DIY CG3 - EQ2 Autoguiding

[MyRomeo]

Hello everyone, long time no post, I'm very much a seasonal astronomer!

After a nice summer off I've decided on this years DIY project and have been researching how to add two axis auto guiding to my otherwise low end, basic EQ3-2 mount. This will not be for a-focal astrophotography but using the EQ mount to hold my camera and 300mm lens. 

I've ordered a couple of steppers and arduino R3 development board and plan to get these guiding using the ASCOM standard drivers.

Never done anything like this before so its really new to me. Ive downloaded the programming software for the ASCOM driver and the Arduino program and think I have my head around that. I've been lucky enough to find someone elses source code that runs auto guiding on RA so I need to modify it for DEC. 

Hardware is due Tuesday and I can get started.

One question I do have right up front tho, I have historically used a microsoft xbox webcam but since upgrading my macbook to El Capitain beta this no longer works (I run everything in vmware). 

Can anyone recommend a webcam that would be suitable for use with a 50mm f1.8 nikkor lens and a means of connecting said devices? 

Thanks!

[Dr_Ju_ju]

If you don't want to re-invent the wheel, then I can recommend the AstroEQ control system from http://www.astroeq.co.uk/purchase.php

I modified my EQ5 using this as the controller (Ascom Compliant, with drivers etc.) & fitting NEMA 17 motors to the mount with belt drives...

have a look at this thread, which has lots of info http://stargazerslounge.com/topic/188877-astroeq-for-eq-mounts/page-1?hl=+eq5 +motor +control

[MyRomeo]

Thanks for them links mate, very interesting.

I agree Astro EQ would have been easier however part of this project is for me to learn arduino programming and get my head around the Ascom driver too.

My mount has absolutely no guiding or motor control at the moment other than a basic dc motor drive on RA. This little project should be interesting.

In related news the items were dispatched today with expected delivery date of yesterday... Didn't realise the Royal Mail did a 'yesterday' service!

Take Nothing but Pictures, Leave Nothing but Footprints

[MyRomeo]

It begins... Slowly.

Hardware has arrived and tests ok.

Managed to get the motors to turn using a test sequence. Also got PHD communicating with the arduino using the Ascom driver but no control yet.

Long way to go but it's fun to learn.

[MyRomeo]

Update. This week has been interesting. I now have the arduino software working and responding to pulse guide instructions from PHD2 for RA+/-

Test fitting the motor today and found the RA shaft a bit stiff, quick strip and lube and motor drives both directions happily.

Next step is to manufacture a bracket to secure the motor before moving on to the DEC drive.

Don't worry, I'll post parts list and software once it's all working so others can auto guide their eq3-2 too

[Cornelius Varley]

Interesting idea, although I'm a bit puzzled by the photograph. The photograph shows a Celestron CG3, which is the equivalent of the Skywatcher EQ2 not the EQ3-2 (Celestron CG4)

[MyRomeo]

Interesting idea, although I'm a bit puzzled by the photograph. The photograph shows a Celestron CG3, which is the equivalent of the Skywatcher EQ2 not the EQ3-2 (Celestron CG4)

You know you could be right. I've always assumed the CG3 on the end was the same as an EQ3-2. I'm not exactly an expert on these things.

Not to worry, guess I'm auto guiding a CG3 then

[JamesF]

I don't think it matters if it's an interesting project

Where you might run into some challenges with the smaller mounts though is that the gears on the RA and DEC axes have fewer teeth, so you can't control them as accurately as the larger ones.  Doesn't mean you won't be able to achieve something useful though.

James

[MyRomeo]

Thanks James.

I'm having great fun getting it all working. I should be able to achieve a reasonable level of accuracy with the steppers I'm using as one revolution is 4076 steps so plenty control available.

I've been working on adding DEC control to the Ascom driver tonight, managed to get the code working but need to test it tomorrow.

Even with the smaller mount I think guiding in RA and DEC should allow for some pretty interesting long exposures. I only plan to use my dslr on the mount, not a scope so focal length will be typically up to 450mm (300mm lens, 1.5x dx crop)

[MyRomeo]

Can a moderator update this thread title to DIY EQ2 / CG3 auto guiding?

Thanks

[MyRomeo]

Well I hit a bit of a brick wall with this, the Arduino controls the steppers correctly and using ASCOM driver I can control it manually via PHD2. All works lovely on an empty mount but once the camera, lens and counterbalance are fitted the steppers just don't have enough torque to accurately drive and they stall. Rather than lose the project I am going to modify my motorised barn door tracker for auto guiding instead. of course this will only be in RA so will need a more accurate alignment to start. Not a worry tho. 

I'll have to look in to some larger steppers in order to autogude the EQ2. 

I'll update my barn door thread when I have more progress to report. It shouldn't take much modification I hope!

3D printed, motorised barn door

M