Dob to Mount/GOTO/Track??

Hi Guys!

I have a 10" Starhopper Dobsonian and I like the optics and tube but the stand is breaking my heart!

www.celestron.com/c3/product.php?ProdID=22

I cant afford to update the entire scope at this moment in time, I was wondering if anyone has upgraded their Dob to a goto or at least a tracking scope?

There are a few projects online but was just wondering if anyone can hand on heart recommend one of them?

I dont mind a bit of diy electronics as long as there is a map of sorts!

Or even if I can upgrade/mod the existing stand so that it will stay where I leave it! tightening plastic against plastic between wood isnt working!!


I look forward to hear any and all suggestions!!

Graham.


btw Great Site!! I just stumbled upon it looking through Dave and Carls site!!

Welcome Graham

Is the main issue the Alt bolts not holding the optical tube assembly firmly enough?

I have a Skywatcher 8" Dob and one of the two Alt bolts has a clutch mechanism and this works well (a simple system of funny washers).

Could it be that you do not have "Variable-tension clutch system" as Celestron call theirs? If not maybe you could source these.

With regards to upgrading to a goto - I bought an equatorial mount (Skywatcher EQ6 Pro) and I can use the Dob mount for casual sessions or go through the extra hassle and have a tracking / goto system.

One can make a Dobsonian a "push too" system. That is install digital setting circles so that the mount knows where its pointing and it tells the operator which direction to push so that a target can be located. I don't have any specifics on this but believe that it is not uncommon. But I don't think that that would address your fundamental problem - if I read your posting correctly.

Mark

Hi Mark, Thanks for your reply.

Yes it has that variable clutch system but lets say you want to keep it aimed at the moon you cant simply tighten, you have to move it away and tighten it to let it fall back in place...if that makes sense..

The problem with getting a ready to go goto mount is the price at the moment.

The "push to" system is interesting but would still have to sort out the clutch/holding system.

G

Graham

I'm not sure what you mean by "to keep it aimed at the moon you cant simply tighten, you have to move it away and tighten it to let it fall back in place".

The problem that you're encountering - was it always there or is it something that has degraded over time?

If the former then it might be a procedural problem - if the latter then maybe something does need some rework.

Just in case its a procedural probem - this is what I do and it works for me.

The bolt that does not have the clutch mechanism goes into the dobsonian mount opposite the side of where you stand to look through the eyepiece. It is tightened to just more-or-less make contact - maybe a bit more. The bolt with the clutch mechansim goes into the side closest to you when you're viewing. This bolt is the bolt that creates the necessary tension. It is tightened enough not to lock the scope in position but to give it sufficient tension not to fall / rise with varying imbalances due to eyepiece etc.
Once set - one should be able to gently push the scope around and it should rest without drooping etc where it was last pointed. The tension bolt should not need revisiting very often unless you change to a lighter / heavier eyepeice.

Is it possible that what you do is different from the above and your problem lies there?

Mark

Hi Mark,

I do as you describe to tighten onto an object but it still drops slightly into place, only slightly but its stall a fall, I didnt think that weight of an eyepieces would affect it that much..my favourite general setup is with a 2" barlow and a 2" lens so maybe that might have something to do with it..

but even getting the up-down correct is one thing, the left-right is also difficult as to get to the tightening knob is under the scope.

and naturally as soon as everyhing is steady the object just smiles back and moves away!!

I was thinking something along the lines of attaching some sort of a worm gear to the base stand for left and right, and If I can make somesort of a wegde, without it falling over, and turn the motor onto a certain speed I could be able to start tracking and get some use out of my neximage!!

Hi Graham,

Welcome to our humble home! I think if you were to DIY a GoTo or even a tracked electronic mechanism for your Dob, it will be expensive and tedious. You will have to butcher and remake your mount to start, there is no easy fix.

The Push To system is pretty good in order to manually locate objects, but takes some time to get set up with any degree of accuracy (it does need to be accurate). However, once that has been done, you then have an excellent poor man's GoTo at your finger tips.

If DIY is your fortay, you could make an equatorial wedge+mount and use the tube assembly on that. Any 10" OTA is worth keeping if you can. As the mount you have is giving you some irritations, you don't want to loose heart in dragging your scope out on nights that work in your favour, for the sake of a couple of bolts.

I don't know the mount that you and Mark are talking about, BUT would it be worth thing about removing the existing mechanism clutch and all and modifying it to use locknuts-on-bolts to get the tension? A neat little addition would be to spot-weld a mini spanner to the locknut on the viewing side that you just need to grab'n'lock (grab'n'unlock') when you want to move and lock onto a target.

Seanie.