unable to balance in declination

[Ryan Parle]

Hi all,

Recently i replaced the crappy standard crayford focuser on my Moonlite 80mm Apo with a moonlite 2.5" rotator focuser, the moonlite is a really nice bit of kit and with the rotator has now made it possible for me to fully automate my imaging rig. But it has one down side, its a pretty heavy lump of kit and when combined with the rest of my imaging chain (EOS 50d, OAG & atik 16ic-s guide camera) i cannot mount the telescope in a position where it will balance on the declination axis. As the whole focuser assembly rotates i am limited to how far back i can mount the dovetail bar without causing any fouling as the focuser rotates.

So it looks like i will have to find a way of adding some weight to the objective end of the telescope to help counter balance the weight of the focuser. Can anyone suggest a good way to do this?

I have thought of a couple ideas:

1: Adding weight directly to the OTA, probably around the Dew shield. i have some lead flashing that would probably do the job, but it is a little bit "Heath Robinson" for my liking.

Pros:

Cheap, I have some suitable materials already.

Probably a better method as it keeps the weight distribution aligned with the axis.

Cons:

would probably look a bit "Heath Robinson"

Could be tricky to hold weight in place without risk of scratching the OTA

2: Fit a longer dovetail bar extending further towards the objective end of the OTA and use an off the shelf counter balance such as the ADM V series Counter Weight

Pros:

Clean tidy installation, pleasing on the eye

Unlikely to cause any damage to OTA or other parts

Cons:

Weight distribution is not as well aligned along the axis of the telescope.

Price, will cost a lot more than using stuff i have around the house, but when i've gone to the expense of the fancy focuser what difference does another £100 or so make.

[wxsatuser]

You could try the longer dovetail method and add weight to it.

I made an extension to the scope dovetail out of another dovetail and put a lump of lead on it.

The lead was a preformed balast weight out of one of my Gscale trains but you can use what you like

as long as its heavy enough. The weight ended up being just under the dewshield of my ED80.

[Stu]

I think the longer dovetail method is probably best, but you can probably avoid the cost of the ADM counterweight if you want to. You just need a dovetail clamp and can bolt some weight to that. I bought some old kitchen scales weights and drilled a hole through the middle so I could do just that. It helps me balance my Ercole mount.

Stu

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[Earl]

the adm counter weights work well

http://www.firstlightoptics.com/adm-countweight-kits.html

[Ryan Parle]

Looks like the dovetail mounted setup will be the one to go for then. FLO don't list the counterweight kit for the vixen dovetail, i will get in touch with them to see if they can get it, failing that Rother Valley Optics do list the vixen version so i can get it from them.

[Earl]

http://www.firstlightoptics.com/adm-countweight-kits/adm-mds-counterweight-kit.html

This does fit a vixen also

[Ryan Parle]

http://www.firstlightoptics.com/adm-countweight-kits/adm-mds-counterweight-kit.html

This does fit a vixen also

Ok, what is the difference between the ADM MDS series and the V series kits?

would I be right in assuming that they both have the same major width and taper angle, with the MDS series having a shallower depth of taper and a shoulder but the vixen has a deeper section and no shoulder? Not sure if the ASCii sketch below will work:

Vixen:

  _______

 /              \

/________\

MDS:

___________

|_                 _|

  /________\

[Ryan Parle]

Ok it nearly worked, for some reason the forum put in an extra "Return" in the middle of the Vixen image.

[Stu]

Gosh, haven't seen a good old ASCII sketch for a while :-)

That's basically the difference Ryan. They are not interchangeable though, the MDS clamps don't fit the Vixen. I'm not totally sure of the merits of one over the other to be honest, possibly just lighter weight

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[Earl]

mds does fit vixen, i used to use two with guide rings to attach to a wo vixen bar

[Stu]

Thanks for the correction Earl, I thought I had tried in the past but obviously my memory is as bad as ever!! :-)

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[Stu]

My apologies Ryan, I tried to remove the space but it doesn't seem to be playing ball! Will try again

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[Stu]

Gosh, that was a mission. Sorted now :-)

[Earl]

the only diference is the depth, mds is about 50% width is perfectly fine.

[RyanParle]

Thanks Earl. I'll get one ordered this week.

[lensman57]

If you are handy with DIY you can place riser blocks on top of a long dovetail and use the overhang at the rear of the dovetail to push the scope up on the mounts yoke.  

A.G

[RyanParle]

If you are handy with DIY you can place riser blocks on top of a long dovetail and use the overhang at the rear of the dovetail to push the scope up on the mounts yoke.  

A.G

I am fairly handy with diy projects and making some riser blocks is on my list of things to do, but due to the design of the rotator assembly riser blocks would not really be an option for helping to balance the OTA, they would need to be about 150-200mm thick to gain enough clearance for the rotator to work.

I need to add a set of risers about 25mm thick to prevent the rotator motor cable from snagging on the mount.

[Scott]

I was dead against using a Ankle/Wrist weight when I got my 60mm frac. tried long dovetails, weight on the dovetail but could not get proper balance and still be able to rotate the focuser through its 360 degrees and in the end bought  a set of 2x2kg ankle weights. 1 2kg weight over the top of the dew strap and everything balances perfectly. Sometimes we gotta just let go of the ocd .

[lardy]

I had this made to allow balancing while changing EP's

[RyanParle]

Ok so i have just received the MDS counterweight kit and can now confirm that it is NOT compatible with the vixen dovetail. I will have to contact FLO now and try to arrange to return it.

[Stu]

That's a pain Ryan, I suspected so but didn't check, my apologies. FLO will sort you out

For anyone in doubt, here's the photo!

Stu

[Grotemobile]

2014-04-17 11.52.53.jpg

I had this made to allow balancing while changing EP's

That's a neat bit of kit.Good idear.

Steve

[RyanParle]

Turns out that i didn't need to return it to FLO, i have a firend who uses MDS kit on his 14" meade RCX and was in need of another MDS clamp to fit on his coranado solarmax 60, he gave me £22 to cover the cost of the Vixen type clamp.