Thursday, January 18, 2007

Borg 45ED and remote focusing solutions

On realizing my remote solar telescope project, I need a remote focusing solution. The simplest way to control a telescope remotely via Internet, is to access your home desktop via a remote control manner, for this to work, you don't need client-server style application for all the individual operations like slewing, photograph taking, focusing, etc. Solutions like Windows remote desktop, VNC, etc can do the job very nicely. If the resolution (color depth and dimension) of the screen matches, even 10 fps with webcam capturing can be done without major issue.

Therefore, all I will need to is to buy a motorized focusing solution which can be controlled via a PC. On scanning the web, there're many solutions out there, and they have one thing in common - EXPENSIVE. Common solutions like JMI SmartFocus, Robofocus, and a couple of even more expensive options.

However, there's one big exception, it's the 1240 focusing motor from Meade. It can be controlled via Autostar through the RS-232 connection, and since it's designed for low end scopes, the Meade DS series, and so the price is less than one-fifth of the closest price alternative! Therefore, I took the plunge and ordered a 1240 focusing motor, but later I found that it's hard to mate with other focuser, and so I searched around and found a DS focuser, it's a 2" plastic rack and pinion focuser.

In order to use this focuser + focusing motor, I custom made a tube, plus related adapters to connect it to the Borg 45ED lens. After a few months of purchasing individual components, waiting custom parts to be made, and cutting the tube for proper focusing range, it's ready.

The first light is very frustrating. Like any low end stuff, any potential problems become real. Backlash, image shift, too rough focusing, vibration, etc... as long as you could think of, become real headache!

My conclusion is that, the very poor Meade DS focuser has no cure. I tried to add plastic padding to reduce the image shift, I tried to adjust the focuser tension, anything I could think of, even to add grease, nothing really help to bring it to acceptable level. They improve somehow, but not enough to be useable. Therefore, I took another plunge to order a metalic crayford focuser from China, this crayford is widely seen in many US dealers, so I suppose it's good enough.

I took the 1240 focusing motor and the Chinese Crayford to my local friend who makes adapters for me, and after one or two weeks, he told me it's extremely hard to make such a bracket. So, I gave up and got everything back home.

I searched around and found an electronic focusing solution from the UK, namely the PFocuser, the price is far more expensive than the 1240, but still around 1/2 of those solutions that I mentioned earlier. Therefore, I ordered one. It's quite nicely made, except the motor gear box is plastic, but it works too. However, the bracket which comes with it, does not fit very well, and so, backlash was still there. Accurate focus couldn't be obtained. And on mounting that bracket to the focuser, I will need to use that two tension/locking screws of the Crayford. That means, I couddn't adjust this two parameters any more. This is a big drawback.

Let me say, the Chinese Crayford is okay, the PFocuser solution is good, but they simply do not come together as 1 + 1 = 2, but instead it's less than 2, so I gave them up, too.

Searching around, I found a new product from Shoestring Astronomy, which is basically a simple controller to connect to any DC motor, you could adjust the speed of it, and it comes with ASCOM driver, and a simple GUI so that you can control the motor neatly. Best yet is the price tag, it's even cheaper than the PFocuser box! It's compatible with nearly any JMI motofocus, and thus I begin to keep an eye on astromart to look for any decent potential solutions at right price.

One morning, I found someone selling a second hand NGF-S at a very competitive price, I send an email to the seller and it's still available, and then I send paypal at once.

The JMI NGF-S arrived in great shape! Zero backlash, zero image shift, very well made! Just a little bit heavy, but it's perfectly okay! Then, I asked Shoestring Astronomy and they confirmed that the FCUSB is compatible with the NGF-S, so I send paypal really quick!

At the same time, I ordered a Borg 45ED II from a local dealer with suitable adapter to connect to the NGF-S, after calculating the back focus requirements. These individual pieces arrived in separate days, but close enough so that I can individually unit test them, and finally with an integration testing. All work as expected, and it's out of my expectation!

Borg 45ED II, 3rd reincarnation:-

Lesson learned: never buy cheap stuff, go ahead and buy the best you can afford, second hand deal could be nice, especially when it's a quality product from major brands, they are designed to last forever basically. And cheap stuff are designed to cut cost, to compromise useability for cost.

Finally, I've tried to drive the NGF-S via FCUSB, it works flawlessly, and the speed drop is not noticeable at all, and it even allows finer control than the original hand box. The original hand box is not required in this configuration, the size of the FCUSB is very similar to the JMI hand box.

Among all the solutions, I love the current combination most. The JMI NGF-S combine quality and integrated motor as a complete solution, via the FCUSB provides the capability of the much more expensive computerized solution of JMI, and yet it's much cheaper.

PFocuser is also a very decent product, provided that one can find a good mounting solution for the particle focuser that one has. However, Meade 1240 focusing motor left too much to be desired, except probably the cost.

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