Vignetting or Sensor malfunction ??

[carlosgib]

Hi guys, I purchased a Proline 16803 some three years ago (give or take) , but due to moving houses and building an observatory I kept the camera/filterwheel safe in-house. So some four months ago I have it mounted inside my Dome an everything functioning fine (software etc).

 I started initially using Narrowband (Astrodon 3nm -Ha, OIII, SII) without any real issues , images had no vignetting as such, but a couple of weeks back a started with RGB and to my surprise I had darker corners of which in a form of a wavely pattern!!.

 This appeared in both Red & Blue filters (as in blue not finish the imaging with the greens). I am providing images, one Ha (3nm) filter with no issues and two another showing the darker corners when compare to the whole image, also there is NO hot center to justify the light rolloff that any converging optic does. I have measure using 'IRIS' software and there is a 50% reduction in ADU reading from the center and around areas to the dark corners area. This very usual,  If I am wrong and taking into consideration an article from EO Edmund when the sensor is too large for the lens design the image appear to fade away degrade towards the edge, thus vignetting, the DN at these corners is 50% lower then the center of the image, this goes against the article 5 to 10% (with a F5) reduction of relative illumination.

 Vignetting is difficult given that I am using a Tak CCA 250 reflector with the 16803, with a resolution of 1.49/pixel is a sweet spot and it's not over or under sampling, and using the correct size filters (square 50mm). BFD is spot on, the other issue could be collimation, but this would have happened to the narrowband images as well.

 Your expect recommendation will be helpful.

[Laurin Dave]

Hi, given that it looks fine on the Ha I'd take a look at the other filters and make sure they were clean.  

[michael8554]

What are your Flats like? 

Michael