Binoviewing with Tessa

[JeremyS]

After all the discussion in the last 24 h on binoviewers I thought I try my William Optics set on the Tak TSA 120, Tessa.

I only have one pair of eyepieces: the WO 20 mm UWA that were supplied with the unit. I also used the 1.4 x Barlow that is supplied.

Some very nice views of the moon and Venus in the darkening skies. Images easy merged and clear. The whole moon easy fits in the FOV, but I could do with some more magnification. 

I tried some of my Tak LE's: 12.5, 10 and 7.5 mm. I only have individuals so only used one eye to test them out, but got the impression that I'd be looking at a 7.5 mm eyepiece to have decent higher mag views of planets, based on what i saw of Venus. I'd especially like to binoview Mars as some of the best views I have had of Mars were in 2001 with my Tak FS 102 and borrowed binoviewers, but I can't remember the mag.

Two questions emerge:

1. I'm reluctant to shell out on a duplo set of Tak eyepieces, in case I don't really take to the binos, so what do you suggest i go for that are cheaper? I tried some orthos, but the eye relief is difficult enough with one eye. I recall @mikeDnight likes Plossls?

2. When I try to use the binos without the Barlow, only  part of the device fits into the diagonal, so it's not properly secured. This is with a Baader clicklock, but it's the same with a Tak 1.25-inch diagonal and a TeleVue. Do others have this situation? It's not rate limiting as I'd probably use with the Barlow in any case. The pic shows the binos with the Barlow installed and inserted into the diagonal.

[GazOC]

I've got a couple of the old Sirius Plossls, they strike a good balance for me between cost/ FOV/ eyerelief and weight 

[Rainmaker]

I would suggest that you double up on the LE7.5.  The LE7.5 and the LE5mm are ED eyepieces. 

The 7.5mm will give you 120x if used without the barlow lens,  I have found this to be a very useable magnification for many targets. 

I previously had pairs of Naglers, DeLites etc.  My current binopairs are the LE30,18, 7.5 and 5 as well as the Panoptic24s.  Of those I mostly use the LE18 and 7.5, both give very sharp, contrasty views.

 

[JeremyS]

10 minutes ago, Rainmaker said:

I would suggest that you double up on the LE7.5.  The LE7.5 and the LE5mm are ED eyepieces. 

The 7.5mm will give you 120x if used without the barlow lens,  I have found this to be a very useable magnification for many targets. 

I previously had pairs of Naglers, DeLites etc.  My current binopairs are the LE30,18, 7.5 and 5 as well as the Panoptic24s.  Of those I mostly use the LE18 and 7.5, both give very sharp, contrasty views.

 

Thanks Matt. Have the LE5 and 7.5 always been ED? How do you tell? I’ve had mine for a few years And I’d hate to double up and find the new ones are different.

[Rainmaker]

Jeremy, as far as I am aware they have always been made with ED.  I have had sets from each of the 3 generations of 7.5mm and 5mm LEs and optically they have been the same.

The differences have been with graphics on the housing.  Does  you setup reach focus without the barlow?  by removing the extension tube?

I found that I had better results using the Baader 1.25x GPC in the diagonal instead of barlows like the WO.  The GPCs were designed by Roland Christen to counter spherochromatism caused by the binoviewer prisms and as they also move the focal point out, they help with light path issues.

Edited May 5, 2020 by Rainmaker

[JeremyS]

8 hours ago, Rainmaker said:

Jeremy, as far as I am aware they have always been made with ED.  I have had sets from each of the 3 generations of 7.5mm and 5mm LEs and optically they have been the same.

The differences have been with graphics on the housing.  Does  you setup reach focus without the barlow?  by removing the extension tube?

I found that I had better results using the Baader 1.25x GPC in the diagonal instead of barlows like the WO.  The GPCs were designed by Roland Christen to counter spherochromatism caused by the binoviewer prisms and as they also move the focal point out, they help with light path issues.

Thanks Matt.

No I can't really use the binoviewers without the Barlow as the nose piece does no fit far enough into the diagonal to present a secure fixing without it (It's mainly the Barlow that is engaged within the diagonal).