Improving on the Veil

[Craig123]

Hi 

I have been having a go at the Veil this week.I got about 3 hrs in ha and wondered if more hours will give more detail.Im also not as sure about focusing with ha filter  but was just using fwhm on artemis capture so wonder if it's a little out of focus.Any tips on improving.I tried taking darks but they havent loaded up right in Astroart by the looks of it.I'd like to get lrgb at some point.Many thanks

[Tim]

It's a great start, well done, in fact your image reminds me of my first ever visual view of the veil in a big dob.

You will be able to get a lot more detail with two things, longer exposures and tighter focus. Do you have a Bahtinov mask? They make manual focusing very accurate indeed.

HTH

Tim

[Craig123]

18 minutes ago, Tim said:

It's a great start, well done, in fact your image reminds me of my first ever visual view of the veil in a big dob.

You will be able to get a lot more detail with two things, longer exposures and tighter focus. Do you have a Bahtinov mask? They make manual focusing very accurate indeed.

HTH

Tim

Thanks Tim...those  subs are 20 minutes each.Do you mean add more or take even longer subs?.How does the Bhatinov work in conjunction with fwhm.Do I get the best I can fwhm and then use mask or just forget about fwhm altogether.

Thanks.Craig

[Adreneline]

Hi.

I can sympathise with the focus issue - it ruined many of my early images and took me ages to resolve all the problems.

I use Artemis and FWHM to focus and find it very satisfactory, whether using LRGB or narrowband. I always aim to get the lowest FWHM possible for the prevailing seeing conditions. I use manual focus on a Samyang 135mm and motorised/remote focus on an SW-ED80/WO-ZS71. I've tried using a Bahtinov Mask but haven't found it to be that easy but I accept many swear by them.

When using a CCD camera I image using SGPro; I've tried using the automated focus feature in SGPro and find it really difficult for some reason - i always end up going back to Artemis.

When using my DSLR I image using BYEoS and find using the FWHM focus feature works very well; again others have had difficulties and prefer to focus using the Live View on the camera.

I always take flats after every imaging session for each filter. I have a set of Dark and Bias images which I use repeatedly; you can take them during daylight hours.

It would be interesting to know what equipment you used to take the Veil image; it might help others to offer more focussed (excuse the pun) advice.

Adrian

[Craig123]

Thanks Adrian.Yes I feel more likely to get the focus right with Fwhm at this stage although I  was given a Bhatinov with the scope.I took darks and bias but they are not on the image as I must have messed something up in Astroart.

My gear consists of Heq5,Sywatcher Ed80 pro,Atik 314l plus mono and qhy5ii mono on a finder guider.I am just gearing up to try and use Ascom aswell.

 

[MarsG76]

That indeed, you are.

 

[Dragon_Astro]

A good start there

I only use a Bahtinov mask to focus with and its spot on. As you've probably found, it's hard focusing with an Ha filter on, so I focus with the mask using the brightest star I can find in the FOV or one near it and slew back to the target dso.

The Veil above just needs more data, 3hrs of 20 min subs doesn't really give you that many to stack together, compared to 3hrs worth of 5/6minute subs. More subs stacked will give you the detail that you want and get rid of the speckle noise in the background, esp if you use darks too.

[Craig123]

3 minutes ago, Dragon_Astro said:

A good start there

I only use a Bahtinov mask to focus with and its spot on. As you've probably found, it's hard focusing with an Ha filter on, so I focus with the mask using the brightest star I can find in the FOV or one near it and slew back to the target dso.

The Veil above just needs more data, 3hrs of 20 min subs doesn't really give you that many to stack together, compared to 3hrs worth of 5/6minute subs. More subs stacked will give you the detail that you want and get rid of the speckle noise in the background, esp if you use darks too.

Great..it seems im on the right track  more or less.Are you saying I would be better off shortening exposures and doing more subs ?...thats a surprise although tbe first night i was out i was doing 10 min subs due to clouds and there seems to be more definition.I didn't use those subs on the above as it wasn't centred so well.

[Dragon_Astro]

Correct, the more subs you stack, the more good details you'll get and the unwanted noise will be processed out.

So naturally, the shorter the subs (5-10mins) the more you'll collect over a few nights and end up with a better result than you would've using very long subs.

Theres only so much the CCDs pixels can take too before they're full, you don't get anything back in return. So that's when you end up with big round blobby looking stars, rather than fine points of light.

[Craig123]

Ahhh..i see.So I should have stuck to 10 mins or less.Thats very helpful.Thanks.

Hopefully I can combine 20 min subs with 10 ?

[newbie alert]

52 minutes ago, Dragon_Astro said:

 

Not sure if agree with some of the comment here..surely 3 hours of integration time of 20 min subs in comparison to 3 hours of 5 min subs isn't going to stack up the same.. forgive me as I'm relatively new to astro and even more so on ccd imaging but the whole stacking system rely on signal to noise ratio ..stacking adds more signal and dependant on how deep you fill those well depth up depends on how much signal there is..a 20 min sub is going to have 4 times more signal than a 5..i did a test myself on a single 10 min sub with a DSLR as opposed  to 4x3 min subs stacked and there was more detail in the 10 min single sub than 12 mins of stacked 3 min subs..with a DSLR which is going to introduce far more noise than a cooled ccd..so in my head I proved that longer exposure reveals more details.. what's people's thought on this with far more experience?

Obviously  we are talking on a ccd level and not the cmos type sensors which do better at shorter subs 

[Dragon_Astro]

Would the quality be there though? Not just amount of detail.

Using 20min subs, you'd only get 9 subs in 3hrs. Using shorter subs, you'd collect twice/three times as many subs, with a smoother image.

The Veil in the OP is starting to show blown/burnt areas in white on the left side, a sign of over exposure. 

[Craig123]

9 minutes ago, Dragon_Astro said:

Would the quality be there though? Not just amount of detail.

Using 20min subs, you'd only get 9 subs in 3hrs. Using shorter subs, you'd collect twice/three times as many subs, with a smoother image.

The Veil in the OP is starting to show blown/burnt areas in white on the left side, a sign of over exposure. 

Should say I did a little curves and sharpening/clarity in LR and PS..my very rudimentary skills in processing astro could be the cause of that.

[Craig123]

13 minutes ago, Dragon_Astro said:

Would the quality be there though? Not just amount of detail.

Using 20min subs, you'd only get 9 subs in 3hrs. Using shorter subs, you'd collect twice/three times as many subs, with a smoother image.

The Veil in the OP is starting to show blown/burnt areas in white on the left side, a sign of over exposure. 

Here is the  original stack of shots without PP

[newbie alert]

3 hours ago, Dragon_Astro said:

Would the quality be there though? Not just amount of detail.

Using 20min subs, you'd only get 9 subs in 3hrs. Using shorter subs, you'd collect twice/three times as many subs, with a smoother image.

The Veil in the OP is starting to show blown/burnt areas in white on the left side, a sign of over exposure. 

Still not sure that I'm with you on this..with a cmos sensor is agree that keeping the exposures shorter does help but it's because they suffer more with ampglow from the electronics..sure there's a ceiling level on exposure time due to sky conditions,light pollution etc but I fail to see that 5min sub is better than a 10min..20 mins maybe too much for uk skies unless it's a real dark sky location...

[Tim]

8 hours ago, Dragon_Astro said:

Correct, the more subs you stack, the more good details you'll get and the unwanted noise will be processed out.

So naturally, the shorter the subs (5-10mins) the more you'll collect over a few nights and end up with a better result than you would've using very long subs.

Theres only so much the CCDs pixels can take too before they're full, you don't get anything back in return. So that's when you end up with big round blobby looking stars, rather than fine points of light.

Sorry, but I dont agree with this. Narrowband targets only start to reveal their true extent and contrasting darker areas through longer exposures in my experience, with a CCD camera like the Atik 314. A minimum of 20 minute, but preferably 30 minute or longer will bring that nebula to life, there is a lot absent. Yes, you are still going to want to collect a good 20 or 30 subs, and yes it takes time. CMOS cameras are different and can be used at a higher gain for shorter subs. You can blow stars easily, but the narrowband targets that you can reach full-well on can probably be counted on one hand, and the veil isn't one of them. Compare this deep exposure for what is really there for the taking  https://www.astrodelciel.it/Astronomy/Halpha/i-4q9pgkJ/A

I like a  Bahtinov for manual focusing because as long as you use it right, it cannot be wrong, you either have perfect focus, or you dont, and it is obvious, especially with a Ha filter where a longer exposure is required to bring out the diffraction pattern, which mostly eliminates seeing issues, something that can sometimes cause issue with FWHM focusing in my experience. But whatever method you use, be absolutely anal about checking, re-checking, and checking again later, don't waste clear skies on softly focussed pictures!

At the end of the day, go with what works for you and your gear. 

[Craig123]

Yes.I had a look at a few other ha shots of this target and there is so much going on its amazing...and I  just want to get more of it.. AND it fits handily on the fov of the 314 so  I think I will keep on with it. It was a surprise to me you can  image  even in July so   all good so far with this first project before August   ? ?..Next I will try and trust in the mask .Thanks.

[ollypenrice]

I entirely agree with Tim and disagree with Dragon_Astro on the matter of NB sub lengths. You have to capture the signal in the first place and get it above the noise floor. In short subs you are unlikely to do this. For me NB subs need 20 to 30 minutes. With a CCD camera you can shoot lots of short subs and get a smooth but shallow result. To go deep you need long subs in which the fainter structures will show.

Craig 123, a good example of faint structure is just beginning to show in your image: it's the 'second broom handle' which separates from the main one and rises steeply up and away from it.

Using 30 minute Ha subs I found it easy to make this far more visible. (The image below is a greyscale rendition of HaOIIILRGB because I don't have my pure Ha stack handy. However, the 'second broom' is predominantly an Ha feature.

The idea that your image shows signs of over exposure is not correct either, in my view. I don't think that any stretched image can show such signs because any reaching of staturation may arise from the stretch - and probably does. The way to see if your data is overexposed is to look at the linear stack. I shoot in subs between 15 and 30 minutes and find that, apart from stellar cores in luminance, I hardly ever need to shoot shorter subs for over exposed areas. M42 is an obvious case when we all need to do so but ti's an exception. So stick with your 20 minute subs. 

Focus: I find Artemis FWHM works fine for refractors though it wasn't a success with data from a 14 inch reflector because the values jumped around wildly. However, with refractors I do an initial B-mask focus on a bright star and then refine it and maintain it with FWHM. I don't think you are in tight focus though. I would try using 3 second subs, always bin1, for FWHM. Longer subs let the seeing average out a bit, so giving you more stable readings.

Olly

 

[Dragon_Astro]

I stand corrected then  

Carry on as you were....clear skies ?

[Craig123]

2 hours ago, ollypenrice said:

I entirely agree with Tim and disagree with Dragon_Astro on the matter of NB sub lengths. You have to capture the signal in the first place and get it above the noise floor. In short subs you are unlikely to do this. For me NB subs need 20 to 30 minutes. With a CCD camera you can shoot lots of short subs and get a smooth but shallow result. To go deep you need long subs in which the fainter structures will show.

Craig 123, a good example of faint structure is just beginning to show in your image: it's the 'second broom handle' which separates from the main one and rises steeply up and away from it.

Using 30 minute Ha subs I found it easy to make this far more visible. (The image below is a greyscale rendition of HaOIIILRGB because I don't have my pure Ha stack handy. However, the 'second broom' is predominantly an Ha feature.

The idea that your image shows signs of over exposure is not correct either, in my view. I don't think that any stretched image can show such signs because any reaching of staturation may arise from the stretch - and probably does. The way to see if your data is overexposed is to look at the linear stack. I shoot in subs between 15 and 30 minutes and find that, apart from stellar cores in luminance, I hardly ever need to shoot shorter subs for over exposed areas. M42 is an obvious case when we all need to do so but ti's an exception. So stick with your 20 minute subs. 

Focus: I find Artemis FWHM works fine for refractors though it wasn't a success with data from a 14 inch reflector because the values jumped around wildly. However, with refractors I do an initial B-mask focus on a bright star and then refine it and maintain it with FWHM. I don't think you are in tight focus though. I would try using 3 second subs, always bin1, for FWHM. Longer subs let the seeing average out a bit, so giving you more stable readings.

Olly

 

Thanks for that Olly.I had a feeling the focus wasn't as sharp as it could be.It's the aspect that  concerns me most at the moment.For some reason I have the idea it is easier to focus when binning so I did it with x4 on a 4 second loop.Is it possible to add further subs to these ones and  if they are tighter then the image will improve or is it better to start again a fresh.Enjoyed looking at your uploaded shot and seeing what is possible on the Veil.I'm also wondering how much the Luminance would have added to the faint structures in your shot and brought out featues that ha would not...perhaps I should go for some luminance next time the moon is out of the picture.

Thanks

Craig

[ollypenrice]

5 hours ago, Craig123 said:

Thanks for that Olly.I had a feeling the focus wasn't as sharp as it could be.It's the aspect that  concerns me most at the moment.For some reason I have the idea it is easier to focus when binning so I did it with x4 on a 4 second loop.Is it possible to add further subs to these ones and  if they are tighter then the image will improve or is it better to start again a fresh.Enjoyed looking at your uploaded shot and seeing what is possible on the Veil.I'm also wondering how much the Luminance would have added to the faint structures in your shot and brought out featues that ha would not...perhaps I should go for some luminance next time the moon is out of the picture.

Thanks

Craig

If you bin while using FWHM you'll get lovely numbers but poor information. 

If you are handy in post processing then it would be possible to extract the best of your soft focus subs to add to tighter focus subs later. It would not be possible to explain how to do this in one forum post. It's a shameful, indefensible pile of skulduggery...In my view you did well with that first shoot but you can do even better with focus nailed.

Olly

[Craig123]

1 hour ago, ollypenrice said:

If you bin while using FWHM you'll get lovely numbers but poor information. 

If you are handy in post processing then it would be possible to extract the best of your soft focus subs to add to tighter focus subs later. It would not be possible to explain how to do this in one forum post. It's a shameful, indefensible pile of skulduggery...In my view you did well with that first shoot but you can do even better with focus nailed.

Olly

I will put a little note about no binning with Fwhm im my astro  set up help sheets.Thanks again.

[Craig123]

On 27/07/2018 at 19:32, Tim said:

. Compare this deep exposure for what is really there for the taking  https://www.astrodelciel.it/Astronomy/Halpha/i-4q9pgkJ/A

 

Hi Tim.I had a look at a Bhatinov video on YouTube and I agree..it looks a great method and something of a contrast to all the other stuff you have to do in set up so I will try it tonight if clear.I had a look through the other shots on the link above.Is that your work?.Very nice and inspiring as I hope to go for Elephants trunk when I need a break from the Veil. What is the site the pictures are on..is there info about how they were done ?

Thanks

[carastro]

Quote

How does the Bhatinov work in conjunction with fwhm.Do I get the best I can fwhm and then use mask or just forget about fwhm altogether.

You don't use the two methods simultaneously.  

I find you need a steady sky to use FWHM, my experience has been it jumping all over the place and not knowing which reading to take, so I went back to using a Bahtinov mask which I find very reliable.  I use Artemis as well and for narrowband you need to lengthen the exposure slightly and loop x 3 (for faster download) to use the mask, probably 3 secs binned x 3 will do it.

You should add some Oiii to this when you get a chance, combined with the Ha makes a lovely coloured image.

Carole

[tooth_dr]

I hope you don’t me posting this here. My image looks so very similar to yours, it is also around 3 hours exposure but in 5 minute subs, with an Atik mono CCD.

Mine top image

Craigs bottom image