Help please! I'm looking for advice on how to really use a cheshire eyepiece.

Equipment Collimation Help Needed
9 replies•899 views
Andy Wray avatar
Andy Wray avatar
I struggled to take this photo through the Cheshire, but wondered what this would tell you if you saw it?  (obviously I have added the coloured lines).

Obviously it shows me I have an offset secondary and that I have very bad inclusion of my focusser draw tube into the OTA.  Despite that, I am looking for advice on the alignment of the primary and also if this tells you anything about my secondary alignment?

and yes, there are a lot of light leaks, but that is due to the device I use to make sure my cheshire is centered ... I'm OK with that.

I do plan to move on to an autocollimator next, but would like to master the cheshire first.

Any help would be greatly appreciated.

Sorry about the plants, however we have them at most of our windows.

Engaging
Andy Wray avatar
Andy Wray avatar
[Deleted]
Jacob Heppell avatar
Jacob Heppell avatar
Do you have a center spot on the primary? It's used as a reference to center the primary to the focuser. I have a catseye hotspot.
So was there something in particular concerning you?
Also, the cheshire alone won't get you're scope collimated as it is only concerned with the primary. The autocollimator you mentioned is also 100% essential for full correction of collimation errors involving the secondary.
andrea tasselli avatar
andrea tasselli avatar
Get Vic Menard's guide to collimation. This is the best advice I can give short of doing it myself. Incidentally, I can't see much from the picture.
Arun H avatar
Arun H avatar
Jacob and Andrea have given excellent advice. You will need to center mark your  primary if you have not done so. Get a quality Cheshire - Catseye is the best I know of. The attached (see p.11) goes over what to look for. It is pretty straightforward. Autocollimator collimation is also discussed. Vic Menard's book should cover the same or similar material, since these techniques were developed by Vic Menard and Jason Khadder.


pensack.pdf
Helpful
Andy Wray avatar
Andy Wray avatar
Thank you all.  I will follow up on the recommendations.
Well written Respectful
Andy Wray avatar
Andy Wray avatar
Jacob Heppell:
Do you have a center spot on the primary? It's used as a reference to center the primary to the focuser. I have a catseye hotspot.
So was there something in particular concerning you?
Also, the cheshire alone won't get you're scope collimated as it is only concerned with the primary. The autocollimator you mentioned is also 100% essential for full correction of collimation errors involving the secondary.

Thanks Jacob!  I have a center donut-shaped spot that was factory-applied and which disappeared behind the central dark spot after I collimated the primary using a barlowed laser.  I have also just ordered an autocollimator as that has been recommended on several occasions before.

Ref my concerns: nothing in particular, but just wanted to check on here with more experienced folks that there was nothing obviously wrong in the photo.

I'm happy with all the recommendations I've received on here and will just practise until I get it perfect (plus do a lot more reading).
Clint Lemasters avatar
Clint Lemasters avatar
This article on cloudy nights is well respected and I found it very helpful. 

https://www.cloudynights.com/articles/cat/articles/collimation-and-the-newtonian-telescope-v4-r2599
Steve Ward avatar
Steve Ward avatar
https://www.youtube.com/watch?v=8G98RTP6jbY
Jacob Heppell avatar
Jacob Heppell avatar
Andy Wray:
Jacob Heppell:
Do you have a center spot on the primary? It's used as a reference to center the primary to the focuser. I have a catseye hotspot.
So was there something in particular concerning you?
Also, the cheshire alone won't get you're scope collimated as it is only concerned with the primary. The autocollimator you mentioned is also 100% essential for full correction of collimation errors involving the secondary.

Thanks Jacob!  I have a center donut-shaped spot that was factory-applied and which disappeared behind the central dark spot after I collimated the primary using a barlowed laser.  I have also just ordered an autocollimator as that has been recommended on several occasions before.

Ref my concerns: nothing in particular, but just wanted to check on here with more experienced folks that there was nothing obviously wrong in the photo.

I'm happy with all the recommendations I've received on here and will just practise until I get it perfect (plus do a lot more reading).

No worries mate. The cheshire/autocollimator can be used with the white donut but it works much better with a catseye hotspot.
As I'm sure you can appreciate, collimation is the single most import thing to learn with Newtonians.
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