EQ6 tracking issues

[Phillyo]

Hey guys, I think I'm having some issues with my EQ6. I've aligned it to polaris using the EQmod method so hopefully fairly accurate and i've managed a 6min exposure unguided of the veil neb fine, no star trails. Slew to the soul neb and i can't get 30 seconds without star trails...

Where am I going wrong? I've done a 3 or 4 star alignment using CdC and EQMod too...

Thank you,

Phil.

[sharkmelley]

I'm more interested to know how on earth you managed a 6min trail-free unguided sub on on a EQ6!   

Mark

[Phillyo]

Only at 346mm focal length ;-) megrez 72 apo with FF/FR

[Phillyo]

Why oh why did I ever sell my other EQ6?!

I've managed to grab a single ten minute exposure, unguided with the Megrez 72 with 0.8 FF/FR and it's still bang on with tracking! I couldn't believe it!

So this is my single 10min exposure, ISO 1600 with the modded 450D. I gave it a VERY quick pop through Photoshop to reduce the brightness with levels and a little curve that's it.

Happy boy? I think so!!

Phil

[tingting44]

wow thata unreal for an unguided shot! how do you get 600s subs with out guiding?

[sharkmelley]

Typically, an unmodified EQ6 would be expected to have approx 25 arcsec of periodic error which would cause 25 arcsec star trails in a long (5 min) exposure.  Using a 450D on a 346mm focal length scope means are imaging at 3 arcsec/pixel which means the star trails would typically be around 8 pixels long.

If you are not seeing those trails then you are the lucky owner of a very good example of an EQ6!

Mark

[Phillyo]

If I zoom right in close to the full resolution image of a smaller star I can see a tiny amount of star trailing at 10min, however I'm still over the moon with what I'm getting. I was thinking of getting a guiding set up next but not sure if it's worth it if I can get these results. For now anyway. Obviously I'll guide in the future but I might get a CCD as my next upgrade instead. Decisions decisions.

Thanks all.

Phil

[VigdisVZ]

How's your balance?

[Phillyo]

Pretty poor Carl, I need to mount the megrez onto a dovetail somehow to be able to move the weight forward on the mount a bit. I think I've got some ideas but I'll have to give them a try later this afternoon.

Phil

[sharkmelley]

By the way, it's a lovely image of the veil for a single 10minute sub!

Mark

[ollypenrice]

The inconsistency will probably be balance, which will be very critical in trying to image unguided. Keeping the dynamic balance perfectly consistent across the sky is very tricky and some slight east heavy imbalalnce will be important, probably.

Everybody needs to guide, including those without guidescopes; the fancy 'unguided' mounts guide on their own hi-res encoders and a sky model to correct for varying atmospheric refraction.

Olly

[Phillyo]

Thanks Olly, I thought as much. It's on my "to buy" list, which just keeps getting bigger and bigger...the joys of astrophotography I guess?

Phil