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Unitron 510 Notes

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#51 jgraham

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Posted 17 July 2023 - 08:46 AM

I keep waiting for reports on how well the Big Unitrons perform. They look amazing. Your observing reports on the 6" Unitrons are a lot of fun to read.

 

Speaking of observing reports... that's where we're kinda heading with the 510. I'm still waiting for a night of good seeing, but I was delighted to see that I could split Antares as it lay low over my southern horizon; a first for me after many years of trying. The color contrast was beautiful. Now that I know what I'm looking for I'll try again with some of my other scopes. I can stare at epsilon Lyra all night. Izar was fun in the 155 as the companion tended to lay on/near a diffraction ring, its a gorgeous split in the 510. I am sooo looking forward to viewing beta Monoceros with the 510!

 

The Sky is a Very Big Place. :)


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#52 combatdad

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Posted 17 July 2023 - 09:03 AM

You're not going to find many observing reports on the 5 inch and 6 inch Polarex/Unitrons...due to limited numbers and general use.  I sense the majority are in the hands of collectors who don't spend much time under the stars.

 

Your 5 inch, like all Polarex/Unitron refractors, is a great DS hunter.  Two of my favorites are the triplets, Iota Cas and Zeta Cancri.

 

Dave


Edited by combatdad, 17 July 2023 - 01:55 PM.


#53 CHASLX200

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Posted 17 July 2023 - 06:08 PM

Speaking of 8 inch...here is a pic of the Mega-Godzilla...a mighty 9 inch!

 

More history and pics of the scope on the Unitron History site: https://www.unitronh...tron-model-900/.

 

Enjoy!

 

Dave

I think someone on here was trying to pawn off a fake 9" Unitron a while back.  Maybe around 2 years ago. There was also a 11" i think in Sky& Tele back around 1981 that looked like a Unitron on a big Byers mount.


Edited by CHASLX200, 17 July 2023 - 06:09 PM.


#54 starman876

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Posted 17 July 2023 - 08:24 PM

Speaking of 8 inch...here is a pic of the Mega-Godzilla...a mighty 9 inch!

 

More history and pics of the scope on the Unitron History site: https://www.unitronh...tron-model-900/.

 

Enjoy!

 

Dave

first time I saw Those pictures of the scope I could hardly believe my eyes,  The lens in the case is the same lens I saw pictures of a couple of years ago,



#55 C8 Ronald

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Posted 18 July 2023 - 01:00 PM

I've seen the 9 Inch in the flesh, it was HUGE, with all the bells & whistles attached aswell. Absolutely a dream!

However, it can only be used in a big observatory due to its weight and size.


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#56 starman876

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Posted 18 July 2023 - 03:04 PM

I've seen the 9 Inch in the flesh, it was HUGE, with all the bells & whistles attached aswell. Absolutely a dream!

However, it can only be used in a big observatory due to its weight and size.

Darn , wish I could have seen that scope up close.   All the rumors for years that were centered around that objective.  Dave sure stayed on the scent and found it. bow.gif bow.gif



#57 deSitter

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Posted 18 July 2023 - 04:19 PM

Imagine every possible Unitron OTA and finder riding on that monster :) And 5 solar projection screens and 6 Unihexes with a plate camera on the 9 and the 4.

 

-drl


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#58 CHASLX200

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Posted 18 July 2023 - 06:02 PM

I've seen the 9 Inch in the flesh, it was HUGE, with all the bells & whistles attached aswell. Absolutely a dream!

However, it can only be used in a big observatory due to its weight and size.

I would need a bigger boat for sure and i bet it cost more than my whole street. That is a dream scope for a true rich person.



#59 jgraham

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Posted 18 July 2023 - 08:16 PM

My 3rd evening out with the 510 marked the beginning of the shift from familiarization to using the telescope. This was the first opportunity to test the assembly procedure that I describe above and the first genuinely clear evening, though it clouded up before it got fully dark. I have a variety of manual and computerized mounts that I can use depending on my plans for the evening. I often enjoy using these classic telescopes on their original mounts since they are so simple, rugged, and comfortable to use with the manual controls within easy reach of the eyepiece right where my hands expect to find the in the dark.

 

One feature that I often have trouble with is the use of straight-thru finders. The finder is my primary star-hopping tool and I’m just not flexible enough to use a straight-thru finder except at low altitudes, in which case they are a nice option to have. Dave provided me with a finder bracket that he used to hold a 60mm finder. I scrounged through my spare finders and couldn’t come up with a 60mm that would fit, but I did have a classic orange tube 50mm right angle finder from University Optics, so I swapped out the original screws installed in the bracket with longer screws, and I was able to mount the 50mm. As a bonus, these 50mm finders were built for University Optics by Nihon Seiko and I have seen them referred to as baby Unitrons. :) If you look closely at the photograph below you can see the NS maker’s mark on the dew shield.

 

Unitron 510 Finder (7-5-2023)-1.jpg

 

With the finder sorted out, the next thing that I like are effective slow-motion controls that allow me to easily slew the scope in an organized manner over small distances as I move from star to star. I practice my own brand of star-hopping that I like to describe as a celestial nature walk. Rather than a method of locating specific objects, I like to use it to explore a region of the sky. I typically start with a bright star as my starting point, and then using my S&T Pocket Sky Atlas as my guide I slowly walk from star to star, pausing at each one to take a peek though the scope, marking my way as I go in pencil on my map. If I find something interesting, I’ll draw a circle around it and make a note in my notebook. I usually use either a 2” 56mm Meade Super Plossl (36x) or a 2” 26mm QX (77x) in the scope and if I find something interesting I may switch to a 14mm (143x), 8.8mm (227x), or 5.5mm (364x) 1.25” Meade UWA eyepiece. I found the slow-motion controls of the 510 to be very effective and responsive, making it possible to leave the scope all the way up at 364x while using the finder to center stars, though it requires a light touch to make small adjustments.

 

The image quality was exactly what you would expect from a Unitron with stars showing sharp, compact Airy disks surrounded by sharp, tight diffraction rings. A big difference that I immediately noticed between the 510 and my 4” f/15 150 and 155 is a much smaller Airy disk, and often only a single, very tight diffraction ring. Multiple stars are just amazing. I could star at the Double Double (epsilon Lyra) all night. Just gorgeous!

 

The star-hop from this particular even is shown below. Lyra is one of my favorite summer star-hopping regions with a rich field of stars, colors, multiple stars, clusters, and asterisms. This also shows how the slow-motion controls made it easy to navigate the field one star at a time. One issue that I am going to look at is a bit of backlash in the controls and locks. The mass and moment arm of the mount and telescope amplifies their effects. I hope to add a set of shims to snug up the mount a bit. In the meantime, it’s easy to just set the balance a tiny bit off so that the telescope pre-loads the backlash. This pre-load is easy to tweak with the Unibalance.

 

Star-hop (7-10-2023)-1.jpg

 

Unfortunately, I did run into a bit of a problem. When there were bight stars in the field I noticed a veil of haze across the field, indicating a possible problem with the objective (or other optical element). Superficially, the objective looked clean, but when I took a close look with a bright flashlight, I could clearly see a hazy film between the elements. Ugh. While this is common with refactors of this age, there’s nothing that I dread more than pulling the lens apart for cleaning. I have cleaned the objectives on most of my classics, including my 150 and 155, but nothing scares me more than taking one of these old objectives apart. If you’re lucky, they come right out, if not, one false move and you can get a nasty chip. However, if I wanted to clean between the elements, I had no choice.

 

But that is a story for another day… :)

 

(Spoiler alert, it turned out well.)

 

Enjoy!


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#60 jragsdale

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Posted 18 July 2023 - 08:58 PM

I think someone on here was trying to pawn off a fake 9" Unitron a

while back. 

That was an 8¼" f/15 scope with a 6" Unitron focuser. Origin was unknown but after lots of digging it was determined to be an ATM endeavor by John E Dalton of Brookfield, CT.


Edited by jragsdale, 18 July 2023 - 08:58 PM.


#61 CHASLX200

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Posted 19 July 2023 - 05:51 AM

My 3rd evening out with the 510 marked the beginning of the shift from familiarization to using the telescope. This was the first opportunity to test the assembly procedure that I describe above and the first genuinely clear evening, though it clouded up before it got fully dark. I have a variety of manual and computerized mounts that I can use depending on my plans for the evening. I often enjoy using these classic telescopes on their original mounts since they are so simple, rugged, and comfortable to use with the manual controls within easy reach of the eyepiece right where my hands expect to find the in the dark.

 

One feature that I often have trouble with is the use of straight-thru finders. The finder is my primary star-hopping tool and I’m just not flexible enough to use a straight-thru finder except at low altitudes, in which case they are a nice option to have. Dave provided me with a finder bracket that he used to hold a 60mm finder. I scrounged through my spare finders and couldn’t come up with a 60mm that would fit, but I did have a classic orange tube 50mm right angle finder from University Optics, so I swapped out the original screws installed in the bracket with longer screws, and I was able to mount the 50mm. As a bonus, these 50mm finders were built for University Optics by Nihon Seiko and I have seen them referred to as baby Unitrons. smile.gif If you look closely at the photograph below you can see the NS maker’s mark on the dew shield.

 

attachicon.gif Unitron 510 Finder (7-5-2023)-1.jpg

 

With the finder sorted out, the next thing that I like are effective slow-motion controls that allow me to easily slew the scope in an organized manner over small distances as I move from star to star. I practice my own brand of star-hopping that I like to describe as a celestial nature walk. Rather than a method of locating specific objects, I like to use it to explore a region of the sky. I typically start with a bright star as my starting point, and then using my S&T Pocket Sky Atlas as my guide I slowly walk from star to star, pausing at each one to take a peek though the scope, marking my way as I go in pencil on my map. If I find something interesting, I’ll draw a circle around it and make a note in my notebook. I usually use either a 2” 56mm Meade Super Plossl (36x) or a 2” 26mm QX (77x) in the scope and if I find something interesting I may switch to a 14mm (143x), 8.8mm (227x), or 5.5mm (364x) 1.25” Meade UWA eyepiece. I found the slow-motion controls of the 510 to be very effective and responsive, making it possible to leave the scope all the way up at 364x while using the finder to center stars, though it requires a light touch to make small adjustments.

 

The image quality was exactly what you would expect from a Unitron with stars showing sharp, compact Airy disks surrounded by sharp, tight diffraction rings. A big difference that I immediately noticed between the 510 and my 4” f/15 150 and 155 is a much smaller Airy disk, and often only a single, very tight diffraction ring. Multiple stars are just amazing. I could star at the Double Double (epsilon Lyra) all night. Just gorgeous!

 

The star-hop from this particular even is shown below. Lyra is one of my favorite summer star-hopping regions with a rich field of stars, colors, multiple stars, clusters, and asterisms. This also shows how the slow-motion controls made it easy to navigate the field one star at a time. One issue that I am going to look at is a bit of backlash in the controls and locks. The mass and moment arm of the mount and telescope amplifies their effects. I hope to add a set of shims to snug up the mount a bit. In the meantime, it’s easy to just set the balance a tiny bit off so that the telescope pre-loads the backlash. This pre-load is easy to tweak with the Unibalance.

 

attachicon.gif Star-hop (7-10-2023)-1.jpg

 

Unfortunately, I did run into a bit of a problem. When there were bight stars in the field I noticed a veil of haze across the field, indicating a possible problem with the objective (or other optical element). Superficially, the objective looked clean, but when I took a close look with a bright flashlight, I could clearly see a hazy film between the elements. Ugh. While this is common with refactors of this age, there’s nothing that I dread more than pulling the lens apart for cleaning. I have cleaned the objectives on most of my classics, including my 150 and 155, but nothing scares me more than taking one of these old objectives apart. If you’re lucky, they come right out, if not, one false move and you can get a nasty chip. However, if I wanted to clean between the elements, I had no choice.

 

But that is a story for another day… smile.gif

 

(Spoiler alert, it turned out well.)

 

Enjoy!

Maybe find a used 60mm finder with Uniclamps. I was lucky to buy one new in 1987 for the 4" F-152.

Attached Thumbnails

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Edited by CHASLX200, 19 July 2023 - 05:51 AM.

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#62 jgraham

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Posted 19 July 2023 - 07:03 AM

The 510 came with the 60mm guide scope and I have one on my 155 as well. I don’t recall what the field of view looks like, but I’m planning on checking it out (again). I may try mounting an ASI294MC camera on it and using it as a video finder. These can also come in handy at outreach events to preview what we are looking at through the eyepiece. I’ve also got checking out the Unihex on my short list.

 

So much to do, so few clear nights…

 

:)



#63 starman876

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Posted 19 July 2023 - 02:43 PM

it is so nice to have all those unitron toys that came with that scope.   when you set everything up it looks so beautiful



#64 combatdad

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Posted 19 July 2023 - 02:58 PM

Unfortunately, I did run into a bit of a problem. When there were bight stars in the field I noticed a veil of haze across the field, indicating a possible problem with the objective (or other optical element). Superficially, the objective looked clean, but when I took a close look with a bright flashlight, I could clearly see a hazy film between the elements. Ugh. While this is common with refactors of this age, there’s nothing that I dread more than pulling the lens apart for cleaning. I have cleaned the objectives on most of my classics, including my 150 and 155, but nothing scares me more than taking one of these old objectives apart. If you’re lucky, they come right out, if not, one false move and you can get a nasty chip. However, if I wanted to clean between the elements, I had no choice.

 

But that is a story for another day… smile.gif

 

(Spoiler alert, it turned out well.)

 

Enjoy!

Don't wait too long, John!  We're all waiting anxiously!!

 

Dave



#65 deSitter

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Posted 19 July 2023 - 03:30 PM

My 3rd evening out with the 510 marked the beginning of the shift from familiarization to using the telescope. This was the first opportunity to test the assembly procedure that I describe above and the first genuinely clear evening, though it clouded up before it got fully dark. I have a variety of manual and computerized mounts that I can use depending on my plans for the evening. I often enjoy using these classic telescopes on their original mounts since they are so simple, rugged, and comfortable to use with the manual controls within easy reach of the eyepiece right where my hands expect to find the in the dark.

 

One feature that I often have trouble with is the use of straight-thru finders. The finder is my primary star-hopping tool and I’m just not flexible enough to use a straight-thru finder except at low altitudes, in which case they are a nice option to have. Dave provided me with a finder bracket that he used to hold a 60mm finder. I scrounged through my spare finders and couldn’t come up with a 60mm that would fit, but I did have a classic orange tube 50mm right angle finder from University Optics, so I swapped out the original screws installed in the bracket with longer screws, and I was able to mount the 50mm. As a bonus, these 50mm finders were built for University Optics by Nihon Seiko and I have seen them referred to as baby Unitrons. smile.gif If you look closely at the photograph below you can see the NS maker’s mark on the dew shield.

 

attachicon.gif Unitron 510 Finder (7-5-2023)-1.jpg

 

With the finder sorted out, the next thing that I like are effective slow-motion controls that allow me to easily slew the scope in an organized manner over small distances as I move from star to star. I practice my own brand of star-hopping that I like to describe as a celestial nature walk. Rather than a method of locating specific objects, I like to use it to explore a region of the sky. I typically start with a bright star as my starting point, and then using my S&T Pocket Sky Atlas as my guide I slowly walk from star to star, pausing at each one to take a peek though the scope, marking my way as I go in pencil on my map. If I find something interesting, I’ll draw a circle around it and make a note in my notebook. I usually use either a 2” 56mm Meade Super Plossl (36x) or a 2” 26mm QX (77x) in the scope and if I find something interesting I may switch to a 14mm (143x), 8.8mm (227x), or 5.5mm (364x) 1.25” Meade UWA eyepiece. I found the slow-motion controls of the 510 to be very effective and responsive, making it possible to leave the scope all the way up at 364x while using the finder to center stars, though it requires a light touch to make small adjustments.

 

The image quality was exactly what you would expect from a Unitron with stars showing sharp, compact Airy disks surrounded by sharp, tight diffraction rings. A big difference that I immediately noticed between the 510 and my 4” f/15 150 and 155 is a much smaller Airy disk, and often only a single, very tight diffraction ring. Multiple stars are just amazing. I could star at the Double Double (epsilon Lyra) all night. Just gorgeous!

 

The star-hop from this particular even is shown below. Lyra is one of my favorite summer star-hopping regions with a rich field of stars, colors, multiple stars, clusters, and asterisms. This also shows how the slow-motion controls made it easy to navigate the field one star at a time. One issue that I am going to look at is a bit of backlash in the controls and locks. The mass and moment arm of the mount and telescope amplifies their effects. I hope to add a set of shims to snug up the mount a bit. In the meantime, it’s easy to just set the balance a tiny bit off so that the telescope pre-loads the backlash. This pre-load is easy to tweak with the Unibalance.

 

attachicon.gif Star-hop (7-10-2023)-1.jpg

 

Unfortunately, I did run into a bit of a problem. When there were bight stars in the field I noticed a veil of haze across the field, indicating a possible problem with the objective (or other optical element). Superficially, the objective looked clean, but when I took a close look with a bright flashlight, I could clearly see a hazy film between the elements. Ugh. While this is common with refactors of this age, there’s nothing that I dread more than pulling the lens apart for cleaning. I have cleaned the objectives on most of my classics, including my 150 and 155, but nothing scares me more than taking one of these old objectives apart. If you’re lucky, they come right out, if not, one false move and you can get a nasty chip. However, if I wanted to clean between the elements, I had no choice.

 

But that is a story for another day… smile.gif

 

(Spoiler alert, it turned out well.)

 

Enjoy!

The first time I cleaned an achromat I thought I would soil myself. It went so easily that I thought - wow. I must have done something right :) I have one right now waiting for the treatment! A 3" AO.

 

-drl



#66 starman876

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Posted 19 July 2023 - 05:15 PM

My 3rd evening out with the 510 marked the beginning of the shift from familiarization to using the telescope. This was the first opportunity to test the assembly procedure that I describe above and the first genuinely clear evening, though it clouded up before it got fully dark. I have a variety of manual and computerized mounts that I can use depending on my plans for the evening. I often enjoy using these classic telescopes on their original mounts since they are so simple, rugged, and comfortable to use with the manual controls within easy reach of the eyepiece right where my hands expect to find the in the dark.

 

One feature that I often have trouble with is the use of straight-thru finders. The finder is my primary star-hopping tool and I’m just not flexible enough to use a straight-thru finder except at low altitudes, in which case they are a nice option to have. Dave provided me with a finder bracket that he used to hold a 60mm finder. I scrounged through my spare finders and couldn’t come up with a 60mm that would fit, but I did have a classic orange tube 50mm right angle finder from University Optics, so I swapped out the original screws installed in the bracket with longer screws, and I was able to mount the 50mm. As a bonus, these 50mm finders were built for University Optics by Nihon Seiko and I have seen them referred to as baby Unitrons. smile.gif If you look closely at the photograph below you can see the NS maker’s mark on the dew shield.

 

attachicon.gif Unitron 510 Finder (7-5-2023)-1.jpg

 

With the finder sorted out, the next thing that I like are effective slow-motion controls that allow me to easily slew the scope in an organized manner over small distances as I move from star to star. I practice my own brand of star-hopping that I like to describe as a celestial nature walk. Rather than a method of locating specific objects, I like to use it to explore a region of the sky. I typically start with a bright star as my starting point, and then using my S&T Pocket Sky Atlas as my guide I slowly walk from star to star, pausing at each one to take a peek though the scope, marking my way as I go in pencil on my map. If I find something interesting, I’ll draw a circle around it and make a note in my notebook. I usually use either a 2” 56mm Meade Super Plossl (36x) or a 2” 26mm QX (77x) in the scope and if I find something interesting I may switch to a 14mm (143x), 8.8mm (227x), or 5.5mm (364x) 1.25” Meade UWA eyepiece. I found the slow-motion controls of the 510 to be very effective and responsive, making it possible to leave the scope all the way up at 364x while using the finder to center stars, though it requires a light touch to make small adjustments.

 

The image quality was exactly what you would expect from a Unitron with stars showing sharp, compact Airy disks surrounded by sharp, tight diffraction rings. A big difference that I immediately noticed between the 510 and my 4” f/15 150 and 155 is a much smaller Airy disk, and often only a single, very tight diffraction ring. Multiple stars are just amazing. I could star at the Double Double (epsilon Lyra) all night. Just gorgeous!

 

The star-hop from this particular even is shown below. Lyra is one of my favorite summer star-hopping regions with a rich field of stars, colors, multiple stars, clusters, and asterisms. This also shows how the slow-motion controls made it easy to navigate the field one star at a time. One issue that I am going to look at is a bit of backlash in the controls and locks. The mass and moment arm of the mount and telescope amplifies their effects. I hope to add a set of shims to snug up the mount a bit. In the meantime, it’s easy to just set the balance a tiny bit off so that the telescope pre-loads the backlash. This pre-load is easy to tweak with the Unibalance.

 

attachicon.gif Star-hop (7-10-2023)-1.jpg

 

Unfortunately, I did run into a bit of a problem. When there were bight stars in the field I noticed a veil of haze across the field, indicating a possible problem with the objective (or other optical element). Superficially, the objective looked clean, but when I took a close look with a bright flashlight, I could clearly see a hazy film between the elements. Ugh. While this is common with refactors of this age, there’s nothing that I dread more than pulling the lens apart for cleaning. I have cleaned the objectives on most of my classics, including my 150 and 155, but nothing scares me more than taking one of these old objectives apart. If you’re lucky, they come right out, if not, one false move and you can get a nasty chip. However, if I wanted to clean between the elements, I had no choice.

 

But that is a story for another day… smile.gif

 

(Spoiler alert, it turned out well.)

 

Enjoy!

you can clean it.  Go real slow.  Lots of organic cotton balls.  Zeiss lens cleaner.  Put down lots of towels to cushion anything that falls.  were surgeons gloves.  Mark the lens so you do not mess with the way they mate and their orientation to each other.   Place a larg tin can with a soft cloth over it to push the lenses out of the cell when you remove the lens retaining ring.  make sure you buy a spanner wrench to remove the lens retaining ring.   You should have not issue cleaning the lens.


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#67 deSitter

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Posted 19 July 2023 - 05:25 PM

you can clean it.  Go real slow.  Lots of organic cotton balls.  Zeiss lens cleaner.  Put down lots of towels to cushion anything that falls.  were surgeons gloves.  Mark the lens so you do not mess with the way they mate and their orientation to each other.   Place a larg tin can with a soft cloth over it to push the lenses out of the cell when you remove the lens retaining ring.  make sure you buy a spanner wrench to remove the lens retaining ring.   You should have not issue cleaning the lens.

The Zeiss lens cleaner is manna from Beta Herculis.

 

-drl


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#68 CHASLX200

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Posted 19 July 2023 - 06:19 PM

I think the chances of finding used 5" Uniclamps will be like 1 in a mil.  I don't even ever see the 60mm finders pop up.
 



#69 jgraham

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Posted 19 July 2023 - 07:21 PM

Heh, heh, cleaning it is the easy part. Getting a priceless lens out of its cell and back without chipping it is the part that I loose sleep over. Details to follow, but all went well... twice! I now have a pristine lens set, and I can stop worrying about it. :)
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#70 jgraham

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Posted 22 July 2023 - 05:34 PM

Ugh. I'm trying to find minutes to update this, but life keeps interfering.

However...

Last night was so much fun I had to make at least a short update.

We had clear-ish evening, but monster humid. I set the 510 up on my Atlas and went to bed until 2am to take peek at Saturn. I got up to find the sky hazy and the scope soaking wet. I had the lens cap installed and added a dew heater to fight off the fog, though the scope was way too tall to check the objective. Regardless, Saturn was amazing! A bit dim from the haze, but no signs of image breakdown at 364x. We are slowly loosing the rings as ring plain crossing approaches, but the Cassini Gap, ring shadow, planet shadow, and detail on Saturn were all easily visible. Several mooons were visible showing a limiting magnitude of about 11. I backed off to 227x which brightened things up a bit, and to 142x to go wide-ish. The view at 142x was amazingly sharp edge to edge across the field.

After about an hour I slewed over to Jupiter, stopping by Neptune along the way. Neptune showed a gorgeous blue-green color with just a hint of a disk. Jupiter was low, but amazing with 3 moons and the Great Red Spot crossing the meridian.

I hit a few double stars (Almach looked wonderful), and called it a night around 4:30. I just had to check the box of seeing how the 510 would perform with Saturn and Jupiter, and it did not disappoint.

Wonderful!
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#71 combatdad

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Posted 23 July 2023 - 08:55 AM

Great session, John!  Thanks for sharing.  Jupiter's moon shadow transits with the M510 are pretty spectacular!

 

Dave



#72 jgraham

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Posted 23 July 2023 - 07:11 PM

As I described above, close inspection of the objective showed that there was a hazy film between the elements and the only course of action was to remove the lens for cleaning. This is not unusual for telescopes of this age and I have done this several times before with other refractors including my Unitron 150 and 155. This is a fairly simple process if the lens can be easily removed. If not, then there is a very real risk that one wrong move will chip the lens. The thought of damaging the lens of the 510 was very concerning to say the least, but there weren’t a lot of options.

 

Before starting the process, I checked the collimation using Turk’s centering mask and a laser collimator. As expected, the collimation was spot-on.

 

The lens cell of the 510 is similar to other adjustable Unitron objectives with the cell attached to the tube with 3 spring-loaded screws The lens elements are held in the cell with a retaining ring that is in turn secured with 3 pairs of push/pull screws. The first step was to mark everything so that they can be put back in exactly the same orientation. Next, the 3 collimating screws were carefully and evenly backed out while holding the cell. Once free, the cell was placed face-up on a clean surface. The retaining ring was then removed by removing the 3 pull screws and then lifting the retaining ring off and setting it aside. While holding the lens assembly between lens tissues the lens stack was placed face-down onto a cylinder padded with lens tissue. The lens cell is then lifted off of the lens stack, which hopefully comes out of the cell, leaving the front and back elements on the padded cylinder.

 

Good news and bad news…

 

The good news is that the front element easily slipped out of the cell.

 

The bad news is that the rear element did not; not surprising, but disappointing. I applied a little pressure to the rear element to see if I could gently nudge it out of the cell, but if you’re not careful you can easily pinch the optic and chip the lens. Since I didn’t need the rear element to be removed from the cell to clean the lenses, I decided not to push my luck and I left the rear element alone.

 

Close inspection showed that the hazy film was on the front face of the rear element. I cleaned both elements starting with a puffer bulb to blow off any loose dust, then a gentle cleaning with a lens tissue moistened with isopropyl alcohol (IPA) and ultra-pure water, repeat with a lens tissue moistened with just ultra-pure water, and finally the ole’ breath fog and a dry tissue.

 

Once the lenses passed the flashlight test the procedure was reversed and the lens stack was re-assembled. Since I didn’t touch the push screws the retaining ring should have gone right back to where it was, and no adjustment should be required. The cell was reattached to the tube with the collimation screws slowly and evening turned all Wo the way in, and then backed out ½ turn. The lens was then collimated using only adjustments that tightened the screws.

 

Whew! Job over. A few nights later I had a chance to check out the results and test using the 510 on my Orion Atlas EQ-G. (More on that later.) The final checkout looked great! Star shapes were perfect with sharp, compact Airy disks and sharp, tight diffraction rings. And… no hint of haze even with bright stars in the field. Woohoo!

 

Except…

 

I couldn’t stop thinking about the rear element being stuck in the cell. If it were really stuck bad things could happen. If I was lucky all that I may see is a bit of stress on the objective in the form of pinched optics. Worst case; differential thermal expansion between the lens and cell could result in catastrophic stress on the lens ending with either a chip or (heaven forbid) a crack. Now to be honest the lens has seemed to survive pretty well over the past 50+ years so it was probably okay, but that’s the problem with being an engineer, you worry too much. My biggest fear was that while I was testing to see if the rear element was really stuck or just firmly held I may have inadvertently cocked it just enough to lock it in the cell, which would be a bad thing. I just had to know for sure. So, once more into the breech, it had to come out again.

 

Having done it once before, this time I paid close attention to each step. Once the front element was out  I took close look at both lenses and I was pleased to find that both edges of both lenses had a generous chamfer, making it unlikely that I would chip the edge unless I did something very unwise. Next, a close examination of the rear element shows that it was not stuck, just firmly held. If I gently, carefully, and evening apply a load to the back edge of the lens I could nudge it forward. So, I gently moved it back, made sure that it was evenly seated, cleaned and puffed everything off, put it back together, reset the collimation, and gave it a thorough check out (again on the Atlas) and all was well.

 

One thing that I should mention is that I could see the erosion of the coating on the back face of the rear element that Turk describes in his extensive refurb thread. Casual inspection of the lens doesn’t show is, but you can see it of you look very closely with a bright light. It doesn’t seem to have any notable effect on the image quality. I also noted a few scratches on both of the inner faces between the two lenses, which indicates that lens has been taken apart before.

 

Soooo, this little adventure has come to a successful conclusion, and I can move forward knowing that the objective lens is optically and mechanically in great shape!

 

Next up… some observing notes with the scope now that I am spending less time working on it and more time using it. Also, I managed to sneak in an all-night imaging session with some interesting/fun results.

 

The Journey Continues…

 

Enjoy!

 

A few pics...

 

The separated front element (left) and the rear element in the cell (right)...

 

Lens Elements (7-19-2023)-1.jpg

 

That might be some of the coating erosion visible in the reflection at the top of the rear lens. The damage to the coating can only be seen in reflected light.

 

A close-up of the rear element showing the generous chamfer around the edge of the lens...

 

Chamfer (7-19-2023)-1.jpg

 

The lens back on the scope after the first cleaning. You can see a few dust flecks that I removed during the second cleaning. I should have taken a before picture, but I didn't...

 

Lens Assembly (7-19-2023)-1.jpg

 

You can see the 3 collimation screws that hold the cell and the 3 pairs of push/pull screws on the retaining ring.


Edited by jgraham, 23 July 2023 - 07:14 PM.

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#73 starman876

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Posted 24 July 2023 - 02:14 PM

did you check for the  Newton rings?  Just wondering



#74 jgraham

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Posted 24 July 2023 - 04:01 PM

Not yet, but I am going to. The star test looks absolutely perfect, so I wasn't too concerned. But, it's on my short list.

#75 combatdad

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Posted 25 July 2023 - 06:40 AM

Not yet, but I am going to. The star test looks absolutely perfect, so I wasn't too concerned. But, it's on my short list.

This is a pic Tom took of the rings back in 2014 (during his restoration).

 

Dave

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  • M510Rings_2014.jpg

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