15 replies to this topic

[Daniel B]

Without the extension tube I can't focus, with the extension tube I can't focus either, because it doesn't go in far enough. Does anyone have a solution, other than not using the extension tube and not pushing the eyepiece all the way into the focuser? I was thinking about cutting/shortening the barrel, but I don't know how important the length of it is ? I don't understand why Apertura sells this extension tube knowing full well that it is useless, and of course they also know the focus problem with the 30mm.
 

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Edited by Daniel B, 14 October 2024 - 11:00 AM.

[Neanderthal]

It is NOT useless. There is no problem with the 35mm extension provided, in fact it is very normal to need it to use that 30mm you have. Here are several things to check:

 

1. The focuser has a travel "lock" screw, make sure it is not locked into place. In fact, it's common for folks to just remove it altogether and store away.

2. Your Primary mirror might be "walked" up towards the top of the OTA. This is common from using all 3 of the collimation screws.

3. Are you trying to use this during the day? Try it again at night, on a far-away object.

[Daniel B]

It is NOT useless. There is no problem with the 35mm extension provided, in fact it is very normal to need it to use that 30mm you have. Here are several things to check:

 

1. The focuser has a travel "lock" screw, make sure it is not locked into place. In fact, it's common for folks to just remove it altogether and store away.

2. Your Primary mirror might be "walked" up towards the top of the OTA. This is common from using all 3 of the collimation screws.

3. Are you trying to use this during the day? Try it again at night, on a far-away object.

Well... You are probably right about be the lock screw   With it I can extend the eyepiece holder up to 32mm, without up to 42mm. I'll check that tonight, but pretty sure the issue was that.
So is it normal that the barrel does not fit completely into the extension? Because that's what made me doubt and what made me angry. It stopped me from thinking, I immediately got stuck on this point thinking that the issue came from there... I must say that I slept badly last night and that put me in a bad mood.
 

[SeattleScott]

Some 2” barrels are longer than others. So it can certainly be the case where some barrels don’t insert all the way.

Your described situation can only occur if your focus travel is less than the extension (35mm). Having only 32mm with the focus lock screw would explain this. Opening it up to 42mm will solve the problem. And yes you might have walked up your mirror.

[Daniel B]

And yes you might have walked up your mirror.

What does it mean ?

[SeattleScott]

What does it mean ?

If you always turn the collimation screws the same way, over time you can walk your mirror up (or down). A solution is to mark one screw and not touch it. Only adjust the other two collimation screws. That way you don't raise or lower your mirror.

[Bulldawg54]

My 30mm super view doesn’t seat all the way down in the extension either. The extension has a “lip” that prevents the eyepiece from going all the way into it, likely yours does too. I had the same issue and removing the lock screw was the answer for myself, ymmv.

[Daniel B]

If you always turn the collimation screws the same way, over time you can walk your mirror up (or down). A solution is to mark one screw and not touch it. Only adjust the other two collimation screws. That way you don't raise or lower your mirror.

Not at all

 

What does this have to do with the eyepiece holder locking screw?

[Daniel B]

My 30mm super view doesn’t seat all the way down in the extension either. The extension has a “lip” that prevents the eyepiece from going all the way into it, likely yours does too. I had the same issue and removing the lock screw was the answer for myself, ymmv.

Yes that was it...I'm going to take it apart and see why it's blocking.

[Bill Weir]

Scope? Show us a photo of how you have it in the focuser. Is this a Skywatcher dob?

 

Bill

Edited by Bill Weir, 14 October 2024 - 11:14 PM.

[SeattleScott]

Not at all

What does this have to do with the eyepiece holder locking screw?

Has absolutely nothing to do with the locking screw.

[LordNewton]

On my AD8 I do not use the extension tube with the 30mm Super View. I simply do not insert the eyepiece all the way in to the focuser. I lock it in place with with a few mm space to spare. The 30mm Super View is known not to come in to focus with the focuser racked all the way out. It needs a few mm more outwards travel.

[Daniel B]

Without the locking screw I gain 7 millimeters, it would take 5 more to be comfortable. I am thinking about a 5mm ring that would remain permanently on the barrel of the eyepiece.

[Noto]

Without the locking screw I gain 7 millimeters, it would take 5 more to be comfortable. I am thinking about a 5mm ring that would remain permanently on the barrel of the eyepiece.

Get a few O-rings from your local hardware store and slip as many as you need over the barrel (inside diameter 2" of course). Check out my post from an older thread for the picture.

[Daniel B]

Get a few O-rings from your local hardware store and slip as many as you need over the barrel (inside diameter 2" of course). Check out my post from an older thread for the picture.

Very good idea ! 

[Daniel B]

Got the O rings, works like a charm.

Thanks mate 

Btw, I don't have to take off the locking screw to gain the full range. I unscrew it enough and that's it. I like to use it with heavy eyepieces, because they sometimes glide down alone with their weight.