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OAG with Dim Stars

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#1 philwollenberg

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Posted 23 September 2018 - 07:10 PM

Lookings for a little help here.  I have the following setup:

Televue NP-101IS (540mm FL)

Losmandy G11

Celestron OAG w/ QHY 5L-IIM

SBIG STF-8300M w/ FW8-8300

 

I have been having mixed results with this setup in terms of guiding.  I am always around 1.5-2” avg RA and Dec guiding.  I normally let PHD choose the guide star.  When I do this, often it loses the star. More recently I tried to choose my own with a little better brightness.  Many of the brighter stars are peaked out.  I have tried to choose a longer exposure which allows the faint stars to be more developed and I was hoping to average the seeing.  This actually seems to not work as well as say 1-2sec.   My gain has been around 10.  Here is what I was thinking.  Perhaps with the OAG, the very faint stars have a width far less than seeing (due to my long 540mm FL).  PHD likes them due to the shape and picks them.  I am thinking I need to pick a larger guide star by setting my QHY gain low to allow a deeper well.  I will get only a few stars but they will be larger but not peaked and be less affected by seeing.  I can attach logs if needed.  Thoughts?

 

Phil

 

 



#2 baron555

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Posted 23 September 2018 - 07:26 PM

Try a different guide camera.  Like a Lodestar X2.



#3 philwollenberg

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Posted 23 September 2018 - 07:34 PM

I recently bought a SBIG ST-I.  I have not had it out yet.  Would this be on the right track?



#4 the Elf

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Posted 24 September 2018 - 02:11 PM

Is there a reducer in the OAG? There is an expensive one on the market that has a reducer included. I got a cheap 1.25'' reducer from TS on my guide cam. That gives a larger FOV and a wider selection of stars and boosts the signal. See here: https://www.youtube....h?v=S3lZcLt_zDU   at 8:15.



#5 pedxing

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Posted 24 September 2018 - 02:19 PM

Set up binning in the camera driver. That will raise your guide star SNR values significantly.


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#6 Goofi

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Posted 24 September 2018 - 02:34 PM

I've got the older version of your scope (NP-101), and use an OAG all the time with it. I've never had an issue finding guide stars.

 

I'd check the binning on your guide camera. I run mine binned 2x2; but I have a pretty sensitive camera. Others I know run theirs binned 4x4. I don't think you need to change cameras or software or anything else, just a setting in PhD2.  smile.gif

 

 

Oh, as for the guide RMS ... that could be good, depending on what image scale you are imaging at. If you feel it's off, check your balance on the mount first, and settings in PhD second.




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