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Moonlight Focuser the solution to Dob Bino?

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#1 -Starfighter-

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Posted 16 July 2014 - 10:32 AM

So, I had the understanding that I could not use my W/O bino in my Orion XT10i because I didn't have enough in focus. Is this not the case? I have read in another thread that the solution may be a new focuser with a longer draw tube like the moonlight?

#2 Oscar56

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Posted 16 July 2014 - 10:54 AM

Star:

I installed a Moonlight with a 2.37" draw tube BEFORE getting my Burgess 24 binoviewers. I still only have about 2mm of in focus left with the binos. No idea how the original Orion focuser would have worked.

#3 Mark9473

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Posted 16 July 2014 - 01:37 PM

It's not a longer draw tube that you need, but a shorter focuser body.

#4 beatlejuice

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Posted 16 July 2014 - 02:19 PM

It's not a longer draw tube that you need, but a shorter focuser body.


Not necessarily true. You may need the longer drawtube to reach focus in mono with the lower profile focuser.

Eric

#5 Mark9473

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Posted 16 July 2014 - 02:34 PM

I was just saying that a longer drawtube is no cure for insufficient in-focus, which is what the OP asked about.

#6 -Starfighter-

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Posted 16 July 2014 - 03:22 PM

Ahh Ok, so the moonlight may have a low enough profile to accommodate the Bino's? I guess the other question is, "Is there anyone else using W/O bino's with a XT10i?"

#7 beatlejuice

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Posted 16 July 2014 - 03:39 PM

I was just saying that a longer drawtube is no cure for insufficient in-focus, which is what the OP asked about.


For sure, I was just making sure that the OP was aware that the longer draw tube may very well be necessary if he still wants to use his eyepieces in mono with the lower profile focuser.

Eric

#8 -Starfighter-

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Posted 16 July 2014 - 04:07 PM

Really? Actually a useful tip because I didn't realize if I went lower profile I would loose focus with some mono EP's.

#9 JustaBoy

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Posted 16 July 2014 - 04:26 PM

That's only a very minor problem - not having enough out-travel.

Just get one of these if need be:

It's simply a tube with the ID of your eyepiece on one end and it's OD on the other.

http://agenaastro.co...sion-tubes.html

#10 beatlejuice

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Posted 16 July 2014 - 05:59 PM

Really? Actually a useful tip because I didn't realize if I went lower profile I would loose focus with some mono EP's.


You may or may not but either way if you are thinking of changing focusers you should measure the distance from the telescope tube to the shoulder of each of your eyepieces when they are focused. Those numbers will never change and are useful to know before you make any changes.

I am starting to get the impression that you have yet to try the W.O.'s in your XT10. If this is true you may be jumping the gun a little bit as far as their performance is concerned.

Eric

#11 -Starfighter-

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Posted 16 July 2014 - 06:42 PM

I have tried them in the XT10i and I can only make it work balowed. The problem with that is the mag is too high.

#12 beatlejuice

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Posted 16 July 2014 - 06:59 PM

I have tried them in the XT10i and I can only make it work balowed. The problem with that is the mag is too high.


You will have to use some kind of barlow for them to reach focus no matter what focuser you use.
Even with the Binotron the best that I can do is about 1.3x
Unless a scope is made or modified specifically for binoviewers, viewing with eyepieces at their native focal lengths is just not part of the equation.

Eric

#13 Eddgie

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Posted 17 July 2014 - 07:21 AM

I have tried them in the XT10i and I can only make it work balowed. The problem with that is the mag is too high.



As others have said, a longer focuser tube won't do anything at all.

A lower profile focuser might help you get focus with the 1.6x Barlows that comes with the William Optics and similar binoviewers, but not always.

Once again, we are at the point where I say this.

By the time you add a new focuser to your scope, you could have bought a used Denk II for the money you spent on your binoviewer, a new focuser, and three pairs of eyepeices.

Now, you are at a point where you may want to consider just going ahead and upgrading.

But even here, there may be issues.

In some cases, you might need an OCS extension tube to reach focus in low power, but this will raise your lowest mag from 1.3x to maybe 1.4x. Still, the larger prisms of the Denk II will allow eyepecies with a wider field, so you still come out pretty far ahead.

Second, in this case, the longer focuser tube is indeed desirable becuase with the Denk II, in high power mode, there may not be enough out travel to reach focus.

The solution to this is to simply release the binoviewer OCS tube in the focuser and slip it out a bit.

If you go this route and later decide that you don't like slipping the Binoviewer/OCS in and out, you can then consider a new focuser.

But putting a focuser on now to me would not be nearly as cost effective as selling the WOs and putting the $350 into a new focuser and still being stuck with a small prism and a 1.6x field.

I know the "Get some Denk IIs" record groove is wearing thin, but I keep saying it because I keep reading situations like this.

And you may need two speed focuser you do upgrade.

The single speed does not have enough resistance to keep the focuser from creeping in under the weight.

Anyway, if you are enjoying binoviewing and think that you would do a lot more of it if you could reach lower powers, then it may be time for you to consider upgrading.

If your current focuser is a dual speed, you will be able to reach focus in low power with the Denk Supersystem (maybe not 1.3x, but again, larger prisms mean lower power eyepecies than you can currently use and you might be able to reach focus at 1.4x) and for sure, you will reach focus at medium power. At high power, you might have to slip the unit out a bit, but a lot of people do this and don't mind it.

Sorry.. I know I sound like a broken record, but someone needs to step up and suggest that you step back at this point in time and analyze your options.

Adding a new focuser for a low power of 1.6x does not seem all that great an investment when for a few hundred dollars more, you could just move to a Denk II and get three very useful powers.

If your current focuser is not a two speed though, may not be an option for you.

#14 -Starfighter-

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Posted 17 July 2014 - 10:34 AM

Thanks Eddgie, I appreciate your candor and it looks like the Denk's are my only option. You don't sound like a broken record. It's just that I keep hearing all these different options. The only reason I have been mulling this over time and again is because I want several upgrades anyway. I have the single speed focuser that comes with the scope and want to upgrade because the focus is just not precision enough and not to mention the items you previously noted.. Once I started looking into new focusers inevitably the bino issue comes up again and away we go. Either way I am now clear on what is needed. Time to start saving up for the Denk's and a new focuser...

#15 REC

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Posted 17 July 2014 - 12:41 PM

FYI...I went the same route as Ed suggests. My WO BV would not focus in my 10" Dob. The DenkII with the PS does focus with the OCS.

I had a beautiful view of the Double Star Cluster in the BV using the low power arm of the switch.

Have fun!

#16 Eddgie

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Posted 17 July 2014 - 08:33 PM

Well, if you are going to upgrade the focuser anyway, then it makes sense just to keep the WO for now.

I put a Moonlight on my 12" even though I could reach focus on low power mode without it. For me, the goal was to reach focus in all three power settings without having to slip the Binoviewer out for high power.

This is where the long tube becomes most important I think.

If you mount the focuser with no spacers and use a long tube, if you ever go to a Denk II, you should be fine.

It takes a bit of planning to know exactly how long a tube you need, but the good thing about Moonlight is that if you get one that is to short, you can always order the right length later on.

#17 Messyone

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Posted 22 July 2014 - 05:33 AM

Ahh Ok, so the moonlight may have a low enough profile to accommodate the Bino's? I guess the other question is, "Is there anyone else using W/O bino's with a XT10i?"

I look up XT10i and get a dob with 63mm secondary and f4.7 mirror. Is that correct?
Assuming that is ...what???? My Orion Optics UK scope is 10" mirror f4.8 with a 63mm secondary and I have no trouble focusing with a Feather touch 2.5" drawtube and the1.6x OCS. For mono I have to add a paracorr, ES HR in my case, or if I can stand the coma (which I can't) a 50mm extension tube. Change the secondary to a 65mm one and I get focus without the OCS....just with a couple of mm to spare.
Don't quite get why an expensive binoviewer is the other option here...am I missing something about the XT10i Dob?
Really really really confused why so many Newtonian owners can't reach focus with a sub f5 Newtonian.... :shrug:
Matt

#18 Eddgie

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Posted 22 July 2014 - 06:28 AM

I missing something about the XT10i Dob?



Not unique to this scope. It is very common for a great number of dob models to not be able to reach focus with binoviewers even using the 1.6x Barlow.

They simply were not designed to work with binoviewers.

Truss dobs can be modified by cutting the poles and installing a larger secondary mirror, but this of course lowers contrast some, and makes it necessary to use extensions for mono-vision.

No on needs to buy an expensive Denk or other option, just like no one needs to buy a telescope or an eyepeice.

They do it because the Denk or Earthwin systems allow you to reach a wide range of of powers and the power swtich reduces the need to change eyepeices.

So, you can modify the scope, but for most dobs, to reach focus without resorting to a 2" Barlow or expenisve focuser (or a combination), it may be necessary to modify the scope.

But no one has to buy any of this stuff.. It is just a choice we make based on our own desires.

I desired to reach focus at the lowest possible power and still be able to use the power switch to avoid changing eyepeices. The Denk did not seem all that expensive because it allowed me to reach all of my goals.

But to others, it costs to much. Each individual has to choose.

#19 -Starfighter-

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Posted 22 July 2014 - 10:19 AM

Ok, I am going to do this one step at a time, first the focuser, then the bino's.

#20 beatlejuice

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Posted 22 July 2014 - 01:05 PM

Ok, I am going to do this one step at a time, first the focuser, then the bino's.


I would suggest the reverse. You can adapt the focuser to work with the binos but not so easily, if at all, the reverse.

Eric






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