Using DSLR on scope.

[sanmatt]

HI all

I have been able to get my DLSR (nikon D90) onto the scope (Skywatcher Explorer 150pl) using a T2 ring, my husband says I use the 2x Barlow and not the other T adapter otherwise I wont get any magnification.

Is this right? Do I marry up the camera to the scope vis the 2x Barlow and the T ring and nothing else?

If this is the case, then why do I have or do people have adapters, do they use those with a Barlow or any sort of mag?

How does all this work please?

I still havent gotten the motor tracker fixed so I can't track at the moment, so not really sure what I'm going to do tonight - I just know it's clear here and I want to try something

Thanks Sandra

[RikM]

No, you don't use the barlow with a DSLR, just the T-ring straight onto the t-thread of the 1.25" adptor. The barlow will give you a smaller field of view (you may think of this as increased magnification) but it will also put you at f/10 rather than f/5 so you will need much longer exposure times. Which is even more of a problem if you don't have tracking motors running.

Until you get the motors going, try a few quick snaps of the moon. It's easy to find, easy to focus on and will give you great satisfaction.

Edit: just realised you have the PL not the P so you are at f/8 (I think) already. You may as well stick to the moon and planets with this scope. You may even want to think about getting a little webcam and nosepiece instead of your DSLR. AVI files are the way to go for lunar / planetary.

[sanmatt]

Ok I shall do that thank you

but in the future when the retailer sort themselves out and give us a motor that works (!) how do I do things without a Barlow, do I not use any mag at all?

[RikM]

Ok I shall do that thank you

but in the future when the retailer sort themselves out and give us a motor that works (!) how do I do things without a Barlow, do I not use any mag at all?

Correct:icon_salut:

[sanmatt]

rightyoh!

Thank you Rik.

[ollypenrice]

Forget the term magnification, which is meaningless in imaging.

You want - a fast focal ratio. This goes as the square so F5 needs a quarter the exposure time of F10. The slowest workable ratio in my opinion is F8 and faster would be better, especially if you are not using an accurately autoguided tracking mount.

The extent to which you are 'zoomed in' on a target depends on the focal length. A camera lens might have a FL of 50mm. A small widefield refractor might give 350mm. A very big refractor might be 1000mm and an SCT 2.5 metres. The longer the focal length the more accurately you have to track the sky.

So for simplicity the rule is

-fast F ratio (for shorter exposures.)

-short focal length (for tolerant tracking.)

Olly