Now I've taken a few images with this RC8 I've noticed streaky stars in one corner of the images, see top right in the attached image. If I run the subs through ccd inspector the tilt etc changes depending on how much tension I apply to the set screws on the focuser and which way the filter wheel is pointing. Looks like I need a new focuser before I tackle collimation.
A moonlight with a stepper motor including postage is close to US$500 which is basically half the price of the scope. Is there a cheaper option? Moonlight want US$190 just to add the stepper motor where as a robofocus motor can be had for half that. Has anyone successfully added a robofocus motor to a moonlight focuser?
Alternately, are there any alternatives that I won't have to sell an body organ to buy?
Which set screw are you referring to? If it's the one that holds the camera, why don't you tap another hole or two to hold the camera more securely.
This is the weakest link in the chain, and it's easy to fix.
The focus lock screw shouldn't cause any problems - the linear guide rail won't have any play at all.
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Looks like I need a new focuser before I tackle collimation.
I would collimate it before replacing the focuser, especially if you are worried about the expense. Also check if the primary is moving and collimated properly.
I had a robofocus on my, but I took it off. The focus never shifted from night to night, and it's easy to do manually anyhow.
Once the tension is set correctly, there's no need to move that screw. Set the tension, collimate the scope and leave that screw nice and tight.
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I want motor driven for narrowband.
If you want it and it will make you happy, get it! I thought you were looking for alternatives.
If you are on a budget then I'm just saying you can make do with the stock focuser. I hang a STL off mine, and it's quite a heavy camera. A new focuser isn't going to fix your collimation.
If you need help collimating it, have a read of these:Link 1Link 2
You don't need CCD Inspector to collimate it - just look carefully at the shape of the stars in the corners.
James
I have that collimation site in bookmarks already but I'm really not keen to touch it while the focuser seems to be moving around. Curvature plots from ccd inspector seem to be all over the shop even on the same target. If I set the tension screw tight enough to hold the camera and wheel, then the focuser won't move in properly, it will stick. If I set the tension screw so the focuser will move properly, then it slips if you try and refocus at too high an altitude.
Yes, motor driven focusing will make me happy, the narrowband filters seem to need to be individually focused and I want to do it from inside not outside. RGB filters are fine and don't need it, but there's no point doing RGB from the backyard when the moon is up. So about 80% of the time it will be doing narrowband.
I might strip the focuser down and rebuild it first I think.
Can't go wrong with a Moonlight focuser Robin, was the first thing I replaced on my RC, although mine was one of the first sold in Oz so I paid a lot more than you.
Collimation isn't that hard just remember not to touch the back plate screws ever as these are factory set, but looking at you image I would'nt think collimation is an issue
I already did, looks very similar to a standard GSO crayford except the tube is on a track.
Not much to adjust though apart from the 10:1 tension nut and greese the bearings. I did stick a cheshire in the scope and collimation is out. The rain has started again here, so all stop
Robin the Moonlite with stepper control is a superb bit of gear for AP and well worth the cost. It is as solid as a brick dunny and highly accurate. Suprised to here you say it is only $190 more. What would you use as a controller??? The moonlite controller is a ripper but would add about another $500 to the price. Ron has pinned them so the robofocus controller will also work. Certainly dont regret buying mine.
Robin the Moonlite with stepper control is a superb bit of gear for AP and well worth the cost. It is as solid as a brick dunny and highly accurate. Suprised to here you say it is only $190 more. What would you use as a controller??? The moonlite controller is a ripper but would add about another $500 to the price. Ron has pinned them so the robofocus controller will also work. Certainly dont regret buying mine.
Mark
Mark, I've had a couple of tri-knob moonlites on newts over the years and they've never let me down but I've never needed one with a stepper. I have a robofocus box already setup and working for the tak when it's in use, so thats the controller. I was hoping not to spend anymore cash on this stuff but if I want reliability with repeatable results here, I think I'll have to. Does the stepper model have a clutch built in so you can turn the knob by hand?
Mark, I've had a couple of tri-knob moonlites on newts over the years and they've never let me down but I've never needed one with a stepper. I have a robofocus box already setup and working for the tak when it's in use, so thats the controller. I was hoping not to spend anymore cash on this stuff but if I want reliability with repeatable results here, I think I'll have to. Does the stepper model have a clutch built in so you can turn the knob by hand?
No Robin the motor and shaft are locked solid so the only way to focus is by the controller. This is why Ron made a 2 speed controller for them as they were a right pain to use for visual obs with the movement being too slow. They are pretty much an AP only setup and deliver highly repeatable results working well with autofocus routines. Your robofocus controller should plug straight in I believe.
Another option is the feather touch. Got one on mine and it is pretty solid. It also comes with the option of temperature compensation and a type of robo focus.
Another Robofocus motor from either Robofocus or Peter Lee is a cheap way to get control of whatever focuser you use and is cheap to transport to another scope with just a simple clutch and coupler.
Cheers guys. I have a feeling a feather touch will always be out of my price range. Doug, I'm sort of thinking an old 2.7" tak focuser might be the shot. Easy to robofocus with one of the new clutched couplers, I've got a couple of them here already, and all my tak adapters, including the reducer, would fit. Would just need an adapter to reduce the focuser flange down to size. I'll procrastinate for a few months
Doug, I'm sort of thinking an old 2.7" tak focuser might be the shot. Easy to robofocus with one of the new clutched couplers, I've got a couple of them here already, and all my tak adapters, including the reducer, would fit. Would just need an adapter to reduce the focuser flange down to size. I'll procrastinate for a few months 
