RHO Ophiuchus Cloud Complex

[Ryderscope]

My first attempt at a mosaic with my widefield rig using the ASI6200 camera and Canon 200mm prime lens. I'm pleased with where this has landed and I'm sure will provide plenty of opportunities for widefield targets. Data captured in May and June this year.

it's a fascinating area and a popular target for obvious reasons. So many deep sky objects of interest. For this project I imaged in LRGB only but I'm interested to go back next year to see if there is any Ha to be had. Most images of this area are LRGB only but in theory one should be able to grab some Ha from Sharpless 2-9 surrounding the star Alniyat. I will have a shot next season and see how it goes.

Here is a link to the image on Astrobin. (https://astrob.in/ziuft6/0/)

Full acquisition details can be found in Astrobin post.

Comments and critique welcome.

Clears skies,
Rodney

[strongmanmike]

Wow! great result Roddles :thumbsup: gotta be happy with that! :eyepop: beeeeautiful :painting:

Don't recon Ha is necessary but I guess it would be interesting to find out, huh?...:question:

Happy Days! :thumbsup:

Mike

[gregbradley]

Wow, that is a class leading image. Stunning. I am also amazed at how perfect the stars are in the corners from a Canon lens. I did not expect that.\

Colours are great and the details are spectacular.

Greg.

[Ryderscope]

Thanks Mike, Sh2-9 and possibly LBN 1103 would be the candidates for some Ha exposures. Worth a shot for next season (maybe the clouds will have cleared by then :cloudy: :D )

[Ryderscope]

Thanks Greg, it has taken some experimenting to get the lens working ok with this combo. I need to step it down to about f5.6 to get a decent field and use a step down ring as a mask to avoid diffraction spikes from the lens iris.

[rustigsmed]

great rendition Rodney - nice work

[atalas]

:eyepop: awesome :thumbsup:

[Nikolas]

Wonderful detailed image, the dust clouds really stand out!!

[AstroViking]

Excellent image. That should be one for the "trophy wall".

Cheers,
V

[Retrograde]

Very nice Rodney.
I love this part of the sky & your rendition is excellent. :thumbsup:

[Stonius]

Lovely image, Rodney, well captured. I like the ruffly details in the emission nebula.


Can I ask a silly question; Is your 200mm lens f5 native or did you stop it down from 2.8 (and if so, how considering the iris is electronicaly controlled and no camera is attached to do that). I ask because I understand lenses function better at the middle of the fstop range and I wonder if this was a choice or simply a function of the lens.


Nice work!


Markus

[Ryderscope]

Thanks for al the positive comments everyone.

@Markus,
The lens is native f2.8 and with the lens wide open there is significant star distortion around the edges of the field of view. By experimenting with different f stops I found that I had to stop it down to at least f5 or more to have a satisfactory image. Further to that, I don’t like the diffraction effects that come from the lens iris so rather than stopping the lens down with the internal aperture controls, I leave the lens iris wide open and use step down rings on the front of the lens to reduce the aperture. The set up that I’m using now has a 37mm step down ring resulting in a focal ratio of 200/37=5.4. This calculation would be approximate due to the fact that the step down ring is in front of the lens but is close enough for my estimations.

Also, to respond to your observation re how to control the lens iris with no camera attached. This can be done actually as I am using the Astromechanics adapter which provides the mechanical connection between the 6200 camera and the lens and also includes the electronics to control the aperture and focusing. I don’t use the aperture control but do use the focus control so that auto focus is possible from my image acquisition software (SGP Pro).

[Mickoid]

Superb! The best I've seen, worth an APOD for sure. :thumbsup::thumbsup:

[Ryderscope]

Many thanks Michael. I will make sure to submit it to APOD and see how we go :D

[Dave882]

Lovely! Just beautiful!!

[Stonius]

Ah Rodney, thanks very much for the detailed technical rundown. Those adapters sound ineresting. I wasnt aware of their existence. Autofocus routines on an eos lens sound good!

[Ryderscope]

Thanks David.

[Dilsh]

Amazing shot Rodney. Something for us beginners to aspire to for sure.
Currently going through some focal length envy generally but a shot like this wants me to get a widefield lens.

Breath taking.

Thanks for sharing.

Dilshan

[Ryderscope]

Thank you Dilshan. You raise a good point about one’s choices in settling on a preferred equipment configuration. There is never a “one size fits all” scenario and each choice has its pros and cons. I’m happy with where I’ve landed in having two complete separate configurations, the Tak TSA120 for close up work and the ASI6200/Canon lens for the wide field targets.

[strongmanmike]

Yeah, two great systems there Rod :thumbsup:...In my case, I'd love the third, which would be basically your wide field system, then I would have all bases covered...except planetary :question: :lol:

Mike

[Stonius]

I'm assuming the iris blades gave diffraction spikes, or was something more than simple aesthetics?

[Ryderscope]

Yes it is the iris blades that give the diffraction spikes. In the case of camera lens though the diffraction spikes tend to be flat 'fan' like blades on the bright stars which I feel are somewhat of a distraction. Different to the diffraction spikes from a Newtonian reflector for example which are much finer and (in my opinion) look ok.

[Joves]

This is awesome!

I’ve had a couple of attempts at Rho and have struggled somewhat. It’s actually quite a challenging target.

Well done!!

[Ryderscope]

Thanks Aaron.

[Ryderscope]

Great idea Mike. Of course that would mean installing another pier & mount and maybe a second obs to complement the new dome. You could then have simultaneous image capture sessions running. Think of all the photons that could be grabbed then :D

[LKD]

Great detail in the orange reflection nebulosity around Antares. Nice image

[Addos]

Very nice widefield Rod, well done

[Stephane]

This image is just sensational. Well done indeed.