Siebert Optics Ultra 13mm/15mm and APM 12.5mm HI-FW

[DAT]

Has anyone got any experience with the above eyepieces? (I have a gso 8" f 5.9)

Someone on CN pointed me in the direction of Siebert Optics, specifically the Ultra range as I wear glasses and looking for a large fov.

Seems like a nice small scale company but cannot find any user reports on those fl in that range. The spec of the 15mm seems spot on, 13mm may not have enough er for me. Longer focal lengths seem very well priced.

I was also looking at the APM option, lots written about it and the main problem seems to be EOFB. With my experience I probably would not notice that although I do observe from a light pouted area, could that be a problem. Would be good to hear from someone that has used this

Morpheus 12.5mm keeps coming up and I have used a 9mm but whilst amazing, it isn't my favourite. Due to lack

 of experience, I find eye placement a bit tricky which can lead to black outs and an off putting brown if observing the moon (CA?).  Otherwise its great, would be happy to buy used...

Other options in similar focal lengths then get even more expensive and heavy (TV, ES...)

Your thoughts and/or alternative suggestions would be much appreciated

[Louis D]

I have the APM Hi-FW 12.5mm and really enjoy using it.  It's better in every respect than my Nagler T4 12mm (eye relief, lack of SAEP, etc.).  Personally, I have never noticed EOFB in the APM.  It's really bad in the 12mm NT4 by way of comparison.

You might also check into the Founder Optics Marvel / StellaLyra LER UWA 14mm 80 degree.  It is 2" only, but it gets great reviews.

[DAT]

1 hour ago, Louis D said:

 

You might also check into the Founder Optics Marvel / StellaLyra LER UWA 14mm 80 degree.  It is 2" only, but it gets great reviews.

Thank you, is that also known as the Orion LHD? I was hoping for a 1.25" to make use of filters I already have

[Alan White]

I note your issue with the Morpheus 9, could I safely presume that you do not wear glasses?

I use and adore the 12.5 Morpheus, nut wear glasses, the eye cup is used fully down and no spacer for glasses use.
But if no glasses it needs the spacer and the eyecup to stop the eye being beyond the focus spot produced.
(I probably have the terminology wrong above, others may correct me on this) but this is the difference between being a pain to use and
being a dream in use.
 

[DAT]

1 hour ago, Alan White said:

I note your issue with the Morpheus 9, could I safely presume that you do not wear glasses?

I use and adore the 12.5 Morpheus, nut wear glasses, the eye cup is used fully down and no spacer for glasses use.
But if no glasses it needs the spacer and the eyecup to stop the eye being beyond the focus spot produced.
(I probably have the terminology wrong above, others may correct me on this) but this is the difference between being a pain to use and
being a dream in use.
 

Actually I do, I swap from hovering over the lens to pressing against the eye cup. I just need to practice

[Alan White]

1 hour ago, DAT said:

Actually I do, I swap from hovering over the lens to pressing against the eye cup. I just need to practice

Once mastered the eyepieces are very enjoyable to use, the feel wider than they are tagged.
 

[Louis D]

8 hours ago, DAT said:

Thank you, is that also known as the Orion LHD? I was hoping for a 1.25" to make use of filters I already have

You could fit a 2" to 1.25" step ring into the eyepiece to allow for 1.25" filter use:

[Louis D]

3 hours ago, DAT said:

Actually I do, I swap from hovering over the lens to pressing against the eye cup. I just need to practice

Try sliding your glasses down your nose slightly to increase the distance until resting them on the flipped down eye cup is at the proper standoff distance.

[DAT]

19 minutes ago, Louis D said:

You could fit a 2" to 1.25" step ring into the eyepiece to allow for 1.25" filter use:

Nice idea, had not thought of that. I am assuming thought that would act as a field stop and reduce the foc or am I talking rubbish? Either way, I think it’s a good option. Thank you

[Louis D]

1 minute ago, DAT said:

Nice idea, had not thought of that. I am assuming thought that would act as a field stop and reduce the foc or am I talking rubbish? Either way, I think it’s a good option. Thank you

It's unlikely to have much impact on a 14mm 80 degree eyepiece since the 13mm Ethos is a 1.25" eyepiece (with 2" skirt), the 14mm Morpheus (measured 78 degrees) is a 1.25" eyepiece, and the 16mm Nagler T5 is a 1.25" eyepiece.  I think they put it in a 2" housing to ease the design slightly.  It really depends on the diameter of its field lens.  Even then, I doubt it much exceeds 27mm in diameter.

[DAT]

13 hours ago, Louis D said:

I have the APM Hi-FW 12.5mm and really enjoy using it.  It's better in every respect than my Nagler T4 12mm (eye relief, lack of SAEP, etc.).  Personally, I have never noticed EOFB in the APM.  It's really bad in the 12mm NT4 by way of comparison.

You might also check into the Founder Optics Marvel / StellaLyra LER UWA 14mm 80 degree.  It is 2" only, but it gets great reviews.

Would you say you prefer your apm to the morpheus 12.5?

[Louis D]

I have the Morpheus 14mn rather than the 12.5mm.  I haven't done that much head to head competition between them.  They have very different distortion characteristics, so are a bit hard to compare.  The Morpheus stretches objects close to the edge like 98% of well corrected astro eyepieces while the APM squashes them.  As a result, the APM actually has the wider true field of view of the two.  It's even a little wider than my ES-92 12mm due to it also stretching objects.

[Don Pensack]

I find the APM 12.5 to have noticeable and objectionable edge of field brightening.

That's too bad, since otherwise it's fine.

The 12.5mm Morpheus is a great eyepiece--sharp, great contrast, easy to use.  It's also lighter than the APM.

It's an easy choice, IMO.

[Louis D]

I recomposited my 12mm to 14m UWA eyepiece ruler images together so it's easier to see the differences in presentation.  It's also obvious which have objectionable SAEP.  All are sharp to the edge at f/6.

[Louis D]

29 minutes ago, Don Pensack said:

I find the APM 12.5 to have noticeable and objectionable edge of field brightening.

That's too bad, since otherwise it's fine.

I've yet to notice the EOFB in the APM.  Of course, I'm generally not under dark skies like Mt. Pinos where I might be able to detect it.

[Don Pensack]

It was speculated the EOFB was due to its angular magnification distortion, except the Docter/Noblex 12.5mm has no EOFB and has strong AMD as well.

Baffles?  Lens polish at the edges of the lens? Field stop too large?  Unknown cause.

But I lent the eyepiece to five other observers, and they all saw the same thing.

If your circumstances don't allow it to be seen, keep it, because though tests show it's edge is only average at f/4, its other problem, FC, is very minor, and it was quite sharp at f/5.75.

[Louis D]

I really like its long eye relief, easy to hold FOV, and seemingly complete lack of SAEP.

I will keep an eye out for EOFB in the APM.  It is really bad in my 12mm NT4.  One night, it was decreasingly hazy edge to center.  I swapped it with the 12mm ES-92 and the haziness disappeared.

I'm not much of a faint fuzzy hunter under dark skies, so I'm pretty insensitive to EOFB.  I'm much more sensitive to SAEP because my pupils rarely dilate very far due to the increasingly severe light pollution around my backyard where I observe from.  I'm hoping once the wife and I retire that we can move to a darker site not too close to any major cities.