Using a DSLR?

[Les R]

I've got an adapter on order for my nexstar 6SE and canon 550D which will hopefully arrive shortly.

Last night I used the telescope for the first time (as the moon was out!) so thought I'd take a peek.

Now I was viewing using a 25mm eyepiece and the moon over filled the scopes view. Obviously to zoom in or out, I would need to decrease or increase the eye piece..... And I understand fully.

But what I'm unsure of, is using the DSLR, obviously there is no room to play about. Whatever the scope shows on the cameras CCD, is what it's gonna get.

Now going back to my 25mm eye piece, the moon was too big to fit..... So what should I expect to see through the view finder of the DSLR? Hopefully that makes sense! I'm assuming the eyepiece will have greatly magnified things and the moons image is going to be relatively small, but obviously with an 18mp image wouldn't have any problems to be blown up to compensate?

Am I on the tint track? Excuse what's probably a daft question (that I will know the answer to anyway when the adapter arrives), but it's bugging me not knowing!

Many thanks.

[MarkS]

A DSLR chip size is generally around 24mm x 16mm
Focal legth of your 6SE scope is 1500mm
The chip therefore gives a minimum field of view of 16/1500 = .0107 radians  i.e. 0.6 degrees
The moon is approx 0.5 degrees in diameter, so it will fit.

[The Thing]

You can probably get a suitable focal reducer if you want to fit in bigger objects.

[Les R]

A DSLR chip size is generally around 24mm x 16mm
Focal legth of your 6SE scope is 1500mm
The chip therefore gives a minimum field of view of 16/1500 = .0107 radians  i.e. 0.6 degrees
The moon is approx 0.5 degrees in diameter, so it will fit.

So its going to be pretty similar to  what I can see now with the 25mm eyepeice?

I had a nasty feeling the captured image was going to be quite small and would need to be blown up. (Not an issue with 18MP I guess!)


Cheers again

[The Thing]

I had a nasty feeling the captured image was going to be quite small and would need to be blown up. (Not an issue with 18MP I guess!)

Les, the usual problem I have (8" SCT) is the object is too big, not too small. Most of the pretty nebulae you see images of here and things like the Leo Triplet are big targets, bigger than the Moon. Andromeda galaxy is huge for an SCT/DSLR. Things like the Ring Nebula and other planetaries are small. Scale is hard to get from images!

[Les R]

I had a nasty feeling the captured image was going to be quite small and would need to be blown up. (Not an issue with 18MP I guess!)

Les, the usual problem I have (8" SCT) is the object is too big, not too small. Most of the pretty nebulae you see images of here and things like the Leo Triplet are big targets, bigger than the Moon. Andromeda galaxy is huge for an SCT/DSLR. Things like the Ring Nebula and other planetaries are small. Scale is hard to get from images!

Crikey. I didnt think that would be the case. Would be good to see something that shows comparible sizes.

[Fay]

you could download the free program CCD CALC. put scope & camera, focal reducer details in & click on the various Messier, NGC numbers etc, & you will have an idea of what you can get with the scope and camera you are using


http://www.newastro.com/book_new/camera_app.php

[Les R]

you could download the free program CCD CALC. put scope & camera, focal reducer details in & click on the various Messier, NGC numbers etc, & you will have an idea of what you can get with the scope and camera you are using


http://www.newastro.com/book_new/camera_app.php

That looks really good. Thanks for that! All I need to do is work out how to use it! My Camera - Canon 550D isnt listed, but think its the same as the 5D and Nexstar 6SE isnt, but Ive just amended to show it as F10 1500mm. Not sure at all on the other settings.

My adapter arrived today and camera is all fitted and ready to go.... but even the moon is covered in clouds!

[mickw]

The 550D has an APS-C sized sensor 5344 x 3516, pixel size 4.17

You've obviously sussed how to create new scope in CCD Calc.

You can find some other useful info and links to info here:
http://forum.orpington-astronomy.org.uk/index.php?topic=7106.0

[Roy]

I've just downloaded the program and stuck in the details for my camera and scope. It's truly a fantastic little program and a great help for someone starting out.

Roy