120mm f/8.3 achromat adjust lens

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Jones
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120mm f/8.3 achromat adjust lens

#1

Post by Jones »


Got the Orion version used locally. First look at the moon showed a yellow haze eveywhere. Have not had an achro in years, everyone talks about a blue haze around everything. Planet views were also bland.

So I did the top lens rotation of 90 degrees just to see what would happen. WOW!?! That fixed everything. All the yellow disappeared and now had a slight blue haze along moon edges. Jupiter was fantastic at 200x, as good as any apo in definition and sharpness. Even at 250x the 120mm achro was real close to the 115mm apo. But at 300x the achro finally fell behind as the scattered colors started to soften the view.

This scope is the best mid f/number achro I have ever used, or the others needed some fine lens tuning.
Arizona- where the sky's are not cloudy all night.

Triple lensed fracs are so yummy when looking at planets.
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Re: 120mm f/8.3 achromat adjust lens

#2

Post by Lady Fraktor »


If you have a clear night try spinning the lens a bit more.
Turn it 1/8th until it looks worse then start turning it back 1/16th turn until you find the best location then mark the orientation.
Good achromats are a lot of fun to use.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: 120mm f/8.3 achromat adjust lens

#3

Post by notFritzArgelander »


I had that scope back in the 2003 Mars opposition! It was a terrific performer after I collimated and optimized the objective! I remember being blown away by Olympus Mons and the Tharsis volcanos.

It’s one scope I really regret selling. Two years later I moved and a friend twisted my arms to sell it. I’m too accommodating sometimes. :)

LF’s suggestion for checking to assure optimization is a good one. You have to work a little with this (and the Meade and Celestron versions) but they’re really great performers for the price.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: 120mm f/8.3 achromat adjust lens

#4

Post by rocdoc »


Interesting. Anyone know of a tutorial on how to do this? I should try with mine (I have the Celestron version).
Properly collimated cornea-lens-vitreous optical apparatus, projecting on retinal sensor slightly limited by deuteranomaly, feeding through stock optic nerves into functional primary cortex, processed through frequently misfiring and buggy integrative cortex.
Other instruments: Skyline 8" Dobsonian, on a dob pod; Celestron Omni XLT 120 w GSO crayford focuser and Meade 5000 diagonal on Stellarvue M2C mount and Meade LX70 tripod; Oberwerk Binos: 25x100 Deluxe IF on Benro tripod with Oberwerk 5000 head or Farpoint parallelogram; 10x50 Ultra, usually on 3 Legged Thing Punks Trent monopod with Dolica trigger grip head; 8x42 Sport ED hand held. Main EPs: ES 82º 24mm and 11mm, Celestron Luminos 19mm and 10mm, Meade UWA 14mm, Meade HD-60 6.5mm. Filters: UHC, 13%, blue. Finders: RACI, Telrad, RDF, reticle.
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Re: 120mm f/8.3 achromat adjust lens

#5

Post by notFritzArgelander »


rocdoc wrote: Thu Aug 13, 2020 11:38 am Interesting. Anyone know of a tutorial on how to do this? I should try with mine (I have the Celestron version).
I looked for the resource I liked and it’s not there....

Anyway, Celestron has a page for collimating https://www.celestron.com/blogs/knowle ... -telescope

And here’s a link from Oz https://www.ozscopes.com.au/collimatin ... scope.html

The optimization is just a matter of rotating one lens with respect to the other in decreasing angular intervals until any deviation in any direction makes it worse.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: 120mm f/8.3 achromat adjust lens

#6

Post by notFritzArgelander »


Here’s more. I like the use of a Cheshire as in these instructions from Agena https://agenaastro.com/agena-1-25-coll ... ctors.html

Another longer take http://philjay2000.tripod.com/usefulst ... ntures.pdf
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: 120mm f/8.3 achromat adjust lens

#7

Post by rocdoc »


Thanks [mention]notFritzArgelander[/mention] . But in the original post [mention]Jones[/mention] mentions lens rotation. Is this an additional procedure on top of collimation? I would think that if collimation is on point the actual orientation of the lens shouldn't matter, but sounds like it does?
Properly collimated cornea-lens-vitreous optical apparatus, projecting on retinal sensor slightly limited by deuteranomaly, feeding through stock optic nerves into functional primary cortex, processed through frequently misfiring and buggy integrative cortex.
Other instruments: Skyline 8" Dobsonian, on a dob pod; Celestron Omni XLT 120 w GSO crayford focuser and Meade 5000 diagonal on Stellarvue M2C mount and Meade LX70 tripod; Oberwerk Binos: 25x100 Deluxe IF on Benro tripod with Oberwerk 5000 head or Farpoint parallelogram; 10x50 Ultra, usually on 3 Legged Thing Punks Trent monopod with Dolica trigger grip head; 8x42 Sport ED hand held. Main EPs: ES 82º 24mm and 11mm, Celestron Luminos 19mm and 10mm, Meade UWA 14mm, Meade HD-60 6.5mm. Filters: UHC, 13%, blue. Finders: RACI, Telrad, RDF, reticle.
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Re: 120mm f/8.3 achromat adjust lens

#8

Post by notFritzArgelander »


rocdoc wrote: Thu Aug 13, 2020 2:01 pm Thanks @notFritzArgelander . But in the original post @Jones mentions lens rotation. Is this an additional procedure on top of collimation? I would think that if collimation is on point the actual orientation of the lens shouldn't matter, but sounds like it does?
Indeed it does. Rotating one lens is a standard trick of the trade to optimize performance.

Each lens surface has errors. Depending on how those errors align and the nature of the errors, they can either add or cancel at the focus point. Rotating one lens to optimize maximizes the degree to which the errors cancel at the focus.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: 120mm f/8.3 achromat adjust lens

#9

Post by Jones »


The factory should have paired up the lenses in the best orientation. Sometimes they rotate around over the years.

I finally got around to rotating the top lens a second time. Went 45 degrees more clockwise for a total of 135 degrees from where it started and the view of Jupiter is slightly better than last night. Really good detail at 250x with a 4mm. Tried the 3.3mm for 300x but that was too much power.

Had the same problem with a SkyWatcher 120ed and the lens rotation shuffle took longer to find the best position. Wrote a detailed thread under telescope brands.
Arizona- where the sky's are not cloudy all night.

Triple lensed fracs are so yummy when looking at planets.
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Re: 120mm f/8.3 achromat adjust lens

#10

Post by Lady Fraktor »


It can take some patience to get it in the right orientation but once it is the views can be much improved sometimes.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
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Re: 120mm f/8.3 achromat adjust lens

#11

Post by notFritzArgelander »


The trade off is that if the factory optimizes rather than settling for “good enough “ then they charge more.... Glad it’s working out!
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: 120mm f/8.3 achromat adjust lens

#12

Post by Jones »


Not content to leave well enough alone, noticed that the shims between the lenses are just plastic tape! When Surplus Shed was selling off the A. Jaegers lenses in 2012 I discovered that .004 thick brass shims worked very well for those lenses. So I cut some tiny rectangles and attempted to use these as spacers, but they would not stay in place, they fell out, or spun around while tightening the retaining ring. Tried bending them into an L shape, but there is not enough room in the lense cell for an extra .004 spacer on lens edge. In desperation cut spacers out of that sticky back aluminum tape. Could not find my calipers to measure but they look like .003".

Tried it out on Jupiter tonite and could see little difference. Maybe less blue haze around edge of planet. Saturn was really sharp and more clarity since it is higher, and the moon Titan looked more of a pinpoint star than usual. So conclude that less is more. The tape shims were about .006 to .008 thick the aluminum foil about half that.
Arizona- where the sky's are not cloudy all night.

Triple lensed fracs are so yummy when looking at planets.
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Re: 120mm f/8.3 achromat adjust lens

#13

Post by Lady Fraktor »


I normally use Aluminium foil (tin foil for some).

Aluminium Foil Roll, Standard is 0.014 mm thickness.
Aluminium Foil Roll, Heavy Duty is 0.020 mm thickness.
Aluminium Foil Roll, Extra Heavy Duty, is 0.024 mm thickness

The good thing about using it is it can be folded to make thicker shims.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
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Re: 120mm f/8.3 achromat adjust lens

#14

Post by The Wave Catcher »


I know this thread is getting a little dated but I thought I’d share something I did to improve my 102 mm, f/4.5 achromatic DSO refractor for planetary work.

Being such a short and fast refractor I really expected bad chromatic aberration. It really isn’t that bad and I’ve really enjoyed the telescope. However, there was some room for improvement. I created an aperture mask and now it works like a poor man’s apochromatic. I found a plastic lid from an old yogurt container that fit the dew shield perfectly. I carefully cut a 60 mm diameter hole in the middle and painted the whole thing black. This makes my telescope an f/7.65 telescope and falls within the Sidgwick standard that says the focal ratio should be at least 3 times the aperture in inches to minimize chromatic aberration.

The results were amazing! Surely I’ve lost some theoretical resolution but I couldn’t really use it any way at the higher powers without the mask due to the aberration. I can see lots of details on the planets and the Moon looks incredible. When looking at stars I had a bit star burst like pattern in them before that I thought was just my old eyes but with the mask they a clean, sharp pin points. Last night I was able to see one of Rigel’s companion stars, Rigel B for the first time.

Instead of messing with the delicate lenses of your telescope you may want to try an aperture mask first and see if you like the results.

I don’t know why manufacturers don’t include these with achromats. Without the mask they are still great for DSO, comets, following satellites, etc.

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Astro-Tech AT102ED, 102 mm, F/7, ED Achromatic Refractor
Astro-Tech AT80ED, 80 mm, F/7, ED Achromatic Refractor
Bresser AR102s, 102 mm, f/4.5, Achromatic Refractor

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Re: 120mm f/8.3 achromat adjust lens

#15

Post by Lady Fraktor »


Many do have a aperture mask built into the dust cover.
Handy on some targets but reduces the light gathering on others.
Spinning a lens to optimize the view makes it work best under all situations and does not take much time to do.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
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