APM 7.7 to 15.4 mm Zoom - initial review

[Second Time Around]

I've only had a little time with my APM Super Zoom but here are my preliminary thoughts, including compared with my Mk IV Baader Hyperion zoom.

I bought the APM as it specifies that it accepts a Dioptrx astigmatism corrector, and supposedly is parfocal.

It may be parfocal to those with younger eyes but at f/6 is only so for me from 7.7 - 12mm.  As a comparison my Baader zoom is also parfocal from 8-12mm - so exactly the same.  It's just that the Baader goes up to 24mm compared with only 15.4mm for the APM.

On behalf of Marcus Ludes of APM I sent my spare Dioptrx to the makers KUO in China.  On receiving my Super Zoom I initially thought that a Dioptrx wouldn't fit because of the additional 37mm thread above the 43mm thread.  However, it does so if you add a Baader 43 x 0.75 mm extension, or better still a 43 to 42mm step down ring.  To allow the fit to be secure and yet still enable the Dioptrx to be adjusted, an O-ring is needed with the former but not the latter.  So many thanks, Marcus!

Unlike the Baader, the eyelens doesn't rotate when zooming.  This is inconvenient when using a Dioptrx, and downright fiddly and time consuming when using 2 of them with binoviewers.  So another plus for the APM.

There's not quite enough eye relief for me to see the full FOV (field of view) with a Dioptrx attached, so I'm perfectly happy with a reduction to an almost constant 66 deg rather than the initial spec of 75 deg.  This may be the reason I didn't notice any EOFB (edge of field brightness).

The apparent FOV is just less than the Baader at the shortest focal length, but (like most zooms) the Baader reduces rapidly at lower powers.  Indeed, the APM has a wider actual FOV at 15.4 mm than the Baader does at 24mm.

Unlike the Baader, there is some AMD (angular magnification distortion).  However, this isn't a problem for me, partly again because of not being able to quite see the full FOV, and partly because I don't sweep with this eyepiece.

Sharpness and contrast are at least as good as the Baader but I need to do some further testing here, including on my f/4.8 Dob.

The zoom action is beautifully smooth, and I love the 7 intermediate click stops.

It's a dual 1.25 and 2 inch eyepiece.  However, as noted by others it needs extra infocus when used in the 1.25 inch configuration.  The location of the focal plane may be the reason that I measured that my Barlows amplify more than their specs suggest, especially with the APM used as a 1.25 inch.

To sum up, I'm very pleased with this eyepiece, and it's almost certain that the APM is going to replace the Baader zoom as my workhorse eyepiece.

So thanks again, Marcus!

Edited November 7, 2022 by Second Time Around

[Louis D]

Good report.  A little disappointed to hear that even with a Dioptrx you can't see the entire FOV.  BTW, did KUO ever send your test Dioptrx back to you?

I'm surprised you needed only 8mm of additional in-focus in 1.25" mode.  Looking at the diagram below, I figured it to be much more than that.

The diagram showed it would be closer to 32mm inward from the 1.25" shoulder, or 24mm inward of the 2" focus position.  Did the housing get significantly changed or did the focus point end up somewhere between the 1.25" and 2" shoulders instead of 8mm above the 2" shoulder?

[Don Pensack]

I interpreted his remarks to mean 8mm in travel in 2" mode, i.e. with a typo.

Because 1.25" should require 32-8 = 24mm more in travel than in 2" mode which itself focuses 8mm in from the focal plane of the scope (even more in travel needed, when adding the height of the adapter).

A lot of people have been unable to use the eyepiece in 1.25" mode.

 

[badhex]

9 hours ago, Second Time Around said:

I've only had a little time with my APM Super Zoom but here are my preliminary thoughts, including compared with my Mk IV Baader Hyperion zoom.

I bought the APM as it specifies that it accepts a Dioptrx astigmatism corrector, and supposedly is parfocal.

It may be parfocal to those with younger eyes but at f/6 is only so for me from 7.7 - 12mm.  As a comparison my Baader zoom is also parfocal from 8-12mm - so exactly the same.  It's just that the Baader goes up to 24mm compared with only 15.4mm for the APM.

On behalf of Marcus Ludes of APM I sent my spare Dioptrx to the makers KUO in China.  On receiving my Super Zoom I initially thought that a Dioptrx wouldn't fit because of the additional 37mm thread above the 43mm thread.  However, it does so if you add a Baader 43 x 0.75 mm extension, or better still a 43 to 42mm step down ring.  To allow the fit to be secure and yet still enable the Dioptrx to be adjusted, an O-ring is needed with the former but not the latter.  So many thanks, Marcus!

Unlike the Baader, the eyelens doesn't rotate when zooming.  This is inconvenient when using a Dioptrx, and downright fiddly and time consuming when using 2 of them with binoviewers.  So another plus for the APM.

There's not quite enough eye relief for me to see the full FOV (field of view) with a Dioptrx attached, so I'm perfectly happy with a reduction to an almost constant 66 deg rather than the initial spec of 75 deg.  This may be the reason I didn't notice any EOFB (edge of field brightness).

The apparent FOV is just less than the Baader at the shortest focal length, but (like most zooms) the Baader reduces rapidly at lower powers.  Indeed, the APM has a wider actual FOV at 15.4 mm than the Baader does at 24mm.

Unlike the Baader, there is some AMD (angular magnification distortion).  However, this isn't a problem for me, partly again because of not being able to quite see the full FOV, and partly because I don't sweep with this eyepiece.

Sharpness and contrast are at least as good as the Baader but I need to do some further testing here, including on my f/4.8 Dob.

The zoom action is beautifully smooth, and I love the 7 intermediate click stops.

It's a dual 1.25 and 2 inch eyepiece.  However, as noted by others it needs extra infocus when used in the 1.25 inch configuration.  I measured this as approx 8mm.  The location of the focal plane may be the reason that I measured that my Barlows amplify more than their specs suggest, especially with the APM used as a 1.25 inch.

To sum up, I'm very pleased with this eyepiece, and it's almost certain that the APM is going to replace the Baader zoom as my workhorse eyepiece.

So thanks again, Marcus!

Great review for a great EP. I cannot use it in 1.25" mode with my TS102 but can't remember if I've tried it with my ZS73. I also noted the AMD but didn't find it to be intrusive as I'm not doing large sweeps with it. 

[Second Time Around]

My apologies over the 8mm figure.  This was a last minute addition to the review from my original notes.  I seem to have forgotten to take into account the adapters I was using and can't remember what I did use.

The testing was done on my Altair 72mm f/6 EDF.  Mine is an earlier version with 97mm of focal adjustment, so no problems with infocus.

I'll delete the 8mm figure.

[Second Time Around]

10 hours ago, Louis D said:

Good report.  A little disappointed to hear that even with a Dioptrx you can't see the entire FOV.  BTW, did KUO ever send your test Dioptrx back to you?

Whether the full field of view can be seen with a Dioptrx will vary from observer to observer, depending on the shape of the face, especially that of the eye sockets.  My eye sockets are small and deep, so I can't see the full FOV in a lot of eyepieces that aren't a problem for others.

I wasn't expecting it, but yes I did get my spare Dioptrx back from China via APM.

 

[Second Time Around]

One of the things I wanted to highlight was that the APM zoom certainly isn't parfocal to me, and in fact is no more so than the Baader Mk IV in the low focal length range (up to 12mm).

The Baader is often criticised for this, but my observations suggest perhaps unfairly.

It would make sense that parfocality is easier to achieve in a 2x zoom (like the APM and the Leica) than in the far more common 3x zooms (Baader and many others).

Whether a zoom is parfocal or not depends very much on the observer, with older ones like me usually having more of a problem.

I'm therefore going to be doing some more testing, including at the longer eyepiece focal lengths and also with my f/4.8 Dob, plus different Barlow lenses.  The latter seem to improve parfocality, especially those with higher amplification, but I want to record just how much.

In the meantime I'd welcome comments and findings from others.

 

[badhex]

17 minutes ago, Second Time Around said:

One of the things I wanted to highlight was that the APM zoom certainly isn't parfocal to me, and in fact is no more so than the Baader Mk IV in the low focal length range (up to 12mm).

The Baader is often criticised for this, but my observations suggest perhaps unfairly.

It would make sense that parfocality is easier to achieve in a 2x zoom (like the APM and the Leica) than in the far more common 3x zooms (Baader and many others).

Whether a zoom is parfocal or not depends very much on the observer, with older ones like me usually having more of a problem.

I'm therefore going to be doing some more testing, including at the longer eyepiece focal lengths and also with my f/4.8 Dob, plus different Barlow lenses.  The latter seem to improve parfocality, especially those with higher amplification, but I want to record just how much.

In the meantime I'd welcome comments and findings from others.

 

I also do not find it to be parfocal. It's not miles off especially if I focus at 7.7mm then back out, but it requires at least some tweaking across the range for me. 

[HollyHound]

On 07/11/2022 at 10:43, Second Time Around said:

One of the things I wanted to highlight was that the APM zoom certainly isn't parfocal to me, and in fact is no more so than the Baader Mk IV in the low focal length range (up to 12mm).

 

On 07/11/2022 at 11:01, badhex said:

I also do not find it to be parfocal. It's not miles off especially if I focus at 7.7mm then back out, but it requires at least some tweaking across the range for me. 

I have also found it isn’t parfocal, but it only requires a very small tweak from one end to the other, and when changing a few clicks either way it’s perfectly fine 👍

It’s proving to be a great zoom and now lives permanently in my grab and go FC-76DCU 😀

[HollyHound]

On 07/11/2022 at 06:02, Don Pensack said:

A lot of people have been unable to use the eyepiece in 1.25" mode.

Agreed 👍

On my grab and go FC-76DCU, I have a T2 extension ring in place for my other eyepieces (ES 24 and Nagler Zoom 3-6), which I can remove for the APM (in 1.25”) and thus achieve focus. However, then I can’t swap to those either eyepieces without having to insert an extension ring again 😬

My solution is to use the APM Zoom in 2” mode, keep the extension ring in place, and pop the Baader 2” to 1.25” Clicklock adaptor into the 2” Clicklock when using those eyepieces… plenty of focus range then to use all eyepieces.

These three eyepieces now cover all I need for grab and go 😀

Also with the addition of that M43 extension on top of the zoom, I’ve been able to fit the adjustable eyepiece top from the Hyperion Zoom and allows me to adjust for eye relief… when screwed fully down it would allow glasses use without danger of scratching 🤔

Unfortunately, these are only available with the Hyperion Zoom and not separately… fortunately I prefer the supplied fixed narrower eyepiece top when using my two Hyperion Zooms in the binoviewer.

Edited November 9, 2022 by HollyHound

[Westmoorland]

I've just become aware of this new eye piece. It's close click stops seem a lot more useful for pushing detail out of planets than the Baader mk 12: the latter's gap between 8x and 12x put me off, as well as lack of eye relief. I'm currently awaiting delivery of a Masuyama 32mm as my first low power piece and might get the APM zoom next to get going with my C9.25 which so far I've only used with a Morpheus 14mm.

[Stu]

4 hours ago, Westmoorland said:

I've just become aware of this new eye piece. It's close click stops seem a lot more useful for pushing detail out of planets than the Baader mk 12: the latter's gap between 8x and 12x put me off, as well as lack of eye relief. I'm currently awaiting delivery of a Masuyama 32mm as my first low power piece and might get the APM zoom next to get going with my C9.25 which so far I've only used with a Morpheus 14mm.

I know click stops are convenient and allow you to know which focal length you are using, but with my Nag zoom I just put it wherever the best/optimum view is regardless of the click stops.

The APM is intriguing and I’m sure the constant afov is a nice feature. My Leica is roughly 60 degrees up to 80 at the shorter end so pretty wide for a zoom but it would still be nicer if it stayed wider all the way through the range.

As for parfocality, I confess I’ve never seen it as a huge issue. I always refocus when changing eyepieces anyway, just to check it is bang on, and I read somewhere that your eye prescription affects whether a zoom stays parfocal or not; they never have for me and I just accept that.

[Louis D]

Complete nonparfocality as in my Speers Waler 5-8mm zoom is a huge pain.  It's impossible to dial in the best magnification in real time because you have to zoom, focus, zoom, focus, etc.  I've tried zooming while focusing simultaneously without much success.  It would have been nice if Glenn had invested more effort in the mechanicals to include some cams to maintain focus while zooming as with camera zoom lenses.

[Stu]

1 hour ago, Louis D said:

Complete nonparfocality as in my Speers Waler 5-8mm zoom is a huge pain.  It's impossible to dial in the best magnification in real time because you have to zoom, focus, zoom, focus, etc.  I've tried zooming while focusing simultaneously without much success.  It would have been nice if Glenn had invested more effort in the mechanicals to include some cams to maintain focus while zooming as with camera zoom lenses.

True enough, yes.

[Zermelo]

6 hours ago, Stu said:

The APM is intriguing

is "intriguing" Stu-speak for "I haven't bought it yet" ?

[Stu]

40 minutes ago, Zermelo said:

is "intriguing" Stu-speak for "I haven't bought it yet" ?

Yes! 🤣🤣🤣

[Alan White]

1 hour ago, Zermelo said:

is "intriguing" Stu-speak for "I haven't bought it yet" ?

That made me chuckle and I can see where you picked up on this....

19 minutes ago, Stu said:

Yes! 🤣🤣🤣

And nothing like an admission of temptation in aswere, made me grin as well.


Oh how we all cannot help ourselves when it comes to kit!

[John]

I'd love to try the APM zoom but I don't think that I'm prepared to buy it to do that. Happy to read others experiences of it though and an in-depth comparison with good fixed focal length alternatives plus the Baader zoom as a benchmark would be excellent 🙂

I invested in the Leica ASPH zoom a few years back plus a VIP barlow to extend it's range but somehow it didn't convince me to abandon my fixed FL eyepieces, hence my caution over this new(ish) zoom.

Edited April 26, 2023 by John

[Stu]

3 minutes ago, John said:

I invested in the Leica ASPH zoom a few years back plus a VIP barlow to extend it's range but somehow it didn't convince me to abandon my fixed FL eyepieces, hence my caution over this new(ish) zoom.

It either reflects my laziness, or perhaps the relatively short times I have available for observing but I more often use my Leica Zoom than my fixed length eyepieces. On axis I find it doesn’t lose out in any way to XWs for example. If out for a longer session then yes, I do use my XWs/Nags/Morpheieieieiei but that is fairly infrequent currently.

[HollyHound]

18 hours ago, Stu said:

It either reflects my laziness, or perhaps the relatively short times I have available for observing but I more often use my Leica Zoom than my fixed length eyepieces. On axis I find it doesn’t lose out in any way to XWs for example. If out for a longer session then yes, I do use my XWs/Nags/Morpheieieieiei but that is fairly infrequent currently.

I'm in the same position right now... my time for observing has been much limited the last few months (due to a busy work contract, involving customers in late time zones) 😬

The grab and go setup with the APM Zoom permanently attached, has been great for grabbing short sessions when I have time... I don't see any meaningful loss of image quality in that configuration either 👍

[Deadlake]

I'd be interested to know if the Leica is worth the extra over the APM. 

The Leica is meant to be a step up, but so far with the APM EP's I own I've not seen the need to jump to TeleVue (XWA 20 mm vs E21 for example).

Is the Leica really that much better?

Main use would be to fill a hole in the 7-15 mm range when portability is key.

I'd take a TOE 4 mm, Zoom (insert name) , 20 mm XWA and 30 mm UFF.

Actually either the 20 mm XWA or 24 mm UFF depending on weight or if I was bringing a smaller diagonal.

[Don Pensack]

The Leica is 8.9-17.8mm, so not as applicable as the APM 7.7-15.4mm

It is also a LOT more expensive and needs a special adapter for telescope use.

The APM has a wider apparent field in the 15mm range as well.

 

[Louis D]

So, has anyone compared the APM SZ doubled with a Barlow to roughly 4mm to 8mm against the Svbony 3-8mm?  I have the latter and find it very nice except for the tight eye relief.  The doubled APM SZ might be a nice alternative, but it would rival my 5-8mm Speers-Waler for length.