Experience with Celestron C8-SGT, esp. photography?

[chrisc (Chris)]

Hi everyone,

I'm on the cusp of upgrading to a new scope (and a new mount, as while it's fun finding one's way about the sky "manually", I need a goto system that can track accurately for photos).

Current options:

(a) Meade 8-inch LX-200-ACF for $4,000 AUD, plus another $800 or so for a decent equatorial wedge. All-singin, all-dancing GPS assisted alignment, etc., and ACF optics.

(b) Celestron 8-inch C8-SGT for $2,300 AUD, on an equatorial mount with GOTO system, with no need for a wedge. No GPS, but quite happy to do without it.

I guess it boils down to whether the ACF optics make _that_ much of a difference ($2,500 difference, in fact?!), and whether there is anything particularly dodgy about a C8-SGT that I should be aware of??

Intended use is general observational use for both lunar/planetary and deep sky objects, and photography of same with a DSLR via either prime focus or eyepiece projection.

Any enlightening comments?

Though I was initially drooling over the LX-200-ACF I am now heavily leaning towards the C8 as I suspect it will do what I need it to do, comfortably, at around half the price.

Thanks in advance for all comments, ridicule and suggestions. :-)

Cheers,
Chris

[mithrandir (Andrew)]

I have a C8-XLT on an CG5-ASGT mount with an Orion ST80 plus flip mirror and guide camera on top. There is a Moonlite focuser and either QHY8 or Sony a200 on the back of the C8. That is about the maximum the mount will carry.

When it arrived the backlash was pretty bad but it would track as long as you kept the exposure time down.

It had to go in under warranty for a circuit board failure and they fixed the backlash so now it tracks better, but still not really good enough for long exposures. About 5 mins is the limit.

If I was starting from scratch I'd get a different mount. Probably a Losmandy G11. The Celestron CGE-Pro is just too expensive.

The genuine Celestron GPS unit is definitely not cheap, but I never get the time or location wrong.

There are a few sample moon shots in this thread: http://www.iceinspace.com.au/forum/s...ad.php?t=58976

[wasyoungonce (Brendan)]

I'm using a C8 and it's a great scope but for a beginner I suggest you also use a .63 FL reducer. This will allow you to take shorter exposures. You get a smaller image scale but it's still more than useable.

ATM I am trying C8@F10 photography and it's working out ok. I have some issues with gradients and background noise but the image scale is excellent. However you need longer exposures compared to lets say a F6.3 scope. That said I'm using a G11 mount so I can track easily (so far).

If I were to re-start all over...I'd look maybe at a short tube Newtonian reflector (around F4/F5) and definitely a G11 mount. I'd don't know how this type of tube would go on a G11 but I'd suspect up to a 10" would be ok as long as the tube length was not too long (larger moment of inertia in small breezes with longer tubes). An OTA like this will give you good results reasonably easily without breaking the bank. This'll give you experience to assess what OTA you really want.

The ACF optics are supposed to be pretty good but there again the C8 is no slouch either. Maybe consider a C8 edge?

Finally, IMHO a C8 on a CG5 (ASGT) mount is marginal for long astrophotography but fine for planetary.

As you can see...a different person a different opinion. Obviously Andrew has a fair bit of experience with essentially the same setup you want but I had great trouble with my C8 on a C5 mount. This combo was fine for visual and the mount was ok for my ED80 astrophotography.

edit:

Here is a link to CCDCalc. You can use this to assess different OTA & CCDs image scales.

[chrisc (Chris)]

I've settled on buying a Skywatcher HEQ5 Pro equatorial mount with SynScan goto system.

Now I' just need to decide on an OTA to bung on it.

The simplest/cheapest option will be (as you suggest, wasyoungonce) a short fast Newtonian (e.g. a 200mm job for about $600).

I'm pondering the merits of still getting a Cassegrain or Maksutov scope, and putting a FL reducer on it, though, as the advantages in optics, compactness of the instrument, and being able to hang all my gear off the back end of the scope rather than sideways from a Newtonian's focuser assembly, and the ability to use the scope for narrower field deep sky viewing are tending to sway me...

Any thoughts?

Chris


P.S: I really can't justify the cost of a Losmandy mount, despite agreeing they are obviously very very nice. :-)