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Thinking of restoring an old Newtonian

Equipment Reflector DIY
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#1 fyferoni

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Posted 26 May 2024 - 03:50 PM

TLDR: I was given an old Konus Newtonian (mount, eyepieces, scope, rings, etc) by my dad, and was thinking of restoring it and using it for AP and visual.

 

When I was a kid, my dad had this old reflector on a wobbly EQ mount that he would bring out occasionally to show my and my brother Saturn and Jupiter. I have a lot of fond memories of it, and when my dad was telling me the other day that he was going to chuck it, I asked to have it to see what I could do with it. After spending some time looking it over, I realized that the tube and optics have held up shockingly well. 

 

It's held it's collimation through multiple moves and even an unfortunate incident involving the tube itself when the finderscope got dinged. I have no knowledge on Konus or the quality of the optics overall, but I imagine they're not terrible given the build quality of the OTA itself. The surrounding gear is another story though. The mount was worthless, the focuser is only a single speed, and at one point someone lubed it to oblivion, and it won't hold position no matter how tight I try to get it. The finderscope was a plastic piece of garbage as well.

 

The only things I think are worth saving are the rings and the tube. I understand this thing is probably not worth the money it'll take to get it functional, but it's more of an heirloom project for me and my dad, and has more sentimental than practical value.

 

I'm hoping some of you (much more) knowledgeable DIYers would be willing to help me source some parts and give me some advice along the way! I have photos attached of the OTA below detailing the brand and specs of the tube, but I'll list everything down here as well:

 

 

SCOPE DETAILS

  • Konus - Konusmotor-500 Electronic
  • Newtonian Reflector
  • Aperture - 114mm
  • Focal Length - 500mm
  • Focal Ratio - f/4.3
  • Model number: #1780
  • Focuser: Single speed, 1.25in.
  • Finderscope: broken
  • Mount: worthless

INITIAL THOUGHTS ON REPAIRS

  • I'll definitely need to source a new finderscope. I was thinking something simple like this guy and mount it on the top rings with a new rail:
    https://www.svbony.c...-finder/#F9177A
  • I don't know if the focuser can be saved, or if I even want to save it. I also was interested in using a 2in. focuser instead of a 1.25in. I'm not even sure this scope could illuminate that wide, but it would make finding things like a coma corrector way easier. I was thinking of this GSO linear bearing crayford, but please send me recommendations and advice if you know of something better! 
    https://agenaastro.c...dual-speed.html
  • For a coma corrector, I would think I'd need something like this guy? I shoot on a refractor currently, and don't know much about coma correctors!
    https://agenaastro.c...-corrector.html
  • As for mount, I'd just use my eq6-r Pro and shoot with my ASI-533 MC Pro which I think would be a nice pairing for such a small reflector.
  • I know there will be all sorts of extras, like spacers/saddles/dovetail plates that I'll need to get it to a point where I can bring it all together as well.

Thanks CN community! I'd love your thoughts and advice if you've ever attempted something similar, and if you need any other details, let me know in the comments!

 

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#2 Garyth64

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Posted 26 May 2024 - 04:09 PM

If the mirror's coating are fine, and the scope gives good images, leave it as it is. smile.gif


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#3 Sky King

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Posted 26 May 2024 - 04:44 PM

Found this review for you. Parts often are listed on CN classified too.

 

Contact Agena or our host Astronomics and be sure that focuser will fit. It's nice but may not work with this scope. For a coma corrector, the Baader Mpcc has good reviews and I like it. Also the Starizona reducer/corrector is well liked (and should be at that price) and will take you from F/4 to F/3. I use a guide scope instead of a finder. Maybe you could switch them out when needed. Fond memories and great images, what more could you ask for? 

 

Good luck! 

 

Al


Edited by Sky King, 26 May 2024 - 05:11 PM.

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#4 scottinash

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Posted 26 May 2024 - 04:51 PM

A club member had one of these that I got to look through several times years ago and it gave excellent views via quality eyepeices.  I agree with Garyth64.

 

fyi-
https://www.cloudyni...-newtonian-r727


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#5 fyferoni

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Posted 26 May 2024 - 05:10 PM

Found this review for you.

 

Contact Agena or our host Astronomics and be sure that focuser will fit. It's nice but may not work with this scope. For a coma corrector, the Baader Mpcc has good reviews and I like it. Also the Starizona reducer/corrector is well liked (and should be at that price) and will take you from F/4 to F/3. I use a guide scope instead of a finder. Maybe you could switch them out when needed. Fond memories and great images, what more could you ask for? 

 

Good luck! 

 

Al

Thanks Al! That’s the one, and it’s exciting to see it’s actually a decent quality scope, minus some of the accoutrement. Gary, unfortunately the focuser is unusable. The slightest weight or movement against it causes movement, and I’m probably going to use it primarily for imaging, which the weight of the camera would be a non starter. I think my dad mistakenly used some sort of lubricant because he didn’t realize he just had the focuser tightened down.



#6 MeridianStarGazer

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Posted 26 May 2024 - 05:34 PM

A scope that short does not need a finder.

Wipe the grease off the focuser.

The scope was well designed for a goal. Chop it up to fit other goals, and it likely won't be worth it.

Edited by MeridianStarGazer, 26 May 2024 - 05:36 PM.

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#7 fyferoni

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Posted 27 May 2024 - 01:31 PM

A scope that short does not need a finder.

Wipe the grease off the focuser.

The scope was well designed for a goal. Chop it up to fit other goals, and it likely won't be worth it.

That would be all well and good, but I'm not sure how to deal with coma with a 1.25in focuser. To my knowledge, nobody sells a 1.25in. coma corrector, unless I'm mistaken? I'd be happy to go that route if that were the case.



#8 MeridianStarGazer

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Posted 27 May 2024 - 02:10 PM

That would be all well and good, but I'm not sure how to deal with coma with a 1.25in focuser. To my knowledge, nobody sells a 1.25in. coma corrector, unless I'm mistaken? I'd be happy to go that route if that were the case.

Many beginners use f4 scopes without a corrector. I saw the coma even on a night I did not see it at f5. But it was not obnoxious. Stars were sharp in the middle 30 degrees.
...
Well, low power was 40 degress. So 2/3 of that was 26 degrees sharp. It was still usable.

Edited by MeridianStarGazer, 27 May 2024 - 02:26 PM.

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#9 Garyth64

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Posted 27 May 2024 - 02:12 PM

What size secondary is in the scope now?

Do you know how far outside the tube the image plane is?

What is the size of the camera sensor?  

 

So in going to a 2" focuser, one reason is for a coma corrector.  And I'm thinking that if you want to dedicate this scope for photography, your secondary may not be large enough.  The secondary should be large enough to illuminate the entire sensor.


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#10 Sky King

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Posted 27 May 2024 - 03:45 PM

Upgrading the focuser can be a challenge. I upgraded my GSO 6" from a single speed to a 10 to 1 dual-speed focuser and the improvement was terrific. A linear bearing focuser can support the weight of the camera and accessories much better. This website helps you calculate the right focuser. This post is about upgrading the focuser. I would contact Agena or whoever you plan to buy one from for help. 

 

Also depends on how good you are at modifications, and how far you are willing to go. You might need to move the position of the primary mirror to reach focus. Taking measurements and discussing this is a good first step. Likely someone at Agena or Astronomics is expert on this. But I can tell you your focuser looks like the weak link in the chain.  


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#11 dan_h

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Posted 27 May 2024 - 07:02 PM

Thanks Al! That’s the one, and it’s exciting to see it’s actually a decent quality scope, minus some of the accoutrement. Gary, unfortunately the focuser is unusable. The slightest weight or movement against it causes movement, and I’m probably going to use it primarily for imaging, which the weight of the camera would be a non starter. I think my dad mistakenly used some sort of lubricant because he didn’t realize he just had the focuser tightened down.

These old rack and pinion focusers were simple  in operation.  Unless the gears are stripped you can adjust the action using the two screws at the knob shaft.

 

dan


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#12 Jon Isaacs

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Posted 27 May 2024 - 07:44 PM

I would check the optics. I know that some Konus 8 inch F/5s had spherical mirrors, some had parabolic mirrors. I suspect the same is true of the 4.5 inch F/4.4.

 

Gary mentioned the secondary size, in my experience ,the rod style secondary mounts do not hold collimation.

 

There are a number of potential issues if one wants to use this scope for imaging, besides a proper focuser and coma corrector, there are issues like tube flex under the weight of the camera. And back focus with the existing mirror locations and the new focuser.. just mounting the focuser will be a challenge .

 

I think it's wiser to use this scope visually and honor your father by using it the way he used it, the way it was meant to be used.

 

Photographically, it's a can of worms.

 

Jon


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#13 Sky King

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Posted 27 May 2024 - 09:23 PM

It would take very little time to find out if there is a linear bearing focuser that would fit it, would the primary or secondary be ok or need adjusted, and what else would be required. Then he could decide if that's what he really wanted to do. As I said previously, "Also depends on how good you are at modifications, and how far you are willing to go." Maybe fyferoni has a shop full of tools and 20 years experience, like the guy in this video:

 

Anything is possible.  Not even looking into it and you're licked before you started.  At some point he could just buy a nice wide field astrograph, but that wasn't what he was asking.

 

He also noted, "It's held it's collimation through multiple moves and even an unfortunate incident involving the tube itself when the finderscope got dinged."


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#14 Jon Isaacs

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Posted 28 May 2024 - 04:04 AM

Sky King:

 

I have experience adapting 2 inch focusers and coma correctors to small aperure scopes like this Konus.

 

- It's a 4.5 inch F4.4. There are no 2 inch focusers that fit. The tube has to have a hole bored out and then an adapted made. (This adds to the potential issues with back focus.)

 

The GSO Linear Bearing Focuser, the only one I know of, it's a standard height focuser, 3.0 inches. It's unlikely that it's short enough to provide the additional back focus needed for astrophotography. 

 

https://agenaastro.c...dual-speed.html

 

- Holding collimation for visual without a coma corrector and holding collimation with a coma corrector for astrophotography are quite different. 

 

- swapping the secondary for a larger secondary can be problematic, often there is not enough room so the secondary slider must be moved, if there's room. 

 

- if fyferoni had a shop full of tools and 20 years experience using them, fyferoni would not be asking us for help.

 

- Doing this right is a can of worms. By that I mean it's a project that will likely be long and involved with many lessons learned. When all is said and done, it will likely be a mediocre imaging scope at best if it works at all. 

 

Jon


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#15 Sky King

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Posted 28 May 2024 - 10:25 AM

Here Be Dragons!  (from old maps).

 

There are good suggestions for cleaning and adjusting the stock focuser and restoring this beauty to workable visual use, and also warnings of dangerous waters for AP if you try and put a focuser on it. 

 

With today's prices putting a lot of money in this scope is a hard choice.  


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#16 fyferoni

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Posted 28 May 2024 - 10:44 AM

Awesome feedback all around! Appreciate you guys taking the time to think through stuff like this. This is all things I didn't think through, and don't have the wherewithal just yet to understand on my own.

 

Sky King, it's very generous of you to give me the benefit of the doubt when it comes to my skills and expertise lol.gif  though unfortunately i'm very much an amateur. I love a challenge of learning new skills (working with optics in a newtonian sound like a fun skill to learn) but I'm also reticent to permanently damaging the scope further.

 

I've got experience in AP with refractors, but modifying scopes to the extent you implied Jon might be beyond my skillset. I think it's a good idea to instead repurpose this guy for visual use only, if the headache with working with a small and specialized tube like this might frankenstein this thing into something mediocre. Your thoughts were well said and helpful to understand the level of work required to make it happen!

 

If that's the case. Then replacing the 1.25in focuser could be a good option? I tried again last night to get some of the gunk out of it and clean/tighten it as much as I could, but the dang thing still has so much play I can pull it in and out with barely any effort. Maybe disassembling the focuser entirely and attacking it with a solvent would solve that issue?

 

Also, I think I'll pick up a short 8x50 finder to put on top, or maybe even a red dot sight. The eyepieces it came with were broken at this point as well (one got cracked in the move, the other is just gone). Do you guy have any good 1.25in eyepiece suggestions? I have a 9mm plossl that came with my dob, but I'd also like a wider field of view as well.

 

Any thoughts? What eyepieces would you pair with this focal length for planetary and galaxy viewing?


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#17 Sky King

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Posted 28 May 2024 - 11:00 AM

Awesome feedback all around! Appreciate you guys taking the time to think through stuff like this. This is all things I didn't think through, and don't have the wherewithal just yet to understand on my own.

 

Sky King, it's very generous of you to give me the benefit of the doubt when it comes to my skills and expertise lol.gif  though unfortunately i'm very much an amateur. I love a challenge of learning new skills (working with optics in a newtonian sound like a fun skill to learn) but I'm also reticent to permanently damaging the scope further.

 

I've got experience in AP with refractors, but modifying scopes to the extent you implied Jon might be beyond my skillset. I think it's a good idea to instead repurpose this guy for visual use only, if the headache with working with a small and specialized tube like this might frankenstein this thing into something mediocre. Your thoughts were well said and helpful to understand the level of work required to make it happen!

 

If that's the case. Then replacing the 1.25in focuser could be a good option? I tried again last night to get some of the gunk out of it and clean/tighten it as much as I could, but the dang thing still has so much play I can pull it in and out with barely any effort. Maybe disassembling the focuser entirely and attacking it with a solvent would solve that issue?

 

Also, I think I'll pick up a short 8x50 finder to put on top, or maybe even a red dot sight. The eyepieces it came with were broken at this point as well (one got cracked in the move, the other is just gone). Do you guy have any good 1.25in eyepiece suggestions? I have a 9mm plossl that came with my dob, but I'd also like a wider field of view as well.

 

Any thoughts? What eyepieces would you pair with this focal length for planetary and galaxy viewing?

You could take the focuser apart and clean it, but be careful how it comes apart and if there are bearing that fall out, etc. You could also find a replacement focuser. Check with them first and make sure it will fit. You could email them a picture and measurements of your current focuser. Check on CN classified for a finder. Good Luck!


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#18 Garyth64

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Posted 28 May 2024 - 11:08 AM

Sometimes the shims in the focuser get worn or fall out. When the screws are tightened, make sure that they are pushing against a shim, and just not on the focuser tube.

Replace the old shims with thicker ones, and the slop should be eliminated.  I've reworked many old sloppy focusers and got them working just like new.


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#19 Don H

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Posted 28 May 2024 - 03:42 PM

I would recommend a nice, basic RDF. A larger finder will make your very portable scope off balanced and more bulky to carry outside. The stock RDF on my 114/450 gets just about every object I point it at in the 3.6 degree fov of my 24 Pan. Very often I just leave a 13mm T6 in the ep and even with that 2.4* fov, most objects are somewhere in the ep or very close. While those are pricey eps for an economy scope, I have found that they help compensate for no CC and give me very pleasing rich field views. I also like the 2.3* fov of an 18mm Radian. Your scope would get over 2 degrees at 27x. You would be surprised how many objects are visible and begin to reveal detail at 27x. Astronomics sells the nice Paradigm Dual ED eps for a great price, and they have an 18mm. The 25mm AT ep might be a nice low power ep, but at 20x things are getting small and the larger exit pupil will make the sky background a bit brighter. But it would give you a nice, rich field if your sky is somewhat dark. Your 9mm would be a nice bump up and still give you about 1 degree. You may want to try and evaluate the mirror and collimation with your 9mm doing a low power star test before going a lot further spending money. If you have a Barlow you can size up the images of planets to judge quality further, although this scope's strength might be the nice low power views it can provide.

 

I believe you can adjust the focuser to work well by removing all grease, maybe adding shims, and using the stock adjustment screws. This is provided the rack and pinion teeth are not badly damaged. The Agena 1.25" replacement might be a very nice upgrade. You would want to look at its dimensions and compare them to your existing focuser to judge if it would work.

 

I didn't use my 114/450 much until I got rings and put it on an alt/az mount. Then it became a nice g&g set up and I discovered a whole new way of looking at things in a rich field view.

 

Good luck as you continue...

 

 

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#20 fyferoni

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Posted 30 May 2024 - 10:43 AM

I would recommend a nice, basic RDF. A larger finder will make your very portable scope off balanced and more bulky to carry outside. The stock RDF on my 114/450 gets just about every object I point it at in the 3.6 degree fov of my 24 Pan. Very often I just leave a 13mm T6 in the ep and even with that 2.4* fov, most objects are somewhere in the ep or very close. While those are pricey eps for an economy scope, I have found that they help compensate for no CC and give me very pleasing rich field views. I also like the 2.3* fov of an 18mm Radian. Your scope would get over 2 degrees at 27x. You would be surprised how many objects are visible and begin to reveal detail at 27x. Astronomics sells the nice Paradigm Dual ED eps for a great price, and they have an 18mm. The 25mm AT ep might be a nice low power ep, but at 20x things are getting small and the larger exit pupil will make the sky background a bit brighter. But it would give you a nice, rich field if your sky is somewhat dark. Your 9mm would be a nice bump up and still give you about 1 degree. You may want to try and evaluate the mirror and collimation with your 9mm doing a low power star test before going a lot further spending money. If you have a Barlow you can size up the images of planets to judge quality further, although this scope's strength might be the nice low power views it can provide.

 

I believe you can adjust the focuser to work well by removing all grease, maybe adding shims, and using the stock adjustment screws. This is provided the rack and pinion teeth are not badly damaged. The Agena 1.25" replacement might be a very nice upgrade. You would want to look at its dimensions and compare them to your existing focuser to judge if it would work.

 

I didn't use my 114/450 much until I got rings and put it on an alt/az mount. Then it became a nice g&g set up and I discovered a whole new way of looking at things in a rich field view.

 

Good luck as you continue...

Super great info Don! Appreciate it! I'll look into all those and see what feels right for budget/needs. I think I want to lean towards planetary viewing with this guy, as I have an 8in. dobsonian that's been great for deep sky observing. Having the dob and this guy on an alt/az would be a great duo to do night tours with friends and family.

 

Do you have an alt/az that's decently portable that you recommend? My eq6-r pro isn't exactly the 'grab and go' kinda mount for going to dark sky sites haha.

 

The eyepiece game is one i'm hesitant to dip my toes into (i've already got the AP affliction, and my bank account is crying uncle), but it would be nice to have a good quality high power eyepiece to replace the one that came with my dob. It's a 9mm plossl, and the eye relief is prety rough, especially with me needing glasses.


Edited by fyferoni, 30 May 2024 - 10:44 AM.


#21 Don H

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Posted 30 May 2024 - 04:01 PM

Super great info Don! Appreciate it! I'll look into all those and see what feels right for budget/needs. I think I want to lean towards planetary viewing with this guy, as I have an 8in. dobsonian that's been great for deep sky observing. Having the dob and this guy on an alt/az would be a great duo to do night tours with friends and family.

 

Do you have an alt/az that's decently portable that you recommend? My eq6-r pro isn't exactly the 'grab and go' kinda mount for going to dark sky sites haha.

 

The eyepiece game is one i'm hesitant to dip my toes into (i've already got the AP affliction, and my bank account is crying uncle), but it would be nice to have a good quality high power eyepiece to replace the one that came with my dob. It's a 9mm plossl, and the eye relief is prety rough, especially with me needing glasses.

My Versago II would be a nice match. It is only 13 lbs, or a bit over 17 when the scope and rings are added. But Orion no longer offers them for sale. I would not get the Versago E that they still sell, as it has a bad reputation for being quite shaky. If you search for alt/az telescope mounts, you will find a number of offerings, although manual mounts seem to be getting less popular in favor of motorized goto systems. Getting a mount that is rated for at least twice your scope weight is a good starting point. My VII is rated for 15 lbs, but I only am putting about 5 lbs on it, so it is quite steady. 

 

I would think your 8" Dob would be way better on planets. The power of the small scope is its ability to give you wide field views at low magnifications. When I used my 114 to see things like the Pleiades in a nicely framed field, or M31, M33, M101, M83, M81/82, Markarian's Chain, M16, M17, M24 (a real treat) M8 and M20, and many other objects, it was a revelation. I never imagined so much detail could be seen at low power. Adding a UHC filter gave me my best views of the North American Nebula and the Rosette. It also showed me things like the Monkey Head, PacMan, Heart and Soul, and several more objects that my larger scopes did not show entirely in their smaller fields of view. The Double Cluster, Caroline's Rose, M35 with NGC 2168, or M38 with NGC 1907, M6, M7 and many other open clusters are quite rich and interesting. While my yard is pretty dark, I would think many of these things could still be enjoyed even under more LP. 

 

A nice upgrade for you 9mm might be the AT 8mm Dual Paradigm. I am not sure if the DP eps are parfocal, but if you got the 8, 18 and 25, you'd have a fine set for any telescope. And it supports our sponsor of CN.



#22 EJN

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Posted 30 May 2024 - 04:17 PM

I would check the optics. I know that some Konus 8 inch F/5s had spherical mirrors, some had parabolic mirrors. I suspect the same is true of the 4.5 inch F/4.4

 

I bought a Konusmotor-500 OTA, used, for cheap on a whim once, to see how it compared with an Orion Starblast.

Images were awful. I removed the mirror and tested it, definitely spherical.




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