Autofocuser for a Celestron Nexstar 8SE

[davedownsouth]

I know the topic of DIY autofocusers has probably been done to death, but just thought I would share my experiences of making one this evening.  I got most of the technical / clever bits from Motionco, and two metal brackets (for attaching the motor to the scope) from B&Q.   I have got to say that this was quite a bit easier that I was expecting it to be.  Making the bracket and attaching it to the scope took ~3 hours, but this was me taking my time and following my old dad's motto of measure twice, cut once  .  As a result, I did not [removed word]-up at any stages, a very rare occurrence for me .  I wanted the motor to be very easy to attach / remove in the dark, and I think the bracket I have ended up with does a pretty good job, it is just a pity it looks a bit ugly  .  Got to say that it works brilliantly, and the main reason I built this was because I was finding it really difficult to get my arms in to position to focus the scope, while trying to look at the laptop screen during imaging, with the image was jumping about all over the place every time I touched the focuser knob .  Now I can just do this really easily, straight in front of the screen and the focusing control is really fine, much better than I can do with my hand and virtually no image wobble.  Here are a couple of pictures, and if any one is remotely interested in how I did it / exactly what bits you need to buy, please post in this thread and I will add step by step instructions with pictures, but not tonight, I need some sleep .  

A few quick pictures:-

[m.tweedy]

looks good. how about one of these

http://www.motionco.co.uk/timing-belts-timing-belts-c-25_45_27.html

may give that extra bit control

[davedownsouth]

Hi Michael,

I did buy one of these with all the other bits and pieces, but completely got the size wrong .  I will get another one some time soon, but the elastic band will do for now.

[red dwalf]

Looks like an excellent job and as I have the same scope and feather light focuser, i would be very interested to see how you did this.

[BlueAstra]

This was my similar effort with a SW autofocusser.

http://stargazerslounge.com/topic/86999-c8-sct-motor-focusser/?hl=%2Bmicrotouch

[davedownsouth]

Looks like an excellent job and as I have the same scope and feather light focuser, i would be very interested to see how you did this.

Sorry, I missed this, I will put the pictures up tomorrow .

[davedownsouth]

Here is how I did it.  There are probably much better ways of doing this, but this worked for me and it was fairly easy, but if you do not have the right tools it will be pretty difficult.  As I do not want to write a long, time consuming post and loose it just before hitting Post, I am going to do this in several posts.  First, what do you need:-

From Motionco:-

Reversible Speed Controller for DC Motors, 6V to 24V, 6A; Model Number - SW6-24DC6A.  Price - £21.30

Planetary Gearmotor, 1014:1 ratio; Model Number - GMP16D1014.  Price - £27.07

Note.  After ordering this I phoned Motionco and asked them to put a 1.5 meter wire on it, which they did, but more about this later.

Aluminium MXL Pulley, 24T, 3mm Bore; Model Number - PLMXL024AL-03.  Price - £4.30

NB. you could use a smaller / bigger one of these, but if it does not have a 3mm bore size, you will need to buy a Bore Reducer as well so that it can fit on the Gearmotor.

If you could find a way of powering the speed controller from a cigarette lighter thing, this would be all you would need.  I did not know how to do this so I also bought:-

Connector for 12V Battery to Speed Controller; Model Number -  LDTAM-DC5521.  Price - £3.43

12V Rechargeable Battery Pack, Ni-MH, 2500mAh; Model Number -  BAT12V2500NM.  Price - £20.20

Battery Charger for 4.8v to 12v Ni-MH Packs; Model Number -  CHG48012VNM.  Price - £12.20

A picture:-

From B&Q:-

Some M4 Nuts & bolts:-

You will also need Two 60 x 60 x 60 cm brackets, of the type shown in the next post.  I got these from the timber section of B&Q; where you join bits of wood together.  They cost ~ £3 each.

Tools:-

In addition to a hack-saw, drill with metal drill bit, various screw drivers and Alan keys (which I am assuming most people will have), you need a semi-circular metal file.  I did not have one of these so I had to buy one from B&Q (cost ~£5). 

A picture of the tools (minus the drill / hack-saw):-

An elastic Band; Pink or Yellow is acceptable .