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bojan
27-08-2009, 11:53 AM
Finally, after many months fiddling with various ideas and availability of parts here its is.
The design is based on and using some scrapped components and parts I managed to collect over the years in my drawers and boxes.

Basically, it is a variant of WPO design (http://www.astroman.fsnet.co.uk/newspec.htm)

It uses a small flat 45° mirror (1x3mm) coming from what seems to be the moving coil of the sensitive microamp meter (the type that uses reflected light beam as pointer-indicator). I have couple of those devices, the mirrors appear to be of very high quality.
I am focusing the light of the single star to that mirror (the plan is to place it in the focus of my MTO-1000A telephoto lens, but currently I am experimenting with 50mm lens, as visible on photos), from where the light bounces 90° into 50mm lens (Industar 50 from my old Zenit camera). collimated spectrum beam is to be reflected back by blazed grating (Edmund Optics most likely, still not purchased, currently I am using a piece of DVD) back into the lens, passing closely near the small mirror (but not striking it).
The secondary focus is some 15 mm further than small mirror, where I intend to place the camera, Phillips PCVC690K or something else with BW CCD chip.
What you see on the photos is a terrestrial (erecting) eyepiece (10x microscope actually), currently used for viewing the spectra.

Now the real work may begin ;)

sheeny
27-08-2009, 12:41 PM
Looks like an interesting project!

Al.

Merlin66
28-08-2009, 06:52 AM
Bojan,
Looking good!
A DVD is a 1200 lpm equivalent....
Keep up posted on developments.
Optometrics gratings are cheaper than Edmund and just as good.

bojan
28-08-2009, 11:30 AM
Ken, thank you for this info.
The prices are indeed much better than Edmund, and there is much more info available on their website about grating performance.
I think I will go for the smallest one for the start (12.7x12.7mm, it is suitable for the lens system I am using), 1200g/mm, 500nm blaze wavelength (http://www.optometrics.com//App_Themes/optometrics/pdfs/gratings/1200g_mm_Ruled_500_nm_Blaze.pdf), this one looks the best in terms of efficiency over the visible & IR spectrum, and it will cover the CCD sensor I plan to use (TC237, I have build the camera based on this chip a long time ago, was inspired by Audine design, but never really used it).
I can mount it inside the housing, just above the mirror, on short cables..

Merlin66
29-08-2009, 09:09 AM
Bojan,
As a multipurpose grating you may find the 600lpm a better starting point.
If you want more resolution you can always use it in the 2nd order.
Fulvio Mete's spectro does this very successfully...
http://www.lightfrominfinity.org/gli_strumenti.htm

robin_astro
01-09-2009, 06:09 AM
Hi Ken,

Using the second order is a possibility if you have plenty of light but remember that the efficiency of a blazed grating used in the second order will be much lower (perhaps 5 -10x)

Cheers
Robin