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Here is the thing. I have collimated my Newtonian with the Ocal Collimator with various success. I have just found out that if i turn the collimator /camera) it goes of collimation immediately, if i turn it back, collimation is back. What is the problem? Is my focuser tilted, or the camera-sensor tilted, or is it something else? Help is very appreciated. CS Haakon |
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| Usually is the focuser. |
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| Thanks again, Andrea! |
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| Agreed. Some focusers have tilt adjustment built into them.... personally I just shim the base in the direction I need. |
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Thanks Brian! Mine has a built in tilt adjustment. So i will get to work! CS Haakon |
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I have observed the same effect on my Lacerta Newton - collimation fine with OCAL and with Laser - rotate the devices - collimation off.... no tilt adjustment on focuser.... what a shame. I have to live with it I guess.... CS Georg |
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Hallo Georg, you could shim the base, like Brian says above. I will do that on my telescope, because the adjustment screws does not really function. CS Haakon |
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I though I had a problem with the focuser too but I just tested the ocal and there's a massive tilt on the sensor. Here's how it looks rotated at 180°   |
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Hallo Emil, do you mean the sensor of the Ocal camera? CS Haakon |
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Haakon Rasmussen: Yes, the ocal camera sensor. I tested my farpoint laser collimator too and that's also out of collimation. No wonder I can't collimate my newtonian. Emil |
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| If you're testing it using the scope then you are not doing it right. You need an independent test (rig). Same applies to the Ocal. Conversely, if by other means the scope could be guranteed to be collimated it could be used to collimate the laser (not sure the Ocal can, though). |
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Hallo Emil, sensortilt would explain the problems i have getting good collimation using my IMX571 camera. My collimation was much better when i had the ASI294 McPro camera. Smaller sensor and bigger pixel. I do not have a test-rig, so i guess for me i would sell the Ocal and buy me an Autocollimator from Farpoint to be able to achieve better collimation. What do you think? CS Haakon |
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andrea tasselli: I made a testing rig a while ago to test my laser and used it for the ocal too. I just attached a few M42 extension tubes to the camera so I can rotate it without changing its position. Emil |
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Sounds good. Could you please provide a photo of this rig? I am not good at doing these things without seeing first. CS Haakon |
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Haakon Rasmussen: It seems the Farpoint Autocollimator are hard to come by at the moment ? |
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| To test a laser collimator you would need either a lathe carefully set up, a flat mirror and a 10m baseline or a heavy V-block machined to very high accuracy (parallelism) and (at least) a 10m baseline. And a graduated target. That's the way I test my laser and the Farpoint one and the latter passed the test with flying marks. As for the Ocal what you have found is that isn't centered against the center of rotation of the rig you have used (as far as I understand from your post) but as far as the main Ocal function is concerned (centering the secondary) this isn't an issue. |
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| Yes the Farpoint Autocollimator is sold out at the moment. |
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Just a hint from a beginner: Noctutec in Germany is one of the suppliers for the OCAL and on their website they mention that one shall not rotate the OCAL. I don't have one myself, I just read out. Reach out to Armin from noctutec, to find out why it should not be rotatet. Clear skies! Jens |
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| What type of focuser is mounted on your ONTC? |
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2" V-power from 2019. My telelscope is a UNC from TS. CS Haakon |
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Hello colleagues, hello @Haakon Rasmussen I am sorry but I don't fully agree with some statements here above, especially the statement that says that a newtonian colimation needs a tilt ajustment for the focuser : - either the colimation is done with primary and secondary adjustments - either a sensor tilt is managed with a tilt device at the camera level I have a Lacerta also and it took me some time and some understanding of "what is colimation with a newtonian" to understand that tilt adjustement at the focuser is not necessary, I thanks Towny Nawratil, Vic Mesnard and Jason Khadder for the time they took via mail or PM to explain me that. The Ocal is for me the most precise tool that you can get for a daytime colimation, but you must use it for what it can give you and you must understand what it gives you: it gives you a very precise geometrical reference that you will use for the alignment of others axis. For me, it is very unlikely that the screenshot of @Emil Andronic comes from a sensor tilt, the most propable cause is that the Ocal is not properly calibrated It is like when you use a chesire : you need a reference for the axis of the focuser and the center of the sensor is not precise enough. First : the Ocal comes with a serial number that need to be used for getting seetings that are when the software is launched, did you use the right values ? Second: if you want to get a better tuning of the "ocal center" you can use insert a M42 tube end use this a reference for the calibration of the center of the OCAL with the "Center Offset" feature in the screen shot here under, I found that with -4 Vertical and 3 Horizontal, the rings are properly and better centered, you can see the internal thread of the M42 tube :  The OCAL is so accurate that you can see the differences that comes when you change something at the focuser level, the main reason for that is the accuracy of the "focuser axis", it is normal to see a difference after a rotation, here after the difference that comes by changing the coma corrector with another :  the other reason is the flexion that you may have, here under is an animated GIF that shows a difference with and without a weight of 2 kg added on the focuser :  My advice would be to first check that you have a good and valid reference for the "center" that you will use for the axis of the focuser all the best and clear skies Jean-Baptiste |
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Thank you Jean-Baptiste. I will check again all my numbers. I always place the Ocal on my Coma Corrector with 55mm distance using the Wall of the Coma Corrector as reference for the center. I tried witout the CC and it got worse. Some say it is better to place the Ocal direkt on the CC without the 55mm. What do you think? CS Haakon |
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Hello Haakon Personally, I think that the closer you are to your "astrophoto configuration" the better it is. In addition, with the 55mm your sensor will be closer to the focal point. In my case with the coma corrector , the image is a little blury, so I may make the tuning without any CC ;-) in all the case, the final steps is at night with stars : star test and if necessary final adjustment with Hocus FOcus that comes with NINA : the sensor analysis is a must for the last steps, be it colimation adjustments or tilt adjustments CS Jean-Baptiste |
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Do you use the camera for the Star testing? Like Tommy Nawratil? Or eyepiece? CS Haakon |
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| The camera, all is in position, including the sensor for the acquisition |
