C8, Baader focuser and a Starizona SCT corrector - Forums

Topic starter

Nov 5, 2023

I own an old Orange tube Celestron C8. It's in excellent (like new) shape with good clean optics capable of some well defined sharp DSOs. I know that some of you may say,"Just order a Celestron Edge HD and be done with it." $2000 for the scope and reducer and I'd be set. However, I already own the scope and a Baader SCT focuser. The only purchase would be the Starizona flattener/ reduced at $399. The Baader threads on to the scope and I would also get a Baader "Click Lock" which attaches to the focuser. The question is, putting the Starizona corrector at the end of the focuser. What do you think that will do to the reduction and flattening of the field? The focuser Is motorized so can be used with NINAs autofocus. I don't really want to try to "motorize" the scopes focuser. The Baader is so much more accurate and reliable. I've already done some astrophotography with the scope, Baader focuser and an Astro-Physics reducer. However, the AP piece does nothing to flatten the field, hence the Starizona piece is necessary. I'll more than likely just purchase the Starizona piece but would appreciate your opinions. Starizona won't comment on this setup 🤔.

Mike

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Ashraf AbuSara

Nov 6, 2023

Hello Mike,

You should be able to put the corrector onto the back of the Baader SCT focuser. Starziona does talk about this setup in their documentation here:

"The SCT Corrector has a 2” diameter body, allowing it to fit into a 2” visual back or 2” focuser drawtube. Ideally, the SCT Corrector will be mounted as close to the back of the telescope as possible. The performance of the lens does not change significantly if the SCT Corrector is farther from the telescope, but the focal reduction factor changes, reducing the field of view and increasing the telescope's focal ratio."

https://cdn.shopify.com/s/files/1/0327/2569/6648/files/SCT_Corrector_III_Instructions.pdf

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Emilio Frangella

Nov 6, 2023

i use this reducer, but i didnt put an additional focuser in the middle. I bought a celestron focus motor and it works pretty well. The additional focuser would very useful if the SCT had a mirror lock mechanism, but unfortunately it doesnt. Without that, the focus will shift no matter what you do, at that point it's useless in my opinion to throw another motorized focuser in the imaging train.

Mike H - Sky View Observatory

Topic starter

Nov 6, 2023 · Edited: Nov 6, 2023

Emilio, I'd rather not use the additional focuser but the Celestron focus motor will not work on the old Orange tube knob. At least as far as I know 🤔

edit: Please Note : This focus motor is compatible with all Celestron SCT's from 6” to 14” in aperture that have been produced since the year 2006; it is not compatible with 5” SCTs or older models.

Mike

Emilio Frangella

Nov 6, 2023

oh sorry, i wasnt aware of that - in that case you are right, no other option. The reducer should still work without any problem, your scope will be a little slower but nothing noticeable in my opinion

Ashraf AbuSara

Nov 6, 2023

Emilio Frangella:
i use this reducer, but i didnt put an additional focuser in the middle. I bought a celestron focus motor and it works pretty well. The additional focuser would very useful if the SCT had a mirror lock mechanism, but unfortunately it doesnt. Without that, the focus will shift no matter what you do, at that point it's useless in my opinion to throw another motorized focuser in the imaging train.

I use a standard C11 XLT with an EAF installed on the Baader Diamond Steeltrack crayford focuser. Not having the mirror locks is not a big deal as long as you make sure the last motion while focusing the primary mirror native scope focuser manually is counterclockwise, because it will support and push the mirror against gravity. The mirror remains relatively stable and as long as you automate refocusing every hour of imaging or so as you track the sky it will work well. The crayford focuser has the advantage of getting rid of image shift during focusing which can be quite big.

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Emilio Frangella

Nov 6, 2023 · Edited: Nov 6, 2023

Ashraf AbuSara:
Emilio Frangella:
i use this reducer, but i didnt put an additional focuser in the middle. I bought a celestron focus motor and it works pretty well. The additional focuser would very useful if the SCT had a mirror lock mechanism, but unfortunately it doesnt. Without that, the focus will shift no matter what you do, at that point it's useless in my opinion to throw another motorized focuser in the imaging train.

I use a standard C11 XLT with an EAF installed on the Baader Diamond Steeltrack crayford focuser. Not having the mirror locks is not a big deal as long as you make sure the last motion while focusing the primary mirror native scope focuser manually is counterclockwise, because it will support and push the mirror against gravity. The mirror remains relatively stable and as long as you automate refocusing every hour of imaging or so as you track the sky it will work well. The crayford focuser has the advantage of getting rid of image shift during focusing which can be quite big.

I guess i am lucky, my c11 never suffered from image shift. I tried with a crayford but the difference was non existent

Lynn K

Nov 6, 2023

Hi Mike, I have used the Starizona SCT III reducer/flattener with a C11 &C9.25. I used a Starlight 2" crayford focuser on the rear of the scopes. I bring the scope to infinity focus used the stardard SCT focuser. As mention above using counter clockwise motion. I then push the Starzona reducer into the Starlight focuser untill it hits the stop. I then back off about about 2mm. This has worked well. I use an Opect/Starlight Quicklync focuser motor.

I purchased a Starizona SCT reducer version IV last year. I have used it on the C9.25 with the Optec Leo focuser. Using the same procedure above, it worked well.

However, I have never been able to get a good V curve for auto focusing. But, have not attempted to do so in years. I just use remote focus. I have a permanent Pod set up, and run from the house. I mostly image with refractors.

Lynn K.

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