M109 Vacuum Galaxy

[gonzostar]

Hi

This image was taken over a couple of nights

154 mins worth of 4* lights.(including flats, bias and darks)

Used Canon 450d DSLR (un-mod)

With the 102 ES APO refractor with a AVX mount.Stacked with DSS and then "processed" in PS

Any tips on how to "sort" out the backgroung issues

Cheers for looking

Dean

 

[andrewluck]

As well as a high level of noise there's also a lack of any colour in the image. Did you dither the guiding when collecting the images?

I don't use DSS so just a couple of generic points here. I suggest looking through the original images and reject any that are significantly noisier than the rest (passing cloud etc). Then, leave the calibration frames out and just register and stack the light frames and see what it looks like. Does it have colour, is it noisier etc. That will enable you to make an assessment of whether it's the calibration frames/process that's contributing to the issues.

Andrew

[gonzostar]

Hi

Thanks for the reply. 

I am going to take your points on board which will no doubt improve image. Hopefully will improve image. But a couple of questions

How do you dither with PHD2?

Also will take another look at the frames and re-check. I am concerened that CLS light pollution filter takes away colour? or is it me over processing the image?

Dean 

[andrewluck]

I'm not a PHD2 user but it's going to depend upon what your image acquisition program is and whether the two can communicate with each other.

The CLS filter will alter the colour balance but it won't remove all colour.

Andrew

[alacant]

Hi. Try stacking without dark frames. On my 700d, they create more noise. If you didn't, dither the next set of light frames and stack accordingly with k-s. Your camera control program e.g. APT can be used to send the dither commands to PHD2 or lose PHD2 and take shorter unguided light frames with APT controlling the dither.

So, bias and flat frames; yes. Dark frames; no. ISO 800. HTH.

[gonzostar]

Will try again w/o darks, and use suggested settings. The iso setting was 800. Dont have a camera control programme  at moment. Still relying on cable release with  time delay  Ashame PHD2 dosent do a automatic dither? 

[andrewluck]

You can manually dither; after each exposure, stop the guiding, move the mount a small amount & restart guiding, take the next image.

As your current set of lights hasn't been dithered I suggest hot pixel removal on each subframe before stacking. For effective outlier rejection during stacking though you really must find some way of dithering the images.

Once you've restacked, post a cropped, unprocessed tif file here and we can investigate further.

Andrew

[gonzostar]

 

Thanks for reply Ok so stop the guiding after each sub. Is there a sequence of moving the mount directions slightly eg N-W-S-E ? And thankyou for wanting to investigate futher. Will re-process soon

m109-vacuum-unprocessed-tiff-gonzostar.TIF

[gonzostar]

Good Luck  

[alacant]

15 hours ago, gonzostar said:

PHD2 dosent do a automatic dither? 

Hi. The dither is handled by the camera control software whilst PHD2 looks after the star position after the dither. I think it has to be initiated from the camera software since PHD2 knows nothing of your imaging camera even if you have OAG. Have a look here anyway as they have an app which links PHD2 to other apps which do not have PHD2 support. HTH.

 

[gonzostar]

Hi Thanks for the link very useful. I am thinking of getting backyard EOS to "control" the DSLR and hence dithering. Now that i am more confident with PHD2 and managed to collect a couple of hours worth of 5 min subs over a  couple of nights of M94. Yeah hay  

[alacant]

15 hours ago, gonzostar said:

Is there a sequence of moving the mount directions slightly eg N-W-S-E

Hi. Make it as random as you can; you're trying to record the stars on a different part of the sensor for each snap. Probably best to stop guiding, then re-choose a/the guide star afterwards, otherwise PHD2 will throw a fit. Give it time to settle into smooth guiding again of course. HTH.

[gonzostar]

I have a few fallings out with PHD2. We have come to some kind of agreement!  

[spillage]

you can use apt to dither and nearly everything included can be used in the free mode. it worked out of the box for me and is great for setting up you exposure settings.