Good scope for photos in Galaxy Season...?

[ollypenrice]

Beware of the various focal reducers. What some of them don't tell you is that the corrected circle is very small. Even Celestron's own probably won't cover a full frame camera. There was a Lepus reducer with a tiny circle, I recall. Do insist on seeing the full corrected circle specification.

I've imaged at about 0.6 arcseconds per pixel from this site, which is pretty good. I get very good FWHM on occasion but I still think it was too slow to be really useful and I would rather have tried binning or larger pixels. The camera in question wouldn't bin properly though. (It wasn't one of my Atiks.)

From the UK I wouldn't want to be going below an arcsec per pixel, I don't think. However, Tim posted some results suggesting that he did succeed in resolving very fine detail and the Nyquvist theorem is under attack in some circles. Quite a few serious imagers are convinced that they defy it. I'm just a pragmatist and don't have a point of view on that, or any great understanding of the theory.

Olly

[ChrisLX200]

You can always 'bin' a small pixel sensor with a couple of caveats: being careful not to saturate any pixels (smaller pixels have a lower well-depth),  and overall the sensor will still be less sensitive than one having native large pixels. Still, the ability to image at high resolution on occasion is worth it IMHO. As for choosing a pixel size to match your scope well, that's a minefield of argument and debate. I work on the general principle that you can get away with over-sampling at the cost of reduced FOV and sensitivity, but under-sampling will give you square stars which never look pretty. At the end of the day it's a question of avoiding extremes (or buying more cameras )

ChrisH

[PhotoGav]

All this has exploded my small brain, already crammed with so much new Astro-info that it is trying to process! But thank you all for your input. It has been one hell of a journey through the theoretical world of long focal length Astro photography, with a very healthy dose of practical input too.

Now, the good news is that my local (ish) scope shop has just taken in a second hand... You guessed it... 8" EdgeHD. Reasonable price too. It's as though it was meant to be!!!

[nmoushon]

Good luck with your purchases! Do remeber when you get it you will have 3 weeks of clouds hovering over your garden.

As a little side note: All the above information in regards to cameras is very useful and should be taken into consideration. But since you already have a camera and no budget to buy a new one yet I wouldn't worry about. Enjoy your new scope and take some pic with it. They might not be the best you could possibly get with that scope but they will be a good stepping stone on the big curve of long FL imaging. When you do get the budget to buy a CCD you can revisit this info to help you make the correct choice.

[PhotoGav]

Thanks. Yes, I will just get on with some pics and struggle up the latest learning curve!

As for new-gear-cloudy-skies, I apologise to all for the inevitable prolongation of the biblical plague of cloud, wind and rain we are currently enduring...

Fingers crossed!

[PhotoGav]

So... Here it is... The first light with the Celestron 8" EdgeHD. Not quite the galaxy I acquired the scope for, but it was just a relief to have a clear sky so soon, slightly dominated by this bright thing, so it seemed to make sense to not ignore it!

That's 77 images shot with an EOS 1DX stacked in Nebulosity and processed in CS3. Frightening how much this image has cost to acquire...!

So, the new journey has started and I am very much looking forward to the moon hiding, the skies clearing and being able to get down to working out how to guide this great big tube. In the meantime, looks like it's going to be clear tonight, so I might embark on the other direction I have been meaning to for a while - Jupiter. Oh, there's another dirty great curve to clamber up!

Thanks for all your help folks - I'm chuffed to bits with the new addition to the Astro-Arsenal.

[Martin Meredith]

From the UK I wouldn't want to be going below an arcsec per pixel, I don't think. However, Tim posted some results suggesting that he did succeed in resolving very fine detail and the Nyquvist theorem is under attack in some circles. Quite a few serious imagers are convinced that they defy it. I'm just a pragmatist and don't have a point of view on that, or any great understanding of the theory.

Olly

Interesting. One way to defy Nyquist is to use stochastic sampling (i.e. not sampling on a regular grid). This is closer to what the eye does. There's no free lunch though -- Instead of any high frequencies folding back into the image as aliasing, they spread out over all spatial frequencies as noise (a bit like the curved spider vs straight spider situation re contrast). Perhaps in the future CCDs will be 'grown' on a more random grid... But I can't see how current imagers on a regular grid can defy Nyquist, and I'd be interested to find out more.

Martin

[Quatermass]

I really should get a coma corrector but I just fix the eggy stars with processing in photoshop :-) most galaxy's I image are bang in the middle were everything is ok so I'm not bothered. I had an ed80

and sold it preferring my 200p sounds crazy I know but the ed80 was just not my kind of scope. The 200pds would be a very nice scope for galaxy's. I guess it depends on how close in you want to go for me though the 200p does everything I want. :-) apart from getting rid of clouds that is ;-)

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