5 replies to this topic

[Deadman45]

Hello everybody,

 

After doing AP with my Nikon D5600 for few years, I bought an ASI 533mc Pro to enhance my picture. But I still wanted to use my Nikon lenses, so I use a ZWO filter drawer for Nikon adapter. So my camera, with the 11 mm spacer, is directly connected to the filter drawer (without filter) and then there is the lens. This setup is what is recommended by ZWO (link). I am using an ASIair+ and I do the focus with it. But I have an issue, it seems that half of the picture (bottom left) is focused (pin point stars), but the other half not (upper right). (see picture, M31 one shot 180s, 200mm)

I have this issue using my Nikon 55-200mm DX lens and my Tokina 90mm macro lens, so the lenses are perhaps not the issue.

I think it's even worst with my Tecnosky APO 60/360, but I think I miss the 55mm backfocus. I will try again with it tonight and put the right spacers.

 

So my question is do you have an idea what can be the issue? I saw some posts talking about tilt, backfocus, ... but I cannot find the solution.

 

Thank you very much in advance.

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Edited by Deadman45, 09 August 2024 - 10:58 AM.

[Kevin_A]

Looks like your focus is off for sure. Use a Bahtinov mask to focus and both of those lenses are not great for astro. It will not be the camera as the 46.5mm (29+17.5mm) backfocus is correct and the camera has nothing to do with your image quality. 

[Andros246]

There’s also the fact you have roughly 25 percent smaller pixels now which amplifies lens aberrations/tilt/issues that many lens deal with.

[Deadman45]

Ok. Thanks for your answers.
I will try to find a way to get a better focus with those lenses.
What I found strange is that only half of the picture is in focus. For me, if it is not focused, everything should be blurred, no?

[Andros246]

Ok. Thanks for your answers.
I will try to find a way to get a better focus with those lenses.
What I found strange is that only half of the picture is in focus. For me, if it is not focused, everything should be blurred, no?

It might be tilt or sag, but I don’t know how to correct it without a tilt plate.

[italic]

This is certainly tilt coming from somewhere. I have a huge problem with tilt on my cheap 50mm lens and haven't had the motivation to deal with it yet. You can buy a tilt plate, or you can try using shims, but I don't have experience with those. My guess is the tilt comes from the bayonet mount because mine has quite a bit of wobble to it, although threads or the sensor are always a possibility.