New 85 degree Pentax XWs on the way

[Don Pensack]

3 hours ago, Louis D said:

The usable eye relief of the original mushroom top 30mm ES-82, which is slightly better than the 31mm NT5, is just too tight to be comfortable panning around with eyeglasses.  Both have about a 30mm diameter eye lens, which is simply not enough for an 82 degree field to be comfortable to use with eyeglasses.  It's doable, but not easy.

Here's a size comparison of my 29mm ES-92 (labelled 12 obviously) with my decloaked 30mm ES-82 and 40mm Pentax XW-R:

I don't use the 29mm ES-92 regularly, but instead break it out occasionally to liven things up a bit.

Maximum possible eye relief with a 30mm lens at 82° = 17.26mm from a horizontal line across the eye lens.

If the eye lens is concave, add the concavity to the 17.26mm figure to get the "from the glass" eye relief figure.

[HollyHound]

6 hours ago, Louis D said:

It seems like you'd want to keep the Masuyamas for the lightweight set given how big and heavy the new XW-85s are.

I would agree, except that this lightweight set is also minimalist now too and basically consists of Nagler Zoom 3-6, APM SuperZoom 7.7-15.4 and ES 24 (68 deg)... All 1.25" 😁

Therefore, both the Masuyama 16 and 26 (just) are already encompassed (discounting the extra FoV) 🤔

However, I'm still thinking about how this might all work out 🤣

[HollyHound]

1 hour ago, Don Pensack said:

As long as your scope is longer than f/8, you'll like it.

At f/5, I could see almost 50% of the field out of focus with astigmatism, so the Masuyama (which has excellent contrast, BTW) is not an eyepiece for the shorter f/ratios.

Agreed... that's exactly what I found too. The Masuyama 16 and 26 really do have superb contrast and rendering (if that's even a term we can use here), but in my FC-76DCU (f/7.5) there is field curvature visibly for quite a significant portion of the FoV. However, when used in the FC-100DZ (f/8), FOA60-Q (ff/15) or Mewlon 180 (f/12), it's really not an issue... at 56 years old, I find I'm really quite susceptible to field curvature and astigmatism, but don't have an issue in those scopes.

Confirming what I mentioned earlier, I found only the last 15% maybe of the FoV had field curvature on the XW 16.5 in the FC-76DCU... this was removed with a (very) slight shift in focus only (just a nudge on the focuser) 👍

[MalcolmM]

1 hour ago, Don Pensack said:

As long as your scope is longer than f/8, you'll like it.

At f/5, I could see almost 50% of the field out of focus with astigmatism, so the Masuyama (which has excellent contrast, BTW) is not an eyepiece for the shorter f/ratios.

Thanks @Don Pensack. I had read various reports about this (quite possibly some from you) but thought I'd give it a go anyway. I've a mixture of long and short FL scopes so hopefully I'll have no regrets!

Malcolm 

[nicholasastro]

Does anyone know the Paracorr type 1 settings for the 16.5mm and 23mm XWs in case I decide to give either of these a try at some point?

I wish the 30mm XW setting was the same as for the 1.25" versions but I find I need to shift from setting 1 to 5 for the 30mm. I'm aware however that the tunable top parfocalizes eyepieces within the range.

Thanks

 

Edited February 11, 2023 by nicholasastro

[HollyHound]

2 hours ago, nicholasastro said:

Does anyone know the Paracorr type 1 settings for the 16.5mm and 23mm XWs in case I decide to give either of these a try at some point?

I wish the 30mm XW setting was the same as for the 1.25" versions but I find I need to shift from setting 1 to 5 for the 30mm. I'm aware however that the tunable top parfocalizes eyepieces within the range.

Thanks

 

I no longer have the Paracorr unfforunately, but do recall having to shift for XW30/40 and the 1.25" variants 🤔

No easy way of knowing if the new XWs align with the 2" or 1.25" variants.... perhaps one for @Don Pensack, as I've read a few posts of his talking about Paracorr, and he's also tested these new XWs 🤞

[Sunshine]

I'll stick with the current 70 degrees, any larger and I get nausea as I feel like I'm falling into space 😂

[HollyHound]

12 minutes ago, Sunshine said:

I'll stick with the current 70 degrees, any larger and I get nausea as I feel like I'm falling into space 😂

Sounds like me with the Ethos 😁I'm finding that 85 degrees is the perfect sweet spot 👍

[Don Pensack]

5 hours ago, nicholasastro said:

Does anyone know the Paracorr type 1 settings for the 16.5mm and 23mm XWs in case I decide to give either of these a try at some point?

I wish the 30mm XW setting was the same as for the 1.25" versions but I find I need to shift from setting 1 to 5 for the 30mm. I'm aware however that the tunable top parfocalizes eyepieces within the range.

Thanks

 

Setting E on Paracorr II, and the middle setting (3) on a Paracorr I.

The 30mm XW should use the same setting.  Its focal plane is at the shoulder, just like the XW85°.

The 3.5-20mm 1.25" XWs should use setting 5 (the lowest setting--1 is the highest setting) if used with the 1.25" Paracorr adapter, but that is still not optimum.

Here is why:

the Paracorr I has its focal plane at setting 3, the middle, when used as a 2" device.  The focal plane is coincident with the 2" opening.

That is why the 2" Pentax eyepieces will all use that setting--their focal planes are at the shoulder.

the 1.25" Pentax all have their focal planes at the shoulder as well.

But, the TeleVue adapter raises the eyepiece 10mm above the focal plane of the Paracorr I at setting 3.

To get the XWs to the correct place means you need to drop the Paracorr top from setting 3 by 10mm, the height of the adapter.

Settings on the Paracorr I are 1/8" apart, so lowering the top to setting 5, all the way down, only gets you 6.35mm of in-travel, which does not optimize the Pentax XW 1.25" eyepieces.

You need to lower the top by another 3.65mm, but that is not possible.

For the Pentax XW 1.25" eyepieces, you need the TeleVue In-Travel adapter, which gets you another 6mm of in-travel with those eyepieces (it gets another11.5mm of in travel with some 1.25" eyepieces). 

With that adapter, they can be used slightly above the lowest setting.

You need that adapter for all 2" eyepieces that have their focal planes at the shoulder (e.g. Morpheus 4.5-14mm, Pentax XW 70, etc.).  TeleVue 1.25" eyepieces have their focal planes 6.35mm below the shoulder, so can use the 10mm tall adapter.

 

The Paracorr II's minimum setting is 10.2mm below the focal plane, so avoids this problem.

 

[nicholasastro]

2 hours ago, Don Pensack said:

Setting E on Paracorr II, and the middle setting (3) on a Paracorr I.

The 30mm XW should use the same setting.  Its focal plane is at the shoulder, just like the XW85°.

The 3.5-20mm 1.25" XWs should use setting 5 (the lowest setting--1 is the highest setting) if used with the 1.25" Paracorr adapter, but that is still not optimum.

Here is why:

the Paracorr I has its focal plane at setting 3, the middle, when used as a 2" device.  The focal plane is coincident with the 2" opening.

That is why the 2" Pentax eyepieces will all use that setting--their focal planes are at the shoulder.

the 1.25" Pentax all have their focal planes at the shoulder as well.

But, the TeleVue adapter raises the eyepiece 10mm above the focal plane of the Paracorr I at setting 3.

To get the XWs to the correct place means you need to drop the Paracorr top from setting 3 by 10mm, the height of the adapter.

Settings on the Paracorr I are 1/8" apart, so lowering the top to setting 5, all the way down, only gets you 6.35mm of in-travel, which does not optimize the Pentax XW 1.25" eyepieces.

You need to lower the top by another 3.65mm, but that is not possible.

For the Pentax XW 1.25" eyepieces, you need the TeleVue In-Travel adapter, which gets you another 6mm of in-travel with those eyepieces (it gets another11.5mm of in travel with some 1.25" eyepieces). 

With that adapter, they can be used slightly above the lowest setting.

You need that adapter for all 2" eyepieces that have their focal planes at the shoulder (e.g. Morpheus 4.5-14mm, Pentax XW 70, etc.).  TeleVue 1.25" eyepieces have their focal planes 6.35mm below the shoulder, so can use the 10mm tall adapter.

 

The Paracorr II's minimum setting is 10.2mm below the focal plane, so avoids this problem.

 

Thank you Don for the really clear explanation, which helps a lot.

I meant setting 5 for the 1.25" XWs. I get these mixed up as they are not numerically marked on the Paracorr 1.

I have only just bought the 30mm XW and not played around with the settings enough to find the optimal setting, but it's good to know setting 3 is ideal for all 2" XWs. The 16.5mm XW is now becoming particularly tempting if it can easily be used alongside the 30mm XW, which I'm really happy with based on first impressions. It has an intrinsic clarity that I don't often see to the same extent in wide field eyepieces.

Even at setting 5, I had a suspicion the 1.25" eyepieces were not quite optimal in the longer focal lengths, so it's good to know there is an option to buy an In-Travel adapter to assist with this!

Incidentally, with the 14mm XW, I feel certain any off-axis aberration isn't due to field curvature in my 1773mm focal length dob, but I do see a small amount in the 20mm XW. Here's hoping the In-Travel adapter could further assist with FC, as I find the Paracorr does help to clean things up a bit?

I'll take a look and see where I can get an In-Travel adapter here in the UK. Thanks again.

 

 

Edited February 11, 2023 by nicholasastro

[HollyHound]

1 hour ago, Don Pensack said:

The 30mm XW should use the same setting.  Its focal plane is at the shoulder, just like the XW85°.

If and when I get another Paracorr, that is very useful information... thanks, as always Don 👍

[nicholasastro]

3 hours ago, nicholasastro said:

Thank you Don for the really clear explanation, which helps a lot.

I meant setting 5 for the 1.25" XWs. I get these mixed up as they are not numerically marked on the Paracorr 1.

I have only just bought the 30mm XW and not played around with the settings enough to find the optimal setting, but it's good to know setting 3 is ideal for all 2" XWs. The 16.5mm XW is now becoming particularly tempting if it can easily be used alongside the 30mm XW, which I'm really happy with based on first impressions. It has an intrinsic clarity that I don't often see to the same extent in wide field eyepieces.

Even at setting 5, I had a suspicion the 1.25" eyepieces were not quite optimal in the longer focal lengths, so it's good to know there is an option to buy an In-Travel adapter to assist with this!

Incidentally, with the 14mm XW, I feel certain any off-axis aberration isn't due to field curvature in my 1773mm focal length dob, but I do see a small amount in the 20mm XW. Here's hoping the In-Travel adapter could further assist with FC, as I find the Paracorr does help to clean things up a bit?

I'll take a look and see where I can get an In-Travel adapter here in the UK. Thanks again.

 

 

I just looked into the Televue In-Travel adapter Don.  Do you think that lowering the top by the amount required would provide an obvious improvement at the field edge in the case of the longer focal length 1.25" XWs?

I ask because unless I'm mistaken, it would appear that this adapter requires you to fiddle with an Allen key for tightening and loosening - a set screw would be more convenient unless you have a separate adapter permanently attached to each eyepiece?

Edited February 11, 2023 by nicholasastro

[Don Pensack]

8 hours ago, nicholasastro said:

I just looked into the Televue In-Travel adapter Don.  Do you think that lowering the top by the amount required would provide an obvious improvement at the field edge in the case of the longer focal length 1.25" XWs?

I ask because unless I'm mistaken, it would appear that this adapter requires you to fiddle with an Allen key for tightening and loosening - a set screw would be more convenient unless you have a separate adapter permanently attached to each eyepiece?

The small setscrew can be lightly tightened so you can simply rotate the eyepiece slightly to insert it.  Not loose, but not tight.

Then, eyepieces can be inserted and removed by slightly rotating them in and out.

It sounds harder than it is.  I've been doing it for years.  It helps the setscrew has a nylon tip, so low friction.

Now, if it turns out that your eyepiece barrels vary enough in size that some are loose and some are tight, then you may have to come up with another option.

And if the eyepiece gets too loose when the setscrew hits the undercut on the barrel it could be a problem (all my 1.25" have smooth barrels).

In that case, you may have to fill the undercuts on the barrels with metal tape to have them slide in and out easily.

Or use the 2" Pentaxes in setting 3 and use the 1.25s in setting 5 and just refocus the scope, knowing the coma correction won't be ideal, but still a lot better than no correction.

Edited February 12, 2023 by Don Pensack

[nicholasastro]

16 hours ago, Don Pensack said:

The small setscrew can be lightly tightened so you can simply rotate the eyepiece slightly to insert it.  Not loose, but not tight.

Then, eyepieces can be inserted and removed by slightly rotating them in and out.

It sounds harder than it is.  I've been doing it for years.  It helps the setscrew has a nylon tip, so low friction.

Now, if it turns out that your eyepiece barrels vary enough in size that some are loose and some are tight, then you may have to come up with another option.

And if the eyepiece gets too loose when the setscrew hits the undercut on the barrel it could be a problem (all my 1.25" have smooth barrels).

In that case, you may have to fill the undercuts on the barrels with metal tape to have them slide in and out easily.

Or use the 2" Pentaxes in setting 3 and use the 1.25s in setting 5 and just refocus the scope, knowing the coma correction won't be ideal, but still a lot better than no correction.

Many thanks for sharing your experiences with the Televue In-Travel adapter - all sounds pretty encouraging Don.

As long as the barrel does not become marked after rotating the eyepiece., then this looks like a viable option.

In my case, I would only be using XWs, which of course have undercuts but I would hope the barrels would be the same size.

I can imagine it's not straightforward to develop an adapter with a thumb setscrew given the need for it to be so thin, hence the constraint of using an Allen / hex key, which I understand is also the approach adopted on the Astro Systems Ultra Low adapter. Do you know whether this device would also be an option?

 

 

Edited February 12, 2023 by nicholasastro

[Don Pensack]

17 hours ago, nicholasastro said:

Many thanks for sharing your experiences with the Televue In-Travel adapter - all sounds pretty encouraging Don.

As long as the barrel does not become marked after rotating the eyepiece., then this looks like a viable option.

In my case, I would only be using XWs, which of course have undercuts but I would hope the barrels would be the same size.

I can imagine it's not straightforward to develop an adapter with a thumb setscrew given the need for it to be so thin, hence the constraint of using an Allen / hex key, which I understand is also the approach adopted on the Astro Systems Ultra Low adapter. Do you know whether this device would also be an option?

 

 

No, the Astrosystems ultra-low adapter is not an option.

Here is why:

The eyepieces in question are not small enough to insert into the recessed section of the Ultra-Low adapter.  They will rest on the top of the adapter, just like they would in the TeleVue in-Travel adapter.

However, the opening of the 1.25" bore in the TeleVue adapter sits only 5.5mm below the surface the eyepiece rests on, which is no problem--the setscrew will grab.

In the Astrosystems Ultra-low adapter, on the other hand, the 1.25" bore starts 14.7mm below the surface the eyepiece rests on and the setscrew is many mm below that.

The setscrew will likely miss the eyepiece entirely, or, at best, grab only the bottom couple mm of the barrel.  It might work, but I could not guarantee it.

That Ultra Low adapter works great with eyepieces small enough to fit into the recess, but not with eyepieces with shoulders too wide to fit into the recess.

The TeleVue In-Travel adapter, on the other hand, has a shorter recess, so a wider eyepiece can rest on its top and still have enough barrel inserted to have it grab the eyepiece's barrel.

 

I use the In-Travel adapter in the Paracorr with a 17.5mm Morpheus in my 12.5" because otherwise it cannot come to focus in the Paracorr, and the 17.5mm also rests on the top of the adapter,

yet the 1.25" barrel inserts almost to the bottom of the adapter.

I use all the Morpheus in the In-travel adapter in my refractor to make them closer to  parfocal with other 2" eyepieces that require more out travel.

[nicholasastro]

2 hours ago, Don Pensack said:

No, the Astrosystems ultra-low adapter is not an option.

Here is why:

The eyepieces in question are not small enough to insert into the recessed section of the Ultra-Low adapter.  They will rest on the top of the adapter, just like they would in the TeleVue in-Travel adapter.

However, the opening of the 1.25" bore in the TeleVue adapter sits only 5.5mm below the surface the eyepiece rests on, which is no problem--the setscrew will grab.

In the Astrosystems Ultra-low adapter, on the other hand, the 1.25" bore starts 14.7mm below the surface the eyepiece rests on and the setscrew is many mm below that.

The setscrew will likely miss the eyepiece entirely, or, at best, grab only the bottom couple mm of the barrel.  It might work, but I could not guarantee it.

That Ultra Low adapter works great with eyepieces small enough to fit into the recess, but not with eyepieces with shoulders too wide to fit into the recess.

The TeleVue In-Travel adapter, on the other hand, has a shorter recess, so a wider eyepiece can rest on its top and still have enough barrel inserted to have it grab the eyepiece's barrel.

 

I use the In-Travel adapter in the Paracorr with a 17.5mm Morpheus in my 12.5" because otherwise it cannot come to focus in the Paracorr, and the 17.5mm also rests on the top of the adapter,

yet the 1.25" barrel inserts almost to the bottom of the adapter.

I use all the Morpheus in the In-travel adapter in my refractor to make them closer to  parfocal with other 2" eyepieces that require more out travel.

Thanks for clarifying this Don. The Televue In-Travel adapter it is then!

Really appreciate your great advice 🙂

 

[Louis D]

I found this In-Travel adapter diagram showing the adapter differences graphically:

So, if like me, you are already using a low profile 1.25" to 2" adapter like the one that comes with GSO diagonals, the In-Travel adapter won't buy you anything outside of a Paracorr.  If there was a notch in the Paracorr tunable top for the 1.25" locking thumbscrew, you could probably use the GSO adapter in it.

My Dob's focuser also has this 2" insertion barrel notch to allow 1.25" and 2" eyepieces to be parfocal if both focus at the shoulder, which most of mine do.  I wonder why the Paracorr tunable top does not?

I can understand why folks would despise switching between 2" and 1.25" eyepieces if they are forced to be non-parfocal due to the construction of the 2" insertion barrel and 1.25" adapter combination as in the Paracorr.  It's already bad enough that my 10mm Delos focuses 0.25" below the shoulder forcing me to rack my focuser outward 0.25" relative to most of my other eyepieces.  I suppose I should just invest in 0.25"-worth of 1.25" inner diameter O-rings for it to parfocalize it.  I'm guessing TV thinks all 1.25" eyepieces should focus 0.25" below their shoulder, thus the 10.5mm height of their adapter.  Even that doesn't quite compute because 0.25" equals ~6mm.  What's with the extra ~4mm?

[Don Pensack]

Louis,

There is method to their madness.

The 31mm Nagler, 21mm Ethos, 17mm Ethos, 17.3 Delos and 14mm Delos all use setting A, with the Delos both using the 10.5mm tall adapter.

There was no setting that far in for those eyepieces in the Type 1 Paracorr.

Setting B works for the 22mm Nagler and the 6mm and 8mm Ethos (the Ethos are used as 1.25" eyepieces).

A Hi-hat style adapter was necessary for safety on the 6mm and 8mm Ethos--a flat top is less safe--but the 16.5mm tall Hi-Hat adapter wouldn't have worked for the 6mm and 8mm Ethos or the 2 longer Delos eyepieces.

The Ethos 6 and 8 could have used an adapter 2.5mm taller, but the 17.3 and 14mm Delos could not.  Hence, 10.5mm and it works with all TeleVue 1.25" eyepieces, even the 40mm Plössl, at the other extreme setting of the Paracorr.

Virtually all the rest of the 1.25" TeleVue eyepieces use setting D with the 10.5mm tall adapter.

They would all focus closer to the 2" eyepieces with the 16.5mm tall High-hat adapter, but then the 17.3mm and 14mm Delos would not have been able to come to focus, nor the 6mm and 8mm Ethos.

The In Travel adapter allows the 17.3mm and 14mm Delos to be parfocal with all the other 1.25" eyepieces.  It isn't necessary if you don't care about parfocality.

But, a 10.5mm tall adapter allowed all the TeleVue 1.25" eyepieces to focus in the range of the Paracorr's travel, and no other height would have.

[Louis D]

9 minutes ago, Don Pensack said:

But, a 10.5mm tall adapter allowed all the TeleVue 1.25" eyepieces to focus in the range of the Paracorr's travel, and no other height would have.

Couldn't they have simply designed the tunable top to have more travel range upward by 16.5mm and gone with a flush 1.25" adapter?  That would also negate the need for the High Hat adapter.  It might require a more clever extension design, but I have 1970s/1980s manual camera lenses and macro lenses that can extend 6 inches on internal helicals and maintain optical alignment, so I know it can be done.  Some even do it via nesting tubes to maintain compactness. 

The only issue would be getting it low enough to not need the In Travel adapter for any eyepieces.  Again, a more clever barrel extension design might have been workable here as well.

The Paracorr 2 costs over $500, so it's not like it's a budget device that couldn't afford to have better mechanicals.  All these adapters seem to scream that this was not a well thought out extension device.

[Don Pensack]

21 hours ago, Louis D said:

Couldn't they have simply designed the tunable top to have more travel range upward by 16.5mm and gone with a flush 1.25" adapter?  That would also negate the need for the High Hat adapter.  It might require a more clever extension design, but I have 1970s/1980s manual camera lenses and macro lenses that can extend 6 inches on internal helicals and maintain optical alignment, so I know it can be done.  Some even do it via nesting tubes to maintain compactness. 

The only issue would be getting it low enough to not need the In Travel adapter for any eyepieces.  Again, a more clever barrel extension design might have been workable here as well.

The Paracorr 2 costs over $500, so it's not like it's a budget device that couldn't afford to have better mechanicals.  All these adapters seem to scream that this was not a well thought out extension device.

They had to design the Paracorr so that eyepieces could get closer to the lenses than in the Paracorr I.

And the adapter had to support the eyepieces that had a combination 1.25" and 2" skirt which needed a longer support for the 1.25" barrel that goes up inside the 2" skirt.

So a flat top adapter would require redesigning their dual-sized eyepieces.  A Hi-Hat style adapter is taller (some people do need a taller adapter), AND is compatible with 1.25" eyepieces with 2" skirts.

I would emphasize the In-Travel adapter was only designed to parfocalize the 17.3mm and 14mm Delos with the other sizes.  That adapter is not necessary to use the 17.3mm and 14mm in the Paracorr.

Only one 1.25" adapter works with all TeleVue (and nearly all other brands)--it's the one that comes with the Paracorr.

As a company that offers almost 50 different eyepieces, TeleVue is also under no obligation to design their equipment to work with everyone else's eyepieces.

Yet, by and large, their equipment does.

 

[Louis D]

18 hours ago, Don Pensack said:

And the adapter had to support the eyepieces that had a combination 1.25" and 2" skirt

Once again they are haunted by that bad design (hybrid skirts) from way back when.  The screw-on/off 2" adapter paradigm works much better.  It's a shame Al didn't go with that approach when he was starting out.

[jetstream]

19 hours ago, Don Pensack said:

Only one 1.25" adapter works with all TeleVue (and nearly all other brands)--it's the one that comes with the Paracorr.

Hi Don, I use the TV intravel adapter and leave it on the superb 17.3mm Delos, a top favourite of mine. I also use a Baader adapter #2408151 to leave on another favourite , the 12.5mm UWA .

I had the good fortune to chat with Al Nagler a few years ago- what a great guy- and he gave me the heads up on how to use the PCII with most any eyepiece. I'm still amazed that the PCII can improve the views of some things such as nebula like the Veil and also planetary nebula.

I'm off topic- of course lol but how do you find the 17.3mm Delos? I sure like mine, Gerry

[Don Pensack]

I compared the 17.3mm Delos to the 17.5mm Morpheus and kept the Morpheus, though the fields are identical in size.

There was just something about the 17.5m I liked a bit more.  I don't remember now just exactly why.

But, the 17.3 Delos as a very nice eyepiece.