telrad mounting

[m37]

Hi

Just got my Telrad delivered from FLO.

First of all, IT'S MASSIVE!!! I was expecting something the size of a red dot finder. Ace.

Secondly, has anyone got any tips for how far along the OTA to mount it? I was thinking as far back as possible. Would this change how accurate the Telrad representation in Stellarium is?

Planning to clean tube with isopropyl alcohol solution and a lens tissue first so the sticky stuff sticks. Might sling on some cable ties just for good measure. Got loads anyway.

cheers for any hints or tips

[Ally8446]

Depends what scope you have, just be aware of balance of your O.T.A.

It makes no difference with ref to stellarium as the image is projected at infinity.

The sticky tabs are more than enough. Once it's on you will literally struggle to pull the damn thing off.

Hope this helps.

Clear skies

Ally

[Oddsocks]

Hello M37,

The Telrad will always project the same size reticule against the sky irrespective of distance from the observers eye.

(You can prove this indoors if in doubt, just switch it on, line it up with a round object such as a door handle a couple of metres away and look at the inner circle projected over the door handle, now move the Telrad towards or away from your eye, the inner circle and the door handle will always be the same size)

The Stellarium representation will always be the same whatever the distance you choose.

However, to be able to see both the inner and outer circle of the reticle in the glass panel the distance should not be more than about 300mm (12").

Attach the Telrad to your OTA with electrical insulation tape for the first couple of times you use it, it takes a little while to decide where the best position will be and once you use the supplied adhesive foam-pads you won't be able to easily peel them off again to move it elsewhere.

If you do get it wrong though you can obtain double-sided foam pads from several DIY or craft stores.

William.

[m37]

Thanks, that's helpful. Getting dark now so here we go!

[Carbon Brush]

If you do need to remove the sticky pads, it can be done without paintwork damage.

In a few hours to days, you can often gently but firmly pull and the pad will slowly release.

But leave them for a long time and they really harden. So assistance is needed.

You can soften the cured adhesive using isopropanol, or the 'citrus' type cleaners for degreasing.

In either case, a gentle push into the pad using a stick will help the solvent get right in, rather than just working on the edges, thus speeding removal. Think of using a cocktail stick, cotton bud, etc. That way any unintended paint contact should not do harm.

Softening cured adhesive is always a lengthy procedure. Waiting for the solvent to permeate the pad. It can range from 'cup of tea' to 'come back in 2 hours' and maybe a second application.

Hope this isn't needed!

[m37]

Thanks again, everyone. Went out last night and butted it up against where the focuser meets the OTA. Followed Oddsocks' advice and attached it with electrical tape till it was in the best place then stuck some cable ties round it. Going to leave it like this for a few nights till I've tried it out a bit more then I'll mount it with the sticky pads.

Only problem I had was I left the dew shield open and it got very soggy!

Cheers, and how great are these clear skies!!!???

[madsarmy]

Once it's on you will literally struggle to pull the damn thing off.

Tell me about it. You could stick a concrete block to your forehead there that strong.

I had to remove mine the other week to put on my new scope. I thought I was going to snap the base. I couldn’t use a solvent, as I was concerned it would damage the plastic scope tube (Celestron 130eq). The mount finally gave but the sticky pads are welded to the scope tube. Going to try a test area using some Tamiya thinners. As this is for plastic modelling kits no damage should be done.

[Big Si]

I have had the same problem with removing motorcycle emblem badges when refurbishing the petrol tank or bodywork.

Dental floss is the best way to handle these pads. Get a long length, wrap the ends around a couple of pencils / dowel (not fingers) and then slide the floss in the gap between the telrad and the telescope. Using a gentle sawing motion, gradually pull the floss all the way along, cutting the pads. If it starts to stick, then use an occasional drop of washing up liquid as a lubricant.

Then you can clean the remains of the pads off the base of the telrad and the telescope with your solvent of choice.

Si