Need a quick advice on the collimation of SW 10" F4.7 Dob.
I have been using my DOB for past few months, and I believe with a pretty good collimation. I don't have collimation caps, cheshire or expensive high precision laser tools. I only use my own eyes and a cheapish TS (Telescope Service, Germany) LA2 simple laser + barlow for return laser.
I know you will grill me that this is not a good tool or a good way to collimate, and not precise at all. But I think I have been managing, reasonably, to collimate my DOB after reading many collimation-related posts here. And I don't think I had or have any image quality/sharpness issues if my DOB was indeed mis-collimated. What do I know, but I am still more or less happy with the way I collimate. Btw, the TS laser seems to be well collimated too, checked.
I read a few days ago that for a properly collimated fast DOB (like mine with F4.7), the focuser field, edges of the secondary and the primary should be concentric, with all centres (including the primary donut) overlapping in one spot when looked through the focuser, except for a slight offset of the secondary shadow slightly towards the primary mirror. For a slow DOB, everything should be concentric without secondary shadow offset.
After reading this, I checked and everything was concentric without secondary shadow offset (like the 2nd situation above for a slow DOB). Then I loosened everything and started the collimation from scratch several times, and every time I was getting consistently similar results (everything concentric without secondary shadow offset).
I read further through posts, and some people are saying that for recent DOBs you don't need secondary shadow offset, as this has been already taken into account when designing and/or fixing the secondary mirror on its base. But I don't seem to find many similar accounts from many people.
I am confused now. I did acquire the DOB three months ago new, but the model is old one and was available for many years I guess.
So which one is it? Is it true that new models do not display secondary shadow offset (and my DOB happens to be one), or am I doing the collimation wrong?
Any similar experiences with recently acquired SW 10" flextubes?
Two photos attached, ideal collimation for fast and slow DOBs. Mine look like for slow DOB at the moment. But I don't have any perceptible image quality issues. So just leave it like that?
Edited by Baatar, 13 September 2019 - 06:14 AM.