20 replies to this topic

[KeithC]

Can a quality barlow give you as nice of an image as simply buying a longer focal length scope?  In other words, are there any obvious losses when using a barlow?  My only experience with them has been the very cheap ones included with 60mm refractors.  My scope is an F6 refractor and I've always enjoyed low power wide field of views.  Now I'm itching to up the magnification a bit but I despise tiny focal length eyepieces.  If this has already been answered then please just direct me to the thread or article.  Thanks!

[areyoukiddingme]

Short answer is yes when you have a quality barlow, which is easy to do today. Powermates are also worth a go as they don't change the eye relief of the eyepieces and produce a constant magnification factor independent of spacing, unlike barlows.

[T1R2]

It can, but if the scope is an achromat it will not change the fact that it has chromatic aberration (if that's what you're thinking to do) even though its a focal extender, the CA will still be there. Now if its an apo telescope and already well color corrected then it wont harm the image quality as long as the Barlow/ FX is of decent quality like an ES 2x FX or similar. 

 

If you don't like tiny 4mm orthos and Plossl's then I'd suggest an Astro-Tech Paradigm / BST Planetary 5mm or 3.2mm if you need that strength magnification, maybe even a TMB Planetary II clone in the FL you need for your scope without the Barlow/ FX  but those are of varying quality, some people think they're just fine and others have complaints of stray light if a bright object is near the outside field stop or light scatter halo around planets. 

 

Now you may even be able to find a used TMB PII that was sold by Astronomics (now discontinued)  and is a registered TMB that may be a little better quality than the Burgess TMB clones and the same price range I think they were about $60 when they first came out. 

 

But I think I would go with the AT Paradigm if it came down to it. See what magnification you need and then match that with the right FL EP they have or the right FL with a Barlow. 

[KeithC]

This is a color free ED Triplet.  Thanks for the suggestions!

[CrazyPanda]

Now I'm itching to up the magnification a bit but I despise tiny focal length eyepieces

 

DeLites and TOEs will reach the magnifications you want while maintaining some comfort in the process, without compromising quality in any significant way.

 

In theory a long native focal ratio is better for simple orthos and plossls than barlowing a short focal ratio telescope if you go by these spot diagrams:

 

 

I don't know what that means in terms of a telecentric though - because a telecentric does not have diverging light cones.

 

Many planetary observers swear by the 2.5x Tele Vue PowerMate.

[Mike W]

Also Radians can be found in the 3mm etc. range

[The Ardent]

Quality Barlow Powermate 

[PJBilotta]

If you have a color-free triplet, then Barlow away. There are so many excellent Barlows and telecentrics (Powermates) available now that deliver superb, higher-power views with your mid-power eyepieces, that's it's tough justifying the investment in short focal length eyepieces. A decent Barlow will turn a set of four eyepieces into eight, and you will never notice it's there.

I think it's wise to try out several Barlows, and you can do this affordably by picking them up here used. Some require a lot of refocusing when you insert them, and others are parfocal (meaning they require little to no refocusing).

I've tried perhaps a dozen. Televue, ES, Baader, Nikon, Celestron and more. All have been excellent and "invisible" when using them. I continue to be amazed at my 30-year-old Celestron Ultima shorty which weekly sells here for $50-$60. It's virtually perfect, and requires just a little bit of focus adjustment in my system.

Don't bother with a 3-4mm eyepiece you will rarely use. Get good mid-range 18-10mm eyepieces, and Barlow then when you need a closer look. You'll not regret it.

[Mike W]

Never liked barlows, go for Radians, Delos or Delite.

[Ernest_SPB]

In start topic we see wrong alternative: Barlow vs. long focal scope. Actual alternative is rather simple: Barlow vs. short focal eyepiece.

Edited by Ernest_SPB, 16 April 2025 - 02:03 AM.

[Jon Isaacs]

In start topic we see wrong alternative: Barlow vs. long focal scope. Actual alternative is rather simple: Barlow vs. short focal eyepiece.

 

I use Barlow's when I need more magnification than my 3.5 mm Nagler or 3.5 mm XWA provide.

 

Jon

Edited by Jon Isaacs, 16 April 2025 - 02:25 AM.

[russell23]

Can a quality barlow give you as nice of an image as simply buying a longer focal length scope?  In other words, are there any obvious losses when using a barlow?  My only experience with them has been the very cheap ones included with 60mm refractors.  My scope is an F6 refractor and I've always enjoyed low power wide field of views.  Now I'm itching to up the magnification a bit but I despise tiny focal length eyepieces.  If this has already been answered then please just direct me to the thread or article.  Thanks!

Yes - if it is a quality barlow.   One thing that a barlow will tend to do is improve the edge of field if the eyepiece is not sharp to the edge.  For example, in my 115mm f/7 EDT the 20mm XW is not sharp to the edge.  When I use the 20mm XW in the same scope with a 1.6x Nikon, 2.4x Dakin, or 3.0x TeleVue barlow it is sharp to the edge.

 

In your specific situation it would be helpful to know what eyepieces you are using or thinking about getting to use with your f/6 refractor. 

[dmgriff]

I do not know your eyepiece barrels and focal lengths, but, a 2.5in PowerMate or such may give you more focal length options than one new eyepiece.

Edited by dmgriff, 16 April 2025 - 03:50 PM.

[izar187]

Never liked barlows, go for Radians, Delos or Delite.

Or Pentax XW, or Vixen SLV, or TOE, or Siebert SS4.

 

There are lots of good short focal length longer eye relief options these days.

Far more, that are far easier to look thru, than those short ep's of yesterwhen.

Short zoom ep's too.

IMHO+E a modern short focal length ep or 2, is a good thing to have with a short focal length scope.

Edited by izar187, 16 April 2025 - 09:25 PM.

[Tropobob]

We all agree that the barlows provided with beginner-grade 60mm refractors are rubbish. 

 

However, the cheap ones from Amazon are much better.  I suggest buying one of these from a known brand such as Celestron, and seeing what U think.  

 

I have even stacked two 2x barlows on top of each other (probably gives 4x, but not sure) and had good results with a Morpheus eyepiece. 

[manolis]

Good quality barlows are practically invisible with the exception of the few rare nights of excellent conditions

where a low element high quality eyepiece married with an excellent scope will make a difference.

but a high quality eyepiece and scope with a high quality barlow will not be far behind.

even the lengedary zeiss II came with a barlow.

The 2.5 powermate should be in every eyepiece case if you can afford it.

just my opinion.

[Jon Isaacs]

Or Pentax XW, or Vixen SLV, or TOE, or Siebert SS4.

 

There are lots of good short focal length longer eye relief options these days.

Far more, that are far easier to look thru, than those short ep's of yesterwhen.

Short zoom ep's too.

IMHO+E a modern short focal length ep or 2, is a good thing to have with a short focal length scope.

 

It's more about the focal ratio than the focal length.  My scopes are mostly around F/5 so even with a focal length of 1500mm or more, I use 3.5mm eyepieces with a 2x Barlow and occasionally a 3x Barlow.  I use the 5mm and 3.5 mm as a pair, leaving the Barlow in place.  

 

With the Morpheus's, a 3x Barlow works nicely, the 12.5 mm = 4.2mm, the 9mm = 3 mm, the 6.7 mm = 2.2mm and the 4.8mm = 1.6mm.  

 

One nice thing about Barlows is that the magnification is a function of the spacing between the Barlow's optics and the focal plane.  That means, I can pull the eyepiece back and refocus and gain up to about 10% magnification...  

 

jon

[Highburymark]

I have an F/6 60mm ED, and use Delite 3mm, TOE 2.5mm and HR 2.4mm to ramp up the power. As someone who began stargazing with nothing more sophisticated than 6mm and 4mm Plossls to view the planets (your word ‘despise’ would be an apt way to describe the experience), each of these more modern planetary eyepieces is luxurious in comparison. Using a Delite 3mm is no different to any of the longer focal lengths. Barlows are great if you want to avoid forking out for a high-mag EP that won’t get much use, but there’s no reason to avoid dedicated 2.5-3mm eyepieces on the basis of comfort.

[Jon Isaacs]

I have an F/6 60mm ED, and use Delite 3mm, TOE 2.5mm and HR 2.4mm to ramp up the power. As someone who began stargazing with nothing more sophisticated than 6mm and 4mm Plossls to view the planets (your word ‘despise’ would be an apt way to describe the experience), each of these more modern planetary eyepieces is luxurious in comparison. Using a Delite 3mm is no different to any of the longer focal lengths. Barlows are great if you want to avoid forking out for a high-mag EP that won’t get much use, but there’s no reason to avoid dedicated 2.5-3mm eyepieces on the basis of comfort.

 

I use Barlows for several reasons..

 

-  To achieve magnifications beyond available eyepieces provide. 

 

-  To provide wide fields of view beyond what available eyepieces provide.  The 2.4mm HR, the 2.5 TOE are 42degree and 52 degree eyepieces, the 3 mm Delite is a 60 degree eyepiece.  A 2x Barlow with the 4.8mm XWA provides a 2.4 mm eyepiece with a 110 degree AFoV..   With my 12.5 inch, that's about 600x, narrow fields of view do not go well with manual tracking at high magnifications.

 

- To fine tune the magnification and fill gaps.   The gap between the 7mm and 5 mm Type 6 Naglers often falls right in the planetary magnification range.  In my 10 inch, that's 206x to 288x.   Barlowing the 13mm and 11 mm type 6 Naglers fills that gap with 222x and 262x magnifications.  The 13mm + 2x barlow can be "zoomed" to 244x simply by by pulling the eyepiece back.  

 

-  Taking advantage of the mild zoom effect as mentioned above.  

 

Jon

[sevenofnine]

I've found my ES 2x focal extender to be very transparent in the optic chain. It seems like it's almost not there. Good luck with your choice! 

 

https://agenaastro.c...w-fe02-125.html.

[Albie]

I would think that a powermate or any decent TeleXtender would be a nice alternative to a typical barlow . I have had a few barlows over the years such as the Celestron Ultima 2x , Antares 2x and the Televue 2x . The Meade 5000 2x TeleXtender is now my preferred way of extending the magnification of my ep's when needed , love how it maintains the eye relief .

Edited by Albie, 20 April 2025 - 09:40 AM.