Collimating the Takahasi Epsilon 130D

After spending many days and nights trying to collimate my Tak Epsilon 130D I would like to ask other Epsilon owners for their collimation process of the primary mirror. When buying my Tak from Lacerta Optics, I also got a collimation primer by Tommy Nawratil describing the recommended collimation process for a Newton. Since I respect Tommy very much for his experience and know-how about collimation, I was happy to try it out.

The prerequisite of the process is of course that the laser itself is aligned, as well as the seconday mirror. I have verified both.

The first step collimating the primary is carried out with a laser. This is easy, straightforward and well-known probably to all Newton-owners. The second step is the fine tuning on a star. Here you observe the extrafocal image of a star in both directions out and inwards from the focal point and adjust the primary so that the shadow of the off-center secondary mirror swaps sides by exactly 180 degrees. The manual is in german, unfortunatelly I didnt find an english version, so its hard for me to describe the process in detail in English here.

My experience now is that I get reasonably sharp round starts when I collimate with the laser. However and ironically, the stars become horrible with the fine tuning. Consistently, after fine tuning, the laser indicates that the collimation is completely off. I ran through this process several times because I didnt want to believe it, but the results were always the same.

So either Tommys collimation primer doesnt apply to the Epsilons, or something else is wrong with my Epsilon ?

Are there any Epsilon owners out there using a laser and Tommy primer for collimation as well ? Or is there another recommended way to collimate I am unaware of ? I will try a barlowed laser for collimation as soon as I can get one.

Traditional knowledge of collimation for Newtonian scopes cannot be applied easily to an Epsilon. It is a hyperbolic Newtonian vs. a parabolic Newtonian.

The first thing I will say is ditch the laser, you’re not going to get very far with that on a hyperbolic scope, especially with the off-center secondary mirror. You’re more likely to make it worse.

Get the Takahashi collimating scope made for the Epsilon and use that. You need a brighter than normal light source to collimate an Epsilon, the mirror spots can be hard to see. It should also be very evenly distributed, no point light source. I use my iPad screen with a flashlight app that just has a solid white screen, turned up to full brightness.

I start with the scope on the mount, pointed straight up. Let gravity help you here. Put the light source on top and work on the primary mirror. Remove the direct light source and tweak the secondary mirror with a distant light source. Use the direct light source to confirm. Once you are visually collimated according to the Tak collimating scope you can take some star shots and use CCD Inspector to perfect it.

Once you collimate and lock it down you won’t need to do it again for a very long time in my experience. I haven’t needed to adjust mine for the last year and a half.

I had a 180 ED that I was never quit satisfied with. I agree the laser only gets you so far. One thing I found was that the spot on the mirror was OFF… so do not take that to be the bible… also note that the whole eyepiece slides back and forth in slots where it attaches to the tube and may have been moved if you have a used scope… I also used CCD Inspector…

Thanks for the hints.

Looks like I will try the following three methods and compare them

using laser collimation only with a threaded laser
using collimation with a barlowed laser (should eliminate any residual misalignment of the laser)
using the Tak collimation eyepiece

My experience until now is that laser collimation gets you pretty close already.

The idea is also to learn something. It only needs time and clear skies, so it may take some weeks.

The mystery of the collimation has been solved. It turned out that the optical axis of the focuser is tilted w/r to its rotational axis. This amounts to 3mm at the backfocus distance, which is quite a bit. It probably is due to a tilted inner thread of the focuser where the camera or eyepiece adapter is connected.

Therefore, whenever the Epsilon is collimated, the collimation is gone when the focuser is rotated. That is including the adjustment of the secondary mirror. Thats why just by adjusting the primary I never managed to fix the collimation, even when the collimation was perfect the day before in another position of the focuser.

Currently I am arranging with my Tak dealer that the scope is sent back, possibly to Japan, for repair.

BTW: Apart from this problem I found that, after some practice, collimating an Epsilon with the Tak collimation eyepiece and tube is relatively easy, fast (20mins) and very precise.

The mystery of the collimation has been solved. It turned out that the optical axis of the focuser is tilted w/r to its rotational axis. This amounts to 3mm at the backfocus distance, which is quite a bit.

This is good to know. Every user of this scope says that rotation will make it lose collimation. When I spoke to Takahashi America, they claimed that it isn't, but your explanation confirms it.

I have a Epsion 160 with a newer Corrector, it's a fantastic scope and I got collimated with under a " error using a howie glatter collimator with a tublug and ccd inspector, you have to collimate it in the position where your chip will be positioned and then after everything is good and the camera is on there, very slightly tweak the secondary (i know blasphemy…

to get it to a good position.

I would avoid full frame sensors…and like you I spend many nights "fixing collimation" and having to restart again, also the dew shield will confuse ccd inspector (again wtf…but true).

And even if it's look colimated with the eyepiece collimation tool and even the howie glatter …it doesn't mean it's perfect

Good luck

My Tak is back from repair now. My Tak-dealer Lacerta thankfully arranged with Takahashi Europe that I can sent it in to France. It took them about 5 weeks to repair. The focuser was replaced. The new focuser is better, but there is still a tilt and it is still bad for collimation to rotate it more than 45 degrees. Tak says that this is normal.

What puzzles me a bit is that it seems to be impossible to create a focuser without a noticable tilt. Noticable means a rotation of the order of 1 millimeter where the optical axis touches the seconday mirror. To me the task appears to be at about the same level of engineering as manufacturing a working hub of a bicycle wheel. There are much more complicated things mankind manages like producing a car engine, not to speak of bringing a helicopter to Mars and flying there. So why cant this be done !? I am sure buyers of premium telescopes like the Taks would spent some extra money for a focuser thats reliable without any bad suprises — or at the very least customers should be warned in the manual of their telescope that collimation is lost when rotating the focuser. It would save them A LOT of time and frustration. After all, the Tak Epsilons are excellent telescopes.

Meanwhile I am using the Tak with an ASI EAF filter wheel and the ASI 6200MM Pro full frame camera. With this setup there will probably always be a tilt. The collimation alone is not enough. The camera comes with a tilt adjuster, but it is extremly user-unfriendly. You have to disassemble the optical train and the filter wheel to adjust the tilt. Lukily my first try already got me pretty far. But I will test the camera tilting unit of Astronomik soon. I will report the results seperatelly in this forum.

I‘m also currently in the market for a TAK e160ED and I‘m reading everything I can find.

What seems true is that no one can make a focuser that holds the Collimation when the draw tube actually rotates as well.

My 4“Starlight on a TEC140 is also not perfect here.

So I rotated the focuser where the laser best hit the center of the objective lens. Then I locked the rotating mechanism to never touch it again.

Rotating devices at the end of the draw tubes work better and this is what I plan to do with the epsilon as well.

Best regards,

Stephan

I had an E-130D that I kept for about 3 months and had to return. My issue was triangular stars/pinched optics that could never be fixed no matter what I did.

Collimation wise, the Tak tools are pretty good to use. You want to collimate the primary mirror with the mirror pointing down. In that orientation, the smaller push screws are always making contact with the base of the tube and you can use the pull screws to adjust. The secondary can be collimated with the scope in a horizontal position with the LED panel a small distance in front. I simply had it stand on an LED light panel for primary collimation.

I did try to fix a Baader heavy duty quick changer as a rotator at the end of the draw tube. As robust as it looks, it didn't work. It was quite easy to introduce minute amounts of tilt that caused chaos. Perhaps something like a Pegasus motorized rotator may be better here, but the simple rotators that work with slower scopes will fail badly.

I fully aggree that the Tak tools are a relatively easy and precise way to collimate. I find it especially easy and fast to adjust the secondary mirror with them - once you get the hang of it. The problem is the manual, which is hard to understand due to translation issues. Maybe someone should go through the effort of writing a better manual ((maybe this someone should be me)).

Speaking of the secondary mirror, with a tilted focuser axis, it is not enough to adjust the primary when the focuser is rotated. You have to readjust the secondary as well. This is frequently overlooked when using a laser collimator only.

Stephan Linhart:
I‘m also currently in the market for a TAK e160ED and I‘m reading everything I can find.

What seems true is that no one can make a focuser that holds the Collimation when the draw tube actually rotates as well.

My 4“Starlight on a TEC140 is also not perfect here.

So I rotated the focuser where the laser best hit the center of the objective lens. Then I locked the rotating mechanism to never touch it again.

Rotating devices at the end of the draw tubes work better and this is what I plan to do with the epsilon as well.

Best regards,

Stephan

Hi Stephen, I have an Epsilon 160ed and it arrived perfectly collimated, rotating the focuser didn't throw it off either. I got it in December and it has held collimation well.

Regards,
Richard.

Hi Richard,

so there also are better and not so good examples of the e out there.

Hope mine does not suffer from these issues when it arrives in a few months.

Best regards,

Stephan

I just want to mention that I recently purchased the camera tilting unit (CTU XL) from Astronomik. It offers a very convenient way to adjust backfocus and tilt during observation. No need to disassemble the optical train. During its large size compared to the sensor size tilts can be corrected very precisely. In my case I found that I have a 0.08mm tilt in the image train, and the improvement in image quality is significant.

Hi everyone,as a user of E180 for mor than 7 years i should say
rotating the focuser didn't throw it out of collimation.I know how difficult is to collimate it but the scope's mechanic is excellent and for me every one or two years needs to be collimate again.

My Moonlight focuser worked quite well…. also realize that you can have chip tilt…. you can tell if this is the problem by rotating the camera and seeing if the collimation error rotates with the camera….. of course you can have chip tilt AND collimation AND focuser problems….

… you can see them all have an effect at F2.8…..

My Moonlight focuser worked quite well.... also realize that you can have chip tilt.... you can tell if this is the problem by rotating the camera and seeing if the collimation error rotates with the camera..... of course you can have chip tilt AND collimation AND focuser problems.... ... you can see them all have an effect at F2.8.....

I just checked the moonlight web site. They do have focusers for the Tak Epsilons . May be an option for Tak owners with a crappy focuser. Thanks @jerryyyyy for the tip

Oh well, I think I need some help interpreting my latest attempts to correct a tilt in my images. My Tak is very well collimated, I checked it this afternoon. However, in one corner of the nighttime images it looks like stars are out of focus by a lot. They look like bananas, or rather like a star in the center very much out of focus, but only a segment of it. I tried to use the tilt corrector to enlarge the backfocus in that corner and indeed I have got a much improved image in that corner now. However, moving to another object in the milky way I found that all weak stars in that corner are little straight lines perpendicular to the direction to the center of the image. According to textbooks, this is indicative for a too large backfocus. So this seems to be contradictory to the fact that the image improved by enlarging the backfocus in that corner with the tilt corrector.

So what I am trying to understand is: Under which circumstances can stars be out of focus in only one corner of an image ? And what is the difference to the situation that the backfocus is wrong in one corner due to a (sensor) tilt ? Is there a difference at all ?

Hello all together!

Since I'm also struggling a bit with the alignment of my Epsilon 130ED, I wanted to ask you which TAK collimation tools you use?
Is it something like that?

collimation tool

There is yes also a second part to it....

Thanks and best regards,
Markus

Markus Blauensteiner:
Hello all together!

Since I'm also struggling a bit with the alignment of my Epsilon 130ED, I wanted to ask you which TAK collimation tools you use?
Is it something like that?

collimation tool

There is yes also a second part to it....

Thanks and best regards,
Markus

Yes, you need the eyepiece and the tube. And I would really recommend them compared to other methods, because collimation is easy and precise and can be done during daylight. The only problem is Takahashis collimation manual. The manual is correct, all the steps are as they should be, but the English translation from Japanese is a bit difficut to unterstand. You need to actually work with it to really understand what they mean. If you need help with it, feel free to ask me (also in german if you like).
Regards, Götz

Thank you very much!

Markus

Hey, rereading this thread. Please reread what I said about chip tilt. If you rotate the camera and the error rotates with the camera, it is the chip INSIDE the camera that is slightly off. If this is off, you can mess with the Tak until the cows come home. My SBIG was way off. My Nikon was perfect….

Hello!

Yes, that is a point that always needs to be considered. Actually, everything between the corrector and the chip can be skewed as well.
To check this, a friend built me a device where you can shine a laser on the chip and rotate the whole assembly. The laser spot reflected from the chip should not move. SX CCD describes something like this on their site.

Cheers,
Markus

I know that I have a tilt, and most likely it is a sensor tilt. It is difficult to prove the sensor as the culprit though, because I would have to disassemble the optical train including the filter wheel completely to rotate the camera wrt to the rest of the optical train, then redo the collimation and all the flats. Anyway, a tilt corrector should be able to correct any tilt in the optical train after the focuser, unless its the pull of gravity, i.a. when the optical train assembly is not stiff enough.

I meanwhile was able to resolve some of my earlier confusion with the tilt: when you have elongated stars in one corner of the image due to a tilt, and the software with which you analyze the image transforms it so that north is always up, the corner will change after meridian flip ! Also, the apparent location of the three screws of my camera tilting unit wrt the image change. I made a little sketch of the situation:

The tilt and screw locations are rotated after the meridian flip. My image processing software (Siril) additionally mirrors the image for whatever reasons. This makes it a challenging endeavour to adjust the tilt at 3am in the morning with a meridian flip occurring in the middle of it.

I will prepare a web site with a collection of sketches of all the tilting problems and solutions I encountered. This will probably also include typical star images for the various situations like out-of-focus, out-of-backfocus, tilt etc.

@jerryyyyy : was your sensor tilt north-south , east-west or something inbetween ? I am asking because an assumption that the tilt is either parallel to the long or the short side of the sensor will actually make the search for the correct adjustment a little easier (fewer degrees of freedom...).

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