Looking for source(s) for CaK Blocking Filter(s)

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Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

Hello to all,

I'm very new to solar astronomy, and in need of learning in all spectra, but the first thing I need is to get my CaK scope rigged up for operations. It's a 70mm Coronado Cak SolarMax, and my understanding is that the CaK blocking filter (b/f) is not functional. So, I either need a new one, or need to have the existing one fixed. Given that I don't know anything about this item, I don't know if it's repairable, on not.

Would anyone here know of a retail source for CaK blocking filter that would work properly with the Coronado SolarMax 70mm scope? I read that Coronado b/f's allow proper functioning if used on a Lunt solar scope, but that the Lunt b/f's won't provide a safe viewing situation when used on a Coronado scope; so, I'm wondering if there's a proper solution to get this SolarMax CaK scope operational, or not.

Thanks for reading my post, and for any information you might be able to provide!

Tim


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by marktownley »

Hi there and welcome to the forum.

Not really familiar with the scope directly, if you post some pictures of the failed components it will help to diagnose a fix.

Mark


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Montana »

A very warm and sunny welcome Tim. Have you bought this CaK Coronado second hand and were told it doesn't work or have your tried imaging with it and it doesn't work? a little more detail would be really useful to help. Can you post a picture of what the blocking filter looks like?

Alexandra


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Bob Yoesle »

I'm assuming you bought this

More than likely the main narrow blocker (same as CaK PST "No1" filter) has been removed and the remaining filters are probably "rusted." Per Mark and Alexandra, we'll need to see the components. I'm guessing you have essentially an objective and telescope OTA, but really no functional filters, and you'll need a suitable Lunt CaK 1200 or 1800 for this scope - which should work fine.


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Montana »

Bob, if the actual CaK filter is missing then what would be the point of buying the scope? this filter cannot be replaced as they are no longer made, you would be better off buying a Lunt CaK wedge with your money and using your own telescope, surely?

Andy Devey has a Coronado 90mm CaK and it is years old and the filters still work excellently. If it is just a rusted secondary filter then removing it and replacing with a Baader K line filter worked like a dream with my PST :) But like you say, it is worrying to hear the vital bit could be missing.

Alexandra


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by marktownley »

Assuming it is the one in the link Bob posted, looking at the blocker, you may wish to try a Baader K line in there if you have one to borrow, this is strictly for imaging not visual!


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

Mark, Alexandra, and Bob... I have photos. Just need to figure out how to post them here; and, I'm getting some sort of "submitted form was invalid" warning. The system won't let my message go through.

Well, it beats me. I don't know how to get an image into the post. The front solar filtering assembly looks good. In the rear portion of the main housing, there appears to be an optical element with two relatively clear lenses. That assembly looks fine. In the real of the scope, there is a diagonal mirror that screws onto a metal tube that's about 3 inches long, and that tube has a small enlarged portion at the front end which serves to prevent the tube from being fully withdrawn out the back end of a housing. The back end of that tube has some sort of filter on it, and it has a couple of rough concentric circular patterns in the element. I took a photo through it, of the sun, and the image shows those horrible circular rings of blobs.

The diagonal looks fine, but the seller stated that something is missing, in the ad, and I'd guess that the filter element that IS in the back end of that metal cylinder is the item that has been spoken of as being "rusted".

Given my current lack of knowledge, I don't know if the purchase of a Lunt CaK blocking filter would replace the piece that's got the horrid concentric rings of blobs in the filtering element.

I need to try to figure out how to post the photos here...

Tim


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

Hello Alexandra and Mark (and Bob?),

I'm unsure of whether I'm responding correctly to the messages that you've all sent, but thank you for your time and help. I found a manual for the original Solarmax scopes, so now I hope to use proper terms for the parts that are described. I've requested that the Administrator grant me the ability to post photos, so we'll see whether that is approved.

For my Solarmax, it's my understanding that a filtering element of the original CaK blocking filter is missing. You asked why I would have bought the scope, knowing that there was something missing from a part that is no longer being produced, and the answer to that is that I am sometimes impulsive and more often than being impulsive, I'm dumb. Frankly, I made the presumption that I could add a Lunt CaK blocking filter to the Solarmax scope, and press ahead.

If you peruse CloudyNights or Astromart, you may be familiar with the feeling that when one sees something interesting, one must submit a bid yesterday in order to have a chance at winning the race to purchase. That's how I felt when I saw the 70mm Solarmax, in need only of a blocking filter.

Well, I believe that the filtering element at the rear end of the drawtube is deteriorated (what you experienced folks term "rusted"), and so I think I'm watching the chickens come home to roost, much sooner than I suspected. Time will tell. Is that element at the rear of the draw tube called a secondary filter?

So, if you know of any solution to the problem of a rusted secondary on a Solarmax, I'll be happy to hear of it! Thank you for anything you might offer...

Tim


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Montana »

Tim, to post images they have to be JPEG, Tiffs won't load.

Press the Full Editor & Preview button

At the bottom of the post you will see a tab which says options/attachments. Click on the attachments tab

Add file

wait for it to download

Place your curser in the post where you would like the picture to be, then click 'place in line'

Then submits post (or add more photos in the same way.

I hope this helps
Alexandra


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

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Hi Alexandra!

Thank you for those detailed instructions!! I followed the instructions in the FAQ section, for getting Administrator permission to post photos, and Stephen wrote back stating that the FAQ info wasn't correct. He said anyone can post photos, and told me the basics of what you described. Your instructions were perfect, though! Nicely done.

Now, all I see is a message full of jargon, so I guess I won't know about the success of it until I launch the message.

I've written to Lunt, asking whether they sell anything that will return my Solarmax to service, and am waiting for a response. I'm assuming that their CaK blocking filter might replace the Coronado blocking filter, but that if the filtering element (what you termed the "secondary") in the rear of the drawtube assembly is suffering from significant deterioration, I don't imagine that Lunt will be able to replace that portion of the chain.

It's my own fault, of course, for pouncing on the used Solarmax tube without correctly assessing the situation. My main recourse would be to see if anyone has the ability to refresh the secondary filter in the drawtube, and to then look into a Lunt blocking filter that will replace the Coronado's incomplete blocking filter. My only positive feeling from this is that it's better to dump $650 down the loo for the purchase of a known problem than to have flushed $1,500-2,000 down there in the purchase of something with hidden problems; but, far better to have flushed nothing by having some idea of what I was about, right? LOL. Some of the rewarding things in my life have resulted from mistakes, though, so I can't say that the errors have always been negatives in the balance of things.

At any rate, many thanks to you, and others like Mark and Bob, for giving your time and thoughts to the issues others are having! You deserve a place with your name attached, in the points of light that we all look up to on the clear nights of our lives.

Tim


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by EGRAY_OBSERVATORY »

Unfortunately Tim, this is an example of buying second-hand items and in the case of any Solar-scope is a no-no in my opinion, especially Solar-scopes as there are significant safety-issues relating to items to view/image the Sun with.

Not quite so bad, if one knows exactly who the previous owner was, or through a recognised and established retailer with a warranty of sorts.

We humans have just one pair of eyes to protect at all times...

Terry


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

Hi Terry!

Thank you for your very pertinent thoughts!! Yes, eye safety is paramount. In this case, I understood that the CaK scenario is geared toward imaging, and that's my plan. I'm just past age 60, and figured that imaging was all I'd be doing with the CaK scope.

Unfortunately, if all viewers are limited to doing solar observations with first-hand, newly-purchased, gear, a large proportion of the viewers will be shut out of the activity due to the price of the new gear. I bought a used Lunt solar wedge, several months back, and as I used it the first couple of times, I wondered how much of a risk I was accepting as I maneuvered the scope to get the sun into line. How much risk does one undertake, when they use a newly-purchased solar wedge for the first time? I'm not capable of estimating the risks, nor of eliminating them all except by refraining from all risky activity; just as I'm not able to afford all the activities in which I have an interest.

But for CaK imaging, I don't see any great physical risk, because the camera is going to be doing the looking. But that's only if I can get the Coronado scope up and running! If not, I won't be looking through it at all; so, perhaps buying shoddy used solar gear CAN be construed as a safe route to take, because if I can't get it fixed, I'll never end up using it!


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by EGRAY_OBSERVATORY »

Some true words there Tim and thanks for sharing those.

Indeed this Solar-viewing can be expensive and usually is, largely due to a limited-market for the manufacturers and suppliers.

Do you have access to a local astronomy club (when they are open again of course) as to be able to borrow or at least look at and make a decision on which way to go forward in a desire to be able to image through CaK filtered telescopes. Obviously not all clubs may have one, but often their members can point to ways forward for you. Equally here on SolarChat - I'm sure others will advise you from their own scope experiences as to what can be done to safely get you using your own CaK enabled telescope.

I recall Alexandra mentioning about using another scope with a compatible CaK filter (if you have such a scope), so that would be a better way forward and count the losses - possibly ??

Best wishes
Terry


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by marktownley »

Hi Tim.

Thanks for the pictures, it is a great help. By all means see what Lunt says, but all you need to do to fix this for imaging is to do away with the coronado blocking filter (that is the dead part) and use a Baader K-line filter on the nosepiece of your camera.

Mark


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Montana »

I agree with Mark.

At Christmas I had a similar problem to you but with my Coronado CaK PST. Perhaps you would like to read this thread and see if any of the filters are similar in the 70mm in position? viewtopic.php?f=9&t=30309

I found that by removing the rusted filter by the CaK filter - which was fine, did the trick. I used a Baader K line filter instead and it worked. Try removing the worse filter and having ago. This is purely for IMAGING ONLY, you will never be able to go back to visual, but then you may not be able to see CaK visually anyway.

Good luck
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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by marktownley »

Images 4, 5 & 6 show the important filter that passes the 2.2a peak at 393nm and is absolutely fine. It just needs a 'blocking filter' and this is where the Baader K-line will replace the damaged Coronado one...


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Mooncakes4All »

Hello Mark and Alexandra,

Thank you both for your messages! Alexandra, I will review the thread that you referenced, this evening. Gotta get the kids fed with lunch, and then have an afternoon full of concrete and flagstones to prevent being murdered by my missus. She thinks home improvements take precedence over astronomy... At my age, sleep comes first, and then anything that doesn't require much exertion. Somehow, 5-10 years ago, having children as I approached 60 didn't seem so ridiculous. Having done it, I now see the folly. Sort of like buying that damaged Solarmax. While I did it, it made sense. Now that it's done, it seems stupid. Lol. So, we press forward and make the best of things. The kids are generally fun, though, if I get my mind right and then ignore reality all day long.

Questions for either of you:

1) So, what I thought was simply an optical element is actually the important filtering element! I'm happy to hear that it looks fine to you both! I, too, thought that component looked great, but I thought it was just some sort of optical corrector, and couldn't make sense of it because it didn't seem to be doing much magnifying. is THAT item (in photos 4-6) the primary CaK filter? I believe that Mark indicated it as such, but just want to double-check.

2) The element pictured in the first few photos, that has all the blobs of various forms... which sits at the rear of the drawtube. Would either of you be able to put a name on that filtering element? I believe that there's some sort of CaK filter that should have been in the diagonal area of the blocking filter, so it seems to me that that blocking filter is missing, and thus this filter element at the rear of the drawtube isn't a CaK blocking filter. The discoloration certainly affects the image being produced, and so I'd like to pull it from the chain of elements, but don't know how the scope will function without the presence of the drawtube. Would either of you know, with some specificity, what that filter element does, or what it's called?

3) Given what Mark has stated, it sounds like if I took the scope as is, and worked backward from the main CaK filter that's looking fine, what I need to produce is something that would include a focuser, a Baader K-line filter, and an imaging sensor. It would be up to me to set those elements up, in whatever way is functional. Which is to say, if I were to use the existing drawtube as a physical portion of the chain, optically, that filter with the ugly blobs could have it's optical filter element drilled out as it adds nothing useful to the optical chain. Is that correct?

Thank you both, if there are any answers that either of you could provide to those 3 questions. I will continue to seek info from Lunt, concerning the use of one of their blocking filters; but for the present, the purchase of a Baader K-line filter seems to be quite an economical path to take and I'll see about going that route. I'm still waiting for my back-ordered ZWO 178mm to be processed, so it may be a short while before I've got the camera for the job. I do have several color cameras, but believe that the mono's are the preferred path to take. I can use the fastest frame-rate color camera, while waiting for the mono order to be fulfilled.

I'll let you both know what transpires, as I'm able to move forward; and of course, thanks to you both for giving me your time and thoughts, as I wouldn't get anywhere without you! You're very much appreciated!!

Tim


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Re: Looking for source(s) for CaK Blocking Filter(s)

Post by Bob Yoesle »

Hi Tim,

The "blob" filter is a "rusted" Induced Transmission filter, and it can't be replaced by anything I know of for CaK use. The secondary filter(s) appears to be the missing filter from the eyepiece side of the diagonal. These can be replaced with the Baader K line. The objective appears to be incorporating a tilted ERF before the objective, and from your photos looks to be pristine.

So the Baader K line looks like it will be all you need to do camera imaging - but lacking the ITF for IR blocking, this scope will not be suitable for visual use, although adding a KG3 filter will help with the long IR. However, I'm not sure it would be safe in either case for visual use unless you use it with a Lunt module, which will have the requisite CaK ITF and other necessary filters built in.

With the CaK wedge, a Herschel prism acts like the ERF, and in that case it will be a double stacked CaK telescope. However, you would not want Lunt wedge prism for DS use, nor the Baader K line. You'd just want to use the other filter components of the CaK wedge.


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