An F4.5 ED80 ??????

[philj]

A little project Ive been planning since I got the ED80.

I saw the Altair 0.6 reducer flatteners awhile back and that started the thought process off so at the IAS I got one. It quickly became evident that theres not enough back focus on the ed80 stock focuser so using that was out.
I didn't want to chop 3 inches off the tube and reduce the scope resale value so I dug around and found my old Meade 127 focuser which is decidedly shorter in the body and together with a new philjay special design of adapter and rotator this could be made even shorter.

So once the ali was sorted I made a start and the test run was today in daylight with both the Atik and 1000d. The 1000d was easy with just a 10mm spacer between reducer and camera, it reached focus on a distant tree with about 1.4" draw tube extension.

The Atik was a bit more complicated so required a good 40mm spacers to get the correct reducer to chip distance but this was easy enough as I have lots of spacers. I now have a single spacer in place instead of the multiple ones shown, it now looks a bit more elegant

So heres a few snaps of the project, including a screen shot of the distant tree with the Atik

The focuser is compact and rotates by unlocking the screw shown, rotating and then locking. I'm quite proud of that design  
The draw tube on the replacement focuser has been shortened also to stop it interfering with the light cone because the focuser is closer to the objective and the new draw tube was longer than the SW.

All I need to do now is test it under the stars. I'm not sure of the effectiveness of this as it's rather quiet in tinternet land about these 0.6x reducer flatteners, either that's because they are not that great or because they need so much back focus that folks give up or don't bother.
So watch this space

If it doesn't work Im not to fussed, the old focuser can go back on and all Ive lost is a bit of time playing on the lathe which I don't mind one bit

[michael.h.f.wilkinson]

Very nice project. Looking forward to first light. My APM 80mm F/6 with TRF2008 0.8x reducer reaches F/4.8, but F/4.5 should be even nicer

[philj]

Cheers Michael, I was wanting to have a play on my lathe and out of all the many projects I have in my head lined up this was the easiest at the mo. Been wanting to mangle some metal for awhile now. Theres something satisfying about turning a bit of metal into a pile of swarf

Not sure it will perform like a posh APM

[michael.h.f.wilkinson]

My APM is not that posh. It is the same as the TS 80mm F/6 triplet, not a fancy LZOS job.

[nmoushon]

Nice innovative mod! 

If you are looking at a faster ED80 I would suggest the SW Equinox. One of the best doublets for the price. I use a .67x reducer with mine and image at f4.18, though my reducer is of an unknown brand but I've never had any problems with it. Even with the more common .7x reducer you are still imaging at 4.375.