Using a DSLR Zoom Lens

[DanLXIX]

I want to do some wide(r) field shots and I was looking at something around 80mm to buy when it occurred to me I have something in this range already, but it's not a scope. Has anyone had decent results from using a zoom lens?

It's not a great time of year to be trying this now I suppose given where I live dusk is already 10pm, but I was considering buying a dual mount so I can put my DLSR with my Sigma 120-400mm next to my guidescope. The Sigma has a zoom ring lock so creep shouldn't be a problem but will I have any other issues?

[Nik271]

I have taken some good images with the Sigma 70-200 F2.8 on Canon 250D so the answer is yes, it can be done.  At these focal lengths the image scale is very forgiving, so you can take 40-60 second exposures unguided. The only thing to watch is for the abberations of the lens itself, it may have distortions and astigmatism near the edge of the field. Vignetting can easily be corrected with flats. 

I think the main reason people don't use telephoto lenses is that for equivalent focal length and aperture a refractor works out much cheaper -  most modern lenses have image stabilization and focusing motors which add significantly to the weight and cost. But of course if you already have the lens, it's a good alternative to a scope.

[DanLXIX]

That's good to know thanks.

I could probably correct the lens aberrations on the final image in Lightroom because that has lens correction, so I think I'll give this a go

[michael.h.f.wilkinson]

I got these shots of NEOWISE last year with a Sigma 50-100 F/1.8 at 100 mm and full aperture.

I also used it with my ASI183MM-Pro on some wide targets (at 100 mm and full aperture)

Stars are not perfect, but I am quite happy with the results