10 replies to this topic

[vrodriguez2324]

For a few years now my hyperwide set has been a mix of Optimus, Ethos, and XWAs in the following focal lengths: 20 - 13 - 9 - 7 - 4.7 - 3.6

 

This set worked well in my 8 inch f/5 reflector and 4 inch f/7 refractor, but the addition of a 14XXG last year revealed a gap I wanted to fill. 

 

With the Paracorr I get the following magnifications: 95x - 146x - 210x - 271x - 404x - 527x. I felt jump between 271x - 404x was a little wide. I tried combinations of Barlows which worked okay but I really wanted to just get a dedicated eyepiece without having to replace any of my current units. 

 

So after a lot of thought, patience, and luck in the classifieds I settled on an eyepiece that would fill the gap. It arrived earlier this week: the 5.5mm ES100 for 345x. San Diego has been very cloudy for over a week so I haven't had a chance to try it out but I will as soon as we get some clear skies. 

 

I predict the 5.5 ES 100 to be a good eyepiece and on par with the XWAs. For those who have had experience with it, how did you like it?

 

-Victor

Attached Thumbnails

• 

[Jon Isaacs]

Victor:

 

That gap has been an issue for me too.  The two eyepieces I have been pondering:  The 6mm Ethos or the 5.5mm Explore Scientific.  My past experiences with ES 100 degree eyepieces have not been so good but a friend has the 5.5 mm I can borrow.

 

That gap is pretty big in the 22 inch, about 400x to 590x.  I have the 8mm Ethos and 7mm XWA.  The 8mm-6mm-4.8mm seems pretty good. That would be 352x, 470x and 588x.  

 

The 10mm Ethos with my 1.75x Barlow is a 5.7mm which would be 495x.. 

 

I am not in the buying mode right now so I just live with it.  

 

Jon

[Sarkikos]

I'm happy with my Ethos / Ethos-SX set.  But I replace the 21 Ethos with a 20 XWA, for the lighter weight.   This gives me 20, 17, 13, 10, 8, 6, 4.7 and 3.7.

 

I don't see any obvious gaps.  Though, if Tele Vue came out with a 2.7 Ethos-SX, I'd probably go for it. 

 

Mike

[vrodriguez2324]

 

My experience with ES100s was actually a good one. The 9m ES100 completed my first final set (here you see them grouped by families (Tele Vue, Explore Scientific, and Baader). 

 

30 - 24 - 17 - 12 - 9 - 6.5 - 5

 

It was different than the rest of my set, but I liked it so much it became the catalyst for the bifurcation of my collection. 

 

It was only sold because I got a full set of Optimus. My previous experience with the 9 makes me feel confident in the 5.5.

 

It's raining again today =(

 

[Jon Isaacs]

Currently my set of Ethos and XWAs:

 

20mm XWA, 13mm XWA, 13mm Ethos, 10mm Ethos, 9mm XWA, 8 mm Ethos, 7 mm XWA, 4.8 mm XWA and 3.5 mm XWA.  

 

The 9mm XWA is a nice eyepiece but redundant because the 13mm-10mm-8 mm Ethos is just about perfectly spaced.  

 

It occured to me that with a 1.5x-1.6x Barlow, it could fill the 7mm-4.8mm gap..  That could possibly be the 2 inch 2x GSO Barlow used as the nosepiece.  I would need to measure the magnification factor and the backfocus.

 

Another possibility is using the 1.25 inch 2X GSO Barlow in the 1.5x mode.  I tried this out mechanically, I removed the 2 inch skirt, screwed the Barlow in place.  And since I am using my 100 degree set as 2 inch eyepieces, I just used a 2 inch to 1.25 inch adapter.  It seems promising, I could just leave it that way and use it as if were a 6mm eyepiece.  

 

Edit:  I just tested the combination and it turns out it is parfocal (just a slight tweak) with the 9mm un-Barlowed so that that means it would make using it with the Paracorr straightforward..

 

I do need to measure the magnification.  I can see it replacing the 7mm XWA so I would have 10mm-8mm- ~6mm - 4.8mm giving me 282x, 352X, 470x and 590x.  It all depends on the quality of the view and the actual focal length. If it were closer to 5.5mm, then the 7mm would remain.

 

Jon

Edited by Jon Isaacs, 01 April 2025 - 10:56 AM.

[Mike Q]

I ran a ES 5.5/100 over at the observatory a couple of times last year.  Its a solid eyepiece but the eye relief is pretty tight.  I have given thought to getting one for my XX16G but given my skies i cant really justify it.

[Jon Isaacs]

I ran a ES 5.5/100 over at the observatory a couple of times last year.  Its a solid eyepiece but the eye relief is pretty tight.  I have given thought to getting one for my XX16G but given my skies i cant really justify it.

 

My friend lent me his ES 5.5mm 100 degree yesterday and the skies were clear for a while last night.  I was able to make some observations with both the ES 5.5mm and the 9mm XWA with the 1.25 inch Barlow in the 1.5x mode.  I was using the WO Zenithstar 103, it's about F/7.

 

The Barlow scheme shows quite a bit of astigmatism out towards the edge.  That configuration is not workable.  Maybe there is another 1.25 inch 1.5x Barlow that would work but that one certainly didn't.

 

The ES 5.5mm 100 degree turned out to be a good fit.  I found the eye relief to be adequate with the eyecup rolled down, a bright star taken to the edge of the field remained sharp.  And what is nice is that it is parfocal with the 7mm and 4.8 mm XWAs. It is supposed to be clear for a few nights so I hope to get some views under dark skies in one of the Dobs. I am optimistic.

 

Jon 

[vrodriguez2324]

Currently my set of Ethos and XWAs:

 

20mm XWA, 13mm XWA, 13mm Ethos, 10mm Ethos, 9mm XWA, 8 mm Ethos, 7 mm XWA, 4.8 mm XWA and 3.5 mm XWA.  

 

The 9mm XWA is a nice eyepiece but redundant because the 13mm-10mm-8 mm Ethos is just about perfectly spaced.  

 

It occured to me that with a 1.5x-1.6x Barlow, it could fill the 7mm-4.8mm gap..  That could possibly be the 2 inch 2x GSO Barlow used as the nosepiece.  I would need to measure the magnification factor and the backfocus.

 

Another possibility is using the 1.25 inch 2X GSO Barlow in the 1.5x mode.  I tried this out mechanically, I removed the 2 inch skirt, screwed the Barlow in place.  And since I am using my 100 degree set as 2 inch eyepieces, I just used a 2 inch to 1.25 inch adapter.  It seems promising, I could just leave it that way and use it as if were a 6mm eyepiece.  

 

Edit:  I just tested the combination and it turns out it is parfocal (just a slight tweak) with the 9mm un-Barlowed so that that means it would make using it with the Paracorr straightforward..

 

I do need to measure the magnification.  I can see it replacing the 7mm XWA so I would have 10mm-8mm- ~6mm - 4.8mm giving me 282x, 352X, 470x and 590x.  It all depends on the quality of the view and the actual focal length. If it were closer to 5.5mm, then the 7mm would remain.

 

Jon

I can see why in your case the 9mm may be redundantly spaced. The 10-9-8-7 is a little crowded with only a 1mm difference between them in this range.

 

The 7 to 4.7 gap is the biggest. Like you I've tried to fill the gap with barlows as well. I actually found the 13 Ethos with my 1.25 inch Celestron Xcel Lx 2x barlow put up a very nice view. The celestron 2x is really like 2.3x (others and myself think it is a GSO 2.5x Barlow in a different housing, the GSO is also 2.2 or 2.3x depending on the eyepiece of course). 

 

My 13 Ethos with the 2.3x barlow was about 5.5mm. I have to find my notes where I jotted down the drift times. 

 

Anywhoo. I got in a few quick observations on those clear nights a few days ago with the 5.5 ES. My preliminary conclusions are that it is a darn good eyepiece, fits in my set perfectly. The difference in focal lengths decreases all the way down my progression.

 

20 - 13 - 9 - 7 - 5.5 - 4.7 - 3.6

 

Jon, hold on to the 7mm XWA!

[Jon Isaacs]

Victor:

 

Right now I'm thinking that while the 7 mm - 4.8 mm gap is large, it's not much different than the 7 mm - 5 mm gap of the type 6 Naglers which I've used for years. 

 

At this time I'm thinking that the 20-13-9-7-4.8-3.5 spacing of the XWAs is really quite usable, maybe not ideal but close enough. 

 

If I really want an effective 5.5 mm focal length, I can simply remove the Paracorr and use the 4.8 mm XWA and live with a little coma..

 

My friend Bruce has a Paracorr but doesn't use it as it would mess with his well crafted system of using the 17 mm and 13 mm Ethos plus the A-P Barlow and TV 2 inch Barlow with spacers to find tune the magnification. That's in his 18 inch F/4.5 Obsession.

 

Jon

[vrodriguez2324]

Victor:

 

Right now I'm thinking that while the 7 mm - 4.8 mm gap is large, it's not much different than the 7 mm - 5 mm gap of the type 6 Naglers which I've used for years. 

 

At this time I'm thinking that the 20-13-9-7-4.8-3.5 spacing of the XWAs is really quite usable, maybe not ideal but close enough. 

 

If I really want an effective 5.5 mm focal length, I can simply remove the Paracorr and use the 4.8 mm XWA and live with a little coma..

 

My friend Bruce has a Paracorr but doesn't use it as it would mess with his well crafted system of using the 17 mm and 13 mm Ethos plus the A-P Barlow and TV 2 inch Barlow with spacers to find tune the magnification. That's in his 18 inch F/4.5 Obsession.

 

Jon

My set was just fine also, Jon. 

 

In fact I was using a Meade 5.5 UWA as a place holder. But often I would just skip it and go straight from the 7 down to the 4.7 and didn't give it a second thought. 

 

I like your idea of just removing the Paracorr to achieve the desired mag  I've read the thread where AstroMaster has described his well crafted system in detail. He's got it down to a science for sure.

[Astro-Master]

My set was just fine also, Jon. 

 

In fact I was using a Meade 5.5 UWA as a place holder. But often I would just skip it and go straight from the 7 down to the 4.7 and didn't give it a second thought. 

 

I like your idea of just removing the Paracorr to achieve the desired mag  I've read the thread where AstroMaster has described his well crafted system in detail. He's got it down to a science for sure.

I've been using the ES 5.5 100* eyepiece for years now, it's a good high power eyepiece, I believe it's the best of the ES 100* eyepieces. 

 

I used it in my 18" Dob with the TV Big Barlow with extensions for a power of 1,300x on the Eskimo Nebula on a night with perfect seeing, and the view was absolutely stunning!

 

Last August I had a nice view of the Ring Nebula with the central star using the ES 5.5 and the Astro-Physics Barlow at powers of about 750x to 800x, under good but not great seeing.