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Hughsie

Capturing Spectra for analysis

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Hi,

I have spent a lot of time reviewing tutorials and reading guides on spectroscopy and I am close now to pressing ahead with a night under the stars. In terms of gear I plan to use the following;

Celestron Nexstar 6SE; Star Analyser 100 and the ZWO ASI174mm camera

Just two questions, I have a ASI120mm and ASI1600mm, does one of these three cameras have a benefit over the other? Also, in regard to capturing the spectra I was planning to take short AVI's, then take flat and dark AVI's and then stack into Autostakkert to get a single image. Would that be the way forward or is there another better route to take?

Thank you in advance,

John

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John,

Your ASI 174mm with a 11.3 mm wide chip would be a good starting point.

I'd suggest starting without using flats and darks. The ASI 174 is a pretty "quiet" IMX 174 LLJ chip and spectral flats with a grating are problematic. 

I call using the gratings "Spectroscopy 101" - it gives you the opportunity to gain practise in acquiring spectral data and experience in processing the data.

I use and recommend John's BASS Project for spectral processing.

https://uk.groups.yahoo.com/neo/groups/astrobodger/info

 

 

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Posted (edited)

Hi John, I'm new to this but I to am using a star analyser 100, I've only used my zwo asi 224mc at the moment but plan to use my zwo asi120mm too. No need for darks or flat's.  Shoot 2 mins avi and stack 50 frames in autostakker3, I saved to tiff. I've still yet to process the four Spectra I imaged a few night's ago but Merlin66 is great when you need help. I'd say don't get hung up on which camera. Capture Spectra and learn the work flow in processing that. I found capture the easy part, lol. 

I'm using BASS Project as recommended by Merlin66 and others.

Edited by Nigella Bryant
BASS comments added
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Thank you both for your reply’s. Most helpful.

John.

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I’ve not done this for a while but from memory I think BASS project software does the stacking for you. Have you got a reducer for your 6se? I got excellent results with my SCT 9.25 + .63 reducer, an SA100 and my ASI174mm camera.

 

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Hi Chris,

Yes, I have the .63 reducer but wasn’t sure whether to use it or not. Seemed like a bunch of added complication what with back focus. Also, when using the calculator on RSpec-Astro to judge dispersion and coverage it didn’t seem to make much difference.

Happy to hear alternate views.

John

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John,

Adding  a reducer gives smaller star images, but doesn’t always give a increase in resolution.

Keep it simple for starters.......

Get some data, analyse it then decide......

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Chris,

At the moment BASS Project can stack images....but not directly from AVI files.

You can use AS3! to stack your AVI files to a format usable by BASS Project.

 

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4 hours ago, Merlin66 said:

Chris,

At the moment BASS Project can stack images....but not directly from AVI files.

You can use AS3! to stack your AVI files to a format usable by BASS Project.

 

Ok, I haven’t used it for a while so thanks for clarification. I have also used AS!2 for spectra images and often for other work.

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Posted (edited)

Taking spectra is like any other astro imaging. The key is to get the best stacked image. ie the sharpest spectral features (without software sharpening), lowest noise, full bit depth (ie stack the avi to give a 16bits mono image)  without any saturation in the spectrum, that you can to pass to your spectral analysis program.  With bright targets  planetary imaging techniques work well.  Spectroscopy of faint targets is more like deep sky imaging with longer exposures (Your ASI1600mm will be perfect for that when you are ready)

Cheers

Robin

Edited by robin_astro

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