Reducer?

[Flatman]

Just getting started in astrophotography. I've acquired quite cheaply a Sky-Watcher EvoStar 120. Not the newer ED version, but the 1000mm focal length unit. I don't have a camera for this yet, but am working my way through the ZWO stable because I'll probably buy an ASIAIR controller.

Question: Would I get better images if I use a reducer/flattener? Rang the importer (Tasco) and was told no such optic is available from SW that suits this OTA. There are 3rd party flatteners out there, and I guess I could source one of those.

[PRejto]

Hi Chris,

Given this is an achromate without a great focuser, I'd venture to say that you may find it to be quite challenging to obtain decent images, reducer or not. The issue will be focusing, focuser shift due to the weight of the camera, the difficulty(?) of adding an electronic focuser to the existing focuser, chromatic aberration, and how do you intend to guide? What mount?

If you do try a camera I would only try a mono camera plus a set of filters. Forget about luminance. If you shoot RGB you can focus for each colour and hopefully the resulting star images are close enough in size that you don't run into serious stacking errors when you generate the colour image. I think luminance images will be way too blurry due to the fact that each colour will have a somewhat different focus point. Focus in luminance is likely to be an "average" position of all colours and I'd guess not very sharp.


1,000 mm is a nice focal length if you want to try for a larger galaxy image. The reducer will speed up the system but at the sacrifice of focal length. If your aim is large nebula it could be worth it, but I'd seriously consider investing the money in a better OTA more suitable for imaging. The reducer/flattener will not correct the basic issue with this OTA of chromatic aberration.

Sorry if this sounds pretty negative. I could be wrong. Others may chime in.

Peter

EDIT: After I wrote the above I found this thread: https://www.cloudynights.com/topic/918255-achromat-imaging-experiment/
With the right filter and stopping down the aperture a pretty decent result may be possible even with a colour camera. Still, nothing is going to beat or match an apo (or ED) refractor. And there are still issues of guiding and mount choice and focusing.

Here is another good thread: https://stargazerslounge.com/topic/335668-imaging-with-achromatic-refractor-and-mono-camera/
NB imaging might be okay....

[Flatman]

Thanks Peter. Maybe not what I'd like to hear, but it agrees with other opinions I've seen.