Options for balancing an ED80 on HEQ5

[Lonestar70]

Hi Everyone,

I hope this is posted in the right place... apologies if not.

I currently use my SW ED80 pro on my HEQ5 mount and have found that balancing the thing in DEC impossible (no problem in RA), especially when it has the focal reducer/field flattener and DSLR attached, without resorting to adding a home made weight to the front end of the dovetail bar.

The use of a longer dovetail bar is not really practical, since it would interfere with the focuser (now motorised) and ,possibly, the camera... and the OTA is already as far forward in the tube rings as it can be.

As I am just starting to look into guiding using an SPC900 LX modified camera in conjunction with the 9 x 50 finderscope (which will add more back end weight) and, whilst I appreciate a little camera heavy is desireable,... the current setup leaves a lot to be desired.

I would appreciate any suggestions any of you may have as to how else this balance might be achieved?

And how much 'Camera heavy' will PHD tolerate?

Best regards,

Sandy.

[swag72]

I did resort to a homemade weight as well as a dovetail that was as long as I could get. I've since got a longer Losmandy dovetail, but haven't taken it out of the packet yet! I know that there are others who use a weights solution. It really was the only way I could achieve balance and for me it works well. I know that people have said about the extra weight on the mount, but my setup is so light that it doesn't seem to affect it in any way.

You do want the scope to be camera heavy. Mine is balanced so that when I undo the clutch the scope gently falls backwards. I'd say that it's not very heavily weighted. Certainly doesn't drop like a stone.

[Lonestar70]

Good evening Sara,

Thank you for your valued input ... it would seem that we both have come to the same conclusion.

I am not too worried about the additional weight since, as you say, the total package is well within the limits for the mount... it just looks somewhat odd/untidy and I just wondered if perhaps a better solution could be achieved... but hey' if it gets the job done then thats what counts I suppose.

I have seen some of the images you have posted on this forum, and if they came from the setup pictured above then they are a standard for me to aim for.

Now... if only the grey skies, rain, snow, howling winds and yet more cloud would remove themselves from the scene, perhaps some of us here in the UK could get out and do something.

Thanks again Sara,

Clear skies to you.

[Psychobilly]

I use one of a pair of adjustable leg weights (the ones with pockets that hold bags of "shot") wrapped around the OTA.

Peter...

[swag72]

Cheers Sandy, thanks for your kind words. Yes all of my images on the fourm that I've posted over the last 10 months have been with the setup in the picture, including my silver painted concrete flower pot weight!! It works well and gives me great balance.

[martin_h]

I never had any problems balancing an ED80 and filterwheel/CCD, I use a longish dovetail bar, if the focuser gets in the way, rotate the scope in the clamps. In one setup I had the focuser "upside down" - ie on top....doesnt matter where it is...There is no UP in space !

[Lonestar70]

Hi Martin,

Thanks for your thoughts...

Yes I did consider using a longer dovtail bar, as you say it doesn't matter which way up the scope is... my main concern with this method was that is got in the way of the camera (DSLR) possibly preventing it being turned to frame the shot and the fact that the balance point would mean having BOTH tube rings forward of the attachment point to the mount... thus creating a single bending point at the mount attachment closest to the first tube ring... possibly leading to flexture since the back end of the dovetail bar would not be attached to anything behind the attachment point.

By clamping between the tube rings this is avoided... as the 2 tube ring attachments work in opposition too each other... if you see what I mean.

Perhaps I am being to critical/analytical in thinking this...Too much engineering training in my youth methinks...

Maybe I will give it a try and see what happens.

I take your point about there not being an UP in space... does it also follow that there is no DOWN... Not sure NASA would agree with us though... they would never get any of their rockets back :grin:

Cheers and clear skies

[Gina]

I need to sort this one out on my system (though an NEQ6 mount) if I want to use the Atik setup (314L+ and EFW2) with an ED 2x Barlow for close-ups of very bright objects such as the core of M42. The camera seems a mile from the scope to get focus - not just the Barlow but an extra 100mm extension tube and the focuser quite well out. With that setup it is very camera heavy. There are various options that I haven't explored yet. It does seem to work as it is. There was an hour of clear sky in the direction of Orion the other night and I had just got all set up - focused and PHD all set up and guiding fine, exposure sorted out not to overexpose the trapezium stars, and about to start my imaging run, when the cloud came back and that was that! Shortly after it started raining (again)

[Lonestar70]

Hi Gina, it’s so nice to finally make your acquaintance.

I have been following your many exploits/projects, trials and tribulations, successes and, sadly, the occasional misfortune for some time prior to joining the lounge.

They have certainly given me the incentive to get my act together and sort out a decent set-up for myself… albeit; I am unable to install an observatory.

I already have a large (engineering) workshop and there is just not the room (or damagement approval) to add yet another large home for my hobbies.

There was an hour of clear sky in the direction of Orion the other night

Orion! ... Oh yes…! …I vaguely remember him… he’s the one with the flashy sword and a bow and arrow being chased around by a couple of dogs and a unicorn whilst annoying an old bull isn’t he?

Last seen up here in 1812 December 2012 due to the rubbish weather.

It would be nice just to catch a glimpse of a star now and then, let alone a whole constellation…and for a whole hour … I jest of course.

All we’ve had here since December is Clouds, rain, snow, howling gales, more rain… did I mention clouds?

Ho hum!!

Returning to the balancing issue…

Yes, finding a system that suits changing the various capture equipment, more often than not having vastly different weights, is not so easy to achieve is it? … Especially when the basic ED 80 is already focuser heavy when mounted at the back of the dovetail.

My current arrangement (similar to that used by Sara), being a fixed weight, is fine for my current DSLR camera set-up… but is not really flexible enough to accommodate the large changes in weight distribution if I choose (seriously being considered) to go down a similar route to you.

I have already stated, my concerns with the use of longer dovetail bar with regard to bending point… and, whilst not entirely ruling it out, my current thought is to fabricate some sort of sliding weight counter balance arrangement mounted on the back of the objective end of the dovetail bar. This, hopefully, will permit, reasonably simple, re-balancing when a camera change is made, or other attachment is added, without the need to unclamp the main dovetail bar at the mount… always a risky operation in the dark… and cold.

Decisions, decisions… !!!!

Methinks it is time to get down to the workshop, crank up the lathe and milling machine and coble something together… Now where did I put that lump of unobtainium??

What other ideas do you have Gina?

Best regards.

[Gina]

Hi Sandy - thank you for your kind words Glad if I've given encouragement

I think your idea of a sliding weight is a good one I tried adjusting the balance on my system the other night, by loosening the main dovetail clamps and found I could hardly lift the mass of cameras. scopes and assorted gubbins, so I tightened them up again immediately. If I dropped that lot on my foot I'd be crippled for life! So I will not be moving the whole lot again - that's staying put. If I need to alter it I'll take some weight off first. So a moveable weight seems the way to go.

I think the usual dovetails will be quite strong enough. The main weight (at least in my case) is very close to the mount and the bending moment will only be due to the sliding weight. I was thinking that to reduce the maximum bending moment it might be possible to use a longer dovetail and uses either end but, on second thoughts, I think it might interfere with cameras etc. Have to see. It's heavy rain and blowing half a gale ATM so I'm not going out to the obsy to check until the weather subsides a bit.

P.S. Wish I had a lathe and milling machine

[Lonestar70]

Hi Gina,

Thank you for the + vote on the sliding weight idea.

I tried adjusting the balance on my system the other night, by loosening the main dovetail clamps and found I could hardly lift the mass of cameras. scopes and assorted gubbins, so I tightened them up again immediately. If I dropped that lot on my foot I'd be crippled for life

That would be my main fear also... especially in the dark when you cannot see the clamp positioning clearly.

It's not the best clamp arrangement at the best of times.. and anyway, you have had enough heart stopping mishaps... you certainly don't need any more.

I will see what I can come up with and will post the results. Probably best if I do that in the DIY section.

In the words of Cptn. Oates... " I may be some time"

If it works out ok and you think it would suit your set-up then I am sure I could be persuaded to make a second set.

Us oldies have got to stick together you know!! :grin:

Keep happy and healthy.

[Lonestar70]

Hi All,

Having done some more work on this subject and having rejected the long dovetail idea, since I think it could introduce unwanted flexture from the single point mounting... the following is the result of my playing around with a sliding weight balancer attachment.

I first needed to establish the approx weights required for different set-ups

Using the standard SW 210mm heavy-duty dovetail bar, and the scope pushed as far forward in the scope rings as possible, the scope is mounted on the HEQ5 at the back of the dovetail... Right under the focuser.

With my Nikon D90 DLSR (quite a heavy lump), SW FR/FF and stepper motor focuser drive attached and with the focuser at normal focus position it was established that the counterweight necessary to balance the assembly in DEC was as follows: -

900gm (approx 2lb) at the front of the dovetail bar.

450gm (approx 1lb) at the front of the dew shield.

To simulate a set-up similar to Gina’s with SW FR/FF + powered filter wheel + Atik CCD camera and the necessary extensions I fitted an additional 80mm long x 2” dia extension and racked the focuser all the way out.

In this configuration the required balance weights were: -

1587gm (approx 3½ lb) at the front of the dovetail bar.

680gm (approx 1.5lb) at the front of the dew shield.

From this it was clear that a sliding weight of around 800gm (approx 1.75lb) would satisfy both requirements.

The standard heavy duty SW dovetail bar supplied with the ED80 pro had 2 convenient tapped holes (albeit one was ¼” UNC and the other was M6) available towards the front end, so these were used as the mounting points for the balancer assembly.

The main T shaped mounting block was made from aluminium and was tapped 5/16” BSF on one vertical face to accommodate the slide bar.

The slide bar is made from 5/16” dia stainless steel and is 270mm (10.625” long) including the threaded section which screws into the T mount block… thus it extends outward to almost the end of the dew shield.

The outer end of the slide bar is drilled and tapped M5 to accommodate a safety stop.

Originally I made a single sliding weight of some 880gm from a convenient piece of 1 3/4” dia brass bar that I had in my stock drawer (I did not see the point of cutting off an odd 3/8” or so as to make it exactly 800gm)

This was drilled and tapped in 2 places M6 for the locking screws.

The locking screws for the weight, and the stop screw for the end of the slide bar were made from stock 9/16” brass bar and knurled for easy tightening.

The first photo shows all the original component parts.

When first attached to the scope I found that the single weight was a little tricky to position easily, so I cut it in half in the lathe leaving me with 2 weights of 430gm (0.92lb) each. These proved far easier to set.

These last 2 photos show the final assembly with the 2 weights fitted.

In reality, I only need to use 1 weight for my DSLR set-up, when taking the weight of the slide bar, end stop and mounting block into consideration, since

the original weights established would have been inclusive of this weight.

I will keep the second one for later, when I go for a full CCD set-up.

I can now easily balance the scope in DEC; whatever I choose to fit at the focuser end and I am very pleased with the outcome.

I accept that this method does add a little extra weight, however, it is well within the capabilies of the HEQ5 and it overcomes the possibility of flexture when using an overhung long dovetail bar.

I hope this gives some of you an idea of how to go about such a balancing act.

Best Regards and clear skies to all.

Sandy

[Lonestar70]

On reflection, I think I should have posted my last entry in the DIY section but wanted to keep it along with the previous posts on this subject.

If the modorators feel the entire subject should be moved to the DIY section then please do so.

My appologies if it is in the wrong place.

Best Regards.

Sandy.