About Klaus Helmerichs solid carbon tube

[Acrab67]

Hi,

I own an Orion Optics UK 250mm f4'8 tube. It is the previous model SPX with 1/8 optics. The fact is that the tube already has a couple of buns and also suffers from the problem that it is very flimsy.
I have been thinking of replacing it with a Klaus Helmerichs carbon tube, although they are very expensive. It would be to adapt the primary cell, a JMI EV-1n focuser, and the original spider. Has anyone had experience buying these tubes?
Thank you.

[Stu]

I believe @Captain Scarlet is the man for this job 👍

[Captain Scarlet]

Indeed yes I have two of his tubes. One for a 300mm mirror and the other for a 200mm mirror. They are extremely stiff, and I cannot fault them. I went for the carbon tube lined with 6-7mm of hardfoam, which in addition to helping the  stiffness, provides better purchase for accessories bolted on to the tube such as focuser, finders, spider and main cell. The only stipulation I would recommend is to drill your own holes. You can do yours at leisure going up 0.5mm at a time, whereas he does them more quickly. Re the focuser hole, drill a pilot hole of course, but for the main event use a sharp hole-cutter _backwards_. 
BTW I didn’t regard them as that expensive for what they were. But it was 1.5-2 years ago.

Cheers, Magnus

PS @ONIKKINEN also has a CH tube I believe.

 

Edited March 21, 2023 by Captain Scarlet

[Acrab67]

Thank you for your appreciations.
I understand that the tube has a larger internal diameter than the original, right? You reused your spider or mounted a new one. I understand that you also had to use longer screws to hold the mirror cell. Did you make the holes in the tube?
Thank you

[Captain Scarlet]

I think he’ll do whatever tube size you want. I initially ordered a tube to replace the one on my SW 300p, and he said don’t worry about specifying the size, I have just such a SW cell as a template. Unfortunately SW must have slightly changed their 300p cells at some stage, as the tube was 2-3 mm too big in diameter (I did ascertain with him that it was indeed two slightly different cells, not his craftsmanship). Luckily too big rather than too small! So I shimmed it. Eventually I replaced the SW cell entirely with an OO cell which I knew in advance I was going to have to use 9mm of spacing on each of the three corners.

The 200mm tube I ordered to fit my VX8 cell, and that fit pretty well straight up.

The only other suggestion I’d make is give it extra length, effectively dew-shield and long baffle in one! I did that for my 200mm you can probably see from one of the pics.

M

Edit: to answer the extra questions I’ve just noticed. Yes I did all my own holes after the original SW-cell ones. And I was actually able to re-use all the spiders too. I used some modified flat-plate door hinges to give me extra circumference for the 200mm tube, which as @ONIKKINEN says below has a larger external circumference because of the thickness of the tube.

Edited March 21, 2023 by Captain Scarlet

[ONIKKINEN]

I replaced the flimsy VX8 aluminium tube with a thicker carbon tube from Klaus helmi not too long ago last year. I ordered mine to be a little bit longer than the original to act as a dew shield like suggested above although looks like mine is a little bit shorter (maybe should have asked 5-10cm more). Pretty sure he will make your tube with exactly the measurements you give him, so no worries about getting a different sized one than your mirror cell allows as long as you measure what you want. The new one is 5mm thick whereas the old one was maybe 1mm, so the rings will not fit the thicker tube diameter but i wanted to upgrade them anyway since they are not very robust in the VX lineup of scopes. Looking at the bill i ended up paying 386€ including shipping for the 8'' tube with no holes pre drilled so i wouldn't call it all that expensive if you look at the prices of premade carbon tubes sold in TS such as this one: https://www.teleskop-express.de/shop/product_info.php/info/p14357_TS-Optics-Carbon-Tube-Upgrade-for-the-DIY-of-a-8--Newtonian-telescope.html .

Very robust (mine was 5mm thickness with some kind of sandwiched core) and thermally stable* even in difficult conditions:

*Takes longer to cool down though since its much thicker, consider having some kind of fan on the mirror cell to help with cooldown times.

One thing to keep in mind though is that you probably should prepare for a wait time of several months. He did originally mention in e-mails that it would take a few weeks instead of months, but it kept being delayed for many reasons and took about 6 months if i recall correctly. Long delivery times seem to be a common experience with ordering these tubes so i would prepare to not see it in a while regardless of the original shipping estimate. It is well worth the wait though, so its not a real gripe i have with the product. Would buy one again if a future scope could use a better tube, highly recommended even with the waiting time!

[Acrab67]

Thanks. 

[Acrab67]

By the way, it seems that this man passes the email right?