ED127 help please

[pmrid]

Could someone with an ED127 (the f7.5 FL 952mm one from North Group) let me know the distance from the back of the scope to the image plane?

By back of the scope, I would ideally like the distance from the last metal of the OTA with no focuser attached but that would be a bit of an ask. So I'd be happy enough to get the distance from the FRONT edge of the red metal where it meets the white metal of the OTA.

I'm trying to figure out what (if any) adapters I might need to get to fit my Moonlite focuser onto it.

Peter

[h0ughy]

Peter you might need to get the flange from Moonlight that screws on - go look at imaged of my 127 in the observatory thread and you will see

[h0ughy]

see the scope near the crash test dummy http://www.iceinspace.com.au/forum/attachment_browse.php?a=87172

[LewisM]

Moonlite make a direct fit for these - just make sure yu tell them if CF tube or Aluminium tube. The Explore Scientific scopes - popular in the USA - are North Group scopes. Nathan here had a Moonlite fitted to the CF tube 127 I bought from him.

[mithrandir]

Peter, how are you attaching the Moonlite? I've got a Moonlite focuser for mine that completely replaces everything from the end of the white tube section.

[LewisM]

That's exactly how mine was too - didn't seem like it was an add-on/custom flange at all, but made as-is.

[pmrid]

Thanks for the input so far.

To answer the questions, I already have a large-format CSL (for SCT/RC) attached to an RC8 and as a focuser it is a beaut. I already have another RC with a FeatherTouch so decided that I'd mount up the ED127 on my second pier and put the AP .67 reducer on the ED127 to run it at F5(ish) and so have scopes imaging at about 650mm as well as 1600.

But I don't want to have to spend any more on this setup than necessary so I planned to take the CSL off the RC and use it on the 127. I appreciate that the drawtube will be a lot shorter than the conventional refractor-type focuser but Moonlite make extenders for their bottom flanges so I'm confident that I can get both a lower flange to connect it and an extender if I need it and at a modest cost.

BUT the question remains, how much does the imaging plane hang out the back of these 127s.

Peter

[Logieberra]

Correct me if I'm wrong, but if you point the scope at a light source (or anything nicely illuminated) with no camera or end adapters (unobstructed light path) you can measure the focal point (from a metal back surface) by simply casting the refracted light on a flat surface, like a wall. Just move scope away from wall until the object (e.g. a light fixture, whatever it points to) snaps into focus on the wall. There you have it. Crude, but works.

[Geoff45]

Foolproof method, as long as the light source is reasonably distant--a street light, say.
Geoff

[LewisM]

This is the technique I used to establish the adapter length required to bring my FSQ85 and FLI ML8300 image train length (quite long!).

I used an adjustable rod and card assembly similar to the solar projectors of old, and used the moon for the purpose

[pmrid]

As a rough-and-ready technique, that's well known and pretty obvious. It would be great if I had the scope in my hot little hands to use it. But it is still in transit and my reason for asking for someone with a bleedin' tape measure to use it was that I want to order whatever additional extenders I will need when the scope does arrive.

So getting back to my initial question, and without wishing to seem ungrateful for what I am sure was well-meant advice, is there no-on out there with a ED127 set up for imaging who also owns a tape measure and can whack it across the imaging train to let me have that measurement?

Peter

[Logieberra]

Wow...

[pmrid]

Yeah, you're right. That was a bit strong.
I've gone ahead and ordered some bits that I may need. So my request for help becomes otiose anyway.
So thanks anyway but let it go.
Peter

[Logieberra]

:)