What eyepieces for F/4 scope?

[Major]

Hello folks.

Could anyone recommend relatively good EPs for fast scope? I'd look for 4mm, but after reading forum the choice is not obvious anymore .

[Pig]

Hiya,
F4 is quite a fast scope and would require premium eyepieces to cope with the demands made upon the eyepiece, Televue are a good choice along with Pentax XW's. It can be quite difficult to determine how eyepieces will perform at these speeds as not many producers publish reference material. A quick call to the retailer may be the most worthwhile option.
I could without fear recommend the Televue 3-6mm Zoom as this is a superb eyepiece but it does come at quite a high cost.

[michael.h.f.wilkinson]

Much depends on what you want to spend, and the size of the scope. In a 20" F/4 scope a 4mm EP pushes all the way to 500x, which is a bit much under most skies, but for an 8" F/4 you reach a very useful 200x. At F/4, you need quality EPs, so something like the Ethos 3.7mm should be great, but very expensive. As you are in planetary magnification range, a smaller FOV might serve you well, so the Delos 3.5 or 4.5 mm might be a good choice, as would be the Pentax XW 3.5 and 5mm. They also sport long eye relief, which is essential if you wear glasses while observing. I also have some Vixen SLVs, which I haven't used at F/4, but down to F/6 they certainly have XW-like performance (albeit over a smaller FOV) at a much lower cost. If eye relief is not a problem, you could also look at Naglers, if you want a wide field, or orthoscopics, if you don't

[Pig]

I can add to Michaels post above and confirm the Vixen SLV range performed without any issues in an 80mm F5 shorty refractor. They are also a very light eyepiece which may also be beneficial should balancing your scope be a greater than normal consideration for you.

[michael.h.f.wilkinson]

A Paracorr will sort out coma, and create a slightly slower light cone, but it will not solve the astigmatism in cheap wide-angle EPs. I tried a MaxVision 24mm 68deg EP in an 20" F/4.1 and it performed poorly towards the edge, any coma from the scope drowned out by astigmatism of the EP. A 22T4 Nagler (with a much wider FOV) showed no such issues. Note that the MaxVision was only rated for F/5 according to the manufacturer, and in an F/5 scope it performed well

[Timebandit]

A F/4 is a very fast scope indeed.  The problem with very fast scopes a F/4 they are very testing on the eyepieces quality needed to be used to get good performance .To my knowledge there is only one manufacturer that tests there eyepieces to F/4 and that is televues. You can get from the Humble plossl in the televues range from about £90 to the top of the range wide angle Ethos at £600 plus . 

I have used in my fast scope at F/4.6 dobby televues with good results also the Pentax XW. But I have also used the William Optics uwan(which are cheaper than televues wide range) with very good results and I understand the skywatcher Nirvana are supposed to be the same eyepieces. But at F/4 you do need to be very careful with eyepiece choice to get something that works in a very fast scope.

I hope the above helps☺

[Moonshane]

I have two f4 scopes and use a paracorr plus televue eyepieces.  that said any eyepiece will 'work' with my scopes. Even a cheap Meade 15mm plossl provides respectable images without the paracorr.

That said I'd still recommend Televue as they are excellent.  My favourites are Delites,  Panoptics and Plossls. I also use my nagler 6-3 zoom a lot.

[rockystar]

After reading you "First Light With the Kids" report, I assume this is for your heritage 100, so that will only accept 1.25" eyepieces, and you will need something that isn't too heavy, or it will over-balance your scope. You will probably be better of with some decent plossels or maybe some bst starguiders (£50 each). I think a 4mm will be OK, as that will give you x100 magnification, which it fine for your scope - i wouldn't go much beyond that though, so probably wouldn't recommend using a barlow with a 4mm (it might be ok), maybe a 6mm will be better if you have a 2x barlow?

[Major]

Thank you all for input, very educating indeed and I appreciate it a lot!

Rockystar

yes, it would be for little Heritage. I do have a barlow with it, but let's just say that it performs best while in ziplock bag and its box...  4mm is as short as I'd go with it as for moon it will be enough and I've read somewhere that f = shortest ep.


You lot gave me something to think about. Will just have to check prices and get one, will visit Rother Valley Optics tomorrow and see what they have.

Cheers

[Putaendo Patrick]

While normally large fast telescopes (most Dobsonians of 250mm or more aperture, for example) will be very demanding on eyepieces, the good news is that with your smaller Heritage 100 you won't have the same problems to the same noticeable extent. Rother Valley Optics doesn't appear to carry the BST Explorer range, but has others worth looking at. For example:

http://www.rothervalleyoptics.co.uk/skywatcher-planetary-uwa-58deg-eyepieces-125.html  4mm and 5mm available, 16mm eye relief

http://www.rothervalleyoptics.co.uk/altair-lightwave-ler-125-planetary-eyepieces.html  5mm available, 20mm eye relief.

As pointed out in another of your posts, the standard Plossl design is perhaps the best value but will have very short eye relief. However, when used with a relatively decent Barlow, the EP will retain its original eye relief. So you might consider a x2 Barlow with an 8mm eyepiece. The http://www.rothervalleyoptics.co.uk/celestron-omni-x2-barlow-lens-125.html  is really quite good for the price. Although this is initially a more expensive option, it will double the range of all eyepieces you may want to buy in the future.

 

[Dave In Vermont]

I have a 200mm F/4 Newtonian scope. I found that Plossl's worked quite well - and they won't break the bank price-wise. I'd try one of these first - before selling your children into slavery. It was obvious to me that the more lens-elements in an eyepiece - the more problematic it became to use on my F/4 Newt. At least for visual.

Experiment Ho!

Dave

[John]

For a scope which costs around £95 I think plossls make a lot of sense. The Vixen NPL range are nice examples of that eyepiece design:

https://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html

The standard Skywatcher eyepieces are still not bad and cost quite a bit less:

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-sp-plossl-eyepieces.html

You can find plossls on the used market for under £20 each if you want to keep the budget tighter.

I'm not running the scope down by mentioning the price by the way (they are nice and very portable scopes !) but to get a wide angle eyepiece that is corrected well enough for an F/4 newtonian the cost per eyepiece is going to be at least as much as the scope cost, which you might feel is a bit extravagant unless the eyepieces will be used in larger scopes in due course.

 

[Major]

I'd try one of these first - before selling your children into slavery

Oh no, I can't sell my kids.... with them would go my excuse for more gear . But their mother on the other side.... for spares.... hmmm ...

So today I rushed after work to RVO, only made it about 30 mintues before closing time and had a look at availible eyepieces. Mind you, wasn't sure if I'd bring anything back home, but then I spotted Pocket Star Atlas - tiny little book, that I thought would be so helpful while outside. Looking at the laptop and then back up there is not the best idea ever, so book and red torch it is. It contains few maps of the sky and at 4.99 I considered it a good bit of knowledge to absorb.

Then I had a look into my pocket with loose change (it really was, I had about 45 quid in coins ) and into cabinet with EPs. Have seen SW wide angle, they let me try it to the eye and have very close look, but I spotted one Vixen NPL 8mm for 30 quid. Didn't think too long and got that 8mm. Now I need good Barlow.... and maybe bigger scope .

Then quuickly back home to have a daytime test, but sky is covered in thick layer of clouds. Guess not tonight, but will deffo test it as soon as I can.



Best spent 35 pounds today     

Once again thank you all for your valuable posts in this thread.

Cheers,
Tom

[John]

Good purchases Tom - I'm sure you will enjoy both

 

[Putaendo Patrick]

Excellent shopping! Very useful star atlas and the Vixen NPLs are first rate! Reckon you'll use the new 8mm much more than the supplied 10mm. And try it on the Moon with the supplied Barlow - it'll give you a rather vague and poor idea of where you will be going with a better quality Barlow!

[Ben the Ignorant]

How about a barlow that can take an f/4 beam (which certainly means a 4-lens 2" unit), and buying more forgiving eyepieces for the resulting f/8 beam?

[Major]

I already know what is next on the shoping list - laser collimator . I've tried Vixen on few trees and picture was not as sharp as I'd expect, to be sure tried 10mm kit EP and results were the same. Didn't notice that with 25mm (as much), but still saw picture quality a bit lesser... which would explain difficulties with fiocusing on some fainter objects I guess?

Guess it will have to wait a bit though, this week is crazy, work is picking up and oncoming move don't make it easier time wise... but will get there sooner or later. If the skies get clear, I might just knock up home made collimator cap for now.

Book is just brilliant, simple, but enough for a start.

Ben, any particular Barlow in mind?

[Ben the Ignorant]

Explore Scientific makes a 2" 2x barlow, Orion makes one, too:

http://www.telescope.com/Accessories/Barlow-Lenses/Orion-High-Power-2-2x-4-Element-Barlow-Lens/c/3/sc/41/p/113913.uts?ensembleId=260

Don't be afraid of the price, other brands sell the same thing at lower prices. But before you commit, check with the retailers if the backfocus changes much. Celestron also distributes a splendid 2" 4-element barlow but it's a 2.5x multiplier; a friend uses one for visual and photography, there's no way to tell something has been added to the optical train except the change of image scale, it has no defects.

[John]

I think Tom's scope is 1.25" fit only so it would require a barlow of that size.

For the money, the Revelation / GSO 2.5x is pretty good:

http://www.telescopehouse.com/revelation-astro-2-5x-barlow-lens.html

Again, I'm assuming that you don't want to spend more than the scope cost on this accessory !

 

[Ben the Ignorant]

They also make 4-element barlows in 1.25" format but a modern 3-element barlow will do in 1.25".

[Major]

That's right John, little Heritage is 1.25" fit.

Regarding spending, it's very thin ice really. I know I just started and my setup is very basic, but it would be wise to invest some more money in quality gear I could use further down the road. I've very bad feeling it's not gonna end up here . As to spending more than the scope is worth, I wouldn't really mind it - after fun with photography I know optical gear is not cheap and generally you get what you pay for.


Edit:
Thank you both for links!

[John]

You do get what you pay for but there are also some items around that give you excellent performance for relatively modest outlay. This forum is a great place to uncover those

If you want to invest more then there is no shortage of choices of ways to empty your bank account on eyepieces etc

There is a sort of law of diminishing returns though and while a £50 eyepiece will be noticably better than the ones that come free with scopes the step up for £100, £200 or more apiece brings much more subtle improvements for the additional investment.

Also, the best eyepieces around will not actually show you anything more than the budget ones. The presentation is better but at the end of the day a £300 scope would enable you to see far more than spending £300 on eyepieces would. Your Vixen NPL would still work pretty well in the £300 scope too !

 

 

 

[Major]

That is very good point about bigger scope. I'll just learn sky a bit and finally would like to get something bigger, using finderscope on Heritage is very akward....


 

[Ben the Ignorant]

I had overlooked the scope is a small Heritage; when I saw the title of the thread and the request, I assumed the scope would be in the range of some Vixen newtonians, or a Sky-Watcher Quattro. Still, good apo barlows in 1.25" don't cost too much, like these:

http://www.teleskop-express.de/shop/product_info.php/info/p3002_Antares-2x-Barlow---1-25----Twist-Lock-Klemmung.html

http://www.teleskop-express.de/shop/product_info.php/info/p1892_TS-Optics-TSShorty-2x-Apo-Barlowlinse--1-25-Zoll--3-elementig---foto-visuell.html

I was trying to do several things in the same time; focus can't be at several places during the same moment.

[Charic]

59 minutes ago, Ben the Ignorant said:

I had overlooked the scope is a small Heritage;

....and 7 others before Rockystar threaded?
I just can't imagine an Ethos or even a Delos in the little Heritage, but without trying, who knows?

I use revelation Plössl's, They would be fine if not perfect for the H100, but the field of view and eye-relief may not be comfortable  if  shorter than  9mm. A  better upgrade to the supplied eyepieces might be an 8mm BST Starguider, possibly the 12mm. These could both be Barlowed to achieve 4mm & 6mm, should the scope and conditions allow.

Major!.....don't wast your money on a Laser?  Even the new ones come with problems, they often  need  tweaking / tuning (collimating) like your scope, and can have serious consequences if its not accurate. Were talking Laser, but this is not a scientific, accurate piece of kit?
You would achieve just as good a result by just using the focuser dustcap with a 1mm hole in it, or an old used 35mm film container! You cut the base of the tub, put a 1mm hole in the middle of the lid, clip it back on the tub, put it in the focuser, learn collimation? 

Seriously, If you want the best tool, buy yourself a Cheshire Tool, it's the most accurate, or a film cap, or just by eye with the H100, as I doubt it even has a centre spot? ( prove me wrong!)