Drilling into OTA...yes or no?

[Catweazel]

Ok folks, here's a good one for you...

I have had my Telrad finder stuck on to the OTA of my Evostar 120 with strong adhesive tape, but last night it fell off due to the freezing temperature (no harm done luckily)

Anyway, I was considering drilling the OTA to get the Telrad base permanently fixed, but then I thought, how do I do it? It can't go at the lens end, as I would have to take the lens out to do it. The alternative is to have it at the focuser end (I have also just changed focusers adding a Crayford, which has no finder bracket, so the Telrad would have to be a substiute for the 9x50).

So to get to the point...if I do it, I assume that it will have to be bolted on, so, will the small bolts needed interfere with my view when observing?

Otherwise, I thought I could use thick cable ties?

Am considering whether to do this with my 200P also (i.e add a Telrad base so that I can share the Telrad between the 2 scopes)

Not sure how to go with this one; any help much appreciated

[sloz1664]

Personally I would go for the cable ties, coupled with strong double sided tape.

Dismantling a refractors could create misalignment before you even tackle the drilling op,

negotiating any baffles, swarf etc... not including trying to assemble small nuts and bolts.

At some time in the future you may not want the Telrad or you may want to sell the Evostar.

Lining up the Telrad is no big deal for tape & ties & it makes it non permanent.

Just my thoughts.

cheers

Steve

[rory]

i also used cable ties when i had the telrad on my refractor. cheap , easy and no worries of it falling off.

[IanL]

How do you mount the OTA? I assuming it is scope rings with piggy-back camera holes on top, which I think is most of the standard Skywatcher rings you get with the Evostars?

You could drill the Telrad base with one hole and screw it to the top of a single ring, though it might be susceptible to slipping out of alignment. Alternatively you could get some metal bar and drill it with two holes to fix it to both camera holes on the rings, plus drill a pair of holes in the base and matching pair in the bar for something a bit more secure.

[tich]

I drilled holes in the mount of my Telrad base & removed the shoe from my 200P & used the existing holes to bolt the Telrad to as I wasn't keen on the sticky pads. It seems plenty solid enough although I'm not sure how you would mount it to your refractor , I would guess using tie wraps & sticky pads would be the way to go.

[Peter Drew]

I'd go with whichever method you're comfortable with. I would drill the OTA as I'm used to doing it. Strangely, from a resale perspective, if you do this sort of thing to an average telescope it's seen as an improvement, but done to a Takakashi or Astrophysics, it's considered "damaged".

[Catweazel]

Thanks for all of the replies so far. It seems like sticky tape & cable ties looks a safer bet. I wonder if I can get long enough cable ties to go around the 200P as well? Hopefully!

Back on the subject of drilling, I am a little concerned that using small screws with bolts will be visible in the EP? I am still thinking of screwing a SW finder shoe to the body of the Evostar, just above where the focuser ends. Can anyone who has done this sort of thing confirm that it won't interfere with the view down the scope? I'm probably being over cautious but...

Thanks. CW

[RikM]

I use Rigel finders rather than Telrads but the concept is similar. I have just used the double sided sticky pads that come with the bases. They have proved quite sufficient for me. I have two finders and 6 bases spread around my telescopes and I swap the finders about quite a bit depending on what I am using. No sign of slippage or unsticking of the pads whatsoever, after up to three years for the oldest one.

[8kids]

I drilled my 300pds with no problems, my rdf is now rock solid.

[Gina]

You can get quite long cable ties but if the longest doesnt reach you can use two (or more) joined together. Also worth trying garden centres as they do very long tree ties - they're just the same as cable ties but usually green.

[rory]

yep, simply join cable ties together once its all tied up cut off the excess to make it neat,jobs a goodun.

[Catweazel]

I use Rigel finders rather than Telrads but the concept is similar. I have just used the double sided sticky pads that come with the bases. They have proved quite sufficient for me. I have two finders and 6 bases spread around my telescopes and I swap the finders about quite a bit depending on what I am using. No sign of slippage or unsticking of the pads whatsoever, after up to three years for the oldest one.

My Telrad was stuck on OK for a year with the pads, but I recently put it on a 4" riser, in an attempt to reduce back/neck ache, and I think that this, together with the temperature last night was just too much for those sticky pads

I will definitely try the pad/cable tie combination first, and only resort to the drill if really necessary.

I think that I will drill the lower part of the OTA to fit that finder shoe though, as I recently got a RACI finder, and want to use it on all my scopes; Looking at the design of the Crayford, if I keep the screws within the area where the focuser tube runs, it won't interfere with viewing.

Thanks to all CW

[starguest]

I think that I will drill the lower part of the OTA to fit that finder shoe though, as I recently got a RACI finder, and want to use it on all my scopes; Looking at the design of the Crayford, if I keep the screws within the area where the focuser tube runs, it won't interfere with viewing.

Yes, I suppose knowing where the actual cone of useable light is going within tube and possibly it isn't with the 3mm or so that a nut would intrude into the inside. I recently did a 200P to move the finder to a more comfortable position and it obviously has easier access and for the swarf aspect, making a little 'bubble dome' with sellotape to go around where the holes will be and extra sticky tape pointing toward the holes' points helps capture the swarf.

[Moonshane]

not sure how thick the tube wall is but could you drill and tap holes? then there would be little or no intrusion. I doubt that a nut would intrude though.

I have never had problems with sticking Telrads after using number plate sticky pads. I figured if number plates remain on in all weathers, a telrad should. I get mine from a local factor for about 20p for the job.

[nightfisher]

I have drilled plenty of refractor OTA`s its a bit scary first time but just use common sense, and make sure no swarf gets any where near the optics, whenever i get a frac i usually drill and mount a finder shoe a bit further up from the focuser, so i can use my 9x50 r/a finder