No aperture on telescope can I add one?

[toddpe]

My telescope has a fixed aperture (13.8), but I want to be able to change that. I am currently using a Meade ETX 90-EC with a Canon EOS 30D. If there is a way, I am currently thinking of upgrading to a better camera so it would be helpful if it weren't camera specific.
Thanks!

[Gabby76]

The aperture is 90mm, the focal ratio is 13.8

The ratio can sometimes be changed either using a barlow to make it act like a longer telescope or a focal reducer which will make it act like a shorter telescope.
What type of AP are you attempting?

[toddpe]

Thanks for the correction, I got confused by the abbreviations of the front. So I'll just give them how they're printed. D=90mm F=1250 f/13.8
I am not using the eyepiece but the photo port on the back to T-thread adapter to EOS adapter. So is there an adapter for an EOS mount or T-thread?
Thank you!

[Ozman13]

Do you mean your ETX90 with 90mm of aperture has a focal ratio of f/13.8 and you want to change that to a faster speed to help with your exposures?

If so, you want a focal reducer. There are a couple of ways to go about this with varying degrees of success. The cheapest (and you guessed it, the most likely least pleasing) is to get a 1.25" .5x reducer. This will likely cause a lot of vignetting with your current camera. The much more costly (and likely most effective but still far from ideal) is to get an adapter to convert the rear cell threads of your scope to standard SCT threads and use a standard SCT .63x focal reducer.

You should be aware there are reports of your scope being damaged by adding too much weight to the rear cell, the whole rear assembly pulled free from the rest of the tube.