SMC - ASI6200/EF200mm lens

[Ryderscope]

I've been working on a new configuration for a while and it is making sufficient progress at this point to post an image and get some feedback. The configuration is my ASI6200 camera with a Canon EF200mm f2.8 lens piggy backed on my Tak TSA120/QSI683 combination. The TSA120 is performing the role of guide scope whilst imaging with the ASI6200. See attached image of the hardware configuration.

I purchased the Canon lens adapter from Astromechanics (Russia) to mount the 200mm lens on to the ASI6200 camera. This adapter allows for the direct control of the focus motor and aperture setting in the lens. I've been using the SGP Pro auto focus routine to directly control the focus on the lens. The driver for the lens adapter also allows for the setting of aperture and this was stepped down to f5.6 with a view to reducing coma around the outside of the field.

The vital details for the image are:
* ZWOASI6200 camera
* Canon EF200mm f2.8 lens @ f5.6
* 24 subs, Ha @ 1200s, Gain 100

For those unfamiliar with the ZWO ASI6200 camera, it a full frame CMOS sensor with small (3.76 micron) pixels. This makes for a challenging time in setting up one's image train as it will very quickly show up any optical or mechanical aberrations that are present.

Subs were taken around full moon time so some work was required to remove gradients.

A quick process in Pixinsight thus:
* Calibration and cosmetic correction
* Registration
* Integration
* A quick denoise routine
* Gradient removal
* Stretch with histogram and curves

I've uploaded the image as full frame, uncropped with two versions, the full 9576x6388 frame and at a 50% reduction in resolution for 4788x3194 pixels.

Click here for full resolution. (https://astrob.in/l16c0h/0/)

Click here for 50% resolution. (https://astrob.in/3t8li4/0/)

One of the main challenges now is to know when to stop fiddling and start taking images. With the ASI6200 it is difficult to get the spacing and tilt spot on. On the other hand however, the large field and small star size mean that one has to pixel peep to greater depths when hunting down any ugly bits that may be present. It is a case of getting things to a point where the final image quality is acceptable for 'normal and reasonable viewing' (whatever that is) :D.

I would be interested interested in the thoughts of others on this forum on the above and any feedback upon viewing of the posted results.

Clear skies,
Rodney

[gregbradley]

That looks great Rodney.

Do you have a filter wheel attached as well?

Greg.

[strongmanmike]

Holy crappola Rodney! The full res image is magnificent, get that thing humming dude, can't wait to see the full RGB et al results you're gunna get with that! :thumbsup:

I want one for Eagleview!! :lol:

Mike

[Ryderscope]

Yes, I have the ZWO 2" x 7 EFW and have fitted the Astronomik round 50mm filters. The Deep Sky LRGB and 6nm Ha, OIII, SII. The filter wheel isn't obvious in the first photo so I've attached another one taken at an angle so that you can see the filter wheel behind the lens.

RW

[multiweb]

Beautiful lens and that's a really neat setup for widefield imaging. Lot of fun ahead. :thumbsup:

[Ryderscope]

I definitely recommend getting one for Eagleview. Just think of the wide field vistas that you can get :D
Btw: The metrics from this set up are as follows:
* FOV: approximately 10d x 7d
* Image scale: 3.9" per pixel
If I recall correctly that is about the image scale that you get with your FSQ106 yes/no?

Install two piers and you can have a narrow field set up running with the Orion AG and a wide field set up with the ASI6200/200mm lens. The only thing lacking would the time to process all of the data :D

CS,
Rodney

[strongmanmike]

Yep! That sounds like a great idea mate :thumbsup: I will still have my NJP mount aaaand the manual 2.3m Sirius dome too...hmmm?

Mike :question:

[Ryderscope]

Thanks Marc, yep - lots of projects on the way for sure :)

[Andy01]

Love it Rodney, great project and you're going to have a fab time imaging Rho etc with that setup - looking forward to more! :thumbsup:

[Ryderscope]

Thanks Andy, I agree - some of the wide field very colourful areas in Ophiuchus will be wonderful targets. I'm still chasing some technical issues at the moment though which I need to work through. It looks like this wide field configuration is showing up some polar alignment errors that I may have and which show up in 30 minute exposures. Seeing as I haven't touched my polar alignment in over five years it wouldn't hurt fine tuning it. Notwithstanding the extra work it is always worth it in the long run.

CS,
Rodney

[PRejto]

Very nice!

I'm curious about the 8 spikes on the brighter stars. Is that a microlens effect on the CMOS? Or, is it the inbuilt diaphragm of the Canon lens?

Thanks,
Peter

[rustigsmed]

nice work Rodney - looks like you have got that dialled in really nicely. also that sounds like a really nice adapter too - might have to look it up. excellent result.

cheers

russell

[Ryderscope]

Yes, the diffraction spikes are caused by the diaphragm in the lens that is used to step down the aperture. I have a step down ring which screws into the 72mm lens filter thread on the front of the Canon lens which reduces the aperture to something approaching an f6.0. I will fit this when I finish getting everything else working ok. It is definitely necessary to step down the lens as the stars around the edge of the field are pretty awful with the lens wide open.

[Ryderscope]

Thanks Russell, I see that you have the ASI6200 as well so it is worth a shot if you have a good lens at hand. Be prepared to spend some time fiddling with spacing and tilt though :D