Lunt/APM HDC- XWA 13 mm 100°/110° v OVL MWA 100°/110° Eyepieces

[Piero]

6 hours ago, Louis D said:

He will need to rack the focuser pretty far out to account for the removal of the extension tube.  I'm not sure how long the 1.25" VIP barlow nosepiece is, as this might take up some of the difference.

As far as I remember from pictures, Neil uses 3x15mm extension rings. These plus at least 20mm for the nosepiece of his clicklock 2" to 1.25" adapter has a total extra travel of about 65mm at least. 

By subtracting this travel from his 80mm extension tube, one should get how much the focuser is extracted: about 15mm.

[Piero]

The downside of using the VIP Barlow as I said is that the 1.25" nosepiece is supporting the whole structure. This is quite robust as it is attached to the Barlow via T2 thread, but personally I don't like this much.

It is also not necessary unless one wants to use the barlow in 1.25" focusers.

In Neil's position, I would get the Baader Tak attachment I mentioned in another thread and attach the barlow element to it, therefore replacing the 1.25" nosepiece. He could then attach his clicklock adapter on top of the original 2-to 1.25" adapter coming with the VIP barlow.

Doing so, the VIP will always stick into the focuser via 2" connection, which is more solid.

This combination will require a bit of outward travel in the focuser, but not much.

The rings could be added between the two adapters.

If he decides to get a baader, Leica or Zeiss zoom at some point, he can simply remove the top clicklock and screw the top ring into the adapter of the zoom via T2 connection. This is very handy.

This is my VIP barlow. It screws on the Zeiss zoom adapter or baader adapter for the docter via T2. 

[Louis D]

We could rename this thread "Fun with astro bits and bobs". 😁

[pregulla]

On 12/06/2019 at 06:06, Louis D said:

I think the Paracorr is supposed to go first since you need to maintain a constant distance between the primary and the corrector lens (ala the SIPS version).  I can't reach focus with a barlow or telecentric magnifier when using my GSO CC, so I remove the CC since slowing down the light cone greatly reduces coma anyway.

My understanding is that Balrow helps with eyepiece aberrations (for ones that struggle in faster scopes), like astigmatism, but it doesn't help with coma or any other aberration that comes from the objective.

[Louis D]

4 hours ago, pregulla said:

My understanding is that Balrow helps with eyepiece aberrations (for ones that struggle in faster scopes), like astigmatism, but it doesn't help with coma or any other aberration that comes from the objective.

Coma decreases along with increasing f-ratio of the objective for Newts, and using a Barlow seems to decrease the amount from the objective that I can see.  Enough that I don't bother with the CC.  On the other hand, I've found that astigmatic eyepieces still look bad in slow scopes like my f/12 127 Mak despite the general consensus that f/12 is gentler on eyepieces than f/6.

[Littleguy80]

On 12/06/2019 at 22:19, Piero said:

🙄 If you...

- remove the extension tube

- put a 1.25" to 2" adapter into the focuser

- put the VIP barlow into this adapter (1.25" nosepiece)

- put eyepiece into the barlow

don't you reach focus?

 

I can see that you are using the VIP barlow in 2" mode and believe that that is the reason why you need the extension tube.

Hi Piero. I tried this last with the 9mm but didn’t have sufficient back focus to reach focus. My extension tube method setup will only work with 2 of the 15mm spacers. If I add a third then I also run out of back focus. I’ve ordered the Tak adapter for further experimenting. I’m not sure if that configuration with help but worth a go. 

[Piero]

10 minutes ago, Littleguy80 said:

Hi Piero. I tried this last with the 9mm but didn’t have sufficient back focus to reach focus. My extension tube method setup will only work with 2 of the 15mm spacers. If I add a third then I also run out of back focus. I’ve ordered the Tak adapter for further experimenting. I’m not sure if that configuration with help but worth a go. 

Ok. If you need help with the installation of that adapter, drop me a line. I can send you more detailed photos of mine.

[Littleguy80]

39 minutes ago, Piero said:

Ok. If you need help with the installation of that adapter, drop me a line. I can send you more detailed photos of mine.

Fab. Thank you very much  

[Littleguy80]

On 15/06/2019 at 13:00, Piero said:

Ok. If you need help with the installation of that adapter, drop me a line. I can send you more detailed photos of mine.

@Piero If I described you as anything less than a hero I’d be doing you a disservice. With the Baader VIP in 2” mode with the Tak adapter all my focus issues go away. With my dob it works using my standard Clicklock extension tube. No need for the extra long 80mm extension tube. The Baader Zoom will focus with three 15mm T2 extension tubes fitted in the frac with 2” diagonal. I haven’t found anything it won’t work with so far. In 1.25” mode, I’ve really struggled with focus issues which has limited the usefulness of the Barlow.

All I need to do now is figure out what the magnification factors are with in 2” mode with varying numbers of T2 extensions.

Thank you so much for the tip and advice. Really appreciate it. 

[Piero]

12 minutes ago, Littleguy80 said:

@Piero If I described you as anything less than a hero I’d be doing you a disservice. With the Baader VIP in 2” mode with the Tak adapter all my focus issues go away. With my dob it works using my standard Clicklock extension tube. No need for the extra long 80mm extension tube. The Baader Zoom will focus with three 15mm T2 extension tubes fitted in the frac with 2” diagonal. I haven’t found anything it won’t work with so far. In 1.25” mode, I’ve really struggled with focus issues which has limited the usefulness of the Barlow.

All I need to do now is figure out what the magnification factors are with in 2” mode with varying numbers of T2 extensions.

Thank you so much for the tip and advice. Really appreciate it. 

Too kind, Neil!

I only shared what other members posted previously. The real hero is the inventor of the VIP barlow: a true modular flexible design with outstanding optics in my opinion.

For the magnification factor you need to use the formula coming with the instructions and update it with the distance. 

Anyway that adapter moved the barlow lens up few mm (2-4mm?). So the resulting factor will be slightly smaller but not much compared to the original VIP where the lens is on the 1.25" nosepiece.

The only thing about the VIP that I haven't figured out is why they don't sell it with this adapter directly. I mean, almost all focusers are 2" and the VIP is much easier to use in this way instead of inserting it completely into the focuser. 

Anyway, I am glad that it works better for you now. I love my VIP barlow. Some experimenting is needed but that's fun!

[Piero]

You could use 1.25" EPs in this way:

1.25" to 2" adapter +

15mm spacer(s) +

1.25" to 2" adapter with the VIP attached to the Tak adapter attached on the 2" side (as you already do).

 

With the zoom, you can remove the first adapter and screw the spacer onto the zoom barrel.

With 2" EPs, you can replace the top adapter with a 2" clamp. EPs with large field stop might show vignettes though.

Edited June 20, 2019 by Piero

[Littleguy80]

I took a few measurements with my Lunt XWA 9mm. Without the two T2 spacers the distance between the field stop of the eyepiece and the barlow element is 4mm closer. This gives a magnification factors of 1.94x. Attaching the eyepiece via the M48 thread as opposed to inserting it into the 2"-1.25" means the field stop is further away which why you don't need the T2 spacers. 

2" mode on the left giving 1.94x and 1.25" mode on the right giving 2x. Adding the three 15mm T2 spacers in 2" mode takes the magnification factor to 2.64x. In that scenario my Baader Zoom becomes a 9.1mm to 3mm. Assuming my measurements and calculations are correct!

Edited June 21, 2019 by Littleguy80

[John]

You are gradually getting that "baseball bat" look in the right hand pic Neil !

 

[Don Pensack]

On 11/06/2019 at 20:06, Louis D said:

I think the Paracorr is supposed to go first since you need to maintain a constant distance between the primary and the corrector lens (ala the SIPS version).  I can't reach focus with a barlow or telecentric magnifier when using my GSO CC, so I remove the CC since slowing down the light cone greatly reduces coma anyway.

Since the light rays after the Powermate are parallel, it should probably go first since getting the eyepiece correctly placed relative to the Paracorr lens is critical for best coma correction.

FWIW, my best lifetime view of Jupiter was with PowerMate + Paracorr + 8mm Ethos, at 456x, in literally perfect seeing (Pickering 10).

[Don Pensack]

Many of these eyepieces are from the Chinese firm of United Optics in KunMing (KUO),

They are sold under Telescope Service, William Optics, SkyWatcher, StellarVue, and Lunt/APM labels.

There are slight differences in the barrels.

[Louis D]

On 12/07/2019 at 13:04, Don Pensack said:

Since the light rays after the Powermate are parallel, it should probably go first since getting the eyepiece correctly placed relative to the Paracorr lens is critical for best coma correction.

FWIW, my best lifetime view of Jupiter was with PowerMate + Paracorr + 8mm Ethos, at 456x, in literally perfect seeing (Pickering 10).

If you look a few posts down from the one you quoted, I corrected myself after some research with the Wayback Machine :

Richard Keppler asks about positioning the new 4x Powermate with a
Paracorr. Which goes first?

Unlike the 2x Big Barlow which must go ahead of the Paracorr, either way
is fine with the 4x Powermate and either way is approximately parfocal
for most eyepieces.

 

Nick Black asks if there are any problems using a Big Barlow with a
Paracorr.

Not if you place the Big Barlow ahead of the Paracorr. In other words,
eyepieces should always go directly into the Paracorr when using a Big
Barlow. Since the 2" Big Barlow won't slip all the way into the
Paracorr, it does not reach its parfocal point and changes the Paracorr
correction.

As an aside, you can place Tele Vue 1.25" Barlows or Powermate into the
Paracorr because these are parfocal devices.

 

Which then raises the question of how to use the Big Barlow with SIPS.

Edited July 14, 2019 by Louis D

[Don Pensack]

KunMing United Optical (KUO) is the manufacturer of the 100/110°:

Lunt

APM

StellarVue

SkyWatcher

Telescope Service

William Optics

It's unrealistic to think that the coatings are different in any of them--the manufacturer couldn't make any money doing that.

As to who makes the 100° eyepieces that are really closer to 90° (like the Meade), I don't know.