Long Eye Relief EP's

[Donkeyears]

Hi folks,

I have a Celestron 127 SLT MAK and as a spectacle wearer would like peoples opinions on LER EP's, I'm looking at the Williams Optics SPL 12mm and the Skywatcher 15mm. Bearing in mind my scope is almost F12 will I see any better with the WO than with the Skywatcher, as I read somewhere that you can get away with lesser eyepieces on slow scopes. Sorry for the long winded approach, just wanted to make sure I explained it correctly.

Thanks in advance

[Steep]

I've got the same scope and find the red dot finder gets in the way more if I'm wearing specs so I'm interested in the answer to this question too.

[msinclairinork]

Can't comment on the EP's you mentioned but I have a Baader Hyperion 17mm and it has realy long eye relief and is a great EP..good quility, wide AFOV and LER.

Michael

[John]

The Skywatcher LER's (the ones in the kit) are not great, even in a slow scope. The WO SPL is in a different league altogether.

[SimonR]

Just a bit of background, in theory;

Eye relief diminishes as the focal length of the eye piece diminishes, this can become a problem much below perhaps 15mm. This is a particular problem with plossls because their eye relief is usually only 80% of their focal length. You can get around this by using a longer eye piece and Barlowing it so that it is effectively shorter. It will retain its original eye relief.

We could take this further. Select a plossl with good eye relief, a 20mm perhaps with eye relief of around 16mm. Add a small specially designed Barlow to make it a 12mm. Now design another Barlow to make it 10mm, and so on: 8mm 7mm, 6mm... This is essentially what most 'planetary' eye pieces are - one of the basic designs such as a plossl, with a built in Barlow lens. If you ever see a range of eye pieces of differing focal length and they all have exactly the same eye relief this is what the manufacturer has done.

[John]

..... If you ever see a range of eye pieces of differing focal length and they all have exactly the same eye relief this is what the manufacturer has done.

But some manufacturers do it much better than others

[NGC 1502]

as a spectacle wearer would like peoples opinions on LER EP's.............I read somewhere that you can get away with lesser eyepieces on slow scopes.....

Long eye relief EPs are good with any scope, especially if you

wear specs.

Yes, slow focal ratio telescopes (F8, F10, F12 etc) are less

demanding on eyepieces, fast scopes, F4, F4.5, F5 etc are more

fussy with eyepieces, if you want sharp to the edge of field

of view.

Best regards, Ed.

[SimonR]

But some manufacturers do it much better than others

I'm sure that's true. I intended the above as information without an opinion.

[opinion starts]

If you have a good Barlow then that's an option, but I can see the convenience of having it in a single optimised package. I try not to think too much about brands but there will be real differences in the degree and accuracy of the lens polishing and the quality of the coatings.

[opinion ends]

[perrin6]

I have the WO 6mm SPL and I love it - it's very comfortable to look through and incredibly contrasty too. I would like the 12.5mm for nebula viewing.

[Donkeyears]

Thanks for all the comments, if I get a WO 12.5 and a decent 2x Barlow, the 12.5 wiil then be a 6mm effectively, with the same amount of eye relief ?

[John]

Thanks for all the comments, if I get a WO 12.5 and a decent 2x Barlow, the 12.5 wiil then be a 6mm effectively, with the same amount of eye relief ?

Yes, but bear in mind that a 6mm WO SLP costs £69 and a nice barlow can cost that.

[jamespels]

Hi DonkeyEars,

I have just been through exactly the same process... I own a TAL 2M (f8, 1200mm FL) and spent a long time considering lower cost EPs to go with the 25mm TAL Plossl that came with the scope.

To summarise stuff I found out (note I am new to this too and may have got some of it wrong!):

- The TAL 25mm Plossl has plenty of eye relief for me and is comfortable to use, though I do end up with my specs lens touching the EP from time to time. I therefore consider 25mm to be the smallest practical Plossl for me. This also appears to be a well-received EP and gets generally the best reviews of similar EPs in its price bracket (<£50).

- the WO SPL is based on the TMB Planetary EP design which is very highly regarded in its price bracket.

- the TMB Planetary II (as sold by Sky's The Limit - recommended, btw) uses same / similar optics (though there are various issues concerning the use of TMB branding in non-licensed designs - I THINK these ones are genuine!) and is about £10 - £20 cheaper than the equivalent WO EP.

- TMB's Planetary design was never intended to be used at FL > 9mm and image quality degrades for EPs much bigger than this; it becomes a judgement call whether to use a bigger Planetary or go for Plossl + Barlow (or something else) at this size.

- above 25mm, a decent Plossl is by far the most cost-effective budget (say £50) LER EP.

- The TMB design uses 5 or 6 elements (not sure which one, or both, is genuine!); the Barlow will have another 2 (maybe even 3) elements - his is a lot of glass so I would buy a smaller EP (say 6mm) rather than Barlowing a 12mm.

For reference, I have kept the TAL 25mm Plossl (giving 48x mag) and added a Series 500 40mm Plossl from Sky's the Limit (30x) and a 6mm TMB Planetary from the same place (200x). I have also added a TAL 2x Barlow from FLO to convert the above to 12.5mm (96x) and 20mm (60x). I will try the Barlow with the 6mm Planetary to give 3mm (400x) but I don't hold out much hope of it being usable!

The new EPs only arrived yesterday and seeing was pants near me last night so I have only had the briefest look through them but both are very comfortable with glasses on.

Incidentally, think a bit about if you need to wear your glasses - if you have a straight power correction then the scope focuser should be able to handle this for you. It is only if you have another issue (I have bad astigmatism) that you will really need to wear glasses. A decent ophthalmic optician will be able to advise (for questions like this, find a decent independent - the big chains are more interested in just selling you things!).

Hope this helps,

J.

[Donkeyears]

Hi DonkeyEars,

I have just been through exactly the same process... I own a TAL 2M (f8, 1200mm FL) and spent a long time considering lower cost EPs to go with the 25mm TAL Plossl that came with the scope.

To summarise stuff I found out (note I am new to this too and may have got some of it wrong!):

- The TAL 25mm Plossl has plenty of eye relief for me and is comfortable to use, though I do end up with my specs lens touching the EP from time to time. I therefore consider 25mm to be the smallest practical Plossl for me. This also appears to be a well-received EP and gets generally the best reviews of similar EPs in its price bracket (<£50).

- the WO SPL is based on the TMB Planetary EP design which is very highly regarded in its price bracket.

- the TMB Planetary II (as sold by Sky's The Limit - recommended, btw) uses same / similar optics (though there are various issues concerning the use of TMB branding in non-licensed designs - I THINK these ones are genuine!) and is about £10 - £20 cheaper than the equivalent WO EP.

- TMB's Planetary design was never intended to be used at FL > 9mm and image quality degrades for EPs much bigger than this; it becomes a judgement call whether to use a bigger Planetary or go for Plossl + Barlow (or something else) at this size.

- above 25mm, a decent Plossl is by far the most cost-effective budget (say £50) LER EP.

- The TMB design uses 5 or 6 elements (not sure which one, or both, is genuine!); the Barlow will have another 2 (maybe even 3) elements - his is a lot of glass so I would buy a smaller EP (say 6mm) rather than Barlowing a 12mm.

For reference, I have kept the TAL 25mm Plossl (giving 48x mag) and added a Series 500 40mm Plossl from Sky's the Limit (30x) and a 6mm TMB Planetary from the same place (200x). I have also added a TAL 2x Barlow from FLO to convert the above to 12.5mm (96x) and 20mm (60x). I will try the Barlow with the 6mm Planetary to give 3mm (400x) but I don't hold out much hope of it being usable!

The new EPs only arrived yesterday and seeing was pants near me last night so I have only had the briefest look through them but both are very comfortable with glasses on.

Incidentally, think a bit about if you need to wear your glasses - if you have a straight power correction then the scope focuser should be able to handle this for you. It is only if you have another issue (I have bad astigmatism) that you will really need to wear glasses. A decent ophthalmic optician will be able to advise (for questions like this, find a decent independent - the big chains are more interested in just selling you things!).

Hope this helps,

J.

Thanks for that, I think I'll order the 6mm TMB and just barlow my original 25mm EP, I was also looking at getting the TAL barlow as it is quite well rated for its price. TMB plus Tal just over the price of the WO SPL.