ngc4565 LRGB - up close ;-)

[ChrisLX200]

This was captured using my ODK12 over the past week under a near-full moon. It could use a better L channel as the faint bits are mostly gone (washed out by moon glow).

Scope: ODK12 f/6.8

CCD: Atik490EX @ 1x1 (0.37 arcsec/pxl ! )

Mount: 10-Micron GM1000HPS

Guide: unguided

Filters: Baader LRGB

Data: 8 x 600s/channel (LRG and B )

ChrisH

[hobsey]

Nice!

I like that a lot. 

[ollypenrice]

Whoa, those are seriously tiny stars!  Good image. Maybe just a tad up in the greens for me? 

Yves and I did this at 0.66"PP and thought that was a fair old pixel scale. Do you think 0.37 is working?*

Olly

*Edit. By which I mean, 'Working to produce more final resolution than you'd have in Bin 2.'

[johnrt]

Smashing! The moon has taken it's toll, but when you've got a new ODK waiting to get going you take what you can get! This looks like it's going to be an outstanding set up, looking forward to what's to come from you!

[swag72]

This is seriously good stuff..... Those stars are tiny!!! Your ODK is working like a dream

[Big Bang!]

I like that.

Chris, can you explain a bit about the effect that over or under sampling has on an image.  I have an Atik One 9, and quite often use that un-binned if the seeing is good - gives me a scale of about 0.38"/pix.  How does one recognise the effects of oversampling?

Gus

[Twisted Lip]

That is simply stunning

Will

[toxic]

WoW very nice indeed

[derrickf]

Nicely done Chris. Did you not use flats or did the flats not fully correct some of the dust motes due to the bright background?  Very impressive tracking performance by the 10-Micron mount!!

@Gus (Big Bang): provided that your subs have sufficient signal to be sky noise  limited (rather than read noise limited) there are no significant negative effects of oversampling. 

 

Derrick

[Petergoodhew]

So it IS possible to produce awesome LRGB images when the moon is full!

Stunning image.

 

Peter

[Big Bang!]

34 minutes ago, derrickf said:

Nicely done Chris. Did you not use flats or did the flats not fully correct some of the dust motes due to the bright background?  Very impressive tracking performance by the 10-Micron mount!!

@Gus (Big Bang): provided that your subs have sufficient signal to be sky noise  limited (rather than read noise limited) there are no significant negative effects of oversampling. 

 

Derrick

Thanks Derrick

Does that mean, in effect, that if the seeing is really good and you are not imaging a really faint object you are unlikely to see significantly negative impacts of using a scale of less than 1"/Pix?  Have I understood that correctly?

Gus

[simmo39]

Nice!

[derrickf]

27 minutes ago, Big Bang! said:

Does that mean, in effect, that if the seeing is really good and you are not imaging a really faint object you are unlikely to see significantly negative impacts of using a scale of less than 1"/Pix?  Have I understood that correctly?

Yes, that's correct - I routinely image at around 0.46 second/pixel. On nights of good seeing at my site the average seeing is around 2.1 arcseconds and reaches 1.8 on exceptional nights. In order to properly sample features at 1.8 arcseconds seeing you need a plate scale of 1.8/3.3 = 0.55 arcseconds/pixel so I am moderately oversampled for my average seeing and barely oversampled for nights of exceptional seeing.

Don't be afraid of imaging at sub 1 arcsecond platescale :-)

Derrick

[laudropb]

Great image.

[ChrisLX200]

Wow, lots of replies so many thanks to everyone!

It is very over-sampled data (in theory, given my local seeing conditions) but I'm not sure I would actually gain anything by going with 2x2 binning. I think I have get more post-processing options with finely sampled data. Apart from the Green channel the colour data was OK-ish even under the full moon (albeit gradients and needed sorting out). However a better result will always be achieved under a dark sky and I propose to replace the more important Lum channel if I get the chance. I'll also add some Ha data too if the mount continues to behave (will need 30min subs with a Ha filter)

I took on board what Olly said about the green cast :-) which is quite obvious now, so I re-processed rather than just run SCNR on it. The Green channel massively affects how the Red channel behaves when they are all combined so just knocling the Green off doesn't really correct in my experience.

This ODK12 has caused me endless problems, not least because it's clearly more of a challenge to work at 2040mm focal length than 660mm with the refractor. The field isn't flat (which it's advertised to be), it won't even focus unless it has cooled for an hour - can't even focus it well enough to run a mount model which needs plate-solving to work! The collimation is a pig - I had bought a rather expensive Howie Glatter laser (the one with a rings diffraction plate) and thought I had it sussed. Nope. In the end I put a high-power eyepiece in the thing and collimated the old-fashioned way using a star test, that finally sorted the silly star shapes I was getting. The 10-Micron mount _will_ work unguided with it provided all the ducks are lined up - any issues with balance tends to throw it off though. The fine DEC balance adjustment system I've recently installed really helped and last night the model error was 5.5" RMS - which is good enough, and should allow for 30min unguided exposures.

Oh, and yes - I do need a new set of flats, the old ones were invalidated by some changes I made and they're not fully correcting...

Anyway, this is the re-process:

ChrisH

[swag72]

Interesting your thoughts on the ODK12 Chris - I have found my field to be flat with the larger KAF8300 - Is there a chance that the corrector was moved at all from its factory settings? It does take a while to cool down, but it will certainly focus before cooled, but shifts a lot as it continues to cool. Collimation I haven't had to touch since getting it (although I had to tweak the spacing with the Ronchi grating.

Perhaps the 10" is a much easier beast after all .

[Barry-Wilson]

Wow, that really is an image scale suited to galaxies.  Despite the moonlight induced loss of detail in the edge-on dust lane, this is a great image Chris and you must be pleased after your efforts to bring the 12" ODK to an imaging standard.

[ChrisLX200]

4 hours ago, swag72 said:

Interesting your thoughts on the ODK12 Chris - I have found my field to be flat with the larger KAF8300 - Is there a chance that the corrector was moved at all from its factory settings? It does take a while to cool down, but it will certainly focus before cooled, but shifts a lot as it continues to cool. Collimation I haven't had to touch since getting it (although I had to tweak the spacing with the Ronchi grating.

Perhaps the 10" is a much easier beast after all .

You know, I'm thinking something may not be right with mine and that I should take it back to Orion Optics to get it checked out. They're fairly close so it's not much effort.

Chris

[ChrisLX200]

Thanks Barry,

Chris

[Moonshane]

Stunning image Chris of one of my favourite galaxies despite the challenges. I have zero knowledge of imaging preventing me making any meaningful technical comment.

[ChrisLX200]

Thanks Shane ;-)

Interesting weather we're getting, I noted a 'shower' approaching on RainAlarm so nipped out and put the cover over the scope, went out 15min later only to find the lot was covered in snow! Shook that off and carried on... ;-)

ChrisH

[Moonshane]

I was observing the sun in bright sunlight today and no cloud - started raining and then about an hour later we had a hailstorm!

[ChrisLX200]

Some good clear patches tonight enabled me to add more Lum data - now more than double at 25 x 600s (although I lost a few subs to bright satellites). Also captured some 3nM H-alpha but it doesn't look like it would add much detail - just modulate the red channel a bit. Pleased that the mount tracked well unguided at 20min exposures though. There are far more background galaxies in this image than there are stars!

ChrisH

[derrickf]

That's a big improvement over what was already a good image. The extra luminance has enabled you to be less aggressive with sharpening and now shows actual detail in the dust lane rather than the somewhat over-sharpened earlier version.

Glad to hear that you had no tracking problems.

Derrick

[opticalpath]

That's fantastic, Chris!  One of my favourite subjects. Impressively good tracking and enviable tiny stars!

Adrian