First night out with Star Analyser.

[Dave]

This will keep me amused for a while.

And I can do it on a fairly grotty night, like tonight.

Great fun.

[Merlin66]

Good start, but some issues....

Which camera are you using?

Was the zero order star and the spectrum sitting horizontal across the chip?

(you show banding in the Vega and Deneb which are not real - probably an artifacts caused by the camera alignment)

[Dave]

I knew it wouldn't be quite right the first time I did it.

I haven't compared these to "proper" spectra yet to see how good (or bad) they are. I was pleased just to get some sort of a result the first time I tried it.

Which lines in particular on those two are the extra ones?

I had the spectra crossing diagonally across the camera.

I used an 8" Newtonian with a flashed SPC880NC Webcam.

I was very surprised to find that the zero order star and the whole spectrum wouldn't fit in the frame together as the field of view was too small with the locking ring in place. I might try it without the locking ring in next time to get things a little bit more compact and fit in the field.

So yes, I need some more playing around to get things right.

I will have a look around and see if there is a tried and tested work pattern I could use to get better results. Unless you can suggest a link to one?

Dave

[Merlin66]

Dave, using a webcam which is only 3.5mm wide means that the grating has to be pretty close to the CCD chip to record both the star and the spectrum. 30mm or less.

Unfortunately all or most of the lines you've recorded are artifacts......

Next time you can check your spectrum against Richard Walkers excellent spectral atlas:

Richard Walkers Page

( down the bottom rhs)

Try to get the spectrum rather than the star in focus - Vega should show definate bands in the blue - when these are visible and as sharp as possible you're in business.

Check out Robin Leadbeater's webpage - he helped develop the Star Analyser and has some very good hints.

ROBIN'S ASTRONOMY PAGE SPECTROSCOPY

[Dave]

Ah! I have processed another exposure of Vega made at a slower shutter rate and much brighter. It seems better, but could still be improved further. I think I am heading in the right direction... Maybe!!!?

[Dave]

Now processed another brighter spectra of Arcturus.

So, I think I know what I need to do for next time I have a go:

1. Change the optical setup/shorter nosepiece/Use DSLR so I get the reference star in the same field of view as the spectrum.

2. Make the spectrum brighter on the screen (I was worried about doing this in case I lost the dark lines I could see on the monitor).

3. Process them gently (I should have already knew this) so that I don't produce dark lines that don't actually exist.

Oh, and check my results against standards when available just to make sure they are adequate and I don't upload rubbish.

Dave

[Merlin66]

Sounds like you're on the right track.

What imaging program are you using?

Registax for stacking?

Be very careful of applying any sharpening...usually it causes more problem than it fixes.

The colour stretch makes it easier to visualise the spectrum, but processing it through say Vspec to generate a profile makes it possible to calibrate by wavelength and then compare with reference spectra and even correct for the instrument response.

Onwards and Upwards.

[Stardog]

Dave, Using a Nikon D90 with a 100 Star Analyser I got a pretty spectrum of Vega. Take a look at the following link. You will be able to get this kind of results in short order. The exposure was 1.2 second 200 ASA. The distance from the grating to the chip is was about 100mm. It was not necessary to stack the image. All I needed to do was calibrate the image in Rspec and correct for instrument response.

http://groups.yahoo.com/group/RSpec_Real_Time_Spectroscopy/photos/album/1402669623/pic/975562612/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

[Dave]

There's lots to get involved with here...

I have sourced a short nosed webcam adapter, to try and get the reference star in the field of view. I will try my Nikon D300 using the inch and a quarter adapter as well, to see if that help as well. So much to try, so little time (or clear skies).

[Dave]

Tried to use the DSLR with the Star Analyser this morning and, as I thought, I couldn't reach focus as the camera is too far out when I use the inch and a quarter adapter on my Skywatcher Newtonian.

Looks like I will just have to persevere with the webcam me feels or have a try with my small refractor instead.

Unless someone can suggest a good way of attaching the DSLR to the Newt?