NGC3631 - Nice galaxy in Ursa Major

[lukebl]

Hi all,

First outing for ages, I had a go at imaging this lovely small, but strangely unnoticed, face-on galaxy in Ursa Major. It's reasonably bright and compact, and visually I could see it quite plainly as bright as nearby M108 and 97, so it's strange that it's not on the Messier list. Worth someone with better kit than mine imaging this one.

Here is the full frame. Canon 450d, 24 x 5min exposures, SW250PDS. Processed in DeepSkyStacker and Photoshop.

Here is a 3x drizzle in DeepSkyStacker:

[dogfish]

That's really nice. I think I saw that last night in my 12" dob (I say thought, as it was my first outing for ages too and my star hopping felt a bit rusty).

Cheers, Martin

[RogerTheDodger]

Drizzle?

[Digz]

Nice shot. That is kinda small isnt it. Ever though about trying a barlow?

[lukebl]

Thanks, gents.

Drizzle?

Drizzle, basically reprocesses part of the image and enlarges it to produce a final image with more pixels than the original. Quote from the DSS technical info: "Basically each image is super sampled just before being stacked, like twice or thrice enlarged (it can be any value greater than 1 but DeepSkyStacker is only proposing 2 or 3 which are common values), then projected on a finer grid of pixels.

The result is that the size of the final image is doubled (or tripled) and that a small object that was occupying only a few dozens pixels, will be using twice or thrice the number of pixels and will be easier to post process."

Nice shot. That is kinda small isnt it. Ever though about trying a barlow?

Not really. That would increase the focal ratio and radically increase the exposure required, and require particularly accurate guiding. As I understand it a 2x barlow, for instance, would increase the required exposure by 4x.

Anyway, I quite like wide views of galaxies!

[Digz]

I never really thought of a barlow having that kind of effect. Does it really have that much of effect!

I must admit, it is nice to have some space (pardon the pun) for a galaxy to sit in.

[lukebl]

.... Does it really have that much of effect!...

I believe so. Increasing the magnification 2x increases the surface area of the object being viewed by 4x (i.e. 2 squared), thus making it 4x dimmer and, conversely, requiring 4x the exposure. I guess this just applies mainly to diffuse objects like galaxies or nebulae.

But I am sure there are others who can give a more scientific explanation!

[Digz]

Ok, thats good to know for future reference. Thanks

[mdstuart]

I have seen 3631 but it was pretty faint according to my notes..

I will have to try it again...

Mark

[RogerTheDodger]

Thanks Luke, never heard it called drizzle before.

[kris h]

Great image Luke I agree i like wideview galaxies images

the more stars the better i say