Focus aid for Canon 10D

[RichardSimon]

I need suggestions on how to achieve the best possible focus using my 10D when mounted on a telescope.

I am using my D10 while attached to a telescope for astrophotography. So far, my results are so-so. I use mirror lock up, anti-vibration pads for the tripod, and a computer for control, so I believe that I have eliminated most sources of vibration - I am not touching the camera or scope to make the exposure. My biggest problem, I believe, is achieving accurate focus. In this situation, the telescope does the focusing; the camera is, in effect, attached to a manual focus lens. The problem: the focusing screen on the 10D is difficult to use for high precision manual focusing under dim lighting. While trial and error focusing using the computer is possible, it is quite tedious, and I am not satisfied with the results. I have done better in the past using the same telescope, an eypiece and a G2 - and that's a lot of extra optics! The 10D should be able to achieve far suerior results, once I improve my focusing technique.

Do any of you know of any focusing aids for the 10D? Either a replacement for the matte screen or a clip-on magnifier could be very useful. As things stand now, if I look through the telescope with an eyepiece, I can easily focus and see details far smaller than I can see through the 10D viewfinder. This means that there is no easy way to achieve the best possible focus through the 10D!

By the way, I have done a simple offset-ruler tests, and computer-screen moire tests; the focusing system in my 10D seems to be spot-on.

Thank you for any suggestions.

[Roger_Cavanagh]

Richard,

This mob do something: http://www.brightscreen.com/.

Cannot testify to how good they are, but it's the only option I've seen for cameras like the 10D that aren't designed to have interchangeable screens.

Not cheap, and you have to send them the camera.

Regards,

[Longwatcher]

Another suggestion is the Angle finder C which magnifies the viewfinder image. It helps me to focus better sometimes (if I get the viewfinder set right in the first place - pure operator error)

[RichardSimon]

Two great suggestions - thanks!

Tim, can you confirm that the Angle Finder C works properly with the 10D? It would have the advantage that, when the camera is mounted on the end of the telescope, looking through the camera would be much less painful.

[Longwatcher]

Works great for me.

The way the Angle Finder C goes on it would be unlikely to have any problems. I really love that thing when laying down taking pictures of the flowering weeds in my yard.

So far everything that fit the D60 works fine with the 10D except the EP-EX15 eyepiece extender and the USB cable (I like the 10D's better).

Even the eyepiece extender fits close enough with a little work. Not the way it should, but it stays on and I can see through it.

Still wish there was a good (for me) or changeable focusing screen on the 10D, especially when I put the 2x extender on the 100-400, but life wouldn't be any fun if everything was perfect.

[kfong]

Angle Finder C works great for moon shot, but for planets and stars you'll need something else. I have set up for prime focus photograpy using a 2X extender with an effective focal length of 2600mm and f/20. and Jupiter is still a dim dot. It's diameter would be only about 60 pixels for D60, 10D. No way you can focus it accurately without some other aids.
Tried a Hartmann mask, now the dot(s) are even dimmer. I can hardly see the dots and never mind distinguishing them from being almost merged to totally merged.
Just received a Ronchi screen from stellar Technologies International (http://www.stellar-international.com), but have no chance to try it out since the nights are cloudly since.

Ken

[P.C. Plod]

Magnifier S works well for me on a D60. Not for telescope use though. It is a lot cheaper than the Anglefinder C but is discontinued. You may be lucky and find one at a dealer. I did.

[RichardSimon]

P.C.,
Magnifier S sounds might be a cost effective option. Has anyone tried one on the 10D?

Ken,
Sounds like your setup is very similar to mine (I am at 1900mm and f/15, or ~2x that with a Barlow). The telescope (a Meade ETX 125) has electric focus.

I have had good results in the past using a Canon G2 and an eypiece; I am hoping that I will be able to do much better with the 10D, due to the combination of lower noise and far fewer optical surfaces. With the G2, I used software (G2Remote) that gave me a continuous webcam-like preview from the G2 to a laptop, focus as best I could, then fine adjust with a series of exposures. This was a place where the G2's 3x digital zoom actually made things easier: small images had good scale and were still quick to download. I could focus best on bright stars, the moon, or Saturn, then slew to the object of interest. My best photos were with computer control, and careful selection to discard the ones with focus, tracking, or seeing problems (the majority!).

With the 10D, I am hoping to take advantage of its better sensitivity, ideal pixel size, and prime focus. The improvements come at a price, though: even with third party software, live preview is probably impossible. I am eagerly waiting for the release of Breeze Systems' 10DRemote to see if my remote control of the camera can be improved.

I am continually impressed by the breadth of experience and knowledge of the readers of this forum! Thanks again to everyone.