View Full Version here: : Adjustable Slit Added to Beamsplitter
25-08-2009, 08:37 PM
Further to Ken's modified Flip-Mirror beamsplitter I have 'hardwired' in an adjustable slit.
The slit was purchased from The Surplus Shed for US$15.
Top left - Modification (threaded unit) to allow the slit to thread directly into the Orion Flip-Mirror unit.
Bottom left -Attached unit.
Top right - unit with splitter up.
Bottom right -Unit with splitter in place.
28-08-2009, 08:34 AM
A neat arrangement!
As you know I've asked Surplus Shed to "modify" a T2 spacer to accomodate the adjustable slit; still waiting on the "good" news!
All you need to do now is machine a female T thread section for the front of the slit and you can mount it onto the scope and/ or use it to mount the spectroscope.
I'm assuming you'll use the adjustable slit as a diaphragm stop??
( I'm still in transit so no access to my stuff at home!!)
31-08-2009, 05:44 PM
I have produced a 1.25 nosepiece for the adjustable slit mechanism and have some 2" alum. bar to make a female eyepiece 'socket'. A small lathe and 15 minutes work does it. The hardest part was aligning the screw holes to hold it on:rolleyes:.
31-08-2009, 06:32 PM
A small lathe certainly comes in handy!!
When you finally put it all together, the V relief on the slit edge should face towards the grating to minimise reflections etc.
While you have the lathe out, you should consider making a larger knob for the adjustment screw. I use a 50mm diameter disk and the movement from 10 micron to 30 micron is only about 3mm on the circumference.
05-09-2009, 10:20 AM
Have now manufactured the grating holder/swivel.
Having made this and ordered the 30mm 600l/mm grating, I now think a 50mm grating would suit my set-up. Might need a scale up.
Plan is to use a 200mm f4.5 colimating lens with a 135mm f3.5 camera lens.
05-09-2009, 05:01 PM
Very professional! I'm sure the final assembly will be a credit to you and should work very well!! Are you going to use a micrometer for grating adjustment? I've just re-done the system on my classic spectro to incorporate a digitial dial gauge and find it very easy to use. Worth considering. (The adjustable stop sets the grating to the zero image, re-set the digi dial to zero then move the arm to the calibrated position for the various lines in the spectrum.)
Keep us posted as you progress....
07-09-2009, 07:39 PM
135mm lens has arrived.
Progress can begin.
2. lenses laid out
3. Image of slit by holding 135mm lens directly on 200mm and both focused at infinity. Cannon 300d unmod, ISO400, 1/60sec exp Jpeg, full frame ES globe.
Waiting for the grating to arrive.
07-09-2009, 09:11 PM
Oooooh man, you make it look so simple!!!
The layout ( what's the angle beteen the lenses?) looks ok.
You may want to use a laser to collimate/ align between the slit and the camera. The height of the optical axis should give some clearance on the body of the 135mm lens ( not much but just enough to allow the focus ring to rotate)
Machine up an adaptor for the camera(s) ( you can use the correct camera body "insert" to match the 135mm lens by breaking apart a x2 std camera adaptor for the camera) and make a 1.25" female port. This will allow you to use Webcams, DMK, QHY5 and almost any other camera that you can fit a nosepiece to. Remeber the back focus requirements vary!!!!!( I have spacers on mine)
I found you sometimes had to "tweek" the camera lens focus to get everything focused....depends on the camera body etc.
Certainly looking good!!
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