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Ca K telescope

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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Re: Ca K telescope

Post by hunterknox » Wed Jan 15, 2014 8:57 pm

I used to use an iOptron Minitower mount with my Tal PST mod. It worked but it wasn't what you'd call confidence inspiring. There is the Pro version available - that has a higher capacity but I wouldn't want to pay what it costs to find out whether it works or not.

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Re: Ca K telescope

Post by sullij1 » Thu Jan 16, 2014 3:24 am

Is anybody doing solid, consistent image runs on Alt/AZ mounts? Equatorial seems to be the standard for imaging. ALT/AZ for grab and go visual - Right?
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Re: Ca K telescope

Post by astrodanco » Thu Jan 16, 2014 3:39 am

Certainly not for imaging. For outreach I tried Alt/Az mode with the AZ-EQ6 mount. It promised much. It didn't deliver. Now I use it in EQ mode only.

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Re: Ca K telescope

Post by Montana » Thu Jan 16, 2014 12:34 pm

Is there any particular reason you don't like the alt/az other than field rotation?

We have asked for a quote from Rick for a Celestron Omni 102 and an iOptron Minitower Pro. The iOptron MT Pro gets a good review from Ian Morison and I remember him loving it and showing it off at a 'show and tell' at the astro club, he was using it with a Takahashi 130.

Any opinions welcome, I have asked for Rick's opinion too.

Alexandra and hubby

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Re: Ca K telescope

Post by pauljones » Thu Jan 16, 2014 6:34 pm

I don't do solar imaging on an alt/az mount but I do all my planetary and lunar imaging with a ServoCat driven Dobsonian. If you keep the video runs short enough, field rotation is not an issue. It seems to work.

It makes animations annoying as over a long period of time, field rotation is obvious. But for just one image, it's fine. Solar video runs (in my hands, at least) are shorter, so I think would also be fine. If you have a choice and the money, EQ is better. But if you own an alt/az, you can use it.

I assume here it is a driven alt/az of course.

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Re: Ca K telescope

Post by marktownley » Thu Jan 16, 2014 6:42 pm

Is there any particular reason you don't like the alt/az other than field rotation?

We have asked for a quote from Rick for a Celestron Omni 102 and an iOptron Minitower Pro. The iOptron MT Pro gets a good review from Ian Morison and I remember him loving it and showing it off at a 'show and tell' at the astro club, he was using it with a Takahashi 130.

Any opinions welcome, I have asked for Rick's opinion too.

Alexandra and hubby

Any reason you're plugging for the alt /az over the eq?
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Re: Ca K telescope

Post by TheHubby » Thu Jan 16, 2014 7:06 pm

Any reason you're plugging for the alt /az over the eq?

Evening Mark,

For non physics people like me, I just want a tripod and mount to work when I pick it up and not have to work out where north is, what the weight is like e.t.c.

The little Merlin does this for me and when I see Alexandra spend 15 minutes mastering the EQ6 I think she could be observing rather than fiddling.

You have to remember I have the attention span of a gnat and need to pick equipment up, work with it and put it away quickly. I won't be spending hours outside, only about an hour. The alt az mounts are built for simple astronomers like me, but I realise they are inferior.
Negative comments welcome to aid learning, as competing with Alexandra on her old borrowed equipment means I will always be 3 steps behind.

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Re: Ca K telescope

Post by marktownley » Thu Jan 16, 2014 8:16 pm

Any reason you're plugging for the alt /az over the eq?

Evening Mark,

For non physics people like me, I just want a tripod and mount to work when I pick it up and not have to work out where north is, what the weight is like e.t.c.

The little Merlin does this for me and when I see Alexandra spend 15 minutes mastering the EQ6 I think she could be observing rather than fiddling.

You have to remember I have the attention span of a gnat and need to pick equipment up, work with it and put it away quickly. I won't be spending hours outside, only about an hour. The alt az mounts are built for simple astronomers like me, but I realise they are inferior.

Ahhh, fair enough. I'm probably just slap dash with my EQ, all I do is take it out, plonk it to face north and away I go, minute or two max....
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Re: Ca K telescope

Post by swisswalter » Fri Jan 17, 2014 5:31 am

Hi Hubby

here the same, I take out the EQ6, put it on the place it was setup and aligned and shoot. A matter of some minutes. The G11 I even leave in the garden the whole year with a bag on top of it. Setup time 90 seconds ;-)
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Re: Ca K telescope

Post by Valery » Fri Jan 17, 2014 6:34 am

Hello all,

Let me add, solar funs, that a telescope for CaK is not that simple optically. The reason is that at this wave length _all_ refractors have severe spherical aberration, OVERCORRECTION. In other words, their objectives have longer focus for outer zones and shorter focus for central zones. Of course, we consider that these refractors you all use for CaK telescopes are visual refractors and optimized for cental wave lengths (yellow-green for a human eye).
So, a CaK telescope must be specially made and figured/optimized for a 393nm wave length.

Which scopes are the best for CaK from what you ca find on the market?

1. Takahashi's TOA-130. These telescopes have orthochromatic color correction and better corrected (for SA) at 393nm.
2. Simpliest Fraunhoffer refractors of smaller apertures and very long F/D, at least F/10 and also they need to be severely
UNDERcorrected for green light.

All shorter achromats and especially ED doublet and triplets will work with severe SA at the demanded CaK line.


Hope this helps.


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Re: Ca K telescope

Post by marktownley » Fri Jan 17, 2014 7:02 am

I like your description of SA valery 8)
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Re: Ca K telescope

Post by brianb11213 » Fri Jan 17, 2014 8:50 am

Is there any particular reason you don't like the alt/az other than field rotation?

We have asked for a quote from Rick for a Celestron Omni 102 and an iOptron Minitower Pro. The iOptron MT Pro gets a good review from Ian Morison and I remember him loving it and showing it off at a 'show and tell' at the astro club, he was using it with a Takahashi 130.
Field rotation & orientation is the only real issue here.

I have an MT Pro, I like to use it for outreach because it's so easy to carry & set up compared with an equatorial with similar load handling capability. It would be fine for solar imaging except for the extra hassle that working out field orientation poses, and for the fact that field rotation makes mosaicing difficult & effectively rules out time lapse / video work.

In my experience a Tak 130 might be a bit much for a MT Pro (unless the wind was really calm) but it works well with a 110mm f/7 apo.

Pedro

Re: Ca K telescope

Post by Pedro » Fri Jan 17, 2014 11:38 am

Very interesting thread.

For Ca-K imaging I use two different apo refractors with excellent results:

1- TV101 F/5.9 @ F/10 + LUNT1200 CaK module
2- IKHARUS 102 F/7 @ F/10 LUNT1200 CaK module

Pedro

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Re: Ca K telescope

Post by swisswalter » Fri Jan 17, 2014 5:45 pm

Hi Hubby and wife of it

I'm not having any problems with all my 13 scopes using a Cak filter of the KLUNT type. The best results I get with the bargain scopes ;-). Take a week off, travel to switzerland and get a cheap scope ? Make sure to discuss the sight seeings with Mark and his wife ;-)
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Ca K telescope

Post by TheHubby » Fri Jan 17, 2014 9:57 pm

Well everyone, I've made a start and ordered the filter.

The Lunt LS18CaKMDd2 calcium approach for refractors up to 102mm opening - with 90 ° deflection - with B1800 blocking filter.

It's going to take 3 weeks to arrive by which time I will have hopefully settled on the scope and mount by then.

(I must admit I nearly ordered the Ha B1800 filter by accident as they nearly have the same name but Alexandra insisted on checking the order before I made the order)

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Negative comments welcome to aid learning, as competing with Alexandra on her old borrowed equipment means I will always be 3 steps behind.

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Re: Ca K telescope

Post by astrodanco » Fri Jan 17, 2014 10:00 pm

Only three weeks. You lucky dog. I waited many months.

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Re: Ca K telescope

Post by swisswalter » Sat Jan 18, 2014 8:44 am

Hi Hubby

great. But the article number you mentioned is the B1800 :?
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Ca K telescope

Post by marktownley » Sat Jan 18, 2014 9:01 am

Fun times ahead in Cheshire! :)
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Re: Ca K telescope

Post by marktownley » Sun Jan 19, 2014 3:20 pm

Simpliest Fraunhoffer refractors of smaller apertures and very long F/D, at least F/10 and also they need to be severely UNDERcorrected for green light.

Hi Valery, is there a 'list' anywhere that would tell us the telescopes that were undercorrected for green light?
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Re: Ca K telescope

Post by robert » Sun Jan 19, 2014 3:29 pm

I want to repeat what has been said about all az mounts because it could be very disappointing to have a high quality CaK filter and good optics with it. It will suffer field rotation which will make high quality imaging impossible. Setting up an eq mount even very roughly is very much better.
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Re: Ca K telescope

Post by Montana » Sun Jan 19, 2014 4:17 pm

Thanks Robert, I don't have any problem imaging with the PST on my little alt/az mount, I have even done timelapse OK with it, so long as you don't suffer from sea sickness it's OK to watch :lol:

Alexandra

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Re: Ca K telescope

Post by marktownley » Sun Jan 19, 2014 9:05 pm

Thanks Robert, I don't have any problem imaging with the PST on my little alt/az mount, I have even done timelapse OK with it, so long as you don't suffer from sea sickness it's OK to watch :lol:

Alexandra

I hear what you're saying, but at CaK wavelengths you have 1.6x the resolution for a given aperture compared to Ha. 100mm aperture has 2.5x the resolution of a 40mm, multiply these together and you are looking at a factor of 4 i.e. 4x less time for field rotation to become apparent compared to your PST. If you do plan to do any timelapse with this setup and CaK wavelengths field rotation will be apparent... Just something to be aware of...
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Re: Ca K telescope

Post by TheHubby » Sun Jan 19, 2014 9:33 pm

I hear what you're saying, but at CaK wavelengths you have 1.6x the resolution for a given aperture compared to Ha. 100mm aperture has 2.5x the resolution of a 40mm, multiply these together and you are looking at a factor of 4 i.e. 4x less time for field rotation to become apparent compared to your PST. If you do plan to do any timelapse with this setup and CaK wavelengths field rotation will be apparent... Just something to be aware of...

My imaging knowledge is limited so I won't be doing timelapses.

I will give that job to Alexandra who can do that properly on the TEC140
Negative comments welcome to aid learning, as competing with Alexandra on her old borrowed equipment means I will always be 3 steps behind.

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Re: Ca K telescope

Post by Valery » Mon Jan 20, 2014 8:29 pm

[quote]Simpliest Fraunhoffer refractors of smaller apertures and very long F/D, at least F/10 and also they need to be severely UNDERcorrected for green light.

Hi Valery, is there a 'list' anywhere that would tell us the telescopes that were undercorrected for green light?

Hi Mark,

There is no such list of telescopes undercorrected in a green light. But I can tell you, that MOST of chinese refractors are under corrected. So, they have better, than normal refractors, correction in a very deep violet.
As more your refractor is under corrected in green, as better for CaK.
Some years ago I bought such severe under corrected (in green!) objective 120mm F=1000mm. It has very very good correction in a CaK line.
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Re: Ca K telescope

Post by solarchat » Mon Jan 20, 2014 8:35 pm

I've never seen this in any refractor and don't know how you can under correct a lens . But, I'm not mechanically or optically inclined. I do know I've never noticed any fringes in any single wavelength telescope application.
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