View Single Post
  #344  
Old 11-06-2016, 12:53 PM
Shiraz's Avatar
Shiraz (Ray)
Registered User

Shiraz is offline
 
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,823
Quote:
Originally Posted by codemonkey View Post
Here's a couple of dodgy flats (pointed at my ceiling with no OTA connected) demonstrating the vignetting with 1.25" filters with the camera connected directly to the Orion Nautlius 7x1.25" EFW.

The vignetting itself isn't so bad. The filters are clearly not centered, but the main issue is that it's inconsistent. Between the two frames I rotated the filter wheel to another filter, then back to the original. This will make taking flats annoying.

Previously with the 674 and 1.25" filters I was able to take flats maybe every two weeks or so and then use them across all the filters. Now, for proper correction, I'd need to take them every time I change filters, even if I change it back to the one the flats were taken with.
Good point, but it might not be as bad if you test in a converging beam. I have an ancient Atik FW (probably worse than yours) and just did a few flats with my f4 system (which is really on the edge when it comes to filter alignment sensitivity). I moved off-filter and back on between the subs. At the same point in the darkest corner, the levels were:
26426
26318
26440
26063
25925
26504
26222
26758
26598
The levels in the centre of the field were much more consistent. Clearly not perfect, but I think that I can live with minor positioning errors causing a few percent error in brightness in the far corners of my images and will be sticking with the 1.25 filters for now. Not sure how much of a problem that will cause with colour, but will see.

Edit, just took the two widest apart flats and flat calibrated one with the other. The result was very flat, so should be OK.

Last edited by Shiraz; 11-06-2016 at 02:14 PM.
Reply With Quote