Ethos parfocal 2"

[guillaume320]

Hello,

If I get the 8 and 6mm Ethos, what's the best solution to have them parfocal (in 2 inch) with the 21mm?

Regards,

Guillaume

[martinl]

When used in 1.25” mode with the Televue high-hat adaptor they are parfocal with the 21mm. Another option would be to add 2” barrel extensions and parfocalising rings, but the rings would have to be slightly below the end of the original 2” barrels so the extensions would have to be quite long. 

[alanjgreen]

Hi Guillaume320,

I have both the E6 and E8 and use them in my 20" dob in "2inch mode". I have made them parfocal with the Ethos13 so that I can use them at the same Paracorr2 setting to save a load of messing about in the dark

Here is a pic of my case...

You can see that the E6 and E8 and both wearing Televue 30mm eyepiece barrel extentions. This is the first thing you need. Don't be tempted to buy cheaper Revelation 30mm extensions from Telescope House (to save money), they don't screw onto the Ethos and you will have to send them back (I know, I tried & failed with these )

https://www.widescreen-centre.co.uk/astronomy-eyepieces-and-barlows-tele-vue-eyepieces-barlows-and-powermates/tele-vue-eyepiece/tele-vue

Next, buy some 2" parfocal rings like these from 365Astronomy (these are what I used above)

https://www.365astronomy.com/365Astronomy-2-Parfocal-Eyepiece-Ring-Parfocalizing-Ring-ONE-PIECE-ONLY.html

Then, I got my scope setup with the Paracorr2 & Ethos13 at focus. I removed the E13 and inserted the E8 (leaving focuser & paracorr as they were) and gently lifted it back out of the focuser while looking through it, after a "short lift" it was at focus point - this is the position where I fixed and tightened the par-focal ring!

If you are using a paracorr2 then the Ethos21mm uses a different position in the Paracorr2 to the rest of the set. But if you have them match the E13 in the same setting as the E13 then they are parfocal with the 21mm too, as the 21mm comes to the same focus point when you turn the paracorr2 to its designated setting.

If you are not using a paracorr2 then you would need to play around above, but I cannot guarantee that they can be parfocal with the 21Ethos without the Paracorr as the 21mm is the eyepiece that takes the most infocus (more than all the others in the set!) and the E8/E6 take the most out-focus !

 

Are you using Paracorr2? You don't need to own an E13 to repeat the steps above...  Setup so that the ethos 21 is at focus point with paracorr2 in position "A". Now, remove the E21 and move paracorr2 to position "H". Insert ethos8, look through it and "lift" it back out of the paracorr2 very slowly. It will reach focus in a few mm, this is where you need to fix the parfocal ring so that this much of the E8 stays outside the paracorr2. In these steps do not touch the telescope focus knob. They are now parfocal, with one needing paracorr2 "A" and the other using paracorr2 "H"  

 

HTH,

Alan

[guillaume320]

Awesome...

Yes, setup is including a Paracorr 2...

So TV barrel extender, and parfocal ring...got it

Regards,

Guillaume

[alanjgreen]

5 hours ago, guillaume320 said:

Hello,

If I get the 8 and 6mm Ethos, what's the best solution to have them parfocal (in 2 inch) with the 21mm?

Regards,

Guillaume

The ethos 8 is very good  in my big dob at x250. Almost a "wow" every time. I have not had the ethos 6 long so we are still building our relationship... at x350 I have only used it on planetary so far. Hoping for some great conditions during "galaxy season" so I can use it on some small bright galaxies...

What scope have you got?

[guillaume320]

Scope is going to be OOUK VX12 1/10... (will receive it in February)

With the Paracor making it a 1380mm, the 21mm will give me x67, the 8mm x172 and for high power the 6mm 230x. 

I've been considering the 4.7, but I'm not sure the skies of northern Europe will be good enough to take 290 magnification... thoughts?

G

[alanjgreen]

43 minutes ago, guillaume320 said:

Scope is going to be OOUK VX12 1/10... (will receive it in February)

With the Paracor making it a 1380mm, the 21mm will give me x67, the 8mm x172 and for high power the 6mm 230x. 

I've been considering the 4.7, but I'm not sure the skies of northern Europe will be good enough to take 290 magnification... thoughts?

G

Sounds good. No need to get them all at once. The 13mm ethos will be good in your scope at x100 and its price is much less than the 21ethos. 

i would probably get a 13mm and 8mm first. (x100 and x172)

then add the 21 

then add the 6

if you get to use the 6 a lot with good results, and find you need more for some targets then get the 4.7 (hold fire on the 4.7 until you “want” it  

If you can get them second hand then you can save a large amount of money ! It’s nice to add them as you go, keeps the “first time” feeling going and lets you save up for the next one...

if you already own the 21ethos, then TeleVue recommend a set of 21,13 & 8 as “all you need”. I started with 21, 13 & 10. Then found I wanted an 8 as I was using the 10 a lot and many objects seemed to want more power, so I added an 8 and wow, it’s good. So I have added a 6 as the final one. I won’t be going any lower than 6mm.

[guillaume320]

Great feedback Allan, thanks...

I haven't got any Ethos yet, so will definitely have a closer look at the 13mm... 21, 13, 8, 6 looks like a great lineup

G

[John]

Ethos seem to fall into two groups or sub sets:

21-13-8

or

17-10-6

The 4.7 and 3.7 tend to be considered separately and can be added to either of the above groups.

Of course you can mix the sets (I have 21-13-8-6) or have the whole lot if the budget can stand it

[martinl]

15 minutes ago, guillaume320 said:

Great feedback Allan, thanks...

I haven't got any Ethos yet, so will definitely have a closer look at the 13mm... 21, 13, 8, 6 looks like a great lineup

G

Have you had a chance to try any Ethos? The combination of 15mm ER and 100 degree AFOV is not for everyone, especially eyeglass wearers. I got the 21-10-6mm set when I used contacts for observing, but now that I observe more with my glasses I prefer Delos due to the 20mm ER. 72 degree AFOV is plenty, for me at least. 

[alanjgreen]

20 minutes ago, martinl said:

Have you had a chance to try any Ethos? The combination of 15mm ER and 100 degree AFOV is not for everyone, especially eyeglass wearers. I got the 21-10-6mm set when I used contacts for observing, but now that I observe more with my glasses I prefer Delos due to the 20mm ER. 72 degree AFOV is plenty, for me at least. 

I think the 100 degree comes into its own on a manual dob (with no tracking). Even a drop to 72 degree means a lot more nudging. 72 degree is a big drop in fov! If not Ethos then try Nagler type 4 next...

i do agree that Delos are comfortable to use with glasses  

i think that if you do not currently own any Ethos then a second hand 13mm is the place to start. If you don’t get on with it then you can sell it for what you paid for it and nothing lost. Make sure you buy one that has all the original boxes, end caps and the “little screw” (which you don’t actually need but can’t be bought as spares)

Ethos are very different to use if you have not tried one. The immediate field of view seems “unbelievable” (mind blowing in fact) at first experience. But it takes time to learn where to best place your eye. Give your brain time, you will soon be using it without any thought whatsoever...

When I use my Delos now, I find eye placement harder than any of the Ethos, I have just got used to Ethos. 15mm is plenty of eye relief for non glasses wearers and I find them very comfortable to use.

My only complaint is why TeleVue designed them as 1.25 and 2”. Its a pain to have to pay more for barrel extenders to make them useable, extenders should be provided free of charge in a £500+ eyepiece  

Alan

fyi, there is a 13mm on astrobuysell at the moment...

http://www.astrobuysell.com/uk/propview.php?view=133472

(make sure you see some pictures before buying though and verify it has all the boxes, caps and screw)

[iPeace]

I have a couple of barrel extenders off my Ethos in the spares box - if you're interested, just shoot me a PM.

[Louis D]

1 hour ago, martinl said:

Have you had a chance to try any Ethos? The combination of 15mm ER and 100 degree AFOV is not for everyone, especially eyeglass wearers. I got the 21-10-6mm set when I used contacts for observing, but now that I observe more with my glasses I prefer Delos due to the 20mm ER. 72 degree AFOV is plenty, for me at least. 

I have the 12mm and 17mm ES-92 which are like Delos on steroids.  They have about 1mm to 2mm less usable eye relief due to the recessed eye lens than the Delos, but the view is similar in that it is out there in front of you and pinpoint sharp to the edge.  You don't have to bury your eye into it to see the whole field.  They are huge and heavy, though.

1 hour ago, alanjgreen said:

I think the 100 degree comes into its own on a manual dob (with no tracking). Even a drop to 72 degree means a lot more nudging. 72 degree is a big drop in fov! If not Ethos then try Nagler type 4 next...

Tried that route with the 12mm and 17mm Nagler T4s.  Both are hard to hold the view with eyeglasses.  Each have about 3mm to 4mm less usable eye relief than the Delos which makes using them with eyeglasses very difficult.  They are also extremely finnicky in holding the view.  Get just a fraction of a millimeter closer than where the field stop pops into view, and it starts blacking out.  It's tiresome to use them.  They are much lighter and smaller than their ES-92 counterparts, though.  I'd give the edge to the ES-92s over the NT4s except for size.

[guillaume320]

10 hours ago, martinl said:

Have you had a chance to try any Ethos? The combination of 15mm ER and 100 degree AFOV is not for everyone, especially eyeglass wearers. I got the 21-10-6mm set when I used contacts for observing, but now that I observe more with my glasses I prefer Delos due to the 20mm ER. 72 degree AFOV is plenty, for me at least. 

Hi Martin,

Thanks... I hadn't considered eye relief, but I'm happy to report I have very good eyesight so I don't think this will be an issue. Nudging a manual dob on the other hand will be preoccupying me more I think.

G

 

[guillaume320]

9 hours ago, iPeace said:

I have a couple of barrel extenders off my Ethos in the spares box - if you're interested, just shoot me a PM.

Thanks for the offer!  But right now I think I might start with the 13mm, so won't need the extenders till I get the 21 I guess...

[iPeace]

2 hours ago, guillaume320 said:

Thanks for the offer!  But right now I think I might start with the 13mm, so won't need the extenders till I get the 21 I guess...

I used extenders on the Ethos not so much for parfocality (?) but to give them all a uniform 2" barrel. This just seemed right for the size of the eyepiece and enabled use of 2" filters on all of them.

[martinl]

3 hours ago, guillaume320 said:

Hi Martin,

Thanks... I hadn't considered eye relief, but I'm happy to report I have very good eyesight so I don't think this will be an issue. Nudging a manual dob on the other hand will be preoccupying me more I think.

G

 

You should be OK then. I agree that 13mm is probably the best place to start - good all round focal length for DSOs with most scopes. 

Personally I don’t find nudging to be a huge problem, but I do appreciate the wider FOV when it comes to finding objects. I still use my Ethos 21mm for that reason, then stepping up to a 12mm or 8mm Delos for higher powers. 

[alanjgreen]

4 hours ago, guillaume320 said:

Thanks for the offer!  But right now I think I might start with the 13mm, so won't need the extenders till I get the 21 I guess...

You will only need the extenders if you buy 6 or 8 mm and want to use them in 2" mode.

Whether you have a 21 is irrelevant.

I agree with @iPeace that the extenders are useful on the other 1.25/2" Ethos as otherwise the unusual lower surface is not easy to get straight into a 2" focuser (in the dark). If you recheck my pic from my first post then you will see that I fitted cheaper Baader 14mm barrel extenders to my 13mm and 10mm. This still allowed me to fit the EP into the original Televue foam within my EP box while making it easier to get them into a 2" focuser in the dark.

https://www.firstlightoptics.com/baader-planetarium/baader-hyperion-finetuning-ring.html

Don't worry about fitting filters to the EPs, you will fit them onto the bottom of the Paracorr2 directly. Then you can change EP but the filter is still there!

[guillaume320]

2 hours ago, iPeace said:

I used extenders on the Ethos not so much for parfocality (?) but to give them all a uniform 2" barrel. This just seemed right for the size of the eyepiece and enabled use of 2" filters on all of them.

A very, very impressive collection you have...!!!

[guillaume320]

1 hour ago, alanjgreen said:

You will only need the extenders if you buy 6 or 8 mm and want to use them in 2" mode.

Whether you have a 21 is irrelevant.

I agree with @iPeace that the extenders are useful on the other 1.25/2" Ethos as otherwise the unusual lower surface is not easy to get straight into a 2" focuser (in the dark). If you recheck my pic from my first post then you will see that I fitted cheaper Baader 14mm barrel extenders to my 13mm and 10mm. This still allowed me to fit the EP into the original Televue foam within my EP box while making it easier to get them into a 2" focuser in the dark.

https://www.firstlightoptics.com/baader-planetarium/baader-hyperion-finetuning-ring.html

Don't worry about fitting filters to the EPs, you will fit them onto the bottom of the Paracorr2 directly. Then you can change EP but the filter is still there!

All duly noted... Thanks for all the feedback, it's hugely appreciated!

[iPeace]

48 minutes ago, guillaume320 said:

A very, very impressive collection you have...!!!

Old photo. I have since moved to smaller, lighter eyepieces.