Do I need better balancing or to connect motors to eq3-2 and 150p

[Lastsplash]

Hi all

I have been using a eq3-2 with a skywatcher 150p for around 6 months now for planetary shots - using a canon 450d (videoing and then stacking) and I am pleased with the results. I find the balancing of the scope difficult when the camera is attached and I think that is due to its weight and pushing the limits of the EQ3-2.

 

I find that I cannot get the image to stay completely still - I try to balance with the weights but it either goes one way or another on the RA axis - the dec seems fine. I have tried a few things including strapping a weight to the opposite side of the camera and having the camera up or in the down position. It does move quite slowly but as you can see from the image of Orion (2 seconds) I do get star drag.

 

I have purchases an onset motor kit, but have not fitted it yet. From your experience would this resolve the movement or do I need to get better at balancing the scope and then move onto the motors? 

[Carbon Brush]

You have done well with those images.

Rather than upgrading the EQ3, I would give thought to a larger mount.
But as you already have the onstep awaiting unboxing, why not try it? Nothing to lose.
Your star drag can come from all sorts of places.
Balancing a biggish newt and big camera is quite involved.
Think about doing it for the part of the sky you are imaging, rather than all over.
Also a bit of off balance force to take out backlash may help. Apologies if you know this.
Bottom line though is you have a 150P 'sail' to catch a light breeze, on a low cost cost undersized mount.
Some people strip/adjust mounts to minimse backlash in the drive train.
Sorry if this is blunt, but having spent many wasted evenings chasing errors.....

If you want to avoid spending on a larger mount, why not look for a low cost refractor?
By having the lump of camera on the scope axis, you ease the balancing.

In the past I have had 3-5 minutes unguided acceptable images from EQ5 and 200mm F4 to F5 reflectors, with a DSLR.
But it took some effort and was not easily repeatable. And only on a still night.
However, tens of seconds was usually well within reach.

HTH, David.


 

[Xilman]

Two things:

Is the motor running too fast or too slow? If so then even if the system is perfectly balanced the stars will still be trailed.

If you add more weight to one side, does the direction of drift change?  If so, you will need to add or subtract ever smaller weights until the drift is acceptable.

A common way of dealing with drift, and I've used it myself quite often, is to take subs with an exposure short enough that the drift is small enough and then stack the subs.

Very occasionally, I deconvolve an image using a PSF taken from one or more trailed star images. This is very much second best, in my experience.

[Xilman]

4 minutes ago, Carbon Brush said:

You have done well with those images.

Rather than upgrading the EQ3, I would give thought to a larger mount.

Advice which goes back many decades but, sadly, which many people don't receive until after they have spent their budget is as follows.

Spend as much on the mount as you do on the telescope which is attached to it.

Only Dobsonian owners can get away with ignoring this rule.

Professionals have another rule: the observatory building costs as much as the telescope or the mount.

 

 

 

[Lastsplash]

Wow thanks for the responses it gives me a lot to think about and try.

 

I may fit the onset motors and see if it helps.

 

the weights I added did not make much difference which seemed strange. Also I found balancing was easier when the clutch wasn’t on is this normal? I found that moving the counterweights when the clutch was on did not change the movement.

 

Will tightening up the worm gear help or hinder?

 

once I have the motors fitted I will report back.

 

I agree my life would have been a little bit easier if I got a better mount I think this will be the next step

 

once again thanks again

[malc-c]

The weight of the 150p plus the camera, and the weights is really pushing the EQ3 to its limit.  Read through any thread of similar description where people hope to get XXX scope and mount but want to image as well as visual and you'll see that the consensus is to upgrade the mount one step larger, ie a 150P / EQ3 is fine for visual, but a 150P / EQ5 is more capable as an entry level imaging rig.  200P is fine for visual on an EQ5, but again on an HEQ5 becomes a decent entry into imaging.   If you really want to scope (no pun intended) for the future, then skip a mount, eg 150P on an HEQ5, 200P on an EQ6 which provides a very sturdy option.

Its an old video, but this covers how to balance a scope in all three axis 

 

[bosun21]

5 hours ago, Lastsplash said:

Also I found balancing was easier when the clutch wasn’t on is this normal?

The clutches must be loosened when balancing both the RA and DEC axis.

[Lastsplash]

Hi

Thanks for all the advice - this has been great.

 

I agree - a EQ5 would make my life a lot easier - the EQ3-2 came with the scope so I am seeing what I can do before upgrading - it will be my next step.

 

I have not had chance to fit the onstep motors yet but did take advice and took shorter exposures to reduce drag and stacked in deepspace stacker. It did help and the motors may improve it even more. Once again thanks for this great advice and I will save for a better mount. See attached for last nights try

Orion 2.TIF

[Lastsplash]

Sorry forgot to say  I did 1 second exposures

[Cosmic Geoff]

You do not say what kind of motors (if any) are currently fitted to your EQ-3.  If it's motorised, there should be a speed adjustment or a choice of sidereal/lunar/solar rates. How good is your polar alignment?

You still have slight trailing at 1 second exposure. Maybe it's not tracking at all? I have regularly made exposures of 20 seconds (tracked but unguided) without noticeable trailing. 

[Lastsplash]

Hi Geoff 

no I haven’t fitted the motors yet. This is the next job.

I have an onset kit still in the box waiting to be fitted hopefully this should help

[Xilman]

2 hours ago, Cosmic Geoff said:

You still have slight trailing at 1 second exposure. Maybe it's not tracking at all? I have regularly made exposures of 20 seconds (tracked but unguided) without noticeable trailing. 

Note that slight trailing will happen if the polar alignment isn't good enough ...

 

(Edit: ssorry, I didn't spot this point had already been made.)

Edited January 20 by Xilman
Add apology.

[malc-c]

23 hours ago, Cosmic Geoff said:

You still have slight trailing at 1 second exposure. Maybe it's not tracking at all? 

Makes you realise just how fast we are spinning