CPC800 finder scope upgrade.

[MrFinster]

After finally getting a good clear sky and a location relatively midge free, I had 5 alignment failures trying to set up on sky align.

Turns out that the finder scope cradle and base seem to be incapable of being installed in exactly the same orientation every time its fitted so i couldnt even get the target stars to appear in the finder and the EP.

It nearly ended up in the reservoir i was observing next to untill i noticed the mount was off center.

I have made my mind up on the telrad with a riser but my questions are these.

Firstly, would I be better having a conventional finder scope as well as the telrad?

secondly, what suggestions do people have for a good finder scope and how I could get the thing mounted as I want rid of the factory supplied rubbish mount.

[AstroJOE]

Hi MrFinster, I can't answer your Telrad question but what I can say is that I have the CPC1100 which as far as I'm aware has the same finder scope and brackets as the 800 but I've never had a problem getting it aligned. Quite the contrary actually it's always been absolutely spot on every time I've used it....whether that's at home on my observatory or out in the field. To be honest I've found the finder scope to be pretty good for a standard piece of kit. A few slight teaks to get the finder and eyepiece in sync (usually on a static terrestrial object) and I'm away. Have you checked to make sure the GPS was working as it should?

[MrFinster]

Hi MrFinster, I can't answer your Telrad question but what I can say is that I have the CPC1100 which as far as I'm aware has the same finder scope and brackets as the 800 but I've never had a problem getting it aligned. Quite the contrary actually it's always been absolutely spot on every time I've used it....whether that's at home on my observatory or out in the field. To be honest I've found the finder scope to be pretty good for a standard piece of kit. A few slight teaks to get the finder and eyepiece in sync (usually on a static terrestrial object) and I'm away. Have you checked to make sure the GPS was working as it should?

Yep, the GPS is fine, the first thing I checked. it displayed my lat and long which concurred with the GPS on my sat nav, the local time was indicating correctly.

The problem was when i came to a nice big fat star to set up the finder scope, i assumed quite reasonably that it should at least point the same way when I next fit it back on, providing the positioner screws hadnt been touched.

I couldnt get the star to show in the eyepiece if it was in the finder. The cradle which holds the finder doesnt seem to fit on the foot plate the same way twice, it rides up when you gently tighten the mount screws to finger tightness, i had to physically hold it in the indents whilst I tightened the screws.

[nicks90]

that sounds faulty, like the machining is out somewhat on the shoe.

[brantuk]

Hmmm... the finder cradle only goes into the footplate one way round and the screw indents should line up with the screw ends so when you tighten them they automatically line up. Do you have a picture of the cradle from the side with the screw indents? Is the footplate screwed firmlyand squarely onto the top of the ota? Mine has never given this problem and I've had two CPC's.....

I did upgrade to a 9x50 RACI though (the Orion one) for which I had to source an Skywatcher Sct shoe (or footplate). Telescope House do them for around £15. But it wasn't because of any problem - I just wanted a right angled finder cos I find it easier to use.

[Northern Soul man]

Hi Ya Mr Finster, just wondering if you have the finder in the cradle the right way - sorry if you have mate but just check that with the finder scope pointing forwards, the retaining pins should be on the right hand side and the front ring of the holder is where the rubber o ring sits in the bracket holder closest to the front of the finder scope, only, like the other posts - never had any problems with it, I remove and re fit after setting up/taking down and never had any problems with it, set up, switch on, check GPS and date/time, point her at polaris, check finder alignment, look through the scope and I'm away with the fairy's!!!! Paul.

[MrFinster]

Hi Ya Mr Finster, just wondering if you have the finder in the cradle the right way - sorry if you have mate but just check that with the finder scope pointing forwards, the retaining pins should be on the right hand side and the front ring of the holder is where the rubber o ring sits in the bracket holder closest to the front of the finder scope, only, like the other posts - never had any problems with it, I remove and re fit after setting up/taking down and never had any problems with it, set up, switch on, check GPS and date/time, point her at polaris, check finder alignment, look through the scope and I'm away with the fairy's!!!! Paul.

It can only go on one way as you say, The rubber ring that holds the finder in the front ring is recessed properly, when it comes to fine adjusting to center a star in the crosshairs whilst the star is centered in the EP, i had to virtually unscrew the two adjusters untill they almost stopped touching the finder scope which defeated the point of having adjusters, that's when I noticed that the cradle was not sitting straight on the base plate.

The cradle slots on fine, the screws locate into the indents fine, it just moves out of position when the cradle screws are tightened. I think its just a very bad casting as there doesnt appear to be any evidence that the indents are precisely machined into the metal.

I will have a look at it again this week and see if its curable by possibly drilling two small depressions in the base plate indents to keep the screw tips in the desired place.

[Northern Soul man]

Mr Finster, Thanks for the reply, it seems as there is something really wrong with the casting (seems twisted , you having to adjust so much) - it should line up (or in line with) the base, you ask about another finder - I had an Orion RACI finder, but taking out the stock finder and replacing it with the Orion didn't work - the casting which holds the finder was quite long, the Orion (being shorter) didn't fit at all. To be honest I would persevere with the original finder - as with Goto, once aligned, you could remove this - where I observe from is quite light polluted and once aligned, there's no need to use it, its hard to try and look through when up at the zenith and have found the accuracy of the Goto really precise, but not sure of your conditions where you observe from - keep us informed and I hope you can get it sorted. Paul