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Old 06-11-2021, 02:41 PM
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Anth10 (Anthony M)
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Silver Coin Galaxy

Hi,
It's been a long while since I last took to DSO imaging but finally after getting my autoguiding setup (somewhat) and the new shed/obsy setup for play I have had a crack at NGC253 over three separate evenings this week.

UVIR CUT (30min ISO 200)60sec subs
Hutech IDAS V3(60min ISO 400/800 split)60sec subs
Ha (first attempt using this filter 30min ISO 1200)90sec subs

It has been a real test getting the newt to stay on target and with the addition of a new extension bar I've been able to get the RA and Dec balanced to cope well enough to maintain consistent guiding although only over shortish exposure times due to the long focal length.

Plenty of trials leading up to composition of my first HaRGB image with the Canon 60D.

Happy to get back to what I really enjoy!
Cheers,
A
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Old 06-11-2021, 05:54 PM
Pepper (Steve)
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That’s a beaut mate.
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Old 07-11-2021, 01:06 PM
Mickoid (Michael)
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Nice to see you back on the road and for getting your obs and setup running smoothly. This is a really good result from your suburban location, great job! The focal length will certainly have an impact on guiding accuracy so if this is done with a long focal length, all the more impressive.
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Old 08-11-2021, 07:12 AM
John W (John Wilkinson)
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Nice picture Anthony - well done. Cheers John W.
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Old 09-11-2021, 10:39 AM
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Anth10 (Anthony M)
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Thanks for your comments Steve, Mick and John.

I've noticed that the Canon generates a lot of heat when taking multiple subs in succession which makes it a challenge to keep noise down. I tried using low ISO to combat this whilst trying to achieve reasonable signal. It's all fun and a new learning curve applying Ha data which I'll be looking forward to improving.

Cheers
A
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Old 09-11-2021, 04:53 PM
Startrek (Martin)
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Anthony,
Excellent image of the Sculptor with some great detail in the spirals and core
The only observation is the colour ( tan / brown cast ) which is usually caused by filters , Ha , CLS , Narrowband etc...
Most galaxies are better imaged with a DSLR or OSC during the new moon period without filters or at least just with a UV/ IR cut filter. If your imaging in light polluted suburban skies ( Bortle 6 to 8 ) the filter will assist with reducing the effect of skyglow and capturing good detail at the expense of creating a colour cast and not the “true RGB” colour of the galaxy
Try imaging without the filters , that way you can capture the best colour balance the object emits ( most galaxies only emit low levels of Ha anyway )
Try imaging this object again without a filter
Also most DSLR’s ( not just Canon’s ) run at high temperatures when doing long exposure AP ( anywhere from 18C to 39C depending on time of year and location ) I used a 600D for 3 years under Bortle 8 skies. In summer my 600D would be running at 35C whether I was taking a 90 sec sub or 300 sec sub. I’ve never imaged galaxies with filters, initially with my Canon 600D for 3 years and in the last 2 years with my ZWOASI2600MC both under Bortle 8 Sydney and Bortle 3 South Coast in my Obs. Processed images always have great RGB colour contrasts on no cast at all
The Canon 60D has an ISO sweet spot of ISO 800 ( same as my old 600D ) where you maximise your dynamic range
With galaxies try the “lucky imaging technique” ISO 800 , 60 or 90 sec exposures and at least minimum 4 hours to 6 hours on the object
I’m sure you notice an improvement during processing your colours
My 2 cents .....
Well done !
Good luck !
Martin
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Old 09-11-2021, 08:09 PM
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Anth10 (Anthony M)
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Martin,
This advice is well received. Thankyou for your insight. I agree that using the V3 narrowband filter has caused the colour cast you mention of. I have to say to be honest the short integration from the imaging using the uv/ir cut was far more true to colour and although only half an hour spent it was showing far more promise than the hour of filtered integration using the V3.
I usually image at iso 800 as you suggested but tried a different tact lowering it to minimise noise- there was banding present in the subs as a downside which comes from lack of signal perhaps-
This was my first attempt using Ha and again you’re right- not much gained from the galaxy but the core did help sharpen a little.

Appreciate your tips.
Cheers,
Anthony.
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Old 09-11-2021, 09:08 PM
Startrek (Martin)
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Quote:
Originally Posted by Anth10 View Post
Martin,
This advice is well received. Thankyou for your insight. I agree that using the V3 narrowband filter has caused the colour cast you mention of. I have to say to be honest the short integration from the imaging using the uv/ir cut was far more true to colour and although only half an hour spent it was showing far more promise than the hour of filtered integration using the V3.
I usually image at iso 800 as you suggested but tried a different tact lowering it to minimise noise- there was banding present in the subs as a downside which comes from lack of signal perhaps-
This was my first attempt using Ha and again you’re right- not much gained from the galaxy but the core did help sharpen a little.

Appreciate your tips.
Cheers,
Anthony.
Lowering your ISO will reduce resulting signal more than reducing your noise. ISO is just the level of amplification of your signal ( amount of photons hitting the sensor ) via the Analog to Digital unit in your camera
ISO 800 is the best setting for dynamic range across the image ( white point to black point ) and adjust ( lower ) your exposure times , takes more and more exposures to increase Signal and Dither your subs plus use Calibration frames with your stacking to reduce noise
Banding can be minimised by dithering your subs ( when using a DSLR , dithering is a must ) I use to dither every frame by a calculated number of pixels ( makes a huge difference in noise floor in particular fixed pattern noise
Are you taking calibration frames ?
Flats are a must ( dust donuts and vignetting removal ) to produce a flat field
Darks are a must ( reduces thermal noise or hot pixels ) separate darks with cap on scope not internal noise reduction darks.
Calibrate your Flats with either Dark Flats or Bias frames

Here’s the Astro settings I used on my Canon 600D ( I’m sure they would be applicable to the 60D )

Cheers
Martin
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Old 10-11-2021, 05:41 AM
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Anth10 (Anthony M)
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Martin,
Very generous to share your knowledge here. Yes I do use cal frames and only recently have taken the approach of using darks with the dust cover on the scope instead of the camera cap. I have never seen so much noise in the subs I’ve recently taken and I can only put it down to the fact that I am now autoguiding(it’s been a long time coming). In the past my slightly off polar alignment was most likely assisting the sub frames due to the drift acting as dithering! I will no doubt take on board the concept and see if I can change the settings in PHD to accomodate this.
I’m glad you have spelt out the science behind ISO settings vs noise.
I have only ever managed 30-40sec subs prior to autoguiding and even then stars weren’t the best shape. I’ve now been able to hit 90sec with PHD using this heavy OTA and this has changed the game.

With 800ISO using the us/ir cut at 90sec I’m going to have to see how much sky glow washes out the subs. It’s takes in a lot of light my scope! My reason for installing guiding on the system was primarily to entertain the idea of Ha imaging as it needs longer exposures. But even now I have come to learn that DSLR imaging with Ha filter isn’t ideal due to the Bayer matrix anyway.

One thing leads to another…I’ll keep using the 60D for as long as I can before I decide on upgrading to CCD cooled cam.

Cheers mate.
A
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Old 11-11-2021, 05:26 PM
Startrek (Martin)
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Originally Posted by Anth10 View Post
Martin,
Very generous to share your knowledge here. Yes I do use cal frames and only recently have taken the approach of using darks with the dust cover on the scope instead of the camera cap. I have never seen so much noise in the subs I’ve recently taken and I can only put it down to the fact that I am now autoguiding(it’s been a long time coming). In the past my slightly off polar alignment was most likely assisting the sub frames due to the drift acting as dithering! I will no doubt take on board the concept and see if I can change the settings in PHD to accomodate this.
I’m glad you have spelt out the science behind ISO settings vs noise.
I have only ever managed 30-40sec subs prior to autoguiding and even then stars weren’t the best shape. I’ve now been able to hit 90sec with PHD using this heavy OTA and this has changed the game.

With 800ISO using the us/ir cut at 90sec I’m going to have to see how much sky glow washes out the subs. It’s takes in a lot of light my scope! My reason for installing guiding on the system was primarily to entertain the idea of Ha imaging as it needs longer exposures. But even now I have come to learn that DSLR imaging with Ha filter isn’t ideal due to the Bayer matrix anyway.

One thing leads to another…I’ll keep using the 60D for as long as I can before I decide on upgrading to CCD cooled cam.

Cheers mate.
A
If your looking to upgrade in the near future to a cooled Cmos camera then I can thoroughly recommend the ZWOASI2600MC to replace the 60D. What this camera can do is astonishing in both light polluted and dark skies. I’ve had mine for 15 months now and love it.
I use a 2600MC in my 6” and 8” newts and next year I’m hoping the minister for finance will allow me to buy a TS 10” f5 carbon fibre newt
Cheers
Martin
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Old 12-11-2021, 11:55 AM
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Anth10 (Anthony M)
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Quote:
Originally Posted by Startrek View Post
If your looking to upgrade in the near future to a cooled Cmos camera then I can thoroughly recommend the ZWOASI2600MC to replace the 60D. What this camera can do is astonishing in both light polluted and dark skies. I’ve had mine for 15 months now and love it.
I use a 2600MC in my 6” and 8” newts and next year I’m hoping the minister for finance will allow me to buy a TS 10” f5 carbon fibre newt
Cheers
Martin
Gee Martin,
If I could I'd say yes to that, but at 0.7kg it would add even more strain on the 18kg payload I'm running atm! The 60D weighs 450g which feels like a brick hanging off the OTA whilst the cost is a bit exe $$$$$ for me (maybe one day...).
I'm happy for you mate, the TS would be amazing but a lot of sweet talking would be necessary to land that hehehe. Good luck.

Anthony
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Last edited by Anth10; 12-11-2021 at 12:42 PM.
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