Neon lamp to set spectroscope

[athornett]

The camera used on the CCDSPEC is the QHY6 - this does not have an IR/UV cut off filter does it? I can't see it on specs when I look camera up on line

Andy

[athornett]

Hi Robin,

I will take another spectrum of the RELCO starter bulb with longer exposure to see if I can bring out more lines. Do you think my current identifications look about right?

Andy

[robin_astro]

4 hours ago, athornett said:

Hi Robin,

 Do you think my current identifications look about right?

Andy

Probably,  it is a bit difficult to tell from here.  I suggest identifying the lines that ISIS uses to calibrate the ALPY that I listed up the thread.

Your spectrograph has roughly the same resolution as the ALPY (R~500) and these lines are known to be reliable and give a very accurate calibration to better than 1A with the ALPY.  I have attached a list of wavelengths of the 13 lines. They correspond to lines identified in the spectrum by Richard Walker using his DADOS with 200l/mm grating (R 900).  If you identify a many of the lines in yourspectrum as possible and make a 3rd order fit,  any wrongly identified lines will immediately stand out as they will have larger errors.   

Cheers

Robin

ISISP_ALPY_lines.txt

[athornett]

On the RELCO starter spectrum below, my CCDSPEC spectrum is graphed against the ALPY spectrum from Three HIlls Observatory from Robin above, and I have marked the lines I identified together with those lines that ISIS use for calibration - this gives some more lines for me to use at LRO.

Andy

 

[robin_astro]

On 06/10/2018 at 12:46, athornett said:

The camera used on the CCDSPEC is the QHY6 - this does not have an IR/UV cut off filter does it? I can't see it on specs when I look camera up on line

Andy

Hi Andy,

It should not do, being a mono camera but there  definitely seems to be some filtering going on somewhere comparing yours and my spectra, which is limiting the response, particularly important at the blue end where there is often useful information. Perhaps it is  the AR coating on the CCD cover glass or the spectrograph lenses perhaps?)  The earliest ALPY's had an IR blocking filter but this was very soon removed as it gave problems with ripples in the spectral response.  The UV end was never blocked though

[robin_astro]

13 minutes ago, robin_astro said:

there  definitely seems to be some filtering going on somewhere comparing yours and my spectra, which is limiting the response, particularly important at the blue end where there is often useful information.

I guess the different sensitivities of the CCD in the two cameras (Sony ICX259AL compared with ICX674) could also be having an effect. (The ICX674 in my ATK 428 camera is known for its high sensitivity in the blue but the difference is perhaps greater than I would have expected.)  We will see better when you move on to  instrument response correcting your star spectra. 

Robin