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Old 18-04-2020, 09:46 PM
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turbo_pascale (Rob)
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Electronic Focusing with an SCT

Given some of the problems I'm having with my 10" LX200GPS Mount, I'm going to try and de-fork it and run it off my EQ6 Pro as an experiment. I know reversing the process is going to be a tiny bit fiddly, but the alternative is to fight with the mount for months and I'm not really up for that at the moment!

When I was imaging with it, I could use the microfocuser, but after deforking that won't be an option, plus, I'd ideally be looking to automate the focuser as I don't want to be going in to the dome at all (it's already very tight quarters as it is).

I currently have an EAF on my 80ED, and it works great. It's dialled in with SGP and works all night long to keep focus runs regularly through the night.

What's the general consensus on the best way to adjust focus on the SCT (for imaging). Obviously I get it as close as I can with the course control, but what are COST EFFECTIVE options?

So far my research has come up with:
- Crayford/R&P focuser mounted to the back of the SCT somehow and the options of:
--> Arduino based stepper motor kits (looks interesting)
--> EAF Kit on the Crayford/R&P setup (a bit more expensive but robust in my experience)

- Frankenstiening the Meade Microfocuser (not really keen on that)

- Super expensive retail offerings (These seem to run $1500-$4500 depending on what colour they are painted )
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Old 19-04-2020, 08:41 AM
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The_bluester (Paul)
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Could you make a bracket and fit an EAF to the original Meade focuser shaft? I have the Celestron focus motor on my SCT and while it does OK, if I was to go again I would make a bracket and figure out a way to mount an EAF on it as it is more consistent than the Celestron motor and includes a temperature sensor which the Celestron motor does not. That is a big omission IMO given how sensitive an SCT is to temperature changes inducing focus drift. When I use the SCT and expect substantial temperatur changes over the night I have it doing a focus run about every 20 minutes due to not having the temperature sensor to trigger it and even then you can get some out of focus subs early in the night.
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Old 19-04-2020, 09:11 AM
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multiweb (Marc)
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Did a small bracket for my C11 with a sharpsky pro controller and motor clamped on the pin of a starizona micro focuser.

PS: sorry just realised you don't want to use the primary focus. Well you still can stick a crayford at the back and automate the same way or get a motorized moonlite focuser. The sharpsky pro controller will run these as well out of the box.
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Old 19-04-2020, 10:12 AM
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Merlin66 (Ken)
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Depends what you really want to achieve...
I've used many electronic focuser options on my earlier Meade and now the Celestron SCT, primarily for spectroscopy.
I now just use the JMI electronic focuser on the C11 - remote control through FocusPal.
HTH
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Old 19-04-2020, 10:49 AM
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Thanks for the input everyone.

My main goal is to be able to automate this, and to avoid the mirror flop, which means I need to lock the mirror, which means a main mirror focus adjustment isn't really a solution.

I currently run the EAF on a bintel dual speed focuser. It was a bit tricky to mount it (none of the holes lined up in the provided bracket well), but I've got it working.

Although, just getting a SCT mount crayford and moving the EAF over is probably the most cost effective - the 80ED I found did not really change focus during a night's imaging, although I set it to do a focus run every hour just in case.

I think that's probably my best bet.

Anyone got an SCT Crayford for sale?
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Old 19-04-2020, 10:58 AM
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Merlin66 (Ken)
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Rob,
Based on my ten years experience with Meade SCT’s.
You will always have some mirror slop, due to the baffle and the unique Meade focuser pin arrangement.
I found running the mirror through the focusing range (30 turns) regularly re-spreads the grease on the baffle and reduces movement.
Even with the mirror lock (on a 12” SCT) there were issues.
The Meade rear micro focuser #1206? Worked reasonably well for me, the MAPUG site has details to build a separate handcontroller.
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Old 19-04-2020, 11:53 AM
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redbeard (Damien)
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Hi Rob,


If you are a little technical, you can still use your Meade Micro Focuser if you make a simple dc motor controller for it. I have made one as have others here on IIS. I used an Arduino and DC motor control module. (See pics). Nothing flash but it has the 4 speeds/inward/outward control and supports the LX200 focuser Ascom in basic form. Also PC control. Now, it looks ugly though. LOL. Happy to share code etc. $30 - $40 in parts if you were to build it.



Cheers,
Damien.
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Old 19-04-2020, 12:02 PM
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turbo_pascale (Rob)
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Quote:
Originally Posted by Merlin66 View Post
Rob,
Based on my ten years experience with Meade SCT’s.
You will always have some mirror slop, due to the baffle and the unique Meade focuser pin arrangement.
I found running the mirror through the focusing range (30 turns) regularly re-spreads the grease on the baffle and reduces movement.
Even with the mirror lock (on a 12” SCT) there were issues.
The Meade rear micro focuser #1206? Worked reasonably well for me, the MAPUG site has details to build a separate handcontroller.
I used to manually focus and then lock the mirror (I have a 10") and I always used the microfocuser, and it was not a big issue for me, however, because I'm deforking it, that seemed to me to be a bit of a problem as there's no where to plug it in.
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Old 19-04-2020, 12:06 PM
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turbo_pascale (Rob)
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Quote:
Originally Posted by redbeard View Post
If you are a little technical, you can still use your Meade Micro Focuser if you make a simple dc motor controller for it. I have made one as have others here on IIS. I used an Arduino and DC motor control module. (See pics). Nothing flash but it has the 4 speeds/inward/outward control and supports the LX200 focuser Ascom in basic form. Also PC control. Now, it looks ugly though. LOL. Happy to share code etc. $30 - $40 in parts if you were to build it.
I thought about building a controller, but was a bit concerned about the lack of ASCOM driver (I really need to run it remotely). I've built a few gadgets with Arduino's and Raspberry Pi's as well, so sounds like it's doable.

If you can point me to some schematics and code, I'd love to take a look. Could be a quick win for me. If it doesn't pan out, the SCT mount Crayford will work too.

Thanks!
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Old 19-04-2020, 12:14 PM
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Quote:
Originally Posted by redbeard View Post
and supports the LX200 focuser Ascom in basic form. Also PC control.
Damien,

In terms or repeatability of the movement, how good is it?
I used to do everything manually with the hand controller, and that was easy enough, but I'm looking to be able to run this automated in SGP.

With stepper motor based units, you get a pretty good level of repeatability.

What's you're experience with this if you're using the absolute values programatically rather than just running it in/out manually?
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Old 19-04-2020, 03:56 PM
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redbeard (Damien)
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Quote:
Originally Posted by turbo_pascale View Post
Damien,

In terms or repeatability of the movement, how good is it?
I used to do everything manually with the hand controller, and that was easy enough, but I'm looking to be able to run this automated in SGP.

With stepper motor based units, you get a pretty good level of repeatability.

What's you're experience with this if you're using the absolute values programatically rather than just running it in/out manually?

You are going to need a stepper motor focuser if you want to automate things. The Meade focuser is only a DC motor. The software I wrote lets you control the motor by using timed movement or manual mode, which is better than just manual but it's not very reliable in respect to exact values as there are none because of the dumb DC motor and no encoders in the focuser.

The Ascom part is also written into the software but it uses the Meade LX200 Classic Ascom driver and happened by accident. I decided to use the Meade RS232 protocol focus commands to control the motor just cause, (I could have used any control commands), and it turns out, that the LX200 Classic Ascom also uses these commands and that is why it works. However, the LX200 Classic Ascom is a crappy driver in my opinion and keeps adjusting for backlash which is annoying. I tested it in Backyard EOS and control did work from within the application.


So if you just want to be able to re-use your focuser, then this or something like this is ideal, however, with automation I would go for a Moonlite focuser or similar with stepper motor control and temperature sensing.


I've attached the Arduino code for you to have a look at but I don't have any schematics as I built this as is on the fly. The Arduino code should spell most of that out by using the pin references etc. (I can always help too if you are interested).
I need to test the Windows code as I have not only moved to Win 10 recently but upgraded to the latest Visual Studio which won't open the older files. I have to setup VS 2010 first which I need to do anyhow.



I built this focuser controller as I put my Meade Zero image shift focuser onto a Meade ETX125 which has no control for the focuser.


So, I guess if you want automated, this may not be the solution. If you just want to be able to control the focuser as before, then this would suit well.


The benefit of the PC software is controlling the focuser manually which I find is very handy when you are running other astro software on the PC anyhow. Ascom is not a highlight here but it does work as if you have a LX200 focuser.



Any questions let me know.



Cheers,
Damien.
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Old 19-04-2020, 06:52 PM
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turbo_pascale (Rob)
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Thanks Damien.

It's a pity.

I really need it to be automated - everything I've been doing the past little while is focusing (pardon the pun) on making sure I can kick off and let it go all night on it's own in the dome.

At another level, having SOME control over it and using the microfocuser is still an option, but not achieving the goal quite right.

A friend has suggested that maybe looking to see if there is a stepper motor that could be dropped in to it, that might be an option, which I suspect could then be run with this project:

https://sourceforge.net/projects/ard...ocuserpro2diy/
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Old 20-04-2020, 01:07 PM
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redbeard (Damien)
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That sounds fun, retro fitting the Meade focuser to stepper motors.
DC motors never cut the automation.



Treat yourself to a Moonlite or similar and save all the fuss you will have with DIY. I have a Moonlite focuser and the good thing about them is they have their own adapter for the back of the Meade which means the opening is larger than 2", you can fit your focal reducer inside the Moonlite as it has a thread specifically for that, they are very strong and can handle extra weight as well as having many options for draw tubes etc. Other good brands may be similar. And it all just bolts on ready to go.



I'm curious of the issues you are having with your current Meade mount. I ask as I have a 10" LX200GPS on a Milburn wedge too. Is it GPS related or something else? Or are you over it and definitely going down the EQ option.


Cheers,
Damien.
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Old 20-04-2020, 03:27 PM
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Quote:
Originally Posted by redbeard View Post
That sounds fun, retro fitting the Meade focuser to stepper motors.
DC motors never cut the automation.
Well, if I bypass the motor entirely, and just connect to the drive shaft with the EAF I have, I think it may be doable with maybe only drilling a single hole in the microfocuser (and something to keep the bracket mounted).
The ZWO EAF has a coupler (which I didn't use with the 80ED) which has the same 5mm shaft diameter as the microfocuser drive gear. I think I can get that to work. Total spend will probably be close to $0 as I've got pretty much all the things I need.
Although, I don't have a drill press. Maybe I should buy one to drill that single hole?
I've got to measure the overall backfocus though - will probably need to get an extension tube anyway. It comes down to how rigid a connection I'm going to get I suppose.



Quote:
Originally Posted by redbeard View Post
Treat yourself to a Moonlite or similar and save all the fuss you will have with DIY.
It's just too expensive. I get it - It's just so much more than it's worth - like $1000-1500 at the low end based on the various ones I've seen around.

Quote:
Originally Posted by redbeard View Post
I'm curious of the issues you are having with your current Meade mount. I ask as I have a 10" LX200GPS on a Milburn wedge too. Is it GPS related or something else? Or are you over it and definitely going down the EQ option.
I've had nagging problems with guiding in DEC in particular and just general annoyances with it in imaging. There have been a bunch of physical problems with it, which I'm spending time and money throwing at it. Which I don't mind, longer term, but at the pace that I can work on it and test the fixes, I've decided to give it a break this season, and just actually image on a mount I've got working. Funny part is that the EQ6 was supposed to be my "travel scope", but I have been more productive with that in 3 months than I have been in 15 years with the LX200GPS.
I'll probably put it back together again in the future (I just bought the Buck's gears but hadn't installed them yet!)
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Old 20-04-2020, 05:47 PM
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redbeard (Damien)
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One hole, sounds pretty easy especially for the price.

Best of luck.


Cheers,
Damien.
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Old 20-04-2020, 09:21 PM
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Well, I'm hopeful (probably overly optimistic!)

Outside of the hole, it looks completely reversable, so I might try it anyway.

If I do, I'll let everyone know how it goes.
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