Collimation of Coronado SolarMax III

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Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Hello,
While waiting for the sun to clear the trees at my house yesterday I happened to glance at the laptop screen and noticed that all of the out-of-focus sun images coming through the leaves looked like footballs (the American oval type) with a dark center so far off to one side it was almost touching the edge of the light oval. I know that the sun shining through trees is not a very scientific test, but it looks just like my SCT when way out of collimation. Is there an accurate way of testing the collimation on a Coronado SolarMax III, and if so, a way of adjusting it if it is off?
I'm using a Televue 2x Powermate and ZWO ASI 178 MM with the scope.
Thanks so much,
Arnie


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Sounds a little surprising Arnie, as if the scope was ok on a previous session and not knocked sufficiently, then a collimation problem unlikely.

I suggest imaging without the Powermate and then with it and posting the results here, so we can see what might be the problem.

Terry


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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Hi Terry,
Thanks for the suggestion. The scope has never had anything happen that would knock it out of alignment, unless it happened during shipment. That being said, I don't know what things may have been like when I first got it a year ago as in the past I always waited to set up until after the sun was out of the trees. I saw the unusual appearance described above purely on accident. It is cloudy now again in Oregon, but the next clear day I will take a look at the sun through the trees again without the Powermate.
To be continued...
Arnie


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Re: Collimation of Coronado SolarMax III

Post by marktownley »

Hi Arnie,

Welcome to the forum. Try when the sun is out of the trees, take a prime focus image of the sun using the 178 with the ghosts visible in the image.

Can you see detail on the surface of the sun and prominences normally when the sun is not in the trees?

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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Hello Mark,
Thanks for your response. While I don't have an image currently taken at prime focus with the ghost images in the FOV, I do have these two recent ones with the ghost images out of the FOV. These are both taken with the 2x Powermate. On previous occasions, both with and without the Powermate, and both visually with the CEMAX eyepiece and imaging with the ZWO ASI 178, I am able to see and image disc detail and prominences. My concern is that I'm not getting all the detail I could out of this scope if there is a collimation problem. BTW, these images are stacks of the best 25% of a few thousand frames, no wavelets or other sharpening applied yet. Also BTW, I love your website. I have learned a lot from it!
12_04_26_lapl5_ap193.jpg
12_04_26_lapl5_ap193.jpg (7.72 KiB) Viewed 2899 times
12_13_23_lapl5_ap473.jpg
12_13_23_lapl5_ap473.jpg (10.48 KiB) Viewed 2899 times
Terry, here is the image you asked for, thanks to a short unexpected break in the clouds! This is the sun through the trees without the Powermate. The sun was focused while still clear of the trees. This is the exact same appearance as with the Powermate, just smaller. The multiple images are oval with the dark center off to one side. [attachment=3]Solarmax-collimation-frame.jpg
What do you think?

Thanks so much again,

Arnie
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Solarmax-collimation-frame.jpg
Solarmax-collimation-frame.jpg (86.37 KiB) Viewed 2899 times


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Re: Collimation of Coronado SolarMax III

Post by Montana »

Oh I see what you are talking about now!! is this a refractor or an SCT?
If a refractor, then wouldn't the central obstruction be in the etalon itself not the telescope. If this was the etalon central obstruction, don't you tilt it to get centreline wavelength, if so, the etalon will be not straight but angled.

I might be very wrong as I am not technical but I don't see how else you can get a central spot in a refractor.
Alexandra


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Hello Arnie.

With the SolarMax-3 and with no PowerMate or any other item in the imaging-train, the last image "Solarmax-collimation-frame.jpg (86.37 KiB) Viewed 8 times" would appear that the Etalon has come adrift within the scope as "detached", or the scope is not pointing directly at the Sun when the image was taken.

The previous two images, do not obviously show a problem when ever they were taken, possibly except fine-focusing.

So to clarify for further assistance, please advise:-

1. The mount details or if not a driven-mount, then confirm a tripod in use ?

2. The bare SolarMax-III without any possible double-stacking ?? Also no other filters or a camera-Tilter should be fitted except those for visual use only. Also confirm if a Diagonal or Erector prism is being used of any type. In other words what is the visual-train from the objective lens to the camera ??

3. Focused on target with an EyePiece first ??? Do you see any problem ???
Then with:-
4. ZWO ASI-178MM camera put in place of the E.P. and any (fine-focusing-likely) using which download/imaging program ????
(If able take and post a screenshot of the capture program before/after taking the image shown on the screen - showing the program settings).

5. Taking say three of four images and post them with the above here. Do not crop any of these images..

6. TAKING SINGLE-FRAME CAPTURES SHOULD BE SUFFICIENT FOR US TO SEE WHAT THE CAMERA IS SEEING and no need for any other processing except to save and send here as JPEG format of no more than 2-Mbytes each image.

Please also date/time each image for our reference to the Sun's activity itself.

We have a number of folks on SolarChat who have both SolarMax and Lunt equivalent types of Solar-scopes and although I use Lunt 60mm scopes, between us we should confirm what is the problem. I also have two ZWO ASI-178MM etc., cameras in constant use with no known problems..

I trust this is as a simple way of putting any of us in the frame (so to speak) so we can better advise you and correctly.

Best Wishes
Terry


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Also Arnie, absolutely no PowerMates/Barlows or Focal-Reducers should be used for fault-finding, as they themselves can affect or cause some problems, which can be verified after the basic operation - as in my post above.

Also how was the scope stored over what period of time, could assist in fault-finding ?

Cheers
Terry


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Re: Collimation of Coronado SolarMax III

Post by Bob Yoesle »

Hi Arnie,

First, your "normal" images have a vary large scale (magnification) and may simply be showing the effects of poor seeing conditions or poor focusing. I would start with a lot less image amplification (no Barlow, etc.), and really pay attention to focusing. If your etalon(s) had a de-contacting problem, you would likely not see any H alpha detail or prominences, so I wouldn't be concerned with that.

When way out-of-focus, an etalon with a central obstruction will evidence the obstruction just like a reflector telescope with a central obstruction. Out-of-focus imaging through trees is very unconventional, and does not present a valid or reliable optical test methodology so little can be said from the image you are showing. If you can remove the etalon(s) and do a star test, by all means do so. Try this with a known-good diagonal, and then with your blocking filter on a sufficiently bright star.

To check the collimation you must first insure the focuser is aligned with the mechanical axis of the OTA and points at the center of the objective; for example as shown here. You generally can not do this well with an internal etalon with collimator optics which complicate matters, and it would be difficult/almost impossible with an internal etalon that has the central spacer obstruction. Neither of these constraints appear to exist with the SMIII.

After doing that, you can use a Cheshire eyepiece (if there are no intervening internal etalons) to to see if the objective itself is collimated, as described here. Since I believe the SMIII uses no internal etalon or collimation optics, this should be the way to check the objective's collimation.

A good article on refractor collimation can be found here.

I don't know if the SMIII objective has provision for collimation adjustment. If it does not and the objective is significantly out of alignment, a return is warranted to get this fixed.

If your objective and focuser collimation is good, any other issues - if they exist - are likely confined to objective mechanical constrictions resulting in deformity (pinching) and/or astigmatism, or the blocking filter components. Misalignment of the diagonal mirror of the blocking filter would be my first rule-out, followed by the ITF and order selection filters being significantly astigmatic - which to my knowledge has never been reported.

Good luck.

Bob


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Re: Collimation of Coronado SolarMax III

Post by Bob Yoesle »

Addendum to the above: Since the out-of-focus central obstruction itself appears circular, you may likely have an offset vignetting issue, which can arise from the focuser or diagonal being offset from the optical axis; or this may be the tree's multiple apertures not being perfectly circular, etc.

Solarmax-collimation-frame.jpg
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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Wow! What a great forum! Thanks for all the replies. It's cloudy here again in Oregon so I can't get any new images without the Barlow, but I endeavor to answer all the other suggestions here:

Alexandra: I, too, thought about the tilt of the etalons. After getting the above image on screen, I rotated both etalons (individually) and the T-max tuner through their full range of motion. The offset position of the central dark area did not change, so I don't think it's related to the tilt of the etalons.

Terry: 1. the scope is on a Losmandy G-11 mount, permanently and accurately polar aligned. When set to solar tracking rate, I don't have to touch the motion controls for the whole two hours the sun is visible between the trees.
2. The visual train consists of the double-stacked SolarMax III 70mm, a BF-15 diagonal, then either a ZWO ASI178MM camera inserted into the diagonal directly for whole disc imaging, a 2x Televue PowerMate inserted as far into the diagonal as it will go (it will not seat fully due to it's length) with the camera in the PowerMate, or the 18mm CEMAX eyepiece (both with and without the PowerMate)
3. I can see disc detail and prominences with the eyepiece.
4. With the ZWO 178 I use SharpCap v4 (build 8025), generally with exposure times 3ms for the disc, 8-9ms for bright regions of prominences and up to 30ms for really faint outer regions of prominences. I leave the gain alone right around 300 - 325.
5 and 6. Will do as soon as the weather clears.

Scope has been in service since August of last year. During the brief sunny season here, it is on the mount in a roll-off roof observatory. During the long cloudy season it is inside in its case with a desiccant, stored securely with all the other equipment.

Bob: I would LOVE to do a star test on this scope! The manufacturer's description states that the etalons are easily removed to allow the scope to be used as a regular 420mm f/7 refractor with a regular star diagonal. For the life of me I can't figure out to remove the etalons and have not found any instructions online (no instructions came with the scope, either). If you know of written or video instructions somewhere I'd love to have a link. It was my inability to perform a star test that led me to this forum for help.
Thanks for the inks on refractor collimation. I have all the proper tools. Now I just need to be able to get the etalons off!
The image I posted of the oval lights with the dark circular off-center obstructions actually was taken at focus. To perform this test I used just the camera (no PowerMate), focused on the disc and let the sun drift behind the trees.

To summarize, I don't know if this scope is out of collimation. I do get acceptable images, both with and without the Barlow, and visually. It's just that the image I saw quite accidentally before the sun had cleared the trees reminded me so much of an out-of-collimation SCT, and I have seen the difference between "acceptable" planetary images and "excellent" planetary images when the collimation is spot-on. If there is an accurate way to measure collimation of this scope that doesn't involve vegetation, I'd like to make sure I'm getting every bit of detail out of it that I can.

According to the ever-changing weather prediction, I may be able to get the aforementioned test images Sunday or Monday.

Thanks so much again for all your help,

Arnie


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Hello Arnie, thanks for the point-replies.

2 & 3... suggest that the camera and PowerMate combination - may well have something to do with the snag - so only with a clear-view of the Sun (absolutely nothing in the way including trees, leaves etc.), if the E.P. of say between 20mm and 10mm are resolving good images, then definitely with those two and NO-Barlow at all, then try the camera.

If then - there is little or no problem, then the Barlow will be the likely cause, so have a good close look through that and also take the opportunity of checking the camera-sensor carefully in case there is something in either, which should not be there...!!

The important things is:- if an eye-piece resolves a good visual-image, then likely nothing wrong with the scope...

4...All SharpCap settings are reasonably correct - depending on seeing-conditions of course and will always be different when using any Focal-Reducers or Barlows of any different make and sizes.

Always do the easy-tests first, as I've requested - before getting involved in taking telescopes apart without the full-knowledge of what you might damage or wrongly assemble - as if any warranty still exists, it will never cover such work or damage. Also in the case of your SolarScope, there may well be considerable delays in get service and/or parts from vendors/manufacturers - at present.

I also have left my three scopes on the mount throughout the years, but humidity-issues can cause problems unless the observatory is humidity-controlled - which mine is down to 35 - 40% constantly... Never had any corrosion/rusting issues - ever... (EP's, camera-sensors, telescope-lenses and of course Etalons and Blocking-Filters etc., could be damaged by high-humidity levels)...

Please keep me appraised - thanks
Terry


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Re: Collimation of Coronado SolarMax III

Post by DeepSolar64 »

Arne,
Is your SMIII a single or double stacked model? I own two SolarMax II scopes, a 60 and a 90. Both have stacking etalons. On a double stacked scope a secondary " ghost " image is often seen. I simply turn the T-Max tuning wheel of the stacking etalon to move it out of the field.

I haven't had any collimation issues with either of my Coronados.

James


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Thanks James for advising that useful extra information and just yesterday having read-up again on these scopes - could be a significant extra-snag that needs be identified to resolve the issues that Arnie is having.

But of course using trees to check collimation is not the way forward.. !!

(I was hoping you would come-in on this post - thanks)

Regards
Terry


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Re: Collimation of Coronado SolarMax III

Post by Bob Yoesle »

Hi Arnie, James, and Terry,

Arnie has used this scope and filter system previously and it would seem logical he’s familiar with double stacking and ghost images: In response to Mark’s request he states he removed the ghost images from the FOV and gets “acceptable” images both visually and with imaging. He is concerned he may not have “excellent” results, and desires a method to check collimation other than viewing/imaging through tress - which was the origin of his concerns.

He is not raising the issue of ghost images or how to deal with them. Furthermore, double stacking two relatively heavy front etalons will not affect the telescope’s optical collimation unless the OTA is made out of thin cardboard or the objective cell is loose. A secondary DS ghost image would be faint compared to the primary image and likely not capable of creating the asymmetry shown in the “through the trees” image he has supplied, which also shows the asymmetry seeming to change from top to bottom in his picture through the trees.

Moreover, for the best possible double-stacking performance, one should not move the ghost image(s) out of the field of view of the eyepiece or camera. Instead, one should generally only use enough tilt to remove any overlap and give a little bit extra cushion of space to clear any prominence activity. Any additional tilt after this may actually push the DS filter towards the blue wing or off-band, and possibly introduce additional contrast non-uniformity, unless the DS etalon is tuned so high as to require extra tilt to get on-band (and contrast uniformity may still suffer or become even worse).

The proper placement of a ghost image for both viewing and imaging:

DS ghost.jpg
DS ghost.jpg (528.54 KiB) Viewed 2754 times

Arnie’s task now is to remove the etalons in order to do a proper optical collimation check of the OTA and corrective alignment if needed. The etalons should unscrew from each other and the objective cell as they are designed to do. If they are so tight that he cannot do this by bare hands, warmer temperatures and a strap wrench or two may be in order. Then following the guidance described above for refractor collimation he should be able to determine if there is a collimation issue. Once this concern is addressed and resolved satisfactorily, any additional issues – if they exist – can then be addressed. This would include local seeing and aperture limitations, internal baffling, BF diagonal centering, etalon quality, focusing and image acquisition, etc.

Best wishes,

Bob


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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

13_27_43_lapl4_ap810_wv-25pc.jpg
13_27_43_lapl4_ap810_wv-25pc.jpg (42.73 KiB) Viewed 2716 times
13_53_56_lapl5_ap1135_wv-25pc.jpg
13_53_56_lapl5_ap1135_wv-25pc.jpg (36.93 KiB) Viewed 2716 times
14_18_10_lapl6_ap121_ap25pc.jpg
14_18_10_lapl6_ap121_ap25pc.jpg (5.31 KiB) Viewed 2716 times
Hello everybody,
Thanks for the continuing discussion and advice on this matter. It's still overcast here in Western Oregon so I can't get any images yet, but I can at least address some of the points recently brought up.

1. The image that started this whole thing, the one through the trees that looked like an uncollimated view through my SCT, was originally done with the 2x Barlow in place. After one of the earlier suggestions, I repeated it without the Barlow. The images look identical, except for the second one being half as big. The one that I posted was with the Barlow, but the one without it, just the scope with the ZWO 178 directly in the diagonal (which I can post if anybody wants to see it) is exactly the same. So I don't think that it is a Barlow issue.

2. The scope is double-stacked. When viewing or imaging, I adjust the front etalon just enough to move the ghost images out of the FOV of the ZWO chip. When using the scope visually, the ghost images are still in the FOV of the 18mm eyepiece, but far enough away from the main image so as not to interfere. Then I adjust the back etalon to get best contrast for either disk or prominences, then adjust the T-max tuner. After that I may tweak either or both etalons a bit for the best view possible.

3. I do see detail both visually and imaging. I just don't know if it is all the detail possible to see with this scope under my conditions (living under the jet stream). That's why I'm trying to figure out how to check collimation. When the weather clears I'll try removing the etalons again to do a star test. In the meantime, while I know it was asked to supply an unprocessed single frame for review, all I have right now are SER files. If it helps, here's one taken of the full disk with just the ZWO 178 directly in the diagonal, followed by a close-up of the active area in the upper right taken immediately afterwards with the 2x Powermate, and then a prominence taken with the 2x Powermate in place. All processed in AutoStakkert and Registax. It just seems like the prominence images could be sharper. Please feel free to also let me know if I'm making a mountain out of a molehill.

Thanks so much again! I'll post the single frames as soon as I see the sun again on a non-work day.

Arnie


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Re: Collimation of Coronado SolarMax III

Post by EGRAY_OBSERVATORY »

Other than a slight Etalon tuning in the first 13_27_43_lapl4_ap810_wv-25pc.jpg (42.73 KiB) image, there is no other problem Arnie. :D

The second image as 13_53_56_lapl5_ap1135_wv-25pc.jpg (36.93 KiB) only requires a slight more contrast in the processing, but perfect otherwise.

The third image 14_18_10_lapl6_ap121_ap25pc.jpg (5.31 KiB maybe a tad overexposed from the camera, but that is quite normal for Ha-prom captures (quite often) and in any case can be dealt with in the camera adjustment and processing stages...

So no collimation issues as far as Solar-imaging is concerned and most unlikely for night-sky issues either as expected. :seesaw

Obviously SolarChat itself is not really for Deep-Sky imaging and any advice for that part of astro-imaging, should really be for another website to deal with. :bow

Happy Days, so nothing now to worry about...!! :bow

When you are ready and with your weather, I'm sure we would look forward to seeing your Solar-imaging results on the appropriate
" This is SolarChat !! " page, where many of us can post relevant comments of... Thank you in advance... :hamster:

Best Wishes
Terry


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Re: Collimation of Coronado SolarMax III

Post by marktownley »

Looking at these images there's absolutely nothing wrong with the scope Arnie.


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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Thanks so much, Terry and Mark, for your assessment of the images. Not ever having done this before this summer I have nothing to compare to like I do with the years of planetary imaging through SCT's. I am so relieved to hear you both feel there is not a problem. I'll stop obsessing over it! Now to look around and see what else this great forum has to offer.
Thanks again,
Arnie


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Re: Collimation of Coronado SolarMax III

Post by DeepSolar64 »

marktownley wrote: Mon Aug 23, 2021 7:17 am Looking at these images there's absolutely nothing wrong with the scope Arnie.

I agree.


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Re: Collimation of Coronado SolarMax III

Post by Bob Yoesle »

Hi Arnie,

As suspected, there is likely little to no issue with your telescopes collimation, although it never hurts to check this out just to be sure and gain some peace of mind.

Unfortunately, the full disc image reveals you are having a significant issue with contrast uniformity. There is a more or less central on-band bar, and on either side of this your filter system is significantly off-band. This could be due to a number of factors, some of which might be mitigated via fine tuning the tilts of the DS filters, and additional tweaks of the "rich view" mechanism.

Where do you live in Oregon? I travel there frequently. If you'd like to get together send me a PM with your phone number and perhaps I can be of some assistance in assessing the situation and coming up with some solutions.


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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Funny you should mention that. I actually talked with a Meade service rep a while ago and was told that the uneven field was to be expected for this scope. Going under that assumption, when I do full disk images, if there are interesting features across the whole of the disk, I will image it two to three times, adjusting the etalons to optimize the view at different areas of the sun. Then I blend the best parts of each image in Photoshop. If I can avoid this extra step and get entire disk images with just one video, that would be wonderful!


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Re: Collimation of Coronado SolarMax III

Post by Bob Yoesle »

Hi Arnie.

That's a hilarious statement from Meade Coronado! But from my and others experience with MEADE you may not have spoken to someone who knew what they were talking about. The stated rationale for going to front mounted etalons over internal etalons was allegedly for the improved [contrast] performance - "external 'True' H-α etalon filters giving higher contrast views and sharper features compared with models using smaller internal H-α etalon designs. Now you can tune for the highest contrast views of your favorite solar features without sacrificing image quality" - which is generally true for contrast uniformity only - if done correctly. The MEADE statement is like saying buying better tires will give you better performance than your cheaper tires, and then stating the new tires poor traction is to be expected.

Here's an example of what very good (pre-Meade Coronado) and properly tuned front double stacked etalons can do.

The complexity of both tilt tuning and RichView tuning makes adjustment a bit difficult. Additionally, the high CWL of the MEADE etalons can make them inferior for tilt tuning, and the implementation of RichView tuning with pressure only applied to the central spacer is less than ideal. In fact it is deleterious. I'm working on a fix for this...

You appear to have too much tilt in one or both of your etalons, and MEADE's RichView tuning widens their band-pass. So it might be better to use less tilt and more RV tuning to reduce the contrast non-uniformity and give up a bit of the higher disc contrast you would otherwise have from double stacking.

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Re: Collimation of Coronado SolarMax III

Post by OregonAstronomer »

Hi Bob,
Your analogy about Meade's statement is quite apropos. I never was truly satisfied with it, but short of investing in a high quality refractor and Lunt or Daystar etalons less than a year after buying the Coronado, there wasn't much else to do!
I tilt the front etalon just enough to get a decent view of the disk. As I adjust the rear etalon I can see bright areas moving across the face of the disk so I adjust it to get the most uniform appearance possible. The degree of tilt seems to vary with where on the sun I am concentrating, and of course whether I am imaging the disk or prominences. I have to admit that looking at the laptop screen, I rarely see much of a change no matter how far the RV tuner is turned.
It is cloudy here today, but hopefully I'll be able to try your recommendations over the weekend.
Thanks again for all your advice,
Arnie


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