Bresser 152/760 Refractor on CG5-GT mount: HELP

[Omnipaulus]

Hi there,

I had owed Dobs before and although they are great, I'm afraid I got the refractor bug. I just got my new Bresser 152/760 for Christmas which was at a fantastic price (£345.00, New, £30 off from a voucher). I already possessed a CG5-GT which I used on a 120mm refractor, and I thought it would be able to bear the Bresser....until it arrived: IT IS A BEAST OF A TELESCOPE!!! ENORMOUS!!! I mounted it on the CG5 just for a test drive, got it balanced and, although when I look at the plastic bits and bobs of it my heart trembles, it seemed to have taken the weight of it OK, with the heaviest payload I could conjure: 2"Diagonal with a 2" Barlow and a 2" Eyepiece.  

Sincerely: do you think that, within this maximum limit the CG5 will survive? I do not do Astrophotography, only observing or using a webcam. I cannot afford a new mount now, but I do not want to destroy the one I have.

Please could you shed light on this dilemma?

Thanks and clear skies to all.

[John]

I used to use an F/8 6" refractor (Skywatcher) on a CG5 mount with a 16" steel pillar extension and the 2" steel tubed tripod. It was OK for visual as long as I minimised how often I touched the scope and used a dual axis drive system.

[michael.h.f.wilkinson]

The CG5 is similar to my Vixen GP. They are pretty tough, and if the balance is right, the mount will not fall over or collapse. What will happen is that vibrations take longer to damp out, the more so as your scope has a fairly long tube (compared to my C8). Mounts do not break or collapse until you go WAY over the rated payload. Long before they fail catastrophically, they become a catastrophe to use, because the image is all wobbly.

[brantuk]

One of my chums bought this exact combination to our dark site once and I had the same thoughts as your self - it looked like Jodrell Bank on an EQ-2 lol. But the CG5GT is a donkey that can carry three times it's own weight up Everest and back - so long as it's not all one sided.

It balanced up fine in the field with the legs fully extended and seemed to handle the Bresser very well with no "goto" problems slewing - and tracking was spot on. I think, with good balancing, you'll be fine.

(Yes I agree - visual only - that's what we did with it.)

[Omnipaulus]

Dear All,

All of you have been fantastic already with your responses (I liked the comparison of the CG5 to a donkey on mount Everest   )............... 

Thank you very much indeed....

[michael.h.f.wilkinson]

Poor donkey, should have sent a yak instead

[Omnipaulus]

Poor donkey, should have sent a yak instead

KKKKKKKKKKkkkkkkkkkk

[Omnipaulus]

The CG5 is similar to my Vixen GP. They are pretty tough, and if the balance is right, the mount will not fall over or collapse. What will happen is that vibrations take longer to damp out, the more so as your scope has a fairly long tube (compared to my C8). Mounts do not break or collapse until you go WAY over the rated payload. Long before they fail catastrophically, they become a catastrophe to use, because the image is all wobbly.

Would vibration damping pads be of any help?

[michael.h.f.wilkinson]

Would vibration damping pads be of any help?

They will help, but I do not know to what extent. Some people put a heavy weight on the accessory tray of the tripod to help damp out vibrations

[brantuk]

"Would vibration damping pads be of any help?"

On the donkey? Probably lol

But you'd really only use vibration pads on a mount when imaging - otherwise they don't make a noticeable difference. But for observing a good solid dovetail and rings would be important. Can't remember what ours had but I'd recommend the adm shoe/dovetail upgrade and c'n'c rings - it's a big scope after all.

[Omnipaulus]

"Would vibration damping pads be of any help?"

On the donkey? Probably lol

But you'd really only use vibration pads on a mount when imaging - otherwise they don't make a noticeable difference. But for observing a good solid dovetail and rings would be important. Can't remember what ours had but I'd recommend the adm shoe/dovetail upgrade and c'n'c rings - it's a big scope after all.

The rings and dovetail seem quite solid. At least I can say that they are heavy! But I will look at the upgrades you mentioned.

Just to imagine a donkey wearing vibration damping pads....KKKKKKKKkkkkkkkkk".......I know the devil wears Prada, but I did not know donkeys wore Vixen....

[John]

Would vibration damping pads be of any help?

I have a set of the Meade ones and they do help quite a lot. They don't stop vibrations but they ensure that they dampen down a lot quicker so you can get back to observing. I use them often.

[Omnipaulus]

Thanks everyone for your help: let me just ask a couple of things to clarify:

1- The specifications of the CG5 GT says that the payload is up to 10kg: is that only referring to the telescope? If i add an extra counterweight does that add up to the payload (the telescope itself weights 10kg: the extra counterweight is 5kg): how does it work?

2- In GOTO mounts: if i know more or less were to point the telescope, can i point it more or less to the right direction manually  before commanding the telescope to find whatever i need it to find, and so avoiding long slewing, or, say i want the telescope to point from the moon to Jupiter, i need to allow the mount to do it on its own?

Please forgive my ignorance.

Thanks,

[ollypenrice]

The mount is not at risk if it's balanced. It has hardly any more work to do than it does when carrying a small scope. If it out of balance then the drives may struggle. I have one of these big achromats as well. They go very cheaply and are really pretty good. Mine gets almost no use any more since we have a TEC140 available but at one time the big achromat was often in demend. I like it.

Olly

[SnakeyJ]

The scopes very nice and does great widefield visual and very respectable on planets, with a little CA and shorter focal length aside.    Bresser sell these on the Exos2 mount, which is a rebadged Meade LDX75.   This is almost identical to the CG5, with slightly lighter tripod, but the mount's machining and finish are far superior which makes it appreciably more solid - at least the one I have is!

No doubts the CG5 will be adequate for visual, but I've only used the EXOS2 and HEQ5 manually.

Re your question:

2- In GOTO mounts: if i know more or less were to point the telescope, can i point it more or less to the right direction manually  before commanding the telescope to find whatever i need it to find, and so avoiding long slewing, or, say i want the telescope to point from the moon to Jupiter, i need to allow the mount to do it on its own?

Once you have polar aligned and done a 1,2 or 3 star alignment you should not release the DEC and RA clutches - if you do you will have to return the OTA to the home position and repeat the star alignment routine.     Some of the modern and more expensive mounts have dual axis encoders, which do allow you to release the clutches and manually position the OTA, giving you the best of both worlds - I think the Celestron Advanced VX is about the entry level here with a  similar capacity to the CG5 and price of around £ 800, though not certain of the accuracy of the encoders.

[Omnipaulus]

thank you very much one and all for all your help. I think I will now bite the bullet and see what happens. in the meanwhile i did my first solar observation today using a baader solar filter and my 120 acro. Fascinating stuff.

CHeers.

[Grotemobile]

The best thing you can do is

put a ADM sadde on the CG=5

http://www.firstlightoptics.com/celestron-mounts/adm-dual-saddle-upgrade-for-eq5-and-cg5-mounts.html

It does make a lot of difference

Steve