Eyepieces - advice on selecting a set please

[wulfrun]

First off, the scope in question is a Skywatcher Heritage 114P Virtuoso, so 114mm f/4.4 and fairly modest capability and with tracking but not Go-To. Note that I'm new to astronomy, at least in the practical sense. I won't get my hands on the scope until Christmas but I'm thinking ahead about an eyepiece set, not least because I expect the 10 & 25mm supplied to be mediocre and limiting, at best. With this in mind there's no rush and bear in mind that I have no strict budget. Saying that, I don't want to go way over-spec and break the bank for no good reason. However, I suspect that this may not be my last or only scope, so I'd want any purchases not to be useless on future equipment.

I've read multiple articles so I understand things like magnification, FOV, exit-pupil and so on. My "experience" though, is not based on practice. I'm also new to scopes so there are probably pitfalls that I have no idea about. I do have a lot of experience in photography (terrestrial not astronomical) so the basic concepts aren't new.

I have in mind a set of 3 eyepieces plus a Barlow, 2x seems to be the sensible choice. I have not yet developed any preference for DSOs, planetary etc so I'm aiming for a general, starter set that would cover a useful range and is based on the new scope's capability.

I'm looking at either BSTs in 5mm, 8mm and 18mm plus 2x barlow OR Celestron X-Cel in 5mm, 7mm and 18mm plus 2x barlow. BSTs seem to get a decent reputation. Either of these gives me from x28 up to x200 in reasonable steps and all fit within sensible ranges for exit-pupil and magnification. The mid-range FLs fall into the "about 2mm exit-pupil" sweetspot, I believe. I could swap out the 18mm end for a 25mm for x20 but I'm old enough that the 5.7mm exit-pupil is likely a waste and I have a reasonable pair of 10x50 binoculars (Pentax SP WP) for low-power use. I know the highest magnification is close to the theoretical limit and wouldn't often be usable anyway but I'd be getting it almost for free, so why not have it available.

My questions then: are the choices reasonable? Have I picked sensible quality? Are the Celestrons worth 40% (ish) more than the BSTs? Anything glaringly obvious that I've missed? One other question: barlows - there's no such thing as a free lunch so where should one be avoided? I didn't find any explanation of the pros and cons in my reading but I think they are the astronomical version of a photographic teleconverter, which I do understand well enough.

I'm very much open to alternatives for make, or FL/FOV choice. I'm also open to not buying anything yet, or to a different set, if that's a more sensible approach.

Apologies for the long-ish post but I wanted to explain my logic so it's there to be picked apart. I'd rather learn from my mistakes the cheap way, from those with better knowledge!

 

[Ally8446]

I'd say go with the BSTs, they're a cracking eyepiece for the money. 

One thing I would point out. I don't see the point in you getting a Barlow with the EP focal lengths you have stated. The 18mm barlowed would give you the equivalent of 9mm, you would already have an 8mm. Also, 8mm and 5mm barlowed would give you 4mm & 2.5mm respectively. Those kind of powers would very rarely be usable in UK skies. 2.5mm would probably be unusable as the magnification would be too great. My advice would be to go for 18, 12 & 8mm, forget about the Barlow for now.

Just my opinion of course. 

Clear skies

P.S You wouldn't happen to be from Wolves ? Going on your name of Wulfrun. 

[wulfrun]

31 minutes ago, Ally8446 said:

I'd say go with the BSTs, they're a cracking eyepiece for the money. 

One thing I would point out. I don't see the point in you getting a Barlow with the EP focal lengths you have stated. The 18mm barlowed would give you the equivalent of 9mm, you would already have an 8mm. Also, 8mm and 5mm barlowed would give you 4mm & 2.5mm respectively. Those kind of powers would very rarely be usable in UK skies. 2.5mm would probably be unusable as the magnification would be too great. My advice would be to go for 18, 12 & 8mm, forget about the Barlow for now.

Just my opinion of course. 

Clear skies

P.S You wouldn't happen to be from Wolves ? Going on your name of Wulfrun. 

Thanks for the opinion, it's always good to hear - whether one agrees or not - and the nudge towards BSTs. Your ideas would give me x28, x42 and x63. Are you suggesting that more than x63 is likely useless in the UK? That comes as a surprise! I can well believe it true from my back-yard but under better conditions what would be feasible? Before you say it, no I haven't fallen for the idea that magnification is everything...just sometimes nice to have on hand. Half the idea of choosing this scope is that it's very portable to darker skies.

Yes, I live in Wolves but I was born in Bloxwich (someone has to be).

EDIT: for not a lot more I could, instead, get the Hyperion Zoom 8-24mm, with a slight sacrifice of FOV at the 24mm end. It seems to be well thought of. Any opinions welcome.

Edited October 10, 2020 by wulfrun

[Kyle Allen]

The 8mm BST is a great eyepiece. How about getting 18, 8 and a 2x Barlow lens? That would cover low, medium and high power with your scope. You can add a 12mm later if you feel that you are missing something in between. Obviously, the 18mm barlowed would be too close to the 8mm to be useful but it will effectively give you a 4mm and will only cost the same as an extra eyepiece. I have the BST Barlow lens and it seems fine to me.

You can have a play around with different eyepiece combinations on this site: http://astronomy.tools/calculators/field_of_view/ 🙂

[wulfrun]

19 minutes ago, Kyle Allen said:

The 8mm BST is a great eyepiece. How about getting 18, 8 and a 2x Barlow lens? That would cover low, medium and high power with your scope. You can add a 12mm later if you feel that you are missing something in between. Obviously, the 18mm barlowed would be too close to the 8mm to be useful but it will effectively give you a 4mm and will only cost the same as an extra eyepiece. I have the BST Barlow lens and it seems fine to me.

You can have a play around with different eyepiece combinations on this site: http://astronomy.tools/calculators/field_of_view/ 🙂

 

Seems a pretty reasonable suggestion, thanks. I had also considered 25mm and 8mm plus barlow for a slightly greater variety.

I've seen that diagram and it's quite useful to see what it shows in the EP. I knocked up a spreadsheet that calculates all the relevant stuff for me - for any given eyepiece/barlow - but of course that just gives numbers without context.

Edited October 10, 2020 by wulfrun

[Ally8446]

Your maximum magnification would be around x225. It's generally accepted that the maximum mag is 50x the scope aperture. That said, 5mm ep barlowed would give you 200x mag, usable but only in exceptionally good conditions. The target would move across your very narrow fov so quickly. 

I lived in Wolves for 8 years but have lived in Wales for the last 16.

Edited October 10, 2020 by Ally8446
Additional content

[wulfrun]

6 minutes ago, Ally8446 said:

Your maximum magnification would be around x225. It's generally accepted that the maximum mag is 50x the scope aperture. That said, 5mm ep barlowed would give you 200x mag, usable but only in exceptionally good conditions. The target would move across your very narrow fov so quickly. 

I lived in Wolves for 8 years but have lived in Wales for the last 16.

I think there may be crossed wires here. I know the theoretical maximum is around x225, I also know that "seeing" and other factors make that rarely possible. I meant what would you consider a realistic maximum in the UK, given the scope? I'm hoping the Virtuoso mount will at least keep things in the FOV usefully well - reviews suggest it will.

[Ally8446]

20 minutes ago, wulfrun said:

I think there may be crossed wires here. I know the theoretical maximum is around x225, I also know that "seeing" and other factors make that rarely possible. I meant what would you consider a realistic maximum in the UK, given the scope? I'm hoping the Virtuoso mount will at least keep things in the FOV usefully well - reviews suggest it will.

I would agree that there are wires crossed ☺️

Imo you should be able to use an 8mm very regularly. On the occasion, 5mm. I'd doubt you'd ever get to use 2.5mm (5mm barlowed) 

[Dantooine]

3 hours ago, wulfrun said:

First off, the scope in question is a Skywatcher Heritage 114P Virtuoso, so 114mm f/4.4 and fairly modest capability and with tracking but not Go-To. Note that I'm new to astronomy, at least in the practical sense. I won't get my hands on the scope until Christmas but I'm thinking ahead about an eyepiece set, not least because I expect the 10 & 25mm supplied to be mediocre and limiting, at best. With this in mind there's no rush and bear in mind that I have no strict budget. Saying that, I don't want to go way over-spec and break the bank for no good reason. However, I suspect that this may not be my last or only scope, so I'd want any purchases not to be useless on future equipment.

I've read multiple articles so I understand things like magnification, FOV, exit-pupil and so on. My "experience" though, is not based on practice. I'm also new to scopes so there are probably pitfalls that I have no idea about. I do have a lot of experience in photography (terrestrial not astronomical) so the basic concepts aren't new.

I have in mind a set of 3 eyepieces plus a Barlow, 2x seems to be the sensible choice. I have not yet developed any preference for DSOs, planetary etc so I'm aiming for a general, starter set that would cover a useful range and is based on the new scope's capability.

I'm looking at either BSTs in 5mm, 8mm and 18mm plus 2x barlow OR Celestron X-Cel in 5mm, 7mm and 18mm plus 2x barlow. BSTs seem to get a decent reputation. Either of these gives me from x28 up to x200 in reasonable steps and all fit within sensible ranges for exit-pupil and magnification. The mid-range FLs fall into the "about 2mm exit-pupil" sweetspot, I believe. I could swap out the 18mm end for a 25mm for x20 but I'm old enough that the 5.7mm exit-pupil is likely a waste and I have a reasonable pair of 10x50 binoculars (Pentax SP WP) for low-power use. I know the highest magnification is close to the theoretical limit and wouldn't often be usable anyway but I'd be getting it almost for free, so why not have it available.

My questions then: are the choices reasonable? Have I picked sensible quality? Are the Celestrons worth 40% (ish) more than the BSTs? Anything glaringly obvious that I've missed? One other question: barlows - there's no such thing as a free lunch so where should one be avoided? I didn't find any explanation of the pros and cons in my reading but I think they are the astronomical version of a photographic teleconverter, which I do understand well enough.

I'm very much open to alternatives for make, or FL/FOV choice. I'm also open to not buying anything yet, or to a different set, if that's a more sensible approach.

Apologies for the long-ish post but I wanted to explain my logic so it's there to be picked apart. I'd rather learn from my mistakes the cheap way, from those with better knowledge!

 

Hello,

I would be tempted to get an explore Scientific 8.8mm 82 degrees eyepiece. It would give you a magnification if 57x and the same field of view as the 12mm BST at 41x. I think you would use this a lot. A barlow on that would give 114x. I would used that as a centrepiece and build around it. But that’s just me and we are all different. The stock 25mm would probably be usable but the 10mm would be lacking. 

[Ricochet]

Having used the 1145P and some of the eyepieces in question I would say:

• The 5-12mm Starguiders will work well in your scope
• The 5-12mm X-Cel LXs will also work well in your scope. Having owned a 7mm I think they might have better coatings than the Starguiders, but having sold it I can't check. If they do have better coatings then yes, they are worth the extra money, but if they don't then maybe not.
• The 18 and 25mm Starguiders and X-Cell LXs will be awful in your scope. At the longer focal lengths I suggest you look at the Explore Scientific 68° range. If you want to maximise FoV then go for the 24mm, if you think the exit pupil is too large, perhaps the 20mm instead. As you will get a 25mm with the telescope you can check this for yourself before you buy a replacement eyepiece.
• A 2X barlow will be useful with the short focal length eyepieces to try to squeeze a bit more magnification out of the telescope for lunar and planetary. You won't be anywhere near atmospheric limits without the barlow.

Also, finding a way to increase the diameter of the focuser wheel will greatly increase the ability to focus the telescope. I made a 3D printed ring to push fit over one of the wheels and was so impressed with it that I made one for my own scope the next day.

[wulfrun]

1 hour ago, Ricochet said:

Having used the 1145P and some of the eyepieces in question I would say:

• The 5-12mm Starguiders will work well in your scope
• The 5-12mm X-Cel LXs will also work well in your scope. Having owned a 7mm I think they might have better coatings than the Starguiders, but having sold it I can't check. If they do have better coatings then yes, they are worth the extra money, but if they don't then maybe not.
• The 18 and 25mm Starguiders and X-Cell LXs will be awful in your scope. At the longer focal lengths I suggest you look at the Explore Scientific 68° range. If you want to maximise FoV then go for the 24mm, if you think the exit pupil is too large, perhaps the 20mm instead. As you will get a 25mm with the telescope you can check this for yourself before you buy a replacement eyepiece.
• A 2X barlow will be useful with the short focal length eyepieces to try to squeeze a bit more magnification out of the telescope for lunar and planetary. You won't be anywhere near atmospheric limits without the barlow.

Also, finding a way to increase the diameter of the focuser wheel will greatly increase the ability to focus the telescope. I made a 3D printed ring to push fit over one of the wheels and was so impressed with it that I made one for my own scope the next day.

Thanks, that's very helpful. I'll see if anyone else weighs in on the BST vs X-Cel LXs. The Explore is fair jump in investment, especially the 8.8mm 82-degree suggested above; I'll probably hold off on either of those until I see how I get on with the supplied 25mm before comitting. Out of curiosity, is there a technical reason you say that the 18-25mm BST/X-Cel LX would be awful or is that purely experience-based? I am not doubting you but if there's a technical explanation I'd like to understand it - I have that kind of mind and it's useful knowledge.

Noted on the focuser, I'm sure I can cook something up. I'll mull over the 5-12mm range to try and avoid duplication with barlowing, although that might not be easy.

Also, no-one's yet offered an opinion on the Hyperion zoom. Unless it's a poor choice it'd still be in the running so I'm still after bad/good idea opinions.

[Dantooine]

8 minutes ago, wulfrun said:

Thanks, that's very helpful. I'll see if anyone else weighs in on the BST vs X-Cel LXs. The Explore is fair jump in investment, especially the 8.8mm 82-degree suggested above; I'll probably hold off on either of those until I see how I get on with the supplied 25mm before comitting. Out of curiosity, is there a technical reason you say that the 18-25mm BST/X-Cel LX would be awful or is that purely experience-based? I am not doubting you but if there's a technical explanation I'd like to understand it - I have that kind of mind and it's useful knowledge.

Noted on the focuser, I'm sure I can cook something up. I'll mull over the 5-12mm range to try and avoid duplication with barlowing, although that might not be easy.

Also, no-one's yet offered an opinion on the Hyperion zoom. Unless it's a poor choice it'd still be in the running so I'm still after bad/good idea opinions.

I’ve not used the baader zoom but I would think it’s because of the very narrow field of view at the 24mm end of things. 

[John]

17 minutes ago, wulfrun said:

.... Out of curiosity, is there a technical reason you say that the 18-25mm BST/X-Cel LX would be awful or is that purely experience-based? I am not doubting you but if there's a technical explanation I'd like to understand it - I have that kind of mind and it's useful knowledge....

 

I don't know about the 18mm but the 25mm BST Starguider is not particularly well corrected in faster scopes, which means that stars will look more like seagulls in the outer half of the view. The challenge with the 114mm F/4.4 newtonian is that it is a rather fast scope and therefore it creates optical challenges for lower cost eyepieces with wider than average fields of view.

If you are not careful you can invest 2x - 3x as much as the scope has cost on decent quality eyepieces when you could have actually bought a scope with much more performance for the same overall investment.

As you don't actually have the scope yet, I'd be tempted to say don't buy any additional accessories for it until you have used it with what it comes with a few times. After that at least any future investments will be influenced by some of your own personal experiences

 

[Ricochet]

12 minutes ago, wulfrun said:

Out of curiosity, is there a technical reason you say that the 18-25mm BST/X-Cel LX would be awful or is that purely experience-based?

It is based on experience of using the Starguiders and reading similar reports about the X-cel LXs, which make sense considering the design of these eyepiece lines.

Essentially, each eyepiece is the same 4-element set of lenses with different singlet or doublet barlow-like lens in the nose piece. The shorter the focal length of the eyepiece, the stronger the "barlow" and the slower the light cone when it reaches the main set of lenses. As slower focal ratios are easier for an eyepiece to correct, you can see why the shorter focal lengths are better corrected. 

[wulfrun]

Thanks to all for the input. I'll give it all some thought and not rush into anything, possibly even wait till I've used the scope a bit and see where that leads me. I was aware that it's a "fast" scope and would require decent eyepieces to give its best. I have a better understanding now, at least.