TMB Eyepiece

[bomberbaz]

Who has or has had them. Just looking at a 4.5mm version but not sure if the qualities good enough for a 100ED, that's around the maximum for the OTA I think. Just a little worried that if it suffers light scatter or any other issue that will take away some of the pleasure of using the scope.

I could get a meade 5000 or Delos at this size but it would be a lot of expense for an eyepiece that would not see huge levels of useage so that's why I was thinking about one of these at under £40 a throw.

[John]

200x is not excessive for the ED100 Steve. The moon, double stars, Mars, Saturn, Jupiter on nights of good seeing, Uranus and Neptune and small planetary nebulae will all respond to that sort of magnification quite readily.

I'd probably want to be able to go as far as 250x on some of those targets when the conditions are good.

The TMB planetaries are quite decent but there are many clones around and I don't think that 4.5mm was one of the original TMB / Burgess focal lengths so the "TMB" monika bears no relevence to the design and performance.

If you want minimal light scatter for reasonable cost I'd suggest an orthoscopic but I can't recall if you were a glasses wearer in which case you need longer eye relief ?

[bomberbaz]

27 minutes ago, John said:

200x is not excessive for the ED100 Steve. The moon, double stars, Mars, Saturn, Jupiter on nights of good seeing, Uranus and Neptune and small planetary nebulae will all respond to that sort of magnification quite readily.

I'd probably want to be able to go as far as 250x on some of those targets when the conditions are good.

The TMB planetaries are quite decent but there are many clones around and I don't think that 4.5mm was one of the original TMB / Burgess focal lengths so the "TMB" monika bears no relevence to the design and performance.

If you want minimal light scatter for reasonable cost I'd suggest an orthoscopic but I can't recall if you were a glasses wearer in which case you need longer eye relief ?

Thanks for that John, I was thinking more along the line of exit pupil tbh as at 4.5mm eyepiece you will have a 5mm exit pupil so just being aware of floaters in the eye beyond that. The TMB I have seen is being sold by sky's the limit so thought it must be the real deal however I will ask the question of them.

You are right I am a glasses wearer so anything shorter than 16 and it starts to get difficult.

I could always powermate the lvw 8mm and see how that behaves for floaters.

[John]

The exit pupil of a 4.5mm eyepiece used in an F/9 scope is .5mm. Floaters start to bother me when I get down to .4mm.

Re: the TMB 4.5mm being the "real deal" have a look at this:

 

In short, I doubt that the late great Thomas Back of TMB had anything to do with the 4.5mm or most of the other clones that are around to be honest.

[YKSE]

Steve,

If I were you, I wouldn´t buy any new EP just because someone joking about "a possible hole".

I would at least  use the scope a few weeks for the intended targets, and come to my own conclusions.

[Stu]

Whilst I agree with Yong, when you chose to buy, the Vixen SLVs get excellent reviews and have nice long eye relief....

[alan potts]

Steve.

I think I would either hold out for a Delos which is an excellent eyepiece or Powermate the 8mm. I tested a couple of these TMB's, or at least that was what they claimed to be, the 2.5mm was not bad but the 6mm was awful. I too do not believe 4.5mm was ever in the original design group.

[mikeDnight]

10 hours ago, bomberbaz said:

Who has or has had them. Just looking at a 4.5mm version but not sure if the qualities good enough for a 100ED, that's around the maximum for the OTA I think. Just a little worried that if it suffers light scatter or any other issue that will take away some of the pleasure of using the scope.

I could get a meade 5000 or Delos at this size but it would be a lot of expense for an eyepiece that would not see huge levels of useage so that's why I was thinking about one of these at under £40 a throw.

Ive had all the TMB Planetaries and they gave exceptional views of the planets, especially when you consider the price. In fact only about a fortnight ago, paulastro called round to my place and brought his TMB's with him, and they were sharp, clean and were very comfortable to use. In side by side comparison with my Pentax XW's they were in no way the poor cousin, but quite a worthy adversary. They have quite good eye relief too, and with a 60° AF they can be used comfortably on an undriven mount without any trouble. Orthoscopic will deliver sharper views but you'd be better using a longer focal length along with a barlow for comfort, especially if you want glasses while observing.

Better still with your ED, two 18mm orthos in a binoviewer with a 2x Barlow screwed to its nose. 

Mike 

 

[cs1cjc]

On 04/03/2016 at 13:06, John said:

In short, I doubt that the late great Thomas Back of TMB had anything to do with the 4.5mm or most of the other clones that are around to be honest.

The different focal length TMB Planetary eyepieces only differ in the field Smyth lens assembly, before the field stop which acts as a barlow.  The eye group is identical in all focal lengths, from 2.5mm to 9mm.  Designing a Smyth lens for a new focal length, such as 4.5mm or 7.5mm not in the original series, would not be a difficult optical design task.  There would be no incentive to change eye group from the Thomas Back design.