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Eyepiece Advice


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Once I complete my second imaging rig, I want to bring my EvoStar 120 back into use as visual scope. I'll be mounting it to an alt-az mount and star hopping around.

 

Could someone give me some eyepiece advice? I currently have the 2 standard skywatcher eyepieces - 28mm and 10mm. I also have an additional SW 6mm plossl.

On my reflector I had 2 inch 28mm eyepiece that I found a lot more comfortable to use that the 1.25 stock ones.

My main targets will be fun stuff like the moon, planets and doubles.  I'll also point at brighter DSOs... but that's not super important. The idea is I want a scope to mess around with during imaging sessions.

Can anyone recommend some useful eyepieces? Not ones that'll break the bank, just give pleasant and comfortable views. I wear glasses and must admit the Skywatcher ones I have, can be a little hard on the eyes,

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Hi Paul, take a look at the Explore scientific wide angle 2" lenses. the 82 degree options give a great F.O.V. and are easy on the eyes. They do 18, 24 and 30mm so pretty good for scooting around the solar system and beyond. they also offer 4.7 to 14mm at 1 1/4". The ultra wides are brilliant for the money. Looking through them is like having your head in a space helmet! Certainly worth checking out. Gary

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You mention that you have previously found a 2 inch eyepiece comfortable, but to use one with a refractor you will also need a 2 inch diagonal. 

Do you have a 2 inch diagonal? If not, they are not that cheap and it would therefore increase your outlay. 

Nightspore has mentioned the TMB clones and he has recently posted a useful review of them. They are surprisingly cheap and available through amazon. As a result of his review I have purchased two and am happy with them. The quality and FOV (58 deg) will be an improvement over the stock pieces you have, although they are available mainly in shorter focal lengths being aimed at planetary viewing.

Eyepieces are quite a personal thing and what suits one may not suit another: personally I find Plössls uncomfortable to use in the shorter focal lengths and something with a wider FOV suits me better.

I have only been doing all this for a few months and have therefore obtained eyepieces through the used marketplace. This has allowed me to try a number of EPs and then to sell on those that didn’t suit me without any noticeable loss before settling on those I liked. Eg Having obtained a used BST starguider I found it of good quality and comfortable to use. I therefore obtained some of the other focal lengths that interested me. On the used market I averaged about £35 a piece.

 

It may help if you stated an approx budget per eyepiece and weather you have any particular focal lengths in mind?

 

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1 hour ago, Sonyme said:

They do 18, 24 and 30mm so pretty good for scooting around the solar system and beyond. they also offer 4.7 to 14mm at 1 1/4". 

 

Some of the ES have quite restrictive eye relief. It doesn't always bother me as I'm used to 4mm ortho's but ES's own estimations of ER can be a bit jackanory.

 

YaXfdWcl.jpg

 

I bought the 2" ES 18mm to replace my 19mm Luminos. I quite like the Luminos, even with all their problems, I don't even mind the EOFB. The 19mm is a bit heavy for most of my rigs so I decided on the 18mm ES.

 

42TLMmTl.jpg

 

I can only really use it in fast scopes (f/4.9 or f/5) as in anything slower I need to evolve a compound eye to use it. Great optics though. I wouldn't recommend it to a glasses wearer. The 28mm is a lot easier and one of my favourites.

 

AYPXqYgl.jpg

 

Of the 1.25" the 8.8mm is outstanding, the 6.7mm is good. There's been controversy about field curvature with the 14mm and all sorts of wacky conspiracy theories. I don't think it suffers badly, it's just not a 13mm Nagler. I think a lot of the 1.25" share a commonality with some older Meade EP's. I believe both were made by JOC.

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Intersting stuff guys - I don't have a budget in mind - but sub £100 would be ideal, but if that's not achievable I have no aversion to saving for a couple of months.

I do indeed have a 2 inch diagonal - it's the stock Skywatcher one - it has 1.25 adapter.

Also the scope is an f/8. I find with the 6mm it suffers a little with resolution and the FOV is hard to manage.  

This is a bit hard to describle but I found with the Skywatcher 2 inch 28mm it was like looking into a view that opened up. I didn't have to shuffle to see. With the smaller ones it's more like looking down the core of a toilet roll tube! I often find my eyeball darts around and leaves me seeing black. This is probably just a practice thing - but I do suffer from terrible eyes.

 

You've given me food for thought - I'll have a look around and see what's out there.

 

 

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On the back of this post I did some googling on exit pupil and eye relief earlier today. Maybe some more knowledgeable posters here will add some more authoritative wisdom?

 

The exit pupil is eyepiece focal length / scope f-ratio so in your case, it's 6/8 or 0.75mm. For someone my age (possibly not too dissimilar to yourself???), my eye pupil in nighttime darkness is likely to be between 4-5mm, so an exit pupil of 4-5mm is ideally matched. Advice seems to be that for smaller, brighter targets, smaller exit pupils are recommended, down to ~1mm. In your case, eyepieces with focal length less than 8mm may cause that 'toilet roll' effect that you mentioned.

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Rough Rule of thumb:

 

Rich field ~ 6-4mm exit pupil.

 

Deep sky ~ 4-2mm exit pupil.

 

lunar/planetary, doubles ~ 1-0.5mm exit pupil.

 

OIII filters best with 3mm or greater exit pupil.

 

Most zooms have between a 5mm and 1.5mm I believe. 

 

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7 hours ago, Nightspore said:

Rough Rule of thumb:

 

Rich field ~ 6-4mm exit pupil.

 

Deep sky ~ 4-2mm exit pupil.

 

lunar/planetary, doubles ~ 1-0.5mm exit pupil.

 

OIII filters best with 3mm or greater exit pupil.

 

Most zooms have between a 5mm and 1.5mm I believe. 

 

What a great little rule of thumb🙂

i have recently started to try and understand exit pupils and how they effect differing targets and you have explained it in a few words. Thanks.

 

PS does the use of a Barlow lens effect the exit pupil?

 

(This last question is not just for me as I was going to ask Paul if he had a Barlow as that may effect his choice of eyepieces.)

Edited by Marmot
Asses question.
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4 hours ago, Marmot said:

What a great little rule of thumb🙂

i have recently started to try and understand exit pupils and how they effect differing targets and you have explained it in a few words. Thanks.

 

PS does the use of a Barlow lens effect the exit pupil?

 

(This last question is not just for me as I was going to ask Paul if he had a Barlow as that may effect his choice of eyepieces.)

 

A lot depends on your own eyes and the size and type of scope you're using. I'm slightly photosensitive, my pupils dilate easily, and as a consequence can often benefit from a wide exit pupil. As I tend to use smaller apertures I like wider exits for rich field and for certain nebulae with an OIII. I can get a 6mm exit with a 36mm Baader Aspheric on my 60 EDF (10x). The slower the scope the less easy to get a wider exit pupil. I had 5.5mm with my 72ED this morning with a 32mm Tak' ortho' and I could see the Eastern and Western Veil with a broadband OIII. Later, without the filter, I saw the Lagoon and Trifid Nebulae. 

 

I saw both globulars in Hercules with a 6mm Tak' ortho for basically a 1mm exit pupil (70x).  Later I observed Saturn and Jupiter (Io transit) at an 0.6mm exit pupil (105x). I tried the 6mm ortho' with a Barlow for 140x (0.51mm exit). This was great for some doubles, not bad on Saturn, but the conditions weren't good enough for Jupiter and I went back to an 0.6mm exit and 105x (4mm Tak' ortho'). 

 

A Barlow basically increases the focal length of the scope. A 2x Barlow just doubles the focal ratio. I can sometimes get away with an 0.3mm exit pupil, but the conditions need to be good and it's easier with a larger aperture. I got as small as an 0.4mm  exit pupil with both my 102mm Starwave refractor (238x) and my 150mm Newtonian on Mars last year. That was *360x with the 150mm Newtonian! I wouldn't have tried that with Jupiter of course lol. Mars isn't such a high contrast target.

 

*Either a 2.5mm TMB clone or a 5mm ortho' in a 2x Barlow.

 

If you get four eyepieces that gives between 5 - 7mm, 1.5mm - 2mm, 1mm and 0.5mm exit pupils you should theoretically be able to see any target. 

 

Or you can get three eyepieces and a 2x Barlow to halve the focal length of the 1mm exit pupil eyepiece to 0.5mm. 

 

Another rule of thumb is that the diameter of the aperture in millimetres roughly equals the magnification at 1mm exit pupil.

 

My 72ED DS Pro gives 70x with a 6mm eyepiece. The 72ED is f/5.8 (approximately f/6). 

Edited by Nightspore
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  • 2 weeks later...

Out of interest, has anyone ever tried a 100 deg eyepiece?  Obviously they're pretty pricey but I'd love one! Any brands anyone has tried?

 

In answer to the OP, I love the Altair Ultraflat eyepieces - I've got quite a few of those.   Just find them comfortable to use on all my scopes.

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On 7/22/2021 at 8:35 PM, Incisive_Solutions said:

In answer to the OP, I love the Altair Ultraflat eyepieces - I've got quite a few of those.   Just find them comfortable to use on all my scopes.

I have been looking at these. The 10mm in particular looks like a great replacement for my stock skywatcher 10mm

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1 hour ago, paulgrover68 said:

I have been looking at these. The 10mm in particular looks like a great replacement for my stock skywatcher 10mm

 

These 10mm 'SvBony' aspherics are incredibly good for 14 quid. I use a pair for my bino.

 

SsykGwsl.png

 

Although I've swapped the barrels for smoothies. 

 

8TvRW07l.jpg

 

You have to use these to realise how good the 10mm and 23mm plastic fantastics are. They have been sold as 'Vite' and Meade. The 4mm should be avoided; it's basically a DIY spectroscope lol.

 

UmXT7e3l.jpg

 

 

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58 minutes ago, paulgrover68 said:

I have SvBony barlow and that is pretty darn good for the money.  I'll check them out.

 

I don't know who actually manufactures these aspherics. Some Chinese OEM no doubt lol. There were rumours Synta were going to bundle the 10 & 23mm with some of their scopes, although nothing ever came of it. 

 

The housings are plastic, although the aluminium barrels are well finished. One of the lens elements (most probably the eye lens) is a polymer material. I guess the aspheric shape is easier to mass produce as a polymer plastic.

 

They've often been referred to as the first disposable eyepieces. Although mine have lasted a few years and the bino pair were last used on the most recent Mars opposition.

 

They are also virtually indestructible and can be dropped and possibly drop-kicked without incurring any real damage. The 23mm is outstanding and virtually as sharp and contrasted as my 25mm Ohi orthoscopic. The 10mm is almost as good and pretty easy to merge with as a pair in a binoviewer. 

 

Avoid the 4mm though. It has serious lateral colour; almost certainly attributable to the additional Smyth lens in the barrel.

 

kpsQrZol.jpg

 

The 10 & 23mm don't have the Smyth. It's been conjectured that the 4mm is only the 10mm with a barrel tele-negative lens. Either way, it's basically the 'turkey' of the set. 

Edited by Nightspore
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You can't go wrong with a set of GSO Plossls for the money.

 

Wans1QZl.jpg

 

Sharp, well contrasted, with good colour separation and very little edge astigmatism.  There are nine in the range: 4, 6, 9, 12, 15, 20, 25, 32 and 40mm. They are often sold under other names. All of mine are branded GSO except the 32 & 40mm which are 'Revelation Astro'. 

 

QGCnXrtl.jpg

 

I even have a bino pair of 12mm GSO Plossls (albeit now with Williams Optics barrels). 

 

Comparison Test of Three Plossl Eyepiece Types: Brandon, Tele Vue and GSO Revelation

 

W5hqegd.jpg

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2 hours ago, MarkAR said:

They seem well priced at less than £30 each.

 

 

I think they're probably the best value on the market. 

 

v47rqv1l.jpg

 

They easily hold their own with the NPL's. I was using the 12mm GSO recently while viewing the Double Cluster with my 72ED. Perseus is getting higher and I'd only taken three or four eyepieces out with me as I'd mainly expected to observe Saturn/Jupiter and split doubles. I had the 12mm GSO Plossl as it was lightweight and gives me a 2mm exit pupil (35x). I thought I might get a chance of some open clusters even with a bright Moon. The Double Cluster was pretty stunning through the GSO Plossl with no noticeable edge astigmatism. The GSO's are over a tenner cheaper than the NPL's. 

 

Bzdgqjpl.jpg

 

I recently added the 20mm GSO Plossl to make the set. I've been using some of the GSO's for years though. The 6mm and 9mm Barlow excellently and are very good for planetary observing. I still use them now. I'd say contrast, transmission and colour separation rivalled Tele Vue. The only EP's with more contrast are orthoscopics IMO. Even then it's close. It's worth pointing out that GSO are phasing out their undercuts. Most of the undercuts that remain have a bevelled lower lip. The lower lip bevel (like on Tele Vue) makes them comparatively easy to extract from a compression ring. The Plossl barrels are a distinctive 30mm in length. They are very well finished and blacked/baffled internally. The filter threads basically fit everything. They're a bargain for under 30 quid.

Edited by Nightspore
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