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M27 Dumbbell Nebula from Rother Valley 9.7.2010

Started by Carole, Jul 11, 2010, 23:35:55

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Carole

My image from the Friday night.  My first one of the Dumbbell.  
24 x 5min subs, Darks and Bias - guided.  
(Did the flats straight onto the memory card and it saved them as Jpeg and DSS didn't like them, so no flats).

Original post removed, as superceeded by one below in post 10. 

Would like to know why my stars always come out like blobs of white paint, and no colour variation.

Carole




Mike

Not bad for a first go. The stars are like that because your focus is out. You'll get it with practise.
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

MarkS


Well done - that's better than my first Dumbbell!  I guess that's a crop of the original?  If it is a full scale crop (i.e. not shrunk) then your focusing looks pretty good as well.

The "blobs of white paint" stars are the brighter stars where the signal has become saturated.  The question is, are they blobby and saturated in the original subs or have they become blobby and saturated during your processing sequence?

Mark

Rocket Pooch

Hi Carol,

Not bad :-) did you manage to get this done without any help, if so I'm impressed..

Don't worry about the white stars and also the slight guiding issues its an ok image, the thing to do now is just practice and practice then your focusing and capture will become a lot better, you can allways go back and process the images again and again later.

Chris

RobertM

That's very good Carole.  As Mark points out the stars are white because all the RGB layers are saturated and therefore at the same level (i.e. maximum) ... R+G+B in equal measure gives white.

I think Chris has covered the rest.

Robert


Carole

Thanks every-one.  In answer to your questions and comments:

Yes this is a crop as the original is too small, but I did not understand what you meant by
Quote(i.e. not shrunk)
Quotein fact it is enlarged and then cropped.  I've posted the original uncropped version BEFORE processing in Photoshop which will hopefully answer your second question as well
QuoteThe "blobs of white paint" stars are the brighter stars where the signal has become saturated.  The question is, are they blobby and saturated in the original subs or have they become blobby and saturated during your processing sequence?  
Did very little processing on this, just brought out the nebulosity with levels, then isolated the nebula while I adjusted the sky colour which was brown because I did not use a CLS filter and that was about it.

Stacked unprocessed full frame:


Quotedid you manage to get this done without any help
Yes did this on my own on the Friday night.  
Saturday night was a different matter as my mount had a nervous breakdown, but that's another story.

QuoteThe stars are like that because your focus is out. You'll get it with practise.
Oh gawd!!  I'm using the bahtinhov mask now and thought I'd cracked it, the central line looked dead centre and I think Mark even looked at this.  However Mark has now set me up and taught me how to use Nebulosity and Bahtinhov grabber so hopefully it will get better.

Carole

Carole

Quoteslight guiding issues
Hi Chris, could you elaborate as I thought the guiding was OK. 

Thanks
Carole

Mac

nice capture,
Just a bit of info,
If you are going to save your images, try not to use jpeg, as these are compressed images and some of the data that you have spent hours
capturing is lost, either use raw or tiff.
Raw being the preferred.
you can then use the software that came with your camera to batch convert the raw files to tiff and then process them
that way all the very fine detail is not lost.

Mac.

Mike

I didn't realise it was a crop of a MUCH larger image. That was why the stars looked a little weird.

We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

Carole

QuoteI didn't realise it was a crop of a MUCH larger image
All my images are this tiny, which is why I don't like the Megrez and flattener. 

Have recently acquired an ETX125 OTA only which can be mounted on the CG5 so once I have had a bit more practice will start using that.  this was also why i was looking at one time to buy a 2" Barlow, but want to be sure I can get focus before I purchase one, which was why i was trying to borrow one. 

QuoteIf you are going to save your images, try not to use jpeg
Mac, I don't get rid of the original TIFFs so always have them still for re-processing, but I didn't think the OAS site would accept TIFF files, and my own webmaking software won't import Tiff's either. 
I stack in Raw, process in TIFF and then I convert to Jpeg for posting on the Forum. 
Am I wrong then and the Forum will accept Tiff files?

Carole


Carole

OK, based on comments above, I have had another go at processing this, and have processed the sky separately from the nebula, but not sure if this is regarded as cheating.



Carole

RobertM

Quote
QuoteI didn't realise it was a crop of a MUCH larger image
Quote
All my images are this tiny, which is why I don't like the Megrez and flattener. 

Then you are choosing targets that are too small and wasting all the field of view.  Try something much bigger next time, there's plenty up there to choose from...


Mac

If you are doing all you processing in raw / tiff then that's excellent as you are using all the available data.
Once you have finished all your tweeking / swearing / stacking ect,
convert your finished image to 8 bit and then save it as a jpg.

Mac.

Mike

I agree with Robert. There are some fantastic wide field targets to choose from. The sky is full of nebulae, some of them massive.
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

Carole

QuoteThere are some fantastic wide field targets to choose from. The sky is full of nebulae, some of them massive.

I will given time, but I don't want to be excluded from doing these sort of objects. 
I think things will get better when I can use the ETX125 OTA for this sort of stuff and when my mount is behaving itself.  Meanwhile I'll just regard it as practice. 

What did you think of the re-process 4 posts back?

Carole