My low-cost DIY RA drive for EQ5 mount

[kman42]

On 23/04/2017 at 20:37, kens said:

That depends on your imaging scope. Autoguiding software like PHD2 http://openphdguiding.org/ can resolve down to around 0.1 pixels. As a simpe rule of thumb, a guidescope should have a focal length in the order of 1/4 the focal length of your imaging scope. Many people adapt a finderscope for the purpose.

What kind of guiding camera is usually recommended? 

[kens]

Its more critical when using an OAG. But my criteria would be:

1. Mono (not essential but better)
2. Reliable frame rate (usually driver dependent)
3. Reasonably sensitive
4. For OAG use sensitivity/big pixels and mini profile become important.

I have a preference for ZWO - their drivers seem to be better. I've got the ASI120MM-S. This is the USB3 version. The older USB2 version had connection issues when plugged into USB3 hubs. One thing about the ASI120 when used with a guide scope is that it has a 1/4" thread in the back so you can use a bracket to hold it solid. Even so I stil lgot flexure. Now that I use an OAG the mini version would be better or the ASI290 mini (more sensitive but smaller pixels). I also have a Toupcam which I don't use much due to driver issues on Linux.

[kens]

On 07/01/2019 at 01:12, theropod said:

I think you should look into using “unsigned long millis” to control/eliminate your sktech halting delay statements. I am currently rewriting my code for the DIY alt/az I built employing not only this feature but also employing proportional motor speed based on joystick mapping. Since I am not a C expert by any means this is a steep learning curve for me, but the Arduino is capable of great precision if the code is written tightly. Even you simply change your current delay statements to delayMicroseconds you can achieve far greater timing control.

Yeah, the same desire to mess with things is part of my makeup too.

You should also consider using the Timer1 interrupt rather than using delays. Interrupts will take precedence over anything else going on at the time.

[jase1973]

On 14/01/2019 at 12:19, kman42 said:

I just did some tests with the tracking mount.  After getting perfect polar alignment using the drift technique, I achieved a tracking accuracy ratio of 9000/FL (compared to the general rule of 500/FL for untracked astrophotography). In other words I was able to shoot 45 second exposures at 200mm and 30 second exposures at 300mm with no streaking. This was pointing at Sirius (almost at the zenith)  where tracking times will be the worst. 

question for you re your mount, did you get it new? who made it?

I assumed mine was Orion as it came with my 2nd hand scope. 

[kman42]

On 18/01/2019 at 11:12, kens said:

Its more critical when using an OAG. But my criteria would be:

1. Mono (not essential but better)
2. Reliable frame rate (usually driver dependent)
3. Reasonably sensitive
4. For OAG use sensitivity/big pixels and mini profile become important.

I have a preference for ZWO - their drivers seem to be better. I've got the ASI120MM-S. This is the USB3 version. The older USB2 version had connection issues when plugged into USB3 hubs. One thing about the ASI120 when used with a guide scope is that it has a 1/4" thread in the back so you can use a bracket to hold it solid. Even so I stil lgot flexure. Now that I use an OAG the mini version would be better or the ASI290 mini (more sensitive but smaller pixels). I also have a Toupcam which I don't use much due to driver issues on Linux.

Do you have to go through a Laptop, or can you control things through Arduino?

[kman42]

20 hours ago, jase1973 said:

question for you re your mount, did you get it new? who made it?

I assumed mine was Orion as it came with my 2nd hand scope. 

I got the scope and mount both secondhand. The mount is a Skywatcher EQ5.

[kens]

1 hour ago, kman42 said:

Do you have to go through a Laptop, or can you control things through Arduino?

You need to go through a laptop or something like a Raspberry Pi because you need a driver to operate the camera. Thinking about it, a RPi plus Arduino would be a nice combination as you can run PHD2 on the RPi and code the Arduino to work with LX200 guiding commands.

[jase1973]

On 19/01/2019 at 06:25, kman42 said:

I got the scope and mount both secondhand. The mount is a Skywatcher EQ5.

I thought skywatchers were white, it it marked skywatcher in any way?

 

[kman42]

11 hours ago, jase1973 said:

I thought skywatchers were white, it it marked skywatcher in any way?

 

It's not marked anywhere that I've found, but it looks identical to Skywatcher mounts except that it's a different colour. Maybe it's an older version?

[kman42]

So after a bit of research, I think I've got a plan for a budget tracking setup.

I am planning to aquire a range of manual focus lenses for astro work, eg. 200mm F/4, 135mm F2.5, 300mm F4.5. I can use one of these lenses as a guide scope. I will get an M42 to 1.25" adapter to fit the guide camera, and will get this guide camera or similar: https://www.ebay.com.au/itm/T7C-ST4Guide-Star-Monocular-Telescope-Electronic-Eyepiece-Camera-CMOS-Equatorial/113342001852?epid=19025357936&hash=item1a63b5b2bc:g:wNcAAOSw-HRb2Y7A:rk:22:pf:0

Then I will fabricate a rail to mount both DSLR imaging camera and the guide camera setup to the EQ5 mount.

I will probably go for a Rasberry Pi to control the guide camera and stepper motor via arduino, so that I don't have to carry a laptop around.

I can choose a guide lens based on the imaging focal length I am using. That will save the cost of a dedicated guide scope.

Thoughts? 

[Gina]

If you're using an RPi you don't need an Arduino.

[kman42]

31 minutes ago, Gina said:

If you're using an RPi you don't need an Arduino.

Really? The RPi can directly control the stepper motor? I am completely new to RPi. 

[Gina]

I use an A4988 stepper driver which is controlled from GPIO lines on the RPI. 

My blog Setting up a Raspberry Pi for Astro Imaging and Control - Ubuntu Mate  may be helpful.

Edited February 3, 2019 by Gina

[Superjezz]

I would like to make this for my scope but by my calculations I will need 1 quarter step of my motor every 0.78 sec. I have no idea about arduino coding and need help in adjusting your code to suit. What changes should I make to it?

[upahill]

As John78 said the AstroEQ would be a perfect fit for a next step. Goto, autoguider, ascom support etc.

The motor mouting you have done is a really neat solution. When I tried it I went with a larger pulley ratio and it really threw off the ability to tuck it all away neatly.

On 21/01/2019 at 10:59, jase1973 said:

I thought skywatchers were white, it it marked skywatcher in any way?

 

Also have this mount in black, was billed as Skywatcher too but unbranded - identical in everyway though. Possibly an older version or one they sold for OEM rebranding?

[RY123]

Hi, can you help me with circuit diagram for this thing. I am totally new to this. 

Thanks in advance

[steviebee]

I have an old Skywatcher EQ3 mount and that is Black.