130P and micro 4/3 focusing

[John78]

Hopefully a quick query, which I think the answer to is some modifications on a lathe...

So I bought a 130P with a 2" focuser from Astroboot for £45 which arrived today, had some quick first light visuals at Jupiter and the sliver of the moon everything seemed good optically so I enthusiastically swapped out the EP for my Olympus OMD-EM5 and I can't get it close enough to focus, it's about 5 or 6mm short (I just held the body above the focuser to gauge the distance).  The adapters I've got are pictured (less a 1.25" adapter for the T2) they all appear to fit properly in the image train but I can't focus.

The only way I can envisage getting closer is turning down the OD of the camera body adapter so it's the ID of the focus tube and sliding it straight down the tube?

Will I reach focus with the coma corrector if I buy that or will it still be short?

Has anyone successfully got a micro 4/3 camera on a 130P tube?

My EPs and webcam both focus fine.

 

As a side note I assume the tubes are cheap on Astroboot because the screwed on supplied dovetail appears to be 90 degrees out from where it should be so the focuser is straight up so you either need to stand on a chair or be a GIANT to see through it...  Or straight down requiring a hobbit, Unless I'm being exceptionally dense tonight ?  I'll make some tube rings for it to get it setup sensibly.

 

fog is starting to descend again now ?

 

Thanks is for any guidance!

[goose35]

if its like my 150p then remove the dovetailed adaptor part as in image 1 and a 2 inch adaptor should go straight in the tube. I will just go do some quicky snaps of mine. 

[Cornelius Varley]

The dovetail on the OTA is in that position because the tube is from the AZ-GOTO 130P

[happy-kat]

Are you running out of inward or outward focus? (I'm suspecting inward)

[John78]

Yeah running out of inward travel, I just don't see how to move the sensor closer to the secondary without making the OD of the part that mounts on the camera body smaller as it won't fit down the tube.

[goose35]

Ok on my 150p i remove this part

 And a 2 inch adapter or coma corrector fits in this part of the tube direct. This is 2 inches

But if its like my 130 focuser which is an older version of SW focuser looking simlar to yours it is over 2 inches so  i got a  adapter from baader wich replaces the end on the focus tube. in my case it was a 60 mm threaded tube. This adapter also has other thread sizes

[happy-kat]

The standard 650mm 130p doesn't reach focus with a camera it runs out of inward travel. Sometimes a barlow helps, or a bit of diy and move the primary mirror up (which the 130p-ds has) though you then may need an extension tube to focus with an eyepiece.

[John78]

6 minutes ago, happy-kat said:

The standard 650mm 130p doesn't reach focus with a camera it runs out of inward travel. Sometimes a barlow helps, or a bit of diy and move the primary mirror up (which the 130p-ds has) though you then may need an extension tube to focus with an eyepiece.

Would you know how far up roughly?  Is it drill some new holes in the tube and cut the end off or can fit longer screws in the existing mirror holder?

After a few minutes of googling it appears another option is modifying the focuser you can (apparently) get 11mm extra inward, it already needs removing and modifying as it sticks out hugely into the tube when focused inwards so that might be an option.

[John78]

Just waiting for it to be an acceptable hour to start using a dremel tool and then the mirror will be moved up 20mm ?

 

If my guesstimation is accurate that should bring the camera into focus and still focus an EP, but as long as the camera will focus and I can still collimate it's ok to me.

[happy-kat]

Hope this goes well for you

[John78]

Well what's the worst that can happen it was only £45 ?

 

The end is gone, just need to clean it up and redrill the mounting holes...

 

[happy-kat]

You meant business then :-) Dremmels are great.

[Waldemar]

That is one of the minuses of using a DSLR... 44 mm backfocus. Most CCD camera's don't have such a long backfocus , only ± 17 mm, hence no problem with focusing.
On the other hand: not needing a laptop in the field is definitely a plus.

Your focuser being in the wrong position for viewing means it is in the right position for imaging. Radial balancing of your scope is a lot easier that way:
http://brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/gleanings/balancingequatorial.html

An easier way then all the arithmetic is to lay your scope on two thin aluminum t-bars, with the T upside down on a table and watch it roll to the radial point of gravity (pog).
Move the dovetailbars accordingly, or turn the scope in the rings, so the pog is on the downside... Now your mount will be balanced in all positions once the DEC and RA balancing is done.

this does make a difference in tracking!

Waldemar

[John78]

I was surprised balancing was easy yesterday but my previous refractor was bum heavy now with the camera the other end its simples...

 

The grunt work is complete, can focus to infinity and beyond now - and the focuser doesn't protrude too far into the tube at infinity... Time to have a first ever attempt at collimation ?

[John78]

looks like the secondary is out a couple of mm on both axes from being central - so will fix that first...