Does anything go between a DSLR and telescope?

[maclean]

Hi Guys,

Appart from the obvious mount, does anything go between the telsecope and DSLR when mounting it on?

Is it the case that if I were physically capible of holding my camera steady enough, simply removing any lens on it and removing any eyepieces in the telsecope and simply move the camera closer and further from the scope, it would at some point focus on the camera sensor?

Also my camera is a crop canon 60d, does using it with a telescope do the same thing as with a standard lens and crop off the top bottom and sides of the image taking my 1200mm telescop and making it an apparant (1200 x 1.6) 1920mm in comparison to what a full frame DSLR would produce?

Cheers

Guys

[themos]

Yes to the first question!

and yes to the second (if you want to use focal length to determine field of view). A lot of us just use "New Astronomy CCDCalc" program to see what the field of view is for various cameras and focal lengths.

[VigdisVZ]

You mean piggyback or direct focus?

In direct focus you need the right T-2 ring (Canon) and some kind of adapter that goes from the T-2 ring to either 2 inch or 1.25 inch on your focuser.

My SW Explorer came with the camera adaptor (it's actually part of the eyepiece mount).

Not really sure on the crop factor/sensor size, haven't been delving that deep with my Nikon yet.

[maclean]

Thanks guys, yeh im thinking of direct focus... Is there any reason to have one over the other with regard to a 1.25 or 2" mount thingy?

Regarding piggy backing, what is this used for? Can DSO be imaged via biggybacking? Or is this just making use of your telescope mount for some wide angle long exposure shots of the milky way?

[allcart]

Piggybacking, is mounting the camera and lens on top of the scope via the screw thread on the tube ring. There are better more secure ways of mounting the camera but you get the idea. You can use any lens you fancy using. telephoto's or wide field its up to you. If you don't own any telephotos then direct focus will give you a very long lens indeed.

The biggest problem I can see is that with direct focus you only have one focal length to use. piggybacking lets you use any focal length you like.

[VigdisVZ]

Thanks guys, yeh im thinking of direct focus... Is there any reason to have one over the other with regard to a 1.25 or 2" mount thingy?

Regarding piggy backing, what is this used for? Can DSO be imaged via biggybacking? Or is this just making use of your telescope mount for some wide angle long exposure shots of the milky way?

Essentially you'd like the 2" inch mount if your focuser is that big, the bigger the better.

Piggybacking is for imaginging the same stuff your're pointing your scope at but not thru the scope itself. You can have wide angles, telephoto lenses or even other scopes attatched piggyback if your mount allows for it. And since the piggybacked camera tracks with the mount, you can definetly grab DSO's with it (except the might be a bit small on the image for obvious reasons).

[maclean]

Ah okay,

So for example I have a few camera lenses, but the biggest ranged zoom lens is the 18 - 135mm kit lens that came with it... So I've taken a few messing around shots with this lens, but the moon still appears quite small even @ 135mm, so I just assumed it was impracticle for astro photography to use standard camera lenses.

However with the piggy backing you gain solid tracking, therefore does the sky light up like magic when you are able to track for hours with the shutter open?

[themos]

There are many DSO that are larger than the Moon. I wouldn't go for hours on one exposure, you'd be completely saturated. Five, ten minutes maybe.

[themos]

here's a 135mm shot with a 450D to see what I mean.

http://www.astrobin.com/19257/

[Cath]

dust bunnies go between the telescope and the camera

[JamesM]

If you haven't got it already, I would strongly recommend to you or anyone else entering into astrophotography to get hold of a copy of Steve Richards' "Making Every Photon Count" (FLO £19.95) which will tell you what kit you need and why you need it to take good consistent images. Well laid and comprehensive in its instructions, it is a book that might well save you some money by helping you to buy the right kit from the start. There is a bit of steep learning curve at the beginning (especially when you add processing into the equation) but eventually it levels out and Steve's book will most certainly play its part in getting you to that part as soon as possible.

Clear skies and look forward the results of your endeavours!

James