Sigma EOS Lens - Rho Ophiuchi Cloud Complex

[MarsG76]

Hi Astrolovers,

Sharing with you my latest image, this time of the Rho Ophiuchi (& Antares) Cloud Complex. The difference with this image compared to my other astro images is that I wanted to image some wide field objects, but use some of my EOS lenses.
I have a collection of lenses for my DSLR kit which are not getting enough use, all L series Canon or EX series Sigma and a lot of Prime lenses which should be great for astro imaging with my QHY268M.
Of course the dilemma was to get the perfect back focus spacing... and I did have a situation where I thought that I nailed it, but as it turned out later on my second image, it was close but not perfect.... Long story short is that I did eventually nail it and now have expanded my imaging FOV/focal length options. The filters are held in place with a modded filter holder which adds absolutely no length to the BFL imaging train and is very easy to change filters.

Any way, if anyone is interested, I'll write up a post in "equipment" to what I did to nail 44mm BFL.

This is image has been imaged with a Sigma EX 150mm f2.8 prime lens, with my QHY268M in LRGB. Guiding was carried out by my 80mm refractor as a guide scope at 500mm, so guiding was much more accurate than the image needed.

The total integration time for this image was 8 hours and 42 minutes for all of the LRGB filters... Exposures: L:31x60s, 31x120s & 31x180s @ Gain:31 & R:60x60s, G:60x120s, B:52x180s @ Gain:62/OFS:25.

One thing to mention is that guiding at this focal length was a joy... no matter what happened, the worst RMS guiding accuracy was about 1/5th of the pixel resolution that was imaged by the Lens... so absolutely no motion blur was registered, the only limitation which was possible was seeing and transparency.

Clear Skies,
Mariusz

 

[Roy Foreman]

Very nice image. I have long wanted to image this region but sadly from my location it is just too low down, so I'll just have to be content with admiring images like yours. Well done !

[Elp]

Awesome image, guiding with a DSLR is good to the point of whether it's even needed, even wind or vibration due to walking around the tripod has no effect on the subs.

[MarsG76]

14 minutes ago, Elp said:

Awesome image, guiding with a DSLR is good to the point of whether it's even needed, even wind or vibration due to walking around the tripod has no effect on the subs.

I used a DSLR lens but imaged with a QHY268M at -10C and LRGB filters... Imaging at these focal lengths guiding might not be that critical, but I still prefer to guide simply because I know that with guiding there will be no drift possible at all during the night... and I'm able to dither between subs to improve the SNR.

 

[MarsG76]

26 minutes ago, Roy Foreman said:

Very nice image. I have long wanted to image this region but sadly from my location it is just too low down, so I'll just have to be content with admiring images like yours. Well done !

Thanks for the comment... if Antares is low down from your location, you just might need to spend more time on the area and perhaps use a Neodymium filter for the luminance subs to counter any skyglow.

[Elp]

Did you stop the lens aperture down?

[MarsG76]

1 minute ago, Elp said:

Did you stop the lens aperture down?

No, using a EOS mount adapter I had no control over the iris and the lens remained fully open... f2.8.

[Mr Spock]

Lovely image. I too have this lens (Nikon fit) but use it for insects rather than astro.

[MarsG76]

9 minutes ago, Mr Spock said:

Lovely image. I too have this lens (Nikon fit) but use it for insects rather than astro.

It's a great lens... love the fact that it works as a conventional semi-telephoto and a 150mm macro lens... awesome quality Japanese made glass.