New NGC7000 and Pelican Nebula from last night

[Daniel]

Hi All, had a so-so night last night, was quite misty so all my subs were coming out quite washed out and seem to have picked up a blue halo which i think was because of the cloud (wasn't as bad on pelican a little later on once the clouds had died down a bit), wanted to try my focal reducer out so i stuck with it and still managed to resolve some images, not as happy with these as the other one I did, but I thought I'd post them to show you guy's how the meade 0.63 focal reducer / flattenner was performing.

details are as follows :-

NGC7000 = 60x60s ISO 400
Pelican nebula = 101x30s ISO 800

Darks and Flats Applied to both

Darks = 17x60s ISO 400 for NGC7000
           31x60s ISO 800 for Pelican

Flats = 99x1/100 ISO 100 For Both

Anyway, as I mentioned these aren't up to the other one but im happy to try out the focal reducer and the quickly made light box for taking the flats, tried a stack without flats and without them it's pretty terrible, can't wait to use them all the time now.

These haven't been processed much either yet, just curves and levels applied.

Oh, a couple of quick questions by the way, firstly, does anyone know if there are any field flatteners which aren't focal reducers aswell? there great for these big sweeping nebulae but not for smaller things such as the elephants trunk i plan on imaging soon (tried it last night but cloud was terrible at the time)

also, when taking darks frames, could I take the camera off the scope and put the lens cap on as long as I keep it outside at the same temperature or should it stay exaclty in place?

Anyway, sorry for the long message, Didn't plan on it being this long when i started, i'll just shut up now and post the image...............

[JohnP]

Hi daniel,

Yep for darks you can take camera off the scope - as long as temp is the same & exposures/ ISO it shouldn't matter. Obviously camera needs to be light tight. Make sure you put some black tape over the viewfinder as well because I think with long exposures light can leak in via viewfinder to the chip...

Cheers,  John.

PS - Image not too bad - like you say need to sort out coma/ flattener...

[Fay]

You did work hard, Daniel.

The stars seem to be gathering in both images, top & bottom on the left. It is ok if you have room around the main object, for cropping, but often nebulae need the whole frame.

Anyway you have not done too much processing yet.

I mailed Williams Optics regarding  the setup of ED80/350D & the Mk III FR/FL. They said that they had  never tested it on this scope & would recommend the MKII which is what I have.  They said it is difficult to avoid vignetting  etc, It seems it is a black art like guiding, matching up the various components. Chris did make another suggestion in this thread which you may have read.   

Look forward to seeing your final results. You may be more happy then. You are getting on really well.

[Daniel]

Oh, by the way, on the subject of vignetting, if your using a large chip DSLR to image with, i can recommend the T-Adapter I got, it's got the 2" bayonette built into it so has no smaller apeture to screw the 2" adapter onto like most T-Rings have, giving you the full 2 inches to see through. i'll try to dig out the website of where i got it, doesn't cost as much as a T-ring and T-adapter combined and is much better

[Mike]

What kit as used?

[Daniel]

This was done on the 80ED on the CG5 mount again, Canon 40D with meade 0.63 focal reducer / flattener and CLS filter

right now with the lack of night hours im loving the fact the lot takes all of 20 minutes to be up and running

[MarkS]

Daniel,

You have a good couple of images there - especially considering the short total exposures and very short subs.  The central portion of each image is very clear and well focused but there are problems towards the corners. 

1) In the corners the stars appear slightly elongated - it looks to me like rotation around the centre.  Does this elongation appear on each sub or only after stacking?  What do you use for stacking?  Does it have the capability of de-rotation?  I remember my CG5 was not easy to polar align accurately (I had no polar scope) and this may be your problem also.  Easily addressed in software - just de-rotate during stacking.  If the problem is not a slow rotation over 1 hour but the elongation appears in each sub-image then maybe you have a problem with vibration.

2) You appear to have a problem with background gradients - especially in the blue channel.  I currently have the same problem with my combination of DSLR + CLS filter.  The CLS filter does a very good job at removing light pollution except that it leaves a residual blue background gradient.  Again, I don't know what chosen software for stacking is and what options it may (or may not have) for gradient removal but you can always subsequently use IRIS which has a number of tools available.  Tutorial here:  http://www.astrosurf.com/buil/iris/tutorial4/doc14_us.htm

Well done Daniel - keep up the good work!

[RobertM]

Lovely image Daniel.  You won't see any problems due to field rotation on any of those subs so as the rotation seems to be in all four corners it'll be your stacking software that's not aligning properly.  Once you get that sorted you'll get rid of those nasty elogated stars in the corners and the whole image will benefit greatly.

It looks like you're experimenting with different ISO's, have you a preference for higher or lower settings ?  I did read that the 40d and 450d are more optimised for high ISO noise reduction and because of that there is no advantage in using lower settings - any thoughts ?

Robert

[Mike]

Nice image Daniel. I'd agree it looks like alignment issues in the stacking procedure. Looks like a manual 2 star alignment is needed.

[Fay]

As with me having the same problem, it always seems ok where there are not many stars in the corners & is very noticeable because of the rich Cygnus star fields.

I have one of those adpators, Danel, with full 2" aperture.

Don't forget, you have done really well & you have only just started!!!! It is interesting reading your accounts as they hare helpful to others.

Fay 

[Mike]

Fay you were supposed to show me this at the last imaging session. Grab me at the next observing or imaging or even the monthly with your laptop and MaximDL on it and i'll show you how to fix it.

[Fay]

Thanks Mike. It was too busy at the last session as Mark gave his talk, but will catch you next time.

[Daniel]

Hi All, thanks for the advice / encouragement, I'll check my subs when I get home from work tonight, I stacked using DSS, but used 100% of the images, maybe I should have dropped the threshold a bit so it threw away more.

Also, would DSS counter for the de-rotation automatically or would i have to set that up myself?

not sure how I got those background gradients, unless they were cloud (which i was shooting through) the other image of the north american I did the other week didn't have them, although I wasn't using the focal reducer on that one

Thanks again

Daniel
:O)

[Rocket Pooch]

Daniel,

Great images, you have it sussed now.


If you have photoshop, open the images, do a de-speckle and then re-sample the images down, they will look a lot better.

Chris


p.s. see you at dsc hopefully, I will be there with the caravan and a heap of beer.

[Daniel]

i've checked my subs and it seems the distortion you can see is indeed on the original subs, so i guess this must be field rotation. might have something to do with the balancing I did on the scope, I was experimenting with how much to bias the north side with the weights, guess i may have pushed it too far!

one good thong though, by reducing the percentage of subs DSS accepts I seem to have got rid of most of the blue hue, which i guess was something to do with the cloud in many of the shots

[Mike]

p.s. see you at dsc hopefully, I will be there with the caravan and a heap of beer.

Woohoo !!!   Can't wait.