OSC Omega

[Peter Ward]

While the world doesn't need another Omega Cent it was well placed last night for a kind of a mini-review here (http://www.atscope.com.au/BRO/gallery488.html)

While I am pleased with the result, my thoughts about OSC cameras remain mixed. They are a lot of fun, but are a challenge to use on very faint objects from urban skies.

[Atmos]

It’s come out pretty well Peter.
My experience with OSC under suburban skies is that the smaller the FOV the better along with higher resolution.

Out of curiosity, why did you run BackgroundNeutralisation on every frame opposed to just the final integration.

[Peter Ward]

Every frame. Easy enough with image containers ;)

That said higher intensity values still have too much green, so post-stack tweaking still required.

BTW clicking on the image will now take you to a full-res version....for the pixel peepers :)

[gregbradley]

Quite a good result. A lot of blue stars, is that accurate?

Well, look who's gone over to the dark side eh?

A good break there with the adapters working out, it looks nice and solid and square.

As far as gain goes for the ASI183mm Pro I have followed threads on CloudyNights about best settings and you are right there are lots of opinions.

What I found from Jon Rista and 2nded by Ben on this forum was gain 53 for LRGB and gain 111 for narrowband and 300 seconds for each.
I have also used 10mins for narrowband as well and I think I will make that standard. 10 minutes for LRGB though gives oversaturated stars on the Honders.

QHY uses a different scale but its a guide.

As far as offset goes all that does, if I understand it correctly, is shift the black point of the histogram much like levels and curves in Photoshop. So not a real important thing to touch as far as I can see. In fact the ASI driver for the Sky X just has gain as the variable there is no entry for the offset (the simpler the better).

On the 183mm I am finding 300 seconds gain 53 -10C works well and 300-600 seconds gain 111 -10C for narrowband. 60 seconds would be a pain to process but perhaps it works better. Read noise is lower with higher gain so there is a guiding principle. Dynamic range also falls with higher gain so there is the counter principle.

A lot of LRGB and Ha and O111 subs show almost no amp glow as the signal is so strong but S11 shows lots.

As you say it calibrates out well although it can on worst case leave some remaining slight noise.

I would up the gain or exposure for S11, probably simply the exposure as shifting gain in a sequence of shots is not available in the Sky X driver.

As to oversaturating wells, at 15,000 its not that different to the ICX694 CCD and I am getting nicer looking stars than I ever got with that CCD.

As far as pattern noise goes, again I find if the exposure is long enough that pattern noise is swamped by signal and it disappears. The balance between that and oversaturating pixels is the key and that would vary with aperture and F ratio.

Greg.

[Peter Ward]

:lol:

No...the extra saturation of the blue stars, while not accurate, is an intentional tweak by yours truly.

I think mono-CMOS might be and easier/better choice for deep sky...very much so if you want to add narrow band data.

That said, while my new STXL runs rings around the QHY OSC (and cost 6x as much...) for deep sky, I bought the camera for planetary imaging (where it excels).

This was a bit fun to test the waters. I think the result is actually quite good....remarkable really...as the camera costs way less than many "big brand" filter sets, let alone the rest.

[multiweb]

Looks like a really nice little rig. :thumbsup:
Your SBIG dark is pretty clean.

[Peter Ward]

Ta Marc. The KAF16200 darks certainly have "salt and pepper"...somewhat invisible at the uploaded image size...but none of the banding/amp glow.

My thoughts are CMOS images can be fairly readily cleaned-up and calibrated.
I've simply not worked out the best work-flow as yet.

I re-worked and uploaded the data using PI masks and colour calibration. I applied a smidge of wavelet sharpening.
Looks more "crunchy" now.

[gregbradley]

That worked very well. More pop now.

Greg.

[Phil Hart]

Thanks for the posting the brief review and comparison images/notes Peter - makes for interesting reading. And it's a nice image too :).

My CMOS image coming up shortly..

Phil

[Peter Ward]

Ta. You may ask, but might want to PM me so not to break the IIS TOS. ;)



Thanks Phil.. Have to say I looked long and hard at going to a 35mm CMOS astro-cam....well I did indeed pull the trigger on the EOSRa...but it's not the same.

I suspect we are in for a treat when you publish the results from your new toy!



Thanks Greg, yep I think it has that "rice-bubble" look now (snap/crackle/pop :) )

[h0ughy]

No need to say how hard it is to image in the city with a OSC but you always get a great result. You have discovered that processing is a completely different science to mono. But it can give one a result that normally wouldn't have . I found I run at -5 to keep consistency with warm nights as the cooler isn't like the dearer cameras. Would be interested to find out how you did your flats?
I find that the light pollution fluctuates and each image is different. The noise that you end up getting in the light frames can be problematic especially if it is smoke or dust .
But as your testing has shown there is life and hope. Software has always been an issue. I can think that those who would use the camera would probably purchase APT to aid in capture. Third party and cheap as to run. As for the USB 3, if it's deepsky then a self powered usb2 cable will do the trick, but with usb3 planetary work you're stuffed. There is no fix for that I have found, and I have bought most things to make it work. I end up moving laptop within range of the primary USB cable. Not pretty but functional..
But it is gratifying to see real reviews.

[topheart]

Interesting discussion. Thanks Peter and Co.!!

Cheers,
Tim

[Placidus]

The dark frame comparison says it all. Nice work.

Omega is a good target to show what the beastie can do on a bright object. The image is crisp and crunchy.

[Decimus]

An absolutely wonderful image of Omega Centauri, Peter - and the blue stars are magnificent :)

Cheers,
Richard

[Peter Ward]

Very kind of you Richard.

A bit fun, but not my A-game.

I have a much better version here (http://www.atscope.com.au/BRO/gallery428.html)

[Ryderscope]

We can’t have too many Omega Cents Peter and this one is a fine rendition. You’ve managed to punch through the suburban haze well again too. Thanks for sharing.