I am about to receive my first 80ED refractor and wanted to try imaging beyond 30 seconds with it. Y'all been there before too right?
Most folks would use this as their cute guidescope but this will be my primary imaging refractor (for now)... but it seems silly to have a 60mm guidescope or something on an 80mm scope! What's the picture I'm not seeing here?
How do you guide a guidescope (80ED)
Started by
m1618
, Apr 10 2014 03:49 AM
2 replies to this topic
#2
cloud_cover
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Viking 1
Posted 10 April 2014 - 05:23 AM
Try a 50mm finder/Guider. Lots of flavors available from places such as Astronomics (Forum Hosts 
), Agena, Orion, Stellarvue etc. Just make sure you get a good, rigid ring system. Be very wary of using spring loaded brackets (as in most of them except Stellarvue and Astronomics) as that will introduce lots of flexure. Such a setup, properly mounted will be good for up to 1000mm and possibly more.(I personally regard a resolution ratio of 1:5 as being safe, that is, the actual sampling resolution of each pixel (in arcsec) of the imaging scope vs the guidescope. This calculation of how much sky each pixel "sees" takes into account the focal length of each scope as well as the size of the pixel on each CCD) One thing I like about the 50mm setup is often I don't need to find a guidestar. There's usually one available almost anywhere I point up to 2s guider CCD exposure so I don't really have to fiddle with the guidescope's alignment.
You can also DIY one of these by getting an adapter to join the T-Thread of most CCDs to the (usually SCT Male, for Celestron, Orion and Vixen finderscopes, or at least the ones I've handled. I'm not sure about other brands) threads of the 50mm finder.
Hope it helps!
), Agena, Orion, Stellarvue etc. Just make sure you get a good, rigid ring system. Be very wary of using spring loaded brackets (as in most of them except Stellarvue and Astronomics) as that will introduce lots of flexure. Such a setup, properly mounted will be good for up to 1000mm and possibly more.(I personally regard a resolution ratio of 1:5 as being safe, that is, the actual sampling resolution of each pixel (in arcsec) of the imaging scope vs the guidescope. This calculation of how much sky each pixel "sees" takes into account the focal length of each scope as well as the size of the pixel on each CCD) One thing I like about the 50mm setup is often I don't need to find a guidestar. There's usually one available almost anywhere I point up to 2s guider CCD exposure so I don't really have to fiddle with the guidescope's alignment.You can also DIY one of these by getting an adapter to join the T-Thread of most CCDs to the (usually SCT Male, for Celestron, Orion and Vixen finderscopes, or at least the ones I've handled. I'm not sure about other brands) threads of the 50mm finder.
Hope it helps!
#3
m1618
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topic starter
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Posted 11 April 2014 - 12:48 AM
Thanks for the tip! I got on it right away and found some old DIY posts using typical 50mm finders.
For the sake of others going down this similar path...here's what I ended up doing:
1.5 x 1.0 PVC bushing (part#049081133269 Home Depot) $0.86!
Grind down the misc. pvc sticking out on top to make the guide scope press flush flat. Use thick tape to provide friction between bushing, nose piece, barrel, and to scope.
The main thing I want to contribute to the DIYfers out there is that the White Meade LXD75 era type finder was just 2-3mm shorter in FL than the Blue one that came with my SCT. The white one reached focus without any modifications! Whereas the Blue one didn't snap into focus. Luck? Heck, my SSAG was used $100 and spare finder was in my parts bin. Happy.
For the sake of others going down this similar path...here's what I ended up doing:
1.5 x 1.0 PVC bushing (part#049081133269 Home Depot) $0.86!
Grind down the misc. pvc sticking out on top to make the guide scope press flush flat. Use thick tape to provide friction between bushing, nose piece, barrel, and to scope.
The main thing I want to contribute to the DIYfers out there is that the White Meade LXD75 era type finder was just 2-3mm shorter in FL than the Blue one that came with my SCT. The white one reached focus without any modifications! Whereas the Blue one didn't snap into focus. Luck? Heck, my SSAG was used $100 and spare finder was in my parts bin. Happy.
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