TheSkySearchers

An APM Telescope 7.7mm - 15.4mm zoom with a constant 75° AFOV and 20mm eye relief!

https://www.apm-telescopes.de/en/hot-pr ... ector.html

Wow. And it's not even April first.

Anyone care to order one? I'm looking forward to the reviews.

That’s an interesting design.

That's nice

Maybe on April 1st they could release a 15-32mm 68° for us SCT/Mak folks

Markus has been working on this for quite some time, there is a discussion in the Vendor thread at CN.
Thought I would post it since delivery is supposed to be soon.

It gets rid of that backwards AFOV and is parafocal as well.

Lady Fraktor wrote: ↑Mon May 24, 2021 4:28 pm Markus has been working on this for quite some time, there is a discussion in the Vendor thread at CN.
Thought I would post it since delivery is supposed to be soon.

It gets rid of that backwards AFOV and is parafocal as well.

Any hints about how it's done?

notFritzArgelander wrote: ↑Mon May 24, 2021 4:32 pm Any hints about how it's done?

I will have to re-read some of the thread, I was just skimming through the article between calls at work.

As of yesterday,
it looks like besides the pre-orders, there is still nothing to grasp.
There will certainly be a review from Don Pensack, and from the first users.

The discussion is going on here: https://www.cloudynights.com/topic/7581 ... fov/page-7

I am also very curious regarding its optics design, even if not as a potential buyer,
JG

j.gardavsky wrote: ↑Mon May 24, 2021 6:39 pm As of yesterday,
it looks like besides the pre-orders, there is still nothing to grasp.
There will certainly be a review from Don Pensack, and from the first users.

The discussion is going on here: https://www.cloudynights.com/topic/7581 ... fov/page-7

I am also very curious regarding its optics design, even if not as a potential buyer,
JG

Thinking about it a bit more, my guess would be that the field stop position varies.... I'll check the link.

notFritzArgelander wrote: ↑Mon May 24, 2021 6:50 pm

j.gardavsky wrote: ↑Mon May 24, 2021 6:39 pm As of yesterday,
it looks like besides the pre-orders, there is still nothing to grasp.
There will certainly be a review from Don Pensack, and from the first users.

The discussion is going on here: https://www.cloudynights.com/topic/7581 ... fov/page-7

I am also very curious regarding its optics design, even if not as a potential buyer,
JG

Thinking about it a bit more, my guess would be that the field stop position varies.... I'll check the link.

This would also explain the large outer diameter of the APM zoom, as the field stops in the ultrawides are thanks to the intrafocal design big.
Another point may emerge to become clarified, if the eye relief stays or shifts, and if the distortion changes when zooming or not.

Zeiss has tried a new zoom design it with Harpia, and this APM China zoom might have got the inspiration from Harpia. But I don't have the Harpia.

Let's wait,
JG

Eager to see if this new zoom meets expectations which seem to grow by the hour with anticipation. Nice that it holds 70 degrees AFOV through its range. I wouldn't be unhappy if eye relief varies as long as it's not down to single digits. In two different places on their website, APM say ER will be both 20 mm and 18 mm, but it's not clear if that varies with range. Pretty good regardless.

The difference is from the different focal lengths.
It is quite a while since anyone has made a zoom with constant FOV, the TeleVue Nagler 2mm-4mm, 3mm-6mm with 50° AFOV and the Antares Speers-Waler 5mm-8mm with 75°-78° AFOV.
These were all made in the early/ mid 2000.

I need to see photos of its eye end to get an idea of what its actual effective eye relief will be. That is to examine how recessed the zoom's eye lens is, how low the eyecup can go. I wear glasses, no full FoV, no buy.

Therefore I shall await objective reviews first. Eye placement & exit pupil behaviour are equally as important.

Reviews will be nice to have, hopefully this will be sold soon.
The APM page is showing it now but I have not heard of anyone purchasing it yet.

Markus of APM said about 2 weeks ago that he now expects them to arrive to him in August.

WilliamPaolini wrote: ↑Mon Jun 21, 2021 5:33 pm Markus of APM said about 2 weeks ago that he now expects them to arrive to him in August.

Thank you for the update Bill, any chance of a head to head with the Baader zoom?

Lady Fraktor wrote: ↑Mon Jun 21, 2021 7:27 pm

WilliamPaolini wrote: ↑Mon Jun 21, 2021 5:33 pm Markus of APM said about 2 weeks ago that he now expects them to arrive to him in August.

Thank you for the update Bill, any chance of a head to head with the Baader zoom?

That would be a very interesting review.

Unfortunately not as I gifted my Baader Zoom to a newbie two years ago since I was not using it. It was gifted to me by Bill Rose. Of course, if someone has both eyepieces and wants to loan them to me I will do a comprehensive review. But truthfully, I think a constant AFOV zoom is really in a different league so more appropriate to compare against fixed focal lengths of same caliber. If I got my hands on the APM Zoom I would compare it against the 7 XW, 9 Morpheus, 10 XW, 12 & 14 Morpheus.

Given it is 75 degree AFOV, the off-axis will have either (or in combination) rectilinear distortion (RD), angular magnification distortion (AMD), and/or some level of astigmatism, just depending how the designer decides to correct things for what they consider the best view. Since APM states that it works well for terrestrial use, I would assume (conjecture) then that would have a greater level of AMD vs. RD so that tree trucks and other straight features remain fairly straight in the off-axis. May folks do not like AMD but I find it quite OK as long as not too severe. But again, whether this eyepiece has it to any degree is unknown obviously since no one has one yet.

When Markus floated the idea of this eyepiece I was initially interested since it is a nice focal length range, especially when one adds a 2x Barlow with it. So that eyepiece, a Barlow, and say a 30mm wide field would be all one would need to have a full range of magnifications at their disposal. But form factor is also important to me and right now the pics of it look rather larger than I like. So at the moment not willing to shell out that much money to take a look see since the size looks a bit out of my preference range. Plus it is a heavy beast at 35 ounces (1 kg; 2.2 lbs - same weight as a Nagler 31T5 and looks a bit longer as well)!! APM is calling it a "Super" Zoom...unfortunately for me a bit super large and super heavy as well. I would always take a loaner though to run it thru its paces :-)

For comparable size I think it will be close to the dimensions of my Speers-Waler 5-8mm but the SW only weights 0.5kg
If as you say the AMD is not to severe I think it will be a interesting eyepiece.

Comparison with the Leitz zoom will be closest.