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It was along the horizontal axis. If it is there, you can tell if it is your camera easily if you turn the camera (CCD) 90 degrees and the error turns 90 degrees. If the error is still there oriented the same way, it is your optical train. One of the lazer manufacturers told me this... Hotek from the way back I think. There can be other problems with the Tak and focusers, but they are optical/mechanical and can be corrected, but if you mix a camera chip problem with the optics you are in a mess trying to fix it with the optics. |
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The thread is really interesting and useful. Finally the 160ed arrived and had the first light with it. I have the Tak collimating tools and tweaked collimation before use, as it was a bit off. Using the tools and the manual it is not so difficult after some initial head scratching over the difficult to understand manual. One thing that is very important , that was mentioned here before, is proper lighting. I put a flat box at 100% brightness on the Tak, which works really well. Stars in the corner are not perfect, but it is difficult to understand what the main issue is. Sensor tilt, bad collimation or incorrect distance to corrector. I experimented with the corrector distance +- .5mm. It gave very little effect but kept it on the shorter side as it seemed to result in slightly better stars in the corners. Edit, fotgot to link the image Epsilon 160 First Light |
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Götz Golla: My tilt was 100% E-W so it was easy to identify by rotating the camera.... looking at the new images these look pretty good to me... the distortion seems to be symetrical in each corner and is not a lot.... there is always the crop tool... Hard to see what is going on in color images. For me easiest is to take some pics with clear/L. In PixInsight there is a tool/script under Scripts/Image Analysis/Aberation Inspector/Spotter.... gives you what is in the corners and you can see patterns of distortion... this is my Stellarvue... hopefully OK  : |
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Yes, I discovered the usefulness of an aberration inspector too. Since I dont use PI, I use the one included in ASTAP. You can learn a lot about your optics. You can, for example, do some test with your system being slightly out of focus in both ways and compare the images. Here are some examples. Focuser too far out  Focusser too far in  My system in focus with a tilt. The upper right corner is too far out:  Since the CTU was already at minimum, the other two corners needed to by moved out so that all corners look the same:  After focussing the stars are looking much better:  |
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| Yes! Nice work. Looks like your tilt was in both X and Y. |
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Just a fast question: do You have a centermark on Your primary mirror? I have a bigger brother of Your Epsilon a 210mm and is a completely different beast even from the 180mm one. The mechanics are completely different and my primari has an hole in the center 'cos it is really an RC telescope used in prime focus using a ROHSS corrector which is very different to the classcical Wynne one used for parabolic or spherical telescopes that have coma. The hyperbolic is "aplanatic" that means free of coma. If Your primary has a mark, You coluld use classical newtonian collimation procedures, You only have to be certain about the distance of the sensor from the last corrector lens and, far more important, about the perpendicularity of the sensor to the optical axis. It is really a fixed focus telescope so You need to be in that exact point not only for focus but also for best performances. Let me know. |
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Giovanni Paglioli: Hello Giovanni, you must have a Mewlon 210 then ? I dont know what the best method for collimating the Mewlon is, but for the Epsilons I have become a fan of the method recommended by Takahashi using the collimating eyepiece. It is quick and easy and very precise, and it covers the adjustment of the secondary and the primary. Yes, the Taks have a center mark on the primary and secondary mirror. In the case of my Epsilon 130E I only at first thought that collimation is a problem, but the real problem was a tilt in the optical train. It is not related to the Tak itself, but either to the camera or (most probably) to the filter wheel. It was a time-consuming process to find the right CTU and the right way to correct for the tilt. Another problem of at least some of the Epsilons including mine is that the collimation is gone when you rotate the focusser. Thats why I will probably migrate to another third-party focusser sometime this year. But thats another story. |
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Hello again! I don't have a mewlon, my scope is an Epsilon like Yours. The smaller models up to the more "modern" 180 are very different from the bigger sizes ones (200, 210, 250 and 300-350) in terms of mechanics and, in these bigger models, the primary mirror has an hole in the center. Reason of that hole are more than one, the main is that the primary has to be holded in a different way for not intruducing astigmatism in the system, a very common problem shared with RC's. The Epsilon series in fact is a true RC without the secondary hyperbolic mirror, using instead a special corrector called Rohss for the use at the prime focus. What we normally call Newton is not an optical scheme in classical terms, it's just a focus scheme like cassegrain or coudè etc. In fact You have an RC at prime focus with a newtonian focus position. You can remove the secondary mirror and place the corrector on the spiders if only the primary diameter is large enough, with small diameters in fact, the obstruction of a camera in front of the primary is simply too large to be convenient, that's why You have a Newton focus. My collimating procedures needs to be different from Yours 'cos of the hole in the primary that has no centermark. Any kind of optical scheme produce a round illuminated field that is identical in every place in terms of abberations when collimated. If You rotate the camera and see different results the problem is that Your optical axis is non-cohincident to mechanical axe. Something is off axis mechanically. If You have a collimated laser You can experiment that simply by putting it on and, looking at the reflected by the secondary spot of the laser, rotating the laser in the focuser. Indipendently of the fact that the secondary is collimated to the primary the laser spot should not move while You are rotating it, that's becouse the secondary is a flat surface. If You see the spot moving or making small circles then Your focuser is off axis and it could be the source of Your problems. With a primary and secondary marked You can collimate the system just like any Newtonian scope but without the corrector in place. When You're on collimation, any rotation of the focuser should not introduce any change in the resulting image in terms of abberations. Sometimes with very precise and sensitive system like the Epsilons, it is not uncommon to find sensors mounted not perfectly squared in the camera, specially if it is an "economic" CMOS one... Good cameras has the grade of perpendicularity of the sensor expressed as a +/- offset in the specs. Let me know |
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Götz Golla: I will not say "I told you so" but I am not at all surprised at this. When I eventually bought a refractor I bought a Stellarvue 130 for the same or lesser price than a Tak FSQ 106 because I had seem horror stories of their quality control on their refractors. The Stellarvue's optics are just top notch. Everything is lined up just right and the glass is great. See if they would give you the $ back since the trip to Japan is a bit like Gulliver's Travels.... alternatively you can learn all the optics and do it yourself.... as you seem to have done. |
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I would love to replace the TAK focuser with a Moonlite focusser. Unfortunatelly Moonlights current statement on their website is:[left]MoonLite is not able to make and ship Manual versions of our focusers due to severe supply chain issues.[/left][left]Only motorized versions are available to ship at this time. We are forced to phase out all manual versions and are removing them from our web page as the last of each model are sold.[/left] [left]I got a confirmation via EMail from Ron @moonlite that it is not possible to attach my ZWO EAF motorfocus, and the Moonlite motorfocus does not work with my ASIAIR pro. So I am stuck here  A new telescope with larger focal length will come at some point. @jerryyyyy : Thanks for the tip about Stellarvue. They do not easily sell to Europe, only after receiving an "=mediumadvanced bank wire transfer", so no credit card, paypal etc. This is sad. Most major telescope manufacturers have several dealers all across Europe. [/left] |
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Götz Golla: The thread on Cloudy Nights about the 160ED (same focuser as this from what I can tell) revealed that the MoonLite really isn't an upgrade over the stock Tak focuser. A few people upgraded to an Optec, but that is about a $1,300 upgrade. |
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Götz Golla: If you are interested, I can bring this issue to the attention of the owner Vic... they are locals (150 miles away) and I went to their facility before buying. Another person with good contacts there on Astrobin is Jon Talbot. He has the 152... I could not fit that in my ROR. |
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The Epsilon scopes are best collimated by throwing everything you know about Newt collimation out the window and embracing the Takahashi collimation tools. The entire collimation process can be completed in the daytime and there's no need to tweak it under the stars. In fact, if you do you are likely to cause more harm than good. Once the scope is collimated you should not rotate the focuser at all. Doing so can risk throwing the collimation off. This is common for Newts in my experience. Someone had mentioned to avoid full frame sensors and I disagree with that, at least for the e160ED. This was taken with the QHY600 Mono. https://www.astrobin.com/full/khu01o/0/ There's some residual flaring I'm tweaking it with spacing adjustments but that's a pretty well corrected 2.25 Degree field. I did replace the stock focuser with the Optec Leo, as the focuser I had was not stable enough for imaging with a large tiny pixel chip. |
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Amen on do not move the focuser once you have it right. The mechanical aspects of the focuser are almost impossible to move and keep constant, i.e. rotate... remember that CFZ is 0.017 mm. I have learned a lot from my Tak and mention it in this post on the much easier scope I now have with a CFZ of 0.104 mm. I still have tilt with a full frame sensor but it is negligible and CCDInspector, love that program, really blows it up... you can see the same thing with numerical values in PI. https://www.astrobin.com/uge2ex/D/ |
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Stephan Linhart: Moonlite produces such focuser. I rotate it for up to 60 degrees. No problem. Takahashi USA set focuser and adjusted mirrors. So for, so good. Rotation of focuser doesn’t affect collimation. |
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Götz Golla: Why do you need ZWO motors on fine piece of equipment as Moonlite focuser? Get their V3 motor; it is not very expensive. It has zero backlash. |
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For those that might not like the standard crosshair for the Takahashi collimation tube, I made a 3D printed cap design. It is a new version of another user's Takahashi Collimation insert for use with Epsilon scopes. I made the crosshairs internally glued in place instead of the way the original maker did it. . Glue one side of the crosshair line (original Tak or your own) with cyano and then tighten using a toothpick as shown and then glue the other side. May need to be scaled or tape used underneath to suit your printer. 3D Printed Collimation Cap |
