A 16" RC telescope for imagaing planets and galaxies?

[Andrew INT]

Dear All,

What are your thoughts on this telescope for the use of imaging planets and small galaxies? https://www.altairastro.com/product.php?productid=16734

I understand (I may be wrong) that this type of uncorrected  RC could only image in optical wavelengths. I suppose this means that imaging with OIII and Ha etc. is out of the question?

I have only ever imaged with a DSLR and a Webcam, so not too sure how inhibitive this telescope would be in the long run. The corrected versions are substantially more expensive. 

Perhaps I should focus towards getting a SCT?

Any advice greatly welcomed!

Cheers,

Andrew

[riklaunim]

Well, RC are very good at imaging everything, including narrowband imaging. For planetary imaging a RC design would be an overkill but still it would work (even with the higher obstruction). For small DS objects - you would need a solid, equally expensive mount and good dedicated DS camera + maybe RC focal reducer/flattener (if not built in) and a lot of free space to operate such big OTA Total cost would be very high.

Used SCT C14 are way cheaper and they are very good at planetary imaging. Very challenging at DS imaging due to big focal length (and good mount requirement).

[Geuse]

Who cares...it looks cool !! 

[ronin]

Ha is at the red end of optical, 653nm so that should be no problem.

O III is optical also, 500nm.

[Andrew INT]

Thanks for the info Riklaunim,

I am looking to treat myself to a good set-up once I pass my astrophysics degree (finally) next year. I plan to use a mesu 200 mount and house it all in a 2.7m observatory dome.

My main concern is the difference in price between the link above, and corrected RC telescopes. The link above hints that this particular scope may not be suitable...but Im not sure.

[GuillermoBarrancos]

Have you thought about the Mount to support that monster? As I am sure it will be somewhere in the range of 40kg.

Your HEQ5 Mount will collapse under that load.

EDIT: Nevermind, you just beat me to it yourself lol.

[Andrew INT]

Indeed it would Guillermo!

I just need to figure out what would be the best CCD to use, and what the FOV on the chip would be. I suppose it would also need a flattener too ideally?

[nmoushon]

Andrew,

As above this will work fine in all wave lengths and for both planetary and all DSOs. Most RCs have a native F/8 instead of F/10 like the SCTs. So if that is true about this one you will have 3248mm FL. For perspective a 11"Edge sits at 2800mm(F/10) and the 14" at 3900mm FL(F/11). You are sitting with a lot of FL and will require a LOT of dedication and persision to get it to accurately track. The Messu, I think, should have no problem slinging that 16" around and with a good OAG and sensitive guide cam you should be able to get some nice long subs.

One nice thing about the RCs is their native faster optics than SCTs. With this size scope and FL you will never run out of small galaxies to image. Also when combined with a reducer you will have a decently fast scope that will provide some very nice close ups of nebula without the need of very long exposures and lots of them. With a .8x reducer you drop down the just under 2600mm FL @F/6.4, give or take a bit depending on your spacing of equipement. But this is about the range most CDKs sit at native. So I think it could give you lots of objects to choose from. Though as you have thought you will need a flattener and/or reducer/FF.

One downside that I've heard of with RCs is their collimation. I've heard they CAN BE a real pain to collimate and have troubles keeping collimation. But I can't comment if this specific scope has those problems or not, but something to look in to. Also one downside, well I think it is, is that it has open system so dust can more easily gather on your optics which then will require cleaning. Not sure if you want to bother with that or not (or if its even a concern to you) but for me I wanted as little maintenace as possible.

When looking at a CCD make sure you have your scope and mount set in stone. As pairing the right CCD to the right scope is just as important as pairing the scope to the mount. I would start a new topic for this so that you don't get off topic for this one. There are a lot of factors to consider like your obsy location, sky conditions, ect. You could spend another ten thousand on a camera but if its not paired correctly with your scope and sky conditions it could end up working just as well as one costing only two thousand.

[GuillermoBarrancos]

I think that is a bit of a problem with all that focal length. You end up with a very expensive CCD camera that has large pixels.

Even with the KAI 11002 sensor with 9 Micron pixels you would image at 0,57 arcsec pixels. Binning 2x2 would bring it just over 1 arcsec pixels.

Tho, as you go after small targets, binning shouldn´t be too much of a problem.

It really depends on your planned budget for a CCD.