Trouble focussing on artificial star

[Ade Turner]

Hello.

I’m looking for suggestions please.

I bought an artificial star so that I could collimate my Celestron 8 Edge HD in comfort during the day. I have a pretty long garden and set up my scope at one end and initially a bright target light on a step ladder at the other to get everything lined up. This was about 120’ away from the scope.

I got tantalisingly close to focus, but it would simply not rack out any further. Sadly, I can’t increase the distance between scope and target. Is there anything else I can practically do to make this work please? TIA.

Image train: 8 Edge HD > 0.7 Reducer > ASI 533MC

EDIT: sorted now thanks. Just ordered an Ocal Colimator.

Edited October 13, 2022 by Ade Turner

[CraigT82]

Did you need more outwards focus or inwards focus? Assuming outwards like with a newt when focusing on close objects so you can use an extension tube or similar

[powerlord]

a mirror ? stick it where scope is, and scope next to star. double the distance ? of course it'd have to be a good mirror - like a secondary mirror.

Alternatively, I love my ocal collimator. use it to collimate all 3 of my newts and my C925. can be done inside, anytime.

[Ade Turner]

2 hours ago, CraigT82 said:

Did you need more outwards focus or inwards focus? Assuming outwards like with a newt when focusing on close objects so you can use an extension tube or similar

Inward I think. The numbers on my EAF are decreasing so I assume inwards. An extension tube sounds like it could work to reduce the distance required, thanks, but wouldn’t that screw up my required back focus?

[Ade Turner]

2 hours ago, powerlord said:

a mirror ? stick it where scope is, and scope next to star. double the distance ? of course it'd have to be a good mirror - like a secondary mirror.

Alternatively, I love my ocal collimator. use it to collimate all 3 of my newts and my C925. can be done inside, anytime.

That should work but it would need to be precisely aligned - not sure I’m capable of achieving that, and I don’t have a mirror of suitable quality.

Thanks for the tip about the Ocal though. Not come across it before. I’ve seen other more expensive solutions which rely on lasers but couldn’t justify the cost. This might do the job! Cheers 😉

Edited October 13, 2022 by Ade Turner

[powerlord]

I liked it so much I rewrote the manual for them (v2). I do see FLO still selling customer returns sometimes, so not everyone loves em - but for me once I got the hang of it I find them great. It's soo easy to just recheck em anytime once calibrated. I would suggest you read my manual a bit first before you buy so you see what it does (and doesn't!) do.

https://www.firstlightoptics.com/other-collimation-tools/ocal-electronic-collimator.html

v2 manual on that page.

[Ade Turner]

13 minutes ago, powerlord said:

I liked it so much I rewrote the manual for them (v2). I do see FLO still selling customer returns sometimes, so not everyone loves em - but for me once I got the hang of it I find them great. It's soo easy to just recheck em anytime once calibrated. I would suggest you read my manual a bit first before you buy so you see what it does (and doesn't!) do.

https://www.firstlightoptics.com/other-collimation-tools/ocal-electronic-collimator.html

v2 manual on that page.

Sold! Thanks for the recommendation 😁

I’ve watched a few videos now and can see how it works. Looks so much easier than fiddling on a freezing night with an unstable star image (bortle 7/8 round here, seeing is mostly abysmal).  And bye bye artificial star  😂

[powerlord]

my thoughts exactly. I know folk that say "nothing beats a real star check" , etc. And fine, ok I get that - but it's not black magic - centre everything and it's done. if you wanna do a star check after that fine, and it will just confirm what you already know - stuff is centred and it's as good as it can be.  I struggled for ages with the C925 for example - 5 mins with the ocal, and job done - it's been perfect since.

I should be on commission.

stu

p.s. I'm not. honest.