Synscan always a degree off

[Galactic Wanderer]

Hello everyone,

II have a question about my synscan. Whenever I slew to an object which is fainter than 4mag (I live in London), I cannot see it anywhere on the camera or eyepiece. When I took a picture of M13 I had to look around for it with my synscan which was a real waste of time. So for example, when I tried to image M51 last night, I couldn't see anything in the camera. If I spend time imaging an empty bit of sky, it will be a waste of a clear night. Is it a question of polar aligning well?

seb

[cloudsweeper]

I haven't got that same set-up, but I can make general comments.  My GoTo is usually well within 15 or 20 arcmins, so what it slews to is in the EP - although that doesn't mean you can actually see it of course!

The 'scope must be level, lat/long entered correctly, date and time accurate.

Alignment must then be done carefully - two named stars, or three bright objects.  Using a planet is supposed to be good too, but the one-star method isn't so good (esp. if you aim for something far away from that star).

And that's about it - targets always found, but there's no harm also checking against the Sky Atlas.

(Apologies if this is way off what you are asking about - I can only speak for Celestron GoTo!)

Doug.

 

[SteveNickolls]

Hi Seb,

+1 to Doug's comments about aligning accuracy. I have the Alt-Az Synscan and it is good at aligning, the more I use it the more happy I get about its accuracy. I would advise too using a cross haired eyepiece to get a better alignment on your stars. Start off with a say, 32mm eyepiece and swap down when the star in in the FOV and centre more exactly. You can also do a trial shot of say 30 secs exposure and check the Live View against the star patterns on Stellarium, adjusting if the object is not thought to be central. However depending on your target object sometimes there's nothing to be seen in the finder or eyepiece or Live View and then you rely on the mount accuracy.

Best of luck.

Cheers,
Steve

[jambouk]

You need to be ball-park polar aligned for the GOTO to work well throughout the night, but you don't need to be bang on. Leveling the mount isn't important for the EQ mount if you are setting up each night.

A reticle eye piece, or using the camera's live view (on maximium zoom in) will help to get the alignment stars bang in the middle of the FoV when aligning. Doing a three star alignment will help to reduce cone error and other errors and give you the best possible GOTO accuracy.

What alignment method are you using at present? 

James

 

[Galactic Wanderer]

7 hours ago, jambouk said:

You need to be ball-park polar aligned for the GOTO to work well throughout the night, but you don't need to be bang on. Leveling the mount isn't important for the EQ mount if you are setting up each night.

A reticle eye piece, or using the camera's live view (on maximium zoom in) will help to get the alignment stars bang in the middle of the FoV when aligning. Doing a three star alignment will help to reduce cone error and other errors and give you the best possible GOTO accuracy.

What alignment method are you using at present? 

James

 

2-star alignment for now.

[jambouk]

Two star alignment is ok if the two stars are the same side of the meridian and the targets are that side of the meridian too. A three star alignment will likely give you you more accurate goto if you are planning to goto all over the sky.

james

 

[michael8554]

A 1 minute exposure at your 12800 ISO will show a hint of most DSO's.

If you're off target, take it at low res and feed into PlateSolve2, it will report your true RA/Dec within 30 secs.

In my opinion accurate GoTo is only needed if you're whizzing around the sky all night long.

But if you only want to find one object to image on all night long, Sync on a star near your target first, then your GoTo the target will probably be spot on.

Michael

[Galactic Wanderer]

On 6/11/2016 at 21:23, michael8554 said:

A 1 minute exposure at your 12800 ISO will show a hint of most DSO's.

If you're off target, take it at low res and feed into PlateSolve2, it will report your true RA/Dec within 30 secs.

In my opinion accurate GoTo is only needed if you're whizzing around the sky all night long.

But if you only want to find one object to image on all night long, Sync on a star near your target first, then your GoTo the target will probably be spot on.

Michael

Even in light polluted London?

[michael8554]

6 hours ago, Galatic Wanderer said:

Even in light polluted London?

Hmm, maybe not, but the point is to not spend all night on empty sky, try test exposures first.

Good luck

Michael