DSLR - Refractor, Am I doing it right?

[Stevp]

Hi everyone,

I've recently purchased a Canon EOS 660D and I'm wondering if I'm connecting correctly to my Evostar 90 refractor.

I've got it connected, but after a bit more reading I'm not sure if I'm doing it "right".

I have T-ring, which I connect to the camera, no problem, it's from here i'm getting confused.

In my first efforts, I have removed the diagonal and can screw the T-ring directly on to the thread on the bottom of the focuser. It seems like this is how it's designed to work, so thought I was doing it right, I can get focus and take pictures. Although, after further reading, it seems that some people go down the route of putting a T-adapter on to the T-ring and using it directly in place of an eyepiece into the diagonal. From what I can make out this then gives the ability to add filters, but is also adding the diagonal in to the mix and using the 1.25 in size rather that the size of focuser which is a little wider. Are the people that use this method just doing so because they can't connect directly to the focuser?

Please can someone point me in the right direction?

On a related note, should I always be using a filter in the mix somewhere to help protect the camera sensor from dust? Or can/should it be done without filters?

Any help would be much appreciated.

Cheers

Stevp

[rfdesigner]

Hi

Firstly try not to think so much of 'right' or 'wrong', more better or worse. If you've achieved focus, then that's about the only 'right' that you need, everything else is optional, and the key here is achieving focus on an object at infinity, not the other side of your lounge. If you're using a DSLR then the only filter you might want is a UV/IR blocker, but only if you've modded the DSLR to make it more sensitive to Hydrogren-Alpha light at 656nm. You won't NEED any filters for a bulk standard DSLR.

Re dust, if your camera is fixed to the refractor then there's your dust filter.

clear skys!

Derek

[Stevp]

Thanks Derek,

That's what I was hoping to hear!

I'm still very new to DSLR photography so I'm on the bottom step of a very tall ladder, so to speak. I tried out the camera on the telescope one night last week and I think I can get the focus right with the method I connected to the scope with. My initial efforts were a little out of focus, but I think that was more a user error than the setup.

I've not modded the camera in any way, that's maybe a project for future years.

Cheers

Stevp

[Tinker1947]

if you have GoTo on your mount then Focus would be a medium bright star, Liveview to focus lock it in place then GoTo your DSO, if your not using GoTo then the Liveview will focus on really dim stars but the fine tuning knob on my 10-1 wheel only needs a couple of degree's to come into and go out of Focus the other side. Use a remote to fire the the Shutter, ISO i use is 800, if you don't have a remote or laptop or you don't want the Laptop to soak up the Dew, get one of these, place it in a freezer bag and attach to your mount.....

http://www.amazon.co.uk/Timer-Remote-Control-RS-60E3-Canon/dp/B003WD0IKO/ref=sr_1_2?ie=UTF8&qid=1351608304&sr=8-2

Check it will work with your Camera....

[Bizibilder]

The advantage of using the screw thread mount is rigidity and security. The downside is that it is difficult to rotate the camera for the best orientation for your target as the camera could then be loose on the thread. You can overcome this by rotating the whole scope in its tube rings. The advantage of the "slide in" adapter is you can rotate the camera more easily - but with loss of rigidity - and can, as you summise, screw filters into the adapter.

The one good thing you have found is eliminating the diagonal - that has two slide in joints, both of which are far from secure! And it puts the camera "out to the side" where it will unbalance the whole set-up. Diagonals are a real pain and are best reserved for visual work if at all possible.

[rfdesigner]

Thanks Derek,

That's what I was hoping to hear!

I'm still very new to DSLR photography so I'm on the bottom step of a very tall ladder, so to speak. I tried out the camera on the telescope one night last week and I think I can get the focus right with the method I connected to the scope with. My initial efforts were a little out of focus, but I think that was more a user error than the setup.

I've not modded the camera in any way, that's maybe a project for future years.

Cheers

Stevp

If you're struggling with focus, then you should try one or both of two methods

1. Use a program that will report the 'FWHM' of your focussing star, then tweak the focus to minimse the reading.

2. Use a bahtinov mask (you can buy these or make them yourself), very easy to get good focus.

clear skys

Derek

[Stevp]

Thanks Derek i've not come across either of those before, i'll do some research. Is there a particular program that you could suggest to point me in the right direction? Cheers.

[rfdesigner]

Nebulosity 3 will do it. and you can download the demo version for free. The demo version won't save data properly but you wouldn't need it to, just use it for focussing.

Derek