I spotted Bintel discounting this adjustable eyepiece projection doohickie. Looks like a handy piece of gear I thought, especially at that price. Slot in any eyepiece I fancy, and utilising the built in adjustment capability, take photos with my 1000d, I thought.
WRONG!
Disappointingly, I can only achieve focus with my 8” GSO using the 25mm EP. With the other EP’s I can achieve focus on very close objects but that’s not what I wanted it for. I don’t want to go to the trouble of shifting my primary mirror as I want to use my scopes mostly for visual observing, but I did try using my collapsible dob with a shortened focal length to see if I could get some success that way. No luck there either. Maybe I wasn’t careful enough. I was getting a bit cheesed off with the whole business by then. Anyway, what I would like to ask is,
has anyone cracked using one of these things (subsequent research suggests not, doh!) and if not, why the bloody hell does anyone sell them? Some of them are quite expensive!
Well at least you get a cheap 1.25" to T thread adaptor.....
Yes, with the currently available quality barlows/ Powermates I'm not sure too many amateurs still use "eyepiece projection" to achieve longer effective focal lengths for lunar and planetary imaging......and a lot of the sexy new eyepieces are too large to fit these things....
Thanks fellers.
Yes, it does give me a few more options than I had and it didn’t cost much and at least it's nicely machined. It will take a filter too, which my previous Barlow/T-ring mount wouldn’t. I just thought the EP projector would offer more magnifications. Fortunately, the Barlow T-ring mount section, which is too wide for the projector, unscrews, so I will be dropping the Barlow into the projector at the next opportunity!
All good fun ay?
Yes, I had a similar problem with a fixed-length eyepiece adapter extension - would only work with 25mm EP 0n 8" f5 Newtonian. I then bought extra tubes and acheived focus with 15mm and 9mm, however the camera was now half an arm's length out from the OTA and putting a big load on the standard focusser (fortunately it is a lightweight DSLR). I bought a strong replacement focusser but discovered that, being low-profile, it required all my tubes again to acheive back focus. I didn't think of trying the Powermate Barlow, also acquired recently, instead of an eyepiece, I suspect I will still require a lot of extension tube.
Still can't get my head around the need for so much back focus e.g. the new focusser has a built-in 50mm extension, but that is still 60mm short of what I need to get (visual) focus with any 1 1/4" EP. The original focusser has the eye lens 170mm out from the OTA, yet I read lots of threads dealing with how to get enough inwards focus. perhaps some IIS expert can explain
To Rick, if the question was for me too: Yes the camera does focus with just the T-ring/nosepiece into the original focusser. Waiting for gale-force winds to abate before checking with Barlow again.
I have a 200mm f6 newt. In its original set up I could focus a camera with a barlow and with eyepiece projection with any eyepiece that would fit in the tube, but could not get enough in focus for prime focus. I had to move (reluctanly) the primary mirror forward about 50mm. I now have to use a 50mm extension for visual which is ok. I have a few older orthoscopic eyepieces that worked ok last time I tried to image saturn with ep projection. I will need to try some newer ep s to see if there is any difference with focus. I have not done any high magnification photography for a while, but have a new 5x barlow I am waiting to try out on Jupiter.
I am just trying to work out if there is any difference between scopes that are opimised for photography or for visual
which brings the EP quite a bit closer to the secondary,
since you can remove the stock 2"=125" adapter,
and additionally the EP itself can be mounted further down the projection adaptor
Do you unscrew the 1.25" nosepiece from the projector and screw in the 2" camera adapter instead?
That would have the same effect as moving the mirror wouldn't it. It does seem, as many IIS posters have discovered, that you need to get closer, or use a Barlow to put the focal point further out from the focuser.
Do you think it's due to the extra length of the projector that you cant get close enough for prime focus? That seems to make sense to my sketchy grasp of what's happening with this approach.
Yep - the 2 inch replaces the 1.25. nosepiece
I actually bought the 2" to see if i could get the DSLR closer to the secondary for prime focus, because the stock barrel adapter on the scope adds about 1cm...
unfortunately it didn't help....
you don't use the projector for prime focus at all -
you connect the nosepiece straight to the t-ring....but it is still too long.
(I am not going to move my primary - too much like hard work)
As long as the EP physically fits inside the projector, and
with the 2" in place - an EP - or as suggested earlier, a barlow,
will effectively move to "inside" the focusser....so gets much closer
to the secondary....
Will post some pics later this evening to illustrate what i mean....
Quote:
Originally Posted by CJ
Hi Sharkbite. Hmm, interesting indeed.
Do you unscrew the 1.25" nosepiece from the projector and screw in the 2" camera adapter instead?
That would have the same effect as moving the mirror wouldn't it. It does seem, as many IIS posters have discovered, that you need to get closer, or use a Barlow to put the focal point further out from the focuser.
Do you think it's due to the extra length of the projector that you cant get close enough for prime focus? That seems to make sense to my sketchy grasp of what's happening with this approach.
perhaps some IIS expert can explain
