new eyepiece

[wayneh]

Hi all just got my new sky- watcher 200p today , have to say i love it and boy is it big :-) it came this a 10 & 20 eyepiece but im looking at geting a 2" one, what do you all think of this one http://www.firstlightoptics.com/skywatcher-eyepieces/sky-watcher-swa-70-eyepieces.html.

 Is it any good ?? or would you all think of another one i could get. look at getting the 32 

   cheers Wayne

[LukeSkywatcher]

These are the new range of SW eyepieces?. I have not read any reviews yet. I think one of the members here is giving them a test drive on behalf of FLO and will report back.

Any decent 8mm EP is good for observing planets.Its what a lot of us use (some use 6mm). A decent 32mm EP is great as a work horse for scanning the skies and giving you wide field views in general (love my wide field views).

Perhaps a 15mm would be nice to slip right in the middle of what you have.

Then again,is it too soon to start buying new ones?. Try the ones you have and see how you like them and how they work for you. 

Others will be along shortly to advise you on the technical side of things. I tend not to worry about that side of things if i enjoys the views i get.

Paul.

P.S.~~congrats on the new scope. 

[emadmoussa]

I've got the 3.5mm, and so far pretty happy with it. Ready my review on FLO website.

[bingevader]

Yes, they are the new Sky Watcher 70^o eyepieces and so as yet there are few reviews of them.

As Paul has said, we're hoping John here on SGL is going to test them for us.

Again, as Paul has said, I'd spend a good while getting used to your 'scope before contemplating any eyepiece purcahses.

I have the 32mm PanaView from SkyWatcher which is also 2" and 70^o, so I'd be interested to hear what difference the extra 3 lens elements make.

The Panaview is a little soft around the edges, but a lovely eyepiece for the money, still one of my favourites.

Cheers

[wayneh]

thanks for the quick answers lads, was just looking for a eyepiece to scan the sky's with. will have a look at the 32mm panaview, i have had a few goes with me brothers old scopes ( astroeddie of here ) and all his were 2" ones so in time want to end up with a few of them  ,

[LukeSkywatcher]

Another 32mm EP that is liked by many and is pretty affordable is the 32mm GSO. Its a great EP.

[Qualia]

Hi all just got my new sky- watcher 200p today , have to say i love it and boy is it big :-) it came this a 10 & 20 eyepiece but im looking at geting a 2" one, what do you all think

Congratulations on the new telescope, Wayneh . You've got a wonder-scope that should serve you well for the coming years.

My advice would be a bit more conservative than the other lads' and I'd suggest that you play around with your scope for a couple more sessions this week before buying a new eyepiece. Get a feel for what your scope can do, the kind of things you like looking at and what magnifications you think would suit those objects best. Keep on asking questions here and if you hang on for just a few more observation session, I think you'll be able to make a much more informed enquiry and decision. It'll also give you time to look around the secondhand market and see what kind of things are on offer and at what price.

[Charic]

wayneh.........give the supplied lenses a run. Qualia.....  hits ithe nail on the head.

In my `new to the hobby views` because the supplied lenses are  not Plossl or Nagler, do we need to change them straight away? Ive just spent £49 on an 8mm BST `Starguider` and Im using that instead of the supplied 10mm, and never even looked through another lens before purchase to see if it was ok, yet the supplied 10mm isnt too bad. I believe the Starguider is a better quality lens than my supplied 10mm kelner/Modified Achromat , and the 25mm is just fine for wide/ish views at present ( there are wider views, but you lose magnification - I`m not sure I want to go much wider,  at present my 7x50s provide  wide views)  but with the scope, I want to get  closer) Your intentions and wants will change so quickly with this hobby. Ive always believed that a telescope was just for looking at  further / distant things, maybe a bit further than binoculars? so I want magnification to see further.  I opted to buy the 8mm as my first high power lens. Now the fun starts, do I buy the full branded set, Just a Zoom, Odd /Even focal lengths, Barlow, will the magnifications get duplicated? Whoa! the list goes on. I`m working on 6-8mm for High power 9-17mm Medium and 25-32mm for low power , so 3 lenses ( 8mm, 12mm & 30mm should suffice) with a 4th lens ie; a decent 2xbarlow, I would  effectively have 4,6,8,12,15 & 30mm lenses, all well within the abilities of my scope on a good night (thats my plan ) I wish you well in your lense learning, pull your hair out, what should I buy,  stresses over the coming Days/Weeks

[Astro Imp]

You have a fine scope that under good conditions will show you plenty.

Qualia has given good advice, take your time, see what the supplied EPs can provide and decide what/where you need improvement. You will have plenty of time to empty you wallet, just make sure you make as an informed decision as you can.

Good luck and enjoy.

[ronin]

Would say take your time but those supplied eyepieces can be bad enough to spoil the experience.

If your brother has a couple of 1.25" eyepieces to use/borrow then do that as the idea is to see things and it is better to see them at least reasonably.

As to buying a 2" that is your choice. I personally wouldn't as there is a good range of 1.25" eyepieces around but if the idea is to compliment that one's your brother has, so getting a good selection between the two of you then it makes some sense.

[wayneh]

Thanks for all the advice lads but got just one more Q, i have read that a fast scope will need certain lens mine is a F5. what 3 lens would you go for ant what make looking at spending around £80-100 for each lens..

  cheers Wayne

[Charic]

wayneh......In astronomy, the f-number is commonly referred to as the focal ratio, which is calculated by dividing the focal length of the optical system by its aperture. In your case an 8" mirror is actually 203.2mm (convert inches to mm by multiplying by 25.4 i.e. 8x25.4= 203.2) despite what is says on the label? (therefore you have an f/4.9 scope even faster?) the `Fastness` of a photographic lens normally describes how much light and exposure time it is able to achieve compared to another lens, and the lower the f/ number the greater the control of the depth-of-field achievable.

The science of focal ratios is the same, its the principle that differs. In photography the focal ratio varies the depth of field, and the amount of light reaching today’s sensors. Because there is no depth of field to be concerned with in your telescope, then I would consider the f/ratio not that important enough to worry about what "special" lenses are required?

My scope says D=200 F=1200 on its label, so I either have an f/6 or an f/5.9. Again the difference is not important.

Your telescope has theoretical design limits, and on-top of that the `seeing` conditions of the atmosphere that your looking through. Therefore you need to know the Highest possible magnification achievable under working conditions and your lowest magnification, and then somewhere in-between will be a Medium power lens.

My telescope (Skyliner) has a low magnification of about 29x and 400x being the maximum. I`ll probably get a 12mm for `optimal` viewing because of the design of the scope, then for low power use, I can go as high as 41mm, but that would need a 2" adaptor, and I`m sticking with 1.25" ((31.75mm) lenses so will will probably look at the 20-26mm range and finally an 8 – 6mm for high power. As I already have the BST 8mm I`d probably Barlow the 12mm too 6mm. That would  also retain the same eye relief from the 12mm eyepiece, but at a higher magnification of 200x against 100x , which fortunately is about the maximum magnification I want to use on this scope.

Therefore I purchase the 12mm and 26mm, then with a Barlow, I’ll have nothing? (just checked! - as BST doesn’t arrive in 1.25" 26mm format, so, it will be the 25mm) but I`ll still end up with 8mm 12mm and 25mm lenses, and by use of  a 2x Barlow, I’ll have 4mm, 6mm and 12.5mm lenses, effectively a full `set` for this particular scope, and no overlap of  any focal lengths? This is a change to the lenses I spoke of further up the thread. I hope this helps. Take care.

[Qualia]

 i have read that a fast scope will need certain lens mine is a F5. what 3 lens would you go for ant what make looking at spending around £80-100 for each lens..

The idea of fast and slow came from photography.  A lens with a focal ratio of less than f/5 is fast because it requires less exposure time to make the same photo as, say, a slower telescope with a higher focal ratio.

Now, I'm no expert on this but I think that by equating the idea of fast and slow into visual astronomy we're talking about the way light enters the telescope.

In a fast telescope, say, f/5 and less, I think the light cone comes in at a steeper angle and so it is bent more or needs to be doing more bending when entering the eyepiece. It's something like that, but don't quote me on it! Anyway, the upshot is that faster scopes are more demanding on eyepieces and generally need better quality ones than slow scopes to avoid off-axis aberrations such as coma which has the tendency to turn pin point stars into lazy comet-shapes. Another consideration we can point out is that regardless of the eyepieces used, fast scopes need more accurate collimation, so you've also go to get this right to avoid annoying aberrations - especially when viewing planets, for exmaple.

Now, regarding eyepieces....Many astronomers - myself included - follow quite a predictable path when it comes to buying EPs and to a lesser extent Barlows. For whatever the reason, sound or not, many of us start out buying new and cheap stuff but soon arrives a day when we want to upgrade but now we find ourselves in a situation where we have one quality EP and a case full of relatively cheap EPs that on the secondhand market are pretty worthless. The same can be said of a Barlow.

So, I'd say premium eyepieces are never a waste of money, especially if you buy them used. These EPs might even become 'lifers', so you never have to upgrade again or you could always re-sell them without losing much - if any - money, especially if you have already bought them secondhand. Premium eyepieces, then, simply hold their value more than cheaper ones.

With that said, with something like a 200mm f/5, I feel one only needs one decent long focal length EP, this is great for scanning the sky, star hopping and fitting in relatively large obejcts, something around the 40x to 50x which gives you around 1.4º, 1.5º true field of view.

From this, in my own case with a 250mm f/5, I worked out that if I took my telescope's aperture and divided it by 2, I ended up with 125. If I looked at that in terms of magnification I would require a 10mm EP. I then divided that 10mm by my scope's focal ratio and ended up with an exit pupil of 2mm. This I figured would be the general work-horse for the 10". I reckon you could do something very similar with the 8" and look for a general work horse eyepiece at around 125x.

From this reasoning, I figure little steps could be made on a 1.3 or 1.4 ratio.

So, for example, from the hypothetical 125x mag, or 10mm workhorse EP, I'd divide the mag or multiply EP's focal length by 1.3 or 1.4. So, I end up with 96x to 89x, or an EP of around 13mm to 14mm, or an exit pupil of between 2.6mm to 2.8mm. In my own case, I'd go for something around the 90x.

If you then got yourself a 2x Barlow (which I happen to not like but for higher magnifications I use a set of Orthos), you'd have a useful range of magnifications of 90x, 125x, 180x and 250x. Sure, there is room for improvement but you get an idea of what is possible with just 2 EPs and a Barlow.

Hope this helps a little

[Charic]

A huge learning curve this astronomy! I should have started a DCC model layout, surely that`s easier to understand?

Anyhow, A bit more on this subject. I what  like Qualia says, premium lenses are an investment, but so early in the game its difficult to choose wisely, and the costs are sometimes prohibitive. Normally more money means better quality, but not always the case, my old GMT Master II ?  kept worse time than a basic watch from poundland, but they still told me the time?, so price isnt always the top choice. recommendation is a good choice, and experience is another. I`d love to own a full set of lenses. that way you` would cover every magnification that was possible for the scope, and still only end up using a select few, because of the look and feel with the final result. Now back to the f/ratios and lens choices, Whether a telescope is used visually or photographically, the `speed` of a telescope is obtained, as we know, by dividing its focal length by its aperture, and the resulting number (the `focal ratio`) is  fixed for the telescope, it cant be changed unlike a camera (Oh yes it can he says? You can reduce the f/ratio by fitting a Barlow lens ~ so my scope becomes f/12 from an f/6) But its still the aperture that is all important. The brightness of what your looking at through the  lens is the result  of  aperture, nothing else - the larger the aperture the better, it captures light photons from Space, allowing you to see the dimmer objects, and also increasing the resolution of the telescope. The extended objects ( such as the galaxies and other DSO`s) should always appear brighter at lower magnifications with larger apertures. Shorter focal lengths and lower magnifications can actually help you see more? The longer (focal length) f/ratio telescopes can provide greater magnification (eyepiece dependent), but with a reduced field-of-view. Those telescopes may offer better planetary or lunar observations. At the other end, shorter f/ratio telescopes should provide the widest fields-of-view with the least magnification ( if using the same eyepiece ).
Having a fast f/ratio telescope for visual observing, is telling you that it should deliver a wider field of view  and a brighter image. now depending of your choice of eyepiece,whether you/we can all see or feel this difference, who knows. the learning continues. Take care.

[ronin]

An f/5 scope sits more or less on the boarder of where the less costly eyepieces operate, some of the plossl sets may well give poor results, the TV plossl's will work fine, both plossl's.

From assorted posts:

BST Starguiders are good at f/5, £47  from Skys the Limit.

Celestrons X-Cels good at £65 from FLO

TV plossl's at £65-70 from Telescope House and Green-Witch.

After those I am unsure, Skys the Limit have another BST eyepiece, 70 degrees and again @£47, not sure of it's performence.

Since the removal of one of the TV range there seems to be a bit of a jump in prices from one level to the next.

To me the Starguiders are good (have the full set), no real difference in performance compared to the Celestrons, but the Celestrons have a slightly better selection at the shorter focal lengths.

Both the BST's and the X-Cels have decent eye-relief and are reasonably par-focal within the set, 2 useful properties.

[bingevader]

Have a look at these too. Meade 5000s that never made it to market under that brand name. The 28mm would make a very decent indeed widefield 2" EP, as an alternative to the 32mm.

Cheers

[Blazar]

All superb advice. just out ofcuriosity, did you have a look/ read of this:

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

Might help a little.

Regards

[astroeddie]

My little bro ( ) goes a bit heads first at times. He's ordered the 28mm 2". I've advised him to see what the SW eye piece quality is like. In time get another couple of higher mag eye pieces.

  ENJOY your scope and LEARN the skies !!!!!

Easy enough said, but now for these black clouds .......     

[wayneh]

Hi all and thanks for all the help you have giving me, im going for the 32mm PanaView from SkyWatcher and a 8mm Baader Hyperion Eyepieces to start with, then after that i will see what i think of them before i spend any more lol   cheers once again

[Space Beagle]

Sound choice with the Panaview 32mm! It's one of the ep's i've had in the past, which I wish i'd not sold on! I recall it being very good in my own 200P.

Please let us all know how you get on, ta!

Doc

[bingevader]

I start almost every session with my PanaView! Yep, it's a little soft around the edges. My goodness the Andromeda Galaxy was awesome last Wednesday. I tried more magnification, but kept coming back to the Panaview.

Good choice.

The 8mm BST will be sound to by all accounts and a good focal length in the 200p.

Cheers