Skywatcher 100ed Pro and flattener?

[GrampyG]

I have the SW100ED Pro with the flattener/reducer which I am using for astrophotography. The SW has a focal length of 900mm and with the flattener/reducer, 765mm. I read on one of the forums that scopes (refractor) of 800mm and above do not need a flattener.

Any thoughts?

Thank you

G

[AstroNebulee]

I would of thought you'd still need one as why would they make a reducer flattener for the 100 ED else, but I'm probably wrong 👍

[Budgie1]

You can use the 100ED DS Pro without a flattener but the edges may have odd shaped stars.

I got an OVL field flattener for my 100ED DS Pro for when I wanted the full 900mm focal length with a camera.

[GrampyG]

Hi Martin

The flattener will do nicely; will allow me to use it at 900mm. I currently have the flattener/reducer. Question, does the OVL screw straight into the focuser tube, and the 55mm backfocus assembly for the camera then screw into the rear of the OVL? Sorry if it is a silly question.

Thank you

G

[Budgie1]

2 hours ago, GrampyG said:

Hi Martin

The flattener will do nicely; will allow me to use it at 900mm. I currently have the flattener/reducer. Question, does the OVL screw straight into the focuser tube, and the 55mm backfocus assembly for the camera then screw into the rear of the OVL? Sorry if it is a silly question.

Thank you

G

The OVL FF pushes into the 2" eyepiece mounting on the focuser, it doesn't screw on like the SW FR/FF does. The camera & spacers do screw onto the FF though.

[howzat]

I have the Starizona Apex 0.65 for my Esprit 80ED Pro. It is a superb piece of optics. They supply a long version for the ED100. Make sure you put the best quality glass on your triplet refractor. Or you will degrade the picture quality. 

[GrampyG]

Hi Martin

 

Thank you for your reply. If it is a simple push fit how is it best retained? I may be missing something here.

G

[michael8554]

20 hours ago, GrampyG said:

I read on one of the forums that scopes (refractor) of 800mm and above do not need a flattener.

I hadn't heard that before.

What I have read is that as refractor FL increases, Chromatic Aberration becomes less apparent.

Flatteners serve a different purpose that may still be necessary at 800mm FL.

Michael

[GrampyG]

Doh!! Already have the appropriate fitting for the SW!!😬

Michael, thank you for your reply.

I've been using the SW 0.85 reducer/flattener but would like to try the scope at is maximum of 900 mm

[GrampyG]

Got the OVL. Tried last night and managed to get 3 subs before the perishing clouds rolled in. Stars look perfectly round edge to edge.