Startup idea - cheap camera rotator

[Gina]

Thank you Ian   I fully understand   And yes, I do have an observatory.  And if I set up a second mount outdoors I shall make some sort of cover for it.  At present I have enough to get on with

[Gina]

30 minutes ago, The Admiral said:

Well, if you've got an observatory where you can set it up properly and leave it, nothing, and clearly many advantages. But for myself, I have to drag everything down from upstairs and take it into the garden each time I want to use it. And I can't see the Pole Star so alignment would be that bit more complicated. And I want to spend what little time I have using the gear rather than setting up. Also, I'm not after salon-class images, but take great satisfaction in being able to reveal an object which to to the eye is but a grey smudge. It is I suppose what could be regarded as entry-level astroimaging which doesn't cost an arm and a leg. Perhaps I should turn the question around, "What's the matter with an Alt-Az mount?"  I'd like to squash what appears to be a prevalence of view that one must have an EQ mount if one wants to embark on astroimaging. That is simply not the case. I'm not suggesting, Gina, that you are questioning that in your post, but it does give me a chance to get on my hobby-horse

Ian

Thank you Ian - I fully understand   And yes, I do have an observatory.

[Gina]

I'll get used to editing and sorting out posts on here one day, I'm sure

[Ajhayter]

4 hours ago, spaceman_spiff said:

Brilliant link, thanks! 

Just to add I'd be interested if you can get a solid prototype. I'd try it myself but I really don't have the tools or the time

I would say if you can make the controlling software run on Linux this is a great Raspberry Pi project. You'd have the Pi running linguider or similar for the guidecam sending guidance updates to the alt-az (using direct control kinda like EQMod perhaps?), while also being able to calcuate and control rotation rate, and also being able to act as a USB controller for the imaging camera (DSLR trigger)? You could even query the mount to get the current target to inform the rotation speed, no input required. Just point and go! Or maybe just updating the arduino controller with the target manually is the way to go.      

For something like this it would be a shame to limit this to Windows/Mac devices and the associated high battery consumption.

 

Thinking it through even if your's ended up being £200, you add another £150 for the OAG, another £150 for a basic guidecam and bolt on your DSLR and some other minor extras and (lots and lots of work later!) you could be getting some crazy imaging with a large aperture dob on a (relative) budget!

[VilleM]

1 hour ago, spaceman_spiff said:

This is an interesting idea...I could easily write a program with two main modes - de-rotation and framing. In the second mode, the rotor would move at faster speeds to attain the correct orientation and would then stop for imaging. If I use a stepper motor then I can track how far it rotated moved the camera...possibly even giving the user an angle reading (useful for taking flats later).

As for the interchangeable plates, it's a good idea...but more parts = more cost. I think the prototype will just be the barebones mechanism. I was thinking of using my freezer for testing it at sub zero temperatures!

Here in Finland temperature can easily go to -30C in winter. One of the best lubricants wich is very common in astronomy community here is "superlube" and it works very well. Almost everyone changes their EQ mount lubricants to this. http://www.super-lube.com/what-is-super-lube-ezp-158.html

Stepper motor is definedly way to go, expecially if you can give angle reading that would be great. Are you going to create your own program completely or add on for existing ones? ASCOM would be good because its universal.

-V

[spaceman_spiff]

2 hours ago, Ajhayter said:

Just to add I'd be interested if you can get a solid prototype. I'd try it myself but I really don't have the tools or the time

I would say if you can make the controlling software run on Linux this is a great Raspberry Pi project. You'd have the Pi running linguider or similar for the guidecam sending guidance updates to the alt-az (using direct control kinda like EQMod perhaps?), while also being able to calcuate and control rotation rate, and also being able to act as a USB controller for the imaging camera (DSLR trigger)? You could even query the mount to get the current target to inform the rotation speed, no input required. Just point and go! Or maybe just updating the arduino controller with the target manually is the way to go.      

For something like this it would be a shame to limit this to Windows/Mac devices and the associated high battery consumption.

 

Thinking it through even if your's ended up being £200, you add another £150 for the OAG, another £150 for a basic guidecam and bolt on your DSLR and some other minor extras and (lots and lots of work later!) you could be getting some crazy imaging with a large aperture dob on a (relative) budget!

Great, thanks for the interest!

Regarding the programming of the device, my brother was going to set up an Arduino to receive commands that are given from a python program I will write. So it should be controllable through a linux system (or any os). I like the idea of receiving data from the mount to get the correct rotation rate and mount flipping data. I think the easier to set up the better. 

Despite some of the drawbacks (problem with flats, guidescope issues...ect), it's worth a shot!

Dan 

[cytan]

Hi,

   I am the author of the open source field derotator: https://github.com/cytan299/field_derotator and just saw your topic. After reading the postings here and the suggestions as to how to control the field derotator, please let me say that nearly all the suggestions are already covered in my design:

• The derotator can run standalone without a laptop.
• The derotator can be controlled by wifi if necessary.
• It uses an Arduino and stepper motors.
• It talks to the mount to get pointing data.
• Hall switch to indicate a home position, so that stepper motor counts can be measured.
• Its basically "plug and play", i.e. connect the derotator and controller and press start. That's it.

You can have a look at the picture of the Crab Nebula that I took with my LX200 and derotator at https://cytan299.github.io  that shows how well derotation actually works. IMO, the myth that derotation doesn't work came from the cr*p that companies built in the early days. If designed correctly, derotation works very well.

IMO, I don't believe the op's goal for building a derotator for $200-$300 is possible. You can have a look at my bill of materials for the cost of building one derotator https://github.com/cytan299/field_derotator/tree/master/bom  and it comes up to about $650. That's with some economies of scale and with no profit. My actual cost since this is an R&D project was $1600.

Perhaps the op thinks that by printing out the derotator, it will save money. Unfortunately, I had considered that too. The problem is the strength of the material. It's hard for plastic to not warp or break with a camera+OAG+filters connected to it. Therefore, I'd suggest using aluminum. Unless you can do your own machining, that's where 1/3 of the cost comes from.

One other thing that I must emphasize, derotation does not work without an OAG. My theoretical writeup for why this is so, can be found at https://github.com/cytan299/field_derotator/tree/master/field_derotator_formula.

Finally, I'd encourage the op to download my design and study it. I understand that people want to create designs from scratch because it's more fun that way. IMO, a working derotator + controller source code + computer laptop source code can serve as a guide for any improvements in the op's design.

cytan

[michaelmorris]

Many imagers are looking to automate more of their imaging.  Whilst automatic plate solving, dithering, autoguiding and focusing seem to be becoming (relatively) easy to automate, I'm not sure remote framing of images is anything like as advanced. There is an ASCOM protocol for field rotators, so could the production of relatively cheap method of remotely rotating the field of view to a pre-determined angle be field worth exploring?

[michaelmorris]

Hi Dan

Any news on progress with this project?

[spaceman_spiff]

14 hours ago, michaelmorris said:

Hi Dan

Any news on progress with this project?

Some...We managed to 3D print the parts for the outer casing and the internal supports (holding motors and circuit board) but they are way too flimsy. We have bought in some machined parts including the threads but the cost goes way up as a result. We were able to test some of the algorithms for autoguiding on a de-rotated field seems to be successful so far. I've written the programs control the arduino in Python and although very buggy it all works.

As you can imagine, other priorities have slowed me down recently, my contract as a postdoc researcher expired recently and have been having large commutes to bring money in...not fun.

Anyway, I will keep you posted.

Dan.

[michaelmorris]

Thanks