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t-ring adapter on .965 - 1.25" adapter dslr focusing?


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I'd first like to apologize for the repost, I just recently found this forum and I believe this would be a better place for the post.

I just purchased a Meade 4504 and so far observing has been pretty great. However, I have a Nikon D5200, and would love to use it for astrophotography. The issue I've run into is that the 4504 uses .965. I know that I could modify it for 1.25 by upgrading the focuser. This is a little more modification than I want to do at the moment though. I have seen .965 - 1.25" adapters for sale. Has anyone tried using a .965 - 1.25" adapter and a t-ring adapter for imaging? I feel like I have seen somewhere that it is possible, but focusing was a real pain. Any ideas?

Sorry again for the repost, I'm just a newbie.

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Hi Texwarhawk,

I followed a couple Yahoo threads about this telescope with exactly this question and it seems there is no easy answer, the focal point is too close to the limit of travel of the focuser to allow a normal DSLR to reach focus.

The most tried option was to move the primary mirror further up the tube by fitting longer springs and spacers behind the mirror but although this moved the focal point further out from the focuser it introduces cut off and vignetting in the camera image because the focuser draw tube is so narrow.

The only really successful results with DSLR users were achieved by people who both moved the mirror as described and changed the focuser for a low-profile large bore crayford type but this is rather an expensive upgrade for this telescope.

All is not lost though, there are a couple of suggestions that might work but I have not tried them myself on this telescope so I hope other SGL members may confirm them, or suggest better alternatives.

A method that should work using the Meade .965" camera adaptor which is available on e-bay and elsewhere for about $15, this has a direct "T" thread at one end that would screw into a camera "T" adaptor to suit your Nikon D5200.

To use this adaptor you fit a low power .965" barlow lens in the focuser draw tube to move the focal point further back, then slide your lowest power eyepiece inside the adaptor body, tighten the clamp screw, attach to the camera "T" thread end and finally fit the camera adaptor into the barlow.

This is called eyepiece projection photography.

The fiddly bit is finding the right distance to clamp the eyepiece inside the barrel of the camera adaptor to reach focus. I used this method years ago with a Meade LX200 when I first got interested in planetary imaging.

The results though are limited by the quality of the barlow and eyepiece and because the field of view is very small tracking errors become difficult to manage and of course your images are rather limited in scale.

The other solution which might work is to abandon the idea of using your DSLR for now and go for one of the web-cam based camera's with a laptop or notebook computer.

These camera's mostly come with a 1.25" nosepiece so you would need a .965" to 1.25" adaptor which cost a few dollars. The web cam cameras only need about half an inch of back focus, much less than a DSLR.

Before you decide one way or the other it's a good idea to measure how much back focus you actually have available, to do this take the scope outside when there is a good size moon and point the scope at the moon, remove any eyepieces or barlow from the focuser and wind the focuser all the way in. Hold a piece of white card over the end of the focuser draw tube and gradually move the card back and away from the focuser, where the moon comes into sharp focus on the card is the limit of back focus available.

My guess is you won't have more than an inch in which case the eyepiece projection method would be best if you dont want to start modifying the scope.

If you have about an inch and a half then the web-cam camera should work.

Finally, you could always just piggy-back your Nikon D5200 on to the telescope tube, with a wide-to-mid length lens on the camera you will get much better images than from the eyepiece projection method!

Best of luck....hope you are successful.

William.

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