SCT Celestron 9.25 for Solar Imaging

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fmiscio
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SCT Celestron 9.25 for Solar Imaging

Post by fmiscio »

I am new to Solar Imaging, and I would like to use my old Celestron 9.25. I have my eyes on an Off axis ERF, a quark Combo and a Baader Planetarioum TZ4. Is this configuration acceptable?

Thank you for your help :bow


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Re: SCT Celestron 9.25 for Solar Imaging

Post by marktownley »

Hi there and welcome to the forum.

Your c9 is f10 already, stopping it down is going to make it closer to f20/f30, so using the TZ4 in addition would put it around f80/f120, which, is way too high. Is the c9 your only scope or do you have a smaller refractor?


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Re: SCT Celestron 9.25 for Solar Imaging

Post by fmiscio »

Thank you for the reply. Yes I have a RedCat 51 250mm F 4.9, but I use it mainly for wide field astrophotography.


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Re: SCT Celestron 9.25 for Solar Imaging

Post by marktownley »

If you are going to stop the SCT down (with off axis ERF) then you will be running around 60-70mm aperture I guess? If this is the case then you would not need the TZ4.


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Re: SCT Celestron 9.25 for Solar Imaging

Post by fmiscio »

I hope you can help me here.
I have a celestron 9.25 with an off axis ERF and a quark combo HA,;trying to take some images with a ZWO 174.
No matter what I do I fail to have a decent focus. I assume is the backend focus the issue.
An Celestron 9.25 has a back focus of 139 mm and the Quark adds 99mm is that correct?
Also if I need to put extension rings to achieve the Blackfoot us distance am I correct in assuming the the extensions go after the Quark combo?
Basically SCT + Quark + Ext rings + zWO

Thank you for your help.


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Re: SCT Celestron 9.25 for Solar Imaging

Post by Ljungmann »

You will NEVER get a decent image with that configuration!
You will need a 1.25" SCT wedge drawtube from Daystar.
The filter needs "to look" off-axis too!!. The Quark needs to tilt a little bit. It will never show you any h-alpha details at all. You will be outside the center line. And please look at the Sun visually and see the features etc. before trying to take photos again.
Why Daystar do not say how to use a off-axis SCT - I don't know!
The photo shows you my former 9.25 SCT and my old Daystar. The filter was a ATM Daystar filter - now upgraded to a Quantum. You can se the tilt wedge just before the filter and you can see that the filter + diagonal has a slight off-axis tilt.
IMG_1926.jpg
IMG_1926.jpg (361.59 KiB) Viewed 99 times


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Re: SCT Celestron 9.25 for Solar Imaging

Post by marktownley »

In addition to the above, is the scope collimated well?


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Re: SCT Celestron 9.25 for Solar Imaging

Post by fmiscio »

So, it is collimated well enough, as I use it for Moon and deep space photography.
I am aware of the tilt aspect/requirement and the alignment as highlighted in their guide.
This is my first attempt to capture the sun and I have to admit I never realised I needed a 1.25" SCT wedge drawtube, their instructions are indeed not clear. I have to ask...
How is the draw tube dealing with the backfocus element? and also what do you meant will never show you any h-alpha details at all?

Thank you again


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Re: SCT Celestron 9.25 for Solar Imaging

Post by Ljungmann »

If you do not tilt the filter in an off-axis SCT you will not be able to see any h-alpha features. It is the way an interference filter works. It will be several Angstroms from the center line. I don't know about the Quark wedge draw tube. But the Quantum filter wedge I still have do not change the backfocus point. You can see the wedge on page 1 in the Quark Combo manual. http://www.daystarfilters.com/downloads ... al-new.pdf


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Re: SCT Celestron 9.25 for Solar Imaging

Post by fmiscio »

Thank you for the clarification on the h-alfa feature I MIS interpreted your reply.

The main issue I have is the focus, even before I manage to get to any Alfa feature.

In essence my question is about reaching backfocus.
As my SCT has a backfocus of 139 mm and the Quark adds an additional 99 mm with the wedge, I was wondering whether I needed to add extension tubes between the Quark and the Camera to reach the 238 mm needed.

Best Regards


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Re: SCT Celestron 9.25 for Solar Imaging

Post by marktownley »

fmiscio wrote: Wed Apr 07, 2021 12:20 am In essence my question is about reaching backfocus.
As my SCT has a backfocus of 139 mm and the Quark adds an additional 99 mm with the wedge, I was wondering whether I needed to add extension tubes between the Quark and the Camera to reach the 238 mm needed.
Easiest way is just to try it!


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Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
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