Which eyepieces for a F/10?

[Fordy_638]

Hi all,

I recently bought a evo 925 and I'm now looking for some eyepieces. I'm new to this and the more I research the harder the decision making becomes with regards to expanding my eyepiece collection from the stock pair I have.

I'm confused about fast scopes and slow scopes and what FOV I should be going for. I was looking at perhaps a zoom ep, perhaps Hyperion 3 or Celestron deluxe. Are these wise choices?

I don't Mind buying individual eps, my budget is around £50-£75 each and looking for 2-3 for now. Or maybe the more expensive zoom as has more options.

I'm just not sure whether some eps suitability with my scope? Can someone please point me in the right direction? I would like to see planets, just so you know what I'm after.

Ta.

[Knighty2112]

You really don't need to worry about fast or slow scopes unless you plan on doing astro imaging. If not then don't worry about it. If you go for anywhere between 32mm to 2mm should be fine with your scope. Don't own a zoom EP, so can't really comment on those. Also, would be worth while getting a good Barlow lens, as this will double you range of FOV's and magnifications without have to have lots of different sized EP's.

[Dave In Vermont]

The Baader Hyperion Mark III 8 - 24mm Zoom EP is an excellent EP. It's really best to consider it a 20mm to 8mm as the 24mm has only a 40° field-of-view (FOV), which is really a bit to narrow for most tastes. But such is true with all zoom EP's you're likely to find. But all in all, it's outstanding. I highly recommend it.

The Baader Hyperion EP's are also very nice. They work very well in F10 SCT's from most accounts. But then F10 SCT's are not terribly picky about what variety of glass you feed them. If you've got the £££'s, the Baader Morpheus-line have been getting rave reviews from end-users, though I have yet to try them. I also concur that a good Barlow would be a fine addition. But do realize that at F10, it's quite easy to reach a maximum magnification before you go too high and your image degrades - depending on 'seeing' conditions. So a Barlow will have a somewhat limited amount of usable applications before you wind up with 500X or something else ridiculous! With a Barlow, you want one with the best quality  possible that allows it to disappear in the optical-pathway. This means one that doesn't dim the view or cause vignetting (blurring). Though I hate to endorse TeleVue, for a Barlow I do suggest spending the extra £'s and going that route, or other top-end glass. Your Barlow will not only increase the magnification of the image in the eyepiece, it will also magnify any imperfections in the Barlow and/or eyepiece itself. So go for the best.

Before you jump into buying new EP's, do get used to the scope with the supplied EP's - which should be a 40mm and a 13mm. These give you 58.75X and 180.76X respectively. See what you think about these amounts of power before you decide which other EP's you'd want to add. A 2mm, which Knighty mentioned (he must be kidding) would give you 1175X! Don't even think about it! You'd need to be observing from the Moon on a dark night in the bottom of a crater to get away with that!

Enjoy your new scope!

Dave

[Stu]

You really don't need to worry about fast or slow scopes unless you plan on doing astro imaging. If not then don't worry about it. If you go for anywhere between 32mm to 2mm should be fine with your scope. Don't own a zoom EP, so can't really comment on those. Also, would be worth while getting a good Barlow lens, as this will double you range of FOV's and magnifications without have to have lots of different sized EP's.

The terms fast and slow scope are relevant for observing because of the impact they have on the quality of eyepieces you need. Slow scopes (will long focal ratios such as the 925) are far less demanding on eyepieces than faster scopes down at f5 and below. The edge performance in faster scopes is far more difficult to maintain and only the likes of Televue specify their eyepieces as working well at f4.

On the 32mm to 2mm comment, the 925 has along focal length at 2350 (if I remember correctly). A 10mm eyepiece would give you plenty of mag at x235, an 8mm would give x293 which is about all you will ever need. Given this, a Barlow is most likely unnecessary too.

A 2mm eyepiece (for instance the Televue 2 to 4mm zoom) is useful in a short focal length, fast refractor, perhaps something like a Skywatcher Esprit 80mm which has the optical quality to take high mags but only a short focal length (400mm). A 2mm do will give x200 in this scope vs the x1175 it would give in the 925.

So, whilst Fast and Slow scopes don't have the same impact as in imaging, their characteristics are still important to understand for visual.

[Knighty2112]

Sorry! My bad! Should have done the maths to work out that a 2mm EP would push your scope past its limit. With a focul length of 1200mm for your scope a 4mm EP will come in right on the button at 300x. However, there won't be many times you'll be able to use it at full mag like that unless the seeing is really good. A 2mm EP is too much for this scope. An 8mm will give 150x. I find a 2x Barlow is better to use with some EP combinations, like 32mm, 25mm, 20mm and 15mm also as you get an easier view through the EP's because the lenses are wider than higher magnification EP's, rather than having to squint into an EP when you get down below 8mm size EP's. This will effectively give you a 16mm, 12.5mm, 10mm and a 7.5mm EPs, so will in effect have 8 EP's for the price of 4. If you splash out on good quality EP's then with a good quality 2 x Barlow this is still a good option to think about in my eyes. I regularly use a 2xBarlow on my ST120 scope and nearly push it to its limit (240x) OK when viewing the moon at least. Not had much chance to test it out on the planets fully yet due to the weather.

[Stu]

Sorry! My bad! Should have done the maths to work out that a 2mm EP would push your scope past its limit. With a focul length of 1200mm for your scope a 4mm EP will come in right on the button at 300x. However, there won't be many times you'll be able to use it at full mag like that unless the seeing is really good. A 2mm EP is too much for this scope. An 8mm will give 150x. I find a 2x Barlow is better to use with some EP combinations, like 32mm, 25mm, 20mm and 15mm also as you get an easier view through the EP's because the lenses are wider than higher magnification EP's, rather than having to squint into an EP when you get down below 8mm size EP's. This will effectively give you a 16mm, 12.5mm, 10mm and a 7.5mm EPs, so will in effect have 8 EP's for the price of 4. If you splash out on good quality EP's then with a good quality 2 x Barlow this is still a good option to think about in my eyes. I regularly use a 2xBarlow on my ST120 scope and nearly push it to its limit (240x) OK when viewing the moon at least. Not had much chance to test it out on the planets fully yet due to the weather.

Please be careful giving advice as this is all incorrect. A C925 has a focal length of 2350mm, it has an aperture of 235mm and is f10. A 4mm eyepiece will give an impractical x587 mag, not the x300 you stated. All the other mags quoted are wrong too.

Another benefit of a longer focal length scope is that you can use longer focal length eyepieces to get higher mags and these are often more comfortable with longer eye relief.

[laudropb]

I have found the Celestron X-Cel eyepieces to be very good value at around £60 each.

[Knighty2112]

Sorry. When I did an Internet search on that scope it came up with models that had a focul length of 1,200mm, not of 2,350mm. That's a hell of a longggg telescope! I'll learn to keep my mouth shut before I spew forth any incorrect statements!

[Northern Soul man]

Hi Ya Fordy, a very warm welcome to the land of the skywatchers!! excellent scope mate a good choice for the Planets - I think I read somewhere that the 925 is the "sweet spot" when it comes to observing the planets so you will do very well mate nice 1.

I tend to keep it simple when observing Moon/Planets - most nights I can get away with a 12mm EP on Jupiter/Saturn - maybe a little more on Saturn say 12 - 9mm, also MArs is coming around in a few months - Mars can take a little more power - so say anything from maybe 10 - 8mm - very difficult to observe - small and very bright at opposition - also low down this time around so you may need to back off the mag a little as the atmosphere when observing low down makes the disk very shakey/blurry and very hard to pin down detail - but the major landforms - Syrtis Major to name one and the polar caps will stand out very distinctly if the atmosphere steadies enough.

The Moon will take high magnification very well - the upper limits of the scope will work well here - even down below 8mm - but a very small field of view and more difficult to get a sort of "snap to focus" when using higher powers and the atmosphere will dictate your highest powers - but well worth a good look at higher powers - so big and so bright!!!

EP's are very difficult to suggest as there are so many, but as others have said working at F10 allows the cheaper EP's to be used with very good results - I have a set of Hyperions - I think these are good down to about F7 but I only have long focal length scopes so others will chip in here, Also, I used a set of 4000 Meade superPlossl's for such a long time and still use them with my little 127 Maksutov - the longer focal lengths say from 32mm to around 12mm have good eye relief, but the 9mm and 6mm are like looking through pin holes - a bit of an acquired taste - you really have to get your eye in close with these beauties!

The zoom as mentioned will give you a very good range of mags - but the SCT's have very narrow FOV's from about 1/2 to a degree or so - fine for the Moon/Planets - I can spend hours just letting the scope track with the object in the centre of the field - with the zoom, you can quickly change powers to see what suits the conditions, the Hyperion zoom has a click lock so a little clicking sound when you reach 24, 20, 16, 12 and 8mm's but you can also stop in between these points to make the most out of the seeing - not like you have to change EP's all the time.

At F10 the £40 - 50 EP's work just as good as the £100 when you are just looking at the centre of the EP whilst the scope is tracking - what's called on - axis, its only when you position the object away from the centre portion of the field - called off - axis that things begin to show how well each EP corrects here - this is when EP's which are much more expensive - I think there are exceptions like the Max visions and the Explore Scientific - tend to correct aberrations much better giving more pleasing views - this is where things get very personal - some observers can put up with the "defects" of the EP much more than others - its the same as everything hobby wise - as some say you only get what you pay for and on the whole - the more you pay for an EP - the better correction off axis there is - I think it becomes more apparent if you have a Dobsonian scope and need to "push" the scope to track - where as the SCT will happily track at fairly high powers all night.

Not sure if you can get to a club and try out as many EP's as possible - I was in this position a long time ago and just used the EP's which come with the scope - for as long as I can remember - trust me the on axis views are really very nice - my first EP was one of the Meade 4000's a 26mm I think - remembering that I was new to the hobby- so the views were all new to me and I made the most of every clear night - so I think I fall into the "use it and get the most out of it" brigade - its only when you read reviews of EP's that it starts to make you think what all the fuss is about - and at a price point well beyond what I wanted to pay for 1 EP !!! - remember what I said earlier about my Meade 4000 Super Plossl's - YES - I still have them and use them - especially on my 127 Maksutov - looking at the solar disk (with the correct solar filter in place of course!!) is a real pleasure with these little beauties!!

Paul.

[Stu]

Sorry. When I did an Internet search on that scope it came up with models that had a focul length of 1,200mm, not of 2,350mm. That's a hell of a longggg telescope! I'll learn to keep my mouth shut before I spew forth any incorrect statements!

Well it has along focal length but is an SCT so is actually quite compact

[Knighty2112]

Well it has along focal length but is an SCT so is actually quite compact

Good job. A 2 meter long scope would be very unwieldy!

[ollypenrice]

The SCT is a natural on the planets and has no need of Barlows with even moderate FL eyepieces. However, the long focal length means a constrained field of view and I'd always want to reach the maximum possible FOV in at least one of my eyepieces. 

Olly

[nmoushon]

I just got a 9.25" EdgeHD and have been looking for EP as well. As Olly said the FoV is very narrow at F/10 so you will want wide EP. The widest I have atm is a 2" 24mm with 68 degree FoV. That coupled with my .63x reducer fits a full moon perfectly. There is just enough space around the moon so you dont have the squished feeling when looking at it. For most other scopes people tend to buy a barlow to give them two EP settings for one EP but with the long native FL of the SCT I would suggest getting a reducer. This also speeds up the f/ratio and helps with nebulea targets a bit, especially if you have bad LP like me. 

Now your budget isnt big but I would suggest saving and looking at EP that have a wide FoV. This is very nice when viewing larger objects as you get a big of the field around the object as well. Now not all your EP need to have this but it is nice to have a couple. I'm currently looking at getting a wider EP of somewhere in the 35-50mm range. You will want one near this wide if you don't get a reducer as sometimes it can be hard to find objects if your goto is off a bit...especially at F/10. I'm also looking for a a EP in the 10-15mm range for planetary/lunar viewing at native F/10. I have a 6mm but find that because of my local seeing that it is usually too high a mag to keep the imaging clean. If you have poor seeing on avg like me too high a mag will make the image "jump" around more and you can actually loose quality of your view. So you will have to judge that for yourself. 

[Northern Soul man]

I just got a 9.25" EdgeHD and have been looking for EP as well. As Olly said the FoV is very narrow at F/10 so you will want wide EP. The widest I have atm is a 2" 24mm with 68 degree FoV. That coupled with my .63x reducer fits a full moon perfectly. There is just enough space around the moon so you dont have the squished feeling when looking at it. For most other scopes people tend to buy a barlow to give them two EP settings for one EP but with the long native FL of the SCT I would suggest getting a reducer. This also speeds up the f/ratio and helps with nebulea targets a bit, especially if you have bad LP like me. 

Now your budget isnt big but I would suggest saving and looking at EP that have a wide FoV. This is very nice when viewing larger objects as you get a big of the field around the object as well. Now not all your EP need to have this but it is nice to have a couple. I'm currently looking at getting a wider EP of somewhere in the 35-50mm range. You will want one near this wide if you don't get a reducer as sometimes it can be hard to find objects if your goto is off a bit...especially at F/10. I'm also looking for a a EP in the 10-15mm range for planetary/lunar viewing at native F/10. I have a 6mm but find that because of my local seeing that it is usually too high a mag to keep the imaging clean. If you have poor seeing on avg like me too high a mag will make the image "jump" around more and you can actually loose quality of your view. So you will have to judge that for yourself. 

Just a point here - you need to be careful with long focal length EP's whilst using a .63 focal reducer - on my 11" SCT I get vignetting (quite bad and very noticeable!!) using my 36mm Aspheric - so may be worth you trying to borrow EP's and test for yourself to see at what point the vignetting starts.

Paul.

[John]

Just a point here - you need to be careful with long focal length EP's whilst using a .63 focal reducer - on my 11" SCT I get vignetting (quite bad and very noticeable!!) using my 36mm Aspheric - so may be worth you trying to borrow EP's and test for yourself to see at what point the vignetting starts.

Paul.

Thats a good point. The F/6.3 reducers were designed for use with 1.25" accessories. When I tried one with 2" eyepiece / diagonal I got vignetting of the field of view as well.

It's an uphill struggle to get a wide field out of an SCT - I found it less expensive to buy an 8" F/5 newt which delivered twice the FoV as an 8" SCT for around the same cost as a decent 2" diagonal.

"Horses for courses" - as Olly says SCT's are not wide field scopes.

[Stu]

I agree with that John. Don't fight the narrow fov, use the scope for what it's good at.

[Northern Soul man]

Yes, quite right John - my wide filled views under my light polluted skies are obtained with a couple of pairs of binoculars - 10 x 50's and 15 x 70's - more than enough for me - I always wonder how a wide field Frac would perform under my light polluted skies - I get by with my long focal scopes, I even find when viewing DSO's that most of them do actually fit the FOV - surely a fast Frac would show a much smaller image but not sure if the wide field would make the back ground sky too bright to diminish contrast or not - I think I read somewhere that it makes no difference what so ever ??

Paul.

[John]

I use a 102mm F/6.5 refractor for wide field - I can get up to 4 degrees of sky with that

[ollypenrice]

You can still go for the widest field the SCT will support. If you have a 2 inch back I don't think the 0.63 reducer adds any benefit because the baffle tube imposes the field stop. I don't know the ins and outs of how to get the widest field from the 9.25 but that information will be 'out there.' In my 10 inch SCT I use a Nagler 26.

Olly

[nmoushon]

Just a point here - you need to be careful with long focal length EP's whilst using a .63 focal reducer - on my 11" SCT I get vignetting (quite bad and very noticeable!!) using my 36mm Aspheric - so may be worth you trying to borrow EP's and test for yourself to see at what point the vignetting starts.

Paul.

Oh good point. I did forget to mention that. Though my current 6mm EP is 1.25" so I dont notice any either way. But it good to mention thanks for bring it up.

[YKSE]

There're some necessities for SCT you need to take into accout too, i.e. a dew shield, dew heater tape, and heater control.

I agree with other's about using your stock eyepieces to start with, so that you have a general idea how they work in the scope, and what properties you think your new eyepieces should have (wider FOV, better eye relief, etc).

There's a good guide here about how you choose suitable eyepieces:

http://stargazerslounge.com/topic/43171-eyepieces-the-very-least-you-need/

As I see it, you have two routes to choose: stay in 1.25" eyepieces only, or have mixed set of 1.25" and 2" eyepieces, do take your time before decision.

1.25" only: you need only buy the f/6.3 focal reducer and some 1.25" eyepieces, this is an easy/inexpensive to get wider FOV (about 1.2° max) with only 1.25", assuming that this will be your only scope or you're only buying SCTs.

Mixed 1.25" and 2": You'll need to buy a 2" diagonal and 2" eyepiece(s). advantage is that if you're get a small refractor, you'll have the 2" eypiece(s) for wide field observing.

For 1.25" only, I would recommend a 32mm revelation plossl, and a Baader mark III zoom with barlow, this will cover all you the range of eyepieces you need, the zoom with barlow is also your collimation tool.

For 2" , I can recommend 40mm Skywather Aero and the Baader Zoom too, covers most the range you need too.

There're many other good ideas about good eyepiece upgrades, as you can read here:

http://stargazerslounge.com/topic/217907-first-eyepiece-upgrade-what-you-wish-you-had-done/

[Fordy_638]

Hi Ya Fordy, a very warm welcome to the land of the skywatchers!! excellent scope mate a good choice for the Planets - I think I read somewhere that the 925 is the "sweet spot" when it comes to observing the planets so you will do very well mate nice 1.

I tend to keep it simple when observing Moon/Planets - most nights I can get away with a 12mm EP on Jupiter/Saturn - maybe a little more on Saturn say 12 - 9mm, also MArs is coming around in a few months - Mars can take a little more power - so say anything from maybe 10 - 8mm - very difficult to observe - small and very bright at opposition - also low down this time around so you may need to back off the mag a little as the atmosphere when observing low down makes the disk very shakey/blurry and very hard to pin down detail - but the major landforms - Syrtis Major to name one and the polar caps will stand out very distinctly if the atmosphere steadies enough.

The Moon will take high magnification very well - the upper limits of the scope will work well here - even down below 8mm - but a very small field of view and more difficult to get a sort of "snap to focus" when using higher powers and the atmosphere will dictate your highest powers - but well worth a good look at higher powers - so big and so bright!!!

EP's are very difficult to suggest as there are so many, but as others have said working at F10 allows the cheaper EP's to be used with very good results - I have a set of Hyperions - I think these are good down to about F7 but I only have long focal length scopes so others will chip in here, Also, I used a set of 4000 Meade superPlossl's for such a long time and still use them with my little 127 Maksutov - the longer focal lengths say from 32mm to around 12mm have good eye relief, but the 9mm and 6mm are like looking through pin holes - a bit of an acquired taste - you really have to get your eye in close with these beauties!

The zoom as mentioned will give you a very good range of mags - but the SCT's have very narrow FOV's from about 1/2 to a degree or so - fine for the Moon/Planets - I can spend hours just letting the scope track with the object in the centre of the field - with the zoom, you can quickly change powers to see what suits the conditions, the Hyperion zoom has a click lock so a little clicking sound when you reach 24, 20, 16, 12 and 8mm's but you can also stop in between these points to make the most out of the seeing - not like you have to change EP's all the time.

At F10 the £40 - 50 EP's work just as good as the £100 when you are just looking at the centre of the EP whilst the scope is tracking - what's called on - axis, its only when you position the object away from the centre portion of the field - called off - axis that things begin to show how well each EP corrects here - this is when EP's which are much more expensive - I think there are exceptions like the Max visions and the Explore Scientific - tend to correct aberrations much better giving more pleasing views - this is where things get very personal - some observers can put up with the "defects" of the EP much more than others - its the same as everything hobby wise - as some say you only get what you pay for and on the whole - the more you pay for an EP - the better correction off axis there is - I think it becomes more apparent if you have a Dobsonian scope and need to "push" the scope to track - where as the SCT will happily track at fairly high powers all night.

Not sure if you can get to a club and try out as many EP's as possible - I was in this position a long time ago and just used the EP's which come with the scope - for as long as I can remember - trust me the on axis views are really very nice - my first EP was one of the Meade 4000's a 26mm I think - remembering that I was new to the hobby- so the views were all new to me and I made the most of every clear night - so I think I fall into the "use it and get the most out of it" brigade - its only when you read reviews of EP's that it starts to make you think what all the fuss is about - and at a price point well beyond what I wanted to pay for 1 EP !!! - remember what I said earlier about my Meade 4000 Super Plossl's - YES - I still have them and use them - especially on my 127 Maksutov - looking at the solar disk (with the correct solar filter in place of course!!) is a real pleasure with these little beauties!!

Paul.

[Fordy_638]

Thanks for your reply, I appreciate you taking a lot of time out to write such a post. I've taken on board what you've said and am grateful for the advice.

Fordy.

[Arminovski]

Hi 

I don't know if these fit your bill or not considering what others wrote about the baffle tube in your SCT and the possibility to use 2" eyepieces but explore scientific wide angle /gso superview ones with 68-70 degrees fov are well within your budget (about £45-£70 each on offer and depending on the focal length). Apparently from what I've read about them they should be fine at F10 and they are all the same eypieces, just branded differently. Assuming that it is possible to use them with your scope they should give you close to 1.1 degree portion of the skye. I've bought them from astroshop.eu in Germany and they are still on offer.

[Highburymark]

Yes, quite right John - my wide filled views under my light polluted skies are obtained with a couple of pairs of binoculars - 10 x 50's and 15 x 70's - more than enough for me - I always wonder how a wide field Frac would perform under my light polluted skies - I get by with my long focal scopes, I even find when viewing DSO's that most of them do actually fit the FOV - surely a fast Frac would show a much smaller image but not sure if the wide field would make the back ground sky too bright to diminish contrast or not - I think I read somewhere that it makes no difference what so ever ??

Paul.

if I knew how to post a yellow smiley face giving your comments the thumbs up, I would do Paul. With all the cloudy weather we've been having recently I haven't had much chance to use my Equinox (80mm) bought a few months ago. But a clear night beckoned earlier this week, and I also had a newly acquired Panoptic 35mm to try out. In the little Equinox, the Panoptic was stunning. Even from the middle of London, I had fantastic views of the Hyades, M45 and M42. Made all the more enjoyable because until now my main scope had been the F10 Evo SCT - so I really enjoyed the wider views. But I finished off the evening looking at the same targets through my 15x70 binoculars - and was amazed at how good they were. No, they didn't resolve the Trapezium as clearly at the heart of M42, or reveal as many stars in M45, but they provided 80% of the 'wow factor' of the telescope when looking at wide field targets. It brought home to me once again just how excellent a good pair of binoculars are - so much better than many cheap telescopes.