Eyepiece projection imaging

[dawson]

An astro-mate who isn't yet on EMS has asked me about eyepiece projection imaging with a dslr and a hyperion zoom. He's not after award winning images.

I found this article on the topic for him to read:

http://www.astronomysource.com/2011/10/13/eyepiece-projection/

But i wonder if many EMSer have tried this method and if they have any comments. I've never used the baader zoom, and wasn't sure how easy it is to click it from one focal length to another accidentally and whether the EP is parfocal at all four focal lengths and any focal lengths in between.

My limited experience of eyepiece projection was on jupiter in dslr-video mode, and that it appeared to cut down the brightness of the planet greatly, and i found focus as hard as always to sort out.

With an unguided CG-5 mount i suspect he is going to be limited to very short individual exposure times if wanting to try this technique on DSOs.

Any comments / experience / tips for him will be greatly received.

Thanks.

Jd

[catman161]

I have tied using the T2 adapter for the Hyperion zoom mark 3 to attach my ASI120MC firefly to do a bit of afocal however i could bot get it to focus properly at all. To me it seemed that there needs to be more space between the camera and the eyepiece but i wasn't sure how to achieve this so haven't tried again since!

Sorry bot very helpful!

[dawson]

Might something like this add more length:

 

http://www.ebay.co.uk/itm/Baader-T-2-Extension-Tube-15mm-BNIB-UK-Stock-1508154-/221372960808?pt=UK_Telescope_Eyepieces&hash=item338adb5028

 

JD

[Brantuk]

Yup - we had a go with a baader zoom and a dslr and it was very fiddly getting it in the frame. It has 5 click stops but remains in focus between each stop - but the mag level has to be set first or you'll turn the camera round when zooming.

 

We just managed half a dozen shots before giving up. The image, though dimmed, was well bright enough, but blurry. Bear in mind it was our first attempt at AP with an Sct (CPC 800). So we were very inadequate about it all lol.

[dawson]

Thanks Kim.

 

JD
 

[xanthic]

I tried it on mine once. As Kim says, the eyepiece rotates with the zoom and the weight of my camera was easily causing it to move. This is quite annoying and I was not impressed with the images I got either.

[catman161]

Might something like this add more length:

http://www.ebay.co.uk/itm/Baader-T-2-Extension-Tube-15mm-BNIB-UK-Stock-1508154-/221372960808?pt=UK_Telescope_Eyepieces&hash=item338adb5028

JD

Nice one! Thanks JJ

[xanthic]

That EP is parfocal for terrestrial use but not for use near infinity. So you do need to refocus between stops.

[Orion]

I don't know of the technique is the same as that I used with a film slr. But the eyepieces I used were fixed fl's, usually a 4-6, or even 9mm that sat inside an epp adapter. The relative position if the eyepiece could be moved toward or away from the film which made the effective focal length of the reflector massive e.g. 40, 000 mm. Because the film was 24x36mm, it was reasonably easy to get a planet sych as saturn on the film, and easier nowadays with driven systems. I can imagine the difficulty it could be with a web cam of small chip size. But a dslr chip size is abour the same as that if old 35mm film isn't it? So should be easy to get the object centred. As for focusing, I used to use the micro prism and split field prism in the middle ans align up like a range finder focuser. It took ages - the object being knocked out of field by the slightest attempts at manual focussing. In the end, I accepted focus and even uc it drifted outside, id use the drive system to allow it come back in, or have the object on the other side of fov and allow the object to drift in slowly by slowing RA motor. That way, I avoided backlash from focussing. It actually was a frustrating pain. But decent images when object centred - using the cardboard cap method (card over main scope to allow opening shuuter, cap off, expose 1, 2, 3 seconds etc, cap back on, close shutter. Dslr would have great advantages over that, and I assume he will be doing video imaging rather than single frames? I don't know how fast an exposure can be made on dslr single frame. Resolution may be better than on video, but longer exposure needed and affected by movements in tracking, refraction, poor seeing etc - if the exposures are anywhere longer than a fraction of a second. With iso (asa) 400, 6mm lens on 8.75" f5.6 NR, exposures for moon, Jupiter were in the 1-3 second range. Plenty of time for telescope shimmy and blurring. Dslr - go for it, I intend to try that when I get a dslr.

[Guest]

I've recently bought a T-ring and T-mount. With the bad weather we've been having, it is still early days but I think it's better.