Help choosing a camera for my Rasa 11

I wouldn't be so quick to jump to the obvious wide field answer.   You need to ask yourself what you are interested in imaging, and then leverage to get there as best possible.   There are multiple possible use cases for the RASA with significantly different results.   Wide field is obvious, but have you considered / rejected narrow field?    The RASA combined with an ASI183 (for example) would give you a small field with small pixels, but allow for very nice resolution images of galaxies and smaller targets (but not so much for the smallest of planetary nebula).    There's quite a bit of joy in imaging at f/2.2 in OSC.   It's extremely convenient and low-hassle.   If you're in dark skies, this is a great choice.   If you're in the city, you have other issues (filters, etc.).

In my case, I have a RASA11 with an ASI183mcPro OSC, and I use it in Bortle 1 skies to to do acceptable work on galaxies and nebula in the ~1 degree field range.   If you go wider field to take advantage of a ~3 degree field, you'll have lower quality PSF to the edge, but that nice big field.    If you want to see what the smaller/higher quality field use case looks like, see my page or other user pages with RASA+ASI183.  

https://www.astrobin.com/users/dmsummers/

Best wishes as you sort out what you are trying to do....   CS   DougS

I have used many ZWO one shot color (OSC) cameras on my RASA 11 over the years, from ASI2600MC Pro, ASI2400MC Pro, ASI294MC Pro, and my ASI533MC Pro which is currently on it.  I do have decent luck with a filter drawer where you can add one 2" filter in such as a light pollution or nebula filters.  If you put a filter wheel in from of that telescope you will get whacky 3 and not 4 full star spikes which looks funny.  QHY10 was also great on this scope for many months.
There is a good web site called Astronomy Tools (https://astronomy.tools/calculators/ccd_suitability) that will allow you to pick your scope and camera and it will tell you if the combination is over or under-sampled.  This is not super critical, but should really be factored into your decision, especially if you want good results with the least pain.  Also that site will give you the Field of View or what you will see with respect to known astro objects, like M311 for example. https://astronomy.tools/calculators/field_of_view.

Also seeing pictures from other astrophotographers has inspired more than one scope and camera purchase so that also can be helpful.

This is not a quick start hobby.  For a first scope I would not have recommended either the RASA or the Edge SCT, but a small refractor.  They are simple and will give you the best results with the least learning curve.  That said the RASA is an awesome scope but suffers from some ills being so fast at f/2.2.  Try not to let it frustrate you, ask questions, there are tons of people that did what you are doing and are happy to help, but you need to have reasonable expectations.  I have been doing this for almost 10 years and have 2 backyard observatories and still struggle at times.

Clear Skies,
Tom

Whilst I'm mindful of the question you are asking there are a few things to consider , along with the camera, that may make your life easier- one you've mentioned is automated focusing. Remember that some automated focusers have variable backlash like the ZWO that can be difficult to tame as it is often inconsistent and varies according to temperature and thread travel when it moves the RASA mirror. I find the Pegasus Zero much better in this respect as it has no or very little backlash.

I would suggest you explore the Baader UFC filter system for your RASA and initially use the ASI2600 class of camera as it is not so demanding on the requirement to be using a totally flat field. I would only consider the IMX455 sensor when you are comfortable that your field is flat with an initial APS-C size sensor- there really is a world of difference in the need to be very precise when you venture into full frame sensors with the RASA 11.

Having an accurate, as mentioned, automated focusing system with no backlash will make your life much easier as the step size to accurately focus needs to be in micro metres which is easily achieved with electronic devices. Backlash can cause your V-curves to be inaccurate and in worse cases can take much longer to achieve focus than what would normally be expected.

Back focus needs to be precisely at 72.8 mm for the RASA 11 and you do need to take into account the change of focal length from the use of filters.

I also suggest you get yourself a precise parts custom adapter that screws over the camera mounting assembly and dispense with the locking ring clamp that compresses the default camera plate for camera attachment- its felt back can cause tilt. The Assembly with a rotator can be seen in this post https://www.cloudynights.com/topic/908836-a-most-fortunate-configuration-event-very-rare-three-lucky-strikes/

With the RASA V2 the mirror alignment in my experience is quite precise. I've never needed to collimate the lens assembly. I suggest you explore back focus and adapter levelling before even touching the lens collimation to avoid perhaps an unnecessary world of pain.

Automated focusing needs to happen on each filter change and at least every 30 minutes in environments with rapid temperature changes. The focus is sufficiently sensitive to this.

There is a lot initially to consider for a new RASA setup. When you get these aspects fine tuned it is a very rewarding instrument but don't be frustrated if you don't get instant optimal results you just need to be patient and work through each challenge. Celestron never said it was going to be an easy instrument to  set up and get working well. I think they are a bit liberal with some basic facts that would make us better informed before committing to a purchase.

Good luck.

Best wishes,
Mark

This is all really great advice, I would add one additional tool to look into  http://telescopius.comif you're not already aware of it. 

The telescope similar is a great way to plan and compare different camera/scope combinations, as well for planning once you start taking pictures.


Sean

no matter what camera you get you better get this to get it working: https://www.asgastronomy.com/photon-cage/

I use the ZWO ASI2600MC Pro with my RASA11 and have been getting some decent results with it.  I use either an IDAS NBZ nebula-enhancing filter or an Optolong L-Pro, mounted in a filter drawer.  I have the scope assembly mounted on an AP1200GTO, an old but solid mount which has proven quite reliable.  I use a mini-Borg 50 scope for guiding, with a Starlight Xpress Ultrastar guide camera.  I do focusing with the aid of a ZWO EAF.  For capture software I use Sequence Generator Pro.

I agree with the people who say you should get a small refractor first and learn to do imaging with that before you try a temperamental beast like the RASA11. That said, I haven't found the RASA11 extremely temperamental.  But it does have its idiosyncrasies, and one of them is that focusing can be a challenge, especially at the outset.  

I learned to do astrophotography with a William Optics FLT-132 refractor.   I would recommend starting out with a smaller scope like the WO Redcat or one of the other refractors, nothing bigger than 70-80mm at first.  

Whichever way you go in the end, I wish you the best of luck.

Cheerio
Jerry L. Floyd

I found that the RASA 11" can be used with the CEM70G mount which I have however I've got an upgrade in place for the CEM120. The RASA 11" is surprisingly bigger than the C11 SCT so a beefier mount is beneficial.

I have the RASA11 V2 for several years - I would recommend the ZWO ASI2600MC Duo OSC - easier to collect data and process than mono. The Duo built in guider will take into account any potential mirror flop as well - works fine with dual narrowband (Ha and O3) filters.  I would also recommend purchasing the RASA 11 ASG Photon Cage, the RASA 11 Standard M54 package with built in filter adapter (see https://www.asgastronomy.com/store/asg-photon-cage-rasa-11-m54-package/) - the Photon Cage will provide tilt, precise backfocus, and removable filter slider capabilities.  Finally, you will need dew shield - I would recommend Celestron's aluminum dew shield with cover cap as well as Celestron dew heater ring (it will need a regulated heater power as a function of outside temperature - dew heater controller).  enjoy the RASA 11 

Thank you to everyone for all the knowledge and suggestions!  A bit overwhelming… After reading through all the replies I can see I have a lot of learning ahead of me.  So many of you suggested the ASI2600mc so that is what I ordered.  High Point mentioned the duo had some issues so I went with the pro (even though it’s on b/o.)  I already have the Celestron auto guider so I assume that will work?  Did I make the right choice?

I also ordered the Photon adapter system (with filters) the L-extreme filter, dew ring & controller.
I neglected to inform that I’m using CGX mount.

I  went ahead and ordered the 8” EdgeHD bundle, ASI533mc pro, optolong uhd filter, dew ring,  Apertura all night power supply, Lepus telecompressor and wide angle eyepiece kit.  

Have  I missed anything?  (Except for the challenge of learning).  

Thanks again!!!  What a wonderful community!
 I can’t wait to post my first pic!

Thank you to everyone for all the knowledge and suggestions!  A bit overwhelming… After reading through all the replies I can see I have a lot of learning ahead of me.  So many of you suggested the ASI2600mc so that is what I ordered.  High Point mentioned the duo had some issues so I went with the pro (even though it’s on b/o.)  I already have the Celestron auto guider so I assume that will work?  Did I make the right choice?

I also ordered the Photon adapter system (with filters) the L-extreme filter, dew ring & controller.
I neglected to inform that I’m using CGX mount.

I  went ahead and ordered the 8” EdgeHD bundle, ASI533mc pro, optolong uhd filter, dew ring,  Apertura all night power supply, Lepus telecompressor and wide angle eyepiece kit.  

Have  I missed anything?  (Except for the challenge of learning).  

Thanks again!!!  What a wonderful community!
 I can’t wait to post my first pic!

Awesome!  I'm excited for you and I admire your courage!  I started out with a Celestron C8 which I'm still using, exclusively. I use it at F7 with the SCT Corrector IV and F2 with the Hyperstar v4.  For planetary at F20 (barlowed native).

Couple of things to ask about:
1.  Did you buy the Optolong L-eXtreme F2 filter for the RASA or the regular L-Extreme to use with the EdgeHD?

2.  The Celestron dew ring must be used with the Celestron Dew Controller so I hope that is what you bought.

3.  For guiding the key thing to remember so you don't drive yourself crazy is to keep the guiding error in arc seconds at or below your main image scale.  The RASA's image scale with the ASI2600 is 1.25"/pixel so as long as your guiding error is less than that you'll be seeing-limited which is good.  It is best to eliminate factors you can control when there are image issues.  The EdgeHD paired with the 533 yields an image scale of .33"/pixel.  Far more demanding and less forgiving.  Guiding errors at longer focal lengths are magnified so keep that in mind for guiding.  Don't forget to make sure your polar alignment is spot on.