Focussing guidescope

[eikie]

For my evostar 80ed I want to use the finderscope as a guidescope.

 

For this I bought a ASI 120mm mini and a Skywatcher 9x50 Finder to C Adapter

However, after pointing it at the moon, I found out I couldn't get it in focus.

When using sharpcap, the resulting image did show a vague outline of the edge of the moon, but clearly out of focus.

I know you can turn the ring on the 9x50 finderscope and thereafter turn the entire front lens, but clearly not far enough (tried Both ways).

 

Anyone using the same setup who can give me some pointers?

Edited February 8, 2020 by eikie

[fozzybear]

On the 9x50 finderscope you could try removing the locking ring on the end of the finderscope to give you more travel of the lens?

with the asi120 bern does an t2 adapter for this finderscope

https://www.modernastronomy.com/shop/accessories/finder-guider-adapters/fg-sky-watcher-clones/sky-watcher-clones-to-t-thread-adapter-for-straight-through-finders/

[tooth_dr]

1 hour ago, eikie said:

For my evostar 80ed I want to use the finderscope as a guidescope.

 

For this I bought a ASI 120mm and a Skywatcher 9x50 Finder to C Adapter

However, after pointing it at the moon, I found out I couldn't get it in focus.

When using sharpcap, the resulting image did show a vague outline of the edge of the moon, but clearly out of focus.

I know you can turn the ring on the 9x50 finderscope and thereafter turn the entire front lens, but clearly not far enough (tried Both ways).

 

Anyone using the same setup who can give me some pointers?

I use a 120MM and a 9x50 finder with a C adapter.

This one below - it doesnt have a flange like your and so screws a bit further into the body of the finder.  You flip the locking ring 180deg and this will give you more travel too.

[Ronclarke]

I also use one of these and have no problem getting focus, highly recommended! 😀

[eikie]

Well, beautiful clear skies so out I went and whatever I do, I can not get my 9x50 scope plus asi 120mm focused. 

 

Removed the rocking ring, twisted the lens fully in and out, but no focus...

 

Nobody who had the same setup? Am at my wits end, I must be missing something....

[TerryMcK]

I have exactly the same setup. Remove the focus ring and screw on the lens again. Then screw the lens in until around 4mm of thread is showing and you will be nearly there. Focus is only a hair around this area and you may find no more than half a turn or so gets you in focus. My scope is the 9x50 straight through finder scope which has a 180mm focal length. There is another finderscope by skywatcher which carries the diagonal and that is much shorter. That one will NOT work with the C adapter as the focal length is too short.

[eikie]

1 hour ago, TerryMcK said:

I have exactly the same setup. Remove the focus ring and screw on the lens again. Then screw the lens in until around 4mm of thread is showing and you will be nearly there. Focus is only a hair around this area and you may find no more than half a turn or so gets you in focus. My scope is the 9x50 straight through finder scope which has a 180mm focal length. There is another finderscope by skywatcher which carries the diagonal and that is much shorter. That one will NOT work with the C adapter as the focal length is too short.

Thanks, I will try later tonight. I do have the same finder scope, if you have it working, I should be able too..

 

--EDIT--

 

Well, I just can't get it in focus. Either I did something wrong when assembling it, or in the software, but the moon remains a vague light blob, no matter how much and in what direction I turn the main lens.

 

Stars are completely invisible.

Edited February 7, 2020 by eikie

[tooth_dr]

2 hours ago, eikie said:

Thanks, I will try later tonight. I do have the same finder scope, if you have it working, I should be able too..

 

--EDIT--

 

Well, I just can't get it in focus. Either I did something wrong when assembling it, or in the software, but the moon remains a vague light blob, no matter how much and in what direction I turn the main lens.

 

Stars are completely invisible.

Please post photos of the camera end side on. My 120MM is touching the metal of the finder.

Edited February 7, 2020 by tooth_dr

[eikie]

4 minutes ago, tooth_dr said:

Please post photos of the camera end side on. My 120MM is touching the metal of the finder.

I will, but it is going to be tomorrow.. Thanks in advance.

[eikie]

10 hours ago, tooth_dr said:

Please post photos of the camera end side on. My 120MM is touching the metal of the finder.

I might have made a couple of mistakes.

 

Firstly, the cam is a 120mm MINI, that might be a different one you have?

Secondly, when I looked at it this morning, I noticed a piece of "tubing", which came with the cam could be broken down in two parts.

It was just screwed together so tightly, I thought it was just 1 piece.

Because of this I am able to reduce the distance between the cam and the front lens by 1 to 2 cm. Hopefully that might be it.

 

First picture is how I had it yesterday night, second picture is of the tube broken down in three parts (left is the part with a piece of glass to project the sensor, middle and right is the broken down tube which I thought to be one piece).

Last photo is of the cam now attached with only the glass protector and the small ring from the tube. Can't connect the cam without those two.

 

Hopefully the 1,5 cm I lost is enough to get it in focus now, but with that storm and subsequent bad weather coming, I won't find out for a long time..

 

[tooth_dr]

3 minutes ago, eikie said:

I won't find out for a long time..

A picture would have saved you a lot of trouble as the spacer was your problem and we would have picked up on that.

There is no need to wait, you can (and should) get it to close focus during the day. Simple point the finderscope (detached from telescope if easier) at a distant object e.g. trees or house and get it focused.  Then at night you will be very close to the desired focus position. 
 

Let us know how you get on. 

[eikie]

1 hour ago, tooth_dr said:

A picture would have saved you a lot of trouble as the spacer was your problem and we would have picked up on that.

There is no need to wait, you can (and should) get it to close focus during the day. Simple point the finderscope (detached from telescope if easier) at a distant object e.g. trees or house and get it focused.  Then at night you will be very close to the desired focus position. 
 

Let us know how you get on. 

Lesson leared, a picture is worth more than..

 

I'll try this as soon as possible, thanks all for the input...

Edited February 8, 2020 by eikie

[fozzybear]

Eikie,

You won't be the first or last on this one as caught me out to. Glad and hope you have this sorted.

Andy

 

[eikie]

On 08/02/2020 at 09:58, tooth_dr said:

 

Let us know how you get on. 

Well, you were right.

 

Just tried aiming and focussing on a house some distance away and I was able to get focus (more or less).

 

So I am confident next time I can use the guidecam as intended...

[tooth_dr]

19 minutes ago, eikie said:

Well, you were right.

 

Just tried aiming and focussing on a house some distance away and I was able to get focus (more or less).

 

So I am confident next time I can use the guidecam as intended...

That is excellent news! Get ready for the next problem 😂