DSLR vs DSI/LPI

[lineout]

Apologies if this has been covered before but I would like to know peoples opinions on which is better for astrophotos. A DSLR (Canon EOS 10D) or the Meade DSI/LPI.

Second question. Is it possible to accurately focus through the eyepiece of a DSLR? I tried the other night and couldn't seem to get a sharp image of a star when I took a photo.

Cheers

[[1ponders] (Paul)]

Hi lineout.

IMO the DSLR by a long shot, though the DSI or LPI will be handy for autoguiding camera.

Focusing through the viewfinder is a challenge that is for sure. Are you using it at prime focus (attached to the telescope focuser) or piggyback and imaging through the camera lens?

If through the lense then you might be best off focusing as best you can, taking a picture, zooming in to view it on the screen and then adjusting the focus. Do this until you achieve focus. I use a piece of blue tac pushed agains the focus ring and lens body to add a bit of resistance to the action. Otherwise it is hard to get the very small movements you need to achieve accurate focus.

Alternately you can use the autofocus if you have a really bright star of a bit of the moon available (switch to manual focus on the lens after getting this or you'll stuff up your focus again ). Failing this you can autofocus on a realy distant object in the afternoon, put your blu tac against the focus ring and lens body to prevent movement and then turn off the autofocus. You won't be able to put the lens cap on after that though or you will move your focus position.

Or you can try to make a hartmann mask and focus on a really bright star.

These are very rough methods, the best bet is to use a focusing program like DSLR Focus

[ballaratdragons (Ken)]

There are also other alternatives to the DSLR or DSI/LPI.

It all depends on what you want to image too.

There are also DMK's, Toucams, SBIG's, G-Stars, etc.

All give differing results on different objects (Planetary, Deep Sky).

[lineout]

Originally Posted by [1ponders]

Hi lineout.

IMO the DSLR by a long shot, though the DSI or LPI will be handy for autoguiding camera.

Focusing through the viewfinder is a challenge that is for sure. Are you using it at prime focus (attached to the telescope focuser) or piggyback and imaging through the camera lens?

If through the lense then you might be best off focusing as best you can, taking a picture, zooming in to view it on the screen and then adjusting the focus. Do this until you achieve focus. I use a piece of blue tac pushed agains the focus ring and lens body to add a bit of resistance to the action. Otherwise it is hard to get the very small movements you need to achieve accurate focus.

Alternately you can use the autofocus if you have a really bright star of a bit of the moon available (switch to manual focus on the lens after getting this or you'll stuff up your focus again ). Failing this you can autofocus on a realy distant object in the afternoon, put your blu tac against the focus ring and lens body to prevent movement and then turn off the autofocus. You won't be able to put the lens cap on after that though or you will move your focus position.

Or you can try to make a hartmann mask and focus on a really bright star.

These are very rough methods, the best bet is to use a focusing program like DSLR Focus

I'm using it in prime focus (attached to an electronic focuser). I am going to get DSLR focus once I get a laptop but for now I'm restricted to maunally focussing via the viewfinder in my camera. I might try on something a bit brighter than M83!!!!! Maybe the moon when it rises later tonight.

[[1ponders] (Paul)]

Try Jupiter.

[rogerg (Roger)]

Originally Posted by lineout

Apologies if this has been covered before but I would like to know peoples opinions on which is better for astrophotos. A DSLR (Canon EOS 10D) or the Meade DSI/LPI.

Personally, I summarise the answer to this as:
- DSI is a good compelte all-in-one package. Together with the software that comes with it, it is a neat package that's easy to use and produce nice (but small) photo's.

- DSLR will ultimately give nicer images but requires more fiddling around and is not as easy for the first-timer. You need to choose the DSLR, choose the software to focus it, choose the software to process your images, and then get all 3 talking together. It's not hard in the end, but it's not a "one stop solution easy for the first timer" I don't think, when comparing it to the DSI.

Originally Posted by lineout

Second question. Is it possible to accurately focus through the eyepiece of a DSLR? I tried the other night and couldn't seem to get a sharp image of a star when I took a photo.

It's hard to achieve sharp focus without using software like DSLRFocus (so not through the eyecup of the camera).

[acropolite (Phil)]

DSLR, The others are little more than Toys.

[Dennis]

The LPI is a “Lunar & Planetary Imager” which is geared towards taking images of the bright Moon and bright Planets. Whilst it does have a maximum exposure of 16 seconds, it is not really suited to deep sky astro photography, and so I would remove the LPI as a potential candidate if you would like wide field, deep sky photographs where sub frame exposures are usually 2 to 10 minutes each.

Also, the LPI doesn’t offer much imaging real estate, 640x480 pixels is quite a small area in terms of today’s sensors for deep sky.

Cheers

Dennis