Jump to content

Narrowband

Colour or mono CMOS with an achromatic refractor?


AMcD

Recommended Posts

I am planning to upgrade my reliable, but now ageing, QHY8 to a CMOS camera.  It will be used with my 6” TS152 achromatic refractor and 2.5” field flattener.

Should the fact that I will be using it on an achromat influence my decision when choosing between a colour or mono CMOS camera?

Many thanks,

AMcD

Link to comment
Share on other sites

1 hour ago, AMcD said:

Should the fact that I will be using it on an achromat influence my decision when choosing between a colour or mono CMOS camera?

It can.

Chromatic aberration is easier to control with mono camera.

With OSC camera - you don't have a choice - you will always record all information at single focus point. With mono camera, you can refocus with each filter, choose to use only RGB imaging instead of LRGB imaging thus only recording part of spectrum at it's best focal point or do narrowband imaging which does not really care about CA at all. Single wavelength can always be brought to perfect focus (and that scope has good spherical correction so spherochromatism is not issue either).

 

  • Like 1
Link to comment
Share on other sites

1 hour ago, vlaiv said:

It can.

Chromatic aberration is easier to control with mono camera.

With OSC camera - you don't have a choice - you will always record all information at single focus point. With mono camera, you can refocus with each filter, choose to use only RGB imaging instead of LRGB imaging thus only recording part of spectrum at it's best focal point or do narrowband imaging which does not really care about CA at all. Single wavelength can always be brought to perfect focus (and that scope has good spherical correction so spherochromatism is not issue either).

 

Many thanks - that is very helpful indeed.  I was erring on the side of mono and your advice has greatly assisted.  

A

Link to comment
Share on other sites

4 hours ago, vlaiv said:

It can.

Chromatic aberration is easier to control with mono camera.

With OSC camera - you don't have a choice - you will always record all information at single focus point. With mono camera, you can refocus with each filter, choose to use only RGB imaging instead of LRGB imaging thus only recording part of spectrum at it's best focal point or do narrowband imaging which does not really care about CA at all. Single wavelength can always be brought to perfect focus (and that scope has good spherical correction so spherochromatism is not issue either).

 

 

Hello there,

I suppose that the same holds with an ED doublet like the SVBONY 102ED/7 I ordered? Or is it OK to shoot LRGB with this scope?

N.F.

 

Link to comment
Share on other sites

3 hours ago, nfotis said:

 

Hello there,

I suppose that the same holds with an ED doublet like the SVBONY 102ED/7 I ordered? Or is it OK to shoot LRGB with this scope?

N.F.

 

ED doublet will have much smaller issues with star bloat / CA. There will be some - but not nearly as much as fast and large Achromat scope.

RGB will no doubt work fine.

With LRGB - you'll either have to handle a bit of star bloat in your luminance layer with some star reduction techniques or you can take Astronomik L3 luminance filter.

That L filter is a bit narrower then standard luminance filter and will remove farthest parts of spectrum thus taming any small bloat produced with ED doublet scopes.

  • Like 1
Link to comment
Share on other sites

On 21/11/2021 at 08:09, AMcD said:

I am planning to upgrade my reliable, but now ageing, QHY8 to a CMOS camera.  It will be used with my 6” TS152 achromatic refractor and 2.5” field flattener.

Should the fact that I will be using it on an achromat influence my decision when choosing between a colour or mono CMOS camera?

Many thanks,

AMcD

Mono, I dont even have to stop and think about it. It wont be perfect but it will have much less CA than in an OSC. 

 

Adam 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.