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Burgess/TMB Planetary 8mm vs Agena Starguider DualED 8mm

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#1 aatdalton

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Posted 23 August 2019 - 11:13 AM

I've recently come to own both these eyepieces and I'm looking to see which one to keep and which to pass on to the classifieds. They're really similar in function, both around 60° aFov. 

 

As a newer observer, when I get a good dark, clear night to compare them what should I be looking for? Anything specific to either of these eyepieces that might be good to try to notice? Any opinions on either of them?



#2 lylver

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Posted 23 August 2019 - 11:36 AM

I tested both series, not all focal length.

 

Sincerely, global field correction is better on the Starguider and all similar clones and rebranded (paradigm, BST, X-CEL-LX, HD-60)

Pentax XL initiated this nice medium corrected formula but manufacturing is not so good as Pentax do.

 

On the contrary, the pentax XL 10.5 I have is soft at f/5, the Starguider seems better : formula has evolved ?

 

I kept my original TMB 2.5, 4 & 7mm for center sharpness, contrast and well contained scatter, but the well corrected FOV is half field to 2/3 field on my f/5 scopes (refractor ou newton)

 

-------------------------

I still have an eye on a other optic formulas that are less popular now :

- Vixen LV, NLV, SLV : good eye relief but short FOV.

Disassembled, barlow broken by a fall, the eye part is very good starting at f/8 for the broken LV I took a look at. I don't know all (fl & model) but short fl LV aren't top.

 

- SPLER 55° (astroplan/erfle redesigned + barlow), I have a nice opinion about William Optics SPL 12.5mm on a medium scope (over f/7), other model/brand can be better.


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#3 aatdalton

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Posted 23 August 2019 - 11:48 AM

I tested both series, not all focal length.

 

Sincerely, global field correction is better on the Starguider and all similar clones and rebranded (paradigm, BST, X-CEL-LX, HD-60)

Pentax XL initiated this nice medium corrected formula but manufacturing is not so good as Pentax do.

 

I kept my original TMB 2.5, 4 & 7mm for center sharpness, contrast and well contained scatter, but the well corrected FOV is half field to 2/3 field on my f/5 scopes (refractor ou newton)

 

I still have an eye on a other optic formulas that are less popular now :

- Vixen LV, NLV, SLV : good eye relief but short FOV.

Disassembled, barlow broken by a fall, the eye part is very good starting at f/8 for the broken LV I took a look at. I don't know all (fl & model) but short fl LV aren't top.

 

- SPLER 55° (astroplan/erfle redesigned + barlow), I have a nice opinion about William Optics SPL 12.5mm on a medium scope (over f/7), other model/brand can be better.

That's helpful, thank you. To be clear, my TMB is supposedly an original Burgess, not a clone or a MkII.



#4 cst4

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Posted 23 August 2019 - 12:17 PM

I wound up with both of these eyepieces as well.  My TMB is one of the originals and my Dual ED is a Paradigm.  I've been comparing them for months trying to decide which to keep and which to sell.  It's a tough call as they are both really good eyepieces.  In my 8" cass at over 240x I decided I preferred the TMB.  I find it to be a little more comfortable to use at high power and I can see a little more detail on the planets through it.  Plus the image seems a little brighter and slightly cooler in tone in the TMB which I like on planets.  I will also add that I found the TMB to be a better daytime spotting scope eyepiece.  So I had reluctantly decided I would let the Paradigm go.  However, I recently got a 102ED refractor and in this scope at nearly 90x I am now leaning towards the Paradigm.  It just seems to be the better DSO eyepiece and I keep reaching for it over the TMB.  The background seems a little darker and it has a more immersive feel.  So it's back on the table...  I may just have to keep them both! 

In summary they are both very good and it may largely come down to what scope you are using them in, the objects you are looking at, and your own personal preference.  



#5 aatdalton

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Posted 23 August 2019 - 12:21 PM

I wound up with both of these eyepieces as well.  My TMB is one of the originals and my Dual ED is a Paradigm.  I've been comparing them for months trying to decide which to keep and which to sell.  It's a tough call as they are both really good eyepieces.  In my 8" cass at over 240x I decided I preferred the TMB.  I find it to be a little more comfortable to use at high power and I can see a little more detail on the planets through it.  Plus the image seems a little brighter and slightly cooler in tone in the TMB which I like on planets.  I will also add that I found the TMB to be a better daytime spotting scope eyepiece.  So I had reluctantly decided I would let the Paradigm go.  However, I recently got a 102ED refractor and in this scope at nearly 90x I am now leaning towards the Paradigm.  It just seems to be the better DSO eyepiece and I keep reaching for it over the TMB.  The background seems a little darker and it has a more immersive feel.  So it's back on the table...  I may just have to keep them both! 

In summary they are both very good and it may largely come down to what scope you are using them in, the objects you are looking at, and your own personal preference.  

I think that lines up with my initial impression too. The TMB seems sharper in the center and good for planets or double stars while the ED might be better for smaller DSOs like globulars. I wish I had Saturn or Jupiter high up enough to test on right now. 



#6 vtornado

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Posted 23 August 2019 - 12:40 PM

I have been trying to figure out what eyepieces to thin out too.

 

My target is Jupiter, centerfield, 10inch f/5 dob.

 

I have been comparing TMB clone 5mm to paradigm ed 5mm

Same for 8 TMB vs 8mm paradigm.

 

The 5mm tmb is better then the paradigm ed, center field more festooning better colors are apparent.

The 8mm the paradigm is better than the tmb.  But this is only

marginally so, not leaps and bounds.

 

And ... I highly suspect this is more to do with sampling of the eyepieces then

fundamental design differences, or manufacturing tolerances.

 

If eyepieces are anything like computers (I work in the business)  parts are outsourced from

all over.  In a certain computer even with the exact same make and model. the inside parts change.

internal parts are bought in batches, and when the batch runs out another batch Is purchased,

Maybe from the same vendor, maybe from a competitor.  Even though the spec sheet of two different

batches are the same, they are not exactly the same.  the word similar comes to mind.


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#7 MartinPond

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Posted 23 August 2019 - 09:28 PM

I have seen performance variation in the same series...

and the same issues with the same FL....different units.

Seems to be some optimal mfg. tolerance vs. design thing..



#8 lylver

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Posted 12 November 2019 - 12:06 PM

What ruined the reputation of an eyepiece is sometimes a little change when manufacturing it.

 

I get 2 rares originals TMB coming from UK. They have the same issue that Tom Trusock decribed in his old 2005 review.

 

There were the 4mm and 6mm (clic on the link) 

I received them today : internal tube has no powder paint and the retaining ring is high. So the baffling near the barlow is not good.

 

Better image for proof I guess, I took with a led lamp under the eyepiece. Flare can be fixed easily, better is to baffle with a ring but paint too.

The external ring of light is from the barlow : it passes the field stop/baffle and rebound in the tube.

 

The best is pristine (4mm) : no dust.

IMG_20191112_135108c.jpg IMG_20191112_135012c.jpg

 

I dismounted the 6mm that has been conflictual between Bill Burgess and Thomas Back. This one is the original design : Smyth lens + König 2 / 1. I will check if the Smyth is air-spaced.




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