New HM Spectroscope Improved

[theodog (Jeff)]

Hi All,
Given some time and availability of an optical fibre (JayCar, Lismore), I have added it to the spectroscope from,
http://www.iceinspace.com.au/forum/s...t=44620&page=2

Optical fibre is from digital conection between entertainment devices. It is about 1m long and seems to be 1mm dia.
The fibre dumps directly onto the slit.

Tests should begin tonight, sky being clear.

[sheeny (Al)]

Looks interesting, Jeff!

Keen to see how it goes.

Al.

[Merlin66 (Ken)]

Well worth trying. You'll probably find with the fibre optic that you'll lose light going through to the collimator. The exit beam will probably be around f2-f3.
(Holding a focussed star on the end of the fibre is a bit of fun as well!!!!)

[theodog (Jeff)]

Originally Posted by Merlin66

Well worth trying. You'll probably find with the fibre optic that you'll lose light going through to the collimator. The exit beam will probably be around f2-f3.

I was mostly worried about the loss through the fibre. I have included a spect of an energy saver light. Average of 20 1sec exp through a hand-held 200mm lens at f4.5. 3m away. Meade DSI camera.

Originally Posted by Merlin66

(Holding a focussed star on the end of the fibre is a bit of fun as well!!!!)

Oooooh yeh. I think this could be the down fall. I am going to try a seperate guidescope, but have to keep my current configuration for an activity with my students ( I'll probably get them to use the SA). Possibly 2-3 weeks.

[Merlin66 (Ken)]

From what I've seen, providing there are no serious kinks in the fibre, the transmission losses are pretty low ( that's why they are used for broadband) The losses occur on the inlet and outlet. For a spectroscope application the f ratio's and NA really need to be considered.
( the resolution of the flouro spectrum isn't as good as you achieved previously??!)
BTW I've just finished the conversion of a Vixen flip mirror to a beamsplitter. ( The vixen has a SOLID 2" nosepiece and T threads on the body at both the guide and imaging side - ideal for connecting to spectroscopes etc) removed the original mirror and drilled a 12mm hole through the "flip" platform then placed a 70/30 beamsplitter ( Ex our friends at Surplus Shed!) on the front. Aligned with a laser, using the small 1.3mm grub screws on the platform and it looks good! Much better than the Meade OAG design or the Vixen cube option.
(There's quite a series of postings from Richard on the Amateur Spectroscopy forum re fibre optics)

[theodog (Jeff)]

Originally Posted by Merlin66

( the resolution of the flouro spectrum isn't as good as you achieved previously??!)

I have included a S. dump comparing results from the optical fibre test and an older spec of Daniel's (jinxta) neon globe assembly.
The resolution seems very close as far as A/pix, not sure about the width of the lines.
The optical fibre feeds onto the slit and I figure the light beam should be something close to parallel

[theodog (Jeff)]

Originally Posted by Merlin66

BTW I've just finished the conversion of a Vixen flip mirror to a beamsplitter.

Looks very interesting. Any chance of a parts list (inc. numbers)?

[Merlin66 (Ken)]

jeff,
The 2 A/pix is the dispersion not resolution. So if you are using similar gratings I'd expect them to be similar, the resolution is the FWHM measure of the lines and in one of the early spectra the yellow lines were almost resolved; I didn't see this in your latest?
I'll take some photos of the modified Vixen flip mirror set-up.
I paid 50GBP for the Vixen (new) and I think about $8 for the beamsplitter.

The beamsplitter was a standard 70/30 <1mm thick item from Surplus Shed - I'll find the #
The only "trick" was to soak the actual vixen mirror in acetone over night to get it to "lift off" the plate' it's a front surface mirror 30 x 35mm x 1mm thick stuck in place with double sided tape and rests on four very small grub screws ( 0.9mm hex wrench) - these can be used to align the mirror. The T thread attachments makes it a more robust ( and shorter connection between the scope and the spectroscope)