EDIT: QHY support responded with the following statement:
“We can basically confirm that this phenomenon stems from the light-gathering limitations of the Minicam8M sensor structure at extremely fast focal ratios (F4), rather than from mechanical obstruction or contamination of the optical path.”
The whole experience from start to end with QHY has been a nightmare, I shouldn’t have strayed from ZWO x.x
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Hello all,
I’ve been having a strange issue with my minicam8M. It seems to have part of the frame cut off at the top and bottom of the image.
Up until now, I have been using this camera with a long FL telescope, where the image would bounce around enough that the bands would get averaged out during stacking, but now that I’ve put it on a Carbonstar 150, its extremely noticeable, and is making the camera almost useless.
Here is a stacked image through the Carbonstar 150 with a GSO Coma Corrector, and the Minicam8M through the luminance filter, notice the dark bands on the top and bottom of the image. It’s so severe, that the background gradient tool can’t fix it without significant artifacts.
📷 mc8_f4_stack.jpeg
Looking at the flats, you can see a clear band going across the bottom of the image, it seems to have higher contrast the brighter your target image is, so flats don’t work correctly (Not to mention, there is really bad internal reflections you can see splotched all over this frame, which also change with light intensity so that flats don’t remove it all):
📷 mc8_f4_flat.jpeg
At first, I thought this was light leaks, and while I did find some around the focuser that I fixed, it didn’t fix this issue. Now when I have the endcap on the scope, it sees no light.
I thought that there was an obstruction within the OTA, but the artifact stays in place if you rotate the Minicam. I then though it was the filterwheel, but it stays in place even during filter movements (At high framerates I can watch the filter wheel move, the artifact stays in place).
I then wanted to rule out the GSO CC, so I bought the Apertura PRCC designed for this scope, but the artifact did not go away (Although the PRCC works much better than the GSO CC in other areas!).
I then decided to eliminate the camera altogether and reverted back to my ASI533MC Pro with a single filter screwed onto the end of the CC. Everything looked very clean, with the artifact not showing up on flats or stacks. I just had a bit of vignetting that flats couldn’t fully fix in the far corners.
📷 533_f4_stack.jpeg
📷 533_f4_flat.jpeg
Has anyone else seen this issue with the Minicam8, or other 585 sensors? I’m also reaching out to QHY for their feedback.
