New Tak Orthobarlow coming

[JeremyS]

Tak is about to release a a 2X “orthobarrow”:  https://www-takahashijapan-com.translate.goog/ct-news/topics/23xii15_info_2xOB.html?_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=no&_x_tr_pto=wapp

[Louis D]

I couldn't figure out from the translated description if the black optics section is removable and 1.25" filter threaded.  If so, it might work well with binoviewers to reach focus.  Right now, I use the optics section of a Meade 140 APO Barlow for this purpose.

[bosun21]

42 minutes ago, JeremyS said:

Tak is about to release a a 2X “orthobarrow”:  https://www-takahashijapan-com.translate.goog/ct-news/topics/23xii15_info_2xOB.html?_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=no&_x_tr_pto=wapp

Didn't realise that Tak were now getting into the barrow market 🤣.

[John]

Under 100 quid by the look of it 🙂

[Don Pensack]

On 16/12/2023 at 09:20, Louis D said:

I couldn't figure out from the translated description if the black optics section is removable and 1.25" filter threaded.  If so, it might work well with binoviewers to reach focus.  Right now, I use the optics section of a Meade 140 APO Barlow for this purpose.

The black section containing the lens is smaller in O.D. than the 1.25" barrel above it.

That does not augur well for the threads on the lens portion to be the 28.5x0.6 filter tread.

Highly unlikely, I'd say.

[Louis D]

Maybe by sheer luck, it's that weird thread size on Arcturus (and other entry level) binoviewers' nosepiece upper end.  It's somewhere around 26mm from what I've read and been able to figure out.

[Mr Spock]

"cancels out the very slight chromatic aberration of TOA"

What? TOA has CA?

Looks like a simple two element Barlow for about £73. It will be interesting to see how it performs in real life.

[John]

49 minutes ago, Mr Spock said:

"cancels out the very slight chromatic aberration of TOA"

What? TOA has CA?

 

I was surprised to see that as well 🤔

[vlaiv]

If I recall correctly, a prominent lens maker once said that any properly designed and well executed negative doublet does not introduce visible aberrations in the image.

Not sure if there is need for "Ortho" barlow if above is true ...

[dweller25]

The “Bartholomew” must be awesome if it can correct the ‘chromatic aberration’ in a TOA 🙂

Or is it marketing hype ?

[mikeDnight]

On 18/12/2023 at 14:47, dweller25 said:

The “Bartholomew” must be awesome if it can correct the ‘chromatic aberration’ in a TOA 🙂

Or is it marketing hype ?

It's undoubtedly hype! I dare say there's some CA in a TOA but you'd never see it. I even question if it could be imaged. May be I'm just not overly sensitive to minimal CA; to me my DZ doublet is as pure as any apo, and with my binoviewers I use prisms and a Ultima SV triplet barlow, and also a cheap SW delux baflow. I can't see any difference optically between them. I'd be more tempted by the Masuyama barlows than the Tak. At least the Masuyama have pretty engraving on them!

[Mr Spock]

I'll stick to my Powermate. TeleVue have that side of things down to a tee. My FC-100 and the preceding Starfield showed no signs of CA in use. There may be some residual CA as they are doublets but I can't see it.

There's a lot of hype from all sides regarding these scopes. Best cure for that is to look through one 

[F15Rules]

It also looks from the illustration as if the 2 rear retaining screws are set screws with no brass compression ring?

If so, that means screw marks on eyepiece barrels, and possible less than ideal alignment of eyepieces in the barlow barrel..

If so, that would be disappointing for a high end brand like Takahashi..

Dave

[Ricochet]

3 hours ago, F15Rules said:

If so, that means screw marks on eyepiece barrels, and possible less than ideal alignment of eyepieces in the barlow barrel..

The first thing I thought when I saw the M42 thread was that I could screw a clicklock to it. 

[Don Pensack]

On 25/12/2023 at 11:29, F15Rules said:

It also looks from the illustration as if the 2 rear retaining screws are set screws with no brass compression ring?

If so, that means screw marks on eyepiece barrels, and possible less than ideal alignment of eyepieces in the barlow barrel..

If so, that would be disappointing for a high end brand like Takahashi..

Dave

Easy enough to replace brass or steel screws with nylon ones, or teflon-tipped steel ones.  You only need two screws with large heavy eyepieces.  Otherwise, one screw is enough.

 

As an aside, though, if it leaves a mark on the eyepiece, that will affect its optics exactly zero.  It might net you a trace less in re-sale, but do you buy every eyepiece with the presumption it will be resold?

As for tilt, you can perform this experiment--tip the eyepiece ever-so-slightly as you tighten it down.  Can you see a difference in focusability?  Unlikely.  

And a brass split ring shoves the eyepiece against one side of the focuser or accessory no differently than a thumbscrew directly on the eyepiece.  A brass split ring is not a collet,

and it does not tighten down around the eyepiece uniformly, nor hold the eyepiece in the center.  It is merely a way of putting a brass surface between screw and eyepiece.

If you want to center the inserted accessory, then you need a Twist-Lock system.

 

Edited December 29, 2023 by Don Pensack

[Don Pensack]

21 hours ago, Ricochet said:

The first thing I thought when I saw the M42 thread was that I could screw a clicklock to it. 

Though this would change the magnification factor of the Barlow by pulling the eyepiece back from the lens.

By how much, I don't know, but it would likely increase the Barlow's magnification by 1.15-1.25x.

[Louis D]

On 26/12/2023 at 13:42, Don Pensack said:

If you want to center the inserted accessory, then you need a Twist-Lock or Click-Lock system.

According to @Tiago Ferreira, the Baader Click-Lock does not center the eyepiece/camera/etc.  See video below queued up to about 3:00 where he demonstrates it pushes in from only one side.  Basically, it sounds like an eccentric cam was used to achieve the clamping effect rather than using a true collet action.

 

[Don Pensack]

That is true of the 2" to 1.25" Click-Lock adapter as well.

 

[Don Pensack]

He makes a really big deal about the fact the Baader Click-Lock does not center the accessory inserted.

However, being shoved off center by 0.002" to 0.004" (0.1mm) at most is really not a problem.

Even a coma corrector's sensitivity to being off center is minimal.

Focuser axis error tolerance for high power collimation is 0.002D with a Paracorr 2, where D = diameter of the primary objective.

In a 10" scope, that is 0.508mm, where the off-centering due to being shoved to one side never seems to exceed 0.1mm in well-machined focusers.

So, whereas he was disappointed the inserted accessory didn't stay centered in the Click-Lock mechanism, the issue is really not an issue.

Even if the focuser has sloppy machining and the shove is 0.2mm off center.

Astrophotographers can correct with flats, and visual observers will never notice.

[John]

When I was playing with Chromacor CA/SA correctors in refractors a few years ago, centering of the Chromacor on the optical axis of the scope was an important part in securing the maximum impact on CA and SA reduction. To achieve this the recommendation was to use an adapter with 3 set screws set at 120 degree intervals so that you could fine tune the centering of accessories. Moonlite adapters have 3 set screws but there might be others around as well. Chromacors may have been a bit fussier over centering than a laser collimator or cheshire eyepiece though 🤔

Edited December 29, 2023 by John

[Mr Spock]

I use a Baader ClickLock when collimating with a laser. It doesn't move the laser at all when tightening. A normal compression ring does.

[Highburymark]

5 hours ago, Mr Spock said:

I use a Baader ClickLock when collimating with a laser. It doesn't move the laser at all when tightening. A normal compression ring does.

Agree. I use Clicklocks on two pairs of binoviewers with eyepieces as short as 4mm - and they are perfect. And an added benefit: none of the undercut melodrama.

[bosun21]

I am a great fan of the Baader clicklock systems and fit them all the time. I have had no problems with them collimating my reflectors and SCT's. The added security also gives me peace of mind.

[JeremyS]

Not sure what the angst over retaining screws is about. Tak uses them on quite a few accessories, like the extenders. When the accessory is well engineered to tight tolerances, they work well.

Whilst I use the Baaader clicklock system a lot, it’s pretty ugly and last night one of mine seized while holding an EP as I commented on another thread.

[MalcolmM]

52 minutes ago, JeremyS said:

it’s pretty ugly and last night one of mine seized

I have to agree here. I use a 2" clicklock and 2" to 1.25" clicklock converter in order to shorten the lightpath to use binoviewers. I much prefer the look of the Tak visual back parts and on a few occasions the 2" has seized and is very difficult to free. The 2" looks very clunky on the back of a Tak!

On the original topic(ish), I tried the old Tak Barlow and it is the only Tak part I have been disappointed with. I couldn't get it to come to focus on my 100DC or 60CB and returned it. It possibly needed an extender or a shortened light path, but I simply couldn't use it as a drop in accessory. I wonder will this new part simply drop in?

Malcolm