spectroscopy

[graham.hobart]

I am resurrecting my SA100 spect grid, with probably a colour ZWO 1200 and I am looking for tips re scopes. This will be a dedicated spect scope sitting on top of a solar scope, so does being an achro matter?
I did the calculator on the r Spec website and a sweet spot for spectra was an 80mm f6.5 skywatcher - but it is rather expensive
looking for cheap and cheerful as I have to buy rings also:thumbsup:

[graham.hobart]

Does having diffraction spikes as in an RCT affect the spectra?

[bojan]

Probably not enough to be a problem.

[StuTodd]

Hi Graham,

You already have DSLR camera gear?

You can use the SA100 as an "objective grating" by drilling a 32mm hole in the centre of a spare lens cap and inserting the SA100 into that, then put the cap onto a 135mm lens. You will get lovely results, be able to take fantastic multi-spectra images AND no need to buy a scope etc.

Piggybacking a DSLR then means you can track, remove the SA100 lens cap and use the lens for widefield etc etc.

As for your question, no, spikes won't make a difference to your spectra.

[graham.hobart]

Cheers all, excited to try anything as I don't have the time for multi hour long exposures anymore (or ever actually!!)
:thanx:

[Merlin66]

Graham,
The SA100 works well in any scope. Preferably f5 or greater.
No issue with spider diffraction.
Poor achromats can give rise to "fishtail" shaped spectral images. (See attached)
As you probably know, a mono camera will give better result.
Any other questions, just ask.

http://www.astronomicalspectroscopy.com/How_to.html

[graham.hobart]

Thanks Ken, I will ask if need be as I know we have an expert in our midst!!
Cheers. Will try for a better scope and mono then.
graz:thanx:

[StuTodd]

All I was trying to put across is that there is no need to buy a telescope just for using the SA100.

Stu

[Merlin66]

Stu,
No issue, the use of objective gratings is very popular, Uwe has shown some very good and higher resolution results used objective gratings.
The grating is very flexible......spectroscopy 101
It provides the opportunity of gathering Spectral data and practicing Spectral processing.
Check out our webpage for details and other ideas.

[tomfield]

Indeed, Uwe is a great example of someone who has shown what's possible with a Star Analyser.

Here, link (https://groups.io/g/RSpec-Astronomy/message/6932), for example, is a recent posting of his, including a pdf with a nice explanation of the science of the objects he's observing.

[bojan]

Linked pdf doc is interesting....
He was using 3 gratings in series, as visible on the image?
Or this is just the way he kept them between uses?


Also, grism arrangement is different, usually there is only one prism (this is my setup)

[Merlin66]

Bojan,
I'm pretty sure he only uses one grating at a time but multiple prisms to correct the different dispersions.

[Merlin66]

https://groups.yahoo.com/neo/groups/astronomical_spectroscopy/conversations/messages/13983

Bojan,
This link gives a better explanation.

[bojan]

That was my understanding as well..

The use of multple gratings results in very confusing spectra, it is impossible to separate spurious signals from real ones.