Explore Scientific EPs - and advice on an all-round EP kit

[stephenb (Stephen)]

Amazing the amount of replies I've receive on this thread, so thank you to you all. I've been attempting to digest all the information and offer a reply.

Firstly I didn't want to turn this into a TV vs ES discussion (Ford/Holden, Apple/PC) but I know some people are passionate about their products and I appreciate your advice, thanks

My biggest concern is eye relief and AFOV and if I purchase one or two eyepieces will they be comfortable for me - and if they're not I've just blown my money. I may be fretting too much over this (as I often do).

Having said that, I have rarely used top quality glass and have owned GSO/Bintel EPs for several years, so anything will be a step up in quality (The TV 27mm Pan trounced anything I tried from GSO)


I recently sold my Powermate is is was just too cumbersome and heavy for the finely balanced SDM


So, here is my refined list....


1 - 27mm TV Pan (keeping for the moment)

2 - ES 14mm 82° (1.25") or.... ES 18mm 82° (2")

3 - ES 8.8mm 82°

[stephenb (Stephen)]

Originally Posted by Don Pensack

Well, whatever eyepieces you decide on, a good starting point for an 18" f/4.5 (assuming a Paracorr in the focuser) is a set:
30mm/15mm/10mm (+/- 1mm)
or, without a coma corrector (which I wouldn't recommend at f/4.5):
26mm/13mm/9mm
Then, add eyepieces in-between or above as needed, but at least you'd have "the basics".

Thanks for your reply Don, I've sent you a PM.

[Camelopardalis (Dunk)]

Originally Posted by stephenb

So, here is my refined list....


1 - 27mm TV Pan (keeping for the moment)

2 - ES 14mm 82° (1.25") or.... ES 18mm 82° (2")

3 - ES 8.8mm 82°

I'd go with the 14 and not the 18, as the 18 would be too close to the FOV of the 27 Panoptic.

Since they're so reasonably priced, you might want to consider chucking the ES 11mm in there for the nights where 8.8 might be too much...the 11 is another cracker for the $ IMO.

This may be the breaker for you though - note that none of ES82/100, Nagler T6 or Ethos are particularly generous with eye relief, you will have to get in there with the rubber cup for the full experience!

[Camelopardalis (Dunk)]

...and if you save all that $, treat yourself to the ES 30mm...it'll widen your view considerably over the 27 Panoptic

[MortonH]

The ES 11mm is particularly tight on eye relief. I sold mine for that reason. The 8.8mm has ok eye relief but lately I've been wishing it had a bit more.

Go in between the two and get a Pentax XW or Delos 10mm?

[Astro_Bot]

Actually, the ES 82d 14mm is the only one in the line-up that I wouldn't recommend - due to field curvature apparent in the outer 20% of the field - I used to own one. Pick any other ES eyepiece.

Forget about the relative AFOV (68, 82, 100). IMHO, that's just a personal preference for how you want your view "bordered". All that you can comfortably take in is in the inner 65-70 degrees or so; 68 degrees is enough, and beyond that is window dressing.

Having said that, I have some 82d eyepieces, but that's because I like the view at that focal length - if there'd been a 68 degree eyepiece at that same focal length, with the same performance, I'd probably own it!

BTW, Don's advice is good, if a little short on explanation. Selecting eyepieces is usually best done by picking your lowest and highest practical magnifications (based on a number of factors, including how often you will get to use it/them), selecting corresponding eyepieces at those extremes then in-filling using f/stop intervals (halving the exit pupil area), though mostly you would start with double f/stop intervals (a double f/stop below is equivalent to halving the eyepiece focal length). So, for example:

27mm Pan = exit pupil of 6mm at your focal length (a good figure - largest practical size is 7mm for young eyes and 5mm for old eyes, with 6mm being a good in-between number)

Double f/stop below 6mm is 3mm exit pupil >> 13.5mm focal length.
Double f/stop below 3mm is 1.5mm exit pupil >> 6.75mm focal length.
In-filling at single f/stop intervals also gives 19mm and 9.5mm focal lengths.

So, if the 27mm Panoptic is your starting point, you would have the following set:
27mm, 19mm, 13.5mm, 9.5mm, 6.75mm.

But, don't get too hung up on these numbers - they're only a rough guide. For example, I also have a 40mm eyepiece for wider views (not applicable to you as the exit pupil would be far too large) but didn't want more than 5 widefield eyepieces, so I omitted some focal lengths and picked others in between f/stops to cover the range.

Specifically, my ideal range would be:
40mm, 28mm, 20mm, 14mm, 10mm, 7mm

Restricting myself to commercially available eyepieces and with some focal lengths in between f/stops (in bold):
40mm, 28mm, 18mm, 11mm, 6.7mm.

This arrangement works very well for me. Your mileage may vary.

[Varangian (John)]

Originally Posted by stephenb

Amazing the amount of replies I've receive on this thread, so thank you to you all. I've been attempting to digest all the information and offer a reply.

Firstly I didn't want to turn this into a TV vs ES discussion (Ford/Holden, Apple/PC) but I know some people are passionate about their products and I appreciate your advice, thanks

My biggest concern is eye relief and AFOV and if I purchase one or two eyepieces will they be comfortable for me - and if they're not I've just blown my money. I may be fretting too much over this (as I often do).

Having said that, I have rarely used top quality glass and have owned GSO/Bintel EPs for several years, so anything will be a step up in quality (The TV 27mm Pan trounced anything I tried from GSO)


I recently sold my Powermate is is was just too cumbersome and heavy for the finely balanced SDM


So, here is my refined list....


1 - 27mm TV Pan (keeping for the moment)

2 - ES 14mm 82° (1.25") or.... ES 18mm 82° (2")

3 - ES 8.8mm 82°

I do not recommend the ES 82 in the 14mm it is far inferior to the rest of the 82 range. Not only are stars seagulling in the outer 25% but the field here is actually blurry!

[Camelopardalis (Dunk)]

No seagulling or significant field curvature in my scope, so I suggest you check your scope/eyes

[Astro_Bot]

Originally Posted by Camelopardalis

No seagulling or significant field curvature in my scope, so I suggest you check your scope/eyes

Hmmm. If you're the one that can't see a frequently-reported aberration in an eyepiece, then shouldn't you be the one getting an eye exam?

[Steffen]

My guess would be a poor/defective sample. Sample variation is still a big issue in this industry (esp. in the "affordable" price brackets), and equipment reviews rarely pay enough heed to that.

Any review rating that is based on a single sample of the reviewed item should be taken with the proverbial grain of salt, until substantiated by similar ratings given by others.

Cheers
Steffen.

[Camelopardalis (Dunk)]

Originally Posted by Astro_Bot

Hmmm. If you're the one that can't see a frequently-reported aberration in an eyepiece, then shouldn't you be the one getting an eye exam?

I'm probably due

But I also use a scope corrected for field curvature...

[Astro_Bot]

Originally Posted by Steffen

Any review rating that is based on a single sample of the reviewed item ...

Field curvature has been reported many times in the ES 82d 14mm by many reviewers. So has flaring from off-axis bright objects in the "old" ES 82d 8.8mm, since corrected by a revised baffle/field stop design.

[Camelopardalis (Dunk)]

But does that automatically mean I'm wrong?

Maybe it's worst in a Newtonian and all the reviewers had Dobs? That'd be a useful data point, and helpful to the OP.

[Astro_Bot]

There's are factors such as visual accommodation (i.e. you may have better and/or different-shaped eyes to other reviewers), target viewed and expectation to be considered.

I wouldn't say you're wrong, merely in a teensy, tiny minority ...

I reviewed in an f/10 ACF SCT and f/7.5 refractor, but there have been reviews in Newtonians as well.

But, hey, what would I know? I actually liked Tron: Legacy.

[AG Hybrid (Adrian)]

Nawwww. My ES 14mm 82 has noticeable field curvature towards the outer field. It could also be an aberration magnified by coma as well. I should try it in the ES coma corrector. It should clear things right up.

[Camelopardalis (Dunk)]

I can live with that. I liked Tron Legacy too

[MortonH]

The reports of field curvature in the ES82D 14mm eyepiece didn't stop me buying one for my slower scopes. But in faster scopes I've read it can be a problem.

My 14mm ES82D is perfect in a f/12 Mak and good in a f/7 refractor. However, the other day I did solar observing with my ZS66 (f/5.9) and noticed that sunspots were in focus on one limb of the sun but very slightly out of focus on the other side. The difference was focused out with a very minor adjustment. Perhaps this is the FC of the eyepiece?

[stephenb (Stephen)]

Originally Posted by Astro_Bot

Actually, the ES 82d 14mm is the only one in the line-up that I wouldn't recommend - due to field curvature apparent in the outer 20% of the field - I used to own one. Pick any other ES eyepiece.

Forget about the relative AFOV (68, 82, 100). IMHO, that's just a personal preference for how you want your view "bordered". All that you can comfortably take in is in the inner 65-70 degrees or so; 68 degrees is enough, and beyond that is window dressing.

Having said that, I have some 82d eyepieces, but that's because I like the view at that focal length - if there'd been a 68 degree eyepiece at that same focal length, with the same performance, I'd probably own it!

BTW, Don's advice is good, if a little short on explanation. Selecting eyepieces is usually best done by picking your lowest and highest practical magnifications (based on a number of factors, including how often you will get to use it/them), selecting corresponding eyepieces at those extremes then in-filling using f/stop intervals (halving the exit pupil area), though mostly you would start with double f/stop intervals (a double f/stop below is equivalent to halving the eyepiece focal length). So, for example:

27mm Pan = exit pupil of 6mm at your focal length (a good figure - largest practical size is 7mm for young eyes and 5mm for old eyes, with 6mm being a good in-between number)

Double f/stop below 6mm is 3mm exit pupil >> 13.5mm focal length.
Double f/stop below 3mm is 1.5mm exit pupil >> 6.75mm focal length.
In-filling at single f/stop intervals also gives 19mm and 9.5mm focal lengths.

So, if the 27mm Panoptic is your starting point, you would have the following set:
27mm, 19mm, 13.5mm, 9.5mm, 6.75mm.

But, don't get too hung up on these numbers - they're only a rough guide. For example, I also have a 40mm eyepiece for wider views (not applicable to you as the exit pupil would be far too large) but didn't want more than 5 widefield eyepieces, so I omitted some focal lengths and picked others in between f/stops to cover the range.

Specifically, my ideal range would be:
40mm, 28mm, 20mm, 14mm, 10mm, 7mm

Restricting myself to commercially available eyepieces and with some focal lengths in between f/stops (in bold):
40mm, 28mm, 18mm, 11mm, 6.7mm.

This arrangement works very well for me. Your mileage may vary.

I've spent most of the afternoon digesting the latest replies, including Astro Bots and it is starting to gell with me. Yes I tend to agree, i've always thought to myself that the AFOV is not a critical element and more of a comfort element of the eyepiece.

I've taken in all your advice, comments and recommendations - cheers to you all. Today I've ordered the ES 18mm 82D from VTI Optics. This hits 131x. I was surprised that they offered a very competitive price (AUD $212) compared to the overseas stores (e.g. OPT USD $190 + shipping)

[Camelopardalis (Dunk)]

Congrats Stephen! Look forward to hearing what you think of it

[stephenb (Stephen)]

Originally Posted by Camelopardalis

Congrats Stephen! Look forward to hearing what you think of it

Thanks Dunk, I know your advice was to with the 14mm and not the 18 (too close to the 27mm Pan?) however I thought I'd look at a 4-piece set 80x, 130x, 180x & 220x.