C11 / CGEM / Pier - adequate mount for imaging?

[aparker]

Hi all,

I'm currently doing EAA and starting to dabble in more serious AP, using a C8 on a CGEM mount.  The mount is set up on a pier I built, rather than a tripod.  I hope in the future to upgrade to a C11, but am unsure that the CGEM is going to be enough mount for that scope for imaging purposes.  I anticipate using a fairly lightweight imaging train, but still expect OTA plus guidescope plus filterwheel plus camera to hit ~33 lbs, versus the mount's "rating" of 40 lbs.

Any practical experience or advice from others with this setup would be very helpful.

Thanks!

 

 

[gnomus]

I 'started' imaging with a CGEM and Edge HD 8" and found it very taxing - and I had virtually no success.  Is there any particular reason that you have for wanting to begin AP with such a long focal length?  Most advice I have seen is to begin with a shorter focal length refractor.  Certainly I only started to make progress when I bought myself an ED80 (much cheaper than a C11 too!!).     

[Owmuchonomy]

As Gnomus says, what are you aiming to image? That will dictate what kit you need. A C11 will be great for planets but a massive headache for pretty much anything else. Deciding what FOV you want to achieve is a good start and then work backwards to scope and camera combinations to get a decent imaging resolution. Then decide what mount you need to carry the kit.

[aparker]

Thanks for the feedback.  From a focal length standpoint I am thinking three things.  Hyperstar for wide field like large nebulae and galaxy fields (550 mm), Optec 0.5x reducer/flattener for galaxies (1375 mm), native FL for planetary nebulae.  I have not yet thought about or gotten interested in imaging solar system objects.  I have in mind being able to "do it all" with one telescope and interchangeable bits.  I've had a fair amount of luck doing realtime imaging/observing with my 8" EdgeHD at both 1330 mm and native 2000 mm with short unguided subs up to 60 sec.  For longer exposures I am assuming I will need to guide.  I am also planning this whole escapade in the context of a permanent observatory, or at least an outdoor shelter adequate to allow the mount to stay on its pier 24/7/365.  I would anticipate spending some time drift aligning the heck put of it.

Another option for me (easier, cheaper) is just to stick with the C8, but like everyone, I'm greedy for aperture...

[ollypenrice]

Aperture in AP is a complicated issue. Even a quick glance at good deep sky widefields shows that you don't need it. While the Hyperstar is very fast it does not usually produce very good widefield images. Check out the star sizes. Keeping star sizes down is a very big issue in widefield imaging and you need all the optical help you can get. You won't get much help from a Hyperstar. It would also be quicker, easier and not very different in cost just to swap the big SCT for a small refractor for widefield.

I think you are too concerned about the mount's payload and not sufficiently concerned about its accuracy. Take focal length out of the story and look, instead, at pixel scale in arcseconds per pixel. You need to be thinking about guiding with an average error in pixels of about half your imaging pixel scale. Once you get into SCT territory this can be a tall order. Not impossible but not a pushover.

Olly