184 replies to this topic

[Starman1]

What does getting older have to do with using a 31T5?

 

Mike

I guess the idea is that if the eyepiece yields an exit pupil that it too large for the pupil of the observer's eye it is too low a power for the observer in that scope.

People's dilated pupils get smaller with age.

My dilated pupil diameter should confine me to a 23mm low power in my f/5.75 dob, though I do use a 30mm from time to time.  I recognize my pupil diameter is reducing the brightness a lot, however.

In my f/4.3 dob, however, my low power will be a 22mm eyepiece.

[bocanegra1]

Would be nice that someone having TV’s Powermates tests the H EPs with these to check the degree of compatibility.

[RLK1]

Any ETA for the 12mm model at this point?

[Starman1]

Any ETA for the 12mm model at this point?

Robert said in the thread on the Vendor Forum:

https://www.cloudyni...0th/?p=14098423

[RLK1]

Robert said in the thread on the Vendor Forum:

https://www.cloudyni...0th/?p=14098423

Thanks, looks like the 12mm is headed for a July 2025 debut...

[Houdini]

Would be nice that someone having TV’s Powermates tests the H EPs with these to check the degree of compatibility.

A user on the French Astrosurf has used a Powermate 2X to barlow the Houdini 20 to a 10 mm eyepiece, with a 500 mm F/4 telescope. See http://www.astrosurf...comment=2511972 .

 

The relevant paragraph translated to English by an online tool:

 

Before the clouds came, I pointed the M51 and checked that this Houdini would acclimatize to a Powermate 2x. Well, I wasn't worried, but I prefer to be exhaustive. So I had a 10mm and a 200x magnification. Well, it works like a charm, with a clear field of view. I never use a paracor with a powermate, especially with 1kg eyepieces, so I was able to get a half-degree field without distorting the stars at the edge. All in all, as you'd expect, the powermate doesn't change a thing.

Edited by Houdini, 27 April 2025 - 05:32 PM.

[bocanegra1]

A user on the French Astrosurf has used a Powermate 2X to barlow the Houdini 20 to a 10 mm eyepiece, with a 500 mm F/4 telescope. See http://www.astrosurf...comment=2511972 .

The relevant paragraph translated to English by an online tool:

👍👍

[astrophile]

Second night under stars with H20 in 10” f/6 dob. Ref post #20 for initial impressions. Conditions last night: Clear, “meh” transparency, average seeing, low ground humidity, LP Yes (Bortle 4.5 to 5-ish).

Main goal, to examine the views more closely for field curvature and image behavior toward edge of field.

Bottom line, I did not perceive FC even when looking carefully for any change of focus from center to edge of field. Stars would go a bit astigmatic out at the last 10% but I attribute that to my own mild astigmatism that I normally don’t bother to correct at a telescope. Indeed, when I did try it with prescription glasses on, the stars largely cleaned up at the edge.

I also tried out Regulus at the very edge. There was indeed some vivid blue fringing but only out at the extreme edge. Not a spot I’ll ever place a bright star for observation.

Finally, I tried to replicate CrazyPanda’s focus experiment with M3. Couldn’t do it though—at my place both M3 and M5 are smack in the nasty DC suburbs light dome that time of night; that plus my 10” mirror and only 76x made them too small, dim, and contrast-limited to pick out individual faint stars for the test.

I’m in my 60’s and unquestionably presbyopic and focus-accommodation limited. Maybe I have just enough remaining to accommodate any FC in this eyepiece/scope combination (f/l 1530)…or does f/6 vs 4.3 make some kind of difference? Anyway, for me the point is moot, I find the f/6 dob an excellent use case for the Houdini and I’m very happy to have it. One of these months, if weather and moon and work ever cooperate, I’ll try it out in the 16” f/4.3 up at the WV dark site.

[Olimad]

Maybe it has already been asked, but would you consider making a Houdini eyepiece that maximizes the coma-corrected true field of view in the 1.25" format (around 27mm fieldstop)?

[Houdini]

With the current coma-correcting designs the longest focal length that would fit in the 1.25" format would be about 13 mm focal length and have about 20 mm field stop.

The Houdini 12 with its 18.0 mm field stop has 26 mm diameter lenses in the barrel, so already quite close to the limit.

[Olimad]

With the current coma-correcting designs the longest focal length that would fit in the 1.25" format would be about 13 mm focal length and have about 20 mm field stop.

The Houdini 12 with its 18.0 mm field stop has 26 mm diameter lenses in the barrel, so already quite close to the limit.

Thanks for the infos.

And with less AFoV, would It be more doable?

[Houdini]

I guess not, this kind of design with the focal point inside the eyepiece and a negative first element will inevitably not maximize the field stop in the barrel.

 

A design similar to the UFF 30, with a positive first element, works better for maximizing the field stop.

Slimmed down to a 20 mm 72° eyepiece, it has a field stop of 25 mm.

[Sarkikos]

Thanks for the infos.

And with less AFoV, would It be more doable?

With less AFOV, it would not be as useful.  Coma increases laterally from center of field to edge of field.  Coma correction is more crucial for wider AFOV's.

 

Mike

[Starman1]

I guess not, this kind of design with the focal point inside the eyepiece and a negative first element will inevitably not maximize the field stop in the barrel.

 

A design similar to the UFF 30, with a positive first element, works better for maximizing the field stop.

Slimmed down to a 20 mm 72° eyepiece, it has a field stop of 25 mm.

Robert,

The 30mm Ultra Flat Field has a 70° field and a 36.3mm field stop (virtual), as measured.

If it were a 20mm it could have fit in a 1.25" barrel?  Interesting.

 

They should have done so, because their 24mm (actually 24.7mm) has a 27.6mm field stop and noticeable vignetting.

It was designed for maximum field stop and eye relief, ignoring the consequences.

The 30mm was the last eyepiece in that series that was designed, and I guess Ackermann had more freedom to explore alternative designs.

Had they started with the 30mm and gone shorter, the line would have been quite different.

 

Sorry for the segue.  Back to coma-corrected eyepieces.

Edited by Starman1, 29 April 2025 - 09:08 AM.

[Bob4BVM]

Robert,

The 30mm Ultra Flat Field has a 70° field and a 36.3mm field stop (virtual), as measured.

If it were a 20mm it could have fit in a 1.25" barrel?  Interesting.

 

They should have done so, because their 24mm (actually 24.7mm) has a 27.6mm field stop and noticeable vignetting.

It was designed for maximum field stop and eye relief, ignoring the consequences.

The 30mm was the last eyepiece in that series that was designed, and I guess Ackermann had more freedom to explore alternative designs.

Had they started with the 30mm and gone shorter, the line would have been quite different.

 

Sorry for the segue.  Back to coma-corrected eyepieces.

I would certainly have voted for the 20mm in a 1.25" barrel it could fit.

As it is, it is just another monstrous-69mmOD EP that almost no one can use in bino mode.

Even in 2"barrel, I wonder if it could have been built with Bino viewing in mind, like the APM 30UFF.

Looking at the many examples of bloated EPs on the market, I doubt that any mfgr even thinks about BT users 

CS
Bob

Edited by Bob4BVM, 29 April 2025 - 03:42 PM.

[slavicek]

I would certainly have voted for the 20mm in a 1.25" barrel it could fit.

As it is, it is just another monstrous-69mmOD EP that almost no one can use in bino mode.

Even in 2"barrel, I wonder if it could have been built with Bino viewing in mind, like the APM 30UFF.

Looking at the many examples of bloated EPs on the market, I doubt that any mfgr even thinks about BT users 

CS
Bob

This eyepiece is unique in being coma-correcting eyepiece. It has it's specific market niche. Binoviewing is not it.

All (=dozens) my 1.25" eyepieces come in pairs for binoviewing. However looking thru 2" wide FOV eyepiece is "wow" too. So every eyepiece has it's place. Unfortunately we cannot have it all in one eyepiece...

[Bob4BVM]

This eyepiece is unique in being coma-correcting eyepiece. It has it's specific market niche. Binoviewing is not it.

All (=dozens) my 1.25" eyepieces come in pairs for binoviewing. However looking thru 2" wide FOV eyepiece is "wow" too. So every eyepiece has it's place. Unfortunately we cannot have it all in one eyepiece...

You're right of course.

But for those of us who "bino-view" with 2" eyepieces, it would be nice to see the coma-correcting effect in bino mode. So would be nice to see the 20H shrunk down to say 50mm OD or so.

I have a few pairs of 2" EPs which do fit this bill, except for the CC part.

BTW, looking thru a pair of 2" wide FOV eyepieces is more "wow" than just one.

Edited by Bob4BVM, 30 April 2025 - 02:20 PM.

[Houdini]

If we had paid more attention to the binoviewing capabilities we could have reduced the upper part of the body from 64 to 62 mm diameter. I think we'll do that in future production runs.

 

To shrink it further to 55 mm diameter you'd have to reduce the AFOV to about 75°. It would still be a 2" eyepiece.

The design is the easy part, the real difficulty is finding enough users or enough $$ to get it into production.

[Olimad]

Do you think that KUO has the capacity to produce high qualitative low elements eyepieces (ortho, plössls)?

[betacygni]

This eyepiece is unique in being coma-correcting eyepiece. It has it's specific market niche. Binoviewing is not it.
All (=dozens) my 1.25" eyepieces come in pairs for binoviewing. However looking thru 2" wide FOV eyepiece is "wow" too. So every eyepiece has its place. Unfortunately we cannot have it all in one eyepiece...

I actually think binoviewing is a great niche for this product. Integrating a coma corrector with binoviewers is problematic, most don’t bother. It’s the only reason I’m looking at the Houdini, would be great if future iterations focused on minimizing physical size and 1.25” form factor where possible. From a business perspective every binoviewer user is eyepiece sales in multiples of two…

Edited by betacygni, 30 April 2025 - 09:10 AM.

[Starman1]

I actually think binoviewing is a great niche for this product. Integrating a coma corrector with binoviewers is problematic, most don’t bother. It’s the only reason I’m looking at the Houdini, would be great if future iterations focused on minimizing physical size and 1.25” form factor where possible. From a business perspective every binoviewer user is eyepiece sales in multiples of two…

A quite serious question to ask, however, is what percentage of scope users of newtonian scopes use binoviewers.

I doubt it exceeds a fraction of 1%, so designing an eyepiece to be compatible with binoviewers, or bino scopes, may be commercially unviable.

 

However, if designing the eyepiece for binoviewing does not inhibit any other characteristic being designed into the eyepiece, there is no commercial disadvantage in designing the eyepiece

for binoviewer compatibility.

 

As Robert mentioned, though, it would have meant sacrificing the ultrawide apparent field that he went for in the eyepiece.

[betacygni]

A quite serious question to ask, however, is what percentage of scope users of newtonian scopes use binoviewers.
I doubt it exceeds a fraction of 1%, so designing an eyepiece to be compatible with binoviewers, or bino scopes, may be commercially unviable.

However, if designing the eyepiece for binoviewing does not inhibit any other characteristic being designed into the eyepiece, there is no commercial disadvantage in designing the eyepiece
for binoviewer compatibility.

As Robert mentioned, though, it would have meant sacrificing the ultrawide apparent field that he went for in the eyepiece.

Agreed, I don’t think it makes business sense to design an eyepiece specifically for binoviewer use (though I think that market has been growing fast, at least based off forum activity), but I think considering it in overall design is smart. Look at the 24mm Panoptic for example, I don’t think Televue started out making the eyepiece specific for binoviewers, but design considerations such as the tapered upper body for nose clearance, and now recently removal of undercuts, says there is a market to be tapped into. I think the Houdini already is going for a niche market, the binoviewer side of things percentage of sales wise might be surprisingly large if it checks the right boxes. I’ll definitely be trying out the 12mm.

[Fivemileshigh]

Finally last night was decent. I was able to compare to 20H to the 21E/Paracorr in my 20in f/3, in my friend's 24in f/3.3 and to the the 20Nt5 in my FOA-60Q Binoscope. I didn't spend extensive amounts of time comparing them, just enough to form an opinion.

 

TLDR: it's a great eyepiece.

 

In the FOA, the image quality is on par with the Televue, just with a little more field, and of course, more comfort.

 

In the dobs, we feel the 21E/paracorr is very slightly ahead on sharpness in the very outer field. Keep in mind the 21E is effectively an 18.3mm with the paracorr, and if you look carefully you can see the difference in magnification and background brightness, so that could explain it as the difference is barely perceptible.

 

In my opinion, the 20H is a game changer if you need something light. The 21E/paracorr weighs far more. I have a 12in f/3 suitcase travel scope in mind that would greatly benefit from this lightweight eyepiece.

 

If otoh you already have a SIPS and a set of eyepieces you are happy with, this is probably not that useful. It should also be said that if you do have a SIPS, you can't just pop this in and use it because without the optical unit in place, the focal plane is too far down.

 

A second use case is if you are constrained by a budget, in which case just get one and don't look back.

 

Another yet unfilled niche use case is fast(er) newtonian binoscopes. The 20H will likely enable you to save quite a bit of optical path compared to a system with a paracorr, allowing a smaller secondary.

 

The 20mm Houdini is a keeper for me, and I look forward to the 12mm and others.

 

Richard, the binoscope use case is a fairly unfilled niche. If you can get the housing diameter down to 62, or even 63mm, this would be the widest field superwide-angle eyepiece on the market, and worth pursuing imho.

 

Nitpick: the rubber eyeguard is a loose fit on the barrel, it actually comes off with the cap when removing it.

 

Cheers, well done,

 

Dumitru

[Starman1]

Nitpick: the rubber eyeguard is a loose fit on the barrel, it actually comes off with the cap when removing it.

Dumitru

Same here. Loose fit on the rubber eyecup.

[Bob4BVM]

Finally last night was decent. I was able to compare to 20H to the 21E/Paracorr in my 20in f/3, in my friend's 24in f/3.3 and to the the 20Nt5 in my FOA-60Q Binoscope. I didn't spend extensive amounts of time comparing them, just enough to form an opinion.

 

TLDR: it's a great eyepiece.

 

In the FOA, the image quality is on par with the Televue, just with a little more field, and of course, more comfort.

 

In the dobs, we feel the 21E/paracorr is very slightly ahead on sharpness in the very outer field. Keep in mind the 21E is effectively an 18.3mm with the paracorr, and if you look carefully you can see the difference in magnification and background brightness, so that could explain it as the difference is barely perceptible.

 

In my opinion, the 20H is a game changer if you need something light. The 21E/paracorr weighs far more. I have a 12in f/3 suitcase travel scope in mind that would greatly benefit from this lightweight eyepiece.

 

If otoh you already have a SIPS and a set of eyepieces you are happy with, this is probably not that useful. It should also be said that if you do have a SIPS, you can't just pop this in and use it because without the optical unit in place, the focal plane is too far down.

 

A second use case is if you are constrained by a budget, in which case just get one and don't look back.

 

Another yet unfilled niche use case is fast(er) newtonian binoscopes. The 20H will likely enable you to save quite a bit of optical path compared to a system with a paracorr, allowing a smaller secondary.

 

The 20mm Houdini is a keeper for me, and I look forward to the 12mm and others.

 

Richard, the

. If you can get the housing diameter down to 62, or even 63mm, this would be the widest field superwide-angle eyepiece on the market, and worth pursuing imho.

 

Nitpick: the rubber eyeguard is a loose fit on the barrel, it actually comes off with the cap when removing it.

 

Cheers, well done,

 

Dumitru

At last an actual observing report, thanks Dumitru !

 

I concur on the bi-newt comments.

Actually IMO of the binoscope use case is , it's a completely unfilled niche.

Having a CC'g EP that negates the need for struggling to design a Paracorr into the newtonian lightpaths is a huge advantage from the design perspective.

That, and having a drop-in coma solution is a game changer for all the bi-newts out there which were built sans paracorrs.

Of course BT use depends on the EP O.D.   I read somewhere that the max OD of the 20H is 69mm. Is that correct ?  In the end bino use lives or dies on the OD number.

CS

Bob

Edited by Bob4BVM, 30 April 2025 - 02:22 PM.