Strange colour and weird background noise

[david_taurus83]

Hi Barrie

You don't need a guide setup or PHD2 to dither. You can still do this with APT but it does need to be connected to your PC so EQMod or similar. I done a project a while back with 30s exposures, no guiding and APT set to dither the mount every 5 frames or so. Works very well.

[barrie greenwood]

20 minutes ago, david_taurus83 said:

Hi Barrie

You don't need a guide setup or PHD2 to dither. You can still do this with APT but it does need to be connected to your PC so EQMod or similar. I done a project a while back with 30s exposures, no guiding and APT set to dither the mount every 5 frames or so. Works very well.

Hi .

I've a laptop apt and eq mod that will connect to the mount so how do I go about doing the above .

I spent a good bit of time last week getting the scope set up and sorted and then a good bit of the time freezing in the garden 😬gathering the subs and the result was dismal 🤣 light pollution from the moon played a big part in this issue with the color rings so I need to work on that but by the sounds of it the walking noise is easy to correct..

But ive no idea how to use the dither without guiding. 

Regards Baz

[david_taurus83]

In the Guide tab set it to APT Dithering. Then set the frequency between images and the distance. Try 12 for distance to start with. You don't want it to move by a huge amount but it should be fairly noticeable between subs. Keep the settle time something like 5 or 10 seconds as it will give the mount a chance to clear any backlash in RA if its present. Make sure you have the correct focal length entered in the Tools tab as APT will need this to calculate the number of steps to move the motors.

You can practice this during the day. Try and focus on something far away ( like a tree) and setup an image plan. Get it to dither every 5 frames. It should take 5 images (short exposure during the day) and then it will move the mount slightly before starting the next image. If you can focus on a tree or something for away you should see the tree drift slowly as the mount is tracking but every image after a dither should jump slightly to a different position and then repeat for 5 frames again. That way you can tell its all working and your ready for the next night out. 👍

 

[barrie greenwood]

Thanks ill give it a go tomorrow I'm using a nikon d90 that I can't connect to the apt program as there is no lead that will work apparently so if I set the delay on my intravoltmeter to allow the move and settling afterwards it may work 

Regards 

[david_taurus83]

14 hours ago, barrie greenwood said:

Thanks ill give it a go tomorrow I'm using a nikon d90 that I can't connect to the apt program as there is no lead that will work apparently so if I set the delay on my intravoltmeter to allow the move and settling afterwards it may work 

Regards 

Don't think that'll work. APT needs to know when the picture has been took. You can't time it.

[david_taurus83]

The blurb says the D90 is compatible but you need a serial cable or DCUSB, whatever that is? 🤷

[barrie greenwood]

21 minutes ago, david_taurus83 said:

The blurb says the D90 is compatible but you need a serial cable or DCUSB, whatever that is? 🤷

Morning bud 

Where did you find that info. 

I've looked before and could not find one 

Regards

[david_taurus83]

It's on the APT website. There's a list of compatible cameras. Apparently the D90 needs a serial cable? Don't know what a DSUSB is!

[david_taurus83]

Have a look here

[bottletopburly]

You have possibly a Nikon that uses lossy compression there is a fix take a read of the CN thread https://www.cloudynights.com/topic/746131-nikon-coloured-concentric-rings/page-8#entry10867894

basically you need to convert to Adobe dng then run through a program by mark smeddley which corrects files before stacking give it a go .

[Mick J]

On 05/03/2021 at 10:06, barrie greenwood said:

The flame photo I had the problems with was over 200 stacked 30 seconds exposure photos  if I increase the iso it makes the film faster in old terms catching more photons but adds noise .

I don't do this stuff and may be wrong but I don't believe increasing iso allows catching more photons, may well add noise.

DSUSB cables, may be easier to get a cheap Canon DSLR

Edited March 6, 2021 by Mick J
spelling

[barrie greenwood]

3 hours ago, Mick J said:

I don't do this stuff and may be wrong but I don't believe increasing iso allows catching more photons, may well add noise.

DSUSB cables, may be easier to get a cheap Canon DSLR

Iso is the same as the old film speed in photography it relates to the sensitivity of the film or sensor in a digital so it picks up more light the faster the fim or higher iso.

There's a home brew lead for the camera  on the cloudy nights site so I'll be making that tomorrow when the parts come from amazon 

Regards 

[Mick J]

50 minutes ago, barrie greenwood said:

There's a home brew lead for the camera  on the cloudy nights site so I'll be making that tomorrow when the parts come from amazon 

Regards 

I saw  the 'homebrew' and it looks doable,  good luck with it.

[ollypenrice]

Earlier in the thread the term 'crushing' the blacks was used. I'm not sure if this is the way I'd put it. The usual term is 'clipping' the blacks, which seems more accurate to me. Clipping means, quite simply, cutting them out. 'Crushing' implies compressing them. Both sins are possible in post processing but I think 'clipping' is the regular culprit.

Here's a healthy image with a healthy histogram.

And, below, we have the same image black clipped. Compare the histograms to see that what has been clipped is the left hand side of the histogram and notably the flat line before the peak. This contained all the faint data.  The temptation, which must be resisted, is to use black clipping like this to remove LP, gradients, noise, etc. Each needs to be addressed in its own terms. Clipping clips everything, most notably the picture!

 

Olly

[barrie greenwood]

8 hours ago, bottletopburly said:

You have possibly a Nikon that uses lossy compression there is a fix take a read of the CN thread https://www.cloudynights.com/topic/746131-nikon-coloured-concentric-rings/page-8#entry10867894

basically you need to convert to Adobe dng then run through a program by mark smeddley which corrects files before stacking give it a go .

So I take all my lights darks flats etc and convert the lot to dng files and run it through thst program then process them 

Edited March 6, 2021 by barrie greenwood

[bottletopburly]

2 hours ago, barrie greenwood said:

So I take all my lights darks flats etc and convert the lot to dng files and run it through thst program then process them 

Yes 👍

[michael8554]

I know the difference between Clipping and Crushing, as Olly has demonstrated, but I'm guilty of using Crushing to describe both operations.

Michael

[barrie greenwood]

Well I had another go but noise is still a problem 

[barrie greenwood]

On 06/03/2021 at 11:26, bottletopburly said:

You have possibly a Nikon that uses lossy compression there is a fix take a read of the CN thread https://www.cloudynights.com/topic/746131-nikon-coloured-concentric-rings/page-8#entry10867894

basically you need to convert to Adobe dng then run through a program by mark smeddley which corrects files before stacking give it a go .

Tried out this but unfortunately  the nikon D90 isn't supported by it 😕

[michael8554]

Hi Barrie

The walking noise pattern has gone,  but as you say the amount of noise is a problem. 

You'll have to help us out here:

Exposure, number of subs, what ISO, stacking settings etc etc ?

Michael

[barrie greenwood]

Exposure is 35 secs.

Iso is 400.

85 lights and 25 of everything else bias etc.

In dss I just allow it to use its defaults. 

And process in pixinsight .

I think that there was thin high level cloud at some point and the site is hardly a dark site it seems worse after all these led lights started going up.

Is the noise camera related or environmental related just seem to be struggling with it wheres a couple of years back with the same set up there seemed to be no where near as much noise .

Regards 

Edited March 7, 2021 by barrie greenwood
Add more content

[sharkmelley]

8 hours ago, barrie greenwood said:

Tried out this but unfortunately  the nikon D90 isn't supported by it 😕

You're right - sorry about that, I need to fix it!  The Nikon D90 uses the exactly same compression scheme as the D5300, so in the meantime the earlier version, version 2 will work fine because it applies the Nikon D5300 correction which is identical to the required D90 correction.

https://www.cloudynights.com/topic/746131-nikon-coloured-concentric-rings/?p=10860569

Mark

[barrie greenwood]

8 hours ago, sharkmelley said:

You're right - sorry about that, I need to fix it!  The Nikon D90 uses the exactly same compression scheme as the D5300, so in the meantime the earlier version, version 2 will work fine because it applies the Nikon D5300 correction which is identical to the required D90 correction.

https://www.cloudynights.com/topic/746131-nikon-coloured-concentric-rings/?p=10860569

Mark

Thanks Mark I'll try again 

[barrie greenwood]

Ok ive succeeded in sorting out a home brew set up for the nikons that need the lead to run the camera with apt  

Works well and cheap to produce