Eyepieces for glasses wearer??

[Smiffy]

Hi all

 Complete newbie here.

I have just "inherited" a nice telescope from my Son, and am looking for a couple of replacement eyepieces that are glasses wearer friendly.

Does anybody have any recommendations please?

I've been looking at the Celestron X-Cel LX series.

Do any glasses wearers use these, and do they do the job please?

Any advice would be welcome.

Many thanks

Rob

[Marmot]

Hi Rob

As a non glasses wearer, i don’t have experience of viewing with glasses. However, what I can say is that the eyepiece you use should have sufficient ‘eye relief’ to allow your eye to be correctly positioned allowing for your glasses. The term ‘eye relief’ relates to how far your eye is from the lens and is usually listed in the technical specs for any eyepiece. (Easily found by searching on the Net).

I have found that eye pieces are a very personal thing and there are so many out there. A lot will depend on what you are intending to view.

Over the past year I have experimented with a few eyepieces (EPs) but have always purchased through the used market in order that I could resell any I didn’t like with only a minimal, if any, loss.

I have a Celestron X Cel LX in 25mm. It was recommended by another forum member (Nightspore) who has Considerable experience with various kit. (I am fairly sure he will comment on this thread). 

If you do consider the X Cel Lx, just be carefull not to confuse them with the X Cel (no LX on the end) which were, I believe, the previous version and don’t seem to get such good reviews.

[Marmot]

An eyepiece that gets universally good reviews is the ‘Starguider ED series’. I have come across numerous reviews comparing the Starguiders and X Cel LXs against each other. Many reviewers feel that the Starguiders ‘punch above their weight’ considering what they cost. The weak link in the set would appear to be the 25mm and for that reason I have avoided that particular EP although I have acquired a few others, all of which I am pleased with and all of which cost me about £35(give or take) each on the used market.

[Marmot]

Attached is the list of tech specs given by FLO in relation to the starguiders. You will notice that against the eye relief (16mm) it states ‘suitable for spectacle wearers’.

They are also shown as suitable for Scopes of F5 and above: I think yours is about F7 so that also is within the recommendations.

 

Edited November 16, 2021 by Marmot

[Nightspore]

The 25mm BST StarGuider is fine at around f/8 and slower. 

 

 

With faster scopes it can display some lateral astigmatism. I don't know the eye relief. 

[Smiffy]

Thanks for the information guys. My Son is coming down for a few days over Christmas, and is going to run through everything with me and we'll try out the eyepieces that he has. 

I'm sure they will be just the "standard" ones that came with the 'scope when he bought it.

I'll see how I get on with them initially, and if I feel the need to change them for something more comfortable I'll certainly take your recommendations onboard.

Would this be a good upgrade and price please?

https://www.365astronomy.com/optical-accessories-1/eyepieces-(31.7mm,-1.25-)/planetary-eyepieces/bst-explorer-starguider-ed-eyepiece-kit-3.2mm-12mm-and-25mm-eyepieces

 

He has mentioned to me a few times that the motorized mount is going to be the hardest thing to get my head around... I've watched the video. How hard can it be!! 😂

 

 

Really appreciate the help.

Rob

 

 

 

 

Edited November 17, 2021 by Smiffy

[Nightspore]

The StarGuiders are decent 60 degree field eyepieces. The 3.2mm is very good as a planetary eyepiece IME. As I said earlier, the 25mm is good in slower scopes. You need to ascertain what the focal ratio of the scope is. 

 

 

The catadioptric Maksutov Cassegrain above has a 127mm aperture with a 1540mm focal length. 1540/127 = 12.1. Making the focal ratio f/12.1. 

 

 

The 102mm achromatic refractor above has a focal length of 500mm. Making it f/4.9. The Maksutov is considered a 'slow' scope for high magnification and has a limited field of view. The achromat is a 'fast' scope and primarily used for wide field, low magnification viewing (often as little as 14x). Eyepieces will perform differently depending on the focal ratio. Some may exhibit edge distortion in fast scopes where stars near the field stop will be stretched or distorted into long lines.

 

 

Some expensive eyepieces can compensate for this effect. 

 

 

The Altair 102mm ED doublet above has a focal ratio of f/7 and is a good all round scope. It can be used both for high magnification and as a rich field low magnification instrument. As at f/7 it is a good compromise between the two more specialist scopes above. It also has high quality optics and most eyepieces perform well in it without displaying any distortions. Before buying any eyepieces you need to consider:

 

1/ What the focal ratio of your scope is.

2/ What you are primarily interested in observing (planetary/lunar, rich field or deep sky).

3/ How much you want to spend.

Edited November 17, 2021 by Nightspore

[Nightspore]

 

I don't wear eyeglasses but the X-Cel range seem to work for many that do. I'm pretty sure these are exactly the same as the newer Meade HD 60 series (almost certainly same light train by same original equipment manufacturer). These are better in faster scopes in my experience than the StarGuiders. I have a few X-Cels.

[Marmot]

Starguiders are approx £48. New when purchased individually, so the link you give, for a set of 3, works out slightly cheaper. However it seems to restrict you to the 3 eyepieces shown.

Your scope probably comes with a basic 25mm eyepiece that may well be sufficient for the time being and you may decide to spent your money on alternative focal length EPs (at least as a start).

All scopes have a maximum realistic magnification. There are many factors that effect this, but some of the rules of thumb I have read are:

 

1. The Max mag is the same as the telescope lens diameter in millimetres.

2. Calculate the telescope lens diameter in inches and multiply it by    between 30 and 50. (Depending on conditions.

 

As I say, this is merely what I have read. So many factors come into play: seeing conditions, the steadiness of your mount etc etc etc.

 

One of the EPs in the link you give is 3.2mm which would give a pretty high mag with your scope. Would your scope handle it and would it be a mag that you would often use? If you put an EP in your scope that gives too high a mag you will just end up with a blurry image. To get the most from what you see it should be clear and crisp and that is why a less magnified image can be more pleasurable.

 

It sounds like you are being very sensible in trying to obtain information before committing to any purchase. EPs are not cheap and make a difference to your viewing enjoyment. Carefully consider what magnifications would be useful and what spread of EPs you would get best use from. Another way of increasing that spread is by obtaining a Barlow lens which effectively increases the magnification of any given EP. Barlows themselves vary in quality (and cost) just as EPs. 

If you look in the reviews section, I believe that Nightspore has reviewed more than one type of Barlow.

 

 

[Nightspore]

8 hours ago, Marmot said:

 

 

1. The Max mag is the same as the telescope lens diameter in millimetres.

2. Calculate the telescope lens diameter in inches and multiply it by    between 30 and 50. (Depending on conditions.

 

 

 

 

 

Calculating the maximum magnification of a particular scope is never straightforward. Usually twice the aperture diameter in millimetres would be considered the theoretical limit. As this gives an 0.5mm exit pupil.  As you get an exit pupil narrower than 0.5mm it becomes increasingly more difficult for the human eye to detect light.

 

 

In old money the aperture size in inches multiplied by 50x would give an approximate 0.5mm exit pupil. Although for a long time 60x per inch was often considered the theoretical maximum. I can often achieve 60x or 75x per inch with a 2.88 inch ED refractor. Conditions and the actual target will dictate a lot though. Last year I was regularly getting 300x on Mars with my 150mm f/6 Newtonian (0.5mm exit pupil).

 

 

Although occasionally I could get a pretty sharp 360x (60x per inch). Mars often responds well to high magnifications. I wouldn't expect 360x on Saturn or Jupiter, particularly with a reflector.  The 102mm Altair Starwave has S-FPL 53 Ohara glass and I've occasionally pushed this to 300x on some targets.

 

 

However; refractors and reflectors respond differently to magnification. A good ED doublet or triplet refractor can achieve higher magnifications more easily as the light is refracted rather then reflected and there is no aperture obstruction. This lack of an obstruction produces greater acuity and contrast. 

Edited November 17, 2021 by Nightspore

[Smiffy]

21 hours ago, Nightspore said:

Before buying any eyepieces you need to consider:

 

1/ What the focal ratio of your scope is.

2/ What you are primarily interested in observing (planetary/lunar, rich field or deep sky).

3/ How much you want to spend.

 

Thanks for your input guys.

This is the actual telescope I am getting and my primary interest will be planetary/lunar.

https://www.rothervalleyoptics.co.uk/skywatcher-explorer-130p-synscan-az-goto-telescope.html

As far as finances are concerned, I don't want to go "top end" at this moment in time, but by the same token I don't want to be buying rubbish. Middle of the road, I guess!!

I have absolutely zero interest in Astro photography by the way.

I paid my son £150.00 for the 'scope. Does that seem about right??

Edited November 18, 2021 by Smiffy

[Marmot]

The link you provide relates to a scope of F5. This would be classed as a fast scope. The Starguiders specs state they are OK with F5 and above. Nightspore also states that X Cel LXs work with fast scopes.

Fast scopes have a reputation for being a bit more demanding on EPs.

If you check out the review section you will see a review (by Nightspore) on the ‘TMB’ clone planetary eyepieces. These can be obtained at a reasonable price through amazon.

[Nightspore]

2 hours ago, Smiffy said:

 

Thanks for your input guys.

This is the actual telescope I am getting and my primary interest will be planetary/lunar.

https://www.rothervalleyoptics.co.uk/skywatcher-explorer-130p-synscan-az-goto-telescope.html

As far as finances are concerned, I don't want to go "top end" at this moment in time, but by the same token I don't want to be buying rubbish. Middle of the road, I guess!!

I have absolutely zero interest in Astro photography by the way.

I paid my son £150.00 for the 'scope. Does that seem about right??

 

I think 150 quid is quite reasonable lol. At f/5 the Explorer isn't an ideal lunar/planetary scope to be honest. It's relatively fast as many Newtonians are nowadays. The primary reason is that most are actually aimed at astrophotography and faster scopes are better for photography. I'm just a visual observer as well. 

 

 

Your Explorer does have a parabolic mirror though which is good. I have an old 130mm f/7 Explorer somewhere which had a spherical primary and slightly wobbly focuser. A fast scope will be good for wide angle low power views of open clusters and nebulae. 

 

 

Don't panic though, there is a way to slow your Explorer for lunar/planetary!

 

 

Barlow lenses come in many shapes, powers and sizes.

 

 

Your Explorer has a bundled Barsta/BST-made 2x short Barlow featuring a T-thread (above right). These are sold under a variety of brand names and are actually quite good quality. The Barlow is placed into the eyepiece holder in the focuser and then the eyepiece is placed into the Barlow. The negative lens of the Barlow effectively doubles the focal length of the scope. Making your 650mm Newtonian a 1300mm focal length and slowing the focal ratio to f/10. This basically halves the focal length of any eyepiece used with it.

 

 

Speaking of which, the EP's bundled with your scope are almost certainly these Synta 'Modified Achromats' which I'm fairly convinced are a form of reversed Kellner. Combined with the Barlow these would be 5mm and 12.5mm. 

 

 

There's more! Not only can you place the eyepiece in the Barlow itself, the lens elements themselves can often be threaded off and then threaded directly into the eyepiece barrel. This increases the magnification of the eyepiece by about 1.6x. 

 

 

The 25mm MA's are actually quite decent. I used a pair in my binoviewer for a while. The eye relief should be acceptable for glasses wearers. They have plastic housing and aluminium barrels with a 56 degree field of view with good eye placement ergonomics. The 10mm aren't as well liked by many. I believe they feature chromed brass barrels. With the Barlow the 10mm would give 130x with the added advantage that the Barlow would actually increase the eye relief. This is useful for some people who find short focal length eyepieces difficult to use because of a lack of eye relief. You should easily see the rings of Saturn and its Cassini Division at 130x. Surface features on Jupiter and good detail on the Moon as well. 

[Nightspore]

2 hours ago, Marmot said:

The link you provide relates to a scope of F5. This would be classed as a fast scope. The Starguiders specs state they are OK with F5 and above. Nightspore also states that X Cel LXs work with fast scopes.

Fast scopes have a reputation for being a bit more demanding on EPs.

If you check out the review section you will see a review (by Nightspore) on the ‘TMB’ clone planetary eyepieces. These can be obtained at a reasonable price through amazon.

 

OEM's often state a lot of things lol. The 25mm StarGuider isn't good at f/5.8. Trust me on this. 

 

 

You know when the Millennium Falcon jumps to light speed and the stars all stretch out?