Using a 6-inch SCT (C6) for Solar Imaging

[charley5]

Hi Everyone:

I am getting back into solar imaging after a long hiatus. I am now living in India. One of the scopes I am considering using is the Celestron NexStar 6SE telescope. I used a 5-inch refractor with a Daystar Quantum filter several years ago. Now I am considering using the C6 with a Baader Herschel Prism. Since this scope does not accept 2" eyepieces, I am not even sure I can use this filter on it. I am interested in imaging solar granulation, and the growth of sunspots.

I am just wondering if anyone has had experience using a 6-inch SCT? Any recommendations regarding this scope? Should I get a different mount? Do I need a front-mounted filter to protect the optics? Should I get a better focuser? Any other suggestions?

Thanks,

-Charles

[Montana]

A very warm welcome Charles

I'm not sure you should use a Herschel wedge on an SCT? I have experience with a C11 but not a C6. I use Baader solar film on the front and have had good granulation with it, I generally get good results but you must buy the photographic film if you wish to image, as I found the visual film too dark.

https://www.flickr.com/photos/alexandra ... 535593245/

https://www.flickr.com/photos/alexandra ... 535703357/

Alexandra

[marktownley]

Welcome to the forum! Do you still have the 5" frac?

[charley5]

A very warm welcome Charles

I'm not sure you should use a Herschel wedge on an SCT? I have experience with a C11 but not a C6. I use Baader solar film on the front and have had good granulation with it, I generally get good results but you must buy the photographic film if you wish to image, as I found the visual film too dark.

https://www.flickr.com/photos/alexandra ... 535593245/

https://www.flickr.com/photos/alexandra ... 535703357/

Alexandra

That's great. Thank you, Alexandra. That's very helpful. I shall look into this kind of filter. Your granulation photo is amazing, by the way! I will also take H-Alpha images as well. I was thinking of the Quark, but there is such variability in quality, and customer service not hugely responsive (at least a few years ago) so I am hesitating in that regard.

Thanks again,

-Charles

[charley5]

Welcome to the forum! Do you still have the 5" frac?

No. I sold it several years ago. It was the ES 5" carbon fiber version. Great scope for the price!

-Charles

[marktownley]

Why the c6 in particular then?

[thesmiths]

For solar granulation, a Solar Newtonian is also an excellent choice. It is cheaper than a Baader Herschel wedge. a 150mm aperture is a good place to start.

[LauraMS]

On a SCT, you must not use a Herschel wedge because the full heat concentrates on the secondary mirror and may also get into contact with the central light baffle at the main mirror, potentially causing damage.

For broadband ("white light") a front mounted Baader film (ND =5 got visual, ND=3.8 for astrophotography) is the best option (see here my images on the Edge11: viewtopic.php?t=23238 )

For the C6, a 6 inch Baader D-ERF front mounted energy rejection filter is also available and may be combined with a Herschel wedge. Also Halpha might be feasible using a Quark Chromosphere in combination with the D-ERF. Never tried that myself but considered doing this as a travel setup. Images might look like others at 6inch, e.g. viewtopic.php?p=361027#p361027

[charley5]

Why the c6 in particular then?

Three reasons:

I live in India, and it is difficult to acquire certain equipment domestically. There are perils getting stuff shipped from NA.

The 6-inch is portable.

The 6-inch has the focal length I am looking for.

I have some doubts less about the optics, but more about the native focuser, and using an azimuth mount.

-Charles

[charley5]

For solar granulation, a Solar Newtonian is also an excellent choice. It is cheaper than a Baader Herschel wedge. a 150mm aperture is a good place to start.

I haven't seen any Solar Newtonians available commercially, and I also doubt they would be available in India. Plus, depending on their focal length, their portability is not great, compared to the SCTs.

[charley5]

On a SCT, you must not use a Herschel wedge because the full heat concentrates on the secondary mirror and may also get into contact with the central light baffle at the main mirror, potentially causing damage.

For broadband ("white light") a front mounted Baader film (ND =5 got visual, ND=3.8 for astrophotography) is the best option (see here my images on the Edge11: viewtopic.php?t=23238 )

For the C6, a 6 inch Baader D-ERF front mounted energy rejection filter is also available and may be combined with a Herschel wedge. Also Halpha might be feasible using a Quark Chromosphere in combination with the D-ERF. Never tried that myself but considered doing this as a travel setup. Images might look like others at 6inch, e.g. viewtopic.php?p=361027#p361027

Your images are great, Laura. That is exactly the type of images I want to achieve. I would love to contact you by pm if any questions arise as I am gathering the right equipment. My main concerns now are how to mount the Baader film to the front of the telescope; what to do about improving my focuser; which CCD camera to get; and will the azimuth mount that comes with the scope be good enough?

Thanks again,

-Charles

[LauraMS]

Shure, Charles, contact me anytime. But don't forget the helpful people here...

Baader Film comes with a mount, no problem. But don't forget that myb broadband images were done with almost double the aperture compared to a C6...

If you would want to try the Halpha route, you will need to have somebody build a cell for the ERF for you. Shouldn't be a problem but don't forget that nobody has used a C6 before for Halpha, so some experimentation my be needed. As an alternative, Baader sells the 8 inch Triband SCT with built in ERF (not removable).

Best, Laura

[charley5]

Shure, Charles, contact me anytime. But don't forget the helpful people here...

Baader Film comes with a mount, no problem. But don't forget that myb broadband images were done with almost double the aperture compared to a C6...

If you would want to try the Halpha route, you will need to have somebody build a cell for the ERF for you. Shouldn't be a problem but don't forget that nobody has used a C6 before for Halpha, so some experimentation my be needed. As an alternative, Baader sells the 8 inch Triband SCT with built in ERF (not removable).

Best, Laura

Thanks, Laura. This is very helpful!

-Charles

[Bob Yoesle]

Shouldn't be a problem but don't forget that nobody has used a C6 before for Halpha, so some experimentation my be needed.

Not exactly true, as a 6 inch SCT is apparently what Mark Wagner of Solar Spectrum uses with a Baader DERF:

M Wagner's H alpha rig SM.jpg (273.78 KiB) Viewed 2206 times

Mark should therefore be a good resource to see about doing this, and his Suna or the equivalent Baader Sundancer H alpha filters would be my recommendation.


Bob

[charley5]

Shouldn't be a problem but don't forget that nobody has used a C6 before for Halpha, so some experimentation my be needed.

Not exactly true, as a 6 inch SCT is apparently what Mark Wagner of Solar Spectrum uses with a Baader DERF:


M Wagner's H alpha rig SM.jpg


Mark should therefore be a good resource to see about doing this, and his Suna or the equivalent Baader Sundancer H alpha filters would be my recommendation.


Bob

Thanks so much for this information, Bob. I shall look into it!

-Charles

[mdwmark]

Hi Group,
I saw what Bob's posted. The C-6, it is so much easier then stetting up a 6" refactor. Depending on the filter I'm testing. I'll use a Baader's SunDancer2 telecentric. It is smaller and the 3X give me that F30 which is good for most filters. I'm really surprise more people don't use them. Even the C-5 with an DERF should work out fine.
Mark W

[charley5]

Hi Group,
I saw what Bob's posted. The C-6, it is so much easier then stetting up a 6" refactor. Depending on the filter I'm testing. I'll use a Baader's SunDancer2 telecentric. It is smaller and the 3X give me that F30 which is good for most filters. I'm really surprise more people don't use them. Even the C-5 with an DERF should work out fine.
Mark W

Fantastic. Thank you. Do you have any samples of images taken with a C6 that I can link to?

-Charles

[mdwmark]

Hi Charles,
I'm afraid I don't. I from the really old school. I did film, and had an Astrovid camera to watch it on TV. But haven't gotten into digital yet. I think the processing part holding me back. I knew my way around a dark room really well.
Where I live the seeing is usually not that good. But it holds up visually just fine. What I have read, if it holds up visually with a camera and processing it's even better. I'm sure there is the old argument what is better. Refactor or SCT . But for setting up the SE-6 , it's up and running in a couple minutes.
One thing I do know , it has to be easier then imaging with those larger solar SCT's. Maybe some one will chime in on they work for imaging.
Mark

[Dennis]

Hi Charles,
I'm afraid I don't. I from the really old school. I did film, and had an Astrovid camera to watch it on TV. But haven't gotten into digital yet. I think the processing part holding me back. I knew my way around a dark room really well.
Where I live the seeing is usually not that good. But it holds up visually just fine. What I have read, if it holds up visually with a camera and processing it's even better. I'm sure there is the old argument what is better. Refactor or SCT . But for setting up the SE-6 , it's up and running in a couple minutes.
One thing I do know , it has to be easier then imaging with those larger solar SCT's. Maybe some one will chime in on they work for imaging.
Mark

It is indeed a very interesting aproach to go for a compact C6 instead of a long 6" refractor. Reasons against the C6 could be:
-more expensive then a achromatic refractor
-central obstruction will reduce contrast
-mirror system will reduce contrast

On the other hand.. when i wanted to upgrade aperture from my 6" f/8 achro for me there basically was only the sct route.
I never regretted the decition and it is in fact a very comfortable and fast 4 min. setup for the aperture (C9.25"), functionality and compactness. And indeed i dont miss the better contrast of the refractor, since i only do imaging with this, Photoshop takes care of the contrast.

Visually a unobstructed scope of same aperture will always win.