M33

[Kevin Phillips]

Yesterday I planned to capture M33 fir the second night running.  Eq5 mount, 900mm ed celestron refractor. ZwoISA294 colour tec camera. Guided. Also used an alrair cut off light pollution filter that also helps to keep the stars nice and tight and blotted out. 

The scope was also on a pillar this prevents  the camera from geting stuck on one of the legs.  (As it did so in the past.). 

18 light frames. 40 flat, 40 dark flats and 40 darks. It was process through startools. Thanks to Willam who also assisted me in my efforts  second tine I used a pillar so I need a little help with that and since I had very little sleep the night before I decide to take 40 winks. On a die hard note It was reported by my wife I finally got to bed not 6am like the morning before but 7am. Hope you enjoy M33.

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[Trev S]

Hi Kevin,

That's a good image, there's a lot of detail in there.  I know from experience  this is a difficult target as a lot of the outer detail is very faint. This hobby does require a lot of late nights.

Do you find the light pollution filter cuts out much of the image itself or does it let that through okay?

[Kevin Phillips]

I find that it dose cut the blues out, but it makes the stars tighter. I am reprocessing it again tosee if I can improve on it.

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From: croydo...@googlegroups.com <croydo...@googlegroups.com> on behalf of Trev S <trevs...@gmail.com>
Sent: Monday, September 13, 2021 10:47:20 PM
To: croydonastro <croydo...@googlegroups.com>
Subject: [croydonastro - 6982] Re: M33

 

Hi Kevin,

That's a good image, there's a lot of detail in there.  I know from experience  this is a difficult target as a lot of the outer detail is very faint. This hobby does require a lot of late nights.

Do you find the light pollution filter cuts out much of the image itself or does it let that through okay?

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[Kevin Phillips]

Good day everyone. M33. Looking to improve on it. I think brought out some good details there. O will later have another go. It seems that at times I have process tge sane capture a few times ti get as I wanted to be.

Kevin

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From: croydo...@googlegroups.com <croydo...@googlegroups.com> on behalf of Kevin Phillips <thewels...@live.com>
Sent: Tuesday, September 14, 2021 12:17:45 AM
To: croydo...@googlegroups.com <croydo...@googlegroups.com>
Subject: Re: [croydonastro - 6982] Re: M33

 

To view this discussion on the web visit https://groups.google.com/d/msgid/croydonastro/LO4P123MB5318A7433168114105B5947FBAD99%40LO4P123MB5318.GBRP123.PROD.OUTLOOK.COM.

[tcos...@gmail.com]

Hi Kevin

That’s a definite processing improvement on your first image as some of the fainter bits of the galaxy are now visible and you have also captured some of the red hydrogen alpha star forming regions.  I don’t know where you are imaging from and how bad light pollution is from your site, but M33 is quite strong in the blue wavelengths, so if the sky filter reduces the blue wavelengths, only use it if you really have to.  Also, I’m not sure what your light sub-exposure times were, but for a relatively faint deep sky object like M33 they should each be roughly 5 minutes long, assuming you are using an autoguider. You should get as many light exposures as sensibly possible, given your equipment setup (ie whether it’s a permanent setup or if you have to set it up and take it down each time you image. Looking at how any sub-exposure you took, I would say you need more light exposures and less flats and darks. I image in LRGB channels separately using a mono camera and take only 5 good flats per channel. The software which I use for dark/flat/bias calibration (CCDStack2) allows the user to create master darks, flats and bias frames which are averages of a larger number of sub-exposures. The master dark and bias frames can be used over and over again for different targets (subject to the cooled CCD camera temperature being set the same, eg -20 degrees C). Flats have to be taken every time you change your imaging setup, but you don’t need huge numbers to get a good average master flat. I would encourage you along this route as you want to spend most of your time taking light sub-exposures.  Hopefully, this will save you some time.  

I find astrophotography hugely rewarding but there is a lot to learn (I’m still learning) and it does take perseverance and patience. However, the nights are now definitely getting longer, so keep your eyes on the weather forecasts to take advantage of the opportunities!

Best wishes

Tim

To view this discussion on the web visit https://groups.google.com/d/msgid/croydonastro/LO4P123MB53180AB852963BDFA901C56EBADA9%40LO4P123MB5318.GBRP123.PROD.OUTLOOK.COM.

[John Mills]

Hi Kevin,

That's a really nice image. Plenty of detail including the Ha regions.
Well done ;-)

ATB John

On 14/09/2021 16:49, Kevin Phillips wrote:
> Good day everyone. M33. Looking to improve on it. I think brought out
> some good details there. O will later have another go. It seems that at
> times I have process tge sane capture a few times ti get as I wanted to be.
> Kevin
>

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[Kevin Phillips]

Thanks John

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From: croydo...@googlegroups.com <croydo...@googlegroups.com> on behalf of John Mills <ejm...@millseyspages.com>
Sent: Tuesday, September 14, 2021 8:51:43 PM
To: croydo...@googlegroups.com <croydo...@googlegroups.com>
Subject: Re: [croydonastro - 6987] Re: M33

 

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[William Bottaci]

Good image Kevin; I particularly like the second one you processed. This is encouraging to image this galaxy again.
Just to be sure, this is all Kevin's work; from setting up, imaging and processing.

The UV cut-off is at 450 nm (we see blue from 400) so some of the blue light doesn't get through, which is a shame, but for £49...
Overall, yes, the filter has to be used, for the reasons evident below in the filter details. It simply screws into the camera 1¼ -inch nosepiece and therefore, with this colour camera, no filter wheel.

The equipment has to be set up on each occasion, and as Kevin wrote, an auto-guider is in use. Kevin does excellent polar alignments using SharpCap, typically less than 5 arcseconds each time, but practicalities intervene and we're not sure the setup can endure 5 minute exposures and still aim true.
All the same I agree it's worth trying now we have darker skies and when there is no moon. Kevin, would you be willing to do a few test exposures at 5 minutes?

The filter is from Altair which has three features:
 - UV/IR cut-off: essential as sensors are sensitive into the UV and IR, beyond our vision, and the light is beyond that which a refractor can focus and certainly not designed to do. The effect otherwise is out of or soft focus stars, looking bloated and with a purple fringe. Whilst the refractor is an ED doublet it would be like a cheap achromat or worse otherwise.
 - Tri-band pass in 2 windows: in other words it lets through Hα in one window, and Hβ and OIII in another. Bandwidth of each window is nothing to write home about, roughly 60 nm each, but then it was just £49.
 - Light pollution: blocks most of Sodium and Mercury vapour lamps.
In total it blocks about 40% of the visible spectrum. That's 40% of starlight, and hopefully 0% of the three bands and 100% of the devil's own glow. So this is used as a factor in exposures.

We have a library of Darks, 40 frames each of 30, 60, 90, 120 seconds, each at both -10 and -15ºC (ZWO ASI294MC Pro colour, can go up to -35ºC below, but these were done for summer) so that's 8 files as SharpCap was used to process them into one file each of 23 MBs. Saves time at the telescope, time processing in Deep Sky Stacker, and space on rapidly shrinking disk.

I am of the opinion that, whilst there are diminishing returns, having less Darks and Flats is not going to improve an image. 40 were chosen because having a library there is not any downside to so many, but if anyone knows better do please say.
We do aim for as many Lights as is practical, and at least a hundred. The reason so few on this occasion is due to clouds.

As you say Tim, processing goes a long way, and there are lots to learn. A shame that this fun is so time consuming, but 'what can you gonna do?'

Location is now Kenley Observatory for all Kevin's imaging.

Exposures are either 90 or 120 seconds; only one time per run of course. 5 minutes is nice, but see the above and below - in other words, Kenley has light polluted skies of Bortle 5, and the filter lets through 40% of starlight.
SharpCap (Pro version only) has the Smart Histogram feature, whereby with one exposure on the night it recommends an exposure setting. It'll be interesting to try this next time; we should have been using this before now.
The consensus for this camera is that it prefers lots of shorter exposures rather than less longer ones; but we haven't taken this as a rule, just a tentative guide. Ultimately, as it's the signal to noise ratio that is the target; it's whatever exposure will achieve that.
Advice and conditions vary, so I recommend, Kevin, that we try up to 5 minutes, as it's the only way to know for sure.

Thanks for sharing.
William



On Wed, 15 Sept 2021 at 03:40, Kevin Phillips <thewels...@live.com> wrote:
Thanks John

On Tue, 14 Sept 2021 at 20:51, John Mills <ejm...@millseyspages.com> wrote:
Hi Kevin,
That's a really nice image. Plenty of detail including the Ha regions.
Well done ;-)
ATB John

On Tue, 14 Sept 2021 at 20:25, <tcos...@gmail.com> wrote:
Hi Kevin
That’s a definite processing improvement on your first image as some of the fainter bits of the galaxy are now visible and you have also captured some of the red hydrogen alpha star forming regions.  I don’t know where you are imaging from and how bad light pollution is from your site, but M33 is quite strong in the blue wavelengths, so if the sky filter reduces the blue wavelengths, only use it if you really have to.  Also, I’m not sure what your light sub-exposure times were, but for a relatively faint deep sky object like M33 they should each be roughly 5 minutes long, assuming you are using an autoguider. You should get as many light exposures as sensibly possible, given your equipment setup (ie whether it’s a permanent setup or if you have to set it up and take it down each time you image. Looking at how any sub-exposure you took, I would say you need more light exposures and less flats and darks. I image in LRGB channels separately using a mono camera and take only 5 good flats per channel. The software which I use for dark/flat/bias calibration (CCDStack2) allows the user to create master darks, flats and bias frames which are averages of a larger number of sub-exposures. The master dark and bias frames can be used over and over again for different targets (subject to the cooled CCD camera temperature being set the same, eg -20 degrees C). Flats have to be taken every time you change your imaging setup, but you don’t need huge numbers to get a good average master flat. I would encourage you along this route as you want to spend most of your time taking light sub-exposures.  Hopefully, this will save you some time.  

I find astrophotography hugely rewarding but there is a lot to learn (I’m still learning) and it does take perseverance and patience. However, the nights are now definitely getting longer, so keep your eyes on the weather forecasts to take advantage of the opportunities!

Best wishes
Tim

On Tue, 14 Sept 2021 at 16:49, Kevin Phillips <thewels...@live.com> wrote:
Good day everyone. M33. Looking to improve on it. I think brought out some good details there. O will later have another go. It seems that at times I have process tge sane capture a few times ti get as I wanted to be.
Kevin

On Tue, 14 Sept 2021 at 00:17, Kevin Phillips <thewels...@live.com> wrote:
I find that it dose cut the blues out, but it makes the stars tighter. I am reprocessing it again tosee if I can improve on it.

On Mon, 13 Sept 2021 at 22:47, Trev S <trevs...@gmail.com> wrote:
Hi Kevin,

That's a good image, there's a lot of detail in there.  I know from experience  this is a difficult target as a lot of the outer detail is very faint. This hobby does require a lot of late nights.
Do you find the light pollution filter cuts out much of the image itself or does it let that through okay?

[Kevin Phillips]

Thank you William for that explanation. Think we should use sharpcap to determine what exposure settings should be fir next session. But yes should aim 4 to 5 mins exposure time. Thank you again william for your comments. Professing is challenging it takes time to learn about. I use startools but then it needs ti go into photo shop or abode photo shop yo clean it up. 

Kevin

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From: croydo...@googlegroups.com <croydo...@googlegroups.com> on behalf of William Bottaci <w.bo...@gmail.com>
Sent: Thursday, September 16, 2021 1:25:55 PM
To: croydo...@googlegroups.com <croydo...@googlegroups.com>
Subject: [croydonastro - 6993] M33

 

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