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I was given a 1995 vintage Tasco "302003" Newtonian telescope recently and have had some exciting success with it. I have managed to view the Moon in beautiful detail and also had my first glimpse of Jupiter (with Enceladus Ganymede & Europa in the same shot!).

I was able (with very considerable difficulty) to photograph both Moon and Jupiter scenes by holding my camera up to the eyepiece. Far from ideal but it has really fired my imagination about doing more astronomical photography.

Here's a picture of my telescope and it's accessories. Despite spending the last 15 years in the back room of a charity shop, it's in brand new condition and all the parts are present including the tripod and all fixings!...

enter image description here (Blue arrows indicate places where eyepiece lenses can be inserted).

My camera is a Nikon D40 (APS-C format, DX lens ring system).

Is it possible to modify this telescope's eyepiece (a rack-and-pinion tube-length adjustable type) so that I can attach my camera in order to take photographs of astronomical subjects? Photographs of the Moon would be my primary goal.

I am happy to make severe modifications to the telescope if necessary. But I realise that certain measurements would be absolutely critical to making good photographs possible. I think I can make an adaptor that goes between the eyepiece socket and the camera. But I don't know all of the parameters I will have to know to design such an adaptor.

Problems I believe I need to solve...

  • I think that holding the camera's central axis perfectly concentric with the eyepiece's axis is critical.
  • I need some sort of Relay Lens between the secondary mirror and the camera body.
  • Keeping the rack-and-pinion tube adjustment (actually a fairly sturdy mechanism) is important and would allow better focusing of the picture as the camera is not likely to have enough auto-focus range to cope with the 700mm F length.

I do have a small Milling machine and most of the basic machine tools. I have a ready supply of aluminium stock and industrial plastic stock (RG1000) that I can build an adaptor from.

Is this project feasible?

I'm not looking for perfect photos, but rather something that is better and more convenient than holding my cellphone camera close to the eyepiece and holding my breath! :)

My astronomy/optics knowledge is practically zero but I'm a fairly savvy mechanical engineer and can build things to a specification.

Thank you for reading, I look forward to your responses.

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    $\begingroup$ What you need is called a T2 adapter. There are adapters for the standard 1.25" and 2" eyepiece tubes behind the focuser. They attach to your dslr (where you would usually attach the lense). The T2 adapters are brand specific though. If you have a Canon camera you need a Canon T2 adapter. Also, you won't need any "Relay lense". Just put the camera at the correct distance behind the focuser tube to get it into focus on the cameras sensor and you are good to go $\endgroup$ – RononDex Aug 22 '17 at 15:31
  • $\begingroup$ I didn't realise it was that simple. I've ordered a cheap T2 / Nikon DX adaptor. My only concern now is that I've got nothing but thin air between the sensor and the infinite void. Knowing my luck within an hour of using this I'll have a spider building a nest behind the mirror mechanism! Perhaps I can rig up one of my UV filters over the small "dust cover hole" to keep out some of the atmosphere. $\endgroup$ – Wossname Aug 22 '17 at 18:12
  • $\begingroup$ If the T2 adapter is not adequate, you can make a custom adapter with a metal lathe and an aluminum cylinder. Mine works nicely, and since I had the lathe and spare aluminum, was a lot cheaper than storebought. $\endgroup$ – Wayfaring Stranger Aug 24 '17 at 14:37
  • $\begingroup$ @Wossname most astrophotographers only use "air" between sensor and the void xD. Unless you do planetary photography where you usually need barlow lenses to increase zoom $\endgroup$ – RononDex Aug 25 '17 at 7:46
  • $\begingroup$ @RononDex, so it seems. However, DSLR sensors will electrostatically attract dust and other airborne particles. These will cause shadows to form on any (normal) photographs taken in daylight unless the sensor is cleaned. It's not a good idea to leave a DSLR body open to the atmosphere for prolonged periods. $\endgroup$ – Wossname Aug 25 '17 at 9:12
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The problem you have with many newtonian reflectors - especially smaller ones - is that to use them for prime focus photography (where you're effectively using the telescope like a big telephoto lens) , you need to set things up so that the camera sensor ends up at the focal plane of the telescope. And in a DSLR, the sensor is some way inside the camera body (behind the shutter, which is behind the mirror.

With a newtonian scope, the focal plane is usually somewhere inside the focuser tube, and many newts don't have enough focuser inwards travel to let you get the focal plane the 40mm or so beyond the end of the focuser that you need to get it to reach a DSLR sensor.

(With other types of scope that use a separate star diagonal, things are usually easier - you can leave the star diagonal off, which has the same effect as a big chunk of inward focus).

With a newtonian, if you can't reach prime focus, there are three basic options - either take photos through the eyepiece (afocal photography) as you already tried,

or move the main mirror further up the tube (which moves the focal plane further out, giving you more in focus). It also means the light cone is fatter when it reaches the secondary mirror, so you may lose some light as the outer part of the light cone misses the secondary.

or you can try using a barlow lens - that replaces the last bit of the light cone with a longer, narrower angle version (which increases the magnification and moves the focal plane further out). That MAY or MAY NOT let you reach infinity focus; it's not guarenteed, but may help. You can get barlows that have a T-Thread on the output end, so you can attach a T ring directly to the barlow (yours doesn't look like one of this type) and then hook the camera up that way. (as an added benefit, since you end up with a closed tube setup (the barlow lens closes off the access to the camera, it also keeps spiders and dust out of the camera :) ).

If you have a look at the bottom bit of the barlow (with the lens) you may find that you can unscrew it. You might be able to make a short top section with a T thread for the T ring at the back, and a suitable thread for the lens at the front; you'd probably need to make it the same diameter as the eyepiece barrel (to fit in the focuser) with a fatter bit at the back for the T thread and to stop it sliding all the way into the focuser. I've used a commercial 1.25" barrel T threaded barlow (somewhat shorter than yours) for lunar and solar (WITH A SUITABLE FRONT OF SCOPE FILTER - DON'T TRY LOOKING AT THE SUN WITHOUT ONE) imaging with an APS sensor camera.

(You may need to check your scope - older ones often used a .965" barrel rather than the current 1.25" (or 2") barrel size used by most modern astro scopes.)

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  • $\begingroup$ Great information, thank you. I like the idea of moving the main mirror inwards to get access to the primary focus point. My tube is a 1.25" type. My Nikon D40 has a marking on the exterior indicating the position of the sensor plane it coincides with the tripod socket screw (as with most SLR cameras). $\endgroup$ – Wossname Aug 24 '17 at 16:13
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    $\begingroup$ One side note - looking at the parts list, you may have one of the eyepiece style solar filters. These are NOT SAFE. The problem is that you have unfiltered sunlight focused on the filter - and that includes heat as well as light, which means the filter is prone to split due to the heat buildup, which then lets unfiltered sunlight through, damaging your eyesight. They're especially dangerous if you try to use them with the full aperture of the scope rather than the small hole in the front scope cover. $\endgroup$ – JerryTheC Aug 24 '17 at 23:28
  • $\begingroup$ One possible trick for moving the mirror forward that would avoid having to drill new holes in the tube for the primary mirror mount - depending on how the primary mirror collimation works (if it's adjustable) - if the mirror holder is attached to the base part only with bolts and springs, you may be able to replace the bolts with longer ones (and longer springs, or sleeves around the bolts to support the existing springs), thus moving the mirror up inside the tube, $\endgroup$ – JerryTheC Aug 24 '17 at 23:34
  • $\begingroup$ It's also worth checking to see if the black bit on the outer end of the focuser unscrews, On some newtonians, this may reveal a T thread. If it does, you can attach the T ring and camera direct to the end of the focuser, which gets the camera a bit closer in (with a separate T-adapter, many also have a T thread on the front nosepiece section, which unscrews - so you can attach the T ring just to the nosepiece bit, which again lets you get the camera closer in.) $\endgroup$ – JerryTheC Aug 24 '17 at 23:40
  • $\begingroup$ Thanks for the safety info Jerry. Actually I'm only interested in night-time astronomy, but it's good to know anyway. Yes there is a thread on the focusing tube, I've already ordered a T2 adaptor for my SLR :) $\endgroup$ – Wossname Aug 25 '17 at 6:55

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