Lodestar 2 and OAG

[Rodd]

20 minutes ago, Yawning Angel said:

Aha, got it now.

The light path to both sensors needs to be the same length, as governed by the focal reducer / scope spec . Looking at the photo, the 1600 is much closer to the reducer than the SX (my blue arrows). You might be assess this roughly like so (in daylight):

Rack the focus in, as far as it will go to start

Remove (unscrew) the adaptor, marked in red

Extent the OAG prism turret down into the light path until it's basically flush with the top plate

Hand hold the SX to the top plate of the OAG

Move the focus out and see if you can get anything - it'll be hit and miss, but you should spot a roughly focused image

It that works, you can look at replacing the adapter with a slim T2 to C mount...I linked one back in the depths of this thread :-)

 

OK--I understand.  Even though this has been said I did not get the 2 distances has to be the same.  This means I need a spacer between the OAG and reducer--which the vendor specifically said I did not.  I have fired the vendor.  I tried a spacer between the OAG and filter wheel--but that just pushes the 1600 further back--which, now that I think of it--should have the same effect.  I tried moving the focuser all the way in and out--there was no change to the lodestar subs.  I find daytime to be difficult as there is so much light--only a very, very short exposure through an Ha filter results in an image that is not washed out.  The Lodestar cant take a .001 sec exposure like the 1600 can.  Maybe the Lodestar is not working right.  I will try what you say today.  Thanks.  

Rodd

[ollypenrice]

On 3/17/2018 at 12:36, RayD said:

You could try by eliminating an issue with the OAG prism by installing the Lodestar directly in a 1 1/4 eyepiece holder in your focuser to make sure you can indeed get focus, and it will then let you calculate a rough distance.  It's a basic starting point but may stop you chasing around in circles.

I would do this. I recently installed a replacement Lodestar into a robotic rig I host and it produced elongated stars. I then lent the guys my spare Lodestar and that was fine in the same OAG, so the camera has a problem, probably a tilted chip. I'd check it a normal scope to eliminate/confirm camera and OAG problems.

Olly

[Rodd]

5 minutes ago, ollypenrice said:

I would do this. I recently installed a replacement Lodestar into a robotic rig I host and it produced elongated stars. I then lent the guys my spare Lodestar and that was fine in the same OAG, so the camera has a problem, probably a tilted chip. I'd check it a normal scope to eliminate/confirm camera and OAG problems.

Olly

I haven't looked through an eyepiece in years--never with the TOA--I will have to look at the chart to see what goes where.  I think I have the necessary parts.  Daytime seems more practical--but not sure the Lodestar can take short enough exposures--it could not yesterday--unless focus was so bad it just appeared that way--maybe in focus the light wouldn't be so bad.

[Yawning Angel]

All the parts in my imaging train are ZWO, right up to the reducer, and it didn't all work correctly without some messing - hang in there!

Keep the OAG as close as possible to the reducer. I strongly suspect it's lightpath is currently too long. My test should help prove that

Before you sack the supplier - Do you know, or can the supplier confirm, the backfocus distance for the Scope / Reducer? Someone earlier mentioned it might be 73.5mm? My napkin maths says you're currently at maybe 91mm with the spacers after the reducer and the that ZWO adapter in place.

(My estimates - your spacers look like 16mm or so, the Prism is 9.5mm insider the OAG, The turret is 33mm, adapter is about 20mm, SX backfocus is 12.5mm = 91mm) Looking at these rough numbers, you might get away with just dropping the spacers from the reducer, if you can. Otherwise, swapping the 20mm adapter for a slim one will bring it into the ballpark.

It looks like it'll come together, in principal at least :-)

[Rodd]

11 minutes ago, Yawning Angel said:

All the parts in my imaging train are ZWO, right up to the reducer, and it didn't all work correctly without some messing - hang in there!

Keep the OAG as close as possible to the reducer. I strongly suspect it's lightpath is currently too long. My test should help prove that

Before you sack the supplier - Do you know, or can the supplier confirm, the backfocus distance for the Scope / Reducer? Someone earlier mentioned it might be 73.5mm? My napkin maths says you're currently at maybe 91mm with the spacers after the reducer and the that ZWO adapter in place.

(My estimates - your spacers look like 16mm or so, the Prism is 9.5mm insider the OAG, The turret is 33mm, adapter is about 20mm, SX backfocus is 12.5mm = 91mm) Looking at these rough numbers, you might get away with just dropping the spacers from the reducer, if you can. Otherwise, swapping the 20mm adapter for a slim one will bring it into the ballpark.

It looks like it'll come together, in principal at least :-)

This setup as is was designed by the supplier--there are a few connection parts that were hard to get--1 was custom made.  I can't just change them.  My OAG can't be much closer to the reducer--right now its about 1/4 inch or so (don't know the actual distance to report in mm).  It can't be much less as there is not 1 part that will work.  The Prism arm can't be any shorter or it won't penetrate the light cone.  

[Davey-T]

That looks a pretty poor design of OAG to me perhaps it only works with a ZWO guide camera.

Dave

[Rodd]

36 minutes ago, Davey-T said:

That looks a pretty poor design of OAG to me perhaps it only works with a ZWO guide camera.

Dave

That would explain allot--but others use it with the Lodestar.  I have the capitol of gremlinville at my home, so I am not surprised that it doesn't work.  

[Davey-T]

Taken mine off to check, not much help maybe as it's an Atik setup, but can confirm that the CCD sensor and Loadstar sensor are both around 45mm but the Loadstar is in and adjustable holder that can be raised and lowered to focus it.

Are you sure the prism is fitted correctly flat face forwards and flat face upwards.

Dave

[Rodd]

33 minutes ago, Davey-T said:

Taken mine off to check, not much help maybe as it's an Atik setup, but can confirm that the CCD sensor and Loadstar sensor are both around 45mm but the Loadstar is in and adjustable holder that can be raised and lowered to focus it.

Are you sure the prism is fitted correctly flat face forwards and flat face upwards.

Dave

Prism is fitted flat face toward the scope, weird angle face toward the camera.  

[Davey-T]

53 minutes ago, Rodd said:

Prism is fitted flat face toward the scope, weird angle face toward the camera.  

I think it should have a flat face towards the scope and towards the Loadstar.

Dave

[Rodd]

Just now, Davey-T said:

I think it should have a flat face towards the scope and towards the Loadstar.

Dave

Well its a flat face toward the scope--but the lodestar sits atop the prism pedestal--its a hole

[Davey-T]

Like this.

Dave

 

[Rodd]

1 minute ago, Davey-T said:

Like this.

Dave

 

Yes--the prism is fixed to the pedestal, and there are only 2 ways to insert it--flat face toward scope or flat face toward imaging camera.  Mine is set flat face toward scope.

[Davey-T]

Then as I said if you look down the guide scope hole without the camera fitted, find a bright star and focus it roughly with the main focuser you should be able to focus it with the Loadstar to find where it focuses.

Dave

[Rodd]

7 minutes ago, Davey-T said:

Then as I said if you look down the guide scope hole without the camera fitted, find a bright star and focus it roughly with the main focuser you should be able to focus it with the Loadstar to find where it focuses.

Dave

I am returning the OAG.  I cant take this any more.  Thanks for the help....I am out of steam

Rodd

[Davey-T]

I use the OAG on my SCT but I have guided it successfully with various piggy backed guide scopes.

Dave

[Rodd]

I am thinking of an Astrodon MMAOG--or a good guidescope.  I might only use the ASI 1600 on my refractors and leave the STT-8300 for the C!!Edge

[Davey-T]

14 minutes ago, Rodd said:

I am thinking of an Astrodon MMAOG--or a good guidescope.  I might only use the ASI 1600 on my refractors and leave the STT-8300 for the C!!Edge

Probably the best pixel match anyway.

Dave

[Rodd]

7 minutes ago, Davey-T said:

Probably the best pixel match anyway.

Dave

All because SBIG won't change out y filter wheel, which I have been complaining about since I got the camera.  And I just realized the MMOAG is over $1,000.  

[Davey-T]

Wonder why they're so pig headed about it, the astro' community being relatively small and well connected you'd think they would change it for public relations purposes even if they think there's nothing wrong with it.

Dave

[Rodd]

1 hour ago, Davey-T said:

Wonder why they're so pig headed about it, the astro' community being relatively small and well connected you'd think they would change it for public relations purposes even if they think there's nothing wrong with it.

Dave

That's what I thought

[Clownfish]

I know this is obsolete now, but I just saw this and wanted to mention that I have a ZWO OAG, Lodestar X2, ZWO EFW and ASI 1600MM working together well.

I needed to add a 16mm spacer between the EFW and the ASI1600. camera.  So the final train is:
Scope > OAG > EFW > 16mm spacer > ASI1600MM

Then, the Lodestar could come to focus - BUT not when it was seated all the way into the holder.  I had to pull it out a bit - but not so much as to be unstable.
I could still lock the lodestar in - but not by much.  At least it works.

Peter

[newbie alert]

What oag is it, as a friend that uses a 1600 with a starlight xpress filterwheel  plus lodestar, and the other that uses a starlight xpress/ lodestar with a 383 have both needed to adapt theirs...

One shimmemed the face of a lodestar to give more inward focus, the other adapted the stalk in some way again to give more inward travel...