RC 8'' and new CMOS sensors... I'm lost :-( - Forums

Topic starter

Oct 18, 2021 · Edited: Oct 18, 2021

Dear RC 8'' users,

I'm writing this post as I feel a bit lost with the new generation of CMOS cameras.
Today I'm using a Moravian G2-4000 camera with a QE efficiency of around 50% and when I look at the new Sony IMX sensors generation with QE at 90% it makes me definitely feel that it's time to evolve and change my camera.

But looking at all the cameras on the market, I see that pixels are all around 3.75 microns which gives me an approximate 0.48 sampling..
… and the chips are big.. from APS-C to Full Frame which is not supported natively by our scope…

I feel lost and want to ask you… which camera are you using with your RC 8''

Are some of you already using new CMOS like the Moravian C3-26000 or Zwo2600 ?

And in terms of sensor size, did some of you already tried APS-C APN with the RC 8'' ?

Your help will be welcome because at this precise time, I have the feeling that nothing will fit with my RC 8'' and to be honest I don't want to go back to small fcals and do wide field astrophotography. I love this scope because it gaves me more possibilities with deep sky objects and even on nebulas I can zoom in which has more interest to me that having the entire nebula on the frame but without details..

I'll be glad if some of you have experienced or tested new CMOS sensors on our scope.
Your feedback is more than welcome.

Thank you very much
Cheers

Fabio

Scotty Bishop

Oct 18, 2021 · Edited: Oct 18, 2021

I have used APSC plenty with an 8RC. It definitely covers it. You can also use a refractor reducer and flattener on one and they work perfectly. The 2600 sensor will be no problem at all, but you will need to take flats with it because the corners may be a little dark.

Helpful Concise

Fabio Mirra

Topic starter

Oct 18, 2021

Thank you so much for your feedback Scotty, much appreciated.
I'll then seriously reflect on this possible option and think about the Moravian C3-26000.
Wish you a nice day
Fabio

Well Written Respectful

Rod Kennedy

Oct 18, 2021

Using a compressor, like the Astro-Physics CCDT67 Telecompressor running at 0.8x, then 3.75µm pixels (for me a ASI1600MM Pro) yields roughly 0.64 arcsec/pixel which I think is perfect fine (slight oversampling). You can't really run this type of compressor at the nominal 0.67x because it was designed for a different scope; so factor in 0.8x in your calculations.

In any case I think ASI2600 without a compressor can work with 36mm filters, and in post processing you can deal with oversampling to resample back to the recommended range. Rod

Helpful Concise

Fabio Mirra

Topic starter

Oct 18, 2021

Thank you very much Rod.
Yes as I understood from reading different forums, we can deal with the oversampling during processing.
Personnaly I don't want to use a reducer because I'de like to continue with the native focal length of 1624mm which allows me to chase some faint objects.
This is why I actually own this instrument rather than a refractor.
I think I'll try my chance and experience :-)

Fabio

Brian Boyle

Oct 18, 2021

Hi Fabio,

I run my RC8 with a TS2inch flattener (no reduction), ASI6200MM full frame sensor and resample x 2 in processing.

The flattener does a great job over the full frame, but the 2inch focuser does vignette in the corners. However, the big loss for me is field-of-view over a native f4 systrm.

i tried reduction, but the image quality caused by non-flatness more than about 8-10mm off-axis was horrible. Even at 0.8x.

I think @Scotty Bishop has it right in using an APSC sized sensor with a little reduction.

I had purchased the full frame for another telescope, but had to use it on my RC8 when my 1600MM broke.

Now if only I could find a 0.67 x reducer/flattener that worked over full frame sensors, and the focuser to hold it which still screws onto the RC8.
(I dont think that combo exists!).

So while i wait for world supply chains to make a TS 200mm f4.56 Astrograph a reality for me, i will continue to use the RC8 at 1600mm in my typical 4arcsec seeing.

CS Brian

Helpful

Fabio Mirra

Topic starter

Oct 18, 2021

Hi Brian,

Thank you for your feedback.

Which focuser do you have on your RC ?
Personnaly I own a Starlight Feather Touch Focuser which works perfectly, even for my G2-4000 which is near 2 Kg.
Do you still have the original focuser ? Or maybe I misunderstood your issue and in this case sorry

As Rod says here above, the recommended reducer is the Astro-Physics CCDT67 Telecompressor running at 0.8x, he was right.
Lot of people using the RC 8'' are recommending this reducer on several forums.

I give me some time of reflection, but it seems that APS-C format would fit and this is already a very good news.
Sounds good to me :-)

Have a nice evening
Fabio

Helpful Respectful

Brian Boyle

Oct 18, 2021

Hi Fabio, i still have the original focuser

I agree that should be my next upgrade and i have heard that the Starlight is a great option. Thanks for the suggestion
CS Brian

Fabio Mirra

Topic starter

Oct 18, 2021

@Brian Boyle

Hi Brian,

This is the one I have on my RC = FTF2015 BCR :   https://starlightinstruments.com/store/index.php?route=product/product&product_id=60
I've also add a stepping motor HSM20 :   https://starlightinstruments.com/store/index.php?route=product/product&product_id=356

Otherwise you still have the Moonlite option for which I've read a lot of good reviews as well.
There's also the possibility to add a motor to it.

Clear sky to you
Fabio

Rod Kennedy

Oct 18, 2021 · Edited: Oct 18, 2021

In the end the arcsec/pixel is the right thing to look at. Longer focal length and bigger pixels or shorter focal length and smaller pixels can be made equivalent. I have two galaxy hunting RC telescopes/rigs running at 0.64 and 0.67 arcsec/pixel. When I tried 0.335 arcsec/pixel (a ASI294MM with 1x1 binning) I couldn't see any improvement and the files were 4x the size. Personally I would be very happy with 0.48 arcsec/pixel and a 2600 sensor.

As an aside, because I do have a (weak) compressor then no dust/pollen ever gets in (zero motes for over a year). If I were running uncompressed I would thinking how protect the exposed optics close to the camera.

CS Rod

Helpful Insightful Respectful Engaging