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BB Reviews the Bresser Messier AR-102L

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#26 belgrade

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Posted 07 April 2019 - 06:08 PM

It’s hard to understand why at least Explore Scientific doesn’t import 102mm and 127mm “long focus” achromats, considering they import all sorts of (lower-end) scopes...
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#27 Bomber Bob

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Posted 07 April 2019 - 07:32 PM

I hope this thread and others at least generate some interest in high F-ratio achromatics -- if not some sales.  If there's enough demand, vendors will respond -- just look at the "economy" 6" F8 EDs that have popped up.

 

IMO, these F13+ fracs are a good choice for us city dwellers with bright skies.  Put a quality lens in a light OTA.  That keeps down on the mount size.  Edmund did that 60 years ago with my 4" F15 -- still my favorite scope.  


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#28 Steve Allison

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Posted 07 April 2019 - 08:14 PM

My 75mm and 100mm long focus refractors are on smooth,"swing to view" alt-az mounts with tall tripods. The balanced tube assemblies are a pleasure to use, needing only a tiny tug now and then to follow celestial objects. Very laid back and relaxing!

 

Also relaxing is the forgiving depth of focus, which lets you slide into the point of best focus, rather than hold your breath and cramp your wrists trying to turn the focus knob the tiniest bit...

 

With the tall tripods, the finders scopes are easy to use without stooping over.

 

My achros make for a very relaxed and enjoyable evening, and the images they put up are very nice and satisfyingly sharp and contrasty. What little color they display on bright objects doesn't bother me in the least, because I observe solely for pleasure and I am not involved in researching the spectra of stars or some such.


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#29 barbie

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Posted 07 April 2019 - 09:05 PM

I was out observing bright and close doubles with my Celestron/Vixen SP C102 last night and had a very enjoyable session.  It is a really fine achromat!!  Very well corrected and a joy to observe with!  Can't wait to test it out on the planets this summer!!  I managed to split Sirius and Castor was a textbook perfect split with nice airy disks seen at high power.


Edited by barbie, 07 April 2019 - 09:11 PM.

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#30 memento

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Posted 08 April 2019 - 04:43 AM

With the AR-102L lens, the DPAC bars are railroad straight, but the two central bars thicken a bit towards the middle of each.  At 3 bars, only the center-line bar thickens -- yet there's no bowing in or out... Very strange.  I switched from the green to red LED, and the effect was more obvious -- but that could be the way my eyes respond to the color.

 

Since I've run all of my scope lenses through DPAC, I went back through the archives, and I found 2 lenses with similar "bubble middle" bars:  the vintage unknown maker 5" F5 triplet, and the 1956 Space Scope 151 60mm F15 (made by the predecessor to Astro Optical):

 

attachicon.gif DPAC - SS151 (OF) D01.jpg

I am by no means an expert in DPAC tests but what you describe as "thickening" looks to me that the bars are bended outwards just ever so slightly? Maybe they bend only in the center portion of the aperture, then the thing would have like "zones" but I am not sure if refractors ever have that. Anyway it could correspondend with the slight undercorrection that you already mentioned before?

 

Curious how the scope will measure up against your other 4" refracs if you get the chance for more comparisons.

 

I'm actually kind of interested into this by now. The really superior Starwave 102mm f/11 ED is still like 4 times the price of the Bresser. On the other hand I'm not sure if the Bresser would be a sensible upgrade to my Vixen 90mm achromat (which I'd never sell anyway). I could always keep my eyes open for a Vixen 90L (90/1300) as well. Again, not sure if 10mm aperture is really a difference worth to worry about. One thing I love about all those f/13 or longer refracs is how you can stay with long-ish f/l eyepieces, there's never any need for barlows or complex high-eyerelief eyepieces when observing Moon or the planets.


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#31 precaud

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Posted 08 April 2019 - 08:14 AM

Bob, is your Nikon a DSLR or some other with a long lens assembly? I find that cameras with short distance between the front lens and the CCD work best. The lens needs to get really close in to the eyepiece. I have several cameras that do really well; Fuji F30, Canon A530/A540/A550, Canon S30. They all have very compact zoom lenses with low distortion. The latter is an oldie but probably the best of them, with a nice large low-noise CCD designed before pixel mania took hold. You can pick up used working Canon A550's for $10-15 on eBay, and just use it for DPAC/collimation/flat fringe pics. Handily, it runs on AA batteries....


Edited by precaud, 08 April 2019 - 08:19 AM.


#32 Bomber Bob

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Posted 08 April 2019 - 08:17 AM

As a reminder:  Right now, I'm testing the scope as delivered -- I haven't made any changes / modifications to the OTA hardware.  (IMO, the owner of a brand new scope shouldn't have to!)  Also, the DPAC photos that I posted are from other refractors -- not this AR-102L.

 

Before I DPAC it again, I'll check the lens & cell, and see if there are any issues.

 

Right now, out of the box, this is a decent long frac with very good views of double stars & clusters.  But those aren't the best test objects; and, not the main reason I'd buy one of these living in town -- I want to see fine detail on the planets.  Then, I'll know if it's worth the price.


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#33 Astrojensen

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Posted 08 April 2019 - 10:24 AM

I'm actually kind of interested into this by now. The really superior Starwave 102mm f/11 ED is still like 4 times the price of the Bresser. 

???

 

The Bresser 102/1350 is 300 euro at TS; the Altair 102/1100 ED is 700 euro at Altair, so a little over twice the price, nowhere near four times. And both the optical and the mechanical quality is head and shoulders above the Bresser. The focuser is much bigger, the cell is all metal and adjustable, the dew shield is sliding, the tube is fully baffled, etc. 

 

I am astounded that they can sell the Altair at that price, frankly.

 

 

Clear skies!
Thomas, Denmark


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#34 BinoGuy

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Posted 08 April 2019 - 10:26 AM

Thanks BB.  Really looking forward to a planetary test.  I expect to pull the trigger this weekend, absent serious bad news.



#35 Bomber Bob

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Posted 08 April 2019 - 10:30 AM

I am astounded that they can sell the Altair at that price, frankly.

 

Maybe it's an un-advertised introductory price?


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#36 memento

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Posted 08 April 2019 - 10:44 AM

Oh I stand corrected. The 102/11 ED is 599 Pounds = 700 Euros, I thought it would be 100 Pounds more actually. Did they drop prices?

The Bresser is 259 Euros currently at TS.

 

And then it depends on where you live, how much the scopes will be when delivered to your doorstep.

 

I find it in both cases weird that these two scopes are not offered by all the big dealerships world-wide, like most others are.


Edited by memento, 08 April 2019 - 12:16 PM.

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#37 Astrojensen

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Posted 08 April 2019 - 12:47 PM

Oh I stand corrected. The 102/11 ED is 599 Pounds = 700 Euros, I thought it would be 100 Pounds more actually. Did they drop prices?

The Bresser is 259 Euros currently at TS.

 

And then it depends on where you live, how much the scopes will be when delivered to your doorstep.

 

I find it in both cases weird that these two scopes are not offered by all the big dealerships world-wide, like most others are.

The price today is the same as when I bought it. And yes, I find it to be a bit of a mystery, that the f/11 ED isn't offered by more dealers. TS, Stellarview and others already offer other scopes from the same manufacturer. Perhaps they think the interest would be low, but that's not what we're seeing here on CN. 

 

 

Clear skies!
Thomas, Denmark 



#38 memento

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Posted 08 April 2019 - 02:02 PM

TS, Stellarview and others already offer other scopes from the same manufacturer. Perhaps they think the interest would be low, but that's not what we're seeing here on CN.

Maybe TS first want to sell their stocks of those 102/11 Achromats – it's 499 Euros, down from 699 (which would be totally useless compared with the Altair ED). I am not sure if these scopes and the Altair ED are made by the same OEM?

 

https://www.teleskop...Dual-Speed.html

 

In contrast to the Bresser, I find that TS achromat offering now much less interesting. In my opinion, either go for the cheapest rig – which is the Bresser 102L – or directly aim for the Altair 102/11 ED. But maybe let's better wait for more observations from Bomber Bob first ...


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#39 Astrojensen

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Posted 08 April 2019 - 02:19 PM

 

In contrast to the Bresser, I find that TS achromat offering now much less interesting. In my opinion, either go for the cheapest rig – which is the Bresser 102L – or directly aim for the Altair 102/11 ED.

That would be my advice as well and I've also given it in other threads. The Altair ED essentially makes any 4" achromat that is close to its price completely irrelevant. The Bresser still has a nice niche, because it's so incredibly low priced. The price of the TS 102/1100mm achromat should be considerably reduced, if they want to sell it now. People aren't stupid and words of the Altair 102/1122 is getting around now. 

 

 

Clear skies!
Thomas, Denmark


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#40 BinoGuy

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Posted 08 April 2019 - 03:11 PM

Sure, it is niche because of the price... but that niche also translates in to practicality at the expense of quality of the views.  In this case I am primarily planning to use it for nighttime outreach (moon, Jupiter, maybe some asterisms) and solar CaK.  For EU217+shipping, well I'm more willing to risk it around children.

 

edit  she = sure  thanks autocorrect 


Edited by BinoGuy, 08 April 2019 - 03:30 PM.

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#41 Don Taylor

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Posted 08 April 2019 - 08:00 PM

The Altair ED essentially makes any 4" achromat that is close to its price completely irrelevant. 

 

 

Clear skies!
Thomas, Denmark

Thomas: I agree with your comment - although (as you know) I've had the Kunming 102 F11 Achro for some time. It's a fine scope. I chose it over the Synta 100 F9 ED because of the better mechanicals and potentially reduced Seidel aberrations, and I'm not particularly sensitive to CA.  However, I NEVER expected to see a relatively long focus ED scope like the Altair 102 F11 ED on the market.

 

The Altair ED improves further on an already nice scope.  Anybody wanna buy a nice 102mm Achro?


Edited by Don Taylor, 08 April 2019 - 11:01 PM.


#42 Bomber Bob

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Posted 08 April 2019 - 09:12 PM

Violet Fringe

 

Got lucky tonight when the center of a Gulf Low moved in before sunset, swept all the clouds away, and gave us great DSO seeing.

 

I started with the waxing crescent Moon.  Depending on the eyepiece, got the violet fringe along the limb at about 100x.  It was distracting with the UO HD Orthoscopics, but barely noticeable with the Nagler 7 and spectros Plossls.  I'll check back around First Quarter, when I usually see yellow fringe on the brightest parts of crater walls in my "shorter" achromatics.

 

Mars... Got a nice disk at 180x with the spectros PL7.5 -- sharper than the Nagler 7.  Just for fun, popped in the Radian 4.  I got a disk surrounded by a blue/red halo at 337x.

 

Switched to the 2" GSO dielectric diagonal, and my 2" Erfles & Plossls, and did some sweeping.  Picked out M35 at 0047Z (1947L), and M37 about 5 minutes later, both at 45x with ER30.  Not bad with the waxing Moon relatively close -- and not long after sunset, too.

 

So, false color is like my 4" F10, but will vary with diagonal & eyepiece types.  If you like lunar observing, I think you'll be happy with the resolution & contrast -- very nice along the terminator.  


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#43 barbie

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Posted 08 April 2019 - 10:32 PM

When I was observing with my Celestron/Vixen SP C102 the other night, I noticed that it was not that far behind my former SW Evostar 100 ED.  The Vixen had a better star test and stars at high powers were more round and more cleanly dispalyed than in my ED100 so I'm guessing that the C102 has better corrected optics. Just the very slightest hint of color was seen and it was not distracting at all.  So even though the C102 has a little color, spherical correction is better than my former ED100 and stars appeared to be sharper, especially at high magnification.  I will be comparing my SP C102 against my Bresser AR90L at some point in the near future.   I am expecting the SP C102 to beat it in terms of spherical correction at least. False color is VERY minimal on this fine Japanese achromat which I will never part with even  though I have two Tak fluorites now.


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#44 memento

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Posted 09 April 2019 - 04:05 AM

Violet Fringe

 

I started with the waxing crescent Moon.  Depending on the eyepiece, got the violet fringe along the limb at about 100x.  It was distracting with the UO HD Orthoscopics, but barely noticeable with the Nagler 7 and spectros Plossls.

 

Mars... Got a nice disk at 180x with the spectros PL7.5 -- sharper than the Nagler 7.  Just for fun, popped in the Radian 4.  I got a disk surrounded by a blue/red halo at 337x.


So, false color is like my 4" F10, but will vary with diagonal & eyepiece types.  If you like lunar observing, I think you'll be happy with the resolution & contrast -- very nice along the terminator.  

I would have thought false color would be less than with a 4" f/10. I got curious and ran the different apertures and f/l ratios through this Excel chart (APO calc) from a German site:

http://www.astro-oku...ses/apocalc.xls


That chart gives the relation between the diameters of the perfect spot (airy disc) and the spot size including the longitudinal CA in percent. A 80/1200 achromat would be my personal reference here as I owned one and found that one's color correction was virtually perfect for my eyes. (I understand others with better eyes will have more discerning demands on color correction.)

So here are some numbers I got for that spot size (with vs. without longitudinal CA):

 

144% => 102/1100 ED (yes, amazing good!)

199% => 080/1200

244% => 102/1350

251% => 090/1000

294% => 102/1000

 

So the Bresser should be virtually the same as a 90/1000 (that I currently own). And, yes, sometimes I find the false color on Moon distracting in my 90/1000, and tend to use quality Huygens/Ramsden eyepieces, which reduces it significantly. This matches your statement about the color correction of the Bresser above.


However, the longitudinal CA of a 102/1000 achromat should be significantly higher according to these numbers, so I am left wondering if the Bresser 102/1350 cannot beat this scope by some margin.

I often read about "quality" achromats that the longitudinal CA is said to be less than that of somewhat lower-quality ones. However my understanding is that all classic achromats, no matter if Towa, Vixen, Bresser, Synta, use the same glass pairings? So there should never be any significant difference in longitudinal CA if the aperture and f/l ratio are the same?


Edited by memento, 09 April 2019 - 08:14 AM.


#45 Bomber Bob

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Posted 09 April 2019 - 11:53 AM

I've been testing the Bresser as delivered and solo.  This weekend, I'll take it apart & check the hardware, and post about the internals.  

 

When the weather cooperates, I'll start setting the Bresser up along with either my Dakin 4" F10 or Edmund 4" F15 for Side-by-Side comparisons.  At this point, it's similar to the F10, which despite its false color, is an excellent refractor -- why I kept it.


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#46 Bomber Bob

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Posted 09 April 2019 - 07:40 PM

Bresser Break-Down (Dead Ahead)

 

Bresser AR-102L S17 (Components).jpg Bresser AR-102L S18 (Components).jpg Bresser AR-102L S19 (Components).jpg Bresser AR-102L S20 (Components).jpg

 

[Cue:  Boz Scaggs]


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#47 Bomber Bob

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Posted 09 April 2019 - 07:46 PM

"One word: Plastics."  --  The Graduate

 

The only metal in the lens cell & shade assembly are the 4 tiny screws that secure it to the tube.  The heavy 4" glass is held in by a thin threaded retaining ring.  Gray glue had been applied at points on the circumference, and at some point (probably during its trans-Atlantic voyage), a small area broke loose, and 2 threads slipped skyward.  So, the lens was not level within its cell during the 1st DPAC test.  I popped it back in, and tightened it.

 

I don't see any easy way to collimate the lens -- the 4 tiny screws have no slip room (unlike some old Japanese refractors).  There are no alignment marks on the lens edges, either.

 

It's a Baker, rather than Fraunhofer:  There's a 3mm black plastic band separating the 2 elements (my Dakin 4 is also a Baker design with a 7mm band / gap).  With that plastic band, I wouldn't have heard a "clink" while handling the lens cell.  I bet the crown tilted a bit during testing -- wouldn't take much to throw-off the DPAC.

 

I may remove the ring, put the lens cell on the DPAC, slowly rotate the crown until I get the best pattern, then mark the edges, and tape the elements to fix that alignment.  I've done that with other lenses, and it boosts performance -- sometimes by a large margin.

 

There are 3 baffles.  If I kept this scope, I'd flock both ends up to the last baffle facing the sky / focuser.  I may do that anyhow -- can really boost contrast.

 

On the plus side, the 2 extension tubes are well-machined, and the fit feels strong enough to hold my 2" diagonal & bino-viewer (though I wouldn't need that extra back focus).


Edited by Bomber Bob, 09 April 2019 - 08:25 PM.

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#48 precaud

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Posted 09 April 2019 - 08:47 PM

Try rotating the cell among the four screw holes. You may find a rotation that cancels the lens tilt. My C102GT was that way.

 

Either the OTA and is not cut off square, or the camera lens has bad distortion...



#49 Bomber Bob

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Posted 09 April 2019 - 09:14 PM

My Nikon curves the field in close-ups (DPAC patterns included).  The tube edge looks straight to me, but I'll check it.

 

I marked the tube & cell before I removed it for the 1st DPAC.  If the screw holes in the tube & cell allow other positions, I'll test that, too.

 

I'll get the lens elements aligned & set, and I'll do as much collimation as the OTA allows.  I should see a difference between as delivered & as corrected.  

 

If an inexperienced amateur bought this scope, I hope they'd check CN before discarding it.



#50 memento

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Posted 11 April 2019 - 04:23 AM

Yay. The design of that lens cell really isn't nice. I recall having read already in other reviews that especially the retaining ring is way too flimsy, exactly like what you report.

 

Still, I'm curious how good the scope will perform now that you adjusted the lens.

 

I even wonder if they should have made a version with a cheaper focuser, but a better lens cell instead. My reasoning is that folks who buy this, will mainly use it for what a long frac is good for – the Moon, planets, some DSO objects like maybe smaller open clusters and such. Then you might use smallish eyepieces anyway, and even really basic focusers will handle those without problems.

 

Also, if one wants to upgrade the scope, it's much easier to upgrade the focuser than to upgrade the lens cell.




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