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New Hot > APM 1.25" ED comacorrected Barlow 2.7x

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#1 APM M.Ludes

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Posted 11 June 2012 - 02:37 PM

APM comacorrected 1.25" ED Barlow 2.67 x, designed by Gerd Düring/Germany. The Barlow use the chinese ED Glas FK61 ( similar to Ohara FPL51), has blackenededges, a measured transmission von over 99% from 400 nm to 700 nm, optimized for F/4 Newtonian-Telescopes. The barlow has a negative focal length of - 62.9 mm and a working backfocuse of 105 mm from center last lens to focuse ( eyepiece field stop). You will need now a 1.25" eyepiece holer 104 mm long

Barlow-Element in screw in housing US $ 95
Barlow with nice eyepieceholder US $ 149

On Stock now

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#2 BillP

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Posted 11 June 2012 - 04:12 PM

Markus,

Is this a doublet or triplet like the old Klee. Air spaced or all cemented?

Would you have a pic of one mounted in the eyepiece holder?

#3 BWAZ

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Posted 11 June 2012 - 05:29 PM

What is the spec for the thread? Is it 1.25" filter-thread compatible?

#4 APM M.Ludes

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Posted 13 June 2012 - 10:38 AM

Hi Bill

1, its a doublet but thanks to the used real ED-Glas its apochromatic

2, its airspacest

3, we mashcine the holder now,takes around 1 week , then I post it

#5 APM M.Ludes

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Posted 13 June 2012 - 10:38 AM

it has both sides standart filter thread M28.4

#6 suburbanskies

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Posted 26 June 2012 - 05:28 PM

Markus, how sensitive is this barlow to spacing? Would it be possible to use on a binoviewer for a Dob? Any idea how much backfocus it would use?

#7 APM M.Ludes

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Posted 27 June 2012 - 02:00 PM

it is not sensitive at all for spacing.
It works also a perfect optical path corrector and almost fully compensate the optical path of the binoviewer

#8 APM M.Ludes

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Posted 28 July 2012 - 04:05 AM

Designed by Gerd Duering / Germany

Due Forum discussions pushed, Gerd Duering in Germany designed a new, improved coma corrected ED-Apochromatic Barlowlens, optimized for parabolic mirrors with f-ratio f/4. But it works also as a super high quality Apo Barlow in any other normal Telescope.

This Barlow uses as ED-element the Chinese ED glas FK61 (similar to Ohara FPL51), the lenses are soft cemented and applied on both sides with a broadband multicoating with over 99 % transmission for wavelength from 400 nm to 700 nm.

The optimal backfocus is 105 mm from center of the last lens. The focal length of the barlow is - 62.9 mm, the clear aperture 22 mm.

This barlow offers with its 22 mm aperture in secondary focus a 100 % illuminated photo-visual field of 30 mm diameter when used with 105 mm backfocus.

The 2-part adapter is photo-visual optimized, visual with the optimal backfocus of 105 mm with the new APM-Deluxe Centering Brass-Clamp. This top Deluxe adapter has a length of 55 mm and can be unscrewed, than you get a photographic T2 thread (M42 x 0.75 mm) for use with DSLR with T2 adapter ring.

This Barlow increase the diffraction limited field of view and imaging circle of your fast newtonian and dobsion very much. Observe the planets in your eyepiece at a off axis position with identical image quality as in center of the eyepiece. Observe Double Stars at the edge of your eyepiece Field with same resolution as in center. Observe Galaxies and Planetary Nebulae and galaxie fields all over the eyepiece field with same sharpness. If you have a fast Dobsonian in which Gobuar clusters like M13 or Omega Centauri cover the full eyepiece field, see with this barlow the globular resolution towards the eyepiece edge with same sharpenss as in center.
The edge distorion even in modern Tele Vue eyepieces is reduced to a level you will not see in even 2,3,4 times more expensive barlowlenses.

To my knowledge it is worldwide the only 1 Barlowlens using a expensive ED Glas to archieve apochromatic correction.

First results with the ED-Barlow has been amazing!


Delivery contains:

1 1/4" ED-Barlow Element
2-part Adapter

Barlow-Element in screw in housing US $ 95 > in stock
Barlow with nice 1 pc eyepieceholder US $ 149 > in stock

Barlow with 2 part adapter, see drawing attached US $ 149 > 1,2 weeks delivery time

we ship worldwide for $ 20 include insurance

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#9 APM M.Ludes

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Posted 02 August 2012 - 03:16 PM

the users feedback reporting one of the best barlowlenses ever made , we have them in stock, include the new adapters

#10 APM M.Ludes

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Posted 17 August 2012 - 01:29 PM

I read the discussion on the eyepiece forum where I cannot answere.
1, the Barlow is Apochromatic
2, the Barlow is comacorrected to a image circle of 30 mm
3, the coma correction was tested on the bench
4, the coma correction was tested at artifical stars
5, the coma correction was tested on stars by images

on Top to this writing on the forum " If it really corrects for the coma in a F/4 Newtonian, then it must add coma to a scope that is free from coma"

this statement is correct, but need some additional info: The barlow adds in a coma free telescope like a 4"F/8 Apo the same amount of coma a 4"F/8 newtonian has and thats almost invisible.

On Top, compare this new barlow to any other barlow in your hands , not only on Newtonians but also on apos and see how well our barlow is even corrected there against non coma corrected barlowlenses.
The reason for this is the design and the real ED Glas. To my knowledge there is no other barlow on the market which use real ED glas only the FFC which is not named to be a barlow.

So try to read the german forum http://forum.astrono...nde_#Post923634

or go out and compare it at your scope against others. We have no reason to claim its comacorrected , if it would not be the case, we are not foolish

#11 BillP

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Posted 17 August 2012 - 06:23 PM

Markus,

Received the the Barlow...thanks! Built like a tank :) I was skeptical that unscrewing the small Barlow housing and putting that directly onto the eyepiece would work well..was worrying that there would be some vignetting. However, there was not...nice and clean with no vignetting even in my 14XW.

FYI, the stated magnification was spot on. My bench test showed it operates at 2.7x. Placing the Barlow elements directly onto the barrel of the 14XW yielded a 1.5X Barlow magnification. Nice that it can work in both modes. For fun, I took the Barlow housing off of a GSO 2x I have and put yours in its place. With the length of the GSO's housing your lens set operates at 2.1x. So have lots of flexibility.

Btw, I evaluated how its magnification increases and decreases by distance offset from the shoulder of the visual housing you supplied. It operates at Magnification = 0.016x + 2.7, where "x" is the offset distance in millimeters.

Thx!

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#12 ///^**^\\\

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Posted 18 August 2012 - 01:45 AM


Of course there is a change in mag. with a change in spacing but is there any change in the performance of the coma correction by changing the spacing by screwing the barlow directly to the eyepiece. Or even with the mentioned GSO barlow housing how well does the coma correction elements of the Barlow tolerate different spacings.

#13 BillP

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Posted 18 August 2012 - 04:57 PM

That is a valid point and something to assess. However, the formula I posted is VIP if you are a planetary observer and you Barlow because where the field stop is placed in the eyepiece related to the shoulder of the eyepiece varies quite a bit. I have some eyepieces where the field stop is more than 10mm offset, so theses eyepieces will produce 2.86x instead of 2.7x. These small differences can cause all kinds of mis-assessments when deciding on two eyepieces for your planetary use.

A 12T4 is a good example as its field stop is offset almost 20mm! So a 12T4 used with this APM Barlow means the field stop is 20mm below the shoulder of the Barlow, decreasing its magnification from 2.7x to 2.38x, so it becomes an effective 5mm eyepiece instead of the expected 4.4mm. So this combination in my XT10 would produce 240x instead of the expected 272x if I assumed 2.7x. Quite a difference!

#14 suburbanskies

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Posted 18 August 2012 - 08:11 PM

Of course there is a change in mag. with a change in spacing but is there any change in the performance of the coma correction by changing the spacing by screwing the barlow directly to the eyepiece. Or even with the mentioned GSO barlow housing how well does the coma correction elements of the Barlow tolerate different spacings.


According to the designer, the range that still provides "good" image quality is 2.1x to 3.5x. Even if you disagree with what is considered good, the range appears wide.

Mark

#15 BillP

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Posted 29 August 2012 - 08:57 PM

I agree. I set it at approximately 2.15x and got good results...less than that and the off-axis developed FC and astigmatism in the outer 25-33%. At 2.15x I had just a very very slight amount of FC right at the field stop. And btw, I did verify with observations that it did indeed clean up the coma when using my 10" f/4.7. At 2.7x there was not substantial coma visible in the off-axis of my 20mm XW given it had a 2.7x Barlow under it, but a conventional 2.7x Barlow showed some slight coma and the APM had none. Even down the the 2.2x operating range it showed no coma (the TV 2x which operates at 2.1x showed lots in the outer 33% of the FOV).

#16 APM M.Ludes

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Posted 05 September 2012 - 10:36 AM

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in stock for any day shipping at APM

#17 APM M.Ludes

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Posted 23 September 2012 - 05:11 PM

the barlow was the hot Item at our last weekend starparty in many Dobs. Customers could move Jupiter across the FOV and see everywhere the same details

a must for dob owners

#18 APM M.Ludes

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Posted 11 October 2012 - 02:56 PM

more and more customers buy and like it, if you have any type of Newtonian, its a hot item improving your telescope performance a lot

#19 APM M.Ludes

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Posted 15 November 2012 - 04:02 PM

this Apochromatic Barlow is available from stock !!!!

#20 Doug Culbertson

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Posted 15 November 2012 - 04:24 PM

Markus, have you tried this barlow with the Leica ASPH zoom? If so, any vignetting or other issues noted?

Thanks

#21 APM M.Ludes

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Posted 16 November 2012 - 06:37 AM

Hi Doug

yes I did , no vigneting issues, but the focallength of the barlow is 105 mm and attaching it to the Leica , means it works with much lesser backfocuse, so I see quality reduction of course, so I do not advise to use it such way

#22 Doug Culbertson

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Posted 16 November 2012 - 11:17 AM

Thanks Markus!

#23 APM M.Ludes

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Posted 08 December 2012 - 03:35 PM

the coma correcting barlow is avilable from our stock, we can ship any day you order

#24 Sunspot

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Posted 08 December 2012 - 09:21 PM

Markus,

I am envisioning using a barlow like this with my Mewlon 250 and Flea3 webcam for planetary imaging. Your 1.8x I have works with a lot of extension tubes (but is perfect for my C14). This should eliminate that need. Does that sound right? Also, as I mentioned when we talked in Tucson I'm really hot to get your new 152mm ED doublet next year for dedicated solar. This barlow should give me sufficient amplification for killer sunspot images! Does that sound reasonable to you?

Thanks!!
Paul

#25 APM M.Ludes

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Posted 09 December 2012 - 02:17 AM

Hi Paul

2 times YES to your question






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