Spectra data of PN acquired with Alpy as reference

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Sam Anderegg
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Joined: Tue Nov 20, 2018 3:50 pm
Location: Langenthal
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Spectra data of PN acquired with Alpy as reference

Post by Sam Anderegg »

Dear community,

I am running a school obvervatory in the city of Langenthal Switzerland (*), of course under light-polluted skies. This year I am happy to coach again a high-school student who wants to study planetary nebuale (PN) for his final thesis.

In 2016, I bought an Alpy 600 spectrograph from Shelyak incl. guiding and calibration modules, but only used it for first steps taking star spectra. Two years ago another high school student used our SA-200 grating for her final thesis. We will mount the Alpy behind a 36-cm RC mirror (f/8). We have a focal reducer and also recently purchased two extra slits (10 and 50 micron) to experiment with higher and lower resolution (R) than with the default 23 micron slit that comes with the guiding module. We will use Demetra for data acquisition and processing.

Question: would anybody share for training purposes their spectral data of PN acquired with such an Alpy spectrograph?

We havn‘t had the time and good weather yet but plan to record spectra of suitable and interessing PN (different excitation classes) over the next 3-4 months.

N.B.: for people with some background in physics, I can highly recommend the book „Physics& Dynamics of Planetary Nebulae“ by Grigor Gurzadyan, Springer-Verlag 1997.

Many thanks in advance and clear skies
—Sam

(*) http://www.sternwartelangenthal.ch (in German only)
Robin Leadbeater
Posts: 1926
Joined: Mon Sep 26, 2011 4:41 pm
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Re: Spectra data of PN acquired with Alpy as reference

Post by Robin Leadbeater »

Would the raw data from this observation be useful to you ?
https://britastro.org/observations/obse ... c36516d29a

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Robin Leadbeater
Posts: 1926
Joined: Mon Sep 26, 2011 4:41 pm
Contact:

Re: Spectra data of PN acquired with Alpy as reference

Post by Robin Leadbeater »

There are also some spectra of other PNe taken using the ALPY 600 in the BAA spectroscopy database
PNe_in_BAASDB.png
And Francois Teyssier's analysis of NGC6293 here might also be of interest
http://www.astronomie-amateur.fr/feuill ... C2392.html

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Sam Anderegg
Posts: 6
Joined: Tue Nov 20, 2018 3:50 pm
Location: Langenthal
Contact:

Re: Spectra data of PN acquired with Alpy as reference

Post by Sam Anderegg »

Dear Robin,

many thanks for your feedback and hints. I already stumbled across Francois Teyssier's page. I will also point the student to the BAA database to look at these low-res spectra.

Most interesting would be indeed your raw data of NGC 7026 from last September. I assume that you've been using the Alpy calibration module and the default slit with 23 microns. My personal e-mail is anderesa@gmail.com if you need it.

Clear skies
--Sam

PS: I have personally met Richard Walker several times since he is also Swiss. I will certainly arrange a meeting with im and my student.
Robin Leadbeater
Posts: 1926
Joined: Mon Sep 26, 2011 4:41 pm
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Re: Spectra data of PN acquired with Alpy as reference

Post by Robin Leadbeater »

Hi Sam,

Yes a standard ALPY 600 with 23um slit and calibration and guider units on a Celestron C11 with a focal reducer running at f5.5
(See the warning below about focal reducers. I use one because I am mainly interested in maximum sensitivity on faint objects)

I will email you a dropbox link with the raw images in the next few days. (I need to dig them out of the archive)

The potential problem with detailed analysis of planetary nebulae using the ALPY is the resolution is a bit too low to cleanly separate some of the key lines needed to calculate the parameters (Francois used a LISA with bit higher resolution) Using the 10um slit would give better resolution, matching than of the LISA but you lose a lot of light, particularly with extended objects like this.

Watch out for problems with chromatic aberration if using the reducer. An accurate flux calibration (response correction) is important if you are comparing the relative strengths of the emission lines. Any chromatism makes this more difficult, particularly with extended objects as the proportion of light at different wavelengths selected by the slit will be different when measuring the reference star compared with the extended target.

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Sam Anderegg
Posts: 6
Joined: Tue Nov 20, 2018 3:50 pm
Location: Langenthal
Contact:

Re: Spectra data of PN acquired with Alpy as reference

Post by Sam Anderegg »

Hi Robin,

great advice. I will discuss this issue when using a reducer with my student. Perhaps we won't use the reduce and instead work with different slits (10, 23 and 50 microns). His main goal is to learn, identify the main lines and enjoy this experiment. I warned him that it will be difficult to identify, measure and compare relative intensities of "key lines" such as the pair [S II] at 6716/6731 which can be used to estimate the density of the electron gas. But at least the student can learn the method from https://web.williams.edu/Astronomy/rese ... rcise3.php

Kind regards
--Sam
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