1.25" narrowband filters and 383L+

[joelshort]

Is anyone using an Astrodon 1.25" OIII filter with an EFW2 filter wheel and 383L+ camera?  If so, what kind of vignetting do you get in your system (and what's the focal length and f ratio of your scope)?  I'm currently using Baader narrowband filters, which I believe have the largest clear aperture and so don't get hardly any vignetting down to about f/5.2  But I get gradients with the OIII filter and want to move to a narrower bandpass filter if the vignetting isn't too bad.
joel

[ruitripa]

Hi Joel,

DO you know the inner diameter of the filter support? Maybe I can simulate.

[joelshort]

Unfortunately I do not know the inner diameter of the Baader OIII filter.  I will pick up a caliper tomorrow and measure the diameter.

[Guy Walsh]

I know its not answering your question directly but the title is fairly cast wide..

I use 1.25 Astronomik LRGB, O3, Ha  & a Lumicon S2 on my 383L+ and MK1 USB wheel, I modified the male - male adapter that attaches the nose to filter wheel by grinding it shorter, this minimises the distance between CCD & Filter surface... I can now use my Megrez 110 f/5.9 + WO MKII 0.8 reducer without a dark shadow... flats show some gradual dimming but nothing alarming.

Hope this helps.
Guy

Little tip:

Cut the adapter diagonally across the center jut a thread depth with a fine hack saw blade, this will aid its removal with a flat edge such as a butter knife or rear of the hack saw blade in a vice.. sometimes these adapters are a nightmare to remove..

Update 2:

Astronomik 1.25 filters have a working surface diagonal of 24.35mm ( 0.958")
Suprise  ... Lumicon is 24.96mm ( 0.982")

Lumicon wins the 1.25 filter size shoot out, now we need someone with Astrodons..

[Lex]

Hi all,

I also had this vignetting shadowsand i did exactly the same work than guy.
I grinded down the adapter between the cam and my FW, this works really well and the shadows are gone 

Best Lex

[joelshort]

Guy and Lex,
Thanks for the reply.  I'm using the Atik EFW2 filter wheel, and there really isn't any space between the camera and FW.  So I can't grind down the adapter in order to get the filters closer to the CCD.  Like you, Guy, with my baader filters I don't get ANY vignetting at f/6.5.  With a reducer on my AT8RC (bringing it down to f/5.2) I get just a hint of vignetting which is easily removed with flats.

Still waiting to hear from anyone using Astrodon 5nm OIII 1.25 filter...

[Chris]

The Baader have about the largest size that's possible to get out of a 1.25" filter.  I don't know about the Astrodon but maybe Don of Astrodon would answer.

In any case a small amount of vignetting at the corners isn't the end of the world and flat fielding - which will help with other imaging problems - should be able to cure it.

Chris

[Max]

Hi all

Here you can see a flat with Baader filter.

Optic: GSO RC8 with AP0.67 reducer. So the system works with f5.3
Filter: Baader CCD Filter red - 1,25” Interference filter
Atik 383L+ with Atik EFW2-1 and Atik OAG.

A small part from the prism of OAG is also to see - sorry. There I have to perfom a better adjustment.

Best
Max

[joelshort]

Max,
That's exactly the same setup that I have, and my flat image looks the same as your's.  Just to be clear, I have the Baader filters, but I'm looking for anyone who has an Astrodon OIII filter.  I get significant gradient with the Baader OIII and I'd like to hear from anyone who is using an Astrodon 1.25" OIII as to the vignetting present with that filter.
joel