Switching from GEM to ALT-AZ

[johncneal]

My first purchase was a fairly typical system - NEQ6 Pro mount and a Celestron Edge HD 8. Augmented with an Atik CCD, filter wheel, a guide scope from Altair and the usual dew shield, dew controllers etc etc. I've used the system on and off for the last couple of years for visual and imaging sessions and it all works for the most part. Unfortunately, for a variety of reasons I'm unable to leave it permanently set up - everything has to be stored in the house in a largely dismantled state. Inevitably, the whole process of setting up, polar alignment, balancing,  star aligning and calibration each night and taking down again wastes half of any typical UK observing session. It also makes it difficult to maintain it in a consistent, well running, configuration. Needless to say this is proving a major disincentive, particularly when observing windows are short - only had the thing out about three times this year.

Despite these problems, and inspired by subject matter I covered through the Central Lancashire Introduction to Astronomy course, the system has got me interested in spectroscopy and I've managed to do some interesting low resolution work - something I'm now much more interested in than deep sky imaging and would like to do more of.

So, to the point of my post, I'm considering selling the NEQ6 / EdgeHD 8 setup and replacing it with a Celestron CPC Deluxe 800 HD. My thinking here is that the Alt-Az configuration should be a lot quicker and easier to set up. I accept that this scope (even with a wedge) is very much second best for deep sky imaging but as I mention that would be a secondary interest. Experience with low res spectro work to date demonstrates that exposure times with the Atik camera (a cooled 414EX mono) are way shorter than for deep sky work and should be well within the tracking capabilities of the CPC mount - reasonable tracking for up to 30 seconds is asserted by many.

Clearly this is another significant purchase so I'm curious if anyone has any actual measurements of typical tracking drift on a well set up CPC 800 HD - arcsec/min type figures etc?? And what about pointing accuracy? (I accept these are partly dependent on number and quality of star alignment and on mount leveling, ota balance etc). Similarly, I'd love to hear if my feel for much reduced setup times is correct. Seems to me putting up the tripod north/south and placing the fork mount/ota unit onto it shouldn't take more than a few mins and another 5-10 to add dew shield etc. Star alignment is said to take less than 5 mins - this would reduce my setup time to no more than about 20-30mins. Does this fit with existing owners experience?

I'd also be interested to hear if anyone yet has any experience with the new Celestron PlaneWave Instruments (CPWI) telescope control software suite.

As always on SGL, constructive comments and observations most welcome.

john 

[nicoscy]

John,

Years ago I had the CPC800. Your assumption re set up and alignment time is 100% correct, however I will caution you as to the weight of the mount and scope.

You need to be very careful as the dual fork and scope combo is quite heavy. It sent me for a short trip to the ER for a couple of injections for pain and to relax the muscles, after I pulled something in my back trying to heft the combo on the tripod.

If you are good with that, all you need is a dew shield and a decent power pack and you are off to the races. A 3 star alignment takes very little time (yes, you will be done in under 5 minutes), however, regarding drift, I will leave this to more knowledgeable folks to answer.

Another use of this scope would be for EAA. You can easily fit the scope with the cheap but cheerful 0.63x reducer, or even the new Starizona 0.4x reducer and enjoy EAA. Or, just get the Hyperstar compatible version and you are down to F2, which permits imaging with an alt/Az mount.

Many options, as long as your back is happy  If in my future I enter into a healthy relationship with an obsy at the back of a nice house, I will set up a CPC9.25 myself for all of the above!

[Cosmic Geoff]

I bought a CPC800 to use for planetary imaging. I don't have figures, but the mount is really solid and tracks well. there is almost no backlash.  Like you, I wanted a stable mount that did not require polar aligning etc etc.  In this respect I am totally satisfied.  Setup time is longer than I hoped but is as indicated in the previous posts. (With a C8 SE one can just pick up the whole assembly and carry it outside, making setup time very low).  BTW you do not need to align the tripod N/S - that's a Skywatcher feature, not Celestron. 

On the downside, the fork/OTA assembly is disagreeably heavy, about44lbs/21Kg, and you have to be able-bodied to manhandle it.

Re wedge, the relevant wedge costs 400 pounds and I have not seen much positive written about the portable fork/wedge arrangement. A case of "should have kept the NEQ6"?

Re focal reducer, I have read that, far from being cheap, the Edge HD focal reducer is far more expensive than the C8 reducer and costs several hundred pounds.

Edited July 17, 2019 by Cosmic Geoff

[alan potts]

I would not have though an 8 inch would be too heavy, I carry my 12 inch LX SC without massive tripod and set them up , tripod first of course. Set up once the sky is clear from start to finish is only about 6-7 minutes with a 2 star alignment though I have never timed it.

Alan

[nicoscy]

Alan, it depends on "status" of back. With L4-L5 and L5-S1 disk issues, I can only describe myself as an idiot for purchasing the CPC800 and moving it about!

[alan potts]

14 minutes ago, nicoscy said:

Alan, it depends on "status" of back. With L4-L5 and L5-S1 disk issues, I can only describe myself as an idiot for purchasing the CPC800 and moving it about!

Yes I can agree with that, I guess size comes into it too, I am about 6 foot and fairly strong, or do I mean strange, now I am doing AP the 12 inch or Dob do not see much light and to sell them here is next to impossible.

Alan

[nicoscy]

Sigh, unfortunately strength does not come into play once you slip and land on your back and your disks bear the brunt of it

But back to John's queries:

John,

- Make sure you get a heated dew shield. Since you will be using external power (be it socket / power pack), you might as well get the rig 100% dew-proof!

- Also in case you have the possibility to make it happen, get a tripod dolly for the scope and just roll it outside and secure the wheels.

 

[Alan White]

To the OP.

Why do you need such a large and heavy rig / scope if AP is the game?
I would have thought a smaller lighter Refractor would be suitable and more portable.

For visual a good 4" refractor on an alt az makes it a very easy scope combo to own.

 

[nicoscy]

Aperture?

[johncneal]

Thanks folks, these are all very helpful and encouraging comments. I'll obviously have to do my own 'risk assessments' but at 19kg the CPC is only 3kg heavier than the weighty NEQ6 mount I've been hauling in and out of the house for the last few years. It also looks as though the CPC ought to be easier to handle than the awkwardly shaped NEQ6 lump. Fortunately I am in the position of having someone to help with the lifting most of the time so hopefully the weight shouldn't be an issue.

Just a reminder that AP isn't the main objective here - low res spectroscopy is the main goal with a bit of visual/planetary work - hence the longer fl and 8in aperture.

I'll hang on to the dew shield and heater kit from my existing EdgeHD setup so have that covered as well.

j