First go at Rho

Retrograde (Pete) · #1 10-06-2015, 12:41 PM

Hi all,

this is my first attempt at the Antares/Rho Ophiuci complex. It was also the first real test of a recently acquired Pentax 6x7 165mm f2.8 lens.

I did previously attempt a couple of quick test pics with the lens wide open at f2.8 but found the CA around bright stars far too intrusive. This one is stopped down to f4 (hence the diffraction spikes) and although some CA remained it was reduced enough that I was able to remove most of it in processing. Unfortunately I wasn't able to keep much colour in most of the stars. Hopefully at f5.6 CA will be almost negligible so I'll try that next.

Ended up using just 4 x 4 min un-guided subs (each sub was actually 4 x 1 min using the camera's multi-exposure mode) through a Pentax K-5 DSLR (unmodded).

Somewhat larger version at Astrobin http://www.astrobin.com/full/184790/0/

traveller (Bo) · #2 10-06-2015, 01:42 PM

Very good Pete, I'd be chuffed with a shot like that.

rustigsmed (Russell) · #3 10-06-2015, 04:08 PM

Nice one Pete!

strongmanmike (Michael) · #4 11-06-2015, 12:58 AM

That's pretty good Pete and what ever CA was present you look to have handled it quite well. I would love to have ago with some old Pentax 6X7 lenses with my big FLI ProlIne some day. I used to use a Pentax 6X7 and various lenses back in the mid 80's with some success using film, here's some Halley's shots

Show us how F5.6 goes

Mike

Retrograde (Pete) · #5 11-06-2015, 02:15 PM

Quote:

Originally Posted by traveller

Very good Pete, I'd be chuffed with a shot like that.

Thanks Bo - appreciate the comment!

Quote:

Originally Posted by rustigsmed

Nice one Pete!

Thanks Russell.

Quote:

Originally Posted by strongmanmike

That's pretty good Pete and what ever CA was present you look to have handled it quite well. I would love to have ago with some old Pentax 6X7 lenses with my big FLI ProlIne some day. I used to use a Pentax 6X7 and various lenses back in the mid 80's with some success using film, here's some Halley's shots

Show us how F5.6 goes

Mike

Thanks Mike - really nice 'old-school' pics by the way!

Interesting you should mention Comet Halley as the mount I used for this (& almost all my images) is the trusty old Vixen SP I purchased back in 1985 so that I could take pictures of Comet Halley! Sadly I've lost access to the original slides of the ones I took (I still have some prints) and 20-odd years of not doing much astro means I virtually went back to being a beginner.

LewisM · #6 11-06-2015, 05:43 PM

Rho rho rho your boat, gently down the galactic stream...merrily merrily merrily merrily life is such a dream.

Enough prose. Nice job!

silv (Annette) · #7 11-06-2015, 08:42 PM

beautiful!

a question of taste, probably: I would prefer a version with less star detection.
The ocean of stars is distracting from the main features of your composition. What do you think?

Retrograde (Pete) · #8 12-06-2015, 11:45 AM

Quote:

Originally Posted by LewisM

Rho rho rho your boat, gently down the galactic stream...merrily merrily merrily merrily life is such a dream.

Enough prose. Nice job!

Haha - I prefer 'If there's a bustle in your hedge-rho....' personally.

Thanks Lewis - I appreciate the comment.

Quote:

Originally Posted by silv

beautiful!

a question of taste, probably: I would prefer a version with less star detection.
The ocean of stars is distracting from the main features of your composition. What do you think?

Thanks silv!

Please excuse my ignorance but what do you mean by "star detection"?
Are you referring to the star detection algorithm in the stacking software?
I've never really played with this (I use DSS) other than to ensure the stacking works successfully.

strongmanmike (Michael) · #9 13-06-2015, 07:21 AM

Quote:

Originally Posted by Retrograde

Thanks Mike - really nice 'old-school' pics by the way!

Interesting you should mention Comet Halley as the mount I used for this (& almost all my images) is the trusty old Vixen SP I purchased back in 1985 so that I could take pictures of Comet Halley! Sadly I've lost access to the original slides of the ones I took (I still have some prints) and 20-odd years of not doing much astro means I virtually went back to being a beginner.

Yes, t'was amazing how much astro stuff got sold around that time and how many people took up astro endeavours

You could photograph those prints so you had a digital version..?

Mike

silv (Annette) · #10 15-06-2015, 01:22 AM

Hey Pete,

indeed that algorithm (in DSS as well) I was referring to.

Your astrophotography background, I understand, is from pre-digital times.
So you might just be used to so many detected stars because film showed what film got.

You could play around with that parameter in DSS and see whether you like your image with less stars in the background, too.
From what I remember, DSS doesn't reduce the image or detail quality when you reduce the amount of detected stars.
Have a go and compare results?

cazza132 (Troy Casswell) · #11 15-06-2015, 01:07 PM

Nice work Pete. Blacks clipped a tad much maybe. I don't mind the diffraction spikes, but they will show up more when you stop down. Great first attempt! More subs will allow more stretching of the darker end of the histogram with less noise. What mount did you use for tracking?

Retrograde (Pete) · #12 15-06-2015, 03:07 PM

Quote:

Originally Posted by strongmanmike

You could photograph those prints so you had a digital version..?

Mike

Ideally I would like to scan them to avoid reflections from the glossy paper they're printed on.

Quote:

Originally Posted by silv

Hey Pete,

indeed that algorithm (in DSS as well) I was referring to.

Your astrophotography background, I understand, is from pre-digital times.
So you might just be used to so many detected stars because film showed what film got.

You could play around with that parameter in DSS and see whether you like your image with less stars in the background, too.
From what I remember, DSS doesn't reduce the image or detail quality when you reduce the amount of detected stars.
Have a go and compare results?

Thanks silv that's good info. I'll give it a go when I get a chance & see what I can come up with

Quote:

Originally Posted by cazza132

Nice work Pete. Blacks clipped a tad much maybe. I don't mind the diffraction spikes, but they will show up more when you stop down. Great first attempt! More subs will allow more stretching of the darker end of the histogram with less noise. What mount did you use for tracking?

Thanks Troy. Yep black is probably clipped a touch more than I would've liked. I used multiple iterations of noise reduction so it's far from smooth (which is partly being hidden by the clipping).

I'm not sure about the spikes myself. If I find an aperture I'm happy with then I might even try making up a circular field-stop to fit in the front. Hopefully the lens might be long enough not to suffer from too much vignetting.
I used a Vixen Super Polaris mount that I've had since 1985. I'm amazed it still worrks so well as I've done nothing to it. That said I've pretty much reached the limit of what I can do with it as I need longer subs at lower ISO to reduce the noise etc.