Alpha Crux Lo-Res spectrum

[Merlin66]

The attached image shows Alp Crux (B0.5iv) spectrum obtained with a 207l/mm grating mounted on an ED80 using ATiK 314 camera.
The dispersion is 16.6A/pixel
A work in progress, but shows the more prominent lines.
(A B0v comparison from Miles database and the B0 planck curve for info.)
Processed using BASS Project 1.9.7

[Terry B]

Very interesting Ken.
Going back to very low res. :D

[beren]

:thumbsup: very nice Ken .

[Merlin66]

Beren,
You should be able to obtain similar, or better! results using your grating.
The dispersion of 16A/pixel is low, a target of 10A/pixel may be slightly better.
Give it a go.......

[beren]

Have a bit of data to go through including Alpha crux from last week, be good to see what results I get. I used a mono ccd this time and I think from a brief process of Sirius the dispersion was 14A/pixel, I was using a 10" reflector ( not sure if this good with the spider vanes). Downloaded the bass project software too.

[Slawomir]

Hi Ken,

Have been experimenting with different exposures for capturing spectra. I was worried that getting into non-linear region in pixel response I will be distorting spectra, but it seems that I perhaps should go for longer exposures still?

Attached is an un-calibrated spectra with two different exposures. I am still not being able to identify specific absorption lines...loving the challenge! :-)

Suavi

[Slawomir]

I think I've got the calibration right. Can go and get some sleep now.. :-)

[Merlin66]

Suavi,
Yes, you could give it a lot more exposure without fear.
Yes, your calibration looks good.
I notice you haven't selected a binning zone (and background sky removal zones) - you should do this....Selection tab/Quick active and sub regions, use the mouse to select a strip across the spectral image.
I've made up a label set ....
Just unzip to the BASS Project folder and use the label icon (three from the top right) to load it.

[Merlin66]

Suavi,
What dispersion were you getting with your set-up?
Ken

[Slawomir]

Thank you Ken for your hints and help.

I will need experiment with adding your labels and properly orientating the spectrum and removing sky background.

Dispersion is about 4.5 A / pixel (need to work out the exact spacing to the grating).

[Merlin66]

Suavi,
After calibration BASS will give you the dispersion - below the chart, right hand side...
You can then compare this dispersion with your spacing (and binning if used) to confirm.
I use TransSpec.

[Slawomir]

Thank you Ken.

BASS indicated dispersion of 0.8899 nm/pixel, or about 8.9 Angstrom/px.

A bit busy at the moment, but will certainly continue learning how to properly do low resolution spectroscopy with my telescope.

Suavi

[Merlin66]

Suavi,
Understood!
The 8.9 A/pixel is a good starting point.
Onwards and Upwards.