Twist up eyecups

[Mike_S]

Just tried my Pentax XW and OVL Myriad for the first time. The Pentax is meant to have 20mm eye relief and the Myriad 15mm. However I can rest my face against the Myriad and get a comfortable view. With the Pentax, I have to hold my eye quite a way off the eyepiece as my eye lids and lashes seem to get in the way making my field of view very narrow or uncomfortable. Anybody had this with a Pentax XW before or other eyepiece with twist up eye cup?

[John]

I have 4 Pentax XW's - I don't wear glasses to observe so as per the Pentax guidance (when I bothered to read it !) I use them with the eye cups in the highest position and find them very comfortable and the full field of view easy to see. The eye cup is the whole top section of the eyepiece with the XW's and it twists gently upwards moving around 12mm from it's inwards position.

I also have TV Delos with their slide up and lock eye cup system (again the whole top of the eyepiece moves) and also use those in the uppermost position.

 

[Mike_S]

I am getting more blackouts with the Pentax. Never had this before. Even with it twisted all the way up. Could it be too much magnification? It was high power on the moon as it's cloudy and thats all I could see really. Or could the design just not suit me? Odd that the Myriad of the same size is easier to see the full field of view. 

[Mike_S]

Just seen this on another forum. I need to address this. Not sure why I am getting it so bad. 
"Are there situations where blackouts are more likely? Yes, with eyepieces having short focal lengths and very long eye reliefs (e.g. Radians, Pentax XWs, Vixen Lanthanum, Orion ED) or eyepieces with an unusual characteristic called "spherical aberration of the exit pupil" (TeleVue nagler Type 1s). This last characterisitic is rare in modern eyepieces, so isn't likely to be an issue."

[Mike_S]

Hang on! Just realised. I was not twisting the eye cup up on the Pentax. I was only unscrewing the top ring. I think I might be alright now! Clouds have come over so will try it again tomorrow hopefully

[John]

27 minutes ago, MSammon said:

Hang on! Just realised. I was not twisting the eye cup up on the Pentax. I was only unscrewing the top ring. I think I might be alright now! Clouds have come over so will try it again tomorrow hopefully

I had a feeling that was what was happening. The top section of the rubber eyecup unscrews but that is not the twist up eye cup, as you have now found out.

With the eyecup in the lowest position, you will get blackouts and other issues. It's the same with some other eyepieces of a similar design as well - eye positioning is quite important.

Edit: I've just tried my 7mm XW with the eyecup right down and get blackouts, a seemingly resticted field and I can see my eyelashes.

 

[Mike_S]

Okay great, phew. It felt like I was going blind!

[Louis D]

The  top section unscrews all the way off to reveal an M43 thread to attach a camera adapter either for afocal or eyepiece projection photography.

[mikeDnight]

I never used the twist up eye shield on my XW's and didn't experience a problem with my eyelashes touching the eye lens on any of them. I did get the blackout on occasion,  but that was due to me letting my eye wander off axis. I'm not sure what to think of extendable eye shields. Perhaps I'm not keen on letting my eye touch the eyepiece body, as it can introduce some vibration when my big hooter touches the side of the side of the eyepiece. Eye shields are a good idea in principle though, as they help to keep the eye on axis and offer a measure of shielding from stray light.

[F15Rules]

With my XW/XLs I used to screw the eyecup as far "in" (lowest position ) as it would go, then gradually rotate the eyepiece holder outwards until it felt most comfortable and I could see the whole FOV. In my experience Pentax XW/XL ranges are some of the most comfortable eyepieces out there.

I really like the new Morpheus range which have similar eye relief but offer two screw on eyecups of different heights to suit different observers. I find these excellent, so much better than the original versions which were poorly fitting and flimsy.

What's more, the Morphs have a 76deg FOV: 6 deg more than the XW, but somehow it seems more in use - and I can take in the whole field no problem (I don't wear glasses to observe).

I'd probably choose fixed height vs adjustable eyecups, but others may well feel the opposite. But there is no doubt that either way, optimum comfort is essential to get the most from your scope and eyepiece combination☺.

Dave