of value and prior had the spanner ring in it. All the ones I’ve ever seen. If you can work out the distance you might try running the mirror all the way out to the stops and using a crayford in combination with extensions to focus. In that configuration the mirror only moves under the usual thermal expansion but not tilt by focus travel. That’s the way a lot of folks successfully worked around the issue. Recently I discovered my Skywatcher 180 Mak has slop in the focuser. For whatever reason they keep putting oversized retaining rings over the focus bearing. It’s really stupid. I think they must be aware. It’s likely a mass produced part that they use in a variety of scopes. Cheaper than building a new one to spec. I had a feeling I should have waited for the Intes. These companies are not at all what they used to be. Any product whose purpose is optical enhancement should at minimum perform its function. I’d rather have a functional ugly scope than a pretty yet poorly working one. The whole thing angers me. There’s companies that care but it’s ultra expensive to manufacture and test your own scopes. It’s almost impossible for a company to survive outside of the mass production slave labor curse China has placed on the world. As a result I gladly pick up older equipment over the new. When I can afford it I go to the greats. I want to kidnap the major CEO’s and force them to take a tour of Takahashi’s quality control department. Astronomy is a very demanding hobby. People are constantly being turned off the hobby by junk that doesn’t accurately do its job. Bring back the wood and metal. I recently purchased a bracket that’s function was to allow an eaf mounted on a specific focuser and the bolt holes weren’t completely drilled out. You can’t make this up. I need to get my hands on a bunch of busted C models and start having a serious look. I’ve considered starting a company that produces quality replacement parts for the junky new stuff. The technology allowing quality parabolic mirrors to be mass produced means nothing when you mount it in a jacket of plastic junk. It’s borderline sacrilegious

[@dumpydalekobservatory]

@@GarnettLeary I hear you there I call my RASA "my pain in the ass" it's been a love hate relationship since I got the thing, the only plus is that is didn't cost a ton of money so it's not like I've threw thousands of bucks at the thing. I had the optics checked out by a guy here in the UK called Es Reid who knows about optics he checks out Skywatcer Esprits for Flo & he said it has beautiful optics, but like you say it's a shame they house it in cheap junk as the centre lens group comes loose & I do not over tighten it but apparently it's a common issue, there's the lens flop in my version & when you're shooting at F2.2 the scope has to be perfect. I will say when it is all dialled in on an imaging run it's a phenomenal scope but it does give me a lot of grief. I will check it out when I strip it down again to see if I can do anything to improve it.

[@GarnettLeary]

If you have a minute let me know what you find. I actually keep a journal for information like this.

[@dumpydalekobservatory]

@@GarnettLeary Will do I'll probably upload a video when I flock it but that won't be until galaxy season starts

[@frackcenturion]

i was about to give up on my etx80 ota until now

[@GarnettLeary]

Don’t. It’s a very good instrument

[@TheUrbanAstronomer]

Great video Garnett! I messed up a barlow by flirting with disaster. 😅

[@GarnettLeary]

How in the world did you do that? Please tell. If you let me know I’ll give you a truly embarrassing Andromeda story.

[@TheUrbanAstronomer]

@@GarnettLeary "Cleaning" 😁 all the elements came out.

[@GarnettLeary]

Nice. I shot three hours of Andromeda data before I realized I was shooting jpeg. Let my wife borrow the camera that morning and she took it out of manual. That one is on my Instagram without this description lol.

[@TheUrbanAstronomer]

@Garnett Leary Woops! 😅

[@gamers7800]

5:27 yes you were flirting with disaster. I’m too clumsy myself, at that point I would have destroyed the mirror. Yikes!🤭🤭🤭

[@GarnettLeary]

Some folks toss humor in. Some like mixing horror with astronomy lol. Hope you’re well man. Merry Christmas. I hope you have an awesome holiday.

[@DP-kj7ke]

1.5” 12point socket fits on the big metal knob in the middle to unscrew the mirror assembly. No way I could do it with my hands alone…came off pretty easily.

[@nataala_]

Great stuff Leary; thank you. I modded my ETX-125 already with the Wegat back; buck cannot find focus. Do you have a rough number for the position of the focal plane with the Wegat back in place please?

[@GarnettLeary]

What gear are you using in combination with it? I will try to emulate it and measure.

[@nataala_]

@@GarnettLeary Many thanks. I have the Sony A7s, the Nikon D800 and the ZWO ASI 294 as my preferred cameras. I also have the TeleVue 2x Big Barlow for if I ever need to use it.

[@GarnettLeary]

Give me a few days as I’m out of state but I’ll definitely get you some useful info asap.

[@nataala_]

@@GarnettLeary Thank you so much indeed bud! I really appreciate this. Do stay safe.

[@GarnettLeary]

I haven’t forgotten you. Just dropping in to let you know I’m planning on answering your question. An SCT to 1.25” adapter I need arrives Monday. I’ll be able to give you a bunch of focus options and distances soon. I plan to test with a ZWO 1600mm, a Crop and full frame dslr, an ASI 120MC-S, and a bunch of barlows and reducers. I just recently modded mine and this is a project scope. I’m mapping it out already. I’m a bit OCD as I keep entire image train setups made up in dedicated cases to each scope I own. It’s a bit much lol. I’ll get back to you soon. Just letting you know I hadn’t forgotten helping you out.

[@jesset2688]

Where would a person be able to get a finder/ guide scope mount like yours?

[@GarnettLeary]

This is for the mod: wegatoptical.com/ This is the rings: optcorp.com/products/parallax-5-75-mounting-rings-for-etx-125-telescopes-5-75in Here’s a finder shoe: Universal Dovetail Base forTeleescope Finder Scope - Ideal for Installation of Finder Scope, Green Laser Pointer Bracket Etc - for Sky-Watcher Vixen and Some Celestron Telescope Dovetail Accessories www.amazon.com/dp/B013Q40RTA/ref=cm_sw_r_cp_api_glt_fabc_HKS4SSJFFMP0DPFDTAC0

[@dallas69]

Thank You Simple fix Well not so simple to De Fork But Once you DeFork it is a Simple Fix Now I would think to improve the loose collar lock or prevent loose collar from backing off lock it down. Add loctite purple 222 simi permanent hold loctite blue 242 better more permanent hold loctite Red 271 permanent hold takes heat to break down the adhesive.

[@dallas69]

Primary mirror work Work on or near the P mirror with metal or any tools. Or just to protect P mirror while working near them. Cut a hole in paper or Cardstock or cardboard place the paper over the P mirror and do the work. Even cleaned plastic food container work as P mirror protector. Clear plastic seems to work best.

[@GarnettLeary]

Good ideas

[@chronoboat11]

Did that ever focus clearly???

[@GarnettLeary]

Yes

[@SonOfSpock]

Thank you for this great video! I followed your instructions because I was also suffering from focus shift. The middle ring that you tightened was indeed a bit loose. I used a spanner wrench to tighten it. First I tightened it a little bit, and I still had the focus shift. Then I went and tightened it some more until I was feeling some significant resistance from the ring. Focus shift did get a little bit better, but I still have it a little bit. Should I go in and try to tighten the ring some more? I’m afraid I’ll crack the mirror if I go any tighter. Any ideas? Thanks again! UPDATE: I just took it apart again, and there seems to be zero wobble with the mirror when I move it by hand. I’m not sure if I have to live with this slight focus shift.

[@GarnettLeary]

How about the spacer? What kind of shape is it in? Does it feel soft or brittle? You can also clean and grease the threaded rod to improve movement. Something people say helps is to put a clothes pin on the focus knob. It allows for finer focus adjustments. Sounds crazy but is practical.

[@ohwell2790]

Perhaps some of your viewers would be interested in reading a paper on separation of 3 DSO's in Hercules. I wrote for a physics course back in 2007 I am now 76. Journal of double stars 3" tasco author Darrell Grisham. What can be done with small aperture telescope with no computer or electric drive. Just ordered a Orion 150 mm Mak and should arrive sometime late Jan 2021. I am going to thank you for that.

[@GarnettLeary]

That’s awesome. Provide a link and I’d be happy to share it here and on my community page. Clear skies.

[@davidbrandenburg8029]

shouldn't the deforking have started the video? , the deforking was what I needed!

[@GarnettLeary]

Yes most definitely.