RA Tracking

[IvanT]

Hi,

Please correct me if I'm wrong, but it's my understanding that for long exposure DSO imaging it's only necessary to track in RA, assuming of course that the mount is accurately polar aligned, is that correct?

If so, I presume I'm correct in saying that a tracking upgrade for a EQ5 mount only needs a RA motor? That being the case, how does the SyncScan GoTo upgrade for the EQ5 "GoTo" a predefined location if it is only motorized in RA?

Sorry if that's a stooopid question.

[Ant]

If the mount is perfectly polar aligned and in an ideal world - yes you only need to drive the mount in RA.

A tracking upgrade minimum would be an RA motor (not even sure that you can buy RA drives on their own for the EQ5 (think the kit comes with RA and DEC as standard).

But for GOTO you need the Synscan upgrade, gives goto and well as very fast slewing...

HTH

Ant

[IvanT]

(think the kit comes with RA and DEC as standard)

Thanks for that, TBH I would have thought the same, but the description of the Skywatcher - SynScan PRO GOTO Version 3 Upgrade Kit for EQ5 confused me, assuming of course that I'm looking at the correct upgrade

Hardware Features:

SynScan V.3 Firmware Updateable Hand Control: New features include ongoing firmware updateability via the internet, Pointing Accuracy Enhancement (PAE), and capability to store star alignment data. Also can accept new GPS mouse attachment.

High precision stepper

motors

Motor Controller: Micro-step driving with auto-power saving feature

Resolution: 0.288 arc second

Slew Rate: 0.5x, 1x, 8x, 16x, 32x, 64x, 400x, 500x, 600x, 800x

Tracking Rate: Sidereal, Lunar, Solar

Tracking Mode:

R.A. tracking

ST-4 type Autoguider Interface: Support 0.25x, 0.5x, 0.75x 1x guiding rate

Maximum Payload Capacity: Approx 9kg

Power requirement: 11 to 15 V DC 2 Amp Tip positive (Power supply not included)

So, on the one hand it talks about motors (plural) but then states that the tracking is RA, or does it simply mean that for GoTo there are two motors (RA & DEC) but it only tracks in RA?

confused.com

[Merlin66]

There's two motors supplied; one for the RA to track the sky and the other for the Dec axis to allow you to fully move the mount between objects using the hand controller.

The Dec is not normally in use during tracking the stars.

[IvanT]

That's explains it, thanks!

[Cornish astronomer]

Hi,

agreed thet only one motor needed for if tracking, if you have a good polar alignment.

This is how Equatorial Platforms for Dobsonians track with only one motor.

In this case the platform itself plays the part of a polar aligned mount, 'cos its set to your latitude angle.

[IvanT]

One further question. Is the guiding functionality supplied by the SyncScan Goto upgrade or is a PC with appropriate guiding software installed necessary?

i.e. Could I use SyncScan to point at say Vega, press a button on the control unit and have it track it?

[Ant]

With synscan you complete a star alignment (1, 2 or 3 stars). Then you can slew to an object (say Vega) - the scope then will automatically move with Vega. This is where you find out how accurate your drives / polar alignment is.

This isn't guiding though, for guiding you'll need a guide camera / laptop / software.

Ant

[Shibby]

...But you would have a guide port. Please correct me if this is wrong, but technically you could plug a guide camera (if you bought one in the future) straight into the controller and bypass the need for a laptop.

Although, as stated, tracking is merely having the RA axis motor turned on - no need for a PC (though I still like to use one to sync with Stellarium).

[ollypenrice]

I am very surprized by the number of people saying you don't need to guide in Dec. (Obviously in theory you don't but my feeling is that in reality you do.) I have never ever managed to get a polar alignment good enough to turn off the dec motor and of all the imagers who come here I have never known any do so either. You tend to run a low aggressivity in Dec correction but I have always found I did need it, sometimes only in one direction. If you are not observatory mounted and drift aligned (and I am both) then I'd say you wouldn't have a hope in hell of making it work for DS imaging.

There is backlash in your dec drive and even if you run camera end heavy, as I would advise, you will still get variations that way.

I'll be interested to see how many agree with me. I may be in a minority!

Olly

[Ant]

If the mount is perfectly polar aligned and in an ideal world - yes you only need to drive the mount in RA.

I did say with perfect polar alignment and in an ideal world...

My mount ALWAYS needs RA and DEC to guide.

Ant

[Shibby]

I only track (that's track) in RA. No sign of any star trails on 2 minute exposures (though my FOV is quite large at 1.6deg).

[IvanT]

I'm not planning on guiding just yet, already spent way more than I'd planned to. I just want a setup that will allow sufficiently long exposures to capture some of the detail DSOs have to offer.

I realize that there is a lot to it and will take a lot of effort before things start to come good, but if the SyncScan GoTo upgrade coupled with the kit I already have will eliminate the huge drift problem I observed with even a very short 5 sec exposure then that's what I'm after for now.

[SteveP]

... but if the SyncScan GoTo upgrade coupled with the kit I already have will eliminate the huge drift problem I observed with even a very short 5 sec exposure then that's what I'm after for now.

Ivan

Are you using the manual slow motion tracking controls on your mount? You might find you can do better than 5secs exposure once the manual controls have been mastered

Steve

[IvanT]

Are you using the manual slow motion tracking controls on your mount?

I didn't attempt any manual tracking Steve, weather permitting, I'll give that a go tonight. Thanks for the suggestion.

First though, I'm hoping to see a nice circular path being followed by Polaris when viewed through the polar scope

[glennbech]

I think you'll be able to do at least 60-90 second exposures (of course at reasonable focal lengths) with good polar alignment. Maybe a bit more if you're willing to throw away some bad frames.

If you have a low noise DSLR and can set you ISO to 1600, you can easily image bright DSOs and get stunning images using stacking.

Happy hunting !

[ollypenrice]

Okay, I was thinking about 5 mins as a minimum and 15 mins as an Ha ideal so I think we all really agree. That's good to know since I thought I was perhaps missing something important! (Wouldn't be the first time...)

Olly

[SteveP]

Olly, there is something important missing here and no matter how good the polar alignment nor how many subs are stacked, the result will always be poor without some way for the mount to track!!!

HTH

Steve

[ollypenrice]

Olly, there is something important missing here and no matter how good the polar alignment nor how many subs are stacked, the result will always be poor without some way for the mount to track!!!

HTH

Steve

Can't argue with that!

Olly