Using a plate solving camera instead of encoders to find observation targets

[Rod]

I’m a visual observer and normally use an inclinometer and a degree circle to find observation targets. This works reasonably well but often objects are just outside the eyepiece field and it takes a bit of looking to locate them. Recently I’ve found a much better solution.

For the last few months I’ve been playing with a Skysolve camera developed by Dale Eason:

https://github.com/githubdoe/skysolve

I’ve also been trying out a new software program called Cedar. Cedar works with the same hardware as Skysolve:

https://github.com/smroid/cedar-server/blob/main/building.md

With either Skysolve or cedar, the camera communicates with SkySafari on a phone or tablet and shows you exactly where your scope is pointing. It’s a bit like having encoders attached. Once lined up so the camera is pointed at the object in the centre of the eyepiece it remains very accurate.

The hardware is a raspberry pi 4, an Innomaker IMX296 camera and a suitable lens. The rest is a 3 printed holder. Below is the one I made. It’s just a RPI case I found on thingiverse and added an L bracket to. I added a mount for a quikfinder and a holder for a Powerbank. It sits in the Telrad mounting bracket. I have 4 scopes with telrads so I can mount this on any of them. There are specific cases designed for Skysolve on thingiverse.

Here is a short video showing what the movement between objects is like. In this case I’m using cedar software:

https://drive.google.com/file/d/1JtAcygXyx_TYWBLVQWy1RnGN-KQROi3T/view?usp=drivesdk

As you can see, it’s best to move the scope in a series of short hops towards the target to allow the camera to solve its position and ensure you are moving the right way.

Another advantage of this system is that it does not care what mount it’s on. You can use it on a dob as I usually do, an equatorial mount or an equatorial platform. At a public night I had a scope on an equatorial platform. It was fun to monitor the objects position as the public lined up and looked at eta carina. I immediately knew if one of them had knocked the scope out of position.

This has been a fun project so I’m looking forward to the warmer weather and the opportunity to use this system more.

Rod.

[peter_4059]

It's amazing what can be done on an RPi. Plate solving has made an enormous difference to imaging and this application is another clever use of the technology.

[By.Jove]

So which one did you like better - SkySolve or Cedar ?

[Rod]

Sorry Jove I just was your post.

I like both programs in different ways. I find cedar much easier to set up. I also think it’s faster. It has a handy aiming app which makes manual knobs almost redundant. Skysolve has the advantage that it runs like an encoder based program on SkySafari so you get those handy arrows that tell you which way to move the telescope. You can do something similar in cedar by jumping into a web based app but your eyes get hit with bright light in the process. Interestingly Skysolve will run on my 10 year old iPads quite well. Cedar will not. Skysolve I find needs a better quality lens.

Both programs are free so I would suggest trying both.

Hope that answers your question.

Rod.

[bigAl]

Another similar solution is piFinder. I have ordered parts to make one up.

[Rod]

Hi Alan

I looked at the pifinder and it’s impressive. It was a bit expensive for me. Please make sure you tell us all about it. From memory it has its own accelerometer and a built in screen so moving to targets will be quicker and if you wish you can find targets without using SkySafari.

Rod.

[bigAl]

Will do Rod. Yes the cost is high. Even building oneself the parts are quite expensive despite already having a spare pi.
Alan

[ChrisV]

Sharpcap has push-to with plate solving. I've used it and it's great. Enter the target name and it tells you how many degrees to move/down + left/right (or N/S + E/W).

You'll just need a guide scope + camera that's aligned with the main scope