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Old 05-06-2019, 11:58 PM
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The beginnings of a lobster

Finally got out in the backyard and got some photons. Not a lot of data yet and my O3 data had issues - much more bloated than the Ha and oddly suffered from some kind of radial distortion (coma?) unlike the Ha. It could have been the slight defocusing of the guide camera (in an OAG) when the O3 filter refocussed. Weirdly the 3nm O3 filter needs much shorter flat exposures than the 5nm Ha? Is that normal? Anyway, despite the poor O3 stars, I scraped together a quick HOO image: https://www.astrobin.com/full/408897/0/

5nm Ha 40x180s, 3nm O3 40x180s shot though an 8" Quattro on an EQ6-R with a ZWO ASI1600MM-Pro.
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Old 06-06-2019, 07:09 AM
Placidus (Mike and Trish)
Narrowing the band

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That's ROOLY good despite the optical issues mentioned. You've got a lovely balance between showing bright detail and faint features, preserving the overall feeling and structure (rather than trying to show every last photon in the dark regions and ending up with a dull flat image as some do).

Short OIII and long Ha flats will happen if you use a blue light source (like early evening sky or an LED with not much red in it). The reverse happens if you use an incandescent bulb for flats.

Defocusing the guide camera should not normally cause guiding issues unless it's to the point where the guide star is too faint and blurry to see. Slight guider defocusing can actually be beneficial for those where the guide camera pixels are big or the guider focal length is short, as it spreads the guide star over more than one pixel and gives a better estimate of the centroid. Severe defocusing to the point where the software can't see the guide star at all will of course be catastrophic, but that would produce a squiggly trail, not what you had.

Bad seeing always affects OIII much more than Ha. Also anything like a flappy heating wire for a dew shield or secondary mirror heater will produce worse diffraction spikes with OIII.

Despite all that, one of the best, most pleasing Lobsters we've seen.
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Old 06-06-2019, 09:14 AM
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Thanks for the comments on the O3. It makes a lot of sense and stops me worrying something is failing at the filter end. It occurred to me that what might have been the real problem was focus. I think I disabled autofocus on filter change for some recent RGB imaging (filters are all parfocal). Then the emphasized radial distortion and bloated stars in the O3 make much more sense... maybe...
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Old 06-06-2019, 10:13 AM
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strongmanmike (Michael)
Woohoo it's clear

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It's good to just get out huh? Some lovely detail in there Ben, nice informative response from M&T too

Mike
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Old 06-06-2019, 11:36 AM
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Quote:
Originally Posted by strongmanmike View Post
It's good to just get out huh? Some lovely detail in there Ben
It is great to get out but Iím still feeling it... imaging and one day cricket on the TV taking their toll! Hoping to add some more data Sunday night and get better focus and shorter subs with the O3, plus some S2.
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Old 06-06-2019, 11:54 AM
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Woohoo it's clear

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Originally Posted by Benjamin View Post
It is great to get out but Iím still feeling it... imaging and one day cricket on the TV taking their toll! Hoping to add some more data Sunday night and get better focus and shorter subs with the O3, plus some S2.
Good luck
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Old 07-06-2019, 09:41 AM
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Probably moving away from what was interesting in the previous images but have allowed more O3 through in this version. Better? I don’t know anymore... Time to get better/more data!
https://www.astrobin.com/408897/F/?nc=user
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Last edited by Benjamin; 07-06-2019 at 08:28 PM.
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Old 07-06-2019, 07:31 PM
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Slawomir (Suavi)
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A great image Ben; your 200mm Newtonian is certainly a very capable instrument - and your data processing as well
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Old 07-06-2019, 08:41 PM
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Thanks Suavi. The Quattro is turning out all right. The mirror still flops around too much so need to secure that a bit better but other than that Iím loving the f4 speed, carbon fibre resistance to the cold/shifts in focus, and (mostly) the diffraction spikes! Also seems a good match in regard to focal length/pixel size for the ASI1600MM-Pro. I was hoping winter would bring abundant clear skies to QLD, but seems it might be as bad as the summer :-/
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Old 08-06-2019, 09:00 AM
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Andy01 (Andy)
My God it's full of stars

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Looking good Ben! By co-incidence I'm chipping away at the same object as well - it's a fascinating target, but sure needs lots of data!
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Old 08-06-2019, 10:25 AM
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Thanks Andy. Yes, lots of data needed! I think there are parts of it that are a bit like the Cats Paw; flat areas that donít give up much detail. Also you have super abundant areas that suit a certain focal length/pixel size and then the micro details at the core that may never be fully resolved. With only 4 hours I found myself playing with colour balance mostly and wondering if a less saturated, flatter version might be better. Anyway, clear skies coming I hope for all of us.
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Old 08-06-2019, 11:04 AM
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Wasn't fussed with the first iteration, but I rather like the final version. Nice colour variations, and good depth...this isn't the brightest sucker in the sky, so you've done well.
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Old 08-06-2019, 11:07 AM
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Thanks Peter. Looking back at the versions I’ve made of this has become quite an education. It would be great to do this more often to avoid some of the pitfalls.
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Old 08-06-2019, 12:06 PM
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Looking very good Ben.
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Old 08-06-2019, 08:37 PM
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Looking very good Ben.
Cheers Pete.
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Old 10-06-2019, 10:41 AM
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A first crack at a SHO version. Got much better O3 last night but only 9 minutes of S2! Hopefully more tonight and some RGB stars to top it off.
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Last edited by Benjamin; 10-06-2019 at 12:12 PM.
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Old 10-06-2019, 11:08 AM
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That's looking pretty good. The Lobster is not a photogenic object so you have done very well there.

Greg.
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Old 10-06-2019, 11:46 AM
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Originally Posted by gregbradley View Post
That's looking pretty good. The Lobster is not a photogenic object so you have done very well there.
Cheers. I think once I get more S2 and tone down the O3 a bit (in the core) it might spring to life a bit more. Iím starting to get a feel for what I want out of it I think.
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