Andromeda galaxy M31, M32, M110

[JR]

My imaging session last week was worse than I thought, being ever so slightly out of focus as well as having a higher than expected number of cloud white outs.

This is a stack of 13 of the 41 exposures I took before pulling the plug on work in progress due to cloud.  They are back garden 25 second exposures at high gain 330 using a ZWO asi533MC pro camera for the first time, cooled to -11°.  I followed a ZWO recommendation for DSO gain/exposures (their driver includes 3 options which ZWO has evaluated  https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html).  Esprit 80ed f5/400.

I stacked using DSS and processed in Pixinsight.  6 minutes of exposures and three days to make progress with Pixinsight for the first time, following an excellent Youtube tutorial to fathom out this utterly incomprehensible but superb software.  All I will say is that it's much simpler than it seems when you know how to do it, but you could say that about solving the Rubik's cube. 

The image is as out of the camera, not cropped or a composite.  As I thought, it wasn't going to be a NASA web site astronomy picture of the day and there are still signs of earth clouds.  Colour seems to have vanished during the processing.  But there was more than I expected given the restricted data.  There is a hint of NGC 206 in the top right of the galaxy, which is a bright star forming region 10m years old, in a spiral arm of the Andromeda galaxy.

Some really clear weather soon please!

James

Sent from my iPad

[John Mills]

Hi James,

That's a really nice image you have there. These ZWO CMOS cameras are
pretty good and know a few who use them.

A shame as you say the focus is a bit soft, but overall the stars look
nice and round across the FOV. Have you ever considered motorising the
Esprit 80 ED focuser using a Lakeside? They are well worth the outlay
and using a program like FocusMax you will get perfect focus every time.
Just sit back and it does it for you :-)

Fine also on learning your way around PixInsight. I've never tried it
out, but my old PC runs Win7 32bit and PI only works on 64bit PCs.

No imaging from here. The weather is atrocious with strong winds and
rain. Been like this for over a week now and Sods Law decrees this will
always happen during a New Moon! Such is life ;-)

Cheers,
John

On 12/01/2021 10:09, 'JR' via croydonastro wrote:
> My imaging session last week was worse than I thought, being ever so
> slightly out of focus as well as having a higher than expected number of
> cloud white outs.
>
> This is a stack of 13 of the 41 exposures I took before pulling the plug
> on work in progress due to cloud.  They are back garden 25 second
> exposures at high gain 330 using a ZWO asi533MC pro camera for the first
> time, cooled to -11°.  I followed a ZWO recommendation for DSO
> gain/exposures (their driver includes 3 options which ZWO has evaluated
> https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html

> <https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html>).

>  Esprit 80ed f5/400.
>
> I stacked using DSS and processed in Pixinsight.  6 minutes of exposures
> and three days to make progress with Pixinsight for the first time,
> following an excellent Youtube tutorial to fathom out this utterly
> incomprehensible but superb software.  All I will say is that it's much
> simpler than it seems when you know how to do it, but you could say that
> about solving the Rubik's cube.
>
> The image is as out of the camera, not cropped or a composite. As I
> thought, it wasn't going to be a NASA web site astronomy picture of the
> day and there are still signs of earth clouds.  Colour seems to have
> vanished during the processing.  But there was more than I expected
> given the restricted data.  There is a hint of NGC 206 in the top right
> of the galaxy, which is a bright star forming region 10m years old, in a
> spiral arm of the Andromeda galaxy.
>
> Some really clear weather soon please!
>
> James
>

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[William Bottaci]

Hello James, even with the slightly out of focus stars it's not a bad
image at all, especially given the low number of frames.
You don't mention if you used any calibration frames...

I'm surprised you achieved such a wide field of view. The field of
view with your equipment (as stated) is: 1.08° square
Source: https://astronomy.tools/calculators/field_of_view/

And the difference between Messiers 32 and 110 is: 0.93°
Source: https://cads.iiap.res.in/tools/angularSeparation

and from an estimation it seems your image field of view is about 1.6° square.
Even with a reducer the 80 mm at f/7.5 (600 mm) would be too narrow.
Be interested how you managed that.

Thanks for sharing. William

On Tue, 12 Jan 2021 at 14:15, John Mills <ejm...@millseyspages.com> wrote:
Hi James,
That's a really nice image you have there. These ZWO CMOS cameras are
pretty good and know a few who use them.

A shame as you say the focus is a bit soft, but overall the stars look
nice and round across the FOV. Have you ever considered motorising the
Esprit 80 ED focuser using a Lakeside? They are well worth the outlay
and using a program like FocusMax you will get perfect focus every
time.
Just sit back and it does it for you :-)

Fine also on learning your way around PixInsight. I've never tried it
out, but my old PC runs Win7 32bit and PI only works on 64bit PCs.

No imaging from here. The weather is atrocious with strong winds and
rain. Been like this for over a week now and Sods Law decrees this
will always happen during a New Moon! Such is life ;-)
Cheers, John

On Tue, 12 Jan 2021 at 10:09, 'JR' via croydonastro
<croydo...@googlegroups.com> wrote:
My imaging session last week was worse than I thought, being ever so
slightly out of focus as well as having a higher than expected number
of cloud white outs.

This is a stack of 13 of the 41 exposures I took before pulling the
plug on work in progress due to cloud. They are back garden 25 second
exposures at high gain 330 using a ZWO asi533MC pro camera for the
first time, cooled to -11°. I followed a ZWO recommendation for DSO
gain/exposures (their driver includes 3 options which ZWO has
evaluated
https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html

Esprit 80ed f5/400.

I stacked using DSS and processed in Pixinsight. 6 minutes of
exposures and three days to make progress with Pixinsight for the
first time, following an excellent Youtube tutorial to fathom out this
utterly incomprehensible but superb software. All I will say is that
it's much simpler than it seems when you know how to do it, but you
could say that about solving the Rubik's cube.

The image is as out of the camera, not cropped or a composite. As I

thought, it wasn't going to be a NASA website astronomy picture of the

[JR]

Thanks very much for your comments John. Much appreciated, as is your advice about automating the focuser.

I had a look at the Lakeside last night and see it will operate with SkyX, which isn't always possible but necessary in my set up. I'm always nervous. The ZWO533 took some considerable coaxing before it would communicate, requiring the ASCOM platform drivers, unlike my little ZWO120 which seems happy with the ZWO ones. Then still not working there was a lucky find on the internet suggesting running SkyX in Windows administrator mode. Bingo! These things still aren't plug and play.

It looks very good. I'll start saving.

Sorry to hear your weather is as bad as ours.

best wishes

James

Sent from my iPad

> On 12 Jan 2021, at 14:15, John Mills <ejm...@millseyspages.com> wrote:
>
> Hi James,

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[JR]

Thanks for your interesting comments William.

I used 40 darks and 60 bias frames, and also applied flats/dark flats but found it introduced a ring of false colour so recalibrated without them and got a much better result. Must be how I did the flats though in particular I positioned the histogram as recommended.

I think the fov riddle is solved using the 400mm focal length for the Esprit 80 as it's f5 not f7.5. Interestingly, the calculated focal length comes out a little bit longer using ZWO's spec of the Sony chip at 3.76μm pixels. [FL = (pixel size x 206.3 conversion factor radians to arc seconds)/pixel scale]. Astrometry.net gives pixel scale of 1.89 arcsec/px.

Alternatively, the focal length is longer than spec if the pixels are really 3.76μm. I use the Skywatcher flattener that does not reduce. Possibly it raises focal length. Another explanation is the distinction between pixel pitch and size. The pitch is the distance between pixel centres, and size is the actual size, which has space around it. 3.66μm actual pixel size brings everything into line.

FOV is 1.58° x 1.58°. The chip is square at 11.3 x 11.3mm. This is very misleadingly described as a 1" chip in ZWO's on line literature and has fooled several buyers. Clearly it isn't 1" even on the diagonal. I read somewhere that the terminology harks back to what size objects you could get through the open neck of cathode ray tubes - a ships in bottles unit of measurement - and maybe a convenient marketing approach rather than a touch of nostalgia.

The square shape is unusual. It seems to be a good compromise between camera cost while still accommodating a useful range of objects especially on the diagonal. Luckily I think Andromeda and satellites on a slope oblige with a better composition. (The usual presentation is the other way up but it seems to work fine as it is and I think it's how it would appear naked eye from earth if you want verisimilitude.)

The images are also that much more 'close up' without having to crop and expand to fill the screen. Vignetting needs less if any correcting though flats will still be needed for dust. Another advantage of this camera is that ZWO has genuinely been able to eliminate amp glow from the chip.

The stats are in the attached Astrometry plate solve.

James

[William Bottaci]

Hello James, thank you for your reply.
Written in haste, it didn’t occur to me to wait before posting. For
some reason I thought you were using the Skywatcher 80 ED f/7.5. When
I had a clear moment and thought again I realised that it couldn’t be
no matter what the configuration. Checking this morning, 400 not 600
mm ... was my face red?

Stacking is just about only to do with reducing noise (of various
kinds), with dust removal and evening the field as additions. It can
be problematic if the same temperatures and exposure times are not
observed for some frames, as well as other less fundamental reasons.
If not too noisy then just the Lights will be satisfactory, especially
if cooling.

A square chip makes more sense than rectangular for astro-imaging.
Rectangular is mostly how we see (our eyes) the world, because of
gravity things tend to be laid out horizontally more than vertically.

Yes, the sensor diagonal goes back to ye olde TV video tubes. Call me
cynical but I think the specification is still around because it
sounds bigger than it really is; as you say. I just take a third off;
it varies a little but good enough.

The actual orientation of this galaxy (I like your word), as I imagine
it, is to draw a line from M32 to M110 (brighter spherical to fainter
elliptical) and it should point upwards to the 1 o'clock position,
actually slightly less/earlier. If you rotate your image to the right
(and because it's square you can) you'd be close.
Ah! Your plate solve says as much :}. I use the useful but quirky:
http://www.sky-map.org/

for this.

Altair imagers are known for amp glow. They say you should stack
images to remove this, but not always practical.

Thanks again, William

On Wed, 13 Jan 2021 at 09:34, 'JR' via croydonastro
<croydo...@googlegroups.com> wrote:
Thanks very much for your comments John. Much appreciated, as is your
advice about automating the focuser.

I had a look at the Lakeside last night and see it will operate with
SkyX, which isn't always possible but necessary in my set up. I'm
always nervous. The ZWO533 took some considerable coaxing before it
would communicate, requiring the ASCOM platform drivers, unlike my
little ZWO120 which seems happy with the ZWO ones. Then still not
working there was a lucky find on the internet suggesting running SkyX
in Windows administrator mode. Bingo! These things still aren't plug
and play.

It looks very good. I'll start saving.

Sorry to hear your weather is as bad as ours.
best wishes
James

2021-01-12

[Trev S]

Hi James,

The lack of clear skies is very frustrating. I took some data on M31 at the start of November and have been hoping to get some more, but over two months later there hasn't been a decent clear night. 

Based on the small amount of data I did manage to take, M31 seems to be quite a difficult subject.  The core is quite bright and tends to drown everything else out making it difficult to get detail in the outer arms. 

I might try a set of short and a set of long exposures and combine them using masks, if we get any clear skies by February that is!

My result so far, stretched a lot as you can see from the noise

[William Bottaci]

Hello Trevor, yes, noise shows when there's not enough light yet you
stretch as far as you can. It is well worth the effort though from how
it appears, and it is well framed. Well done.

Can I ask what (equivalent) focal length you used?
Thanks for sharing, William

2021-01-13

My imaging session last week was worse than I thought, being ever so
slightly out of focus as well as having a higher than expected number
of cloud white outs.

This is a stack of 13 of the 41 exposures I took before pulling the
plug on work in progress due to cloud. They are back garden 25 second
exposures at high gain 330 using a ZWO asi533MC pro camera for the
first time, cooled to -11°. I followed a ZWO recommendation for DSO
gain/exposures (their driver includes 3 options which ZWO has
evaluated
https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html

Esprit 80ed f5/400.

I stacked using DSS and processed in Pixinsight. 6 minutes of
exposures and three days to make progress with Pixinsight for the
first time, following an excellent Youtube tutorial to fathom out this
utterly incomprehensible but superb software. All I will say is that
it's much simpler than it seems when you know how to do it, but you
could say that about solving the Rubik's cube.

The image is as out of the camera, not cropped or a composite. As I

thought, it wasn't going to be a NASA website astronomy picture of the

[John Mills]

Hi James,

Yep, the Lakeside works fine with TSX. Either using the imaging package
which is an addon for TSX or with FocusMax. I use FMax, but it would
certainly work with other software such as SGPro which can do
auto-focusing. Of course, you can manually focus the Lakeside also. It
easier to push a button than turn a knob! Without doubt, its the most
useful piece of astrokit I have... I'd be lost without it ;-)

BTW, weather here is still terrible, very cloudy and quite cold!

Cheers,
John

On 13/01/2021 09:34, 'JR' via croydonastro wrote:
> Thanks very much for your comments John. Much appreciated, as is your advice about automating the focuser.
>
> I had a look at the Lakeside last night and see it will operate with SkyX, which isn't always possible but necessary in my set up. I'm always nervous. The ZWO533 took some considerable coaxing before it would communicate, requiring the ASCOM platform drivers, unlike my little ZWO120 which seems happy with the ZWO ones. Then still not working there was a lucky find on the internet suggesting running SkyX in Windows administrator mode. Bingo! These things still aren't plug and play.
>
> It looks very good. I'll start saving.
>
> Sorry to hear your weather is as bad as ours.
>
> best wishes
>
> James
>
> Sent from my iPad
>
>> On 12 Jan 2021, at 14:15, John Mills <ejm...@millseyspages.com> wrote:
>>
>> Hi James,
>>
>> That's a really nice image you have there. These ZWO CMOS cameras are pretty good and know a few who use them.
>>
>> A shame as you say the focus is a bit soft, but overall the stars look nice and round across the FOV. Have you ever considered motorising the Esprit 80 ED focuser using a Lakeside? They are well worth the outlay and using a program like FocusMax you will get perfect focus every time. Just sit back and it does it for you :-)
>>
>> Fine also on learning your way around PixInsight. I've never tried it out, but my old PC runs Win7 32bit and PI only works on 64bit PCs.
>>
>> No imaging from here. The weather is atrocious with strong winds and rain. Been like this for over a week now and Sods Law decrees this will always happen during a New Moon! Such is life ;-)
>>
>> Cheers,
>> John

[tcos...@gmail.com]

Hi James and Trev

Here’s one of M31 I produced back in 2017 with 7 hours 15 mins of LRGB and Ha imaging time. Interestingly, I used 5 minute unbinned subs (except for the Ha which was binned x2) with the Tak 85 refractor at f/3,9 and QSI 690 CCD for this image. In processing terms, there is little actual detail in the core so that can be scaled down relatively easily eg by using levels on a feathered core region, but more subs and imaging time are needed to bring out the fainter detail in the arms of the galaxy. I’ve also subsequently taken the sub-exposures for a 4 pane mosaic image of M31 using the Tak 85 but need to swot up on how to bring it all together to create a final image!

KR

Tm C

 

From: croydo...@googlegroups.com <croydo...@googlegroups.com> On Behalf Of Trev S
Sent: 13 January 2021 14:59
To: croydonastro <croydo...@googlegroups.com>
Subject: [croydonastro - 6741] Re: Andromeda galaxy M31, M32, M110

 

Hi James,

The lack of clear skies is very frustrating. I took some data on M31 at the start of November and have been hoping to get some more, but over two months later there hasn't been a decent clear night. 

Based on the small amount of data I did manage to take, M31 seems to be quite a difficult subject.  The core is quite bright and tends to drown everything else out making it difficult to get detail in the outer arms. 

I might try a set of short and a set of long exposures and combine them using masks, if we get any clear skies by February that is!

My result so far:

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[trevsie7]

Thanks William. This with my Esprit 80ed at f5, 400mm focal length. The camera was my ZWO ASI1600MM which has a sensor 17.6x13.3mm. I had a flattener fitted but no reducer.

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[JR]

Hi Tevor

I think you have good dust lane detail already and it looks well worth pursuing, if we ever get some good skies!

As for the core, I have two suggestions in the absence of shorter exposures.    Both adjust the earlier effects of processing, which is possible, mostly at least, in contrast to attempting the impossible of undoing saturated pixels.

The first method is a mask in Photoshop to isolate the core and adjust it down.

The alternative is to try a compound curves adjustment of this sort of shape, which will adjust down the brights and have a small effect on the rest.

 

If you want the incredible, this image was taken by Nico Carver with just over 15 minutes of exposure at a dark sky site 2 hrs drive from Boston.  He used a Canon 60d on a static tripod, with a Canon 200mm lens, at iso 3200, taking 992 exposures of 1 second each.  The galaxy was reframed every 50 frames.  Calibration frames were also taken:-

https://youtu.be/pXcRKoxTPVg

James

[JR]

That's excellent Tim.  If only I could do these things as well even with 7 hours.

Trevor:  What gain/exposure setting are you using for that image of M31?

On the question of the core, Tim, do you know if Pixinsight has a ready made 'process' or script to handle it.   I couldn't see one but that means nothing in a software labyrinth. I noticed in my first go with Pixinsight that the core was far less blown out using the auto 'nuclear button' STF stretch than Curves in Photoshop, so it may already be incorporated.  It would be handy if there were a separate off the peg process just for galaxy cores.

I have only ever done one mosaic and used Microsoft Image Composite Editor, ICE, on two fully processed frames.  Basic, but you couldn't see the join as Ernie used to say, or should I say it was a seamless experience?

James

Sent from my iPad

On 13 Jan 2021, at 20:46, tcos...@gmail.com wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/croydonastro/1806301d6e9ed%241f4f9b00%245deed100%24%40gmail.com.

<Andromeda Galaxy M31 Final November 2017 Tak 85.jpg>

[trevsie7]

James, the ZWO camera ASCOM software for my camera has three pre-set gain settings (Highest Dynamic Range, Unity gain, Lowest Read Noise), though it is possible to choose any numeric gain setting. I used the "Lowest Read Noise" setting which is gain=300, offset=50 as I find this gives the most data for the least exposure time with lots of light pollution.  I used this ZWO document as a reference, which basically says the LRN setting can give better results if more short exposure images are stacked

https://astronomy-imaging-camera.com/tutorials/cooled-asi-camera-setting-in-ascom-driver.html

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[JR]

Thanks Trevor.  Very helpful.

James

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On 14 Jan 2021, at 12:22, trevsie7 <trevs...@gmail.com> wrote:



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[JR]

Thanks very much John. Extremely useful to know that!

James

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