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Giant Floating Brain - NGC6888 Crescent Nebula


badgers

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I was going to say good luck with it but it doesn't sound like you need it. You make your own luck.

I'm really looking forward to seeing the results of your hard work. Thanks for letting us know.

I'll pop over and say hello at Kelling if you're around.

Dave.

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I just went for A3 this time, 460ex pictures are 2750x2199 and the FITS files come in at around 12MB each at 1x1.

I think to go bigger than A3 you'd want to be working with a mosaic, although I've not tried the upscaling methods in PixInsight yet.

My dream this winter is to do a mosaic of M31, with my focal length and sensor I'd need to do at least 9 panels, but that would be perfect resolution for a nice big print.

Dave I'm at Blue 252, please do pop by : ) I'm there Friday night, Saturday night and Sunday night, although I might not be around during the day on Saturday.

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I'm not sure if the 4 hours of collimation, the focuser resquaring or retweaking the spacing to the CCD has done this but:

med_gallery_19171_1868_74449.jpg

Corners and centre of image (5x5 minute subs, guding through light haze).

Can I declare my war with eggy stars over ?

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The 150P seems a fine scope when set up. It's almost persuading me !

To be fair that Camera (ICX694 Sony Sensor) is a revelation. I could probably sellotape it to a broom handle and put a milk bottle over the end as a lens and it would still perform : )

Hoping that these sensors get cheaper and more widespread because the low-noise characteristics and sensitivity are excellent.

But my little 150P seems happy again.

My big decision now is whether or not to buy a small APO for widefield, something like the TS APO80 F/6

or to buy the ASA 0.73 reducer corrector that would bring my 150P down to F/3.8.

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I'm not sure if the 4 hours of collimation, the focuser resquaring or retweaking the spacing to the CCD has done this but:

Can I declare my war with eggy stars over ?

Anton, looks good - to my eyes, at least! Do you have a idea whether it was the collimation or CCD spacing which did the trick?

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I was out by just over 1.5mm (too long) and this interacted significantly with the tilt in my system.

I measured 43mm from coma corrector to CCD which puts me at 56mm all in now.

If my focal plane was dead on square or I had a smaller sensor, I might not have noticed anything.

There is still a little tilt left (according to CCD inspector) but the corrector seems to be in a much better position now and so the remaining tilt isn't wreaking havoc. Bottom line is that tilt + bad corrector placement interact very strongly with each other as you might expect.

I guess the further out your corrector is from its optimal spacing the smaller its 'sweet spot' will be and the easier it is to tilt out of the area of full correction.

As for the source of my tilt/shift, I think there is always some from a little focuser and tube movement, but much of the chronic tilt I saw seemed to come from the secondary not presenting a perfectly circular target under the focuser.

I remember looking down my sight tube and thinking... yep that's circular... but the collimation camera showed that visually I was out.

The Astronomy shed video was really useful for this, I went and bought a cheap webcam that I'll be using for this from now on.

http://www.youtube.com/embed/8ROvNH5uwDo

I managed 2x20 minutes last night on IC1396 to compare to last week and the star shapes also looked great to me right up to the corners.

There is still a tiny shift in some corners but only right on the edges which would likely get cropped out. There is definitely room for a little improvement on spacing and maybe tilt, but it seems very close now.

Thanks,

Anton

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I remember looking down my sight tube and thinking... yep that's circular... but the collimation camera showed that visually I was out.

The Astronomy shed video was really useful for this, I went and bought a cheap webcam that I'll be using for this from now on.

http://www.youtube.com/embed/8ROvNH5uwDo

Anton

I've seen that video of Dions, and I recently fitted a 35mm film canister to an Asda cam for the very same purpose. I was shocked how far my secondary was out. It just demonstrates how hard it can be to make that "is it circular?" judgement when you're relying just on your eyes!

I'm glad your eggy-shaped star journey is coming to an end. I still have a little way to go, but hopefully I'll get there soon! :D

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My big decision now is whether or not to buy a small APO for widefield, something like the TS APO80 F/6

or to buy the ASA 0.73 reducer corrector that would bring my 150P down to F/3.8.

Almost exactly the same decision im having to face, stick with a refractor (double up) or get a fast newt (Quattro). The quattro would be faster and a lot cheaper than two ED80's + 314L, but im not sure if its worth the aggro. Ive also looked at the TS 80/480, but from what ive learnt so far - a flattener is mandatory for imaging, so that bumps up the cost even more. Also, others have expressed doubts about QC with that scope so it might turn out to be a bit of a gamble. Next step up is an APM, which is where it starts to get a bit expensive, but very nice indeed - a pair of those would be ideal (but it aint gonna happen!).

I think your star shapes are fine now. And even if they were a tiny bit out, nobody would notice once youve processed the data.

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