Different star types - a challenge

[Richard N]

Appreciating that there are several main types of stars, what would be your suggested "best" example of each type that can be observed on a small telescope? Thought one of each might make a fun observing session. I'm in the UK.

Cheers

Richard

Edited July 28, 2021 by Richard N
Typo

[AstroMuni]

What scope do you have, Richard? And whereabouts do you live - as in a light polluted city or relatively dark skies are visible?

Edited July 28, 2021 by AstroMuni

[John]

Interesting challenge

This webpage describes the principle star types and gives examples that can be seen. Some categories are going to be harder than others !:

https://www.astronomytrek.com/list-of-different-star-types/

 

[AstroMuni]

Good link John.

@Richard N install a software like Stellarium or Night Sky app on Apple devices and look around for these.

[vlaiv]

It would certainly be interesting challenge.

I have one addition. It is not cheap when purchased, but can be made relatively cheaply that will enhance this type of challenge.

Ready made solution is called StarAnalyzer. It is filter like device that can be screwed in the eyepiece and will show you the spectrum of stars while you observe. It is transmission grating and it will disperse light from the star into a line spectrum. One can examine spectrum and try to identify prominent lines in it to go along with spectral type.

SA is a bit expensive, but there is alternative DIY type of solution that only involves access to laser printer and transparent plastic sheets used for overhead projectors. Transmission grating can also be printed and used in front of objective lens (at telescope aperture). One just needs to print as fine grating as printer will allow (say at 600dpi - lines that are 2-3 dots wide and separated the same).

View with Star analyzer

 

[Richard N]

39 minutes ago, AstroMuni said:

What scope do you have, Richard? And whereabouts do you live - as in a light polluted city or relatively dark skies are visible?

Thanks for your reply. I have a 127/900 reflector and I live in a Bortle 5 area.

 

[AstroMuni]

4 hours ago, Richard N said:

Thanks for your reply. I have a 127/900 reflector and I live in a Bortle 5 area.

Thats good news. You should be able to view a lot more stars mentioned in the list above. Good luck with your hunt!

[Zermelo]

Here's another site:  https://telescopenights.com/know-your-star-types-here-are-14/  that includes a couple more types with examples. 

[Zermelo]

6 hours ago, vlaiv said:

It would certainly be interesting challenge.

I have one addition. It is not cheap when purchased, but can be made relatively cheaply that will enhance this type of challenge.

Ready made solution is called StarAnalyzer. It is filter like device that can be screwed in the eyepiece and will show you the spectrum of stars while you observe. It is transmission grating and it will disperse light from the star into a line spectrum. One can examine spectrum and try to identify prominent lines in it to go along with spectral type.

SA is a bit expensive, but there is alternative DIY type of solution that only involves access to laser printer and transparent plastic sheets used for overhead projectors. Transmission grating can also be printed and used in front of objective lens (at telescope aperture). One just needs to print as fine grating as printer will allow (say at 600dpi - lines that are 2-3 dots wide and separated the same).

View with Star analyzer

 

This is a revelation to me, @vlaiv.

I bought a second-hand SA-100 a while back, but put it on the shelf until (or even if) I get a setup capable of taking half-decent images. I assumed that using it visually would just show some pretty rainbows that all look the same.

Can you estimate what sort of magnitude stars would show something interesting, with a 150mm newtonian (Bortle 4)?  By which I mean, a spectrum that is obviously weighted towards a specific colour, or even showing absorption or emission lines that can be seen with the eye?

[Starslayer]

1 hour ago, Zermelo said:

Here's another site:  https://telescopenights.com/know-your-star-types-here-are-14/  that includes a couple more types with examples. 

Nice link.  Lots to see and learn here. Similar to several others but I liked the immediate simplicity of this one. 

[vlaiv]

2 hours ago, Zermelo said:

This is a revelation to me, @vlaiv.

I bought a second-hand SA-100 a while back, but put it on the shelf until (or even if) I get a setup capable of taking half-decent images. I assumed that using it visually would just show some pretty rainbows that all look the same.

Can you estimate what sort of magnitude stars would show something interesting, with a 150mm newtonian (Bortle 4)?  By which I mean, a spectrum that is obviously weighted towards a specific colour, or even showing absorption or emission lines that can be seen with the eye?

I really don't know. I tried my SA200 few times on 8" Dob just to see how it works. I was able to easily see spectra of brighter stars (not sure how bright - but fairly bright like brighter than mag5-6).

Like you, I'm holding back to do spectroscopy with camera (hopefully soon), but will certainly have another go visually because I really like this challenge.

I do know few things that will make a difference if you decide to give it a try.

- focal length of eyepiece will magnify spectrum as well - higher magnification of spectrum - less bright it will be

- distance from eyepiece will affect dispersion - larger distance (like with 1.25" extension) more dispersion. This is a bit like magnification but there is a difference.

Increased dispersion will magnify only spectrum while it will keep star image the same. If you have poor seeing, you might want to use higher disperesion with longer FL eyepiece. In good seeing - it is best to magnify by eyepiece rather than change dispersion.

Maybe using zoom EP would be good idea - that would let you trade off detail and brightness (spectrum when magnified looses brightness as light spreads around).

- try both with and without dark adaptation. Eye has different sensitivity over spectrum in these two different "modes". Dark adaptation will make you more sensitive to light but you'll loose a bit of sharpness - which will make lines harder to see.

- Don't focus on star - focus on spectrum. Due dispersion star and spectrum don't come to focus at the same point. Dual speed focuser surely helps to focus on particular part of spectrum (spectrum can't focus all at once either as it is "tilted", and depending on level of dispersion - you might notice different focus across spectrum or not).