Advice on small refractor for visual

[LDW1]

You are probably right, I hope so. Its an interesting conversation ! 

[Paz]

On 24/09/2019 at 08:11, Stu said:

 

Thanks to all for the comments, they do help to think about what matters. In my case it is figuring out the size/weight limit for my circumstances and intended use and then within that getting the best scope I can - but it is a personal preferences thing and what suits me won't necessarily apply to (or necessarily make sense to) everyone else. Whatever I were to get for a small scope I'll still have other bigger scopes so any time I get aperture fever I can roll out something bigger if circumstances permit.

The the thing that has I think hit the nail on the head is the above picture of a 72mm buried in a small case with lots of other stuff - that is the kind of set up I'm thinking of.

One interesting thing I have noticed when testing the ST80 is the effect of good balance on the altitude axis - better balance means less friction is needed on the head and so the smoother/easier the altitude movement can be. It follows that little things like the ability to move the dovetail bar back and without having to make up a workaround to achieve that, as Stu mentions, could potentially be a big help.

[Stu]

Just to add an image of how I have to attach a second dovetail to allow me to mount the scope far enough forward to reach balance, without fouling the focuser. One day I'll find some suitable spacers to avoid this extra weight, which is one benefit of the Altair version.

[LDW1]

18 hours ago, Stu said:

Just to add an image of how I have to attach a second dovetail to allow me to mount the scope far enough forward to reach balance, without fouling the focuser. One day I'll find some suitable spacers to avoid this extra weight, which is one benefit of the Altair version.

Why didn’t you just buy a longer dovetail, say a 13” ? They aren’t that much money. Why does the focuser have to be in that position in relation to that of the dovetail ?

Edited October 4, 2019 by LDW1

[Stu]

3 hours ago, LDW1 said:

Why didn’t you just buy a longer dovetail, say a 13” ? They aren’t that much money. Why does the focuser have to be in that position in relation to that of the dovetail ?

I use the scope on an alt az mount and like the focuser to be in a normal horizontal position. Bolting the additional dovetail on gives it sufficient space so it doesn't clash. I already have longer dovetails but that would not work, that was the whole point of my comment about the spacers.

[LDW1]

8 hours ago, Stu said:

I use the scope on an alt az mount and like the focuser to be in a normal horizontal position. Bolting the additional dovetail on gives it sufficient space so it doesn't clash. I already have longer dovetails but that would not work, that was the whole point of my comment about the spacers.

I guess I just couldn’t get my head around it as with all my short scopes I never had a problem with balance, with the focuser mounted on my AZ’s. Thats why the longer dovetail so that the actual scope hung out over the back of the mount somewhat but the balance / weight distribution was still excellent, thats how the AZ’s are designed and that Equinox for its size is not light !

[Stu]

4 hours ago, LDW1 said:

I guess I just couldn’t get my head around it as with all my short scopes I never had a problem with balance, with the focuser mounted on my AZ’s. Thats why the longer dovetail so that the actual scope hung out over the back of the mount somewhat but the balance / weight distribution was still excellent, thats how the AZ’s are designed and that Equinox for its size is not light !

Yep, well it depends to an extent what diagonal and eyepieces you use, but certainly with this one (and it sounds like others have similar experience from the comments) you need to get the weight forward to achieve balance properly. It's not about weight but about balance, the Equinox 80mm will have a heavier objective which means less of a requirement to move it forward to achieve balance.

[LDW1]

I just tighten the az knob down to get the proper vertical tension when using one of my 2” eps. It works perfectly even when using my longer, heaviest scope, you just have to use a little more force when going through the vertical movement, its the way they are designed / built, its a great mount ! But if you have to double up on the dovetail then .........

Edited October 5, 2019 by LDW1

[Stu]

19 minutes ago, LDW1 said:

I just tighten the az knob down to get the proper vertical tension when using one of my 2” eps. It works perfectly even when using my longer, heaviest scope, you just have to use a little more force when going through the vertical movement, its the way they are designed / built, its a great mount ! But if you have to double up on the dovetail then .........

I often observe at high powers and want/need smooth motion. Alt az mounts work much better when they are balanced both side to side and front to back. That way you can have minimal clutch applied and nice smooth motion. The doubled up dovetail is not elegant, and would be better with spacers as I have mentioned once or twice before, but on this scope it is the best solution for a horizontal focuser and well balanced configuration. I believe the Altair is possibly a better option simply because it has the spacers and avoids this problem.

As mentioned, the 80ED has a heavier objective so needs less balancing than the 72mm scopes.

[Paz]

In field testing with my st80 I have identified altitude balance and the minimisation of vibes as the two outstanding issues I need to make sure I have covered.

On the topic of altitude balance I would like things balanced with little or no need for using friction to hold position, so the idea of a dovetail that can go back far enough in order to hold the scope forward is a good one.

With vibes I think lower weight will make a difference, and not being too greedy in expectations of huge magnifications will also help.

[Mark Daniels]

With fluid head cost 320. Red dot finder from a rifle (aluminium) 30. Weight with skywatcher tripod 7 kg. Get upto 100x which is about maximum practical.  But perfect at around 25-69x
been using all summer fits in small camera rucksack. 

[Paz]

On 11/11/2019 at 21:39, Mark Daniels said:

With fluid head cost 320. Red dot finder from a rifle (aluminium) 30. Weight with skywatcher tripod 7 kg. Get upto 100x which is about maximum practical.  But perfect at around 25-69x
been using all summer fits in small camera rucksack. 

IMG_2787.MOV

That's a nice set up, is that a Sky Watcher ED50?

[Mark Daniels]

19 hours ago, Paz said:

That's a nice set up, is that a Sky Watcher ED50?

Yes it is used a 90* with a 2 x barlow on the end. Focuses well no CA get the same if not better views as my SW102 travel but at half the size snd a 1/3 of the weight.