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JAS

DIY remote filter wheel

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I have been toying with the idea of upgrading to mono CCD imaging for a while, after spending a lot of time looking around the forums I have decided to go for it. I have decided to go for the Atik 460EX, being quite a large amount of money and the need for a filter wheel to go with it I have decided to try and build the filter wheel.

It will need to be as thin as possible to fit my newt, I will be using an Arduino to controll it and at a later date I might have a go at making it ascom compatible, but that will probably be pushing my abilitys too far!

I have made a start with it, and there is still a long way to go, but I thought I would post my progress so far to see what input anyone has :smiley:.

I have started things off with a small stepper motor I salvaged from a printer, this had a small nylon gear on it so I punched a wheel from 3mm alloy at work and went about cutting the teeth to mesh with the gear. As luck would have it the gear matched up with the 1.25mm pitch of an M8 bolt, so I used an M8 spiral flute tap to cut the thread.

DSC_0177_zpse8181739.jpg

DSC_0186_zps095fbd84.jpg

I then made up a hub using a bearing I had, and had it anodised black so that i could be put together.

DSC_0168_zpsa4d51905.jpgDSC_0169_zps8c7cc3e7.jpg

DSC_0172_zps661fabd8.jpg

This all went together ok but left me the problem of holding the 1.25" filters in place. I went in to my local telescope shop and managed to get some old eye piece barrels (thanks Charls :grin: ), then parted them off into 3mm thick sections. They will be glued into the wheel later to screw the filters in.

DSC_0185_zpsd4fef4e1.jpg

I have now made a front and rear cover roughly to the shape and size I will need, they are held together with 16mm stand offs.

DSC_0184_zpsf736dc7c.jpg

DSC_0183_zpsd01897ef.jpg

DSC_0180_zps6e90e0aa.jpg

DSC_0182_zps8b26c18d.jpg

I fitted the stepper to the case and gave it a try using the stepper focuser I made following the SGL automation design and code. The stepper motor is 12v 9.6 ohms motor, it turned the wheel with no problems and needed 22386 steps to turn the wheel one rotation, this took just under 6 secounds. I had to space the wheel 2mm from the hub to allow the motor to engage the wheel and allow enough space for the filters.

I am now looking at sensors for the home position, I have ordered a hall sensor from here, http://www.hobbytron...l-effect-switch and some 2mm magnets from here, http://www.ebay.co.u...984.m1439.l2649 to try. I have also ordered an easydriver board to drive the stepper motor as the focuser setup worked so well with it.

There is still a long way to go, I need to sort out the home position, I can then count steps to each fiter.

The punched wheel is bowed from the punching, I think I will need to machine it from scratch, I wil get it all working with this wheel first.

I will need to conect my skywatcher coma corrector to one side and the camera to the other, this will need M48 and M42 threaded adaptors making, but I am unable to cut metric threads on my lathe, so I will need to adapt some existing fittings or pay to have them cut!

Any thoughts/ ideas are very welcome :grin:

Thanks for looking

Jason.

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Lovely looking project. Thanks for posting the images and please do keep us up-to-date on how it's going.

This:

This all went together ok but left me the problem of holding the 1.25" filters in place. I went in to my local telescope shop and managed to get some old eye piece barrels (thanks Charls :grin: ), then parted them off into 3mm thick sections. They will be glued into the wheel later to screw the filters in.

is absolutely inspired. A very smart solution to a pig-awkward problem :)

James

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Well done Jason, very impressive. i wil be very interested to see how you progress.

Ian

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Thanks James/ Ian, I will keep things updated as I go, It might take a while tho!

The filter thread was a real head scratcher, I was originaly looking for some old filters to chop up and glue in but I couldn't find anything cheap enough.

The magnets and hall effect sensors arived today, so I have spent some time drilling some holes in the wheel to mount them.

I decided to put one magnet oposite each filter, this will confirm the filter is in position. I also added a single magnet as a home position, I am thinking I will program the Arduino to go to the home position every time there is a filter change, then use a step count to go to the selected filter, along with a magnet count to confirm movment. There will also then be a magnet activating the sensor if the wheel is in the correct position.

Anyone have any thoughts on that?

DSC_0189_zps07ade540.jpg

I have also cut an access hole in the cover so that I can change filters without taking it all apart, and made up a little cover.

DSC_0190_zps07fdcd30.jpg

DSC_0191_zpsba707fa9.jpg

Next thing on the list now is to setup the Arduio and sensors on a bread board and see if I can get it to work as I want....

Jason.

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That is looking really sweet. Lovely job on all the metalwork, I'm really rather jealous.

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Hi Jason,

why are you unable to cut metric threads on your lathe? You only have to convert your TPI

to suit your metric threads, change your 55 degree screw-cutting tool to a 60 degree tool and

you should be good to go.

cheers

Steve

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I was assuming that I couldn't cut metric threads on an imperial lathe?

I will look into it, I have not tried any thread cutting on it yet. I will have to give it a go over the weekend.

Jason.

Sent from my Nexus 10 using Tapatalk 2

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Looks like you are correct Steve, I have just found this:screw%20cutting%20big.jpg

Not sure if I have the relevant gears at home, I will have a look later.

Jason.

Sent from my Nexus 10 using Tapatalk 2

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I think I'd only go to the home position on power-up or reset. Once you know where "home" is, you can count magnet pulses (and reset counters as necessary to account for any slippage or misalignment) to work out where you ought to be which will make filter changes quicker.

James

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Lovely bit of machining Jason and this looks very much a Rolls Royce solution. I particularly like the cut out for access to change individual filters without dissasemling the whole wheel.

I'm currently getting the bits to convert my £ 60 Ostara 5 x 1.25" manual filter wheel to arduino controlled (same model as the OO fitlerwheel conversion by AstronomyMark. I shall use a friction drive, with stepper on spring tensioned swing arm. I was thinking of using standard opticla end of travel sensors like this from ebay - though was a little concerned about possible stray light - now thinking that the hall effect sensors and magnets might be a better idea.

There's quite a good sketch up on the AstronomyMark site which will make a fair start point, though it will need to be modded to allow for the magnetic sensors. Although I won't get quite the same accuracy with friction drive, the encoders should provide sufficient location accuracy to compensate. I will program mine to start from a home position, advancing in one direction only, keep a positional count/variable for filter location - worst case I should be able to lift the motor off and rotate back to home simply enough.

I think Gina did one of these last year, so might be worth asking how she got on with ASCOM control.

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I particularly like the cut out for access to change individual filters without dissasemling the whole wheel.

I have to admit that when I saw the original images I thought that nine filter spaces meant you'd never need to change one at all :)

James

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I have to admit that when I saw the original images I thought that nine filter spaces meant you'd never need to change one at all :)

I seem to be forever taking one out (mainly the PP742) to use on another camera - might have to buy a spare if one comes up on ABS or classifieds. This always seems to be a nuiscance on mine with two allen and three cross headed bolts per side - and for some reason I always undo the wrong side first - should've learned by now!

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Very nice piece of work there.

I will have to do something similar in the future once I have done everything else on my list :grin:

Will follow with interest.

Nigel

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I think I'd only go to the home position on power-up or reset. Once you know where "home" is, you can count magnet pulses (and reset counters as necessary to account for any slippage or misalignment) to work out where you ought to be which will make filter changes quicker.

James

That sounds like it should work James, I will give it a try.

Lovely bit of machining Jason and this looks very much a Rolls Royce solution. I particularly like the cut out for access to change individual filters without dissasemling the whole wheel.

I'm currently getting the bits to convert my £ 60 Ostara 5 x 1.25" manual filter wheel to arduino controlled (same model as the OO fitlerwheel conversion by AstronomyMark. I shall use a friction drive, with stepper on spring tensioned swing arm. I was thinking of using standard opticla end of travel sensors like this from ebay - though was a little concerned about possible stray light - now thinking that the hall effect sensors and magnets might be a better idea.

There's quite a good sketch up on the AstronomyMark site which will make a fair start point, though it will need to be modded to allow for the magnetic sensors. Although I won't get quite the same accuracy with friction drive, the encoders should provide sufficient location accuracy to compensate. I will program mine to start from a home position, advancing in one direction only, keep a positional count/variable for filter location - worst case I should be able to lift the motor off and rotate back to home simply enough.

I think Gina did one of these last year, so might be worth asking how she got on with ASCOM control.

I also looked at that type of optical sensor, and come to the same conclusion. I will have a good look at the sketch from your link, it looks like he has made a custom program for the PC too.

I think Gina brought a filter wheel and CCD package in the end and shelved her project.

I have to admit that when I saw the original images I thought that nine filter spaces meant you'd never need to change one at all :)

James

I hope I don't need more than 9 filters, they cost too much!!!!!!!

I thought it would be best to add the facility now than regret it later.

Very nice piece of work there.

I will have to do something similar in the future once I have done everything else on my list :grin:

Will follow with interest.

Nigel

Thanks Nigel' I will keep this thread updated.

Jason.

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Wonderful project - lovely job :)

I think Gina brought a filter wheel and CCD package in the end and shelved her project.

Almost right :) I bought a CCD second hand and decided to buy a filter wheel to go with it. My home made filter wheel was designed for use with a DSLR (seems daft when I think about it now :D ) and for 36mm unmounted filters. But I couldn't get the OIII 36mm filter and for a mono CCD camera I wanted 7 holes and mine only had 5.

There is a slight possibility that I might resurrect my home made wheel project. I'm going for a dual imaging rig using two mono CCDs. When I was doing my FW project I ordered Baader Ha, OIII and SII filters in 36mm unmounted size. I received the Ha and SII filters but FLO were unable to source the OIII one to match.

Edited by Gina

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I have been looking at the OAG I brought from FLO last week, it has the M48 thread on one side to fit directly to my coma corrector with a 1mm spacer. The other side is removable and has a male M42 thread. To save on space I am now planing to remake this part without any thread, I will then drill and tap 3 or 4 holes in it and bolt it directly to the cover of the filter wheel. Pics to follow when I get started.

Here is a drawing of the proposed layout, although the OAG is shown back to front :confused:

If it goes to plan I can use a 1.5mm shim on the coma corrector to get 55mm.

filterwheel2_zps82b8fdde.jpg

And this is a basic layout of the wheel and cover.

fliterwheel_zpsc1ffa37f.jpg

Jason.

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Hi Jason,

Glad you found the screw cutting chart. A Myford lathe... very nice.

Looking at your 2D cad drawing & what looks like cnc press turret work.

What soft & hardware are you using.

cheers

Steve

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You obviously know what you are looking at Steve, a fellow sheet metal worker perhaps?

It's an Amada Acute Cnc, using Amada's AP100 2D cad, and linia5 tooling software.

Jason.

Sent from my LT15i using Tapatalk 2

post-11618-136906055079_thumb.jpg

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I did not have any time to spend on this project over the weekend due to family comitments, but I have made a little progress tonight with the adaptor for the OAG.

DSC_0194_zpsfc42e838.jpg

This is the first part with the new self centering 4 jaw chuck I brought recently, I must say I am very happy with it :grin: .

It took a while to put all of the little grooves on the inside to disperse any stray light, they are only just visible in the picture.

Just need to index, drill and tap the 3 retaining screw holes and then part it off. That will then be ready. I will probably have it anodised black at a later date.

Jason.

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Very neat. Are the internal grooves all parallel then? I think I'd have been tempted just to put a fine thread up the middle.

James

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Thanks James, the grooves are parallel, I did think about a fine thread but I have yet to try my hand at cutting a thread on the lathe and didn't want to risk messing it up!

This is something I intend to have a go at in the very near future. I would like to cut the M42 thread for the camera adaptor myself if I can get it good enough.

Jason.

Sent from my Nexus 10 using Tapatalk 2

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You obviously know what you are looking at Steve, a fellow sheet metal worker perhaps?

It's an Amada Acute Cnc, using Amada's AP100 2D cad, and linia5 tooling software.

Jason.

Sent from my LT15i using Tapatalk 2

Nice one Jason,

I'm an ex toolmaker & now a manufacturing engineer.

In my time I have purchased 3 Amada turret presses One pega king & two pega queens.

Also purchased two Finnpower turret presses. All for other companies, not for my own gain, unfortunately.

Started my programming manually writing the gcode programes, being taught at the Amada training centre at Kidderminster, back in 1991.

I eventually used Radan's Radpunch for my progamming, but that was some 13 years ago. I now design special purpose tooling

using Solidworks 2013.

cheers

Steve

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Thanks James, the grooves are parallel, I did think about a fine thread but I have yet to try my hand at cutting a thread on the lathe and didn't want to risk messing it up!

This is something I intend to have a go at in the very near future. I would like to cut the M42 thread for the camera adaptor myself if I can get it good enough.

I'm just girding my loins to do exactly the same sort of thing :)

The problem that strikes me with cutting threads on a lot of astro fittings, especially for the beginner, is that often the length of the threaded section is quite limited -- perhaps only five millimetres. The margin for error before stopping the cut and bumping into another part of the component is therefore quite small. I'm wondering if it makes sense (or is even possible) to cut such threads with the lathe running in reverse, cutting the thread from left to right.

James

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Nice one Jason,

I'm an ex toolmaker & now a manufacturing engineer.

In my time I have purchased 3 Amada turret presses One pega king & two pega queens.

Also purchased two Finnpower turret presses. All for other companies, not for my own gain, unfortunately.

Started my programming manually writing the gcode programes, being taught at the Amada training centre at Kidderminster, back in 1991.

I eventually used Radan's Radpunch for my progamming, but that was some 13 years ago. I now design special purpose tooling

using Solidworks 2013.

cheers

Steve

Sounds good Steve, you have a lot more time in the trade than I do.

I have only done a limited amount of G code, I also went to Kidderminster for training with Amada!

I'm just girding my loins to do exactly the same sort of thing :)

The problem that strikes me with cutting threads on a lot of astro fittings, especially for the beginner, is that often the length of the threaded section is quite limited -- perhaps only five millimetres. The margin for error before stopping the cut and bumping into another part of the component is therefore quite small. I'm wondering if it makes sense (or is even possible) to cut such threads with the lathe running in reverse, cutting the thread from left to right.

James

I was talking to our machinist at work about exactly the point you have made yesterday. I need to cut an M42 thread 3mm long up to a sholder, he suggested turning the lathe by hand as it is sutch a fine thread!

I am going to try this method on some scrap material.

Jason.

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I was talking to our machinist at work about exactly the point you have made yesterday. I need to cut an M42 thread 3mm long up to a sholder, he suggested turning the lathe by hand as it is sutch a fine thread!

I am going to try this method on some scrap material.

That's not an idea I'd thought of. I've seen modifications involving putting a handwheel on the end of the leadscrew. I guess that might help in this situation. Given that I don't want to have to make the handwheel up before I attempt to cut my first thread I may well just make up a crank to go in the back of the spindle.

Or I'll ask on one of the model engineering forums. Now there would be a plan :)

James

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