how good is my OTA really ? Celestron Omni XLT 150

[glowingturnip]

Hi All,

So I've been dabbling with astro imaging for a few years now, and like many, started off with distinctly basic equipment which I've added to and added to, so now I think it's starting to border on becoming a decent set-up.  I'm especially looking forward to when I can take delivery of my new mount, which I'm hoping will make lots of difference.  Current kit as per my sig.

The one significant part that I've not really done anything to (apart from add a dual speed focuser, bolted a guidescope on top of, use a CC with and keep collimated) is the OTA, which is the standard Celestron Omni XLT 150 reflector - 750mm focal length, 150mm aperture, f5.

How do people think this OTA compares with some of the better mid-range imaging OTAs ?  In particular, I'd be interested to see how it compares with the SW 130 PDS (or 150PDS I guess) since there are some stonkingly good photos on this site from that OTA.  I'm kind of hoping that since it looks the same, and is I believe made in the same factory by Synta, that it would be an equivalent OTA, but I imagine I'm probably kidding myself !

So what do people think - is it up to scratch, or not really ?  Be honest - if it's not, then I have another splurge at some point to look forward to, if it is, then I can knuckle down and get on with it !

Cheers

[michael.h.f.wilkinson]

I think the Celestron 150 F/5 comes from the same source as the SW 150 PDS (Synta). Overall quality is probably the same, but where they may differ is in the quality of the focuser, and the precise location of the focal point. Newtonian focusers usually have little travel, so some scopes are optimized more for visual use (focus comparatively close to the optical tube), whereas others are optimized for imaging (focal plane further outside the tube). The former may have problem reaching focus with a camera, whereas the latter might require extension tubes with some EPs. If you can get focus with your current scope and camera, and the focuser seems up to the job, I would not invest in a new scope, but give the current one a try first

[ronin]

I would suspect it is the same optics.

The "difference being the location of the primary (bit higheer up), maybe a marginally bigger secondary as the light cone will be a little larger and a focuser that enables a DSLR to get at the prime focus.

So I doubt the main objective is different (maybe could be perhaps).

The secondary may be a slight improvement, it is likely to be the item that is optically better, just fairly easy to do.

The focuser again might be better just more solid and robust as it is intended or expected to carry a DSLR which is heavier then the average eyepiece. So that may be a more beefed up item and so better.

[Chris]

I think your xlt has better coatings on the mirror, so now you've upgraded the focuser and assuming you can now reach focus I would say it's a good imaging scope and probably compares well to the 130/150pds. 

[Earl]

You can get get good results with the right coma corrector and these scopes, just need to get collimation good, there is plenty of life in it untill you decide to upgrade to a F4 newt.

Im no fan of imaging with newts personally however they do dilver the goods when well tamed if you are willing to put in the effort.

[glowingturnip]

excellent, thanks for those comments guys, I shall stick with it then. 

Yeah, the focuser works fine with the DSLR - DSLR at prime focus is about mid-travel on the focuser with no problems.  If I'm doing detailed lunar work with a barlow and webcam then it's racked quite far out, but I have enough tube for it, so no problems there either.  The focuser is a lot stiffer now after I did the mod, so more likely to stay in place, hopefully.  It does still only have the 2 thumb-screws holding everything in, mind.

[Uplooker]

I am using my SW150P (old blue tube) for imaging. I have replaced the focuser, initially with a Revelation crayford and recently with a Moonlite CR2. I have replaced the primary collimation washers with substantial springs, which aid with collimation and maintaining it. I have also fully flocked the tube to reduce stray light and improve contrast.

You can get get good results with the right coma corrector and these scopes, just need to get collimation good, there is plenty of life in it untill you decide to upgrade to a F4 newt.

Im no fan of imaging with newts personally however they do dilver the goods when well tamed if you are willing to put in the effort.

I use a SW 0.9 CC, which reduces the FL from 750 to 675 thereby making the scope f4.5

I am sure I could get a better scope or switch to a frac but at the moment I do not see the advanage. With most things in life - greater and greater expense does result in diminishing returns.

So in answer to the OP question, I think if you have done the required tweaks that others have already mentioned i.e. focuser etc. then you have a pretty good imaging scope

[JB80]

I am using my SW150P (old blue tube) for imaging. I have replaced the focuser, initially with a Revelation crayford and recently with a Moonlite CR2. I have replaced the primary collimation washers with substantial springs, which aid with collimation and maintaining it. I have also fully flocked the tube to reduce stray light and improve contrast.

Can I ask in regards to the revelation focuser did you need to buy a mounting plate?

I asked this question elsewhere because a lot of these focusers claim to be for scopes of larger aperture than the 150mm newt.

[Uplooker]

Yes, I did have to buy an alternative mounting plate. As best as i can remeber I got it from Astroboot. I did need to get an mate with a lathe to open up the hole in the mounting plate to accept the focuser. I also had to modify the OTA.Your right though, even when the manufactureers state suitable for 6 inch tube, its not!