- Newton's Rings
- light leak
This is the only way I have found to get rid of Newton's Rings when using the ZWO ASI 1600MM camera to get the entire sun in the frame using the Coronado Solar Max II 90mm scope, either single or double stacked. It is a little fiddly to use the small wrench provided to adjust the screws. ZWO provides no instructions with the adapter nor online. I found it easiest in finding the right tilt to loosen all the screws first, which allows a roughly 2.5mm gap all around. With the adapter connected to the camera, which is connected straight through to the focusing tube (no diagonal), view the image on the computer monitor. The sun does not need to be in good focus, the rings show up anyway. Slowly tilt the camera around with the loose adapter until a tilt position is found that eliminates the rings. Tighten the screw(s) appropriately on the closed side. Then narrow the gap on the opposite side until the rings will just disappear. Adjust the screw(s) on the gap side to set the adapter rings securely. I did not need to reposition the screws to different holes on the adapter. My final gap is 1.58mm. The tilt adapter is very nicely and solidly made. I detect no light leak through the gap. The tilt does not appear to affect the sharpness of focus across the frame. If a Barlow lens is added, it may be necessary to readjust to widen the gap. As always, ordering from OPT has been an excellent experience.
The product is well-made and appears to work. However, I only gave it 3 stars because it seems impossible to find any documentation about how to use it. I finally found something on a forum that describes the process you use to configure it. It’s a non-trivial exercise with trial and error. It also appears like the setting only works at one focal length, so if you’re getting good results with a full disk image and then you put in a Barlow you have to redo everything. But again that’s not stated anywhere because there are no instructions…
great service one surface of the adapter has a dent