Lunar photography

[don.harvey]

This is my first post, so excuse ny ignorance. I have a Canon EOS40D with Bintel Tring etc with a Meade 10 inch Lightbridge. I seem to be having problems with prime focus on the camera. Eyepiece viewing has been crisp. I have tried a 25mm Plossl inside the tube, and the camera straight into a "shorty Barlow". Just can't get the camera in focus. Any advice for a newcomer?
Don

[citivolus]

It sounds like you may need an extension tube in front of the t-ring.

Suggestion: In the dark, find a bright star or the moon. Put the camera in to live view, and then remove it from the scope. Pull it back slowly, trying to keep the light from the scope hitting the sensor. See if it reaches focus.

Eric

[don.harvey]

Thanks Eric, I'll try that

[Dennis]

Hi Don

Problems of bringing an image to focus in a camera after attaching it to a telescope focuser usually involve what is termed “Back Focus”.

Sufficient “Back Focus” allows you to attach the camera to the focuser, and then wind the focuser in, or out, until the image is in focus on the camera display.

Newtonian reflectors appear to suffer from not enough “Inward Travel”; that is, you cannot wind the focuser sufficiently in to achieve focus before the focuser hits the end stop on its maximum designed inward travel. This seems to be common for Newtonians and some users can get over this by fitting a low profile focuser, which provides the extra inward travel required.

SCT’s however, focus by moving the main mirror so they have an enormous range of focus and most cameras should easily come to focus in an SCT.

If a low profile focuser does not work on a Newtonian, then some people modify the ‘scope by raising the primary mirror up inside the optical tube, so the image is then projected further outside the focuser tube, hopefully allowing the camera to then come to focus.

Cheers

Dennis

[xelasnave]

I had the same on the 12 inch wont go in far enough... I think I managed with a 3x or a 2x barlow... I have just discovered the same problem when I try to use colour filters on may main capture scope as 150sn... glad I found out before I bought a HA filter.

You may find just holding the camera at the EP may do it for you.. My first shots were of the Moon holding a litle 2 meg family camera at the EP...I have seen folk get ohotos of the Moon with phones that have a camera.

So the good news is its the set up not you... good luck with the adventure.

alex

[xelasnave]

AND my manners forgive me..welcome to ICEINSPACE form me.
Great to have you here

alex

[Phil]

Hi Don i have the 16" and found there is not enough in focus with my 30D so to get focus i would have to change the focus-er to a low profile focus-er.
Don't no if this any help but this is what i have found.
Phil

[iceman]

Hi Don, :welcome: to IceInSpace.

The others have answered you already - not enough in-focus. Common for newtonians, unfortunately.

[bonox]

my first draw tube camera adapter had a lens in the end of it - I assume that was to correct for the lack of back focus in the newtonian for which it was designed?

Could the same be done again? You aren't exactly short of light for lunar shots!

[Outbackmanyep]

I noticed on my 10" GSO dob the inward travel stops on a knurled ring that screws into the draw-tube, i machined that knurling down smooth and it gave me another 3mm of travel, enough to be able to photograph the moon @ prime focus through it......

One pic shows the bright aluminium ring that used to be knurled, this stopped the inward travel on the drawtube housing when it had the knurling on it, so i machined it and the other pic shows it a little further in which allowed me to focus the image.
On your telescope this may not be the case......