focussing DSLR

[billmster]

am hoping to to link up my Canon 350d with my ETX90. am I better to buy an electric focusser or software? should I get the angle viewer?

[moondog]

To focus my Canon 350 D I use a home-made Hartman mask. It's a circle of cardboard to fit over the object lens like a lens cap This has 3 holes approx 20 - 30 mm diameter equally spaced at 120 degree angle from the centre.

With an eyepiece point the scope at a bright star. Remove the EP and connect the 350 D at prime focus. Place the Hartman mask over the object lens. Look through the 350 D finder and adjust the focus until the 3 stars you initially see become one. Lock the focuser.

Job done, camera is focussed.

Using the finder or go-to move to object you want to image.

I think this is the fastest and certainly cheapest way of obtaining a good focus on a DSLR !

Good luck

MD

[FLO]

am hoping to to link up my Canon 350d with my ETX90.

It isn't something I would recommend. Though it does have a camera fitting, the ETX90 does not have the strength or drive accuracy to produce good images. If you want to image anyway, you would be better off using a 32mm and a compact camera looking thru the eyepiece to photograph subjects like the Moon or the Sun with a suitable solar filter.

'Weasners Mighty ETX Site' is a mine of information on ETX scopes:

http://www.weasner.com/etx/menu.html

Hope that helps.

BTW, welcome to Stargazers

[Kenny_10_Bellys]

Billmster, I'm afraid Steve is quite right, your setup is not up to the task. I got myself an ETX-105 and when I got my own DSLR I thought I'd get the prime focus coupler and try some shots. Not happening. The scopes motors aren't up to moving correctly with that much weight on the end, anything more than 45 degrees high in the sky is impossible to get to without fouling the camera and the whole setup is so shakey that even the mirror slap moves the scope. Focusing and using the DSLR proved extremely difficult too, it's so hard to se detail in the viewfinder. I had to finally give up with the DSLR on that scope.

If you really want to take shots with the small ETX you need to get yourself the Meade LPI, or indeed any webcam that you can modify or buy to fit the scope. It's so light and small that it causes no problems and the software that comes with it is excellent for taking combined and stacked shots. You can even use it for tracking if you need to. It's not sensitive enough to get nebulas and so forth, but bright stars and of course the moon and planets are just what it's designed for. I recommend you start with that.

[anthony]

It might be of use -

here is a link to a hartman mask template generator.

I did it and cut out the triangles rather than the circles. The images still merge to one but you start to get diffraction spikes at focus which helps a lot. Also the triangles take less time to cut out with a blade!

Anthony

[Jamie]

Anthony i can't see the link mate.

[geppetto]

This is it Jamie

http://billyard.servehttp.com/Hartmann.html

[Jamie]

Cheers Philip.

[Greg]

Excellent link Phill,

Been looking for somthing like that for ages.

Stick it in the links section so others can find it.

Greg

[billmster]

thank folk for all your help.distressed that it would seem I have wasted money getting adapters for the 350D.I do have a toucam and the meade!! so I shall revert to them

Billmster

[anthony]

Anthony i can't see the link mate.

Oops! Sorry 'bout that, Philip has posted it now though. Handy little thing

Anthony

[Kenny_10_Bellys]

The webcam route is fine, the only real downside being the fact that you also need to humph around a laptop and power supply along with your scope. At least the ETX's are small and relatively portable compared to a heavy mount and scope. It makes a refreshing change to just sit there with a laptop on your knees taking photos and fixing the focus from it's screen, rather than crouched in a Z shape trying to focus through a barely visible viewfinder. You can also control the scope directly from the laptop if you're feeling extra geeky, a sure way to impress the ladies.