Need focuser suggestions

[KathyNS]

I now have two reasons to look for a new focuser. I am looking to address slippage of the Crayford mechanism and possible (suspected but not yet confirmed) lateral movement. My focuser load is 4 lbs, including Paracorr, filter wheel, and camera. The scope is a Newtonian, and the focuser is oriented downward in the home position, meaning that it is always some variation of down no matter where it is aimed. A motor for autofocus is a must.

I have looked at Starlight. They only have one 2" rack and pinion model, and it is expensive. Baader has a Crayford that has diamonds impregnated into the mechanism, allowing it to boast a 13 lb capacity. Might work, and it is not too expensive, but the motor for it costs considerably more than the focuser itself!

Any suggestions would be welcome.

[Stuart]

I've been happy with my Starlight system. Wayne answers emails very quickly and handles any issues. I don't have any experience with anything else.

[dritter]

I have the 2" Starlight FTF2015BCR in my Mak-Newt and it works really well. It is a crayford design, but you'd never know it. It feels as solid as any R&P focuser I've ever used and it has no problems at all carrying a fairly heavy CCD camera and large filter wheel (an STF8300M with FW8). There is no slippage and no play in the mechanism.

To fit the Starlight 2" focusers into your existing base, you will probably need a base adapter of some kind as well. My guess is that the same adapter ring that works for the MN190 will also work with your Newtonian. Getting an adapter ring and keeping the original base is less costly and simpler to install than getting a new base. Below is an image of the focuser mounted on the MN190 original base.

Starlight Instruments FTF2015BCR on an MN190 Mak-Newt

The TeleVue 2" to 1.25" eyepiece adapter in the image is a separate item (it's the top part with the orange dust cap).

If I recall correctly, the focuser ships with just an open 2" drawtube. So if you want an eyepiece adapter or a dust cap you need to get that separately.

Also, this particular model has a fairly short travel (1.5" only). This prevents the drawtube from being too long and protruding into the OTA. For the camera, I use a simple t-thread to smoothbore 2" adapter. I just place the camera in the focuser like it was a 2" eyepiece and use the thumbscrews on the top of drawtube to hold it. The hold is very secure and normally the camera hangs upside down when the scope is parked. So yes, I am very confident it will not fall out.

To use the scope visually, the focuser is too close in and the travel is too short. So it needs an extender so the eyepieces can come to focus. For the MN190, the extender needs to be about 2" long or so. I have another newt with a similar short travel focuser and for visual use that one needs a extender of about 35mm or so. So if you use the scope visually, or if your camera consumes very little back-focus, an extender of some kind will probably be needed.

[KathyNS]

Thanks, Dave!

What kind of weight is your total camera package? Mine is about 4 lbs. I had looked at Starlight rack & pinion focusers, but hadn't really considered their Crayfords. If it can handle the weight, it might be an option.

The short focuser travel is not an issue for me. The entire range of movement over a 20 degree temperature drop is less than 1mm. This is an imaging-only scope, so focusing eyepieces is not an issue. My camera load starts with a Paracorr, which inserts into a smooth 2" tube, so that will not be a problem.

Just to be clear, are you suggesting that I keep my existing GSO/Orion base and attach the Starlight to it?

[dritter]

My camera is probably about 4 lbs as well.

I've never actually weighted it though. From the specs, the camera body and filter wheel combined are a little over 3lbs. Then adding in the cables, and filters and adapters probably makes is closer to 4lbs. Maybe a little less but not much. I don't use a corrector though, the Mak-Newt field is flat enough that it doesn't need one. And I use a separate guide scope and not an OAG. So that helps keep the weight off the focuser as well.

From your description, it sounds like your current camera setup will drop right in, so that shouldn't add any difficulties at all.

And yes, if the base on your Newt is the same style as the MN190 base, you can keep the original base and just get an adapter ring to match the original base to the Starlight focuser.

And my guess is that it will be the same style. If your current base can accept a standard 2" GSO focuser, then the MN190 adapter ring from StarlLight will fit it for sure. Turns out that the original MN190 focuser is the exact same size as the GSO replacement focusers, which is also the same size as a number of generic 2" focusers sold under the Sky-Watcher and Orion brands. So the MN190 adapter ring works for a whole bunch of scopes actually.

The Starlight part number for the adapter ring is A20-MN190 and in the text description it says "This adapter will also fit stock bases that have a 3.075" opening." No picture posted on their website though, but you can always ask them directly and they should know for sure if it will or will not work with your scope.

[KathyNS]

I nearly had a heart attack with I saw the price of the Starlight focus motor and electronics! With the exchange rate, that put the total price way out of reach. But it looks like my current Rigel focus motor might be able to fit the Starlight with just some new mounting hardware. That would make it a real possibility.

Thanks for the adapter info. I'll ask them about it.

[dritter]

Yes, the Starlight focuser system is pretty expensive. I have one on one of my other scopes and it was more than a little painful getting out the credit card for that. If you can get the hardware from Rigel for your existing focuser, it should work just fine and will substantially reduce the total cost. I have a Rigel focuser on yet another scope and it works very well.