Celestron C150-HD

[D_253]

Does anyone own one or Have owned one? This is the hybred design. It has the "extra lense" built into the secondary. I need to collimate this scope. I really need some help. I have no tools at this time. What would be the best? This is a f/7, 1000 mm fl. I'm sure my biggest problem is with centering the secondary and the tilt. There is not much info on these scopes. Any help???

[RobH]

Hello.

Do you own one of these telescopes?

The reason I ask is that you seem to have the Celestron C150HD 6 inch Newtonian reflector confused with the Celestron Edge HD scopes. The Edge scopes are a Schmidt Cassegrain design with the addition of a field flattening lens built into the rear of the scope, where the focuser goes, the smallest of which is an 8 inch scope. These scopes are specifically designed to produce a flat photographic field.

No lenses are built into the secondary mirrors on either scope. The Edge scopes are also a lot more expensive than the basic newtonians.

I suspect that you have the newtonian, in which case you need to look at Astro Baby's guide to collimation.....that will explain all :-)

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

[Stu]

I used to have a C150HD a number of years ago. I think the scope does have some form of reducing lens, perhaps in the focus tube, which shortens the tube length required.

Correction to this, looks like the corrector is in the secondary housing. I remember I tried to getting mirrors recoated by OO and they managed the primary but couldn't remove the secondary. See link

http://www.cloudynights.com/item.php?item_id=974

I never really needed to collimate mine properly so unfortunately can't be too much help. I used to find it was ok up to around x150 but got soft quickly after that point.

Stu

[Stu]

This any use? If you haven't already got it, there are collimation instructions towards the back.

ftp://downloads.celestron.com/pub/manuals/telescopes/c_series/31056_c15hd/manual/31056_c150hd.pdf

Stu

[RobH]

I used to have a C150HD a number of years ago. I think the scope does have some form of reducing lens, perhaps in the focus tube, which shortens the tube length required.

Correction to this, looks like the corrector is in the secondary housing. I remember I tried to getting mirrors recoated by OO and they managed the primary but couldn't remove the secondary. See link

I stand corrected (excuse the pun!!).....standard newt collimation will still be fine though.

[Stu]

I agree for the primary but the secondary appears to be fixed ie not collimatable (if there is such a word?!)

Stu

[D_253]

It is strange. On the secondary there is a center bolt. There a 3 screws but they are on the side. They do seem to change the tilt. I was just hoping someone had one and could share there thoughts. Maybe this is why they discountinued this design. I beleave they call these Bird-Jones designs. Some have a corrector in the focuser, and some have it in front of the secondary. That's the way this one is. It is in front of the secondary.

[RobH]

It must be collimateable (maybe that's the word!)....it's a newtonian with a corrector, but all the light path is the same as a newt, and if you can't adjust the secondary then, unless it's built to extremely tight tolerances and factory set perfectly, then you'll never be able to collimate it.

Do you have a photo of the secondary/corrector ?

[D_253]

I think I have it figured out. Rob, you can rotate the secondary by loosening the 3 side screws and turning the center bolt. The 3 side screws do tilt the secondary also. I just can't see how to move it in or out. But it seems to be centered in the focuser as is. I have it adjusted now to where I can look though a home made collimation cap and see the 3 clips on the main mirror. I think I'm going to order a Combination sight tube / Cheshire tool monday.

[drhodes]

My C150-HD has the barlow between the primary and secondary mirrors. I spoke with Celstron tech support and they told me that it has to removed in order to collimate the telescope. Has anyone ever tried removing the barlow, temporarily or permanent?