2 replies to this topic

[curlingdan]

Good Morning,

 

I posted this elsewhere, and then realizing that thread was over 3 years old....so posting here looking for information.

 

I'm hoping to use my Sigma 150-600mm zoom camera lens with a dedicated astro camera.  It appears the lens defaults to a pretty small opening, attaching a Nikon adaptor ring to attach to the asto camera doesn't change the size of the opening.  Guessing it is controlled by my Nikon Camera.

From what I've read stopping down from 5.? is preferable anyway, can't tell what the default opening/closing actually is.....

Hoping the guided tracking and 3 min or so exposures (100's is the plan) will give a good result.

If anyone knows of a way to make the Sigma open full, I'd really appreciate some advice.  Actually I appreciate any advice....

Like one other poster said in a thread, I started with an MSM mount (no clue why now), which led to an ASIAIR,  which led to a SWSA 2i, which led to the Sigma 150-600, which after a trip to Kanab Utah's dark sky led to an AM5 mount which of course led to a ASI 2600MC Pro......and I still have the sigma and really hoping I can use it.

My credit card is really burned out by the way

Cheers

[fmendes]

Ugly solution: Mount the lens on your Nikon camera, set aperture, half-press the shutter and, while half-pressed, disconnect the lens. While you're at it, adjust focus to infinite.

 

But then I'm puzzled about how you'll adjust focus. You may need a variable backfocus ring. The problem with these is that the lens shifts elements inside the lens for each zoom and focal point. A slightly near or far from infinity adjust may cause abberations.

[curlingdan]

Ugly solution: Mount the lens on your Nikon camera, set aperture, half-press the shutter and, while half-pressed, disconnect the lens. While you're at it, adjust focus to infinite.

 

But then I'm puzzled about how you'll adjust focus. You may need a variable backfocus ring. The problem with these is that the lens shifts elements inside the lens for each zoom and focal point. A slightly near or far from infinity adjust may cause abberations.

UGH is right, but thanks for this info, gave a quick try with a small lens on the Nikon and found out quickly I need 3 hands.  Well all I can do is just mount the thing and see what happens.  I'm using an AM5 mount so if the lens and astro camera don't play nicely and can put the lens on the Nikon and it on the AM5 and shoot that way till I can buy an  Askar Scope - I'm thinking Askar V 60mm / 80mm Triplet Modular Apo Refractor Telescope....Agena Astro of course.  

 

It's a hobby so only money.....right ???

 

Thanks for the feed back, much appreciated !