Do-it-yourself RH-200 Focuser Upgrades

Newly upgraded Veloce with FLI Atlas focuser.

Newly upgraded Veloce with FLI Atlas focuser.

Victoria, as she is called, is my Officina Stellare RH-200 astrograph, or the Veloce. Eight inches of aperture at f/3 (3.46 corrected T/value) she is the Ferrari of my collection. When I first bought her, she had the standard manual focus and I’d carefully (and manually I remind you) watch the HFD or FWHM values from a focus star while moving it back and forth with a small dial on the back. The Veloce is the most thermally stable scope I have too, so often I was lucky and I only had to do this once per night.

Gino and Giovanni repairing my baby at NEAF 2013.

Gino and Giovanni repairing my baby at NEAF 2013.

It did not take long however and I wanted automated focus, so I inquired with Gino at Officina Stellare, and they sent me the motorized focuser kit for the Veloce. This was RoboFocus compatible, and for a few years I was largely satisfied. Of course, there is a long story of how I damaged the Veloce putting this on myself, and I hand carried it to NEAF in 2013 where Gino and Giovanni “took care of me” so to speak. They ended up cannibalizing the RH-200 they brought to the show for parts to repair what I had damaged on the existing focuser on mine. This was way above and beyond the call of duty, and I am most grateful to my two friends!

Step 1 is to identify and remove the tip/tilt screws.

Step 1 is to identify and remove the tip/tilt screws.

This is not about that incident however, as it is poorly documented, and possibly best forgotten… rather, I recently redeemed myself by upgrading Victoria again, this time with an FLI Atlas focuser. It turns out, even I can do this without having to resort to a mobile factory repair! The story of this upgrade begins when I was at the Advanced Imaging Conference in 2015 when I told Giovanni Dal Lago that I had acquired an Atlas and was wanting to know how easy it would be to retrofit my scope with it (well aware that they do sell a package with the Veloce and Atlas already together). He assured me this was an easy upgrade, and even had the exact adapter I’d need there at the booth. He very kindly let me take it home with me.

The bare back of the Veloce.

The bare back of the Veloce.

It has taken a few months for me to get to the upgrade due to other “entropy”, but once I started it only took about an hour. The first thing you have to do is remove the existing focuser assembly, and this includes the back tip/tilt plate. The smaller of the tip/tilt adjustment screws simply push against the back of the rear of the scope, but the larger screws actually screw into the scope and hold the whole thing on. Carefully removing the four larger screws will completely separate the focuser and the back plate. There are several very thin washers on the backs of these screws, take care not to loose them. I also completely removed the smaller push screws as well to get them out of the way.

VeloceAtlasStep3

Five more bolts remain to completely remove the old focuser.

Once the whole assembly is removed, on the back side you’ll find four screws that hold the focuser to the rear plate. These are the same size as the screws that hold the plate to the back  of the scope. Also a larger bolt that is actually the main screw/worm for the focus movement. This one is very long, and you have to remove it completely as it also contains the thumb locking wheel. You will not be able to remove the focuser completely from the rear plate without taking it out. I was briefly tempted to cut the bolt to save time, but then sanity reminded me that at some point in time I may want or need to put this back on.

The rear tip/tilt plate with and without the Atlas adapter.

The rear tip/tilt plate with and without the Atlas adapter.

With the tip/tilt plate completely empty now, it was a simple matter to screw the Officina Stellare supplied adapter into place. The adapter is threaded to mate with the tip/tilt plate, and the rear side has the indentation that the Atlas attaches and clamps down on.

Washers replaced, screws held up by tape.

Washers replaced, screws held up by tape.

Now, to a whole group of the population who like myself are perhaps less than superbly mechanically inclined, we know taking things apart is easy… putting them back together is the tricky part. Remember all those small thin washers? They need to go back on, so I put the screws back through the holes in the plate, and then put a small piece of tape over them to keep them from falling out. I could invert the whole assembly and put the washers back in place.

Ready to mate to the Atlas.

Ready to mate to the Atlas.

Now, carefully I could turn the assembly back on it’s side and reattach to the rear of the Veloce one bolt at a time. First I got all of them started being careful not to jostle things so that the washers would drop off. Once the bolts were threaded though, they were captive and I was golden.

I learned something from this exercise about the push pull pins… it’s really just push. The larger bolts loosen the tip/tilt plate, but it’s the smaller screws that push against the back of the scope that provide the tension. Loosen the smaller screws, and tighten the larger screws to draw it in. Or, loosen the larger screws, and tighten the smaller screws to push out. Both should be tight for a rigid system. This is one of those things that I sort of already knew… but now I really know. Seeing how this adjustment works more intimately has improved my confidence for the next time I’m out under the stars tweaking the alignment.

The final product. Ready now for a filter wheel and camera!

The final product. Ready now for a filter wheel and camera!

Finally, the rear of the Veloce is ready to accept the Atlas focuser. A question I momentarily struggled with was which way is forward? A good part of me wanted to make the FLI logo forward, this puts the heaviest end of the focuser closer to the scope, and moves the camera in/out on the back side. I went with the logo out for one reason. It is easier to attach/detach cameras on this side of the focuser without having to run it out any. I like the idea of being able to remove the camera, or put on a camera without having to have power and a computer to move the focuser. If I have any lingering doubts about this project, it’s about this choice. I reserve the right to flip the focuser after a night or two under the stars.

Of course I have a new toy now, so the weather gods will likely make me wait a while…

Richard

 

 

 

 

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