A balanced question!

[Andrew INT]

My lovely wife is buying me an ADM dual mounting bar from FLO so that I can finally try my hand at auto-guiding.

http://www.firstlightoptics.com/adm-guidescope-rings-and-systems/adm-vixen-type-dual-mounting-bar.html

My question is this: I will be using a 200mm skywatcher explorer together with a startravel 102T as a guide. Does anyone else use this set up – I’m not sure if I will need an extra counter-weight. Also, what are the benefits of having the 14” bar over the 11”?

Many thanks for any advice,

Cheers, Andrew

[earth titan]

Hi Andrew.

I use a similar set up but on an NEQ6. I have to say, and I'm sure you already know, that the amount of weight you're putting on the HEQ5 will make guiding a little difficult so balance will be vital.

There is a very good guide on balancing scopes using that set up here:

http://www.wilmslowastro.com/tips/g11gemini.htm#balancing

This is what I use and it is easy to follow.

[dmahon]

If you're going to the expense of the dual mount bar, make sure you have

1) decent dovetails

2) decent saddle

I'd go Losmandy rather than vixen.

Unfortunately, it all weighs quite a lot.

[Andrew INT]

Hi Andrew.

I use a similar set up but on an NEQ6. I have to say, and I'm sure you already know, that the amount of weight you're putting on the HEQ5 will make guiding a little difficult so balance will be vital.

There is a very good guide on balancing scopes using that set up here:

http://www.wilmslowa...i.htm#balancing

This is what I use and it is easy to follow.

Cheers for the link: looking forward to trying out the kit next month. I plan to get a more chunky mount in a couple of years, so this is really just to ley me try out the method.

[Andrew INT]

If you're going to the expense of the dual mount bar, make sure you have

1) decent dovetails

2) decent saddle

I'd go Losmandy rather than vixen.

Unfortunately, it all weighs quite a lot.

Thanks for the advice - it feels like a bit of a knowledge hop for me next month...

[Jessun]

+1 for losmandy. Especially if you plan to upgrade the mount anyways. Are the ADM's tip in or slide in? If you plan to travel at all with your setup I'd personally recommend a tip in type saddle. It's just a bit easier and safer to work with I've found - especially if you're on your own setting up.

[Luke]

+1 for Vixen (though we use an SCT and refractors, not a Newtonian). I feel the dual Losmandy, which we use on our NEQ6, is a bit heavy for our HEQ5. I'm assuming the bar adds to the strain on the mount??

[Andrew INT]

Thanks for all your advice. Do you think I will need to also buy and extra counter-weight? I think the answer will be yes since the are both pretty much at the and of the bar with just the 8" newtonian and DSLR.

Do you think extra weight or an extension bar is best?

[Jessun]

Once balanced, the momentum is the same regardless whether you go for an extra CW or the extension. The extra CW however would add strain on the bearings. Strain is perhaps too strong a word here, but friction will go up a notch, as will the wear.

The mount may still last decades, and there's no hard data to back up an absolute answer regarding wear.

I used three CW's on my HEQ5 from time to time with no issues.

[Andrew INT]

Well, I have only just managed to get out and set my dual scope up (having caught chicken-pox over christmas!). I do indeed need extra weight!

Stargazing live showed one of my images yesterday and so my wife (bless her) has said I can treat myself to a counterweight or extention bar. At the moment, with both weights at the extream end of the bar, the mount is far from balanced.

Since I'm on a tight budget (having just spent £30 to have the screws on the 102ST bar drilled to make them countersunk since it wouldnt sit in the ADM clamp), do you think three CW's at the end of the bar would be more effective than two CW's at the end of an extended bar? I'm thinking that if the set-up is always well balanced the extra CW is the best option and not introduce too much stress. Any thoughts?

Thanks once again for all your advice.

Andrew

[ollypenrice]

I wouldn't do it this way. I'd use a tiny finder guider or Off Axis Guider on the big scope to guide. Hand on heart I don't think the side by side will work for you on this mount.

Even when perfectly balanced a side by side introduces a new moment, or vastly magnifies one that already exists. This is the moment working against Dec. With a single scope the main scope is symmetrical over the saddle plate. With a side by side the two scopes move outwards from the saddle and create the (almost) new and considerable moment to which I refer. When you add to this the considerable mass of all the hardware you really are punishing the mount and it won't, I think, respond co-operatively.

If an OAG will let you come to focus (I don't know if it will...) this would be far better and more likely to work. I've had some experience of side by sides and they are very hard to get right if the mount isn't well within limits. I also suspect, from experience, that PA has to be better with a side by side.

Olly

[StuW]

If you go for the Extension bar and find a source, please let us know as I've been looking for one myself and FLO can't get them anymore.

[Steve Ward]

http://www.astro-engineering.com/prod/telescope-accessories/dec-shaft-ext/heq5.html

[Andrew INT]

Thankyou all once again. Olly, I bow down to your greater knowledge and experience. To be honest, I think the HEQ5 is already past its limit with and 8"newt and a DSLR, let alone and extra refractor and mountings. What you say makes good sense.

I am not too keen on the idea of OAG due to the fiddly nature of the beast. I plan to have a full hardware upgrade in a year or two (once we move house I'll start going down the road to observatory). With this in mind, I'll take good note of what you've said but still use my dual bar and scopes to get me used to the process of guiding. My scope is set up between 20-25 nights per year so hopefully it will cope for a little while.

I've ordered an extra CW from FLO this evening and I'll see how things work out. I'll review by birthday wish-list in November to include a smaller scope if it all goes wrong...

[Jessun]

Olly and I sometimes find ourselves having different views on the HEQ5 and what it can carry. I used it with great success with an 8''RC unreduced so the FL is 1.6m on this fella! This was mounted on a side-by-side bar together with an ED80 and all the usual extras. The HEQ5 soldiered on !

If it works, it works. I too had 3 CW's to balance my OTAs and the mount was easily guided to as good as I could expect really in my miserable seeing. I can see though, that Olly with much, much better skies can quicker discover an issue with a mount itself than what I can. Perhaps I always assumed seeing dictated my star size, so I'll actually leave that question open.

On one side it's a given that reducing the weight/bulk/dimensions of a setup is always benificial - making an OAG from that point of view a no brainer. It certainly is on my wish list too.

But on the other hand, there is very little info on the various forums about gear, worm or bearing replacement issues - leading me to think that it's not that big an problem. The mounts generally will last just fine even with heavy loads - up to max and a touch above. It's dead easy to get the balance wrong and cause much more strain on the components...

I look forward to see how you get one with the kit!

/Jesper

[Andrew INT]

Thanks for the extra info Jesper; that sounds great to me...although I will still heed Olly's words of warning.

I think the HEQ5 is a great mount but I think that maybe poor quality control creeps in from time to time. Ive heard some people say that even with spot on polar alignment they can only track unguided for 30 seconds. I have no issues with tracking for 90 seconds even without PEC.

Im really looking forward to trying out the new kit and just finding out what happens...and all the new skills I need to learn....

Many thanks once again.

Andrew

[Jessun]

...although I will still heed Olly's words of warning

True, when Olly speaks, it's best to listen. Olly very rarely loses a sub. I can go 75 days without seeing a single star...

My message is simply - give it a crack, there's no risk involved. It may or may not work. If it doesn't then rethink, but no harm done in trying.

/Jesper

PS I sold my HEQ5 - but wish I didn't...

[Andrew INT]

Cheers Jesper!

Give France a hug from me and my wife: we plan to buy our second home in Paris....one day!