robin_astro

Watched it here in Cumbria for about half an hour when  the the skies cleared. Cloudy to the north now though.

Lumix LF1 30sec

It is indeed remarkable what can be observed with modest equipment thanks to modern sensor technology. With the addition of a relatively simple spectrograph it is even possible to verify the redshift of these and even more distant objects. Here are some quasars at  4.3-4.5 redshift (over 12 billion years light travel time)

https://britastro.org/observations/observation.php?id=20210411_134753_85f4b3ebf4faaefe

Cheers

Robin

There are many very high resolution spectra downloadable from the ESPaDOns spectrograph in the polarbase archive

http://polarbase.irap.omp.eu/

eg

but again the flux calibration is suspect as there are some differences in  the continuum shape between spectra and problems with overlapping echelle orders so probably only the normalised spectra are reliable

Robin

I assume it is Sirius A, the bright main sequence star you want not the faint white dwarf Sirius B? Do you need a high resolution spectrum or will a low resolution spectrum do?

I know what the spectrum should look like and I expected it to be simple to find a spectrum but it is proving surprisingly difficult.

It is not in UVES POP bright stars

https://www.eso.org/sci/observing/tools/uvespop/bright_stars_uptonow.html

and those in the ELODIE archive clearly have a poor flux calibration as it should look like an A1v star

http://atlas.obs-hp.fr/elodie/fE.cgi?ob=objname,dataset,imanum&c=o&o=sirius

There are some low resolution amateur spectra in the BAA and AAVSO databases but they have obvious problems, either poor flux calibration or poor wavelength calibration or both

https://britastro.org/specdb/

https://app.aavso.org/avspec/search

I will keep looking and see what I can find

Cheers

Robin

5 hours ago, dan_adi said:

With optical scope we have plate solving, auto guiding , but what about radio scopes?

Unless you have an array of linked radio telescopes several km apart, radio images are very fuzzy compared with optical images (because the wavelength is so much longer) so you don't need the same accuracy of pointing and tracking. For example with the setup you linked to (a 2.3m dish operating at 1.4GHz) a point radio source would look like an approximately 5 degree diameter blob so a degree or so out on pointing does not matter.

Cheers

Robin

The Star Analyser on its own is to produce spectra of objects that appear as points which rules out objects like the sun though you can take low resolution spectra of the sun using the star analyser by catching the glint of sunlight off a needle, for example here

http://www.threehillsobservatory.co.uk/astro/spectroscopy_14.htm

You can make simple slit spectrographs based around the Star Analyser for example my SEPSA design

http://www.threehillsobservatory.co.uk/astro/spectroscopy_18.htm

and a slit could be incorporated into my fully collimated "junk box" spectrograph

http://www.threehillsobservatory.co.uk/astro/spectroscopy_19.htm

These are low resolution designs which can be useful for faint objects, though the length of the spectrograph becomes rather unwieldy if you try to increase the resolution using a longer focal length lenses so most designs use higher dispersion gratings. like the ALPY for example which uses a 600l/mm grating

With any slit spectrographs for stellar spectroscopy you and have to consider how you are going to find the star and keep it in the slit. This is normally done using a mirror slit guider built into the spectrograph. All commercial spectrographs for the amateur include one as does the 3D printed Star'Ex and LowSpec designs, Here is an example of a complete system designed around a grating similar to the SA200

http://www.burwitz-astro.de/spectrographs/tragos/index.html

The Solex spectroheliograph, used to image the sun in specific wavelengths  is a very different instrument though which needs much higher resolution than an instrument based around the Star Analyser could achieve.

If you are interested in the kind of things an image taken through the  Star Analyser on a telescope can show about stars here is an example on my BAA page

https://britastro.org/observations/observation.php?id=20201216_234948_8cabda965bfe692f

Cheers

Robin

It is below the horizon at closest approach for us in the UK but it might be possible to pick it up later in the night. Using the latest  ephemeris from Horizons

https://ssd.jpl.nasa.gov/horizons/app.html#/

It rises above the horizon again for me in the North of England at ~01:30 and is 8 deg above my horizon at 4:30 UT but it will be ~mag 13 by then

Cheers

Robin

23 minutes ago, robin_astro said:

even if you just image the sky through a diffraction grating (or prism) each star produces its own spectrum against the sky background

 

The first stellar spectral classification systems were developed in the late 19th, early 20th century using spectra recorded using this technique by  the women of the  "Harvard Computer" team

https://en.wikipedia.org/wiki/Harvard_Computers

and you can see a modern example of an objective prism spectra here by Mike Harlow

https://britastro.org/observations/observation.php?id=20221003_080406_1603b0503cc5bcca

Cheers

Robin

19 hours ago, Sunshine said:

One would assume that Asside from our own stars light enveloping our solar system and whatever other background stars light is mixed in with the light of Sirius that it would be difficult to single out the particular spectrum from one particular star. Unless there is something I am missing, which I’m sure there is.

A slit can be used to separate out the object of interest and the subtraction of the sky background  measured above and below the star can be subtracted but even if you just image the sky through a diffraction grating (or prism) each star produces its own spectrum against the sky background as here for example using my Star Analyser grating

https://britastro.org/observations/observation.php?id=20201216_234948_8cabda965bfe692f

and the sky background above and below the star can be subtracted in the same way

https://britastro.org/observations/observation.php?id=20210406_144443_9e1c6a4cf219d14d

Cheers

Robin

I find Prof Ned Wright's cosmology FAQ is as good a  place as any to go when questions like  this come up

https://astro.ucla.edu/~wright/cosmology_faq.html

also his page here

https://astro.ucla.edu/~wright/errors.html

(Since the age of the internet and the apparent "democratisation of science" which appears to mean the promoting and rejecting of theories from people who do not have clue  and have not bothered to do the spade work have equal merit, the number of omissions he mentions from this list  which are too crazy to waste time on has grown exponentially)

As a UCLA professor of cosmology about the same age as me, he has been doing this stuff all his working life so hopefully should have as good a handle on this any anyone else by now 😉

https://astro.ucla.edu/~wright/intro.html

Robin

18 hours ago, Sunshine said:

I guess since it is an apparent feature of M31 it is associated with M31

We don't know this yet for certain. All we know at  the moment is that it is in the direction of M31. It could be nearby.  A radial velocity measurement might help hence the planned spectroscopic work as explained in the paper  (M31 as a whole is moving towards us at 300km/s)

"A spectrum of the [O iii] emission arc would offer radial velocity information which could establish an association with M31 and its halo. A follow-up spectroscopic study of this emission arc is ongoing."

They mention in the research note an ongoing spectroscopic study  to measure radial velocities. That should help clarify the origin. 

Robin

27 minutes ago, robin_astro said:

Is there a peer reviewed paper to go along with this discovery explaining the various alternative explanations touched on in the video?

Here we are (in RNAAS so not peer reviewed)

https://iopscience.iop.org/article/10.3847/2515-5172/acaf7e

Robin

Discovery of a feature near M31 would be more accurate. Despite the title, as the video explains (6.05)  it is not clear if it is actually associated with M31 or within our galaxy or even something in between.  Is there a peer reviewed paper to go along with this discovery explaining the various alternative explanations touched on in the video?

Cheers

Robin

Too low for me but here is another further north of a different type, ( a type 1a, an exploded white dwarf). SN 2022aaiq is  in NGC 5631 under the pole  in Ursa Major so the further north you are the better !)

https://www.wis-tns.org/object/2022aaiq

Discovered by amateur Patrick Wiggins three weeks ago, it is still currently  mag 14. It is quite close to the galaxy core though so might be an interesting visual challenge ? (I am not a regular visual observer)  Here is a typical image by Wim Cuppens

https://www.flickr.com/photos/snimages/52535076314/

and my spectrum (in black) overlaid on a matching type 1a spectrum

https://britastro.org/specdb/view_image.php?obs_id=12942

Cheers

Robin

2 minutes ago, robin_astro said:

The downside is you would have to scan across the wavelengths to collect the full spectrum ie over 100 separate exposures so pretty inefficient for single point astro targets.

It might be useful for survey spectroscopy of star fields though, picking out a set of specific wavelengths of interest without the issue of overlapping spectra you get with slitless spectroscopy.

Like this example wide field experimental Star Analyser objective grating setup I have been testing 😱  (anyone spot the Wolf Rayet star ?)

Cheers

Robin

20 hours ago, wimvb said:

 

“If you’re into astronomy, you might be interested in measuring the spectrum of light that you collect with your telescope and having that information identify a star or planet,” he said.

 

Difficult to say as the paper is behind a paywall

https://www.science.org/doi/10.1126/science.add8544

but from the abstract it seems to be an electrically tunable filter (like a monochromator) rather than a true spectrometer. Good for spectral imaging, though currently at low resolution of 3nm (R~150 similar to a Star Analyser for example). The downside is you would have to scan across the wavelengths to collect the full spectrum ie over 100 separate exposures so pretty inefficient for single point astro targets. It would be cool to be able chose the wavelength you wanted for narrow band imaging though instead of having a wheel full of filters.

Cheers

Robin

1 hour ago, vlaiv said:

That is effectively just compensating for mount performance. Over such large field, tilt component of seeing is random and averages to 0, so what is left is just due to mount.

This is to improve planetary visual views so the field is not very wide as planets are small (a few tens of arcsec). The fast bulk movement of the planet when viewing at high magnification  in poor seeing is significant and obvious even  with a static mount and this first order movement could be corrected using a tip tilt adaptive optics system working on the planet image via a beam splitter.  Potentially in principle the same technique could even be used to correct the next order field distortion to keep the planet round using a deformable mirror or lens and if you had a system which observed the planet using conventional lucky imaging to continuously produce an optimised image of the planet you could even use that to fully correct the visual view, though that would need a fast computer and a fully deformable corrector and (deep pockets!)

Of course none of this is useful for planetary imaging as you need a high speed imaging system to do this so it is easier to use these images for conventional  lucky imaging post processing

Cheers

Robin

Simple affordable tip tilt adaptive optics are available (which moves the whole field to follow the seeing which is effectively image stabilisation or fast guiding) This can be effective for small apertures where the atmospheric turbulence scale is larger than the aperture so in bad seeing can potentially reduce the PSF of star images in long exposures beyond what traditional guiding can achieve. I have not heard of anyone using this type of system visually but in any case it would only stabilise the image, not improve the sharpness of planetary detail. 

Cheers

Robin

It looks to be at the location of a  red object in images  but from the list of references apparently also appears in X ray source catalogues. Described as a globular cluster candidate in SIMBAD, though the note there suggests contradictory descriptions in the literature.

https://simbad.u-strasbg.fr/simbad/sim-id?Ident=2MASS J01350885%2B3031503

Previously catalogued at Vmag 17.3 so a ~4 mag brightening.  

Robin

Your description of the M27 dumbbell nebula is incorrect. This is not a supernova remnant as you describe but a planetary nebula, a  star not massive enough to produce a supernova which after the red giant phase has shed its outer layers in powerful stellar winds leaving the hot, though no longer energy producing core, a white dwarf which illuminates the surrounding gas with UV photons exciting it to glow in emission lines specific to the elements in the gas.

M1 the crab nebula with a pulsar, a spinning neutron star at its centre is a good example of a supernova remnant produced when a massive star explodes

Cheers

Robin

4 hours ago, Knight of Clear Skies said:

caused by ionized neon at lower altitudes

Nitrogen, not Neon.  The photos are still spectacular though. The nitrogen spectrum has a number of lines at the blue and red end but not in the green, which combine to produce the pink colour. This reference has a set of nice spectra and images showing the colours generated.

https://www.windows2universe.org/earth/Magnetosphere/tour/tour_earth_magnetosphere_09.html

Fun fact:- blue and red without green also produces the  pink colour seen in reflected sunlight from the JWST sun shield as in my spectrum here

https://britastro.org/observations/observation.php?id=20220327_125654_228ed4b0a22ce097

On the other hand it shows how close together the stars forming in this cloud are relative to the distance to our (next) nearest star

Robin

5 minutes ago, robin_astro said:

As well as the difference in wavelength with much less extinction in the IR due to dust, I think the Hubble image was taken in narrow band filters which would significantly dim the stars relative to the emission from the nebula 

Here is how Hubble saw the same region in the IR. The stars are all there 🙂

https://www.nasa.gov/image-feature/eagle-nebula-s-pillars-of-creation-in-infrared

Robin

As well as the difference in wavelength with much less extinction in the IR due to dust, I think the Hubble image was taken in narrow band filters which would significantly dim the stars relative to the emission from the nebula 

Robin