Attaching a ZWO ASI Camera to my WO Zenithstar 73?

[_Belial]

Good morning stargazers,

 

I've just taken delivery of a lovely ZWO ASI 183MC-Pro, a nice little upgrade from my old canon DSLR.

However, I'm just a little baffled as to how I actually connect it. Currently I'm just using a t-ring with a mount adaptor to a 1.25" straight into the telescope. However this camera seems to have a much wider connection on it which doesn't take a t-ring like my dslr. Also in the box are a 21mm and 16mm extender, do I need to use those?

 

I'm sure this seems like a very basic question, I just want to make sure I know what i'm doing before I head out and spend a night setting it up.

 

Thanks in advance

 

 

Edited May 29, 2020 by _Belial

[michael.h.f.wilkinson]

My ASI183MC (non pro) has a T2 thread and came with a T2->1.25" nosepiece. I am not sure the Pro version is any different in this respect. The manual can be found here: https://astronomy-imaging-camera.com/manuals/ASI183_Manual_EN.pdf

[jimjam11]

You would be expected to use this with the flattener (or reducer) which exposes the right thread. You would typically use some of the spacers to reach the correct back focus for a flat field.

https://www.firstlightoptics.com/reducersflatteners/william-optics-adjustable-flattener-for-zs73.html

 

[rickwayne]

If you're not using a flattener or reducer with a fixed backfocus...I seem to recall there was a 1.25" nosepiece in my 183MM's box which would screw into the 11mm spacer (also in the box; it was already attached to the camera when I got mine). I guess yours has a 21mm instead.

If you have the flattener, then as jimjam says you have to use the right set of spacers that everything adds up to the advertised backfocus distance. It looks as if the WO flattener has 48mm threads.

[TerryMcK]

If not using a flattener then remove the 1.1/4” rotolok from the scope. You will need a 2” adapter which is 47mm long or so (I had an old Sky-Watcher one which sufficed). Something like this https://www.firstlightoptics.com/adapters/baader-2-inch-click-lock-cl-extension-47mm.html there are cheaper versions of course. Then attach all of the extension tubes that came with the camera - this makes up 55mm nose length. You can then insert this into the 2” adapter. This will give you enough to enable the scope to come to focus on the sensor when fully inserted.

If you don’t use the 47mm spacer, from what I recall, you may find it difficult to achieve focus even though the focuser comes out quite a way. When you start taking images with this non flattened setup you will also find that stars at the edge of the field are elongated. Then the next purchase will be the WO dedicated adjustable flattener for the ZS73. At this point you will no longer need the 47mm spacer and the camera will screw directly onto the back of the flattener.

The flattener is worth its weight in gold as, because it is 1x, it does not reduce the image at all. It produces completely round stars from edge to edge.

[TerryMcK]

Looking back through my settings for the William Optics ZS73 and the ZWO ASI183MC Pro OSC

• Without flattener but with a 47mm extension tube (the camera 55mm tubes [nose] is inside the 47mm extension tube). Focus is achieved at 54mm focus extension.
• With flattener and camera complete with 55mm tubes screwed directly to the flattener. Focus is achieved at 46mm focus extension.

Those figures will get you in the ball park and are of course dependent upon any filters you may use. Tune with the Bahtinov mask built into the lens cap.

[_Belial]

2 hours ago, TerryMcK said:

flattener

Thank you all so much for your reponses on this, I'd watched some youtube videos on flateners and thought yes, I'll get one one day, didn't realise how essential they would turn out to be Alas FLO + RVO don't have the flatener for my Zenitstar in stock so I'll have to wait a while, I do have a 47mm extension tube though so I guess I'll try it with the 1.25" adapter. Still so much to learn, there was me thinking, ok buy a telscope, shove a camera at the end of it, job done :))

 

Thanks again, invaluable information from you all.

[rickwayne]

5 hours ago, _Belial said:

Still so much to learn, there was me thinking, ok buy a telscope, shove a camera at the end of it, job done :))

Now THAT'S comedy. Well delivered.

Edited May 30, 2020 by rickwayne