Celestron OAG qhy5l-ii

[rodrigol]

I'm currently testing my new OAG with a Nikon D7200 and ZWO ASI 290 on a C11 Edge HD and I can achieve focus with both quite easily. But getting focus with the guider camera, which is a qhy5l-iic, is not working for me. I also have a qhy5l-iim, which I've yet to take out of the box. 

The current setup is below and consist of C11 Edge reducer+OAG large SCT adapter (https://www.celestron.com/products/large-sctedgehd-adapter-for-off-axis-guider) +OAG + T-thread spacer + main camera. 

I've tried with a variety of CS-C spacers and ended up managing to focus the guide camera on a relatively far away tree with 2x50mm + 3x5mm spacers giving 115mm total. But this just looks silly and is unworkable at night. 

Can someone please comment and point me in the right direction, please? 

 

 

[Dr_Ju_ju]

Shrink the tube to the guide camera, to me it looks a little excessive.....

[Dr_Ju_ju]

Here's my setup, with OAG, FW etc.  I'm using a ASI120 mm as the guide camera, but when I had the QHY fitted, it wasn't far different

[rodrigol]

Thanks! It looks as if I've been adding too much when in fact I should have been using much less. Any idea if I have to remove the CS adapter from the qhy5l-ii? 

 

[Dr_Ju_ju]

You'll need an adaptor to mate the camera to the OAG, but after that I'm not sure as I don't have the exact same equipment.

FYI, the knob below the ST4 port, is the focus adjuster (by moving camera in\out), the one below that, is the 'intrusion' into the light path, which needs to be adjusted so that no shadows are cast on the main imaging camera, but the guide camera is able to 'see' enough stars. On some targets this can be problematical if not enough stars are visible....

[rodrigol]

Hi Dr_Ju_Ju, 

Thanks for comment 🙂 Do you find the ASI 120 is a good guider cam compared to the qhy5l-ii? They are different beasts and 0Need to know in order to decide if qhy5l-ii are any good for OAG guiding. 

Thanks! 

 

[michael8554]

As a rough guide, in the image below, X is roughly the distance from the OAG prism to the main camera chip, when in focus.

So the Guidecam has to be X from the OAG to the guidecam chip, to be in focus.

Oh, and you should really take the strain off the guidecam USB, such as taping the USB cable to the camera body, with a nice smooth curve to the socket, not the tight bend you have now.

Michael

Edited July 2, 2019 by michael8554

[MarsG76]

I think you need to shorten the distance.. I've had focus issues with my guide CCDs in the beginning and it was the distance of the camera in the OAG... 

 

[MarsG76]

to add to above... I recommend setting the focus in the DSLR and searching for focus in the OAG camera during day time.. that will give you a good indicator of where the OAG focus is.

[michael8554]

Slight redesign, my first image would only work with a Flip-Mirror.

 

[rodrigol]

Many, many thanks for the feedback. I tried again to get the setup working with a qhy5l-iim as that has a shorter Cs adaptor and is a more sensitive camera. I simply could not get to see anything to focus with on the guide camera. I may need to dissemble the oag from the scope and check the prism is low enough to capture some of the light path. It's weird because I really see nothing and I'm getting frustrated that the only way to see anything in daylight through the guider port is with a very long stack of adapters. 

I'll report back ASAP but first want to thank you guys for the help. You rock! 

 

Edited July 3, 2019 by rodrigol

[MarsG76]

18 minutes ago, rodrigol said:

Many, many thanks for the feedback. I tried again to get the setup working with a qhy5l-iim as that has a shorter Cs adaptor and is a more sensitive camera. I simply could not get to see anything to focus with on the guide camera. I may need to dissemble the oag from the scope and check the prism is low enough to capture some of the light path. It's weird because I really see nothing and I'm getting frustrated that the only way to see anything in daylight through the guider port is with a very long stack of adapters. 

I'll report back ASAP but first want to thank you guys for the help. You rock! 

 

Hope that you work it out.. OAG imaging open another level of imaging.

 

[michael8554]

You only need to remove the ZWO, then look in to see if the prism is in the light path from the scope. 

You do have the prism facing the right way, don't you......... 🙂 ??

I'd estimate the QHY needs to be almost directly attached to the OAG, without spacers. 

You should then be able to alternately focus the QHY and then the ZWO, with the ota focuser, to see how close you are to correct spacing. 

Or instead

Focus the QHY on a distant light with the ota focuser.

Then adjust the ZWO spacing, much easier to see that image's focus than the QHY. 

Okay, so then your critical Reducer spacing is wrong. 

 No problem, add/remove spacers to correct, add/remove same amount from QHY. 

Michael 

[rodrigol]

Hi Michael,

Many thanks for the tips. I believe the prism is the right way (diagonal facing the camera). I'll get home later on a check the height of the prism...

Again, many thanks for your advice!

 

[rodrigol]

Dropping the prism has improved things a lot. The ZWO 290 has a relatively small sensor so there is little to worry regarding the prism shadow. I guess it will be an issue with the DSLR. 

Some progress 😁

 

[rodrigol]

Argh. Have lost a lot of time on the oag and don't think Ihave the right guide camera for it. OAG will go in the box until I can afford one. Thanks everyone for your patience. 

 

[GraemeH]

Don't give up on it - I have the same guide camera (QHY5Liim) working in the Celestron OAG with my Edge HD8.  My setup had the camera screwed to a C-T adapter, then a 6mm T spacer (supplied with the OAG) and screwed to the guide turret (I've since modified it using a 1.25" 0.5x reducer screwed to the camera to increase the FOV for guiding, meaning that the camera now pushes further into the guide port to achieve focus).  I found the best way to focus everything was to get my main camera (DSLR) focused on a distant roof top using the primary mirror focuser in the scope, then adjust the guide camera focus using the helical focuser on the OAG.

Hope you get it working.

[rodrigol]

Hi GraemeH, 

Would you mind posting a picture of your setup? I've got the C11 edge focal reducer in as well but don't think this is getting in the way. 

Thanks for the support 👍

[GraemeH]

5 hours ago, rodrigol said:

Hi GraemeH, 

Would you mind posting a picture of your setup? I've got the C11 edge focal reducer in as well but don't think this is getting in the way. 

Thanks for the support 👍

I'll try to take a more helpful image to show my setup when I'm home later this evening, but for now I can share an older picture that might help a little.

Graeme

 

[rodrigol]

Hi GraemeH, Many thanks! You've got some nice output from your EdgeHD in astrobin! Congrats!

 

[rodrigol]

Hmmm... Maybe my issue is that I'm using the wrong m48 spacer between the oag and the main camera. I'm using the 11.55 spacer. I'll try without... 

 

[michael8554]

9 hours ago, rodrigol said:

Hmmm... Maybe my issue is that I'm using the wrong m48 spacer between the oag and the main camera. I'm using the 11.55 spacer. I'll try without... 

 

With respect, you can't just "try" removing and adding spacers to the imaging camera.

Firstly, the optimum back focus to the DSLR chip for the Edge Reducer is 146mm, so if you originally installed it correctly, taking 11.55mm out will make the spacing wrong, possibly leading to coma in your images !!

Secondly, in all the diagrams in the Celestron Off Axis Guider Manual, the guidecam is connected with only a 6mm spacer and a short M42 adapter on the camera.

That may not be exactly the correct spacing in your case, but for sure all those long spacers need to come off your setup.

Then place the guidecam chip X mm away from the prism as shown in my diagram.

The helical focuser gives you some wiggle room.

Michael

[rodrigol]

Your are right! I totally agree. I was just thinking aloud...

This is where I am at the moment but not have tested. I just want to know if this seems reasonable. I've used all the spacers at my disposal for the imaging camera to get ~146mm from the reducer. And given that, I've measured the distance from the centre of the OAG to the main camera sensor (~115mm) and reproduced that from the prism to the guide camera sensor. Does this make sense now?

Edited July 12, 2019 by rodrigol

[michael8554]

That's better, Reducer and guidecam spacing now look correct. 

Moon's out, an easy target to fine-tuned on! 

Michael 

[rodrigol]

Just wanted to report that I nailed it! 😁

Thanks to everyone that gave me their advice and time. 😎 This community rocks! 

I used the moon and focused the ASI1600MC first, moved it to the field of view of the guider, and proceeded as adviced here. Indeed the fov is narrow and a reducer is a great idea! 

Thanks to all!