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like I said we are stumped because for a few subs the other night the halos shrunk drastically and deconvolution in PI and blur x both worked correctly
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1.20
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check for dew or icing on the camera/filters/optics?
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8.34
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Having had a CDK 14 for several years I have to say I have never seen anything like this. Mine is stock as far as fans go and I used to run them at 100% and now have throttled that back to about 75%. Heater is also stock and I run PWI3 (which uses backplate temp instead of mirror temp for the primary since I do not have their focuser). When imaging it is set to maintain 1.2 degrees above ambient. Also, I do not have the shroud on mine. Yeah, I know lots of folks use the shroud but frankly I think using a shroud is counterproductive unless you have a lot of ambient light issues (for which there are better solutions). It is just a sail asking for wind and guide issues and my with and w/o shroud tests have convinced me that I am right. I would at least have a look at one other possibility. What mount is it on and how windy was it on nights when you saw this? Since it is more on brighter stars, I have to wonder if it is not doing occasional quick guide excursions away from ideal and the nearly undetectable guide results only show up when BXT finds them and thinks they are real detail. The question I would ask is are the "false stars" always in the same place relative to the main star from one sub to the next and one night to the next and do they happen more on windy nights? If they are always in the same numbers and positions, then it is probably thermal or more likely optical, if they move around and/or are better on calmer nights, maybe guiding. FYI, mine is on a L350 and beyond a certain wind level (especially if it is gusty) I forget about using the CDK and switch to my secondary short FL scope. As far as a collimation check, I would suggest Innovations Foresight system as it can give you a number. |
0.90
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I've looked at both your fits files and didn't see anything out of the ordinary. I ran btx on them and did a good job. Do you have a Delta-T on your CDK? If not, I recomend one depending your temperature swing. Comparing your images to a couple of mine with my CDK14 they look good.
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1.51
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Bill McLaughlin: Yea , I use pwi3 with delta t to control the heaters using the dew heater management script that uses an ASCOM RH sensor. Run the fans all night via the Pegasus Astro variable voltage output. i also don’t use the shroud because like you said even with the slightest breeze it ruins everything haha cdk14 is riding on the same mount as my ago idk was , paramount me2 and even when I saw guiding excursions because of wind I never saw anything like I am with the PW I’ve checked for dew , filter etc etc I’m out of options now and the only thing I can think of is the halos are from either A) some sort of reflection internally B) boundary layer issues or C) Matt though at worst something with the baffle or corrector. I have seen others with the issues with the spots after deconvolution caused by either the shroud interfering with the light path or temperature issues but like I said both Matt from PW and I have never seen those halos before , leading to the spots. The halos are definitely the cause of the spots after deconvolution. cant be guiding also because you can see them on shorter exposures with and without guiding and I can go 6 minutes without guiding before I see any elongation with the me2. All I know is when those halos finally go away and I get normal looking stars the issue with decon goes away. |
8.11
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Is it possible to take a test image with a clean imaging train, nothing between the optics and the sensor?
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1.51
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Tony Gondola: Yes , I already did I’ll post it when I get near my computer for you. thanks for trying to help , calms my nerves haha |
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1.51
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Tony Gondola: If this helps any here is the raw halo and and accentuating its features   in the raw if you look also close enough you can just make out the dark rings and that dark line , in line with the bottom spider vein I just processed it to make it more apparent
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1.51
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And this the view down the baffle….  and this is straight down the baffle with my phone. |
9.89
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It's thermal, nothing else could do that.
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1.51
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andrea tasselli: That explains why I was able to get rid of the halos the one night. If that's the case than I am going to have to come up with something to get better air flow. I noticed the one night it was really bad the primary would not get any lower than about 1.5 degrees above ambient and it was about -1c that night and I open the observatory and turn the fans on at least 2 hours before dark. I'm wondering if the shorter lower tube of the ag optical scope helped with this, hence why I never had any temp issues with it and that was with only 2 fans blowing towards the back of the mirror. I am going to completely disconnect the delta t next night I'm out I am almost wondering if it is turning heaters on when it shouldn't be because there is no way this scope is that sensitive to temperature. Flipping the fans at this point is not an option because I really don't feel like taking the whole scope off the mount and apart so I'm going to remove those mesh filters and see if I can get any more air flow. |
1.51
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@Anthony Grillo did you double check if the primary cable from the Delta-T output is connected to the primary input on the scope? I once had the wires / connections ‘crossed’ by mistake. |
6.78
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Just took a look at your original images, and it does look indeed something thermal/dew related. What has your RH typically been during this first week? I'm sure you've looked at all of these, but the ones that have not been discussed in the thread before: - Is the cover-window heating of the camera on? A bit of dew on the camera might cause something like this - Are the cables of the Primary/Secondary connected the right way around on the Delta-T? - What's the delta you set between ambient and mirror temperature for each mirror? If it's low like 0.5-1°C, you may want to try 2-3°C or so. Also curious the script is that you describe that uses an ASCOM RH sensor? One of the (many) issues with the Delta-T is that it's not using any RH information to control mirror temp. Finally a few thoughts on the CDK itself. - I found that on my CDK14 star shapes of bright stars improved when taping off the screw holes on the front ring. Somehow it looked like this gave an interference pattern that made its way across the baffle. This looked somewhat different though, so don't think it will be the same in your case, but doesn't hurt to stick some tape on them en see what happens. - Just over the main mirror is a sort of 'aperture' ring. Besides covering any defects at the edges of the mirror, I believe this is also designed to guide the in-blowing air from the fans over the mirror surface to remove the boundary layer. On my scope this ring is poorly made/mounted, but seems to be doing its job. If on your scope it is even worse, perhaps it may have lost some of its functionality. Not sure if any of the above will help you, but just thinking along. |
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1.51
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Willem Jan Drijfhout: 60% humidity and overall, pretty dry the few nights I had it out. I shut the heaters off altogether the last couple nights, but I had it set for 1.5 above or 5c above dew point with the dew heater management. The script can be found from a link in the cdk issues topic in these forums, PW never really advertised it they just released it, I guess. Cables are all good I just checked them, and the camera heater is set to on. I did tape up all those holes after reading about the issue in the cdk group. My aperture ring looks pretty normal with the normal slight bulging, but I cannot really see anything out of the ordinary. I am almost wondering if somehow delta t is running the heaters without pwi3 displaying they are on maybe?? Next night out I am going to try the shroud again with the spacers I printed, make sure the heaters do not run at all and run the fan all night, a couple people said the shroud helps with temp fluctuations. It has to be something stupid I am doing, there is no way this scope is that sensitive to temp. With out ago idk we only ran the fans to cool the mirror down before night and then shut them off, that primary temp never budged. I thought maybe I should tweak collimation again, go over my backspacing again and check secondary spacing but I don't see how that would lead to halos like that. All i can do now is wait until the next clear night and throw everything i can at it haha |
1.43
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I get similar halos with my RC6 and the Optolong Ha 7nm filter. It's not on all stars but some. I just attributed it to the brightness of the star and maybe stray light from other stars. I do need to put the longer baffle attachment, maybe you're having a similar issue.  |
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1.51
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Yup, so after a bunch of testing I am almost positive its two issues. 1) crappy filters 2) That "demon star" issue that is temperature related producing the deconvolution artifacts. I still get some haloing with no filter, but it looks more normal now. I am going to try flipping the filter even though they are mounted, so I will probably have to unmount them. Even though this happened with both optolong and antlia , so it looks like I am going to have to shell out more money for chroma (anyone interested in a qhy268m with filter wheel and oag?? brand new!! lol) Also think I am going to tweak collimation some more and hopefully that will help. As for the spikes causing the artifacts I am not so sure what to do. It takes the cdk forever to even get the primary within 2 degrees of ambient with fans on all the time. Have the primary heater off all the time and the secondary set to either 30% or to kick on when the temp drops below 2 degrees above ambient and my stars still look wonky. Yes, this is more than likely just me screwing something up but sheesh the only thing bad I can say about the ago idk compared to the cdk is that collimation takes a little more work. As of right now both mirrors are holding at 1 degree above ambient so with secondary heater and fans on so we will see, I guess. anyone with any ideas or tips would be more than appreciated and sorry for putting everyone through the ringer, maybe I had some high cloud when I tried no filter the other night that I didn't notice. |
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9.89
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Never heating anything, that's my only suggestion in case like yours. Most if not all filters in circulation have no preferential direction and I cannot see for the life of me what is wrong with these. Try very short exposures, 5s at most, high in altitude and rich in stars. No filter or just R. Send in the fits.
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1.51
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andrea tasselli: The antlia ones I am using apparently have a preferred direction and a few people I have talked to have benefitted from flipping them. I have to check for a coated side and a reflective side and if flipping doesn't help, I have someone helping me that is going to lend me some chroma filters to test before I finally swallow my pride and just buy them. Planewave also suggested that I try and make the aperture ring over the primary bulge a little more to let more air through before I try to flip them. Here is a no filter raw and a HA raw, didn't save any of my other test images but the halos showed in all filters at whatever exposure, it was that clear cut last night. what is also crazy is that when using meta guide to check the airy disc, you could clearly see that when I turned the fans off the image went to crap almost instantly and the program had a hard time even keeping track of the star. Even though, my primary and secondary were only 1 to 1.5c above ambient RAW no fliter M12024-12-22030300.00-9.60(1).fits HA antlia ic4102024-12-2210030600.00-10.60.fits can't miss the halos in that HA one |
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1.43
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Anthony Grillo:andrea tasselli: I have Antlia filters, the mirror like side goes towards the scope. The blurry or double image side towards the camera, if you hold something up to them, you'll see it, but I noticed it was evident that one side looked literally like a mirror, the other side you could see colours. However, if they're mounted, I'm hoping yours didn't get mounted backwards. |
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1.51
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Darryl Ackerman:Anthony Grillo:andrea tasselli: I have not had a chance to check yet but so far from what I’m hearing I think that may be the case , the halos they are causing are just to extreme. Even if they are mounted backwards I have taken mounted ones apart before to use unmounted so I’ll just do that |
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9.89
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Anthony Grillo: I'd really love to see what a 5s exposure look like and these are just more of the same. Obviously the "blob" is already there in the halo and I'd left wondering if the direction it is pointing has anything to do with the upward direction (that is, the direction of a putative heat plume). |
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1.51
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andrea tasselli:Anthony Grillo: Shorter exposures with the filters show the same thing just dimmer with no filter shorter exposures show no sign of halo but because of the spikes I still get decon artifacts. on most exposures with the filters those artifacts go all the way around the star after decon but without they show a preferred direction. It’s for sure a mix of reflections from the filters and the star spike affect from temperature variations causing the artifacts. |
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6.78
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Anthony Grillo: Interesting, so the bulging aperture ring is by design? |
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1.51
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Willem Jan Drijfhout:Anthony Grillo: Thats what I took away from the convo lol should be hearing back from them after the holidays so I will ask them again |
