Morpheus Colour Fringe during daytime use

[Graham1]

Hello SGL,

I recently took the plunge a bought a 17.5mm Morpheus eyepiece. So far I haven't been able to try it at night but during a daytime check I have seen that the outer 5% of the FOV has a orange/red colour fringe which I can't eliminate via eye positioning. I'm unsure if this is the "Ring of Fire" effect. Is this normal for a Morpheus or a fault?  Thanks for any help.

 

[Knighty2112]

Might help to know what scope were you using to look through it with? What is the scopes focal length?

[Graham1]

Hi Gus,

I was using it with an 8" Celestron Evolution, so 2000mm or thereabouts.

Graham

[Knighty2112]

OK, that’s a nice long focal length. If it had been much shorter fl then that could have maybe caused an issue perhaps. Used to own a 17.5 Morpheus and never had any issues with it, but never used it for daytime views so not sure if this is normal or not. Was the scope in focus whilst you were looking through the EP?

[Louis D]

I've not read reports of this issue with the 17.5mm Morpheus, but anything's possible.

Try to take a picture through the eyepiece during the daytime using your cell phone's wide, or better yet, ultrawide angle camera.  In my experience with slow scopes like your SCT or my Mak and an ultrawide angle phone camera, you'll get a rainbow effect if you've got true ring of fire which is actually chromatic aberration of the exit pupil (CAEP).  You can see it below in the 30mm ES-82 and 26mm Meade MWA Easy images below.

[Graham1]

Gus, yes it was in focus.

Louis, I've taken your advise using a distant tree on the horizon, with the attached result.  It's a good representation of the visual effect. I've never seen anything similar with previous EPs, but to be fair this is my first foray past Plossls, SLVs and BSTs into wider fields.

 

 

[Highburymark]

Hmm. It’s obviously vignetting quite significantly - can you see the field stop visually at all, or is your image an exact representation of what you see through the eyepiece?

I’ve seen similar edge colour in my APM 100 degree 20mm - particularly with an F/6 60ED during daytime - but it’s much less exaggerated than your pic. 

[Zermelo]

I'm certainly no expert, but to me it looks different from the CAEP examples in @Louis D's post - it's not a rainbow effect, it looks more like a neutral tone that's "bled" into the image from outside , as if the edge is defocussed. Misplaced field stop?

[Graham1]

If i take my glasses off I can see the field stop, and i can get fleeting views where the orange/red is gone and there is a very thin blue coloured ring inside the stop, which to me is more what i expected to see. I think I'm going to have to wait to try it on the moon and stars.

[globular]

This eyepiece has enough eye relief for most glasses wearers to see the field stop. Have you adjusted the eyecups correctly?  Folded down for glasses use may work best. 

I'd also try (in the day) with a shroud (if you have one or just a towel or pillowcase if not) to rule out any stray light or glares.
(or wait for night time if you have more patience than me)

[Louis D]

It looks like you haven't gotten the camera lens in close enough to take in the actual field stop.  As you say, you should see a thin blue line just inside of the blackness of the actual field stop.  You may not be getting your eye in close enough, either.  Make sure you don't have the included eye cup extender on the eyepiece.  Also, make sure the eye cup is fully folded down when wearing eyeglasses.

[Don Pensack]

I examined my 17.5mm Morpheus in my 4" apo just now.

There is a thin blue line directly at the field stop.

The orange coloration seen in the image is visible in the field right up until the eye hits the field stop, at which point it disappears and there is no color at the edge (other than the thin blue ring).

The edge of the field is very slightly vignetted.  You'd never notice it at night.

 

BTW, the Pentax XWs exhibit this as well, though the outer field is yellow, but, like the Morpheus, the color completely disappears at the exit pupil.

So the coloration is only visible when you are too far from the eyepiece.

[Louis D]

I can always tell when I have the camera at the right spot for my AFOV images because the field stop pops into view and going any further inward produces blackouts.  Of course, if there's massive SAEP/CAEP in the eyepiece, or if there is no distinct field stop, this complicates matters for me taking my images.  I then have to find the best distance that represents what the eye sees.

[Graham1]

Thanks all for taking the time to help with this and to Don for trying out a similar setup with a known "good" EP, which is always the acid test. It's clear that the issue is me not folding the eyecup to get my eye close enough when wearing glasses.  As an observer of many years it's a schoolboy error - the new world of wide(r) fields caught me out!  I'm now looking forward to the darker skies  and seeing what a £200+ EP brings. 

[F15Rules]

1 hour ago, Graham1 said:

I'm now looking forward to the darker skies  and seeing what a £200+ EP brings. 

Graham,

I think you will be delighted with your Morpheus at night. It's one of my favourite eyepieces, and, along with the 9mm, IMO the best of a very good wide field range 👍.

Dave