Paracorr

[paul acreman]

Hi,

Can the complete range of Delos eyepieces work correctly with the last available tuneable parcorr 1 ?

thanks

[garryblueboy]

Mine all work with the mk1 

[paul acreman]

Thank you

[John]

If you buy a complete set of Delos it's worth noting that the 17.3mm and the 14mm reach focus at a point that is about 8mm further inwards than the rest of the range.

 

[paul acreman]

So I would need a ‘in travel’ televue adapter to focus the 17.3 and 14 mm?

Would that be only when using the paracorr or even without?

[John]

I've never needed to use a Paracorr so I don't know how it affects that. It looks as if the TV "In-Travel" adapter would make all the Delos eyepieces par focal:

http://www.televue.com/engine/TV3b_page.asp?id=23&Tab=_intrav

 

[paul acreman]

Thank you John understood,

As long as that problem can be overcome at the 14-17 mm range

[John]

The focus point of the 17.3 and 14mm Delos suited me because it is much closer to where my Pentax XW's reach focus so they play together quite nicely

[jetstream]

I just focus other TV EP's using the PCII after setting it up for a 21E- or any other TV EP.

[Don Pensack]

The Delos 3.5-12mm have their focal planes 6.4mm below the shoulder the eyepiece sits on, requiring the eyepiece move out 6.4mm from setting 3 to compensate.

The 1.25" adapter in the P1 is 9.7mm tall, so the eyepiece needs to move in by 9.7mm to compensate.

9.7in - 6.4out = 3.3mm in.

Each setting of the P1 is 3.2mm apart, so that means the setting should be setting 4, or 1 tick up from setting 5, which is all the way down on the P1 top.

That, as it turns out, is the setting for nearly all of TeleVue's 1.25" eyepieces, and now you know why.

 

The focal planes in the 17.3mm and 14mm, Delos, however, are 12.2mm HIGHER in the eyepiece than the other focal lengths.

The Paracorr can only move in 3.2mm from setting 4 for the other two focal lengths, leaving them 9mm short of focus, and NOT optimized for coma correction.  Oops.

So TeleVue made the In-Travel adapter for those, which drops the shoulder of the 17.3mm and 14mm about 1.5mm BELOW the top of the Paracorr, or 11.2mm lower than the P1 adapter.

We have to move in about 12.2mm to achieve optimum correction in the P1 for the 17.3mm and 14mm, though, so the same setting as the other

Delos in the standard P1 adapter is only 1mm off from perfect.  So, using the In-Travel TeleVue adapter, we use the same setting of the P-1 as the other sizes using the standard adapter,

and just move the focuser a tiny little bit to compensate.  You could move the top in 1mm from setting 4, but, in practice, no one would bother.

 

So, in summary:  Delos 3.5-12mm, setting 4 (1 step from all the way down on the top) using the standard adapter, and Delos 14-17.3, setting 4 using the In-Travel adapter. 

Hope that helps understand why the In-Travel adapter was made, and why you need it for the 14mm and 17.3mm in the Paracorr 1.

You need it for the Paracorr 2 as well.

 

Edited June 28, 2020 by Don Pensack

[paul acreman]

Thank you for that,really helpful.

I understand the settings required.

[John]

When you started out, if anyone had told you that you might spend as much on eyepieces as you had the 16 inch scope you would have thought "no way !" but you can see how it's easily possible to do that

Keep away from the Ethos's, that's my advice

[alan potts]

I had both the Mk 1 and 2 for a while when the Mk2 came out, I only noticed a little difference when using Ethos eyepieces which I imagine were a pipe-dream when the Mk 1 was launched, I do feel the Mk 2 improves stability all round though and is generally the better paracorr but at near on 500 quid, it should be.

Alan

[Louis D]

3 hours ago, alan potts said:

I had both the Mk 1 and 2 for a while when the Mk2 came out, I only noticed a little difference when using Ethos eyepieces which I imagine were a pipe-dream when the Mk 1 was launched, I do feel the Mk 2 improves stability all round though and is generally the better paracorr but at near on 500 quid, it should be.

Alan

Apparently, the Mk2 really shines at sub-F/4 focal lengths where the Mk1 began to struggle.  What f-ratio was the scope you were comparing the two in?

[Don Pensack]

The difference is primarily what f/ratio they correct to.

The Paracorr 1 removes coma in a 40mm field down to f/5 and the corrected field narrows below that.

The Paracorr 2 removes coma in a 40mm field down to f/3.5 and the corrected field narrows below that.