Drilling holes in OTA for new focuser

[astro_john_palmer]

Hi All,

I bought a new focuser for my old Celestron C8N Newt. It was suggested the focuser should fit the existing bolt holes, but unfortunately not.

So, before I start drilling holes, anyone have any tips/tricks to avoid me making a hash of it?

Thanks!

[Robindonne]

If i were you i would look for an adapterplate if these are available for your combo.   If not then i assume its the only option.  I‘ve seen a lot newtonians where new holes were made for the focusser.  Dont know if its always the best looking option

[Timebandit]

 

Hello. See if you cannot get some type of adaptor plate first.

If an adaptor plate is not available . place some masking tape around the tube area first. This will make it easier to mark out correctly. And help prevent the drill bit slipping. Make sure when you mark out the tube , you check and double check your hole positions. Otherwise mistakes are not easily forgiven or covered up. Check and double check before any new holes are drilled.

 

 

 

[Davey-T]

Not easy drilling holes in the right place on a round tube, maybe do one hole first, if it's not quite right adjust with a small rat tail file then bolt the new focuser on and drill the opposite one, bolt that on then drill through the other two.

Dave

[CedricTheBrave]

I just did my 200PDS with a new steeltrack

i was also disappointed that the guide said i could use existing holes as a guide but that wasn't going to work

i covered the area with masking tape, drew on a centre line for both axis making sure they were square then taped the base plate of the focuser onto the OTA

drilled one and bolted it on making sure it was still square then did the diagonal opposite next

it was a nervy experience but all looks ok and shows that the label on the ota is not square!

[NGC 1502]

Hi John from another Essex member.  You have some good advice already given.  I’d like to add that before drilling holes it’s best if the optical parts are removed.  
 

If you’d rather not do that then you could work with the tube at a downward slope so that any debris doesn’t fall onto the primary.   The secondary could be very carefully covered with something soft, and fitted so that the the optical surface is not in contact with the covering.

The holes will leave a burr on the inner side, removable with a hand held larger drill or a countersink bit.  Make sure any remaining debris is removed.

You’ll be absolutely fine if you work carefully 👍

Ed.

 

[astro_john_palmer]

6 hours ago, CedricTheBrave said:

I just did my 200PDS with a new steeltrack

i was also disappointed that the guide said i could use existing holes as a guide but that wasn't going to work

i covered the area with masking tape, drew on a centre line for both axis making sure they were square then taped the base plate of the focuser onto the OTA

drilled one and bolted it on making sure it was still square then did the diagonal opposite next

it was a nervy experience but all looks ok and shows that the label on the ota is not square!

Thanks for the tips 👍 - I had considered the above focuser. In fact the company's video for the product fitting was on a C8N identical to mine. This Focuser said the OTA needed drilling anyway so I avoided it. Ended up with the same issue, except the one I chose doesn't have the alignment bolt holes and base plate the same way this one does.

[astro_john_palmer]

6 hours ago, NGC 1502 said:

Hi John from another Essex member.  You have some good advice already given.  I’d like to add that before drilling holes it’s best if the optical parts are removed.  
 

If you’d rather not do that then you could work with the tube at a downward slope so that any debris doesn’t fall onto the primary.   The secondary could be very carefully covered with something soft, and fitted so that the the optical surface is not in contact with the covering.

The holes will leave a burr on the inner side, removable with a hand held larger drill or a countersink bit.  Make sure any remaining debris is removed.

You’ll be absolutely fine if you work carefully 👍

Ed.

 

Hey Ed,

Thanks for the extra tips on fitting. I spoke to FLO and have asked them to see if any of their other focusers fit the dimensions of my existing holes. Hopefully they have something. If not I'll start carefully fixing the one I have now!