Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Rewarding objects for spectroscopy AND astrophotography

astrophotography beginner dslr
  • Please log in to reply
31 replies to this topic

#1 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 11 January 2020 - 11:03 AM

Having the star analyser installed in a filter wheel of my slow (f/9.4) and low budget imaging system https://www.cloudyni...-100/?p=9742246), I'm always in search for objects that are

1) astrophysically interesting,

2) bright enough (m<11 mag] and

3) are rewarding objects for doing low resolution slitless spectroscopy AND astrophotography (once the object is on the sensor, both aquisitions can be made consecutively without changing the system by simply turning the filter wheel)

 

The famous Blue Snowball (NGC 7662) is such an object: Low-ionisation emission regions and other microstructures can be imaged in this bright planetary nebula and a low resolution spectrum can be recorded due to its relatively small diameter:

 

Folie1.JPG

 

For plasma diagnostics the [O III] lines around 5000 Angstrom should be resolved. However, in my spectrum this is not the case. Only a shoulder is visible. The first derivative of the spectrum reveals the overlaped lines (keeping well in mind that star analyser spectra of non stellar objects should normally not be processed in this way: https://www.cloudyni...tive/?p=9721131

 

Folie2.JPG

 

After background and continuum subtraction the Balmer decrement was calculated. The excitation class was calculated by assuming that the area under the non-resolved [O III] lines can be used as a measure for the sum of N1 and N2:

 

Folie3.JPG

 

The same object recorded with superior equipment:

http://www.krannich-...pn.html#NGC7662

 

Here are some other examples of rewarding objects:

 

https://www.cloudyni...i-and-ngc-1555/

http://www.spectro-a...p?t=1392&p=6342

https://www.cloudyni...77-with-sa-200/

https://www.cloudyni...et-star-wr-136/

Hubble's variable nebula NGC 2261 (no star analyser spectra found so far) - to be recorded

The Pleiades (B and Be stars) - to be recorded

Thor's Helmet with its central Wolf-Rayet star - to be recorded

 

More suggestions are highly welcome! I'm slowly running out of objects....


Edited by mwr, 11 January 2020 - 01:38 PM.

  • robin_astro, giorgio_ne, GoFish and 1 other like this

#2 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 12 January 2020 - 07:37 AM

 

 

More suggestions are highly welcome! 

Eta Carinae but sadly not for us northerly observers though 

https://www.cloudyni...um-01-feb-2016/

 

and while we wait for the next bright  comet, perhaps  C/2017 T2 (PanSTARRS) will be bright enough ?

https://britastro.org/node/20186


  • mwr likes this

#3 gfamily

gfamily

    Viking 1

  • *****
  • Posts: 728
  • Joined: 29 Oct 2013
  • Loc: North Cheshire, UK

Posted 12 January 2020 - 07:48 AM

I'd have thought that Albireo or some of the other distinctly coloured binaries would make interesting targets - not necessarily for spectroscopic analysis, but to show how the spectra have different profiles.

 

https://www.skyandte...l-and-imagined/

 

I don't have a Star Analyser, but I bought a 100 /mm grating that fits in front of my 50mm dSLR lens and gives nice images (here of the Plough)

 

U Maj.jpg

edit for spelling


Edited by gfamily, 12 January 2020 - 07:53 AM.

  • mwr likes this

#4 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 12 January 2020 - 07:49 AM

Christian Buil's iconic shot of an "ordinary" star field in Perseus using the Star Analyser revealing the true nature of the stars it contains

http://www.astrosurf...lyser/wr5_2.jpg


  • JoeVanGeaux and mwr like this

#5 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 12 January 2020 - 10:20 AM

 

 

and while we wait for the next bright  comet, perhaps  C/2017 T2 (PanSTARRS) will be bright enough ?

https://britastro.org/node/20186

Excellent suggestion! The Swan bands should make a good target. I have just updated the comet files in my "Cartes de Ciel" programme and the brightness of C/2017 T2 should be around 9 mag. I will try to record a spectrum using the SA-200 as objective grating (as shown on your website). The last bright comet I have imaged was 46P/Wirtanen using my portable setup but at that time I wasn't aware of the fact that comets are actually good targets for low resolution spectroscopy (https://www.cloudyni...et-46pwirtanen/ https://www.cloudyni...as-polar-scope/).


Edited by mwr, 12 January 2020 - 10:21 AM.


#6 descott12

descott12

    Vendor - Solar Live View

  • -----
  • Vendors
  • Posts: 1,570
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 12 January 2020 - 05:02 PM

I had wanted to capture all the stars in M45. This is my first. I believe it is Alcyone but I am not 100% sure I was on the correct star. It should be a B7iii. My spectrum in not inconsistent with a B or B7 but I seem to have trouble getting deep absorptions in 4000-5000 A range

Attached Thumbnails

  • Alcyone-B.png


#7 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 12 January 2020 - 09:57 PM

Alcyone is a Be star which could explain the absence H alpha and perhaps weak H beta (The emission is probably fillling in the absorption at this resolution). Not sure what all those grey lines are as only the Balmer lines will be particularly strong in a B7 star but yes the spectrum does look rather "soft"  Was the seeing and focus ok at the time? 


Edited by robin_astro, 12 January 2020 - 09:59 PM.


#8 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 13 January 2020 - 02:01 AM

I had wanted to capture all the stars in M45. This is my first. I believe it is Alcyone but I am not 100% sure I was on the correct star. It should be a B7iii. My spectrum in not inconsistent with a B or B7 but I seem to have trouble getting deep absorptions in 4000-5000 A range

What a coincidence! Yesterday night I set up my SA-100 as objective grating (with FD 200mm) to get ready for PanSTARRS and the Pleiades were my first test object. Alcyone is indeed detectable as a Be star (the Fujifilm X-A1 is unmodified and the spectrum is uncorrected and quite noisy because I stacked only 6 frames but H alpha is definetly in emission):

 

Pleiaden_komb.jpg

 

A nice object. I need to get more frames and analyse the other stars of this cluster..... (Richard Walker has published the spectra of the main stars of this cluster in his Atlas).


Edited by mwr, 13 January 2020 - 08:57 AM.


#9 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 14 January 2020 - 01:57 PM

 the spectrum is uncorrected 

The spectra of B star Atlas (27 Tauri) and Be star Alcyone (25 Tauri) - the two brightest stars of the cluster -  were now rectified:

 

Pleiaden_spek2.jpg



#10 descott12

descott12

    Vendor - Solar Live View

  • -----
  • Vendors
  • Posts: 1,570
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 14 January 2020 - 02:33 PM

The spectra of B star Atlas (27 Tauri) and Be star Alcyone (25 Tauri) - the two brightest stars of the cluster -  were now rectified:

 

attachicon.gifPleiaden_spek2.jpg

Those look great. Nice job.



#11 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 14 January 2020 - 03:24 PM

Those look great. Nice job.

Well, the lines could actually look better. When using the SA-100 as objective grating the dispersion should be (theoretically) at 2.5 Angström per pixel (the measured value with RSpec of 2.4 A/Pixel compares well with this value). However, the line broadening due to spectral coma should be eliminated (no converging beam in the objective grating setup) and the maximum resolution is theoretically at 8.5 A (3.4 times the dispersion for a Bayer color filter array). I have measured an average FWHM of approx. 25 A of the Balmer lines, which is considerably higher than 8.5 A. Obviously, the achievable resolution is seeing-limited in my case :-(



#12 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 14 January 2020 - 04:01 PM

Another suggested target for this list for observers further south than me is R Aqr.  A crazy symbiotic star system consisting of a white dwarf and a Mira embedded in a complex nebula from previous interactions between the components and polar jets. 

https://en.wikipedia.../wiki/R_Aquarii

It is the subject of  pro-am monitoring currently and is showing lots of strong emission lines at the moment though they might be tough to resolve at Star Analyser resolution

http://spectro-aras....start=10#p13600

 

Cheers

Robin


  • mwr likes this

#13 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 18 January 2020 - 07:15 AM

 

 

and while we wait for the next bright  comet, perhaps  C/2017 T2 (PanSTARRS) will be bright enough ?

https://britastro.org/node/20186

Two days ago I tried to record a spectrum of PanSTARRS which is yet a rather small and faint object. A small coma with a barely detectable tail were visible (image was taken with an FD 300mm; 30 frames at 60 sec were stacked):

 

panstarrs.jpg

 

However, a spectrum was not visible when using the SA-200 in the converging beam of my 4-inch Maksutov-Cassegrain (20 frames at 400 sec were stacked; due to the movement of the comet the first order images of the stars and their corresponding spectra are blurred because it was stacked "on the coma" using a constant offset; the Wolf-Rayet star WR 4 was nearby and produced an emission line spectrum)

 

Panstarrs_spec.jpg

 

WR4.jpg

 

The integrated magnitude of PanSTARRS should rise from 9 to 8 mag in spring but I'm quite pessimistic that this rise is large enough to get a spectrum with my low resolution and slow (f/9.4) setup :-(

 

Has been somebody able to get a spectrum of PanSTARRS so far ? Neither the BAA database nor the ARAS database contains one.


Edited by mwr, 18 January 2020 - 07:19 AM.

  • descott12 likes this

#14 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 18 January 2020 - 07:49 AM

I've not seen any spectra of C/2017 T2 (PanSTARRS) yet but I plan to try (perhaps with the ALPY 600) if I get the chance. The background stars are a big problem with the Star Analyser where it is currently but perhaps it will be better in April when it moves out of the Milky Way into Camelopardalis

https://britastro.or...17t2_Page_1.png

 

Cheers

Robin


Edited by robin_astro, 18 January 2020 - 07:56 AM.

  • mwr likes this

#15 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 19 January 2020 - 05:31 AM

 The background stars are a big problem with the Star Analyser where it is currently but perhaps it will be better in April when it moves out of the Milky Way into Camelopardalis

https://britastro.or...17t2_Page_1.png

 

Cheers

Robin

Uwe Zurmühl has proposed to use a "beam blocker" construction to block the crowded zero order images of the field stars (Spektrum 55, 1/2019 p. 20): http://spektroskopie...Spektrum55.pdf

I will try it ...



#16 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 19 January 2020 - 12:58 PM

Here is 2017 T2 PanSTARRS from last night with the ALPY. Mainly scattered sunlight (divided out using a nearby G2v star) but some emission lines, particularly CN in the UV at 390nm

 

 

As seen in the guider (11x10s)

T2_2017_PANSTARS_guider_60x10s_20200118_crop.jpg

 

The raw sky subtracted spectrum 15x300sec (The faint spectrum above the coma is a field star which drifted through the slit during the exposure)

_C2017 T2 PanSTARRS_noflat_noinstresp.jpg

 

 

The calibrated spectrum and divided by G2v star

c2017t2panstarrs_20200118_855_Leadbeater.png

 

Cheers

Robin


  • giorgio_ne, RobboK and mwr like this

#17 descott12

descott12

    Vendor - Solar Live View

  • -----
  • Vendors
  • Posts: 1,570
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 19 January 2020 - 01:40 PM

Very nice. What does dividing by the nearby star do?



#18 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 19 January 2020 - 02:18 PM

 

 (The faint spectrum above the coma is a field star which drifted through the slit during the exposure)

 

Did you guide directly on the inner coma?



#19 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 19 January 2020 - 02:22 PM

Very nice. What does dividing by the nearby star do?

It is a similar to the technique used on planets and asteroids. Most of the light from the inner coma comes from the scattering of sunlight from dust so  dividing by the solar spectrum gives the reflectance spectrum of the comet dust.  I chose a nearby star of the same spectral type as the sun as a substitute as it also experiences the same atmospheric extinction as the comet.

 

Cheers

Robin


  • descott12 likes this

#20 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 19 January 2020 - 02:26 PM

Did you guide directly on the inner coma?

Yes. exposures were quite long (3sec I think) but small errors did not matter too much as long as the brightest  part of the coma stayed in the slit



#21 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 21 January 2020 - 04:59 PM

Beside the Pleiades there are more open clusters with Be stars as rewarding objects for astrophotography and objective grating spectroscopy (http://articles.adsa...ApJS...59..769S):

 

NGC 663 (letter S cluster)

h and chi Persei

alpha Persei cluster

 

and finally the Orion OB1 association subgroup 1a (northwest of Orion's belt) which is also a rewarding object for visual observers https://www.cloudyni...d/#entry7682143:

 

Astrophoto was taken using an Omegon MiniTrack; 10 x 1min; UHC filter; 50 mm Canon FD; suburban sky (18 mag/sqr arcsec):

 

 

orion_association.jpg

 

Omega Ori and 25 Ori are bright Be stars within this cluster whose spectra were captured using the SA-100 as objective grating (FD 300mm; 30 x 30 sec; rectified):

 

25_ori.jpg

 

omega_ori.jpg

 

Nearby is the beautiful carbon star W Ori:

 

https://www.cloudyni...copy/?p=9924925


Edited by mwr, 22 January 2020 - 03:51 AM.

  • giorgio_ne and descott12 like this

#22 mwr

mwr

    Vostok 1

  • -----
  • topic starter
  • Posts: 129
  • Joined: 12 May 2018
  • Loc: Germany

Posted 26 January 2020 - 07:00 AM

Although low in the sky at my observing site (25°), the planetary nebula IC 418 (spirograph nebula) is a rewarding object for slitless low resolution spectroscopy because of its small diameter and high surface brightness (SA-200; 10 x 250 sec.). The bright central star is visible in the center of the shell:

 

Folie1.JPG

 

Plasma diagnostics confirmed the low excitation nature of this object. Due to the non-resolved H alpha/[NII] lines, the balmer decrement was calculated using the H beta/H gamma lines:

 

Folie2.JPG

 

A comparison with the high excitation planetary nebula "blue snowball" nicely illustrates the differences between the excitation classes when H beta and H gamma lines were normalized:

 

Folie3.JPG

 

Another low resolution spectrum of IC 418 compares well with the spectrum presented above: https://www.cloudyni...copy/?p=9789039

 

Are some other spectra available that show the resolution of the H alpha/[NII] lines? BAA database contains only very few PN spectra.


Edited by mwr, 26 January 2020 - 02:20 PM.

  • robin_astro and descott12 like this

#23 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 26 January 2020 - 09:49 AM

 

 

Are some other spectra available that show the resolution of the H alpha/[NII] lines? BAA database contains only very few PN spectra.

There's one on Francois Teyssier's website with a LISA

http://www.astronomi...ry_Nebulae.html

Not sure where the fits file is though, perhaps in the ARAS database ?

 

Also a highly detailed professional one here

https://iopscience.i.../10.1086/133438


  • mwr likes this

#24 robin_astro

robin_astro

    Viking 1

  • -----
  • Posts: 867
  • Joined: 18 Dec 2005

Posted 26 January 2020 - 09:54 AM

Also one in the ARAS forum but again no fits file 

http://spectro-aras....it=ic418#p12101


  • mwr likes this

#25 descott12

descott12

    Vendor - Solar Live View

  • -----
  • Vendors
  • Posts: 1,570
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 26 January 2020 - 10:28 AM

Although low in the sky at my observing site (25°), the planetary nebula IC 418 (spirograph nebula) is a rewarding object for slitless low resolution spectroscopy because of its small diameter and high surface brightness (SA-200; 10 x 250 sec.). The bright central star is was visible in the center of the shell:

 

attachicon.gifFolie1.JPG

 

Plasma diagnostics confirmed the low excitation nature of this object. Due to the non-resolved H alpha/[NII] lines, the balmer decrement was calculated using the H beta/H gamma lines:

 

attachicon.gifFolie2.JPG

 

A comparison with the high excitation planetray nebula "blue snowball" nicely illustrates the differences between the excitation classes when H beta and H gamma lines were normalized:

 

attachicon.gifFolie3.JPG

 

Another low resolution spectrum of IC 418 compares well with the spectrum presented above: https://www.cloudyni...copy/?p=9789039

 

Are some other spectra available that show the resolution of the H alpha/[NII] lines? BAA database contains only very few PN spectra.

This is REALLY great stuff.  I always want to run out to my observatory after reading your posts....but it is 10 AM and broad daylight now!


  • mwr likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: astrophotography, beginner, dslr



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics