so I had room for one more scope
picked up from Agenatelescopes GSO 8 inch CC
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Posted 08 December 2019 - 06:53 AM
Posted 08 December 2019 - 06:59 AM
scope itself came - no issues with body or mirrors
so went out and tried it and UGH image was a mess
so I did star test
it was awfully aligned
center disk was way off
so after an hour of playing the fiddle with secondary screws (BTW no instructions- had to use Orion document)
I got it centered
and WOW star image was quite good
so first lesson about this design
its similar to SCT in terms of sensitivity to being out of collmination
Posted 08 December 2019 - 07:03 AM
so of course moon dominated sky
so I did a few runs with that
scope comes with 3 extension rings
1) 2 inch
2) 1 inch
for most apps including visual and most small cameras (not DSLR's)
a 3 inch extension is needed
i did not try bino viewer but I will assume you need to remove extensions for that
Posted 08 December 2019 - 07:08 AM
so im generally pleased with scope
one thing it has an excellent cool down rate
it rather light weight
im just hoping it holds its collmination over time
Posted 08 December 2019 - 10:42 AM
Thanks for the nice review. Would using the 3” extension for visual use increase the focal length quite a bit? Agena says it collimates each of these scopes before shipping but I guess yours got misaligned during shipping.
Posted 08 December 2019 - 11:00 AM
the mirrors are fixrd no increase
you focus at the focuser at end like refractor
its just they allowed you to bite derp
into light cone so it adapts to many
yea i got certificate from agena
i was disappointed
but to be fair
it probably got knocked around
even though box was clean
its a pain because it takes a while to adjust
but at least nothing was broken or bent
its critical you get a good round collapsing circle for
star or else image degrades
Posted 10 December 2019 - 08:13 AM
Is this the first report of one from Agena that is not spot on? If so then it's bad luck. If not then it's something to take into account?
By this I mean it might change one's mind as to where one purchases the scope.
Posted 10 December 2019 - 10:17 AM
Glad you got a new scope. You are right, classical Cassegrains punish observers who don't keep them collimated. I would think your scope will hold collimation well, though. It's a pretty light weight scope, so not a lot of mass shifting around to throw it out of collimation. And I'm sure you'll be more gentle than the package handlers.
I wouldn't worry too much about receiving a scope out of collimation. My newest scope ("new", hah, it's four years old now) arrived out of collimation. Sure, it was a bit frustrating, but nothing was damaged and I got it collimated quickly enough, just like you did. I couldn't withhold a recommendation based on miscollimation.
There are some good threads about collimation in the Cats and Casses forum.
Your lunar photos are pretty impressive.
Posted 10 December 2019 - 06:12 PM
>>Is this the first report of one from Agena that is not spot on?
Every GSO scope is collimated before it leaves our warehouse. Shipping can be rough on scopes, and occasionally - as in this case - a scope might arrive out of collimation. We have had a handful of such reports but those have been a tiny fraction of the total number of scopes shipped. But with any reflector, a buyer should be able and willing to collimate the scope, especially after a long journey.
Edited by Agena AstroProducts, 10 December 2019 - 06:12 PM.
Posted 10 December 2019 - 06:26 PM
I managed to reach focus with my binoviewer using a short light path setup. Baader T2 prism TS binoviewer and direct coupling to the prism. My scope is the same as yours.
Posted 10 May 2020 - 12:52 AM
Beautiful lunar pictures! I received mine on Friday and had it out for first-light that night. The collimation was off just a smidge and was easy to fix. I may tweak is a bit yet as I'm hoping to use this scope for high resolution lunar and planetary imaging and observing. It'll be very interesting to see how it compares with my Mak 7. I'm still working through my first set of test images, but so far I am _very_ impressed with the flat, coma-free field. The focus doesn't seem to be overly sensitive to temperature as I only had to make one tiny adjustment of the focus around 4:00am, similar to a Newtonian.
Posted 10 May 2020 - 12:53 AM
M57 – The Ring Nebula in Lyra – GSO 8” f/12 CC First-Light
Telescope: GSO 8” f/12 Classical Cassegrain @ f/12, Orion Atlas EQ-G
Camera: Full Spectrum Modified Nikon D5300
Filter: 2” Orion Imaging Skyglow Filter
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 16x180sec, ISO 400, saved as RAW
Darks: Internal (Long Exposure Noise Reduction On)
Flats: 32x1/50sec, Sky flats taken at dusk
Average Light Pollution: Red zone, Bortle 8, fair transparency, bright moonlight
Lensed Sky Quality Meter: 18.1 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Backyard Nikon, Deep Sky Stacker, Nebulosity, Photoshop
Posted 10 May 2020 - 09:55 AM
That image was cropped a tad to zoom in on the nebula. Below is an uncropped version showing that there is very little coma across the span of an APS-c sensor...
I also have a 4-panel mosaic of the waining gibbous moon that demonstrated that the field is _very_ flat. I could had sneaked it into a 2-panel mosaic if I had know that ahead of time.
Still learning, which is a good thing!
Posted 10 May 2020 - 10:17 AM
Is it a crop or the coma is zero?
Coma is the same as for a F/12 Newtonian, pretty well nothing for this sensor. David
Edited by davidc135, 10 May 2020 - 10:24 AM.
Posted 10 May 2020 - 11:24 AM
Posted 12 May 2020 - 07:29 PM
Tonight I'm going to spend some time exploring the visual performance of the 8" f/12 GSO Classical Cassegrain. I've turned it over and mounted it on an LX70 using its Vixen rail; a nice option to have for star-hopping. Although there are benefits to fast scopes for deepsky, I enjoy observing with long f/ratio scopes as they usually give sharp, high contrast views. I'm also curious to see how it performs on double stars. I can't stay out late tonight, but it should be a lot of fun!
Edited by jgraham, 12 May 2020 - 07:30 PM.
Posted 16 September 2020 - 10:34 AM
Posted 16 September 2020 - 01:21 PM
1. The rails are not the same width, so neither are the mounting holes. At least not on the GSO/Orion/A-T/other-brands (but same manufacturer) CCs currently out. Can't just switch them "top-to-bottom".
2. A classic cassegrain uses a secondary supported by spider vanes, so of course it has diffraction spikes. But for planetary (non-point) targets, they are much less-to-not noticeable.
Edited by Thandal, 16 September 2020 - 01:27 PM.
Posted 16 September 2020 - 03:00 PM
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