Help with processing

[Hailfire101]

Hi guys.
Can you offer me any help on advice on how to get rid of the gradiation from the center on an image (see below)
I have startools and PS6



Any help would be MUCHLY appreciated.

Thanks.
Mike

[Tim]

The real fix is to take some flat frames and use them to remove the effects of vignetting. Your scope and camera need to be in the exact configuration as the light frames though.

It is sometimes worth planning to crop out the worst of the edges, but this requires getting your target more or less central in the most illuminated area.

I think there is a gradient tool for PS, no doubt someone will be able to help with the image as is.

[Marky1973]

Is this one shot or a stack, Mike? 

Flat frames will help if you haven't taken them and Gradient X Terminator is a plug in for PS that works pretty well. 

Pixinsight has some tools that will help, but that obviously comes at a price. 

Not a star tools user, so can't help there I am afraid! 

[Marky1973]

Tim typed faster! ?

[geordie85]

+1 for gradient xterminator. It's cheap enough and I use it on almost every image I process. 

Definitely a fantastic program and well worth the money 

[Hailfire101]

Brilliant, thanks.
I've installed Gradient xterminator and it has made a HUGE difference. 

I need to start taking flats.

Should I buy one of these, to help me take flats?

https://www.amazon.co.uk/dp/B00DNPCZVG?tag=stargloung-21

[Hailfire101]

Had a quick play, and this is how it looks now.
I'll be glad once I know how to process properly. haha



Thanks again for your help.

[geordie85]

You need to be careful that you don't clip your data.

Take heed of the last post in this thread.

 

[Tim]

Just noticed that the focus is a bit soft on the image too. (got my glasses on now )

You can see the double cross lines from the spider vane.  The thing that will make the biggest single difference to you getting great pictures, is to absolutely nail the focusing process. From there you can build on a solid foundation.

Do you use a Bahtinov mask at all?  Well worth the investment.

 

[Hailfire101]

I do have a reason behind the bad focus.

I was a bit lazy.

I had the camera at perfect focus to infinity while searching for the Whirlpool... But I thought my battery in the camera had died, so took it off the scope. After re attaching it, I had nudged the focus off. And instead of finding a star to refocus on, I just guessed focus using some, 20 second shots.

I guess I was just over excited I had found the Whirlpool.

[Tim]

25 minutes ago, Hailfire101 said:

I guess I was just over excited I had found the Whirlpool.

Yep, it's nice to find something you have been chasing. I remember watching a hardened visual observer transform into an imager when he saw pictures of M51 coming onto the screen

With astro-photography, the devil is in the detail. Lots of little things to get right for an overall great photo. But the focus is a big thing amongst the little things. It is always worth checking it, even if you have to interrupt an imaging run to do it. You don't have to move far from M51 for a bright star

[A4Andromeda]

As a beginner trying to image M42, I am having problems nailing the focusing.

So I get a clear evening at last, polar align and calibrate like a good boy, precise go-to M42 which takes me to the nearest bright star (Nair).

Centre that, off with the star diagonal, on with the DSLR, keeping my crayford focuser on, switch to live view, refocus, nudge the star centrally.

Fit the Bahtinov mask over the dew shield, connect BYE and try to see the diffraction spikes in the enlarged image.

Now here is my problem: I can't get a good view of the spikes, so nudge the focuser to get as small an image as possible and keep taking test shots.

Once I get as good an image as I can, then go-to M42 and hope for the best.

Is there anything else I should be doing?

The attached image is a typical, unstacked frame.

 

Celestron 9.25 SCT, AVX mount, Baader focuser, Canon EOS 550 D, BYE, DSS

[geordie85]

Did you try setting the ISO to its highest value and set exposure time it the highest value? This will help you see what your doing then you can change ISO back down afterwards. Also use the digital zoom. Try a couple of shortish exposures with high ISO also.

[A4Andromeda]

Thank you, that's useful. I have tended to stick with 30 sec @800 ISO.

I'll try that.

[ollypenrice]

On 25/03/2017 at 22:02, Tim said:

Yep, it's nice to find something you have been chasing. I remember watching a hardened visual observer transform into an imager when he saw pictures of M51 coming onto the screen

With astro-photography, the devil is in the detail. Lots of little things to get right for an overall great photo. But the focus is a big thing amongst the little things. It is always worth checking it, even if you have to interrupt an imaging run to do it. You don't have to move far from M51 for a bright star

Seconded. And focus does not last all night. As the instrument cools it will change, sometimes quite fast. Recheck regularly. On the capture side the two non-negotiable 'musts' are focus and guiding.

Olly

[A4Andromeda]

After much playing about with DSS and Digital Photo Professional, I have a final image of M42.

I realise I have to work on focusing and exposure.

Better equipment would produce better results, but I want to see what I can achieve with kit which is relatively cheap (I live in Yorkshire) and simple (I still prefer vinyl to CD/MP3).

Many thanks to all at SGL who have posted helpful encouragement and advice.