Eye pieces and Barlows

[WillG]

Hello!

I'm trying to read up on the differences between Barlows and eye Pieces (also flatteners). I'm almost settled on getting the SkyWatcher Evostar 80ED and using it for photographing DSOs. 

As far as I've been able to research, a Barlow is a focal length multiplier (or divider). It basically shortens or lengthens the focal length. Is that right? 

I've been advised to get a flattener to provide field-edge correction. A Barlow of 0.8x and 2x to provide more verity of views and to widen the field if needed for Andromeda, and other DSOs. And to get some different eye pieces. 

 

Is a Barlow not an eye piece? If I'm primarily using the scope for photography would I be able to put the flattener and the Barlow on at the same time? The flattener I'm looking at says it's a 0.8x, so would that work the same as a 0.8x Barlow? 

 

For viewing, I wouldn't really need the flattener, but a Barlow maybe...would I need an eye piece on top? Or again, can a Barlow be used as an eye piece? 

 

Thanks for any info explaining the difference  

[ronin]

A barlow "multiplies" the focal length of the scope it is attached to.

A reducer does what it says and "reduces" the focal length of the scope it is attached to.

More accurately each changes the size of the prime image that is produced as if the foical length had been altered accordingly.

An eyepiece is for use with your eye, with or without a barlow/reducer in the optical path previously.

Strange to realise that a scope with an eyepiece in it does not produce an image (outside of the scope), tecnically the image is at infinity.

It is collimated light in, collimated light out.

The barlow/reducer take the prime image from the objective and scale it according to their intended design, if you then put an eyepiece in that scaled image is taken and comes out collimated.

A flattener does asd you say it takes the curved image plane from the objective and "flattens" it to produce sharper stars etc at teh edges and corners of the camera sensor.

[WillG]

Thank you ronin,

So for viewing I could have a barlow and an eye piece, but for photography it would be flattener, barlow and  camera?

[Cornelius Varley]

Thank you ronin,

So for viewing I could have a barlow and an eye piece, but for photography it would be flattener, barlow and  camera?

The barlow would probably be unnecessary.