5 replies to this topic

[Larry Alvarez]

Hello everyone.  I finished some videos I've been working on but could not get them exactly right.  Their file size is pretty big and as such will be removed from my website soon.  But for a few weeks I thought I'd post the link here.  They are best if you download the file before playing them.  Their scale has been reduced several times to make them playable on most computers.  2 of them are 5 meg and the other two are smaller.  They show the calcium surface bubbling, boiling and churing.  Interesting, if nothing else.  Happy easter, LA

Calcium Jet Video

Calcium Disk

Calcium Closeup

Calcium Spot

[redvis]

Larry,

First off - great videos!  I liked the last one the best.  Quick question - which CaK scope are you using?  The MaxScope 70 by Coronado?

Also, how are you liking doing CaK imaging?  I'm thinking of getting the CaK 70 by Coronado and doing some CaK imaging but I'd like some advice and experience from you 

Cameran

[Larry Alvarez]

Cam - The 70 rocks and I would highly recommend it!  Keep in mind that its not a visual scope like the H-alpha type scope but for imaging there's really nothing quite like it.  I've seen the Baader filter and its Calcium but not to the point that you can say its that much different from whitelight imaging.  To its credit, it brings out some details that wouldn't ordinarily be seen in regular continuum whitelight.  But 300$ to have a better whitelight filter is not my idea of a good deal.  A couple hundred more and you could get a PST Cak telescope.  I thought about getting one for a time but decided against it because it was built on the same body that the H-alpha PST was built on.  A good body for visual use and perhaps webcam use but not really ideal for hardcore photographic use.  Lack of focus travel, small aperture, small exit aperture and odd mounting hardware made the decision pretty clear for me. 

When I got my scope I was looking for the image that I saw in those old spectro heliographs made by Hale.  The craggy looking surface with the jet black spots surrounded by spider arms of flame and gas filaments was what I was after.  After getting the Calcium scope I can say that I was not disappointed.
Its pretty light weight, is very well built, and is compact enough to take anywhere.  Its got a very even image photographically and with the draw tube on it just about any camera will come to focus. 

Speaking of focus, that's the one thing I can say that I don't like about it.  The focusing unit is a helical system that grips the scope such that you have to shake the scope to focus it.  It takes some practice and getting used to but is workable if you turn it real slow.  I'd rather have a crayford on it but its not made to accept a 3rd party focusing unit.  I was told that the designers main concerns regarding it were safety.  All the pieces to it are none removable.  The BF stays in the scope and there is no way to remove the front filter.  Everything is pretty much cemented in place.  In spite of the focuser its still a very cool scope.  It comes with a nice case and its own mounting clamshell. 

Calcium K-line imaging is alot like H-alpha with the biggest difference being the view through the scope.  K-line is not going to wow you right off because you do not see as much visual detail as H-alpha when looking though the eyepiece.  Some folks don't see any.  But after you connect your camera you'll realize how different it actually is. 

Its a really nice balance to an H-alpha scope and if your serious about imaging the sun its a real slice of heaven. 

Clear Skyz, LA

[redvis]

Hey Larry,

Awesome!  You know I love H-alpha imaging (gonna post some of my images up here soon) and I enjoy imaging with my PST CaK but I think that the 70mm will offer me a lot more resolution vs. the PST CaK. 

My main area of debate right now is whether or not to go for a doublestacked SM60, or a SM70 CaK!  It's a tough choice and I can only go for one this year so I want to make it a good one.  As you know I already have my SM60 filter so I'm not sure if I should upgrade that or go with the SM70 CaK.  I'm pretty happy right now with my 60, so that's why I'm tending to lean toward CaK.

As for the helical focuser, my SM60 is on my Borg 77ED refractor which has a helical focuser, so that party I'm fine with 

Another question - do you find processing the CaK images to be any more difficult than processing H-Alpha?  I'm mainly thinking in terms of Registax stacking since I'm fine with Photoshop.

Thanks for the response Larry.  Your recommendation - 70 CaK or doublestacked SM60? 

Cameran

[Larry Alvarez]

Cam - Whenever I upgrade I examine what I already have and what I started with.  You started with a PST and it was pretty good.  You upgraded to a 60mm scope and it blew the doors off the PST.  Based on your own images there is no comparison between the two photographically for you.  The 60 simply shows more detail.  You've come to another crossroad.  The decision is simple, if you want to explore a completely different view go with the Cak 70.  If you want the same view with a little more contrast then go with the DS.  Personally I'd go with the Cak 70, why get something similar to what you already have.  To achieve the same wow factor you got when you went from PST to 60ms you would have to step up to the 90 H-alpha filter.   

Registax wise the Calcium images are the same to process as the H-alpha.  You may be having trouble with your Cak PST but rest assured the Cak 70 has a much more defined image.  Its sharper and the contrast is such that registax does not have a problem with it.  I'd be glad to send you a small sample of raw video from my scope if you like.

I do not really see <.5 ang as better or an upgrade to h-alpha viewing, I view it in terms of a different flavor, if that makes sense.  Sort of a latteral movement as opposed to a step up.  You get more disk contrast but lose prom contrast.  The sweet spot is also affected and you have to worry about tuning 2 t-maxes.  The amount of light reaching the camera is also less with a <.5 system.  This means that you'll have to get used to a whole new set of techniques when shooting the Sun.  There are several good and bad points but in the end you'll still be looking at H-alpha.

With a Calcium telescope you'll have a completely different view on the other side of the spectrum.  If you have a PST Cak then you know its much different.  The 70mm Cak coupled to a camera like the Lumenera will produce some excellent shots.

Ultimately its up to you but here are some points to consider:
Cons to an external DS
1.  An external DS will make the scope top heavy. 
2. You'll have to tune 2 t-max detuners.
3. You will have to retune your imaging parameters to compensate for less light
4. The sweet spot will change
5. If you use a fitted case, you might have to remove the extra filter before storage
6. Setup and take down time will be extended due to the extra filter install and t-max tune
7. More of a latteral upgrade than a step up from what you currently have
8. If you already have an H-alpha filter you will have to send it in to get it matched to the second filter.

Pros to a DS
1. Images will have much more contrast and appear more 3d
2. You can use the existing telescope and mount system
3. You have the ability to switch between the two filter types
4. 1 stacking filter is cheaper than the Cak 70
5. Photographically, the view has more depth
6. While very similar to the <.7 view it still has some subtle difference that make it cool

Cons to a Cak 70
1. will require a separate dovetail for your mount
2. not a visual scope like H-alpha, its hard to see

Pros to a Cak 70
1. A completely different view to explore
2. 70mm obstruction free aperture
3. Scope is very well constructed and optimised for safety
4. Comes with its own storage case
5.  Is lightweight and easily transportable
6. Is photographically superior to other setups on the market
7. provides a contrasty image that is easy to process
8. Focuser drawtube accomadates several types of cameras

[redvis]

Larry,

Thanks for the reply!  That really clarifies things for me.  I'm going to make my decision (I am strongly leaning CaK) this summer after this horrible semester of school is over 


Thanks again for taking the time out to post all that great advice.

Cameran