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Trying to Set Up OAG

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#1 terry59

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Posted 30 September 2020 - 12:41 AM

I am adding OAG to my FSQ106. I have a SX filter wheel and purchased the SX guide head and ASI290mm mini. When I get the scope focused I can't get the guider anywhere near close. I have to move inward 600 steps for the OAG to reach focus but then the scope is way off. The stars are just long streaks when the scope is focused and PhD can't use them. I tried guiding with the guide stars in focus but the stars walk off the PhD screen. This doesn't happen with the normal guide scope.

 

Any help appreciated



#2 dayglow

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Posted 30 September 2020 - 12:59 AM

Sounds like you need to pull the guide camera outwards (away from the optical axis of the imager) by the distance equivalent to 600 focuser steps.



#3 terry59

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Posted 30 September 2020 - 01:04 AM

Sounds like you need to pull the guide camera outwards (away from the optical axis of the imager) by the distance equivalent to 600 focuser steps.

When I do that the guide scope is completely out of focus....thus my confusion


Edited by terry59, 30 September 2020 - 01:06 AM.


#4 Stelios

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Posted 30 September 2020 - 01:20 AM

If you need more in-focus, you need to add a spacer between the OAG and the filter wheel. 

 

All OAG configs are of this type (spacers are optional):

 

Focuser => [Front Spacer] => OAG => [Back Spacer] => FW => Camera.

 

If you need more in-focus, you need to reduce front spacer and increase (or introduce) back spacer.  If you need more *out* focus, the reverse. 


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#5 terry59

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Posted 30 September 2020 - 09:33 AM

If you need more in-focus, you need to add a spacer between the OAG and the filter wheel. 

 

All OAG configs are of this type (spacers are optional):

 

Focuser => [Front Spacer] => OAG => [Back Spacer] => FW => Camera.

 

If you need more in-focus, you need to reduce front spacer and increase (or introduce) back spacer.  If you need more *out* focus, the reverse. 

Yep, thanks....I need to figure out a solution now



#6 Jeff2011

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Posted 30 September 2020 - 10:35 AM

I have the same issue.  My new guide camera QHY5III-178 won't reach focus because not enough in focus.  Since the SX-OAG is bolted to the SX-FW, I had to add a  5 mm spacer between the FW and camera which worked but introduces some vignetting that is processed out with flats.  I don't know if SX makes a spacer that can fit between the OAG and FW.  A shorter stalk would work also.  I entertained the idea of grinding the stalk but was concerned about metal shavings getting in my image train. 



#7 terry59

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Posted 30 September 2020 - 12:27 PM

Starizona is looking into a ~5mm spacer to go between the OAG and filter wheel



#8 Peter in Reno

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Posted 30 September 2020 - 12:42 PM

Have you tried parfocaling main and guide cameras during the day? Cover the scope with aluminum foil and puncture a small hole in the foil to help control exposure times. Aim for telephone pole, street sign pole or tree trunks far away at least a half a mile away.

 

Peter 


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#9 terry59

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Posted 30 September 2020 - 01:36 PM

Have you tried parfocaling main and guide cameras during the day? Cover the scope with aluminum foil and puncture a small hole in the foil to help control exposure times. Aim for telephone pole, street sign pole or tree trunks far away at least a half a mile away.

 

Peter 

Great idea Peter. Right now we are having a lot of smoke and visibility is poor though



#10 APshooter

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Posted 30 September 2020 - 01:58 PM

Just in case this helps:

 

https://www.cloudyni...flexure-solved/


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#11 terry59

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Posted 01 October 2020 - 07:15 AM

Just in case this helps:

 

https://www.cloudyni...flexure-solved/

Thanks....the answer is obviously a spacer. The problem I have is that the SX OAG piece bolts on to the SX filter wheel  and I don't know of any way to insert a spacer there. I have added a 5mm spacer between the camera and filter wheel which should solve the issue although it is not the correct way. I went this way because I thought it would be straightforward but I'm thinking I may have been better off getting one from QHY that has spacers 



#12 APshooter

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Posted 01 October 2020 - 04:31 PM

Can you insert a spacer after the OAG, between it and the camera?  Note that on my setup I had to move the camera back by 7mm in order for the guide cam to achieve focus.  Even then I added a Scope Stuff C2TT adapter to my lodestar to get it to attach to the focuser stalk (Atik OAG).  At the risk of sounding too simplistic, both cameras need to be parfocal and it takes some finagling to get the spacers in so that both come to focus together.  Once it's set, however, you should never have to change it ever again.  In my case it was far easier to move the camera backwards to let the guider come into focus than the reverse.

 

Find the best focus with the guide camera.  Make note of the focuser position(on the scale or with tape on the barrel).  Now without touching the guide cam, focus the main camera.  Note the focus position on your focuser.  The difference is the size of spacer you need to get both cameras parfocal.  Insert that spacer between the OAG and camera.


Edited by APshooter, 01 October 2020 - 04:35 PM.


#13 Deesk06

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Posted 01 October 2020 - 09:13 PM

Plenty of great responses here.

I am going to keep it sweet and simple. The distance from the main camera to the OAG mirror should be the same distance between your guide camera and OAG mirror (As APshooter mentioned).

When installing it I just made sure to guestimate/measure where the guide camera sensor was. This required me to add spacers.I then went outside during the day and played around with it. I did this again last night, still worked fine.

Keep it simple and don't overthink it. Focus on getting the two distances as close to equal as possible using whatever spacers you need. Bring your main camera into focus and then slightly move the guide camera in/out until that reaches focus as well.

Edited by Deesk06, 01 October 2020 - 09:19 PM.


#14 terry59

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Posted 02 October 2020 - 03:44 AM

Plenty of great responses here.

I am going to keep it sweet and simple. The distance from the main camera to the OAG mirror should be the same distance between your guide camera and OAG mirror (As APshooter mentioned).

When installing it I just made sure to guestimate/measure where the guide camera sensor was. This required me to add spacers.I then went outside during the day and played around with it. I did this again last night, still worked fine.

Keep it simple and don't overthink it. Focus on getting the two distances as close to equal as possible using whatever spacers you need. Bring your main camera into focus and then slightly move the guide camera in/out until that reaches focus as well.

Thanks....yeah, this was supposed to be plug and play since the backfocus of my camera is the same as the SX model. What I have found in reality is that the SX guide head needs to be a few mm thicker or needs the ability to add spacers between it and the filter wheel. My temporary solution was to add a 5mm spacer between the camera and filter wheel


Edited by terry59, 02 October 2020 - 07:15 AM.


#15 Jeff2011

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Posted 02 October 2020 - 11:09 AM

yeah, this was supposed to be plug and play since the backfocus of my camera is the same as the SX model. 

Terry, I suspect the reason you could not focus is the distance between the guide camera's sensor window and the chip.  If you used an SX guide camera then it should have worked.   My old QHY5L-IIm was able to reach focus because I had to take the sensor window off  (it just unscrews) to get to the threads to mount it on the OAG stalk.  With my new QHY5III-178m I do not have to remove the sensor window to attach it to the stalk, but because of the additional distance between the sensor window and the chip,  I can't reach focus without adding a spacer between the FW and camera.  Removing the sensor window exposes the chip to dust and risks damaging the sensor if adjusting down to much on the stalk so that is why I had not tried that with the new camera.    

 

I suspect precise parts could come up with a spacer between the OAG and FW but that would be expensive.  I hope Starizona can find something less expensive than a PP solution. 



#16 ezwheels

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Posted 02 October 2020 - 12:14 PM

I am not certain it is possible as I have never tried but, would it be helpful to unthread the front bezel from the 290MM mini?

 

asi290-e1506067226580.jpg



#17 Jeff2011

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Posted 02 October 2020 - 01:35 PM

I am not certain it is possible as I have never tried but, would it be helpful to unthread the front bezel from the 290MM mini?

 

 

Yes thanks for posting.  That is exactly what I was talking.   I had used my QHY5L-IIm with the bezel removed for years and it worked well except for the occasional dust I would get if I removed the camera from the stalk for other purposes.  But if the camera remains attached to the OAG there is little additional dust that can get in.  The QHY5L-II also has some foam packing around the sensor to protect it from the OAG stalk but my new QHY has a bigger chip and does not have that packing so I am hesitant to try removing the bezel.   I am also not sure if the threads are compatible with the OAG adapter once the bezel is removed from my QHY5III-178 or Terry's ZWO.


Edited by Jeff2011, 02 October 2020 - 01:40 PM.


#18 ezwheels

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Posted 02 October 2020 - 05:35 PM

Ignore my post. I did not know the SX OAG is meant to have the camera threaded to the stalk. I though it was maybe a compression type like the QHY and ZWO versions. 



#19 Peter in Reno

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Posted 02 October 2020 - 06:11 PM

From ZWO web site for ASI290mini:

 

https://astronomy-im...290mm-mini-mono

 

The default back focus for this camera is 8.5mm. The SX FW and SX OAG along with an imaging camera with 17.5mm back focus require the back focus for guide camera to be 12.5mm. Your guide camera should come with M28.5-CS adapter which is 4mm thick which should give your guide camera's back focus to 12.5mm. Have you tried the 4mm adapter to screw into ASI290mini? Hopefully the 4mm adapter will also screw into SX OAG's guide port.

 

Peter



#20 terry59

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Posted 03 October 2020 - 04:33 AM

From ZWO web site for ASI290mini:

 

https://astronomy-im...290mm-mini-mono

 

The default back focus for this camera is 8.5mm. The SX FW and SX OAG along with an imaging camera with 17.5mm back focus require the back focus for guide camera to be 12.5mm. Your guide camera should come with M28.5-CS adapter which is 4mm thick which should give your guide camera's back focus to 12.5mm. Have you tried the 4mm adapter to screw into ASI290mini? Hopefully the 4mm adapter will also screw into SX OAG's guide port.

 

Peter

Hi Peter.....yes there is a 4mm thick piece with the sensor cover that is flush with the top of the camera housing first, then the 4mm thick M28.5-CS adapter that threads into the first piece. The OAG stalk bottoms out at the sensor cover and needs to get closer to the sensor even though the spec says the spacing should now be correct. There is enough space in the housing to get 3mm closer to the sensor. I am trying to figure out what the thread is on the sensor side...it is more than M28.5. When I figure that out (does anyone know what it is?) I am thinking of getting a zero profile adapter that would allow me to get closer but I'd lose the sensor cover protection



#21 Peter in Reno

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Posted 03 October 2020 - 08:48 AM

Hi Terry,

 

You have not yet specified the main camera used for your new SX FW and OAG setup. Your signature says QHY183M and Atik 383L+.

 

If you are using Atik 383L+ camera, then the solution should be simple by screwing M28.5-CS adapter to 290mini and screw M28.5-CS adapter to SX OAG guide port.

 

If you are using QHY183M, then it gets confusing because QHY web site does not clearly specify the back focus of QHY183M according to:

 

https://www.qhyccd.c...atid=193&id=114

 

So, can you tell us which camera you plan to use and if it's QHY183M, can you tell us the connection between QHY183M and SX FW? What adapters are you using in between QHY183M and SX FW?

 

If you are using QHY183M, you need to get appropriate adapters to get main camera's total back focus of 17.5mm to work with SX FW properly and 12.5mm back focus guide camera.

 

Thanks,

Peter



#22 terry59

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Posted 03 October 2020 - 08:48 AM

I am not certain it is possible as I have never tried but, would it be helpful to unthread the front bezel from the 290MM mini?

 

attachicon.gifasi290-e1506067226580.jpg

 

 

Yes thanks for posting.  That is exactly what I was talking.   I had used my QHY5L-IIm with the bezel removed for years and it worked well except for the occasional dust I would get if I removed the camera from the stalk for other purposes.  But if the camera remains attached to the OAG there is little additional dust that can get in.  The QHY5L-II also has some foam packing around the sensor to protect it from the OAG stalk but my new QHY has a bigger chip and does not have that packing so I am hesitant to try removing the bezel.   I am also not sure if the threads are compatible with the OAG adapter once the bezel is removed from my QHY5III-178 or Terry's ZWO.

 

 

Ignore my post. I did not know the SX OAG is meant to have the camera threaded to the stalk. I though it was maybe a compression type like the QHY and ZWO versions.

The sensor cover is at the bottom of the 4mm bezel and sits flush with the top of the camera body. I've removed the bezel, added the M28.5-CS adapter and threaded those onto the stalk. The combination threads fully onto the stalk, the sensor cover sits flush with the top of the stalk and the adapter/bezel sits fully against the focal adjustment locking screw and just above the locking grub screw. I think a zero profile adapter threaded onto the body instead of the bezel/M28.5-CS adapter would allow me to get closer but without any protection for the sensor. I'm out of ideas for getting the sensor any closer at this point. I'll be trying to see if they focus with the 5mm spacer later this morning

 

sigh2.gif


Edited by terry59, 03 October 2020 - 08:50 AM.


#23 Peter in Reno

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Posted 03 October 2020 - 08:53 AM

It would be easier if you tell us what main camera you are using. See my post #21.

 

Peter



#24 terry59

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Posted 03 October 2020 - 09:33 AM

It would be easier if you tell us what main camera you are using. See my post #21.

 

Peter

Hi Peter....sorry I'm using the 383L+...the SX version, mine and Jeff 2011's all have the same backspace. Theoretically they should all plug and play but since the two of us are having the identical problem with identical equipment except the guide scope...all I can say is that the OAG guide head needs to be a few mm wider


Edited by terry59, 03 October 2020 - 09:34 AM.


#25 sn2006gy

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Posted 03 October 2020 - 09:47 AM

I am not certain it is possible as I have never tried but, would it be helpful to unthread the front bezel from the 290MM mini?

 

attachicon.gifasi290-e1506067226580.jpg

It definitely comes off because i unscrewed one of the included adapters and it took that right off. Kind of surprised me lol


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