A focal foto M31. Advice

[FMA]

Hello,

yesterday had m31 in the middle of my eyepiece( zoom Baader). Put the canon with the help of an adaptor and through  the camera I couldn’t see anything. Played with the different mm( 7 to 24) but in live view I always saw black. Played with the focuser of the telescope( 130pds) and nothing. Live view all black. Took 30 sec iso 3200 and photo is all black.

andromeda was still there as I removed canon and checked again.

what I’m doing wrong? Camera can get focus as I took lunar photos before with good detail.

thanks

 

[wornish]

I would try focussing on a bright star first, or better still the moon if its up.

 

 

[FMA]

HI Wornish,

whats the point about focusing in other object with different size-light-distance?

the camera focus with the zoom as I can do lunar photos. the problem is that I don't know how to get something fainter

was asking for some advice) probably im doing something wrong.....

thanks

 

[tomato]

With the camera mounted on the scope and pointed at a bright star, you should be able to see the star on a short exposure (1-2 seconds) to be able to focus the image. A Bahtinov mask on the end of the scope will greatly assist in achieving precise focus if you are doing this manually, but remember to remove the mask before attempting to image the galaxy. 
 

Once focussed, point the scope back on the galaxy and then try extended exposures of 30 secs or longer. I’m not sure if you have an aligned driven equatorial mount, you will need this if you intend to take long exposures. On short exposures, only the core of M31 will be visible.

[michael8554]

You have a dilemma. 

Once you have the camera focused on the moon you need to move to M31 without altering anything. 

(There is no difference in focus between the moon and stars.) 

But I take it you need to take the camera off to see and frame M31 with the eyepiece? 

Then you will have to be very careful not to alter scope position and focus as you reconnect the camera. 

Confirm centering by taking a 1 minute exposure at max ISO. 

Discard that and determine the length of exposure at ISO 800 that doesn't star trail. 

Take lots of exposures and stack them with Deep Sky Stacker and stretch, colour balance etc with image processing software. 

Michael 

[wornish]

On 29/07/2020 at 17:16, FMA said:

HI Wornish,

whats the point about focusing in other object with different size-light-distance?

the camera focus with the zoom as I can do lunar photos. the problem is that I don't know how to get something fainter

was asking for some advice) probably im doing something wrong.....

thanks

 

As said by others for focusing purposes the Moon and Stars are the same.  The distance is effectively infinity as far as the camera is concerned.  Its just a lot easier to focus on the moon.

Or if you focus on a bright star in the region of M31 by simply turning up the ISO on your Canon to over 5000 and you should be able to see the stars in Live View.  Once you have the focus set then turn the ISO back down to 800 or 1600 and take the pics. 

 

 

[FMA]

Thanks for your ideas. I’ll try putting high iso and see if can see it in live view. Focus  in other object and find again m31 I don’t see good idea for me, as I don’t find it easily...and will be lot of movement in tripod/eyepiece.