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Max22

Unable to focus with eyepiece projection

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I recently took my first images of the moon with a T-Ring adapter mounted straight on my telescope, I purchased an eyepiece projection adapter to allow me to increase the magnification for closer photos. Unfortunately, I run out of focus travel before it comes even near focus. I tried extending the focus by putting in a Barlow lens before the adapter, but to no success. DSC_0149-copy (2).pdf  

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Eyepiece projection can be problematical.

Installing a Barlow before the eyepiece projection unit and selected eyepiece will not change the focus plane at the camera very much and will make focusing much harder as you will have doubled or tripled the overall eyepiece power. Using a Barlow or Power Mate by itself is an often used configuration but I’ve never heard it used at the same time as an eyepiece fitted inside the projection unit.

When using eyepiece projection you have two focusing adjustments, the first is the mechanical focuser of the telescope and the second is the physical position of the eyepiece in the barrel of the eyepiece projection unit.

Start with the eyepiece pushed fully to the bottom of the barrel of the eyepiece projection unit, choose a moderate power of eyepiece to begin with and if possible use an eyepiece that has a un-screwable chrome/brass/plastic nose barrel, unscrew and remove the eyepiece nose-piece to allow a greater range of movement inside the projection unit.

Then try to focus with the telescope focuser, if you cannot reach focus, slide the eyepiece further up the barrel of the projection unit, maybe halfway, and try to focus again, if still no joy try with the eyepiece positioned right at the top of the projection unit.

You will find it easiest to begin with using a low power eyepiece but it is a balancing act. Generally low power eyepieces have physically bigger bodys that either wont fit the projection unit or don't have enough forward-aft adjustment range inside the projection unit which is why choosing an eyepiece with a removable nose-piece can be helpful.

The optical design of eyepiece also has an influence, some eyepiece types just will not be able to reach focus at the camera plane.

Last time I used eyepiece projection was many years ago but I remember using 12 and 15mm plossl eyepieces had a good focus range with the chrome eyepiece nose-piece unscrewed and removed before insertion into projection unit. That was with a 35mm film camera.

It’s not going to possible to give you an exact recipe to follow, there are just too many variables involved, but try with the lowest power eyepiece you have that will fit inside the projection unit, with the eyepiece nose-piece removed, and slid to different positions along the inside of the projection unit barrel.

Try this in the daytime, focusing on a distant object NOTE: NOT THE SUN..!!!!! and this will give you a reference point, then use progressively shorter focal length eyepieces until you find the limit that is possible with your combination of equipment.

HTH.

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2 hours ago, Max22 said:

I recently took my first images of the moon with a T-Ring adapter mounted straight on my telescope, I purchased an eyepiece projection adapter to allow me to increase the magnification for closer photos. Unfortunately, I run out of focus travel before it comes even near focus. I tried extending the focus by putting in a Barlow lens before the adapter, but to no success. DSC_0149-copy (2).pdf  

What size eyepiece did you use in the eyepiece projection adapter ?

ps please use .jpg or .png format when uploading images.

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In which direction are you running out of focus travel and what telescope are you using?

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I am running out of travel distance after fully extending the focuser outwards. I used a 25mm eyepiece, to begin with. Does eyepiece projection actually increase the magnification of the images? I've found that just using the T-ring, Saturn is just a bright star and no visible rings.DSC_0137.thumb.png.7f8b1d82fca8386b9fdbaa90be928c17.pngDSC_0166.thumb.png.2bf4eb62048bd88ce660411d5136bbaf.png

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Just now, Max22 said:

I am running out of travel distance after fully extending the focuser outwards. I used a 25mm eyepiece, to begin with. Does eyepiece projection actually increase the magnification of the images? I've found that just using the T-ring, Saturn is just a bright star and no visible rings.

The lunar image doesn't look too bad, just a little small to show greater details. Eyepiece projection depends on two factors. The size of the eyepiece and the distance between the eyepiece and camera sensor. 

A couple of useful links for ep projection

Eyepiece projection calculator

Ann Dittmers lunar photography

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@Cornelius Varley Thanks, I would like to get more detail of the moon on planets. That's the reason that I tried eyepiece projection, in hope that I would be able to increase the magnification of the image and get more detail. 

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