AstroAF - Can A Dew Heater Really Cause Star Aberrations? | Let's Find Out!

[@DeepSpaceAstro]

Nice troubleshooting man! This will help a lot of people I'm sure!

[@AstroAF]

@@DeepSpaceAstro Thanks Rich! You’re running the Pegasus for dew control of your ring, right? I’m really leaning this direction because of this as well as the other power control automation and monitoring it provides. I’ll have a look but if you’ve got a related video lmk! Cheers! Doug

[@DeepSpaceAstro]

@@AstroAF I am, but no video about it.

[@AstroAF]

@@DeepSpaceAstro content opportunities!! 😂

[@robinbrown3896]

It's about 7:29 in your previous video. You did comment on the flat spot. The reason I commented it could be from an obstruction, as I had a similar issue when I put on my dew shield for the RC8, it ended up with a flat spot very similar to what you pointed out, and it was caused by the dew heater cable and is why I removed it. The RC8 was second hand, so I didn't install the heater, but the power connector was mounted through the side of the tube and also caused spiking around the stars. There is an issue at play, though, as your stars look a bit wonky and not round. Sure, this maybe due to tilt, but I don't think so. So there is something not quite right. I can only go on the footage in the video. From experience, using the bathinov on a bright stars is a great starting point, but doesn't always give the correct focus information. A good tip is to focus on the bright star first then look at medium bright stars around the field of view, preferably near the main star and check to see if they are in focus, if not then make adjustments and bring them into focus, while staying on the bright star. If in focus, then one is good to go. However, Your videos are intuitive and well presented.

[@AstroAF]

@@robinbrown3896 thanks! Yeah that flat on one side that flairs on the other side. From researching that I saw similar images on CN identified as astigmatism type of aberration. There is definitely more at play but I feel I’m making progress. The star quality now is so much better than when I started and I’ve realized improvements in autofocus, guiding, and star detection/plate solving. Especially in processing. If I see that flat again I’ll do a hand shadow test to see if I can locate anything that might be an obstruction. Thank you for the tip, I’ll give that a go! Thanks also for watching and commenting! Cheers! Doug

[@Erniej270]

Glad it worked out. PI tip, if you drag the view identifier tab from one image to a second, it will match the second image (zoom and location). Clear skies!

[@AstroAF]

@@Erniej270 Hi Ernie!! lol I was doing that and trying to remember how to match images and it would not come!! I thought to myself that someone will let me know 😂 Really appreciate the tip!! Thank you! Cheers! Doug

[@alomgirmiah]

Nice one and thank you! Also, in pixinsight if you just drag the image header from the first image and drop it into the header of the second one, it will align the scroll and zoom.

[@AstroAF]

@@alomgirmiah Thank you!! I really knew it could be done but couldn’t remember how!! Thanks for the tip! Cheers! Doug

[@SimonT65]

Glad it worked for you. Make sure you have good Collimation before you waste your time with tilt otherwise you could be chasing your tail.

[@AstroAF]

Thanks again Simon! Yes, since the past video where I collimated the corrector and checked the secondary collimation, it was very good. I will check it again before beginning tilt adjustments though!

[@siegfriednoet]

Very interesting because I was also having minor issues with auto focusing after the latest NINA update, coincidence or not ... Never had these kind of issues since a long time, I suddenly had to increase my stepsize and my backlash size. Looking forward to the Tilt adjustment video

[@AstroAF]

@@siegfriednoet oh, really? Are you on the current beta update? I didn’t think that it could be related but I did just update that the other day. Thank you! Cheers! Doug

[@siegfriednoet]

@@AstroAF Yes latest Beta version, just did the update yesterday before imaging. Must be coincidence I guess ... ?

[@AstroAF]

@@siegfriednoet not sure. I’ll keep an eye on it and see. I was surprised that my autofocus was poor and I had to reconfigure a bit as I showed in video. Do let me know if you come across anything. I’ll do the same! Cheers! Doug

[@robinbrown3896]

The first thing I see is your images are slightly out of focus. I looked at your previous video and come to the conclusion the cables of your internal dew heater were causing what appeared to be pinched optics. This was shown clearly, as it showed a large shadow across the star, which indicates an object is in the way. The pinched optics would only come from your primary mirror, but as I see it does not have any issues. I had an internal heater for my RC8 and ended up removing it for a heater strap as it was causing issues with weird reflections and never looked back. The Celestron HD in my opinion have great optics and a very flat field. Collimation can be difficult at the best of times. I have used your method with a camera, but gave up on that method as I found it was too difficult to get the camera perfectly aligned, and then I would question even though the camera looks aligned is it really! So opted for the bench for collimating. Yes, you have tilt but only sightly in one corner. I see you had NINA 'focus offset' activated. The NINA 'focus offset' is a very handy tool and I use it all the time. However, if not used correctly, or aware of some issues, it can cause the 'focus offset' to fail. As it is difficult to focus with some filters, HA, OIII, etc. Focus offset was created to get around this problem. By using a filter like 'LUM' for instants as it will let more light through and then calculates the offset of the other filters. To set up focus offset correctly, it needs to be a perfect clear night and the scope needs to be pointing at the zenith. I don't use a 'lum' filter as I don't have one in my filter wheel and replaced it with a black filter for doing dark's or bias if needed. For instants, if I change my gain settings, then I will do a bias dark run at the end of the session. So my option is to use my 'RED' filter for calculating and offset focusing. So where does the problems lye when it comes to focus offset ERROR. Firstly, if making any adjustments of the focuses mechanical position will render the offset useless. Secondly, doing a focus offset low or near the horizon. Back focus, for the camera on the focus train, is very important and should be taken seriously, if not correct can cause no end of focus problems and can tribute to thinking there is a collimation problem when there isn't. So 1mm can make a big different to perfect focus and filter thickness needs to be taken into consideration. Have you thought of going for a power box like the Pegasus and alike for controlling your equipment? ------------------------

[@AstroAF]

Hi Robin! Thanks so much for watching and leaving a comment! Yes, improving focus is one of the challenges I'm working on and is part of the impetus of the checks I've been doing for pinched optics, corrector and secondary collimation and upcoming sensor tilt. Depending on where you are inspecting within an image field will result in various states of focus due to these and presumably the tilt that I have yet to address. Could you point me to where in the video you saw the shadow? I am certain that the cables for the dew ring are not in the field of view, when running heater, one is captured in a clip attached to the outside edge of the tube and the other is retained in the clip built in to the dew heater itself. I do not have any other cables in front of scope. I suppose it is possible though and I would like to verify in the video. Pinched optics can definitely come from the corrector should it be over-tightened by the retaining ring (dew ring in this place) or over-tightening of the corrector collimation screws. The former is more likely to cause deformation if that is the case. I am definitely considering going back to a strap heater. For now I am running the Celestron ring successfully at about 40% power and it is performing as expected without introducing aberrations. My Lum filter is my autofocus default filter. I have offsets applied to my RGB filters that I am currently using. It has been working very well and the filters are very close to parfocal with very few steps of offset. I am within .5mm of backfocus specification, I actually have a video on that very topic here: kzbin.info/www/bejne/eJfUnoaqd8ieidksi=l4mtl8IZHheTjnJZ I plan on doing a follow-up video of backfocus on the EdgeHD with the .7x reducer. I'll probably be doing that in 3-4 weeks or so. Yes, indeed, I am currently looking at Pegasus and Wanderer power boxes. Both have the features that I need, although the Wanderer has an additional temperature probe in addition to the environmental sensor. I understand that both will work with the Celestron ring but I am currently checking with engineers from the power box companies to verify that is indeed the case. Cheers! Doug

[@williamhouse5081]

I have the Celestron corrector plate dew heater on my RASA 8, I only run when it when temps go below 30° F, the camera and camera fan generate enough heat and airflow to take care of dew.

[@AstroAF]

@@williamhouse5081 Hi! Here in the Midwest’s humid summers, the temps cool sufficiently to get dew consistently overnight. So dew control is nearly a year-round requirement here. My camera has built in dew control too but my problems are definitely at the corrector plate dew control. Cheers! Doug

[@williamhouse5081]

@@AstroAF same here, I live in Iowa right next to a corn field.

[@AstroAF]

@@williamhouse5081 Ah, you know then. Although I wish I could go without heater more often. I live close to a stream and surrounded with trees. Corn fields begin about 1/2 mile away.

[@jesuschrist2284]

I saw a video someone used a second heater band lower down

[@AstroAF]

@@jesuschrist2284 Hi! Yes, I think I saw that video as well! So far I am having success by reducing the power to the ring. Cheers! Doug

[@billmurphypenguins3774]

i was going to say maybe full power is a bit much. I was blaming my poor seeing for poor planetary images but it think excess dew heater heat plays a part

[@AstroAF]

@@billmurphypenguins3774 Hi Bill! Thanks for stopping by! Yes, indeed! When I reduced power to 40% the issue went away. I run it on a controller now but the power reduction was effective for those ambient conditions. Cheers! Doug

[@whatmattersmost6725]

First Doug! I would think it will make a difference?

[@AstroAF]

@@whatmattersmost6725 Hi! Yes, I was very surprised. It was not at all something that I expected! Cheers! Doug

[@KJRitch]

James Lamb has a video on the same subject. kzbin.info/www/bejne/jYi7YZSoocyZmpYsi=8eYuRAcZjzFTow6i I have one of these rings with the Celestron controller. I've never been anywhere I need a dew heater turned on. I use the controller more for the weight to offset the weight of the image train. My Astro Oasis autofocsuer settings are way off from yours. I have it set to 800 and it seems to focus fine compared to a Bahtinov mask. I wonder if the ZWO focusers has the same issues with focus. I don't see reviews showing having to fiddle with the back lash so much or any procedure to calculate the backlash. My ASI071MC has adjustable tilt but ZWO doesn't offer any instructions. I'm sure every camera has tilt. I haven't come across anyone talking about it and making a video so I'm interested is seeing something about tilt remedy.

[@AstroAF]

@@KJRitch Hi! yeah I’m sure I’ve run across his videos. I’m running it at reduced power now and it is working without star distortions. It is probably more of a difference in the backlash of the Celestron focuser than it is the Oasis. I’d be interested in your settings though. Cheers! Doug

[@GregMcCall]

If running the Celestron, then it will only turn power on when the dew point gets close or above the temperature, then it will only turn it on at the rate you set (aggressiveness) until it senses the area near the sensor on ring is above the dew point as the area just needs to be above the dew point. Then it will turn off the ring. The celestron will do the same for its other ports provided you use the sensor (sold separately) under the other dew straps. In that way, different size dew straps are controlled independently and automatically. A finder strap might need less power and the OTA body might need more and turned on longer

[@AstroAF]

@@GregMcCall Hi Greg! Thanks for commenting! I am considering the Celestron controller but I may give Pegasus powerbox a try as it can provide power aggressiveness and comes with environmental sensor. For now, just running at reduced power is working very well. I do want a more permanent solution though. Cheers! Doug

[@GregMcCall]

@@AstroAF Hi, this where the marketing combined with poor engineering fails to explain how it works and tricks people into thinking it’s the same as other dew point controllers. It’s just not so. With no feedback loop on the dew straps (or dew ring), the effectiveness of any heat near that surface is unknown. Different size straps and/or different strap resistances are all variables. So the auto claim is just marginally better than not considering the dew point. The control is a little better than manual. BTW, the Celestron also has an aggressiveness setting (also available in the ASCOM switch controller within say NINA). While I think the physical size of the Pegasus (and wanderer) controllers better and they also seem to have better software, the lack of feedback and the inability to include a feedback loop (and re wanderer work with celestron ring) puts these others at the bottom of my list.

[@AstroAF]

@@GregMcCall Thanks for that insight! I thought the environmental sensor or the Pegasus and Wonderer created that loop. I saw that the wandererbox includes both environmental sensor and a temperature probe, where I think the Pegasus only has the environmental sensor. As I understand it, the Celestron ring’s thermistor is proprietary and does not work with other controllers. I’m tempted to discard the ring and go back to a strap.