50+mm Eyepiece

[Bino Pete]

Apart from a slight difference in price, is there much between these two eyepieces quality wise?

https://www.harrisontelescopes.co.uk/acatalog/Revelation_50mm_Widefield_Eyepiece_2_.html#SID=1393

https://www.harrisontelescopes.co.uk/acatalog/Meade_Series_4000_56mm_Super_Plossl_Eyepiece_2_.html#SID=1137

Thanks.

[YKSE]

If the specification is correct for the 50mm (5 elements), it should be an Erfle, not plossl, which is a 4 element design, therefore not the same.

I have this 50mm, its AFOV is definitely not 60°, more likely around 51° after comparing TFOV with my 40mm 68°.

Both have very long eye relief, eye cup is way too short to be of any help, you'll need to learn to hold your eye in right position to avoid blackout.

I don't expect much optical quality difference between these two, other than that 56mm should give some 25% brighter image because of larger exit pupil.

[Bino Pete]

5 minutes ago, YKSE said:

If the specification is correct for the 50mm (5 elements), it should be an Erfle, not plossl, which is a 4 element design, therefore not the same.

I have this 50mm, its AFOV is definitely not 60°, more likely around 51° after comparing TFOV with my 40mm 68°.

Both have very long eye relief, eye cup is way too short to be of any help, you'll need to learn to hold your eye in right position to avoid blackout.

I don't expect much optical quality difference between these two, other than that 56mm should give some 25% brighter image because of larger exit pupil.

Are there any other 50+mm 2" eyepieces on the market?

[YKSE]

Not many, of more common ones, You have Televue 55mm plossl. Then there're some in the states, like Gary Russell optics.

[Louis D]

Surplus Shed offers 51mm, 53mm, 62mm, 72mm, 80mm and 126mm 2" eyepieces.

If you have a 2.5" to 4" focuser, there's the Siebert Optics Observatory Series.

For 3" focusers, there's the Masuyama 80mm.  There are some vintage 80mm and 100m Zeiss 3" and 4" eyepieces out there as well if you can find them.  Pentax made a 60mm XL in the past.  I think it required a threaded focuser, though I'm sure an adapter could be made for it to a 3" or 4" focuser.

[Stu]

Which scope are you planning on using it in Pete? Keep an eye on the exit pupil generated, it can become very large and cause a very washed out view.

[Bino Pete]

59 minutes ago, Stu said:

Which scope are you planning on using it in Pete? Keep an eye on the exit pupil generated, it can become very large and cause a very washed out view.

Its for my CPC 800

[John]

I used a 50mm eyepiece with a C8 a few years back and I can vaguely recall the secondary shadow being rather more obvious than I'd have liked

 

 

[Stu]

I don't have direct experience of that combination. I used a 31mm Nagler in my C8 and it worked very well. Also a 55mm Plossl in an 8" Mak but that was 4000m focal length so still ok. Worth checking out properly before you buy, John's experience doesn't sound promising.

[Bino Pete]

2 minutes ago, John said:

I used a 50mm eyepiece with a C8 a few years back and I can vaguely recall the secondary shadow being rather more obvious than I'd have liked

 

 

As I already have a 42mm 2" eyepiece, do you think I really need the 50mm one?

[John]

3 minutes ago, Bino Pete said:

As I already have a 42mm 2" eyepiece, do you think I really need the 50mm one?

Not really. My guess is that the 42mm has around the maximum field stop that will fit in the 2" barrel so a 50mm won't show more sky.

 

[YKSE]

I haven't seen secondary shadow with 50mm in my 8", and I did try very hard to see it as it was mentioned before, deep sky, Jupiter or the MOON (in center, partial center, just outside FOV), smply not visible. It is only 5mm exit pupil. I've not seen any secondary shadow when using 32mm plossl in f5 130p, which is 6.4mm exit pupil.

As John has already said, 50mm will not show your more sky, as a matter of fact, GSO 50mm shows less sky than my 40mm Aero. The most important thing with the 50mm is that it gives 5mm exit pupil, instead of 4mm in 40mm, which means 56% brighter image! It was my best chance to see Horse Head nebula, and it did give noticeable better view than 40mm, even though still very, very difficult. I've not had more chance to use in other scopes for large faint fuzies.  For me, getting the HH is money well-spent.

If you're observing only in light-polluted backyard, I reckon 50+mm shouldn't be considerred.