can't get focus on moon with camera

[troypiggo]

First non-cloudy night since I received my first mount and telescope last night. Mount is HEQ5PRO and scope used was ED80 600mm f/7.5.

What a learning experience. The kit I bought (second hand) had no means of powering it from inside the home, and I haven't had a chance to buy car/marine batteries yet. So for tonight it was all manual knob fiddling.

First tried viewing only. Got some eyepieces - a 42mm and 4mm, and a star diagonal so could view through right angle.

Checked out the moon first with 42mm giving 14x magnification. Beautiful. Such detail in the craters etc. Next tried the 4mm - about 150x mag. So close! You could see the atmosphere shimmering making the craters look like viewed through heat haze. And the moon moves so quick at that mag! You could see it moving out of view! (remember, no power so no tracking)

So next thought I'd plug the camera on and snap the moon. Tried mounting the camera onto the diagonal. It wouldn't focus at all through the full range of the scope's focus. Hmm, must try to figure that one out. Must be too far away from some focal point due to the quartz prism?

Took off the diagonal and just mounted the camera on back of scope - prime focus? Now got focus. Hadn't thought about it before, but of course the camera (30D) couldn't read the aperture of the scope, so the exposure meter etc is useless. Just trial and error on exposing the moon I guess.

Haven't downloaded the photo yet. Pretty boring anyway. Will play more.

Looking forward to getting some power, tracking, guiding, and looooong exposures.

But back to the camera not being able to focus through the diagonal. Any ideas on that? I had the 2" diag direct into the back of the scope, and a 2" T ring and camera adapter into that.

[Ian Robinson]

Get rid of the diagonal ... for starters . Ya did that.

Does the telescope bring the moon into focus without an eyepiece in the focus at any point within the distance the focusor drawtube can accomodate (use a bit of cardboard and see) , then you need about 2" move focusor intravel to make allowances for the depth of the camera body (from T to chip).
If this can't be done , you need either a better focusor or maybe a barlow.

Ya did that.

Can you select full manual control , and go to liveview , then just focus with the telescope's focusor. Try 1/60 to 1/250 of second exposures depending on the speed you've selected . If it looks over exposed , drop the a faster exposure , TRIAL N ERROR is the name of the game. http://www.eclipsechaser.com/eclink/astrotec/aphotsmt.htm#guide

Ignore everything except the ASA and exposure reading.

[Octane]

Troy,

I think what you need is an extension tube. I remember needing one too, to image, through the ED80 and a Canon EOS-350D.

These can be had for around $20-$40.

Try Bintel (http://www.bintel.com.au).

I lost my extension tube so am just using the tube from a Bintel ED barlow, with the lens removed.

Regards,
Humayun

[troypiggo]

Ian: you lost me a bit there in your second paragraph. Do you mean to take the eyepiece off the diagonal, but leave the diagonal on, hold a piece of cardboard about the same distance away as what the camera's sensor would be, and try to get focus?

The 30D doesn't have liveview, so can't use that. Focus will have to be through the camera's eyepiece. I do shoot full manual usually.

Octane: Thanks for the link, I'll look into those. So I guess I just need to get the camera a little further away from the diagonal.

[Octane]

Troy,



Spot on, mate. :)

You'll need the 2" (diameter) version.

Regards,
Humayun

[dannat]

Troy I've got a 35mm ext tube lying around you could buy. PM me if you want it. Hardly used

[troypiggo]

Thanks Daniel. I'd like to figure out a bit more about the cause and prevention before committing to that. I'm pretty new to all this and need to experiment a little more :)

I'll let you know.