18” DIY project, how to motorise?

[Dbroz]

Hi everyone

I am just about finished my 18” truss Dobsonian. I’m just seeing if it’s possible to motorise this scope. If so where is the best place to buy the products I need to do so. I have attached a photo of what I’ve built so far

Thanks to everyone

Daniel 233108

[Billyboy78]

Nice looking scope Daniel. You've done well.

I've made a number of scopes over the years, or I should say mountings, and none of them have been a Dobsonian. I hired a club Dob once and I hated it in that I couldn't find anything and it was so easy to lose what I had found. This type of scope was conceived as a alt/az, (meaning altitude/azimuth that is designed to only work up/down and sideways) and to try and get it to track is going against its design. Tracking involves getting one axis to remain parallel to the earths axis, in your case angled up at 38 degrees and rotated at 1 revolution per day to keep the object centred. There are quite a number of specialist mountings that are designed to track and do it well. You can keep your beautiful tube, just reattach it to a different mounting. A classic arrangement is called a German Equatorial Mount (GEM). They can be made out of wood, metal pipe or whatever you have on hand. Do your research, particularly the cloudy nights forum where there are lots of pictures of cheap mounts.

I've had no experience at motorising a dob so I can't help you there.

[Rod]

Hi Daniel

You can certainly motorise your existing dob effectively. Here are some resources that might help:

http://www.siderealtechnology.com

http://www.stellarcat.com/Pages/servocat.html

http://www.bbastrodesigns.com/StepperSystem.html

If you are interested in stepper motor systems then have a talk to Bojan who posts on this forum. He has made a Bartels system and worked with some other stepper based products.

I built a Bartels system which was a lot of fun. I later converted it to a sitech servo system which worked well too. This was for a home made 12 inch truss dob.

My preference these days is an Equatorial platform. I enjoy the simplicity of the platform and the fact it requires no modification of the dob mount. It raises the scope a few inches which can be an issue for taller instruments.

Hope that helps.

Rod

[Dbroz]

Thanks guys for your reply, I will check out these sites too. Again thank you

[sfarndell]

Lovely scope Dan!!

One of the issues with the Mel Bartels system is that it requires a computer and the servocat is a bit pricey. Something that's quite new to the market is the rDuinoscope DIY. Costs about $200-$300 for parts. I've got the parts on order and it'll probably take a few weeks to learn to debug all the programming. Hopefully that'll be long enough for the inventor/some other guru to amend the progamming for an alt/az mount.

http://rduinoscope.byethost24.com

[bojan]

Daniel,

As Rod poited out it is certainly possible to motorize your dobson and it is not hard to do :-)

Have a look at Mel Bartels website (https://www.bbastrodesigns.com/StepperSystem.html) for mechanical details.
Computer is not such a big/bulky problem, I am still using an old Fujitsu Stylistic 1000 for that purpose (I bought it from ebay for couple of $$.. I am using it because it still works and because Bartels software supports encoders, which are great for manual / visual - once aligned, user just needs to stop tracking, move to other object and restart tracking, software will calculate necessary parameters from encoders readings), but you can try with other systems as well, lile OnStep (http://www.stellarjourney.com/index.php?r=site/equipment_onstep) or AstroEQ (https://www.astroeq.co.uk/tutorials.php), both use cheap parts usually used for 3D printers and small CNC machines.

Soundstepper (http://soundstepper.sourceforge.net/) is also good (unfortunately, neither of those above support encoders - which is what is needed to mitigate issues Billyboy78 is mentioning).


I can help you with electronics, I even have couple of spare PCB's (suitable for Bartels-OnStep-SS in my drawers.

[Fleegal]

Hi,

I have recently completed my portable trolley equatorial platform which achieves 75 minutes of tracking for my 16" lightbridge.

Cheers

[bojan]

I have to correct myself here: OnStep does support encoders for about a year or so (I was not aware of that because the version I am using is (still) sufficient for my needs...).

[Dbroz]

Thanks for your replies everyone. I have actually Re made my whole scope. It is now complete and I have also installed ArgoNavis with ServoCat and it works amazing. I did get help from Peter Read from SDM telescopes, he is an amazing person and helped me a lot. I have attached a photo of my new build 238600