Venturing into wide-field-ccd imaging...

[rcj]

Several years ago, my path of astrophotography started from using film SLRs with camera lenses for simple wide field imaging. Only until the later years, then came prime focus (film) and then eventually into prime focus ccd imaging. Wide field imaging still holds lots of promise despite the current popularity with taking DSOs with telescopes. The former allows one to express a greater variety of stellar and non-stellar colours with rich starry background. However, since film is not easily accessible nowadays, and with the coming of bigger ccd chips at lower prices, I'd thought of doing wide-fields using an astronomical CCD (monochrome) camera. This would open the doors to a total control of how u would like the colour image to turn out (varying colour assignment ratios), and additionally the ability to capture h-alpha data with large FOV. However, because of the generic sensitivity of the CCD, and higher resolution with smaller pixels, not many lenses in the current photography market is able to pass the extremely stringent criteria of shooting point sources. Point sources in particular is the most hardy test for any lense out there. Embarking a camera lense into astrophotography is akin to giving it the toughest imaging challenge, be it rectilinear distortion, chromatic aberration, etc. Add to it, the fact that a fast lense would be preferred since starlight (and nebulosity) is dim compared to terrestrial subjects. Another challenge goes into the ability to source/find proper adaptation to mate the CCD camera to these lenses.

After several months of thought and research, I have decided to embark on using old Leica lenses for this new venture - having heard of the fine reputation Leica lenses have in the photography world. Together with purchasing a dedicated CCD camera from SBIG (yes, yet again!) - the ST8300M complete with motorized filter wheel and filters, a solution was then needed to find a way to mate these old Leica lenses to the modern CCD camera.

One could use a direct interface machining solution to mate the Leica to the SBIG filter wheel housing, but I'd thought it was useful to be able to use the lense with an existing Canon DSLR as well. So a twin adapter was worked out where the lense would connect to an EOS adapter, which in turn connected to another EOS-SBIG adapter for the SBIG filter wheel.

I have taken a couple of pictures to show this project, and ultimately, a test wide-field HA image taken last night.

Arrival of the SBIG package consisting of the camera, filters, and wheel (plus other knick-knack accessories).


Opening up the filter wheel to insert in the individual unmounted filters


Filter wheel top housing showing the installation of the EOS-SBIG adapter (to enable the use of Canon lenses)


The next two pictures show the Leica-EOS retrofit ring installation needed to enable the lense connection to Canon cameras, but in my case, to the EOS-SBIG adapter described previously.




Resulting CCD wide-fielding imaging setup on the Losmandy G11 (overkill, 7lb counterweight only).




Test Image of NGC6357-6334 pair around the tail of Scorpius. 2x20min HA subs with moon in sight, and elevation around 40 degrees towards the west. Lots of light pollution since my west is facing the city, very poor imaging conditions, though the sky was clear. Will test this setup further under darker sky conditions in Mersing soon!

[orly_andico]

Remus,

This is the Leica APO-Elmarit-R 180/3.4 or 2.8?

Did you consider the Nikon ED 180/2.8?

Can you post the corners at 100% for us curious folk?

[rcj]

Orly: I am planning to shoot better subs again later tonight, and then update the thread again. This is the R APO-TELYT 180 F3.4 that was manufactured for the Canadian Army originally for maritime distance use. The APO F2.8 is too expensive (equivalent to FSQ106)! I had the Nikon 180f2.8 before. Good lens but you need to stop it down to 5.6 for decent results. The image posted was done wide open.

[rcj]

Some updates for the tonight's test session, follow-up from yesterday's first test session with the wide-field imaging setup:

Night started out promising, thereafter numerous passing cumulus flowed and trickled in from the north-east. Nevertheless, I'd managed to capture a 20-min hydrogen-alpha sub-exposure from the setup of the same region (tail of scorpius). The following is a full-resolution illustration of the corners (and centre) for the lens (wide-open). Mount was not tracking perfectly throughout, but what do you think?



The second image is the sub-exposure (1x20min) (with some preliminary levels/curves processing). Note: uncropped, but reduced in resolution.

[Bergkamp_]

Nice~! =)

[orly_andico]

well.. it is flat

those stars are nice and tight even at the corners., definitely looks better than the nikon 180 2.8 from Jerry Lodriguss' article. i wonder about the color correction though.. (since it's H-a).

[cataclysm]

Looks good enough for me, very few lens can pass such test.

[rcj]

actually, i felt nervous when i took this 20min sub....hoping against hope that maybe it will be nice till the edge....but it did. What I've read, they seem to hold promise, and I was surprised. It reminded me of Pentax refractors in terms of sharpness. I would also assume since this is the APO version, colour correction should be OK, but let's see how it goes during the expedition tests... lens should be a keeper. since it can be mounted on Canon DSLRs now, guys, feel free to use it during the trip!

[orly_andico]

remus, what camera? SBIG 8300? the Olympus E-300/E-500 use the same chip (Kodak KAF-8300) which means the sensor is Four-Thirds (1/2 the area of an APS-C DSLR sensor). That could partly account for the great edges.. since the lens is designed to cover 35mm film and Four-Thirds is 1/4 the area of 35mm film..