Eyepiece Advice

[paulgrover68]

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,

[Nightspore]

 

Any of the TMB clones would be good. 

 

 

See this.

Edited July 13, 2021 by Nightspore

[Sonyme]

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

[Marmot]

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?

 

[Nightspore]

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.

 

 

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.

 

 

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.

 

 

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.

[Nightspore]

Oh yeah, while I'm at it ...

 

SvBony version is cheaper

[Marmot]

Just to give you an idea of cost: there is one of the ES 82 deg FOV eyepieces on eBay. 6.7mm If I remember correctly, and the starting bid is £89.99 

[paulgrover68]

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.

 

 

[Padraic M]

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.

[Nightspore]

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. 

 

[Marmot]

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 July 14, 2021 by Marmot
Asses question.

[Nightspore]

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 July 14, 2021 by Nightspore

[Incisive_Solutions]

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.

[Nightspore]

I have the 15mm UltraFlat. 

 

 

It's similar in overall size to the 19mm Panoptic. I believe they're manufactured by KUO.

[paulgrover68]

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

[Nightspore]

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.

 

 

Although I've swapped the barrels for smoothies. 

 

 

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.

 

 

 

Edited July 26, 2021 by Nightspore

[paulgrover68]

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

[Nightspore]

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.

 

 

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 July 26, 2021 by Nightspore

[paulgrover68]

With their low cost I reckon they'll be worth a whirl on payday

[Nightspore]

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

 

 

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'. 

 

 

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

 

[MarkAR]

They seem well priced at less than £30 each.

 

[Nightspore]

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. 

 

 

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. 

 

 

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 July 30, 2021 by Nightspore

[Nightspore]

2 hours ago, Stephen Waldee said:

 I am delighted to second these recommendations and add my own enthusiastic enjoyment of these eyepieces: I have two  original Back/Burgess models, an Astromania 'clone', an Olivon 'clone', and something else that is also nearly identical: I suspect they came from the same factory.  All are excellent: sharp, high contrast, easy to use (you do not have to hunt around for the "sweet spot"; nor is the eye relief painfully short.)  I have 2.5, 4, 5, 6, and 7.5 mm models and WOULD get the 9 but already have several others at, below, and above 9 that are not far off in performance.

 

I had a long exchange on the phone with Don Pensack, a friend of mine who has sold telescope products for more than 15 years in the LA area of southern California, and a *genuine* eyepiece expert.  He was selling the "Olivon" brand equivalent models until that line was cancelled by the Asian distributor, and agreed that they were bargains and good performers at the price.  FWIW most of my newer eyepieces are from Explore Scientific, though over the years I've owned three Naglers and two other Tele Vue PL types; many from Orion-USA; some Meades; some Vixens.  And I have used friends' Type 6 Naglers on TV scopes: so am definitely acquainted with BEST optical performance.  For 15 years I observed with a friend, equipped with an Astro-Physics 7" StarFire and the whole Nagler line, and saw EVERY object he saw; what a joy! So I acquired a certain taste for clean optical performance from a good eyepiece.  However, I simply cannot afford to pay $500-700 US for one single ocular.  I cannot possibly quantify for you the real difference between, say, a Nagler Type 6 and one of these TMB designed oculars; but I think that when you consider that they can often be acquired for as little as $45 US via Amazon, they are AMAZING! 

 

The apparent field of view is almost 60 degrees, wider than the typical eyepieces supplied with affordable scopes; and they have better coatings (less light loss) and really nice "immersive" views of the deep sky.  To get this for well under $100 US is quite amazing.

 

I have written to the owner of Owl Optics (Dr. Roginsky) years ago to describe my surprised impression of the 2.5 TMB; let me quote that below -- 

========================================================================

Dear Tom:

The 2.5 mm has the following benefits:

1. It works off axis so that I don't have to use a clock drive to do satisfactory hi-res planetary viewing. It's almost exactly as sharp at the field stop, on Mars at 280x, as it is in the middle of the field: NO other eyepiece/Barlow combination I have can match that!

2. It has much lower light scatter than my alternatives.

3. It's sharper than ANY of my Plössls & Erfle "wide field" type oculars. The only thing that matches it for sharpness is -- remarkably -- a 5mm Ramsden! I thought my Baader Hyperions were sharp (I have a 3.5 which, with its optional attachment ring, can achieve a FL of 2.9 mm. The Owl/TMB simply blows it away...)

4. It seems to have higher contrast, so the elusive Martian details are easier to perceive in the dim image provided by a 76 mm aperture instrument!

I can achieve the same magnification with my Orion and Baader and Celestron eyepieces, with one of my various Barlows; but the Owl/TMB unit has one other strange and unexplainable benefit:

5. LOWER perceived eye defects at the same exit pupil!

[In one of my scopes I get an exit pupil of] 0.3 mm, really too small for me, as I can see my floaters and (apparently) the veins in my retinal structure and the 'goo' of the vitreous fluid. This is extremely annoying during lunar observing. I have over the past couple of weeks made some very careful tests, getting the exact same exit pupil by using either a 2x or 3x Barlow and a variety of my other eyepieces: ALWAYS the floaters/eye detritus are objectionable...but they almost completely disappear with the Owl/TMB 2.5! I have no idea why that's the case.

Furthermore, ALL of my Orion non-Plössl eyepieces have problems at high power: I can see fine hairs, dirt specks, and other junk IN FOCUS. I don't see any with the Owl/TMB.

It was a great tragedy that Thomas Back died so young; but he certainly knew what he was doing and bequeathed us some great designs. - SRW

----------------------------------------------------------------------------------------------

Steve & Regina, Ivins UT
http://reginacelestial.byethost3.com
or 
http://celestialregina.x10.mx

In closing, let me admit that both my yacht off Barbados, as well as my 65-floor Manhattan Skyscraper, were paid for by graft and bribes from secretive eyepiece sales elites in Swiss Alps retreats to get me to post this rave...NOT!

 

 

 

 

 

There's some controversy about the TMB clones and how close they are to Back's original design. Possibly some copyright issue. As far as I know Markus Ludes had something to do with the initial setting-up of production of Back's design with a Chinese original equipment manufacturer. TS Optics have a version of it ostensibly made by Barsta. Although as the Barsta/BST website has mysteriously disappeared it's difficult to say for certain . As far as I could ascertain Barsta were two Taiwanese companies that primarily sourced parts from the mainland. 

 

 

There are distinct differences between the housings of the two variants. Identical focal lengths appear to have slightly different focal planes which is possibly indicative of them being from different OEM's. There is a persistent rumour that the 25mm was a manufacturing mistake and should have been 2.5mm. Either way it's a lightweight and competent eyepiece for rich field observing.

 

 

There is no 4.5mm TS Planetary HR equivalent. Some of the HR's have tapered barrels and some have undercuts.

 

 

I honestly can't tell any difference in performance between the two types. I've bought some of the clones new for less than 15 quid. Although they can vary hugely in price, which makes me wonder just how much they actually cost to manufacture. I know one of Back's ambitions was to be able to make high performance eyepieces at affordable prices. Something he definitely achieved. 

 

 

I used these for the last Mars opposition primarily with my 102mm Starwave ED doublet. I have both TMB clones and HR's in 2.5mm and 3.2mm. I thought they compared very favourably with the 3mm DeLite.

 

 

This box is suspiciously Barsta! Don Pensack reckons the BST/Barsta and TMB clones all originate from the same factory. He could well be right but I think they are most likely from different production lines.

 

 

I think I have the set now lol. One day I'd like to discover the real story behind these eyepieces. All of mine get a lot of use with my different scopes. 

[Nightspore]

Oh yeah, while I'm at it ...

 

 

The Smyth lens part of the barrel can also be separated on Celestron Luminos and Orion Expanse eyepieces.

 

 

This can enable any visible dust or debris inside to be removed.

 

 

Don't attempt this with a TV Panoptic as they don't have retaining rings.

Edited March 23, 2022 by Nightspore

[Nightspore]

2 hours ago, Stephen Waldee said:

It's interesting that you can separate the Smyth lens assembly from the Orion Expanse (6, 9); I cannot.  What is the secret?

 

BTW: can someone please explain to me exactly HOW to keep from requoting all the pix in replies? I would like to minimize the file load by only quoting perhaps a line or two of the text.  I have tried NUMEROUS times to edit the quote; can't seem to be done on my Win 7 system with the latest version of Vivaldi browser.  Eventually after I click the little X box that appears ONLY FOR A WHILE on the top left of the quote, I can blunder my way into getting a dialogue box to open up that says "Post only in Plain text"; sometimes if I click on its link, it works and ALL the quoted text AND the pix disappear; which means I have to find and RE-TYPE the part I wish to quote.  Otherwise I will try this over and over and sometimes it NEVER goes to plain text and nothing happens.  In this quote above I tried to remove the pix but retain the text--couldn't do it.  I am new to the forum and have not used this particular forum software package before.  (I can actually program in C so I am not completely computer-illiterate; have been using home computers since the days of CP/M.)

 

I'd appreciate any useful advice but if there's nothing to be done about it...

 

At any rate, Nightspore, you sure are one formidable eyepiece maven! I'm almost afraid to say anything more about oculars here! (tee-hee.)

Steve & Regina, Ivins UT
http://reginacelestial.byethost3.com
or 
http://celestialregina.x10.mx

 

 

 

I just unthread the barrel from the housing on the Expanse. Actually removing the tele-negative Smyth cell group would entail removing its retaining ring. Once the barrel is separated from the housing you can clean the two exposed lens surfaces inside. There's no real need to remove the Smyth cell itself. Unless you really want to lol. I regularly take things to pieces.

 

 

The real secret is putting it all back together so that it works properly. Preferably with no pieces enigmatically left over.

 

 

Not sure how the text box works. Maybe just copy/paste what's relevant?

 

"I would like to minimize the file load by only quoting perhaps a line or two of the text." Like this.

 

I'd like to find a way to remove Bugvaldi from Ubuntu 20.04.4 LTS! ROTFL

 

 

I may be having a word with von Tetzchner about this lol. 

 

 

Edited March 23, 2022 by Nightspore