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NGC772 at f/11

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#1 buckeyestargazer

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Posted 19 November 2012 - 03:34 PM

It's been a long time since I tried to image a galaxy, and as usual someone else beat me to the punch with a very fine image of this interesting galaxy (see this thread: unusual: NGC772 in Aries)

Here's my attempt: NGC772

This image was made using a "synthetic luminance" created from the best LUM, R, G, and B sub exposures. I took the best 50% of subs in each channel and combined them to create a rather smooth and detailed synthetic luminance. I was rather pleased with the result of this synth LUM, so much so that I will probably use this method going forward.

Also, this is my second image using a Tak TOA 1.6x extender, pushing my APM115 f/7 refractor to f/11. The extender narrows the field of view, the tradeoff being that longer exposures are necessary. I started with 10min exposures but soon realized that 20min exposures would be better. I'm still not 100% convinced that using an extender like this is all that great for AP, but I think the result of NGC772 is pretty good considering this is from a 4.5" 115mm refractor and not a larger SCT with more aperture and focal length.

What are your thoughts?

#2 sergeC14

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Posted 19 November 2012 - 07:12 PM

Well Joel,
That's a very good effort at a very nice galaxy! How many subs did you use? All the details are there, but I think it could benefit from more exposures.
I used 5 hours on mine.
It's funny that you took yours in America, and I did mine in the French Alps, a big ocean apart. How cool is that?

Rgds

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#3 buckeyestargazer

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Posted 19 November 2012 - 07:25 PM

Serge,
This is nearly 12 hours already! I don't think any more time will help. I think this is the best I could get with my skies and 4.5" aperture.

#4 sergeC14

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Posted 20 November 2012 - 02:21 AM

oops,
I hadn't realized that! You are right, diameter and sky transparency and light pollution will definetely make the difference!

Rgds

#5 freestar8n

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Posted 20 November 2012 - 03:46 AM

Hi-

I think this is a great thing to try and it worked well. I rarely see refractor imaging at f/11, or with OAG - and this is both. It looks like you have a lot more detail than you would have had without the extender and without OAG, so you are getting the benefit of both. At the same time, in terms of deep enough sub-exposures you do need to go longer at higher f/ratio - and that effect is very real. But that is a tiny little thing and it looks like it benefitted from the added effort.

Nice thing to try - and looks good to me.

Frank

#6 kfir Simon

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Posted 20 November 2012 - 05:30 AM

You managed to pull out great details with lovely colors - well done!

Kfir

#7 zoran

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Posted 20 November 2012 - 07:11 AM

Very nice image, sharp and colorful!
At f11 it is a real achievement!
Regards,
Zoran

#8 buckeyestargazer

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Posted 20 November 2012 - 08:25 AM

Hi-

I think this is a great thing to try and it worked well. I rarely see refractor imaging at f/11, or with OAG - and this is both. It looks like you have a lot more detail than you would have had without the extender and without OAG, so you are getting the benefit of both. At the same time, in terms of deep enough sub-exposures you do need to go longer at higher f/ratio - and that effect is very real. But that is a tiny little thing and it looks like it benefitted from the added effort.

Nice thing to try - and looks good to me.

Frank


Thanks everyone!
Frank, you've encouraged me to keep trying at this. Perhaps I should next try to image NGC772 without the extender and compare the results. An object of this size (7') is almost the smallest sized object I can attempt with my setup. Even in this image, I cropped out about 25%. So those tiny planetaries and smaller galaxies are still out of reach. But I think the extender does open the door to some mid-size galaxies that I might not otherwise attempt.

#9 rigel123

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Posted 20 November 2012 - 02:16 PM

That looks great Joel, nice colors!

#10 J.P.M

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Posted 20 November 2012 - 03:46 PM

Love the "spacey" feel.

#11 freestar8n

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Posted 20 November 2012 - 04:43 PM

Perhaps I should next try to image NGC772 without the extender and compare the results.



I would be very interested in such a result. I wouldn't want to sway you from imaging something else on a good night, but I'm personally interested in how much more detail you get with the extender. I assume the OAG is also looking through the extender (I assume?), and I'm a believer that longer focal length helps both guiding and imaging - as long as the guiding is good and the seeing good enough to show the benefit.

Frank

#12 bill w

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Posted 21 November 2012 - 04:33 PM

nice job joel






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