first light for Alpy 600 at THO

[robin_astro]

First light for my new Alpy 600 spectrograph.

Nothing too exciting I am afraid, just the spectrum of sunlight filtering down through the clouds

Wavelength calibration was done using Ne and Ar lines from a fluorescent light starter

More to come once we get some clear skies

Cheers

Robin

[andrew s]

Looking forward to seeing more Robin. What extra bits did you get - guide unit? Rergards Andrew

[the rev]

Looks good Robin, hope it clears so you can show us more tests.

Kate

[robin_astro]

Looking forward to seeing more Robin. What extra bits did you get - guide unit? Rergards Andrew

Yep I got the guide unit. (I have been spoilt with mirror slit guiding on the LHIRES and did not want to do without it, particularly as this is for faint object work)

A lower cost alternative though could be to use a modified flip mirror ahead of the base Alpy 600 unit with a beam splitter in place of the mirror and view the reflected portion of the beam with a camera as Ken developed for the L200. A further development of that could be to use the flip mirror mechanism to move a diffuser screen up against the back of the beam splitter and feed light from calibration and flat lamps via drilled holes on the bottom of the flip mirror.

Cheers

Robin

[Gasman]

Looks very promising Robin,looking forward to seeing what you can do with it.

Steve

[Merlin66]

Look forward to hearing more about the ALPY.....

Robin, I'm not sure the diffuser idea will work...a second flip reflective surface on/ near the rear of the drop down beamsplitter flip plate and a transfer lens ( to maintain the f ratio) would probably work better.

For the new OVIO reflective slit holder I've added a small flip mirror which accepts the light (via a transfer lens) from an exterior reference lamp source.

This is in testing as we speak.....

[Merlin66]

Robin,

How linear is the spectrum with the grism? Correction of the line curvature? (Use the smile command?)

[robin_astro]

Look forward to hearing more about the ALPY.....

Robin, I'm not sure the diffuser idea will work...a second flip reflective surface on/ near the rear of the drop down beamsplitter flip plate and a transfer lens ( to maintain the f ratio) would probably work better.

For the new OVIO reflective slit holder I've added a small flip mirror which accepts the light (via a transfer lens) from an exterior reference lamp source.

This is in testing as we speak.....

Hi Ken,

I think it should work ok. It would essentially duplicate the approach taken by Shelyak in their calibration module which inserts a side illuminated screen into the light path with the diameter chosen to simulate the focal ratio.

http://thizy.free.fr/shelyak/alpy/DC0018A_Doc_Alpy_Calibration_EN.pdf

This saves using any additional optics.

Cheers

Robin

[robin_astro]

Robin,

How linear is the spectrum with the grism? Correction of the line curvature? (Use the smile command?)

Hi Ken,

It needs a 3rd order fit to get good calibration over the full range ie a minimum of 4 well spaced lines. Balmer lines in an A star could be used but a Ne Ar calibration lamp more convenient. Once the calibration equation is determined it may be possible to use this plus a single calibration point depending on the temperature expansion coefficient.

Cheers

Robin

[robin_astro]

Oh and yes, a smile correction could be used but it is only normally needed for extended objects as a star spectrum is very narrow

Robin

[Merlin66]

Hmmm

I need to get my head around that screen idea....

120sec for a calibration sounds very long!

(I tried a screen but couldn't get a "focused" beam....maybe if the lamp to screen distance is set and the screen is reflective enough....let me mull that over....)