Back to forums

Moravian C5 and CDK12

Russell Croman Astrophotography BlurXTerminator Equipment CMOS
Moravian Users •2 replies•53 views
Timothy Martin avatar
Timothy Martin avatar
I've only just started my journey with this combination, but results have been better than I expected. I wanted to put my initial thoughts here in case anyone else is considering using a C5a-100M camera with the CDK12.

Planewave advertises a 52mm image circle with the CDK12. The C5a-100M has a 54.83mm diagonal. So I was worried I would have to crop around 10% of all my images to deal with this. What I have noticed is that the corners of the sensor are still illuminated enough for flats to deal with any vignetting. But there's some pretty significant astigmatism showing up in the stars right at the corners and a bit less so around the left and right edges. The good news is that it's not so bad that BlurXTerminator in Correct Only mode can't take care of it. Before BXT v2, cropping might have been necessary. And that still may be the case sometimes. But BXT 2 seems to be able to salvage these areas pretty well, so I will frame my targets as though the whole field is available to me.

I would appreciate any other thoughts or comments on this Moravian and Planewave users might have.

CS,
Tim
Well Written Helpful Insightful Engaging
Roberto Botero avatar
Roberto Botero avatar
Tim

Well your evidence agrees with mine even though I don't have a CDK12 or am remote.  I have had my C5 since December 2022 and use it with a 6" f/7.5 refractor (in fact f/5.6 as I use a reducer).  Flats correct for illumination but there is distortion as my reducer doesn't fully correct the field.  BlurXT is magic for those corners and I'm not particularly fussed about AI for this correction.

I also concur with how power hungry the C5 is (as per your other post).  There have also been issues with the USB board of early units and power supply.  Mine was the first where this issue ocurred.   See C5 thread on CloudyNights for details.

Roberto
Timothy Martin avatar
Timothy Martin avatar
Roberto Botero:
See C5 thread on CloudyNights for details.


Interesting thread on CloudyNights. Thanks, Roberto! I wish I'd seen it sooner. I'll post these comments here and over there as well.

I definitely had the power board issue on the first C5 and had to replace and the controller board. That cost me a trip to New Mexico.

And like you, I learned to take darks (and flat darks) at night on roof-closed nights because of the leaky shutter. I have a PLL Alto-Giotto flat panel/cover, but it doesn't seal up tight, so darks during the day are no bueno. But that's no big deal.

I also notice that stretching a dark reveals the seams between the sensor panels. I do seem to remember reading somewhere that the IMX461 is four sensors stitched together. The only time this manifests for me is when I'm trying to capture really, really faint Ha or something along those lines. 

I was initially concerned about the balance issue with that giant filter wheel. I even started off the first few months with the filter wheel rotated 180 degrees. But when I went out to swap the power and CPU boards, I switched it back. That was creating a pier collision issue for me on some targets close to the zenith. The only solution was to just not image those targets withing 8 degrees of the zenith. The rig's OTA is a TOA130. Swapping the filter wheel back to its initial position created a better solution for that issue: just rotate the camera 180 degrees. No more collision issue. I haven't seen any tracking issues do to the imbalance that creates. The TOA is on a 10u GM2000. We'll see what happens with the CDK12 with C5 that I'm about to take out there. I only had one night to field test that rig at home. The CDK will also be on a GM2000--but it will be carrying a lot more weight to begin with. 

I am NOT using the Moravian OAG on the C5. I have a Moravian OAG on the C3 and it's not great. Cheaply made, hard to focus, and it has no way to adjust the prism stalk height. Fortunately, it works okay on that rig, which is a reduced FSQ106. No problem getting stars. But on both the TOA and the CDK, I'm using Optec Sagittas. That required a couple of adapters from PreciseParts, but that was no big deal. The issue I had with the Sagitta was that there was a reflection coming from somewhere near the stalk. Kevin Morefield was actually the person that alerted me to this issue with the Sagitta. It was causing thin streaks to show up at the top-center of the frame extending down about 300 to 500 pixels. Not good. Kevin and I both verified that it was the Sagitta by rotating the OAG slightly. The streaks rotated accordingly. Optec worked the issue very quickly and added some flacking in the spot that was causing the reflection and sent me a brand new one (I sent the other one back once I had the new one). That solved that problem. 

I also had the issue of dew forming on the sensor window when cooling at or below 0C even with the internal dew heater at 100%. On Pavel's advice, I have a dew strap around the OAG-to-focuser adapter. I just always turn that on to 50% (it's plugged into a Pegasus Astro Ultimate Powerbox). I have a trigger in NINA to rap that up to 90% if humidity climbs about 70%. That solved the problem.

What really concerns me is the crack in the lower left corner of the sensor window glass that has been showing up on these units. I haven't seen that yet but dread the day that I do. I'll have two C5s (and a C3) out at Deep Sky West. The last thing I want to have to do is decommission one of my scopes for a month for repairs.
Helpful Insightful