NGC 6334 (Cat’s Paw Nebula) and NGC 6357
Taken 4.10.08
Image details…
Canon 40D (modded)
Canon 70-200mm f4L lens, 200mm @ f4 (+ IDAS LPS filter)
Skywatcher Synscan EQ5 mount
Autoguided with PHD
8x420sec, iso1600, no ICNR – tried taking darks but subsequent stacked image suffered from a speckled noise artefact so darks were dumped!
(see attached lo-res crop)
That's come up very nicely Doug !
Some nice fine detail there.
You really need to start taking flats though.
The problem you mention with your darks is due to variation in ambient temp to your lights I'd say.
When did you take the darks, between your lights or at the end ?
That's come up very nicely Doug !
Some nice fine detail there.
You really need to start taking flats though.
The problem you mention with your darks is due to variation in ambient temp to your lights I'd say.
When did you take the darks, between your lights or at the end ?
Cheers Andrew,
Yes I guessed that that was the reason - darks were taken between the Cat's Paw images and SMC subs which I went for next.
I'm gonna stick with ICNR in future - damn the extra time!!!!
Flats - I'm on it...meant to get some tonight but sorted out backlash in RA on the mount then played some backyard cricket with Sophie (daughter).
Tomorrow!!!
Doug
Yep if in doubt then stick with ICNR, I do too sometimes when there's a risk of a temp difference.
As for flats, I've got to build a flat box, I can't do without one now.
Way to go Doug. There's lots of info in the full shot that could be brought out with a bit more tweaking. As RB said, Flats! That's a horrid dose of vignetting you've got there.
Yep your dark frames are letting you down. Remember if the temp drop by 6deg then your dark current halves. Conversely if the temp goes up by 6 deg your dark current doubles. Not usually the problem though ICNR can be a pain when you are doing those long shots, but with a DSLR it is probably the best way to deal with them unless you are lucky enough to have a relatively stable night temp.
...As RB said, Flats! That's a horrid dose of vignetting you've got there.
Cheers Paul,
Got to bite the bullet and sort out flats very soon.
This image had multiple runs of the GradX-terminator plug in to come out looking vaguely normal!!!
Doug
Hi Doug I know I'm probably a bit late here, but I do have a valid excuse...truly
After having a good look at it mate, it has come up pretty well, it is a nice widefield, and it looks like the guiding is just about spot on as well, nice and sharp.
Na mate I'm not going to say it, about the darks and flats, but it will make a big difference.
I hated doing them In Camera, but, now it is just second nature, and just tell myself, it has to be part of the image run.
Flats arn't really an issue though they only take a minute or two.
Anyway I'll shut up now and just say, well done with this one.
Good one Doug. Nice when you can get a couple in the same shot. I've had to do some flats but can't seem to get around to the darks. Trouble is the temperature seems to vary a lot during the night down here so it rules out doing them at the end of the session. Maybe ICNR is the easiest way, but less lights.
There seems to be nothing you can't successfully image with that camera+lens Doug.... from falling space junk to cats paws to tarantulas... You name it..
I like it Doug and I too have to come to terms with flats. The cats paw is a great little neb which is sadly behind my western horizon shed now. I got some good Ha last month but will have to wait a year to get the colour data now.
Oh,
Re. the backlash you mentioned. Any tricks? I have slightly loaded the counter weights and adjusted the worm gears so there is practically no play in the RA axis. Its driving me mental.
I like it Doug and I too have to come to terms with flats. The cats paw is a great little neb which is sadly behind my western horizon shed now. I got some good Ha last month but will have to wait a year to get the colour data now.
Oh,
Re. the backlash you mentioned. Any tricks? I have slightly loaded the counter weights and adjusted the worm gears so there is practically no play in the RA axis. Its driving me mental.
Cheers Matt,
For your shed read my tree!!!
Re Backlash... in the last week or so I noticed really awful backlash in RA developing - up to 3-4 seconds for movement when pushing the buttons o the controller.
Took the RA assembly apart and found that the brass cog (attached to the cylindrical worm gear) that meshes with the electric motor had become loose as the retaining grub screws had slackened off.
Tightened all up and was good to go!
Doug
Nice one Dougie I'm getting use to these flats and lights etc deal myself for lights I either grab a few shots of the clear sky just before sunset or shine a bright light on a white piece of paper and take shot's of that.
In camera NR does take up a lot more time especially the longer you expose an image. Although not sure of how many lights, darks, biases etc I should take
![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
ICNR can be a pain when you are doing those long shots, but with a DSLR it is probably the best way to deal with them unless you are lucky enough to have a relatively stable night temp.
