The EQ3 DSO Challenge

[Art Gecko]

6 hours ago, Stub Mandrel said:

I'll be trying to break the EQ3 sub-length record soon

 

What is the record?

[Stub Mandrel]

I haven't set it yet

[Peco4321]

@alacant, just set up, hopeful of some astronomy tonight, and I spun the RA around to be like this from an app, just now waiting for Polaris to appear to finish off. Will report back later.  Had to take scope off as I have the weight bar pointing up!  

[Art Gecko]

This is my offering from last night... I chicken'd out of the crescent nebula and had a go at something a bit easier... the Western Veil Nebula, handy for me as it's mostly OIII which is right in the middle of the visible spectrum and great for unmodded imaging!

So this is 20 mins in 60 sec subs at ISO 800 with darks and flats. Probably one of my favourites yet! Wish I could of got more data but the clouds rolled in after a while and stopped the fun.

[Peco4321]

Cracking image @Art Gecko  Might have a go myself soon. Love it. 

[Stub Mandrel]

That's great for the amount of data!

I thought it was red, I must go back and look at my subs again and see if I can get more out of it!

[Art Gecko]

25 minutes ago, Stub Mandrel said:

That's great for the amount of data!

I thought it was red, I must go back and look at my subs again and see if I can get more out of it!

Thanks Neil, I think it does have a lot of Ha in it too that I haven't been able to pull out... needs more time with my camera but it'd still be fainter than the blue... Would be good to see a comparison though!

[Stub Mandrel]

I was sure I had some images of that bit, but only at 135mm. this is the other bit with a modded 450D:

[mikey2000]

I'm suddenly interested in this Veil Nebula!   With my camera and telescope, it looks like a tricky one to frame and with a surface brightness of just 18 or so, it must be super faint.   I suppose I could try a F2.8 (my 70-200/2.8 would get the whole nebula and it's neibour, no problem) The moon's out tonight and veiled in a haze, so I think I'll stay indoors!

 

I wonder.... I've been guiding my 750mm focal lengh scope with a 130mm focal length guidescope.  With a 200mm/2.8 SLR lens, I suppose the pixel scale will be way different and guiding errors will be much harder to see.   Long subs here we come!

[Art Gecko]

47 minutes ago, Stub Mandrel said:

I was sure I had some images of that bit, but only at 135mm. this is the other bit with a modded 450D:

Nice!! You can see the OIII it's just a little swamped in places by the Ha, I guess that's the difference of modding.. much brighter than mine though, it's good!

21 minutes ago, mikey2000 said:

I'm suddenly interested in this Veil Nebula!   With my camera and telescope, it looks like a tricky one to frame and with a surface brightness of just 18 or so, it must be super faint.   I suppose I could try a F2.8 (my 70-200/2.8 would get the whole nebula and it's neibour, no problem)

Try it, it's not as faint as you'd think, I just had very poor luck with the clouds, they appeared as soon as the sky got nice and dark... half my subs looked so blue you'd think it was daylight and weren't really worth using! Just needed more dark time to collect the data..

Edited July 3, 2017 by Art Gecko

[bobro]

4 hours ago, Art Gecko said:

the Western Veil Nebula

Just my sort of image! Sometimes images can seem to be a bit over processed (easy to do) but this one has a lovely natural colour progression to it that is easy on the eye. Lovely and well done!

Edited July 3, 2017 by bobro

[mikey2000]

On 03/07/2017 at 22:17, Art Gecko said:

 

Try it, it's not as faint as you'd think, I just had very poor luck with the clouds,

I'm on it!  It's unexpectedly clear and I'm managing consistent 5minute subs.  Standing by for Veil Nebula!   It's a shame the moon is about 3/4 full :-(

[mikey2000]

Here's a DSS question. ....

 

The background skyglow has changed over the course of my session -  I started a little soon and the sky still had a bit of daylight.  Now it's as dark as it will get tonight but it's time to pack it all away and head to bed.  So, even though they are all for 5 mins, the subs around midnight are noticeably 'bluer' than the nice dark ones now coming in.

 

When I stack them (tomorrow maybe...) should I discard the brighter subs or just chuck them all in?

[Nigel G]

6 hours ago, mikey2000 said:

Here's a DSS question. ....

 

The background skyglow has changed over the course of my session -  I started a little soon and the sky still had a bit of daylight.  Now it's as dark as it will get tonight but it's time to pack it all away and head to bed.  So, even though they are all for 5 mins, the subs around midnight are noticeably 'bluer' than the nice dark ones now coming in.

 

When I stack them (tomorrow maybe...) should I discard the brighter subs or just chuck them all in?

I would stack them all and see the result, you can always start to remove the brighter subs if your not happy with the result  

Nige.

[bobro]

Probably a good idea to ensure DSS stacking has 'Per Channel Background Calibration' set to 'Yes' to ensure a consistent sky background level before stacking.

[Nigel G]

I have always had per channel background cali set to no, and read to keep it that way with DSLR's so not sure about that  

Nige

[bobro]

29 minutes ago, Nigel G said:

I have always had per channel background cali set to no, and read to keep it that way with DSLR's so not sure about that

Probably depends on how an image is subsequently processed e.g. I normally use Kappa Sigma clipping in DSS which (I understand) needs a consistent background level in order to operate correctly. Hopefully someone will be able to explain a bit more about Background Calibration......

[mikey2000]

I found a little nugget in the DSS documentation saying Kappa-Sigma needs Per Channel Background calibration.  So, I did this.  Then I tried two stacks, one with all 20 subs and another with the 16 darkest.  The full 20 gave me serious problems in the corners on one side - all grey and washed out.   The 16 darkest stack was much better.  Here is the result.. (5 min subs, +darks, flats and bias) processed in Startools, LR, and Photoshop.  Click to enlarge

[mikey2000]

This leads to a debayering question.  DSS notices I had 5 min subs and suggested 'AHD Debayering' instead of my usual Bilinear.  I can't find any descriptions of what the difference might be.  Any clues?

[Peco4321]

17 minutes ago, mikey2000 said:

This leads to a debayering question.  DSS notices I had 5 min subs and suggested 'AHD Debayering' instead of my usual Bilinear.  I can't find any descriptions of what the difference might be.  Any clues?

Either way, beautiful image. 

[Art Gecko]

Can't help with DSS questions I'm afraid as I don't use it... But that turned out really nice Mikey!!

[Stub Mandrel]

2 hours ago, mikey2000 said:

I found a little nugget in the DSS documentation saying Kappa-Sigma needs Per Channel Background calibration

Well spotted, that must be deeply hidden!

Advanced debayering gives better results, but needs more data.

[Peco4321]

My attempts last night, both stacked ion DSS and stretched in Photoshop Express:

Veil Nebula, 100 x 30 sec ISO 800, 20 darks and 20 Bias, no flats, would have like some colour but un modded canon 1100d I guess is not up to it, anyway, new find for me, easy to get in the area, any suggestions for getting some colour?

Andromeda Galaxy, 32 x 30 sec ISO 800, 20 darks and 20 bias no flats, was hoping this would turn out better but full moon and it was late so not enough data, any tips for getting a good Andromeda with my set up, 150p, dual motors, canon 1100d?

[bobro]

Hi Peter,

You did much better than my attempt on the Veil last night - reflections inside my scope due to the Moon I think. Perhaps a cowl will help. Clouds too!

If you're not already doing this, before saving the image in DSS set the Saturation shift (Saturation tab) to about 20% before aligning the RGB histogram peaks (RGB/K Levels tab).

Bob

Edited July 9, 2017 by bobro

[Peco4321]

57 minutes ago, bobro said:

20%

I've been setting it at 17%, read it somewhere. Will have a play around and try more data when the moon is out the way.  Typical though, Saturday night, clear skies but a bloody great big bright moon.