My first spectrum using SA100 and Rspec

batema (Mark) · #1 11-10-2012, 03:34 PM

Hi,

We have received our SA100 and Rspec program and I have decided to post what I have done to get some advice.

I used a Canon 400d with the SA 100 prime focussed up the back of the scope. The first image is taken with a William oOptics Flt 110 flourite and was a 2 second shot. I put the image in photoshop (Raw) rotated and cropped so I had star and right hand spectrum which is image 2 and then finally the PDF is of the Rspec program with the image loaded and spectrum produced.

I am probably asking now about callibration. I have found out that the star Formalhault is a A3V star so I have looked at sayiny the spike is the main star and I found it very hard (impossible) to identify specific feature that would allow me to callibrate another point so my x axis pixels become X axis wavelengths. I have not done anything else and know there are lots more to do but I thought I would post my start anyway as we want to include this term 2 next year into our senior physics course so I better get learning.

Mark

sheeny (Al) · #2 11-10-2012, 04:51 PM

G'Day Mark,

Nice first spectrum.

I'm a bit out of practice with my spectroscopy, so I'll stand corrected if I'm found to tell you untruths

.

It looks to me like there could be a few reasons combining to stop you from picking any features.

From your raw frame I suggest the SA is too close to the camera. The further in front of the camera you can get the SA the greater will be your dispersion. I know the Canon has a big sensor but to see -2,-1,0,1 and 2 spectra suggests its too close to see much detail.

There are a couple of lines evident in the second shot, probably Hbeta and Hgamma, but I think there are two problems with the spectrum. The first is that in the green and blue section the green and blue colours are fading towards white in the middle of the image suggesting the spectrum is overexposed. For a colour camera the brightest parts of the spectrum should be vivid colour like it is at the edges of your spectrum. The second is it looks like you have focussed on the star not the spectrum. The blue end of the spectrum is where I think the Hgamma line is visible is reasonably sharp, but less so towards the red end. Don't worry about it, we've all done it!

Looking at your spectrum I would guess the two little absorption lines on the left hand slope of the hill are Hgamma (left one -2200 on your chart) and Hbeta (right one - 2400 on your chart). Try calibrating with them and see how it goes

.

The double hump at the tip of the spectrum I think might be part of the camera response between the green and blue pixels.

On the RHS of the hill, there a possible line at about 3350 on your chart... I reckon there's a slim chance its Halpha, but more likely its the telluric O2 band

(Its usually more dominant than the Ha line - but then that might be right where the spectrum dies...).

Off to a great start!

Once you get a bit more dispersion (spread the spectrum out more) I think you'll find it easier to do all the stuff you need to do. It will be harder to over expose, easier to focus on the spectrum and then the detail will come.

Al.

batema (Mark) · #3 11-10-2012, 07:04 PM

Thank you Al. I know there is a lot to learn but am looking forward to the challenge. I have a spacer so will try that and yes I didn't even think about focussing on the spectrum. I had my Bat mask with a great focus on the star. I also have a QHY-9 and a DMK 21 just for more information. Thankyou for your response and assistance.

Mark Bateman

sheeny (Al) · #4 11-10-2012, 07:09 PM

Tha DMK 21 is exactly the type of camera the SA was designed for. I found I got best results with the SA 75 to 125mm in front of the camera. Once you get the hang of it, you don't need the 0 order image... you can push the dispersion and calibrate on features in the spectrum alone.

The QHY9 is a mono camera too isn't it? Could be worth a play with that too.

Al.

Rob_K · #5 12-10-2012, 12:31 PM

Hi Mark. Nice job starting out, you'll find it a very rewarding experience! Yeah, it looks overexposed to me too and that burns out the detail. Attached are the spectra of some stars, just taken with a SA & a NexImage webcam. No great shakes, among the first shots I did, but you can see a lot of lines that burn out when you overexpose. The bars at the bottom are done by cropping a section along the spectrum, reducing it to one or two pixels height, then expanding it to 20 or 30 pixels height.

Keep up the good work & keep posting your results!

Cheers -

batema (Mark) · #6 12-10-2012, 01:37 PM

Thanks Rob and they look fantastic. I can not wait to be able to produce something like that.

Mark

Merlin66 (Ken) · #7 12-10-2012, 01:47 PM

Practise, practise....practise
The more experience you gain the easier it becomes.
Focus on the spectrum; align the spectrum horozontally across the CDD.
Onwards and upwards.

robz (Robert) · #8 13-12-2012, 05:46 PM

Quote:

Originally Posted by Rob_K

Hi Mark. Nice job starting out, you'll find it a very rewarding experience! Yeah, it looks overexposed to me too and that burns out the detail. Attached are the spectra of some stars, just taken with a SA & a NexImage webcam. No great shakes, among the first shots I did, but you can see a lot of lines that burn out when you overexpose. The bars at the bottom are done by cropping a section along the spectrum, reducing it to one or two pixels height, then expanding it to 20 or 30 pixels height.

Keep up the good work & keep posting your results!

Cheers -

Hi Rob.
I have ordered my Star Analyser and am looking forward to getting it

.
Can you please explain how you obtained the larger and taller spectrum images at the bottom?Is this done in software? I'm a bit confused.

Merlin66 (Ken) · #9 13-12-2012, 06:07 PM

You can get the stretched spectrum as Rob said by grabbing a small section and just stretching to the height you like.
Which processing software will you use? Vspec (freeware) or Rspec (commercial)?

robz (Robert) · #10 13-12-2012, 06:23 PM

Hi Ken, I was thinking of using ISIS?

Merlin66 (Ken) · #11 13-12-2012, 06:59 PM

I haven't migrated to ISIS yet....
Others say it works well......

robz (Robert) · #12 14-12-2012, 11:57 AM

Yeah, it looks good on what it can do and it's free!.
We'll see what happens and I'll report on my findings.

Rob.