back focus??

[labtech1122]

Hi, does anyone know the correct back focus for the antares x0.63 FR, ive got this focal reducer and the #93633-A celestron t adapter sc, the t ring and a canon 650d

[michael8554]

At the risk of rekindling an ages-long argument about the BF of Meade, Celestron, and clone FR's:

The #93633-A Celestron T-Adapter SC, the T- Ring, and Canon 650d, should give you 105mm back focus.

Try that and tweak by a few mm's if it's not perfect.

Michael

[michael8554]

Doing my own searches, the Antares may be one of the 85mm BF items

Measure the focal length by focusing the sun on an outside wall.

If it's about 240mm then BF is 105mm

If it's about 110mm FL the BF is 85mm

Michael

[labtech1122]

8 minutes ago, michael8554 said:

Doing my own searches, the Antares may be one of the 85mm BF items

Measure the focal length by focusing the sun on an outside wall.

If it's about 240mm then BF is 105mm

If it's about 110mm FL the BF is 85mm

Michael

Might be a stupid thing to say but doesn't pointing the telescope at the sun damage it? Excuse my ignorance haha

[labtech1122]

22 hours ago, michael8554 said:

At the risk of rekindling an ages-long argument about the BF of Meade, Celestron, and clone FR's:

The #93633-A Celestron T-Adapter SC, the T- Ring, and Canon 650d, should give you 105mm back focus.

Try that and tweak by a few mm's if it's not perfect.

Michael

Thats what I have been using but all my stars on the edges have rotational trails. I've managed to master up a total length of 87mm so I'm going to try that and see what happenes then buy the appropriate adapters. I can just see my self getting the adapters and not having the right ones. Measure twice, buy once haha

[michael8554]

"doesn't pointing the telescope at the sun damage it? "

Point the FR at the sun, not the telescope !

Only damage might be to the wall ....... 😆

Michael

[labtech1122]

1 hour ago, michael8554 said:

"doesn't pointing the telescope at the sun damage it? "

Point the FR at the sun, not the telescope !

Only damage might be to the wall ....... 😆

Michael

Haha yea that makes sense 🤣 

[sagittariancat]

The back focus of the Antares X0.63 FR is i guess, 55mm. To determine the correct back focus for your combination, simply measure the distance between the T-ring and the focal plane of the camera with a ruler. This is the back focus you need to set.

[michael8554]

"The back focus of the Antares X0.63 FR is i guess, 55mm."

Many FRs have a BF of 55mm, which means they can screw straight onto a DSLR via a M42 T-Adapter.

But these Antares /Meade/Celestron lookalikes have SCT threads, and are maybe 105mm or maybe 85mm BF, but IMO I don't think they will be 55mm BF.

Michael