Baader Zoom AFOV with Barlow?

[Ags]

Two things put me off the Baader Zoom: the sortest focal length is only 8 mm, and the AFOV at 24 mm is only 50°. It might be useful to me with the 2.25 barlow, but how does the barlow affect the AFOV of the zoom throughout its range?

[Stu]

26 minutes ago, Ags said:

Two things put me off the Baader Zoom: the sortest focal length is only 8 mm, and the AFOV at 24 mm is only 50°. It might be useful to me with the 2.25 barlow, but how does the barlow affect the AFOV of the zoom throughout its range?

My understanding (which could be wrong!) is that the afov remains unchanged by adding a barlow UNLESS there is any vignetting. I wouldn’t expect that to occur using the zoom as the afov is quite restricted already at the lower end. Not sure what the field stop is?

[Franklin]

I use the Baader MkIV zoom with the Hyperion x2.25 barlow and the AFOV remains the same.

[John]

The independently measured AFoV of the Baader 8-24 zoom is:

43.8° at 24mm
48.9° at 20mm
54.0° at 16mm
59.4° at 12mm
68.4° at 8mm

(source: Don Pensack's Eyepieces Etc website)

With the Baader Q-Turret 2.25x barlow I can see clear vignetting of the AFoV of the 24mm Panoptic (field stop diameter 27mm) but none with the 17.3mm Delos (F/S diameter 21.2mm).

My guess is that the field stop diameter of the Baader zoom will not be large enough to cause noticeable vignetting even at the 24mm setting.

[Franklin]

9 minutes ago, John said:

43.8° at 24mm
48.9° at 20mm
54.0° at 16mm
59.4° at 12mm
68.4° at 8mm

Those figures agree with my experience at the eyepiece. I think i read on the Baader site figures of 45deg-65deg for the zoom. Either way, when used with the x2.25 Hyperion zoom barlow giving approx. 10.5-3.5mm, the AFoV is unchanged from the BHZ native AFoV.

[Ags]

Combined with the barlow, it looks like an ideal addion to my Zenithstar 66. At its widest it would give 1° fov, and at narrowest it would give 109x magnification. How does it hold up at F6? I used to have fixed focal length hyperions and loved them in a Mak, hated them when I got fast refractors and newts.

[Franklin]

I like the Baader Zoom and barlow combi and use them regularly in my little 62mm refractor. Great for those impromptu solar white light views with the Lunt wedge and Continuum filter.

[Ags]

Actually, this new APM zoom looks a bit delumptious...

[Second Time Around]

4 hours ago, Ags said:

Combined with the barlow, it looks like an ideal addion to my Zenithstar 66. At its widest it would give 1° fov, and at narrowest it would give 109x magnification. How does it hold up at F6? I used to have fixed focal length hyperions and loved them in a Mak, hated them when I got fast refractors and newts.

The Hyperion zoom can be used in much faster scopes than the fixed focal length Hyperions.  I use mine at f/4.8.   

Check out author Bill Paolini's review at https://astronomyconnect.com/forums/articles/the-baader-hyperion-mark-iv-zoom-eyepiece-a-performance-review-with-monoviewing-and-binoviewing.66/

Here's Bill's summary:

"Over the course of testing the Baader Hyperion Mark IV Zoom, the eyepiece showed itself to be a capable and potent observing tool. Optically it provided a bright, high contrast, and controlled view that allowed it to keep up with even premium wide-field eyepieces like the Pentax XWs. Although its Abbe Orthoscopic-like AFOV at the longer focal lengths may be too restrictive for some observing situations, its wide field performance at the shorter focal lengths and its flexibility to perform the function of several eyepieces make it a powerful accessory for any telescope. Its smaller form factor, lighter weight, and zooming function also demonstrated it to be an ideal binoviewing eyepiece, especially when used for lunar observing as it can replace multiple sets of fixed-focal-length eyepieces. The Mark IV also demonstrated that it can be part of a minimalist set of eyepieces for any telescope — especially if accompanied by a 2" 25-35mm wide field for scanning and finding and a 2x or 3x Barlow. Finally, the very smooth action of the Mark IV's mechanics, its quality build, and its range of optional adapters for photography and spotting scopes, and its excellent off-axis performance even in a fast f/4.7 Dobsonian makes it a truly unique and effective astronomical eyepiece."

[Ags]

Thanks for that, it's an interesting read.

[Ricochet]

 

Quote

 

Optically it provided a bright, high contrast, and controlled view that allowed it to keep up with even premium wide-field eyepieces like the Pentax XWs

 

 

Quote

excellent off-axis performance

As someone who owns both XWs and a BHZ, I disagree with both of these points. Where the BHZ excels is when you want a quick grab and go session with only a couple of eyepieces in your pocket. If you're going out for an extended session with a case full of eyepieces the premium fixed focal lengths are superior, revealing more detail and having a higher optimum magnification than the BHZ.

[Ags]

Astronomy may be a science, but looking through an eyepiece is an art!

To be honest, one would surely expect the XWs to beat the Baader Zoom at every individual focal length. What I take from Bill Paolini's review is not the absolute performance of the Zoom versus the XWs, but that the Zoom apparently provides a pleasant and unobjectionable view, solidly "good enough" for regular use. If I want top drawer performance, I have my collection of SLVs and NLVs, and if I want wide-field I have some perfectly serviceable ultrawides. The zoom would step in when I want the ability to change magnification and exit pupil frequently. The convenience means I am more likely to be using the optimal magnification, which can counterbalance a small lack in pure optical performance.

[Ags]

I think I am going to try a Hyperflex 7.2-21.5 zoome next year to see if zooms suit me. If it does, I may or may not upgrade to the Baader. Also looking forward to the first reviews on the APM 75 degree zoom.

[Second Time Around]

On 27/11/2021 at 20:28, Ags said:

Astronomy may be a science, but looking through an eyepiece is an art!

To be honest, one would surely expect the XWs to beat the Baader Zoom at every individual focal length. What I take from Bill Paolini's review is not the absolute performance of the Zoom versus the XWs, but that the Zoom apparently provides a pleasant and unobjectionable view, solidly "good enough" for regular use. If I want top drawer performance, I have my collection of SLVs and NLVs, and if I want wide-field I have some perfectly serviceable ultrawides. The zoom would step in when I want the ability to change magnification and exit pupil frequently. The convenience means I am more likely to be using the optimal magnification, which can counterbalance a small lack in pure optical performance.

The only XW I've owned was the 20mm.  I didn't directly compare it at night with the BHZ as I rarely use the latter at 20mm.  Rather I normally use it at 8-16mm plus at 24mm.

However, despite having high quality fixed focal length eyepieces,  I use my Baader zoom a lot more often.  The zoom plus a Barlow lens and a low power, wide field eyepiece is often all I use the whole evening. 

I have several Barlows of different powers.  The one I use the most is a dual 1.5/2x, and most nights the 1.5x is best matched to the seeing conditions.  

Additionally, at a given magnification the field of view will be bigger with 1.5x amplification.  This is because the vast majority of zooms have a wider field of view at the high power end.

I agree with AGS.  Fixed focal length eyepieces may be slightly better corrected when compared with a zoom at the same magnification.   But that's not always a fair comparison as that magnification may not be the optimum for a given object.  This is because one of the many advantages of a zoom is to be able to dial in precisely the best focal length.  For instance, this may be 13mm or even 13.1mm, which may actually show more detail than shorter or longer fixed focal length eyepieces - even better quality ones.

I particularly like the ability to increase the magnification to make use of brief moments of good seeing (a steady atmosphere).  It takes more time to swap out an eyepiece, and the opportunity may then be missed.  You can't see anything if you haven't got an eyepiece in the focuser!

Having said that, I also agree with Ricochet that there's a place for high quality fixed focal length eyepieces.  There's not much difference on axis, but it becomes apparent as you look away from the centre of the field of view.  So it depends on what object you're looking at.

Ernest Maratovich in Russia does lab tests on eyepieces.  This is the text taken from a review of a Mk IV Baader zoom (not the earlier used Mk III he described as "battered").  This is how Ernest described the image quality:

"Based on the results of star observations under conditions of a 1: 5 apochromat. {i.e. at f/5}

At all focal lengths, the main field aberration is the curvature of the field of view. Curvature is more pronounced at long focus - reduces image contrast from about 60% of the field of view. At a short focus, the curvature is noticeable only in a relatively narrow (20%) band adjacent to the edge of the field of view. In the center of the field of view, image quality is limited only by defects in the observer's eyes. There is no glare. Light scattering is negligible. Distortion is not striking. When changing the focal length (the effort is quite adequate, there is a soft lock at 5 values), the focusing goes away quite a bit, but you still need to refocus."

[Ags]

To be clear, I would only use the zoom for high mags only, either barlowed to split doubles in my frac, or at its native focal length in the SCT for planetary.

[Spile]

The big advantage of the BHZ for me is not having to second guess as to the ideal magnification for a given target. The convenience is a big plus for me and having the matching Barlow for planetary view provides the icing on the cake.

[Splodger]

On 29/11/2021 at 13:56, Spile said:

The big advantage of the BHZ for me is not having to second guess as to the ideal magnification for a given target. The convenience is a big plus for me and having the matching Barlow for planetary view provides the icing on the cake.

Hi there. I have just purchased both the zoom and the Barlow. Baader claim that the Barlow is matched to the zoom and will give better performance than the BHZ with another Barlow - in my case a 2x Tele Vue. Please bear in mind that I cannot test this out myself as I live in Portland, OR and the 10 day forecast is for rain. I am considering returning the barlow and just sticking with the Tele Vue if there is no performance benefit over the Tele Vue. Also i'm concerned that it's going to be a bit fiddly unscrewing the Barlow in the dark. Any thoughts?

[Don Pensack]

19 hours ago, Splodger said:

Hi there. I have just purchased both the zoom and the Barlow. Baader claim that the Barlow is matched to the zoom and will give better performance than the BHZ with another Barlow - in my case a 2x Tele Vue. Please bear in mind that I cannot test this out myself as I live in Portland, OR and the 10 day forecast is for rain. I am considering returning the barlow and just sticking with the Tele Vue if there is no performance benefit over the Tele Vue. Also i'm concerned that it's going to be a bit fiddly unscrewing the Barlow in the dark. Any thoughts?

Baader is interested in selling Baader accessories.  The Baader Zoom works fine fine many different Barlows, the TeleVue among them.

[Spile]

23 hours ago, Splodger said:

Hi there. I have just purchased both the zoom and the Barlow. Baader claim that the Barlow is matched to the zoom and will give better performance than the BHZ with another Barlow - in my case a 2x Tele Vue. Please bear in mind that I cannot test this out myself as I live in Portland, OR and the 10 day forecast is for rain. I am considering returning the barlow and just sticking with the Tele Vue if there is no performance benefit over the Tele Vue. Also i'm concerned that it's going to be a bit fiddly unscrewing the Barlow in the dark. Any thoughts?

Unscrewing or screwing in the Barlow hasn’t been a problem for me. It is something I can do in the dark quite easily. As you may have read in here and on my blog, I prefer to keep it in 2” mode.

[Splodger]

8 hours ago, Don Pensack said:

Baader is interested in selling Baader accessories.  The Baader Zoom works fine fine many different Barlows, the TeleVue among them.

Thanks Don. I think I’ll send the kit back to B&H and order the zoom by itself.