Jump to content


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Help Selecting a Camera for Edge 925

  • Please log in to reply
1 reply to this topic

#1 Aerialistic


    Lift Off

  • -----
  • topic starter
  • Posts: 1
  • Joined: 02 Jun 2019

Posted 20 September 2019 - 07:39 AM



Short time lurker, first time poster. I'm finally at a loss. I know an SCT isn't the ideal first time scope. Eventually I'll save up and get a small refractor, but in the mean time, it is what it is. I was gifted it, so its what I've got at the moment. 


EdgeHD 925

EQ6R Pro Mount

.7x Focal Reducer

ZWO OAG w/ ASI120MM Guide Camera


My question is what camera should I buy.  I'm still debating between OSC and Mono, with a strong leaning toward OSC. I've been doing a lot of research, and I'm delving into the areas of FWHM and Pixel Scale. Initially I was thinking of the ASI294MC, but the pixel scale is .58. Can I use binning to bring it to a more acceptable level? Or is there a better camera I should be looking at?


Thanks for the input. Sorry if this is a repeat question, I've exhausted my ability for internet searches and my head hurts from all my reading.  

Edited by Aerialistic, 20 September 2019 - 07:39 AM.

#2 TelescopeGreg


    Surveyor 1

  • -----
  • Posts: 1,665
  • Joined: 16 Jul 2018
  • Loc: Auburn, California, USA

Posted 20 September 2019 - 12:22 PM

Do you have a DSLR?  If so, I'd start there.  All it takes is a T-ring for whatever brand camera you have.


Regardless of the camera, your issue will be that even with the 0.7 reducer you've got a rather long focal length (1,645mm if my math is correct), which is about 3x what most targets are best framed with.  So besides the pixel scale being a bit small (though not impossibly so), you're aiming a long telephoto lens at the side of an elephant at the zoo.  In the dark.  Hand-held.  The theme for the rest of this is controlling any and all sources of tracking error.  Microns count, and the long focal length magnifies not only the target (which doesn't need magnifying - DSO objects are generally large and dim), but any teeny-tiny little jiggles too.


So, the first priority is to stabilize the image tracking.  You have a good mount, but no mount is perfect.  This means getting an auto guider system of some sort, either a separate guide scope and camera, or an "off-axis guider".  The OAG is more appropriate for your longer focal length, but it's more expensive.  What a guider will do is watch the background star field and use any tiny movement to send "nudge" commands to the mount to correct its aiming.  You will need a computer of some sort (nothing fancy) at the mount to connect the guide camera to the mount, running software such as PHD2 to perform the guiding function.


With the guider in place, the camera can also be used to get your polar alignment dialed in.  The mount's polar axis must be exactly aligned with the Earth's rotation axis, or the imaging target will drift.


Also practice getting everything well balanced, and make sure the telescope tripod is on firm footing.  A raised wooden deck in the back yard is likely not good enough.  Microns are really small.


Finally, all this will take some patience and practice to set up and get everything adjusted.  Take your time, and think about controlling any source of positional or tracking error.  DSO AP is a hobby of a bazillion little tiny details.  None of them are all that difficult, but there are a lot of them.  At some point it will seem overwhelming, but take a deep breath and you can get through it. 


Good luck!

  • Swordfishy likes this

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Recent Topics

Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics