Have you had any star distortion from the Celestron Dew Heater ring (esp. at higher power values)? There has been some discussion of an issue with that on CN.
Too soon to tell. It is certainly plausible. Of course, I have the perfect remedy: just use the Celestron Focal Reducer - then the distorted stars will already be built-in to the image (haha). I will do some testing on this issue. I'm hopping I'll conclude that 50% power will provide adequate dew prevention.
My experience after many trials is keep the power below 25%. Higher values will create thermal distortions of the stars in an 8”SCT. Took me ages to realise this before chancing across the CN discussion. This can mean in winter that the dewring on its own will not kill dew formation around the secondary so i still use a conventional dewshield in autumn/winter to try to minimise this.
@Chris Lee I hope you’re wrong. If the dew heater ring has to be powered below about 50%, there’s no point in using it. I’ve got more learning to do on this. But that requires clear skies. Hence, continued ignorance is in the forecast! Maybe a strategy of full blast heat soaking before imaging, followed by 25% power during imaging.
See if these links work: Astroplan.exe: drive.google.com/file/d/1AUlMUwwMy5WHJ7QvYhvsa_juHsGuaggu/view?usp=sharing Stellarium Catalog: drive.google.com/file/d/1upjRBzZdrqGHlQ41wIZny6ROKodn1y7D/view?usp=sharing
Hi Shawn. Crazy hot, but, yes a week of clear skies. We’ve been limping along with maybe 2 nights imaging per month, so it is welcome. The temps in Dallas were what led me to abandon my uncooled DSLR and get a cooled, dedicated Astro cam. There was just no point in using the DSLR during the hottest months. So, to your question: certainly I do cool the camera, but I don’t want to have cooling system operating at max output, so I only cool to -5 C. Even then, the cooler power is at 70%. For my outdoor miniPC, I leave the top off the plastic box it sits in adjacent to the scope. Oddly, I’ve had more issues with our pathetic winter on the few nights when the air temp drops below 0 C. I do leave the mount outside under a cover, so, it does get pretty hot. But I bring the OTA/camera in every morning after imaging. I’ll take the OTA/camera outside once the mount is shadowed to let the optics come up to temp before imaging (about 1.5 hrs before “dark”). Not sure if that answers your question. Other than what I describe, I just let things take their course. And try not to complain to much since we finally have a few clear nights.
Excellent James, I was waiting for this experiment to confirm the dew heater ring actually works. My way of testing was to not use it and see dew develop and then use it and not have any dew is confirmed by your real experiment. I don't call my experiment real since it was more that I forgot to turn it on rather do the experiment. Thanks for your pixel math processing, I knew there was a way to do something like that in PixInsight but I am not nearly as knowledgable as you or some of the other PI masters. I would bring it in to PS and do some sort of local masked copy/blend to bring the SN into the All data image which would work well but it may not be mathamatically as accurate as your method. At some point when I retire in a few years I hope to really get to know PI a lot better. I did, however, manage do an image a couple of months ago all in PI but the preliminary data was really good. - Cheers Kurt
Thanks for watching, Kurt. I've performed "experiments" like you did many times. You kick yourself, but you learn something too. I'm kind of glad that I did not already have experience with PhotoShop - that forced me to learn PI from the start. If I ever get clear skies again, I'll try starting the imaging session with no heating and step up the power in 1-hour increments to see if the heated corrector plate distorts the stars as many are suggesting. Take care!
Hi James . Thanks again for a very interesting video , however , you should be thrilled that you have Data from before AND after the SN ! This should present a marvelous challenge for a final printed Presentation to hang on your wall . We're still suffering badly from the Wildfire smoke up here and I am going to miss this opportunity . Such is Astrophotography eh ?/SRK
You may do animation. If you get picture of M101 on 19-22 May, it will be awesome, since supernova was not so bright then. So, animation from 3 frames pre, 19-22 May after May25. Unfortunately, I don’t have that critical 19-22 May picture, but I have seen it on web, UA-cam.
@@Aero19612 I know. Awful weather. I would like to borrow this picture in May 19 or 20 from someone in Arizona or somewhere else. I understand some people in TSP took pictures of m101 on May 19. They just didn’t realize and see changes, Japanese dude did.
Another great video, thanks. A great number of us are getting spikes around the stars when we use the ring even at lower powers. Did you not experience that?
I think so. I need to do comparative studies. I’ll follow up with a video. I did do a statistical comparison of FWHM with and without the ring and see no difference (not the same thing as saying the stars aren’t distorted). Not conclusive. But I wonder if the star distortions people speak of (and are probably quite real) can only be seen when highly zoomed in. I freely admit that I’m a “don’t let perfect be the enemy of the good” kind of guy, so I may simply less sensitive to these things. Got to do some more thinking on this. Darn it. Why does every solution to one problem have to create another?
You see a bit of a faint stripe line on the supernova which looks like the results on the CN thread, but the effect is pretty subtle in your case. My understanding is that the heating is causing pinched optics. You can get a similar effect in refractors.
Maybe it's a combo of tightening the screws down too much so that thermal expansion is prevented... Beats me. Tough problem to wrap my head around. I hate dew more than I hate artifacts on zoomed-in stars.
Have you had any star distortion from the Celestron Dew Heater ring (esp. at higher power values)? There has been some discussion of an issue with that on CN.
Yes. I got distorted star when it gets too hot.
@@eduardoflores-nl8gl Same. I have one on an EdgeHD hooked to a P.A. power box. I keep it on low power to avoid star distortions.
Too soon to tell. It is certainly plausible. Of course, I have the perfect remedy: just use the Celestron Focal Reducer - then the distorted stars will already be built-in to the image (haha). I will do some testing on this issue. I'm hopping I'll conclude that 50% power will provide adequate dew prevention.
My experience after many trials is keep the power below 25%. Higher values will create thermal distortions of the stars in an 8”SCT. Took me ages to realise this before chancing across the CN discussion. This can mean in winter that the dewring on its own will not kill dew formation around the secondary so i still use a conventional dewshield in autumn/winter to try to minimise this.
@Chris Lee I hope you’re wrong. If the dew heater ring has to be powered below about 50%, there’s no point in using it. I’ve got more learning to do on this. But that requires clear skies. Hence, continued ignorance is in the forecast! Maybe a strategy of full blast heat soaking before imaging, followed by 25% power during imaging.
James, Is your DSO finder app still available? Keep up the inspiration. CS & GB from South Dakota!
See if these links work:
Astroplan.exe:
drive.google.com/file/d/1AUlMUwwMy5WHJ7QvYhvsa_juHsGuaggu/view?usp=sharing
Stellarium Catalog:
drive.google.com/file/d/1upjRBzZdrqGHlQ41wIZny6ROKodn1y7D/view?usp=sharing
Have you heard or seen any distortion from the heat?
Good question. I've only been able to use it for 2 nights. I'll look into it. Thanks for watching, Rafa!
Off topic question - finally a week of fairly clear skies but high temps in the DFW area. Any strategies for cooling or is it a lost cause?
Hi Shawn. Crazy hot, but, yes a week of clear skies. We’ve been limping along with maybe 2 nights imaging per month, so it is welcome. The temps in Dallas were what led me to abandon my uncooled DSLR and get a cooled, dedicated Astro cam. There was just no point in using the DSLR during the hottest months. So, to your question: certainly I do cool the camera, but I don’t want to have cooling system operating at max output, so I only cool to -5 C. Even then, the cooler power is at 70%. For my outdoor miniPC, I leave the top off the plastic box it sits in adjacent to the scope. Oddly, I’ve had more issues with our pathetic winter on the few nights when the air temp drops below 0 C. I do leave the mount outside under a cover, so, it does get pretty hot. But I bring the OTA/camera in every morning after imaging. I’ll take the OTA/camera outside once the mount is shadowed to let the optics come up to temp before imaging (about 1.5 hrs before “dark”). Not sure if that answers your question. Other than what I describe, I just let things take their course. And try not to complain to much since we finally have a few clear nights.
Excellent James, I was waiting for this experiment to confirm the dew heater ring actually works. My way of testing was to not use it and see dew develop and then use it and not have any dew is confirmed by your real experiment. I don't call my experiment real since it was more that I forgot to turn it on rather do the experiment. Thanks for your pixel math processing, I knew there was a way to do something like that in PixInsight but I am not nearly as knowledgable as you or some of the other PI masters. I would bring it in to PS and do some sort of local masked copy/blend to bring the SN into the All data image which would work well but it may not be mathamatically as accurate as your method. At some point when I retire in a few years I hope to really get to know PI a lot better. I did, however, manage do an image a couple of months ago all in PI but the preliminary data was really good. - Cheers Kurt
Thanks for watching, Kurt. I've performed "experiments" like you did many times. You kick yourself, but you learn something too. I'm kind of glad that I did not already have experience with PhotoShop - that forced me to learn PI from the start. If I ever get clear skies again, I'll try starting the imaging session with no heating and step up the power in 1-hour increments to see if the heated corrector plate distorts the stars as many are suggesting. Take care!
@@Aero19612 I was thinking what if I never learned PS and just started with PI, how would my processing be. I gert a lot of questions on this. Cheers
Hi James . Thanks again for a very interesting video , however , you should be thrilled that you have Data from before AND after the SN ! This should present a marvelous challenge for a final printed Presentation to hang on your wall . We're still suffering badly from the Wildfire smoke up here and I am going to miss this opportunity . Such is Astrophotography eh ?/SRK
Yes, it was a timely supernova. Wish I had clear skies throughout so I could make an animation of the increasing brightness.
You may do animation. If you get picture of M101 on 19-22 May, it will be awesome, since supernova was not so bright then.
So, animation from 3 frames pre, 19-22 May after May25. Unfortunately, I don’t have that critical 19-22 May picture, but I have seen it on web, UA-cam.
Nope. Cloudy from May 18 - May 29. Too bad. Would have been a nice animation.
@@Aero19612 I know. Awful weather. I would like to borrow this picture in May 19 or 20 from someone in Arizona or somewhere else.
I understand some people in TSP took pictures of m101 on May 19. They just didn’t realize and see changes, Japanese dude did.
Another great video, thanks. A great number of us are getting spikes around the stars when we use the ring even at lower powers. Did you not experience that?
I think so. I need to do comparative studies. I’ll follow up with a video. I did do a statistical comparison of FWHM with and without the ring and see no difference (not the same thing as saying the stars aren’t distorted). Not conclusive. But I wonder if the star distortions people speak of (and are probably quite real) can only be seen when highly zoomed in. I freely admit that I’m a “don’t let perfect be the enemy of the good” kind of guy, so I may simply less sensitive to these things. Got to do some more thinking on this. Darn it. Why does every solution to one problem have to create another?
You see a bit of a faint stripe line on the supernova which looks like the results on the CN thread, but the effect is pretty subtle in your case. My understanding is that the heating is causing pinched optics. You can get a similar effect in refractors.
Maybe it's a combo of tightening the screws down too much so that thermal expansion is prevented... Beats me. Tough problem to wrap my head around. I hate dew more than I hate artifacts on zoomed-in stars.