Lodestar 2 and OAG

[Rodd]

1 hour ago, Fellside said:

Rodd

This may be a sound a bit silly but you should be able to wind the scopes main focuser in and out slowly and get the lodestar into focus. Is the OAG fitted the correct way round. Is it looking towards the CCD. I may have missed it but which OAG are you using?

Graham

Moving the focuser in all the way and out all the way had no effect.  I believe the prism is correct--I tried it both ways.

[RayD]

1 minute ago, Yawning Angel said:

This should do the job, and for only 4mm TS-Optics ultra low profile T-2 to C-mount adaptor length only 4mm, T2-CS

Yes I've seen those, that's what I wondered if they supplied with the OAG?  It's definitely going to be a squeeze I think.

[Rodd]

1 hour ago, Yawning Angel said:

I’m running the ZWO asi1600 with both their OAG and Filter wheel, asi120mc guiding. It all stacked up correctly, although it’s a close thing on inward focus travel! For my own sake, I documented the setup, so maybe this could help. Note the back focus of the 120mc is 12.5mm

 

Looks similar to mine--I tried no spacer, a 16mm spacer and a 1mm spacer where you have your 13mm spacer.  Did not help.  Everything else looks the same though I can't measure the various distances like you did.

[Rodd]

1 hour ago, RayD said:

Nice work well done.  This confirms what I said earlier, which is spacers are needed between the OAG and the FW otherwise it can never work.  Does the OAG come with a shallow profile T2 to C mount adaptor as the Lodestar is C mount, not T2 like the ASI?

The oag comes with a 16mm spacer and a 21.5mm spacer--I tried them.  Did not help

[Rodd]

53 minutes ago, Yawning Angel said:

The OAG comes with a 5mm T2 spacer, then T2 to 1.25” adapter for a nosepiece. My mistake when building it up was to include the nosepiece adapter, it adds far too much. Looks like it needs a T2 to C adapter where I’m using the 5mm T2, unless the Lodestar has something hidden for T2? 

One with the nosepiece (too long) one without (just right)

I tried the ASI 174 as well--without the receptacle--thread on.  Did not work.  Well--it worked, but way out of focus and no fiddling with anything helped.

[Yawning Angel]

Just now, Rodd said:

Looks similar to mine--I tried no spacer, a 16mm spacer and a 1mm spacer where you have your 13mm spacer.  Did not help.  Everything else looks the same though I can't measure the various distances like you did.

The distances are purely from the spec sheets. Can you grab a photo of the setup, please?

[RayD]

2 minutes ago, Rodd said:

The oag comes with a 16mm spacer and a 21.5mm spacer--I tried them.  Did not help

Where did you fit the spacers Rodd?  For it to work they would definitely need to go between the OAG and the FW, not in front of the OAG as you would normally expect.

[RayD]

I think you accidentally stuck this in the wrong thread Rodd:

Here is my setup--please keep in mind that I did try a spacer between the OAG and filter wheel--despite my supplier insisting it was not correct. It did not solve my problem. If you are wondering why the Loadstar is off to the side, its because without a spacer, it can't be rotated to be vertical because the shoulder of the lodestar receptacle impinges on the edge of the filter wheel. This is as far as I can rotate it--Maybe it does not matter where the prism enters the light cone--but I am used to imaging sensors and guide sensors to be oriented the same way (self guiding filter wheel.

This definitely won't work, and no matter what your supplier has said, you definitely need spacers between the OAG and filter wheel as your camera only has 6.5mm of back focus, which means from the sensor to the prism in your filter wheel is only about 17mm (give or take), which means your guide sensor can never be far enough away.

With all this noted, the one thing we can't confirm is whether you have enough inward focus travel on your actual OTA focuser to reach focus with this short a back focus, but that's another issue.

[Rodd]

4 minutes ago, RayD said:

I think you accidentally stuck this in the wrong thread Rodd:

Here is my setup--please keep in mind that I did try a spacer between the OAG and filter wheel--despite my supplier insisting it was not correct. It did not solve my problem. If you are wondering why the Loadstar is off to the side, its because without a spacer, it can't be rotated to be vertical because the shoulder of the lodestar receptacle impinges on the edge of the filter wheel. This is as far as I can rotate it--Maybe it does not matter where the prism enters the light cone--but I am used to imaging sensors and guide sensors to be oriented the same way (self guiding filter wheel.

This definitely won't work, and no matter what your supplier has said, you definitely need spacers between the OAG and filter wheel as your camera only has 6.5mm of back focus, which means from the sensor to the prism in your filter wheel is only about 17mm (give or take), which means your guide sensor can never be far enough away.

With all this noted, the one thing we can't confirm is whether you have enough inward focus travel on your actual OTA focuser to reach focus with this short a back focus, but that's another issue.

Where is my image?  I put the image in a wrong thread?  Its no wonder I can't get anything to work!

Here's image if anyone else was looking

[Merlin66]

Hmmm

As everyone has already confirmed - you need a spacer between the OAG and the filter wheel.

For testing, the 21.5mm spacer you mentioned would be a good start.

 

[Rodd]

Just now, Merlin66 said:

Hmmm

As everyone has already confirmed - you need a spacer between the OAG and the filter wheel.

For testing, the 21.5mm spacer you mentioned would be a good start.

 

I tried it--had absolutely no effect!

[RayD]

Rodd just to confirm, can you focus the main camera with the filter wheel and spacer on i.e. does your OTA have enough inward focus travel?

[Rodd]

12 minutes ago, RayD said:

Rodd just to confirm, can you focus the main camera with the filter wheel and spacer on i.e. does your OTA have enough inward focus travel?

The ASI 1600 mmcool pro comes to perfect focus about at the mid point of my focus travel.  There is no way for me to know if I need more inward focus if I could miraculously bring the Lodestar  to focus.

[Merlin66]

OK

Last suggestion.....

Move the focuser inwards about 25-30mm and see if the Lodestar will come to a focus. (Ignore the imaging camera for the moment.)

 

[Rodd]

2 minutes ago, Merlin66 said:

OK

Last suggestion.....

Move the focuser inwards about 25-30mm and see if the Lodestar will come to a focus. (Ignore the imaging camera for the moment.)

 

I tried that--moving the main focuser had little effect on the focus of the lodestar

[Merlin66]

Then there is some seriously wrong with our analysis of your problem.

I don’t know what else to suggest.

 

[Rodd]

2 minutes ago, Merlin66 said:

Then there is some seriously wrong with our analysis of your problem.

I don’t know what else to suggest.

 

You guys are amazing.  I am seriously grateful for the effort.  I wish my supplier, to whom I have given allot of business, would be as helpful as the folks on SGL.  I told him to read this thread and recalculate.  I won't hear from him until Tuesday though--he's off Monday.  Again.  many thanks.  I am just so upset that I am missing 5 consecutive new Moon skies (2% through 0 to 1% I think).  And clear!!  Maybe absence does indeed make the heart grow fonder (if you can get past the anger!).  I will post the successful answer WHEN it happens (I am an optimist at heart).

Ta.     

Rodd

[RayD]

I'm still not convinced that there isn't an issue with the OAG itself Rodd.  If you can focus the main camera at mid point, but not the guide camera by them moving the focuser in further, then it  points towards a problem with the prism.  However, if this is on your FSQ 106, then the focus travel is only 30mm, so half way leaves only 15mm, which may not be enough without the spacer installed.

[whipdry]

Hi Rod, I've been following this.

Looking at you setup compaired to the one further up I'd agree that your missing that 13mm spacer between the OAG & filter wheel if you look below at the back focus for the TOA 130 I think you'll agree.

Takahashi TOA-35 0.7x Reducer =71.5mm for TOA 130

Takahashi F3 0.6x Reducer =56.2mm for FSQ 106

As for the OAG remove it from your setup take the guide camera off & look down towards the prism if you can't see anything clearly through it get it replaced.

Peter

[Rodd]

22 minutes ago, RayD said:

I'm still not convinced that there isn't an issue with the OAG itself Rodd.  If you can focus the main camera at mid point, but not the guide camera by them moving the focuser in further, then it  points towards a problem with the prism.  However, if this is on your FSQ 106, then the focus travel is only 30mm, so half way leaves only 15mm, which may not be enough without the spacer installed.

No this is with the TOA 130--it has much more focus travel (almost 5").  I agree though, there might be a problem with the OAG or the Lodestar for that matter.  Tomorrow during the day I will see if I can get the Lodestar to capture something.  It was about 15 degrees F last night and fiddling with this thing without gloves on was not fun.  

[Rodd]

1 minute ago, whipdry said:

Hi Rod, I've been following this.

Looking at you setup compaired to the one further up I'd agree that your missing that 13mm spacer between the OAG & filter wheel if you look below at the back focus for the TOA 130 I think you'll agree.

Takahashi TOA-35 0.7x Reducer =71.5mm for TOA 130

Takahashi F3 0.6x Reducer =56.2mm for FSQ 106

As for the OAG remove it from your setup take the guide camera off & look down towards the prism if you can't see anything clearly through it get it replaced.

Peter

I tried a spacer there.  No go.  Good idea about looking down the scope though--I'll do that tomorrow.

Rodd

[Rodd]

10 hours ago, RayD said:

I'm still not convinced that there isn't an issue with the OAG itself Rodd.  If you can focus the main camera at mid point, but not the guide camera by them moving the focuser in further, then it  points towards a problem with the prism.  However, if this is on your FSQ 106, then the focus travel is only 30mm, so half way leaves only 15mm, which may not be enough without the spacer installed.

One last question--Even though I got the 1600/OAG to use with the FSQ 106 at F3 specifically, I started using the 1600/OAG with the TOA-130 because the scope was up, I am familiar with it and I thought it would be better to not have to learn 2 things at once.  The connections will be the same (according to my supplier).  But, assuming there is not a defect in any of the elements, will I have to go through something similar when I do switch to the FSQ 106?  Or, if I can manage to get it to work, will I be able to transfer it to another scope fairly easily.

Rodd

[RayD]

7 minutes ago, Rodd said:

One last question--Even though I got the 1600/OAG to use with the FSQ 106 at F3 specifically, I started using the 1600/OAG with the TOA-130 because the scope was up, I am familiar with it and I thought it would be better to not have to learn 2 things at once.  The connections will be the same (according to my supplier).  But, assuming there is not a defect in any of the elements, will I have to go through something similar when I do switch to the FSQ 106?  Or, if I can manage to get it to work, will I be able to transfer it to another scope fairly easily.

Rodd

I would think the back focus distance between the focal reducer and the camera sensor will be different as the 2 OTA's have differing focal lengths.  This means the the set ups would be unique to each OTA.  If your supplier has given you spacers which he has calculated as correct for the FSQ, it's unlikely that they will be identical for the TOA I would have thought.

[Rodd]

46 minutes ago, RayD said:

I would think the back focus distance between the focal reducer and the camera sensor will be different as the 2 OTA's have differing focal lengths.  This means the the set ups would be unique to each OTA.  If your supplier has given you spacers which he has calculated as correct for the FSQ, it's unlikely that they will be identical for the TOA I would have thought.

Seems painfully obvious to me as well......Thanks

Rodd

[Allinthehead]

Hi Rodd. You said earlier in the thread you're losing nights imaging trying to figure this out. I already suggested on a different thread, as has someone on this, to set up during the day. That was how i got my oag to focus with my asi 1600. I needed to add a spacer between the guidecam and the oag to get it to focus. You shouldn't be losing any imaging time as that only adds to the frustration.