lhires III low resolution vs Lisa

Ask your questions, show your results

lhires III low resolution vs Lisa

Postby David Cejudo » Wed Apr 25, 2018 5:54 pm

Hello.

I am new on this forum and eager to enter the realm of spectrography.
I have a Meade 12"LX200 that will use with a spectrograph but still not sure which one to buy.
In fact i am not sure if i will do low or high resolution.

I have read on the specifications of both Lhires and Lisa and i have a question.
How does Lhires behaves respect to Lisa when it is used with a low resolution grating?
Is it better to buy a Lhires III with additional low resolution grating so that i would have both low and high resolution in a single instrument?
Or is Lisa much better in low resolution than a Lhires with a low resolution grating?

And also, which is easier to use remotely?

Thank you.

David Cejudo.
Observatorio El gallinero.
El berrueco, Madrid.
David Cejudo.
Observatorio El gallinero.
El berrueco, Madrid.
David Cejudo
 
Posts: 5
Joined: Mon Apr 23, 2018 9:01 pm

Re: lhires III low resolution vs Lisa

Postby Francois Teyssier » Wed Apr 25, 2018 8:39 pm

For low resolution, LISA is by far the better one, without doubt
You can download spectra from the database: http://www.astrosurf.com/aras/Aras_Data ... iotics.htm
and compare them with the excellent PlotSpectra (Tim Lester)

François
Francois Teyssier
 
Posts: 1151
Joined: Fri Sep 23, 2011 1:01 pm
Location: Rouen

Re: lhires III low resolution vs Lisa

Postby Olivier GARDE » Fri Apr 27, 2018 10:13 am

I think like François. The LISA will be much better in low resolution than the LHIRES III working in low resolution because the optics of LISA has been particularly optimized to get weak target spectra.

You can see the 2 missions reports that we did on the confirmation of planetary nebulae with a LISA :

http://o.garde.free.fr/RapportMissionCALAI-2016.pdf
http://o.garde.free.fr/RapportMissionCalern2017.pdf
LHIRES III #5, LISA, e-Shel, C14, RC400 Astrosib, AP1600
http://o.garde.free.fr/astro/Spectro1/Bienvenue.html
Olivier GARDE
 
Posts: 844
Joined: Thu Sep 29, 2011 6:35 am
Location: Rhône Alpes FRANCE

Re: lhires III low resolution vs Lisa

Postby etienne bertrand » Fri Apr 27, 2018 10:27 pm

Hello David,

With my little experience i can say that it's different about your project. I have 1 spectro for low resolution ALpy600 for working on fint objects galaxy/qso, supernova, comete, maybe nebulae, and Lhires for an other project for working in high resolution on Be stars, VV Cep, RR Lyr,...

- The range for Alpy depend about your captor but you can work about 3650 to 7000/8000A, the slit is 23µm but you can buy 18µm, 15µm in option.
The slit is maximum 23µm for resolution = 550 after you can reduce the slit, the resolution is better but the flux is limited...

- With Lisa you can have biggers slits, and resoultion ~1000 but your spectr begging near 4000A. With Alpy you can working near 3650A.
Alpy is a less expensive that Lisa. I think it's your reflexion, Each spectros have advantages and differences. Lisa is a very good spectro, i think for fint objects is very interested with slit 50µm and bin2x2 Atik, you can have flux. With my Alpy i'm very happy too...

- With Lhires you can working in high resolution but with grating 150mm/tt you can working in low resolution near 500 or better because you have differents slit and now with ZWO ASI with little pixels you can have better resolution, BUT with greating 150mm/tt you can wokring on 2500A range. You can't catch H and K CaII with the same focus, the focus for big spectra begging near 4000A to 6500A or more if you have a big captor CMOS/CCD.

With Lhires you can do anything (but limitation low resolution). For more confort 2 spectros is interestaing.

It's my experiences... Have goods reflexions.
etienne bertrand
 
Posts: 648
Joined: Mon Aug 31, 2015 11:26 am

Re: lhires III low resolution vs Lisa

Postby David Cejudo » Sat Apr 28, 2018 3:26 pm

Hello.

Thank you for your information.
I will carefully study all the options. For the time being i will buy only one spectrograph, so the decision will take a bit of time.
Getting a Lhires III with an additional grating is my most probably option, but i am very far from being sure.

Thank you all!
David Cejudo.
Observatorio El gallinero.
El berrueco, Madrid.
David Cejudo
 
Posts: 5
Joined: Mon Apr 23, 2018 9:01 pm

Re: lhires III low resolution vs Lisa

Postby James Foster » Mon May 07, 2018 9:43 pm

To: David,

I Have both (LhiresIII & LISA) and will soon buy an Alpy600 and convert my LISA for IR only spectroscopy.
One thing to keep in mind if you go for the "LhiresIII only option," you will also have to re-tune the LhiresIII when re-fitting with different gratings.
The mechanical tolerances of getting optimized spectroscopy are very tight. Its not super hard, but you cannot just swap one grating for another without
going though at least some of the procedures on pages 13-23 of the LhiresIII users guide:

https://www.shelyak.com/wp-content/uploads/DC0004A-Lhires-III-User-Guide-English-1.pdf

I used to swap cameras off my LISA to use on my LhiresIII, but the hassle to readjust btw the two systems made me get another Atik 460ex and leave
them "permanently" attached to their respective spectroscopes.

James
James R. Foster
Lhires III (2400 & 1800 ln/mm Grat) Spectroscope,
LISA Visual & IR Kit Spectroscope,
Alpy 600, and Star Analyzer 200
James Foster
 
Posts: 236
Joined: Sun Jan 24, 2016 7:14 am


Return to Beginners corner

Who is online

Users browsing this forum: No registered users and 1 guest

x