Modifying a Dobsonian for DSLR to Focus

[XENOBLADE2 (Shiv)]

Hi everyone,

I've got a Celestron 6" Skyhopper Dobsonian and I'm trying to find a way for my scope to reach focus with a DSLR. I've used a Barlow lens to get focus which works, however I want to be at my native scopes focal length. I've tried bringing the mirror closer by removing 2 springs in the mirror cell but I wasn't able to collimate properly. I took a video of the moon during the day but couldn't determine if I was out of focus or out of collimation or even both. From what I've heard, the newer dobs by Skywatcher have ways to reach focus but since this scope is fairly aged, I don't have it. On Bintel, I've come across the "Celestron T-adapter Barlow Lens" which claims that it can achieve prime focus for some telescopes. Do these work? I'd prefer to DIY something but if it doesn't work, I'll grab one.

So the issue is I need more inward focus (camara needs to go inwards the focuser) which I'm not sure how to achieve. I've got a 3D printer so if anyone here has some ideas please let me know

[Startrek (Martin)]

Does this help ?

https://www.opticscentral.com.au/blo...s-with-a-dslr/

I soley use Newtonians for both visual and imaging and found moving the primary mirror inwards up to 10 or 12mm has resolved most of my focus issues. All depends on where your focal point sits.
A 2 x Barlow could be your ultimate solution

Cheers
Martin

[XENOBLADE2 (Shiv)]

Originally Posted by Startrek

Does this help ?

https://www.opticscentral.com.au/blo...s-with-a-dslr/

I soley use Newtonians for both visual and imaging and found moving the primary mirror inwards up to 10 or 12mm has resolved most of my focus issues. All depends on where your focal point sits.
A 2 x Barlow could be your ultimate solution

Cheers
Martin

Thanks for the link and your help Martin, really appreciate it!

Got another question: I'd like to attach my scope onto my HEQ5 because finding things manually at over 1220mm+ is really annoying. I've looked around into getting 150mm reflector tube rings but are expensive and only sold in OZscopes for $80. Reckon I could 3d print tube rings to connect the OTA to my dovetail? Would be made out of PLA.
Thanks.

[Leo.G (Leo)]

What is the weight of the OTA?
I'd be hesitant to be using 3D printed rings though that might just be my dislike of the stuff, maybe plenty of people do this.
I myself have bought 3mm flat aluminium strip (35mm width) and rolled my own tube rings by making a former first so I got near identical results (which I didn't quite). I did however use a washer spacer to set both rings at an identical height from, the vixen style plate. A bolt and wing nut lock the rings and I have stick on rubber inside so they don't damage my tube.

I did this because I couldn't afford 80mm rings for my old Tasco refractor which originally had a clamshell mount I couldn't adapt to my mount.


Sorry, I'm trying to include an image which is below the size limit but I can't do it for some reason, the site keeps hanging.
It is relatively easy to do if you have access to a vice or a sturdy flat surface to clamp the alloy on, a hammer and something of the appropriate radius to roll them around (not your optical tube).
I'll try again with the image......