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

[Varangian (John)]

Originally Posted by Camelopardalis

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

I suggest you look through one in a fast newt like I was and like OP is, which is what I have done with the 14. I mentioned that I was using other ES EPs in a fast scope. You could even try reading the entire thread maybe? Better still look at a heap of reviews on the 14 on this forum - in particular Bambury's who uses this EP in fast newts like the OP.

[stephenb (Stephen)]

Originally Posted by Varangian

I suggest you look through one in a fast newt like I was and like OP is, which is what I have done with the 14. I mentioned that I was using other ES EPs in a fast scope. You could even try reading the entire thread maybe? Better still look at a heap of reviews on the 14 on this forum - in particular Bambury's who uses this EP in fast newts like the OP.

The ES 14mm 100D has been recommended by my telescope maker so I am 100% confident I will not see any "seagulling".

Edit: Varangian, if you have any links to reviews on IIS I'd be happy to read them (I've done a quick search this morning and located this thread from Erick and John Bambury's post
Cheers

[Varangian (John)]

Originally Posted by stephenb

The ES 14mm 100D has been recommended by my telescope maker so I am 100% confident I will not see any "seagulling".

Yes the 14 mm 100 is perfect I have it myself and I said as much in my earlier posts. As per earlier posts I'm talking about the 14 mm 82 that you mentioned in one of your earlier posts. sheez.

[Varangian (John)]

Originally Posted by WattleHill

Varangian, Do you use a coma corrector on your setup? I have experienced this "sea gulling" effect on the extreme FOV prior to installing a CC. I also used to get this effect on earlier scopes (10" and 12" GSO dobs)

Hi John, I have a CC and it does fix the majority of the problem I had with the ES 82 14 mm. My advice was based on use of the 14 mm 82 without a CC however. There are plenty of EPs out there around 14 mm that you can use on a fast newt without a CC - even though many Dob owners will not use much above this FL without one.

My original advice was based on my personal experience of the ES 82 14 mm with a fast newt. I purchased it under the assumption that the entire 82 ES line was very good but when I tried it in the 4.9 not only did I see sea gulling across the outer 25% but also blurred vision. At first as suggested I thought it was my scope so I collimated about 3 times and tried again - same problem. Then I started to panic about my eyes! I jumpoed on line and found a plethora of reviews on this EP in fast newts and 95% of them recommended to stay away.

[stephenb (Stephen)]

Originally Posted by Varangian

Yes the 14 mm 100 is perfect I have it myself and I said as much in my earlier posts. As per earlier posts I'm talking about the 14 mm 82 that you mentioned in one of your earlier posts. sheez.

Sorry, John, I understand what your saying. Miscommunication , But you are correct, the 100D reviews I am finding this morning across the interwebs are very encouraging.

[Varangian (John)]

Originally Posted by stephenb

Sorry, John, I understand what your saying. Miscommunication , But you are correct, the 100D reviews I am finding this morning across the interwebs are very encouraging.

Stephen, I'll look for the review at lunch time today. I remember coming across a thread recently when I was looking for reviews on the 6.7 82 ES where Bambury states that the designers were 'drunk' when they designed the 14 mm 82 Again, his experiences of it were in a fast newt and mine were the same when I tried it at Heathcote a while back. Other Dob users on the night felt the same.

Not sure if it was CN or IIS but I'll try to find it as it's a great and informative thread for those in the market for a new ES EP.

[stephenb (Stephen)]

Cheers, John, I'm yet to get this dob up to Heathcote due to transport issues, but maybe one day soon....



Interesting USD prices for international postage on the 100D 14mm ES:

Eyepieceetc.com $399 + 83.51 postage

OPT Telecopes: $399 + 64.31 postage

I did communicate with Don Pensack from eyepiecesetc.com who incidently was extremely helpful and he apologised for the postage costs, but I understand that's the fault of USPS - not the retailer's.

I will check with VTI and Extravision today on their availability....

[Don Pensack]

My original advice was based on the idea that a particular scope should start out with a 1X/2X/3X magnification scheme, where X= a particular number based on the aperture. For instance, on an 8", X=50, on a 12.5", X=70, and on an 18", X=80.
That's because the larger scope can use higher magnifications and for the same f/ratio, larger scopes have higher magnifications at the same exit pupil.

Is that all the eyepieces you would need? Probably not as seeing conditions are rarely the same everywhere (people under very steady skies tend to use higher magnifications) and you might find yourself wanting a magnification in between two that are derived this way.

Such a recommendation flies in the face of exit pupil considerations.
Take the 18" f/4.5 scope with a Paracorr. The effective f/ratio is f/5.18,
so a 2mm exit pupil would be a 10.4mm eyepiece = 228X. Most places, that would be too high a magnification for a mid-power eyepiece, even though it is a mid-sized exit pupil.
so though the exit pupil idea seems to work well for small scopes, it doesn't seem to work very well on large scopes, which is the reason I came up with a 1X/2X/3X idea for a basic set of eyepieces to build a collection around.
In my scope, that was 70x, 140x, 210x, or 26mm, 13mm, 9mm and I have built around that idea by splitting the 9mm into an 8 and 10mm and going beyond in the high end to 6 and 4.7mm.
But the idea of a basic set of 3 around which you can build a collection is not a bad one.

And if you choose to use exit pupils to do so, that's fine, but just remember it doesn't work very well in big scopes. I have a friend with a 28" f/4.2 scope. With a Paracorr, his focal ratio is f/4.8. A 9.6mm eyepiece would yield 358X. Where he observes, he can use that magnification fairly often, but not much higher. But that's a 2mm exit pupil, which is mid-power by exit pupil standards.

[Camelopardalis (Dunk)]

Originally Posted by stephenb

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.

4-piece set sounds like a plan Stephen

From the sounds of things, a coma corrector would be a good addition to the collection too, of you're ordering from the US anyway...

[killswitch (Edison)]

Originally Posted by stephenb

Cheers, John, I'm yet to get this dob up to Heathcote due to transport issues, but maybe one day soon....

Interesting USD prices for international postage on the 100D 14mm ES:

Eyepieceetc.com $399 + 83.51 postage

OPT Telecopes: $399 + 64.31 postage

I will check with VTI and Extravision today on their availability....

Wow its gone up in price. Just last year, i picked up the ES 14mm 100d Argon from AgenaAstro for $299 + $45 shipping (USD).

One thing about the 100d eyepiece is that they are heavy and can throw your scope off balance.

[MortonH]

Anyone asked VTI when/if they're getting the 14mm 100D back in stock?

[Varangian (John)]

Originally Posted by killswitch

Wow its gone up in price. Just last year, i picked up the ES 14mm 100d Argon from AgenaAstro for $299 + $45 shipping (USD).

One thing about the 100d eyepiece is that they are heavy and can throw your scope off balance.

Yes I only have a 12" and that is the smallest scope I would use it on. I have to use counter weights when I use the 14mm 100 which is a bit of a pain...

Originally Posted by MortonH

Anyone asked VTI when/if they're getting the 14mm 100D back in stock?

James was o/s when I spoke to him a month ago and said he was replenishing supplies of the 82 series by the end of May. I'm not sure about the 100 series though An email will clear that up.

[Astro_Bot]

I think I need to correct a misinterpretation of my post ...

Originally Posted by Don Pensack

My original advice was based on the idea that a particular scope should start out with a 1X/2X/3X magnification scheme, where X= a particular number based on the aperture. For instance, on an 8", X=50, on a 12.5", X=70, and on an 18", X=80.
That's because the larger scope can use higher magnifications and for the same f/ratio, larger scopes have higher magnifications at the same exit pupil.

Is that all the eyepieces you would need? Probably not as seeing conditions are rarely the same everywhere (people under very steady skies tend to use higher magnifications) and you might find yourself wanting a magnification in between two that are derived this way.

Such a recommendation flies in the face of exit pupil considerations.
Take the 18" f/4.5 scope with a Paracorr. The effective f/ratio is f/5.18,
so a 2mm exit pupil would be a 10.4mm eyepiece = 228X. Most places, that would be too high a magnification for a mid-power eyepiece, even though it is a mid-sized exit pupil.
so though the exit pupil idea seems to work well for small scopes, it doesn't seem to work very well on large scopes, which is the reason I came up with a 1X/2X/3X idea for a basic set of eyepieces to build a collection around.
In my scope, that was 70x, 140x, 210x, or 26mm, 13mm, 9mm and I have built around that idea by splitting the 9mm into an 8 and 10mm and going beyond in the high end to 6 and 4.7mm.
But the idea of a basic set of 3 around which you can build a collection is not a bad one.

And if you choose to use exit pupils to do so, that's fine, but just remember it doesn't work very well in big scopes. I have a friend with a 28" f/4.2 scope. With a Paracorr, his focal ratio is f/4.8. A 9.6mm eyepiece would yield 358X. Where he observes, he can use that magnification fairly often, but not much higher. But that's a 2mm exit pupil, which is mid-power by exit pupil standards.

Don, if you're referring back to my post, with its advice to use f/stop intervals based on exit pupil, as you seem to be, you're overlooking a very important step.

The first step I recommend (as do many people) is:

Originally Posted by Astro_Bot

... 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 ...

In this scheme, you would use the f/stop interval (exit pupil) to fill-in between the magnification extremes, hence whether the smallest exit pupil is considered mid-sized or not is irrelevant.

The absolute size of the exit pupil has to be considered anyway - that's largely how an owner would arrive at the lowest practical magnification along with consideration of effect of a central obstruction (if any). In your method, you address this with a "look up table" of aperture vs. lowest magnification, and whilst that's certainly one way to go, IMHO, it's an unnecessary approximation that doesn't suit all users, although as an eyepiece vendor, if you're there to apply it to each purchaser, I'm sure it would work well. For everybody else, better to calculate exit pupil and use it directly. (In Stephen's case, he already had a 27mm Pan with 6mm exit pupil, so that was not an issue here).

The bottom line is that, whatever method is used, it remains only a rough guide, and neither of us is Stephen.

[garin (Garin)]

Hi Stephen,
I suspect your 18" is an SDM like mine.
In the brief time I've had mine (about a month and a half) I've found the eyepieces I'm favouring are my 13mm Ethos and the 8mm Ethos, I am missing my wide field view and tried another club member's 26mm Nagler and that was really nice, I also found the original Meade QX 26m I sold with my Lightbridge wasn't bad.

[stephenb (Stephen)]

Originally Posted by MortonH

Anyone asked VTI when/if they're getting the 14mm 100D back in stock?

From VTI today, they no longer carry it in thier stock line as there was no demand for it. Extravision hasn't got back to me so I guess it's over to eyepiecesetc.com

ES 18mm 82D should be her early next week. Standby for a review in the coming weeks

[brunono2 (Brian)]

Agena astro is one of the best USA suppliers of astro equipment including ES eyepieces -delivers usually the next day after the order placed; low freight charges and excellent attitude and response if you have any issues with items received

The ES 14MM 100 is USD 399.99

Cheers

BRUNO

[stephenb (Stephen)]

Originally Posted by brunono2

Agena astro is one of the best USA suppliers of astro equipment including ES eyepieces -delivers usually the next day after the order placed; low freight charges and excellent attitude and response if you have any issues with items received

The ES 14MM 100 is USD 399.99

Cheers

BRUNO

Yes, I've been watching Agena Astro for other products, Bruno. I saw their range of e/ps but I was undecided. I'll take another look at them today.

[Astro_Bot]

I've been trying to remain vendor-neutral in recent times, but, since you've raised the topic ... I've had excellent service from Agena Astro (including for ES eyepieces) and can highly recommend them.

[Varangian (John)]

Originally Posted by Varangian

Stephen, I'll look for the review at lunch time today. I remember coming across a thread recently when I was looking for reviews on the 6.7 82 ES where Bambury states that the designers were 'drunk' when they designed the 14 mm 82 Again, his experiences of it were in a fast newt and mine were the same when I tried it at Heathcote a while back. Other Dob users on the night felt the same.

Not sure if it was CN or IIS but I'll try to find it as it's a great and informative thread for those in the market for a new ES EP.

Despite about an hour searching I cannot for the life of me find this post by John B. I came across it looking for reviews on the 6.7mm ES but have had no luck following up. Maybe John B will read this thread and provide his views on the 14mm 82 ES at some stage...

[stephenb (Stephen)]

Thank anyway for your efforts, John.

The ES 18mm arrived today after placing the order on Thursday (including a day for the bank payment to clear). I'll give it a go this evening on the Moon, Mars, Jupiter and Saturn.

I also ordered a pack of 4 eyepiece screw bolt containers but unfortunately the ES and the TV 27mm Pan do not fit in them! Oh well. Looks like I'll have to flog them off on IIS Trade Section

Originally Posted by MortonH

Anyone asked VTI when/if they're getting the 14mm 100D back in stock?

Both VTI and Extravision are not stocking this one...