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BB Reviews the Bresser Messier AR-102L

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#76 Bomber Bob

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Posted 13 April 2019 - 09:00 PM

Plato, Alpine Valley, & Eyepieces

 

Just got in a quick session.  We have tornadoes forecast after midnight.  Apparently, the front responsible drew all the moisture away from The Swamp, as the seeing varied between 7 & 8.  

 

Plato:  Saw 2 of the craterlets for sure (A&C), and possibly a third (D).  Best seen with the vintage spectros PL7.5.  In fact, this eyepiece gave the best views.  The Nagler 7 has a wider field, but the old Plossl has better contrast & resolution -- less glass can show more sometimes.

 

2 - Lunar PLATO Craterlet MAP V01.jpg

 

When the seeing was best, I used the Radian 4 @ 340x.  A dimmer view, but no softness -- Plato's shadows were as sharp as at 181x.

 

Alpine Valley:  I couldn't see the rille along the floor, but I did see the curvy crack that "feeds" the valley, and the 4km crater with the bright wall / ejecta ring on the floor.  Green lines point to some of the finer features that really stood out.

 

AR-102L - ALPINE Valley Features.jpg

 

No false color with the TV or spectros eyepieces.  More folks own the Ohi-made Orthoscopics sold by UO, Baader, etc. than own the Swiss-made spectros.  In these Orthos, I saw varying degrees of light yellow tint on the peaks near Plato, but not on its brightest walls.


Edited by Bomber Bob, 13 April 2019 - 10:17 PM.

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#77 terraclarke

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Posted 13 April 2019 - 09:06 PM

The non-collimatable, flimsey, plastic objective cell would be an instant red flag for me. No need to go further, game over! I would pass with no second thoughts.
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#78 terraclarke

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Posted 13 April 2019 - 09:09 PM

Plato, Alpine Valley, & Eyepieces
 
Just got in a quick session.  We have tornadoes forecast after midnight.  Apparently, the front responsible drew all the moisture away from The Swamp, as the seeing varied between 7 & 8.  
 
Plato:  Saw 2 of the craterlets for sure, and possibly a third.  Best seen with the vintage spectros PL7.5.  In fact, this eyepiece gave the best views.  The Nagler 7 has a wider field, but the old Plossl has better contrast & resolution -- less glass can show more sometimes.
 
When the seeing was best, I used the Radian 4 @ 340x.  A dimmer view, but no softness -- Plato's shadows were as sharp as at 181x.
 
Alpine Valley:  I couldn't see the rille along the floor, but I did see the curvy crack that "feeds" the valley, and the 4km crater with the bright wall / ejecta ring on the floor.
 
No false color with the TV or spectros eyepieces.  More folks own the Ohi-made Orthoscopics sold by UO, Baader, etc. than own the Swiss-made spectros.  In these Orthos, I saw varying degrees of light yellow tint on the peaks near Plato, but not on its brightest walls.


Aren’t the Spectros eyepieces Kellners? I thought you said they were Kellners when you bouht them several years ago.

#79 Bomber Bob

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Posted 13 April 2019 - 09:14 PM

There are 9 spectros eyepieces in my set:  The 3 Big Eyepieces with 35mm barrels are Kellners -- 50/40/30mm -- they can fit the Tinsley's focuser, so I called them the Big Kellners (probably what caused some confusion).  The .965" barreled 25/20mm are Kellners; the 15/10/7.5/5mm are Plossls.


Edited by Bomber Bob, 13 April 2019 - 09:19 PM.


#80 terraclarke

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Posted 13 April 2019 - 09:16 PM

The six 0.965” Spectros eyepieces according to this are:

http://www.anamorfos...ieces-4-filters

5mm Plossl 24,5mm
7,5mm Plossl 24,5mm
10mm Kellner 24,5mm
15mm Kellner 24,5mm
20mm Kellner 24,5mm
25mm Kellner 24,5mm

(That’s the set Xavier had up for sale several years ago.

Edited by terraclarke, 13 April 2019 - 09:19 PM.


#81 Bomber Bob

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Posted 13 April 2019 - 09:35 PM

Terra, I've seen that from Xavier, too.  In fact, I bought this set from Xavier, and it included 4 .965" color filters, and the 35mm to 1.25" adapter. I've also read what I posted on another vendor's site.  What I haven't found - yet - is authentic spectros documentation on these eyepieces.

 

I could take them apart and check... or, not -- unless they get moldy.

 

I really don't care whether they're Plossls, Kellners, or Orthos -- there's no bragging points in design.  The 2 Zeiss .965" EPs I have are Huygenians, yet they're great for lunar/planetary, too.  If the 10mm is a Kellner, it's the sharpest one I've ever used.


Edited by Bomber Bob, 14 April 2019 - 09:31 AM.


#82 barbie

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Posted 13 April 2019 - 09:54 PM

I was observing with my Bresser AR90L and the moon didn't show false color at high power using Celestron Omni Plossl eyepieces.  Craters were razor sharp and shadows were jet black.  I also managed to get good splits on Sirius, Castor and a few of the wider doubles in Ursa Major.  Observing conditions were around an 8 with very thin high clouds beginning to move in ahead of the next front which is due to arrive Sunday morning.


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#83 Bomber Bob

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Posted 13 April 2019 - 10:01 PM

What about the lunar limb?  I have seen a thin faint blue-violet rind in the AR-102L.

 

BIF:  We had some 10+ knot surface wind gusts tonight, and these shook the scope -- visibly at high power.  If you've never used a long refractor, it does happen; so, if you live / observe in a windy place, it's something to consider.


Edited by Bomber Bob, 13 April 2019 - 10:21 PM.


#84 Bomber Bob

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Posted 13 April 2019 - 10:27 PM

The non-collimatable, flimsey, plastic objective cell would be an instant red flag for me. No need to go further, game over! I would pass with no second thoughts.

To be clear:  The retaining ring is the only flimsy part of the plastic lens cell.  It should be metal, but it's not, and gluing it down doesn't help that much.  My Goto HS 452 also has a synthetic lens cell -- but its retaining ring is finely machined brass.

 

My Edmund & Dakin both have metal cells, but they're fixed -- non-collimatable, too.  And unlike my Edmund, the Bresser has a collimatable focuser.


Edited by Bomber Bob, 13 April 2019 - 10:30 PM.

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#85 Peter Besenbruch

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Posted 13 April 2019 - 11:36 PM

Interesting series of reviews, Bob. The lens cell is a bit of a red flag for me, but your comments are interesting. I was able to spot the rille in the Alpine Valley with a 7" Maksutov, and that wasn't all that easy.


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#86 Magnetic Field

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Posted 14 April 2019 - 02:30 AM

Plato, Alpine Valley, & Eyepieces

 

Just got in a quick session.  We have tornadoes forecast after midnight.  Apparently, the front responsible drew all the moisture away from The Swamp, as the seeing varied between 7 & 8.  

 

Plato:  Saw 2 of the craterlets for sure (A&C), and possibly a third (D).  Best seen with the vintage spectros PL7.5.  In fact, this eyepiece gave the best views.

 

attachicon.gif 2 - Lunar PLATO Craterlet MAP V01.jpg

 

I have never been able to split the craterlets C/D in my Vixen VMC 110L (110mm aperture).  I can see either one but not both at the same time.

 

I think I would need the perfect seeing for that.

 

By the way: you could try the following doubles:

 

Iota Leonis and Epsilon Bootis (post #57 in: https://www.cloudyni...-3#entry9272744 ).


Edited by Magnetic Field, 14 April 2019 - 02:31 AM.


#87 Steve Allison

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Posted 14 April 2019 - 02:53 AM

Magnetic Field-

 

As for two lemons, this seems unlikely unless Vixen quality control has taken a nose dive. And I even got the second unit from Vixen directly. Maybe I just want more from a telescope than these Vixen units provide. If you like yours, great, more power to you! 

 

If you had read my post more carefully, you would have seen that nowhere did I state that a central obstruction is "the root of all evil". In fact, central obstructions of less than 20% have virtually no effect on contrast.

 

The Vixen VMC110 has a central obstruction quite a bit larger than this, and has thick curved secondary mirror supports. The two so-called lemons that I owned displayed noticeably less contrast than my 3 and 4 inch F/15 refractors. Even my excellent Meade 2045 4 inch SCT with a smaller secondary percentage-wise than the Vixen and with no support arms for the secondary displays noticably less contrast than my 3 inch achro on targets such as Jupiter and the Orion Nebula. 

 

At F/15 my 3 inch refractor shows very little color in focus, and that is the point. Slight amounts of chromatic aberration can theoretically reduce contrast, but in the real world may not noticeably effect the level of contrast visible at the eyepiece.

 

The purpose of my post was to respond to your blanket statement that "false color greatly reduces contrast",  with you not stating the amount of color you are talking about. To seemingly suggest any amount of false color greatly reduces contrast is as patently false as me saying any size central obstruction greatly reduces contrast. 

 

I have been observing for over 50 years through every type of telescope imaginable- achros, apos, Newtonians, SCTs, Maksutov and even off-axis reflectors. I know what contrast in an image is, how to evaluate it and how a particular telescope design affects it. I have used many of these telescopes side-by-side.

 

For you to state that I have not evaluated contrast but only read about it somewhere on the web is a presumptuous and arrogant statement, as is your statement that I fell for some sort of trap. This kind of immature posturing and unwarranted attack on my credibility does little to bolster whatever points you are trying to make.

 

Steve


Edited by Steve Allison, 14 April 2019 - 03:05 AM.

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#88 Magnetic Field

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Posted 14 April 2019 - 03:30 AM


 

At F/15 my 3 inch refractor shows very little color in focus, and that is the point. Slight amounts of chromatic aberration can theoretically reduce contrast, but in the real world may not noticeably effect the level of contrast visible at the eyepiece.

 

The purpose of my post was to respond to your blanket statement that "false color greatly reduces contrast",  with you not stating the amount of color you are talking about. To seemingly suggest any amount of false color greatly reduces contrast is as patently false as me saying any size central obstruction greatly reduces contrast. 

 

 

1. I will not stop making those blank statements about false color and achromats.

 

2. Believe it or not I have no dog in this fight but want to remind the observer that false colour is a big problem in refractor land. I find it often absurd when people dismiss obstructed telescopes by citing the MTF (modulation transfer function) but at the same time dismiss the fact that chromatic aberration in achromats and to a lesser degree in ed-apos can be as  bad. When was the last time someone mentioned "achromat and MTF" in the same sentence as if it does not exist for achromats or poorly executed ED semi apos..

 

3. On another note: There are a lot of bad VMCs out there. Vixen really needs to get their act together. Their quality control is just a joke. In the UK they increased the price for the VMC 110L by 25% (I think it costs now £400 for the OTA plus red dot finder plus  25mm Vixen NPL without the mount ) and nothing has changed. Anyway I stand by my indirect comment: the Vixen VMC 110L f/9.4 (or a Maksutov) would probably be a better choice than an unwieldy 4" f/14 refractor. The OTA may cost more than the Bresser  AR 102L but the Vixen also has less demands for a good mount.



#89 Steve Allison

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Posted 14 April 2019 - 04:01 AM

Magnetic field-

 

I wanted to like my VMC 110. I really did. The size is handy and I really like the way they look. 

 

Do you know where I could get a decent performing unit to try? If it performed as well as yours seems to, I would probably buy it.

 

Blanket statements are fine, but there are no absolutes. Achros and obstructed telescopes will both have less theoretical contrast than an unobstructed, color free system like the Schiefspiegler I used to own. But it is all a matter of degree. I would still take issue with the suggestion that any color error greatly reduces contrast. Reduces, yes, but greatly? Even in a top of the line Zeiss F/15 achro? How about my Takahashi FS-102 apo?

 

And I would take issue if anyone said any central obstruction greatly reduces contrast. Depends on the size of any obstruction, just as it depends upon the amount of color in a rafractor.

 

I am serious about wanting to try a good performing VMC 110 if, as you say, they are out there.

 

Steve


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#90 terraclarke

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Posted 14 April 2019 - 07:30 AM

Just which orthos are the Ohi-made Orthoscopics sold by UO?

#91 Magnetic Field

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Posted 14 April 2019 - 08:34 AM

He's a troll.gif, Steve - just in here to disrupt BBs review (which is very nice, btw). 

 

If you run out of arguments you are quick to call someone a troll.

 

 

At least I stayed on topic.



#92 Bomber Bob

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Posted 14 April 2019 - 08:46 AM

Just which orthos are the Ohi-made Orthoscopics sold by UO?

 

"The exquisite H.D. 4-element Abbe Orthoscopic oculars that have earned an outstanding reputation over the years. In cooperation with our associate firm Ohi Optical in Japan, these Phase II oculars reach new highs in optical performance."  --   http://www.frontiero...&product_id=105

 

The UO sales sheet that came with my order talks about the renewed partnership with OHI.  I think this ad just copied / pasted the UO publication.  The 3 in the front row were my first, and I added a 9mm later:

 

University Optics Abbe Orthos HD S02.jpg


Edited by Bomber Bob, 14 April 2019 - 08:52 AM.

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#93 Bomber Bob

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Posted 14 April 2019 - 09:00 AM

At least I stayed on topic.

 

Inserting the old & cliche, "My [non-refractor] can whoop your refractor any night." post is off-topic.  Once again, this thread is in the Refractor Forum; and, its topic is a Review of a new(ish?) high F-ratio achromatic refractor.  As a refractor fan, I really don't care what a same-aperture non-refractor can do.  I'm comparing like with like.


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#94 terraclarke

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Posted 14 April 2019 - 09:05 AM

Just which orthos are the Ohi-made Orthoscopics sold by UO?
 
"The exquisite H.D. 4-element Abbe Orthoscopic oculars that have earned an outstanding reputation over the years. In cooperation with our associate firm Ohi Optical in Japan, these Phase II oculars reach new highs in optical performance."  --   http://www.frontiero...&product_id=105
 
The UO sales sheet that came with my order talks about the renewed partnership with OHI.  I think this ad just copied / pasted the UO publication.  The 3 in the front row were my first, and I added a 9mm later:
 
attachicon.gif University Optics Abbe Orthos HD S02.jpg


Oh, okay. I have the 12.5, 18, and 25mm and have not seen any introduction of false color with them when used with my apos. I also have a full set of circle T volcano tops from 4mm up that perform well. My favorites are my set o CZJ orthos (6,10,16, and 25mm) and my Brandons (8, 12, 16, 24, and 32mm).

#95 precaud

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Posted 14 April 2019 - 09:12 AM

I don't think MF is trolling. He's talking sense. The scope being reviewed has issues that are being soft-shoed by the romance of it being an affordable long-focus frac. The measurements provided are inconsistent with the visual results being described. Objectively, there's is much to question here.

 

As one who came into this wanting very much to like it enough to order one, I am grateful to JW for doing this review.

 

I assume going in that any economical frac is going to need some fine-tuning to perform at its capability. What I've read here has not convinced me that this one would be worth the effort, or even possible to bring into "really good" territory. That would require a "really good" objective, something which is supposedly easier to make at longer focal lengths. This one falls short of that. Since the figure is uncorrectable by the end user, that dead-ends this scope for me.

 


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#96 Bomber Bob

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Posted 14 April 2019 - 09:23 AM

The measurements provided are inconsistent with the visual results being described. Objectively, there's is much to question here.

 

Which measurements?  Both DPAC & star tests show under-correction.  DPAC is more sensitive than my visual star tests; however, in my experience, seeing some of those errors is tough.  As I posted before, viewing Jupiter at high power is my standard for refractors, and in SxS's with known good 4" refractors, any serious issues should be apparent.


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#97 Bomber Bob

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Posted 14 April 2019 - 09:37 AM

I have the 12.5, 18, and 25mm and have not seen any introduction of false color with them when used with my apos.

 

I don't think the UO HDs are introducing false color.  I think that the design, coatings, etc. are showing me what's already there.  Some folks might see more CA with them, some less, I just report what I see.


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#98 precaud

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Posted 14 April 2019 - 09:41 AM

The measurements provided are inconsistent with the visual results being described. Objectively, there's is much to question here.

 

Which measurements?  Both DPAC & star tests show under-correction.

 

Yes, but this is the first time you've come out and said that. Most readers don't interpret DPAC photos on a regular basis. Prior descriptions have soft-shoed the faults, shifted them into equipment shortcomings (camera), and focused on the strengths.



#99 Bomber Bob

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Posted 14 April 2019 - 09:59 AM

Yes, but this is the first time you've come out and said that.

 

From Post #55:

 

Both DPAC tests confirm my star tests.

 

Huh?  From Post #62:

 

Inside Focus:  Excellent star test & DPAC patterns with 3 - 5 bars.

Outside Focus:  Fuzzy star test & "bloated" DPAC bars.

At Focus:  Excellent resolution, very good contrast, micro-dot faint field stars, sharp limbs on Mars & the Moon, false color on the limbs.  So far, the views are what I'd expect from a good high F-ratio refractor.

 

I try not to be repetitious, but you're making that difficult.


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#100 precaud

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Posted 14 April 2019 - 10:20 AM

Whatever. Have it your way. To me, that's an optimistic description that soft-shoes the issues. No mention of the obvious undercorrection, which is terminology most here can relate to, as compared to "bloated DPAC bars" which goes right past the reader, including me...


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