Further fibre spectrometer tweaking!

[Gasman]

Hi

Noticing much better calibration now after more tweaking of the optics alignment in the fibre optic spectrometer. A very steady hand is needed as the slightest wrong movement gives you a blank screen. Using a Neon lamp I managed to id 5 lines and using their pixel positions managed to get a best 3rd order fit on screen for the equation Y=ax³+bx²+cx+d and came up with some odd values thus   a= 5.5427e-9

                                                                                                                                  b= -4.303e-5

                                                                                                                                  c= 0.1428

                                                                                                                                  d= 513.283

Anyway after inputting those figures into Spectrum Studio I found the following-

Energy saving lamp with some nice peaks round 546nm & 611nm

and the red laser (labelled as 650nm??)

So I`ve found a crappy old Huygens 24.5 mm fit (remember those ) eyepiece which I`m going to drill out and fit an SMA socket for the fibre and hopefully try it out on my ED80 soon

Cheers

Steve

[Merlin66]

The 546nm is probably the 5460.74 Hg line.

I got a 1.25" aluminium "plug" from the astro boot sale. drilled out nicely for the SMA (AsfA, p 212)

Onwards and Upwards.

[jnp]

Hi Steve,

I dabbled a while ago of mounting a single fibre optic into a 1 mm hole drilled on a clear plastic disc that fits in a t-thread tube.  In addition to holding the fibre optic, the clear disc allows you to use an eyepiece (or web cam) to see what the fibre is actually capturing. I'm sure it gets more complicated, but I didn't really persue this at the time, looses were too high using a DSLR. Perhaps try with a cheapo fibre, (don't ruin an SMA cable).

Curious to know how sensitive the sensor is?

Welcome to this bodging/DIY malarkey

John

[Gasman]

Hi John

Not sure how sensitive it is until I attach it to the scope, it tends to be in real time not sure if it will allow an image to build up, I suspect not so maybe only ok on brighter objects??.

I intend to use the flip mirror I was going to use with my Alpy until I got the guide module. After much measuring and modifying (the mirror lock grub wasn`t long enough) I came up with this setup -

with the mirror down I can focus the scope using the astrometric eyepiece (top connection) which has an illuminated reticle and then if I can keep the end of the fibre at exactly 32mm from the shoulder of the flip mirror I then lift the mirror up which SHOULD put the star on the fiber and in focus   ,well thats the theory.

I won`t be damaging the SMA cable. Its a shame its only 19" long, I`m tempted to fix the spectrometer to the mount but I`m pretty near the maximum load for my NEQ6!! Guiding will be done using the Alpy guide unit.

cheers

Steve