first attempt with the 350d and my lx90

[5ash (Philip)]

Not very good pics as they are slightly out of focus. I can tell on the full size pics as the bloated star images have a small dark centre . will try again. any way here they are M42 and 47 tucani (30 sec at iso1600). they look better than my lpi attempts. Any tips on getting focus other than trial and error.
philip

[[1ponders] (Paul)]

Hi Phillip, you could try using the view screen on the back. Take a short image, view with magnification, adjust focus, Take a short image, view with magnification, adjust focus etc until you have crisp focus. There are a couple of problems using this technique. One is its fairly slow, two you need to remember to delete the images off your card especially if you take quite a few images to get focus otherwise you might just run out of room before you finish taking all your images and darks. And three by viewing each image you introduce more heat into the chip thus creating more noise . Oh and you use battery power, power that could run out in the middle of a session if you're not careful.

You might try using a hartmann mask in conjunction with the previous technique. It may help shorten the process by needing less images as you can see spacially how far out of focus your system is.

You could try to build some sort of magnifier to attach to the viewfinder eyepiece to increase the size of the "live" view.

Or do what I did and get a focusing program. There are quite a few out there that are integrated with capture and processing programs, for example ImagesPlus, but I haven't found one that I prefer to use over DSLR Focus. It's not expensive and it makes life a hell of a lot easier trying to get focus as well as automating your capturing processes

[acropolite (Phil)]

Piggybacking with standard lenses may be a better way to start Philip, that way you can just set the lens to infinity focus and fire away. Here's one I fired off with the standard lens, set to infinity focus, simply laying the camera on the outdoor table, no darks and minimal processing.

[Gama]

Use a Hartman screen, then look at a bright star and focus..
When all 3 stars line up to a single star, your in focus.
Thats how i do it.
But for really good shots, take an image and magnify it a few times. If you only see 1 star then your in very good focus. If you can just see 3 stars, then keep tweaking the focus a little and taking shots to double check. Exposure whould only be about 1 sec or less for a bright star.

[davidpretorius]

great start - a few more cracks at it and then whammo - you are on your way!

[JohnG (John)]

I use DSLRFocus with my 350D, coupled with a 10-1 micro focuser and have found that I achieve focus very quickly. I first manually focus on a bright star near where I am going to shoot, then, using DSLRFocus tweak the focus until I am satified with the result, then use the software to control the shoot. Just be aware when using an SCT that Mirror Flop can be a problem when shooting over the Meridian. I am still learning each time I use the camera, keep at it.

JohnG

[Robert_T]

nice Phillip, I'll be watching your progress keenly... the appeal of these cameras is starting to build

[atalas]

Nice starty Philip .

[anthony2302749]

Hi Philip

Top effort!!

Keep up the good work and with the knowledge that I am impart to you it can only get better.

While a Hartman Mask is a good idea there is a cheap and easier method than this and that is to use diffraction spicks. The method works like this, place two pieces of string on the front of the OTA so that it forms a cross (much like the cross hair in your finderscope). Next you need to take an image and examine the diffraction spicks around a bright star if you see six spicks (2 above the star, 2 below and 2 to the left and right) you have not achieve focus. Continue to image and adjust the focus until you have one single spick (1 above the star, 1 below and 1 to the left and right) at this point you have achieve perfect focus.

To use the above method I would recommend that you control your camera via a laptop and use the supplied Canon “Digital Photo Professional” software. You can take exposure up 30sec and down load directly to the computer to be examined. I also highly recommend DSLRFocus by Chris Venter if you wish to take images longer than 30sec and also it has a nice little routine for achieving critical focus. If you would like I can also help you out with the long exposure serial cable (you can contact me on my private e-mail.)

I have also included an image of the Orion Nebula that I took on my first night out with my new 350D. The image was take through an ED80 piggyback a top an LX200, unguided. Processed with Registax and Photoshop.

Anthony