New Guy Trying to Image with a Barlow Lens - Forums

Topic starter

Dec 9, 2023

Hello, I am fairly new to astrophotography. I use a Canon Rebel T6 through a 6" Newtonian reflector that I believe is f/5.
I recently decided to purchase a 2x Barlow lens and a focal reducer figuring this will give two more choices for field of view.
Unfortunately when I attempted to use the Barlow lens I could not find focus. Eventually using some tubes I was able to get
focus but the camera was sticking out absurdly far from the telescope. Is there a way to find focus with what I have without
having like a foot between the camera and scope or did I waste money on a lens that is not even compatible with the
telescope and camera I own? I honestly thought I would be able to just slot the Barlow into the focuser, the camera into the
Barlow, and then just be able to find focus no problem. Not the case apparently.

Also I have a focal reducer that I cannot find focus with at all that I believe may be the opposite problem of not being able to
move the camera closer to the telescope, but I am unsure. Is there any remedy for this?

I would appreciate any help or advise.

–EvanSpiesTheHeavens

Engaging

Gurjot Singh

Dec 9, 2023

You are correct in the focal reducer will require the camera to be much closer to the secondary mirror. Vice Versa a Barlow lengthens the focal point of then telescope so ur camera will HAVE to sit farther from the scope. There is no way around this. Unfortunately. I think focuser may need an upgrade to handle them.

EvanSpiesTheHeavens

Topic starter

Dec 10, 2023

Gurjot Singh:
You are correct in the focal reducer will require the camera to be much closer to the secondary mirror. Vice Versa a Barlow lengthens the focal point of then telescope so ur camera will HAVE to sit farther from the scope. There is no way around this. Unfortunately. I think focuser may need an upgrade to handle them.

I am a bit confused about this because I have seen others use barlow lenses with reflector telescopes and not need a ridiculous amount of distance from the body of the telescope. Is there a way to calculate the rough distance I need? And why would it be so long for me?

Well Written Engaging

Oscar

Dec 10, 2023

Gurjot Singh:
You are correct in the focal reducer will require the camera to be much closer to the secondary mirror.

Didn't know that myself. I tried to use my guiding camera to do some lunar imaging, but I could only focus like 3 inches more than how far the focuser can travel outwards. I didn't have the spacers to do what I wanted. I wonder how the planetary imager rigs look like if they actually use 3x barlows.

andrea tasselli

Frequent contributor

Dec 10, 2023

Hello, I am fairly new to astrophotography. I use a Canon Rebel T6 through a 6" Newtonian reflector that I believe is f/5.
I recently decided to purchase a 2x Barlow lens and a focal reducer figuring this will give two more choices for field of view.
Unfortunately when I attempted to use the Barlow lens I could not find focus. Eventually using some tubes I was able to get
focus but the camera was sticking out absurdly far from the telescope. Is there a way to find focus with what I have without
having like a foot between the camera and scope or did I waste money on a lens that is not even compatible with the
telescope and camera I own? I honestly thought I would be able to just slot the Barlow into the focuser, the camera into the
Barlow, and then just be able to find focus no problem. Not the case apparently.

Also I have a focal reducer that I cannot find focus with at all that I believe may be the opposite problem of not being able to
move the camera closer to the telescope, but I am unsure. Is there any remedy for this?

I would appreciate any help or advise.

--EvanSpiesTheHeavens

There are no focal reducers available for newtons (other than with coma correctors) so you have been sold something that obviously isn't ever going to work. Take it back, if you can. As for the 2x barlow any and all of mine (I got 4) and the several more I have used in the years require a moderate amount of outward travel but no more than 1", at most. So something is clearly wrong here. Unless you're trying to achieve afocal photograph, in which case a foot is more like it. But then, you really shouldn't.