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DIY Illuminated reticule....


stan26
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I don't think we have a "how to" for a home made illuminated reticule on here, appologies though if there already is one.....

I'm very much a newbie at the time of writing this, so more knowledgable astronomers feel free to correct me on anything for the benefit of other members reading this........

I have just got my first telescope, a skywatcher startravel 102 on a motor driven EQ3-2, and I want to do some astrophotography. Its become all to clear that I will need to perform a "star drift alignment" to get the best possible polar alignment. That means that I will ideally need an illuminated crosshair reticule eyepiece. These can be brought from most astro shops from about £50 upwards. I haven't got £50 spare right now, so after a little research to find out what others have done I thought I would make my own..........

For best results, a star drift align is performed at reasonably high magnification 200x plus maybe, although I have read about sucessful aligning using much less i,e 60x. I only have the standard skywatcher supplied EP's and a 2 x barlow to use. My highest mag EP is a 10mm so I used this for the project. Also its not the best quality EP so I don't mind mod'ing it, Il get a better quality EP in the future for high power stuff......

So, we start with the 10mm skywatcher EP.

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This unscrews into 2 sections. Note that the black half which contains the glass elements of the EP has a central narrower section. The end of the central narrow section is where I need my crosshairs to lay across tight up against it. This point in the EP I believe is called the "field stop" (pro's correct me if im wrong) The reason I need the crosshairs up against this is because it's at the point where they will be in sharp focus, very important obviously. No point having a big blurry cross.........

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In this next pic you can see a test ring and crosshair I made by cutting a bit off an old 35mm film tube. I pushed this down inside the EP to test where the "in focus" point was. If using the same skywatcher EP you won't need to do this because as i explained above it needs to be up agains the FS. Other EP's may vary...?

Note: I use 0.05 mm 8oz fishing line for the cross hairs. I have read about many other materials used, Hair, Copper wire, spidder web..!!

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Once I had established the focus point, material to make crosshairs from etc I then wanted to find a suitable object to use for my finished crosshair ring. The one in the EP above is ok, but I had to slice the ring and chop sections out to get it to fit. This then resulted in the ring distorting slightly at the join meaning the cross would go slightly out of align. So I searched around the home using my test ring as a guide for a suitable apeture screw cap/lid......

and found this!!

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Perfect!, I prefer colgate anyway! (which we had a spare)

So the toothpaste lid was removed. I use a junior hacksaw to cut it down to size and tested its fit. The lid was perfect being slightly tappered alowed for easier push fittment in the EP. It's a very snug fit!

Next was time to mark and cut slots in the ring for the crosshairs. To get the most accurate central cross possible I simply measured and cut out a card 26mm by 26mm square. I drew a line from one corner to the other to produce a perfect crosshair and marked the cut points on the outside of the ring.

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Next I used a very sharp stanley knife to make 4 x approx 4mm slits in the ring on my marks. I then got my 8oz fishing line and cut of two lengths about 5" long and taped a coin to each end to act as a weight to keep the line nice and tight whilst in the ring. Then slotted the two pieces of line into the ring slots with the coins dangling to keep tension. I then put some dabs of superglue where the line go's through the slots and left to dry.

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Whilst waiting for the glue to dry I decided to start work on the Illumination side. I have read various methods of illuminating the reticule. The most common DIY method seems to be having a little LED/bulb in the dew shield or near the secondary mirror on a newt. I was going with this method until I technition at my work over herd my idea's and gave me a piece of "optical cable" use in Mercedes Benz cars for there audio systems. From this point onwards I wanted to make the optical cable idea work......

Mercedes Benz 1mm Optical cable. light entering one end comes out the other. Shine a bright light in one end, a little bright light comes out the other end, Simples....! (this stuff can be got from ebay for like £3 for a few feet!)

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Next I needed to work out a way to get the opical cable into the EP. After much thought I decided to drill a hole through a thin point near the top of the EP under where the rubber eye cup bit sit's. 3 Reasons, 1, its the thinner part of the EP, 2 it means the OC can point down inside the EP between the glass elements section and the outer wall to illuminate the reticule without inruding into the field of view, 3, the rubber eye cup slots down over the 2mm hole I drilled to if all fails it can still be covered up and forgotten about!

NOTE: I drilled the hole at a 45 degrees downward angle to allow the OC to be pushed in with out having to make sharp turns which could damage the glass tube of the OC. There only designed to bend so much.......

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Next I attatched one end of the OC to a bright LED light. I used a small block of rubber to sit on top of my led torch and drilled a hole through it for the OC to go through. This means the OC is pointing straight down at the light path to gather as much light as possible. I would be very difficult to attatch the OC point straight at the light source with this aid. I then taped it all together,

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The other end then simply go's into the hole in the EP and is pushed down the EP untill the desired lighting of the reticule is met. I tight fit drilled hole is ideally needed so that the OC can be wedged in at a particular depth to give the desired amount of illumination.

Below you can see the OC in the EP (light switched on)

IMG_2380.jpg

Edited by stan26
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Below you can see I have made 2 slots in the rubber cup to make a little flap that lifts up to allow access to the drilled hole for the OC.

IMG_2381.jpg

Once the glue on the reticule is dry, align the reticule over the EP and push it down into the EP untill the cross hairs push up agains the central field stop. Any slackenen or distortion of the crosshairs during this proceedure is corrected by pushing the ring a little further down the EP to take up the slack, so the cross is up tight against the FS. Another point to note is that the toothpaste cap I used is thin enough to make a ring that still allows enough gap for the OC to be pushed through.

Then screw it all back together and you have the MK1 STAN-ASTRO ENGINEERING Illuminated Reticule Eyepiece!! lol.

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very poor pictures taken on my phones cam, but gives you an idea of how it looks through the EP.

This one in daylight.

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this one with the front lens cap on the telescope (so full blackout) and with the Optical cable pushed fully in (max brightness) Obviously this would probably be to bright for looking at the night sky, Its just to show you that the cross hairs show up nicely in the OC's ambient lighting inside the EP. We would retract the cable slightly to dim the brightness for actual sky viewing....

reticule1.jpg

Is that dust on the prism..? hmm anyway..

I have tested it in my garden at night and it all seems to be fine. Getting the correct brighness is a simple matter of pushing the OC in a bit further or pulling it out. I will eventually tweek everything using different colour led, permanately fixing the optical cable in the EP etc etc and will apdate this thread accordingly....

I hope that someone out there may find this helpful someday, hense I though I would share it on the forum.

Apologies for spelling....

Regards

Stan.:glasses1:

Edited by stan26
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Stan this is great...

You know.. there's one thing that I've really noticed since joining this forum.. and that is ingenuity is still alive and well!

I've become so used to the "buy new, throw away, don't fix" world we've become that I'd forgotten about these "lost skills". I bought one of these only last week!

I read an article in "The Metro" the other week about anyone under 35 having no idea what DIY is, as it's dying out apparently. (Talking of which one of our great inventors, who I crossed paths with many years ago, Ron Hickman (The Workmate, Lotus Elan) passed away this week) :).

I'm so pleased to see ingenuity lives on... nice one Stan :glasses1:

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Stan this is great...

You know.. there's one thing that I've really noticed since joining this forum.. and that is ingenuity is still alive and well!

I've become so used to the "buy new, throw away, don't fix" world we've become that I'd forgotten about these "lost skills". I bought one of these only last week!

I read an article in "The Metro" the other week about anyone under 35 having no idea what DIY is, as it's dying out apparently. (Talking of which one of our great inventors, who I crossed paths with many years ago, Ron Hickman (The Workmate, Lotus Elan) passed away this week) :).

I'm so pleased to see ingenuity lives on... nice one Stan :glasses1:

I guess I'm an exception to that article being 26 years of age. It is sad to se the lack of ingenuity these days especially in youngsters. I'm lucky enough to have been brought up in a very oldie world hands on family with my dad and grandad both being very handy in a workshop environment. I've constantly had a project on the go around home since I was a very young lad. And it'll carry on by the time my little boy is 13 he'll be able to service the family car!

What ever happend to the great British ingenuity the once lead the world....:p

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  • 8 months later...

Great write-up and awesome project. Being the other side of 40 I do fall into knowing what DIY is. Not as good as this but I did cobble together a new mount for a red dot sight to allow it to replace the poor viewfinder that came with my telescope.

Yes the spirit of innovation is still alive.

Well done Stan.

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  • 10 months later...

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