11 replies to this topic

[John Fitzgerald]

https://www.amazon.c...ct_details&th=1

 

These look exactly like the BST Planetary eyepieces.  The focal lengths are very close.  Is the 7.5mm in the link really 7.5mm, or is it the same eyepiece as the 7 or 8, except for labelling?  The difference seems very, very small.  Same with the 4.5mm.

Edited by John Fitzgerald, 07 December 2022 - 05:21 PM.

[CowTipton]

I believe they're rebranded TMB II eyepieces.

I have no opinion on the quality though.

[Sky Muse]

The Astromania and BST planetaries are the same as these TMB clones that I have...

 

 

No matter which you have, if you want to get the most out of it, the interior of the barrel and the edges of the lenses round should be ultra-flat blackened.

[pj_thomas]

I believe they're rebranded TMB II eyepieces.

I have no opinion on the quality though.

From agena:

"Please Note: While these eyepieces look similar to the TMB / TMB II ED eyepieces (and are also sold by some other sellers incorrectly under the TMB label), they are not the same as or copies of the 6-element TMB eyepieces. The factory making these eyepieces just uses the same external housing for the eyepieces."

[John Fitzgerald]

I got the Astromania 7.5mm Planetary eyepiece.  At f/8, my particular sample is very nearly the equal of a Delite.  It's shockingly good for its cost.  I paid about $44 including tax.  I haven't tested it at lower focal ratios.  I suspect it might falter at f/5.

[great_bear]

I got the Astromania 7.5mm Planetary eyepiece.  At f/8, my particular sample is very nearly the equal of a Delite.  It's shockingly good for its cost.  I paid about $44 including tax.  I haven't tested it at lower focal ratios.  I suspect it might falter at f/5.

I’ve had a few of these “clones” over the years, including the Sky-Watcher version of it. 
 

They are in fact, very good at F5, and present a very nice view with a crisp field-stop and (in my scopes) very even illumination, but they do have the following two issues:

1. Serious glare issues on bright targets
2. When pushing a scope to its maximum, present a rather “mushy” view
   (fuzzy diffraction spikes around bright stars)

So whilst a casual glance at a star field might present a Delite-like view, I would expect that performing a Luna comparison at the edge of the scope’s limit will provide a view that’s very much inferior to a Delite. 

Edited by great_bear, 19 December 2022 - 07:12 PM.

[John Fitzgerald]

I’ve had a few of these “clones” over the years, including the Sky-Watcher version of it. 
 

They are in fact, very good at F5, and present a very nice view with a crisp field-stop and (in my scopes) very even illumination, but they do have the following two issues:

1. Serious glare issues on bright targets
2. When pushing a scope to its maximum, present a rather “mushy” view
   (fuzzy diffraction spikes around bright stars)

So whilst a casual glance at a star field might present a Delite-like view, I would expect that performing a Luna comparison at the edge of the scope’s limit will provide a view that’s very much inferior to a Delite. 

My comparisons were with some close double stars, and Mars.  162x.

[great_bear]

My comparisons were with some close double stars, and Mars.  162x.

In my experience, it’s once the exit pupil drops below 1mm that the fuzziness on (very) bright stars appears. 

[John Fitzgerald]

Computed exit pupil for a 7.5mm eyepiece in my f/8 triplet is 0.94mm.

[great_bear]

Computed exit pupil for a 7.5mm eyepiece in my f/8 triplet is 0.94mm.

Just on the limit there, IMO. 

[John Fitzgerald]

Even with the stated shortcomings, it's still a very good value.

[great_bear]

Even with the stated shortcomings, it's still a very good value.

Very much so - I had an 8mm once that I was very fond of and always regretted selling.