Zoom-fest

[John]

Thanks to a very kind loan from @bomberbaz (Steve) I am going to be having some interesting times comparing these zoom eyepieces for a while. I was hoping for some clear sky tonight but it's looking dodgy just now - must be the process of putting a scope out and lining up the eyepieces that draws the clouds ! 🙄

From right to left they are the APM 15.4mm - 7.7mm, the Baader Mk IV 24mm - 8mm, SVbony 8mm - 3mm and the Tele Vue Nagler 4mm - 2mm. I'm really looking forward to using the APM and the SVbony zooms that Steve has lent me, having read so much about them. I will also be comparing these with good quality fixed focal length equivalents.

 

[JeremyS]

I’m looking forward to this, John!

[Ratlet]

Spoilt for choice!

Absolutely love my 3-8mm svbony, without a doubt the best bang for buck out of all the eyepieces I've bought.

I feel the 8-24mm svbony would be an interesting one to get in the mix, it would round out the low cost side of things.  I could sling mine down to you, but I feel I might miss the boat with timings.  Personally I didn't initially get on with the very tight FOV, but the view through that straw was pretty good 🤣

[inedible_hulk]

Also looking forward to this 😊

[Alan White]

That is an interesting experiment @John, looking forward to reading your findings.

[Franklin]

15 minutes ago, Alan White said:

That is an interesting experiment @John, looking forward to reading your findings.

Ditto!

My money is on the good quality fixed focal length equivalents, but it will be interesting to hear your findings with regards to the shorter fl zooms, Nagler versus the SVbony at the 3mm settings.

[John]

The skies have been clear tonight (eventually) so I have made a good start. I would like a few sessions before reaching any conclusions though, so please bear with me 🙂

As well as the zooms, I've pressed the 14mm Delos, 24mm Panoptic and 8mm Ethos into service so there are some quality fixed focal lengths in play as well.

Tonight I stuck with the ED120mm refractor at F/7.5. No moon so some reasonable DSO viewing was possible once the sky darkened. 

 

 

Edited July 19, 2023 by John

[RT65CB-SWL]

It will be an interesting read, especially the TeleVue v Svbony. 

[Mark at Beaufort]

Interesting John. I will look forward to your findings. I certainty be interested in your opinions on your findings between the Nagler zoom and the SvBony.

[RobertI]

Nice idea John, looking forward to the results. 

[Space Hopper]

Interesting comparison John, and i look forward to reading your results.

I myself own an APM 7-15, and have also tried the Baader 8-24

I much preferred the APM ; that was the 'keeper' for me.

[JeremyS]

Take your time John. It will be good to get your rounded opinion.

[Saganite]

20 minutes ago, JeremyS said:

Take your time John. It will be good to get your rounded opinion.

Couldn't agree more.

I have the APM and I am delighted with it.  The little Svbony zoom is of great interest as a complement to the APM , so I to await your report with great interest John

[Telescope40]

Looking forward to your findings @John - especially the TV zoom v the SVBony 9-3 

regards. John 

[John]

For those of you who have the APM 7.7-15.4mm zoom, do you use it in 2 inch or 1.25 inch mode ?

I'm finding that it simply won't come to focus in at least two of my scopes in 1.25 inch mode. I realised from reading other reports that it would require more inwards focuser travel than many eyepieces but I didn't realise that it was as much as it actually seems to be. In 2 inch mode it seems to reach focus just a bit further out than, for example, Pentax XW's, which is fine.

My scopes are all refractors.

Thanks 🙂

[Saganite]

Hi John,

I have only used mine in 2" mode .  I will have to see what happens in 1.25", not having tried it yet.

Edited July 21, 2023 by Saganite

[Louis D]

23 hours ago, John said:

For those of you who have the APM 7.7-15.4mm zoom, do you use it in 2 inch or 1.25 inch mode ?

I'm finding that it simply won't come to focus in at least two of my scopes in 1.25 inch mode. I realised from reading other reports that it would require more inwards focuser travel than many eyepieces but I didn't realise that it was as much as it actually seems to be. In 2 inch mode it seems to reach focus just a bit further out than, for example, Pentax XW's, which is fine.

My scopes are all refractors.

Thanks 🙂

I haven't used one yet, but from this post of mine from last November, it appears to need 32mm of focuser in-travel in 1.25" mode to put the focal plane of the eyepiece at the focal plane of the telescope.  By way of contrast, it only needs 8mm to accomplish the same thing in 2" mode.

[John]

5 minutes ago, Louis D said:

I haven't used one yet, but from this post of mine from last November, it appears to need 32mm of focuser in-travel in 1.25" mode to put the focal plane of the eyepiece at the focal plane of the telescope.  By way of contrast, it only needs 8mm to accomplish the same thing in 2" mode.

That seems to match what I am experiencing. Thanks 👍

[mr_belowski]

looking forward to seeing your results here, any sneak previews / preliminary findings available?

[Mr Spock]

Shame you haven't got a SvBony 7-21mm in there. It has a good technical test ( http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 ) and it would be interesting to see how it performs as a planetary eyepiece.

[bosun21]

2 hours ago, Mr Spock said:

Shame you haven't got a SvBony 7-21mm in there. It has a good technical test ( http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 ) and it would be interesting to see how it performs as a planetary eyepiece.

I owned a SvBony 7-21mm zoom eyepiece and found it provided clear reasonably sharp images. I didn't like the somewhat narrow FOV at the lower magnification end and sold it. It never occurred to me to keep it as a planetary eyepiece. Reading through the link you provided has left me feeling pleased that I opted to go for my set of Baader Morpheus eyepieces.

[John]

3 hours ago, mr_belowski said:

looking forward to seeing your results here, any sneak previews / preliminary findings available?

Thanks for the interest. I learned a long time ago not to jump to any conclusions when comparing optical equipment. I need to have several decent sessions using the eyepieces on a variety of targets with scopes of different specifications. Due to the weather conditions I have managed just two short sessions under mediocre conditions which told me very little about the comparative merits of these zooms I'm afraid. 

I'm very glad that I don't review equipment like this for magazines where there are deadlines to be met. It must be very difficult to gather enough experience to compose something useful with the current UK conditions🙄

 

[John]

3 hours ago, Mr Spock said:

Shame you haven't got a SvBony 7-21mm in there. It has a good technical test ( http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 ) and it would be interesting to see how it performs as a planetary eyepiece.

I do have a clone of the Hyperflex 7.2mm - 21.5mm zoom. I'm not sure how close that is to the SvBony 7-21 zoom ?

[John]

One thing that I can share is that, for me, the APM 7.7-15.4mm zoom has to be treated as a 2 inch eyepiece. Used in 1.25 inch mode it needs such a lot of inwards focuser movement that it will not reach focus at all in 2 of my scopes and only barely in the others. Used in 2 inch mode the APM zoom reaches focus at around the same position as the Delos 14mm.

Because I currently use refractors, I need to ensure that the 1.25 portion of the APM zoom's barrel clears the diagonal mirror when used in 2 inch mode. This has worked out OK in my Astro Physics and Tele Vue 2 inch diagonals. If I was to use a filter on the eyepiece barrel I think there might be problems though so any filtering of this eyepiece will be applied at the end of the diagonal barrel.

 

 

Edited August 2, 2023 by John

[Louis D]

58 minutes ago, John said:

Because I currently use refractors, I need to ensure that the 1.25 portion of the APM zoom's barrel clears the diagonal mirror when used in 2 inch mode. This has worked out OK in my Astro Physics and Tele Vue 2 inch diagonals. If I was to use a filter on the eyepiece barrel I think there might be problems though so any filtering of this eyepiece will be applied at the end of the diagonal barrel.

Some folks over on CN have been using a 1.25" to 2" Step Up Ring screwed onto the 1.25" filter threads of their ASZ to prevent it from smashing into their diagonal optics, especially prism ones, when used in 2" mode.  The ring's 2" outer surface will stop at the diagonal's 2" safety lip that prevents 2" eyepieces from inserting too far.  It might also be useful for other hybrid eyepieces with extraordinarily long 1.25" barrels when used in 2" mode in diagonals without a lot of excess insertion distance.