Lagoon 7 hours CDK now repro'd

[gregbradley]

I took this over a few weeks. The Ha a little while ago and the LRGB over one night.

Planewave CDK17, FLI Proline 16803 and Paramount ME.

I collimated the scope and checked primary to secondary spacing before this LRGB part of the image.
Collimation need a slight tweak, spacing seemed fine (it has to be accurate to +/- 1mm).

HaLRGB just under 8 hours total. Seeing was poor, focusing was a bit tricky at times as the same focal point would show one in focus and the 2nd would show some poor seeing and it would look a bit out of focus.
The seeing generally improves as the night goes on and the images seemed to be sharpest as usual when taken near the zenith and after midnight.

http://upload.pbase.com/gregbradley/image/135964244/large regular size

http://upload.pbase.com/gregbradley/image/135964244/original large size

Greg.

[allan gould]

Another excellent image Greg. You certainly have mastered all aspects of your scope and it shows.

[multiweb]

Little soft. Bad seeing really shows. Nice field colours though considering. :thumbsup:

[gregbradley]

Thank Allan.



Ooh you're being a bit tough there? See this crop:

http://upload.pbase.com/gregbradley/image/135953517/large

There's a lot of detail in there not normally seen. Can it be sharper? Not with this data as I have maxed it but at another location under better conditions I think so. But its still pretty detailed. You may be used to widerfield images that look sharp but don't show that level of detail.

Having said that if this poor seeing is regular an AO may become quite important as the only road to improving sharpness. Also the reducer which I should receive at any time will help.

It certainly is true that the longer focal length is going to show the seeing a lot more and aperture isn't going to help there.
Hence 4-6 inch aperture being the most popular imaging platform. Its a good compromise between detail and seeing.

Greg.

[multiweb]

I was comparing with Peter Ward's recent shot of the same area and you've got way more aperture so you should be able to level his shot. This one doesn't. AO would be the go IMHO. I've seen shots taken with a 12.5" CDK way sharper than that too, taken from Penrith even. That's why I'm saying your scope can do way better under better seeing conditions.

[strongmanmike]

Yes, it does look soft for sure but the colours are spot on.

If this is a result of the seeing I imagine an AO will do little,they just make your guiding essentially perfect, which "is" pretty useful if your guiding isn't already perfect.

It's a tough one but I am leaning toward focus being the issue here actually :question:

Mike

[marc4darkskies]

I feel your pain ... a 17" aperture and seeing won't give you a break. I had to abandon imaging the night before last because it was so bad - I could barely achieve any focus! BTW I don't bother imaging at all if average FWHM is 4 arcsec or more.

I agree with Marc and Mike. I compared yours with Mr Ward's rendition for detail and the difference is pronounced. It's the detail that lets this image down mate. Did you do some decon?

IMO there is also a blue cast you need to get rid of to make your colour pop.

I admire your work tremendously Greg so I'm sorry if I'm coming across as harsh. But you're a seasoned "pro" with the best equipment and a zillion gorgeous images behind you, so it's only natural folks are going to be more critical.

Cheers, Marcus

[gregbradley]

Always possible Mike. I do focus manually. I have found out how to get Focus Max to work so I should try that. There was quite a variablility in sharpness between subs. You could see the seeing improve as time went on looking through the subs. I did delete the worst. Perhaps I should go through them more savagely as some acutally have some decent seeing in them Must've been early in the morning.

There is plenty of data there really.

I thought the AO helped with seeing?? I now routinely get pretty round stars now I finally got the PEC recorded properly. So tracking errors are pretty minimal and not really an issue.

Thank for the advice.




I did deconvolve all of them including RGB which I don't normally.

I can be more selective in which subs I use as some were pretty sharp.

Have we had a bad period of seeing lately? I must admit looking through the scope visually was like - wow, check out how bad the seeing is. Saturn was boiling in and out of view. I guess when focusing if one shot is sharp, you don't change anything and the next is soft then the seeing is really poor.

I will have another go at this one to see if I can select out the worst.

I did actually interrupt the imaging to do repairs on the scope. I did 60 minutes of luminance. I had collimated the scope and when putting in the visual adapter I loosened the base plate of the focuser thinking it was part of the adapter. Some spacing shims fell out. I out 2 back in and later found a 3rd on the floor. I noticed slight coma and the left was slightly out of focus compared to the right Yikes!

So I pulled everything apart and repositioned the shims so they were venly packing out the focuser plate and the scope returned to normal -Phew. Haven't had that happen since my STL 11 shims fell out after loosening the mounting plate on the face (they are shimmed out by the way and in exact spots to make it orthogonal).

So those 60 minutes of Lum weren't the best.

Regarding the blue cast the smaller image is more blue for some reason and seemed to lose the deeper richer reds of the larger image for
some odd reason. The softness is the issue though.

I did highpass filtering as well as a tad of smart sharpen so there's no room for improvement there. Its in the data that there needs to
be an improvement.

I'm gonna have to get the adapter plate so I can cart it all down to my dark site on a good forecast and see what it can do and make sure the optics are in fact sharp and adjusted correctly.

Thanks for the uplifting words.

Back to the drawing board.

Greg.

[multiweb]

Yep. I haven't bothered imaging at long FL for over a month now. Check the jetstream map. Every clear night we've had has been from average to poor.

[strongmanmike]

I love a good blue cast...better than green or magenta :P :lol:

[richardo]

Hi Greg,
yes I have to agree with the image being a little soft and I've noticed it a bit on a couple of your previous images with the CDK.
I'm sure you have as well, so lets be honest ok.

8 hours is really a huge amount of data for any FL in my opinion, F6.8 is not that slow and should really be showing a truck load of detail. Especially with the Ha data and even in a LP area.
Seeing would have something to do with it but I'm leaning towards collimation... or something else at play here. As with you, I really want to see this scope of yours do better.

Not saying that you're doing anything wrong here, but how are you collimating this thing??

I took a snap in CCD inspector to see what's happening... it is out by a fair bit. Not that CCD inspector is gospel but it has helped me out in the past trouble shoot.
I reckon, get collimation down to perfect, perhaps find a better method to do it. (F6.8 not as critical as F4 but I think for every thing to come together and work well it needs to be spot) use Focus max and things will be better even in LP.

Keep us updated with your findings Greg, we'd all like to see you get the best from this beauty.

All the best
Rich

[Tom Davis]

Up close and personal. I like it!!

Tom

[Peter Ward]

Not bad...but I'd echo earlier comments in that it lacks "snap" in the focus area....though I wouldn't discount seeing or local thermal issues.

By the way, my current camera doesn't have an AO...the are still some way off for large format cameras.....sigh....

[Ross G]

Great photo Greg.

Beautiful colours and a wide, smooth tonal range....at least as important as outright sharpness.


Thanks.


Ross.

[John Hothersall]

Still a good image and I prefer results from larger scopes even in poor seeing. I struggle with collimation at Newtonian F4.5 as it has to be perfect as it slews and often changes and big sensors are more revealing of errors.

John.

[wysiwyg]

Nice one Greg!
Looks like you finally have everything working :thumbsup:

[gregbradley]

Not saying that you're doing anything wrong here, but how are you collimating this thing??

I took a snap in CCD inspector to see what's happening... it is out by a fair bit. Not that CCD inspector is gospel but it has helped me out in the past trouble shoot.
I reckon, get collimation down to perfect, perhaps find a better method to do it. (F6.8 not as critical as F4 but I think for every thing to come together and work well it needs to be spot) use Focus max and things will be better even in LP.

Thanks for that snapshot. I did collimation per the Planewave Instructions which are basically to get a widefield eyepiece, defocus and centre the centre dot. I did that (it was already close) and then they say to check the spacing between the mirrors using a special adapter and a ronchi eyepiece, I did that, then use a high power eyepiece which I did (4mm) and repeat the first step. It seemed fine but I did not check it with CCD Inspector. I think I will buy that program as it has real time
adjustment available.

Seeing is the most likely culprit but collimation may still need work.

Cheers.




Thanks Tom.



An AO unit with a 16803 chip would be pretty awesome.



Cheers Ross.



Thanks John.



Cheers.

[Paul Haese]

Colour looks good to me. I like the detail, maybe it is seeing?? The stars in the right side corners look good, but the stars in the left corners look a little elongated. That might be tilt going on there and giving the suspect reading on CCDstack (which tends to be a little unreliable for my tastes, but I still use it from time to time).

Couple critique suggestions from me.

1. I can see the image overlay in the top corners. Perhaps cropping the image a little just to remove this little distracting aspect.

2. the core looks a little burnt out to me. I like the detail surrounding it but cannot see the core well. (maybe just being picky forgive me if I am)

Other than that I wish I had an image this good of the lagoon at hi res. I would rather see a galaxy though with that kit.:)

[jjjnettie]

A mammoth effort Greg. I hope you get good seeing your way soon.

[gregbradley]

Thanks Paul. I am in the middle of a redo. There are 60 minutes of luminance that were taken after collimation that then showed up the spacers were off under the bottom focuser plate. I pulled it apart and fixed it after that first hour and it was fine after that. So part of the image has this earlier faulty setup which I used. Perhaps I should've started again with only the new data. So the CCD inspector data would also be picking up that. Visually collimation seemed very close and not a noticeable error needing correction. But I don't know how much CCDI will pick up.

One things for sure the spacing between the corrector and the focuser is incredibly demanding of accuracy. These spacers were only about .2 or .3mm thick.

Luminance in the new version is stripped down to only the best 6 subs and it seems noticeably sharper (at least to me hehehe).

Greg.




Cheers JJ. There's always something new to conquer in this hobby. Part of its appeal.

[h0ughy]

yes the air in nsw hasnt been good, i like the scale but it does look a tad soft. colour look good

[gregbradley]

I took on board the softness and reprocessed the image to see if I can regain some sharpness.

I was more picky on the luminance subs and threw out 5 of them that were the soft ones. The remaining 6 were the sharpest of the bunch of about 15.

I think this one is considerably sharper but if still soft then its as far as I can take it without fresh data taken at a time of better seeing. One of the limitations of this game - the seeing.

http://upload.pbase.com/gregbradley/image/135964244/large

http://upload.pbase.com/gregbradley/image/135964244/original

Greg.

[marc4darkskies]

Mate! You've tightened the stars up a bit but I'm afraid they're now looking overcooked! Looks to me like you've applied a lot of decon. You've clobbered your colour balance too reducing the dynamic range of the red and blue channels considerably.

Your original version had great colour (except for the blue cast), so even with the soft focus I'd vote for it as being the better of the two.

Cheers, Marcus

[gregbradley]

Yes I think you're right there Marcus. I softened the stars a tad and made a blend from the older and the new using the colour of the old more and the sharper detail of the new.

Looks a better result now and perhaps as much as I can get out of that run. Same links.

Cheers

Greg.