Guide Scopes [Side-by-Side or Over/Under]

[Benny L]

Hi all,

just wondering how everyone has their guide scopes mounted..

i.e: traditional piggy back style or a side-by-side shotgun style..

what are your reasons for doing so, easier to balance, only way to mount the scope etc

cheers

Ben

[Garyh]

Hi Ben,
Having tried both methods a few years back, I prefer side by side. Much easier to balance when changing gear around and I find I get better results by keeping the center of gravity lower to the EQ head/axis. Also it`s a lot less strain on the drives keeping things low.
Gary

[tempestwizz]

I echo Gary's views/experience, and logic. Also if you utilise one of the dovetail systems available from one of the guys from the links section, changing over scopes and associated balancing is quite quick and simple.
BC

[gbeal]

I don't fully agree. Yes, the weight is closer to the pivot, but in most cases, certainly mine, the associated side by side contraption adds more weight than is saved. If I have a choice, over/under.
Gary

[Omaroo]

Thank you Gary - my sentiments exactly. The double (or even triple-width) saddle is a huge lump on its own. I see absolutely no advantage in side by side - in fact it's harder to fully balance in 3-D around the Dec axis. Invariably you have one large scope (with additional camera) on one side and a smaller guide scope on the other. Where's the balance advantage in that? No only do you have to balance the whole kit and kaboodle forwards and backwards - but now sideways as well. On my setup, the weight on the LHS due to the finderscopes is perfectly offset by the weight of the cable loom on the right.

I much prefer to vertically stack - the weight distribution is far more linear, and I think lighter in overall weight either side of the RA bearing. It really doesn't matter how close to the bearing the weight is - it's either present there or its not. The inertial difference between it being located close to the bearing or not is insignificant, and the weight of the side-by-side saddle is more, so I don't see any advantages other then it being quicker to swap the main scope out....which I never do.

[niko]

though yet to fully implement my little system I went with a under/over option pretty much based on cost. I have had to sacrafice a few little things along the way - ie. will have to remove guidescope if I want to do wide field piggyback photography (which I love) but I'm dipping my toes into a very deep pool and figured I'd just take it one step at a time.

my 2 cents worth anyway.

niko

[Terry B]

I had the opposite experience. I had my scopes piggy backed but found significant flexure. When I bought my side by side mount I was able to remove 5 kg of counterweight and slide the remaining weight further up the shaft.
The flexure is significantly less than before.

Yes you have to balance the mounts in different directions but since mine is permanently attached and I never remove them this only had to be done once.

see http://www.iceinspace.com.au/forum/attachment.php?attachmentid=50491&d=1227612011

[Omaroo]

Terry - good point in reference to an EQ6. A G11 counterwight shaft in comparison is massive - with probably three times the amount of cross-sectional meat. I have a Losmandy D-series plate top and bottom of my OTA either side of a set of steel rings - and the guidescope sits on two clamshells - nil flex that I can detect mechanically or photographically. I don't use guide rings, and solid-mount the guide scope instead. The QHY5 has never failed, yet, to pick up a guide star.

I guess this comes down to extremes, if any, at hand. If we speak of an 80mm refractor with a 60mm sitting on top as guidescope, and then another system that comprises a 12" reflector and 80mm guidescope or greater - on a similar mount, then flexure problems are going to range from huge to non-existent depending on what we carry given that particular mounts' sturdiness. I run a light scope and even lighter guidescope on a good solid mount, so the vertical arrangement suits me much better.

A wide saddle plate might also interfere when cranked right over in RA with cables, motors or part of the mount itself being hit sooner than they should be.

[Paul Haese]

Funny you should ask this question. I have just gone through this process after having a side by side system for a couple of years. With the help of many people I came to the realisation that the side by side was producing differential flexure. I changed it to a piggy back system and now seem to have the flexure under control.

Having said this, I see a lot of great images with side by side systems. Why my system would not work correctly is really a mystery to me, but the bottom line is that I found that piggy back was better. It can be an expensive mistake to make and all I can offer is that piggy back does more often than not come up as having less flexure than side by side.

[dugnsuz]

Hi Ben,
I've used both configurations - 80mm achro guide scope piggybacked on an ED80 as in my avatar, and a side by side plate for my current rig with 80mm guidescope on one side and 40D/lens on the other.

I prefer the side by side setup as I can fiddle with the guidescope without disturbing the imaging scope. I also found that because of the similar tube lenghts of the achro and ED80, the camera ended up under the upper scope's diagonal causing things to get a bit cramped!