NexStar 8SE questions...

[truss]

Whilst not new to the astronomy caper, I'm new to this forum.

I've recently been given a new 8SE and I've had a chance to play with it over the past few nights. The optics are brilliant, even with my poxy Plossl's, it's far beyond what I was expecting. Jupiter and Saturn are very clearly defined, the bigger clusters coming up a treat.

I've managed to test out prime focus photography (Jupiter and Saturn for now) and they come up a treat. I haven't tried stacking yet but for single exposures, I'm impressed. Eyepiece projection though hasn't worked thus far as it's hard to determine where to place the eyepiece in the adapter so that the image is in focus on the sensor. I've got a 25mm piece with a decent eye relief but I haven't been able to find the bugger.

I've been feeding it 12V via mains and via a small 30Wh battery. What I've found is that the battery pack whilst saying it can provide up to 3.5A, was not up to the task. I'd find after an apparently successful Auto Two Star alignment, the alignment was off by about 20".

I have a few questions.

Would fitting a decent wedge be worth it using the 8SE mount (for photography purposes)? Or am I better off getting a decent EQ mount?

Is there a battery pack available small enough and with enough capacity (100Wh+) that doesn't cost the earth (I'm looking at you Powertank)?

The provided red dot finderscope seems decent but feels flimsy. Better options?

The Saxon Cielo range eyepieces, any good?

Oh and I've posted my two piss poor Jupiter and Saturn efforts :lol:


Edit 1-10-2019:
The mount when run off the little battery was off by a whole degree, not 20" as indicated above.

[doug mc]

Nothing wrong with plossls in a Schmidt Cassegrain, unless there is something about 50 degree apparent fields of view you don't like.

[truss]

The eye relief is atrocious on the cheapy 12.5mm, the Celestron 25mm Plossl is a delight however.

[Outcast]

Hi Truss & welcome to the forum;

I can't speak directly to the Celestron SE series but, a mate of mine uses a 7.5AH battery to power his LX90 8" and gets a full night viewing out of that.

I myself use a 24AH SLA for my LX90 but, only because I already had one lying around & also because I use it for my EQ mount & AP setup.

I generally find the LX90 Az/Alt not very power hungry vice the EQ / AP rig which sucks power like it's going out of fashion.

Regarding AP, I highly recommend a bhatinov mask to ensure that you have really sharp focus; these can be found on e-bay for as little as $16. Have a look for the e-bay handle 'I_like_vegemite', that is who I purchased mine from & he will design one for you if he doesn't have an exact match.. I have no idea who he is but, he is in Melb & his products are really good.

For planetary work, use video.. this allows you to capture thousands of frames over a short period of time; stack the video in Autostakkert, sharpen in Registax & final tweak in digital photo processing software of your choice...

I considered a wedge for my LX90 (both commercial & home made), in the end I bought an EQ mount & separate scope & do my deep sky that way instead. I understand though that there are plenty of people out there getting great results of a wedge....

Eyepieces, depends on what you want to do.. I have no experience with the Saxon range you mention but, I have Meade UWA's for widefield (a whole 1.3 degree FOV max in the LX90) & KK Fujiyama Orthos for planetary. I also have a full set of Meade plossls that came with the scope when I purchased it second hand; the plossls are fine, the others are better but, the plossls are fine...

Can't speak for your red dot finder but, I use a Bintel one which is quite robust however, that said, if the one you have is working fine I wouldn't bother changing it until it breaks.... It only has one job really, helping you get that fat 8" tube onto alignment stars... after that, if you have been exact in your alignment stars the goto should handle the rest...

I'm sure others will chime in with ideas for you as well but, hopefully, this helps...

Cheers

[truss]

Thanks for the detailed response Carlton.

Why I didn't consider a small SLA battery is beyond me, not only because they will do the job, but because I can get them at cost price (12Ah SLA for $20). What I found was that the mount itself wasn't power hungry per se, but the little Li-ion battery pack wasn't able to deliver 2A, let alone the advertised 3.5A. The mount appeared to slew correctly and the hand controller was behaving itself, but the alignment was way off, indicating a power shortfall.

I've got a Bahtinov mask lying around somewhere, I don't even know how I came to own one haha. The only problem is that it's for a Meade 4500 Newtonian (epic POS). I'll have to have a chat to my CNC guy and see if he can whip one up to suit the Celestron. If not, they aren't expensive as you've mentioned.

I didn't even consider video, my Canon 7D does a fantastic job with 1080p video. I might give it a shot the next time around.

The red dot finder when aligned is fine, however it is flimsy and the adjustment knobs and mechanism aren't smooth in operation. I've been on the Bintel site and there are a couple of nice looking finderscope options for reasonable coin.

The good Plossl pieces are fine, it's the shorter focal length ones that have very poor eye relief. I was curious about the Saxon pieces because I've read that they are a Saxon branded version of the Celestron X-Cel.

Considering I used to drive a Meade LX200 (12") way back in the day, I think I'm doing okay re-acclimatising to the SCT family.

[Ukastronomer]

If there are any people out there feeling generous pleas contact me

:) :) :)


This is THE best forum for help by the way

[truss]

It was a belated 40th b'day present :rofl:

[truss]

There's an alignment issue with the mount, even with mains power. Using the DSLR camera as the objective (prime focus), the alignment is off by about 15', no matter which alignment method I used. The result is the same if I use the 25mm Plossl as the objective. The location, date and time are on the money, the only thing I can think of is that it doesn't take into account elevation.

Any ideas?

Edit: turns out the alignment procedure is a bit more involved than first thought. I found a guide/primer on the 8SE:

http://www.astronomyforum.net/celestron-nexstar-telescope-forum/115397-8se-6se-primer-new-owners.html

I'll give it a run through the next time I use it.

[rrussell1962]

To be honest having a GOTO accuracy of 15' - about half the width of the moon, is pretty typical of what I have experienced over the 10 years or so that I have had my 8SE. If you have not done so already you could try tweaking the backlash settings, running the CALIBRATE GO TO routine at the start of the evening can also help. Another thing to try would be working out whether your scope is front or back heavy and selecting either the UP or DOWN arrow for the final GOTO approach. I also have found that doing an initial 2 star alignment and then replacing one of the alignment stars can sometimes help (no idea why this should be so). Also don't forget that there is a PRECISE GO TO routine buried in the menu tree somewhere. The Nexstar Resource site run by Mike Swanson is well worth a look.

[truss]

Those are the steps I'll be trying in the next session Russell :)

[truss]

Grabbed a 9AH battery yesterday and built a small weatherproof lead to connect the battery to the mount. It charged overnight (1A charge rate) and it seems good to go. Hopefully the clouds clear up by tonight as the smoke haze is gone and the temps are down again so I can test this new setup.

[StarChildDazee]

Pretty much sums it up.

Nothing much wrong with the Red Dot Finder that comes with the SE8.

Was also considering a wedge for my SE8 but have decided to go with an EQ mount when I can afford it. At 800 bucks i'm thinking money would be better spent on the EQ rather than a Wedge.

I would also recommend the Baader Hyperion Zoom Eyepiece 8-24mm. I hardly use any other eyepieces these days. the 31mm or the 36mm Baader Hyperion eyepieces are good for doing the your alignment.

A Focal Reducer/Corrector is a must. Celestron's 6.3 is excellent...

Cheers, Dazee

[truss]

Now that I've had a few weeks to acclimatise with the 8SE, some observations:

- Alignment isn't an issue if using Two Star alignment and the stars of choice are dead centre during alignment and centering. Alignment with the DSLR hanging off the back is more accurate than through the eyepiece (and easier on the neck).
- The mount tracks surprisingly well for a motorised alt-az, I'm getting no trailing of DSO's at one minute exposures, something I wasn't expecting.
- An EQ mount will be the go for the future, still tossing up getting the wedge.
- The focal reducer/corrector is a must have, will be buying one next week.
- The red dot finder doesn't hold alignment well at all, the optics are fine but the plastic body is rubbish.

[truss]

Bit of an update:

- Work and excessively cloudy conditions meant I've only really been out observing for the past week or so.
- I built a wedge, CNC machined up some aluminium pieces and built a reasonable facsimile of the Celestron mass produced unit.
- However it's showed up the limitations in the single arm alt-az mount. Aligning using EQ South allows for accurate goto, but the tracking is woeful. The mount in straight alt-az mode tracks better.
- The whole assembly is less stable with the wedge fitted, even a slight whisp of wind shakes the OT enough to show up even in short exposure photos.

Looks like I'm shopping for a HEQ5 or better mount and tripod, hell I'm even considering a pier in concrete.

[truss]

And today the power socket just fell apart. Luckily I had an IP67 rated socket and connector set handy, replaced both and a bit of silastic and she's good to go.

I've engaged Celestron about the tracking and they seem to think there's something not quite right as it should track for at least several minutes regardless of the accuracy of the alignment.

[truss]

Some more updates:

- I've given up on running a wedge on the alt-az mount, too much of a headache.
- Struggling to find a good EQ mount for a reasonable price
- OTA needs collimation, the focus just isn't there.