In the words of Southend's Ian - " Getting there"! - 'Seestar S30 Objective lens filter Spectrometer'.

 

1 - Tack bonding the 80 lines/mm. holographic printed
transmission grating film to the 3d printed holder

2- The film holding ring fixed to the grating holder
and gripping the grating firm and flat between them.

 

3 - The magnetic Seestar fixing ring being filled
with epoxy resin doped with iron filings.

" Putting together the separate elements is relatively simple using super-glue gel and two part epoxy resin putty. The grating was obtained from China via the internet. Whether an 80 lines/mm. grating was the right choice remains to be seen when we try it out on the Seestar.The lines per millimetre determine the angle of dispersion, the spread of the spectrum on the camera sensor and the resolution of the spectral profile. Currently, in the JPO stores, we have 100 lines/mm. and 500 lines/mm grating film awaiting future projects. 

1 - This image shows the grating film, which we had previously cut to size, having been tack glued to the 3d printed grating holder. You will note that the grating covers 50% of the full aperture. This was done to help the Seestar's goto, guidance and stacking algorithms, which might otherwise struggle if the full aperture was 100% covered by the grating.

2 - This image shows Kurt Thrust holding the spectrometer, the fixing ring having been bonded to the grating holder, gripping the film flat and firmly between the two. If you look closely, you can see the light from the lamps in the clean room displaying spectra after passing through the grating.

3 - Unfortunately, we did not possess any magnetic fibre for our 3d printer. As the rolls available on the Internet were much larger than our requirements and quite expensive, we decided to try to incorporate iron filings into the design, which might allow the spectrometer to be affixed, when required, to the Seestar using its integral magnets. Joel Cairo runs a fiscally tight ship! The image shows the fixing ring with its central groove now filled with a mixture of epoxy resin and iron filings. If this does not work, we will have to think again and Joel might have to get his wallet out!! The resin takes 24 hours to fully dry, so we shall have to be patient. If the ring does fix to the Seestar magnets, when we  try it tomorrow, we will stick it permanently, to the underside of the spectrometer, using super-glue gel.

The team at the Jodrell Plank Observatory are all getting rather excited as to whether this device will work with the little Seestar S30. Clearly, this spectrometer will not provide spectral profiles to the higher resolution we regularly achieve with our other 500 lines/mm QHY5-11 mono cam- spectrometer attached to the 127mm and 66mm telescopes at the JPO. It will however; benefit from being easy to set up and use, be full mobile and have accurate 'goto' and 'tracking-stacking' software, 

Once we have trialled the spectrometer and obtained satisfactory test spectral profiles for stars, we will be happy to freely share 3d printer STL files for the constituent parts of the 'Seestar S30 Objective lens filter Spectrometer'. - Karl Segin community out-reach coordinator at the Jodrell Plank Observatory.

All the staff at the JPO wish to congratulate Professor Michele Dougherty on being appointed as the new Astronomer Royal !!!!