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Anyone knows what these numbers mean? (sensor tilt)

ZWO ASI2600MC Pro CMOS Tilt
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Menelaos avatar
Menelaos avatar
Hey guys. So i received my new asi2600 mc pro about a month ago and it looks like it has sensor tilt! (unacceptable fact to be honest). Thankfully it has a tilt adapter integrated so i can do something about it. However it turned out to be really difficult. So i checked out the sensor tilt feature in Siril but i have no idea what these numbers mean. the smaller the number is the closer the sensor is to the telescope, or is it the other way around? Any suggestions to make my life easier? Thanks guys.
andrea tasselli avatar
andrea tasselli avatar
The numbers at the four corners should be as close as possible. Ideally, a well corrected system will have all of them nearly identical (the 4 corners and the center).
Monty Chandler avatar
Monty Chandler avatar
Means you have very little tilt.  ASTAP will analyze it for you.  Cheers!
Menelaos avatar
Menelaos avatar
andrea tasselli:
The numbers at the four corners should be as close as possible. Ideally, a well corrected system will have all of them nearly identical (the 4 corners and the center).

but my question is how do i know where to adjust, in or out? The bigger the number is the farther the sensor is from the telescope?
andrea tasselli avatar
andrea tasselli avatar
"the sensor out from the best focus plane" would be the right expression but yes, bigger number compared to the central values means a larger deviation from the aforementioned plane or larger amount of field aberrations. As I expect this to be a newton the residual aberration once coma is corrected is field astigmatism. The plot doesn't however tell you whether you need to tilt in or tilt out and which side is which (top/bottom). You can use ASTAP to do the adjustment on the fly so that you can see the effect of adjuting the tilt screws on the field correction. Assuming you got collimation nailed in…
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Tim Hawkes avatar
Tim Hawkes avatar
andrea tasselli:
The numbers at the four corners should be as close as possible. Ideally, a well corrected system will have all of them nearly identical (the 4 corners and the center).

but my question is how do i know where to adjust, in or out? The bigger the number is the farther the sensor is from the telescope?

I think that the bigger number just means it is more blurred at that position and, as Andrea says, that could mean that to correct it the right side has to be moved either in or out - by a very small amount.
Arun H avatar
Arun H avatar
The tilt adjustment plate on the 2600 MC Pro is horrid. 

And of course, there is an assumption here that it is the camera sensor plane that is the root cause of the tilt, while there can be other sources in the optical/mechanical train the OP is using that is causing tilt. Any how, this excellent thread goes over how to correct it, using NINA or ASTAP. The assumption here would be that the tilt is consistent and not caused due to some mechanical slop somewhere which depends on where the scope is pointed.

https://www.astrobin.com/forum/c/astrophotography/equipment/fixing-the-dreaded-tilt-and-backspacing-error-in-optical-systems-with-objective-analysis/?page=1
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Scott Badger avatar
Scott Badger avatar
How bad is it really? I agree with Monty that it looks pretty slight and fiddling with it may just make it worse…..

Cheers,
Scoty
Tim Hawkes avatar
Tim Hawkes avatar
Scott Badger:
How bad is it really? I agree with Monty that it looks pretty slight and fiddling with it may just make it worse…..

Cheers,
Scoty

This is the sanest answer in my view -- the distortion effect is probably too slight to worry about and at a level that RC BlurExterminator might fix anyway with no noticeable deleterious effect?
Sean Mc avatar
Sean Mc avatar
It might not even be the camera. I battled a tilt issue on one scope only to narrow it down to the extension tube. On another scope, it was the rotator. On a third scope, it was astigmatism.
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Arun H avatar
Arun H avatar
Sean Mc:
It might not even be the camera. I battled a tilt issue on one scope only to narrow it down to the extension tube. On another scope, it was the rotator. On a third scope, it was astigmatism.

Agreed. There is no evidence that it is coming  from the camera though of course, it could be. Lots of people think that cameras with large sensors have tilt while in fact the large sensor is simply recording tilt in the system.
Andrew Ford avatar
Andrew Ford avatar
NINA's HocusFocus plugin has an abberation inspector which plots a 3D map of the apparent tilt, by varying the focus position. You can use this to very quickly determine which way you need to adjust tilt. 

I would also suggest throwing the stock ZWO tilt plate in the bin and getting the rear adjustable upgrade plate. The stock one is only adjustable by removing the camera to access the screws on the front.
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Chris White- Overcast Observatory avatar
Chris White- Overcast Observatory avatar
People blame sensors, but they are the least likely source if tilt. Generally it's an adapter or accessory in your image train. I've measured several zwo tilt adapters with my micrometer and found variance in thickness up to 100 microns!  Same with qhy spacers. You can buy a cheap micrometer and precision calipers to investigate, but as you get closer to the edge of a corrected field, tilt and backspace error compound with field curvature and 3.76 um pixels make it obvious. You can try to fix it, or use blurX.
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