Svbony 8-3 zoom

[Louis D]

Perhaps try a quality Barlow or telecentric magnifier ahead of it to use the 5mm to 8mm settings at higher powers to take advantage of the more generous eye relief at those focal lengths?

[Ratlet]

39 minutes ago, Louis D said:

Perhaps try a quality Barlow or telecentric magnifier ahead of it to use the 5mm to 8mm settings at higher powers to take advantage of the more generous eye relief at those focal lengths?

I feel I should know this, but a Barlow will extend the focal length whilst a telwcentric will maintain it?

[Mr Spock]

8 minutes ago, Ratlet said:

I feel I should know this, but a Barlow will extend the focal length whilst a telwcentric will maintain it?

A telecentric has the same magnifying power as a Barlow but without increasing eye relief. 

[Ratlet]

6 minutes ago, Mr Spock said:

A telecentric has the same magnifying power as a Barlow but without increasing eye relief. 

Gah, got my terminology the wrong way round there, it was the eye relief I was thinking of.  Cheers for the correction. Barlow increases but telecentric doesn't increase the eyerelief?

It has been a long day 😂

Edited April 9 by Ratlet

[Roy Challen]

5 minutes ago, Ratlet said:

Gah, got my terminology the wrong way round there, it was the eye relief I was thinking of.  Cheers for the correction. Barlow increases but telecentric doesn't increase the eyerelief?

It has been a long day 😂

Yep, exactly. It can be a useful property with short focal length orthos and plossls.

[Zermelo]

... but with eypieces that already have generous eye relief, adding a Barlow may test your "floating" skills, hence the telecentric.

Not likely to happen on the Svbony zoom, though.

[Louis D]

Plus, if an eyepiece has borderline kidney beaning (SAEP), a Barlow can exacerbate it, possibly making it unbearable.  A telecentric won't have any such effect.

[Zermelo]

3 minutes ago, Louis D said:

if an eyepiece has borderline kidney beaning

Is that the eyepiece equivalent of "borderline personality disorder" in a person?

[Louis D]

10 minutes ago, Zermelo said:

Is that the eyepiece equivalent of "borderline personality disorder" in a person?

Hey, let's keep my personal life out of this. 😉

[Ratlet]

1 hour ago, Zermelo said:

... but with eypieces that already have generous eye relief, adding a Barlow may test your "floating" skills, hence the telecentric.

Not likely to happen on the Svbony zoom, though.

My 32mm plossl has spades of eyerelief.  Took me a couple sessions to figure out why I was struggling to use it sometimes (glasses off Vs glasses on putting my eye in the perfect place).  Tried it in a Barlow once and gave up.  Needed to put my head in next doors kitchen.

Keeping on topic, I used the 3-8mm with my BST Barlow and it Barlow's very well.  I get reflections (from eye to eyepiece) with my 8mm BST in the Barlow but the svbony didn't have that and the image quality was just as good with the Barlow as without on the zoom.  In both cases it absolutely stomps over the starguider.

Edited April 9 by Ratlet