Not Always Smooth Sailing

[Mike Lewis]

So many who are regulars here have noticed that I just have not been posting any of my own astro images lately. My current setup of having my gear remotely located in AZ and myself in CO can yield great results but I am often not able to use my equipment whenever I would like, as I do rely on my astro friend who lives down there for some set up and power up tasks. Additionally, I have been working on getting an older large observatory mount reconditioned so that I could potentially deploy it down there. Unfortunately, that plan is currently on hold. However, even those 2 situations do not explain my current issues, as I now appear to be in the middle of some troubleshooting, ever since I deployed my new APS-C sized astro camera down there. It now appears that my imaging refractor has issues.

To give an idea of the problems, here is a star field aberration images, that shows the center and corners of what is a critically focused frame, a 30 second image through my new luminance filter:

YUCK. That is awful. There are one or 2 more things to experiment with, but testing so far points at the telescope and not the camera as the problem. I think the larger size sensor on the new camera has contributed to making the issues more obvious perhaps. In any case, this is all unfortunate as the monsoon weather in AZ is finally dying down and I was looking forward to getting some new and exciting datasets with my new QHY268M camera.

Hopefully I can get this issue sorted out, although if the scope needs to go in for repair the manufacturer has already told me they are so backed up that any non-warranty repair like this one will not be able to happen until at least the beginning of the year.

So I am likely offline for at least a while more, but I will continue to check in to enjoy all of the great posts from the many other exceptional astrophotographers here on FW!

ML

 

[AlanLichty]

bummer.......

 

[Ben Egbert]

Sorry to hear.

 

[JimFox]

The Upper right looks really great and the upper left is pretty close. A Collimation issue?

That's too bad. You have been plagued with issues for almost 2 years now. Could this tie into the issue you had last year?

What about the Celestron Edge HD you got? Why not install that and use that?

Also, a new thought. What if you used a reducer on this? Wouldn't that reduce the problem enough that you could use the scope for now?

I am thinking you need to make a trip down to Arizona. Lot's of cool landscapes to take in on the way. I will be going through Arizona in 2 weeks heading towards Santa Fe, we could meet up!

 

[CRTAstro]

I use this diagram to diagnose similar problems and from afar it looks like you may have a 'sensor too far from the flattener' situation. Could also be a bit of tilt as well which is pretty hard to pinpoint as I am in that situation as well

 

[Mike Lewis]

Thanks everyone for chiming in, and for the support on this. What seemed like it would be a banner year for astroimaging has turned out to be pretty much a bust. But that is the way this stuff sometimes goes unfortunately.

@JimFox - Well the Edge 9.25 is planned to go to AZ but is still awaiting rings. The vendor has supplier problems, so unclear when that could get resolved. I have tentative plans to head down in November, hopefully at least that issue is resolved by then. As for collimation, we may check that but it seems highly unlikely since the scope was OK previously and has not been dropped or banged or even transported anywhere since then.

@CRTAstro - Thanks for the diagrams Carlos, I have seen those elsewhere, they can be very helpful. In this case though, the issue is that this is already a 4 element scope, with the flattener built in and supposedly spaced at the factory to the proper spacing. Once that is done then everything should be good once you come to focus. It is possible the corrector has shifted or tilted, but because of issues with disassembly and unavailability of factory service at this time it has not been possible to gain complete access to the corrector. Disassembly has only been able to proceed so far:

This shows the corrective element but still behind the assembly that the focuser threads into. Even with guidance from the factory we are stuck at this step. Feeling the corrector while wearing gloves does not seem to indicate that it is loose however.

Next 2 debugging steps will be to put my friend's QSI683 (same size sensor as my ASI1600 I was previously successfully using on this OTA) on to the scope and see what that looks like. I may also have another friend down in the area in AZ that is using a QHY268C, so I will see if he would try mounting my new QHY268M instead (assuming the different backfocus requirements between the 2 setups can be worked) and then taking a few representative frames. Not sure what may come out of all that. I will post some updates here when/if any new findings come out.

ML

 

[Mike Lewis]

So the plot thickens. last night my friend in AZ put his astro camera (an older CCD-based QSI683 mono camera) on my telescope. This was a significant test because not only is that a separate known working camera from my new QHY268M used to take the ugly shot above, but significantly it also has the same size (smaller) sensor as the previous camera I was using with this scope (an ASI1600 mono). Here is the results of a 30 second frame taken with this newly mounted CCD camera on my same telescope (after it was reassembled of course).

Well, THAT certainly looks better, as well as much more like the results I was previously getting.

So now the analysis switches back to my new camera/filterwheel combo. Starting to think that perhaps some internal reflections are causing issues. The next test will be to remove one of the filters and then do comparison shots between the luminance slot and an empty filter slot. One does note that the inside of the QHY filterwheel is somewhat shiny - not what you would expect. I have also noticed that my adapter stack between the camera/filterwheel and the OTA is using a different QHY supplied spacer/adapter than is shown in their documentation. Not sure if that could be contributing to a light leak of some kind?

Next tests to come hopefully Friday night, weather permitting...

ML

 

[Mike Lewis]

P.S. - lines in this image are column defects in the CCD. Quite a common issue with these type of cameras, and something that does calibrate out with dark frames...But I am glad to be in using a CMOS instead of CCD camera for this as well as many other reasons.

ML

 

[JimFox]

Interesting Mike.

I would think though that it wouldn't be reflections from inside the filter housing. I can't imagine others would not have had the same issue unless this filter wheel housing was just released and you are one of the first users? If it's been out a while, Others should have noticed and contacted QHY about the issue and it would have been resolved. Have you had a chance to google the Filter housing to see if there are complaints about reflections?

Could the sensor not be flat?

I do agree that testing your set up again without a filter in the slot would be valuable, or perhaps just remove the filter assembly all together and add a spacer in the image train instead?

All that has changed from your old setup is the camera and filter housing?

The new moon is next week, perhaps you need to drive down to Arizona so you can test it out first hand?

 

[CRTAstro]

It's looking more like a tilt issue in the camera/efw train if everything else remained the same in the latest test. Maybe replace the efw with a spacer to eliminate it as a suspect. Troubleshooting is so much fun !