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Dear astronomy lovers, I’m having some difficulties with my gear and I hope someone could help. I have a Takahashi FSQ-106ED the older model with the captains wheel. I used this scope with an APS-C sensor camera without any major problems. I have now switched my camera from a Canon EOS 60Da to a Canon EOS R, which is full frame and has 30 megapixels. Allegedly the Takahashi FSQ-106ED has an image circle of 88mm. But I’m already seeing a lot of abnormalities at the corners of the frame. We tested the scope with a Canon EOS 6D, also full frame but bigger and less pixels, this gave a better result. Also, the issue with metal back. I tried getting close to the suggested 178 mm and that just gave nothing, seems like the number isn’t good, or the metal back is elsewhere. We are assuming the metal back is the last non detachable part from the focuser when screwed all the way in. Maybe someone has the answer? So, I don’t know if the Takahashi FSQ-106ED is even good with a 30megapix fullframe, or if the new version is somewhat better. Or if it’s just a metalback problem, or the scope has to be recollimated. Or all of the above. 😀 If someone has any clue, any idea, I would be really happy if you could help! Thanks and Clear Skies! |
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Hi Adrien, at f/5 the depth of field of the Tak is around 100um, even smaller if you are using the reducer, so any issue in the optical train, specially with smaller pixels, would show as elongated stars in the corners. Before blaming collimation, I would suggest to check any sag in the focuser and/or tilt of the sensor. I had a similar issue with my tak fs102+reducer+ASI1600, the culprit was the sensor tilt, that i solved with a CTU tilter. Backfocus is an issue only if you are using a reducer, in such a case you have to measure the distance from the last metal part of the reducer to the focal plane hope this helps cheers Luigi |
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It will be better if you can show pictures of your problematic images. Otherwise it's hard for us to tell what's going on. Unless you use a focal reducer, the back-focus distance doesn't matter at all on FSQ. None of FSQ's lenses move with the draw tube of the focuser. What this means is as long as you can reach focus, the back-focus distance is exactly what it has to be. |
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| I think it's more accurate if you can check the back focus distance from the end of the flattener or reducer - it should be 56mm. I don't have 106 but I understand the 85 and 106 should have the same back focus requirement. |
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| I have also a FSQ 106 ED, the old model. It works fine with my 30 megapixel camera, a DSLR EOS R. It is very important that you attached the camera with precission and that there is no tilt in the focusser. The best thing you can do is attached the camera before setting on the mount. I do this always when i am using a focal reducer from Takahashi and I make always before test images of 30 seconds so that I can see if the stars are correctly sharp in the whole field of the image. When the camera is not correctly attached at the focusser you can get stars in the corner who are not sharp. It also happens that the lleft side of the image the stars are pinpoints and at the right side the stars will be bigger and not pinpoints. It is possible that your focusser is not working well, inspect your focusser perhaps some screws must be tighten. The captains wheel is also a probem. It must be tighten very well otherwise you can get unsharp stars in the corner of your image. Collimating is seldom needed is you handle your scope with caution. Try a following test with a eyepiece, turn the star out of focus and you may seen in the middle of the star disk a grey point. If this not so and the grey point is shifted from the centre, then is collimating needed. Ask your dealer if you can sent the scope to your dealer of sent the scope back to Japan and ask if they will collimating your FSQ again. Succes and if I can help you write me back and sent some images so that I can see what the problem is. The FSQ 106 ED can bear heavy cameras suchs as 6x7 from Hasselblad with a field of 9 degrees. |
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Szia Adrienn! Sikerült megoldani a problémát? Ha nem, jelentkezz, mert szólok a kollegámnak(Tommy Nawratyl) ő nagy mestere ezeknek az APO-knak. Van ilyen lehetőség a cégünknél, hogy beállítás, kollimáció, stb. (teleskopaustria). Nyugodtan írj akár magyarul is. Derltet! |
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| First of all apologies for being late to the party, Did you find a solution to your problem? I'm also using the FSQ-106ED with the capstan wheel with my Canon Ra and have excellent corner to corner imaging, are you using the Takahashi CA-35 ( 50.8 ) Adaptor with your EOS R? |
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Hi Adrien, I used the really old 106N version for years, great scopes. From what I have heard from dealers and friends that used the 106ED captains-wheel version, and don’t get me wrong, there still great scopes, but the ‘captains-wheel’ version was a bad design on Takahashi’s part, as when you loosen the wheel to rotate the focuser, the whole focuser becomes loose and then you need to be really sure that when you re-tighten the captains-wheel that it locks back in square to the scope. I believe that is why they went back to the Camera Angle Adjuster (CAA) version that just rotates the focuser without anything coming loose. I had the same issue with a TEC140ED scope as the FT focusers use the same type of captains-wheel to rotate the focuser, it took me awhile to figure out why my images had bad stars in 1 or 2 corners, and came to find out that the focuser, even though I re-tightened it, it was not square to the scope anymore. I don’t know if this maybe your issue, but maybe something to look into. Just realized the post is a year and a half old. I guess I’m a bit late. :-( |
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| I've no idea why it was there in the first place really especially when you can rotate the camera plane in at least one other position. |
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I've no idea why it was there in the first place really especially when you can rotate the camera plane in at least one other position. The capstan wheel is a legacy design. When FSQ-106ED first came out, I think the original intention was to replace the CAA with the capstan wheel. It is an awkward rotator with risks of crashing the focuser into the mounting plate unless you use Takahashi's mounting plate. There were also mechanical issues. So at some point FSQ-106ED's were also shipped with a separate CAA. In latest models the design was phased out, and it never made to the FSQ-85 and FSQ-130. |
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However, I would say the potential issue with FSQ-106 is not limited to the capstan wheel. It is a four-element refractor and neither doublet is cemented. This gives a lot of degrees of freedom to be misaligned. It is also notoriously difficult to collimate. (The FSQ-85 has cemented front lens group and I believe are much better in this respect.) With smaller and smaller pixels on CMOS cameras these days, the tiniest imperfections are showing up. I bought an FSQ-106ED this year and it has astigmatism. TNR couldn't fix it and it had to be sent to Japan for collimation. |
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However, I would say the potential issue with FSQ-106 is not limited to the capstan wheel. It is a four-element refractor and neither doublet is cemented. This gives a lot of degrees of freedom to be misaligned. It is also notoriously difficult to collimate. (The FSQ-85 has cemented front lens group and I believe are much better in this respect.) I guess that's quite a common problem with with lenses though, as sensors gradually improve the lens imperfections are bound to show up. I know several professional photographers who've been complaining that camera manufactures like Nikon and Canon have been getting away with murder since the digital revolution began and how their old lenses, though lacking in some of the modern features, are significantly better in terms of sharpness. That's evolution. Hopefully my 106 will stand me in good stead for the foreseeable future. Thanks |
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I will chime in with a little different tone. I bought a used FSQ106ED about 5 years ago and have been extremely happy with it. I have had no issue with the catmint wheel rotating system. BUT, I use a fairly light imaging system. I use a Starlight Xpress Trius SX-694 and 1.25 x 7 filter wheel. I image primarily with the 0.73x reducer at F3.64. I have read nothing officially from Takahashi regarding the re-design of the focuser. Like most, it has come through forums such as this one. What I read was that imager taking advantage of the large imaging area were, as expected using large chips which means large CCD cameras, which demands large 50mm filters. AND, all that is very heavy and put a lot of strain on the captain wheel. It seems Takahashi realized that in order to take advantage of the large imaging area, they would need to re-design the focuser and did, 4 times. One should have no issues when using a light DSLR. If you do, then something is off somewhere. I will often point the scope directly down towards the ground, loosen the wheel and retighten. That way there is no gravity applying force to the side of the focuser. There is only centered downward pressure. I am then pretty assured the focuser is orthogonal after being tightened. And it needs to be tight, not just snug. I also have a Starlight Feather touch 3.5" with a captain wheel on a AP130DTX and TMB130SS. The same is true of those. As Takahashi owners know, the scope must always be shipped air to maintain warranty. Other manufactures have tried to make quad and 5 element astrographs and have stopped manufacturing them dew to scopes coming out of square/collimation while being shipped. Skywatcher even shipped it's with spring loaded shipping system and still couldn't keep the scope aligned. So, I think they have gone entirely over to an included flattener to attached latter. I bought my FSDQ106ED used and had it shipped ground. It came through fine due to a well designed shipping box. I have collimated my TMB130SS, but would never attempt to realign or collimate the FSQ106ED. I take it to dark site a couple times a year. That's a 10 hr round trip in a padded case, in the back seat floor of a F150. So for, I have had no issued with collimation. A camera ship does not have to be too far out of orthogonality to render poor corner stars. Rotate the camera. If the same corner are still showing poor stars, then it is the camera. If the corners change, it's the focuser. Lynn K. |
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I think I will rename it the catmint wheel in your honour.  Thanks for your contribution, I am most of the problems are caused by overloading the imaging train which I don't think I will come close to.
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