Number of DSO for imaging via 8" SCT

[souls33k3r]

Hi all,

Stupid question, I know the focal length of an 8" SCT is way too long. So my question as stated in the subject line, how many DSOs would be roughly available to image without a focal reducer? A ball park figure would be awesome.

Cheers

[riklaunim]

With proper lucky-imaging camera (like ASI224) and sometimes even a Barlow - a lot of small planetary nebulae, globular clusters etc.

[souls33k3r]

Sorry let me be very specific about my equipment. No fancy stuff apart from an autoguider and a DSLR camera (non-modded). Purely for imaging Nebulae and Galaxies on an NEQ 6 pro mount.

[Leveye]

If you center them there are many Galaxies that await you. I like to use Stellarium and put in my sensor and scope sizes. You then can size up and compose shots and will will have a better Idea before you start imaging what you'll get. Have at it!

Here's a quick guided Sombrero Galaxy shot of only 7 - 3 minute lights with a C8

[riklaunim]

DSLR may not be the optimal solution as f/10 and long focal length will be nearly only for "lucky" imaging where you take hundreds or even thousands of short exposed frames (like few sec or less). Here is a C11 example http://zwoug.org/viewtopic.php?f=22&t=2086at f/20 Note that ASI224 is a planetary/guide camera.

If you use a stronger binning with that DSLR and good guiding then it can also give good "normal" DS images on long exposures.

[souls33k3r]

Excellent, so all hope is not lost with me trying to image some distance galaxies and nebulae with an 8" SCT then.

Pardon my ignorance but what do you mean by center them? Also I take it (I'm a total noob) that I can crunch all these numbers in Stellarium and will find the answer too correct?

I really do not want to spend extra money on a focal reducer if I can and save up that money to invest into something like a ED80 frac for future DSO imaging

[ollypenrice]

The universe is a big place and it's full of stuff. The problem is, what can you do with the kit you have? You can't bin so you need small bright targets. Try the bright planetaries like the Ring, The Blue Snowball, the Trapezium region of M42, the inner part of the Pleaides (mosaic?) Colourful double stars. (Albireo?) The fundamental problem is the mismatch between camera and telescope so far as DS imaging goes. 

Olly

[michael.h.f.wilkinson]

I would certainly get a focal reducer. They come up second-hand a lot, and solve two problems: at F/6.3 exposure times can be FAR shorter (60% shorter), and the focal length gets far closer to the comfort zone of the EQ6 mount (1280mm). The image circle is smaller (28mm), of course, but that is not much of a problem on an APS-C sensor (26.7 - 28.2mm diagonal)

[souls33k3r]

As always a very sound advice from you olly I know I can always rely on you for that

Michael, mate I'm just weighing my options without having to splash much on a focal reducer for the time being while I move away from planetary imaging (when I get the kit that is). Maybe like I said I might just save up that money on focal reducer and get a decent triplet refractor for a much more substantial DSO imaging