Carina wide field

[Atmos]

Mid afternoon on Wednesday I checked the weather and it was forecasted to be mostly clear from 9pm till 3am. In reality there was 1.5 hours of clear skies and RAIN!

Anyway, managed first light with a Zeiss 135mm f/2 @ F/2.8 with a QHY163M.
I’ve learned that the way I’ve been mounting both a Sigma Art 85mm and Zeiss 135mm has been introducing some nasty tilt. When I first mount it the star images are nicely centred, after sleeping around the sky for a while however it is shifting the lens causing some nasty tilt :/
I think I need to get a larger set of rings for the lens so that I can anchor the lens hood along with the base of the lens.

10x120s RGB (1 hour total).

High Res Version (https://www.astrobin.com/full/341386/0/)

[strongmanmike]

Lovely crisp looking image Colin :thumbsup:

Mike

[gregbradley]

That's a great image Colin. That Zeiss lens is a legend. Did you find it still is the king when you did your research compared to the Sigma Art 135 or the Samyang 135?

Greg.

[Atmos]

Thanks Mike, trying to get something to rival your FSQ but it isn’t quite there!



For general real world usage I’d pick the Sigma over the Zeiss or Samyang because it has auto focus and on a chart test is sharper than either of the other two.

For astro however, the Sigma suffers from poorer CA correction than the other two. Between the Zeiss and Samyang, that’s a difficult one. The Samyang has better colour correction but the Zeiss has better distortion correction which will lead to better coma correction. The differences are slight mind you but I’d say that the Samyang/Rokinon has a slight edge optically for astro. In saying that, sample to sample variances of both may have more of an impact than their optical differences and performance.

[gregbradley]

Yes Samyang has shockingly bad quality control. It literally is a dice throw but some models I think have less issues than others. The 14 and 24 are a crap shoot.

Greg.

[multiweb]

Very neat indeed. Superb colours. :thumbsup::thumbsup::thumbsup:

[Ryderscope]

Very nice work Colin.

FWIW, I’m very happy with the results that I’m getting with the Samyang 14mm lens so far.

[gregbradley]

You might need a support ring. There are generic rings for lenses on the market. Try ebay. You could then mount the ring on a dovetail and support the end of the lens so it does not shift.

Greg.

[glend]

Right you are Greg. I have a very nice camera snd lense support bracket that i purchased ftom Teleskop-Express:

https://www.teleskop-express.de/shop/product_info.php/info/p9723_TS-Optics-Telephoto-Lens-and-Camera-holder-with-Losmandy-style-dovetail-bar.html

No movement with this baby, fully adjustable with a sliding tripod type mounting post, and it comes apart so you can use the Losmandy base on other equipment when not using the camera holder.

[RickS]

Nice work, Colin!

[Placidus]

So long as you don't go pixel peeping at star shapes, it is a very lovely image. Beautiful depth and colour, and nicely processed.

Would love to see a retake once you've sorted out the flexure problem.

We had a vaguely similar problem with the Apogee CG16M, ten position filter wheel, and off axis guider all hanging off the focuser on the PlaneWave. Many kilos altogether. It would flex as the scope tracked in RA. At 3.5m focal length the tilt wasn't an issue, but the whole thing would go out of focus. We fixed it with a long hinged strut to support the camera as it tracked in RA.

[Atmos]

They're worth it if you get a good one though!



Thanks Marc :)



I found the images from the Samyang 14mm on a D7200 to be quite pleasing once dropped to F/5.6, wasn't too happy wide open, just a bit soft. Not sure what my copy was like though compared to others.



Good idea. I'll have to do some playing inside to figure out where the movement is coming from. I am thinking that I need some stability on the end of the lens but I'm not 100% sure yet.



I might need something like this depending on what the gap is on a larger ring compared to the smaller ones. I might need the adjustment.

Thanks Rick :)



You're right, as long as you only look at the High Res and not the Full Res you cannot even tell that there is some serious tilt issues going on.
With Milky Way season coming up I may just have to do large regions of sky that way. It is a way of getting most of what Mike does with his FSQ106 + FLI16803 (FOV and image scale) but without the expense; lens, camera and filters costing as much as a second hand FSQ106. Mikes setup is obviously better and there is no disputing that :lol:

At the moment I have 86mm rings holding both the QHY163M and a part of the lens but it's holding it very close to the filter wheel. I think I need a ~100mm ring to hold the lens hood end for extra stability.

[traveller]

Millions and Millions, well done Colin.

[Atmos]

There is a lot of stars travelling along the spiral arms thats for sure :P

[Camelopardalis]

Great Colin, nice bold colours :thumbsup: