Best high power eyepiece for a Tal

[John]

51 minutes ago, wookie1965 said:

I know the BST is a good eyepiece and I dont need anything that is any better optically I just need something I can get my eye central. I have Meade 4000 (Japan) eyepieces which are great but it only goes to a 6.4mm otherwise I would get a 5mm one as eye position is easy on these.

Interesting. Sounds like you need what is known as a pupil guide. Tele Vue provided them with the Radian series and Nagler Type 4 eyepieces. They are circular black disks with a hole smaller than the eye lens right in the centre - to help position the eye correctly.

Here is a link to the instructions from Tele Vue which might be of interest:

[John]

On the above guidance - interesting to note some other potential benefits of using a pupil guide as well

[cotterless45]

That's neat.

Before comparing manufacturers and specific eps, back to what traps a lot of observers into not the best choice. What are you aiming to see ? 

If it's double stars tighter than epsilon Lyrae , or those binaries with huge difference in magnitude ( double star challenge ),then you're going to need more than 100mm aperture. On the other hand , if it's an ep that you readily turn to the planets and enjoy often colourful and easier binaries , then 100mm and a basic Plossl 6mm will do you fine.

It's also a very personal choice, I couldn't get on with my 5mm Bst , but LeeB snapped it up as being the sharpest crayon in the box. )The 8mm is a delight.

It's  worth trying out eps and I hope that Paul's imminent visit to our area will bring some opportunity. In the meantime , even with old eyes ( "now try this without glasses" ) this well used in my case 6mm ,has been a great buy for those with a long scope,http://www.rothervalleyoptics.co.uk/SPL6.html

Nick.

[wookie1965]

The pupil guides sound very interesting I wonder if you can get them not just for Televue, before taking the plunge and getting the opportunity it would be prudent to try a couple of eyepieces before buying. As you said Nick given that I am going to be in close proximity I could try a couple to make a more informed purchase. 

[John]

2 hours ago, wookie1965 said:

The pupil guides sound very interesting I wonder if you can get them not just for Televue, before taking the plunge and getting the opportunity it would be prudent to try a couple of eyepieces before buying. As you said Nick given that I am going to be in close proximity I could try a couple to make a more informed purchase. 

As far as I know Tele Vue are the only manufacturer that make and supply them for certain of their eyepiece ranges however they are simply a matt black thin plastic disk with a hole of around 10mm diameter in the centre. I reckon you could make some to experiment with from black card perhaps held on to the top of the BST Starguider eyecup with blu tack ?

[michael.h.f.wilkinson]

If you do want a bit more eye relief, and pupil guides don't sort the problem of eye placement, you could consider the Vixen SLV 5mm. I use this extensively as high-power EP in my travel kit, and it is every bit as sharp as the (much heftier) Pentax XW 5, albeit over a much smaller FOV. It has 20mm eye relief, excellent transmission and control of reflections, and I find the ergonomics great. On various star parties I lent my 2 SLVs (15 and 5 mm) to various other astronomers, and they were very impressed. Inexperienced observers also tend to find eye placement easy (especially once they have twisted up the eye cup to the right position).

[Ricochet]

12 minutes ago, John said:

As far as I know Tele Vue are the only manufacturer that make and supply them for certain of their eyepiece ranges however they are simply a matt black thin plastic disk with a hole of around 10mm diameter in the centre. I reckon you could make some to experiment with from black card perhaps held on to the top of the BST Starguider eyecup with blu tack ?

The rubber eyecup on the Starguider is removable, so you could fit it just as in the TV instructions. However, the problem with fitting such a device is that you must be effectively reducing the eye relief to the difference in height between the top of the eyecup and the pupil guide.

Michael's comment about having the SLV's eyecup set correctly applies to the Starguider too. Not having the eyecup twisted up to the proper height makes viewing a lot more difficult.

[John]

9 minutes ago, Ricochet said:

The rubber eyecup on the Starguider is removable, so you could fit it just as in the TV instructions. However, the problem with fitting such a device is that you must be effectively reducing the eye relief to the difference in height between the top of the eyecup and the pupil guide.

I don't know how it would work with non-TV eyepieces but for the sake of a bit of black card and some sissors it might be worth a try. Cheaper than a new eyepiece !

 

 

[Charic]

Where I said -  "is a 5mm just a little too much for an f/10 scope with  0.05mm exit pupil" - Astro Baby had good results with a 5mm Hyperion used in conjunction with the TAL Diagonal, her assessment review appears here........http://www.astro-baby.com/reviews/TAL 100RS/TAL 100RS Review.htm

[John]

I think the exit pupil of a 5mm eyepiece with an F/10 scope is .5 mm ?

.05 would be a challenge !

[Charic]

Your so right John, however I did notice my mistake, along with some spelling and corrected that some hours back, but it appears there's no change to the 0.05?
I'll leave it for now ( the edit ) but yes its 0.5mm.