Lunt 50mm question

ffellah · Post by **ffellah** » Mon Apr 22, 2019 9:05 pm

Hello all: I recently received a Lunt 50mm Ha that I will use as a grab and go solar scope. It has the B600 blocking filter. Yesterday I was out trying to see if I can image with it and neither camera, PG Flea 3 2.5 microns or ZWO 174 5.86 microns, could reach focus. The focuser does not go in enough to reach focus: with the Flea 3 it almost does, but not quite.

The scope is 350mm focal length, F/7.

Any suggestions or experience from the group ?

Thank you,

Franco

MapleRidge · Post by **MapleRidge** » Tue Apr 23, 2019 12:59 am

Hi Franco...

Based on the pic there isn't a lot of easily removable pieces that would free up any in focus.

If you had a low power barlow (1.25x or so) it might push focus back enough to work out. Another thought is to get a lower profile 1.25" eyepiece hold so the camera sits lower, or try to shorten the scope side of the blocker...either should free up some travel. It is hard to tell in the pic, but there looks like a thick black fitting between the focuser and blocker body...can this be removed?

Jus a few thoughts,
Brian

Valery · Post by **Valery** » Tue Apr 23, 2019 1:26 am

The nose of the diagonal need to be replaced with another one with shorter of it's wide part. You can win about 10-15mm.

Or use a Coronado BF10 instead.

Valery

krakatoa1883 · Post by **krakatoa1883** » Tue Apr 23, 2019 12:11 pm

Hello Franco, I had the same problem, the reason is the eyepiece holder which is too long. I solved with this adapter that threads between camera and diagonal

https://www.teleskop-express.de/shop/pr ... ength.html

ffellah · Post by **ffellah** » Tue Apr 23, 2019 2:12 pm

Thank you Brian, Valery and Raf for your advice.

@Raf: so you remove the current eyepiece holder and replace it with the adapter from the link you sent ? How easy Is removing the eyepiece holder from the diagonal ?

Thank you,
Franco

krakatoa1883 · Post by **krakatoa1883** » Tue Apr 23, 2019 4:16 pm

The eyepiece holder is simply screwed on the diagonal by a T2 thread. Use this thread to install the adapter (the other side attaches to the camera nose) and you should be able to image at prime focus. As the adapter doesn't allow to rotate and lock the camera, image orientation shall be changed by rotating the diagonal in the rear of the scope.

I would strongly suggest you to change the original focuser with a better one if you intend to use the scope for imaging. I installed a FT and works fine.

ffellah · Post by **ffellah** » Tue Apr 23, 2019 4:29 pm

Thank you, Raf. Would you mind sending me a link for the FT focuser you installed ?

Thank you,

Franco

Post by **marktownley** » Tue Apr 23, 2019 4:38 pm

Replacing the EP holder on the diagonal with one of these https://www.365astronomy.com/Visual-Bac ... rsion.html and using a short c mount nosepeice on the camera will get you in to focus.

bart1805 · Post by **bart1805** » Tue Apr 23, 2019 5:06 pm

Maybe this is interesting Franco:
https://www.cloudynights.com/classified ... t-ls50tha/' title='Feather Touch Focuser for Lunt LS50THa

pedro · Post by **pedro** » Tue Apr 23, 2019 5:33 pm

I had the same problem when I used a LUNT50 belonging to a friend. You have to use a low profile 1 1/4" adapter (see the second and third photo) to reach focus. Changing the focuser for a FT also helps

IMAGING SETUPS (LUNT50)

skyhawk · Post by **skyhawk** » Tue Apr 23, 2019 6:30 pm

You are using a 2" diagonal that is why

MapleRidge · Post by **MapleRidge** » Tue Apr 23, 2019 6:40 pm

It has the standard Lunt blocking filter body...just needs to have the camera moved closer to the diagonal body or a shorter spaced connecting the focused/blocker body.

Brian

pedro · Post by **pedro** » Tue Apr 23, 2019 7:15 pm

https://www.teleskop-express.de/shop/pr ... short.html
Visual Back T2 to 1.25" - with additional T2 male thread - short

ffellah · Post by **ffellah** » Tue Apr 23, 2019 7:25 pm

Thank you all for your help ! I am glad I consulted the group on this...

Franco

krakatoa1883 · Post by **krakatoa1883** » Tue Apr 23, 2019 7:46 pm

ffellah wrote: ↑Tue Apr 23, 2019 4:29 pmThank you, Raf. Would you mind sending me a link for the FT focuser you installed ?

It is this one

https://www.teleskop-express.de/shop/pr ... ength.html

: Adapter.jpg (91.96 KiB) Viewed 1907 times

Replacing the original holder with a shorter one as suggested by Mark might not work if the nose of your CCD camera is too long because it would end against the blocking filter cell.

Post by **marktownley** » Tue Apr 23, 2019 8:08 pm

I managed to get a 10mm length c-mount to 1.25" nosepiece from ebay, it was good quality and with the other adapter allowed me to get in close. I want to try my Lunt 50 up and running again soon, maybe over the next couple of days. The double stack of external etalons i've used on the travelling setup is too fiddly to quickly get it up and running for imaging. Visually it is great but I want to try the 50 again, if I can get the sloppy etalon on it square again and not slopping around would be good. I went for the moonlite focuser on my 50. I tried the feathertouch but in this instance the Moonlite is superior IMHO, I sold the feathertouch in the end.

MapleRidge · Post by **MapleRidge** » Tue Apr 23, 2019 11:20 pm

Hi all...

I sent this option to Franco earlier this afternoon, but if the helical focuser has t-thread you could remove the nosepiece of the blocker and fit them with a threaded adapter with internal female threads. I have a commercial adapter and the internal threaded ring from a T-ring shown in the pic. I put this together years ago when I received my first Lunt filters for a scope that the supplied adapters would not work.

: blocker_mod.jpg (88.62 KiB) Viewed 1898 times

If there is no thread on the focuser you can ignore this

, just couldn't tell int he pic or on the sample pics on the Lunt website.

Brian

Post by **marktownley** » Thu Apr 25, 2019 12:05 pm

Here's a picture of the back end of my Lunt 50 setup. I use the moonlite focoser, Coronado bf15 and then the tube off a 2x skywatcher Barlow (minus the lens) and then the eyepiece.

: IMG_4914.JPG (1.46 MiB) Viewed 1862 times

GreatAttractor · Post by **GreatAttractor** » Fri Apr 26, 2019 4:22 pm

I have a Borg helical focuser and a custom T2/C-mount low-profile adapter, see the second picture in this thread: viewtopic.php?t=18394

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