Filter distance from sensor and vignetting

[Nerf_Caching]

I’ve been struggling with vignetting since I switched out the 2 inch nosepiece that I thread my narrowband Ha-OIII filter onto. The new nosepiece is slightly longer than the old one and with the filter threaded on, I wonder if that’s why I’ve got an uneven field of illumination in my photos? I hope it’s not something wrong with my camera(the ZWO 585MC Pro). Attached are pictures through my scope of an area of blue sky, with and without vignetting. Would be grateful for any input. 

Edited August 9 by Nerf_Caching

[michael8554]

What do your Flats look like ?

Michael

[Vroobel]

Hi,

From my experience with APS-C sensors, 2" filters and different OTAs, your 585 sensor shouldn't be affected in a such significant way, even if with the longer nosepiece. You can find below a flat frame taken with a 4" 572mm refractor which presents its vignetting on the APS-C sensor.

What scope do you use with the mentioned camera, filter and nosepiece? Is there anything else in the optical train?

 

 

Edited August 9 by Vroobel

[Elp]

It's an easy enough test to do, an image:

Old nosepiece with and without filter,

New nosepiece with and without filter.

[Nerf_Caching]

49 minutes ago, Vroobel said:

Hi,

From my experience with APS-C sensors, 2" filters and different OTAs, your 585 sensor shouldn't be affected in a such significant way, even if with the longer nosepiece. You can find below a flat frame taken with a 4" 572mm refractor which presents its vignetting on the APS-C sensor.

What scope do you use with the mentioned camera, filter and nosepiece? Is there anything else in the optical train?

 

 

I should've included what scope I'm using for starters, my bad. I'm using an Evostar 72ED and two extension tubes for my camera to reach focus. No flattener is being used.

[Nerf_Caching]

56 minutes ago, Vroobel said:

Hi,

From my experience with APS-C sensors, 2" filters and different OTAs, your 585 sensor shouldn't be affected in a such significant way, even if with the longer nosepiece. You can find below a flat frame taken with a 4" 572mm refractor which presents its vignetting on the APS-C sensor.

What scope do you use with the mentioned camera, filter and nosepiece? Is there anything else in the optical train?

 

 

Also the two nosepieces in question. I doubt it’s a reflectivity issue either.

[Nerf_Caching]

17 minutes ago, Elp said:

It's an easy enough test to do, an image:

Old nosepiece with and without filter,

New nosepiece with and without filter.

I've done some further testing without the filter, and it seems like it is the longer nosepiece that is causing the uneven illumination of the sensor. Photo with the shorter nosepiece seems fine to me. Attached below.

[Elp]

You will get some sort of vignette regardless as this is how optics work, a spherical lens projection onto a flat sensor. Filter issues are mitigated a little by placing them as close to the sensor as possible (a lot of the time with filter drawers).

How long is the adaptor your using, I ask as I sometimes use the flattener/reducer front thread to screw my 2 inch filters onto so they're sticking out some distance away from the camera sensor and don't get issues. The 585 is also a small sensor so should be less affected than a larger one.

Your flats when applied to your lights will removed vignette anyway.

Are you using 2 inch filters?

Edited August 9 by Elp

[Nerf_Caching]

6 minutes ago, Elp said:

You will get some sort of vignette regardless as this is how optics work, a spherical lens projection onto a flat sensor. Filter issues are mitigated a little by placing them as close to the sensor as possible (a lot of the time with filter drawers).

How long is the adaptor your using, I ask as I sometimes use the flattener/reducer front thread to screw my 2 inch filters onto so they're sticking out some distance away from the camera sensor and don't get issues. The 585 is also a small sensor so should be less affected than a larger one.

Your flats when applied to your lights will removed vignette anyway.

Are you using 2 inch filters?

Yes I am using 2-inch filters.

[Elp]

Why the need for the nosepiece adaptor?

[Nerf_Caching]

4 minutes ago, Elp said:

Why the need for the nosepiece adaptor?

I'm using it to attach my camera to the telescope like an eyepiece would fit in. Can't thread the camera directly to the scope. Plus my filters can thread on to the nosepiece. Not ideal but it's what I've got.

[Elp]

Do the flats calibrate out the vignette, if so no issue.